BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This invention relates to an oil supply mechanism for an internal combustion engine,
in particular, an oil supply mechanism for an internal combustion engine having an
oil removing (dropping) hole that supplies oil from a valve chamber in a cylinder
head to a timing chain.
2. Description of the Related Art
[0002] Generally, a cylinder head is fixed to an upper portion of a cylinder block of an
internal combustion engine. In the cylinder head, a valve chamber that accommodates
an intake camshaft and an exhaust camshaft is provided. Oil stored in an oil pan is
supplied to the valve chamber via an oil pump or an oil supply passage to lubricate
the intake camshaft and the exhaust camshaft.
[0003] Further, a belt chain is provided at the side of the cylinder block and cylinder
head. The belt chain is wound around a sprocket provided at an end portion of a crankshaft,
a sprocket provided at an end portion of the intake camshaft and a sprocket provided
at an end portion of the exhaust camshaft. Therefore, the rotation of the crankshaft
is transmitted to the intake camshaft and the exhaust camshaft.
[0004] Further, oil that lubricates the intake camshaft and the exhaust camshaft falls into
the valve chamber, and then is supplied to the timing chain through an oil removing
hole provided in a sidewall of the cylinder head. Then, after the oil lubricates the
timing chain, the oil flows back to the oil pan provided below the cylinder block
(see, for example, Japanese patent application publication
2000-97103 (
JP-A-2000-97103)).
[0005] In the above-described oil supply mechanism for an internal combustion engine, however,
because an opening area of the oil removing hole is large, the oil supplied to the
timing chain through the oil removing hole causes a large friction with the timing
chain. Therefore, drive loss of the timing chain may occur.
[0006] More specifically, if the opening area of the oil removing hole is reduced, the amount
of oil supplied from the valve chamber to the timing chain through the oil removing
oil hole is also reduced. However, a sufficient amount of oil to flow back to the
oil pan through the oil removing hole must be secured in all operation regions, i.e.,
from a low engine speed to a high engine speed.
[0007] In particular, because the oil pump rotates in proportion to the rotation speed of
the crankshaft, the amount of oil supplied to the valve chamber increases in an engine
high speed operation region. Therefore, efficient oil return must be secured when
an excessive amount of oil is supplied.
[0008] If the opening area of the oil removing hole is reduced, generation of timing chain
drive loss is minimized by reducing the amount of oil to be retuned to the oil pan.
However, in reality, it is difficult to reduce the opening area of the oil removing
hole, because efficient oil return must be secured when the oil is excessively supplied.
[0009] Thus, with relatively large opening area of the oil removing hole, because the amount
of oil that is supplied to the valve chamber and returns to the oil pan increases
during the period of the engine low speed operation region and engine middle speed
operation region, the oil causes a large friction with the timing chain and timing
chain drive loss is generated. The generation of timing chain drive loss may deteriorate
fuel efficiency.
SUMMARY OF THE INVENTION
[0010] The present invention provides an oil supply mechanism for an internal combustion
engine that prevents increase in timing chain drive loss caused by the oil supplied
to the timing chain, and secures sufficient oil return.
[0011] A first aspect of the present invention provides an oil supply mechanism for an internal
combustion engine that includes a cylinder head that is fixed to an upper portion
of a cylinder block and has a valve chamber therein. A sidewall of the cylinder head
has an oil removing hole through which oil is supplied from the valve chamber to a
timing chain provided on the side of the cylinder head. The oil removing hole communicates
with the valve chamber and the shape of the oil removing hole changes along the vertical
direction.
[0012] According to the aspect of the present invention, when the volume of oil supplied
to the valve chamber is relatively small, i.e., for example, when the internal combustion
engine is in a low or middle speed operation region, oil is supplied to the timing
chain only through the lower portion of the oil removing hole, rather than through
the entire oil removing hole. Accordingly, oil is prevented from being supplied to
the timing chain more than necessary, and the drive loss of the timing chain is prevented
from being increased. As a result, decrease in the fuel efficiency can be prevented.
