JPH0261659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic gap adjustment device for a vehicle brake.

When installing a drum brake on a vehicle, the gap between the drum and the brake shoe (hereinafter referred to as the shoe gap) should be set larger than the regular shoe gap in consideration of work efficiency. It is customary to perform an initial shoe gap adjustment operation to match the regular shoe gap. In the case of a drum brake equipped with an automatic gap adjustment device, this initial shoe gap adjustment work is performed by operating the adjustment device, but the disadvantage is that the structure of the adjustment device is generally complex and the operation is complicated. However, this trouble cannot be tolerated, especially in the case of a micro-adjustment device that performs one fine adjustment during one braking operation.

Further, even in a disc brake incorporating a parking brake device, there is a drawback that the structure of the automatic gap adjustment device is complicated.

Accordingly, the present invention provides an automatic gap adjustment device for a vehicle brake equipped with a multi-thread screw that screws together an adjuster screw and an adjuster nut. The purpose of the present invention is to provide an automatic gap adjustment device with a simple structure by employing a one-way reversible screw that can rotate against an axial force in the direction.

The present invention will be described below with reference to illustrated embodiments.

1 and 2 show a first embodiment in which the present invention is applied to an automatic gap adjustment device for drum brakes. In Figure 1, 1 is a bucking plate, 2, 3
are brake shoes, 4 is an anchor, 5 is a wheel cylinder, and 6 and 7 are shoe return springs, and the above structure is substantially the same as a conventional leading trailing brake.

Reference numeral 8 designates a parking lever, one end of which is rotatably supported by a pin 9 on a brake shoe 2, which is a braking friction material, and a parking cable 10 connected to the other end. Reference numeral 11 indicates an automatic gap adjustment device. The adjuster screw 12 has its base end pivotally supported by a pin 13 with an axial gap δ provided in the through hole 3a of one brake shoe 3, which is a braking friction material, and the tip end of the adjuster screw 12 is freely supported. The forked part 14a at the end of the socket 14 to be inserted is the parking lever 8.
and receives the other brake shoe 2. At the tip of the adjuster screw 12, there is a multi-thread screw (external
a) is threaded, and the multi-thread thread (female thread 15b) of the adjuster nut 16 is screwed into this, and one end of the spring 17 is in contact with the end surface of the brake shoe 3, and the other end of the spring 17 is connected through a washer 18 that reduces frictional resistance. is pressed against the end face of the adjuster nut 16, urging the nut 16 in the direction of screwing out. Therefore, under normal conditions, the adjuster nut 16 is in contact with the end surface of the socket 14, the forked portion 14a of the socket 14 is in contact with the parking lever 8, and the rotation of the parking lever 8 causes the adjuster screw 12 to move in the axial direction. It is connected like this.

Here, the multi-thread screw 15 carved on the outer circumferential surface of the tip end of the adjuster screw 12 and the inner circumferential surface of the adjuster nut 16 will be explained. The multi-thread screw 15 does not rotate relative to the adjuster screw 12 and the adjuster nut 16 in response to an axial force in the compression direction, that is, in the direction of contraction of the automatic gap adjustment device 11, but in the tension direction, that is, in the direction of extension of the automatic gap adjustment device 11. It is a multi-thread screw that rotates relative to the axial force applied to it, but is reversible. That is, as shown in an enlarged view in FIG. 3, the angles formed by the line segment The flank angle α on the right side in the figure, which is the distal end side, is set to be larger than the flank angle β on the left side in the figure, which is the proximal end side. In the case of such a multi-thread screw 15, there are a male thread 15a and a female thread 1.
In response to the relative axial force F ₁ in the tensile (A) direction acting between 5b and 5b, the contact surfaces a with a small flank angle β come into contact with each other, and the adjuster nut 16 rotates against the adjuster screw 12. Screw out. Relative axial force in compression (B) direction between male thread 15a and female thread 15b
For F ₂ , contact surface b with large flank angle α
This results in comradely contact, and an excessive frictional force f is applied to the contact surface b.
acts, and the adjuster nut 16 cannot be rotated.

The effect will be explained. If pressure oil is introduced into the wheel cylinder 5, both shoes 2, which are braking friction materials,
3 fills the gap δ, expands, slides into contact with a drum (not shown), and generates a braking force.

If brake shoes 2 and 3 are worn and the shoe clearance exceeds the regular shoe clearance, both shoes 2 and 3
After filling the gap δ as the spring expands, the spring 1
7, the multi-thread screw 15 changes the flank angle β.
The contact surface a on the side comes into contact, and the adjuster nut 1
6 is rotated and screwed out to substantially extend the adjuster screw 12 to automatically adjust the shoe gap.

The parking brake rotates the parking lever 8 by pulling the braking cable 10 to expand the brake shoe 2 and transmits the reaction force to the brake shoe 3, which is a braking friction material, via the automatic gap adjustment device 11. The adjuster screw 12 is moved in the axial direction to expand the shoe 3 and generate a braking force. At that time, Ajiastas Kuriyu 1
2. The axial force acting between the adjuster nuts 16 is:
Since it is in the compression direction, the contact surface b of the multi-thread screw 15 on the side of the flank angle α contacts, the nut 16 does not rotate, and the adjuster screw 12 acts as a strut.

