JPH0354988Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an automatic brake adjustment device.

(Prior Art) A conventional automatic brake adjustment device is disclosed in Japanese Utility Model Publication No. 61-21623, for example. That is, a piston that is slidably fitted into the cylinder body, an adjustment nut that is non-rotatably supported by the piston and abuts on the contact surface of the piston in a separable manner, and is screwed into the adjustment with a quick screw. an adjusting rod, fixed to one end of the adjusting rod and rotatably slidable into a clutch hole provided in the cylinder body;
It has a movable clutch body that cooperates with a fixed clutch surface provided in the clutch hole.

(Problems to be solved by the invention) Between these conventional brakes: In drum brakes equipped with an automatic adjustment device, when replacing the brake shoe, the adjustment nut must be screwed into the adjustment rod until it returns to its original position. need to be reinstated. This return operation is performed by pushing the piston into the cylinder body while rotating it, and screwing the adjusting nut, which is non-rotatably supported by the piston, into the adjusting rod with a quick screw. As a result, the cup seal attached to the piston rotates and slides into contact with the cylinder body, causing damage and causing liquid leakage. Further, during this return work, it is necessary to remove the dustproof boot that covers between the piston and the cylinder body, which is a complicated work.

(Means for Solving the Problems) This invention was made in view of such conventional problems, and consists of a cylinder body having an inner cylinder part and an outer cylinder part coaxially, and the outer cylinder part. A pot-shaped actuating piston is fitted in a liquid-tight and slidable manner to the inner periphery of the inner cylindrical portion, and the closed end engages with the brake friction member; A hydraulic chamber is defined by an adjuster piston which is fitted freely, and an adjuster nut is provided on the outer periphery of the inner cylindrical portion and is screwed with a reversible screw that sets the normal operation interval by backlash. and the actuating piston are coupled so as to be connectable and disconnectable by a clutch, and an elastic body for urging the connection of the clutch is disposed between the actuating piston and the adjuster nut, and a predetermined pressure or higher is applied to the hydraulic pressure chamber. When the brake fluid is supplied, the stepped surface of the adjuster piston is locked to the cross section of the adjuster nut so as to restrict adjustment movement of the adjuster nut, and a tool is coupled to return the adjuster piston. This is an automatic adjustment device between the brakes and a tool engaging portion provided at the base end of the adjuster piston.

(Function) Therefore, if brake fluid is supplied to the hydraulic pressure chamber,
The actuating piston moves forward and operates, and the brake friction member comes into sliding contact with a rotating body such as a brake drum to obtain braking force. Now, if the operating interval is within the normal operating interval, the operating piston receives hydraulic pressure, and the adjuster nut receives the elastic force of the spring, and moves integrally within the range of the reversible screw's stroke. Braking power can be obtained. When the brake friction member is worn out and the operating gap is larger than the normal operating gap, the operating piston moves further to operate after filling the reversible screw backlash. At that time, the clutch is disconnected, the adjuster nut is unscrewed by the reversible screw under the elastic force of the spring, and the operating period is automatically adjusted until the clutch is securely connected again.

When the brake component is elastically deformed after the brake friction member slides on the rotating body, first, brake fluid at a relatively high predetermined pressure is supplied to the hydraulic pressure chamber, and a return force is generated by the tip surface pressure of the adjuster piston. balances with the repulsive force of the elastic body, and the adjustment movement of the adjuster nut is regulated while the clutch remains disengaged. When further high-pressure brake fluid is supplied to the hydraulic chamber, the adjuster piston is pushed back, and the adjuster nut is
While compressing the spring, screw in using the reversible screw. When the brake fluid is reduced to a predetermined pressure, the adjuster nut is quickly unscrewed to a proper adjustment position where the return force of the adjuster piston and the elastic force of the spring are balanced. Thus,
Over-adjustment due to elastic deformation of the brake component is suppressed.

