[0001] The present invention relates to a method for producing a cylinder head unit of an
internal combustion engine, comprising the steps of casting a cylinder head having
valve openings, providing said valve openings with valve seats by fastening valve
seat blanks and applying a finishing treatment to said valve openings and said valve
seats, wherein during casting of the cylinder head manufacturing reference surfaces
are formed thereon.
[0002] In the past, the cylinder head units for engines were formed by casting aluminum
alloy materials, and valve seats were attached to the valve face surfaces for the
intake valves and exhaust valves. Since these valve seats would be exposed to high
heat as they made repeated contact with the air intake and exhaust valves, they were
formed from a sintered ferrous metal that has excellent resistance to wear and high
temperatures. As is shown in Figure 18, they were pressed into a retaining hole formed
in the openings on the combustion chamber side of the cylinder head for the air intake
ports and exhaust ports to unitize them with the cylinder head unit.
[0003] Figure 18 is an enlarged sectional view of a conventional valve seat that was press-fitted
into the cylinder head. In the figure, 1 is the cylinder head unit, 2 is the press-fitted
type of valve seat, 3 is the retaining hole for the valve seat. The retaining hole
3 for the valve seat was formed by machining around the port opening area of the cylinder
head.
[0004] Conventional press-fitted type valve seats 2 were installed by first making the retaining
holes 3 as described above in the cylinder head unit 1, and then by heating the cylinder
head unit 1 in a furnace to cause the diameter of the retaining holes 3 to increase,
and then pressing-in the valve seats. To wit, the valves seats would be attached to
the cylinder head unit by shrink fitting.
[0005] When this type of valve seat 2 is fitted into the cylinder head unit 1 under high
temperature conditions, the valve guides (not shown) that support the air intake and
exhaust valves are also pressed into their retaining holes. These valve guide retaining
holes are cut at the same time as the retaining holes 3 using a machining process.
[0006] The problem with using press fitting for the valve seats is that it is not possible
to simplify the production process or to shorten the production time. The reasons
are first, the retaining holes 3 for the press fitting must be positioned with high
accuracy to position the valve seats, and the machining processing takes too much
time. Second is the fact that a heating furnace has to be employed in a heating process
for affixing the valve seats 2 to the cylinder head unit. Third, there must be a washing
process using a water washing device prior to the heating process to prevent any cuttings
generated during the machining process from getting into the foregoing heating furnace.
[0007] US-A-3,935,679 discloses a grinding fixture for grinding cylinder head castings,
in particular, for automatic grinding of cylinder head castings for internal combustion
engines, using reference surfaces established during casting in the combustion chamber
cavities. Said grinding fixture supports cylinder head casting during automatic grinding
of the casting and is adapted to level the casting and to hold the casting in the
leveled condition, so that the casting can be passed through an automatic grinding
mechanism to grind off parting lines, flash, flow pins and gating from the upper surface
and side surfaces of the casting.
[0008] Accordingly, It Is an objective of the present invention to improve a method for
producing a cylinder head unit of an internal combustion engine as indicated above
so as to facilitate the simplification of the producing process and the accurate determination
of the positioning of the valve seat length and the valve openings.
[0009] According to the present invention, this objective is solved by a method for producing
a cylinder head unit as indicated above in that a position for said valve seat blanks
on said valve openings is determined on the basis of indexing on said manufacturing
reference surfaces, wherein said position for said valve seat blanks is dependent
from an axial direction of valve guide holes drilled after casting, metallurgically
bonding said valve seat blanks to said valve openings is carried out by applying electricity
to said cylinder head unit through an electrode, a guide rod is advanced coaxially
aligned with said electrode, such that said guide rod enters said valve guide hole
and simultaneously guides said electrode for matching a pushing direction with said
axis of a valve, wherein said electrode is in direct contact with said valve seat
blanks electrically, but isolated from said cylinder head and said guide hole.
[0010] According to a preferred embodiment said manufacturing reference surfaces define
three directions comprising a first end surface on the side of said cylinder head
facing a cylinder body, a second surface parallel to said first surface and a third
surface being perpendicular to both the first and second surfaces.
[0011] According to another preferred embodiment, said valve guide holes are drilled prior
to or after the bonding process of said valve seat blanks.
[0012] According to another preferred embodiment the pressing force and/or said electricity
are applied according to a predetermined pattern.
[0013] Since the magnitude of sinking of the valve seat base material into the opening may
be measured continuously during the whole bonding process it is also possible that
said magnitude of sinking of the valve seat base material into the opening may be
controlled.
[0014] According to a further preferred embodiment the valve seat blank is pressed around
the port openings and electrical resistance is used to heat the zone where the two
are in pressure contact; this causes the temperature to rise at the surfaces where
the two are in pressure contact, causing the atoms to become mutually dispersed. As
a result, a layer of co-crystalline alloy is formed between the metal material of
the valve seat and the component metal materials of the cylinder head unit.
[0015] Since the liquid phase transition temperature of this co-crystalline alloy layer
is low, the foregoing resistance heating causes this transition to a liquid phase,
and while applying pressure to the valve seat blank, a plastic flow is generated that
causes it, along with some stock metal from the cylinder head, to be squeezed out
from the contact zone in which there is a mutual dispersing of the atoms from the
sintered alloy of the valve seat blank and the metal of the cylinder head, which,
in this condition, causes the valve seat blank to become embedded around the port
opening and attached to the cylinder head.
[0016] According to still another preferred embodiment, in attaching the valve seat material
to the cylinder head, compared to the conventional case where valve seats are press-fitted
into the cylinder head, any machining of the cylinder head is superfluous, and in
addition, a heating furnace to heat up the cylinder head for the purpose of attaching
the valve seats also is superfluous.
[0017] Since the press-fitted type valve seats required retaining holes formed to high accuracy
in the first place, no especial guide holes are needed to perform the indexing for
the press fitting or to regulate the pressing direction. However, with the attachment
method of this invention which does not utilize a press fitting structure, some sort
of guide is necessary to determine the position for the valve seats and to apply pressure
upon the valve seat blank in the axial direction.
[0018] According to a further preferred embodiment, in attaching the valve seat blank to
the cylinder head, when contrasted to the press fitting of the valve seat, there is
no need for the boring of special guide holes for the valve seats prior to their attachment.
In addition, the heating process for the cylinder head that utilizes a heating furnace,
and the washing process needed to remove foreign matter therefrom prior to heating
have been eliminated.
[0019] According to a further preferred embodiment in attaching the valve seat blank to
the cylinder head unit, special guide holes for the valve seats need not be drilled
prior to their attachment. In addition, the heating process for the cylinder head
that utilizes a heating furnace, and the washing process needed to remove foreign
matter therefrom prior to beating have been eliminated.
[0020] Further, in attaching the valve seat blank to the cylinder head unit, the indexing
for the attachment openings and the boring of the foregoing holes for component parts
is performed on the basis of common manufacturing reference surfaces, which means
that the positioning relationships between the two remain unaffected by casting tolerances.
Other preferred embodiments of the present invention are laid down in further dependent
claims.
[0021] In the following, the present invention is explained in greater detail with respect
to several embodiments thereof in conjunction with the accompanying drawings, wherein:
Figure 1 is a sectional view of the valve seat area of a cylinder head with the valve seat
attached by the manufacturing method of this invention;
Figure 2 is a sectional view showing the alignment of the valve seat blank with the port openings,
containing only a partial enlargement of the valve seat blank and the cylinder head;
Figure 3 is a front view of a press apparatus used to implement the method of this invention
for manufacturing cylinder heads;
Figure 4 is a side view of a press apparatus used to implement the method of this invention
for manufacturing cylinder heads.
Figure 5 is a sectional view showing the electrode in contact with the valve seat blank;
Figure 6 is a graph showing the pressure application pattern, current value pattern, and amount
of embedding;
Figure 7 is a sectional view showing the formation of the layer of alloy from the metal stock
from the covering film on the valve seat blank and the cylinder head metal stock,
Figure 8 is a sectional view showing the plastic flow created in the cylinder head unity
Figure 9 is a sectional view showing the embedding of the valve seat blank into the cylinder
head unit;
Figure 10 is a sectional view showing the valve seat after final finishing;
Figure 11 is a top view showing an example of shield utilization;
Figure 12 is a block diagram used to explain the method of manufacturing cylinder heads according
to the third invention;
Figure 13 is a block diagram used to explain the method of manufacturing cylinder heads wherein
the nock pin holes are used for the positioning of the valve seat blanks on attachment
openings formed by casting;
Figure 14 is a block diagram used to explain the method of manufacturing cylinder heads according
to the first invention;
Figure 15 is a block diagram used to explain the method of manufacturing cylinder heads according
to the second invention;
Figure 16 is a block diagram used to explain the method of manufacturing cylinder heads where
the attachment openings for the valve seat blanks have been formed by casting, nock
pin holes being used to index the position of the valve seat blanks;
Figure 17 is a sectional view showing other examples where the shape in the contact zone has
been modified: in (a) and (b) a ridge has only been put on the valve seat blank, and
in (c) the ridge only appears on the cylinder head unit; and
Figure 18 is an enlarged sectional view of the valve seat area showing a prior art press fitting
of the valve seat into a cylinder head.
