BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a valve driving apparatus for driving a valve which
opens and closes a suction port or an exhaust port in an internal combustion engine.
In particular, the invention relates to a valve driving apparatus using a direct driving
type valve lifter which can be miniaturized and light-weighted while maintaining a
sufficient lift amount of the valve to improve the operation efficiency thereof.
2. Description of the Related Art
[0002] The valve driving apparatus using the direct driving type valve lifter is disclosed,
for example, in Japanese Patent Unexamined Publication No. Hei 10-331709. The direct
driving type valve lifter includes a tappet portion which comes in contact with a
cam disposed at an upper side of a cylinder head of an internal combustion engine
and a guide portion slidably housed within the cylinder head. The valve lifter is
disposed between the cam and a valve in such a manner that the tappet portion is pushed
by a projected portion of the cam while the cam rotates to slide the guide portion
along the cylinder head. Thus, the valve is moved integrally with the valve lifter
toward its axial direction thereby to open and close a suction port or an exhaust
port at which the valve is provided.
[0003] The tappet portion with which the projected portion of the cam comes in contact is
configured in a substantially flat plate of circular shape so as to perform the linear
contact with the projected portion of the cam. The cam profile is designed such that
the tappet portion is brought in contact with the projected portion of the cam without
deviating from the range of a diameter of the tappet portion and an allowable contact
load is obtained at the tappet portion.
[0004] For example, in order to improve the output of the internal combustion engine with
an increase in an air suction amount, it is necessary to increase a valve opening
area. Since a lift amount of the valve is required to be increased in order to increase
the valve opening area, the tappet portion is so designed as to have such a diameter
that a sufficient lift amount of the valve can be secured.
[0005] To ensure the lift amount required for the valve, the diameter of the tappet portion
must be set according to the lift amount. However, as the diameter of the tappet portion
is set to be larger, the diameter of the guide portion becomes larger with the result
that the size of the valve lifter becomes larger. On the other hand, since various
mechanisms and structures exist in the vicinity of the cylinder head of the internal
combustion engine, the valve lifter is restricted in its position to be disposed.
Thus, the maximum size of the valve lifter is limited and hence it is a problem to
ensure the required lift amount of the valve while disposing the valve lifter in a
limited space. Such a problem is more critical for a small-sized internal combustion
engine.
[0006] When the size of the valve lifter is simply made larger, the inertia weight of the
valve driving system becomes larger, and hence there is a fear that it becomes difficult
to secure the required performance of the engine. Further, when the inertia weight
of the valve driving system increases, it is required to increase the spring force
of the spring system necessary for urging against the valve so as to close it. As
a result, since a contact pressure between the tappet portion and the cam becomes
high, there arises such a problem that the tappet portion and the cam are worn away.
[0007] The conventional valve driving apparatus also suffers from a problem on the lubrication
performance. Such a problem will be described with reference to Figs. 25 and 26. Figs.
25 and 26 show the schematic configuration of a conventional valve driving apparatus
using a direct driving type valve lifter. Fig. 25 shows a state where the valve lifter
is not pushed down whereas Fig. 26 shows a state where the valve lifter is pushed
down.
[0008] As shown in these figures, a cam 902 is disposed at the upper side of a cylinder
head 901 of an internal combustion engine, and a guide hole 903 is defined in the
interior of the cylinder head 901. The cylindrical portion (guide portion) of a cylindrical
valve lifter 904 is slidably housed within the guide hole 903. The cam 902 abuts against
the upper surface (tappet portion) of the valve lifter 904. A valve 905 (a suction
valve or an exhaust valve) is disposed opposite to the cam 902 with respect to the
valve lifter 904.
[0009] The valve lifter 904 is pushed down with rotation of the cam 902 and reciprocatively
moves within the guide hole 903 to thereby repeatedly open and close the valve 905.
An oil reservoir 906 in which lubricant oil 907 is reserved is formed around the upper
portion of the guide hole 903 so that both the tappet portion and the projected portion
of the cam 902 are dipped into the lubricant oil 907 within the oil reservoir 906
when the valve lifter 904 is pushed down by the cam 902.
[0010] In most of the internal combustion engines, a predetermined clearance is defined
between the guide hole 903 and the valve lifter 904 so that the valve lifter 904 is
operable even at an extremely low temperature. Thus, the lubricant oil 907 within
the oil reservoir 906 enters the clearance due to the rotation of the cam 902, the
vertical reciprocation of the valve lifter 904, its own weight of the lubricant oil
907, etc., thereby lubricating the respective portions.
[0011] As described above, the projected portion of the cam 902 comes in linear contact
with the tappet portion of the valve lifter 904. Since the contact portion between
the projected portion of the cam 902 and the tappet portion moves within the range
of the diameter of the tappet portion, a position of the tappet portion at which a
load is applied from the cam 902 changes with the result that the valve lifter 904
is applied with the opposite moment during the reciprocation.
[0012] Thus, when the lubricant oil 907 is at a high temperature, the clearance between
the valve lifter 904 and the guide hole 903 becomes large and the viscosity of the
lubricant oil becomes low so that noises are generated due to the discontinuous oil
film at the clearance and a friction at the clearance becomes large. On the other
hand, when the lubricant oil 907 is at a low temperature, the clearance between the
valve lifter 904 and the guide hole 903 becomes smaller. Thus, the lubricant oil 907
hardly flows along the side portion of the guide hole 903 and the friction becomes
larger. As a result, the output efficiency and the fuel costs of the internal combustion
engine may be degraded and the abrasion of the valve lifter 904 etc. may be caused.
[0013] Further, in most of the internal combustion engines, the cylinder head is made of
aluminum whereas the valve lifter is made of iron. As described above, a predetermined
clearance is defined between the guide hole 903 and the valve lifter 904 so that the
valve lifter 904 is operable even at an extremely low temperature. At a high temperature,
the clearance between the valve lifter 904 and the guide hole 903 becomes larger so
that the valve lifter 904 is inclined at a larger angle with respect to the guide
hole 903 upon application of the above-mentioned moment to the valve lifter 904. On
the contrary, since the tappet portion of the valve lifter 904 is configured in a
plate shape, the rigidity of the outer peripheral portion thereof is high so that
the tappet portion is hardly deformed.
