JP3293072B2 - Drum brake for unit swing type engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drum brake for a unit swing type engine used for a scooter.
In particular, the present invention relates to a support structure for an operation cam for expanding a brake shoe.

[0002]

2. Description of the Related Art Conventionally, in a drum brake used for a unit swing type engine, a brake drum is formed on a hub portion of a rear wheel, and a brake shoe facing the drum is supported on a transmission case side.

[0003] The brake shoe has a pivot base pivotally attached to a fulcrum pin erected on a transmission case, and a pivot end is engaged with an operation cam. This operating cam is usually formed by providing a cam portion at one end of a shaft portion, and the shaft portion is rotatably supported by the transmission case. The operating cam had a shaft end opposite to the cam portion of the shaft portion connected to an operating mechanism including a brake lever, a brake wire, and the like.

The opening of the brake drum is covered with a drum-side wall of the transmission case so that water and dust do not easily enter, and the shaft portion of the operation cam is supported by the wall. In addition, since the transmission case is formed with the minimum thickness necessary to reduce the weight,
A portion of the wall on the drum side which does not require rigidity is formed in a relatively thin plate shape. That is, the bearing is configured by forming the periphery of the through hole thicker than the other portion in the working cam through portion of the transmission case.

[0005]

However, the conventional drum brake constructed as described above has a problem that a brake sound (brake squeal) is generated.

[0006] The brake noise vibrates when the brake lining comes into sliding contact with the brake drum, and the vibration is often transmitted to the transmission case, causing the transmission case to vibrate. Vibration is transmitted to the transmission case via a fulcrum pin and an operation cam, and the supporting portion of the fulcrum pin is located inside the transmission case and at a position closer to the longitudinal center of the transmission case. Therefore, the vibration transmitted through the fulcrum pin hardly generates the brake sound. That is,
Vibration is transmitted to the transmission case via an operation cam firmly supported on the outer portion of the transmission case, and a relatively thin wall portion located near the operation cam support portion vibrates to generate a brake noise. Since the operation mechanism must be connected to the operation cam, it cannot be housed in the transmission case like the fulcrum pin described above.

If the thin wall portion of the brake drum side is formed thick to increase the rigidity of the portion, the vibration becomes difficult and the brake noise is reduced. However, in this case, the weight of the transmission case increases, The unsprung weight increases, which is not preferable. In addition, in this case, the rear portion of the transmission case projects in the vehicle width direction, and the size of the transmission case increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to reduce the brake noise without making the transmission case heavy or large.

[0009]

A drum brake for a unit swing type engine according to the present invention is provided with a brake drum on a rear wheel rotatably supported at the rear end of a transmission case extending rearward from the engine. A pair of brake shoes facing the inside of the brake drum are supported on a rear end side wall of the transmission case via a fulcrum pin and an operation cam, and the operation cam opposes a spring in which the pair of brake shoes are elastically mounted between the brake shoes. In a unit swing type engine drum brake that pushes and spreads to brake a rear wheel, a reduction gear chamber having a side wall that covers an opening of a brake drum is formed at a rear portion of the transmission case, and a bearing is provided on the side wall via a bearing. The rear axle is rotatably supported,
The operating cam is formed from a cam portion that engages with a brake shoe and a shaft portion that is formed integrally with the cam portion and penetrates the side wall, and the operating cam is formed by a portion that supports a rear wheel axle on the side wall. Two peripheral grooves in which a ring made of an elastic material is fitted around an outer peripheral portion of the shaft portion so as to be rotatably supported by a drum cover portion extending to the rear side, and a position between the peripheral grooves. An oil groove into which oil is injected, and an operating cam is elastically supported on the drum cover by a ring made of an elastic material fitted into the peripheral groove. It is formed substantially at the same position in the axial direction as the rear axle support bearing when mounted on the cover.

[0010]

The vibration transmitted from the operation cam to the transmission case is attenuated by the ring made of the elastic material. Further, leakage of oil lubricating between the shaft portion of the operation cam and the transmission case can be prevented by the ring made of the elastic material. Further, the side wall of the transmission case has a relatively high rigidity at a portion for holding the bearing for supporting the axle, and supports the operation cam near a portion where the rigidity is high and the vibration is hard to occur.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. 1 is a side view of a scooter equipped with a drum brake according to the present invention, FIG. 2 is a cross-sectional view taken along line II-II of the drum brake portion in FIG. 1, FIG. 3 is a cross-sectional view taken along line III-III of the transmission case in FIG. FIG. 4 is a plan view showing the mounted state of the operation cam.

