GB2529823A

GB2529823A - Vehicle friction brake

Info

Publication number: GB2529823A
Application number: GB1415504.8A
Authority: GB
Inventors: Daren Steward; Philip Ferdani
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2014-09-02
Filing date: 2014-09-02
Publication date: 2016-03-09
Anticipated expiration: 2034-09-02
Also published as: GB2529823B; GB201415504D0

Abstract

A brake pad 103 comprises a back plate 107 and a brake pad lining 109 for engaging a brake rotor (R, figs 1a-c). At least one aperture 123A-F is formed in the brake pad lining 109 to control heat generation during braking. The at least one hole 123A-F is inset from an exterior edge 113, 115, 117 of the brake pad lining 109, and may be drilled or moulded into the pad lining 109. The apertures 123A-F may extend partially or completely through the lining 109. The apertures 123A-F are preferably proximal to and inset from an outer radial edge 115 of the brake pad lining 109, and arranged along a circular arc 125 having a centre that, in use, aligns with the centre of the brake rotor (R, figs 1a-c).

Description

VEHICLE FRICTION BRAKE

TECHNICAL FIELD

The present disclosure relates to a vehicle friction brake, to a brake pad, to a brake caliper, to a vehicle and to a method of manufacturing a brake pad.

BACKGROUND

A disk brake assembly for a vehicle typically comprises a brake caliper having first and second brake pads for engaging a brake rotor. The brake pads each comprise a back plate for mounting the brake pad to the brake caliper, and a brake pad lining for engaging the brake rotor. The brake pad lining is bonded to and/or mechanically fastened to the back plate. Historically, some brake pads were provided with drilled holes for the purpose of riveting the brake pad lining (a friction material puck) to the back plate. It is also known to incorporate geometric features, such as chamfers and slots, into brake pad linings, typically to control their acoustic properties. For example, it is known from GB 2445835 to introduce notches into the outer edge of the brake pad lining at or near peak areas of wave propagation to reduce brake moan and groan.

The brake pad lining defines a major braking surface for engaging the brake rotor to apply a friction braking force. The resulting friction between the brake pad lining and the brake rotor generates heat which causes the temperature of the brake rotor to increase. However, the increase in temperature may be non-uniform across the brake rotor, for example due to the non-uniform rubbing speed (corresponding to the tangential speed of the brake rotor) which increases towards the brake rotor rim. Due to the higher rubbing speed, higher energy dissipation typically occurs at the outer radius of the brake rotor resulting in higher temperatures.

The localised heating of the brake rotor is undesirable, potentially causing a transient distortion of the brake rotor. Any such distortion of the brake rotor is undesirable since it may result in the generation of unwanted noise and vibrations. The distortion of the brake rotor may cause it to contact the brake pad as it rotates, resulting in the generation of low frequency vibrations (for example, in the range of 20-25 Hz) which would be perceptible to the driver and/or occupant(s) of the vehicle.

To address the problem of non-uniform heating, the brake caliper could be adjusted to move the centre of pressure, for example by implementing a tapered pad, additional shims or modifying conventional chamfers. However, these approaches may prove unreliable in providing a permanent solution or introduce other limitations. Moreover, altering the exterior profile of the brake pad lining can alter the acoustic behaviour of the brake pad.

It is against this backdrop that the invention(s) described herein have been conceived. At least in certain embodiments, the invention(s) described herein can overcome or ameliorate at least some of the shortcomings associated with prior art arrangements.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a vehicle friction brake, to a brake pad, to a brake caliper, to a vehicle and to a method of manufacturing a brake pad.

According to a further aspect of the present invention there is provided a brake pad lining for engaging a brake rotor, wherein at least one aperture is formed in the brake pad lining for controlling the generation of heat during braking, the at least one aperture being inset from an exterior edge of the brake pad lining.

According to a further aspect of the present invention there is provided a brake pad comprising: a back plate; and a brake pad lining for engaging a brake rotor; wherein at least one aperture is formed in the brake pad lining for controlling the generation of heat during braking, the at least one aperture being inset from an exterior edge of the brake pad lining.

The at least one aperture can be positioned to reduce the rubbing path in a localised region of the brake pad lining. The at least one aperture can be positioned to reduce the work performed in a localised region, thereby reducing the generation of heat in that region. The at least one aperture can, therefore, be referred to as a temperature (thermal) control aperture. The heating of the brake rotor can be controlled based on the positioning of said at least one aperture in the brake pad lining. For example, an annular region of the brake rotor swept by said at least one aperture can experience a reduced increase in temperature during braking. The at least one aperture can be configured to provide a localised reduction in the heating of the brake rotor, for example in an annular band. At least in certain embodiments, the work performed by the brake pad lining can be distributed more uniformly over a larger area of the major braking surface of the brake pad lining and the cooperating region of the surface of the brake rotor. As a result, the generation of heat in the brake surface can be more evenly distributed, for example to avoid localised high temperature regions. This arrangement can help to reduce the maximum temperature and/or thermal distortion of the brake rotor. Thermal distortion of the brake rotor can thereby be reduced.