[0013] Further, when a large volume of oil is supplied to the valve chamber, i.e., for example,
when the internal combustion engine is in a high speed operation region, oil can return
to an oil pan from the entire oil removing hole. Therefore, a large volume of oil
can be returned from the oil removing hole to the oil pan while the timing chain is
lubricated. Thus, efficient oil return can be secured.
[0014] Thus, the valve chamber is prevented from being filled with the oil excessively supplied
to the valve chamber. Therefore, the oil level is prevented from exceeding the opening
end of the PCV passage, which communicates between the cylinder head and the intake
passage, on the side of the cylinder head, and thus oil is prevented from flowing
into the PCV passage 43.
[0015] The oil removing hole may include more than one opening portions that are formed
at different positions in the vertical direction.
[0016] According to this construction, when the internal combustion engine is in the low
or middle operation region and the volume of oil supplied to the valve chamber is
relatively low, oil is supplied to the timing chain through the opening portion located
at the lower position, rather than through the entire oil removing hole. Therefore,
oil is prevented from being supplied to the timing chain more than necessary, and
the drive loss of the timing chain is prevented from being increased.
[0017] Furthermore, when the engine is in a high speed operation region and a large volume
of oil is supplied to the valve chamber, oil can be returned to the oil pan from the
entire opening portion. Thus, a large volume of oil can return to the oil pan through
the oil removing hole while the timing chain is lubricated. Thus, efficient oil return
can be secured.
[0018] An upper-most opening portion among the opening portions may be positioned directly
above the timing chain.
[0019] According to this construction, when the engine is in a high speed operation region
and a large volume of oil must be supplied to the timing chain to lubricate the timing
chain, oil is supplied from the opening portion located at higher position as well
as the opening portion located at lower position. At this time, because the upper
opening located directly above the timing chain, oil is effectively supplied to the
timing chain to lubricate the timing chain.
[0020] The oil removing hole may be a single opening portion in which an opening area of
a lower portion is smaller than an opening area of an upper portion.
[0021] According to this construction, when the internal combustion engine is in a low or
middle speed operation region and the volume of oil supplied to the valve chamber
is relatively small, oil is supplied to the timing chain from the lower portion of
the single opening portion, rather than the entire oil removing hole. Therefore, oil
is prevented from being supplied to the timing chain more than necessary, and the
drive loss of the timing chain is prevented from being increased.
[0022] Furthermore, when the engine is in a high speed operation region and a large volume
of oil is supplied to the valve chamber, oil can return to the oil pan through the
entire opening portion. Thus, a large volume of oil can be retuned to the oil pan
through the oil removing hole while the timing chain is lubricated. Thus, efficient
oil return can be secured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The foregoing and further objects, features and advantages of the invention will
become apparent from the following description of example embodiments with reference
to the accompanying drawings, wherein like numerals are used to represent like elements
and wherein:
FIG.1 is an exploded view of an internal combustion engine illustrating an oil supply
mechanism for the internal combustion engine according to a first embodiment of the
present invention;
FIG.2 is a cross-sectional view of the internal combustion engine in the vicinity
of a timing chain to illustrate the oil supply mechanism for the internal combustion
engine according to the first embodiment of the present invention;
FIG.3 is an exploded view of a cylinder head gasket, a cylinder head, a cam housing,
a cylinder head cover gasket and a cylinder head cover to illustrate the oil supply
mechanism for the internal combustion engine according to the first embodiment of
the present invention;
FIG 4 is a view illustrating paths through which lubricating oil flows in the oil
supply mechanism for the internal combustion engine according to the first embodiment
of the present invention;
FIG 5 is an elevation view of the timing chain and the cylinder head viewed from a
front side of the internal combustion engine to illustrate the oil supply mechanism
for the internal combustion engine according to the first embodiment of the present
invention; and
FIG 6 is an elevation view of a timing chain and a cylinder head viewed from a front
side of the internal combustion engine to illustrate an oil supply mechanism for the
internal combustion engine according to a second embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0024] An oil supply mechanism for an internal combustion engine according to embodiments
of the present invention will be described hereinafter with reference to drawings.
