JPS6221150Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an auto-adjustment device for vehicle brake cylinders, and in particular, it is equipped with an over-adjustment prevention mechanism that automatically stops the adjustment operation when hydraulic pressure exceeding a set value is generated in the cylinder. This invention relates to an auto-adjustment device.

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 gap between the brake lining and the inner peripheral surface of the brake drum increases, so an adjuster mechanism provided separately from the wheel cylinder is activated to adjust the brake shoe. It is adjusted so that the braking gap is always constant by expanding it.

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.

Therefore, the purpose of this invention is to improve the auto-adjustment device built into this vehicle brake cylinder so that when a hydraulic pressure exceeding a set value is generated, the adjustment action is stopped and over-adjustment does not occur. The present invention provides an auto-adjustment device for a vehicle brake cylinder.

In accordance with the above object, the present invention provides the auto-adjustment device in which the adjustment bolt is provided with an axial hole whose rear end is open, and the actuator is tightly slid into the hole via a spring. When the distal end protruding from the hole of the actuator comes into contact with the spring retainer which is biased toward the piston by the adjusting spring, and a hydraulic pressure higher than a set value is generated in the cylinder. Further, the actuator is provided with an over-adjustment prevention mechanism in which the actuator sinks into the hole against the spring, presses the spring retainer outward from the center of the adjustment bolt, and restricts rotation of the adjustment bolt. This is a characteristic feature.

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 proximal direction. The brake cylinder device 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 has one end open, 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. As a result, there is a small diameter portion 2 in the cylinder 2 facing this piston 3.
A hydraulic chamber 5 is defined by the piston 3 and the opposing portion 2c of the rear wall of the cylinder having a diameter 2c. Supplied. A nut member 7 having a multi-thread female thread 7a is press-fitted and fixed to the front end of the opposing portion 2c. The adjusting bolt 8 is made up of a shaft portion having a multi-thread male screw 8a and a conical head having a clutch surface 8b.
The shaft portion is screwed into the nut member 7 with a multi-thread screw with a backlash in the axial direction, and the clutch surface 8 of the head
b is placed in contact with a clutch receiving surface 3a of a recess formed at the rear of the piston 3.

The brake shoes are brake shoes 1 and 1'.
brake linings 1c, 1'c, and the inner peripheral surface of the brake drum that rotates together with the wheels (not shown).
It is set equal to the braking gap between

The shaft of the adjusting bolt 8 has a hole 9 opened on the rear side centered on the shaft, and an actuator 11 having an O-ring 10.
is tightly and slidably fitted into this hole 9 via a spring 12.

The actuator 11 is always urged rearward by a spring 12, and is retained by a clip 13 with its conical rear tip 11a protruding from the hole 9 by a predetermined amount.

The spring retainer 14 is always urged in the direction of the piston 3 by an adjusting spring 15 and is in contact with the rear end portion 11a of the actuator 11.
The outer edge 14a in the radial direction of the spring retainer 14 is connected to the multi-start male thread 8a of the adjustment bolt 8.
The spring retainer 14 is formed to have the same shape as the end face portion 8c of the adjusting bolt 8, and the spring retainer 14 comes into contact with the adjusting bolt 8 at a position far from the center of rotation. and,
The spring 12 that biases the actuator 11 is set so that its spring force is compressed when a hydraulic pressure that causes drum deformation is generated in the cylinder 2 during braking. The distance _l1 between the front end of the actuator 11 and the bottom of the hole 9 is set larger than the distance _l2 between the outer edge 14a of the spring retainer 14 and the end face 8c of the adjustment bolt 8, and the set value When the actuator 11 sinks into the hole 9 when the above hydraulic pressure is generated, the outer edge 14a of the spring retainer 14 is pressed against the end face 8c of the adjuster bolt 8 to restrict rotation of the adjuster bolt 8.
The contact position between the spring retainer 14 and the adjusting bolt 8 when a hydraulic pressure higher than this set value is generated is the outer radius of the adjusting bolt 8 in this embodiment, but is not limited to this. It is sufficient that the rotation of the adjusting bolt 8 can be restricted by frictional resistance at the end face, that is, at a position off the axis.

