JPH10167039A - Piston for master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent separation of a metal part and a resin part and to improve strength of a pressure receiving part receiving hydraulic pressure generated in a cylinder bore by covering a base part of the pressure receiving part made of the metal part with the resin part. SOLUTION: An outline shape of a first piston 3 constituted of a pillar body part 25 made of a metal part and a covering part 26 made of a resin part on a base part of a pressure receiving part 27 is formed by molding a resin material on an outer peripheral surface of the pillar body part 25. Ring recessed parts 28, 29 respectively installed with a cup seal and an O ring and a spring receiving part 30 to be locked with one end of a return spring are integrally formed of a resin material, but the covering part 26 is formed of a non- reinforced resin material mixed with no glass fiber, etc. Consequently, at the time of receiving hydraulic pressure on the pressure receiving part 27 with the pillar body part 25 as its base part, it is possible to improve strength of the pressure receiving part 27 in comparison with a conventional piston receiving pressure only with a resin part, and as a joint part of the resin part and the metal part is not disposed in a hydraulic pressure chamber, it is possible to prevent separation of the covering part 26 and the pillar body part 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master cylinder piston used for a brake device or a clutch operating device of a vehicle or the like.

[0002]

2. Description of the Related Art Japanese Unexamined Utility Model Publication No. 4-43558 discloses this type of prior art. According to this, as shown in FIG. 7, the secondary-side piston (second piston) 5
0 is made up of a resin member 51 and a metal member 52. When the movement of the piston 50 is restricted (when the tip 52a of the metal member 52 and the bottom of a cylinder hole (not shown) abut), the resin The metal member 52 reinforces the resin member 51 with respect to the axial force applied to the member 51, thereby compensating for the strength problem inherent in the resin piston. These resin members 51
The metal member 52 and the metal member 52 are fixed to each other by a pressing force when the resin member 51 is formed on the outer periphery of the groove (knurled portion) 52c and the embedded portion 52b of the metal member 52.

[0003]

However, in the conventional piston 50, the resin member 51 and the metal member 5 are not provided.
The ratio of 2 to the resin member 51 is larger, and the pressure receiving portion 54 receiving the internal pressure of the hydraulic chamber is formed only of the resin member 51. And may be damaged.

In order to prevent such damage, it is conceivable to use a reinforced plastic containing glass fiber in the resin member 51. However, the sliding surface of the cylinder hole into which the piston is inserted is considered. In addition, there is a possibility that the glass fiber protruding from the sliding surface of the piston may damage the piston.

Further, the pressure receiving portion 54 of the conventional resin piston 50
Since the joint between the metal part and the resin part is exposed to the hydraulic chamber and receives the pressure of the hydraulic chamber directly therefrom, the adhesion between the resin member 51 and the metal member 52 becomes weak over time. It is conceivable that both members 51 and 52 are peeled off. Then, these two members 51, 5
The liquid pressure acts on the gap generated by the separation of the second member 2, and the resin member 51 is damaged from this.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has a piston for a master cylinder capable of preventing separation of a metal portion and a resin portion and increasing the strength of a pressure receiving portion receiving a hydraulic pressure generated in a cylinder hole. The task is to provide

[0007]

An object of the present invention is to provide a pressure receiving portion having a metal portion and a resin portion, which is slidably fitted into a cylinder hole and receives a hydraulic pressure generated in the cylinder hole. In the piston for a master cylinder described above, the pressure receiving portion is formed by covering the metal portion as a base portion and covering the base portion with the resin portion. .

