JPH11125284A - Disc brake for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a lag in rising of the initial braking originating from thermal affection as much as practicable, suppress the cost of piston seal, and enhance both the productivity and economy. SOLUTION: A cylinder hole 15 is provided circumferentially with a seal groove 20 whose diameter is increasing toward a disc rotor, and a piston seal 17 is fitted in this groove 20. By the piston seal 17, a piston 16 is held resiliently in such a way as movable while an interference is maintained. The piston seal 17 is formed in a circular or long hole section, and one side edge 17b of the piston seal 17 is contacted with the disc rotor side wall 20b of the seal groove 20, and a space C1 to admit deformation of the piston seal 17 in thermal expansion is provided between the piston seal 17 and the liquid pressure chamber side wall 20c of the seal groove 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk brake mounted on various running vehicles including automobiles and motorcycles, and more particularly, a piston for pressing a friction pad against a side surface of a disk rotor with a piston seal. Related to the structure.

[0002]

2. Description of the Related Art In a disk brake used for an automobile or a motorcycle, a piston for pressing a friction pad against a side surface of a disk rotor is housed in a cylinder hole of a caliper body through a piston seal (for example, a special seal). See Japanese Unexamined Patent Publication No. Hei 7-301264).

FIG. 3 shows the relationship between a piston 1 and a piston seal 2, and shows a cylinder hole 4 of a caliper body 3.
A seal groove 5 is provided in the inside, and an annular piston seal 2 is fitted in the seal groove 5 to resiliently and movably move the piston 1 with the piston seal 2.

The seal groove 5 is formed such that the bottom wall 5a is
The cross section is formed in a quadrangular shape whose diameter is increased from c to the disk rotor side wall 5b with a single gradient. Piston seal 2
A so-called square seal narrower in cross-section than the seal groove 5 and having a rectangular cross section is used, and one side surface 2b is brought into contact with the disk rotor side wall 5b of the seal groove 5 so that the piston seal 2
Is displaced toward the disk rotor side end, which is the deepest part of the seal groove 5, so that a space C1 is set between the other side surface 2c of the piston seal 2 and the hydraulic pressure chamber side wall 5c of the seal groove 5. .

[0005] The piston 1 and the piston seal 2 are fitted to each other with an appropriate interference.
To the disk rotor direction of the cylinder hole 4 (rightward direction in FIG. 3)
, The inner peripheral side of the piston seal 2
When the piston 1 is released, the elastic deformation of the piston seal 2 returns to its original shape, and the piston 1 is moved toward the hydraulic chamber at the bottom of the cylinder hole (to the left in FIG. 3). To a predetermined amount.

[0006]

In such a configuration, high-temperature braking heat generated by sliding contact between the disk rotor and the friction pad is applied to the piston 1, the caliper body 3, and the piston seal 2 from the friction pad. It propagates and thermally expands them.

In particular, the rubber piston seal 2 expands significantly compared to the metal or synthetic resin piston 1 and the caliper body 3, but the piston seal 2 has one side surface 2b.
Side expansion is restricted by the contact of the seal groove 5 with the disk rotor side wall 5b.
The piston seal 1 is allowed to expand only in the direction of the hydraulic pressure chamber, as shown by the two-dot chain line in FIG. It expands to the space C1.

On the other hand, the piston 1 and the piston seal 2 have an interference fit with an interference, and since high-temperature braking heat is applied to a wide surface contact, the piston 1 and the piston seal 2 are close to a sticking state. 2 expands while increasing the contact area with the piston 1 and drags the piston 1 toward the hydraulic chamber. For this reason, the retracted position of the piston 1 is retracted more toward the hydraulic pressure chamber than usual, and the gap between the friction pad and the piston 1 at the time of non-operation is expanded, so that the piston stroke at the time of braking increases, This may cause a delay in braking.

The square seal used as the piston seal 2 uses a large amount of material per piece and is a dedicated product formed by a special molding die. High and disadvantageous.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a disk brake for a vehicle which uses a low-cost piston seal and can minimize a delay in initial braking due to heat.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a caliper body provided on a side of a disk rotor, wherein a bottomed cylinder hole for accommodating a piston is provided on the disk rotor side. An opening is provided, and a seal groove which expands in diameter toward the disk rotor is provided inside the cylinder hole,
An annular piston seal is fitted into the seal groove, the piston seal movably holds the piston with a tight allowance, and seals the hydraulic chamber at the bottom of the cylinder hole with a piston seal in a liquid-tight manner. In the vehicle disc brake, the piston seal is formed narrower in width than the seal groove and has a circular or oval cross section, and the piston seal is brought into contact with a disk rotor side wall of the seal groove to form a piston seal. A space is formed between the seal groove and the side wall of the hydraulic pressure chamber to allow thermal expansion deformation of the piston seal.

According to such a configuration, the piston seal has:
By using a circular or oval cross section,
Since the contact area between the piston and the piston seal is greatly reduced as compared with the related art, sticking due to braking heat is reduced as much as possible.

