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Patent Searching and Data


Title:
BRAKE SYSTEM
Document Type and Number:
WIPO Patent Application WO/2016/097735
Kind Code:
A1
Abstract:
A brake system comprising a brake pad (20) having a braking surface (24) and a pressurised fluid supply in fluid communication with the braking surface (24) of the brake pad (20), wherein the system is configured such that fluid from the pressurised fluid supply is provided to the braking surface (24) of the brake pad (20) under non-braking conditions and the pressurised fluid supply or means for supplying gas is configured to supply pressurised fluid at a first pressure and/or flow rate for a first time under non-braking conditions and at a second pressure and/or flow rate for a second subsequent time during that same instance of non-braking, and said second pressure and/or flow rate is less than said first pressure and/or flow rate.

Inventors:
MENNIE, Trevor Michael (St Bride's House10 Salisbury Hous, London Greater London EC4Y 8JD, EC4Y 8JD, GB)
Application Number:
GB2015/054046
Publication Date:
June 23, 2016
Filing Date:
December 17, 2015
Export Citation:
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Assignee:
MENNIE, Trevor Michael (St Bride's House10 Salisbury Hous, London Greater London EC4Y 8JD, EC4Y 8JD, GB)
International Classes:
B60T5/00; B60T13/66; B60T17/22; F16D65/00; F16D65/847; F16D121/06
Domestic Patent References:
WO2013084188A12013-06-13
Foreign References:
US4749063A1988-06-07
GB2497426A2013-06-12
Download PDF:
Claims:
Claims:

1. A brake system comprising:

a brake pad having a braking surface; and

a pressurised fluid supply in fluid communication with the braking surface of the brake pad, wherein the system is configured such that fluid from the pressurised fluid supply is provided to the braking surface of the brake pad under non-braking conditions and the pressurised fluid supply or means for supplying gas is configured to supply pressurised fluid at a first pressure and/or flow rate for a first time under non-braking conditions and at a second pressure and/or flow rate for a second subsequent time during that same instance of non-braking, and said second pressure and/or flow rate is less than said first pressure and/or flow rate.

2. The brake system of claim 1 , wherein the first and/or second time is based on the duration of an immediately preceding braking condition.

3. The brake system of claim 2, wherein the first time corresponds to the duration of an immediately preceding braking condition.

4. The brake system of claim 2, wherein the first time is a predetermined time and the second time is based on the duration of an immediately preceding braking condition.

5. The brake system of claim 4, wherein the second time corresponds to the duration of an immediately preceding braking condition.

6. The brake system of any of claims 2 to 5, further comprising a timer for measuring the duration of an immediately preceding braking condition.

7. The brake system of any preceding claim, wherein the pressurised fluid supply or means for supplying gas is further configured to supply pressurised fluid at a third pressure and/or flow rate for a third time during that same instance of non-braking, and said third pressure and/or flow rate is less than said second pressure and/or flow rate.

8. The brake system of any preceding claim, wherein the pressurised fluid supply or means for supplying gas is configured to run at a first voltage for the first time and a second voltage for the second time, the first voltage being higher than the second voltage and optionally

at a third voltage for the third time, the second voltage being higher than the third voltage.

9. The brake system of claim 8, wherein the pressurised fluid supply or means for supplying gas is powered by a constant voltage source and means are provided for increasing and/or decreasing the voltage supplied to the pressurised fluid supply or means for supplying gas.

10. The brake system of claim 9, wherein the means for increasing and/or decreasing the voltage comprises one or more step-up and/or a step-down converters.

1 1 . The brake system of claim 10, wherein the means for increasing and/or decreasing the voltage comprises a step-up or a step-down converter connected to a plurality of resistors, and each resistor is configured to provide a different voltage output to the pressurised fluid supply or means for supplying gas.

12. The brake system of claim 1 1 , wherein the plurality of resistors are controlled by one or more relays.

13. The brake system of claim 12, wherein the number of resistors is higher than the number of relays.

14. The brake system of claim 12 or 13, wherein there are exactly three resistors and exactly two relays.

15. The brake system of any of claims 12 to 14, wherein the plurality of relays is controlled by an IC chip.

16. The brake system of claim 15, wherein the IC chip is configured to time an immediately preceding braking condition and selectively energise at least one resistor based on the measured time period.

17. The brake system of claim 15 or 16, wherein the IC chip is configured to selectively energise at least one resistor based on a pre-set time period.

18. The brake system of any of claims 1 1 to 17, wherein the plurality of resistors comprises a plurality of variable resistors.

19. The brake system of any of claims 1 1 to 18, wherein the IC chip and/or the step-up or a step- down converter is connected to a brake switch to detect the operation of a brake.

20. The brake system of any of claims 1 to 8, wherein the operation of the pressurised fluid supply or means for supplying gas is controlled electronically.

21 . The brake system of claim 20, wherein the pressurised fluid supply or means for supplying gas comprises a brushless motor whose operation is controlled to vary the pressure and/or flow rate of the supplied fluid.

22. A brake system as claimed in any preceding claim, wherein the brake system comprises a disc brake or a drum brake.

23. A brake system as claimed in any preceding claim, wherein the brake pad has one or more openings in its braking surface for providing said fluid to the braking surface of the brake pad, said pressurised fluid supply being in fluid communication with the braking surface of the brake pad via the one or more openings.

24. A brake system as claimed in claim 23, wherein the one or more openings comprises a single opening, and the single opening is positioned substantially in the centre of the braking surface of the brake pad.

25. A brake system as claimed in claim 23, wherein the one or more openings comprises a plurality of openings, and the plurality of openings are evenly distributed across the braking surface of the brake pad or are concentrated substantially at the centre of the braking surface of the brake pad.

26. A brake system as claimed in any preceding claim, wherein the brake system comprises a brake rotor positioned adjacent to the braking surface of the brake pad, the fluid from the pressurised fluid supply providing a gap between the brake rotor and the braking surface of the brake pad when provided to the braking surface under non-braking conditions.

27. A brake system as claimed in any preceding claim, wherein the pressurised fluid supply is capable of supplying pressurised fluid at a pressure and/or flow rate that is sufficient to separate the braking surface of the brake pad from the braking surface of an opposing brake rotor under non- braking conditions and/or that is insufficient to separate the braking surface of the brake pad from the braking surface of an opposing brake rotor under braking conditions.

28. A brake system as claimed in any preceding claim, wherein the pressurised fluid supply is capable of supplying pressurised fluid at between 0.5 kPa and 700 kPa.

29. A brake system as claimed in any preceding claim, wherein the pressurised fluid supply comprises a pump and/or compressor.

30. A brake system as claimed in any preceding claim, wherein the system is configured to activate the pressurised fluid supply under non-braking conditions only and/or deactivate the pressurised fluid supply under braking conditions.

31 . A brake system as claimed in any preceding claim, comprising a pressurised fluid supply valve in fluid communication between the pressurised fluid supply and the braking surface of the brake pad.

32. A brake system as claimed in claim 31 , wherein the system is configured to open the pressurised fluid valve under non-braking conditions so as to fluidly connect the pressurised fluid supply to the braking surface of the brake pad and/or close the pressurised fluid valve under braking conditions so as to isolate the braking surface of the brake pad from the pressurised fluid supply.

33. A brake system as claimed in any preceding claim, comprising a fluid removal means in fluid communication with the braking surface of the brake pad, the system being configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions.

34. A brake system as claimed in any preceding claim, wherein the braking conditions or given braking operation comprises the brake being activated, and/or an accelerator or throttle not being activated and/or a cruise control system being deactivated.

35. A vehicle comprising the brake system of any preceding claim.

Description:
Brake System

The present invention relates to a brake pad assembly, a brake system, a method of using a brake pad assembly or brake system, and a control system for a brake system. The present invention also relates to a kit and method for modifying a brake pad or brake system. Preferred embodiments of the present invention are directed to brake pads, brake pad assemblies or brake systems for vehicles.

