JPH0814059A - Soundproof structure of 4-cycle engine - Google Patents

Abstract

(57) [Summary] [Purpose] The noise generated by the cam chain is prevented from leaking to the outside to improve quietness, and the cam chain is prevented from falling into the crankcase when the cylinder head is removed, and maintainability is improved. Increase. [Structure] In a four-cycle engine 1 in which a cam chain chamber 21 through which a cam chain 19 for driving a cam shaft 15 passes is provided on one side of a cylinder assembly 3, a wall on the side opposite to the cylinder bore forming the cam chain chamber 21. A connecting member 26 for connecting the portion 24 and the wall portion 25 on the cylinder bore side is provided,
The connecting member 26 was arranged in the annular track of the cam chain 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproof structure for a 4-cycle engine in which noise generated by a cam chain for driving a camshaft is unlikely to leak to the outside.

[0002]

2. Description of the Related Art In a four-cycle engine other than an OHV engine, one or two cam shafts are rotatably supported by a cylinder head, and the rotation of this cam shaft activates a valve mechanism arranged in the cylinder head. It is supposed to do.

In many cases, the cam shaft is driven by a crank shaft via a cam chain. That is, since the driven sprocket is fixed to the cam shaft and the cam chain is wound between the driven sprocket and the drive sprocket provided on the crank shaft, the cam shaft rotates simultaneously with the rotation of the crank shaft.

Since the above-mentioned cam chain passes through the inside of the cylinder assembly and reaches the camshaft from the crankshaft,
The cylinder assembly has a cam chain chamber through which the cam chain passes.

In the case of an in-line cylinder type engine having four or more cylinders, the cam chain chamber is arranged between the second cylinder and the third cylinder, etc., so that noise generated when the cam chain runs is prevented from leaking to the outside. You can

[0006]

However, in the case of a single-cylinder engine, a two-cylinder engine, a V-type two- to four-cylinder engine, or the like, the cam chain chamber is provided on one side of the cylinder assembly, and therefore the cam chain chamber is provided. A part of the wall portion constituting the above, that is, the wall portion on the side opposite to the cylinder bore is adjacent to the outside, and this wall portion resonates with the noise of the cam chain and the noise easily leaks to the outside. There is a point.

Particularly in recent years, the wall thickness of the cylinder block and the cylinder head has been generally thinned in order to reduce the engine weight, and the wall portion constituting the cam chain chamber has also been thinned. Since the rigidity is lowered, the above problems are promoted.

The present invention has been made in order to solve the above problems, and provides a soundproof structure for a four-cycle engine capable of preventing noise generated by a cam chain from leaking to the outside and improving quietness. The purpose is to do.

Another object of the present invention is to prevent the cam chain from dropping into the crankcase at the time of removing the cylinder head to improve maintainability.

[0010]

In order to achieve the above object, in a soundproof structure for a four-cycle engine according to the present invention, a cam chain chamber through which a cam chain for driving a cam shaft passes is provided on one side of a cylinder assembly. In a four-cycle engine, a connecting member for connecting the wall portion on the side opposite to the cylinder bore and the wall portion on the side of the cylinder bore forming the cam chain chamber is provided, and the connecting member is arranged in the annular orbit of the cam chain. Is.

[0011]

According to the soundproof structure of the four-cycle engine having such a structure, the rigidity of the wall portion on the side opposite to the cylinder bore forming the cam chain chamber is significantly increased by the connecting member, and as a result, the side opposite the cylinder bore is formed. Since the wall portion of does not resonate with the noise of the cam chain, the noise of the cam chain is less likely to leak to the outside and the quietness is improved.

Further, since the connecting member is arranged in the ring-shaped orbit of the cam chain, the cam chain does not drop off to the crankcase side when the cylinder head is removed, and the maintainability is improved.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a structure 4 in which a soundproof structure according to the present invention is adopted.
It is a longitudinal cross-sectional view of a cycle engine. The four-cycle engine 1 is, for example, an in-line two-cylinder DOHC engine, and a cylinder assembly 3 is provided above a crankcase 2.
Is provided. The cylinder assembly 3 is constructed by sequentially mounting a cylinder block 4, a cylinder head 5, and a head cover 6 on a crankcase 2.

The cylinder block 4 has two cylinder bores 7 formed in parallel with each other, and the cylinder head 5 has a combustion chamber 8 aligned with the cylinder bore 7.
A piston 9 is slidably inserted in the cylinder bore 7.

On the other hand, a crankshaft is provided in the crankcase 2.
11 is rotatably supported, and the crankshaft 11 and the piston 9 are connected by a connecting rod 12. Therefore, the sliding of the piston 9 is converted into the rotation of the crankshaft 11. The rotation of the crankshaft 11 is transmitted to a transmission (not shown) via a drive gear 13 provided at one end of the crankshaft 11 and becomes an output of the 4-cycle engine 1. An alternator 14 that operates by the rotation of the crankshaft 11 is formed in the crankcase 2.

As shown in FIG. 2, two cam shafts 15 are rotatably supported in the cylinder head 5, and a plurality of cams 16 formed on the cam shaft 15 ... Activate the valve mechanism. A driven sprocket 17 is fixed to one end of the camshaft 15, while a drive sprocket 18 is provided on the crankshaft 11, and a cam chain 19 is wound between the driven sprocket 17 and the drive sprocket 18. There is. Therefore, simultaneously with the rotation of the crankshaft 11, the two camshafts 15 are driven, the valve operating mechanism operates, and the intake and exhaust strokes of the four-cycle engine 1 are repeated.