[0022] In describing an embodiment of this invention, the method for manufacturing cylinder
heads of the third preferred embodiment, which involves the most processing steps,
will be explained first, with reference to Figures 1 through 12.
[0023] Figure 1 is a sectional view of the valve seat area of a cylinder head employing
valve seats attached using the manufacturing method of this invention; Figure 2 is
a sectional view showing the valve seat blank positioned over the port opening, in
this figure only a part of the cylinder head and valve seat are shown in the enlargement.
[0024] Figure 3 shows a front view of a press device which is used in implementing this
invention's cylinder head manufacturing method; Figure 4 is the same shown in a side
view; and Figure 5 is a sectional view showing the electrode in contact with the valve
seat material. Figure 6 is a graph which shows the pressure pattern, the electrical
current values and the degree of embedding. Figure 7 is a sectional view showing the
formation of the alloy layer from the stock metal of the cylinder head and the metal
film covering the valve seat blank; Figure 8 is a sectional view showing the onset
of the plastic flow of the metal from the cylinder head stock; Figure 9 is a sectional
view showing the embedding of the valve seat blank into the cylinder head; Figure
10 is a sectional view showing the finishing of the valve seat, Figure 11 is a top
view showing a shield utilization example; and Figure 12 is a block diagram that explains
the process steps for manufacturing a cylinder head according to the first embodiment.
[0025] In these figures, 11 represents the cylinder head unit of a four-cycle engine; this
cylinder head unit 11 was formed by casting an aluminum alloy material. Formed in
it is a downward-opening dome-shaped concave zone 12 that forms a combustion chamber
and an air intake port 13 that opens at one end of this concave zone 12, and an exhaust
port 14. Also formed when casting this cylinder head unit 11 are manufacturing reference
surfaces that define three directions, they are composed of the cylinder body end
surface, a parallel surface, and another that is perpendicular to the two.
[0026] These manufacturing reference surfaces can be formed, for example, on the concave
zone 12 that forms the foregoing combustion chambers and on the inner wall of the
cam chain chamber (not shown). The manufacturing reference surface formed on the foregoing
concave area can be formed by partially notching upward into the cylinder head in
the area of the concave zone 12, near the spark plug hole (not shown). When forming
the manufacturing reference surface on the inner wall surface of the chain chamber,
etc., one may form it by partially notching the inner wall of the chain chamber, just
as was done for the foregoing concave zone 12.
[0027] The air intake valve 17 and exhaust valve 18 are attached in the upper wall areas
of the foregoing air intake port 13 and exhaust port 14 by valve guides 15, 16, and
valve seats 19 are attached around the openings to both ports 13, 14. The foregoing
valve guides 15, 16 have been press fitted into valve guide retainer holes 11a formed
by machining the cylinder head unit 11. The retainer holes 11a for the valve guides
are formed in a manner such that their axial lines C coincide with the axial lines
of the openings 13a and 14a of the air intake port 13 and the exhaust port 14, respectively.
The machining of the valve guide retainer holes with respect to the foregoing openings
13a, 14a is performed by indexing on the manufacturing reference surfaces that were
formed during the casting of the cylinder head unit 11.
[0028] The valve seat 19 shown in Figure 1 is a ring-shaped piece of valve seat blank that
was attached to the cylinder head 11 by the method of this invention, and subsequently
machined to its finished dimensions. In Figure 2, the foregoing valve seat blank bears
the reference number 20. The valve seat blank 20 is composed of a ring-shaped sintered
ferrous alloy 21 , for example, with a copper film 22 covering its surface.
[0029] As is shown in Figure 2, the valve seat blank 20 is positioned over the openings
13a, 14a for the air intake port 13 and exhaust port 14, the latter being of a shape
such that a part of their outer circumferential surfaces lies adjacent to the inside
of these openings 13a, 14a. In Figure 2, the bottom surface of the cylinder head unit
11 (the surface containing the concave areas 12 forming the combustion chambers) is
facing upward.
[0030] To explain in further detail, the outside circumferential surface of the valve seats
20 assumes an increasingly smaller outside diameter as it gets closer to the side
facing the cylinder head unit, thereby forming a sloping surface. Moreover, the bottom
surface 20b of the valve seat blank 20 is sloped increasingly toward the cylinder
head unit as its axis is approached. This means that the outside circumferential surface
20a and the bottom surface 20b join to form a convex curved surface. In Figure 2,
this convex surface has been labeled 20c.
[0031] In the position of the foregoing openings 13a, 14a that lies opposite the foregoing
convex curved surface 20c is formed a ridge area 23 which partially narrows the inside
diameter of the intake and exhaust ports 13, 14. This ridge area 23 is formed during
the post-casting machining of the cylinder head unit 1. This ridge area 23 comprises
the attachment opening used in this invention.
[0032] To wit, by placing this valve seat blank 20 over the foregoing openings 13a, 14a
as shown in Figure 2, the convex curved surface 20c on the seats comes into contact
with the ridge area 23 on the cylinder head unit 11.
[0033] The inside circumferential surface of the valve seat blank 20 is composed of sloped
surface 20d which slopes in a manner such that the inside diameter of the valve seat
blank 20 diminishes the closer to the cylinder head unit 11, and an axially extending
surface 20e which extends from the sloped surface 20d parallel to the axial direction.
[0034] The press device 24 shown in Figures 3 and 4 is used to join the above-structured
valve seat blanks 20 to the cylinder head unit 11 at the aforementioned openings 13a,
14a.
[0035] A lower platen 26 is affixed to the lower area of the frame 25 of the press apparatus
24 and, positioned above this lower platen, is a movable upper platen 27 which can
be freely moved up and down. The lower end of a rod 28a composed of the working end
of a cylinder apparatus 28, which is disposed in the vertical direction with respect
to the axial line of the top of the press frame, is attached to this upper platen
27.
[0036] The foregoing lower platen 26 and the upper platen 27 are respectively attached through
electrically conducting materials 26a, 27a to an electric power supply (not shown)
which supplies them with electricity. The conducting materials 27a connected to the
upper platen 27 are structured to deform with the rise/fall operation of the upper
platen 27, or to rise and fall with it. Also, in this embodiment, the upper platen
27 forms the anode while the lower platen is the cathode.
[0037] Also attached to the top of the frame that supports the foregoing cylinder apparatus
28 is a laser displacement meter comprising a reflector 29 which reflects laser light
to measure the displacement of the upper platen 27.
[0038] In attaching the valve seat blank 20 using this press device, first the lower electrode
31 is affixed atop the foregoing lower platen 26, and then the cylinder head unit
11 is rested atop this lower electrode 31. At this time, the concave areas 12 that
form the combustion chambers in the cylinder head 11 are facing upward and the axial
line of the port opening to which the valve seat blank 20 will be attached aligned
with the axial line of the rod 28a of the foregoing cylinder apparatus 28.
[0039] Next, as is shown in Figure 5, a guide rod 32 is inserted into the retaining hole
for the valve guide 15,16 for the port to which the valve seat blank 20 is to be attached,
from the side that has the concave areas 12 that form the combustion chambers. This
guide rod 32 is composed of a round metal rod 32a which is covered by a layer of insulating
material 32b such as alumina. The positioning is determined and retained by a stopper
32c that fits into the valve guide retaining hole 11a. In this embodiment, the method
used to form the foregoing layer of insulating material 32b was flame spraying of
alumina or other ceramic material onto a round rod 32a and then polishing to finish.
[0040] After that, the valve seat blank 20 is placed over the port opening and then the
upper electrode 33 is rested atop the valve seat blank 20. This upper electrode 33
has a guide hole 33a into which fits the foregoing guide rod 32. Its lower end has
a tapered surface 33b that closely fits the foregoing sloped surface 20d (Figure 2)
of the valve seat material, and an axially extending surface 33c which fits tightly
around the axially extending surface 20e of the valve seat blank 20 to keep it in
position. There is also a magnet 33d affixed to the lower end of the upper electrode
33 which can magnetically hold and release the valve seat blank 20.
[0041] To wit, by fitting the foregoing guide rod 32 into the foregoing guide hole 33a,
the upper electrode 33 is aligned coaxially with the port opening for the cylinder
head 11; the above mentioned tapered surface 33b and circumferential surface 33c are
in close contact with the valve seat blank 20, thereby positioning it for a coaxial
fitting to the port opening.
[0042] After resting the upper electrode 33 on the valve seat blank 20, the top electrode
33 is rotated and a check is made to assure that the valve seat blank 20 is correctly
fitted therein.
[0043] Then, the cylinder apparatus 28 drives the upper platen 27 downward so that the foregoing
upper electrode is in tight contact. At this time the lower surface of the upper platen
27 is parallel to the top surface of the upper electrode 33.
