JPH1181955A - Lubricating device for four-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricating device in a four-cycle engine, which can ensure operation of intake valves having a number larger than that of exhaust valve. SOLUTION: In a lubricating device in a four-cycle engine, a number of an exhaust cams are greater than that of exhaust cams in order to operate intake valves having a number greater than that of exhaust valves, and a number of intermediate bearing parts 45 of an intake cam shaft, for the intake valves, is greater than intermediate bearing parts 45 of an exhaust cam shaft, for the exhaust cams. The intermediate bearing parts 45 of the intake cam shaft and the intermediate bearing parts 45 of the exhaust cam shaft are adjacently located respectively between intake cams 26 and exhaust cams 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating device for introducing lubricating oil to an intermediate bearing between an intake camshaft and an exhaust camshaft in an overhead cam type four-stroke engine.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 58-113512 discloses a so-called DOHC type four-cycle engine in which a cylinder head is provided with two camshafts for intake and exhaust. In this engine, three intake valves and two exhaust valves per cylinder are linked to the camshaft via rocker arms, respectively, which are connected to the cylinder head via rocker shafts and hydraulic lash adjusters. Supported. The lash adjuster supporting the rocker arm is for automatically zeroing the tappet clearance between the rocker arm and the valve stem. And in these conventional technologies,
The lubricating oil sent from the oil pump passes through the reservoir chamber of the lash adjuster and is then led to the oil supply port of the camshaft bearing, from which it flows out through the clearance between the bearing and the journal. It has become. Further, the number of intermediate bearings of the intake camshaft is the same as the number of intermediate bearings of the exhaust camshaft, and three intake cams are supported by two intermediate bearings disposed on both sides thereof. .

For example, as disclosed in Japanese Utility Model Laid-Open Publication No. 64-53406, this type of lash adjuster is
The body includes a body embedded in the cylinder head, and a plunger fitted to the body so as to be slidable in the axial direction, and a tip of the plunger is in contact with one end of the rocker arm. A high-pressure chamber is formed between the bottom of the body and the plunger, and this high-pressure chamber is connected to a reservoir chamber inside the plunger via a check valve. The reservoir chamber is connected to an oil passage on the cylinder head side through an introduction hole formed in the body, and lubricating oil from an oil pump is supplied to the reservoir chamber and the high-pressure chamber via the oil passage. . Therefore, during operation of the engine, the plunger is constantly pressed against the rocker arm by the hydraulic pressure in the high-pressure chamber, thereby keeping the fulcrum position of the rocker arm constant.

[0004] For example, as disclosed in Japanese Utility Model Laid-Open Publication No. 63-171608, a cylinder head is provided with a bearing portion for receiving journal portions of an intake camshaft and an exhaust camshaft. An oil supply port for supplying lubricating oil is opened in these bearings, and lubricating oil sent from an oil pump is supplied to the bearings via an oil passage in a cylinder head. The length of the oil passage connecting the oil pump and the bearing of the intake camshaft is different from the length of the oil passage connecting the oil pump and the bearing of the exhaust camshaft.

[0005]

The conventional DOHC type 4
In the cycle engine, the number of bearings of the intake camshaft is the same as the number of bearings of the exhaust camshaft, and three intake cams are supported by two bearings arranged on both sides thereof.
Of the three intake cams, the central intake cam is far away from the bearings at both ends, so that the intake camshaft bends at the central intake cam, so that the operation of the central intake valve is reduced by the intake valves at both ends. There was a disadvantage that it did not match the operation.
SUMMARY OF THE INVENTION It is an object of the present invention to ensure the operation of a larger number of intake valves than exhaust valves in a four-stroke cycle engine lubrication system.

