JPS6229707Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement in an automatic pad gap adjustment device for a disc brake.

An automatic pad gap adjustment device for a disc brake includes, for example, a bottomed cylindrical piston that is slidably inserted into a cylinder bored in a caliper, a base that is slidably supported by the caliper, and a tip that is slidably inserted into a cylinder that is bored in a caliper. a thrust member that comes into contact with the inner bottom of the piston, and the thrust member is threadedly engaged with a push rod that advances toward the bottom of the piston when the handbrake is operated, and an adjuster nut that also advances toward the bottom of the piston due to biasing means. When the piston moves excessively due to wear of the friction pad, a thrust tensile load acts on the thrust member, and the adjuster nut moves forward while rotating on the threaded screw, restricting the return position of the piston. It is becoming more and more like this.

In such an automatic pad gap adjustment device, when the handbrake is activated, the thrust member is strongly pressed against the inner bottom surface of the piston, and this pressing force causes the adjuster nut to rotate in the opposite direction and move backward on the push rod. try to. For this reason, the contact surface between the piston and the adjuster nut is usually formed into a cone shape, or a clutch spring is interposed in the contact surface to increase frictional resistance and prevent the adjuster nut from rotating in the opposite direction. .

However, when the contact surface is made into a cone shape, if the accuracy of the cone angle, concentricity of the piston and adjuster nut, and surface accuracy are poor, the cone portion may become jammed or the handbrake may be pressed diagonally when the handbrake is activated. Problems such as the generation of prying forces and wear of various parts within the device and deterioration of its functionality occur.
This requires high-precision machining,
In addition, when a clutch spring is installed, precision in the winding diameter of the spring is required, which makes manufacturing difficult.Furthermore, when the adjuster nut rotates in the normal direction, some rotational resistance force is generated, increasing its minimum operating pressure. There were other drawbacks.

In view of the problems of the prior art described above, the present invention provides an automatic pad gap adjustment device for disc brakes that does not require high precision in component formation and assembly and can completely prevent reverse rotation of the adjuster nut when the handbrake is activated. The purpose is to

For this purpose, the engaging surfaces between the cylinder and the adjuster nut are formed parallel and flat, and a flat clutch facing with a high coefficient of friction is interposed between the parallel and flat engaging surfaces. We have realized a pad gap adjustment device that achieves this.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the structure of an automatic pad gap adjustment device according to the present invention. In the same figure, 1
is a caliper, in which a cylinder 2 and a guide hole 3 with a smaller diameter than the cylinder 2 are bored.A piston 4 in the shape of a cylinder with a bottom is slidably inserted into the cylinder 2, and a guide A base portion 5b of a push rod 5 is slidably inserted into the hole 3. A shaft portion of the push rod 5 extending into the piston 4 is formed with a multi-thread male thread 5a, into which a cylindrical adjuster nut 6 having a female thread 6a is screwed. Reference numeral 7 denotes a retainer that is fitted and fixed to the inner circumference of the piston 4, and a ball bearing 8, a ring 9, and a spring 10 are interposed between the retainer 7 and a stepped portion 6b formed on the adjuster nut 6. , this causes the aziasutana nut 6
is rotatable relative to the push rod 5, and is urged toward the lower part of the piston 4, that is, so that the inner bottom surface of the piston 4 and the tip end surface of the adjuster nut 6 come into contact.

The inner bottom surface 4c of the piston 4 and the tip end surface 6c of the adjuster nut 6 are parallel and flat, and a flat clutch facing 11 is interposed therebetween. The clutch facing 11 is made of a material with a high coefficient of friction, and is usually formed in one layer, but may have a multilayer structure in which friction material 11b is adhered to both sides of a steel plate 11a, as shown in FIG. 2, for example.

On the other hand, the base 5 of the push rod 5 of the caliper 1
A cam 13 is provided at a position facing b via a roller bearing 12. A strap 14 is interposed between the cam 13 and the base 5b, and the strap 14 swings to transmit the rotational force of the cam 13 to the push rod 5.