In these figures, 1 is a scooter and 2 is a power unit of the scooter 1. The power unit 2 is a well-known unit swing type engine in which an engine 4 is provided at a front portion of a transmission case 3 and a rear wheel 5 is provided at a rear portion.
Is provided. The transmission case 3 has a front portion supported on a vehicle body frame side bracket 6 via a pivot shaft 7 so as to be vertically swingable, and a rear portion connected to a vehicle body frame (not shown) via a rear cushion unit 8. I have. In FIG. 1, reference numeral 9 denotes a vaporizer, and 10 denotes an air cleaner case.

The transmission case 3 is divided in the left-right direction of the vehicle body so as to incorporate a V-belt type power transmission device, and as shown in FIG. A drum brake 12 is mounted on a rear portion of the drum brake 11. At the rear of the right transmission case 11, a V (not shown)
A pulley chamber 11a in which the rear pulley of the belt-type power transmission device is arranged, and a reduction gear chamber 11b in which the shaft end of the rear wheel shaft 13 faces.
Are formed. A gear-type speed reducer 14 that connects the rear wheel shaft 13 and the shaft of the rear pulley is arranged in the speed reducer chamber 11b.

The rear wheel axle 13 is supported by a side wall 11c of a reduction gear chamber 11b via a bearing 15, and a hub 16 of the rear wheel 5 is serrated into a portion protruding from the right transmission case 11 to the right side of the vehicle body. I have.

The drum brake 12 is mounted on the right transmission case 1
1, a fulcrum pin 17 and an operating cam 18, brake shoes 19 and 19 connected to the distal ends of the fulcrum pin 17 and the operating cam 18, and a brake lining 20 fixed to each brake shoe 19. , Brake shoe 1
Return pulling 21 between 9 and 19
And a brake drum 22 and the like provided on the hub 16. Since the main structure of the drum brake 12 is the same as that of the conventional drum brake, detailed description of members not related to the present invention is omitted.

The fulcrum pin 17 penetrates through the side wall 11c and is fixed to the side wall 11c.
Brake shoes 19, 19
Is pivotally attached to the robot. As shown in FIGS. 2 and 4, the operating cam 18 includes a cam portion 18a that engages with the brake shoe 19 and a shaft portion 18b formed integrally with the cam portion 18a. And is rotatably supported by the right transmission case 11. The shaft portion 18b of the operation cam 18
A conventionally known operation mechanism 24 that turns the operation cam 18 by operating the brake lever 23 shown in FIG.

The side wall 11c is connected to the brake drum 2
2, the rear wheel axle 13 and the fulcrum pin 1
7, a part which becomes a substantial wall of the reduction gear chamber 11b,
Drum cover part 11d extended to the rear side from that part
And is formed from The operation cam 18 is supported by the drum cover 11d. That is,
The operation cam 18 is disposed so as to be located behind the rear wheel shaft 13 and behind the vehicle body. Further, as shown in FIG. 2, the side wall 11c is formed with a boss for holding the outer ring of the bearing 15, and is formed so that the rigidity of the portion supporting the rear axle 13 is relatively high. The structure for supporting the operation cam 18 is such that the periphery of the operation cam through hole in the drum cover portion 11d is made thicker than other portions to form the boss portion 25, and the shaft portion 18b of the operation cam 18 is fitted into the boss portion 25. It is a structure to make it. The portion other than the boss portion 25 in the drum cover 11d is formed in a relatively thin plate shape so as not to require rigidity, thereby reducing the weight. Conventionally, the plate portion vibrates to generate a brake sound.

An O-ring 27 fitted in the circumferential groove 26 of the shaft portion 18b is interposed between the boss 25 and the shaft portion 18b. By interposing the O-ring 27 between the boss portion 25 and the shaft portion 18b in this manner, a minute gap is formed between the outer peripheral surface of the shaft portion 18b and the hole wall surface of the boss portion 25. The boss portion 25 is elastically supported. As shown in FIG. 2, the peripheral groove 26 is formed at substantially the same position in the axial direction as the rear axle support bearing 15 with the operation cam 18 mounted on the drum cover 11d.

