JPH05141209A - Rocker shaft fitting structure four-cycle engine - Google Patents

Abstract

PURPOSE:To absorb tappet noise vibration to prevent the tappet noise from being conveyed to the outside of an engine. CONSTITUTION:A rocket shaft insertion hole 37B is formed in a cylinder head 13 placed on a cylinder block. A rocker shaft 38B to support a rocker arm 27B is inserted in the rocker shaft insertion hole. A stud bolt 47 to fix the cylinder head on the cylinder block is arranged in contact with the rocker shaft. The rocker shaft insertion hole has an opening provided with a forked portion in front, where a rocker shaft plug to which an elastic material 52 is fixed is fitted. The rocker shaft plug is thrusted at the back by a thrusting member 45 and held and so the elastic material is put in contact with the rocker shaft and the stud bolt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocker shaft mounting structure for a four-cycle engine suitable for preventing tappet noise.

[0002]

2. Description of the Related Art In a four-cycle engine, a rocker shaft is inserted through a rocker shaft insertion hole provided in a cylinder head, a rocker arm is swingably supported on the rocker shaft, and the rocker arm is rocked by rotation of a cam of a cam shaft. The intake valve and the exhaust valve are driven to operate to open and close the intake hole and the exhaust hole at a predetermined timing. The rocker shaft is generally fixed to the cylinder head using bolts or the like, and is provided so as not to move even when the rocker arm swings.

[0003]

However, since there is a slight gap between the rocker arm and the intake valve or the exhaust valve when the operation is stopped, the rocker arm does not push these intake and exhaust valves at the initial stage. Sucking
The exhaust valve may strike the tip of the exhaust valve to generate tapping sound. At this time, since the rocker shaft is bolted to the cylinder head, this tappet sound may be transmitted to the cylinder head via the rocker shaft, and an unpleasant tappet sound may be transmitted to the outside of the engine.

The present invention has been made in view of the above circumstances, and provides a rocker shaft mounting structure for a four-cycle engine which absorbs vibration of tappet sound and prevents the tappet sound from being transmitted to the outside. To aim.

[0005]

According to the present invention, a rocker shaft insertion hole is formed in a cylinder head member mounted on a cylinder block, and a rocker shaft supporting a rocker arm is inserted through the rocker shaft insertion hole. In a rocker shaft mounting structure of a 4-cycle engine in which a stud bolt for fixing the cylinder head to a cylinder block is arranged in contact with the rocker shaft, a rocker shaft mounting structure for a four-cycle engine is provided with a forked portion at a front portion at an opening of the rocker shaft insertion hole. A rocker shaft plug is formed and has an elastic body fixed to the forked portion. The rear portion of the rocker shaft plug is pressed and held by a pressing member, and the elastic body is provided with the rocker shaft and the stud bolt. It is configured to be able to contact with.

[0006]

Therefore, according to the rocker shaft mounting structure of the four-cycle engine according to the present invention, the tappet sound of the rocker arm striking the intake / exhaust valve at the initial stage of engine operation is directly transmitted from the rocker arm to the cylinder head member through the rocker shaft. Or, it tries to be indirectly transmitted to the cylinder head member via the stud bolt, but since the elastic body of the rocker shaft plug is in contact with the rocker shaft and the stud bolt, this elastic body absorbs the vibration of the tappet sound. To be done. As a result, the tappet sound is not transmitted to the outside of the engine.

Further, since the rocker shaft plug can be easily removed from the opening of the rocker shaft insertion hole by removing the pressing member, the rocker shaft can be easily attached and detached.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a rocker shaft mounting structure for a 4-cycle engine according to the present invention, a sectional view taken along the line I--I of FIG. 5, and FIG. 3 applies the embodiment of FIG. FIG. 2 is a side view of the engine, and FIG. 2 is a side view of a business bike type motorcycle equipped with the engine of FIG.

The business motorcycle type motorcycle shown in FIG. 3 has a front wheel 2 pivotally supported by a front fork 1 in front of the vehicle and a rear wheel 4 driven by a 4-cycle engine 3 in rear of the vehicle. The rider straddling the upper seat 5 operates the handle 6 to operate. The 4-cycle engine 3 is mounted in the lower center of the body frame 7, and the seat 5 is installed in the upper center of the body frame 7.