When the brake fluid is discharged from the hydraulic pressure chamber, the pressure is reduced to a predetermined pressure and the clutch takes the proper adjustment position where it is connected, and then the actuating piston and adjuster nut are activated, for example, by the action of a shew return spring, and the reversible screw is released. It returns in one piece according to the situation, ensuring a period of normal operation.

Next, if the brake drum thermally expands due to braking friction heat, and this thermal expansion is picked up and over-adjusted, brake fluid exceeding a predetermined pressure is supplied to the hydraulic pressure chamber after the brake drum has cooled. , the adjuster piston operates as described above, and the normal operating interval is properly provided.

The next step is to replace the brake friction member.
The restoration work of the automatic adjustment device will be explained. During this work, a tool is connected to the tool engaging portion of the adjuster piston, and the tool is pulled to return the adjuster piston. As a result, the adjuster nut that locks on the stepped surface of the adjuster piston,
Screw in with a reversible screw while rotating relative to each other. If the actuating piston is pushed in lightly, the automatic adjustment device will easily return to its original state.

(Example) Hereinafter, an example of this invention will be described with reference to the drawings.

Figures 1 and 2 show an embodiment in which this invention is applied to a wheel cylinder for a drum brake. The cylinder body 1 fixed to the bucking plate 29 has an outer cylindrical portion 3 whose base end is closed by the bottom portion 2.
and an inner cylinder part 4 coaxially. On the inner periphery of this outer cylindrical portion 3, a cylindrical portion 5a of a tip-shaped actuating piston 5 is provided.
are fitted through the cup seal 6 in a fluid-tight manner and slidable in the axial direction. A bottomed cylindrical portion 5b is integrally fitted onto the outer periphery of the tip of the cylindrical portion 5a via an oil seal 9, and the actuating piston 5 is constituted by both portions 5a and 5b. The working piston 5 is
A brake shoe 11, which is a brake friction member, is received and supported in a groove portion 5c formed at the closed end of the bottomed cylindrical portion 5b, and is unrotatable. The inner cylindrical portion 4 has a through hole 4a, and an adjuster piston 7 is fitted into the inner periphery of the through hole 4a through an oil seal 8 in a fluid-tight and slidable manner.

Thus, the cylinder body 1 and the working piston 5
and the adjuster piston 7 define a hydraulic chamber 12. Reference numeral 13 denotes a dust-proof boot that is attached to the outer cylindrical portion 3 of the cylinder body 1 and the operating piston 5, and covers the space between them.

Reference numeral 16 denotes an adjuster nut, which is screwed onto the outer periphery of the inner cylindrical portion 4 with a reversible screw 17. Here, the reversible screw 17 is defined as a screw connection that inevitably undergoes relative rotational movement due to relative movement in the forward and reverse directions in the axial direction between the adjuster nut 16 and the inner cylinder portion 4,
This applies to multi-thread screws. By reversing the reversible screw 17, a normal operating interval, which is a proper operating interval between the brake drum (not shown) and the brake shoe 11, is set. The tip of the adjuster nut 16 has a conical shape and constitutes a clutch 18 that connects and disconnects to a matching conical surface of the bottomed cylindrical portion 5b of the actuating piston 5. This connection of the clutch 18 is urged by a spring 19 which is an elastic body.
The spring 19 is compressed with a bearing 20 interposed between the outward step surface 16a of the adjuster nut 16 and the inward step surface 5b of the cylindrical section 5a.
In the disconnected state, the nut 16 is free to rotate relative to the actuating piston 5. Further, an outward annular stepped surface 7 of the head 7a of the adjuster piston 7
b is connected to the adjuster nut 1 through the bearing 21.
The adjuster piston 7 can be engaged with the inward annular stepped surface 16b of the hydraulic chamber 1.
2 is supplied with brake fluid at a predetermined pressure, and when the head 7a receives the hydraulic pressure, the adjusting nut 16 stops pressing forward (to the left in the figure),
Furthermore, when high-pressure hydraulic fluid is supplied to the hydraulic pressure 12, the adjuster nut 16 is screwed in by the multi-thread screw 17. For this purpose, fluid passages 22a, 22b, and 22c are appropriately formed in the adjuster nut 16 so that the brake fluid flows through the head 7 of the adjuster piston 7.
It is also supplied to the area around a.