[0025] FIGs. 1 to 5 show an oil supply mechanism for an internal combustion engine according
to a first embodiment of the present invention. A construction thereof will be explained
first. In FIGs. 1 and 2, an engine 1, served as an internal combustion engine, includes
an cylinder block 2, a cylinder head 3 that is fixed to an upper portion of the cylinder
block 2, a crank case 4 that is fixed to a lower portion of the cylinder block 2,
and an oil pan 5 that is fixed to a lower portion of the crank case 4.
[0026] A cam housing 6 is fixed to an upper portion of the cylinder head 3. As shown in
FIG 4, an intake camshaft 7 having an intake cam 7a and an exhaust camshaft 8 having
an exhaust cam 8a are rotatably supported by the cam housing 6.
[0027] As shown in FIG. 3, a valve chamber 9 is provided in the cylinder head 3. As described
later, oil that has been lubricated the intake camshaft 7 and the exhaust camshaft
8 falls in the valve chamber 9. The bottom surface 9a of the valve chamber 9 in the
cylinder head 3 extends substantially horizontally.
[0028] As shown in FIG 3, a cylinder head cover 11 is fixed to the cam housing 6 via a cylinder
head cover gasket 10, and the cylinder head 3 is fixed to the cylinder block 2 via
the cylinder head gasket 12.
[0029] A shower pipe 13 (see FIG. 4) is provided in the cam housing 6 and the cylinder head
cover 11. The shower pipe 13 delivers oil by drops onto the intake camshaft 7 and
the exhaust camshaft 8.
[0030] Cylinder bores (not shown) are formed in the cylinder block 2. A piston 14 (see FIG
4) is slidably provided in each of the cylinder bore. Intake ports that communicate
with an intake passage (not shown) and exhaust ports that communicate with an exhaust
passage (not shown) are provided in the cylinder head 3. The cylinder head 3 has an
intake valve 15 that opens and closes each intake port to communicate and discommunicate
between the intake pipe and the cylinder bore, and an exhaust valve 16 that opens
and closes the exhaust port to communicate and discommunicate between the exhaust
pipe and the cylinder bore (see FIG. 4).
[0031] A rocker arm 32 is disposed between the intake valve 15 and the intake camshaft 7.
The rocker arm 32 swings along with the rotation of the intake camshaft 7 to open
and close the intake valve 15.
[0032] A rocker arm (not shown) is disposed between the exhaust valve 16 and the exhaust
camshaft 8. The rocker arm swings along with the rotation of the exhaust camshaft
8 to open and close the exhaust valve 16.
[0033] A crankshaft 17 is disposed in the crank case 4. A camshaft drive mechanism 18 is
disposed between the crankshaft 17 and the intake camshaft 7 and exhaust camshaft
8. The rotation of the crankshaft 17 is transmitted to the intake camshaft 7 and the
exhaust camshaft 8 via the camshaft drive mechanism 18, thereby driving the rotation
of the intake camshaft 7 and the exhaust camshaft 8.
[0034] The camshaft drive mechanism 18 includes a crank sprocket 19, an intake cam sprocket
20, an exhaust cam sprocket 21 and a timing chain 22. The crank sprocket 19 is connected
to an axial end of the crankshaft 17. The intake cam sprocket 20 is connected to an
axial end of the intake camshaft 7 in the cylinder head 3. The exhaust cam sprocket
21 is connected to an axial end of the exhaust camshaft 8 in the cylinder block 3.
The timing chain 22 is wound around the crank sprocket 19, the intake cam sprocket
20 and the exhaust cam sprocket 21, and transmits the rotation of the crank sprocket
19 to the intake cam sprocket 20 and the exhaust cam sprocket 21 to rotate them.
[0035] The timing chain 22 is disposed at the front surface (side surface) of the cylinder
block 2, crank case 4 and cylinder head 3. Note that in this embodiment, the side
at which the camshaft drive mechanism 18 is disposed is the front side of the vehicle.
[0036] In the camshaft drive mechanism 18, there is a large vertical distance between the
crank sprocket 19 and the intake cam sprocket 20 and exhaust cam sprocket 21, because
the intake camshaft 7 and the exhaust camshaft 8 are disposed in the cylinder head
3 located above the cylinder block 2, and the crankshaft 17 is disposed in the crank
case 4 located below the cylinder block 2.