[0014] As a result, when the lift amount is maximum, the posture of the valve lifter 904
changes to a large extent, and the oil film at the clearance is then pushed aside
when the valve lifter 904 hits the inner surface of the guide hole 903, to thereby
generate large metallic sound. Further, since the friction and the degree of the abrasion
become larger, the output efficiency and the fuel costs of the internal combustion
engine may be degraded.
SUMMARY OF THE INVENTION
[0015] The invention has been made to solve the above-mentioned various problems with the
conventional valve driving apparatus for an internal combustion engine using the direct
driving type valve lifter.
[0016] An object of the invention is to provide a valve driving apparatus using a direct
driving type valve lifter which can be miniaturized and light-weighted while maintaining
a sufficient lift amount of a valve in a restricted space to improve the operation
efficiency.
[0017] The valve driving apparatus according to the invention is disposed between a cam
formed at a cam shaft and a poppet valve which is provided in a path formed at the
cylinder head of an internal combustion engine and moves to an axial direction of
the valve to open and close the path. The valve driving apparatus includes a guide
hole formed at the cylinder head; and a direct driving type valve lifter including
a tappet portion which is brought in contact with the cam and pressed by the cam,
and a guide portion having one end portion coupled to the tappet portion and housed
within the guide hole so as to slide freely therein to the axial direction of the
poppet valve in an interlocked manner as a pushing operation of the tappet portion
by the cam.
[0018] According to the valve driving apparatus thus arranged, since the tappet portion
can secure such a diameter capable of realizing a required lift amount and the diameter
of the guide portion can be made small, the valve lifter can be miniaturized and light-weighted.
As a result, it becomes possible to secure a high output efficiency of the engine
while reducing the occupied area of components related to the valve in the vicinity
of the cylinder head. Further, since the components related to the valve can be housed
in a small space, the degree of the freedom for the arrangement of other components
can be improved. Furthermore, since the valve lifter is miniaturized and light-weighted,
the valve driving apparatus can cope with the high speed of the engine.
[0019] Preferably, when the poppet valve driven by the valve driving apparatus according
to the invention is provided at the suction path of the engine, it is possible to
increase the amount of the suction air by using the valve lifter thus miniaturized
and light-weighted, so that the operation efficiency of the engine can be improved.
[0020] In the case where the engine is arranged in a manner that the cam shaft is disposed
on the upper side of the cylinder head, and the suction path is opened at its one
end to the combustion chamber of the internal combustion engine and opened at its
the other end to the upper surface of the cylinder head, the valve lifter is restricted
in its position when the valve lifter is used in the cylinder head having such a suction
path. However, the valve driving apparatus according to the invention can secure a
sufficient lift amount despite of such a restriction.
[0021] In the case where the two or more poppet valves disposed in each of the cylinders
of the engine are driven so as to be opened and closed by the valve lifters, since
the number of the valve lifters is large, the valve lifter is also restricted in its
position. However, the valve driving apparatus according to the invention can secure
a sufficient lift amount despite of such a restriction.
[0022] Cylinder head bolts can be disposed in a sufficient space when the valve driving
apparatus according to the invention is employed. More preferably, even in a case
where the cylinder head bolts are required to be provided close to the valve lifter,
when the valve lifter is disposed so as to be inclined with respect to the axis line
of the cylinder of the engine, the cylinder head bolts can be fastened without interfering
the valve lifter.
[0023] In the valve driving apparatus according to the invention, the guide hole is provided
at an opening edge thereof with an oil reservoir for reserving lubricant oil therein,
the diameter of the tappet portion is at least partially larger than the diameter
of the guide portion and the tappet portion has a projected portion protruding from
outer peripheral surface of the guide portion toward outer diameter direction of the
guide portion. According to such an arrangement, the projected portion moves within
the oil reservoir when the valve lifter is lifted, so that the valve lifter can be
miniaturized and light-weighted. Further, the lubricant oil within the oil reservoir
is forcedly fed to a required portion due to the movement of the projected portion
and so the lubricant oil can be actively supplied to the respective portions of the
valve lifter. As a result, since the friction becomes smaller, the noise caused by
the striking operation when the valve lifter changes its posture can be reduced and
also the degree of the abrasion caused by the striking operation can be reduced. Thus,
the output efficiency and the fuel cost of the engine are improved, and further the
durability and the reliability of the engine are also improved.
[0024] In such a valve driving apparatus according to the invention, preferably, a clearance
is provided between the outer peripheral surface of the oil reservoir and the edge
portion of the tappet portion so that the lubricant oil can be splashed out of the
clearance. Thus, when the valve lifter is pushed down, the lubricant oil is forcedly
fed between the guide portion and the guide hole by the lower surface of the tappet
portion, and further the lubricant oil is splashed from the clearance and so the lubricant
oil is introduced on the upper surface of the tappet portion.
[0025] Further, when the clearance is arranged in a manner that the width thereof toward
the direction perpendicular to the axis line of the rotation center of the cam and
the width in vicinity thereof is larger than the width at the remaining potion thereof,
the lubricant oil can be actively splashed on the cam side.
[0026] Such a technical advantage can also be obtained in the case where the clearance is
provided only at the portion toward the direction perpendicular to the axis line of
the rotation center of the cam and in vicinity thereof.
[0027] Similar technical advantage can also be obtained in the case where the valve lifter
is disposed so as to be inclined toward the direction perpendicular to the axis line
of the rotation center of the cam with respect to the vertical direction, and the
clearance is provided only at a portion toward the downward direction among two directions
perpendicular to the axis line of the rotation center of the cam and in vicinity thereof.
[0028] In the valve driving apparatus according to the invention having the aforesaid oil
reservoir, when the diameter of the tappet portion is smaller than the diameter of
the base circular portion of the cam, the lubricant oil splashed can be directly introduced
to the cam.
[0029] In the direct driving type valve lifter used in the valve driving apparatus according
to the invention, preferably there is provided with an elastic deformation promotion
portion for promoting elastic deformation of the guide portion when the guide portion
is housed within the guide hole. In this arrangement, when the valve lifter changes
its posture during its lifting operation, the elastic deformation of the guide portion
can be promoted. Thus, the noise caused by the striking operation when the valve lifter
changes its posture can be suppressed and the friction can be prevented from increasing,
so that the durability of the valve lifter can be improved, and further the output
efficiency and the fuel cost of the engine can be improved.
