JPS6218782B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine noise prevention device, and in particular to a device that reduces noise by absorbing collision noise generated in a gear transmission mechanism provided between a crankshaft and a primary shaft. Regarding.

Particularly, the engine of a motorcycle has a configuration in which a crankcase and a gear case are integrated, and power is transmitted from the crankshaft to the primary shaft by decelerating the power using gears.

In such an engine, when the gear mesh is set to the neutral position and the engine is idling, noise is likely to be generated in the gear portion. The reason for this is that collision noise is generated from the meshing surfaces due to the bumping of the gears due to fluctuations in the rotation of the crankshaft due to irregular combustion in the engine cylinders.

Conventionally, measures have been taken to prevent this type of noise, such as reducing bump crashes, increasing the accuracy of the center distance, or using helical gears, but none of these measures have been effective. The drawback was that it was expensive and its effectiveness was relatively small. In particular, two-stroke engines are more likely to generate noise than four-stroke engines, and there has been a strong demand for countermeasures against this problem.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned conventional drawbacks, and provides a device that has a simple structure and can reduce the noise of the primary reduction gear, especially the noise during idling.

That is, the engine noise prevention device according to the present invention is applied to a crankshaft in which power is transmitted from the crankshaft via a gear on a primary shaft, and includes the crankshaft and the gear attached to the crankshaft. a protrusion protruding radially outward on the crankshaft, a protrusion protruding radially inward on the gear on the crankshaft, and a protrusion protruding radially inward on the crankshaft; A resilient member is disposed between the protrusion of the crankshaft and the protrusion of the gear on the side in the rotation direction of the crankshaft, and a space is left behind the protrusion of the crankshaft on the side opposite to the rotation direction of the crankshaft. It is characterized by:

In this case, the elastic member is made of a rubber-like elastic material, and the driving side elastic member that transmits rotational force from the crankshaft to the gear is used as the driven side elastic member that transmits rotational force in the opposite direction. It is preferable to make the elastic member larger than the elastic member in order to improve the noise reduction effect and the durability of the elastic member.

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

FIG. 1 is a diagram showing the entire structure of a motorcycle engine and a driving force transmission mechanism suitable for implementing the present invention. The power generated by the explosion in the engine combustion chamber is transferred to the piston 12 and the connecting rod 14.
The signal is transmitted to the crankshaft 16 supported by the crankcase 15 through the shaft, and rotationally drives the crankshaft.

A dynamo (generator) is installed at one end of the crankshaft 16.
18 is attached, and a reduction pinion gear 20 is attached to the other end. A primary shaft 22 is arranged parallel to the crankshaft 16, and a large reduction gear 24 is rotatably mounted on the primary shaft (see FIG. 2) and meshes with the small reduction gear 20. On the other hand, a centrifugal clutch 2 is connected between the reduction gear 24 and the primary shaft 22.
6 is provided, and automatically connects and disconnects power transmission from the crankshaft 16 to the primary shaft 22 according to the crankshaft rotation speed. The rotational power transmitted to the primary shaft is transmitted to the shaft drive mechanism 32 via the bevel gear mechanisms 28 and 30. The shaft drive mechanism extends from the engine to the rear wheels 34 and drives the rear wheels via bevel gear mechanisms 36 and 38 provided at the rear end. In the illustrated example, a spring/screw type torque fluctuation buffer 40 is provided in the middle of the shaft drive mechanism 32. Also,
Reference number 42 indicates a kick drum for starting the engine, 44 indicates a sector with bevel teeth attached to the kick drum, and reference number 46 indicates a primary shaft 2.
2 shows a helical toothed sleeve rotatably and axially movably fitted on the gear 2, and 48 is the large reduction gear 2.
4 and rotates together. Bevel teeth are also formed on the outer periphery of the intermediate sleeve,
This is to operate the engine lubricating oil pump. When starting the engine, when the kick drum 42 and the sector 44 are rotated by a kick lever (not shown), the bevel-toothed sleeve 46 meshed therewith is rotated. Then, due to the axial thrust generated in the bevel toothed portion, the bevel toothed sleeve moves to the right in FIG. 1 and engages with the intermediate sleeve 48.
It becomes possible to transmit rotation. Therefore, in a difficult situation, the engine is started by rotating the crankshaft 16 through the large reduction gear and small gears 24 and 20 independently of the primary shaft 22, and after the engine has been started, the rotation of the large reduction gear 24 is started. It becomes separated and becomes free. The direction of transmission of rotation at this startup is from the large reduction gear 24 to the small reduction gear 20,
This is the opposite direction to the driving time described above.

The mounting structure of the reduction gear 20 will be explained below with reference to FIGS. 2 to 4.

Use the key 50 to attach the internal material 5 to the crankshaft 16.
2 is fixed. The internal member has a shape having a cylindrical boss portion 52A, a protruding portion 52B projecting in the radial direction, and an outer wall 52C, and is fixed by tightening with a nut 56 against the spacer 54 in the axial direction. . The reduction pinion gear 20 is fitted around the internal member 52 so as to be relatively movable in the rotational direction. The reduction gear has a concave portion open at the outer end surface, and there is a gap 58 between the stepped portion formed around the outer end surface and the stepped portion formed on the outer periphery of the wall 52C of the inner member 52, and between the inner inner diameter portion and the inner portion. It is supported on the inner member at a space 59 between the member 52 and the circumferential surface of the boss portion 52A. In this way, a substantially cylindrical sealed space 60 is defined between the recess of the pinion 20 and the internal member.
Note that a protrusion 20A is formed in the concave portion of the pinion 20 and protrudes radially inward, the tip of which is near the outer periphery of the boss portion 52A of the internal member 52, and the space 60 is connected to the driving side and the driven side. It can be divided into two sections.