[0006]

In order to achieve the above object, the present invention provides an intake camshaft and an exhaust camshaft having an intake cam and an exhaust cam, respectively, for operating an intake valve and an exhaust valve. The number of intake valves per cylinder is made larger than the number of exhaust valves, and the intake camshaft and exhaust camshaft are supported on the cylinder head via intermediate bearings, respectively. A first lubrication passage leading to the intermediate bearing portion is provided, and a second lubrication passage from the oil pump to the intermediate bearing portion of the exhaust camshaft is provided. The length of the first lubrication passage is reduced by the second lubrication passage. In a four-stroke engine lubrication system with a length shorter than the length of the intake cam, a larger number of intake cams than the exhaust cam are formed to operate more intake valves than the exhaust valve. Is larger than the number of intermediate bearing portions of the exhaust camshaft, and the intermediate bearing portion of the intake camshaft and the intermediate bearing portion of the exhaust camshaft are arranged adjacent to each other between the intake cam and the exhaust cam. The configuration is as follows. In the present invention, the two intermediate bearing portions of the intake camshaft are arranged between the central intake cam for operating the central intake valve and the intake cams at both ends for operating the intake valves at both ends. And one intermediate bearing portion of the exhaust camshaft is disposed between two exhaust cams that operate two exhaust valves,
The width of the intermediate bearing portion of the intake camshaft can be smaller than the width of the intermediate bearing portion of the exhaust camshaft.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention of a lubricating device for a four-cycle engine according to the present invention will be described with reference to FIGS. In FIG. 3, reference numeral 1 denotes a cylinder block, 2 denotes a cylinder head, and an upper surface 2 a of the cylinder head 2 is covered by a head cover 3. Cylinder head 2
A valve operating chamber 4 is formed between the valve cover 4 and the head cover 3. The valve operating chamber 4 includes an intake camshaft 5 and an exhaust camshaft 6.
Are arranged parallel to each other. Intake valve 19a
-19c and the exhaust valves 20a-20b,
An intake cam 26 and an exhaust cam 27 are formed on the intake cam shaft 5 and the exhaust cam shaft 6.

As shown in FIG. 5, a sprocket 7 is fixed to one end of the intake cam shaft 5 and one end of the exhaust cam shaft 6, and a timing chain 8 is stretched between these sprockets 7. I have. A timing pulley 9 is fixed to the other end of the exhaust camshaft 6, and the timing pulley 9 is linked with a crankshaft (not shown) via a timing belt 10. Therefore, in the case of the present embodiment, the intake camshaft 5 is rotationally driven by the power transmission from the exhaust camshaft 6.

In the cylinder block 1, a plurality of cylinders 11
Are juxtaposed along the axial direction of the crankshaft. As shown in FIG. 3, a pent roof type combustion chamber is provided on the mating surface of the cylinder head 2 superposed on the cylinder block 1.
A recess 13 forming 12 is formed. The recesses 13 are provided corresponding to the cylinders 11, and each recess 13 has a larger number of intake valves per cylinder than the number of exhaust valves as shown in FIGS. Intake ports 14a, 14b, 14
c and two exhaust ports 15a and 15b are opened. These intake ports 14a, 14b, 14c and exhaust ports 15a, 15b are viewed from above.
Centerline of passes through the bore center X ₁ of the cylinder 11, and is provided at a position sandwiching the reference line A ₁ extending parallel to the axial direction of the camshaft 5,6, on the bore center X ₁ is A plug insertion hole 16 is opened.

The cylinder head 2 is connected to the cylinder block 1 via a head bolt 17. Head bolt
As shown in FIGS. 1 and 5, 17 is arranged side by side on the intake camshaft 5 side and the exhaust camshaft 6 side in a line, and is located inside these two camshafts 5 and 6. The intake ports 14a, 14b, 14c of the cylinder head 2 have three intake valves 19,
a, 19b and 19c are individually opened and closed, and the exhaust ports 15a and 15b are individually opened and closed by two exhaust valves 20a and 20b. These intake valves 19a, 19b, 19c
The valve stems 21 and 22 of the exhaust valves 20a and 20b are supported by the cylinder head 2 via a valve guide 23. The upper ends of the valve stems 21 and 22 pass through the cylinder head 2 as shown in FIG. And protrudes into the valve operating chamber 4.

