JPH0237298Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a wheel cylinder built-in auto adjuster for drum brakes.

(Prior art) As a conventional example of an auto adjuster with a built-in wheel cylinder for drum brakes, there is
There is one as shown in Fig. 2 disclosed in No. 131437. An outline of its operation will be explained.

When pressure oil is introduced into the wheel cylinder day 21, it is screwed into the adjuster staying nut 23 rotatably housed in the piston 22 and the adjuster staying nut 23 with a multi-thread screw 23a. The piston 22 does not protrude with the screw member 24 whose teeth 24a are engaged with the pawl members 25 biased by a compression coil spring. At this time, if the lining of the brake shoe 27 is worn and the shoe gap increases, the screw member 24 is prevented from rotating by the pawl member 25, so the adjusting nut 23 will not rotate. , the adjusting screw 26 screwed into the adjusting nut 23 is screwed out, and the lining of the brake shoe 27 slides into contact with a drum (not shown) to generate braking force and adjust the shoe clearance.

(Problems to be solved by the invention) Since the conventional example has a large number of parts, the number of parts is reduced to enable fine adjustment.

(Means for solving problems) The configuration of the present invention is as follows.

A cylinder body having an opening at one end, an intermediate member consisting of a flange portion and a cylindrical portion that are engaged with the open end surface of the cylinder body, and the intermediate member is rotatable relative to the intermediate member and the cylinder body and is accompanied by the intermediate member during forward stroke. A moving piston, an adjusting screw that is screwed to the tip of the piston with a single thread and locks the web of the brake shoe, and a drive ring that is screwed to the rear end of the piston with a multi-thread screw. ,
This is an auto adjuster built into a wheel cylinder for a drum brake, which has a stopper that is fixed to a cylinder body and prevents the drive ring from moving beyond a predetermined gap in the axial direction and from rotating.

(Function) If pressure oil is introduced into the cylinder body from the outside,
The piston moves forward, and if the gap between the drum and the brake shoe, the so-called shoe gap, is within the set range, the piston moves within the range where the drive ring comes into contact with the stopper fixed to the cylinder body, and the adjusting screw is moved. Brake force is generated by sliding the brake shoe that is locked onto the drum in sliding contact with the drum.

In addition, if the brake shoe is worn and the shoe clearance exceeds the set shoe clearance, the piston will move forward and the drive ring will come into contact with the stopper, and the drive ring will not be able to rotate and the piston will not rotate. It moves forward while being rotated by a screw, and the adjusting screw, which is threaded into the tip of the piston with a single thread, is screwed out to bring the brake shoe into sliding contact with the drum to generate braking force. Then, when the brake is released and the piston returns, the drive ring comes into contact with the bottom of the cylinder body, and the multi-thread screw rotates the drive ring, causing the piston to screw into the drive ring. , the flange portion of the intermediate member contacts the open end surface of the cylinder body. In this way,
The shoe gap is adjusted by the amount that the adjusting screw screws out from the piston during braking. The adjustment allowance is a small value based on the pitch ratio of the multi-thread thread and the single thread thread.

(Embodiment) An embodiment of the wheel cylinder built-in auto adjuster for drum brakes according to the present invention will be described with reference to FIG.

1 is a cylinder body, 2 is a piston, and on the open side of the cylinder body 1, between the cylinder body 1 and the piston 2, there are a flange part 3a and a cylindrical part 3b that come into contact with the open end surface of the cylinder body 1. An intermediate member 3 having a diameter is interposed therebetween. and cylindrical part 3
A projection 3c is provided on the outer peripheral surface of cylinder body 1.
The intermediate member 3 is slidable in the axial direction relative to the cylinder body 1, and the piston 2 is rotatable relative to the intermediate member 3. A single female thread 2a is provided at the tip of the piston 2, and a single male thread 4a provided on the adjusting screw 4 is screwed therein. Further, a web 10a of a brake shoe 10 is secured to the tip of the adjusting screw 4.
A multi-thread female thread 2b is provided at the rear end of the piston 2, which is press-fitted into the drive ring 5, and is engaged with a multi-thread threaded member having a multi-thread male thread 5b. A claw 5a is provided on one side of the drive ring 5 in the circumferential direction.
A hemispherical protrusion 5c is provided on the other side to reduce frictional resistance. Reference numeral 6 designates a ring-shaped stopper fixed to the inner circumferential surface of the cylinder body 1, and teeth 6a are provided on the side surface of the stopper to engage with the pawl 5a of the drive ring, thereby forming a clutch. In addition, in FIG. 1, the teeth 6 of the stopper 6
a is formed over the entire circumference, and the pawl 5a of the drive ring 5 that can mesh with this is formed only on a part of the circumference, but the pawl 5a is formed over the entire circumference and the teeth 6a are It can also be formed only on a part of the circumference. 7 is fixed to the front surface of the piston 2, and is attached to the stepped portion 2 of the piston.
This is a wheel for manually rotating the piston, which clamps the intermediate member 3 between the piston and the intermediate member 3.

