JPS6325400Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic braking gap adjustment device for a hydraulically operated brake.

The invention is particularly applicable to, but not limited to, drum brakes. As is well known, a drum brake has a pair of arcuate brake shoes on a back plate, one end of which is a fulcrum, and the other end of which is expandable by the operation of a wheel cylinder. Braking is achieved by pressing the brake lining against the circumferential surface. When the brake lining wears out due to this braking, the braking gap between the brake lining and the inner peripheral surface of the brake drum increases.
An automatic braking gap adjustment device provided separately from the wheel cylinder is operated to expand the brake shoe so that the braking gap is always constant.

The applicant previously proposed that the automatic braking gap adjustment device, which is provided separately from the wheel cylinder that expands the brake shoe, is built into the wheel cylinder, has a simple structure, can be manufactured at low cost, and has a spring retainer. By using this, we have provided an automatic braking gap adjustment device for hydraulically actuated brakes that ensures the screwing out of the adjustment bolt, has a simple structure for preventing rotation of the adjustment nut, and is easy to assemble. 57-148121).

The structure of this device is that a piston is slidably inserted into a cylinder, a hydraulic chamber is defined in the cylinder by the piston and an opposing part of the piston, and a hydraulic pressure chamber is formed between the piston and this opposing part. An adjusting nut and an adjusting bolt which are threaded together are arranged, the clutch part of the adjusting bolt is brought into contact with the clutch surface of the opposing part, and the adjusting nut is attached to a spring having a spring seat part and a plurality of leg parts. The legs of the retainer are fitted into the notches formed in the adjustment nut, and the retainer is further engaged and installed in the communication holes formed in the piston, and the spring is compressed between the spring seat and the adjustment nut. As a result, when the piston is brought into contact with the piston and a braking gap greater than a predetermined value is generated, the adjustment bolt is screwed to move the piston forward, so that the braking gap is always constant.

In order for the automatic braking gap adjustment device with the above configuration to operate normally, it is necessary to assemble the piston and the adjustment nut in complete contact, but in rare cases during manufacturing, the tip of the adjustment bolt may move from the adjustment nut toward the piston. It is conceivable that the parts will be assembled in a protruding state. However, in the above-mentioned automatic braking gap adjustment device, the contact surfaces of the piston and adjustment bolt are formed in a flat shape and come into surface contact, and due to the nature of the multi-thread thread formed on the adjustment bolt, both The screwing resistance of the adjustment bolt is large when the adjustment bolt contacts the piston, so in the unlikely event that the tip of the adjustment bolt comes into contact with the piston while protruding from the adjustment nut towards the piston and is pressed by the spring retainer and spring. There is a risk that the piston and the adjuster nut may not be easily screwed into the clutch portion and may be assembled while remaining protruding, that is, with a gap remaining between the piston and the adjuster nut.

The present invention was developed in view of the above-mentioned circumstances, focusing on the property that a multi-thread screw turns most smoothly when the center point of its tip surface is pressed. The purpose is to provide an automatic braking gap adjustment device that allows complete contact and therefore always operates normally.
An adjustment nut and an adjustment bolt screwed together with a multi-thread screw are arranged in a hydraulic chamber defined by a piston slidably inserted into the cylinder and its opposing part, and the clutch part of the adjustment bolt is A braking gap in a hydraulically actuated brake that abuts against the clutch surface of the opposing portion, while holding the adjusting nut on the piston, and when a braking gap of more than a predetermined value occurs, the adjusting bolt is screwed to advance the piston. In the automatic adjustment device, the adjusting nut and adjusting bolt are arranged in a cylinder in series with the piston, and a spring retainer including a spring seat and a plurality of legs connects the legs to the adjusting nut. The spring is fitted into the notch formed in the piston and is engaged with the hole formed in the piston, and the spring is compressed between the spring seat and the adjustment nut, and the piston and the adjustment nut are connected together. This is an automatic braking gap adjustment device for a hydraulically operated brake, characterized in that a convex portion is formed at the contact portion with the bolt to promote threading of the adjuster bolt.

Hereinafter, an embodiment in which the present invention is applied to a two-leading type drum brake will be described with reference to the drawings.

Figures 1 and 2 show an embodiment of the present invention, in which a pair of upper and lower wheel cylinders 1 (the lower part is not shown) are mounted on the inner surface of a back plate (not shown) that is fixed to the vehicle body. ), and a pair of left and right brake shoes 2, 2 are respectively arranged symmetrically around the center of the back plate.