Brake systems for vehicles typically comprise a brake rotor fixed to the wheel of the vehicle. The brake rotor (which may be a disc or drum) rotates with the wheel when the vehicle is moving. With disc brakes, a pair of brake pads is typically positioned with the respective brake pads on either side of the brake rotor, and the brake pads are typically brought into firm contact with the brake rotor by brake callipers. With drum brakes, brake pads are typically positioned on the inside of the brake drum and are forced outwards into firm contact with the brake drum.

Brake pads are typically fixed to a static part of the vehicle, and do not rotate with the wheel when the vehicle is moving. When the brake is activated, the brake pad is pressed firmly against the brake rotor, and friction between the static brake pad and rotating rotor causes the speed of rotation of the rotor, and therefore the speed of rotation of the wheel, to slow. This in turn slows the vehicle.

When the brake is not being activated, brake pads are usually positioned in close proximity to the brake rotor so that the distance that the brake pad needs to travel in order to firmly contact the brake rotor is small and so that the activation time for the brake is short. This is particularly the case with hydraulically actuated brakes, in which a piston that is provided at the brake pedal of the vehicle to actuate the brake is in hydraulic communication with a piston that is provided at the brake pad to move the pad into contact with the rotor. The brake pedal piston has a smaller diameter than the brake pad piston, such that a larger movement/lower force provided at the brake pedal to activate the brake is converted into a much smaller movement but a much larger force at the brake pad to move the pad. Thus, with hydraulically actuated brakes, the distance between the brake pad and brake rotor is typically necessarily small so that an appropriate amount of force can be applied by the brake pad.

A small distance between a brake pad and brake rotor can also reduce the amount of debris that can accumulate between the brake pad and brake rotor, and can keep the brake pad dry by reducing the amount of water ingress.

In some arrangements, brake pads may even be positioned in light contact with the brake rotor even when the brake is not being activated so as to minimise the distance and time to activate the brake.

However, a problem with these arrangements exists in that intermittent or constant contact between the brake pad and brake rotor when the brake is not being activated generates an undesired braking force that the vehicle has to overcome. This reduces the power and efficiency of the vehicle, and leads to higher fuel consumption. The intermittent or constant contact between the pads and rotor also causes wear on the brake pads and rotors, which can shorten the lifetime of the brake pads and rotors and can produce polluting brake pad dust.

WO 2013/084188, by the present Applicant, discloses an apparatus and method for separating the brake pad from the brake rotor under non-braking conditions. A pressured fluid supply is used to provide fluid to the braking surface of the pad under non-braking conditions. Fluid removal means may be provided to remove fluid from the braking surface under braking conditions.

The present invention seeks to provide an improved apparatus and method.

According to an aspect of the present invention there is provided a brake system comprising a brake pad having a braking surface and a pressurised fluid supply in fluid communication with the braking surface of the brake pad wherein the system is configured such that fluid from the pressurised fluid supply is provided to the braking surface of the brake pad under non-braking conditions.

Advantageously, by providing fluid from a pressurised fluid supply to the braking surface of the brake pad, the brake pad may be forced away from the surface of any adjacent brake rotor under non-braking conditions. The fluid may also act as a lubricant between the brake pad and any adjacent rotor under non-braking conditions. This can remove or reduce the amount of frictional contact between the pads and the rotor under non-braking conditions, which in turn can increase the power and efficiency of the vehicle, and lead to lower fuel consumption. The reduced amount of frictional contact can also decrease the amount of brake pad and brake rotor wear, leading to reduced maintenance costs for replacement brake pads.

The present invention is further advantageous in that the fluid supply may cool the braking surface of the brake pad. This may reduce the incidence of brake fade, which occurs when brake pads become too hot. The fluid may also remove debris and/or water from the braking surfaces of the brake pad and rotor.

The present invention is further advantageous in that any noise generated by contact between the brake pad and an adjacent brake rotor may be reduced or avoided.

The present invention may also provide a substantially fail-safe system, in that any failure in the pressurised fluid supply may result in a brake system that operates in a substantially

conventional manner.

The brake system preferably comprises a disc brake. In these embodiments, the brake system preferably comprises a pair of opposed brake pads, preferably joined by callipers. However, in other embodiments the brake system may comprise a single brake pad and/or may comprise a drum brake.

The brake system preferably comprises a brake rotor positioned adjacent to the braking surface of the brake pad. The fluid from the pressurised fluid supply preferably provides a gap between the brake rotor and the braking surface of the brake pad when provided to the braking surface under non-braking conditions. As will be appreciated, the "braking surface" referred to herein is the surface of the brake that contacts (or is intended to contact) an adjacent brake rotor when the brake is activated. The braking surface is therefore a surface of the brake pad which faces (or is intended to face) an adjacent brake rotor in use. The braking surface may be referred to as a "friction surface" of the brake pad. The brake pad and brake rotor will define opposed surfaces, the braking or friction surface of the brake pad being the surface that contacts (or is intended to contact) the surface of an adjacent brake rotor in use.

The brake pad can take any desired or suitable form. For example, the brake pad may comprise any suitable friction material (e.g. a ceramic, semi-metallic, metallic or carbon fibre material) on a support structure. In embodiments therefore the brake pad may comprise a support structure and a friction material thereon. In these embodiments the friction material defines the braking surface (rotor facing surface) and may define an opposite support structure facing surface. The friction material may be a body of friction material. The friction material may be a single (i.e. only one) layer of material, or may comprise a plurality of layers of one or more materials.

In one set of embodiments, the brake pad (or each brake pad) preferably has one or more openings in its braking surface for providing the fluid to the braking surface of the brake pad, with the pressurised fluid supply preferably being in fluid communication with the braking surface of the brake pad via the one or more openings.

The one or more openings are preferably positioned such that the brake pad does not tip or tilt when fluid is supplied to the surface of the brake pad. As will be appreciated, any inadvertent tipping or tilting of the brake pad may cause a portion of the braking surface to contact an adjacent brake rotor when the fluid is supplied to the braking surface. The one or more openings therefore preferably include one or more openings positioned substantially in the centre of the braking surface of the brake pad. The one or more openings is preferably a single (i.e. only one) opening, wherein the single opening is positioned substantially in the centre of the braking surface of the brake pad. However, in other embodiments the one or more openings may comprise a plurality of openings, wherein the plurality of openings are preferably concentrated substantially in the centre of the braking surface of the brake pad and/or are evenly distributed across the central portion of the braking surface of the brake pad, or are evenly distributed across all of the braking surface of the brake pad (so as to balance out the reactive forces provided by the fluid as the fluid exists the openings). The one or more openings are also preferably positioned such that fluid can be supplied to substantially all of the braking surface of the brake pad.

The size and/or number of openings will depend on the size and type of brake system and/or brake pad. Generally, a larger brake pad and/or more resistive brake system mechanism (e.g.

callipers) will require a larger opening and/or more openings.

The one or more openings may be any desired or suitable shape in cross-section. This refers to a cross-section taken in a plane through and parallel to the braking surface. For example, the or each opening may be circular, square, oval, racetrack shaped or oblong, or may be any other regular or irregular shape. The or each opening may be in the form of a slot. In a particular preferred embodiment, the or each opening is a racetrack shaped slot.

In any of the embodiments, the or each opening is preferably elongated and oriented such that (the longest dimension of) the or each opening runs substantially parallel to the longest dimension of the brake pad. These embodiments are particularly advantageous in that the fluid is effectively and evenly distributed to the majority of the surface of the brake pad (which is preferably also elongated). This can, for example, prevent or reduce the likelihood of the brake pad tipping or tilting. The use of an elongated slot also allows fluid to be distributed (e.g. from a smaller (circular) passage or tube) over a larger area. This means that, for a given fluid pressure, the force that is exerted by the fluid on an adjacent rotor, so as to separate the brake pad from the rotor, may be greater.