The piston seal is deflected and fitted to the disk rotor side end, which is the deepest part of the seal groove, as in the prior art, and the inner and outer sides of the seal contact the piston and the bottom wall of the seal groove. A part of the center of the circle or the oval is in contact with the disk rotor side wall, and a small gap is left inside and outside in the radial direction of the contact part with the disk rotor side wall.

The piston seal that has received the braking heat from the friction pad expands mainly into the space on the hydraulic chamber side,
Part of the space also expands into the space on the disk rotor side. The expansion into the space on the hydraulic chamber side becomes an arc-shaped expansion because the cross-sectional shape of the piston seal is circular or oval,
The contact area with the piston does not increase so much. On the disk rotor side, the expanded portion into the radially inner gap slightly increases the contact area with the piston, and the deformed portion into the space acts as a drag against the force to move the piston toward the disk rotor. Therefore, the deformation force by which the piston seal moves the piston toward the hydraulic chamber by thermal expansion can be suppressed to a very small value.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIG.
A description will be given based on FIG. The disc brake 10 has a pin slide type caliper body 11 guided in the disc axial direction by using a pair of slide pins (not shown).
Is used, and the action portion 11a of the caliper body 11 is used.
A pair of friction pads 12, 12 above the back plate 12 b suspended by hanger pins 13
Are disposed to face each other with the disk rotor 14 interposed therebetween.

The caliper body 11 is composed of the above-mentioned action portion 11a and reaction portion 11b disposed on both sides of the disk rotor 14, and a bridge portion 11c connecting these over the outer periphery of the disk rotor 14. The operating portion 11a is provided with a bottomed cylinder hole 15 having an opening on the disk rotor side, and the reaction portion 11b is provided integrally with a reaction force claw 11d.

A slightly smaller diameter piston 16 is inserted into the cylinder hole 15 via a piston seal 17 so as to be liquid-tight and movable, and a hydraulic chamber 18 is defined between the piston 16 and the bottom of the cylinder hole 15. Is done. A dust seal 19 is attached to the opening side of the cylinder hole 15 between the cylinder hole 15 and the piston 16.
It prevents dust and rainwater from entering inside.

The hydraulic chamber 18 is supplied with hydraulic fluid pressurized by a separate hydraulic master cylinder (not shown) by a driver's braking operation, and the piston 16 advances through the cylinder hole 15 toward the disk rotor to act. Part side friction pad 12
To bring the lining 12 a of the friction pad 12 into sliding contact with the side surface of the working portion of the disk rotor 14.

Due to this sliding contact, a braking reaction force from the friction pad 12 acts on the operating portion 11a through the piston 16 and the hydraulic fluid in the hydraulic chamber 18, and the caliper body 11 is moved in the direction of the operating portion by the guide of the sliding pin. To the reaction unit 11
The reaction force claw 11d pushes the friction pad 12 on the reaction portion side, and the lining 12a of the pad 12 slides on the side surface of the reaction portion of the disk rotor 14 to perform a braking action.

A seal groove 20 is provided at a substantially intermediate position of the cylinder hole 15, and the piston seal 17 is fitted in the seal groove 20. The seal groove 20 is formed in the same shape as that of the related art in which the bottom wall 20a has a single slope and the diameter increases toward the disk rotor. For the piston seal 17, an annular elastic body such as an O-ring having a width smaller than that of the seal groove 20 and having a circular or oval cross section is used, and the outer peripheral edge 17a and one side edge 17b of the piston seal 17 are sealed. The piston seal 17 is deflected and fitted to the disk rotor side, which is the deepest part of the seal groove 20, by abutting the bottom wall 20a of the groove 20 and the disk rotor side wall 20b. Side edge 17c and seal groove 2
At the same time that the space C1 is set between the zero pressure hydraulic chamber side wall 20c and the substantially triangular small gaps C2 and C3 are left inside and outside the one side edge 17b in the radial direction.

When the piston seal 17 is fitted on the disk rotor side, which is the deepest part of the seal groove 20, as described above, the inner peripheral side protrudes into the cylinder hole 15, and the inner diameter is larger than the outer diameter of the piston 16. Piston 1 set to have a slightly smaller diameter and inserted into inner peripheral edge 17d
6 is movably supported with an appropriate interference. The piston seal 17 holding the piston 16 has an outer peripheral edge 17a.
And the inner peripheral edge 17d are compressed from inside and outside, and the contact between the bottom wall 20a of the seal groove 20 and the outer peripheral surface of the piston 16 is increased to seal the hydraulic chamber 18 in a liquid-tight manner.

The present embodiment is configured as described above. When the piston 16 advances through the cylinder hole 15 toward the disk rotor during braking, the inner peripheral side of the piston seal 17 is dragged by the piston 16 to be elastically deformed. When the pushing of the piston 16 is released, the elastically deformed portion of the piston seal 17 returns to its original shape, and the piston 16 is pulled back toward the hydraulic chamber by a predetermined amount.

