JPH0768892B2 - OHC type valve operating device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention relates to a valve train for an internal combustion engine equipped with a rocker arm with rollers.

(2) Conventional technology In an OHC type valve operating device for a conventional internal combustion engine, a rocker arm incorporated in the device is provided with a rocker arm body and a roller which is rotatably supported by a tip portion of the body and contacts a valve operating cam. In a rocker arm with a roller consisting of the above, it is common to provide almost no upward buffering curves on the intake side of the valve operating cam and the opening side of the exhaust valve.

(3) Problems to be Solved by the Invention By the way, in the OHC type valve train having the rocker arm with the roller, the frictional resistance of the connecting portion between the cam and the rocker arm is reduced to improve the engine performance and the fuel consumption. On the other hand, in the valve train equipped with such a rocker arm with a roller, a clearance is generated between the rocker arm body and the rolling roller in addition to the tappet clearance. There is a problem that the hitting sound between each member becomes louder than that using a rocker arm without a roller.

Therefore, the applicant has already provided a valve-opening-side upward buffering curve on the cam surface of the valve operating cam to reduce the hitting noise without causing any hindrance to the intake / exhaust valve opening / closing timing by the valve operating cam. We have proposed a valve operating system designed for this purpose (Japanese Patent Application No.
60-149779 (see JP-A-62-10406).

According to the result of further research and development, one valve system (for example, intake side valve system) and the other valve system (for example, exhaust side valve system) arranged on both sides of the valve camshaft are shown. System),
When the cam nose starts contacting the roller, the component force in the direction toward the rocker arm shaft side of the force that tries to lift the rocker arm main body end via the roller causes the force difference between the intake and exhaust rocker arms and the cam shaft. There is a slight difference in relation to the mutual position and the rotation direction of the cam, that is, the component force on the rocker arm side, which is deviated to the front side in the rotation direction of the nose at the time of starting the contact, is to the rear side in the rotation direction. It becomes larger than that on the side of the rocker arm that is deviated, so that in the former rocker arm, the component force is relatively struck between the roller and the rocker arm body due to the existence of the clearance between the roller and the rocker arm body. The present inventor has determined that the sound tends to be generated.

The present invention has been proposed in view of the above, and changes the gradient of the upward buffering curve on the valve opening side of the valve operating cam that operates each of the two valve operating systems, that is, between the intake side and the exhaust side. Generation of the above-mentioned beating sound by making the rising buffer curve of the valve operating cam that operates the valve operating system on the noisy side gentler than the rising buffer curve of the valve operating cam that operates the other valve operating system It is an object of the present invention to provide an OHC type valve operating device for an internal combustion engine that can effectively reduce the above.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention in order to achieve the above object, according to the present invention, a valve operating cam shaft having a suction / exhaust cam in a cylinder head of a machine body and the cam A pair of intake and exhaust rocker arm shafts are provided on both sides of the shaft, and the intake and exhaust rocker arms are swingably supported on the rocker arm shafts, respectively, and one end of the intake and exhaust rocker arm is provided with the intake and exhaust cams. In an OHC type valve operating device for an internal combustion engine, which is connected to each of the rocker arms, and the other end of which is connected to an intake valve and an exhaust valve, the intake and exhaust rocker arms are respectively connected to a rocker arm body and a tip portion of the body. A roller that is rotatably supported and is in contact with the intake and exhaust cams, and the intake and exhaust cam surfaces are
Each has a base circular portion and a nose portion protruding from the base circular portion, and an up cushioning curve is set at the rising portion of the nose portion, and the nose portion of the intake and exhaust rocker arms is a roller. The cushioning curve constant of the cam for the rocker arm that is displaced to the front side in the direction of rotation of the nose when starting contact is greater than the cushioning curve constant of the cam for the other rocker arm. Is also set smaller.

(2) Operation In each rocker arm, there is some clearance between the rocker arm body and the roller due to unavoidable rattling in the bearing part between them.

