GB2194605A

GB2194605A - Brake piston for use in a disc brake

Info

Publication number: GB2194605A
Application number: GB08718773A
Authority: GB
Inventors: Rolf Weiler; Winfried Gerhardt
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1986-08-29
Filing date: 1987-08-07
Publication date: 1988-03-09
Anticipated expiration: 2007-08-07
Also published as: GB8718773D0; DE3629513A1; GB2194605B; FR2603356B1; FR2603356A1

Abstract

A brake piston, particularly for use in an automotive vehicle disc brake is formed of a piston body (11) and a heat insulating member (9). Both parts have abutment faces (7, 10) which, when applying the brake, are placed into abutting relationship to a pad carrier (8). In an alternative embodiment the face (7) of the piston body is spaced, in use, from the pad carrier by 0.5-1 mm. The heat insulating member may comprise a ring or rings radially inwardly and/or radially outwardly of piston body part (6), and the radially spaced rings may be joined by connecting pieces (15). <IMAGE>

Description

SPECIFICATION Brake piston for use in a disc brake This invention relates to a brake piston for use in a disc brake including a heat-insulating element which is fixed on the end of a brake piston body which in use faces a brake pad and which is capable of being placed, via an abutment face thereof, into a abutting relationship with the pad carrier.

FR-PS No. 1 372 382 discloses a brake piston composed of two parts. Fixed to or in the outer side of the piston body is a heat insulating element which, in applying the brake, with one abutting face, is placed in abutting relationship to the pad carrier, wherein the brake piston body as such does not get into contact with the pad carrier.

An arrangement of the afore-described type is also known from a variety of other publications. By way of example, reference is made to West German DE-PS 0042156A 1. The construction described therein provided for another heat insulating element for force transmissions, which is disposed between the heat insulating element and the pad carrier.

However, basically, the manner of operation is not altered thereby. The heat insulating element continues to fully retain the heat developing during deceleration in the brake disc, in the pad and in the pad carrier.

The piston described therein is made up of four parts thereby unnecessarily complicating assembly thereof.

It is an object of the present invention to provide a piston of simple construction and easy to mount, bearing in mind that the braking heat as developed is allowed to reach the brake fluid in permitted amounts only.

According to one aspect of the present invention there is provided a brake piston for use in a disc brake including a heat-insulating element which is fixed on the end of a brake piston body which in use faces a brake pad and which is capable of being placed, via an abutment face thereof, into an abutting relationship with the pad carrier, characterised in that the brake piston body includes a respective abutment face such that the heat insulating element and the brake piston body can be simultaneously placed into abutment with the pad carrier.

Thanks to the fact that the brake piston body, during applying of the brake, is in contact with the pad carrier, part of the brake heat can be discharged through the piston such that the heat load on the pad and the pad carrier is reduced, involving the advantage that the pad will no longer separate from the pad carrier, which has been observed in cases of excessive heat development.

The amount of heat that can be dissipated through the piston, is reduced as the brake fluid is not allowed to heat up excessively.

Otherwise undesired vapour bubbles will develop in the brake fluid.

For limiting the amount of heat dissipated through the piston, the abutment face of the piston body is to be correspondingly dimensioned. Hence, it is possible for the heat flow to be controlled in special manner.

According to another aspect of the present invention there is provided a brake piston for use in a disc brake including a heat insulating element fixed on the end of a brake piston body which in use faces a brake pad and which is capable of being placed, via an abutment face thereof, into an abutting relationship with the pad carrier, characterised in that the brake piston body comprises an end face which in case of abutment of the heat insulating element with the pad carrier is separated from the pad carrier by an air gap of a width from about 0.5 to about 1mm.

The above object is even achieved in the event that a narrow air gap of about 0.5 to 1 mum is left between the piston body and the pad carrier, once the heat insulating element is in abutment with the pad carrier.

An additional alternative of heat flow control thus resides in so defining the width of the air gap that, under consideration of the heat conductivity of the air, only a predetermined heat flow from the pad carrier, via the air gap, to the piston body will take place.

To ensure easy manufacture of the piston, a circumferential web may be provided on the outer end of the piston body the ring-shaped outer face of which forms the abutment face of the brake piston body, with the width of the circumferential web determining the heat flow.