[0030] Preferably, the elastic deformation promotion portion is provided at the guide portion
in vicinity of the boundary between the tappet portion and the guide portion, whereby
the guide portion can be elastically deformed easily along the guide hole when the
valve lifter changes its posture.
[0031] Further, preferably, the elastic deformation promotion portion provided in the vicinity
of the boundary between the tappet portion and the guide portion is a groove provided
at the peripheral portion of the guide portion. In this case, since the groove can
be used as a recess portion required at the time of performing the grinding process
of the rear surface of the tappet portion and the outer peripheral surface of the
guide hole, the valve lifter can be processed easier.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032]
Fig. 1 is a front view showing the configuration of a valve driving apparatus according
to a first embodiment of the invention;
Fig. 2 is a front view showing the main portion of an internal combustion engine to
which the valve driving apparatus shown in Fig. 1 is applied;
Fig. 3 is a plan view showing the main portion of Fig. 2 seen from the axial direction
of a cylinder of the internal combustion engine;
Fig. 4 is a front view schematically showing the configuration of a valve driving
apparatus according to a second embodiment of the invention;
Fig. 5 is a front view schematically showing the configuration of the valve driving
apparatus according to the second embodiment of the invention;
Fig. 6 is a front view schematically showing the configuration of a valve driving
apparatus according to a third embodiment of the invention;
Fig. 7 is a front view showing the configuration of a valve driving apparatus according
to a fourth embodiment of the invention;
Fig. 8 is a side view showing the configuration of the valve driving apparatus according
to the fourth embodiment of the invention;
Fig. 9 is a front view showing the configuration of the valve driving apparatus according
to the fourth embodiment of the invention;
Fig. 10 is a side view showing the configuration of the valve driving apparatus according
to the fourth embodiment of the invention;
Fig. 11 is a view showing the valve driving apparatus taken along a line VIII - VIII
in Figs. 7 and 9;
Fig. 12 is a front view showing the configuration of a valve driving apparatus according
to a fifth embodiment of the invention;
Fig. 13 is a front view showing the configuration of the valve driving apparatus according
to the fifth embodiment of the invention;
Fig. 14 is a view showing the valve driving apparatus taken along a line XI - XI in
Fig. 12;
Fig. 15 is a front view showing the configuration of a valve driving apparatus according
to a sixth embodiment of the invention;
Fig. 16 is a front view showing the configuration of the valve driving apparatus according
to the sixth embodiment of the invention;
Fig. 17 is a view showing the valve driving apparatus taken along a line XIV - XIV
in Fig. 15;
Fig. 18 is a front view showing the configuration of a valve driving apparatus according
to a seventh embodiment of the invention;
Fig. 19 is a view showing the valve driving apparatus taken along a line XVI - XVI
in Fig. 18;
Fig. 20 is a front view showing the configuration of a valve driving apparatus according
to an eighth embodiment of the invention;
Fig. 21 is a front view showing the configuration of the valve driving apparatus according
to the eighth embodiment of the invention;
Fig. 22 is a view showing the valve driving apparatus taken along a line III - III
in Fig. 21;
Fig. 23 is a front view showing the configuration of the valve driving apparatus according
to the eighth embodiment of the invention;
Fig. 24 is a view showing the valve driving apparatus taken along a line V - V in
Fig. 23;
Fig. 25 is a front view showing the configuration of a conventional valve driving
apparatus; and
Fig. 26 is a front view showing the configuration of a conventional valve driving
apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Now, a description will be given in more detail of preferred embodiments of the invention
with reference to the accompanying drawings.
[0034] A valve driving apparatus according to a first embodiment of the invention will be
described with reference to Figs. 1 to 3.
[0035] Referring to Fig. 1, a valve lifter 101 includes a tappet portion 103 which is in
contact with a cam 102 disposed at the upper side of a cylinder head 111 of an internal
combustion engine. A portion of the tappet portion 103 which is in contact with the
projected portion of the cam 102 is configured in a substantially-flat circular plate.
The projected portion of the cam 102 comes in linear contact with the tappet portion
103. The valve lifter 101 includes a guide portion 104 of a hollow cylindrical shape
continuous to the lower portion of the tappet portion 103. The guide portion 104 is
slidably housed within a guide hole 123 of the cylinder head 111. A diameter r of
the guide portion 104 is set to be smaller than a diameter R of the tappet portion
103.
[0036] With the above configuration, the diameter R of the tappet portion 103 is so set
as to secure the required lift amount of the valve lifter 101, that is, such a lift
amount of the valve lifter 101 as to ensure a tumble ratio of a predetermined value
or more and a desired flow rate. In addition, since the diameter of the guide portion
104 is made smaller, the valve lifter 101 is intended so as to be miniaturized and
light-weighted. In other words, it becomes possible to provide the tappet portion
103 having such the diameter R as to obtain the lift amount capable of securing the
high engine performance while reducing the occupied area of components related to
a valve in the vicinity of the cylinder head 111. Further, since the components related
to the valve can be housed in a small space, the degree of the freedom for arrangement
of other components can be improved with the advantage in space. Furthermore, since
the valve lifter 101 is miniaturized and light-weighted, the valve driving apparatus
is adaptive to the high speed of the internal combustion engine.
[0037] The tip portion of the shaft portion of a poppet valve (hereinafter merely referred
to as "valve") 105 is disposed within the guide portion 104 of the valve lifter 101
so as to abut against the lower surface of the tappet portion 103 and the valve 105
is urged upward by a not-shown spring. That is, the valve lifter 101 is disposed between
the cam 102 and the valve 105. The projected portion of the cam 102 is brought into
contact with the tappet portion 103 by the rotation of the cam 102 to push the valve
lifter 101 downward so that the valve 105 is pushed down together with the valve lifter
101 against the urging force of the spring, thereby opening the valve 105. Since the
inertia load of the valve driving system is made small due to the miniaturization
and the light-weighting of the valve lifter 101, it is not necessary to make the spring
force of the spring larger, thereby making it hard to wear away the cam 102 and the
tappet portion 103.
[0038] The internal combustion engine with the valve driving apparatus according to the
first embodiment will be described with reference to Figs. 2 and 3. As shown in Fig.
