GB2089914A

GB2089914A - Disc brake; piston

Info

Publication number: GB2089914A
Application number: GB8133830A
Authority: GB
Original assignee: Brembo SpA
Current assignee: Brembo SpA
Priority date: 1980-12-22
Filing date: 1981-11-10
Publication date: 1982-06-30
Also published as: IT8026843A0; DE3148873A1; FR2496805A1; IT1134839B

Abstract

The disc brake 1 comprises a caliper body 2, at least one piston 4 housed in the caliper body and subject to fluid under pressure, a pair of pads 5, 6 with friction linings mounted on the caliper body, at least one 6 of which is subject to the action of the at least one piston 4 , in which the end 4a of the at least one piston in engagement with the pad comprises an element 12 made from a material with a predetermined low thermal conductivity, such as ceramics. As shown, the element 12 is in the form of a ceramic ring 13 with portions 14, 15 of differing diameters, portion 14 being inserted in seating 16. As shown, the brake has opposed pistons 3, 4 with ceramic elements 11, 12. During braking, heat generated remains localized in pads and disc; fluid is therefore not liable to deteriorate and braking efficiency is retained. <IMAGE>

Description

SPECIFICATION An improved disc brake The present invention relates to a disc brake of the type comprising a caliper body, at least one piston housed in the caliper body and subject to fluid under pressure, a pair of pads with friction linings mounted on the caliper body at least one of which is subject to the action of said at least one piston, and a disc located between the pads, Disc brakes of the type specified must afford prompt and reliable braking constantly.

Although satisfactory on the whole, known disc brakes presently in use have a few disadvantages which restrict their use.

More particularly, after a period of prolonged use, as opposed to sharp and frequent braking, they exhibit a loss of efficiency. As a result of heating, proper coupling between the piston and the caliper body is adversely affected. Moreover, the characteristics of the brake fluid are altered, as well as its permanent deterioration.

The problem at the basis of the present invention is that of providing a disc brake which has structural and functional characteristics which will satisfy the aforesaid braking requirements, while at the same time overcoming the disadvantages referred to with reference to the prior art.

This problem is solved by a disc brake of the type specified, which is characterised in that the active end of said at least one piston in engagement with the respective pad comprises an element made from a material with a predetermined low thermal conductivity, such as ceramics.

Further characteristics and advantages of the disc brake according to the present invention will emerge from the following description of one preferred embodiment, provided by way of nonrestrictive example, with reference to the one accompanying drawing which is a partiallysectioned view of a disc brake according to the invention.

Referring to the accompanying drawing, a disc brake according to the invention is generally indicated 1.

The disc brake 1 comprises a caliper body 2 attachable to the supporting structure of a vehicle, which is not shown since it is of conventional type.

The caliper body 2 houses a pair of opposed pistons 3, 4 which are subject to the action of fluid under pressure at the time of braking.

A pair of brake pads 5, 6 with friction linings 7, 8 are mounted on the caliper body 2, and are subject to the action of a respective piston 3, 4.

The disc brake 1 further comprises a disc 9 intended to be mounted so as to be fixed for rotation with a wheel of a vehicle, which is not shown because it is of the conventional type, and so that its surface 10 is between the friction linings 7, 8 of the pads 5, 6.

In the disc brake 1 according to the invention, the pistons 3, 4 have active ends 3a, 4a which, being in engagement with respective pads 5, 6, are formed from respective elements 11, 12 of insulating material with a predetermined low thermal conductivity, such as ceramics.

So as not to make the description too dull, only one of the two elements 11, 12, which are substantially similar, will now be described in greater detail.

The element 12 consists of a ceramic ring 13, which has two portions 14, 1 5 of differing diameters.

The smaller diameter portion 14 is inserted in a seating 1 6 made coaxially in the piston 4 and is fixed thereto by an interference fit and/or a suitable adhesive. The portion 14 is provided with a bevelled leading edge 17 to facilitate the insertion.

The larger diameter portion 15, which forms a shoulder 18 with the smaller diameter portion 14, abuts the edge 1 6a of the seating 1 6.

The larger diameter portion 1 5 is provided externally with a recess 1 9 which cooperates with the edge 1 6a of the seating 1 6 to form an annular groove into which is inserted one edge 20 of a bellows gasket 21, the other edge 22 of which is inserted in an annular groove 23 in the caliper body 2.

In correspondence with its front surface 1 5a in engagement with the pad 6, the larger diameter portion 1 5 is provided with a rebate 24 which is intended, in a conventional manner, to move the centre of gravity of the piston 4 away from its axis.

At the time ot braking, the pistons 3, 4, being subject to the fluid under pressure, exert a force on the respective pads 5, 6 with which they are in contact by means of the elements 11, 12. In their turn, the pads 5, 6 are pressed against the surface 10 of the disc 9 with which they are in contact through the friction linings 7, 8. As is known, the friction forces generated by contact between the surface 10 of the moving disc and the friction linings 7, 8 determine the desired braking effect.

The heat generated at surfaces which are in contact as a result of braking is dissipated rapidly to the disc and the pads due to their respective thermal conductivity, whereas it is not dissipated as quickly from the pads to the pistons and the fluid due to the presence of the ceramic elements which have low thermal conductivity.

Therefore, the heat generated remains localised mainly in the pads and, more particularly, in the disc which is especially suited to dissipate it to the surrounding air, since it has a large surface and is moving.

Owing to the smaller amount of heat which is dissipated towards the pistons and the fluid, these reach less high temperatures and consequently the pistons are not subject to irregular movement and the fluid is not liable to deteriorate.

The main advantage of the disc brake according to the invention is that it retains its efficiency even after a number of periods of intense and prolonged braking which generate a great deal of heat.

A further advantage of the disc brake according to the invention is the fact that any deterioration of the brake fluid is avoided.

Claims

1. A disc brake of the type comprising a caliper body, at least one piston housed in the caliper body and subject to fluid under pressure, a pair of brake pads with friction linings mounted on the caliper body, at least one of which is subject to the action of said at least one piston, and a disc located between the pads, characterised in that said at least one piston has an active end in engagement with the pad, comprising an element made from a material with a predetermined low thermal conductivity, such as ceramics.

2. A disc brake according to Claim 1, characterised in that said element is a ring having two portions of differing diameter in which the smaller diameter portion is inserted into a seating in the piston, and the larger diameter portion, which forms a shoulder with the smaller diameter portion, abuts the edge of said seating.

3. A disc brake according to Claim 2, characterised in that the larger diameter portion is provided with a recess which cooperates with the edge of the seating to form a peripheral groove into which is inserted one edge of a bellows gasket, the other edge of which is inserted into a groove in the caliper body.

4. A disc brake according to the preceding claims and according to what has been described and illustrated in the accompanying drawing, for the purposes specified.