JPS6325397Y2 - - 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. Therefore, the applicant first built a brake clearance automatic adjustment device into the wheel cylinder, which is provided separately from the wheel cylinder that expands the brake shoe, and developed a hydraulic fluid system that has a simple structure and can be manufactured at low cost. An automatic braking gap adjustment device for pressure-actuated brakes has been provided.

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, the adjusting nut is held on the piston, and the adjusting bolt is provided with a seal member. This prevents hydraulic fluid from entering the clutch surface of the adjusting bolt's clutch portion and the opposing portion. The adjustment bolt moves toward the piston as the brake lining wears, and the clutch portion separates from the clutch surface. As a result, the adjuster bolt moves toward the clutch surface while spirally rotating, and engages with the clutch surface again to adjust the braking gap.

The purpose of the present invention is to improve the durability of the seal member by configuring the adjustment bolt with two members to stop the rotation of the seal member attachment part in the automatic braking gap adjustment device built into the vehicle brake cylinder. It is an object of the present invention to provide an automatic braking gap adjustment device for a hydraulically actuated brake, which has a simple structure in which the two members are connected and can improve ease of assembly.

In accordance with the above object, the present invention arranges an adjustment nut and an adjustment bolt screwed together with a multi-thread screw in a hydraulic pressure chamber defined by a piston slidably inserted into a cylinder and its opposing part. The clutch part of the adjusting bolt is brought into contact with the clutch surface of the opposing part, while the adjusting nut is held by the piston, and when a braking gap of more than a predetermined value occurs, the adjusting bolt is screwed to move the piston forward. In an automatic braking gap adjustment device for a pressure-actuated brake, the adjusting bolt is comprised of a bolt body having a multithread thread portion at one end and a clutch portion at the other end, and a piston body having a clutch surface at one end and a clutch portion at the other end. The clutch portion of the bolt body is engaged with the clutch surface of the piston body, and the claw portions at both ends of the connecting member are connected to the bolt body and the bolt body with a gap corresponding to the braking gap in the axial direction. A sealing member that engages and connects with the locking groove of the piston body and prevents the hydraulic pressure in the hydraulic pressure chamber from acting on the clutch surface of the opposing portion is fitted into the piston body, and the sealing member is connected to the cylinder. This is an automatic braking gap adjustment device for a hydraulically operated brake, characterized in that sliding resistance is set to be greater than sliding resistance between the connecting member and the locking groove.

An embodiment in which the present invention is applied to a two-leading drum brake will be described below with reference to the drawings.

Back plate fixed to the vehicle body (not shown)
A pair of upper and lower wheel cylinders 1 are installed on the inner surface of the
(the lower part is not shown), 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. By engaging these with the brake shoes 2, 2, the cylinder body 3 and the piston Relative rotation with 5 is prevented.

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, and is further supplied from a hydraulic pressure output port 8 to the lower wheel cylinder. .

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

The piston 5 has a cup chamber 10 at the tip of the small diameter portion 9.
This cup chamber 10 has a brim portion 11 that defines a
communicates with the inside of the hydraulic pressure chamber 4 through a communication hole 12 formed in the collar portion 11 . The adjuster nut 13 is arranged so that its collar portion 13a abuts on the abutment surface 14 of the piston 5 so as to be able to separate from the abutment surface 14 of the piston 5. This asian nut 1
A cutout portion 15 is formed in the collar portion 13a of No. 3 at a position corresponding to the communication hole 12. Then, the spring retainer 16 has its legs 16a fitted into the notches 15 of the adjuster nut 13, and the locking claws 16b at the tips of the spring retainers 16 are inserted into the communication holes 1 of the pistons 5.
2, and the adjusting nut 13 is moved in the axial direction of the piston to the contact surface 14.
Although it can be separated from the piston 5, it is prevented from rotating by the piston 5. The spring 17 is compressed between the spring retainer 16 and the collar portion 13a of the adjuster nut 13.

