JPS5952299B2 - Piston of hydraulic actuator for disc brakes - Google Patents

Abstract

PURPOSE:The piston of the liquid hydraulic operation device for the disc brake which is schemed to reduce the weight by the use of synthetic resin material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a piston for a hydraulic actuation device for a disc brake that is lightweight.

Unlike drum brakes, disc brakes do not have a self-tightening action (servo action) based on a type of wedge effect at the frictional engagement part between the lining and the brake drum.
It is necessary to have high mechanical gain from the brake pedal to the wheel cylinder.

For this reason, the pressure-receiving area of the piston in a hydraulically actuated device for a disc brake is made larger than that of a drum brake, but this increases the weight of the entire hydraulically actuated device including the piston.

In order to reduce the weight of the piston, the piston of a conventional hydraulic actuator is formed into a hollow or cup-shaped body by cutting or forging, as illustrated in FIG.

The piston 5 is fitted into the hydraulic cylinder 4, and its open end is brought into contact with the back plate 8 of the friction pad 10.
0 is brought into frictional engagement with the brake disc 2, and at the same time, this reaction force causes the caliper 3, which is integrated with the hydraulic cylinder 4, to slide against the fixed member 1, and the reaction force piece 6 collides with the back plate 7. The friction pad 9 is frictionally engaged with the brake disc 2 to apply braking force to the brake disc 2.

At the open end, the outer periphery of the piston 5 is removed to form a small-diameter cylindrical portion 13. One end of a cylindrical flexible dust-proof boot 12 is tightly fitted and supported by this small-diameter cylindrical portion 13, and the other end is supported by hydraulic pressure. It is locked in the annular groove of the cylinder 4.

Since such a conventional piston 5 is provided with a small diameter cylindrical portion 13 to which a dustproof boot 12 is attached, achieving weight reduction by making the wall thickness sufficiently thin and uniform requires a complicated process and is disadvantageous in terms of cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piston for a hydraulic actuation device for a disc brake that can be made of synthetic resin to reduce its weight, reduce material costs, and reduce manufacturing costs.

[Structure of the invention]

In order to achieve the above object, the present invention uses a cylindrical body made of a low-quality synthetic resin as a piston of a hydraulic actuating device for a brake, and a cup-shaped body made of a mechanically strong synthetic resin with approximately equal wall thickness. The cup-shaped body includes a large-diameter cylindrical portion that covers the outer periphery of the cylindrical body, a closed end wall that closes one end of the cylindrical body, and an inner diameter that extends in the axial direction from the other end of the cylindrical body. and a small-diameter cylindrical portion whose outer diameter is approximately equal to that of the cylindrical body and smaller than the large-diameter cylindrical portion, thereby reducing the weight of the product, reducing material costs, and manufacturing. This is intended to reduce costs.

The present invention will be explained based on examples.

As shown in FIG. 2, the piston 5 according to the present invention has a cylindrical body 16 made of low-quality synthetic resin inside.
A cup-shaped body 14 made of synthetic resin with high mechanical strength is assembled at both ends and the outer circumferential side of the cup 6 .

That is, the cup-shaped body 14 includes a closed end wall 30 that closes one end of the cylindrical body 16, a large-diameter cylindrical portion 14a that continuously surrounds the cylindrical body 16, and a large-diameter cylindrical portion 14a that continuously surrounds the cylindrical body 16 and the other end of the cylindrical body 16. A small diameter cylindrical portion 14b extending to the side is integrally formed,
An annular groove 15 is formed in this small diameter cylindrical portion 14b for mounting the above-mentioned dustproof boot.

In fact, when manufacturing the piston 5 of the hydraulic actuation device for disc brakes according to the present invention, a cylindrical body 1 is placed inside the mold.
6 and a core or cylinder (not shown) fitted inside the cylindrical body 16, and the above-mentioned glass fiber, metal powder, asbestos, etc. are mixed into the end and outer circumferential side of the cylindrical body 16 and the cylinder. Filled with synthetic resin with high mechanical strength and heated and pressurized.

By doing so, the cup-shaped body 14 is integrally joined to the cylindrical body 16 and molded.

At the same time as this molding, the annular groove 15 is also molded.

Then, by pulling out the above-mentioned cylinder from inside the cylindrical body 16, the piston 5, which is hollow and lightweight as a whole, is provided.

The piston 5 according to the present invention has a cylindrical body 16 disposed inside thereof, so that the inner diameter is uniform over the entire length, and the cup-shaped body 14 made of a synthetic resin with high mechanical strength is approximately over the entire length. It is assumed to have a uniform wall thickness.

The cylindrical body 16 serves as a filler or shape-retaining member.

The cylindrical body 16 is made of a material that is relatively easy to mold and inexpensive, such as polyester resin.