[0037] An oil pump mechanism 24 that drives the rotation of the oil pump 23 using the crankshaft
17 is provided below the camshaft drive mechanism 18. The oil pump drive mechanism
24 includes a crank sprocket 25, an oil pump sprocket 26 and an oil pump drive chain
27. The crank sprocket 25 is connected to the crankshaft 17, and is located closer
to the crank case 4 than the crank sprocket 19. Thus, in FIG 2, crank sprocket 25
is on the right side (in FIG. 2) of the crank sprocket 19. The oil pump sprocket 26
is connected to an axial end of the rotating shaft of the oil pump 23. The oil pump
drive chain 27 is wound around the crank sprocket 25 and the oil pump sprocket 26,
and transmits the rotation of the crank sprocket 19 to the oil pump sprocket 26 to
rotate it.
[0038] The camshaft drive mechanism 18 and the oil pump drive mechanism 24 are covered by
a timing chain cover 28 from the outside and is accommodated therein. The timing chain
cover 28 is made of aluminum alloy and is attached on the front side of the cylinder
head 3, cylinder block 2 and crank case 4, that is, attached on one side in the axial
direction thereof.
[0039] A chain tensioner device 29 is provided between the crank sprocket 19 and the exhaust
cam sprocket 21. The chain tensioner device 29 adjusts the tensile force of the timing
chain 22 at a portion suspended between the crank sprocket 19 and the exhaust cam
sprocket 21 under tension. Further, a chain guide 30 is provided between the intake
cam sprocket 20 and the crank sprocket 19. The chain guide 30 slidably contacts a
portion of the timing chain 22 suspended between the intake cam sprocket 20 and the
crank sprocket 19 under tension to guide the timing chain 22. In this case, one axial
end of the crankshaft 17 protrudes outside the timing chain cover 28, and a crank
pulley 31 is connected to the axial end of the crankshaft 17.
[0040] Further, an oil passage (not shown) is formed in the intake camshaft 7 and the exhaust
camshaft 8. The oil passage extends along the axial direction of the intake camshaft
7 and the exhaust camshaft 8.
[0041] An oil passage is formed in the cylinder block 2 and the cylinder head 3 extending
in a vertical direction. Oil pumped from the oil pan 5 by the oil pump 23 passes through
the oil passage in the cylinder block 2 and the cylinder head 3 and is supplied to
the oil passage in the intake camshaft 7 and the exhaust camshaft 8.
[0042] As shown in FIG 5, an opening portion 41 and an opening portion 42, which are served
as oil removing holes, are formed in a sidewall 3a on the front side of the cylinder
head 3. The opening portion 41 and the opening portion 42 communicate with the valve
chamber 9, and discharge or remove the oil dropped or fallen into the valve chamber
9 from the valve chamber 9 to supply the oil to the timing chain 22. The oil returns
to the oil pan 5 through the space formed between the cylinder block 2 and crank case
4 and the timing chain cover 28.
[0043] As shown in FIG. 2, the bottom surface 9a of the valve chamber 9 is formed of a first
bottom surface 9b and a second bottom surface 9c. The second bottom surface 9c is
positioned on the front side of the cylinder head 3 and is lower than the first bottom
surface 9b.
[0044] The opening portion 41 has a circular shape and at least a portion of the first opening
portion 41 is located above the first bottom surface 9b. The lower end of the first
opening portion 41 is below the first bottom surface 9b and above the second bottom
surface 9c. The opening portion 42 has a generally rectangular shape having an area
larger than the opening portion 41. The center portion of the opening portion 42 in
the vertical direction is located at the first bottom surface 9b. The lower end of
the opening portion 42 is located below the second bottom surface 9c. The opening
portion 41 located higher than the opening portion 42 is located directly above the
timing chain 22.
[0045] The total opening area of the first opening portion 41 and the second opening portion
42 is set such that, when the engine 1 is in a high speed operation region and oil
is excessively supplied to the valve chamber 9 to lubricate the intake camshaft 7
and the exhaust camshaft 8, a sufficient amount of oil can return to the oil pan 5
without staying in the valve chamber 9.
