JPH048654B2 - - Google Patents

Abstract

PURPOSE:To perform roll back quickly by setting the amount of roll back of the piston seal laid on the large diameter section of the two stage cylinder of a two system disk brake more than that of the piston seal laid on the small diameter section. CONSTITUTION:The amount of roll back of the piston seal 16 laid around the seal groove 6 provided on the circumference of the large diameter section 4a of a two stage cylinder 4 is set more than that of the piston seal 17 laid around the seal groove 7 on the circumference of a small diameter section 4b. Therefore, the release of the brake allows a two stage piston 5 to perform the roll back quickly in proportion to the amount of the roll back of a piston seal 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-system derisk brake.

[Conventional technology]

Conventionally, in disc brakes, which perform braking by clamping a disc that rotates together with the vehicle with a pair of friction pads pushed by a piston, in order to cope with failures in the hydraulic pressure supply device and its piping system, the piston is A two-system disc brake is known that performs braking by supplying pressure fluid from separate hydraulic pressure supply devices into cylinders that are movably inserted in a fluid-tight manner.

As an example of such a two-system disc brake, a floating type disc brake shown in a cross-sectional view in FIG. 4 will be explained.
The bridge portion 1a straddles the disk 2 which rotates together with the wheel.
An inner part 1b and an outer part 1c are arranged on both sides of the
It is supported slidably in the disc axial direction by a sliding pin (not shown) of a bracket 3 fixed to the vehicle body.

The inner part 1b has a large diameter part 4a on the side of the disk 2, a small diameter part 4b in the rear part following the large diameter part 4a, and a stepped part 4c.
A two-stage cylinder 4 is formed in a step-like manner, and within this two-stage cylinder 4, a large diameter portion 5a is provided in the front on the disk 2 side, and a small diameter portion is provided in the rear via a step portion 5b. 5c, and a two-stage piston 5 whose rear end on the inner wall 4d side of the two-stage cylinder 4 is closed by the rear end wall 5d is fitted in a liquid-tight and movable manner.

The pressure fluid is sealed in a seal groove 6 provided around the large diameter portion 4a of the two-stage cylinder 4 and a seal groove 7 provided around the small diameter portion 4b, and the two-stage piston 5 is rolled back when the brake is released. At the same time, a first hydraulic pressure supply port 10 is fitted in the vicinity of the stepped portion 4c of the large diameter portion 4a.
A second hydraulic pressure supply port 11 is opened in the vicinity of the inner wall 4d of the small diameter portion 4b, and pressure fluid is supplied from hydraulic pressure supply devices (not shown) of separate systems through both ports 10 and 11, respectively. , actuate the two-stage piston 5,
As a result, the first hydraulic pressure chamber 12 is formed between the piston seals 8 and 9, that is, between the large diameter portion 4a and the stepped portion 4c of the two-stage cylinder 4 and the stepped portion 5b and the small diameter portion 5c of the two-stage piston 5. A second hydraulic chamber 13 is defined behind the piston seal 17 of the portion 5c, that is, by the inner wall 4d and small diameter portion 4b of the two-stage cylinder 4, and the rear end wall 5d of the two-stage piston 5, respectively.

Further, on both sides of the disk 2, friction pads 15, 15 fixed to a pair of pad back plates 14, 14 are arranged, and the inner friction pad 15 is pushed by the two-stage piston 5 to At the same time, the friction pad 15 on the outer side slides into contact with one side.
is pushed by the outer portion 1c and comes into sliding contact with the other side surface of the disk 2, and the disk 2 is pushed by the outer portion 1c, and the disk 2
5, and braking is performed.

[Problem that the invention seeks to solve]

Therefore, if the rollback amounts of the piston seals 8 and 9 are equal, the first hydraulic chamber 12 and the second hydraulic chamber 13 are supplied from the hydraulic pressure supply devices of different systems during braking.
When pressurized fluid is supplied to
Since hydraulic pressure is applied from both the first hydraulic pressure chamber 12 and the second hydraulic pressure chamber 13, the piston seal 9 does not deform, but the piston seal 8 deforms toward the disk 2 side. Then, when the brake is released, the piston seal 8
As a result, the two-stage piston 5 is rolled back toward the inner wall 4d of the cylinder 4, which is the return direction, but the frictional force of the piston seal 9 prevents smooth rollback and slows down the rollback. In particular, when a braking operation is performed when the hydraulic pressure supply device that supplies pressure fluid to the second hydraulic pressure chamber 13 and its piping system fail, pressure fluid is supplied only to the first hydraulic pressure chamber 12, and the piston seal 8 is deformed toward the disk 2 side, and the piston seal 9 is deformed toward the inner wall 4d of the two-stage cylinder 4, so that when the brake is released, the amount of roll back of both piston seals 8 and 9 is equal, and the direction of the roll back is opposite. Therefore, there was a problem that the rollback of the two-stage piston 5 may be hindered.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a two-system disc brake in which rollback of a piston can be performed quickly and reliably.

[Means for solving problems]

In order to solve the above problems, in the present invention, a two-stage cylinder having a large diameter part on the disk side and a small diameter part following it, has a large diameter part in the front and a small diameter part in the rear on the disk side. A two-stage piston is provided, a piston seal is fitted into the large diameter part and the small diameter part of the two-stage cylinder, and a first hydraulic pressure chamber is provided between the two piston seals and behind the piston seal in the small diameter part. A second hydraulic pressure chamber is defined respectively, each hydraulic pressure chamber is connected to a hydraulic pressure supply device of a separate system, and the rollback amount of the piston seal fitted in the large diameter portion of the two-stage cylinder is transferred to the small diameter portion. It is characterized by being set larger than the rollback amount of the fitted piston seal.