On the other hand, the cup-shaped body 14 is made of synthetic resin with high mechanical strength mixed with glass fiber, metal powder, asbestos, etc. as a reinforcing material.

This synthetic resin includes polyethylene terephthalate,
ABS resin, nylon, acetate plastic, polycarbonate, acetate homopolymer, acetal copolymer, noryl resin, polyimide resin, polyphenylene sulfide resin, etc. can be used.

When using nylon, it is appropriate to mix about 30% by weight of glass fiber, asbestos fiber, or powder thereof as a reinforcing material, thereby further increasing the strength.

Also for other synthetic resins, it is useful to mix metal fibers or metal powder instead of glass fibers to improve the strength.

The piston obtained by molding is completed by polishing the cylindrical outer peripheral surface and then applying industrial chrome plating to it.

FIG. 3 shows an embodiment in which the cup-shaped body 14 of the piston 5 is made of a synthetic resin material that is difficult to plate.

That is, a metal cup-shaped body 17 made of a metal plate or a stainless steel plate is fitted on the outside of the cup-shaped body 14.

This metal cup-shaped body 17 is formed by drawing with a press, the closed end wall portion is slightly recessed inward, and a through hole 18 is provided in the center.

This piston 5 is also manufactured by a method similar in principle to that shown in FIG.

As shown in FIG. 4, the metal cup-shaped body 17 is inserted into the cylindrical part 21 of the female mold 20, and the metal cup-shaped body 17 is inserted into the cylindrical part 21 of the female mold 20, so that the metal cup-shaped body 17 flows through the through hole 18 into the gap 19 between the end wall and the bottom surface of the metal cup-shaped body 17. The inside of the female mold 20 is filled with a predetermined amount of a material in which glass fiber is mixed with a synthetic resin having high mechanical strength.

On the other hand, the male type 22 has an annular protrusion 23 on the end face 26 that has the same shape as the piston's outer diameter, and further has a long shaft 24 with an annular groove 25 in the center of the annular protrusion 23 and has a diameter that is almost the same as the piston's inner diameter. It is a provision.

When the cylindrical body 16 is externally supported on the shaft 24 and inserted into the metal cup-shaped body 17, the synthetic resin constituting the cup-shaped body 14 filled in the metal cup-shaped body 17 fills the void 1.
9 and spreads over the outer peripheral surface and both end surfaces of the cylindrical body 16.

Then, by fitting the annular projection 23 into the cylindrical portion 21 and abutting the end surface 26 of the male mold 22 against the end surface 27 of the female mold 20, the internal synthetic resin will also flow into the annular groove 25 of the male mold 22. The cylindrical body 16 and the metal cup-shaped body 17 are integrally joined via the cup-shaped body 14 by heating and pressurizing the metal cup-shaped body 17.
A piston 5 having a predetermined shape is formed.

In this embodiment, the metal cup-shaped body 17 is used, so it does not add much weight, has high corrosion resistance and wear resistance, and the synthetic resin main body (cup-shaped body 14) protects from brake fluid for long-term use. be done.

〔Effect of the invention〕

As described above, the present invention has a cylindrical body 16 made of an inexpensive, low-quality synthetic resin as a shape-retaining member as a core, and a cup-shaped body 14 with high mechanical strength is combined and bonded to the outside of the cylindrical body 16, which is different from the conventional example. It is possible to provide a piston that is easier to manufacture and lighter in weight than the piston.

Furthermore, by using an inexpensive, low-quality synthetic resin for the cylindrical body 16 as a shape-retaining member, and in combination with the cylindrical body 16, it is possible to eliminate waste of resin material used for the cup-shaped body 14, which serves as a strength member. Therefore, material costs can be saved.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an outline of a general disc brake, FIG. 2 is a side sectional view showing a piston of a hydraulic pressure actuation device for a disc brake according to a first embodiment of the present invention,
The figure is a side sectional view of a piston according to a second embodiment of the present invention,
FIG. 4 is a side sectional view for explaining the method of manufacturing the piston. 5...Piston, 14...Cup-shaped body, 14a...Large diameter cylindrical portion, 14b...
Small diameter cylindrical part, 15... Annular groove, 16...
・Cylindrical body, 17...Metal cup-shaped body, 18...
...Through hole, 30...Closed end wall.

Claims (1)

[Claims] 1 Consists of a cylindrical body made of a low-quality synthetic resin and a cup-shaped body made of a synthetic resin with high mechanical strength and having a substantially uniform wall thickness. and a closed end wall 3 for closing one end of the cylindrical body.
0, and a small diameter cylindrical portion 14b extending in the axial direction from the other end of the cylindrical body and having an inner diameter approximately equal to that of the cylindrical body and an outer diameter smaller than the large diameter cylindrical portion. Piston of hydraulic actuator for brakes.