JPH0454347A - Balancer for engine - Google Patents

Abstract

PURPOSE:To reduce a highly accurate machining portion of a balancer shaft without deteriorating a balancer function by absorbing an eccentric amount in an eccentric portion by means of a dog having a backlash in the radial direction so as to connect a gear to a balancer weight. CONSTITUTION:In a balancer shaft 13, an eccentric portion 17, where a balancer driven gear 16 is engaged In a small range, continuous to a shaft portion 15 insertingly supported on a crank case 14 is formed coaxially with a shaft portion 20, with which a boss portion 19 of a balancer weight 18 is engaged. The gear 16 is connected to the weight 18 via a dog mechanism 26. Accordingly, rotation of the balancer shaft 13 by loosening a bolt 37 of a clamp 36 allows the axial center of the gear 16 to be deviated so that a backlash of engagement of the balancer driven gear 16 with a balancer drive gear 23 can be adjusted. In this case, the dog mechanism 26 has a backlash in the radial direction, thus realizing adjustment without difficulty.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an engine balancer device.

(Prior Art) In engines such as motorcycles, backlash of gears is adjusted at a bearing portion of a secondary balancer in order to reduce gear meshing noise.

Conventionally, the adjustment structure is as shown in Fig. 5.
A portion of the balancer shaft 1 supported by the crankcase 2 of the engine is used as a stepped eccentric shaft 3, and the boss portion 5 of the balancer weight 4 is fitted to this eccentric shaft 3 via a needle roller bearing 6.7. A balancer driven gear 8 is fitted on the outer periphery of the balancer weight 5, and the boss portion 5 of the balancer weight 4 and the gear 8 are connected to each other with a rubber damper 9.9 having the same shape interposed between the facing surfaces. The eccentricity δ of the eccentric shaft 3 is 0 with respect to the axial center of the balancer shaft 1.
．． It is said to be about 3 mm.

Therefore, the backlash between the balancer driven gear 8 and the balancer drive gear 10 meshed with it is adjusted by rotating the balancer shaft 1 and adjusting the eccentricity of the eccentric shaft 3. The clamp 11 is fastened with a bolt (not shown), and the clamp 11 is fixed to the crankcase 2 with a bolt 12. By tightening the bolt 12 of this clamp 11, the balancer shaft 1 can be positioned and fixed, eliminating backlash.

(Problem to be Solved by the Invention) By the way, on the eccentric shaft 3 of the balancer shaft 1, a needle roller bearing 6.7 with high rotation and high load slides.
A polished carburized material is used, but this polished part requires high precision and covers the entire length of the boss portion 5 of the balancer weight 4, making it difficult to process and expensive. There was a problem with becoming.

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine balancer device that can reduce the number of high-precision machined parts of the balancer shaft without impairing the balancer function, is easy to machine, and can be obtained at low cost.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in this invention, a gear is fitted to an eccentric portion of a balancer shaft via a bearing, and a gear is fitted to an eccentric portion of a balancer shaft via a bearing, and a gear is fitted to an eccentric portion of a balancer shaft via a bearing. The gears and the balancer weight are connected to each other by absorbing the amount of eccentricity of the eccentric portion by means of a dog having play in the radial direction.

(Function) Since the eccentric part of the balancer shaft is only the part where the gear fits, the range for precision finishing is narrowed, making it easy to perform high precision machining and extending the service life of the bearing. The noise generated by the bearings is also reduced. Further, even if the backlash of the gear is adjusted, it is absorbed by the play of the dog with the balancer weight, so the adjustment can be made without any problem.

(Example) Examples of the present invention will be described below with reference to FIGS. 1 to 4.

As shown in FIG. 1, the balancer shaft 13 has a shaft portion 15 that is inserted through and supported by the crankcase 14, and a short eccentric portion 17 in which the balancer driven gear 16 is fitted is partially formed. Following the portion 17, a shaft portion 20 into which the boss portion 19 of the balancer weight 18 is fitted is formed concentrically with the shaft portion 15. The above eccentric part 1
The amount of eccentricity of 7 is, for example, about 0.3W.