As shown in FIG. 3, the four-cycle engine 3 houses a crankshaft 9 and a crankcase 9 for accommodating a transmission (not shown), and a piston 10 (FIGS. 4 and 5) installed in the crankcase 9. Cylinder block 11 and this cylinder block 1
1 and the combustion chamber 12 between the piston 10 (see FIG.
And a cylinder head 13 that configures FIG. 5).

The reciprocating motion of the piston 10 due to the explosion of the air-fuel mixture in the combustion chamber 12 is converted into rotary motion by the crankshaft 8 via the connecting rod 14, and this rotary motion is decelerated by a transmission (not shown). It is transmitted to the drive sprocket 15 shown in FIG. A drive chain (not shown) is provided between the drive sprocket 15 and the driven sprocket (not shown) on the rear wheel 4 side.
Is wound around and the rotational force of the engine is transmitted to the rear wheel 4. Reference numeral 16 in FIG. 3 is a gear shift lever that selects a transmission gear of the transmission.

As shown in FIG. 5, the cylinder head 13 of the four-cycle engine 3 is provided with an intake hole 17 and an exhaust hole 18 in the combustion chamber 12 one by one. An intake port 19 and an exhaust port 20 are formed in communication with each other. Intake hole 17, exhaust hole 1
8, an intake valve 21 and an exhaust valve 22 are arranged, and an intake manifold 23 and an exhaust manifold 24 are respectively provided in the intake port 19 and the exhaust port 20.
Are connected as shown in FIG.

The intake manifold 23 includes a carburetor 25.
The air-fuel mixture produced by the exhaust manifold 24 is introduced into the combustion chamber 12 when the intake valve 21 is opened.
Discharges the waste gas generated in the combustion chamber 12 to the outside of the engine via a muffler (not shown) when the exhaust valve 22 is opened. Combustion of the air-fuel mixture in the combustion chamber 12
This is done by igniting the sparks of the spark plug 26 shown in FIG.

The intake valve 21 and the exhaust valve 22
The opening / closing operation is performed by the valve operating device including the intake cam 26A and the exhaust cam 26B, the intake rocker arm 27A and the exhaust rocker arm 27B, the valve spring 28, and the like shown in FIGS. 4 and 5.

The intake cam 26A and the exhaust cam 26B are
Both of them are integrally formed adjacent to one cam shaft 29, and are rotatably supported at the substantially center of the cylinder head 13. As shown in FIG. 4, a sprocket mounting flange 30 is rotatably connected to one end of the cam shaft 29, and a cam chain driven sprocket 31 and a flywheel 32 are fixed to the sprocket mounting flange 30 with bolts or the like. The cam chain 34 is wound around the cam chain driven sprocket 31 and the cam chain drive sprocket 33 of the crankshaft 8, and the rotation of the crankshaft 8 is transmitted to the camshaft 29. At this time, 2 of the crankshaft 8
The diameters of the cam chain drive sprocket 33 and the cam chain driven sprocket 31 are set so that the cam shaft 29 rotates once per rotation.

Further, the intake valve 21 and the exhaust valve 2
2 is a valve guide 3 fixed to the cylinder head 13.
5 is inserted. The valve spring 28 is interposed in a compressed state between a spring retainer 36 installed on the head portion of the valve stem and the valve guide 35 or the cylinder head 13, and the valve faces of the intake valve 21 and the exhaust valve 22 are respectively intake valves. The hole 17 and the exhaust hole 18 are urged to be closed.

As shown in FIG. 1, two intake-side rocker shaft insertion holes 37A and an exhaust-side rocker shaft insertion hole 37B are provided in the cylinder head 13, and the intake-side rocker shaft insertion holes 37A are provided in the intake-side rocker shaft. The shaft 38A has an exhaust side rocker shaft insertion hole 37B.
The exhaust side rocker shafts 38B are fitted into the respective parts.
The intake rocker arm 27A and the exhaust rocker arm 27B
Are swingably supported by the intake-side rocker shaft 38A and the exhaust-side rocker shaft 38B at their longitudinal center positions, respectively. The intake cam 26 is attached to one end of each of the intake rocker arm 27A and the exhaust rocker arm 27B.
A, the cam floor 3 that contacts the exhaust cam 26B, respectively
9 is fixed. Further, an adjusting screw 40 for adjusting the tappet amount by contacting the valve stem heads of the intake valve 21 and the exhaust valve 22 is screwed to the other ends of the intake rocker arm 27A and the exhaust rocker arm 27B.