The wheel cylinder 1 is composed of a cylinder body 3 having a cylinder hole 3a with only one end open, and a single piston 5 that slides into the cylinder hole 3a to define a hydraulic chamber 4.The cylinder body 3 has a back plate. is fixed to. A retainer 6 is provided at the outer end of the cylinder body 3, and an engagement groove 5a is formed at the outer end of the piston 5, with which corresponding ends of the brake shoes 2, 2 are engaged. ing. This retainer 6 and the engagement groove 5
Relative rotation between the cylinder body 3 and the piston 5 is prevented by the engagement between the cylinder body 3 and the brake shoes 2, 2.

The wheel cylinder 1 is provided with a hydraulic pressure introduction port 7 for introducing the output hydraulic pressure of a brake master cylinder (not shown) into the hydraulic pressure chamber 4 thereof.

In the hydraulic chamber 4 of the wheel cylinder 1, an automatic braking gap adjustment device A of the present invention is arranged in series with the piston, which will be described in detail below.

The piston 5 has a collar portion 9 at the tip of the small diameter portion 8, and a cup groove 1 formed in the small diameter portion 8.
0 is fitted with a piston cup 11. A circular counterbore hole 1 is provided at the tip of the piston 5.
2 are formed at three locations, and by forming these holes 12, crescent-shaped communication holes 13 are formed in the collar portion 9. The adjusting nut 15 is disposed so that its collar 15a is in contact with the contact surface 14 of the piston 5 so as to be able to separate from it. It is held under pressure. This asian nut 1
5, a notch 18 is formed in the collar 15a at a position corresponding to the communication hole 13 formed in the collar 9 of the piston. The adjustment bolt 19 screwed into the adjustment nut 15 has a multi-threaded part 19a on the piston side and a clutch part 19b on the other side.
and a seal portion 19c formed at a connecting portion between the two, and a distal end portion 19d of the multiple thread portion 19a is formed to protrude into a substantially conical shape. Also,
The spring retainer 16 is attached to the spring seat portion 1
6a and three legs 1 having a locking claw 16b at the tip.
6c.

The piston 5, adjuster nut 15, spring retainer 16 and spring 17 are assembled as follows. First, attach the collar 15 of the adjuster nut 15 to the contact surface 14 of the piston 5.
a to align the communication hole 13 and the notch 18 and bring them into contact with each other. Next, the spring 17 is interposed between the adjuster nut 15 and the spring retainer 16, and the leg portion 16c of the spring retainer 16 is inserted.
into the notch 18 of the adjusting nut 15, and insert the locking pawl 16b into the communication hole 13 of the piston 5.
to be locked. The spring 17 is compressed between the collar portion 15a of the adjuster nut 15 and the spring seat portion 16a of the spring retainer 16.

The adjuster nut 15 assembled in this way resists this spring 17 and is attached to the piston 5.
The collar portion 9 can be separated from the contact surface 14 of the spring retainer 16 by engaging with the leg portions 16c of the spring retainer 16.
It is stopped from rotating.

An adjustment bolt 19 is screwed into the shaft portion 15b of the adjustment nut 15 via a multi-start thread portion 19a so as to pass through a screw hole 15c at the center thereof. The threaded portion between the adjusting nut 15 and the adjusting bolt 19 is provided with an appropriate braking gap between each brake shoe 2, 2, that is, an appropriate gap between each brake shoe 2, 2 and a brake drum (not shown). An axial backlash is set.

A clutch portion 1 is attached to the end of the adjuster bolt 19.
9b is formed, and this clutch portion 19b
is rotatably fitted into a cylinder small diameter section 20 provided on the inner end wall of the cylinder body 3, and faces a conical clutch surface 21 formed on the back wall of the cylinder small diameter section 20. And adjust bolt 1
A sealing member 22 is fitted into the sealing groove 19c of 9 to prevent the hydraulic pressure in the hydraulic pressure chamber 4 from acting on the clutch surface 21.