[0044] Next, the foregoing cylinder apparatus 28 drives the upper platen 27 downward to
hold the foregoing valve seat blank 20 using the upper electrode 33 at a constant
pressure against the cylinder head unit 11. At this time, due to the regulation of
the movement of the upper electrode 33 by the guide rod 32, the direction of this
pressure being applied to the valve seat blank 20 coincides with the axial direction
of the port openings 13a, 14a. Because of this, the pressure on the valve seat blank
20 is in line with the axial direction of the port openings 13a, 14a.
[0045] The pressing force is varied as shown by the solid line showing the pressing force
pattern in Figure 6. To wit, there is a first pressing force P1, a constant and relatively
low level of force that is applied initially, and following that, a relatively higher
constant second pressing force P2 is applied for the duration of the operation.
[0046] After the application of the first pressing force P1, and when the upper platen 27
has stabilized, a reading is taken using the foregoing laser displacement meter 30
of the distance to the reflector, and that distance is recorded as the initial descent
position of the upper platen 27. Then, after the amount of time T1 that is shown in
Figure 6 after the application of the first pressing force P1, a voltage is applied
to the foregoing upper platen 27 and lower platen 26 which creates a current flow
between the platens, to wit, through the upper electrode 33, the valve seat blank
20, the cylinder head unit 11 and the lower electrode 31. At this time, the direction
of the current flow is from the upper electrode 33 toward the cylinder head unit 11.
The broken line in Figure 6 shows the current values, which are varied according to
a current value pattern. To wit, after increasing the current value, the current value
is dropped to near zero, then it is increased again, all the while applying the above
described pressing force, and then returned to zero.
[0047] At this time, the convex surface 20c on the valve seat blank 20 is resting on the
ridge area 23 on the cylinder unit 11 as is shown in Figure 2. Since the surface area
where the two are in contact is exceedingly small, there is a great deal of electrical
resistance to the flow of current described above, causing the area of their contact
to heat up. This heat is conducted to the entire contact interface between the valve
seat blank 20 and the cylinder head unit 11.
[0048] Thusly, as the temperature at the contact interface between the valve seat blank
20 and the cylinder head unit 11 increases, the atomic movement in the two metal materials
pressing against each other in solid phase (the copper of the cooper film 22 and the
aluminum of the cylinder head unit) becomes very active, causing atoms from each to
be dispersed in the other. The degree to which the aluminum oxide film formed on the
surface of the cylinder head unit 11 inhibits the dispersion of the atoms is not clear.
[0049] By means of the above described mutual dispersing of atoms, the composition in the
area of the interface is a co-crystalline alloy consisting of copper from the copper
film 22 and aluminum alloy from the cylinder head unit 11. Figure 7 shows a model
of the interface area at this time. In Figure 7, the area marked by A is that where
there has been a mutual dispersion of atoms and the formation of the foregoing co-crystalline
alloy.
[0050] When the temperature at the foregoing interface rises further and the atoms exhibiting
this dispersion phenomenon become more active and a part of the foregoing co-crystalline
alloy enters the liquid phase, this co-crystalline alloy layer grows, and the interface
between the solid and liquid phase expands with it.
[0051] While this co-crystalline layer continues liquefying, a plastic flow (plastic deformation)
is initiated in the aluminum alloy of the cylinder head unit 11 that lies adjacent
as it is further heated, and as it is pressed by the valve seat blank 20.
[0052] This plastic flow exhibits approximate vertical symmetry as shown in Figure 7, centered
around the area of initial contact, so that, as shown in Figure 8, in conjunction
with the liquefied co-crystalline alloy mentioned above, the plastic flow is pushed
to the outside the contact zone. In Figure 8, the area wherein the co-crystalline
alloy has been pushed out is labeled B. Also, because a part of the copper film 22
on this valve seat blank 20 has been converted into co-crystalline alloy and expelled
from the contact zone, a part of the ring-shaped unit 21 is in contact with the aluminum
alloy, and in this area, there is also a dispersion of atoms between them. The area
in which this dispersion takes place is shown by C in Figure 8.
[0053] Thus, with a part of the co-crystalline alloy being eliminated from the contact zone
and a plastic flow occurring in the aluminum alloy, at time T2 shown in Figure 6,
the valve seat blank 20 begins to become embedded into the cylinder head unit 11.
The application of pressure is increased from the time that this valve seat blank
20 starts to embed until time T3 shown in Figure 6 is reached; this is the second
pressing force P2 that was described above.
[0054] With the increase of the press force, the plastic flow of the aluminum alloy increases,
and the amount of co-crystalline alloy that is expelled also increases. As a result,
in the un-reacted areas of the contact zone lies the co-crystalline alloy composed
of copper and aluminum alloy, and as described above, this phenomenon repeats to further
liquefy and eliminate the co-crystalline alloy. In addition, the sintered ferrous
alloy composing the ring 21 has its atoms mutually disperse with the aluminum alloy
at their increasingly broadening interface.
[0055] From the time when the second press force P2 is applied until time T4 in Figure 6,
the current flow is dropped once to zero, and then it is elevated back to its original
value. The dropping of the current value restrains the heating temporarily, which
restrains the plastic flow, and as shown in Figure 6, there is a temporary decline
in the degree to which the valve seat blank 20 embeds. The reason for temporarily
lowering the current value is to prevent the aluminum alloy from heating to the point
where it becomes molten.
[0056] Then, after the current value is increased again, as was described above, it is gradually
decreased to zero during the T5 to T6 time frame. It is of course the case that so
long as the current is flowing, and even after it has been cut, the above described
reaction continues until such time as the temperature drops to the point when the
reaction is impossible. The embedding of the sintered ferrous valve seat blank 20
into the aluminum alloy proceeds at the same time that the phenomenon of the co-crystalline
alloy layer is created → liquefied → expelled by the plastic flow, and this results,
as shown in Figure 9, by the approximately entire outside circumferential surface
of the valve seat blank 20 becoming embedded in the cylinder head unit 11.
[0057] At about the time that this embedding halts, as shown in Figure 6 (at time T7), the
pressing by the cylinder apparatus 28 is halted, and the upper platen 27 is raised,
after a determination has been made using the laser displacement meter 30 that measures
the distance from the reflector 29 that the platen 27 has reached its final position,
and then the cylinder head unit 11 is removed from the press device 24. The average
current values and the total time of current application were determined using the
completion of the whole process as a basis.
[0058] Next, the amount of embedding of the valve seat blank 20 may be determined by computing
the difference between the position from where the upper platen 27 began its descent
to its final position. Should this value not lie within a pre-determined tolerance
D (see Figure 6), then the attachment would be regarded as defective. In actual practice,
the above described tolerance D was from about 0.5 to 2 mm in this example. While
the tolerance depends upon the material used for the cylinder head unit 11, normally,
it should range between about 1 mm and 1.5 mm.
[0059] A determination is also made for those cylinder heads that pass the above described
embedding evaluation of whether or not the average current value and the total current
application time were within the tolerance values, and if so, production lots that
have passed the pull-out inspection are sent for the final finishing of the valve
seat materials.
[0060] The above mentioned pull-out inspection is performed, for example, on each production
lot of valve seats. After they have been joined, as shown in Figure 9, tensile force
is applied to the valve seat blank 20 to try to pull it away from the cylinder head
unit. To describe this in more detail, a jig is used to hold the inside circumferential
edge of the bottom surface 20b (Figure 2) of the valve seat material, and a tensile
force testing device (not shown) pulls upon this jig in the aforementioned direction;
the test is passed if the force required to separate the valve seat blank 20 from
the cylinder head unit 11 exceeds a predetermined load level.
[0061] It is also possible to perform the same retention tests while heating or to perform
heat shock testing, these in addition to the simple separation test for the valve
seat blank 20 that was described above.
[0062] The heat retention test would involve heating the cylinder head 11, as shown in Figure
9, in a furnace with exposure to the atmosphere to 300° C for from 24 to 200 hours,
cooling, and then performing the foregoing separation test.
[0063] The heat shock experiment could be performed on the cylinder head 11, as shown in
Figure 9, by 10 repetitions of heating it in a furnace to 300° C with exposure to
the atmosphere, removing it from the furnace, and immediately cooling to 0° C by immersing
in ice water, and then checking the valve seat blank 20 for separation or for any
cracks before subjecting it to the foregoing separation test.
[0064] The final finishing of the valve seats shown in Figure 9 may be performed by machining
away the unneeded areas, for example, to the shape shown in Figure 10. This final
finishing removes the unneeded areas and the copper film from the ring 21, but it
leaves the valve seats 19 attached to the cylinder head unit 11 by the atom dispersion
zone C that is shown in Figure 10.
[0065] The metallurgical bond formed between the aluminum alloy of cylinder head 11 formed
in the above described manner and sintered ferrous alloy of the valve seat 19 is essentially
different from a mechanical bond and non-continuous bond that lacks its atom dispersion.