The length of the or each opening (the longest dimension of the or each opening) can be any desired or suitable length depending, for example, on the size and type of brake system or brake pad. However, the length of the or each opening is preferably less than 99% of the brake pad's length, more preferably less than 75% of the brake pad's length, and more preferably less than 50% of the brake pad's length. The length of the or each opening is preferably more than 1 % of the brake pad's length, more preferably more than 5% of the brake pad's length, and more preferably more than 10% of the brake pad's length. The length of the or each opening may be between 2 mm and 50 mm.

The width of the or each opening (the shortest dimension of the or each opening) can be any desired or suitable width again depending, for example, on the size and type of brake system/pad. However, the width of the or each opening is preferably less than 99% of the brake pad's width, more preferably less than 75% of the brake pad's width, and more preferably less than 50% of the brake pad's width. The width of the or each opening is preferably more than 1 % of the brake pad's width, more preferably more than 5% of the brake pad's width, and more preferably more than 10% of the brake pad's width. The width of the or each opening may be between 1 mm and 10 mm.

The depth of the or each opening is preferably the same as the thickness of the friction material of the brake pad. These embodiments are particularly advantageous in that the brake pad can wear down, but the opening will remain of substantially the same geometry. However, in other embodiments, each opening may be less than the depth of the friction material or may extend into the brake pad's support structure.

The or each opening may be an opening which extends all the way through the friction material from one side of the friction material (e.g. the braking surface side) to another side (e.g. other than the braking surface side).

In embodiments, the or each opening is an opening over and above any pores inherent in the material (e.g. friction material) defining the braking surface.

In an alternative set of embodiments, the brake pad (or each brake pad) preferably comprises a porous structure in its braking surface for providing the fluid to the braking surface of the brake pad, with the pressurised fluid supply preferably being in fluid communication with the braking surface of the brake pad via the porous structure. The porous structure may be provided by a suitable porous (braking or friction) material.

The porous structure is preferably positioned such that fluid can be supplied to substantially all of the braking surface of the brake pad via the porous structure. For example, the majority or all of the brake pad surface may be porous.

The majority or all of at least a friction material of the brake pad (i.e. not just the surface region) may also be porous. These embodiments are particularly advantageous in that the brake pad can wear down, but porous structure will remain on the surface of the brake pad. The porous structure may be provided by using porous friction material.

The porosity of the porous structure will depend on the size and type of brake system and/or brake pad. Generally, a larger brake pad and/or more resistive brake system mechanism (e.g.

callipers) will require a porous structure having greater porosity (e.g. a larger region of porous structure on the surface of the brake pad and/or a more open porous structure).

It is envisaged that the braking surface may comprise one or more openings and a porous structure in the braking surface. For example, the braking surface may be provided by a porous structure having one or more openings therethrough.

In accordance with any of the embodiments of the invention, the one or more openings or porous structure may be in fluid communication with a passage or passages in the brake pad, the passage or passages being in fluid communication with the pressurised fluid supply. The fluid is preferably provided to the one or more openings or porous structure or passage or passages via a tube or tubes, preferably having a simple geometry (e.g. a circular cross-section).

The pressurised fluid supply is preferably capable of supplying pressurised fluid at a pressure and/or flow rate that is sufficient to separate the braking surface of the brake pad from an opposing brake rotor under non-braking conditions, i.e. provide a gap therebetween under non- braking conditions. The pressure and/or flow rate may also or instead be insufficient to separate the braking surface of the brake pad from the brake rotor under braking conditions.

The pressurised fluid supply is preferably capable of supplying pressurised fluid at one or more (different) pressures and/or flow rates under non-braking conditions. For example, the pressurised fluid supply (e.g. when activated) may be capable of supplying pressurised fluid at one (and only one) pressure and/or flow rate under non-braking conditions, with that pressure and/or flow rate being sufficient to initially separate the braking surface of the brake pad from the brake rotor under non-braking conditions and sufficient to maintain a suitable gap between the braking surface of the brake pad and the brake rotor under non-braking conditions.

However, the Applicant has identified that, in some brake systems, more force may be required to initially separate the braking surface of the brake pad from the brake rotor when non- braking conditions initially occur (i.e. directly after the end of a period of time during which braking conditions have occurred) than the force required to then maintain a gap between the braking surface of the brake pad and the brake rotor whilst non-braking conditions remain (i.e. until the next instance of braking conditions).

Thus, the pressurised fluid supply (e.g. when activated) is preferably capable of supplying pressurised fluid at two or more pressures and/or flow rates under non-braking conditions. For example, the pressurised fluid supply may be capable of supplying pressurised fluid at a first pressure and/or flow rate (or a first set of pressures and/or flow rates) at a first time under non- braking conditions and at a second pressure and/or flow rate (or a second set of pressures and/or flow rates) at a second subsequent time during that same instance of non-braking.

The first pressure and/or flow rate (or first set of pressures and/or flow rates) may be sufficient to initially separate the braking surface of the brake pad from the brake rotor when non- braking conditions initially occur and the second pressure and/or flow rate (or second set of pressures and/or flow rates) may be sufficient to maintain a suitable gap between the braking surface of the brake pad and the brake rotor whilst non-braking conditions remain. In these embodiments, the first pressure and/or flow rate (or first set of pressures and/or flow rates) is preferably higher than the second pressure and/or flow rate (or second set of pressures and/or flow rates). These embodiments are particularly advantageous in that less power is generally required to supply fluid at a lower pressure and/or flow rate. Thus, switching the pressurised fluid supply from supplying fluid at a first higher pressure and/or flow rate to supplying fluid at a second lower pressure and/or flow rate whilst under non-braking conditions can reduce the power consumption of the brake system under non-braking conditions.

The second time period may extend until the next braking condition is commenced.

Alternatively, there be more than two time periods during each non-braking condition, as will be discussed below.

The "first set of pressures and/or flow rates" referred to above may comprise a first set of one or more discrete pressures and/or flow rates or a first (substantially continuous) range of pressures and/or flow rates. Similarly, the "second set of pressures and/or flow rates" referred to above may comprise a second set of one or more discrete pressures and/or flow rates or a second (substantially continuous) range of pressures and/or flow rates.

The fluid is preferably initially supplied at the first pressure and/or flow rate responsive to non-braking conditions occurring (e.g. when a brake pedal is released, an accelerator is activated etc.). The "first time" referred to above may therefore be at the time of (e.g. coinciding with, directly after, or shortly after (e.g. within 1 second of)) the initiation of non-braking conditions. Fluid at the first pressure and/or flow rate may be supplied (e.g. only supplied) for a predetermined period of time thereafter, with fluid at the second pressure and/or flow rate preferably being supplied directly after or shortly after (e.g. within 1 second of) that predetermined period of time expiring. The predetermined period of time may be a period of time that is less than 5 seconds, such as 1 second. Fluid at the second pressure and/or flow rate may then be supplied at least whilst non-braking conditions remain (or for the majority of time whilst non-braking conditions remain). Fluid at the second pressure and/or flow rate may also be supplied (and continue to be supplied) when and/or during any subsequent instance of braking conditions.

Alternatively, the "first time" may be determined during operation, for example based on the amount of time that the brake had been applied, i.e. the duration of the immediately preceding braking condition. As such, the brake system may comprise a timer for measuring the duration of a braking condition and the pressurised fluid supply may be configured to supply pressurised fluid under non-braking conditions at a first pressure and/or flow rate for a first time and a second lower pressure and/or flow rate for a second subsequent time, wherein the first time is based on the duration of an immediately preceding braking condition. The term "based on" should be understood to mean that the first time is, in some way, proportional to the braking duration. It may be directly proportional, for example a multiple thereof, such as 1 .5, 2, 3 or 4 times the braking duration.

Alternatively, the first time period may correspond to the duration of the immediately preceding braking condition. For example if the braking duration is 1 second then the first time period may be about 1 second. An upper limit of, for example, 5 seconds may be provided for the first time period.