Next, the operation of this embodiment will be explained. As mentioned above, when assembling the automatic braking gap adjustment device according to the present invention, the piston 5 and the adjustment nut 1 are
5 must be brought into contact with each other, but in rare cases, the adjustment bolt 19 may be assembled with the tip 19d of the adjustment bolt 19 screwed into the adjustment nut 15 protruding toward the piston side. However, in this embodiment, the adjuster bolt 1
The tip 19d of the adjusting bolt 19 is formed into a substantially conical shape, and only its apex, that is, the center point, contacts the contact surface 14 of the piston 5. Therefore, the adjusting bolt 19 is in point contact with the piston 5, and the screw rotation is prevented. Friction is extremely low, and the center point is pressed by the abutment surface 14 of the piston 5, and the adjustment bolt 19, which originally protruded toward the piston, is pressed against the adjustment nut 15 by the biasing force of the spring 17. It is very easily screwed into the clutch portion 19b until the piston 5 comes into contact with the clutch portion 19b. Therefore, the piston 5 and the adjuster nut 15 are always assembled in such a manner that they are in secure contact with each other.

To explain the operation of the automatic braking gap adjustment device described above, when no braking is performed, the return spring force is applied to the piston 5 via the brake shoe 2.
This is transmitted to the adjusting nut 15 and the adjusting bolt 19, and enters the clutch portion 19b and the clutch surface 21, generating clutch torque. At this time, since the adjusting nut 15 and the adjusting bolt 19 are threaded together with a multi-thread thread, rotational torque is generated in the adjusting bolt 19, but the clutch torque is set to be larger than this adjusting bolt rotational torque. Therefore, the adjuster bolt 19 does not rotate and the piston 5 maintains its position.

Next, in order to perform braking, a master cylinder (not shown) is actuated to introduce pressure fluid from the hydraulic pressure introduction port 7 into the hydraulic pressure chamber 4. When the piston 5 moves forward in the axial direction, the brake shoe 2 is transferred to the wheel. The braking action is performed by pressing against the inner peripheral surface of the brake drum, which rotates together with the brake drum.

By the way, when the brake lining is not worn to a predetermined level or during braking immediately after adjusting the braking gap, as the piston 5 moves forward, the adjuster nut 15 is brought into contact with the collar portion 9 by the elastic force of the spring 17 via the spring retainer 16. It moves together with the piston 5 while maintaining its state. Since the amount of movement of the adjusting nut 15 is the amount of movement corresponding to back crushing, no rotational torque is generated in the adjusting bolt 19 which is threaded with a multi-thread screw, and the adjusting nut 15 is not adjusted. When the brake is released, the piston 5 and adjustment nut 15 return to their original positions together.

In this normal braking state, the hydraulic pressure in the hydraulic pressure chamber 4 is relatively low, and therefore the frictional coupling force between the clutch portion 19b of the adjusting bolt 19 and the clutch surface 21 of the cylinder small diameter portion 20 is relatively small. Therefore, if the piston 5 moves further outward due to wear of the brake linings of the brake shoes 2, 2, the adjustment nut 15 will be brought into contact with the contact surface 14 by the elastic force of the spring 17 via the spring retainer 16. Piston 5 while maintaining contact state.
move with

This amount of movement is equal to the amount of wear on the brake lining added to the backlash, and since the movement is greater than the backlash, the adjusting bolt 19 moves together with the adjusting nut 15, and the clutch portion 19b of the adjusting bolt 19 is connected to the cylinder. away from the clutch face 21 of the small diameter portion 20. The adjustment nut 15 is pressed against the contact surface 14 of the piston 5 by the elastic force of the spring 17, and its rotation is restricted by the legs 16c of the spring retainer 16, so that the adjustment nut 15 and the adjustment bolt 19 Rotational torque is generated at the threaded part of the multi-thread screw. This allows adjustment bolt 1
9 moves toward the clutch surface 21 while screwing around the adjuster nut 15, and the clutch surface 21
re-engage with. In this way, an automatic adjustment effect is achieved which compensates for wear on the brake linings of the brake shoes 2,2. Here, when the pressure inside the hydraulic chamber 4 is reduced to release the brake, the brake shoes 2, 2 contract due to the return force of the return spring, but the return force is applied to the piston 5, the adjuster nut 15, and the adjuster. This acts as a thrust on the clutch portion 19b of the bolt 19 toward the clutch surface 21, whereby the clutch portion 19b is frictionally coupled to the clutch surface 21, making it impossible for the adjusting bolt 19 to rotate. Therefore, the piston 5 and the adjustment nut 15 are connected to the adjustment bolt 19.
As a result, there is a proper braking force corresponding to the backlash between the brake lining of each brake shoe 2 and the inner peripheral surface of the brake drum. A gap is created.