A balancer driven gear 16 is fitted into the eccentric portion 17 via a needle roller bearing 21, and this driven gear 16 is connected to the crank portion 22 of the crankshaft 22.
It meshes with a drive gear 23 formed at a. Further, a balancer weight 18 is fitted to the shaft portion 20 via a needle roller bearing 24, and the balancer driven gear 16 and the balancer weight 18 are coupled via a dog mechanism 26. This dog mechanism 2
6 is an exploded view in Fig. 3, and Fig. 4 shows the I of Fig. 1.
As shown in the cross-sectional view taken along the line V-IV, a plurality of dogs 2 (in the illustrated embodiment, three in equal distribution chambers) are provided on the outer periphery of the ring portion 28 that protrudes around the shaft hole 27 of the balancer driven gear 16.
9, 29, 29 protrude in the radial direction, and a recess 30 is formed on the balancer weight 18 side to receive the ring portion 28 including the dogs 29, 29, 29. The same number of dogs 31, 31.31 as the dogs 29, 29.29 are provided protrudingly.

When the ring portion 28 and the recess 30 are fitted together, a rubber damper 33 of the same shape is provided between each dog 29 and 31.
A plurality of, for example, six, 33... are interposed. The height of the dogs 29, 29.29 on the outer periphery of the ring portion 28 is set to have a clearance (play) equal to or greater than the eccentricity of the eccentric portion 17 with respect to the inner peripheral surface of the recess 28. There is.

Note that the ring portion 28 and its dog 29°29.
29 is provided on the balancer weight 18 side, and the recess 30 and its dogs 31, 31.31 are provided on the balancer driven gear 1.
It goes without saying that it may be provided at 6. That is, the uneven shapes of the dogs on the balancer driven gear side and the balancer weight side may be configured in the opposite manner and may be the same as in the conventional case.

The balancer shaft 13 is fixed in the same way as in the prior art, as shown in FIG.
This is done by tightening at 7.

Therefore, in order to adjust the backlash of the meshing between the balancer driven gear 16 and the balancer drive gear 23, loosen the bolt 37 of the clamp 36 and rotate the balancer shaft 13. The center position of the driven gear 1G is deviated due to the eccentricity of the eccentric portion 17, and the distance between the center and the balancer drive gear 23 changes, so that backlash can be adjusted. During this adjustment, the dogs 29 and 31 have play in the radial direction, so
The above adjustments are made without any problems.

〔Effect of the invention〕

As described above, according to the present invention, since the eccentric part formed on the balancer shaft only needs to be in a short range where the balancer gear is fitted, the range of eccentric machining is significantly smaller than in the conventional structure, and highly accurate machining is possible. can. Furthermore, since the eccentric portion is shortened, the durability of the needle roller bearing is improved, and the mechanical noise generated from the needle roller bearing is also reduced.

[Brief explanation of drawings]

1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a view taken in the direction of arrow A in FIG. 1, FIG. 3 is an exploded view of the balancer driven gear, rubber damper, and balancer weight in FIG. 1, and FIG. The figure is a sectional view taken along the line IV--IV in FIG. 1, and FIGS. 5 to 7 are sectional views showing the conventional technology. 1.13... Balancer shaft, 2.14... Crank case, 4.18... Balancer weight, 8゜1
6... Balancer driven gear, 10.23... Balancer drive gear, 17... Eccentric part, 26... Dog mechanism, 29.31... Dog, 33... Rubber damper. 8 Applicant's agent Hisashi Hatano Figure 2 Figure 4

Claims (1)

[Claims] A gear is fitted to an eccentric part of a balancer shaft via a bearing, a balancer weight is fitted to an axial part concentric with the balancer shaft via a bearing, and these gears and balancer weight are connected to a dog having play in the radial direction. A balancer device for an engine, wherein the eccentricity of the eccentric portion is absorbed and combined.