The timer may be any suitable electronic timer, as is known in the art. The timer may measure the amount of time that a driver of the vehicle is initiating a braking condition (e.g. the amount of time that the brake pedal is pressed) or the time that the brake pad is actually activated, e.g. the time that the brake pad is in contact with the rotor disc or the calliper is in a braking position.

The longer the brake pad is applied to the rotor disc, the hotter it will become and the more brake dust will be produced. As such, by applying the higher first pressure and/or flow rate for a first time that is related to the braking duration, then the pressured fluid supply can be used to provide an increased cooling effect for hotter brake pads and increased brake dust removal. As previously discussed, operating the pressurised fluid supply at a lower power after the first time period is advantageous.

The distance of separation or gap between the brake pad and brake rotor provided by embodiments of the present invention need only be enough so that the surface of the brake pad does not contact an adjacent brake rotor. The separation is preferably of the order of 1 to 100 microns, preferably of the order of 10 microns. The gap is preferably provided across substantially the entire surface of the brake pad.

As will be appreciated, the capabilities of the pressurised fluid supply will depend on the type and size of the brake system, the number and size of openings in the surface of the brake pad, the porosity of the brake pad, and/or the number of brake pads that are supplied with pressurised fluid. However, the pressurised fluid supply is preferably configured to supply pressurised fluid at one or more pressures or a plurality of pressures or a substantially continuous range of pressures between 0.5 kPa and 700 kPa, more preferably between 0.5 kPa and 200 kPa, even more preferably between 0.5 kPa and 50 kPa, and most preferably between 0.5 kPa and 40kPa. The pressurised fluid supply can be powered in any desired or suitable way. However, the pressurised fluid supply is preferably powered either directly or indirectly by an engine of the vehicle (an engine that drives the wheels of the vehicle). For example, the pressurised fluid supply may be powered by (directly coupled to, e.g. with suitable connections and/or gearing) an alternator shaft of an engine of the vehicle or may be powered by (directly coupled to, e.g. with suitable connections and/or gearing) a drive train of an engine.

Alternatively, the pressurised fluid supply may be powered by electrical power generated by an engine of the vehicle, for example a 12V DC or 24V DC power supply, such as the power supply which is provided to or by the cigarette lighter of a vehicle. These embodiments are particularly advantageous in that a dedicated supply of power (e.g. a battery or generator) is not needed in or for the braking system.

The pressurised fluid supply may be powered (directly) by a DC voltage supply or may, for example, comprise an AC motor that is connected to a DC voltage inverter.

The pressurised fluid supply preferably comprises a compressor or pump capable of producing the necessary pressure and/or flow rate. Generally, a larger brake pad and/or more resistive brake mechanism (e.g. callipers) will require a pressurised fluid supply that is capable of supplying fluid at a higher pressure and/or flow rate. In embodiments in which fluid at a plurality of different pressures and/or flow rates or a substantially continuous range of different pressures and/or flow rates is provided, those different pressures and/or flow rates may be provided by operating the compressor or pump in different configurations or at different speeds (e.g. different speeds in terms of revolutions per minute (rpm) of the motor or impeller of the compressor or pump). The compressor or pump may be stepped between different discrete configurations or speeds (rpms), or the configuration or speed (rpm) of the compressor or pump may be substantially continuously variable. In embodiments, the motor for the compressor or pump may be a brushless motor. The speed of such motors is typically relatively easy to control. Alternatively, a brushed motor may be used.

In order to operate the compressor or pump at different configurations or speeds, the compressor/pump may be run at a varying voltage. For example, the compressor/pump may be run at a first higher voltage to provide the first higher pressure and/or flow rate fluid flow (for the first time period) and then at a second lower voltage to provide the second lower pressure and/or flow rate fluid flow (for the second time period).

The first voltage may correspond to the normal voltage being supplied by the vehicle power supply (e.g. a 12V DC battery), with the second voltage being a reduced voltage (e.g. 6V).

Alternatively, the second voltage may correspond to the normal voltage and the first voltage may be increased voltage (e.g. 18V).

The reduced and/or increased voltage can be provided by using one or more step-up or step-down converters (also known as boost converters and buck converters, respectively). These converters increase or reduce the voltage of a DC supply by reducing or increasing the current respectively (in accordance with Ohm's law). The timer may incorporate a programmable chip (i.e. an integrated circuit) configured to operate a relay. The chip and relay may form part of a timer board.

The chip may be programmed to measure the duration of a braking condition (e.g. the time for which a brake pedal is actuated) and, once braking ceases, to energise a relay, having a pair of change-over contacts, for the first time period. When energised, the relay contacts a first contact, which completes a first circuit having a step-up converter, thus causing the pressurised fluid supply to be powered by a higher voltage for the first time period. Alternatively, the first circuit may have no converter (and the second circuit may have a step-down converter).

Once the first time period has expired, the chip no longer sends a signal to the relay. This results in the relay no longer being energised (i.e. it becomes de-energised) and causes a second contact to be contacted, thus completing a second circuit having a step-down converter or no converter. This causes the pressurised fluid supply to run at a lower voltage for the second time period, which may be until the next braking condition is commenced.

The normal state of the relay may be its de-energised state. In this state, the step-down converter (or no converter) may be selected (via the relay contacts), so that the normal state of the pressurised fluid supply may be the lower voltage running condition.

In an alternative embodiment, the pressurised fluid supply may be configured to supply pressurised fluid under non-braking conditions at a first pressure and/or flow rate for a first time, then at a second lower pressure and/or flow rate for a second subsequent time and then at a third lower pressure and/or flow rate (i.e. lower than the second pressure/flow rate) for a third subsequent time, wherein the first time is a predetermined time, the second time is based on the duration of an immediately preceding braking condition and the third time may extend until the next braking condition is commenced.

In this embodiment, the first time may be a relatively short time, such as 1 to 5 seconds. The first pressure and/or flow rate may be high enough to separate the brake pad from the rotor. The second time may correspond to the duration of an immediately preceding braking condition. The second pressure and/or flow rate may not be high enough to usually separate the brake pad from the rotor but may be high enough to effectively cool the brake pad and pick up brake dust. The third pressure and/or flow rate may be high enough to keep the brake pad and rotor separated during motion of the vehicle until the brakes are next applied.

In order to operate the compressor or pump at three different configurations or speeds, the compressor/pump may be run at different voltages, as discussed above. For example, the compressor/pump may be run at a first higher voltage to provide the first higher pressure and/or flow rate fluid flow (for the first time period) and then at a second lower voltage to provide the second lower pressure and/or flow rate fluid flow (for the second time period) and then at a third lower voltage to provide the third lower pressure and/or flow rate fluid flow (for the third time period). The second voltage may be the normal voltage supplied by the vehicle power supply (e.g. a battery) e.g. 12 V, with the first voltage being a higher voltage provided by a step-up converter, e.g. 18 V and the second voltage being a reduced voltage provided by a step-down converter, e.g. 6 V.

It should be appreciated that it is possible to add further timers and/or relays, with or without change over contacts, within one or more boards. Input and output signals can be configured to turn on and off different converters or circuits by predetermined software programming or by combination of user selectable input or outputs to initiate a single speed output.

In one embodiment, a single step-up or step-down ("boost/buck") converter can be used to provide more than two voltage levels to the pressurised fluid supply, by effectively replacing a variable resistor on a converter board with a plurality of resistors that can be individually selected.

For example, the plurality of resistors may comprise a plurality of variable resistors.

Alternatively, instead of variable resistors, a plurality of fixed resistors (having different resistances) or series resistor chains could be used.

The resistance provided by each variable resistor can be set independently of the other variable resistors, as is known in the art.

For example, by removing the variable resistor of the converter board and connecting the exposed contacts thereof to three variable resistors, three different voltage outputs can each be selected (using additional circuitry).

The plurality of resistors can be controlled by a plurality of relays.

Three resistors can be controlled by only two relays. For example, a first relay can be arranged, when energised, to select a first variable resistor, to provide a high voltage output to the converter board. A second relay can be arranged, when energised, to select a second variable resistor, to provide a medium voltage output to the converter board. When neither relay is energised, the third variable resistor may be selected, to provide a low voltage output to the converter board.