Further, this method also differs metallurgically from the welding method wherein
electrical resistance heating is applied at the interface of two materials to cause
their localized melting, and then the current is cut to allow the liquid phases to
cool and harden.
[0066] To wit, the metallurgical bond that was obtained with the cylinder head in this embodiment
did not leave a residual molten reaction layer, but derives from the formation of
a continues structure by mutual dispersion of atoms at the interface between both
materials.
[0067] In attaching the valve seat blank 20 to the cylinder head unit 11 as described above,
in cases where the effects of the magnetic field generated by the application of current
cause the co-crystallized alloy to be expelled in a specific direction from the junction
area, it is preferable to position a shield 34 adjacent to the upper electrode 33
as is shown in Figure 11.
[0068] Figure 11 is a top view showing the case where a shield is employed. That figure
shows the upper electrode positioned against the valve seat blank 20 and the cylinder
head unit 11. Detailed descriptions of the other parts will be omitted since they
are the same as or similar to the ones described in Figures 1 through 10.
[0069] The shield 34 used in this embodiment is formed from a vertically split cylinder
made of ferrous ferromagnetic material, and the crown area of the outside circumferential
surface points toward the frame 25 of the press apparatus 23. The direction for the
frame 25 position is shown by the arrow in that figure.
[0070] Thus, by employing this type of a shield 34, it is possible to control the direction
and the magnitude of the magnetic field that arises from the application of current,
and as a result, to control the area from the junction where the co-crystalline alloy
is expelled.
[0071] Figure 12 shows the manufacturing procedure used to join the valve seat blanks 20
to the cylinder head 11 using the above described method.
[0072] In Figure 12, as shown in step 101 the manufacturing reference surfaces are formed
during the casting of the cylinder head unit 11. After that, in step 102, the convex
shaped areas 23 are formed as the junction opening around the port openings 13a, 14a.
In step 103, the retaining holes 11a for the valve guides are formed. When these machining
processes are performed, the foregoing manufacturing reference surfaces are used to
perform the indexing.
[0073] Next, during step 104, the valve seat blank 20 is positioned. At this time, the cylinder
head unit 11, after having undergone the machining process, is affixed in the foregoing
press apparatus 24, then, as described above, the guide rod 32 and the upper electrode
33 are used to position the valve seat blanks 20 over the port openings 13a, 14a.
As indicated by a previous step 105, it is also possible to use a washing process
prior to this positioning operating in order to remove any cuttings that were generated
during the machining. This cleaning process can be implemented by water washing, or
by compressed air cleaning of the cylinder head unit.
[0074] After that, in step 106, the valve seat blank 20 is pressed against the cylinder
head unit 11 by the press apparatus 24, and current is based between the valve seat
blank 20 and the cylinder head unit 11. This process joins the valve seat blank 20
to the cylinder head unit 11.
[0075] As was described above, after attaching the valve seat blanks, in step 107, the valve
guides 15, 16 are press fitted into the valve guide retaining holes 11a in the cylinder
head unit. In this embodiment, the valve guides 15, 16 are inserted cold, but in the
case of using a shrink fit method as in the prior art, a heating process 108 can be
applied prior to the press fitting process 107 for the valve guides. In such a heating
process 108, the cylinder head unit 11 would be heated in a furnace, and the unheated
valve guides 15, 16 would be inserted and then held in place by the shrinkage from
cooling.
[0076] After the press fitting of the valve guides 15, 16, step 109 involves the rough machining
of the valve seat blanks; these, along with the valve guides 15, 16, are subsequently
finished off into valve seats 19 in the next step 110. The subsequent processes involve
seating the intake and exhaust valves 17, 18 into the valve seats 19 and inspecting
for sealing, and machining the camshaft bearing areas. This machining of the bearing
can be performed after the finishing of the valve seats 19 and valve guides 15, 16,
or, it can be performed either before or after the foregoing step 103 where the retainer
holes for the valve guides are machined, or step 107 where the valve guides are inserted.
[0077] It is also possible to reverse the above described order for attaching the valve
seat blanks 20 and inserting the valve guides 15, 16. In that case, after the step
103 in Figure 12 where the valve guide retaining holes were prepared, the valve guides
15, 16 would be pressed in (step 107) and then after that, the valve seat blanks 20
would be positioned (step 104), and the valve seat blanks 20 would be pressed, and
current passed through them (step 106). It is also possible to insert a washing process
105, or a heating process 108 involving either cylinder head unit 11 heating, or cooling
of the valve guides 15, 16 prior to the press fitting of the valve guides 15, 16.
[0078] When this type of procedure is used to manufacture cylinder heads, the valve guide
retaining holes 11a can be used for the positioning of the valve seat blanks 20 over
the openings for attachments, so that, compared with the method that uses press fitting
for the valve seats, it is not necessary to drill any special guide holes for the
valve seats prior to attaching them. This method also renders unnecessary any use
of a furnace to heat the cylinder head unit for the purpose of attaching the valve
seats, as it does any need to remove machining cuttings prior to loading the cylinder
head 11 into the heating furnace.
[0079] Further, since the machining of the cylinder head involving preparing the junction
openings where the valve seat blanks will be attached, and boring retaining holes
for the valve guides is performed using common manufacturing reference surfaces, the
positional relationships between the two remain unaffected by casting tolerances.
[0080] In the above described embodiment, the positioning of the valve seat blanks 20 on
the port openings 13a, 14a was performed using the retaining holes for the valve guides,
but it is also possible to use as a positioning guide the holes used for the assembly
of the cylinder head. For example, it is possible to use the nock pin holes (not shown)
which hold nock pins (not shown) that facilitate the positioning of the cylinder head
unit 11 on the cylinder body (not shown). Figure 13 shows the production steps involved
when these nock pin holes are used for indexing the position and pressing of the valve
seat blanks 20.
[0081] Figure 13 is a block diagram showing the procedure for cylinder head manufacturing
for the case when the nock pin holes are utilized for the positioning of the valve
seat blanks after the machining process. In the figure, explanation will be omitted
for those reference numbers that are the same or similar to those used in Figure 1
through 12.
[0082] When the nock pin holes are used for positioning, following the machining of the
openings for attaching the valve seats in step 102, the nock pin hole machining is
performed in step 120. Then, in steps 104 and 106 the valve seat blanks 20 are positioned,
and the valve seat blanks 20 are pressed and current is applied. At this time, the
nock pin holes are utilized to determine the position of the valve seat blanks 20
around the opening and the direction of pressure application.
[0083] After attaching the valve seat blanks to the cylinder head 11 in this manner, in
step 103, the machining is done to make the valve guide retainer holes 11a. The positioning
is also performed for this machining process based on indexing relative to the nock
pin holes. This process is followed by the valve guide press fitting process in step
107, the valve seat blank rough finishing operation in step 109, and by the valve
seat blank final finishing process in step 110.
[0084] As described above, even when the nock pin holes are used for positioning, it is
possible to reverse the order of the valve seat attachment and the press fitting of
the valve guides. In other words, in this case, after the nock pin hole machining
is accomplished in step 120 in Figure 13, then the valve guide retention hole machining
process in step 103 → the valve guide press fitting process in step 107 → the valve
seat blank positioning process in step 104 → the valve seat blank pressing and current
application in step 106 → the valve seat rough finishing process in step 109 → and
the valve seat final finishing in step 110 would be used to complete the process.
[0085] The same types of effects as in Example 1 are realizable when this structure is employed.
[0086] A method of manufacturing cylinder heads conforming to a third embodiment will now
be explained with reference to Figure 14.
[0087] Figure 14 is a block diagram that will be used to explain the manufacturing processed
for cylinder heads according to this third embodiment. In the figure, detailed explanation
will be omitted for those reference numbers that are the same as or similar to the
ones used in Figures 1 through 13.
[0088] As is shown by step 201 in Figure 14 for this method for manufacturing cylinder heads,
manufacturing reference surfaces are cast into the cylinder head unit 11, and the
openings for the attachment of the valve seat blanks 20 are formed. After casting,
in step 202, the positioning of the valve seat blanks over the attachment openings
is based upon indexing relative to the manufacturing reference surfaces. Next in step
203 the pressing and the current passage is performed on the valve seat blanks 20.
In this process, the direction of the pressing of the valve seat blanks is set to
be in the axial direction of the intake and exhaust valves 17, 18, on the basis of
indexing on the manufacturing reference surfaces.
[0089] Thus, after attaching the valve seat blanks 20 to the cylinder head unit 11 in this
manner, in step 103 the retaining holes for the valve guides are bored → in step 107
the valve guides are press fitted → in step 109 the valve seat blanks are rough finished
→ and in step 110 the valve seat blanks receive their final finish processing to complete
the process.
[0090] When a cylinder head is manufactured according to this procedure, the junction openings
where the valve seat blanks 20 are attached are formed during casting, and the manufacturing
reference surfaces that were also formed during casting are used for positioning the
valve seat blanks 20 over the foregoing junction openings. Therefore, compared to
the conventional press fitting of valve seats, there is no machining needed on the
cylinder head prior to the attachment of the valve seats. In addition, there is no
need to heat up the cylinder head in a furnace for the purpose of attaching the valve
seats, and moreover, because the foregoing two processes are not needed, neither is
the washing process.