As shown in FIG. 3 and FIG.
a, 19b, 19c and the exhaust valves 20a, 20b are arranged so that their valve stems 21, 22 extend parallel to each other along a direction perpendicular to the intake camshaft 5 and the exhaust camshaft 6, so that these camshafts 5, 6 along the axial direction. Of the three intake valves 19a, 19b and 19c, the central intake valve
19b is offset radially outward of the combustion chamber 12 with respect to the intake valves 19a and 19c on both sides (both ends). Therefore, the inclination angle alpha ₁ relative to the bore center line X ₂ of the center intake valve 19b is an intake valve 19a on both sides, as shown in FIG. 3,
19c is set smaller than the inclination angle alpha ₂ of the upper end of these three intake valves 19a, 19b, 19c of the valve stem 21 is located substantially collinear extends parallel to the reference line A ₁ ing.

As shown in FIG. 4, a plug insertion hole 24 is formed in the cylinder head 2 and the head cover 3 so as to be continuous with the plug insertion hole 16. The plug insertion hole 24 is provided in each cylinder.
Eleven intake valves 19a, 19b, 19c and exhaust valves 20a, 20
b. On the other hand, as shown in FIG.
The intake camshaft 5 has three intake cams 26 per cylinder, and the exhaust camshaft 6 has two exhaust cams 27 per cylinder. And, as shown in FIG.
Since both of these camshafts 5 and 6 are provided at a position deviated intake valve 19a, 19b, 19c and exhaust valves 20a, the axis Y _1, Y ₂ of 20b, the intake cams 26 and exhaust cams 27
Are the intake valves 19a, 19b,
19c and the valve stems 21 and 22 of the exhaust valves 20a and 20b.

The rocker arm 28 has a valve stem 21,
One end opposite to the contact portion 22 is supported by a hydraulic lash adjuster 30. As shown in FIG. 2, the lash adjuster 30 includes a cylindrical body 31 and a plunger 32 that is slidably fitted in the body 31 in the axial direction. A reservoir chamber 33 is formed inside the plunger 32, and this reservoir chamber 33 is connected to a supply hole 34 opened in the body 31. A high-pressure chamber 35 is formed between the bottom surface of the body 31 and the plunger 32. The high-pressure chamber 35 communicates with the reservoir chamber 33 through a communication port 36 at the bottom of the plunger 32.In the high-pressure chamber 35, a normally-closed check valve 37 that opens and closes the communication port 36, and a plunger 32 extending in the protruding direction A biasing spring 38 is provided.

The tip of the plunger 32 is formed in a spherical shape, and is fitted in a spherical concave portion 39 at one end of the rocker arm 28. Are formed to penetrate. Such a lash adjuster 30 is disposed substantially in parallel with the intake valves 19a, 19b, 19c and the exhaust valves 20a, 20b which are linked to each other. As shown in FIGS. 2 are fitted and held in mounting holes 41 formed in the upper surface 2a.

The intake camshaft 5 and the exhaust camshaft 6 are supported by the cylinder head 2 at a plurality of locations between both ends and intake valves 19a, 19b, 19c. That is, as shown in FIGS. 4 and 5, on the upper surface 2a of the cylinder head 2, journal portions 5 at both ends of each of the cam shafts 5, 6 are provided.
a, 6a and the adjacent intake cam 26
An intermediate bearing portion 45 that receives the journal portion 5b and the journal portion 6b between the exhaust cams 27 protrudes.
The intermediate bearing 45 is provided between the adjacent cam valves 5, 6 between the intake valves 19a, 19b, 19c and the exhaust valves 20a, 20b.
The journals 5a, 5b, and 6 are provided on the lower surfaces of the intermediate bearing 45 and the bearings 44 at both ends.
A fitting recess 46 is formed in which a and 6b are rotatably fitted.