The two relays can be controlled by using an integrated circuit (IC) chip that includes a timing function. The timing function may record the duration of an immediately preceding braking period, and/or selectively energise the first and second relays for first and second time periods respectively.

For example, the chip may energise the first relay (only) for a pre-set first time period (such as 1 second) to provide a high voltage output to the pressurised fluid supply, in order to separate the brake pad from the brake rotor.

After the first time period, the chip may then energise the second relay (only) for a second time period (such as 1 to 5 seconds), based on the duration of the immediately preceding braking period (for example, a multiple thereof), to provide a medium voltage output to the pressurised fluid supply, in order to cool the brake pad and remove brake dust.

After the second time period, neither relay may be energised (i.e. both relays de-energised), for a third time period, to provide a low voltage output to the pressurised fluid supply, in order to maintain the separation between the brake rotor and the brake pad. The third time period may run indefinitely, until the next occurrence of braking or until the ignition is turned off.

The IC chip may also be configured to energise a relay (e.g. the first relay) for another preset period (e.g. 2 seconds) upon ignition of the engine to cause the brake pad to be separated from the brake rotor prior to any motion of the vehicle (e.g. by providing a high voltage output to the pressurised fluid supply).

More than three variable resistors may be provided, in order to provide more than three voltage output levels.

An override function may also be provided, to allow the driver of the vehicle to select a particular mode, such as the medium voltage output mode. This mode would then remain activated until the driver turns it off. The medium voltage output mode may provide a sports-mode

functionality, where extra cooling of the brake pad (and extra brake dust removal) may be desirable or necessary.

Such an arrangement provides a reduction in cost and weight of the control package, compared to using a plurality of converter boards. The arrangement also allows for a reduced power usage and a more compact package. The arrangement allows full control of the, for example, three switched outputs at signal level, such that the current being switched is in the order of milliamps, rather than amps. This allows smaller, cheaper and higher longevity switch/ relay components to be used.

In addition or as an alternative to any of the above embodiments, the chip may be programmed to energise the relay for a predetermined time period upon start-up (i.e. ignition) of the engine in order to overcome any brake stiction that may be present. The predetermined time period may be about 1 or 2 seconds.

The chip may be configured to re-set the measured braking duration to zero, or a pre-set period of e.g. 5 seconds, if the braking condition exceeded a maximum time of say 15 or 20 seconds. This prevents the corresponding voltage output time period (e.g. the first time period where there are two different voltage outputs, or the second time period where there are three different voltage outputs) being excessive, for example when the brakes have been actuated for a long period of time when the vehicle is stationary, such as in traffic or at traffic lights.

Alternatively, the "pressurised fluid supply" can be controlled directly and electronically, for example by driving a compressor/pump using a controllable motor, such as a brushless motor.

Changing the speed of such a motor would control the pressure and/or flow rate of the fluid supply.

As mentioned above, the first time period for which the pressurised fluid supply is operated at a higher speed/configuration may be predetermined or may be determined during use, for example based on the duration of an immediately preceding braking condition.

As will be appreciated, the system is configured to provide fluid from the pressurised fluid supply to the braking surface of the brake pad at least under non-braking conditions. This is preferably achieved by a system control means of the brake system. For example, controlling the compressor or pump to supply fluid at a desired time and/or at a desired pressure and/or flow rate can be achieved by the system control means. It will be appreciated that any of the steps involved in providing fluid from the pressurised fluid supply to the braking surface may be carried out by the system control means of the system. Thus, references such as "the system being configured such that" may be interchanged with "the system comprising system control means being configured such that".

In preferred embodiments, the system (or system control means) is preferably configured to provide fluid from the pressurised fluid supply to the braking surface of the brake pad only under non-braking conditions. Thus, the system (or system control means) may be configured to activate the pressurised fluid supply only under non-braking conditions and/or deactivate the pressurised fluid supply under braking conditions.

The activation/deactivation may be achieved by any desired or suitable means. For example, the power provided to the pressurised fluid supply may be applied or increased to activate the pressurised fluid supply and/or the power provided to the pressurised fluid supply may be reduced or removed to deactivate the pressurised fluid supply. A system control means may be arranged to activate/deactivate the pressurised fluid supply in any of these ways.

Similarly, the brake system may also or instead comprise a pressurised fluid supply valve in fluid communication between the pressurised fluid supply and the braking surface of the brake pad. The system (or system control means) is preferably configured such that the pressurised fluid valve is opened under non-braking conditions so as to fluidly connect the pressurised fluid supply to the braking surface of the brake pad and/or is preferably configured such that the pressurised fluid valve is closed under braking conditions so as to isolate the braking surface of the brake pad from the pressurised fluid supply.

However, the system (or system control means) may provide fluid from the pressurised fluid supply to the braking surface of the brake pad under braking conditions as well as non-braking conditions. In these arrangements, the brake system of the present invention is preferably arranged so as to not reduce the braking efficiency (or so as to only insignificantly reduce the braking efficiency) of the vehicle when the pressurised fluid is supplied to the braking surface of the brake pad. For example, the fluid may be supplied at a first (higher) pressure and/or flow rate (sufficient to separate the braking surface of the brake pad from the brake rotor and/or sufficient to maintain a gap between the braking surface of the brake pad and the brake rotor) for at least some of the time under non-braking conditions, and at a second (lower) pressure and/or flow rate (insufficient to separate the braking surface of the brake pad from the brake rotor and/or insufficient to maintain a gap between the braking surface of the brake pad and the brake rotor) for at least some of the time under braking conditions.

In some embodiments, a pressure release valve may be provided in fluid communication with the pressurised fluid supply. The pressure release valve is preferably configured such that, when the brake is activated and the flow of fluid to the brake surface of the brake system is reduced by the reduced gap between the brake pad and an adjacent brake rotor, the resultant build up in pressure of the pressurised fluid from the pressurised fluid supply is relieved by the pressure release valve. This can prevent damaging the brake system and can reduce the amount of force required to activate the brake (i.e. the amount of force required to bring the brake pad into contact with the brake rotor).

The braking efficiency of the brake system may also or instead be passively or actively improved. For example, the brake system may comprise a fluid removal means in fluid

communication with the braking surface of the brake pad, the system (or system control means) being configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions (and preferably only under braking conditions).

By passively or actively removing fluid from the braking surface of the brake pad, the brake pad can be brought towards any adjacent brake rotor using a reduced amount of force or with the assistance of negative pressure. This can reduce the activation distance and time for the brake system under braking conditions.

The fluid removal means may comprise a fluid removal valve in fluid communication with the braking surface of the brake pad. The system (or system control means) is preferably configured to open the fluid removal valve so as to vent the fluid to atmosphere under braking conditions and/or close the fluid removal valve under non-braking conditions. Alternatively, the fluid removal means may comprise a fluid suction device.

In some embodiments, the fluid removal means comprises both a fluid removal valve and a fluid suction device, the fluid removal valve being in fluid communication between the fluid suction device and the braking surface of the brake pad. The system (or system control means) is preferably configured to open the fluid removal valve under braking conditions so as to vent the fluid to the fluid suction device and/or close the fluid removal valve under non-braking conditions.

The system (or system control means) is preferably configured to activate the fluid suction device under braking conditions and/or deactivate the fluid suction device under non-braking conditions. The activation/deactivation may be achieved by any desired or suitable means. For example, the power provided to the fluid suction device may be applied or increased to activate the fluid suction device and/or the power provided to the fluid suction device may be reduced or removed to deactivate the fluid suction device.

The fluid suction device may comprise any desired or suitable device. However, the fluid suction device is preferably a vacuum or the aforementioned pressurised fluid supply (compressor or pump) operated in reverse or connected in reverse (e.g. using a suitable valve arrangement).