The at least one aperture is surrounded by a major braking surface of the brake pad lining for engaging the brake rotor. By forming the at least one aperture inset from the edge of the brake pad lining, the exterior profile of the brake pad liner and/or the centre of pressure can remain unchanged. Al least in certain embodiments, brake performance and/or Noise Vibration Harshness (NVH) are substantially unaffected by the provision of said at least one aperture in the brake pad lining.

The at least one aperture could, for example, be elliptical or oval in shape. Alternatively, the at least one aperture can be substantially circular. This arrangement helps to distribute dynamic loads around the at least one aperture so as to preserve the integrity of the brake pad lining. The at least one aperture can be a hole drilled in the brake pad lining after it has been mounted to the back plate. Alternatively, the at least one aperture can be formed during fabrication of the brake pad lining, for example during a moulding process. The at least one aperture can have a diameter in the range of 5mm to 30mm (inclusive). More particularly, the at least one aperture can have a diameter in the range of 10mm to 20mm (inclusive). Each aperture can have a diameter of 10mm or of 20mm. In arrangement comprising a plurality of said apertures, the apertures can have different diameters.

The at least one aperture can extend partially or completely through the brake pad lining.

The at least one aperture can be a hole, either a through hole extending through the brake pad lining or a blind hole extending only partially through the brake pad lining. The back plate can be continuous in the region of said at least one aperture. Alternatively, at least one opening can be formed in the back plate in alignment with said at least one aperture. The at least one opening and the associated aperture(s) can form at least one through hole extending through the brake pad. The at least one through hole can promote ventilation.

The at least one aperture can be inset from an outer radial edge of the brake pad lining. The rubbing speed at the radially outer edge of the brake pad lining is higher than at the radially inner edge of the brake pad lining. Disposing said at least one aperture proximal to the radially outer edge can at least partially balance the braking force applied over the major braking surface of the brake pad lining. The at least one aperture can be positioned so as to be disposed proximal to a rim of the brake rotor in brake assembly.

At least in certain embodiments, the at least one aperture can be configured so as not to affect the stiffness and/or noise behaviour of the brake pad. For example, the number and/or size and/or shape and/or position of the aperture(s) can be selected to maintain stiffness and/or noise behaviour and/or mechanical integrity. The brake pad can comprise a plurality of said apertures. For example, the brake pad can comprise two, or more than two of said apertures.

The apertures could be disposed in a linear arrangement. Alternatively, the apertures can be disposed along an arc. The arc can be a crcular arc having a centre coincident with a rotational axis of the brake rotor. Thus, the apertures in the arc can reduce the effective shear area of an arcuate section of the brake pad lining. The thermal heating of an annular swept region of the brake rotor aligned with said at least one aperture is thereby reduced. A centre of each aperture can be arranged in said linear or arcuate arrangement. The arc can be inset from an outer edge of the brake pad liner by a distance of between 10mm and 30mm, for example 15mm inset from the outer edge. Alternatively, the apertures can be disposed in more than one arc. For example, the apertures could be disposed in the first and second arc. The apertures in said first and second arcs could be aligned with each other or could be arranged in an interlocking arrangement.

The apertures can, for example, be uniformly (equi-spaced) or non-uniformly distributed along an arc or a line. An angular offset between adjacent apertures can be the range of 50 to 40°. The angular offset between adjacent apertures can be in the range 5° to 15°. The angular offset between adjacent apertures can be approximately 6.5° or approximately 9°.

The at least one aperture can have a uniform profile along its length, i.e. a profile which is the same irrespective of depth. By way of example, the at least one aperture can have a right cylindrical profile. Alternatively, the profile of said at least one aperture can change along its length. For example, the at least ore aperture can have a non-cylindrical profile.

The at least one aperture could have a tapered or conical profile. Each aperture can have a longitudinal axis which can be arranged perpendicular to the major braking surface of the brake pad lining. Alternatively, the longitudina axis can be inclined at an acute angle to the major braking surface of the brake pad lining. The longitudinal axis can be inclined such that the relative position of the or each aperture to the back plate changes as the brake pad lining wears.

The brake pad is mounted to the back plate. The brake pad lining can, for example, be bonded to the back plate. Alternatively, or in addition, the brake pad lining can be mounted to the back plate by one or more mechanical fasteners, such as rivets. The one or more mechanical fasteners can be disposed in mounting holes formed in the brake pad lining. The mounting holes are distinct from the apertures described herein to control the generation of heat. Other attachment techniques can be used to mount the brake pad lining to the back plate, for example one or more of the following: a welded mesh, sintered layers, a knurled surface and a serrated surface. These attachment techniques can be used in conjunction with the integral moulding of the brake pad lining (i.e. the moulding of the brake pad lining onto the back plate)to mount the brake pad lining to the back plate.

The brake pad can optionally also comprise one or more slots, chamfers or notches formed in an edge of the brake pad lining and/or one or more chamfers. The slots, chambers or notches can, for example, be formed in an inner edge, an outer edge or a lateral edge of the brake pad lining. Any such slot(s), chamfer(s) or notch(es) is distinct from the apertures described herein to control the generation of heat. Notably, the primary purpose of slots and/or chamfers in the brake pad lining is to control noise generation. In contrast, the primary purpose of the at least one aperture in accordance with aspects of the present invention is to control the generation of heat in the brake pad and the brake rotor during friction braking. It will be understood that the number and/or size and/or position of the at least one aperture(s) can be configured to minimise any changes to the stiffness and/or noise behaviour of the brake pad.

The brake pad described herein is suitable for performing friction braking. The brake pad can be configured for use in a disc brake assembly. The brake pad can be configured to be mounted in a brake caliper.

According to a further aspect of the present invention there is provided a brake caliper comprising at least one brake pad as described herein. The brake caliper can comprise a first said brake pad in an outboard position for engaging an outboard surface of the brake rotor; and/or a second said brake pad in an inboard position for engaging an inboard surface of the brake rotor. The first said brake pad can comprise at least one said aperture; and/or the second said brake pad can comprise at least one said aperture. Moreover, the number and/or position of the at least one aperture on each brake pad can be optimised. Thus, the first and second said brake pads can have different numbers of apertures and/or a different pattern of apertures. The first said brake pad or the second said brake pad could be used in combination with a conventional brake pad which does not have any apertures formed therein.

According to a further aspect of the present invention there is provided a vehicle comprising a brake caliper as described herein.

According to a further aspect of the present invention there is provided a method of manufacturing a brake pad, the method comprising: forming at least one aperture in a brake pad lining mounted to a back plate, the at least one aperture being inset from an exterior edge of the brake pad lining. The at least one aperture is surrounded by a major braking surface of the brake pad lining. Thus, the outer profile of the brake pad lining is not altered by said at least one aperture. At least in certain embodiments, the acoustic properties of the brake pad are preserved even when said at least one aperture is formed therein. The at least one aperture can be formed by machining, for example by drilling a hole in the brake pad lining.

According to a further aspect of the present invention there is provided a method of manufacturing a brake pad lining, the method comprising: moulding a brake pad lining; wherein at least one aperture is moulded into said brake pad lining, the at least one aperture being inset from an exterior edge of the brake pad lining.

According to a further aspect of the present invention there is provided a method of manufacturing a brake pad comprising mounting a brake pad lining as described herein to a back plate. The brake pad lining can be mounted to the back plate by bonding and/or riveting. Other attachment techniques can be used to mount the brake pad lining to the back plate, for example one or more of the following: a welded mesh, sintered layers, a knurled surface and a serrated surface. These attachment techniques can be used in conjunction with the integral moulding of the brake pad lining (i.e. the moulding of the brake pad lining onto the back plate) to mount the brake pad lining to the back plate.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying Figures, in which: Figure 1A shows an end elevation of a friction brake assembly comprsing a brake caliper having inboard and outboard brake pads in accordance with an embodiment of the present invention; Figure lB shows a sectional view through the friction brake assembly shown in Figure 1A showing the inboard brake pad; Figure 1C shows a sectional view through the friction brake assembly shown in Figure 1A showing the outboard brake pad; Figure 2 shows a plan elevation of the brake pad shown schematicaUy in Figures 1A and 1B; Figure 3 shows a sectional view along line A-A of the brake pad shown in Figure 2; Figure 4 shows a plan elevation of a brake pad in accordance with a further embodiment of the present invention; Figure 5 shows a sectional view along line B-B of the brake pad shown in Figure 7; Figure 6 illustrates a vehicle comprising the friction brake assembly shown in Figure 1A; Figure 7 shows a comparison of a modelled temperature for the brake pad according to a further embodiment of the present invention and a conventional brake pad; Figure 8A shows a comparison of a modelled temperature for the brake rotor used in conjunction with the outboard brake pad according to the further embodiment of the present invention and a conventional brake pad; and Figure SB shows the location of a measurement area on the outboard surface of the brake rotor for the comparison shown in Figure 8A.

DETAILED DESCRIPTION

A vehicle friction brake assembly 1 comprising a brake pad 3 in accordance with an embodiment of the present invention will now be described with reference to the accompanying Figures. The vehicle friction brake assembly 1 in the present embodiment is a disc brake having particular application in an automotive vehicle V. The terms inboard and outboard" are used herein with reference to a longitudinal centreline of the vehicle V. As shown in Figures 1A, lB and 1C, the vehicle friction brake assembly 1 comprises a brake caliper 5 and a brake rotor (disc) R having an inboard surface SIN and an outboard surface 5OUTh The brake caliper 5 carries an inboard brake pad 3 and an outboard brake pad 103 arranged on opposite sides of the brake rotor R. The inboard and outboard brake pads 3, 103 are in accordance with an embodiment of the present invention. The brake caliper 5 in the present embodiment is a sliding-type caliper comprising a single hydraulic piston P arranged to displace the inboard and outboard brake pads 3, 103 towards each other so as to contact the brake rotor R and apply a friction braking force. The brake caliper 5 could alternatively be an opposed piston-type caliper comprising more than one hydraulic piston, for example two (2), four (4), six (6) or eight (8) hydraulic pistons. The hydraulic pistons are connected to a hydraulic system coupled to a brake pedal, for example via a hydraulic brake cylinder or an electromechanical coupling. It will be appreciated that other types of mechanical or electromechanical actuator could be used in place of the hydraulic pistons to displace the brake pads against the brake rotor R. A sectional view through the vehicle friction brake assembly 1 showing the inboard brake pad 3 is shown in Figure lB. A sectional view through the vehicle friction brake assembly 1 showing the outboard brake pad 103 is shown in Figure 1G.

The inboard and outboard brake pads 3, 103 comprise respective inboard and outboard back plates 7, 107 and brake pad linings 9, 109. The brake pad linings 9, 109 are each formed from a heat-resistant material having a high coefficient of friction. The back plates 7, 107 each have a metal plate having first and second lateral projections 11, 111 for mounting the inboard and outboard brake pads 3, 103 to the brake caliper 5. In alternative arrangements, the first and second lateral projections 11, 111 of the inboard and outboard brake pads 3, 103 could be replaced with flat or round abutments. The brake pad linings 9, 109 are fixedly mounted to the respective back plates 7, 107. In the present embodiment, the brake pad linings 9, 109 are bonded to the back plates 7, 107 using a high-temperature adhesive. Alternatively, or in addition, one or more mechanical fasteners, such as rivets, can be used to mount the brake pad linings 9, 109 to the back plates 7, 107. The brake pad linings 9, 109 could be mounted using other attachment techniques, such as a welded mesh, sintered layers, knurled or serrated surface, which can be used in conjunction with the integral moulding of the brake pad linings 9, 109 to the back plates 7, 107.

The brake pad linings 9, 109 are each in the form of a part-annular segment having a radially inner edge 13, 113, a radially outer edge 15, 115 and first and second lateral edges 17, 117.

The brake pad linings 9, 109 each comprise a major braking surface 21, 121 for engaging the brake rotor R to apply a friction braking force. In accordance with an aspect of the present invention, the brake pad linings 9, 109 each comprise a plurality of apertures 23, 123 inset from the radially outer edges 15, 115 of the respective brake pad linings 9, 109 within the major braking surface 21, 121. The apertures 23, 123 are arranged to reduce a rubbing path in a localised region of the brake pad linings 9, 109. As described herein, the apertures 23, 123 can thereby alter the heat generated by the friction engagement of the brake pad linings 9, 109 and the brake rotor R. The apertures 23, 123 thereby control the generation of heat in the brake pad linings 9, 109 and on the brake rotor R during braking. The apertures 23, 123 are inset from the exterior edges 13, 15, 17; 113, 115, 117 of the brake pad linings 9, 109 so as not to alter their respective outer profiles. The acoustic properties of the brake pad linings 9, 109 are at least substantially unaffected by the presence of the apertures 23, 123.

A plan elevation of the inboard brake pad 3 is shown in Figure 2. The inboard brake pad lining 9 comprises four apertures 23A-D arranged in first and second pairs arranged symmetrically about a radial centreline of the nboard brake pad lining 9. The inboard brake pad lining 9 has a thickness of 12.5mm. The apertures 23A-D have a diameter of 10mm and a depth of 9mm so as to extend only partway through the brake pad lining 9. The apertures 23A-D are blind holes formed by drilling into the inboard brake pad lining 9 after it has been bonded to the back plate 7. In the illustrated arrangement, a type 4 drill having a point angle of 118° is used to form the apertures 23A-D. A longitudinal axis of each aperture 23A-D extends perpendicular to the major braking surface 21 of the inboard brake pad lining 9.

Since the apertures 23A-D do not extend through the inboard brake pad lining 9, the back plate 7 is not penetrated when the apertures 23A-D are formed. In an alternative arrangement, the apertures 23A-D could be formed prior to mounting the inboard brake pad lining 9 to the back plate 7, for example when the inboard brake pad lining 9 is formed.

The apertures 23A-D are arranged along a first circular arc 25 having a centre C substantially coincident with a rotational axis of the brake rotor R of the vehicle friction brake assembly 1. In particular, the centre of each aperture 23A-D is disposed on the first circular arc 25. The first circular arc 25 has a first radius r1. As shown in Figure 2, the angular offset between the apertures 23A, 23B in the first pair and between the apertures 230, 23D in the second pair are is 8.72°. In use, the apertures 23A-D are all disposed at the same radial distance from the rotational axis of the brake rotor. Thus, as the brake rotor rotates relative to the brake caliper 5, an annular region of the brake rotor R is swept by all of the apertures 23A-D. The localised shear area of the inboard brake pad lining 9 is reduced by the apertures 23A-D such that the localised heating in the swept annular region of the brake rotor F{ is reduced. The circular arc 25 is radially inset from the radially outer edge 15 of the brake pad lining 9 by approximately 15mm.

As shown in Figures 2 and 3, the inboard brake pad lining 9 comprises first and second chamfers 27, 29 arranged at the radially inner corners defined by the radially inner edge 13 and the first and second lateral edges 17. The first and second chamfers 27, 29 are provided to control the acoustic properties of the vehicle friction brake assembly 1, in particular to adjust the characteristics of a standing wave established in the brake rotor R. A plan eleva[ion of the outboard brake pad 103 is shown in Figure 4 and a sectional view along line B-B is shown in Figures. The outboard brake pad 103 is disposed in an outboard position in relation to the brake rotor R. The outboard brake pad lining 109 comprises six apertures 123A-F arranged in first and second arrays each comprising three (3) apertures.

The first and second arrays are arranged symmetrically about a radial centreline of the brake pad lining 109. The outboard brake pad lining 109 has a thickness of 12.5mm. The apertures 123A-F each have a diameter of 10mm and a depth of approximately 9mm so as to extend only partway through the outboard brake pad lining 109, as shown in FigureS. The apertures 123A-F are blind holes formed by drilling into the outboard brake pad lining 109 after it has been bonded to the back plate 107. A longitudinal axis of each aperture 123A-F extends perpendicular to the major braking surface 121 of the brake pad lining 109.

The apertures 123A-F are arranged along a second circular arc 125 having a centre C substantially coincident with a rotational axis of the brake rotor R of the vehicle friction brake assembly 1. In particular, the centre of each aperture 123A-F is disposed on the second circular arc 125. The second circular arc 125 has a second radius r2. The angular offset between adjacent apertures 123A, 123B, 123C in the first array and between adjacent apertures 123D, 123E, 123F in the second array is 6.5°. In use, the apertures 123A-F are all disposed at the same radial distance from the rotational axis of the brake rotor R. The second circular arc 125 is radially inset from the radially outer edge 115 of the brake pad lining 109 by approximately 15mm.

As shown in Figures 4 and 5, the outboard brake pad lining 109 comprises first and second chamfers 127, 129 arranged at the radially inner corners defined by the radially inner edge 113 and the first and second lateral edges 117.

As shown in Figures 2 and 4, radial slots 30, 130 are formed in the centre of the inboard and outboard brake pad linings 9, 109 to prevent initiation of a crack or fracture in the brake pad linings 9, 109 due to thermal and mechanical operating loads. In the present embodiment, a single radial slot 30, 130 is provided but more than one slot can be provided in the inboard brake pad lining 9. The slots 30, 130 function to inhibit crack initiation in the inboard and outboard brake pad linings 9, 109 which could potentially result in a partial or complete detachment from their respective back plates 7, 107. In use, the slots 30, 130 also modify the modal behaviour of the brake pads 3, 103 by reducing bending stiffness and vibration frequency, which can help to decouple the pad from any rotor (disc) frequencies. The slots 30, 130 can also reduce brake fade by providing a path for any decomposition products to exit the interface between the inboard and outboard brake pad linings 9, 109 and the brake rotor R. Similarly, the slots 30, 130 can improve wet friction.

The inboard and outboard brake pad linings 9, 109 are integrally moulded onto the respective back plates 7, 107. As shown in Figures 3 and 5, holes 31, 131 are formed in the back plates 7, 107 and a portion of the inboard and outboard brake pad linings 9, 109 extends into the respective hole 31, 131 during the moulding process. The resulting protrusions 33, 133 provide a mechanical key to help mount the inboard and outboard brake pad linings 9, 109 to the respective back plates 7, 107. If the inboard and outboard brake pad linings 9, 109 are formed separately from the back plates 7, 107, the holes 31, 131 can receive the protrusions 33, 133 formed in the inboard and outboard brake pad linings 9, 109 to align the inboard and outboard brake pad linings 9, 109 with the respective back plates 7 to facilitate fabrication.

In the present embodiment, the first radius r1 and the second radius r2of the first and second circular arcs 25 are the same for the inboard and outboard brake pads 3, 103. In alternative arrangements, the first radius r1 and the second radius r2can be different to provide different temperature control on the inboard and outboard surfaces SIN, SOul of the brake rotor R during braking.

The operation of the vehicle friction brake assembly 1 incorporating the inboard and outboard brake pads 3, 103 in accordance with an embodiment of the present invention will now be described. The vehicle friction brake assembly 1 is actuated by operation of a vehicle brake pedal in conventional manner. When the vehicle brake pedal is depressed, the inboard and outboard brake pads 3, 103 are displaced towards each other to engage the brake rotor R. As described herein, the apertures 23A-D, 123A-F formed in the inboard and outboard brake pad linings 9, 109 are arranged to reduce the effective shear area in a localised region. The apertures 23A-D, 123A-F are arranged along the first and second circular arcs 25, 125 to reduce the shear area in arcuate bands of the brake pad linings 9, 109, thereby reducing the work performed by those regions. The dissipation of thermal energy during braking in the annular regions swept by the apertures 23A-D, 123A-F is reduced, thereby resulting in a reduction in the increase in temperature of the brake rotor R in the corresponding regions of the inboard and outboard surfaces SIN, Soum The work done during braking is typically greater towards the rim of the brake rotor R due to the higher rubbing speeds. The apertures 23A-D, 123A-F are inset from the radially outer edges 15, 115 of the inboard and outboard brake pad linings 9, 109 such that the work done proximal to the rim of the brake rotor R is reduced. Accordingly, the dissipation of thermal energy at or proximal to the rim of the brake rotor R is reduced.

The provision of apertures 23A-D, 123A-F in the brake pad linings 9, 109 reduces the effective shear area in arcuate bands of the major braking surfaces 21, 121. The resulting work performed in those arcuate bands is reduced, resulting in a reduction in the increase in temperature in an annular region of the rotor R swept by the apertures 23A-D, 123A-F. The apertures 23A-D, 123A-F are arranged such that the arcuate band is disposed between the radially inner edge 13, 113 and the radially outer edge 15, 115 of the respective brake pad linings 9, 109. Consequently, the annular region of the brake rotor R swept by the apertures 23A-D, 123A-F is disposed between the radially inner edge 13, 113 and the radially outer edge 15, 115 of each of the inboard and outboard brake pad linings 9, 109. The apertures 23A-D, 123A-F effectively transfer the work performed by the inboard and outboard brake pad linings 9, 109 inwardly towards the radially inner edge 13, 113 of the respective inboard and outboard brake pad linings 9, 109.

A vehicle friction brake assembly 1 in accordance with a further embodiment of the present invention wil now be described with reference to Figures 7, BA and SB. Like reference numerals will be used for like components.

This embodiment of the vehicle friction brake assembly 1 comprises a brake caliper 5 having an inboard brake pad 3 and an outboard brake pad 103. The inboard and outboard brake pads 3, 103 are arranged on opposite sides of the brake rotor ft The inboard brake pad 3 is a conventional brake pad having a brake pad lining which does not have apertures formed therein to control heating (having a continuous major braking surface 21 in the present embodiment). The outboard brake pad 103 is in accordance with the present invention and corresponds to the inboard brake pad 3 described in the previous embodiment. Specifically, the outboard brake pad 103 comprises four apertures 23A-D arranged along a second circular arc 125. The generation of heat when the vehicle friction brake assembly 1 is in use will now be described with reference to Figures 7, BA and SB.