Since the pressure receiving portion is formed by covering the metal portion with the base portion and covering the base portion with the resin portion, the liquid pressure generated in the cylinder bore is not received only by the resin portion, and the pressure receiving portion is different from the conventional one. As a result, the strength of the pressure receiving portion can be increased. In addition, since the joint between the metal part and the resin part is not exposed to the hydraulic chamber, separation between the two can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A master cylinder piston according to each embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a tandem type master cylinder showing a first embodiment of the present invention. The first piston 3 and the second piston 4 are slidably movable in a cylinder hole 2 formed inside the cylinder body 1, respectively, with a cup seal 19, an O-ring 20, and a cup seal 2.
The first and second hydraulic chambers 8 and 8 are defined inside the cylinder hole 2 by inserting and inserting the first and second hydraulic chambers 1 and 22. Return springs 5 and 6 are stretched in the first and second hydraulic chambers 7 and 8, respectively, and urge the first and second pistons 3 and 4 toward the opening of the cylinder hole as illustrated. . Bosses 9, 10 formed on the outer periphery of the cylinder body 1
The nipples 14 and 15 of the reservoir body 13 having a conventionally known configuration are provided with the grommet seals 11 and 1 respectively.
The reservoir body 13 is fixed to the cylinder body 1 by a coupling member 18 which is fitted through the protrusion 2 on the cylinder body 1 side and further integrally couples the wing portion 17 on the reservoir body 13 side.

In the present embodiment, the second piston is made of metal, but the first piston 3 is made up of a column portion 25 made of a metal portion and a covering portion 26 made of a resin portion.

Referring to FIG. 2, the outer shape of first piston 3 is formed by molding a resin material on the outer peripheral surface of column 25 having a size approximating the outer size of the piston. . The cup seal 19, the annular recesses 28 and 29 in which the O-rings 20 are respectively mounted, and the spring receiving portion 30 to which one end of the return spring 5 is locked are integrally formed of a resin material. Here, the covering portion 26
Is a non-reinforced material, that is, a resin material in which glass fiber or the like is not mixed.

According to the present embodiment, since the pressure receiving portion 27 of the first piston 3 is based on the column portion 25 made of metal, the hydraulic pressure generated in the first hydraulic pressure chamber 7 is mainly Pillar part 2
5, the strength of the pressure receiving portion can be higher than that of a conventional piston that receives only the resin portion. Also, the joint between the resin portion and the metal portion is not exposed to the first hydraulic chamber 7, and the hydraulic pressure in the first hydraulic chamber 7 is such that the covering portion 26 is pressed against the column 25. Since it acts in the direction, it is possible to prevent separation between the covering portion 26 and the pillar portion 25, and it is possible to improve durability.

Further, since the sliding portion of the first piston 3 with respect to the cylinder hole 2 is the covering portion 26, the sliding portion is formed of a synthetic resin of a non-reinforced member. Therefore, when the first piston 3 slides in the cylinder hole 2, the cylinder hole 2 is not damaged. Also, a pillar portion 2 made of metal
It is not necessary to finish the outer peripheral surface of No. 5, and conversely, the rougher the surface condition, the more the engagement surface with the covering portion 26, so that both can be brought into close contact. Furthermore, since the formed film thickness of the covering portion 26 is substantially uniform, it is possible to reduce surface defects (depression) due to the occurrence of uneven internal shrinkage in the cooling process after gate sealing.

FIG. 3 shows a master cylinder piston according to a second embodiment of the present invention. The piston 33 according to the present embodiment is formed by the column portion 35 of the metal portion and the coating portion 36 of the resin portion similarly to the above-described first embodiment, and is formed on a partial surface of the column portion 35. A threaded engagement portion 38 is formed in the axial direction. Accordingly, the same effect as that of the first embodiment can be obtained, and at the same time, unevenness is formed at a part of the joint between the pillar portion 35 and the covering portion 36. The mutual engagement force can be strengthened, and both are prevented from coming off. In other words, since the bonding is between different materials such as a metal portion and a resin portion, in the present embodiment, the engagement portion 38 is used as a retaining portion to prevent the two portions from coming off reliably, instead of relying only on adhesion at the interface. I have to.

In this embodiment, the projections and depressions of the engaging portion 38 are formed by thread rolling. However, the present invention is not limited to this, and the engaging portion 39 is formed by knurling as shown in FIG. Even in this case, the same effect as described above can be obtained. In addition, the irregularities can be easily formed by performing appropriate plastic working, and the formation location is not limited to only a part of the columnar portion.