Next, the action will be explained.

When pressure oil is introduced into the cylinder body 1 from the outside, the piston 2 moves forward with the intermediate member 3 and the adjusting screw 4, and the gap between the brake shoe 10 and a drum (not shown), the so-called shoe gap, is created. If it is within the set shoe gap, the piston 2 moves until the drive ring 5 comes into contact with the stopper 6, and the brake shoe 10, which is locked to the tip of the adjusting screw 4, slides into contact with a drum (not shown). Generates braking force.

Also, if the brake shoe 10 is worn and the shoe clearance exceeds the set shoe clearance, the drive ring 5
After contacting the stopper 6, the drive ring 5
The pawl 5a meshes with the teeth 6a of the stopper, producing a clutch action and preventing rotation, so that the piston 2 rotates relative to the cylinder body 1 and the intermediate member 3 by the action of the multi-thread screws 2b and 5b. The adjusting screw 4 is screwed out, and the brake shoe 10 is brought into sliding contact with a drum (not shown) to generate braking force. Then, when the brake is released, a shoe return spring (not shown) is activated and the piston 2 returns, and the drive ring 5 comes into contact with the bottom of the cylinder.
The piston 2 rotates under the action of the multi-thread screws 2b, 5b, and is screwed into the drive ring 5 by the amount protruded by the multi-thread screws 2b, 5b during braking.

As a result, Asia Sting Screw 4,
A fine adjustment is made to the value determined by the pitch ratio between the multi-thread screws 2b, 5b and the single-thread screws 2a, 4a.
Therefore, over-adjustment that fills the shoe gap due to thermal expansion is effectively prevented.

(Effects of the invention) An auto adjuster with a built-in wheel cylinder for drum brakes has a simple structure with a reduced number of parts, rotates the piston to finely adjust the shoe gap, and has a rust prevention effect that is not affected by the external environment. We were able to provide

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of an auto adjuster with a built-in wheel cylinder for a drum brake according to the present invention, and FIG. 2 is a sectional view of a conventional example of an auto adjuster with a built-in wheel cylinder for a drum brake. 1: Cylinder body, 2: Piston, 2a: Single thread female thread, 2b: Multi thread female thread, 2c: Stepped part,
3: Intermediate member, 3a: Flange portion, 3b: Cylindrical portion, 3c: Projection, 4: Asia steering screw, 4a: Single thread male thread, 5: Drive ring, 5
a: claw, 5b: multi-thread male thread, 5c: hemispherical projection, 6: stopper, 6a: tooth, 7: wheel.

Claims (1)

[Scope of utility model registration request] A cylinder body having an opening at one end, an intermediate member consisting of a flange portion and a cylindrical portion that are engaged with the open end surface of the cylinder body, and the intermediate member is rotatable relative to the intermediate member and the cylinder body and is accompanied by the intermediate member during forward stroke. A moving piston, an adjusting screw that is screwed to the tip of the piston with a single thread and locks the web of the brake shoe, and a drive ring that is screwed to the rear end of the piston with a multi-thread screw. ,
A wheel cylinder built-in auto adjuster for a drum brake, characterized by having a stopper fixed to a cylinder body to prevent the drive ring from moving beyond a predetermined gap in the axial direction and from rotating.