As a specific means for setting the rollback amount of the piston seal on the large diameter side to be larger than the rollback amount of the piston seal on the small diameter side, for example, the disk side cut surface of the seal groove on the large diameter side is set on the small diameter side. Make the seal groove larger than the cut surface on the disc side.

The tightening allowance of the piston seal on the large diameter side is made larger than the squeezing allowance of the piston seal on the small diameter side.

The surface roughness of one or both of the inner circumferential surface of the piston seal on the large-diameter side and the outer circumferential surface of the large-diameter piston Make it smoother than rough to reduce the coefficient of friction.

There are conventional means such as, and these can be appropriately selected and used.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Incidentally, the same members in the figure as in FIG. 4 are given the same reference numerals to simplify the explanation.

The two-system disc brake of the present invention is constructed in the same manner as the conventional two-system disc brake described above, and has a piston seal 16 fitted into a seal groove 6 provided around the large diameter portion 4a of the two-stage cylinder 4.
The rollback amount is set to be larger than that of the piston seal 17 fitted in the seal groove 7 provided around the small diameter portion 4b, so that the hydraulic pressure supply ports 10 and 11 are connected to hydraulic pressure supply devices of separate systems. Therefore, even when braking is performed by supplying pressure fluid to the first hydraulic chamber 12 and the second hydraulic chamber 13, the rollback amount of the piston seal 16 fitted in the seal groove 6 of the large diameter section 4a is smaller than that of the small diameter section. Since it is set larger than the piston seal 17 fitted in the seal groove 7 of 4b, when the brake is released, the rollback of the two-stage piston 5 is quickly performed due to the large rollback amount of the piston seal 16. Furthermore, even if the hydraulic pressure supply device that supplies pressure fluid to the second hydraulic pressure chamber 13 fails, the amount of rollback of the piston seal 16 is larger than that of the piston seal 17, so the direction of rollback of the piston seal 16 and the piston seal 17 can be changed. Even if the two-stage piston 5 is in the opposite direction, the piston seal 1
Since the rollback amount of piston seal 6 exceeds the rollback amount of piston seal 17, rollback is ensured.

A specific means for setting the rollback amount of the piston seal 16 on the large diameter side to be larger than the rollback amount of the piston seal 17 on the small diameter side is as follows.
For example, the disk side cut surface 6a of the seal groove 6 of the large diameter portion 4a is made larger than the disk side cut surface 7a of the seal groove 7 of the small diameter portion 4b.

The constriction allowance of the piston seal 16 of the large diameter part 4a is made larger than the constriction allowance of the piston seal 17 of the small diameter part 4b.

The surface roughness of one or both of the inner circumferential surface of the piston seal 16 of the large diameter portion 4a and the outer circumferential surface of the piston large diameter portion 5a, the inner circumferential surface of the piston seal 17 of the small diameter portion 4b or the outer circumferential surface of the piston small diameter portion 5c.
The surface roughness of the outer peripheral surface is made smoother than that of the outer peripheral surface to reduce the coefficient of friction.

There are conventional means such as, and these can be appropriately selected and used.

In addition, if the hydraulic pressure supply device that supplies pressure fluid to the first hydraulic pressure chamber 12 and its piping system fail, both piston seals 16 and 17 will deform toward the disk 2 due to the braking operation, and the braking will be interrupted. When released, the two-stage piston 5 is reliably rolled back by the amount of rollback caused by the deformation of both piston seals 16 and 17.

〔Effect of the invention〕

As described above, the present invention sets the rollback amount of the piston seal fitted in the large diameter part of the two-stage cylinder of the two-system disc brake to be larger than the rollback amount of the piston seal fitted in the small diameter part. The rollback of the two-stage piston when releasing the brake is performed quickly and reliably without being hindered by the piston seal fitted in the small diameter part.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a cross-sectional front view showing a piston seal fitted into the large diameter part of the cylinder of a two-system disc brake, and FIG. FIG. 3 is a cross-sectional front view showing a piston seal fitted into a small diameter portion, FIG. 3 is a cross-sectional front view of a two-system disc brake, and FIG. 4 is a cross-sectional front view of a conventional two-system disc brake. 1... Caliper body, 2... Disc, 4...
...Two-stage cylinder, 4a...Large diameter part, 4b...Small diameter part, 4c...Step part, 4d...Dear wall, 5...Two-stage piston, 5a...Large diameter part, 5b...Step Part, 5
c... Small diameter part, 5d... Rear end wall, 6... Large diameter part 4
Seal groove of a, 6a... disk side cut surface of seal groove 6, 7... seal groove of small diameter portion 4b, 7a...
...Disc-side cut surface of seal groove 7, 8, 9...
Piston seal, 10...first hydraulic pressure supply port,
11...Second hydraulic pressure supply port, 12...First hydraulic pressure chamber, 13...Second hydraulic pressure chamber, 16, 17...Piston seal.

Claims (1)

[Claims] 1. A two-stage piston having a large-diameter portion in front of the disk side and a small-diameter portion in the rear is disposed in a two-stage cylinder having a large-diameter portion on the disk side and a small-diameter portion following the small-diameter portion, and A piston seal is fitted to each of the large diameter part and the small diameter part of the stepped cylinder, and a first hydraulic pressure chamber is defined between both piston seals, and a second hydraulic pressure chamber is defined behind the piston seal of the small diameter part. The hydraulic pressure chambers are each connected to a hydraulic pressure supply device of a separate system, and the rollback amount of the piston seal fitted in the large diameter portion of the two-stage cylinder is set to be larger than the rollback amount of the piston seal fitted in the small diameter portion. A two-system disc brake featuring the following features: