JPH0312983Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a disc brake device equipped with a double-structured piston.

[Conventional technology]

In a disc brake system, when braking, the end of the brake pad on the brake disc retraction side is pressed against the brake pad more strongly than the rest of the pad, which can result in high frequency vibrations and noise called so-called squealing. .

Therefore, in order to reduce this squealing phenomenon, for example, as shown in Japanese Utility Model Application Publication No. 118987/1987, the back of the brake pad and the pressing surface of the piston are brought into contact with a spherical surface to equalize the load distribution on the pad. There is something.

In addition, in order to make it difficult for the frictional heat during braking to be transferred to the hydraulic fluid in the cylinder, the piston that pushes the brake pads has a double structure, as shown in Japanese Utility Model Application Publication No. 181131/1983, for example. .

[Problem that the invention attempts to solve]

However, in the case of the above-mentioned former structure, foreign matter such as water and dirt may enter between the back of the brake pad and the piston, causing problems in the smooth swinging of both members. In this case, foreign matter may accumulate between both pistons.

SUMMARY OF THE INVENTION An object of the present invention is to provide a disc brake device that prevents foreign matter from entering between both pistons, maintains smooth rocking of the inner piston, and prevents vibrations.

[Means for solving problems]

In order to achieve the above object, the present invention has a bottomed cylindrical outer piston that is fluid-tightly and movably inserted into the cylinder hole formed in the carrier body, with the opening end facing the brake pad side, and the bottom of the piston and the In a disc brake device that defines a hydraulic chamber between the bottoms of the cylinder holes, one is located inside the outer piston, and one is located at the axis of the outer piston.
An inner piston, the other end of which is in contact with the brake pads, is fitted in a swingable manner, and a bushing part is formed extending from the other end of the dust boot, one end of which is locked in the opening of the cylinder hole. It is characterized by being interposed between the bodies of the pistons.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The disc brake device 1 includes a bracket 2 fixed to the vehicle body that slidably supports a caliper body 3 via a sliding pin (not shown). are integrally connected by a bridge part 6, and the brake disc 7, which rotates together with the wheel, is straddled at the bridge part 6, and the actuating part 4 and the reaction part 5 are arranged on both sides of the brake disc 7, and the brake disc Brake pads 8 and 9 for pinching the brake disc 7 are attached to both sides of the brake disc 7.

A cylinder 10 is formed in the actuating part 4,
The cylinder 10 has a bottomed cylindrical outer piston 1.
1 is fitted in a fluid-tight and movable manner. The outer piston 11 is fitted into the cylinder 10 with the opening 11a side facing the back plate 8a side of the brake pad 8, and the outer piston 11 is inserted into the cylinder 10 with the opening 11a side facing the back plate 8a side of the brake pad 8.
A hydraulic chamber 12 is defined between a.

This outer piston 11 is provided with an inner piston 13 inside thereof. The inner piston 13 has a bottomed cylindrical shape and has an outer diameter slightly smaller than the inner diameter of the outer piston 11.
The outer piston 11 is made swingable by contacting the steel ball 14 disposed between the recess 13b formed on the axis of the outer piston 11 and the recess 11c formed on the inner axis of the bottom 11b of the outer piston 11. A flange 13e formed in an opening 13d that is fitted and protrudes from the opening 11a of the outer piston 11.
is in contact with the back plate 8a of the brake pad 8.

Further, a dust boot 15 is provided between the opening 10b of the cylinder 10 and the outer piston 11 and the inner piston 13.

The dust boot 15 is made of a flexible material such as rubber, and has a locking portion 15b at one end of the bellows portion 15a that locks into a groove 10c carved on the inner periphery of the opening 10b of the cylinder 10. At the other end of the bellows portion 15a,
A bushing portion 15c extending inward from the opening 11a of the outer piston 11 and interposed between the body portion of the inner piston 13 and the bushing portion 15c.
A flange portion 15d that faces the outer piston 11 and engages with the outer circumferential side of the opening 11a of the outer piston 11, and a lip portion 15e that comes into elastic contact with the flange of the flange portion 13e of the inner piston 13 are integrally formed.

A plurality of air passages 15 are provided in the axial direction of the cylinder 10 on the inner piston 13 side of the bushing portion 15c.
f is notched. This air passage 15f
is formed from the end of the bushing portion 15c to the lower surface of the lip portion 15e along the body of the inner piston 13.
3 to the outer piston 11, the air between the inner piston 13 and the outer piston 11 is discharged through the air passage 15f, which facilitates the assembly of the inner piston 13 and prevents the inner piston 13 from swinging. At the same time, it facilitates compression deformation of the bushing portion 15c.