By the way, when the nose part of each cam starts contact with the roller (that is, when each cam starts opening the corresponding valve), the force to lift the end of the rocker arm body via the roller is There is a component force in the direction toward the side, and due to this component force, in each rocker arm, a tapping sound is generated between the rollers and the rocker arm body in relation to the existence of the clearance.
Further, the magnitude of such component force is slightly different between the intake cam side and the exhaust cam side in relation to the mutual position of the intake and exhaust rocker arm shafts and the cam shaft and the rotational direction of the cam, that is, The component force (B in the embodiment) on the side of one rocker arm (the rocker arm 22 for exhaust in the embodiment specifically described below) that is deviated to the front side in the rotation direction of the nose at the time of starting the contact is more preferable. The component force on the other rocker arm (the intake rocker arm 21 in the embodiment) is larger than the component force (B 'in the embodiment), and therefore the hitting sound tends to be relatively loud in the former rocker arm. However, according to the above configuration of the present invention, the rising buffer curve is set at the rising portion of the nose of any of the cams, and in addition, the cam having the larger component force (exhaust cam 17 in the embodiment).
Is set to be smaller than the buffer curve constant of the other cam (in this embodiment, the intake cam 18) of the other buffer (the intake cam 18 in the embodiment), the hitting sound from any valve operating system Is also reduced as much as possible.

(3) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, an engine body E of an SOHC type internal combustion engine includes a cylinder block 1 and a cylinder head 2 that is bonded to a deck surface of the cylinder block 1 via a gasket 3.

A piston 5 is provided in the cylinder bore 4 of the cylinder block 1.
Is slidably fitted, and the piston 5 has a connecting rod 6
Through a crankshaft (not shown).

The cylinder head 2 is a so-called cross-flow type in which intake air and exhaust gas flow in one direction, and an intake port 8 and an exhaust port 9 are connected to a combustion chamber 7 facing the top surface of the piston 5. Suction and exhaust valves 10 and 11 for opening and closing the intake and exhaust ports 8 and 9 are slidably supported on the cylinder head 2, and the intake and exhaust valves 10 and 11 are closed by valve springs 12 and 13 in the closing direction. Biased to.

The cylinder head 2 and the head cover 14 provided above the cylinder head 2 form a valve operating chamber 15, and the valve operating chamber 15 is provided with a valve operating device V for operating the intake and exhaust valves 10 and 11. . In the valve operating chamber 15, between the intake and exhaust valves 10 and 11,
A valve operating cam shaft 16 is rotatably supported in parallel with a Kukank shaft (not shown), and intake and exhaust cams 18 and 17 are integrally provided on the shaft 16.

On both sides of the valve operating cam shaft 16, a pair of rocker arm shafts 19 and 20 which are substantially parallel to the shaft 16 are fixed on the cylinder head 2. The rocker arm shafts 19 and 20 have rocker arms with rollers on the intake and exhaust sides. 21, 22 are swingably supported, and those rocker arms 21, 22 connect the intake / exhaust valves 18, 17 of the valve operating cam 16 and the upper ends of the intake / exhaust valves 10, 11 to connect the cams 18, The rotation of 17 is sucked and transmitted to the exhaust valves 10 and 11, respectively.

As shown clearly in FIG. 2, the rocker arms 21 and 22 with rollers are composed of a rocker arm main body 23 and a roller 24 which is rotatably supported at the tip of the rocker arm main body 23.
Is provided with a shaft hole 25 penetrating the rocker arm shaft 19 or 20 in the center thereof, and a tappet clearance adjusting screw 26 is screwed to the base end thereof, and the lower end of the screw 26 is an intake valve. 10 or the upper end of the exhaust valve 11 is abutted.
Further, the tip of the rocker arm main body 23 is formed in a forked shape, and a roller shaft 28 is fixedly mounted in a roller shaft hole 27 formed therein, and the roller 24 rolls on the roller shaft 28 via a needle bearing 29. The roller 24 is freely supported, and the roller 24 is a valve camshaft.
The 16 intake and exhaust cams 18, 17 are brought into contact with each other.