The pressurised fluid supply may be operated in reverse by the input to the pressurised fluid supply/fluid suction device (that once took in fluid) becoming the output of the pressurised fluid supply/fluid suction device (that now sends out fluid). Similarly, the output of the pressurised fluid supply/fluid suction device (that once sent out fluid) can become the input to the pressurised fluid supply/fluid suction device (that takes in fluid). In this embodiment, the pressurised fluid supply/fluid suction device may have a first input/output and a second input/output. When acting as a pressurised fluid supply, the first input/output takes in fluid from the surrounding atmosphere and the second input/output provides fluid to the braking surface. When acting as a fluid suction device, the second input/out takes in fluid from the braking surface and the first input/output vents the fluid to atmosphere.

However, in another embodiment, the pressurised fluid supply operates in the same direction but is connected in reverse (e.g. using a suitable valve arrangement). In this embodiment, the pressurised fluid supply/fluid suction device has a (permanent) input for receiving fluid and a (permanent) output for providing fluid. When acting as a pressurised fluid supply, the input is placed in fluid communication with the surrounding atmosphere (e.g. by a first valve) and the output is placed in fluid communication with the braking surface (e.g. by a second valve). When acting as a fluid suction device, the input is placed in fluid communication with the braking surface (e.g. by the first valve) and the output is placed in fluid communication with the surrounding atmosphere (e.g. by the second valve).

These arrangements are particularly advantageous in that a single device can act both as a pressurised fluid supply and as a fluid suction device, although not at the same time.

It is not necessary for the fluid removal means to be operated all the time under braking conditions, and it may be desirable to operate the fluid removal means only for a predetermined amount of time for each given braking operation so as to reduce power consumption. In these embodiments, the fluid removal means is preferably operated for between 0.5 to 5 seconds for or during a given braking operation.

Alternatively, the fluid removal means may be operated for the entire duration of the braking condition.

In some embodiments, the fluid removal means can also be used to remove and/or collect brake dust generated by braking operations. In some embodiments, the fluid removal means may be operated both under braking conditions (e.g. to facilitate the brake pad being brought towards the brake rotor and to allow brake dust to be removed/collected during braking) and/or under non braking conditions (e.g. to allow brake dust to be removed/collected after braking). Thus, the fluid removal means may be operable to remove fluid and any brake dust from the braking surface of the brake pad under braking and/or non-braking conditions.

In any of the above aspects and embodiments, the brake system may comprise fluid conditioning means (e.g. air conditioning means) for warming and/or drying and/or filtering fluid to be provided to the braking surface and/or the perimeter void. This can prevent, for example, moisture entering the brake pad assembly and forming a slurry from the brake dust.

The "braking conditions" and/or "braking operation" referred to above can be defined in any suitable way. For example, and preferably, the braking conditions and/or braking operation may comprise the brake being activated, for example via a brake pedal or lever (e.g. hand brake) of the vehicle, and/or an accelerator or throttle of the vehicle not (or no longer) being activated, and/or a clutch mechanism of the vehicle not (or no longer) being activated, and/or a cruise control system for the vehicle being deactivated.

In order to warm and/or dry the braking surface and brake pad, air being supplied to the brake pads may be heated, or hot air may be sourced from the vehicle's engine (e.g. from the manifold) or the vehicle's exhaust. Warming the brake pad may de-ice a frozen pad and/or increase the performance of a cold pad.

Alternatively, ambient air may be used to cool the brake pads to increase performance, as brake pads have an optimum operating temperature range having an upper limit.

In order to determine the optimal temperature of the fluid being supplied to the brake pads, the vehicle or brake assembly/system may be provided with an electronic controller that receives inputs based on the temperature of the brakes, the ambient (atmospheric) air temperature and/or the vehicle speed. Such a controller could be arranged to override any pre-programmed steps of a timer chip that controls the pressurised fluid supply, for example by increasing the first time period.

Other possible inputs to the controller could include any dashboard warnings (such as "high temperature"), tachometer, speedometer, GPS systems (such as sat-nav to provide terrain change information) and engagement of any sport driving modes.

Similarly, the "non-braking conditions" referred to above can be defined in any suitable way. For example, and preferably, the non-braking conditions may comprise the brake being deactivated, for example a brake pedal or lever (e.g. hand brake) of the vehicle not being in use,

and/or an accelerator or throttle of the vehicle being activated, and/or a gear change or a clutch mechanism of the vehicle being activated, and/or a cruise control system for the vehicle being activated.

The system (or system control means) may comprise means for detecting braking conditions and/or a braking operation and/or non-braking conditions. In embodiments, the brake system preferably comprises a sensor arrangement (e.g. in communication with the system control means) for detecting when a brake pedal and/or an accelerator or throttle and/or a cruise control system is being activated.

The "fluid" referred to above can take any suitable form. For example, and preferably, the fluid may be a gas, for example an inert gas or air. The use of air is particularly advantageous in that a dedicated supply of gas (e.g. a gas cylinder) is not needed in or for the braking system.

As discussed above, the system may be monitored and/or controlled by system control means. The system control means may have any desired or suitable form. The system control means may be mechanical, electronic, or may be a combination thereof. For example, the system may comprise one or more processors (e.g. for monitoring/controlling the braking system), sensors (e.g. for detecting whether or not a braking condition exists, for detecting pressurised fluid pressure etc.), valve actuators (e.g. for the pressurised fluid supply valve and/or fluid removal valve), voltage/current supplies (e.g. for the pressurised fluid supply and/or fluid suction device). The system control means may be part of a control system for a vehicle. The system control means may comprise any one or ones of the means listed above.

According to another aspect of the present invention there is provided a vehicle comprising the brake pad assembly or brake system described herein. This aspect of the present invention may comprise any or all of the preferred or optional features discussed herein as appropriate.

The vehicle may be a road or motor vehicle (such as bicycle, an automobile (car, van, etc.), motorcycle, quad bike, truck or bus), may be a rail vehicle (such as a tram or train), or may be an aircraft (having, for example, a landing gear comprising the brake pad assembly or brake system). The vehicle may be any one or ones of the vehicles listed above. The vehicle may have one or more brake pads (e.g. for some or all of the wheels of the vehicle), with one or more or each of those brake pads having pressurised fluid supplied to its surface in the manner described herein and/or fluid/dust removal openings and/or fluid/dust removal means in the manner discussed herein.

According to another aspect of the present invention there is provided a method using the brake system described herein comprising: providing pressurised fluid to the braking surface of the brake pad under non-braking conditions.

These aspects of the present invention may comprise the provision or use of any one or more of, or all of, the preferred or optional features discussed herein as appropriate.

According to another aspect of the present invention there is provided a control system for a brake system (preferably the brake system described herein) and/or for a vehicle, the control system being configured and/or arranged to implement any of one or more of, or all of, the methods described herein.

According to another aspect of the present invention there is provided a computer readable medium comprising software which, when run on a control system for a brake system (preferably for the brake system described herein) and/or for a vehicle, implements any one or more of, or all of, the methods described herein. The computer readable medium may be a physical, tangible, or non- transitory medium, such as a diskette, CD ROM, ROM, RAM, flash memory or hard disk.

As will be appreciated the features of the brake system described above may be retrofitted to an existing conventional brake system.

Thus, according to another aspect of the present invention there is provided a kit for modifying a brake system having a brake pad, the kit comprising: a pressurised fluid supply for placing in fluid communication with the braking surface of the brake pad; and system control means configured to operate the pressurised fluid supply so as to provide fluid to the braking surface of the brake pad under non-braking conditions.

According to another aspect of the present invention there is provided a kit for modifying a brake system having a brake pad, the kit comprising: a fluid removal means for placing in fluid communication with the braking surface of the brake pad; and system control means configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions. These aspects of the present invention may comprise any one or more of, or all of, the preferred or optional features discussed herein as appropriate.