2, a cylinder block 112 of the internal combustion engine is equipped with a cylinder
113. A piston 114 is disposed within the cylinder 113 so as to be reciprocated therein.
A concave-shaped cavity 114a is defined in the top surface of the piston 114 so that
the cavity 114a produces such a reverse tumble flow that a suction air within the
cylinder 113 flows almost just above. A suction valve seat 115 and an exhaust valve
seat 116 are disposed within a combustion chamber 110 of the cylinder 113. The suction
valve seat 115 is openable and closable by a suction valve 117 (valve 105) and the
exhaust valve seat 116 is openable and closable by an exhaust valve 118 (valve 105).
[0039] The cylinder block 112 is coupled to the cylinder head 111 by means of head bolts
109. The valve lifter 101 is disposed to be slanted along the axis of the suction
valve 117 (or the exhaust valve 118) within the cylinder head 111. The guide portion
104 is slidably supported by the cylinder head 111. The suction valve 117 (or the
exhaust valve 118) is disposed within the valve lifter 101 in a state where it is
urged in a direction of closing the valve 117 (or 118) through a retainer 119 and
a spring 120. Each of the suction valve 117 and the exhaust valve 118 is provided
at the cylinder head 111 with a predetermined angle θ relative to the axial line of
the cylinder 113. The angle θ of the suction valve 117 may be identical with or different
from the angle θ of the exhaust valve 118.
[0040] The valve lifter 101 is arranged in a manner that a diameter r of the guide portion
104 (see Fig. 1) is smaller than a diameter R of the tappet portion 103 (see Fig.
1) and the valve lifter 101 is disposed in an inclined manner. Thus, the space in
a plan view can be secured arbitrarily and the degree of the freedom for the angles
θ of the suction valve 117 and the exhaust valve 118 is increased. As exemplarily
shown as for the exhaust valve 118 in Fig. 2, a shim 131 may be disposed between the
valve lifter 101 and the exhaust valve 118 (or the suction valve 117).
[0041] The cylinder head 111 is equipped with a suction port 121 communicating with the
suction valve seat 115 along the axial direction of the cylinder 113 or vertically
and also with an exhaust port 122 communicating with the exhaust valve seat 116. Since
the suction port 121 is disposed along the axial line of the cylinder or vertically
and the suction valve 117 is disposed with the given angle θ relative to the axial
line of the cylinder, a suction air from the suction port 121 can flow just downwardly
into the cylinder 113. As a result, the cavity 114a of the piston 114 can generate
such a reverse tumble flow that the suction air within the cylinder 113 flows almost
just upward. Fuel is directly injected into the combustion chamber 110, and the stratified
combustion can be performed due to the reverse tumble flow of the suction air.
[0042] As shown in Fig. 3, the tappet portions 103 of the valve lifter 101 and the head
bolts 109 are disposed in such a state that the diameter
d of the bolt bearing surface of the head bolt 109 and a virtual columnar shape obtained
by extending the tappet portion 103 with the diameter R axially of the suction valve
117 (or the exhaust valve 118), are overlapped when seen from the plane of the bolt
bearing surface. The head bolt 109 is not overlapped with the tappet portion 103 in
a state where the valve lift amount is 0 when seen along the axial line of the head
bolt 109. That is, the following relation is satisfied:
where p is a pitch of the head bolts 109 and P is a pitch of the tappet portions
103.
[0043] Since the valve lifter 101 is disposed in a slanted state with respect to the axial
line of the cylinder 113, even if the diameter
d of the bolt bearing surface of the head bolt 109 and the virtual columnar shape are
overlapped when seen from the plane of the bolt bearing surface, the head bolts 109
can be fastened without interfering with the valve lifters 101. Further, since the
diameter
d of the bolt bearing surface of the head bolt 109 and the virtual columnar shape are
overlapped when seen from the plane of the bolt bearing surface, the pitch
p of the head bolts 109 can be made smaller so as to realize a sufficient amount of
the valve lift (large lift amount) capable of securing the high engine performance
even if a displacement amount of the internal combustion engine is small.
[0044] In the above-described first embodiment, the description has been given of the case
where the invention is applied to the internal combustion engine of the type that
the valve lifters 101 are inclined with respect to the axial line of the cylinder
113 (that is, toward the direction perpendicular to the axis line of the rotation
center of the cam with respect to the vertical direction) and fuel is directly injected
into the combustion chamber 110. However, the invention is not limited to the structure
of the first embodiment but may be applied to other types of the internal combustion
engine. More specifically, the invention may be applied to the internal combustion
engine of the type that the valve lifters 101 are disposed vertically, that is, in
parallel to the axial line of the cylinder 113 or air-fuel mixture is introduced into
the combustion chamber 110 so long as the tappet portion of the valve lifter 101 is
pushed down by the cam 102. Also, the relation between the pitch P of the valve lifters
101 and the pitch p of the head bolts 109 is not limited to the above-described example,
but other relation may be employed so that the diameter
d of the bolt bearing surface of the head bolt 109 and the virtual columnar shape are
not overlapped when seen from the plane of the bolt bearing surface.
[0045] The valve lifter 101 is disposed between the cam 102 formed at the cam shaft and
the suction valve 117 (or the exhaust valve 118) which is provided at the suction
port 121 (or the exhaust port 122) formed in the cylinder head 111 of the internal
combustion engine and moved along the shaft of the valve 117 (or 118) to open and
close the suction port 121 (or the exhaust port 122). The valve driving apparatus
using the valve lifter 101 is equipped with the guide hole 123 defined in the cylinder
head 111, and the direct driving type valve lifter which includes the tappet portion
103 which is in contact with the cam 102 and pushed down by the cam 102, and the guide
portion 104 which is coupled at its end to the tappet portion 103 and housed within
the guide hole 123 so as to be slid therein along the axial line of the suction valve
117 (or the exhaust valve 118) in an interlocked manner as the pushed-down operation
of the tappet portion 103 by the cam 102. Further, the diameter r of the guide portion
104 is made smaller than the diameter R of the tappet portion 103. With the above
configuration, the diameter of the tappet portion 103 is set to such a value as to
secure a lift amount of the valve lifter 101 necessary for obtaining a tumble ratio
of the predetermined value or more and a desired flow rate. Further, since the diameter
of the guide portion 104 is made small, the valve lifter 101 can be miniaturized and
light-weighted.