[0046] An end of a blowby gas recirculation passage (hereinafter, referred to as a "PCV
passage") 43 is attached at the upper portion of the cylinder head 3. The other end
of the PCV passage 43 is attached to an intake manifold (not shown). The PCV passage
43 is known as a passage that conducts the gas blowing through the gap between the
cylinder and the piston 14 of the engine 1 to the engine 1 through the intake manifold
to combust the gas again.
[0047] The action or effect of the above construction will be described below. As shown
in FIG 4, oil stored in the oil pan 5 is pumped up by the oil pump 23 in the direction
shown by arrows, and is supplied to components to be lubricated, such as the crankshaft
17, the piston 14, the intake camshaft 7 and the exhaust camshaft 8. Oil is also supplied
to the intake cam 7a, the exhaust cam 8a and the rocker arm 32 via the shower pipe
13.
[0048] Further, the oil supplied to the intake camshaft 7, exhaust camshaft 8, intake cam
7a, exhaust cam 8a and the rocker arm 32 falls on the bottom surface 9a of the valve
chamber 9 and is stored in the valve chamber 9.
[0049] Here, when the speed of the engine 1 is in a low speed operation region or in a middle
speed operation region, because the volume of oil supplied to the valve chamber 9
is relatively small, the oil fallen on the bottom surface 9a of the valve chamber
9 moves from the first bottom surface 9b to the second bottom surface 9c and is discharged
from the opening portion 42. The oil discharged from the opening portion 42 lubricates
the timing chain 22, the chain tensioner device 29 and the chain guide 30, and then
returns to the oil pan 5. At this time, because the volume of oil supplied to the
valve chamber 9 is relatively small, even if the oil returns to the oil pan 5 only
through the opening portion 42, oil return efficiency is not much affected thereby.
[0050] When the speed of the engine 1 is in a high speed operation region, because a large
volume of oil is supplied to the valve chamber 9, the oil fallen on the bottom surface
9a of the valve chamber 9 moves from the first bottom surface 9b to the second bottom
surface 9c, and is discharged from both the opening portion 41 and the opening portion
42.
[0051] The oil discharged from the opening portion 41 and the opening portion 42 lubricates
the timing chain 22, the chain tensioner device 29 and the chain guide 30, and then
returns to the oil pan 5. Further, because the opening portion 42 is formed directly
or immediately above the timing chain 22, the oil discharged from the opening portion
42 is supplied immediately and directly to the timing chain 22.
[0052] As described above, according to this embodiment, the opening portion 41 and the
opening portion 42, which have opening areas different from each other, are formed
as oil removing holes in the sidewall of the cylinder head 3. The opening portion
41 having a smaller opening area is disposed at a higher position than the opening
portion 42 having a greater opening area. Therefore, when the volume of oil supplied
to the valve chamber 9 is relatively small, oil can be supplied to the timing chain
22 from the opening portion 42 positioned at a lower place.
[0053] Accordingly, oil is prevented from being excessively supplied to the timing chain
22, and the drive loss of the timing chain 22 is prevented from being increased. As
a result, the deterioration in fuel efficiency is prevented.
[0054] When a large volume of oil is supplied to the valve chamber 9, because oil returns
to the oil pan 5 through both the opening portion 41 and the opening portion 42, a
large volume of oil can be used to lubricate the timing chain 22 and can return to
the oil pan 5. Thus, efficient oil return can be secured.
[0055] In particular, in this embodiment, the total opening area of the opening portion
41 and the opening portion 42 is set such that, when oil is excessively supplied to
the valve chamber 9 to lubricate the intake camshaft 7 and the exhaust camshaft 8,
a sufficient volume of oil can return to the oil pan 5 without staying in the valve
chamber 9. Thus, sufficient oil return is secured.
[0056] Further, the valve chamber 9 is prevented from being filled with the oil excessively
supplied to the valve chamber 9. Therefore, the oil level is prevented from exceeding
the height (level) of the opening end of the PCV passage 43 on the side of the cylinder
head 3, and oil is prevented from flowing into the PCV passage 43.
[0057] In the above-described embodiment, because the opening portion 41, which is disposed
at a higher position, is located directly above the timing chain 22, when a large
volume of oil returns to the oil pan 5 and a large volume of oil is required to lubricate
the timing chain 22, oil is effectively supplied to the timing chain 22 from the opening
portion 41 to lubricate the timing chain 22.