Valve camshaft linked to the rotation of the crankshaft (not shown)
When 16 is driven, intake / exhaust rollers 10 and 11 are opened / closed at predetermined timings via rocker arms 21 and 22 with intake and exhaust rollers.

By using the rocker arms 22 and 23 with rollers in the valve gear V, between the roller shaft 28 and the needle bearing 29,
It is inevitable that some clearance will be generated between the needle bearing 29 and the roller shaft hole 27, and this clearance will be synergistic with the tappet clearance of the valve train, and the hitting sound generated in the valve train will increase. That causes a problem.

Further, in FIG. 1, when the valve operating cam shaft 16 rotates in the direction of arrow A in FIG. 1, the roller 24 rolls to suck and exhaust the rocker arms 21 and 22 on the rocker arm shafts 19 and 20, respectively. The intake and exhaust valves 10 and 11 are opened and closed. In such a process, when the nose portions 18n, 17n of the intake / exhaust cams 18, 17 start contact with the roller 24, the force for lifting the end portion of the rocker arm body 23 via the roller 24 is Component force B ', B in the direction toward the corresponding rocker arm shaft 19,20 side
Due to the component B ', B, each rocker arm 21, 22 produces a struck sound between the rocker arm 21 and 22 due to the existence of the above-mentioned clearance between the roller 24 and the rocker arm body 23. Let Moreover, the magnitude of such component force is
The mutual positions of the exhaust rocker arms 21 and 22 and the cam shaft 16 and the rotation direction of the cam shaft 16 (specifically, the nose portions 18n and 17n described above).
There is a slight difference between the intake cam 18 side and the exhaust cam 17 side in relation to the rotation direction at the time of starting contact with the roller 24), that is, the rotation direction of the nose portions 18n, 17n at the time of starting the contact. The component force B on one rocker arm (the exhaust rocker arm 22 in the illustrated example) that is deviated to the front side is larger than the component force B ′ on the other rocker arm (the intake rocker arm 21 in the illustrated example) side. Therefore, the hitting sound from the rocker arm 22 side of the former, that is, from the exhaust valve system tends to be louder. When the valve camshaft 16 rotates in the opposite direction (opposite to the arrow A), the hitting sound naturally becomes louder in the intake valve system.

Thus, this embodiment based on the present invention is capable of effectively reducing any striking sound in consideration of the difference between the striking sounds in the two valve operating systems. That is, on the cam surfaces of the intake and exhaust cams 18,17, the base circle parts 18b, 1
7b and a nose portion 18n, 17n rising from it are formed, but especially the rising portion of the nose portion 18n, 17n is set up buffer curve Ci, Ce, in addition, the above-mentioned component force is particularly large. Upward damping curve Ce of the cam (exhaust cam 17 in the illustrated example)
Of the other cam (the intake cam 18 in this embodiment) is the buffer curve constant kθi of the other cam (the intake cam 18 in the embodiment).
Is set to be smaller than that (that is, the slope becomes gentle). That is, the rotation angle θi (deg.) Of the intake cam 18 and the exhaust cam 17
The rotation angle θe (deg.) Of the intake cam 18, the lift amount hi (mm) of the ascending buffer curve Ci of the intake cam 18, and the lift amount he (mm) of the ascending buffer curve Ce of the exhaust cam 17 are as shown in FIG. , Kθ again
e <kθi, and, for example, kθe = 0.02 and kθi = 0.029 are set.

If the valve cam 16 rotates in the opposite direction, kθi
<Kθe.

If the valve cam shaft 16 is now rotated, intake and exhaust cams 18,17
The rocker arms 21 and 22 on the intake and exhaust sides are alternately rocked by this, and the intake and exhaust valves 10 and 11 are opened and closed at a predetermined timing. However, as described above, the cam surfaces of the intake and exhaust cams 18 and 17 are Since the up-side damping curves Ci and Ce on the valve opening side are provided respectively, both the intake and exhaust valves 10 and 11 are opened slowly to reduce the noise such as the knocking sound generated when opening the valve, and Of the exhaust system valve operating system, the valve system on the side where noise becomes louder, in this embodiment, the buffer curve kθe of the upward buffering curve Ce of the exhaust side valve operating system is changed to another valve system. In the example, the hitting sound is further effectively reduced by making the value smaller than the buffer curve constant kθi of the upward buffer curve Ci of the valve operating system on the intake side.

