JPS6221793Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an auto-adjustment device for a vehicle brake cylinder, and in particular, when a hydraulic pressure exceeding a set value is generated in the hydraulic pressure chamber in the cylinder, the adjustment operation is automatically stopped and over-adjustment is performed. The present invention relates to an auto-adjustment device that eliminates the possibility of

As is well known, drum brakes are leading
In the trailing type or two-leading type, a pair of arcuate brake shoes are arranged on the back plate so that they can be expanded by the operation of the wheel cylinder, with one end serving as a fulcrum, and the brake shoes rotate together with the wheels. The brake drum is designed to apply pressure to the inner peripheral surface of the brake drum to perform braking.
When the brake lining wears out due to this braking, the braking distance between the brake lining and the inner circumferential surface of the brake drum becomes larger. is adjusted so that the braking interval 〓 is always constant.

Therefore, the applicant first incorporated the adjusting mechanism, which is provided separately from the wheel cylinder that expands the brake shoe, into the wheel cylinder. The present invention provides a vehicle brake cylinder device that can be easily used for trailing or two-leading drum brakes, as well as disc brakes.

The structure of this device is such that a piston is slidably inserted into a cylinder, a hydraulic pressure chamber is defined in the cylinder by the piston and an opposing part of the piston, and a hydraulic chamber is defined between the piston and this opposing part. An adjusting bolt having a clutch surface is screwed into a nut member fixed to the piston, and this adjusting bolt is constantly pressed in the direction of the piston by an adjusting spring, so that the clutch surface of the adjusting bolt is connected to the clutch receiver of the piston. It has a built-in auto-adjustment device that contacts the surface.

The purpose of this invention is to improve the auto-adjustment device built into vehicle brake cylinders so that when hydraulic pressure exceeds the set value, it automatically stops adjusting and prevents over-adjustment. To provide an auto-adjustment device for a vehicle brake cylinder which further suppresses the inclination of an adjustment bolt during adjustment operation, operates smoothly, and is small and compact.

In accordance with the above object, the present invention has a nut member fixed to the opposing part within a hydraulic pressure chamber defined by the piston slidably inserted into the cylinder and the opposing part, and has a step inside. An adjusting bolt having a cylinder attached thereto is screwed into the nut member with a multi-thread screw, and a piece member that connects with the clutch surface of the piston is provided in the front part of the adjusting bolt so that its rotation is regulated and it is movable in the axial direction. Further, an actuator is tightly and slidably fitted into the stepped cylinder via a spring, the front end of the actuator is brought into contact with the piece member, and the protruding shaft portion of the rear end is fitted with an adjuster spring. When the actuator comes into contact with a spring retainer that is biased toward the piston, and a hydraulic pressure higher than a set value is generated in the hydraulic pressure chamber, the actuator moves forward and moves the piece member in the axial direction, thereby locking the piston. It is characterized in that it is pressed against the surface to restrict rotation of the adjustment bolt and prevent over-adjustment.

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

Inside the back plate (not shown), a pair of arcuate brake shoes 1, 1' are arranged so as to be expandable with one end of the shoe webs 1a, 1'a as fulcrums, and a return spring (not shown) is always biased in the extending direction. The brake cylinder arrangement is arranged between the ends of the shoe webs of the brake shoes 1, 1' and is fixed to the back plate. A cylinder 2 of this brake cylinder device is open at one end, and a piston 3 is tightly and slidably fitted into a large diameter portion 2a of the cylinder 2 by means of a piston cup 4. This causes cylinder 2
Inside, a hydraulic pressure chamber 5 is defined by the piston 3 and an opposing portion 2c of the rear wall of the cylinder that faces the piston 3 and has a small diameter portion 2b, and a liquid supply port 6 that communicates with a master cylinder (not shown). Pressure liquid is supplied into this hydraulic pressure chamber 5 by this. A nut member 7 having a multi-thread female thread 7a is press-fitted into the front end of the opposing portion 2c and fixed thereto, and an adjustment bolt 8 is inserted into the multi-thread male thread 8a with a predetermined backlash in the axial direction. They are screwed together. The backlash is set equal to the braking distance between the brake linings (not shown) of the brake shoes 1, 1' and the inner peripheral surface of the brake drum (not shown) that rotates integrally with the wheels.