According to another aspect of the present invention there is provided a method of modifying a brake system having a brake pad, the method comprising: providing a fluid removal means in fluid communication with the braking surface of the brake pad; and providing a system control means configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 is a cross sectional view of a brake system according to an embodiment of the present invention;

Figure 2 is a brake pad according to an embodiment of the present invention;

Figure 3A is a brake pad according to another embodiment of the present invention;

Figure 3B is cross sectional view of the brake pad of Figure 3A;

Figure 4 is a combined pressurised fluid supply and fluid suction device arrangement according to one embodiment of the present invention;

Figure 5 is a cross sectional view of a brake system according to another embodiment of the present invention.

Figures 6A-6D are views of a brake pad assembly according to another embodiment of the present invention.

Figure 7 is a cross-sectional view of a gas pump that can be used in a brake system according to a preferred embodiment of the present invention;

Fig. 8 is a schematic plan view of a car using the brake system of a preferred embodiment of the present invention;

Fig. 9 is a schematic view of a pressurised gas supply line for an air bearing system;

Fig. 10 is another schematic view of the pressurised gas supply line of Fig. 9;

Fig. 1 1 is a schematic circuit diagram of an apparatus for providing a variable voltage output to a pressurised fluid supply, according to an embodiment of the present invention;

Fig. 12a is a schematic circuit diagram of a variable resistor of a prior art converter board; and

Fig. 12b is a schematic circuit diagram of a portion of the apparatus of Fig. 1 1 .

Figure 1 is a cross sectional view of one embodiment of a brake system 10 for a motor vehicle. The brake system comprises a wheel hub 12 (shown in part) and a brake rotor 14 (brake disc) rotationally fixed to the wheel hub 12 by a fixing 16 such as a bolt. The wheel hub 12 and brake rotor 14 rotate about a centreline 18 when the vehicle is moving.

The brake system 10 further comprises a pair of brake pads 20 adjacent to the brake rotor 14. The brake pads 20 each comprise a friction material on a support structure (not shown). The brake pads 20 each have a braking surface 24 of the friction material that faces the brake rotor 14. The brake pads are joined to one another by brake callipers (not shown), and the brake callipers are fixed to a static (non-rotating) part of the vehicle. The braking surfaces 24 (and therefore the friction material) of the brake pads 20 can be forced into firm contact with the brake rotor 14 using the brake callipers. The brake callipers are controlled by the brake pedal of the vehicle.

The brake pads 20 each have an opening 22 for providing pressurised fluid (e.g. air) at a pressure P to the braking surface 24 of the brake pad 20 that is adjacent the brake rotor 14. The pressurised fluid is provided to the openings 22 in the braking surface 24 of the brake pad 20 from a compressor or pump (not shown) via tubes 26. The fluid that is provided to the braking surface 24 of the brake pad 20 is allowed to escape from the brake system by venting to the surrounding atmosphere in the gap between the brake pad 20 and the brake rotor 14.

The operation of the compressor or pump is controlled by a system control means (not shown). The system control means may be in communication with a sensor that detects the operation of the brake pedal and/or the accelerator/throttle of the vehicle so to determine whether or not braking conditions exist.

Under non-braking conditions (e.g. when the brake pedal is not activated and/or the accelerator/throttle is activated), the system control means allows pressurised fluid to be provided from the compressor or pump to the braking surfaces 24 of the brake pads 20 via the tubes 26. This may be achieved, for example, by switching the compressor or pump on and/or by opening a supply valve (not shown) that is in fluid communication between the compressor or pump and the braking surface 24.

When the pressurised fluid is provided to the braking surface 24 of the brake pads 20, the fluid pushes the brake pads 20 away from the brake rotor 14 with a force F A . The force F A works against the force F B of the callipers in their non-braking state. As will be appreciated, F A may vary with the distance D that exists between the brake pads 20 and the brake rotor 14. An increase in the distance D between the brake pads 20 and the brake rotor 14 may decrease the force F A .

Conversely, a decrease in the distance D between the brake pads 20 and the brake rotor 14 may increase the force F A . The force F B may effectively remain the same, but may vary with the distance D (e.g. an increase in D may lead to an increase in F B and vice versa).

The pressure P of the fluid is selected and provided such that, when F A is equal to F B , the brake pads 20 are positioned and maintained at a suitable distance D away from the brake rotor 14. The distance D need only be enough to prevent the brake pad 20 from contacting the brake rotor 14 (e.g. 10 microns). This prevents or reduces the frictional contact between the brake pad 20 and brake rotor 14, increasing the power and efficiency of the vehicle and decreasing brake pad wear.

Under braking conditions (e.g. when the brake pedal is activated and/or the

accelerator/throttle is not (or no longer) activated), the system control means prevents pressurised fluid from being provided to the braking surfaces 24 of the brake pads 20. This may be achieved, for example, by switching the compressor or pump off and/or by closing a valve that is in fluid communication between the compressor or pump and the brake pad braking surface 24 so as to cutoff the fluid supply to the braking surface. This brings the brake pad 20 into contact (or closer contact) with the brake rotor 14, and reduces the braking activation distance and time.

Also under braking conditions, or for a predetermined period of time after a braking operation occurs (e.g. for 1 second), the control system may actively or passively allow fluid to be removed from braking surfaces 24 of the brake pads 20. This may be achieved, for example, by a fluid removal means. For example, the fluid may be removed by switching on a vacuum (not shown) that is in fluid communication with the openings 22 of the brake pads 20, by opening a valve (not shown) in fluid communication with the braking surface 24 that vents to the surrounding atmosphere, or by operating or connecting the aforementioned compressor or pump in reverse. The removal of fluid brings the brake pad 20 into closer contact with the brake rotor 14, and reduces the braking activation distance and time.

In one arrangement, the aforementioned compressor or pump has an input that draws fluid in, and an output that provides pressurised fluid. Under non-braking conditions, the input is fluidly connected to the surrounding atmosphere, and the output is fluidly connected to the openings 22 in the brake pad 20. Under braking conditions, the output is fluidly connected to the surrounding atmosphere, and the input is fluidly connected to the openings 22 in the brake pad 20. Thus, the same compressor or pump can be used both as a pressurised fluid supply and a fluid removal (suction) device.

As will be appreciated the features of the brake system 10 can be retrofitted to an existing brake system. For example, in order to provide the broader embodiments of the brake system 10, openings 20 may be provided (e.g. drilled) though existing brake pads 20 and a tube 26 may be provided in fluid communication with the openings. A suitable compressor or pump may be provided and connected to the tube 26. A suitable system control means may then be provided to control the operation of the brake system 10 in the manner discussed above.

Figure 2 shows a pair of brake pads 20 according to one embodiment of the present invention. The brake pads 20 each have a braking surface 24 with an opening 22 in that surface. The openings 22 can be fluidly connected with a tube 26 (see Fig. 1). The opening 22 in this particular example is a racetrack slot having a length 'b' of 21 mm and a width 'a' of 1 1 mm. Such embodiments are particularly advantageous in that the fluid is centrally, effectively and evenly distributed by the slot to the majority of the surface 24 of the brake pad 20. This can prevent the brake pad 20 from tipping and contacting the adjacent brake rotor 14 when the fluid is supplied to the surface of the brake pad 20.

Figures 3A and 3B show a brake pad 30 according to another embodiment of the present invention. The brake pad 30 has a braking surface 34 with an opening 32 in that surface. The opening 32 can be fluidly connected with a tube 36 to the pressurised fluid supply. The braking surface also has a circumferential track 38 around the perimeter of the brake pad 30. A peripheral wall 37 is formed by an outer peripheral portion of the brake pad 30, and the circumferential track 38 provides a void between the outer peripheral portion of the brake pad 30 and an inner portion 39 of the brake pad 30. The circumferential track 38 can be fluidly connected with a tube 40 via an opening to a fluid or dust removal means, which in this embodiment also acts as the pressurised fluid supply. Figure 3B also shows the steel support structure 42 of the brake pad 30.