Next, the operation of this embodiment will be explained.

When the pressure fluid from the master cylinder is introduced into the hydraulic pressure chamber 5 from the fluid supply port 6, the piston 3 moves forward to the right, moving the shoe web end 1'a of the brake shoe 1' toward the brake drum. Move to.
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 16 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.

At this time, when the piston 3 moves forward, the adjustment bolt 8 is pushed by the adjustment spring 10 via the actuator 11 which is biased by the spring 12, and the clutch surface 8b of the head becomes the clutch receiving surface of the piston 3. The braking operation is performed by moving by the amount of backlash while remaining in contact with 3a. At this time, the adjustment 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 gap becomes more than the backlash, so the piston 3 moves forward due to the action of the pressure fluid, but the adjustment bolt 8 is regulated by the nut member 7 and cannot be integrated with the piston 3. unable to move forward. Therefore, the clutch receiving surface 3a of the piston 3 and the clutch surface 8b of the adjusting bolt 8 are separated from each other. At this time, adjust bolt 8
The rear tip 11a of the actuator 11 is in point contact with the spring retainer 14 at the axial center, and is constantly pushed in the direction of the piston 3 by the adjusting spring 15, so that the rear end 11a of the actuator 11 is in point contact with the spring retainer 14 at the axial center, and is constantly pushed in the direction of the piston 3 by the adjuster spring 15. Rotational torque is generated. Since the nut member 7 is fixed, the adjustment bolt 8 rotates and moves forward only by the rotational resistance of the multi-thread thread. Then, the adjusting bolt 8 rotates until the clutch surface 8b hits the clutch receiving surface 3a of the piston 3, and the frictional resistance between the clutch surface 8b and the clutch receiving surface 3a becomes greater than the rotational resistance.
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 its clutch surface 8b 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 backlash is set equal to the braking gap, even if the brake lining wears out, the braking gap is automatically adjusted to always remain constant.

When a hydraulic pressure equal to or higher than the set value is supplied into the cylinder 2, the piston 3 moves forward, but the hydraulic pressure presses the actuator 11 via the spring retainer 14. As a result, the spring 12
is compressed and the actuator 11 sinks into the hole 9, the outer edge 14a of the spring retainer 14 is pressed against the end face 8c of the adjusting bolt 8, and the adjusting bolt 8 is restricted from rotating due to its frictional resistance and moves forward. I won't. Therefore, when only the piston 3 moves forward and the brake is released, the piston 3 moves backward until the clutch receiving surface 3a abuts the clutch surface 8b of the adjusting bolt 8, so that overadjustment will not occur.

In this way, according to the present invention, when hydraulic pressure is generated in the cylinder to the extent that it deforms the drum, the hydraulic pressure causes the actuator to sink into the hole in the adjust bolt, and the spring retainer is pressed against the adjust bolt, thereby automatically restricting the operation of the adjust bolt and effectively preventing over-adjustment. Moreover, the structure is simple, and has other advantages such as being easy to manufacture and assemble.

[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 hole, 11 is an actuator, 12 is a spring, 14 is a spring retainer, and 15 is an adjustment spring.

Claims (1)

[Scope of utility model registration request] In a hydraulic chamber defined by a piston that is slidably inserted into a cylinder and its opposing part, an adjusting bolt with a clutch surface is screwed into a nut member fixed to the opposing part with a multi-thread screw. In an auto-adjustment device for a vehicle brake cylinder, the adjustment bolt is always pressed in the direction of the piston by an adjustment spring so that the clutch surface of the adjustment bolt is brought into contact with the clutch receiving surface of the piston. An axial hole with an open rear end is drilled in the strike bolt, and an actuator is tightly and slidably fitted into this hole via a spring, with a tip portion protruding from the hole of the actuator. comes into contact with a spring retainer that is biased toward the piston by the adjuster spring, and when a hydraulic pressure higher than a set value is generated in the cylinder, the actuator resists the spring and sinks into the hole, An auto-adjustment device for a vehicle brake cylinder, comprising an over-adjustment prevention mechanism that presses a spring retainer outward from the center of the adjustment bolt to restrict rotation of the adjustment bolt.