JP2556678Y2 - Disc brake - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake used for a vehicle or the like, and more particularly to a disc brake capable of reducing a drag torque.

[0002]

2. Description of the Related Art In general, a disc brake is provided with pads arranged on both sides of the disc and supported movably in the axial direction of the disc, and arranged so as to straddle these pads and the disc, and the leading end is formed on the back of one pad. A caliper having opposing claw portions is provided, and a back surface of the other pad is pressed by a piston fitted into a cylinder formed on the caliper, and a back surface of the one pad is also reacted via the claw portion by a reaction. It is known that the disc is pressed to clamp the disc between two pads to brake the disc.

[0003] Conventionally, in such a disk brake, the piston which has moved so as to protrude toward the disk to press the pad against the disk at the time of braking is restored by the restoring force of the piston seal which seals between the cylinder and the piston. Was returned to the position.

[0004] That is, as shown in FIG. 4, a piston seal 7 attached to a piston seal groove 3 formed on the inner periphery of the cylinder 1 and having an inner peripheral surface brought into contact with the outer periphery of the piston 8 has an inner peripheral surface. Is tightly fitted to the piston 8, it is elastically deformed with the movement of the piston 8. Therefore, when the hydraulic pressure acting on the cylinder 1 from the master cylinder is released, the piston 8 is restored with the restoration of the piston seal 7. Also returns to its original position.

[0005] Here, what is indicated by reference numeral 6 is a boot that covers the protruding portion of the piston 8 from the cylinder 1, which is disposed closer to the opening of the cylinder 1 than the piston seal 7 and has a tip portion. It is attached to the outer periphery of the piston 8 and its base end is attached to the boot groove 2 formed on the inner periphery of the cylinder 1 as shown in the figure.

[0006]

However, in the above-mentioned conventional disk brake, the return amount of the piston 8 does not become constant according to the hydraulic pressure applied from the master cylinder during braking, and the hydraulic pressure is particularly high. In this case, the amount of return of the piston 8 is reduced, and even if a retract spring that biases both pads so as to separate them from each other is provided, the pads do not completely separate from the disk, and a so-called drag phenomenon may occur. there were.

[0007] That is, the piston seal 7 is provided in the groove 3 reduced in diameter toward the inner side of the cylinder so as to exhibit good sealing performance and to generate a predetermined return amount. The amount is substantially determined by the dimensions of the chamfered portion 4 of the groove 3. If the hydraulic pressure is high, slippage occurs between the inner peripheral surface of the piston seal 7 and the outer peripheral surface of the piston 8, and the piston seal 7 returns to its original state. Even if the shape of the piston 8 is restored, the piston 8 does not return to its original position by the amount of the slip.

[0008] This drag phenomenon increases the loss of torque in a vehicle or the like, and has been a great hindrance in improving the fuel efficiency of the vehicle.

The present invention has been made in view of the above-mentioned conventional circumstances, and has as its object to provide a disk brake in which a piston is reliably returned to an original position after braking, and a drag phenomenon is unlikely to occur.

[0010]

A disk brake according to the present invention has a cylinder in which a piston for pressing a pad against a disk is fitted, and a first groove formed in the inner circumference of the cylinder and having an inner peripheral surface formed therein. A piston seal contacting the outer periphery of the piston, and a second seal formed at a position closer to the opening of the cylinder than the piston seal, with a distal end attached to the outer periphery of the piston and a proximal end formed at the inner periphery of the cylinder.
And a boot attached to the groove of the cylinder, wherein the inner peripheral surface of the base end of the boot is brought into contact with the outer periphery of the piston, and the corner of the second groove at the opening side of the cylinder is formed. The chamfer dimension is larger than the chamfer dimension of a corner of the first groove on the opening side of the cylinder .

[0011]

With the disc brake of the present invention, the inner peripheral surface of the base end of the boot is dragged by the outer periphery of the piston.
The base end is deformed with the movement of the piston, and after braking (after the hydraulic pressure from the master cylinder is released), the restoring force of the boot base end also returns the piston to the original position. Will work as follows.

In addition, the size of the chamfer at the corner of the groove that allows the deformation of the base end of the boot can be made larger than that of the groove in which the piston seal is mounted. Can be set larger. For this reason, even if slippage occurs between the piston seal and the piston when the cylinder moves, if the hydraulic pressure is released, the restoring force of the base end of the boot is combined with the restoring force of the piston seal to secure the piston. To the original position.

Further, according to the disk brake of the present invention, since the above-mentioned operation is performed by a conventional boot, the number of parts does not increase.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the disc brake according to the present embodiment includes a torque receiving member 1 fixed to a non-rotating portion of a vehicle on one side of a disc 11 that rotates with wheels.
2 and two legs 1 extending from the torque receiving member 12.
Pads 13 and 14 provided on both sides of the disk 11 while being supported between the disks 2a and 12a and movable in the axial direction of the disk 11, and are arranged so as to straddle these pads 13 and 14 and the disk 11, A caliper 16 movably supported by the legs 12a, 12a via a pin 15.
And retract springs 20, 20 having both ends engaged with the pads 13, 14, respectively, and functioning as springs for biasing the pads 13, 14 in a direction to separate them from each other.

At a position on the back side of the pad 13 of the caliper 16, a cylinder 17 is provided.
A piston 18 facing the back surface of the pad 13 is slidably fitted. The tip of the caliper 16 is the pad 1
4 and the claw portion 1 that faces the back surface of the pad 14
9 and 19 are formed.