C. Effects of the Invention As is apparent from the above embodiments, according to the present invention, in the OHC type valve operating device provided with the pair of intake and exhaust rocker arm shafts on both sides of the valve operating cam shaft, The rocker arms are each provided with rollers, and the rising buffer curves are set at the rising portions of the nose portions of the intake and exhaust cams, respectively, and when the nose portion of the intake and exhaust rocker arms starts contact with the rollers. Since the buffering curve constant of the cam's ascending buffering curve corresponding to the rocker arm that is offset to the front side in the rotational direction of the nose part is set smaller than the buffering curve constant of the cam ascending curve of the other rocker arm, Suction related to the existence of clearance between the rocker arm body and the rollers in each rocker arm,
When the exhaust valve is opened, it is possible to effectively reduce the occurrence of hitting sounds of different magnitudes than those of the valve operating system. Therefore, by adopting the above rollers, the friction resistance of the valve operating system can be reduced. It is possible to effectively reduce the operating noise of the valve operating system as a whole while reducing it to improve the engine performance.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a part of an internal combustion engine equipped with the device of the present invention, FIG. 2 is a perspective view of a rocker arm with rollers, and FIG. It is a graph which shows the going-up curve on the valve-opening side of the exhaust side. E: engine body, Ci, Ce ... upstream buffer curve, kθi, kθe
…… Buffer curve constant 2 …… Cylinder head, 10, 11 …… Intake and exhaust valves, 16 ……
Valve camshaft, 18,17 …… Intake and exhaust cam, 19,20 …… Rocker arm shaft, 21,22 …… Rocker arm with roller, 23 …… Rocker arm body, 24 …… Roller

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References Japanese Patent Application Laid-Open No. 53-112320 (JP, A) Japanese Patent Application No. 48-80377 (Japanese Utility Model Application No. 50-27211) Micro film (JP, U) of the contents

Claims (1)

[Claims] 1. A cylinder head (2) for an engine body (E).
And a valve cam shaft (1 with intake and exhaust cams (18, 17)
6), and a pair of intake and exhaust rocker arm shafts (19, 20) provided on both sides of the cam shaft (16). The rocker arm shafts (19, 20) are provided with intake and exhaust rocker arm shafts (21, 22). Each of them is swingably supported, one end of each of the intake / exhaust rocker arms (21, 22) is connected to each of the intake / exhaust cams (18, 17), and the other end thereof is connected to the intake / exhaust valve (10, In an OHC type valve operating device for an internal combustion engine connected to 11), the intake and exhaust rocker arms (21, 22) roll on the rocker arm body (23) and the tip of the body (23), respectively. It is composed of a roller (24) which is freely pivotally supported and comes into contact with the intake and exhaust cams (18, 17), and the cam surfaces of the intake and exhaust cams (18, 17) have base circle portions (18b, 17b), respectively. ) And a nose portion (18n, 17n) that is raised from the base circular portion (18b, 17b), and is located above the rising portion of the nose portion (18n, 17n). Shock absorbing curve (Ci, Ce) is set, and the nose portion (18n, 17) of the intake and exhaust rocker arms (21, 22) is set.
Nose part (1) when n) starts contact with the roller (24)
The buffer curve constant (kθe) of the ascending buffer curve (Ce) of the cam (17) corresponding to the rocker arm (22) that is displaced to the front side in the rotation direction of the other rocker arm (2
An OHC type valve operating device for an internal combustion engine, which is set to be smaller than a buffer curve constant (kθi) of an upward buffer curve (Ci) of a cam (18) corresponding to 1).