JPS6118264Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of an automatic braking gap adjustment device for a mechanical drum brake, in which a clutch spring is wound around a camshaft so that only the rotational force in the direction of braking movement of the brake arm is transmitted. An adjustment gear having a range formed on the outer periphery that compensates the gear part up to the lining wear limit is fixed to the camshaft, and the tip claw of the gear stopper is engaged with the gear part, and the other end is fixed to the brake panel to perform the braking action of the adjustment gear. The purpose of this is to automatically adjust the braking gap to the lining wear limit, and when the wear limit is exceeded, the braking gap is not compensated for and the braking gap is not compensated for. The idea is to increase the stroke of the brake lever or brake pedal to notify the driver that it is time to replace the lining.

The present invention will be explained below based on an illustrated embodiment.

Reference numeral 1 designates a brake panel, and its outer surface has a brake operation wire attachment portion 2, a speedometer cable attachment portion 3, a groove 4 that engages with a protrusion (not shown) formed on a part of the vehicle body that receives brake torque, and the like. It is formed.

Reference numerals 5 and 5' designate a pair of brake shoes whose base ends 5a and 5'a are pivotally supported on the inner surface of the brake panel 1 by anchor pins 6. 7 and 7' are linings fixed to the brake shoes 5 and 5', and 8 is a roughly U-shaped shaft whose middle part is wrapped around the anchor pin 6 and both ends are locked to the brake shoes 5 and 5'. U return spring, 9, 9' is brake shoe 5,
These are retainers provided at the free ends 5b and 5'b of 5', respectively.

10 is the free end 5b of the brake shoe 5, 5',
The cam shaft 10a is rotatably penetrated through the brake panel 1 by a cam inserted between the free ends 5'b and 5'b.
b, 5'b are pressed against the cam 10 by a shew return spring 8 via retainers 9, 9'.

A brake arm 11 is loosely inserted into a camshaft 10a that protrudes outside the brake panel 1. A bushing 12 is interposed between the brake arm 11 and the camshaft 10a, which is inserted into the camshaft 10a through a washer 13 and a spring washer 14. A nut 15 is fastened to a threaded portion 10b formed at the outer end, and is rotatably provided on the camshaft 10a.

16 is a clutch spring, one end of which is fixed to the brake arm 11;
It is wound around the camshaft 10a so that only the rotational force in the first braking action direction is transmitted to the camshaft 10a.

17 is an adjustment gear made of resin, and a protrusion 17a formed in the axial direction on the inner circumference is attached to the brake panel 1.
The camshaft 10a is fixed to the camshaft 10a by fitting into a groove 10c formed in the axial direction on the outer periphery of the camshaft 10a that protrudes outward. 18 is the outer peripheral portion 17 of the adjustment gear 17
The gear part formed in b is formed in a part of the outer peripheral part 17b (in the illustrated embodiment, within a range of about 45 degrees as shown in FIG. 5) so as to compensate up to the wear limit of the linings 7 and 7'. . 19 has one end 19a fixed to the brake panel 1, and the tip claw part 19b attached to the gear part 1.
The gear stopper is a gear stopper that engages with the adjustment gear 17 and allows the adjustment gear 17 to rotate only in the direction of the braking action. The tooth gets over one tooth of the gear part 18, and when the brake is released, the tooth that got over is caught by the claw part 19b, and the camshaft 1
The return of 0a is reduced by one tooth, and the brake shoes 5, 5' are expanded by that amount to adjust the gap between the linings 7, 7' and the drum brake (not shown), and the linings 7, 7' If the wear exceeds the wear limit, the pawl portion 19b slides against the outer peripheral portion 17b of the adjustment gear 17, and the braking gap is not adjusted.
Brake stroke increases.

A brake operating wire 20 has a brake lever or brake pedal (not shown) at one end, and the other end is attached to the tip of the brake arm 11. Reference numeral 21 denotes a case for the brake operating wire 20, which is attached to the brake operating wire attachment portion 2 with an adjustment bolt 22 and a nut 23.

24 is wrapped around the brake operation wire 20 and connected to the brake operation wire attachment part 2 and the brake arm 11.
A brake arm return spring is contracted between the tips of the brake arm 11 so that the brake arm 11 returns to its initial return position even after adjusting the braking gap.