A cam chain chamber 21 for passing the cam chain 19 is provided on one side of the cylinder assembly 3. The cam chain chamber 21 is configured so that a lower cam chain chamber 21a provided on the cylinder block 4 side and an upper cam chain chamber 21b provided on the cylinder head 5 side communicate with each other to form one chamber. There is.

In the cam chain chamber 21, the cam chain 19
A chain guide 22 and a chain tensioner 23 that maintain the traveling path of the cam chain and adjust the tension of the cam chain 19 are provided.

As shown enlarged in FIGS. 3 and 4, for example, between the wall portion 24 on the side opposite to the cylinder bore and the wall portion 25 on the cylinder bore side of the cylinder head 5 constituting the upper cam chain chamber 21b. , Are connected by a connecting member 26.

For example, the connecting member 26 is formed in a flat plate shape, and fastening bosses 27 and 28 are integrally formed with the wall portion 24 on the side opposite to the cylinder bore and the wall portion 25 on the cylinder bore side.
Is fastened and fixed from above with four bolts 29. Then, as shown in FIG. 2, the connecting member 26 is arranged in the annular track of the cam chain 19.

When such a soundproof structure is provided, the wall portion 24 on the anti-cylinder bore side, which is thin and has low rigidity, is connected to the wall portion 25 on the cylinder bore side, which has high rigidity. The rigidity is greatly increased. Therefore, the wall portion 24 on the side opposite to the cylinder bore does not resonate with the noise of the cam chain 19, and the noise of the cam chain 19 does not easily leak to the outside, and the quietness of the 4-cycle engine 1 is improved.

Further, since the connecting member 26 is arranged in the annular track of the cam chain 19, the cam chain 19 does not drop into the crankcase 2 when the cylinder head 5 is removed, so that the maintainability is improved.

5 and 6 show second and third embodiments of the connecting member, respectively.

In the example of FIG. 5, a connecting member 31 having an intermediate portion bent in a substantially U-shape is fixed by a bolt 29 between the wall portion 24 on the side opposite to the cylinder bore and the wall portion 25 on the cylinder bore side. The side surface of this connecting member 31 and both wall portions 24 and 25
An elastic body 32 such as rubber is mounted between and.

Therefore, the elastic force of the elastic body 32 pushes the wall portion 24 on the side opposite to the cylinder bore and the wall portion 25 on the side closer to the cylinder bore in the direction of separating from each other, and the wall portion on the side opposite to the cylinder bore is pressed.
As a result, the rigidity of 24 is increased.

Further, in the example of FIG. 6, a connecting member 33 formed in a stepped bolt shape is provided so as to cross the upper cam chain chamber 21b. This connecting member 33 is a washer 34.
And a wall portion on the cylinder bore side through the wall portion 24 on the side opposite to the cylinder bore via an elastic ring 35 made of an elastic material such as rubber.
It is fastened to the screw 36 because it is provided at 25.

Therefore, due to the elasticity of the elastic ring 35, the wall portion 24 on the side opposite to the cylinder bore is moved to the wall portion on the cylinder bore side.
It is pressed toward 25, the rigidity of the wall portion 24 on the side opposite to the cylinder bore is increased, and the noise of the cam chain 19 does not resonate. This structure is very simple and can be constructed at low cost, and it is easy to add a connecting member 33 to an off-the-shelf engine later.

The shape and the connecting structure of the connecting members 26, 31, 33 are such that the wall portion 24 on the side opposite the cylinder bore and the wall portion 25 on the side closer to the cylinder bore are connected or the wall portion 24 on the side opposite the cylinder bore is elastic. Other structures may be used as long as they are pressed against.

Further, although the connecting members 26, 31, 33 are provided in the upper cam chain chamber 21b in this embodiment, they may be provided in the lower cam chain chamber 21a.

[0030]

As described above, the soundproof structure for a four-cycle engine according to the present invention is a four-cycle engine in which a cam chain chamber through which a cam chain for driving a cam shaft passes is provided on one side of a cylinder assembly. ,
A connecting member for connecting the wall portion on the side opposite to the cylinder bore and the wall portion on the side of the cylinder bore forming the cam chain chamber is provided, and the connecting member is arranged in the annular track of the cam chain.

Therefore, the rigidity of the wall portion on the side opposite to the cylinder bore forming the cam chain chamber is greatly increased by the connecting member, and the wall portion on the side opposite to the cylinder bore does not resonate with the noise of the cam chain. , The noise of the cam chain is less likely to leak to the outside, and the quietness is improved.

Further, since the connecting member is arranged in the annular orbit of the cam chain, the cam chain does not drop off to the crankcase side when the cylinder head is removed, and the maintainability is improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a 4-cycle engine in which a soundproof structure according to the present invention is adopted.

FIG. 2 is a vertical sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged view of a part III in FIG. 1, showing a first embodiment of the present invention.

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

FIG. 5 is a vertical sectional view showing a second embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 1 4-cycle engine 2 Crank case 3 Cylinder assembly 4 Cylinder block 5 Cylinder head 11 Crank shaft 15 Cam shaft 17 Driven sprocket 18 Drive sprocket 19 Cam chain 21 Cam chain chamber 24 Anti-cylinder bore side wall 25 Cylinder bore side wall 26, 31, 33 Connecting member 29 Bolt

Claims (1)

[Claims] 1. A four-cycle engine in which a cam chain chamber through which a cam chain for driving a cam shaft passes is provided on one side of a cylinder assembly, and a wall portion on the side opposite to the cylinder bore and the cylinder bore forming the cam chain chamber. A soundproof structure for a four-cycle engine, characterized in that a connecting member for connecting the side wall portion is provided, and the connecting member is arranged in an annular track of a cam chain.