Reference numeral 23 denotes a locking member, the body portion 23a of which is located in the recess 1 formed at the base end of the through hole 4a of the cylinder body 1.
a, and the other brake shoe 24 is locked in the groove portion 23b. Reference numeral 25 denotes a spacing member, which has a partially cut-out annular body as shown in FIG.
The locking member 23 is interposed between the flange portion 23c of the locking member 23 and the base end surface of the cylinder body 1.

At the base end of the adjuster piston 7,
A tool engaging portion is formed for returning the adjuster nut 16 to its initial position. In this embodiment, a screw hole 7c for screwing a bolt member 28, which is a tool, is formed extending in the axial direction, and serves as a tool engaging portion.

Next, the effect will be explained. A pair of wheel cylinders in this embodiment are provided point-symmetrically on the backing plate 29 and are used as tooling brakes.

When brake fluid from a master cylinder (not shown) is supplied to the hydraulic chamber 12 in the cylinder body 1, both brake shoes 11, 24 come into sliding contact with the brake drum, and braking force is obtained. Now, if the working gap is within the normal working gap, the working piston 5 receives hydraulic pressure,
Further, the adjuster nut 16 and the adjuster piston 7 receive the elastic force of the spring 19, and move integrally between the backlashes of the reversible screw 17, thereby providing a braking force. One brake shoe 1
1 is worn out, and when the operating interval is larger than the normal operating interval, the operating piston 5 moves further to operate after filling up the backlash of the reversible screw 17. At this time, the clutch 18 is disengaged, so the adjuster nut 1
6 is a reversible screw 1 under the elastic force of a spring 19.
7 to automatically adjust the screw-out and operation time. In this way, during this time, the automatic adjustment device functions as a positive adjuster whose operating range is adjusted during forward movement. Moreover, it is a one-shot type that allows a proper period of normal operation to be achieved with one braking operation.

When the brake drum is elastically deformed after the brake shoe 11 comes into sliding contact with the brake drum, a relatively high predetermined brake fluid is supplied to the hydraulic pressure chamber 12, and the adjuster pressure generated by acting on the head 7a is When the return force of the piston 7 and the repulsive force of the spring 19 are balanced, the clutch 18 assumes the disconnected proper adjustment position, and the adjustment movement (screwing out) of the adjuster nut 16 is restricted. Furthermore, high-pressure brake fluid is stored in the hydraulic chamber 12.
When the brake fluid is supplied to the predetermined pressure, the adjuster piston 7 is pushed back, and the adjuster nut 16 is screwed into the reversible screw 17 while compressing the spring 19. However, when the brake fluid is reduced to a predetermined pressure, the adjustment position described above is reached. The adjuster nut 16 is quickly unscrewed until the end. In this way, over-adjustment due to elastic deformation of brake components such as brake drums is avoided.

When the brake fluid is discharged from the hydraulic pressure chamber 12, the pressure is reduced to a predetermined pressure and the clutch 18 assumes the proper adjustment position where it is frictionally connected. As a result, the reversible screw 17 returns integrally in accordance with the backlash of the reversible screw 17, and a normal operating period is obtained.

Next, the brake drum thermally expands due to the frictional heat of braking, and this thermal expansion is picked up. If the automatic adjustment device overadjusts, the brake drum exceeds a predetermined pressure in the hydraulic pressure chamber 12 after cooling the brake drum. By supplying the liquid, the adjuster piston 7 operates as described above, and the normal operating period is properly provided.