FIG. 5 shows a third embodiment of the present invention. That is, in the above-described second embodiment, a part of the columnar portion is subjected to plastic working to form irregularities, so that a solid portion between the columnar portion and the covering portion, that is, the metal portion and the resin portion is formed. Although the engaging force is obtained, in the piston 43 in the present embodiment, the covering portion 46 covers the rear end surface (right side in the drawing) 45a of the column portion 45, and the rear end surface 45
At a, the two are joined (prevented from coming off). According to this embodiment, the same effects as those of the above embodiments can be obtained.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these embodiments.
Various modifications are possible based on the technical idea of the present invention.

For example, in each of the embodiments described above, the first pistons 3, 33, and 43 have been described, but the present invention is also applicable to the other second piston 4. Also in this case, similarly, a column having a size similar to the external dimensions of the second piston 4 is formed, and a resin material is molded on the outer surface of the column to form the external shape of the second piston 4. May be formed.

In each of the above embodiments, the master cylinder piston for the brake device has been described.
The present invention is of course applicable to a piston for a master cylinder for a clutch operating device.

Further, the outer shape of the piston is not limited to the above embodiments. That is, a so-called caged spring type piston as shown in FIG.
The present invention is applicable. Note that the same reference numerals are given to portions corresponding to FIG. This is, as is known, a return spring 5 that is stretched in the first hydraulic chamber 7.
Is locked between a second piston 64 and a retainer 66 with which a head 65a of a bolt member 65 fixed to the second piston 64 is engaged. The first piston abutting on the retainer 66 63, a bolt member 65
The recessed portion 63a is formed so that the head 65a can enter. Therefore, in applying the present invention, the pillar portion 67 which is a metal portion is used.
Is substantially H-shaped, and the first piston 63 is formed by forming the covering portion 68 with a resin material on the outer peripheral surface and the front portion serving as the pressure receiving portion, whereby the same effects as those of the above embodiments can be obtained. Obtainable.

[0022]

As described above, according to the master cylinder piston of the present invention, the pressure receiving portion for receiving the hydraulic pressure in the cylinder hole is formed by covering the resin portion on the base made of the metal portion. Therefore, the strength of the pressure receiving portion can be increased as compared with the related art, and the durability can be greatly improved by preventing separation between the metal portion and the resin portion.

[Brief description of the drawings]

FIG. 1 is an overall side sectional view according to a first embodiment of the present invention.

FIG. 2 is an enlarged partial cutaway view of a master cylinder piston in FIG.

FIG. 3 is a partial cutaway view of a master cylinder piston according to a second embodiment of the present invention.

FIG. 4 is a partial cutaway view showing a modification of the master cylinder piston according to the second embodiment of the present invention.

FIG. 5 is a partially cutaway view of a master cylinder piston according to a third embodiment of the present invention.

FIG. 6 is a partial sectional view of a master cylinder showing a modification of the present invention.

FIG. 7 is a side sectional view showing a conventional master cylinder piston.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder main body 2 Cylinder hole 3 1st piston 4 2nd piston 7 1st hydraulic chamber 8 2nd hydraulic chamber 25 Column part 26 Coating part 27 Pressure receiving part 33 Piston 35 Column part 36 Coating part 38 Engaging part 39 Engaging part 43 Piston 45 Column part 46 Cover part 63 First piston 67 Column part 68 Cover part

Claims (5)

[Claims] 1. A master cylinder piston having a metal portion and a resin portion and having a pressure receiving portion slidably fitted in a cylinder hole and receiving a hydraulic pressure generated in the cylinder hole. The piston for a master cylinder, wherein the pressure receiving portion is formed by using the metal portion as a base portion and covering the base portion with the resin portion. 2. A cylinder having a size approximating the outer dimensions of the piston is formed by the metal portion, and a resin material is molded on an outer surface of the column to face the cylinder hole. The piston for a master cylinder according to claim 1, wherein the resin portion that forms a piston outer shape is provided. 3. The master cylinder piston according to claim 1, wherein the resin portion is made of a non-reinforced material. 4. An at least one part of a joining portion between the metal portion and the resin portion is formed with unevenness which engages with each other in an axial direction of the piston.
The master cylinder piston according to any one of claims 3 to 3. 5. The master cylinder piston according to claim 4, wherein the irregularities on the metal portion side are formed by plastic working.