[0046] Accordingly, it is possible to secure the high performance of the engine while reducing
the occupied area of components related to the valve in the vicinity of the cylinder
head 111. Also, since the components related to the valve can be housed in a small
space, the degree of the freedom for the arrangement of other components can be improved.
Furthermore, since the valve lifter 101 is miniaturized and light-weighted, the valve
driving apparatus can be adapted to the high speed of the internal combustion engine.
[0047] Since the valve lifter 101 is inclined with respect to the axial line of the cylinder
113, even if the pitch p between the bearing surfaces of the head bolts 109 is made
shorter than the width (P + D) of the tappet portions 103, the head bolts 109 can
be fastened without interfering with the tappet portions 103. Further, since the suction
valve 117 is disposed with the angle θ relative to the axial line of the cylinder
113, the invention is applicable to an internal combustion engine that has a suction
port of the vertical type which generates the reverse tumble flow at the almost just
above portion within the combustion chamber 110 and directly injects fuel within the
combustion chamber 110. It is needless to say that in the internal combustion engine
not requiring a large lift amount of the valve lifter, the lifter can be further miniaturized
and light-weighted without changing the lift amount.
[0048] A valve driving apparatus according to a second embodiment of the invention will
be described with reference to Figs. 4 and 5.
[0049] Fig. 4 shows a state where a valve lifter is not pushed down, and Fig. 5 shows a
state where the valve lifter is pushed down.
[0050] Referring to these figures, a cam 212 is disposed at the upper side of a cylinder
head 211 of an internal combustion engine and the cylinder head 211 is defined with
a guide hole 213. A cylindrical guide portion 215 of a valve lifter 214 is slidably
housed along and within the guide hole 213. A tappet portion 216 is provided at the
upper portion of the guide portion 215. The tappet portion 216 is protruded toward
the outer diameter direction of the guide portion 215 from the circumferential portion
thereof to form a projected portion 230. The tappet portion 216 is continuous to the
upper portion of the guide portion 215 to form an umbrella shape. The tappet portion
216 is configured in a substantially flat circular shape at a portion which is in
contact with the projected portion of the cam 212. The cam 212 comes in linear contact
with the tappet portion 216. The entirety of the outer peripheral portion of the tappet
portion 216 may not be protruded from the guide portion 215, but only a part of the
outer peripheral portion of the tappet portion 216 may be protruded from the guide
portion 215 by changing the diameter thereof.
[0051] The shaft portion of a valve 217 (a suction valve or an exhaust valve) is disposed
within the guide portion 215 of the valve lifter 214 in such a manner that the tip
portion of the shaft portion abuts against the lower surface of the tappet portion
216. The valve 217 is urged upward by a not-shown spring. That is, the valve lifter
214 is disposed between the cam 212 and the valve 217. The projected portion of the
cam 212 is brought into contact with the tappet portion 216 by the rotation of the
cam 212 to push the valve lifter 214 downward, so that the valve 217 is pushed down
together with the valve lifter 214 against the urging force of the spring, thus opening
the valve 217.
[0052] An oil reservoir 218 serving as an oil reservoir portion in which lubricant oil 219
is reserved is formed at the periphery of the upper portion (the tappet portion 216
side) of the guide hole 213. The tappet portion 216 is disposed within the oil reservoir
218 so as to form a slight clearance between the outer periphery of the tappet portion
216 and the inner wall of the oil reservoir 218. That is, it is arranged that the
tappet portion 216 moves within the oil reservoir 218 when the valve lifter 214 is
lifted. As shown in Fig. 4, the depth d of the oil reservoir 218 is set so as to satisfy
the following expression:
, where D is a length from the upper surface of the tappet portion 216 and the bottom
surface of the oil reservoir 218 when the liter 214 is not pushed down.
[0053] Like the valve driving apparatus of the third embodiment shown in Fig. 6, the valve
driving apparatus is arranged in a manner that, when a valve 317 is inclined with
respect to the axial line of the cylinder (that is, toward the direction perpendicular
to the axis line of the rotation center of the cam with respect to the vertical direction),
at least a portion of the rear surface of a tappet portion 316 is positioned below
the oil surface when a valve lifter 314 is lifted.
[0054] According to the valve driving apparatus arranged in the aforesaid manner, the load
is applied from the cam on the right side surface of the tappet portion 216 (316)
in Fig. 5 (Fig. 6) until the lift amount of the valve lifter reaches the maximum value
after the start of the lifting operation of the valve lifter 214 (314). Thus, the
moment acting on the valve lifter 214 (314) is generated to the same direction as
the rotation direction of the cam 212 (312). As a result, the valve lifter 214 (314)
inclines toward the right side in Fig. 5 (Fig. 6) and hence the clearance between
the guide portion 215 (315) and the guide hole 213 (313) on the left side becomes
larger at the upper portion thereof. When the clearance at the upper portion becomes
larger in this manner, the lubricant oil 219 (319) within the oil reservoir 218 (318)
is pushed down (to the direction shown by an arrow A in Fig. 5 (Fig. 6)) by the rear
surface of the tappet portion 216 (316) just above the clearance, whereby the lubricant
oil 219 (319) is filled within the clearance.
[0055] Simultaneously, the lubricant oil 219 (319) is pushed out of the clearance between
the outer peripheral portion of the tappet portion 216 (316) and the oil reservoir
218 (318) (to the direction shown by an arrow B in Fig. 5 (Fig. 6)), and the lubricant
oil 219 (319) is introduced to the cam 212 (312) side. The lubricant oil 219 (319)
within the oil reservoir 218 (318) is stirred by the tappet portion 216 (316) of an
umbrella shape and the sludge etc. is ejected by the lifting operation of the valve
lifter 214 (314).
[0056] After the valve lifter reaches the uppermost position to attain the maximum lift
amount of the valve lifter, moment acts on the valve lifter 214 (314) to the direction
opposite to that having been acted thereon, so that the valve lifter 214 (314) inclines
toward the left side in Fig. 5 (Fig. 6). In this case, although the clearance between
the guide portion 215 (315) and the guide hole 213 (313) on the left side becomes
smaller at the upper portion thereof, since the lubricant oil 219 (319) filled in
the clearance performs the squeeze effect, the valve lifter 214 (314) does not change
its posture rapidly.