The peripheral groove 26 and the O-ring 27
Are located on both sides of the grease groove 28 formed in the shaft portion 18b. For this reason, in the present embodiment, the grease groove 2
The grease (not shown) injected into 8 is sealed in the boss 25 by the O-ring 27. The grease groove 28
Constitute the oil groove according to the present invention.

The drum brake 12 constructed as described above
By operating the brake lever 23, the operating cam 18 is turned, and the two brake shoes 19 are pushed apart to be braked. Then, when braking, the brake shoe 1
9 vibrates, the operation cam 1 together with the brake shoe 19
8 also vibrates, but the vibration of the operation cam 18 is caused by the O-ring 27 made of an elastic material interposed between the operation cam 18 and the right transmission case 11.
And the transmission to the right transmission case 11 becomes difficult.

Therefore, when the drum brake 12 according to the present invention is used, the thin plate portion of the right transmission case 11 (the portion other than the boss portion 25 in the drum cover portion 11d) hardly vibrates. In particular, the two peripheral grooves 26, 26 into which the O-rings 27 are fitted, the operation cam 18 and the drum cover 1
1d, the rear axle support bearing 15 is formed so as to be located at substantially the same position in the axial direction of the rear axle support bearing 15. Therefore, the vicinity of the portion of the side wall 11c of the transmission case 11 that holds the bearing 15, that is, the rigidity is low. The operation cam 18 can be supported in the vicinity of a portion that is relatively high and hardly vibrates. Therefore, it is possible to reliably prevent the vibration of the brake shoe 19 from being transmitted to the transmission case 11 via the operation cam 18. Also, the shaft portion 18b of the operation cam 18
The O-ring 27 can prevent the grease lubricating between the O-ring 27 and the boss portion 25 of the right transmission case 11 from leaking. That is, since the O-ring 27 has a function of reducing the braking sound and a function of sealing the lubricated portion of the operation cam 18, the two functions can be realized with a small number of parts. Moreover, the O-ring 27 is provided on the shaft portion 18b, which has less impact than the cam portion 18a that repeatedly rubs and hits with the brake shoe 19, so that the durability of the O-ring 27 can be improved. . Further, two circumferential grooves 26 and a grease groove 28 are formed on the outer peripheral portion of the shaft portion 18b of the operation cam 18.
Are formed in a concentrated manner, so that these grooves are formed with the hole wall surface of the through hole formed in the right transmission case 11 and the shaft portion 1.
8b, and the manufacturing cost can be reduced as compared with a structure in which it is dispersed on the hole 8b or on the hole wall side. Furthermore, the support portion of the fulcrum pin 17 is located at a position near the center in the longitudinal direction of the right transmission case 11, and the O-ring 27 is mounted only on the operation cam 18 supported on the outer portion of the right transmission case 11. The braking noise can be efficiently reduced.

[0022]

As described above, in the unit-swing type engine drum brake according to the present invention, the brake drum is provided on the rear wheel rotatably supported at the rear end of the transmission case extending rearward from the engine. A pair of brake shoes facing the inside of the brake drum are supported on a rear end side wall of the transmission case via a fulcrum pin and an operation cam, and the operation cam forms a spring in which the pair of brake shoes are elastically mounted between the brake shoes. In a unit swing type engine drum brake that pushes apart and brakes a rear wheel, a speed reducer chamber having a side wall that covers an opening of a brake drum is formed at a rear portion of the transmission case,
A rear wheel shaft is rotatably supported on the side wall via a bearing, and the operating cam is formed of a cam portion that engages with a brake shoe and a shaft portion that is formed integrally with the cam portion and penetrates the side wall. At the same time, the operating cam is rotatably supported by a drum cover portion extending rearward from a portion of the side wall supporting the rear wheel axle, and a ring made of an elastic material is fitted into an outer peripheral portion of the shaft portion. Forming two peripheral grooves, and an oil groove positioned between these peripheral grooves, into which oil is injected. The operating cam is formed by a ring made of an elastic material fitted into the peripheral grooves. The two peripheral grooves are formed at substantially the same position in the axial direction as the rear axle support bearing in a state where the operating cam is mounted on the drum cover, so that the two peripheral grooves are formed from the operating cam to the transmission case. Transmitted vibration There is attenuated by a ring made of the elastic material.