A piece member 9 is fitted to the front shaft portion 8b of the adjusting bolt 8, and this piece member 9 is inserted into a groove portion 9a formed in the axial direction with the rear open, and in the shaft portion 8b in the circumferential direction. An upright pin 10 is engaged, whereby the rotation of the frame member 9 is restricted by the shaft portion 8b and is supported so as to be movable in the axial direction. This piece member 9 is formed with a clutch surface 9b that connects with the clutch receiving surface 3a of the piston 3.

A pair of actuators 12 and 13 are slidably fitted into a stepped cylinder 11 formed on the adjustment bolt 8. In this front actuator 12, a small diameter shaft part 12a with a diameter _A1 is fitted into a small diameter cylinder part, and a large diameter shaft part 12b is fitted into the large diameter cylinder part via a spring 14, and is always pushed backward by the spring 14. Forced. The rear actuator 13 has a large diameter shaft portion 13a with a diameter of _A2 that is clipped to a large diameter cylinder portion 15.
The rear end protruding shaft portion 13
b is in contact with the retainer 16. Retainer 16
is always biased in the piston 3 direction by the adjuster spring 17. The set load of this adjusting spring 17 is set smaller than the set load of the spring 14, and the set load of this spring 14 is such that the set load of the spring 14 is such that the amount of fluid that exceeds the set value that causes deformation of the drum in the hydraulic pressure chamber 5 during braking is set. It is set to be compressed when pressure is generated. The front actuator 12 is connected to the O ring 18 of the small diameter shaft portion 12a, and the rear actuator 13 is connected to the large diameter shaft portion 13.
They are each sealed by an O-ring 19 of a. The respective actuators 12 and 13 may be molded integrally, but if they are divided and molded separately as in this embodiment, even if the diameters of the stepped cylinders 11 and 2 are different, the center Easy to match and can further improve productivity.

The adjusting bolt 8 is formed to be long in the axial direction and have a large diameter, and the actuators 12 and 13 are each incorporated into stepped cylinders 11 formed in the adjusting bolt 8. As a result, the adjusting bolt 8 has a large diameter and has a long engagement length at the multi-threaded threaded part with the nut member 7, making it possible to suppress the tilting of the adjusting bolt 8 as much as possible. Since the actuating elements 12 and 13 are incorporated into the adjusting bolt 8 in this way, the weight of the adjusting bolt 8 can be reduced by the amount of the stepped cylinder 11, and the actuating elements 12 and
Since the brake system 13 is installed internally, the brake device can be made smaller, which is advantageous because the tension length of the brake shoe can be increased.

Next, the operation of this embodiment will be explained. When pressure fluid from the master cylinder is introduced into the fluid pressure chamber 5 from the fluid supply port 6, the piston 3 moves forward in the right direction, and brakes the shoe web end 1'a of the brake shoe 1'. Move toward the drum. As a result, the brake shoe 1' expands using the fixed portion of the brake cylinder device provided on the other side as a fulcrum. Similarly, the brake shoe 1 expands using the fixed portion 20 of the brake cylinder device as a fulcrum, and presses against the inner circumferential surface of the brake drum that rotates together with the wheel to perform a braking action. Assuming that the hydraulic pressure at this time is _P1 , as the piston 3 moves forward, the adjusting bolt 8 is pushed by the adjusting spring 17 via the actuators 12 and 13 without compressing the spring 14, A braking action is performed by moving the clutch surface 9b of the member 9 by the amount of backlash while remaining in contact with the clutch receiving surface 3a of the piston 3. Therefore, adjust bolt 8
does not rotate and is not adjusted. When the brake is released, the piston 3 and adjustment bolt 8 return to their original positions together.

When the brake lining wears out due to repeated braking, the braking distance becomes longer than the backlash, so the piston 3 moves forward due to the action of pressure fluid, but the adjustment bolt 8 is regulated by the nut member 7 and is integral with the piston 3. become unable to move forward. Therefore, the contact between the clutch receiving surface 3a of the piston 3 and the clutch surface 9b of the link member 9 is separated. At this time, the rear end protruding shaft portion 13b of the rear actuator 13 of the adjuster bolt 8 makes point contact with the retainer 16 at the axial center, and the adjuster spring 1
Since the piston 7 is always pushed in the direction of the piston 3, rotational torque is generated at the multi-thread threaded portion with the nut member 7. Since the nut member 7 is fixed, the adjusting bolt 8 rotates together with the block member 9 and moves forward only by the rotational resistance of the multi-thread thread portion. And the clutch surface 9 of the link member 9
b hits the clutch receiving surface 3a of the piston 3, and due to the rotational resistance, the clutch surface 9b and the clutch receiving surface 3a
The piston 3 rotates until the frictional resistance against the piston 3 becomes large and follows the forward movement of the piston 3.

