JPS59183124A - Automatic shoe gap adjusting device for drum brake - Google Patents

Abstract

PURPOSE:To automatically adjust a shoe gap by disposing a piston and a ratchet rod in a cylinder body of a wheel cylinder for a drum brake, which is interposed between a pair of brake shoes in such a manner as to move relatively. CONSTITUTION:When high-pressure brake liquid is poured from an input port 20 of a cylinder body 14, a pressure receiving end 22b of a ratchet rod 22 is pressed to the left. The brake liquid passes through a small hole 22c of the ratchet rod 22 to work upon the right end of a piston 16, thereby moving the ratchet rod 22 and the piston 16 until shoes press a brake drum through a push rod to stop both of them. When a shoe gap is more than an abrasion limit of the shoe while the brake liquid is not operated, the piston 16 pushes up a ratchet click 24 against a spring 28 to move the ratchet rod 22 over the click 24, so that the shoe gap is suitably corrected.

Description

[Detailed description of the invention] This invention relates to a device that automatically adjusts.

1-" When the lining of the brake shoe of a ram brake wears out over a long period of use, the shoe gap widens and the brake operation becomes lax, which can be dangerous. For this reason, the shoe gap needs to be adjusted as the lining wears. In the conventional technology, the wheel cylinder and brake shoe were connected by a flanged screw, and the shoe gap was adjusted by turning 7 lunges and changing the protrusion of the screw depending on the wear of the lining, which was cumbersome for the printing plate and fc. Recently, a device for automatically adjusting the shoe gap has been proposed, but all conventional devices of this type have the disadvantage that they have complicated mechanisms and operations, are prone to failure, and are expensive.

An object of the present invention is to provide a device that can automatically adjust the shoe gap with a simple mechanism and without failure.

The details of the non-inventive embodiments are as follows with reference to the drawings:
1 and 2 show a wheel cylinder 12 equipped with an automatic shoe gap adjustment device 10 according to the invention, this wheel cylinder 12 being slidably inserted into a cylinder body 14 and this cylinder body i. piston 1
The cylinder body 14 is connected to the end of one brake shoe of a pair of brake shoes (not shown), and the piston 16 receives a bushing rod 18 that pushes the other brake shoe apart.
It has a concave portion 16a that abuts on the 8th. cylinder body 1
4 has an inlet 20 through which a pressurized fluid such as oil is injected, and the pressurized fluid is injected from this inlet side into the cylinder body 4 through a pipe (not shown) to cause the piston 16 to move as shown in FIG. As shown, move to the left and push the brake shoes apart via the bushing rod 8 to press them against the brake drum. In the drawings, reference numeral 34 indicates a seal cup, and reference numeral 36 indicates a dart.

The automatic shoe gap adjustment device 10 of the present invention includes a ratchet rod 22 having ratchet teeth 22a inserted into a hole 16a provided at the pressure receiving end of the piston 16 of the wheel cylinder 12 and a pressure receiving end 22b; A ratchet pawl 24 biased by a spring so as to mesh with the ratchet teeth 22a of the rod O, and the cylinder body 14
A stopper is attached to the ratchet rod 22 and abuts against the pressure receiving end 22b of the ratchet rod 22. Ratchet claw U
is the horizontal hole 1GcK of the piston 16! It is freely movable,
It meshes with the ratchet teeth 22a of the ratchet rod 22 by means of a spring path inserted behind it. The stop flange 26 is fixed to the cylinder body 14 by screws 30, 301; in the embodiment shown, a spacer 32, 32' is provided between the stop 26 and the inner wall of the cylinder body 14, surrounding the screws 30, 30'. It is provided.

To explain the operation of the above-mentioned device, brake fluid, which is a pressurized fluid, is injected from the inlet of the cylinder body 14, and when this is done, the pressure receiving end 221) of the ratchet rod n is pushed to the left. On the other hand, the brake fluid is on the ratchet rod 22
The small hole 22c of the pressure receiving end 22b and the cylinder body 14
Pressure is applied to the right end of the piston as shown by the arrow through the gap created between the piston and the piston. Therefore, the piston] 6 and the ratchet rod 22 ('i shoe press the brake drum and move up to 1°.If the pressurizing Vπ body does not act on the wheel cylinder, the shoe (not shown) and the brake drum When the gap is less than the wear limit of the shoe, the movement amount of the ratchet rod is less than S. When the shoe exceeds the wear limit, the piston 16 pushes up the ratchet post against the spring force and moves the ratchet rod z2.
Move over the Karache Soto pawl 24 and move to the left to maintain an appropriate gap between the shoe and the brake drum. When the pressurized fluid is released, the piston 16 moves to the right together with the ratchet rod 22 by a shoe return spring installed between the pair of brake shoes, returning to the state shown in FIG. At this time,
A shoe gap equivalent to S is secured.

In the above embodiment, the invention is applied to a single-piston type wheel cylinder, but the invention can also be applied to a bi-directional piston type wheel cylinder.

According to the invention, as mentioned above, the shoe gap is automatically adjusted when the brake is not applied, which eliminates the need for inspection and improves work efficiency. Since the kIJ adjustment is performed using a simple ratchet mechanism, it is less likely to break down and is also inexpensive and economical.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing the state before and after the operation of the automatic shoe gap adjustment device for a drum brake according to the invention. 10---Shoe gap automatic adjustment device, 12---
---Wheel cylinder, 14-4---Cylinder body, J6----Piston, 18-------Button rod, 1 piece, 22-1---Ratchet rod, 22a-- ---Ratchet tooth, 22b-1-
--- Pressure receiving end, Sae --- Ratchet pawl, 26 ---
-Stopper, 28--Spring. Patent applicant Hino Motors Co., Ltd.

Claims (1)

[Claims] The cylinder body is provided between a pair of brake shoes, and the piston is slidably inserted into the cylinder body. A drum brake wheel cylinder having an inlet for injecting the piston, a ratchet rod provided at the pressure receiving end of the piston and having ratchet teeth and a pressure receiving surface, and a ratchet pawl biased by a spring so as to mesh with the ratchet teeth of the ratchet rod. and a stop horn that is attached to the cylinder body and abuts against the pressure receiving end of the ratchet rod at a predetermined stroke of the piston.