Accordingly, the thin plate portion of the transmission case can be made hard to vibrate without increasing the rigidity, so that the transmission case can be reduced in weight and size, and the brake noise can be reduced. In particular, the side wall of the transmission case has a relatively high rigidity in a portion for holding the rear axle support bearing, and supports the operation cam in the vicinity of a portion where the rigidity is high and the vibration is difficult. Vibration of the brake shoe can be reliably prevented from being transmitted to the transmission case. Further, leakage of oil lubricating between the shaft portion of the operation cam and the boss portion for supporting the operation cam of the transmission case can be prevented by the ring made of the elastic material. That is, since the ring has a function of reducing the brake noise and a function of sealing the lubricated portion of the operation cam, the two functions can be realized with a small number of parts. Moreover, the ring is provided on the shaft portion that has less impact than the cam portion that is repeatedly rubbed and hit by the brake shoe, so that the durability can be improved. Furthermore, since two peripheral grooves and an oil groove are formed in a concentrated manner on the outer peripheral portion of the shaft portion of the operation cam, these grooves are formed on the wall surface of the through hole formed in the transmission case and the shaft portion. The manufacturing is simpler and the manufacturing cost can be reduced as compared with a structure in which the holes are formed on the hole wall side. Furthermore, the support portion of the fulcrum pin is located at a position near the center in the longitudinal direction of the transmission case, and a ring made of an elastic material may be mounted only on the operation cam supported on the outer portion of the transmission case. The braking noise can be reduced efficiently.

[Brief description of the drawings]

FIG. 1 is a side view of a scooter equipped with a drum brake according to the present invention.

FIG. 2 is a sectional view taken along line II-II of a drum brake portion in FIG.

FIG. 3 is a sectional view taken along line III-III of the transmission case in FIG. 2;

FIG. 4 is a plan view showing a mounted state of an operation cam.

[Explanation of symbols]

 Reference Signs List 1 scooter 2 power unit 3 transmission case 4 engine 5 rear wheel 11 right transmission case 11d drum cover 12 drum brake 17 fulcrum pin 18 operating cam 18b shaft portion 19 brake shoe 22 brake drum 25 boss 27 O-ring

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-67335 (JP, A) JP-A-2-204190 (JP, A) Fully open 1-36294 (JP, U) Really open 1948 49728 (JP, U) Fully open 1986-116241 (JP, U) Fully open, 54-165439 (JP, U) Fully open, 62-69638 (JP, U) Fully open, 62-69637 (JP, U) Shokai 56-153629 (JP, U) Shogun 52-18385 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16D 49/00-69/04

Claims (1)

(57) [Claims] A brake drum is provided on a rear wheel rotatably supported at a rear end portion of a transmission case extending rearward from an engine, and a pair of brake shoes facing the inside of the brake drum is provided at a rear end side wall of the transmission case. A unit swing type drum brake for supporting the rear wheels by spreading the pair of brake shoes against a spring elastically mounted between the brake shoes by the operating cam and supporting the rear wheels by a fulcrum pin and an operation cam. , The transmission
At the rear of the case, cover the side wall that covers the opening of the brake drum.
Forming a reduction gear room having
By rotatably supporting the rear wheel axle, the actuating cam, and a cam portion in contact engagement with the brake shoe, while formed from the cam portion and is formed integrally with the shaft portion extending through the sidewall, wherein the actuating cam Supports rear wheel axle on side wall
The outer peripheral portion of the shaft portion is rotatably supported on a drum cover portion extending rearward from a portion to be rotated, and two peripheral grooves into which a ring made of an elastic material is fitted. An oil groove into which oil is injected is formed between the two circumferential grooves; an operating cam is elastically supported by the drum cover by a ring made of an elastic material fitted into the circumferential groove;
After the operation cam is attached to the drum cover,
It is formed at substantially the same position in the axial direction as the axle support bearing.
The unit swing type drum brake for an engine, characterized in that that.