A larger number of intake cams 26 are formed per cylinder than the exhaust cams 27, and the number of intermediate bearings 45 of the intake camshaft 5 is made larger than the number of intermediate bearings 45 of the exhaust camshaft 6. The intermediate bearing 45 of the intake camshaft 5 and the intermediate bearing 45 of the exhaust camshaft 6 are disposed adjacent to each other between the intake cam 26 and the exhaust cam 27. Two intermediate bearings 45 of the intake camshaft 5
Is disposed between the central intake cam 26 for operating the central intake valve 19b and the intake cams 26 at both ends for operating the intake valves 19a and 19c at both ends. The two intermediate bearings 45 are provided with two exhaust valves 20a,
The width of the intermediate bearing portion 45 of the intake camshaft 5 which is disposed between the two exhaust cams 27 for operating the 20b can be smaller than the width of the intermediate bearing portion 45 of the exhaust camshaft 6.

Cam caps 47 are respectively covered on the upper surfaces of the both-ends bearing portion 44 and the intermediate bearing portion 45. The cam cap 47 is provided between the journal portions 5a, 5b, 6
Another fitting recess 48 for rotatably supporting a and 6b is provided. The cam caps 47 are integrally protruded from the inner surface of the head cover 3, and the head cover 3 is fastened and fixed to the bearings 44, 45 via bolts 49 at the position of the cam cap 47. For this reason, a plurality of insertion holes 50 through which the bolts 49 pass are formed on the upper surface of the head cover 3.

An oil passage for supplying lubricating oil to the lash adjuster 30 and the bearings 44 and 45 of the camshafts 5 and 6 is formed inside the cylinder head 2. The details of the oil passage will be described below. I do. That is, as shown in FIGS. 1 and 5, a supply path 57 connected to the oil pump 56 is formed inside the cylinder block 1. Supply path
57 extends vertically at a position deviated to the intake camshaft 5 side, and the upper end thereof is guided to a position substantially equal to the height of the lash adjuster 30 on the intake side. Distribution passages extending in the axial direction of the camshafts 5 and 6 are located outside the intake-side lash adjuster 30 and the exhaust-side lash adjuster 30 on the left and right side walls 58 of the cylinder head 2 forming the valve operating chamber 4. 59a and 59b are formed.

A part of the distribution passages 59a, 59b penetrates the mounting hole 41 in which the lash adjuster 30 is fitted. A communication port 60 for communicating the distribution passages 59a, 59b and the mounting hole 41 with this penetrating portion. Is formed. And the distribution passages 59a,
The communication port 60 of 59b communicates with the supply hole 34 of the lash adjuster 30, and of the distribution passages 59a and 59b, the distribution passage 59a on the intake side communicates with the downstream end of the supply passage 57 via the communication passage 61. . Further, a horizontal oil flow passage 63 extending in a direction orthogonal to the camshafts 5 and 6 is formed in the upper wall portion 62 that forms the upper surface of the head cover 3.

As shown in FIGS. 1, 6 and 9, the horizontal oil flow passage 63 is located between the plug insertion holes 24, and both ends of the horizontal oil flow passage 63 are Passing above. The left and right side walls 64 of the head cover 3 and the inside of the side wall 58 of the cylinder head 2 connected to the side walls 64 have delivery passages 65 extending vertically between the cylinder head 2 and the head cover 3.
a and 65b are formed respectively, and these delivery paths 65
The distribution passages 59a and 59b and the horizontal oil flow passages are defined by a and 65b.
63 and are communicated. Therefore, in the case of this embodiment,
Lateral oil flow passage 63, delivery passages 65a and 65b, and distribution passages 59a and 59
b constitutes a main passage 66 connecting the lash adjuster 30 on the intake side and the exhaust side, and the exhaust-side distribution passage 59b located at the downstream end of the main passage 66 does not open to the valve train chamber 4. It is closed.