Next, the replacement work of the brake shoes 11 and 24 will be explained. First, one brake shoe 24
When replacing the brake drum, if there is stepped wear on the brake drum, pull out the spacing member 25 from the back side of the bucking plate 29 using the locking hole 25a (the bucking plate 29 has an opening for working). 2
9a is formed. ), the locking member 23 is inserted into the recess 1
After the brake drum is fully immersed in the hole a and the brake drum is removed, the brake shoe 24 is removed. Thereafter, the locking member 23 is removed, the bolt member 28 is screwed into the screw hole 7c, and the adjuster piston 7 is returned to its original position by pulling the bolt member 28. As a result, the adjuster nut 16, which is engaged with the step surface 7b of the adjuster piston 7 via the bearing 21, is screwed in by the reversible screw 17. In this state, if the actuating piston 5 is pushed lightly, the automatic time adjustment device easily returns to its original state. Therefore, the actuating piston 5 and the adjuster piston 7 do not rotate relative to the cylinder body 1. There is also no need to remove the boot 13.

Note that a hook may be formed as a tool engagement portion at the base end of the adjuster piston 7 instead of the screw hole 7c, and a tool may be hooked to this hook to return the adjuster piston 7. Similar effects can be obtained as in the embodiment.

(Effects of the invention) As understood from the above explanation, this invention provides the following effects.

(1) Since the automatic adjustment device is built into the cylinder body, it has excellent rust prevention performance and is durable.

(2) Since neither the operating piston nor the adjuster piston needs to rotate relative to the cylinder body, premature wear of oil seals is less likely to occur.
Excellent durability.

(3) By operating the adjuster piston, it is possible to prevent not only over-adjustment due to elastic deformation of the brake component members, but also over-adjustment due to thermal expansion of the brake drum, thereby eliminating problems that would cause the brake friction member to drag. , can be suppressed well.

(4) Since it is a one-shot type that can obtain the normal operating range with one braking operation, initial setting of the normal operating range is easy.

(5) Since the automatic adjustment device can easily return to the initial state, the replacement work of the brake friction member becomes extremely efficient. Moreover, there is no need to remove the dustproof boots. In addition, since the pistons do not rotate and slide against the cylinder body, liquid leakage is less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of this invention, and FIG. 2 is a view showing a spacing member. DESCRIPTION OF SYMBOLS 1... Cylinder body, 2... Bottom, 3... Outer cylinder part, 4... Inner cylinder part, 5... Operating piston, 5a...
... Cylindrical part, 5b ... Bottomed cylinder part, 7 ... Adjuster piston, 7b ... Stepped surface, 7c screw hole (tool engagement part), 11, 24 ... Brake shoe (brake friction member), 12... Hydraulic pressure chamber, 16... Adjuster nut, 16b... Step surface, 17... Reversible screw,
18...Clutch, 19...Spring (elastic body), 20, 21...Bearing, 28...Bolt member (tool).

Claims (1)

[Scope of utility model registration request] A cylinder main body having an inner cylindrical part and an outer cylindrical part coaxially, and a tip that fits fluid-tightly and slidably into the inner periphery of the outer cylindrical part and whose closed end engages with a brake friction member. A hydraulic pressure chamber is defined by an actuating piston having a shape of 1.5 mm, and an adjuster piston that fits fluid-tightly and slidably into the inner periphery of the inner cylindrical portion. An adjuster nut is provided which is screwed together with a reversible screw that sets the operating distance, and the adjuster nut and the actuating piston are connected so as to be connectable and disconnectable by a clutch, and an elastic body that urges the connection of the clutch is connected to the actuating piston. and the adjuster nut, and when brake fluid of a predetermined pressure or higher is supplied to the hydraulic pressure chamber, the step surface of the adjuster piston is arranged between the step surface of the adjuster nut and the adjuster nut so as to restrict the adjusting movement of the adjuster nut. A tool engaging portion that engages with the step surface and connects a tool for returning the adjuster piston,
An automatic adjustment device for a brake, characterized in that it is provided at the base end of the adjuster piston.