[0091] As with the previous example, it is possible to include the same type of heating
process 114 just prior to the press fitting of the valve guides.
[0092] The method of manufacturing cylinder heads according to a fourth embodiment will
be detailed below with reference to Figure 15.
[0093] Figure 15 is a block diagram that will be used to explain the method of manufacturing
cylinder heads Detailed explanation will be omitted for those reference numbers that
refer to the same or similar parts used in the foregoing Figures 1 through 14.
[0094] As is shown by step 201 in Figure 15, the method of cylinder head manufacturing forms
manufacturing reference surfaces during the casting of the cylinder head unit, at
which time the junction openings for the joining the valve seat blanks 20 are also
formed. After the casting, first, the valve guide retainer holes 11a are bored (step
103). After that, it is the same procedure as shown in Figure 12 for Example 1. As
it was with that example, it would also be possible to reverse the valve seat blank
joining process and the valve guide press fitting process.
[0095] When manufacturing cylinder heads using this procedure, the junction openings where
the valve seat blanks 20 will be attached are formed by casting, and the valve guide
retainer holes 11a are used for positioning the valve seat blanks 20 over the foregoing
junction openings. Therefore, compared to the case wherein the valve seats are press
fitted, the method does not require the boring of a special valve seat hole prior
to attaching the valve seat. In addition, it is possible to eliminate the heating
process in the furnace for the cylinder heads, as well as the washing process that
was required before loading the cylinder heads into that heating furnace.
[0096] In Example 4, the valve guide retainer holes 11a were used as an index in the positioning
of the valve seat blanks 20, but it would be possible as well to use the holes in
the cylinder head which facilitate its assembly for the same purpose. For example,
it is possible to use the nock pin holes (not shown) which hold nock pins (not shown)
that facilitate the positioning of the cylinder head unit 11 on the cylinder body
(not shown). Figure 16 shows the production steps involved when these nock pin holes
are used for indexing the position and pressing of the valve seat blanks 20.
[0097] Figure 16 is a block diagram showing the cylinder head manufacturing process when
the nock pin holes are used for positioning the valve seat blanks 20 at the junction
openings that were formed during casting. Detailed explanation will be omitted for
those reference numbers that refer to the same or similar parts used in the foregoing
Figures 1 through 15.
[0098] When the nocking holes are used to determine the positioning, as is shown in step
201 of Figure 16, when casting the cylinder head unit, the manufacturing reference
surfaces and the junction openings where the valve seat blanks 20 will be attached
are formed during the casting process. After casting, first the nock pin holes are
bored (step 120). After that, the steps proceed in the same way as shown for Example
2 in Figure 13. As before, it would also be possible to reverse the valve seat blank
attachment process and the valve guide press fitting process.
[0099] Even with this structure, the effects realized are on a part with those in the example
shown in Figure 15.
[0100] In the above described examples both the valve seat blanks 20 and the cylinder head
port openings 13a, 14a has convex areas (convex curved surface 20c and ridge area
23) formed upon them. The examples featured these convex zones as being pressed against
each other, but it is not absolutely necessary to form convex areas on both parts;
they may be on one or the other parts. This example is shown in Figure 17, (a) through
(c). Irrespective of whether the junction openings where the valve seat blanks 20
are attached were formed during casting or by a machining process, it is possible
to modify the shapes involved as described below.
[0101] Figure 17 is a sectional view showing other embodiments where the shapes at the pressure
area have been changed. In (a) and (b), examples are shown where there is a convex
area formed on the valve seat blank; in (c) the example is for a projection formed
only on the cylinder head. In this figure, explanation will be omitted for reference
numbers that indicate the same or similar parts in the preceding Figures 1-10.
[0102] In the example shown in Figure 17(a), the valve seat blank 30 has approximately the
same shape as used in the previous examples, but there is a flat sloped surface formed
around the port openings 13a, 14a upon which the valve seat blank 20 makes contact.
[0103] In (b) of the same figure, the outer circumferential surface of the valve seat blank
20 is structured to fit into the port openings 13a, 14a. Also, the inside circumferential
surface of the valve seat blank 20 differs from that described in the foregoing embodiments,
it has an axially extending surface 20e that extends through the entire thickness
of the valve seat blank 20.
[0104] In (c) of the same figure, the valve seat blank has a flat sloping surface that comes
into contact with the ridge 23 on the cylinder head unit 11.
[0105] As can be seen from the examples shown in Figure 17 (a) - (c), it is possible to
obtain the same effect irrespective of whether the ridge is placed on the valve seat
blank 20 or on the cylinder head unit 11. As was shown in the examples, when a ridge
is placed on both, it facilitates the generation of a plastic flow of the metal making
up the cylinder head unit 11, and increases, relatively, the amount of that flow,
thereby enabling the area of the contact surface with the valve seat blank 20 to be
expanded for a higher strength junction.
[0106] In the foregoing examples, the material used to make the cylinder head was AC4C stock,
the valve seat blanks 20 were composed of sintered ferrous alloy in ring shapes 21
that were immersed in molten copper to create a film of copper covering them, but
such could have been formed by electroplating, and the materials used and the method
of forming the covering film are not limited to those described in the embodiments.
For example, the material used to comprise the cylinder head unit 11 could be any
of the materials conventionally used for engine cylinder heads such as AC4B stock,
AC2B stock, etc. Any type of sintered ferrous alloy can be used to make the ring shaped
members 21, and there is no great difference whether they are coated by immersion
in molten copper or electroplated. The metal used to coat the ring shaped members
21 can be any that will form co-crystalline metal with the stock of the cylinder head
unit 11. In selecting these materials and the film forming method, the most cost effective
method should be chosen from the perspective of producing cylinder heads as an industrial
product.
[0107] Also, the degree to which the valve seat blank 2 was embedded in the foregoing examples
was detected in the final stage of the process, but the displacement could be continuously
measured while pressing, and then whether or not it was within the permissible tolerance
could be checked periodically. By so doing, it is possible to eliminate defects and
save the time that would be wasted in producing them.
[0108] As explained above, the method of manufacturing cylinder heads according to the first
invention involves forming during the casting process manufacturing reference surfaces
which define three intersecting directions, and additionally, junction openings around
the port openings where the valve seat blanks will be installed, and then after casting,
by using the foregoing manufacturing reference surfaces to index the position of the
valve seat blanks, which are composed of sintered ferrous rings coated with a metal
film, and set them in place, and to again use the manufacturing reference surfaces
as an index to apply pressure to the valve seat blanks in a direction that coincides
with the axial direction of the intake/exhaust valves, and then, by heating the contact
zone between the cylinder head and the valve seats using electrical resistance, causing
the temperature to increase at the contact interface where the two are being pressed
together, and causing the atoms to mutually disperse at that interface. As a result,
a co-crystalline alloy layer will be formed from the metal that coats the valve seat
blanks and the cylinder head stock metal.
[0109] Since this co-crystalline alloy converts to a liquid phase at a low temperature,
the foregoing resistance heating converts it into a liquid phase, and the valve seat
blank, being pressed and heated, causes a plastic flow to cause this metal, along
with the stock metal from the cylinder head, to be expelled from the junction. This
results in contact between the sintered alloy of the valve seat blank and the metal
stock of the cylinder head, with their atoms mutually dispersing, and in this state,
the valve seat blank is embedded into the port opening of the cylinder head unit and
attached thereto.
[0110] In joining the valve seat blanks to the cylinder head unit, no machining of the cylinder
head is required prior to the attaching operation; this compared to the conventional
method where valve seats are pressed in which does required initial machining of the
cylinder head. In addition, the use of a heating furnace for the purpose of heating
the cylinder head for seat insertion is not needed, nor is a wash process needed prior
to those steps.
[0111] Because of this, compared to the conventional press fitting of the valve seats into
the cylinder head, it is possible to eliminate three production steps from the production
process. This is especially advantageous since it was impossible to continue the processing
of the cylinder heads that had been heated in a furnace in the conventional method
until they had cooled off. Accordingly, not only does the method greatly simplify
the manufacturing process but it can shorten the manufacturing time as well. Furthermore,
since the heating furnaces used conventionally would hold and heat a plurality of
cylinder head units at the same time, a great deal of space was required for situating
the furnace. By eliminating it, it is possible to make more efficient utilization
of factory space. Since the elimination of the heating furnace also allows the shortening
of the conveyor line for the cylinder heads, compared to the prior art, it is possible
to shorten the transport time involved between machining processes.