As shown in FIG. 2, a piston seal 21 for sealing between the inner periphery of the cylinder 17 and the outer periphery of the piston 18 is provided inside the cylinder 17. The piston seal 21 is fitted in a piston seal groove 22 (first groove) formed on the inner periphery of the cylinder 17,
The inner peripheral surface is pressed against the outer periphery of the piston 18. The piston seal 21 is made of an elastic synthetic rubber or the like. Here, the diameter of the groove 22 is reduced toward the inner side of the cylinder 17, and it is easier for the piston 18 to slide to the right side than to the left side in FIG. 2 with respect to the piston seal 21. Further, the chamfer dimension of the corner 26 on the opening side of the cylinder 17 in the groove 22 is set in the same manner as in the prior art, so that the restoring force of the piston seal 21 ensures the same return amount as in the related art.

The piston 18 and the cylinder 17 are located closer to the opening of the cylinder 17 than the piston seal 21 is.
Is provided. Boots 23
The boot groove 24 has a distal end mounted on the outer periphery of the piston 18 and a proximal end 23 a formed on the inner periphery of the cylinder 17.
(A second groove), and an intermediate portion thereof is formed in a bellows shape so as to be expandable and contractible. These boots 23
Is also formed of an elastic synthetic rubber or the like.

The chamfer dimension of the corner 25 on the opening side of the cylinder 17 in the boot groove 24 in which the base end 23a of the boot 23 is mounted is determined by the cylinder 17 in the piston seal groove 22 in which the piston seal 21 is mounted. It is larger than the chamfer dimension of the corner 26 on the opening side. The diameter of the boot groove 24 is increased toward the inner side of the cylinder 17, and the depth of the boot groove 24 is set to be greater than that of the groove 22. However, a large amount of returning the piston 18 in combination with the restoring force of the piston seal 21 is ensured. Since the base end 23a of the boot 23 does not need to function as a seal, the boot groove 24 can be set in consideration of only the return amount to be secured.

In the disc brake constructed as described above, when pressure oil acts on the cylinder 17 from a master cylinder (not shown), the piston 18
3 is pressed against one surface of the disk 11, and the claw 19 of the caliper 16 presses the pad 14 against the other surface of the disk 11 by this reaction, whereby the rotating disk 11 is braked (that is, the vehicle).

At this time, if the pressure applied from the master cylinder is not high, both the piston seal 21 and the base end 23a of the boot 23 are displaced by the piston 18, deforming as shown in FIG. 3, and the braking is released. Thereafter, the piston 18 returns to its original position more smoothly than in the past due to these two restoring forces.

Further, even when the pressure applied from the master cylinder is high and slippage occurs between the piston seal 21 and the piston 18, the base 23a of the boot 23 is surely deformed in accordance with the movement of the piston 18. Also in this case, the piston 18 is surely returned to the original position by the restoring force of the base end portion 23a.

Therefore, after the braking is released, the restoring force of the retract springs 20, 20 works effectively,
The pads 13 and 14 are separated from the disk 11 so as to be separated from each other, so that the pads 13 and 14 do not come into contact with the disk 11, and the dragging phenomenon is reliably prevented.

For this reason, according to the above-mentioned disc brake, the number of parts is not increased at all,
It is possible to prevent the drag phenomenon of the pad and improve the fuel efficiency of the vehicle.

[0024]

As is apparent from the above description, according to the disc brake of the present invention, the piston is reliably returned to the original position after braking by the conventionally provided boot, and the pad dragging phenomenon can be prevented. Therefore, there is an effect that the torque loss of the vehicle during non-braking can be reduced and the fuel efficiency can be improved without increasing the number of parts of the disc brake.

[Brief description of the drawings]

FIG. 1 is a plan view of a disc brake, in which a caliper and a pad are cut away at a center of a piston in a radial direction of the disc.

FIG. 2 is an enlarged view of a portion indicated by reference numeral Z in FIG.

FIG. 3 is an enlarged view of a portion indicated by a reference numeral Z in FIG. 1 and shows a state at the time of braking.

FIG. 4 is a diagram for explaining a conventional technique, and is an enlarged view of a seal portion between a piston and a cylinder.

[Explanation of symbols]

 Reference Signs List 11 disc 13, 14 pad 17 cylinder 18 piston 21 piston seal 22 first groove (piston seal groove) 23 boot 23a base end of boot 23b inner peripheral surface of base end of boot 24 second groove (boot groove) 25 corner of the second groove 26 corner of the first groove

Claims (1)

(57) [Scope of request for utility model registration] 1. A cylinder in which a piston for pressing a pad against a disk is fitted, a piston seal attached to a first groove formed in the inner periphery of the cylinder and having an inner peripheral surface in contact with the outer periphery of the piston, A disk, which is disposed closer to the opening of the cylinder than the piston seal, has a tip mounted on the outer periphery of the piston, and a base mounted on a second groove formed on the inner circumference of the cylinder; In the brake, an inner peripheral surface of a base end portion of the boot is brought into contact with an outer periphery of the piston, and a chamfer dimension of a corner of the second groove on the side of the opening of the cylinder is set to a value corresponding to the cylinder in the first groove . Corner surface on the opening side of the
A disc brake characterized by having a size larger than the dimensions .