WO2010069953A1

WO2010069953A1 - Disc brake with improved cooling

Info

Publication number: WO2010069953A1
Application number: PCT/EP2009/067182
Authority: WO
Inventors: Johan Hugelier; Peter De Jaeger
Original assignee: Bekaert NV SA
Current assignee: Bekaert NV SA
Priority date: 2008-12-19
Filing date: 2009-12-15
Publication date: 2010-06-24
Anticipated expiration: 2011-06-19

Abstract

The invention relates to an improved heat dissipating element for a disc brake that enables an improved dissipation of heat from the brake disc. A part of a braking system is provided comprising a thermally conducting open cell porous medium attached on a brake caliper. This provides an immediate cooling of the brake caliper by the naturally or forced airflow which surrounds the driving vehicle and which might make it possible to reduce or miniaturise the brake system or even simplify the brake caliper by omitting a water or oil cooling in the brake caliper.

Description

Disk brake with improved cooling

Description Technical Field

[0001] The present invention relates to brakes for automotive and/or other vehicle wheels. More in particular, the present invention relates to improved cooling efficiency of disk brakes for automotive and/or other vehicles that use a pair of co-axial rotor planes.

Background Art

[0002] The disc brake is one type of device for slowing down or stopping the rotation of a wheel. Disc brakes comprise a disc or discs coupled to the turning wheel. To stop the wheel, friction material in the form of brake pads (mounted in the brake calliper) is forced mechanically, hydraulically pneumatically or electromechanically against both sides of the disc. Friction causes the disc and attached wheel to slow or stop.

[0003] Large amounts of heat are generated in that way. Excessive heat causes, amongst others, warping of the discs which softens the metal and allows it to be reshaped. The generated heat must thus be continuously dissipated for the operating safety of the disc brake.

[0004] A quicker cooling of the brake system would allow the system to withstand greater force and friction and would provide better braking performance.

[0005] The art already improved the brake performance of disc brakes by e.g. ventilated disc brakes, see e.g. US 6,334,515 or US 2008/0017460; and by providing air flow onto the brake discs as described e.g. in US 6,216,829.

[0006] However, especially in Formule 1 and high performant car brake systems, a more efficient cooling of the brake system is desired.

Disclosure of Invention

[0007] The present invention provides an efficient and immediate cooling of the brake system by an element as provided in claim 1.

[0008] An object of the invention is to provide an improved heat dissipating element for a disc brake that enables an improved dissipation of heat from the brake disc with simultaneously a simple and economical design. Such an improved heat dissipating element for a disc brake system might also make it possible to reduce or even miniaturise the brake system or even to simplify the brake caliper by omitting a water or oil cooling in the brake caliper.

[0009] In a first aspect the present invention provides an improved heat dissipating element for use in a disc brake assembly. The improved heat dissipating element comprises a thermally conducting open cell porous medium thermally attached on a brake caliper. This enables an improved immediate cooling of the brake caliper by the naturally or forced airflow which surrounds a driving vehicle.

[0010] In addition, the invention relates to a method for manufacturing such an improved heat dissipating element. This method comprises the following steps: first a brake caliper and a thermally conducting open cell porous medium are provided. Thereafter the thermally conducting open cell porous medium is thermally attached on said brake caliper.

[0011] In a preferred aspect, the thermally conducting open cell porous medium is thermally attached to the brake caliper by sintering, or via a thermally conductive means. The thermally conductive means can be formed by thermally conductive glue, thermally conductive epoxylayer, (soldering) paste, thermally conductive metal layer, e.g. brazing foil, and so on. Alternatively, the thermally conducting open cell porous medium can be attached by means of a co-casting method. Such method is described in DE19650613, second method. In a further alternative, the improved heat dissipating element is produced integrally by casting the heat conducting open cell porous medium together with the brake caliper or by a method of rapid manufacturing. Every one of these attachment methods, reduce the thermal contact resistance and thus improves the thermal conductivity between the heat conducting open cell porous medium and the brake caliper.

[0012] The thermally conductive open cell porous medium can be a graphite foam, a carbon or graphite foam, a carbon or graphite containing metal foam, metal foam, a woven or knitted 3D textile in metal, graphite or carbon, a 3D wire structure made of metal, graphite or carbon.

[0013] In a preferred aspect, the thermally conductive open cell porous medium has an amount of pores per inch (ppi) between 10 and 50 ppi. More preferably, the amount of pores per inch (ppi) is between 15 and 30 ppi, most preferably the amount of pores per inch (ppi) is 20 ppi.

[0014] In another preferred aspect, the porosity of the thermally conductive open cell porous medium is ranging between 91 ,5% and 96,5%, more preferably between 92% and 96%, most preferably between 92,5% and 95,5%. This porosity provides an even more improved direct and immediate cooling of the metal piece. The porosity of the thermally conductive open cell porous medium can be tuned depending on the thermally conductive open cell porous medium used as known by the person skilled in the art. E.g. in the case of an open cell metal foam reference is made to EP 1604756.

[0015] In a further preferred aspect, the thermally conductive open cell porous medium is metal foam, preferably made of aluminium or an aluminium alloy. In another preferred aspect, the metal foam is made of copper or a copper alloy. In a more preferred aspect the metal foam is made of graphite or comprises graphite.

[0016] In an even further preferred aspect, the thickness of the open cell porous medium is between 1 and 6 times the pore diameter. More preferably, the thickness of the open cell porous medium is between 1 ,5 and 5 times the pore diameter, even more preferably between 2 and 4 times the pore diameter. Some examples of such thicknesses are shown in table 1.

[0017] Table 1

[0018] Definitions

[0019] The term "porosity" is to be understood as the amount of air in the thermally conductive open cell porous medium expressed as a percentage of a same volume of dense material.

[0020] The term "open cell porous medium" is to be understood as a porous medium with interconnecting porosity.

Brief Description of Figures in the Drawings

[0021] Figure 1 is a perspective view of a disk brake.

[0022] Figure 2 show a perspective view of an exemplary improved heat dissipating element as used in a brake system.

Mode(s) for Carrying Out the Invention

[0023] Figure 1 shows a conventional prior art disk brake 10 comprising a brake disk 20 and a caliper 30 having caliper pads 40 for controllably applying friction to the brake disk 20.

[0024] Figure 2 shows an exemplary improved heat dissipating element for use in a brake assembly according to the invention. The disk brake 10 comprises a brake disk 20 and a caliper 30, but here the caliper 30 is provided with a layer of open cell metal foam 50 of 20 ppi, with a porosity of 95 %. The layer of open cell metal foam 50 has a thickness of 3,5 mm, which corresponds to approx. 2 times the pore diameter. The layer of metal foam 50 is attached to the caliper 30 by a conductive epoxylayer, in this example Bondmaster® was used. The metal foam 50 is made of aluminium. A total amount of metal foam 50 of 2 dm² of 3,6 mm thickness was attached to the brake caliper. The use of this improved heat dissipating element resulted in a reduced end temperature of the brake caliper by 17°C, compared to a prior art brake system, after a brake test which involved 3 braking cycles from 250 km/h to full stop.

[0025] Another exemplary improved heat dissipating element for use in a brake assembly according to the invention, was produced by attaching a 20 ppi, 95 % porosity, aluminium foam layer of 3,5 mm thickness on the internal brake block of a totally enclosed brake caliper, wherein the brake block is cooled by a forced airflow. The total amount of metal foam added on this caliper was 0,8 dm² of 3,5 mm thickness. This caliper was tested in a simulation of a Formule 1 circuit on 3 different wind speeds. The end temperature of the caliper with the metal foam attached on it was reduced by 10⁰C on average compared to a standard prior art caliper after the same test. These tests demonstrate that the small amount of aluminium foam provide an important amount of cooling for the brake system. It is self evident for a person skilled in the art that similar thermally conducting open cell porous media will provide a same effect.

Claims

Claim 1. An improved heat dissipating element for use in a brake assembly, said element comprising a brake caliper and a thermally conducting open cell porous medium, said thermally conducting open cell porous medium thermally attached on the outer side of said brake caliper.

Claim 2. Improved heat dissipating element as claimed in claim 1 , wherein said thermally conducting open cell porous medium has an amount of pores per inch (ppi) between 10 and 50 ppi.

Claim 3. Improved heat dissipating element as claimed in claims 1 or 2, wherein said thermally conducting open cell porous medium has a thickness between 1 and 6 times the pore diameter.

Claim 4. Improved heat dissipating element as in any of the claims 1 to 3, wherein said thermally conducting open cell porous medium has a porosity between 91 ,5% and 96,5%.

Claim 5. Improved heat dissipating element as in any of the claims 1 to 4, wherein said thermally conducting open cell porous medium is an open cell metal foam.

Claim 6. Disc brake assembly comprising an improved heat dissipating element as in any of the claims 1 to 5.

Claim 7. Method of producing an improved heat dissipating element for use in a brake assembly, said method comprising the following steps: - providing a brake caliper;

- providing a thermally conducting open cell porous medium;

- attaching said thermally conducting open cell porous medium on said brake caliper.

Claim 8. Method according to claim 7, wherein said attachment is realised by soldering, brazing or sintering.

Claim 9. Method according to claim 7, wherein said attachment is realised by using a thermally conductive epoxy-layer.

Claim 10. Method according to claim 9, wherein said thermally conductive epoxy-layer being arranged on the surface of said brake caliper, whereafter said thermally conducting open cell porous medium is arranged on top of said thermally conductive epoxy-layer and a pressure is applied on said thermally conducting open cell porous medium.

Claim 11. Method according to claims 9 or 10, said method further comprising an additional step of hardening said epoxylayer.

Claim 12. Method of producing an improved heat dissipating element for use in a brake assembly having a brake caliper and a thermally conducting open cell porous medium, said method comprising the integral casting of a thermally conducting open cell porous medium together with said brake caliper.