[0112] When casting cylinder heads, manufacturing reference surfaces that define three intersecting
directions are formed and the openings around the ports where the valve seat blanks
make contact are shaped, then after casting, the manufacturing reference surfaces
are used to determine the machining position for making the various holes needed in
the cylinder head structure, and then, these holes are used for indexing the position
of the valve seat blanks composed of sintered ferrous alloy rings covered by a metal
film and then are further used to align the pressing direction upon the valve seat
blanks to match the axial direction of the valve axes for the intake and exhaust valves;
next, electrical resistance heating is used to heat the contact zone between the cylinder
head unit and the valve seat blank, so that the temperature at the contact interface
between the two increases and the atoms mutually disperse. As a result, the metal
material comprising the coating film on the valve seat blanks forms a co-crystalline
layer with the metal stock from the cylinder head.
[0113] Since this co-crystalline alloy converts to a liquid phase at a low temperature,
the foregoing resistance heating converts it to a liquid phase, and the valve seat
blank, being pressed and heated, causes a plastic flow to cause this metal, along
with the stock metal from the cylinder head, to be expelled from the junction. This
results in contact between the sintered alloy of the valve seat blank and the metal
stock of the cylinder head, with their atoms mutually dispersing, and in this state,
the valve seat blank is embedded into the port opening of the cylinder head unit and
attached thereto.
[0114] No especial guide hole is needed, compared to the case for press-fitted valve seats
when a guide hole must be formed to a high degree of precision prior to pressing.
However, the attachment method of this invention does not require this press fitting
structure, no guide at all is needed to accurately position the valve seat blanks
or to apply the pressure in a direction aligned axially with the valve seat blank.
[0115] In attaching the valve seat blanks to the cylinder head unit, there is no requirement
to first make a special valve guide hole, as there is in the press-fitting method,
before attaching the valve seat blanks. Also not needed are a heating process using
a furnace to heat the cylinder head units for the purpose of fitting the valve seats,
or a washing process to prepare the cylinder head units for the heating furnace.
[0116] Because of this, compared to the case where the valve seats are press fitted into
the cylinder head, it is possible to simplify the production process and shorten the
manufacturing time. In particular, the conventional method that employed the heating
process did not allow cylinder head processing during the interval over which they
were cooling down, so the elimination of this heating process can cause a dramatic
simplification of the production process and a shortening of the production time.
Because the conventional heating furnaces would accommodate a plurality of cylinder
heads and heat them all at once, the device required a great deal of space, and eliminating
it allows more effective utilization of factory space. Further, the elimination of
the heating furnace enables the shortening of the conveyor line for the cylinder heads,
thereby shortening the conveyance time between machining devices.
[0117] Further, by using the structural holes that are formed in the cylinder head by necessity
as guides for the positioning of the valve seats and the application of pressure,
one hole can serve multiple purposes, thereby bringing about a cost advantage.
[0118] The method of manufacturing cylinder heads involves forming, during the casting of
the cylinder head, working references surfaces that define three directions and intersect,
and then, after casting, determining the positions for machining the port opening
and the various component holes in the cylinder head on the basis of these manufacturing
reference surfaces, and then shaping the area of the port openings that makes contact
with the valve seat blanks and boring the foregoing component holes, and next utilizing
the foregoing holes to determine the position for the placement of the valve seat
blanks, which are composed of sintered ferrous alloy rings covered with a metal film,
and then, using the holes again as a reference for the application of pressure in
the axial direction of the intake and exhaust valves, followed by the heating of the
contact zone between the cylinder head unit and the valve seat blank using electrical
resistance heating which causes the atoms at the interface between the two to mutually
disperse at the compressed junction. As a result, the metal from the coating film
on the valve seat blanks forms a co-crystalline alloy layer with the stock metal from
the cylinder head.
[0119] Since this co-crystalline alloy converts to a liquid phase at a low temperature,
the foregoing resistance heating converts it to a liquid phase, and the valve seat
blank, which is being pressed and heated, causes a plastic flow to cause this metal,
along with the stock metal from the cylinder head, to be expelled from the junction.
This results in contact between the sintered alloy of the valve seat blank and the
metal stock of the cylinder head, with their atoms mutually dispersing, and in this
state, the valve seat blank is embedded into the port opening of the cylinder head
unit and attached thereto.
[0120] When attaching the valve seat blanks to the cylinder head, it is not necessary to
have a special process beforehand to bore guide holes for the valve seats prior to
their attachment. In addition, it is possible to eliminate the heating furnace and
the heating process that was used conventionally to attach the valve seats, and eliminate
the washing process that was needed prior to loading the cylinder head units into
the furnace.
[0121] Because of this, compared to the case where the valve seat blanks were press fitted
into the cylinder head, it is possible to simplify the production process and shorten
the production time. Especially since the time required in th conventional process
for heating and cooling the cylinder heads has been eliminated, it is possible to
dramatically simplify the production process and shorten the production time through
the elimination of this heating process. Further, since a plurality of cylinder heads
were loaded into the heating furnace and heated at one time in the prior art, the
furnace required a great deal of space, and eliminating allows the more efficient
use of factory space. Further, because of the lack of a heating furnace, it is possible
to shorten the conveyor lines for the cylinder heads between the machining stations,
thereby shortening the conveyance time.
[0122] In addition, the attachment openings where the valve seat blanks are attached to
the cylinder head and the foregoing component holes were positioned on the basis of
common manufacturing reference surfaces, and accordingly, the positional relationship
between the two remains unaffected by casting tolerances. Since this makes it possible
to use the component holes as a reference in accurately positioning the attachment
openings, it is possible to attach valve seat blanks with a high degree of precision.
1. Method for producing a cylinder head unit of an internal combustion engine, comprising
the steps of:
casting a cylinder head (11) having valve openings (13a, 14a),
providing said valve openings (13a, 14a) with valve seats (19) by fastening valve
seat blanks (20) and applying a finishing treatment to said valve openings (13a, 14a)
and said valve seats (19), wherein during casting of the cylinder head (11) manufacturing
reference surfaces are formed thereon, characterized in that
a position for said valve seat blanks (20) on said valve openings (13a, 14a) is determined
on the basis of indexing on said manufacturing reference surfaces, wherein said position
for said valve seat blanks (20) is dependent from an axial direction (C) of valve
guide holes (11 a) drilled after casting, metallurgically bonding said valve seat
blanks (20) to said valve openings (13a, 14a) is carried out by applying electricity
to said cylinder head unit (11) through an electrode (33),
a guide rod (32) is advanced coaxially aligned with said electrode (33), such that
said guide rod (32) enters said valve guide hole (11a) and simultaneously guides said
electrode (33) for matching a pushing direction with said axis (C) of a valve (17,
18), wherein said electrode (33) is in direct contact with said valve seat blanks
(20) electrically, but isolated from said cylinder head (11) and said guide hole (11a).
2. Method according to claim 1, characterized in that said manufacturing reference surfaces define three directions comprising a first
end surface on the side of said cylinder head (11) facing a cylinder body, a second
surface parallel to said first surface and a third surface being perpendicular to
both the first and second surfaces.
3. Method according to claim 1 or 2, characterized in that the position for said valve seat blanks (20) is dependent on knock-pin holes drilled
after casting.
4. Method according to at least one of the claims 1 to 3, characterized in that valve guides (15, 16) are inserted into the respective valve guide holes (11 a) prior
to or after the bonding process of said valve seat blanks (20).
5. Method according to at least one of the claims 1 to 4, characterized in that joining recesses for said valve seat blanks (20) are formed in said valve openings
(13a, 14a) during casting or shaped after casting said cylinder head (11).
6. Method according to at least one of the claims 1 to 5, characterized in that said valve guide holes (11a) are drilled prior to or after the bonding process of
said valve seat blanks (20).
7. Method according to at least one of the claims 1 to 6,
characterized in that said metallurgical bonding of said valve seat blanks (20) comprises:
(a) placing a valve seat base material (20) onto a surface of said openings (13a,
14a) of said cylinder head unit (11), and
(b) pushing an electrode (33) against the end face of said valve seat base material
(20) opposite to said cylinder head unit (11) with a pushing direction matched with
an axis (C) of said intake or exhaust valve (17, 18), whereby said electrode being
adapted to apply electricity to said cylinder head unit (11) through said valve seat
base material (20).
8. Method according to at least one of the claims 1 to 7, characterized in that either the electrode (33) or the cylinder head unit (11) or both are moved towards
each other.
9. Method according to at least one of the preceding claims 1 to 8, characterized in that the pressing force and/or said electricity are applied according to a predetermined
pattern.
10. Method according to at least one of the preceding claims 7 to 9, characterized in that in step (a) said valve seat base material (20) and said opening (13a, 14a) contact
each other along a circumferential line and that this line of contact is provided
by a convex portion (20c) of said valve seat base material (20) and/or a convex portion
(23) of said opening (13a, 14a).
11. Method according to at least one of the preceding claims 7 to 10, characterized in that during step (a) said electrode magnetically attracts said valve seat base material
(20) for placing said valve seat base material (20) on the surface of said valve opening
(13a, 14a).
12. Method according to at least one of the preceding claims 7 to 11, characterized in that after steps (a) and/or (b) the electrode is rotated for checking whether the valve
seat base material (20) is fitted correctly.