The upper wall portion 62 of the head cover 3 is formed with vertical oil flow passages 67a, 67b extending directly above the camshafts 5, 6 in parallel with the axial direction of the camshafts 5, 6. The vertical oil flow passages 67a and 67b intersect with the horizontal oil flow passage 63 inside the upper wall portion 62, and these two passages 63, 67a and 67b communicate with each other. As shown in FIGS. 4 and 8, the vertical oil flow passages 67a, 67b are branched downward at the position of the cam cap 47, and these branch passages 68 are journal parts 5a, 5b,
An opening is provided on the upper surface of the fitting concave portion 48 that contacts the portions 6a and 6b. Therefore, the plurality of branch passages 68 are individually branched from the main passage 66 as schematically shown in FIG. 7, and are located between the intake-side and exhaust-side lash adjusters 30.

As shown in FIGS. 1, 5, 6 and 7,
It comprises a supply path 57, a communication path 61, a delivery path 65a, a horizontal oil flow path 63, a vertical oil flow path 67a, and a branch path 68 from the oil pump 56 to the intermediate bearing section 45 and both end bearing sections 44 of the intake camshaft 5. The oil passage will be referred to as a first lubrication passage. Also, a supply path 57, a communication path 61, a delivery path 65a, a horizontal oil flow path 63, a vertical oil flow path 67b, and a branch path 68 from the oil pump 56 to the intermediate bearing 45 and the both ends bearing 44 of the exhaust camshaft 6. Is referred to as a second lubrication passage. The length of the first lubrication passage is shorter than the length of the second lubrication passage. In FIG. 1, reference numeral 70 denotes a return passage for lubricating oil which is opened on the bottom surface of the valve chamber 4, and this return passage 70 is connected to an oil pan (not shown).

Next, the operation of the embodiment of the present invention will be described. As shown in FIGS. 1 and 2, when the engine is started, the lubricating oil sent from the oil pump 56 is
First, the intake-side distribution passage 59 through the supply passage 57 and the communication passage 61.
a through the communication port 60 and the supply hole 34, the reservoir chamber 33 and the high-pressure chamber of the lash adjuster 30 on the intake side.
Flow into 35. Further, the lubricating oil in the distribution passage 59a flows into the horizontal oil flow passage 63 through one delivery passage 65a, and is supplied from this to the exhaust-side distribution passage 59b through the other delivery passage 65b. The lubricating oil in this distribution passage 59b is
As in the case of the intake side, the air flows into the reservoir chamber 33 and the high-pressure chamber 35 of the lash adjuster 30 on the exhaust side via the communication port 60 and the supply hole 34, and the oil pressure in both chambers 33 and 35 is increased.

The lubricating oil in the horizontal oil flow passage 63 is
a, 67b, and from there, it is supplied to the journal portions 5a, 5b, 6a, 6b of the camshafts 5, 6 through the branch passage 68. In other words, the lubricating oil from the oil pump 56 passes through the first lubricating passage and passes through the intermediate bearing portion of the intake camshaft 5.
The lubricating oil from the oil pump 56 is supplied to the intermediate bearing portion 45 and the both-end bearing portion 44 of the exhaust camshaft 6 through the second lubrication passage. The lubricating oil is applied to the journals 5a, 5b, 6a, 6b and the fitting recesses 46,
Flows into the valve chamber 4 through the clearance between
The oil is returned to the oil pan via a return passage 70 opening to the bottom of the valve chamber 4.

When the operation of the engine is stopped,
Negative pressure is generated in an upstream portion of the supply path 57 on the oil pump 56 side. Then, the branch passage 68 branched from the main passage 66 is opened to the atmosphere through the clearance between the journal portions 5a, 5b, 6a, 6b and the fitting concave portions 46, 48. Atmospheric pressure acts on the opening to the fitting recess 48, and the lubricating oil filled in the vertical oil flow passages 67a, 67b, the main passage 66, the communication passage 61, and the supply passage 57 is gradually reduced by an oil pump. Start returning to 56.

In this case, the lash adjuster 30 on the exhaust side
Is located downstream of the branch passage 68 connected to the exhaust camshaft 6, and the distribution passage 59b
Since b is closed without opening to the valve operating chamber 4,
The lubricating oil guided into the lash adjuster 30 on the exhaust side
It will remain as it is. On the other hand, since the lash adjuster 30 on the intake side is located between the oil pump 56 and the branch passage 68, the lubricating oil in the lash adjuster 30 is returned to the oil pump 56 as time passes. There is a possibility that it will be.

However, the main passage 66 having the above structure is provided without penetrating the lash adjuster 30 on the intake side, that is, the supply hole 34 of the lash adjuster 30 is branched from the communication port 60 of the distribution passage 59a. The lubricating oil returned from the horizontal oil flow passage 63 to the distribution passage 59a is directly transmitted through the distribution passage 59a and returned to the oil pump 56 side. When the wavefront of the lubricating oil passes through the opening of the communication port 60, the opening of the communication port 60 becomes atmospheric pressure, so that the communication between the supply hole 34 of the lash adjuster 30 and the distribution passage 59a is performed by the communication port 60. Will be closed at the opening.

For this reason, the intake-side lash adjuster 30
The lubricating oil inside can be prevented from flowing out to the oil pump 56 side, and even when the engine is stopped, the lash adjuster 30
Most of the lubricating oil remains in the reservoir chamber 33 as it is. Therefore, when the engine is restarted, the air in each part in the oil passage 55 is released from the journal parts 5a, 5b, 6
Since the oil is discharged through the clearance between the a and 6b and the fitting recesses 46 and 48, the oil pressure in the reservoir chamber 33 and the high-pressure chamber 35 is immediately restored, and the tappet clearance is immediately reduced to zero rush after starting. Can be adjusted.

Moreover, if lubricating oil remains in the reservoir chamber 33 and the high-pressure chamber 35, the oil film on the sliding portion between the body 31 and the plunger 32 is not interrupted, and the sliding portion is reliably lubricated. be able to. In addition, according to the embodiment of the present invention, the distribution passage connected to the supply passage 57 via the communication passage 61.
Since the engine 59a is connected to the lash adjuster 30 on the intake side, when the engine is restarted, the lubricating oil from the oil pump 56 is first supplied from the distribution passage 59a to the three intake valves via the communication port 60. The rush adjusters 30 of 19a, 19b, and 19c are supplied. Then, the lubricating oil is guided from the distribution passage 59a to the distribution passage 59b via the delivery passage 65a, the horizontal oil flow passage 63, and the delivery passage 65b, and is supplied to the lash adjuster 30 of the two exhaust valves 20a and 20b. Is done.

Therefore, the number of intake valves 19a, 19b, and 19c is large, and the intake valves that require more lubricating oil are used.
Since refueling is started from the lash adjusters 30 on the 19a, 19b, and 19c sides, the lash adjusters 30 for intake are used.
Although the number of the lash adjusters 30 and the number of the lash adjusters 30 for exhaust differ, it is possible to reduce variations in hydraulic pressure acting on the plurality of lash adjusters 30. Therefore, the reliability of lubrication of the lash adjuster 30 is improved, and the durability of the engine is improved.

Similarly, since the length of the first lubrication passage is shorter than the length of the second lubrication passage, the intake valve 19
a, 19b, and 19c, the number of which is large, and which requires more lubricating oil.
The lubrication of the bearings at both ends is started before the intermediate bearings 45 and the bearings at both ends on the exhaust valves 20a and 20b side where the number of the exhaust valves 20a and 20b is small and the necessity of lubricating oil is low.
Therefore, the intermediate bearing portion 45 and both ends bearing portion 44 of the intake camshaft 5 and the intermediate bearing portion 45 and both ends bearing portion 44 of the exhaust camshaft 6.
Although the numbers are different from each other, variations in the hydraulic pressure acting on the plurality of intermediate bearing portions 45 and the both-end bearing portions 44 can be reduced.