A modelled temperature along a radius of the outboard surface S01 of the brake rotor R during braking is illustrated in a first temperature graph 35 shown in Figure 7. The temperature (°C) is plotted on the V-axis; and a radial position (metres) on the outboard surface S01 of the brake rotor Fl (measured inwardly from an outer rim) is plotted on the X-axis. A first temperature plot P1 shows the modelled temperature on the outboard surface Soul of the brake rotor R used in conjunction with a standard brake pad lining (i.e. having a continuous major braking surface 21 without apertures). A second temperature plot P2 shows the modelled temperature on the outboard surface S0u1 of the brake rotor R when the outboard brake pad 103 incorporates the brake pad lining 109 having apertures 23A-D formed therein according to an aspect of the present invention. The relative position of the apertures 23A-D is illustrated by a vertical line 37 in Figure 7. It will be noted that the modelled temperature of the brake rotor R in the region coincident with the apertures 23A-D is approximately 159°C lower when the brake pad lining 109 in accordance with the present invention is used. The apertures 23A-D cause the brake pad lining 109 to perform more work in a radially inner position, as represented by the lateral offset of the first and second temperature plots P1, P2 along the X-axis in Figure 7. The modelled temperatures indicate that the peak temperature is higher for the brake pad 103 incorporating the brake pad lining 109 in accordance with an aspect of the present invention, but this may be a result of a relatively low resolution of this particular model. Indeed, in practice the peak temperature may be reduced.

A modelled temperature at a measurement area 39 on the outboard surface So1 of the brake rotor R is illustrated in a second temperature graph 41 shown in Figure BA. As shown in Figure SB, the measurement area 39 is disposed on the outboard surface S01 in radial alignment with the apertures 23A-D on the outboard brake pad 103. The temperature (°C) is plotted on the Y-axis; and time (seconds) from initiation of braking is plotted on the X-axis. A third temperature plot P3 shows the modelled temperature for a brake rotor R used in conjunction with a standard brake pad lining (i.e. having a continuous major braking surface without apertures). A fourth temperature plot P4 shows the modelled temperature for a brake rotor Fl used in conjunction with the outboard brake pad 103 having the brake pad lining 109 according to an aspect of the present invention. It will be noted that the model indicates that the temperature increase at the measurement area 39 is reduced for the brake pad 103 incorporating the brake pad lining 109 in accordance with an aspect of the present invention.

It will be appreciated that various changes and modification can be made to the apparatus described herein without departing from the scope of the present invention. For example, the inboard and outboard brake pad linings 9, 109 are not limited to arrangement having four (4) or six (6) apertures, but could have any number of apertures 23, 123. The apertures 23, 123 in each of the inboard and outboard brake pad linings 9, 109 can be arranged along a single circular arc 25, 125 as described herein or in more than one circular arc 25, 125, for example in first and second circular arcs having different radh. The apertures 23A-D, 123A-F could be positioned equidistant between the radially inner edge 13, 113 and the radially outer edge 15, 115 of the brake pad linings 9, 109, or could be positioned closer to the radially inner edges 13, 113.

The inboard and outboard brake pads 3, 103 described herein can be used in conjunction with one or more of the following: a noise shim, a pressure bias shim and, depending on the design of the brake caliper 5, one or more clips. The presence of a noise shim or a clip has no significant impact on the operation of the inboard and outboard brake pads 3, 103 according to certain embodiments of the present invention. If the shim is a pressure bias shim intended to provide a pressure bias, the contact pressure between the inboard and outboard brake pads 3, 103 and the brake rotor R is altered. Accordingly, the work done, and therefore temperature, is affected in the interface between the inboard and outboard brake pads 3, 103 and the brake rotor R. The at least one aperture 23, 123 can be configured to allow for any such changes resulting from the use of a pressure bias shim. For example, the number and/or position and/or shape and/or size of the apertures 23, 123 can be adjusted.

Furthermore, the inboard and outboard brake pads 3, 103 described herein can comprise an underlayer (not shown) disposed between the back plates 7, 107 and the brake pad linings 9, 109. The underlayer can improve bonding ot the brake pad lining 9, 109 to the back plate 7, 107 during the integral moulding process. A typical underlayer has a thickness of approximately 2mm. In use, the underlayer can also help to reduce heat transfer and may modify noise behaviour by increasing damping.

Further aspects of the present invention are set out in the following numbered paragraphs: 1. A brake pad lining for engaging a brake rotor, wherein at least one aperture is formed in the brake pad lining for controlling the generation of heat during braking, the at least one aperture being inset from an exterior edge of the brake pad lining.

2. A brake pad lining as described in paragraph 1, wherein each aperture comprises a substantially circular section.

3. A brake pad lining as described in paragraph 1, wherein each aperture is a hole drilled in said brake pad lining; or each aperture is moulded into said brake pad ining.

4. A brake pad lining as described in paragraph 1, wherein each aperture extends partially or completely through the brake pad lining.

5. A brake pad lining as described in paragraph 1, wherein the at least one aperture is disposed proximal to and inset from an outer radial edge of the brake pad lining.