4 and 5 show a second embodiment in which the present invention is applied to an automatic gap adjustment device for a floating caliper type disc brake.

Reference numeral 20 denotes a caliper main body, in which a piston 22 is fitted into a cylinder 21 on the rear arm of the caliper, and an adjuster screw 24 and an adjuster nut whose rotation is restrained by engagement with a stopper 23 and a width across flats 24a are installed inside the piston 22. 25 are screwed together with a multi-thread screw 15 and inserted, and the nut 25 is in contact with an inner pad 27, which is a braking friction material, via a piston 22. The adjuster screw 24 is connected via a link 28 to a pin 29 rotatably supported on a caliper body 20, which is a brake base, and a parking lever 30 is fixed to the pin 29.

Reference numeral 31 denotes a return spring for the adjuster screw 24, which is compressed and interposed between the flange 24b of the adjuster screw 24 and a spring case 32 fixed to the caliper main body 20, and is used as a return spring for adjusting the adjuster screw 24 during service braking. This ensures the position retention of the screw 24 and the return operation of the adjuster screw 24 when the parking brake is released.

Then, the multi-thread screw 15 for screwing together the adjuster screw 24 and the adjuster nut 25 is set so that the flank angle α on the front end side of the adjuster screw 24 is set from the flank angle β on the rear end side, as shown in FIG. They are screwed together using a multi-thread screw 15 which is set to a large diameter and is reversible in one direction.

During service braking, pressurized oil is introduced into the cylinder 21 from the outside and the disc 33 is compressed by the inner pad 27 and outer pad 26, which are braking friction materials, to obtain the required braking force, but at this time both pads 26 and 27 wear out. When this happens, an axial force in the tensile direction acts between the adjuster screw 24 and the adjuster nut 25, and the multi-thread screws 15 come into contact with each other at contact surfaces a with small flank angles β, as shown in FIG. The adjuster nut 25 is rotated and screwed out, and the gap between the pads 26, 27 and the disk 33 is automatically adjusted.

When applying the parking brake, the parking lever 30 is operated to apply rotational force to the pin 29, which moves the adjuster nut 25, which contacts the adjuster screw 24 and the piston 22 via the link 28, in the axial direction to obtain braking force. . that time,
Ajiasutakuriyu 24, Ajiasutanut 25
Since the axial force acting between them is in the compression direction, the contact surface b of the multi-thread screw 15 on the side of the flank angle α comes into contact, and the adjuster nut 25 does not rotate.

In conventional disc brakes, as shown in FIG. 5, one end of the adjuster screw 24 and the adjuster nut 25 is fixed to prevent the adjuster nut 25 from rotating or being screwed in when an axial force in the compression direction is applied between the adjuster screw 24 and the adjuster nut 25. A clutch spring 34 fixed to the piston 22 was wound around the adjuster nut 25, but according to the present invention, this clutch spring 34 is unnecessary, and the structure of the disc brake is simplified.

As described above, the present invention provides a vehicle that has an adjuster screw and an adjuster nut, and adjusts the gap between a braking friction material and a drum or disk by rotating and screwing the adjuster nut with respect to the adjuster screw. In the automatic brake gap adjustment device for the brake, the adjuster screw and the adjuster nut are set to have a flank angle on the front end side of the adjuster screw screw larger than a flank angle on the rear end side, so that the adjuster screw is reversible in one direction. This is an automatic gap adjustment device that is screwed together.

Therefore, in the conventional automatic gap adjustment device, there is no need for a clutch spring, etc., which is required to prevent the adjuster nut from being screwed into the adjuster screw, and the structure of the automatic gap adjustment device for vehicle brakes is simplified. In addition, the initial shoe gap automatic adjustment work for the drum brake can be performed by only applying the service brake once, resulting in the effect that the work is more efficient.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a first embodiment in which the present invention is applied to an automatic gap adjustment device for drum brakes;
The figure is a sectional view taken along the line A-A in Fig. 1, Fig. 3 is a sectional view showing a multi-thread screw, and Fig. 4 is a sectional view showing a second embodiment in which the present invention is applied to an automatic disc brake gap adjustment device. , FIG. 5 is a sectional view of a main part of a conventional disc brake equipped with a multi-thread screw. 2: Brake shoe (braking friction material), 3: Brake shoe (braking friction material), 8: Parking lever, 11: Automatic gap adjustment device, 12: Adjuster screw, 14: Socket, 15: Multi-thread screw ,1
5a: Male thread, 15b: Female thread, 16: Adjuster nut, 17: Spring, 18: Washer,
20: Caliper body, 21: Cylinder, 22: Piston, 24: Adjuster screw, 25: Adjuster nut, 26: Outer pad (braking friction material), 27: Inner pad (braking friction material), 2
8: Link, 29: Pin, 30: Parking lever, 33: Disc.

Claims (1)

[Claims] 1. An automatic gap adjustment device for a vehicle brake, which has an adjuster screw and an adjuster nut, and adjusts the gap between a braking friction material and a drum or disk by rotating the adjuster nut with respect to the adjuster screw. The adjuster screw and the adjuster nut are screwed together using a multi-thread screw that is reversible in one direction by setting a flank angle on the front end side of the adjuster screw to be larger than a flank angle on the rear end side. Automatic gap adjustment device.