Next, the operation of the above embodiment will be explained.

When braking is performed by operating the brake lever or brake pedal, the brake arm 11 is rotated in the direction of arrow A by the brake operation wire 20, and the camshaft 10a is rotated counterclockwise in FIG. 5 by the action of the clutch spring 16. rotate in the direction,
At the same time, the cam 10 also rotates, the free ends 5b, 5'b of the brake shoes 5, 5' are opened, the brake shoes 5, 5' are expanded, and the linings 7, 7' are pressed against the brake drum. Perform braking.

When the brake is released, the brake shoes 5, 5' are returned by the shoe return spring 8, the cam 10 and the camshaft 10a are also returned, and the brake arm 11 is also returned by the brake arm return spring 24. Rotates in the direction of arrow B and returns to the initial position.

When the linings 7, 7' wear out due to the braking action, the rotation angle of the camshaft 10a and the adjustment gear 17 increases, and when the linings 7, 7' wear out more than a certain amount, one tooth of the gear part 18 of the adjustment gear 17 becomes the pawl of the gear stopper 19. After getting over the part 19b, the pawl part 19b engages with the next tooth, and when the braking action is released, the camshaft 10a returns to its original position by the shoe return spring 8, but since the pawl part 19b has gone over one tooth, the pawl part 19b engages with the next tooth. Only cam 1 does not return to the initial position.
0 stopped slightly tilted, and brake shoes 5, 5'
The free ends 5b, 5'b are slightly opened to compensate for the worn brake clearance.

Therefore, as the linings 7, 7' wear out, the teeth of the gear part 18 successively engage with the pawl part 19b, and the braking gap is automatically adjusted.

Even in this case, the brake arm 11 returns to its initial position due to the resilient force of the brake arm return spring 24 even after the braking gap has been compensated for.

When the linings 7, 7' are worn beyond the wear limit, the pawl portion 19b engages with the last tooth of the gear portion 18 and slides on the outer circumferential portion 17b of the adjuster gear 17 every time a braking operation is performed, and the braking gap cannot be adjusted. If this is not done, the stroke of the brake lever or brake pedal increases and the driver is exposed to the linings 7, 7'.
Notify when it is time to replace.

As described above, in the present invention, a clutch spring is wrapped around a camshaft so as to transmit only the rotational force in the braking action direction of the brake arm, an adjustment gear with a gear portion formed on the outer periphery is fixed to the camshaft, and a gear stopper is attached. Since the tip claw part is engaged with the gear part and the other end is fixed to the brake panel to allow rotation of the adjustment gear only in the direction of braking operation, it is possible to automatically compensate for the braking gap with a simple structure. Since the gear part of the adjustment gear is formed in a range that compensates up to the lining wear limit, the braking gap can be automatically adjusted until the lining wear limit is reached, and when the wear limit is exceeded, the stroke of the brake lever or brake pedal increases. This is an extremely practical idea, as it can notify the driver when it is time to replace the lining.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a front view, Fig. 2 is a rear view, and Fig. 3 is Fig. 2-
4 is a sectional view of FIG. 3, and FIG. 5 is a sectional view of FIG. 3. 1... Brake panel, 5, 5'... Brake shoe, 6... Anchor pin, 7, 7'... Lining, 8... Shoe return spring, 10
...Cam, 10a...Camshaft, 11...Brake arm, 16...Clutch spring, 17...
Adjustment gear, 18... Gear part, 19... Gear stopper, 19b... Claw part, 24... Brake arm return spring.

Claims (1)

[Scope of utility model registration request] A cam of a camshaft passing through the brake panel is interposed between the free ends of a pair of brake shoes whose base ends are pivotally supported on the brake panel, and this cam is rotated by a brake arm to expand the brake shoes. In a mechanical drum brake that performs braking by pressing against the inner peripheral surface of the brake drum, a clutch spring with one end fixed to the brake arm is wound around the camshaft so as to transmit only the rotational force of the brake arm in the braking direction. An adjustment gear having a range formed on the outer periphery that compensates the gear portion up to the lining wear limit is fixed to the camshaft, and a gear stopper is attached to the brake panel by engaging the tip claw portion with the gear portion and allowing rotation of the adjustment gear only in the direction of braking action. An automatic braking gap adjustment device for a mechanical drum brake that is fixed.