The high-temperature braking heat generated by the sliding contact between the disk rotor 14 and the lining 12 a of the friction pad 12 is transferred from the friction pad 12 to the piston 16 and the caliper body 11.
The heat is transmitted to the piston seal 17 and the dust seal 19 to thermally expand them. Of these, the rubber piston seal 17 and the dust seal 19 expand significantly compared to the metal or synthetic resin piston 16 and the caliper body 11, but the piston seal 17 has a circular or elliptical cross-sectional shape. Since the contact area with the piston 16 is greatly reduced as compared with the related art, sticking due to braking heat is reduced as much as possible.

Further, the piston seal 17 has an outer peripheral edge 17.
a, the inner peripheral edge 17d, and one side edge 17b are in contact with the outer peripheral surface of the piston 16, the bottom wall 20a of the seal groove 20, and the disk rotor side wall 20b, respectively. The thermal expansion part is allowed to expand in the space C1 of the seal groove 20, and at the same time a part expands into the gaps C2 and C3 on the disk rotor side (two-dot chain line in FIG. 1).

The expansion into the space C1 on the hydraulic pressure chamber side becomes an arc-shaped expansion by making the cross-sectional shape of the piston seal 17 circular or elliptical, and the contact area with the piston 16 does not increase so much. The force of the expansion portion into the space C1 to move the piston 16 toward the hydraulic chamber becomes small. On the disk rotor side of the piston seal 17, the radially inner expanding portion into the space C2 slightly increases the contact area with the piston 16, and the expanding portion into the space C1 moves the piston 16 toward the disk rotor. Since the piston seal 17 acts as a drag against the force to be deformed, the deformation force for pushing the piston 16 toward the hydraulic chamber due to the thermal expansion of the piston seal 17 can be minimized.

Therefore, according to the present embodiment, the amount of the piston 16 pushed into the hydraulic chamber side of the cylinder hole 15 from the predetermined retreat position becomes extremely small due to the thermal expansion of the piston seal 17, so that the piston 16 is not operated. Since the expansion of the piston stroke between the tip of the piston 16 and the back plate 12b of the friction pad 12 is suppressed to a small value, the delay in the initial braking can be prevented as much as possible.

Further, since a pre-made O-ring or the like having a circular or elliptical cross section can be used for the piston seal 17, the production of the piston seal 17 is smaller than that of the conventional case where a specially formed square seal is separately manufactured and used. The efficiency and economy can be improved.

Although the caliper body has been described as a pin slide type in the above embodiment, the present invention is also applicable to a caliper body of a piston facing type. When the cross-sectional shape of the piston seal is elliptical, the major axis of the ellipse may be aligned with either the radial axis or the central axis of the piston seal according to other design conditions, or these axes may be used. Can be arbitrarily set at an inclination.

[0029]

As described above, according to the disc brake of the present invention, a piston seal having a circular or elliptical cross section is fitted into a seal groove provided around a cylinder hole of a caliper body, and the piston seal is sealed with the seal groove. The space between the piston seal and the side wall of the hydraulic chamber of the seal groove that allows deformation of the piston seal is defined by abutting against the side wall of the disk rotor. Since the bulge is accommodated in the space, the contact area with the piston does not need to be increased so much. Accordingly, the amount by which the piston is pushed into the hydraulic chamber side of the cylinder hole from the predetermined retreat position is extremely small, and the piston stroke between the piston and the friction pad during non-operation is suppressed to a small value. The delay can be prevented as much as possible.

Further, since an O-ring having a circular or elliptical cross section can be used for the piston seal, productivity and economic efficiency are reduced as compared with the conventional case where a specially formed square seal is separately manufactured and used. Can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part of FIG. 1 showing an embodiment of the present invention.

FIG. 2 is a sectional front view of a disc brake showing one embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a disc brake showing an example of a conventional embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Disc brake 11 ... Caliper body 11a ... Working part 11b ... Reaction part 12 ... Friction pad 12a ... Lining 12b ... Back plate 13 ... Hanger pin 14 ... Disk rotor 15 ... Cylinder hole 16 ... Piston 17 ... Piston seal 17a ... Outer peripheral edge 17b ... One side edge 17c ... Other side edge 17d ... Inner peripheral edge 18 ... Hydraulic pressure chamber 19 ... Dust seal 20 ... Seal groove 20a ... Bottom wall 20b ... Disk rotor side wall 20c ... Hydraulic pressure chamber side wall C1 ... Space C2, C3 ... Void

Claims (1)

[Claims] A caliper body disposed on a side of a disk rotor is provided with a bottomed cylinder hole for accommodating a piston, which is opened to the disk rotor side, and the inside of the cylinder hole is enlarged in diameter toward the disk rotor. A ring-shaped piston seal is fitted in the seal groove, the piston seal is movably elastically held by the piston seal with a tight allowance, and the hydraulic chamber at the bottom of the cylinder hole is moved by the piston. In a vehicle disk brake that seals in a liquid-tight manner with a seal, the piston seal is formed narrower than the seal groove and has a circular or oval cross section, and the piston seal is formed on a disk rotor side wall of the seal groove. A space for allowing thermal expansion and deformation of the piston seal between the piston seal and the side wall of the hydraulic chamber of the seal groove. Disc brake.