JPH05133429A - Piston returning mechanism of disc brake - Google Patents

Abstract

PURPOSE:To fix a return amount of a piston according to the size of load fluid pressure when a piston is returned by the elastic restoring force of a rubber ring at the time of releasing pressure of a hydraulic oil pressure system. CONSTITUTION:An elastic ring 7 which is harder and has a higher elastic coefficient than a rubber ring 4 is installed between a sealing groove 5 on the inner surface of a cylinder 2 and an edge surface on an opposite side of fluid pressure of the rubber ring 4 for fluid sealing which is inserted into the groove and is fitted with an interference on the periphery of a piston 3. A space 6 which allows deformation of an elastic ring 7 is formed between the sealing groove 5 and the elastic ring 7, and the second space 8 is formed between the elastic ring 1 and the rubber ring 4 if necessary. As load fluid pressure rises, deformation of the elastic ring 7 increases, and a substantial chamfered amount (size of the space) which determines elastic deformation amount of a rubber ring 4 increases, so that the piston returning amount, increases according to fluid pressure. It is thus possible to solve the problem of an increase in dragging torque due to shortage of the piston returning amount, after high pressure is applied without an increase in the piston stroke when low pressure is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for returning the piston of a hydraulic disc brake during depressurization, and more particularly to a returning mechanism in which the amount of return of the piston is determined according to the load hydraulic pressure.

[0002]

2. Description of the Related Art In a service type hydraulic disc brake, the elastic restoring force of a liquid sealing rubber ring provided between a brake cylinder and a brake piston (hereinafter simply referred to as a cylinder or piston) is used to depressurize the piston. A pullback mechanism is often used. This piston return mechanism is
As shown in FIG. 5, the rubber ring 4 is assembled in the seal groove 5 provided on the inner surface of the cylinder 2, and the rubber ring is fitted around the outer periphery of the piston 3 with a tightening margin. Further, the seal groove 5 is chamfered at the groove edge on the anti-hydraulic side (the side close to the inlet of the cylinder) to form a space 6 between the seal groove 5 and the rubber ring 4 which allows elastic deformation of the ring.

With this arrangement, when the piston is pushed out by the braking fluid pressure, the rubber ring 4 is dragged to the position where it fills the void 6 and elastically deforms. In order to return to the original state, the piston 3 advanced by pressurization is always pulled back by a certain amount at the time of depressurization.

Since the amount of elastic deformation of the rubber ring 4 is substantially determined by the size L of the space 6, the return amount at this time is substantially constant although there is a slight increase or decrease depending on the size of the load hydraulic pressure.

[0005]

In FIG. 5, the return amount of the piston is now Re, the pad 9 for sliding contact with the disk,
Assuming that the amount of compressive strain during braking of 9 is δp and the amount of bending of the caliper 1 due to hydraulic pressure is δc, the distance between the piston 3 and the pad 9 restored by depressurization is determined by the equation ε = Re- (δc + 2δp). A gap ε is created.

If the gap ε is always kept above the required minimum value, the dragging of the pad by the disk D does not occur. However, the amount of compressive strain δp and the amount of caliper deflection δc of the pad increase as the load hydraulic pressure increases. On the other hand, according to the conventional return mechanism, since the return amount Re of the piston is constant, the value of ε decreases as the load hydraulic pressure increases. Therefore, when the set value of the return amount Re is small, the sum of 2δp and δc becomes Re or less and the relation of ε> 0 is established, and the pad remains pressed against the disc by the force of the rubber ring during non-braking. As a result, problems such as so-called increase in drag torque and unnecessary wear of the pad occur.

In order to deal with this problem, the return amount Re
If the amount of deformation of the caliper and the pad at the maximum load is taken into consideration, the piston stroke becomes large when the load hydraulic pressure is small, which increases the required brake fluid amount and deteriorates the pedal feel. An object of the present invention is to eliminate these problems.

[0008]

In order to solve the above-mentioned problems, the present invention provides a rubber ring between a seal groove having chamfered groove edges on the anti-hydraulic side and an end surface on the anti-hydraulic side of a rubber ring, rather than a rubber ring. An elastic ring having a high elastic coefficient is interposed with the brake piston with a gap.

[0009]

The elastic ring deforms in the direction of filling the space between the elastic ring and the seal groove as the load hydraulic pressure increases, and the deformation amount increases until it is restricted by the chamfered portion of the seal groove. In the present invention, since this elastic ring supports the rubber ring,
If the elastic ring is designed to maximize the amount of deformation at maximum load hydraulic pressure, the amount of chamfering that determines the amount of elastic deformation of the rubber ring due to the deformation of the elastic ring (void size)
Becomes larger according to the load hydraulic pressure, and therefore, the return amount of the piston also increases as the load hydraulic pressure increases.