The intake rocker arm 27A includes an intake cam 26.
The intake valve 21 is operated with the valve lift amount and valve timing of A to open and close the intake hole 17. The exhaust rocker arm 27B operates the exhaust valve 22 according to the valve lift amount and valve timing of the exhaust cam 26B,
The exhaust hole 18 is opened and closed.

When assembling the valve operating device as described above,
The intake valve 21, the exhaust valve 22, the valve spring 28, the intake rocker arm 27A, and the exhaust rocker arm 27B are incorporated from an inspection window 41 opened in front of and behind the cylinder head 13. These inspection windows 41 are closed by an inspection cap 42 shown in FIG. Further, the cam shaft 29, the cam chain driven sprocket 31 and the like shown in FIG. 4 are incorporated through an assembling window 43 opened on the left side of the cylinder head 13. The built-in window 43 is closed by a cam chain sprocket cover 44. A cylinder head R cover 45, which is also shown in FIGS. 1 and 6, is bolted to the cylinder head 13 at a position opposite to the cam chain sprocket cover 44.

Now, as shown in FIG. 1, the intake side rocker shaft 38A has a length over substantially the entire length of the intake side rocker shaft insertion hole 37A. At the opening of the intake side rocker shaft insertion hole 37A, a disc-shaped elastic plug 46 made of, for example, rubber shown in FIG.
It is arranged in contact with the end of A. This elastic plug 46
Is the cylinder head R cover 45 as a pressing member.
Then, the intake side rocker shaft 38A is elastically supported.

Further, the exhaust side rocker shaft 38B is formed shorter than the entire length of the exhaust side rocker shaft insertion hole 37B, and one end of the exhaust side rocker shaft 38B abuts one stud bolt 47. Here, the stud bolt 47 is used to connect the crankcase 9 to the cylinder block 1.
1 extends in the direction of the cylinder head 13 and penetrates the cylinder block 11 and the cylinder head 13, and a nut 48 is screwed into the tip of the cylinder block 1.
1 and the cylinder head 13 are fixed to the crankcase 9. One of these four stud bolts 47 penetrates through the exhaust side rocker shaft insertion hole 37B and contacts the end portion of the exhaust side rocker shaft 38B as described above. The rocker shaft plug 49 is fitted into the opening of the exhaust side rocker shaft insertion hole 37B.

This rocker shaft plug 49 is shown in FIG.
As shown in (A), (B), and (C), two protruding portions 51, which are diametrically opposed to each other, are integrally formed as bifurcated portions at one end of a hollow pipe 50 made of metal or resin. A columnar elastic body 52 made of, for example, rubber is fitted into and fixed to these protrusions 51. These two protrusions 51 serve as a cored bar of the elastic body 52.

Further, assuming that the diameter of the stud bolt 47 is b, the distance a between the two elastic bodies 52 is set to a <b, and the side surfaces of the two elastic bodies 52 contact the stud bolt 47. In this state, the stud bolt 47 is sandwiched. Further, in the mounted state of the cylinder head R cover 45, the other end of the hollow pipe 50 of the rocker shaft plug 49 is brought into contact with the cylinder head R cover 45 in a pressed state, and at this time, the tip end portion of the elastic body 52 is at the exhaust side rocker shaft. It is provided so as to contact the end face of 38B. The end surface of the hollow pipe 50 on the side of the protruding portion 51 is formed as an arc surface 53, and the arc surface 53 is configured to separate from the stud bolt 47 when the rocker shaft plug 49 is mounted.

According to the above embodiment, the intake side rocker shaft 38A is elastically supported in the thrust (axial) direction by the elastic plug 46, while the exhaust side rocker shaft 3 is provided.
Since the end surface of 8B is elastically supported by the elastic body 52 of the rocker shaft plug 49, the intake rocker arm 27A
The vibration of the tappet sound transmitted from the exhaust rocker arm 27B to the intake side rocker shaft 38A and the exhaust side rocker shaft 38B is absorbed by the elastic body 52 of the elastic body plug 46 and the rocker shaft plug 49, and the cylinder head R cover 45. Transmission to the cylinder head 13 via the. Further, the side of the elastic body 52 of the rocker shaft plug 49 is attached to the stud bolt 47.
Vibration of the tappet sound transmitted from the intake side rocker shaft 38B to the stud bolt 47 is also absorbed by the elastic body 52 and is not transmitted to the cylinder head 13. For these reasons, it is possible to prevent the tappet sound generated at the initial stage of engine operation from being transmitted to the outside of the engine.