[0057] In the aforesaid valve driving apparatus, at the time of lifting the valve lifter
214 (314), the lubricant oil 219 (319) within the oil reservoir 218 (318) is pushed
by the rear surface of the tappet portion 216 (316) into the clearance between the
guide portion 215 (315) and the guide hole 213 (313). In this manner, the lubricant
oil 219 (319) is supplied to the clearance between the guide portion 215 (315) and
the guide hole 213 (313) irrespective of the viscosity of the lubricant oil 219 (319).
Further, since the lubricant oil 219 (319) is pushed out of the clearance between
the outer peripheral portion of the tappet portion 216 (316) and the oil reservoir
218 (318) and the lubricant oil 219 (319) is introduced to the cam 212 (312) side,
the lubricant oil 219 (319) is supplied to the contact surface between the cam 212
(312) and the tappet portion 216 (316).
[0058] As a result, since the friction at the clearance and the contact surface becomes
smaller, the noise caused by the striking operation when the valve lifter 214 (314)
changes its posture can be reduced and also the degree of the abrasion caused by the
striking operation can be reduced. Thus, the output efficiency and the fuel cost of
the engine are improved, and further the durability and the reliability of the engine
are also improved.
[0059] A valve driving apparatus according to a fourth embodiment of the invention will
be explained with reference to Figs. 7 to 11.
[0060] Figs. 7 and 8 show a state where a valve lifter is not pushed down and Figs. 9 and
10 show a state where the valve lifter is pushed down. Fig. 11 is a diagram showing
a part of the valve driving apparatus cut away along a line VIII - VIII in Figs. 7
and 9.
[0061] As shown in these figures, a tappet portion 416 is protruded toward the outer diameter
direction of a guide portion 415 from the circumferential portion thereof to form
a projected portion (430). An oil reservoir 421 serving as an oil reservoir portion
in which lubricant oil 419 is reserved is formed at the periphery of the upper portion
of a guide hole 413. As shown in Figs. 7, 9 and 11, the oil reservoir 421 is provided
with notched portions 422 which are formed by partially removing the opposite portions
of the inner peripheral wall of the oil reservoir in a convex shape to the direction
(left and right direction in the figure) perpendicular to the axis line of the rotation
center of the cam 412. As shown in Figs. 8 and 10, the portions of the oil reservoir
421 (that is, the portions mainly along the axis line of the rotation center of the
cam 412) except for the notched portions 422 are opposed to the tappet portion 416
through a small clearance therebetween.
[0062] According to the valve driving apparatus arranged in this manner, when the valve
lifter 414 is lifted, the lubricant oil 419 within the oil reservoir 421 is pushed
into the clearance between the guide portion 415 and the guide hole 413 by the rear
surface of the tappet portion 416, so that the lubricant oil 419 is supplied to the
clearance between the guide portion 415 and the guide hole 413. Further, the lubricant
oil 419 is pushed out from the clearance between the outer peripheral portion of the
tappet portion 416 and the oil reservoir 421 mainly along the axis line of the rotation
center of the cam 412 and introduced on the cam 412 side. The lubricant oil 419 within
the oil reservoir 421 is stirred by the tappet portion 416 of an umbrella shape and
the sludge etc. is ejected by the lifting operation of the valve lifter 214. When
the valve lifter 414 is lifted, the lubricant oil 419 is pushed out on the upper surface
of the tappet portion 416 from the notched portions 422, and so much lubricant oil
419 is introduced on the contact surface between the cam 412 and the tappet portion
416, whereby the contact portion between the cam 412 and the tappet portion 416 is
sufficiently lubricated.
[0063] As a result, since the friction at the clearance and the contact surface becomes
smaller, the noise caused by the striking operation when the valve lifter 414 changes
its posture can be reduced and also the degree of the abrasion caused by the striking
operation can be reduced. Thus, the output efficiency and the fuel cost of the engine
are improved, and further the durability and the reliability of the engine are also
improved.
[0064] A valve driving apparatus according to a fifth embodiment of the invention will be
described with reference to Figs. 12 to 14.
[0065] Fig. 12 shows a state where a valve lifter is not pushed down and Fig. 13 shows a
state where the valve lifter is pushed down. Fig. 14 is a diagram showing a part of
the valve driving apparatus cut away along a line XI - XI in Fig. 12.
[0066] As shown in these figures, a valve 517 is disposed so as to be inclined with respect
to the axial line of the cylinder (that is, toward the direction perpendicular to
the axis line of the rotation center of the cam with respect to the vertical direction).
A tappet portion 516 is protruded toward the outer diameter direction of a guide portion
515 from the circumferential portion thereof to form a projected portion (530). An
oil reservoir 526 serving as an oil reservoir portion in which lubricant oil 519 is
reserved is formed at the periphery of the upper portion of a guide hole 513. The
oil reservoir 526 is provided with a notched portion 527 which is formed by partially
removing a portion of the inner peripheral wall of the oil reservoir in a convex shape
on the slanted inner side (left side in the figure) to the direction perpendicular
to the axis line of the rotation center of a cam 512. The portion of the oil reservoir
526 except for the notched portion 527 is opposed to the tappet portion 516 through
a small clearance therebetween.
[0067] According to the valve driving apparatus arranged in this manner, when a valve lifter
514 is lifted, the lubricant oil 519 is pushed out on the upper surface of the tappet
portion 516 from the notched portion 527, and the lubricant oil 519 is introduced
on the contact surface between the cam 512 and the tappet portion 516. Further, particularly,
when the engine rotates in a high speed range, the lubricant oil 519 within the notched
portion 527 is pressed at a high pressure by the tappet portion 516, so that the lubricant
oil 519 is splashed toward the wall surface etc. of a cylinder head 511. Then, the
lubricant oil 519 thus splashed is bounced off the wall surface etc. and introduced
to the projected portion of the cam 512 whose diameter of the base circular portion
is smaller than the diameter of the tappet portion 516. Thus, the contact portion
between the cam 512 and the tappet portion 516 is sufficiently lubricated.