Further, the lip portion 15e is connected to the inner piston 13.
After installation, the inner piston 13 is elastically contacted with the flange of the flange 13e of the inner piston 13 so as to isolate the air passage 15f from the atmosphere, thereby preventing foreign matter such as water and sand from entering from the outside.

Disc brake device 1 configured in this way
Since the inner piston 13 swings during braking, the load distribution on the brake pads 8 is equalized,
Furthermore, even if displacement occurs in the inner piston 13 due to vibration or uneven wall thickness of the brake disc 7, the displacement is absorbed by the bushing portion 15c and is not transmitted to the outer piston 11, causing the outer piston 11 to be displaced in the radial direction. Therefore, the outer piston 11 moves within the cylinder 10 without causing strain, and therefore, no fluid pressure fluctuation occurs in the hydraulic pressure chamber 12, vibration is prevented, and so-called squealing phenomenon and abnormal vibration during braking are prevented. is reduced.

Furthermore, since the bushing portion 15c is integrally formed with the dust boot 15, the number of parts can be reduced, contributing to reductions in manufacturing and assembly costs. Furthermore, both pistons 1 are provided by the lip portion 15e.
Preventing foreign matter from entering between 1 and 13 and depositing sediment.
Rust caused by water intrusion, etc. can be avoided, as well as sticking.
The swinging motion of the inner piston 13 can be maintained for a long period of time.

Next, FIGS. 3 and 4 show another embodiment of the present invention, in which a contact portion 20b protrudes inward from the axis of the bottom portion 20a of the outer piston 20 fitted into the cylinder 10. is integrally formed, the axis of the inner piston 21 is brought into contact with this contact portion 20b, and the opening 20 of the outer piston 20 is brought into contact with the contact portion 20b.
A bushing portion 22a of the dust boot 22 is interposed between the inner piston 21 and the outer periphery of the opening 21a of the inner piston 21.
The displacement is absorbed by the bushing portion 22a and is not transmitted to the outer piston 20.

Further, the bushing portion 22a has a plurality of air passages 22b in the axial direction of the cylinder 10 as in the previous embodiment.
A through hole 21c is formed in the flange portion 21b of the inner piston 21 so as to communicate with the air passage 22b, and when the inner piston 21 is assembled, a through hole 21c is formed so as to communicate with the air passage 22b. Exhaust the air.

In addition, the through hole 21c is for the brake pad 8 after assembly.
Since both pistons 20, 2 are closed by
Foreign matter can be prevented from entering the room.

[Effect of idea]

As described above, the present invention has an inner piston that is fitted into the inner side of a bottomed cylindrical outer piston that is fitted into a cylinder of a caliper body, and which has one end that abuts the axis of the outer piston and the other that abuts the brake pad. a bushing part is formed extending from the other end of the dust boot which is locked in the cylinder hole,
Since the bushing portion is interposed between the body portions of both pistons, the load distribution on the brake pad is equalized during braking, and even if the inner piston is displaced due to vibration of the brake disc or uneven wall thickness, Since the displacement is absorbed by the bushing portion and not transmitted to the outer piston, and no fluid pressure fluctuation occurs in the hydraulic pressure chamber, vibrations are prevented and so-called squealing phenomena and abnormal vibrations during braking are reduced. Furthermore, since the bushing portion is integrally formed with the dust boot, the number of parts can be reduced, contributing to reductions in manufacturing and assembly costs. Furthermore, since it is possible to prevent foreign matter from entering between the two pistons, it is possible to avoid the formation of rust due to accumulation of earth and sand, intrusion of water, etc., as well as the occurrence of sticking, and the swinging operation of the inner piston can be maintained for a long period of time.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention,
Fig. 1 is a sectional view of the disc brake device, Fig. 2 is an enlarged sectional view of the main parts, Figs. 3 and 4 show another embodiment of the present invention, and Fig. 3 is a sectional view; Figure 4 is an enlarged sectional view of the main part. DESCRIPTION OF SYMBOLS 1... Disc brake device, 3... Caliper body, 7... Brake disc, 8, 9... Brake pad, 10... Cylinder, 11, 20...
... Outer piston, 12 ... Hydraulic pressure chamber, 13, 21
...Inner piston, 15, 22...Dust boot, 15c, 22a...Button part, 15f, 2
2b...Air passage.

Claims (1)

[Scope of utility model registration request] A bottomed cylindrical outer piston is fluid-tightly and movably inserted into the cylinder hole formed in the caliper body, with the open end facing toward the brake pad.
In a disc brake device that defines a hydraulic chamber between the bottom of the piston and the bottom of the cylinder hole,
An inner piston is swingably fitted inside the outer piston and has one end abutting the axis of the outer piston and the other abutting the brake pad, and one end of the dust boot is latched to the opening of the cylinder hole. A disc brake device characterized in that a bushing part is formed extending from the other end, and the bushing part is interposed between the body parts of both the pistons.