The rocker shaft plug 49 is fitted into the opening of the exhaust side rocker shaft insertion hole 37B with the elastic body 52 sandwiching the stud bolt 47, and is only pressed and held by the cylinder head R cover 45. If the cylinder head R cover 45 is removed, it can be easily attached and detached.

Further, the exhaust side rocker shaft insertion hole 37
Lubricating oil flows in B, and lubricating oil also flows around the stud bolt 47, but the rocker shaft plug 49
Since the pipe 50 is hollow and the arcuate surface 53 of the pipe 50 is mounted so as to be separated from the stud bolt 47 in the mounted state, the flow of the lubricating oil is not obstructed even by mounting the rocker shaft plug 49. ..

Further, in this embodiment, the elastic plug 4 is used.
6 and the rocker shaft plug 49 are newly manufactured, and the cylinder head R cover 45 is simply processed to correspond to the elastic body plug 46 and the rocker shaft plug 49. Therefore, the manufacturing process is easy and the existing car can be sold. Against the elastic body plug 46, rocker shaft plug 49
Also, it is sufficient to convert the cylinder head R cover 45, and the compatibility with already-sold vehicles is good.

In the above embodiment, the intake side rocker shaft 38A and the exhaust side rocker shaft 38B are inserted into the cylinder head 13 as a cylinder head member. However, a head cover is installed above the cylinder head. In this case, the head cover may be considered as a cylinder head member, and the intake side rocker shaft 38A and the exhaust side rocker shaft 38B may be inserted into the head cover. In this case, the pressing member is the elastic plug 46,
It may be a dedicated part for pressing and holding the rocker shaft plug 49.

[0030]

As described above, according to the rocker shaft mounting structure of the four-cycle engine according to the present invention, the rocker shaft insertion hole is formed in the cylinder head member mounted on the cylinder block, and the rocker shaft insertion hole is formed in the rocker shaft insertion hole. A rocker shaft supporting the rocker arm is inserted, and a stud bolt for fixing the cylinder head to the cylinder block is arranged in abutment with the rocker shaft. A rocker shaft plug having a portion formed therein and an elastic body fixed to the bifurcated portion is fitted, and the rear portion of the rocker shaft plug is pressed and held by the pressing member, and the elastic body is Since it is configured so that it can contact the stud bolt, the elastic body of the rocker shaft plug described above is Can absorb the vibrations more tappet sound, the tappet sound to the outside of the engine can be prevented from being transmitted.

[Brief description of drawings]

FIG. 1 is a sectional view taken along the line I-I in FIG. 5, showing an embodiment of a rocker shaft mounting structure for a 4-cycle engine according to the present invention.

FIG. 2 is a side view of a business bike type motorcycle equipped with the engine of FIG.

FIG. 3 is a side view of an engine to which the embodiment of FIG. 1 is applied.

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

5 is a cross-sectional view taken along the line VV of FIG.

FIG. 6 is a view on arrow VI of FIG.

7A is a perspective view of the rocker shaft plug of FIG. 1, FIG. 7B is a front view of the rocker shaft plug of FIG.
(C) is a side view of the rocker shaft plug of (A).

8 is a perspective view showing the elastic plug of FIG. 1. FIG.

[Explanation of symbols]

 3 4 cycle engine 11 cylinder block 13 cylinder head 21 intake valve 22 exhaust valve 26A intake cam 26B exhaust cam 27A intake rocker arm 27B exhaust rocker arm 37A intake side rocker shaft insertion hole 37B exhaust side rocker shaft insertion hole 38A intake side rocker shaft 38B exhaust side Rocker shaft 45 Cylinder head R cover 47 Stud bolt 49 Rocker shaft plug 50 Hollow pipe 51 Projection portion 52 Elastic body

Claims (1)

[Claims] 1. A rocker shaft insertion hole is formed in a cylinder head member mounted on a cylinder block, and a rocker shaft supporting a rocker arm is inserted through the rocker shaft insertion hole, and the cylinder head is fixed to the cylinder block. In a rocker shaft mounting structure for a four-cycle engine, in which a stud bolt is placed in contact with the rocker shaft, a forked portion is formed in the front portion at the opening of the rocker shaft insertion hole. A rocker shaft plug to which an elastic body is fixed is fitted, and the rear portion of the rocker shaft plug is pressed and held by a pressing member, and the elastic body is configured to come into contact with the rocker shaft and the stud bolt. A rocker shaft mounting structure for a 4-cycle engine, which is characterized in that