[0068] As a result, since the high friction and the high degree of the abrasion can be prevented
at the contact surface, the output efficiency and the fuel cost of the engine are
improved and further the durability and the reliability of the engine are also improved.
[0069] The sixth embodiment of the invention will be explained with reference to Figs. 15
to 17. Figs. 15 and 16 are front views showing the schematic arrangement of the valve
driving apparatus according to the sixth embodiment, wherein Fig. 15 shows a state
where a valve lifter is not pushed down and Fig. 16 shows a state where the valve
lifter is pushed down. Fig. 17 is a diagram showing a part of the valve driving apparatus
cut away along a line XIV - XIV in Fig. 15.
[0070] As shown in Figs. 15 and 16, a cam 631 is disposed at the upper side of the cylinder
head 611 of the engine. The diameter r of a tappet portion 616 is made smaller than
a diameter R of the base circular portion of the cam 631. The tappet portion 616 is
protruded toward the outer diameter direction of a guide portion 615 from the circumferential
portion thereof to form a projected portion (630). An oil reservoir 632 serving as
an oil reservoir portion in which lubricant oil 619 is reserved is formed at the periphery
of the upper portion of a guide hole 613. As shown in Fig. 17, the oil reservoir 632
is provided with diameter enlarged portions 633 which are formed by partially removing
the opposite portions of the inner peripheral wall of the oil reservoir in an elliptical
shape in a manner that the major axis portion thereof is directed to the direction
perpendicular to the axis line of the rotation center of a cam 631(left and right
direction in the figure). Each of the portions of the oil reservoir 632 except for
the diameter enlarged portions 633 is opposed to the tappet portion 616 through a
small clearance therebetween.
[0071] According to the valve driving apparatus arranged in this manner, when a valve lifter
614 is lifted, the lubricant oil 619 is pushed out on the upper surface of the tappet
portion 616 from the diameter enlarged portions 633, and the lubricant oil 619 is
introduced on the contact surface between the cam 631 and the tappet portion 616.
Further, particularly, when the engine rotates in a high speed range, the lubricant
oil 619 within the diameter enlarged portions 633 is pressed by the tappet portion
616 and so splashed. In this case, since the diameter r of the tappet portion 616
is made smaller than the diameter R of the base circular portion of the cam 631, the
lubricant oil 619 thus splashed is directly introduced to the projected portion of
the cam 631. Thus, the contact portion between the cam 631 and the tappet portion
616 is sufficiently lubricated.
[0072] As a result, since the high friction and the high degree of the abrasion can be prevented
at the contact surface, the output efficiency and the fuel cost of the engine are
improved and further the durability and the reliability of the engine are also improved.
[0073] A valve driving apparatus according to a seventh embodiment of the invention will
be described with reference to Figs. 18 and 19.
[0074] As shown in these figures, a valve 717 is disposed so as to be inclined with respect
to the axial line of the cylinder (that is, toward the direction perpendicular to
the axis line of the rotation center of the cam with respect to the vertical direction).
A tappet portion 716 is protruded toward the outer diameter direction of a guide portion
715 from the circumferential portion thereof to form a projected portion (730). An
oil reservoir 736 serving as an oil reservoir portion in which lubricant oil 719 is
reserved is formed at the periphery of the upper portion of a guide hole 713. The
oil reservoir 736 is provided with a diameter enlarged portion 737 which is formed
by partially removing a portion of the inner peripheral wall of the oil reservoir
in a semi-elliptical shape in a manner that the major axis portion thereof is positioned
on the slanted inner side (left side in the figure) to the direction perpendicular
to the axis line of the rotation center of a cam 731. The portion of the oil reservoir
736 except for the diameter enlarged portion 737 is opposed to the tappet portion
716 through a small clearance therebetween.
[0075] According to the valve driving apparatus arranged in this manner, when a valve lifter
714 is lifted, the lubricant oil 719 is pushed out on the upper surface of the tappet
portion 716 from the diameter enlarged portion 737, and the lubricant oil 719 is introduced
on the contact surface between the cam 731 and the tappet portion 716. Further, particularly,
when the engine rotates in a high speed range, the lubricant oil 719 within the diameter
enlarged portion 737 is pressed by the tappet portion 716 and so splashed. In this
case, since the diameter r of the tappet portion 716 is made smaller than the diameter
R of the base circular portion of the cam 731, the lubricant oil 719 thus splashed
is directly introduced to the projected portion of the cam 731. Thus, the contact
portion between the cam 731 and the tappet portion 716 is sufficiently lubricated.
[0076] As a result, since the high friction and the high degree of the abrasion can be prevented
at the contact surface, the output efficiency and the fuel cost of the engine are
improved and further the durability and the reliability of the engine are also improved.
[0077] A valve driving apparatus according to an eighth embodiment of the invention will
be described with reference to Figs. 20 to 24.
[0078] As shown in these figures, a cylindrical guide portion 812 of a valve lifter 811
is housed within a guide hole 806 of a cylinder head 802 so as to slide freely therealong.
A disc-shaped tappet portion 813 is integrally provided at the upper portion of the
guide portion 812. The diameter R of the tappet portion 813 is larger than the diameter
r of the guide portion 812. The tappet portion 813 is configured so as to continue
to the upper portion of the guide portion 812 to form an umbrella shape.
[0079] The tappet portion 813 is configured in a substantially flat circular shape at a
portion which contacts with the projected portion of a cam 803. The projected portion
of the cam 803 is made line contact with the tappet portion 813. The valve driving
apparatus is set in a manner that when the valve 807 is pushed down at the maximum,
that is, when the lift amount of the valve lifter 811 reaches the maximum value, only
the guide portion 812 is housed within the guide hole 806 (the tappet portion 816
is not housed within the guide hole 806).
[0080] A peripheral groove 814 serving as an elastic deformation promotion portion r is
formed at the outer periphery of the guide portion 812 at the root portion of the
tappet portion 813 so that the elastic deformation of the guide portion 812 is promoted
by the peripheral groove 814 when the guide portion 812 is housed within the guide
hole 806.