Further, the lash adjuster 30 and the camshaft 5,
6, the journal portions 5a, 5b, 6a, 6b
Because it is connected to this main passage 66 in a state where it is branched from, only by increasing or decreasing the diameter of the communication port 60 or the branch passage 68,
Rush adjuster 30 and journal parts 5a, 5b, 6
There is an advantage that the hydraulic pressure acting on a and 6b can be freely changed. Further, since the horizontal oil flow passage 63 connecting the intake side distribution passage 59a and the exhaust side distribution passage 59b is provided in the head cover 3, the dimensions of the cylinder block 1 and the cylinder head 2 in the direction of the camshafts 5, 6 are reduced. be able to.

That is, when the horizontal oil flow passage 63 is provided on the cylinder head 2 side, the horizontal oil flow passage 63
Therefore, it is necessary to increase the arrangement interval of the cylinders 11 by a dimension corresponding to the diameter of the horizontal oil flow passage 63, and accordingly, the total length of the cylinder block 1 and the cylinder head 2 becomes longer. However, according to the configuration of the embodiment of the present invention, there is no need to secure a space for forming the horizontal oil flow passage 63 on the cylinder block 1 side.
Can be narrowed, and the cylinder block 1 and the cylinder head 2 can be made compact.

[0034]

According to the present invention, in order to operate more intake valves than exhaust valves, more intake cams are formed than exhaust cams, and the number of intermediate bearing portions of the intake camshaft is reduced. The number of intermediate bearings was larger than the number of intermediate bearings, and the intermediate bearing of the intake camshaft and the intermediate bearing of the exhaust camshaft were disposed adjacent to each other between the intake cam and the exhaust cam. for that reason,
An oil film is formed between the intermediate bearing and the intake camshaft and the exhaust camshaft, and each camshaft rotates, and lubricating oil discharged from the intermediate bearing to the outside flows into the intake cam and the exhaust cam adjacent to the intermediate bearing. The lubrication of each cam is performed smoothly and sufficiently. In addition, both the intake cam and the exhaust cam can be arranged at substantially equal intervals from the intermediate bearing portion, and both the intake cam shaft where the intake cam is located and the exhaust cam shaft where the exhaust cam is located have a small amount of deflection. . Therefore, both the small number of exhaust valves and the large number of intake valves can be reliably operated.

[Brief description of the drawings]

FIG. 1 is a sectional view around a cylinder head.

FIG. 2 is a sectional view of a lash adjuster.

FIG. 3 is a cross-sectional view taken along a line III-III in FIG. 5;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 5;

FIG. 5 is a plan view of a cylinder head.

FIG. 6 is a plan view of a head cover.

FIG. 7 is a schematic diagram showing an outline of an oil passage.

FIG. 8 is a sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a sectional view taken along line IX-IX in FIG. 6;

FIG. 10 is a schematic configuration diagram of a combustion chamber.

[Explanation of symbols]

 2 Cylinder head 5 Intake camshaft 6 Exhaust camshaft 11 Cylinder 19 Intake valve 20 Exhaust valve 26 Intake cam 27 Exhaust cam 45 Intermediate bearing part 56 Oil pump

Claims (1)

[Claims] In order to operate an intake valve and an exhaust valve, an intake cam and an exhaust cam are formed on an intake camshaft and an exhaust camshaft, respectively, and the number of intake valves per cylinder is determined by the number of exhaust valves. The intake camshaft and the exhaust camshaft are each supported by a cylinder head via an intermediate bearing, and a first lubricating passage from the oil pump to the intermediate bearing of the intake camshaft is provided. In a lubricating device for a four-stroke engine, a second lubrication passage is provided from a pump to an intermediate bearing portion of an exhaust camshaft, and the length of the first lubrication passage is shorter than the length of the second lubrication passage. In order to operate more intake valves than valves, more intake cams are formed than exhaust cams, and the number of intermediate bearings of the intake camshaft is made larger than the number of intermediate bearings of the exhaust camshaft, A lubricating device for a four-stroke engine, wherein an intermediate bearing portion of an intake camshaft and an intermediate bearing portion of an exhaust camshaft are arranged adjacent to each other between an intake cam and an exhaust cam.