JPS6069334A - Brake piston - Google Patents

Abstract

PURPOSE:To provide a light and durable brake piston by putting a steel collar cylinder to the inside of a ceramics or fiber reinforced plastics body. CONSTITUTION:A piston body 1 is formed of a ceramic sintered body such as an alumina sintered body or fiber reinforced synthetic resin such as fiber reinforced phenol resin. A collar 3 of a steel collar cylinder 2 usually acts a part of the open end of a piston. The outside base and side of the cylinder 2 are previously machined by knurling and a flame spray layer 4 of metal coarse grain such as nickel-aluminium complex is formed thereon. The thus constructed cylinder 2 is put on the inside of the piston body 1 in a body through fitting with point contact of its coarse surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for a disc brake, and more specifically, the piston body including the sliding part is made of ceramics or TAIF reinforced plastics, and the part including the piston opening end in contact with the friction pad back metal. This relates to a disc brake piston that is made of steel and is integrated by joining the two together.

Conventionally, steel pistons with excellent mechanical properties have been used as pistons for disc brakes, but because they are heavy and have high thermal conductivity, a large amount of heat is generated from the open end of the piston, which is in contact with the high-temperature friction pad back metal. is conducted to the piston side, which has disadvantages such as damaging the sealing member, etc., and raising the temperature of the brake fluid in the cylinder, causing paper lock.

Alternatively, there are ceramic pistons and plastic pistons that are lightweight and have excellent insulation properties.
Ceramic pistons have the disadvantage of low toughness and the open end of the piston often falls off, and cracks may occur at the open end of the piston that joins the hole in the friction pad backing due to intensive use. For example, a piston made of alumina-based ceramics generates a thermal crank when the thermal shock value is about 220°C.

Furthermore, plastic pistons have the disadvantage that the opening end portion of the piston, which comes into contact with the high-temperature friction pad back metal, undergoes rapid thermal expansion and cracks occur.

The present invention has been made to address the shortcomings of conventional disc brake pistons, and the piston body, which includes sliding parts that require small strength requirements, is made of lightweight ceramics or fiber-reinforced plastic with excellent heat insulation properties. The part including the open end of the piston that comes into contact with the friction pad back metal is made of steel, which has excellent heat resistance and mechanical properties, and by combining and integrating the two, it is lightweight and durable, and is made from the friction pad back metal. This invention relates to a new piston for disc pre-keys that prevents the occurrence of paper lock and damage to seal members, etc. by blocking heat transfer.

That is, the present invention has a cylindrical ceramic or fiber-reinforced plastic piston body that is open at one end.
A piston for a disc brake is provided in which a steel flanged cylindrical body with an opening on the flanged side whose outer circumferential surface including the outer bottom and side surfaces is thermally sprayed coated with metal coarse particles is sawn by point contact and integrated.

The ceramics that make up the piston body include alumina (AJ!z O+), zirconia (Zr02), silicon nitride (Si3N!), and silicon carbide (SiC).
) system, etc., preferably with or without the addition of a reactive filler. [The reinforced plastic is a thermosetting resin reinforced with glass fiber or the like, such as fiber-reinforced phenol resin, but resin can also be used.

The thermal spraying materials used for thermal spray coating include coarse grains such as nickel-aluminum composites, nickel-chromium self-fluxing alloys, aluminum bronze composites, zinc, and alumina, of which nickel-aluminum composites are preferred.

This product can withstand temperatures up to 650℃, and
It is a thermal spraying material that can withstand exposure to high temperatures between 11°C and 11°C, has high oxidation resistance, and has high bonding strength and strong resistance.

When coating the outer peripheral surface of a steel flanged cylindrical body with a solvent using coarse metal particles, the steel base is degreased and then roughened by brushing, but it is more preferable to roughen the surface by brushing.
By knurling the outer peripheral surface of the cylindrical body, which has been processed and formed, to create irregularities, the bonding force of thermal spraying is strengthened, which is also beneficial for the saw table with the piston body. In addition, since this process also increases the voids in the saw table, a heat insulating effect due to air can also be obtained.

A rough surface with large irregularities of 200 μm or more is formed on the outer peripheral surface of the pretreated cylindrical body by coating coarse metal particles with a solvent, and then this cylindrical body is brought into point contact with the inside of the piston main body to see a saw table. It is intended to be integrated by If this saw table is made too strong, the coefficient of thermal expansion of the inner cylindrical body is greater than that of the outer piston body, so in practical use, the piston body may crack or break due to expansion due to brake heat, which is undesirable. .

It is also conceivable to use a synthetic resin adhesive to join the saw table, but since the brake heat exceeds 1J:400°C, the adhesive deteriorates due to heat and is not practical.

In the present invention, by using the saw table as described above, a gap of 150 μm or more can be obtained in the saw table, which can sufficiently absorb dimensional changes due to thermal expansion of the cylindrical body. The gap can prevent the occurrence of cracks by alleviating the locally concentrated load on the bottom of the piston body due to compression during brake operation. Also, the molten O4 layer on the coarse metal particles has high damping properties, so it is effective against brake noise.

The present invention will be explained in detail below with reference to embodiments shown in the drawings.

In Fig. 1, 1 is a cylindrical piston body with one end open, its outer surface serving as a sliding surface, and is made of a ceramic sintered body, such as an alumina sintered body, or a fiber-reinforced synthetic resin such as IFL Ift reinforced phenolic resin. has been done. 2
is a cylindrical flanged cylindrical body made of steel and has a flange 3 on its opening side, and the flange 3 corresponds to a portion usually called the opening end of the piston. The outer bottom and side surfaces of this cylindrical body 2 are knurled in advance, and a flame sprayed layer 4 of coarse metal particles such as a nickel-aluminum composite is formed thereon. As shown in the figure, this cylindrical body 2 is integrated with the inside of the piston body 1 by point contact of its rough surfaces to form a piston for a disc brake. Note that 5 is a fitting groove of the piston seal, and 6 is a piston cavity.

[Brief explanation of drawings]

FIG. 1 shows a piston for a disc brake according to an embodiment of the present invention; (A) is a plan view thereof, and ([C) is a sectional view thereof. 1. Piston body 2, cylindrical body with flange 3, flange 4, sprayed layer 5, fitting groove 6, piston cavity Fig. 1 (A)

Claims (2)

[Claims] (1) A steel flanged cylindrical body with an opening on the flanged side whose outer circumferential surface is thermally sprayed coated with coarse metal particles is placed in point contact with the inside of a cylindrical ceramic or fiber-reinforced plastic piston body with one end open. A piston for a disc brake that is characterized by being integrated by interlocking. (2) Ceramic glass is alumina-based, zirconia-based, -
Disc brake piston (3) metal coarse particles according to claim (1), which is a sintered body of either mullite silicon nitride type or silicon carbide type, and the i11 reinforced plastic is fiber reinforced phenolic resin. The disc brake according to claim (1) or (2), wherein is coarse particles of any one of a nickel-aluminum composite, a nickel-chromium self-fluxing alloy, an aluminum bronze composite, zinc, and alumina. piston