[0058] Further, when a large volume of oil is supplied to the valve chamber 9 in a high
speed operation region of the internal combustion engine, oil can return to the oil
pan 5 through both the opening portion 41 and the opening portion 42. Thus, while
the timing chain 22 is lubricated, a large volume of oil can return to the oil pan
5 from both the opening portion 41 and the opening portion 42. Therefore, efficient
oil return can be secured.
[0059] As a result, the valve chamber 9 is prevented from being excessively filled with
oil that is excessively supplied to the valve chamber 9. For example, oil level is
prevented from exceeding the opening end of the PCV passage 43, which communicates
between the cylinder head 3 and the intake passage, on the side of the cylinder head,
and the oil is prevented from flowing into the PCT passage.
[0060] Further, the total opening area of the opening portion 41 and opening portion 42
is set such that, when the engine 1 is in a high speed operation region and the oil
is excessively supplied to the valve chamber 9 to lubricate the intake camshaft 7
and the exhaust camshaft 8, the oil can return to the oil pan 5 without staying in
the valve chamber 9. Accordingly, when the engine 1 is in a high speed operation region,
sufficient oil return can be secured.
[0061] FIG. 6 is an oil supply mechanism for an internal combustion engine according to
a second embodiment of the present invention. The elements same as those in the first
embodiment are denoted by the same reference numerals, and detailed explanation thereof
will be omitted. In FIG 6, an inverted triangular opening portion 51, which is served
as an oil removing hole, is formed in the sidewall 3a of the cylinder head 3. Thus,
the opening area or shape of the opening portion 51 changes in the vertical direction.
In other words, the horizontal width of the opening 51 changes along its height. In
this embodiment, the horizontal width of the opening 51 increases, as the position
becomes higher.
[0062] In other words, the single opening portion 51 has an upper opening portion 51a and
a lower opening portion 51b. The opening area of the upper opening portion 51a is
greater than the opening area of the lower opening portion 51b. In addition, the lower
end of the lower opening portion 51b is located below the second bottom surface 9c.
Note that the upper opening portion 51a and the lower opening portion 51b are divided
by the center of the opening portion 51 in the vertical direction. That is, the upper
opening portion 51a is a portion located above the center of the opening portion 51
in the vertical direction, and the lower opening portion 51b is a portion located
below the center of the opening portion 51 in the vertical direction.
[0063] The opening area of the opening portion 51 is set such that, when the engine 1 is
in a high speed operation region and the oil is excessively supplied to the valve
chamber 9 to lubricate the intake camshaft 7 and the exhaust camshaft 8, a sufficient
volume of oil returns to the oil pan 5 without staying in the valve chamber 9.
[0064] In the second embodiment, when the volume of oil supplied to the valve chamber 9
is relatively small, the oil fallen on the bottom surface 9a moves from the first
bottom surface 9b to the second bottom surface 9c and is discharged from the lower
opening portion 51b. The oil discharged from the lower opening portion 51b lubricates
the timing chain 22, the chain tensioner device 29 and the chain guide 30, and then
returns to the oil pan 5. In this case, because the volume of oil supplied to the
valve chamber 9 is relatively small, even if the oil returns to the oil pan 5 only
through the lower opening portion 51b, oil return efficiency is not affected.
[0065] Further, when a large volume of oil is supplied to the valve chamber 9, the oil fallen
on the bottom surface 9a is discharged from both the upper opening portion 51a and
the lower opening portion 51b, i.e., from the whole area of the opening portion 51.
[0066] The oil discharged from the opening portion 51 lubricates the timing chain 22, the
chain tensioner device 29 and the chain guide 30, and then returns to the oil pan
5.
[0067] As described above, according to the second embodiment, a single opening portion
51 is formed as an oil removing hole in the sidewall of the cylinder head 3. The opening
area of the upper opening portion 51a located in a higher position is formed larger
than the opening area of the lower opening portion 51b, which is located below the
upper opening portion 51a. Therefore, when the volume of oil supplied to the valve
chamber 9 is relatively small, the oil is supplied to the timing chain 22 only through
the lower opening portion 51b.