As described above, since the amount of return of the piston is determined according to the load hydraulic pressure, according to the present invention, there is a problem that the piston stroke is increased under a low pressure load and the clearance between the piston and the pad is decreased under a high pressure load. Are solved together.

[0011]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 is a caliper having a cylinder 2, 3 is a piston inserted in the cylinder 2, 4 is a rubber ring inserted in a seal groove 5 on the inner surface of the cylinder 2, and the rubber ring 4 has a tightening margin on the outer circumference of the piston 3. It is attached and fitted. Also, the seal groove 5
A chamfer is formed on the edge portion of the anti-hydraulic side groove to create the void 6.

Reference numeral 7 is an elastic ring which characterizes the present invention. This elastic ring is made of rubber or synthetic resin that is harder than the rubber ring 4 and has a higher elastic coefficient. As shown in the figure, a gap is created between the elastic ring and the piston 3 and the end surface of the rubber ring 4 on the anti-hydraulic side. It is interposed between the seal groove 5.

Reference numeral 8 designates a second cavity formed by chamfering the inner peripheral edge of the elastic ring 7 on the rubber ring side. When a low pressure load is applied, the rubber ring 4 is formed in the second cavity, as shown in FIG. Elastically deformed so as to fill the place 8. The elastic deformation amount of the rubber ring at this time is a value obtained by adding the amount determined by the size of the second space 8 and the amount generated by the deformation of the elastic ring, but the amount of elastic ring deformation is zero or zero. Since it is close, the amount is almost determined by the size of the second void 8.

On the other hand, when a high pressure is applied, the elastic ring 7 is also elastically deformed as shown in FIG. Therefore, as shown in FIG. 4, the elastic deformation amount of the rubber ring 4 increases proportionally as the hydraulic pressure increases until the deformation of the elastic ring 7 stops. The return amount of 3 also increases with the load hydraulic pressure.

When the amount of elastic deformation of the elastic ring 7 is sufficient to ensure a sufficient amount of piston return when a low pressure load is applied, the second void 8 is not necessary.

Further, when the pad 9 is worn under both low pressure load and high pressure load, a slip corresponding to the wear amount occurs between the piston 3 and the rubber ring 4 as in the conventional brake. The amount of piston return does not change.

[0017]

As described above, according to the present invention, since the amount of return of the piston is determined according to the magnitude of the load hydraulic pressure, the piston stroke is increased which deteriorates the pedal feeling at low pressure load. Can be solved together with the problem of increase in drag torque due to insufficient amount of piston pullback after high-pressure load, which is useful for improving the performance and reliability of the disc brake.

[Brief description of drawings]

FIG. 1A is a sectional view showing an embodiment of the present invention.
(B) is an enlarged view of the main part of the above

FIG. 2 is a diagram showing a deformed state of a rubber ring under a low pressure load.

FIG. 3 is a diagram showing a deformed state of a rubber ring and an elastic ring under a high pressure load.

FIG. 4 is a graph showing the relationship between the piston return amount and the load hydraulic pressure.

FIG. 5 is a sectional view showing a main part of a conventional piston returning mechanism.

[Explanation of symbols]

 1 Caliper 2 Cylinder 3 Piston 4 Rubber Ring 5 Seal Groove 6 Void 7 Elastic Ring 8 Second Void 9 Pad D Disc

Claims (2)

[Claims] 1. A rubber ring is fitted in a seal groove having a chamfered groove edge on the inner side of a brake cylinder on the inner surface of the brake cylinder, and the rubber ring is pressed against the outer circumference of the brake piston to seal the liquid between the cylinder and the piston. In the piston brake return mechanism of the disc brake that pulls back the brake piston at the time of decompression by the restoring force of the rubber ring that elastically deforms so as to fill the void created by the chamfering when pressurizing the A piston return mechanism characterized in that an elastic ring having a higher elastic coefficient than a rubber ring is interposed between the pressure side end surface and the brake piston with a gap provided therebetween. 2. A chamfered portion is provided on an inner peripheral edge portion of the elastic ring on the rubber ring side, and a second portion having a predetermined size is provided between the elastic ring and the rubber ring.
2. The piston return mechanism according to claim 1, wherein the empty space is created.