When the brake is released, the brake shoes 1, 1' are returned to their original positions by the return spring, but at this time, the adjustment bolt 8 is connected to the clutch surface 9b of the link member 9 and the clutch receiving surface 3a of the piston 3. Since the piston 3 is in contact with the piston 3, the piston 3 moves back by the amount of backlash without rotating, and the adjustment is completed. Since this brake shock is set equal to the braking interval, even if the brake lining is worn, the braking interval is
is automatically adjusted to remain constant.

When a hydraulic pressure _P2 equal to or higher than the set value is supplied into the hydraulic pressure chamber 5, the piston 3 moves forward;
The actuators 12 and 13 are also pushed in the direction of the piston 3 by _P2 , the spring 14 is compressed, and the small diameter shaft portion 12a of the actuator 12 protrudes from the adjustment bolt 8, and the piece member 9 is guided by the pin 10. Move in the axial direction. As a result, the piece member 9 is separated from the front surface of the shaft portion 8b of the adjusting bolt 8, and its clutch surface is joined to the clutch receiving surface 3a of the piston 3. The rotation of the block member 9 is restricted by the frictional resistance caused by this joining, thereby restricting the rotation of the adjusting bolt 8 via the pin 10. Therefore, the adjusting bolt 8 no longer moves forward, and the piston 3 and the piece member 9 only move forward as one, and when the brake is released, the piston 3 and the piece member 9 move forward.
In this case, the piece member 9 is the shaft portion 8b of the adjusting bolt 8.
It will not be over-adjusted because it will retreat until it touches the front of the wheel.

As described above, according to the present invention, when a set value of hydraulic pressure is supplied to the hydraulic pressure chamber in the cylinder, the adjusting bolt and the piece member rotate together and move forward to perform the adjusting operation. On the other hand, when the hydraulic pressure is above the set value, the actuator moves the piece member in the axial direction and connects it to the piston, so the rotation of the piece member and adjustment bolt is restricted and they do not move forward. Adjustment is effectively prevented.
The actuator that pushes the piece member is built into the stepped cylinder of the adjusting bolt, which increases the length of the multi-thread threaded engagement between the adjusting bolt and the nut member, thereby increasing the inclination of the adjusting bolt. This has the advantage of suppressing the amount of friction, resulting in smooth adjustment operation, making the device lighter, more compact, and allowing the length of the brake shoe to be extended.

[Brief explanation of the drawing]

The drawing is a sectional front view showing an embodiment in which the present invention is applied to a two-leading type drum brake. 2 is a cylinder, 3 is a piston, 7 is a nut member, 8 is an adjustment bolt, 9 is a piece member, 11
12 and 13 are actuators, 14 is a spring, 16 is a retainer, and 17 is an adjusting spring.

Claims (1)

[Scope of utility model registration request] A nut member is fixed to the opposing part in a hydraulic pressure chamber defined by the piston slidably inserted into the cylinder and the opposing part, and an adjusting bolt having a stepped cylinder inside is disposed. A piece member which is screwed into the nut member with a multi-thread screw and is connected to the clutch surface of the piston is provided at the front part of the adjusting bolt so that rotation is regulated and is movable in the axial direction, and the actuator is provided with the stepped member. A retainer that is tightly and slidably fitted into the cylinder via a spring, the front end of this actuator is in contact with the piece member, and the rear end protruding shaft is biased toward the piston by an adjuster spring. When the actuator comes into contact with the piston and a hydraulic pressure higher than the set value is generated in the hydraulic pressure chamber, the actuator moves forward and moves the piece member in the axial direction, presses it against the clutch surface of the piston, and tightens the adjustment bolt. An auto-adjustment device for a vehicle brake cylinder, characterized in that it regulates the rotation of the brake cylinder and prevents over-adjustment.