The adjustment bolt 18 is composed of two members: a bolt body 19 located at the rear and a piston body 20 located at the front. The bolt body 19 has a multiple threaded portion 19a at the rear and a clutch portion 19b at the front.
A locking groove 19c is formed between the two. Further, the piston body 20 has a clutch surface 20a at the rear and a clutch portion 20b at the front, and a locking groove 20c is formed between the two. Further, the rear end of the piston body 20 is formed with a recess 20d that continues to the clutch surface 20a, and a communication hole 20e that communicates the recess 20d with the hydraulic pressure chamber 4.

The bolt body 19 has a multi-threaded threaded portion 19a that is threaded through the axial center of the adjuster nut 13, while the piston body 20 has a clutch portion 20b provided on the inner end wall of the cylinder body 3.
It faces a clutch surface 22 formed on the back wall of 1. A sealing member 23 is fitted in the piston body 20 to prevent the hydraulic pressure in the hydraulic pressure chamber 4 from acting on the clutch surface 22.

The clutch portion 19b of the bolt body 19 is in clutch engagement with the clutch surface 20a of the piston body 20, and both members have claw portions 2 at both open ends 24a.
They are connected by a cylindrical connecting member 24 having a diameter of 4b. This connecting member 24 connects the claw portion 24b to the locking groove 19c of the bolt body 19 and the piston body 20.
It is flexibly deformed and locked to 20c, making it easy to assemble. Then, the claw portion 24b and the locking grooves 20c, 19
A gap c corresponding to the braking gap is set in the axial direction between either one of the brakes c and c. In this embodiment, it is set on the piston body 20 side, but the bolt body 19
Of course, it may be set on the side. The sliding resistance of the sealing member 23 with the cylinder small diameter portion 21 is due to the claw portion 24b of the connecting member 24 and the locking grooves 19c, 20.
It is set larger than the sliding resistance of c.

Next, the operation of this embodiment will be explained.

When braking is not performed, the return spring force acts in the direction of retracting the piston 5 via the brake shoe 2, and this is transmitted to the adjuster nut 13 and bolt body 19, and from the clutch portion 19b to the clutch surface 20a of the piston body 20. The force enters the clutch surface 22 of the cylinder small diameter portion 21 from the clutch portion 20b of the piston body 20, generating clutch torque. At this time, since the adjusting nut 13 and the bolt body 19 are threaded together with a multi-thread thread, rotational torque is generated in the bolt body 19, but since both clutch torques are set to be larger than this rotational torque, The bolt body 19 does not rotate,
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. 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 certain level or during braking immediately after adjusting the braking gap, as the piston 25 moves forward, the spring retainer 16, spring 17, and adjuster nut 1
3 and the bolt body 19 move together, and the bolt body 1
The clutch portion 19b of 9 is separated from the clutch surface 20a of the piston body 20. However, at this time, since the amount of movement of the bolt body 19 is within the gap c, the clutch portion 19b of the bolt body 19 is in contact with the clutch surface 20.
Even if it is separated from a, no axial force is applied, so no rotational torque is generated and no adjustment occurs. When the brake is released, the piston 5, spring retainer 16, spring 17, adjuster nut 13, and bolt body 19 return to their original positions.

In this normal braking state, if the piston 5 moves further outward due to wear of the brake linings of the brake shoes 2, 2, the adjuster nut and the bolt body 19 move together with the piston 5.

This amount of movement is the gap c plus the wear of the brake lining, and since the bolt body 19 moves beyond the gap c, the bolt body 19 pulls the piston body 20 via the connecting member 24. This generates rotational torque in the bolt body 19, and since the clutch portion 19b of the bolt body 19 and the clutch surface 20a of the piston body 20 are separated, the bolt body 19 moves toward the clutch surface 20a while rotating, and the clutch is closed. Side 2
Re-engage 0a. In this way, a self-adjusting action takes place to compensate for wear on the brake lining of the brake shoe.