[0081] According to the valve lifter 811 thus configured, as shown in Figs. 21 and 22, the
load is applied from the cam on the right side surface of the tappet portion 813 in
Fig. 21 until the lift amount of the valve lifter 811 reaches the maximum value after
the start of the lifting operation of the valve lifter 811. Thus, the moment acting
on the valve lifter 811 is generated to the same direction as the rotation direction
of the cam 803. As a result, the valve lifter 811 inclines toward the right side in
the figure (that is, toward the direction perpendicular to the axis line of the rotation
center of the cam with respect to the vertical direction) and hence the clearance
between the guide portion 812 and the guide hole 806 on the right side becomes smaller
at the upper portion thereof.
[0082] When the valve lifter 811 changes its posture by the moment acting thereon to the
same direction as the rotation direction of the cam 803, the guide portion 812 is
elastically deformed due to the peripheral groove 814 provided at the outer periphery
of the guide portion 812 so that the outer periphery of the guide portion 812 is fitted
to the inner periphery the guide hole 806. Thus, since the lubricant oil between the
guide portion 812 and the guide hole 806 is prevented from being pushed aside and
the oil film is maintained therebetween, the noise caused by the striking operation
when the valve lifter changes its posture can be suppressed and also the abrasion
caused by the striking operation can be suppressed, whereby the friction can be reduced.
[0083] As shown in Figs. 23 and 24, since the load is applied from the cam on the left side
surface of the tappet portion 813 in Fig. 23 after the lift amount of the valve lifter
reaches the maximum value, the moment acting on the valve lifter 811 is generated
to the direction opposite to the rotation direction of the cam 803. As a result, the
valve lifter 811 inclines to the left side in the figure and so the clearance between
the guide portion 812 and the guide hole 806 on the left side becomes smaller at the
upper portion thereof.
[0084] When the valve lifter 811 changes its posture by the moment acting thereon to the
direction opposite to the rotation direction of the cam 803, the guide portion 812
is elastically deformed to the direction opposite to that of the case of Fig. 21 due
to the peripheral groove 814 provided at the outer periphery of the guide portion
812 so that the outer periphery of the guide portion 812 is fitted to the inner periphery
the guide hole 806. Thus, since the lubricant oil between the guide portion 812 and
the guide hole 806 is prevented from being pushed aside and the oil film is maintained
therebetween, the noise caused by the striking operation when the valve lifter changes
its posture can be suppressed and also the abrasion caused by the striking operation
can be suppressed, whereby the friction can be reduced.
[0085] Further, since the peripheral groove 814 provides a recess portion required at the
time of performing the grinding process of the rear surface of the tappet portion
813 and the outer peripheral surface of the guide hole 812, the valve lifter 811 can
be processed easier.
1. A valve driving apparatus using a direct driving type valve lifter which is disposed
between a cam (102, 212, 312, 412, 512, 631, 731, 803) formed at a cam shaft and a
poppet valve (105, 117, 118, 217, 317, 417, 517, 617, 717, 807) which is provided
in a path (121, 122) formed at a cylinder head (112, 211, 311, 411, 511, 611, 711,
802) of an internal combustion engine and moves in an axial direction of said valve
to open and close said path, said apparatus comprising:
a guide hole (123, 213, 313, 413, 513, 613, 713, 806) formed at said cylinder head;
and
a direct driving type valve lifter (101, 214, 314, 414, 514, 614, 714, 811) including
a tappet portion (103, 216, 316, 416, 516, 616, 716, 813) which is brought in contact
with said cam and pressed by said cam, and a guide portion (104, 215, 315, 415, 515,
615, 715, 812) having one end portion coupled to said tappet portion and housed within
said guide hole so as to slide freely therein to the axial direction of said poppet
valve in an interlocked manner as a pushing operation of said tappet portion by said
cam, wherein a diameter (r) of said guide portion is formed to be smaller than a diameter
(R) of said tappet portion.
2. A valve driving apparatus according to claim 1, wherein said path at least includes
a suction path (121) of said internal combustion engine.
3. A valve driving apparatus according to claim 2, wherein said cam shaft is disposed
on an upper side of said cylinder head, and said suction path is opened at its one
end to a combustion chamber of said internal combustion engine and opened at its the
other end to an upper surface of said cylinder head.
4. A valve driving apparatus according to claim 2, wherein at least two of said poppet
valve provided in said suction path are provided in each of the cylinders of said
internal combustion engine.
5. A valve driving apparatus according to claim 1, wherein
said guide hole is provided at an opening edge thereof with an oil reservoir (218,
318, 421, 526, 632, 736) for reserving lubricant oil therein,
the diameter of said tappet portion is at least partially larger than the diameter
of said guide portion and said tappet portion has a projected portion (230, 330, 430,
530, 630, 730) protruding from outer peripheral surface of said guide portion toward
outer diameter direction of said guide portion, and
said projected portion moves within said oil reservoir when said valve lifter is lifted.
6. A valve driving apparatus according to claim 5, wherein a clearance is provided between
said outer peripheral surface of said oil reservoir and an edge portion of said tappet
portion so that the lubricant oil can be splashed out of said clearance.
7. A valve driving apparatus according to claim 6, wherein said clearance is arranged
in a manner that a width thereof toward a direction perpendicular to an axis line
of a rotation center of said cam and a width in vicinity thereof is larger than a
width at a remaining potion thereof.
8. A valve driving apparatus according to claim 6, wherein said clearance is provided
only at a portion toward a direction perpendicular to an axis line of a rotation center
of said cam and in vicinity thereof.
9. A valve driving apparatus according to claim 8, wherein said valve lifter is disposed
so as to be inclined toward the direction perpendicular to the axis line of the rotation
center of said cam with respect to a vertical direction, and said clearance is provided
only at a portion toward a downward direction among two directions perpendicular to
the axis line of the rotation center of said cam and in vicinity thereof.
10. A valve driving apparatus according to claim 5, wherein the diameter of said tappet
portion is smaller than a diameter of a base circular portion of said cam.
11. A valve driving apparatus according to claim 1, further comprising an elastic deformation
promotion portion (814) for promoting elastic deformation of said guide portion when
said guide portion is housed within said guide hole.
12. A valve driving apparatus according to claim 11, wherein said elastic deformation
promotion portion is provided at said guide portion in vicinity of a boundary between
said tappet portion and said guide portion.
13. A valve driving apparatus according to claim 12, wherein said elastic deformation
promotion portion is a groove provided at a peripheral portion of said guide portion.