Further, a disc-shaped disc spring 62 is provided between the internal member 52 and the spacer 54, and the inner diameter portion of the disc spring 62 is clamped between them. As shown in FIGS. 2 and 4, the outer periphery of the disc spring contacts the inner end surface of the small gear 20 and presses it axially outward with a predetermined force, and the friction force generated by the pressing force The relative peripheral speed between the crankshaft 16 and the small gear 20 is made small.

As shown in FIG. 3, within the sealed space 60, a resilient member made of a rubber-like elastic material is provided between the protrusion 52B of the internal member 52 and the protrusion 20A of the pinion 20. 64 and 66 are accommodated. If the crankshaft 16 rotates in the direction of the arrow X in FIG. large elastic member 6
4 is housed therein, and a relatively small resilient member 66 is housed in the space on the rear side in the rotational direction of the protrusion 52B of the internal member, that is, the space on the driven side.

Examples of the shape of the resilient member 64 on the drive side are shown in FIGS. 5 to 7. The resilient member is a space 60
It has a substantially rectangular cross section along the shape of an arc. However, at both ends thereof, stepped portions 64A, 64A as shown in FIG. 6 are provided to form a relief. This escape is from the crankshaft 16 to the pinion 2.
This is to prevent the resilient member from getting caught in the gap between the small gear 20 and the internal member 52 when the resilient member 64 undergoes compressive deformation when the driving torque is transmitted to the gear.

The resilient member 66 on the driven side has a size as shown in FIG. 3, and a predetermined gap is left in the space 60. By leaving a predetermined gap in the space 60 in this way, fluctuations in the rotation of the crankshaft during engine operation are absorbed by the elastic member in the forward rotation direction and by the gap in the reverse rotation direction.
This eliminates rattling in the meshing between the gear 24 and the gear 24, and improves the noise prevention device.

This point will be explained in more detail as follows. That is, the engine driving force is transmitted from the crankshaft 16 to the large reduction gear 24 via the small reduction gear 20.
When power is being transmitted, the drive-side tooth surface of the small gear 20 contacts the tooth surface of the large gear 24, thereby transmitting power. Here, if rotational fluctuations occur due to irregular combustion during engine idling, the crankshaft will have a
This will cause movement in the opposite rotational direction. If the protrusion 5 of the internal member 52 on the engine crankshaft 16
If there is no space 60 between 2B and the pinion 20, the above-mentioned reverse rotation of the crankshaft will cause the pinion 20 to
, the small gear 20 is displaced in the reverse rotation direction by the amount of the meshing crush with the large gear 24,
The drive side tooth flank will be separated from the tooth flank of the large gear. Then, during the next forward rotation, the driving side tooth surface of the small gear 20 comes into contact with the tooth surface of the large gear 24 again. Gear noise is generated by such repetition of separation and contact.

In the present invention, as described above, the protrusion 52
Since the space 60 is provided between B and the driven side elastic member 66, even if the crankshaft reversely rotates as described above, the reverse rotation is not transmitted to the pinion 20 and the driving side elastic member 66 Reverse rotation is absorbed by the generating member 64. Therefore, the drive side tooth surface of the small gear 20 does not separate from the tooth surface of the large gear 24, and is always maintained in a state of contact. Therefore, it is possible to reliably prevent gear noise from occurring due to rotational fluctuations during engine idling.

Since the engine noise prevention device of the present invention has the configuration described above, rotational fluctuations of the crankshaft can be absorbed by the elastic member, and therefore, the meshing of the primary reduction gear occurs after the rotational fluctuations are absorbed. The engine noise caused by the rotational fluctuation can be effectively reduced. In particular, it is effective in reducing noise caused by rotational fluctuations due to irregular combustion during idling operation in a neutral state. Further, it is possible to exhibit a particularly large effect on a two-stroke engine that has relatively large rotational fluctuations.

Furthermore, when using a member made of a rubber-like elastic material as the elastic member, the elastic member on the driving side, in the direction in which the rotational force of the primary reduction gear is transmitted from the crankshaft, is made larger than the elastic member on the driven side. This makes it possible to ensure the strength and durability of the resilient member on the driving side.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the main parts of an engine and power transmission mechanism suitable for using the noise prevention device of the present invention, and FIG. 2 is a sectional view showing the structure of the noise prevention device and primary reduction gear of the present invention. FIG. 4 is a cross-sectional view taken along the line - in FIG. 3 for the noise prevention device. Figure 3 is a sectional view taken along line - in Figure 2, Figure 4 is a sectional view taken along line - in Figure 3, Figure 5 is a front view of the resilient member, and Figure 6 is a sectional view taken along line - in Figure 2. The side view of the generating member, FIG. 7, is a sectional view taken along the line - in FIG. In each figure, the same reference numbers indicate the same parts, 16...crankshaft, 20...reduction small gear, 22...primary shaft, 24...reduction large gear, 52...
...Internal material, 52A...Boss part of internal material, 52B
...Protrusion of internal material, 52C...Wall of internal material, 5
8, 59... Reduction small gear support, 60... Sealed space, 62... Belleville spring, 64, 66... Resilient member, respectively.

Claims (1)

[Claims] 1. In an engine in which power is transmitted from a crankshaft to a gear on a primary shaft, a protrusion that protrudes radially outward from the crankshaft is provided between the crankshaft and the gear attached to the crankshaft. The gears on the crankshaft are each formed with a protrusion that protrudes inward in the radial direction, and the protrusion on the crankshaft and the protrusion on the gear are arranged on the crankshaft rotation direction side of the protrusion on the crankshaft. 2. A noise prevention device for an engine, characterized in that a resilient member is disposed between the protruding portion of the crankshaft and a space is left on a side opposite to the rotational direction of the crankshaft.