At this time, the piston body 20 is pulled and moved by the bolt body 19 via the connecting member 24;
The sliding resistance of the seal member 23 with the cylinder small diameter portion 21 is set to be greater than the sliding resistance of the claw portions 24b, 24b of the connecting member 24 with the locking groove 19c of the bolt body 19 and the locking groove 20c of the piston body 20. Because of this, the piston body does not rotate, and the seal member 23 does not rotate and slide against the cylinder small diameter portion 21, so durability is improved and it can be used satisfactorily for a long period of time, and there is no leakage. effectively prevented.

When the pressure inside the hydraulic chamber 4 is reduced to release the brake, the brake shoes 2, 2 contract under the return force of the return spring, but the return force is applied to the piston 25, the adjuster nut 13, and the bolt body 19.
The piston body 20 is transmitted to the clutch portion 19b.
acts as a thrust toward the clutch surface 20a of the piston body 20, and furthermore acts as a thrust toward the clutch surface 20a of the piston body 20.
0b acts as a thrust toward the clutch surface 22, thereby making it impossible for the bolt body 19 to rotate. Therefore, the piston 5 and the adjusting nut 13 can only move backward by a stroke of the gap c, and as a result, there is a gap c between the brake lining of each brake shoe 2, 2 and the inner peripheral surface of the brake drum. An appropriate braking gap is created to correspond to the

As described above, according to the present invention, the adjustment bolt of the automatic braking gap adjustment device built in the hydraulic pressure chamber of the wheel cylinder is made up of a bolt body having a multi-start thread portion and a clutch portion, a clutch surface and a clutch portion. The two members are connected by a connecting member with a gap corresponding to the braking gap in the axial direction, and a sealing member is fitted into the piston body, and the sealing member is The sliding resistance with the cylinder is set to be greater than the sliding resistance between the connecting member and the locking groove of the bolt body and piston body, so when adjusting the braking interval, the rotation of the piston body is restricted and only the bolt body is screwed. The piston body, on which the seal member is attached, slides only in the axial direction of the cylinder. Therefore, since the sealing member does not rotate and slide relative to the cylinder, the durability of the sealing member can be improved and liquid leakage due to rotation can be prevented. In addition, when the piston body is fixed to the cylinder side, it is troublesome to install the means for connecting the bolt body and the cylinder body, and it is difficult to assemble. When the cylinder body is composed of two members, the bolt body and the cylinder body can be easily locked together by the connecting member, and the assembly is easy and the work efficiency can be improved.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention, with Figure 1 being a cross-sectional front view of the main parts, and Figure 2 showing the state of connection between the bolt body and piston body that constitute the adjustment bolt. FIG. 3 is an enlarged sectional view of the main parts shown, and FIG. 3 is a perspective view of the connecting member. 1 is the wheel cylinder, 2 is the brake shoe,
3 is the cylinder body, 4 is the hydraulic chamber, 5 is the piston,
13 is an adjusting nut, 18 is an adjusting bolt, 19 is a bolt body, 20 is a piston body, and 24 is a connecting member.

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 Braking in a hydraulically operated brake that abuts against a clutch surface of the opposing portion and holds 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 gap adjustment device, the adjusting bolt is composed of two members: a bolt body having a multi-thread threaded portion at one end and a clutch portion at the other end, and a piston body having a clutch surface at one end and a clutch portion at the other end. Then, the clutch portion of the bolt body is engaged with the clutch surface of the piston body, and the connecting member is engaged in the locking groove of the bolt body and the piston body in the axial direction with a gap corresponding to a braking gap. A seal member that connects and prevents the pressure fluid in the hydraulic pressure chamber from acting on the clutch surface of the opposing portion is fitted into the piston body, and the sliding resistance of the seal member with the cylinder is reduced by the coupling member and the locking member. An automatic braking gap adjustment device for a hydraulically operated brake, characterized in that it is set larger than the sliding resistance with the groove.