Advantageously, the insulating element is formed of a ring which is in abutting relationship to the outer side or the inner side of the web. In cases, where the web is very narrow for the afore-mentioned reasons, an outer or inner ring may be provided.

To improve the stability of the piston, the ineternally disposed insulating member can be in the form of a solid disc, the outer rim of which is in abutting relationship to the web.

Confinement of the abutment face of the piston body can also be achieved by providing recesses in or interruptions of the web.

In case of such a configured web, parts of the heat insulating element can engage the re cesses such that a stronger connection is established between the piston body and the insulating element.

Advantageously, the heat insulating member also may corí;prise a double ring, connecting pieces between which rings engage the inter ruptions of the web.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a longitudinal section through a piston, a brake housing and a brake pad Figure 2 is a plan view of the outer end of the piston with another embodiment of abutment surface; and Figure 3 is a longitudinal section through a piston involving an alternative arrangement of the heat insulating element.

Piston 1 is sealingly guided in a bore 2 of a brake housing 3, with internal chamber 4 being filled with brake fluid and piston 1 pressed outwardly, once the brake fluid is pressurised.

The piston may be hollow such as the one shown in Fig. 1, or may be solid.

Moulded radially outwardly to the front end of the piston body 1 is a web 6 which, with the abutment face 7 thereof, may be in abutting relationship with a pad carrier 8.

Attached radially inwardly, on the front end of the piston body 11, is a ring of heat insulating material (insulating ring 9) which, with the outer surface 10 thereof, may also be pled into abutting relationship to the pad carrier 8.

In the illustration of Fig. 1, the ring 9 is radially inward of the web. However, it is also possible for the web 6 to be radially disposed further inwardly, and, for the insulating ring 9 to be radially outward of the web. Moreover, it also possible to provide both an inner ring and an outer ring. Should an inner ring be provided, the same may be replaced by a solid disc. The latter-mentioned alternatives have not been illustrated in any of the drawings.

Another form of embodiment of the web 6 -is shown in Fig. 2. Multiple interruptions 13 of the web and double-ring configuration 14 of the insulating member are provided. With the connecting pieces 1 5 of the double ring engaging the recesses 13 of the web 6.

To provide an air gap 5 between the pad carrier and the piston body, the insulating member may protrude beyond the piston body by the desired width of the air gap, as illustrated in Fig. 3.

Claims

1. A brake piston for use in a disc brake including a heat-insulating element which is fixed on the end of a brake piston body which in use faces a brake pad and which is capable of being placed, via an abutment face thereof, into an abutting relationship with the pad carrier, characterised in that the brake piston body (11) includes a respective abutment face (7) such that the heat insulating element (9) and the brake piston body (11) can be simultaneously placed into abutment with the pad carrier (8).

2. A brake piston for use in a disc brake including a heat insulating element fixed on the end of a brake piston body which in use faces a brake pad and which is capable of being placed, via an abutment face thereof, into an abutting relationship with the pad carrier, characterised in that the brake piston body (11) comprises an end face (7) which in case of abutment of the heat insulating element with the pad carrier (8) is separated from the pad carrier (8) by an air gap (5) of a width from about 0.5 to about 1mm.

3. A brake piston according to claim 1 or claim 2, characterised in that the brake piston body (11), at said end thereof comprises a circumferential web (6) the front face of which forms the respective abutment face (7) which, in particular, is of a circular ring-shaped configuration and the centre of which is the piston axis.

4. A brake piston according to any one of claims 1 to 3, characterised in that the heat insulating element is comprised of one or two rings (9) which are disposed radially outwardly and/or radially inwardly on the brake piston body (11).

5. A brake piston according to any one of claims 1 to 3, characterised in that the heat insulating element is a disc which with the outer rim thereof adjoins the brake piston body (11).

6. A brake piston according to claim 3, characterised in that the web (6) is provided with recesses (13) or interruptions.

7. A brake piston according to claim 6, characterised in that the insulating element (14) has parts thereof is in engagement with recesses (13) in the web.

8. A brake piston according to claim 6, characterised in that the insulating element comprises a double ring (14), connecting pieces (15) between which rings are in engagement with the recesses (13) in the web.

9. A brake piston for use in a disc brake substantially as herein described with reference to Fig. 1, Fig. 2 or Fig. 3 of the accompanying drawings.