13. Method according to at least one of the preceding claims 9 to 12, characterized in that the pattern of applying the pressing force comprises a first pushing force (P1) which
is applied at an early stage of the bonding process and then a second pushing force
(P2) which is applied with a certain higher value until bonding is completed.
14. Method according to claim 13, characterized in that the pattern of applying the electricity starts when a time has lapsed after application
of the first pushing force (P1), wherein a value of the electricity is first increased
then decreased close to zero and thereafter increased again before reduced to zero
during a time in which said second pushing force (P2) is still applied.
15. Method according to claim 13 or 14, characterized in that the second pushing force (P2) is applied when it is recognized that the valve seat
base material (20) has begun to sink.
16. Method according to at least one of the preceding claims 7 to 15, characterized in that the direction and the magnitude of a magnetic flux in the magnetic field caused by
energization is controlled to control the direction of the eutectic alloy removed
from the bonnet portions.
17. Method according to at least one of the preceding claims 7 to 16, characterized in that the magnitude of sinking of the valve seat base material (20) into the opening (13a,
14a) is measured continuously during the whole bonding process.
18. Method according to claim 17, characterized in that said magnitude of sinking of the valve seat base material (20) into the opening (13a,
14a) is controlled, in particular on the basis of said measured sinking value.
19. Method according to at least one of the preceding claims 7 to 18, characterized in that said valve seat base material (20) is made of an Fe-based sinter alloy being provided
with a coating (22) of a metal or metal alloy being capable of forming an eutectic
alloy with that cylinder head unit (11).
20. Method according to at least one of the preceding claims 7 to 19, characterized in that the material of said cylinder head unit (11) is selected out of the group consisting
of AC4C, AC4B and AC2B as set forth in the Japanese Industrial Standard (JIS).
21. Method according to at least one of the preceding claims 7 to 20, characterized in that after step (b) a sampling test is carried out by applying a tensile force to the
bonded valve seat base material (20).
1. Verfahren zur Herstellung einer Zylinderkopfeinheit einer Verbrennungskraftmaschine,
mit den Schritten von:
Gießen eines Zylinderkopfes (11), der Ventilöffnungen (13a, 14a) hat, Versehen der
Ventilöffnungen (13a, 14a) mit Ventilsitzen (19) durch Befestigen der Ventilsitzrohlinge
(20) und Anwenden einer Endbearbeitung auf die Ventilöffnungen (13a, 14a) und die
Ventilsitze (19), wobei während des Gießens des Zylinderkopfes (11) darauf Herstellungs-
Bezugsoberflächen gebildet sind,
gekennzeichnet dadurch, dass
eine Position für die Ventilsitzrohlinge (20) an den Ventilöffnungen (13a, 14a) auf
der Grundlage der Indexierung an den Herstellungs- Bezugsoberflächen bestimmt wird,
wobei die Position für die Ventilsitzrohlinge (20) von einer axialen Richtung (C )
der nach dem Gießen gebohrten Ventilführungsbohrungen (11a) abhängig ist,
das metallurgische Haftverbinden der Ventilsitzrohlinge (20) an den Ventilöffnungen
(13a, 14a) durch Anwenden von Elektrizität an die Zylinderkopfeinheit (11) durch eine
Elektrodre (33) ausgeführt wird,
eine Führungsstange (32), koaxial ausgerichtet mit der Elektrode (33), derart vorverschoben
wird, dass die Führungsstange (32) in die Ventilführungsbohrung (11a) eindringt und
gleichzeitig die Elektrode (33) zum Übereinstimmen einer Druckrichtung mit der Achse
(C) eines Ventiles (17, 18) führt, wobei die Elektrode (33) in direktem elektrischen
Kontakt mit den Ventilsitzrohlingen (20), aber von dem Zylinderkopf (11) und der Führungsbohrung
(11a) isoliert ist.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Herstellungs-Bezugsoberflächen drei Richtungen bestimmen, mit einer ersten Endoberfläche
an der Seite des Zylinderkopfes (119, die dem Zylinderkörper zugewandt ist, einer
zweiten Oberfläche, die parallel zu der ersten Oberfläche ist, und einer dritten Oberfläche,
die rechtwinklig zu beiden, der ersten und der zweiten Oberfläche ist.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Position der Ventilsitzrohlinge (20) von nach dem Gießen gebohrten Schlagbolzenbohrungen
abhängt.
4. Verfahren nach zumindest einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Ventilführungen (15, 16) in die jeweiligen Ventilführungsbohrungen (11a) vor
oder nach dem Haftverbindungsvorgang der Ventilsitzrohlinge (20) eingesetzt werden.
5. Verfahren nach zumindest einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Verbindungsausnehmungen für die Ventilsitzrohlinge (20) in den Ventilöffnungen
(13a, 14a) während des Gießens gebildet oder nach dem Gießen des Zylinderkopfes (11)
geformt werden.
6. Verfahren nach zumindest einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die Ventilführungsbohrungen (11a) vor oder nach dem Haftverbindungsvorgang der Ventilsitzrohlinge
(20) gebohrt werden.
7. Verfahren nach zumindest einem der Ansprüche 1 bis 6,
dadurch gekennzeichnet, dass das metallurgische Haftverbinden der Ventilsitzrohlinge (20) aufweist:
(a) Platzieren eines Ventilsitzgrundmateriales (20) auf einer Oberfläche der Öffnungen
(13a, 14a) der Zylinderkopfeinheit (11), und
(b) Drücken einer Elektrode (33) gegen die Endfläche des Ventilsitzgrundmateriales
(20), der Zylinderkopfeinheit (11) gegenüberliegend, mit einer Drückrichtung, die
mit einer Achse (C) des Einlaß- oder Auslaßventiles (17, 18) übereinstimmt, wobei
die Elektrode vorgesehen ist, Elektrizität an die Zylinderkopfeinheit (11) durch das
Ventilsitzgrundmaterial (20) anzulegen.
8. Verfahren nach zumindest einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass das entweder die Elektrode (33), oder die Zylinderkopfeinheit (11), oder beide in
Richtung auf einander zu bewegt werden.
9. Verfahren nach zumindest einem der vorhergehenden Ansprüche 1 bis 8, dadurch gekennzeichnet, dass die Druckkraft und / oder die Elektrizität entsprechend eines vorbestimmten Musters
angewandt werden.
10. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 9, dadurch gekennzeichnet, dass sich in Schritt (a) das Ventilsitzgrundmaterial (20) und die Öffnung (13a, 14a) entlang
einer Umfangslinie miteinander berühren und dass diese Berührungslinie durch einen
konvexen Abschnitt (20c) des Ventilsitzgrundmateriales (20) und / oder eines konvexen
Abschnittes (23) der Öffnung (13a, 14a) vorgesehen ist.
11. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 10, dadurch gekennzeichnet, dass während des Schrittes (a) die Elektrode das Ventilsitzgrundmaterial (20) zum Platzieren
des Ventilsitzgrundmateriales (20) auf der Oberfläche der Ventilsitzöffnung (13a,
14a) magnetisch anzieht.
12. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 11, dadurch gekennzeichnet, dass nach den Schritten (a) und / oder (b) die Elektrode gedreht wird, um zu Prüfen, ob
das Ventilsitzgrundmaterial (20) ordnungsgemäß eingesetzt ist.
13. Verfahren nach zumindest einem der vorhergehenden Ansprüche 9 bis 12, dadurch gekennzeichnet, dass das Anwendungsmuster der Druckkraft eine erste Druckkraft (P1) aufweist, die in einer
frühen Stufe des Haftverbindungsvorganges angewandt wird, und dann eine zweite Druckkraft
(P2), die mit einem bestimmten höheren Betrag angewandt wird, bis das Haftverbinden
fertiggestellt ist.
14. Verfahren nach Anspruch 13, dadurch gekennzeichnet, dass das Anwendungsmuster der Elektrizität beginnt, wenn eine Zeit nach der Anwendung
der ersten Druckkraft (P1) verstrichen ist, wobei sich ein Betrag der Elektrizität
zuerst erhöht und dann nahe auf Null vermindert, und sich danach wieder erhöht, bevor
er während einer Zeit, in der die zweite Druckkraft (P2) noch angewandt wird, auf
Null reduziert wird.
15. Verfahren nach Anspruch 13 oder 14, dadurch gekennzeichnet, dass die zweite Druckkraft (P2) angewandt wird, wenn erkannt wird, dass das Ventilsitzgrundmaterial
(20) begonnen hat, einzusinken.
16. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 15, dadurch gekennzeichnet, dass die Richtung und die Größe eines Magnetflusses in dem Magnetfeld, verursacht durch
die Energiezuführung, gesteuert wird, um die Richtung der eutektischen Legierung,
entfernt von den Haftverbindungsabschnitten, zu steuern.
17. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 16, dadurch gekennzeichnet, dass die Größe des Einsinkens des Ventilsitzgrundmateriales (20) in die Öffnung (13a,
14a) kontinuierlich während des gesamten Haftverbindungsvorganges gemessen wird.