6. A brake pad lining as described in paragraph 1 comprising a plurality of said apertures, said apertures being arranged along a circular arc having a centre which, in use, aligns with a rotational axis of an associated brake rotor.

7. A brake pad lining as described in paragraph 6, wherein an angular offset between adjacent apertures is in the range of 5°to 400.

8. A brake pad lining as described in paragraph 1, wherein at least one opening is formed in the back plate in alignment with said at least one aperture in the brake pad lining.

9. A brake pad lining as described in paragraph 1 comprising one or more slots, chamfers or notches formed in an edge of the brake pad lining.

10. A brake pad comprising a back plate and a brake pad lining according to any preceding claim.

11. A brake caliper comprising at least one brake pad as described in paragraph 1.

12. A brake caliper as described in paragraph 11 comprising a first said brake pad in an outboard position for engaging an outboard surface of the brake rotor; and/or a second said brake pad in an inboard position for engaging an inboard surface of the brake rotor.

13. A vehicle comprising a brake caliper as described in paragraph 11.

14. A method of manufacturing a brake pad, the method comprising: forming at least one aperture in a brake pad lining mounted to a back plate, the at least one aperture being inset from an exterior edge of the brake pad lining.

15. A method of manufacturing a brake pad lining, the method comprising: moulding a brake pad lining; wherein at least one aperture is moulded into said brake pad lining, the at least one aperture being inset from an exterior edge of the brake pad lining.

16. A method of manufacturing a brake pad comprising mounting a brake pad lining as described in paragraph 15 to a back plate.

17. A method of manufacturing a brake pad as described in paragraph 16, wherein the brake pad lining is mounted to the back plate by bonding and/or riveting.

18. A method of manufacturing a brake pad, wherein a brake pad lining as described in paragraph 15 is integrally moulded to a back plate.

Claims

CLAIMS: 1. A brake pad lining for engaging a brake rotor, wherein at least one aperture is formed in the brake pad lining for controlling the generation of heat during braking, the at least one aperture being inset from an exterior edge of the brake pad lining.
2. A brake pad lining as claimed in claim 1, wherein each aperture comprises a substantially circular section.
3. A brake pad lining as claimed in claim 1 or claim 2, wherein each aperture is a hole drilled in said brake pad lining; or each aperture is moulded into said brake pad ining.
4. A brake pad lining as claimed in any one of claims 1, 2 or 3, wherein each aperture extends partially or completely through the brake pad lining.
5. A brake pad lining as claimed in any one of claims 1 to 4, wherein the at least one aperture is disposed proximal to and inset from an outer radial edge of the brake pad lining.
6. A brake pad lining as claimed in any one of the preceding claims comprising a plurality of said apertures, said apertures being arranged along a circular arc having a centre which, in use, aligns with a rotational axis of an associated brake rotor.
7. A brake pad lining as claimed in claim 6, wherein an angular offset between adjacent apertures is in the range of 5°to 400.
8. A brake pad lining as claimed in any one of the preceding claims, wherein at least one opening is formed in the back plate in alignment with said at least one aperture in the brake pad lining.
9. A brake pad lining as claimed in any one of the preceding claims comprising one or more slots, chamfers or notches formed in an edge of the brake pad lining.
10. A brake pad comprising a back plate and a brake pad lining according to any preceding claim.
11. A brake caliper comprising at least one brake pad as claimed in claim 10.
12. A brake caliper as claimed in claim 11 comprising a first said brake pad in an outboard position for engaging an outboard surface of the brake rotor; and/or a second said brake pad in an inboard position for engaging an inboard surface of the brake rotor.
13. A vehicle comprising a brake caliper as claimed in claim 11 or claim 12.
14. A method of manufacturing a brake pad, the method comprising: forming at least one aperture in a brake pad lining mounted to a back plate, the at least one aperture being inset from an exterior edge of the brake pad lining.
15. A method of manufacturing a brake pad lining, the method comprising: moulding a brake pad lining; wherein at least one aperture is moulded into said brake pad lining, the at least one aperture being inset from an exterior edge of the brake pad lining.
16. A method of manufacturing a brake pad comprising mounting a brake pad lining as claimed in claim 15 to a back plate.
17. A method of manufacturing a brake pad as claimed in claim 16, wherein the brake pad lining is mounted to the back plate by bonding and/or riveting.
18. A method of manufacturing a brake pad, wherein a brake pad lining as claimed in claim 15 is integrally moulded to a back plate.
19. A brake pad lining substantially as herein described with reference to the accompanying figures.
20. A brake pad substantially as herein described with reference to the accompanying figures.
21. A brake caliper substantially as herein described with reference to the accompanying figures.
22. A vehicle substantially as herein described with reference to the accompanying figures.