[0068] Accordingly, oil is prevented from being supplied to the timing chain 22 more than
necessary, and the drive loss of the timing chain 22 is prevented from being increased.
As a result, deterioration in fuel efficiency is prevented. Further, when a large
volume of oil is supplied to the valve chamber 9, oil can return to the oil pan from
the whole area of the opening portion 51. Therefore, while the timing chain 22 is
lubricated, a large volume of oil can return to the oil pan 5 through the opening
portion 51. Thus, efficient oil return can be secured.
[0069] In particular, in this embodiment, the opening area of the opening portion 51 is
set such that, when oil is excessively supplied to the valve chamber 9 to lubricate
the intake camshaft 7 and the exhaust camshaft 8, a sufficient volume of oil can return
to the oil pan 5 without staying in the valve chamber 9. Thus, sufficient oil return
is secured.
[0070] In the first embodiment, two opening portions, i.e., the opening portion 41 and the
opening portion 42 are formed at the different heights. In the second embodiment,
a single inverted triangular opening portion 51 in which the lower opening area is
smaller than the upper opening area is formed. However, more than two opening portions
may be formed.
[0071] While some embodiments of the invention have been illustrated above, it is to be
understood that the invention is not limited to details of the illustrated embodiments,
but may be embodied with various changes, modifications or improvements, which may
occur to those skilled in the art, without departing from the spirit and scope of
the invention.
[0072] As described above, the oil supply mechanism for an internal combustion engine of
the present invention can prevent the drive loss of the timing chain caused by the
oil supplied to the timing chain from being increased, and sufficient oil return can
be secured. Thus, the oil supply mechanism is useful when it is applied to an internal
combustion engine having an oil removing hole to supply oil to a timing chain from
a valve chamber in a cylinder head.
1. An oil supply mechanism for an internal combustion engine (1) that includes a cylinder
head (3) that is fixed to an upper portion of a cylinder block (2) and has a valve
chamber (9) therein, wherein a sidewall of the cylinder head has an oil removing hole
(41, 42, 51) through which oil is supplied from the valve chamber to a timing chain
(22) provided on the side of the cylinder head,
characterized in that:
the oil removing hole communicates with the valve chamber, and the shape of the oil
removing hole changes along the vertical direction.
2. The oil supply mechanism according to claim 1, wherein the oil removing hole (41,
42) includes more than one opening portions that are formed at different positions
in the vertical direction.
3. The oil supply mechanism according to claim 2, wherein an upper-most opening portion
(41) among the opening portions is positioned directly above the timing chain.
4. The oil supply mechanism according to claim 2 or 3, wherein a lower end of a lower-most
opening portion (42) among the opening portions is positioned below a bottom surface
(9a) of the valve chamber.
5. The oil supply mechanism according to claim 2 or 3, wherein the valve chamber has
a first bottom surface (9b) and a second bottom surface (9c) that is positioned lower
than the first bottom surface, and at least a portion of the upper-most opening portion
(41) is positioned above the first bottom surface.
6. The oil supply mechanism according to claim 2 or 3, wherein the valve chamber has
a first bottom surface and a second bottom surface that is positioned lower than the
first bottom surface, and a lower end of an upper-most opening portion is located
below the first bottom surface and above the second bottom surface.
7. The oil supply mechanism according to claim 2, wherein the opening area of the upper-most
opening portion is smaller than the opening area of the lower-most opening portion.
8. The oil supply mechanism according to claim 1, wherein the oil removing hole (51)
is a single opening portion in which the opening area of a lower portion is smaller
than the opening area of the upper portion.
9. The oil supply mechanism according to claim 8, wherein the single opening portion
is formed in an inverted triangle.
10. The oil supply mechanism according to claim 8 or 9, wherein a lower end of the single
opening portion is positioned lower than the bottom surface (9a) of the valve chamber.
11. The oil supply mechanism according to claim 8 or 9, wherein the valve chamber has
a first bottom surface and a second bottom surface that is positioned lower than the
first bottom surface, and a lower end of the single opening portion is positioned
below the second bottom surface and an upper end of the single opening portion is
positioned above the first bottom surface.