In addition, when strong braking is performed, the hydraulic pressure in the hydraulic chamber 4 increases to a predetermined value that causes elastic deformation in the brake shoes 2, 2, brake drum, etc., as described above. A self-adjusting action is performed. When the hydraulic pressure exceeds the predetermined value,
The thrust due to the hydraulic pressure of the clutch portion 19b of the adjusting bolt 19 increases, and the clutch portion 19b
Since the adjusting bolt 19 is held in a frictionally connected state with the clutch surface 21, the adjusting bolt 19 cannot rotate. Therefore, the unrotatable adjusting nut 15 is fastened on the adjusting bolt 19 by the legs 16c of the spring retainer 16, so that when the piston 5 moves further outward due to elastic deformation of the brake drum or the like, the spring 17 By deflecting, the adjusting nut 15 maintains its position together with the adjusting bolt 19, and the abutment surface 14 of the piston 5 is separated from the adjusting nut 15. In this way, the automatic adjustment effect is stopped.

Further, FIGS. 3 and 4 show another embodiment of the present invention, and in the embodiment, a substantially conical convex portion is attached to the tip end 19d of the adjuster bolt 19.
However, in this embodiment, it was formed on the piston 5. That is, unlike the circular counterbore in the embodiment described above, the collar 9 at the tip of the piston 5 has a recess 12 extending in a trifurcated shape from the center.
, and a substantially conical protrusion 12 a is formed at the center of the recess 12 . This convex portion 12a
The action is similar to that of the previous embodiment, and the apex presses the center point of the adjusting bolt 19 to ensure that the piston 5 and adjusting nut 15 are in contact with each other.

In this embodiment, the spring is compressed between the adjuster nut and the retainer, but the separate spring can be omitted by providing the retainer itself with spring properties. Also,
In the embodiment described above, the convex portions 19d and 12a for promoting the screw movement of the adjuster bolt 19 are approximately conical, but the present invention is not limited to this, and may be approximately hemispherical or other shapes that allow point contact. Bye.

Since the present invention is constructed as described above, even if the adjuster bolt originally screwed into the adjuster nut protrudes toward the piston side, when the adjuster bolt and the piston are assembled using a spring or a spring retainer, the center part of the adjuster bolt will not be affected by the biasing force of the spring. The piston and adjuster nut are pressed together and screwed into the clutch side, and the piston and adjuster nut can be screwed together using the conventional manufacturing process without any special attention or effort, and the assembly condition can be confirmed without requiring skill. It is possible to prevent them from being assembled with a gap left between them, and it is possible to ensure that they come into contact with each other, so it is possible to manufacture an automatic braking gap adjustment device that always has good quality, and also to improve the operation after assembly. It also has various effects, such as making it even more reliable.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a cross-sectional front view of the main parts, FIG. 2 is an exploded perspective view of the components of the automatic braking gap adjustment device, and FIG.
3 and 4 show another embodiment, FIG. 3 is a sectional front view of the main part, and FIG. 4 is a perspective view of the piston. 1 is the wheel cylinder, 2 is the brake shoe,
3 is the cylinder body, 4 is the hydraulic chamber, 5 is the piston,
9 is a collar portion, 12 is a hole portion, 12a is a convex portion, 13 is a communication hole, 15 is an adjustment nut, 16 is a spring retainer, 17 is a spring, 18 is a notch portion, 19 is an adjustment bolt, 19b is a clutch portion, 19d is the tip, 20 is the small diameter portion of the cylinder, 2
1 is the clutch surface.

Claims (1)

[Scope of utility model registration request] An adjustment nut and an adjustment bolt screwed together with a multi-thread screw are arranged in a hydraulic chamber defined by a piston slidably inserted into the cylinder and its opposing part, and the clutch part of the adjustment bolt is A braking gap in a hydraulically actuated brake that abuts against the clutch surface of the opposing portion, while holding the adjusting nut on the piston, and when a braking gap of more than a predetermined value occurs, the adjusting bolt is screwed to advance the piston. In the automatic adjustment device,
The adjusting nut and the adjusting bolt are arranged in a cylinder in series with the piston, and a spring retainer including a spring seat and a plurality of legs has its legs connected to a notch formed in the adjusting nut. The spring is fitted into the hole formed in the piston, and the spring is compressed between the spring seat and the adjustment nut, and the piston and the adjustment bolt are brought into contact with each other. 1. An automatic braking gap adjustment device for a hydraulically actuated brake, characterized in that a convex portion is formed on a portion thereof to promote threading of an adjuster bolt.