18. Verfahren nach Anspruch 17, dadurch gekennzeichnet, dass die Größe des Einsinkens des Ventilsitzgrundmateriales (20) in die Öffnung (13a,
14a) gesteuert wird, insbesondere auf der Grundlage des gemessenen Einsinkbetrages.
19. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 18, dadurch gekennzeichnet, dass das Ventilsitzgrundmaterial (20) aus einer Febasierten Sinterlegierung hergestellt
ist, die mit einem Überzug (22) aus einem Metall oder einer Metalllegierung versehen
ist, die in der Lage ist, mit dieser Zylinderkopfeinheit (11) eine eutektische Legierung
zu bilden.
20. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 19, dadurch gekennzeichnet, dass das Material der Zylinderkopfeinheit (11) aus einer Gruppe ausgewählt wird, die aus
AC4C, AC4B und AC2B besteht, wie in dem Japanischen Industriestandard (JIS) fortgesetzt
wird.
21. Verfahren nach zumindest einem der vorhergehenden Ansprüche 7 bis 20, dadurch gekennzeichnet, dass nach dem Schritt (b) einen Probentest durch Anwenden einer Zugkraft auf das haftverbundene
Ventilsitzgrundmaterial (20) ausgeführt wird.
1. Procédé de production d'une unité de culasse de moteur à combustion interne, comportant
les étapes consistant à :
couler une culasse (11) ayant des ouvertures de soupape (13a, 14a),
munir lesdites ouvertures de soupape (13a, 14a) de sièges de soupape (19) en fixant
des ébauches de siège de soupape (20) et en appliquant un traitement de finition auxdites
ouvertures de soupape (13a, 14a) et auxdits sièges de soupape (19), dans lequel pendant
le coulage de la culasse (11) des surfaces de référence de fabrication sont formées
sur celle-ci, caractérisé en ce que
une position desdites ébauches de siège de soupape (20) sur lesdites ouvertures de
soupape (13a, 14a) est déterminée sur la base d'une indexation sur lesdites surfaces
de référence de fabrication, ladite position desdites ébauches de siège de soupape
(20) étant fonction d'une direction axiale (C) de trous de guidage de soupape (11a)
percés auprès coulage, une fixation de nature métallurgique desdites ébauches de siège
de soupape (20) sur lesdites ouvertures de soupape (13a, 14a) étant effectuée en appliquant
de l'électricité à ladite unité de culasse (11) par l'intermédiaire d'une électrode
(33),
une tige de guidage (32) est avancée en étant alignée coaxialement avec ladite électrode
(33), de telle sorte que ladite tige de guidage (32) pénètre dans ledit trou de guidage
de soupape (11a) et guide simultanément ladite électrode (33) pour faire coïncider
une direction de poussée avec ledit axe (C) d'une soupape (17, 18), ladite électrode
(33) étant électriquement en contact direct avec lesdites ébauches de siège de soupape
(20), mais isolée de ladite culasse (11) et dudit trou de guidage (11a).
2. Procédé selon la revendication 1, caractérisé en ce que lesdites surfaces de référence de fabrication définissent trois directions comportant
une première surface d'extrémité sur le côté de ladite culasse (11) dirigé en vis-à-vis
d'un corps de cylindre, une seconde surface parallèle à ladite première surface et
une troisième surface qui est perpendiculaire à la fois à la première et à la seconde
surface.
3. Procédé selon la revendication 1 ou 2, caractérisé en ce que la position desdites ébauches de siège de soupape (20) est fonction de trous pour
tige d'éjection percés après coulage.
4. Procédé selon au moins une des revendications 1 à 3, caractérisé en ce que des guides de soupape (15, 16) sont insérés dans les trous de guidage de soupape
respectifs (11a) avant ou après le traitement de fixation desdites ébauches de siège
de soupape (20).
5. Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que des évidements de liaison desdites ébauches de siège de soupape (20) sont formés
dans lesdites ouvertures de soupape (13a, 14a) pendant le coulage ou formés après
coulage de ladite culasse (11).
6. Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que les trous de guidage de soupape (11a) sont percés avant ou après le traitement de
fixation desdites ébauches de siège de soupape (20).
7. Procédé selon l'une quelconque des revendications 1 à 6,
caractérisé en ce que ladite fixation métallurgique desdites ébauches de siège de soupape (20) comporte
les étapes consistant à :
(a) positionner un matériau de base de siège de soupape (20) sur une surface desdites
ouvertures (13a, 14a) de ladite unité de culasse (11), et
(b) pousser une électrode (33) contre la face d'extrémité dudit matériau de base de
siège de soupape (20) opposée à ladite unité de culasse (11) avec une direction de
poussée coïncidant avec l'axe (C) de ladite soupape d'admission ou d'échappement (17,
18), de sorte que ladite électrode est adaptée pour appliquer de l'électricité à ladite
unité de culasse (11) à travers ledit matériau de base de siège de soupape (20).
8. Procédé selon l'une quelconque des revendications 1 à 7, caractérisé en ce que l'une ou l'autre parmi l'électrode (33) ou l'unité de culasse (11), ou les deux,
est déplacée en direction de l'autre.
9. Procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce que la force de pression et/ou ladite électricité sont appliquées conformément à un modèle
prédéterminé.
10. Procédé selon l'une quelconque des revendications 7 à 9, caractérisé en ce qu'à l'étape (a) ledit matériau de base de siège de soupape (20) et ladite ouverture
(13a, 14a) sont en contact l'un avec l'autre le long d'une ligne circonférentielle
et en ce que cette ligne de contact est fournie par une partie convexe (20c) dudit matériau de
base de siège de soupape (20) et/ou une partie convexe (23) de ladite ouverture (13a,
14a).
11. Procédé selon l'une quelconque des revendications 7 à 10, caractérisé en ce que pendant l'étape (a) ladite électrode attire magnétiquement ledit matériau de base
de siège de soupape (20) pour placer ledit matériau de base de siège de soupape (20)
sur la surface de ladite ouverture de soupape (13a, 14a).
12. Procédé selon l'une quelconque des revendications 7 à 11, caractérisé en ce qu'après les étapes (a) et/ou (b) l'électrode est mise en rotation pour vérifier que
le matériau de base de siège de soupape (20) est agencé correctement.
13. Procédé selon l'une quelconque des revendications 9 à 12, caractérisé en ce que le modèle d'application de la force de pression comporte une première force de poussée
(P1) qui est appliquée au niveau d'un étage précoce du traitement de fixation et ensuite
une seconde force de poussée (P2) qui est appliquée avec une certaine valeur plus
élevée jusqu'à ce que la fixation soit terminée.
14. Procédé selon la revendication 13, caractérisé en ce que le modèle d'application de l'électricité commence lorsqu'un certain temps s'est écoulé
après l'application de la première force de poussée (P1), la valeur de l'électricité
étant tout d'abord augmentée puis diminuée jusqu'à proximité de zéro et ensuite augmentée
à nouveau avant d'être réduite à zéro pendant un temps pendant lequel ladite seconde
force de poussée (P2) est encore appliquée.
15. Procédé selon la revendication 13 ou 14, caractérisé en ce que la seconde force de poussée (P2) est appliquée lorsqu'il est reconnu que le matériau
de base de siège de soupape (20) a commencé à couler.
16. Procédé selon l'une quelconque des revendications 7 à 15, caractérisé en ce que la direction et l'amplitude d'un flux magnétique dans le champ magnétique provoqué
par une mise sous tension sont commandées pour commander la direction de l'alliage
eutectique enlevé à partir des parties de chapeau.
17. Procédé selon l'une quelconque des revendications 7 à 16, caractérisé en ce que l'amplitude de coulée du matériau de base de siège de soupape (20) dans l'ouverture
(13a, 14a) est mesurée en continu pendant tout le traitement de fixation.
18. Procédé selon la revendication 17, caractérisé en ce que ladite amplitude de coulée du matériau de base de siège de soupape (20) dans l'ouverture
(13a, 14a) est commandée, en particulier sur la base de ladite valeur de coulée mesurée.
19. Procédé selon l'une quelconque des revendications 7 à 18, caractérisé en ce que ledit matériau de base de siège de soupape (20) est constitué d'un alliage fritté
à base de fer muni d'un revêtement (22) en métal ou en alliage métallique capable
de former un alliage eutectique avec l'unité de culasse (11).
20. Procédé selon l'une quelconque des revendications 7 à 19, caractérisé en ce que le matériau de ladite unité de culasse (11) est sélectionné parmi le groupe constitué
de AC4C, AC4B et AC2B tel qu'établi dans les normes industrielles japonaises (Japanese
Industrial Standard, JIS).
21. Procédé selon l'une quelconque des revendications 7 à 20, caractérisé en ce qu'après l'étape (b) un test d'échantillonnage est effectué en appliquant une force de
traction sur le matériau de base de siège de soupape fixé (20).