In FIG. 1, 15 is a key plate that prevents the push rod 5 from rotating relative to the cylinder 2, 16 is a retaining ring that fixes the key plate 15, 17 is a dust boot, 18 is a seal, and 19 is an O-ring. , 20 represent oil chambers defined within the cylinder 2, respectively. Further, the oil chamber 20 and the cam 13 are connected to a brake pedal and a handbrake lever, respectively, which are not shown.

With this configuration, when the brake pedal is now depressed, oil is supplied to the oil chamber 20, and the piston 4 moves forward in the left direction in the figure (in the direction of pressing the friction pad 21 against the disc 22), and follows this. The adjuster nut 6 also moves forward to the left while being pressed against the inner bottom surface 4c of the piston 4 via the clutch facing 11. When the friction pad 21 wears out and the piston 4 moves forward by more than a predetermined amount, the inner bottom surface of the piston 4 and the tip end surface of the adjuster nut 6 tend to separate. At this time, a thrust tensile load is applied to the threaded joint between the push rod 5 and the adjuster nut 6, and the adjuster nut 6 extends toward the bottom side of the piston 4 while rotating on the screw of the push rod 5, and then extends through the clutch facing 11 again. It is in a state where it is crimped onto the inner bottom surface 4c of the piston 4. In other words, the total length of the engaging body between the push rod 5 and the adjuster nut 6 increases by an amount corresponding to the amount of wear on the friction pad 21, and the return position of the piston 4 is thus regulated, so that the gap between the friction pads is maintained at a constant value. The Rukoto.

On the other hand, when the cam 13 rotates due to the operation of the handbrake lever, the strut 14 swings, and the rotational force is transmitted to the piston 4 via the push rod 5, adjuster nut 6, and clutch facing 11, and the piston 4 is moved to the left side in the figure. move forward in the direction At this time, a thrust compressive load acts strongly on the threaded portion of the push rod 5 and the adjuster nut 6, and the adjuster nut 6 attempts to retreat to the right in the figure while rotating in the opposite direction on the screw of the push rod 5. Therefore, a clutch facing 11 with a high friction coefficient is interposed between the engagement surfaces of the piston 4 and the adjuster nut 6, and the adjuster nut 6, which is strongly pressed by the clutch facing 11, cannot rotate in the opposite direction. The return position of will be maintained accurately.

As explained above in detail, the pad gap automatic adjustment device according to the present invention forms the engagement surfaces of the piston and the adjuster nut parallel and flat, and the engagement surfaces formed parallel and flat. A clutch facing with a high coefficient of friction is interposed in between, which completely prevents the adjuster nut from rotating backwards and maintains an accurate pad gap even if the friction pads wear out. In addition, the abutting surfaces are parallel and
Forming it flat eliminates the conventional problems of machinability and assembly difficulties, and also reduces jamming and wear between parts during use, ensuring smooth operation. There are some great effects.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an automatic pad gap adjustment device according to the present invention, and FIG. 2 is a sectional view showing an example of the structure of a clutch facing. 1... Caliper, 2... Cylinder, 4... Piston, 5... Push rod, 6... Adjuster nut, 5a... Male thread, 6a... Female thread, 5b
... Base, 4c, 6c ... Engagement surface, 11 ... Clutch facing.

Claims (1)

[Scope of utility model registration request] A cylindrical piston with a bottom is slidably inserted into a cylinder bored in a caliper, and a multi-thread screw whose base is slidably supported by the caliper and whose tip extends into the piston. a push rod, and an adjuster nut rotatably screwed into the push rod and biased toward the bottom of the piston, and the engagement surfaces of the piston and adjuster nut are parallel and flat; An automatic pad gap adjustment device for a disc brake, characterized in that a flat clutch facing is interposed between the parallel and flat engaging surfaces.