Figure 4 shows a combined pressurised fluid supply/fluid suction device 44 according to one embodiment of the present invention which may be used in conjunction with the brake pad of Figures 3A and 3B. The pressurised fluid supply/fluid suction device 44 comprises a compressor or pump 50 having an input 46 for receiving (filtered/conditioned) fluid and an output 48 for providing pressurised fluid.

When acting as a pressurised fluid supply, the input 46 is placed in fluid communication with the surrounding atmosphere by a first 3-way valve 52 via a first filter/conditioner 56 and the output 48 is placed in fluid communication with the braking surface by a second 3-way valve 54. The first filter/conditioner 56 protects the brake pad 30 and/or compressor or pump 50 by collecting particles and/or removing moisture from the surrounding atmosphere.

When acting as a fluid suction device, the input 46 is placed in fluid communication with the brake pad 30 by the first 3-way valve 52 via a second filter 58 and the output 48 is placed in fluid communication with the surrounding atmosphere by the second 3-way valve 54. The second filter 58 acts to collect braking dust generated under braking.

The first 3-way valve 52 and second 3-way valve 54 in this embodiment, are under the control of a system control means.

Figure 5 is a cross sectional view of a brake system according to another embodiment of the present invention. Figure 5 shows a brake pad 60 in contact with a brake rotor 62. The brake pad 60 comprises braking material 64 and a support structure 66.

The brake pad 60 comprises a central opening 68 for providing fluid to the braking surface of the brake pad 60, a first perimeter opening 70 for providing fluid to the brake pad 60, and a second perimeter opening 72 for removing fluid and brake dust from the brake pad 60. Fluid is

simultaneously provided and removed by a circulating compressor or pump 76. A filter/conditioner 78 is provided between the second perimeter opening 72 and the compressor or pump 76 to collect brake dust generated during braking and/or remove moisture. A diverting valve 80 (a 3-way solenoid valve) is located between the compressor or pump 76 and the centrally located opening 68. The diverting valve 80 is also located between the compressor or pump 76 and first perimeter opening 70.

The diverting valve 80 acts to provide fluid from the compressor or pump 76 to the centrally located opening 68 under non braking conditions so as to separate the brake pad 60 from the brake rotor 62. The diverting valve 80 acts to provide fluid from the compressor or pump 76 to the first perimeter opening 70 under braking conditions to aid the removal of brake dust. The diverting valve 80 in this embodiment is under the control of a system control means. A peripheral wall is provided by a silicone skirt 74 around the brake pad 60. The skirt 74 translates with brake pad 60 under braking conditions so as to span the gap between the brake pad 60 and the brake rotor 62 under braking conditions, thereby preventing brake dust from the braking surface of the brake pad 60 from entering the surrounding atmosphere under braking conditions. In doing this, the skirt 74 also creates a perimeter void 82 for directing fluid which is provided by the first perimeter opening 70 around the outer periphery of the brake pad 60. The fluid entrains brake dust before being removed by the second perimeter opening 72.

Figures 6A-6B show a brake pad assembly 100 according to another embodiment of the present invention.

Figure 6A is a plan view of the brake pad assembly 100. The brake pad assembly 100 comprises a brake pad 102, and a support structure 106 of the brake pad 102. The brake pad 102 comprises an upper braking surface 104 made of braking material. The brake pad 102 is provided with a central opening 108 in the centre of the braking surface 104 for providing fluid to the surface of the brake pad 102 in the manner discussed above.

In this embodiment, the brake pad assembly 100 comprises a peripheral wall provided by a flexible/resilient silicone skirt 1 10 which extends around the perimeter of the brake pad 102. The skirt 1 10 comprises partitions 120 which space the skirt 1 10 from the vertical sides of the brake pad 102 and which provide channels 122 down the sides of the brake pad 102.

The skirt 1 10 also forms a perimeter void 1 18 between the brake pad 102 and the skirt 1 10. Although only part of the perimeter void 1 18 is shown in the part section though line d-d (as shown in Figure. 6D), it will be appreciated that the perimeter void 1 18 extends around the periphery of the brake pad 102 between the skirt 1 10 and the brake pad 102, i.e. below the channels 122. The channels 122 are in fluid communication with both the braking surface 104 of the brake pad 102 and the perimeter void 1 18. This arrangement allows fluid (e.g. air) containing brake dust from the upper braking surface 104 to flow down through the channels 122 and into the perimeter void 1 18. The fluid containing brake dust can then circulate around the periphery of the brake pad 102 in the perimeter void 1 18.

(In some embodiments which are not illustrated, the skirt may provide a further (inner) peripheral wall which may, for example, be bonded to the sides of the brake pad 102. In these embodiments, the void may be provided between the peripheral wall and the further (inner) peripheral wall. In these embodiments, the partitions may be between the peripheral wall and the further (inner) peripheral wall, with the partitions providing channels to the void.)

The skirt 1 10 further comprises a first opening 1 12 to a first spigot 1 14. The first opening 1 12 allows the removal of the fluid containing brake dust from the perimeter void 1 18. The skirt 1 10 also comprises a second opening (not shown) to a second spigot 1 16. In some embodiments and/or circumstances, the second opening also allows the removal of fluid containing brake dust from the perimeter void 1 18. However, in other embodiments and/or under other circumstances (as will be discussed below), the second opening may be used to provide fluid to the perimeter void 1 18 so as to help circulate the fluid containing brake dust around to the first opening 1 12.

Figure 6B is a part section through line A-A of Figure 6A. Figure 6B shows the brake pad assembly 100 adjacent to a brake rotor (e.g. a brake disc) 124. Figure 6B shows the braking surface 104 of the brake pad 102 in contact with an opposing braking surface 126 of the brake rotor 124. Figure 6B also shows the perimeter void 1 18 which is formed between the skirt 1 10 and the brake pad 102, and shows one of the channels 1 12 which is formed by adjacent partitions 120 (see Fig. 6A). Figure 6B also shows the opening 108 in the brake pad 102 for providing fluid to the braking surface 104 of the brake pad 102.

Figure 6C is a part section through line B-B of Figure 6A. Figure 6C again shows the brake pad assembly 100 adjacent to the brake rotor 124, with the braking surface 104 of the brake pad 102 in contact with the opposing braking surface 126 of the brake rotor 124. Figure 6C also shows the perimeter void 1 18 which is formed between the skirt 1 10 and the brake pad 102, and shows one of the partitions 120 which spaces the skirt 1 10 from the sides of the brake pad 102.

Figure 6D is a part section through line C-C of Figure 6A. Figure 6D again shows the brake pad assembly 100 adjacent to the brake rotor 124, with the braking surface 104 of the brake pad 102 in contact with the opposing braking surface 126 of the brake rotor 124. Figure 6D also shows the perimeter void 1 18 which is formed between the skirt 1 10 and the brake pad 102 and shows the first opening 1 12 which allows the removal of fluid containing brake dust from the perimeter void 1 18 via spigot 1 14.

As will be appreciated, the skirt 1 10 can readily be fitted to the brake pad 102 by, for example, stretching the skirt 1 10 and mounting the skirt 1 10 around the brake pad 102. The skirt 1 10 could also be retrofitted to a conventional brake pad in a similar manner.

The use of the brake pad assembly 100 of this embodiment will now be described with reference to Figures 6A-6D.

Under non-braking conditions, fluid (e.g. air) is provided to the braking surface 104 of the brake pad 102 via the opening 108 in the braking surface 104. Fluid may be provided, for example, using a pressurised fluid supply (e.g. a pump or compressor output). Although not necessary in this embodiment, the fluid may be provided at a pressure and/or flow rate which is sufficient to separate the braking surface 104 of the brake pad 102 from the brake rotor 124 as discussed above in relation to other embodiments.

Fluid containing brake dust is also removed from the perimeter void 1 18 through the spigot 1 14 via the opening 1 12 in the skirt 1 10. Fluid containing brake dust is also preferably removed from the perimeter void 1 18 through the opening in the spigot 1 16. Fluid may be removed, for example, using a vacuum (or a or the pump or compressor input).

Thus, under non-braking conditions, fluid passes from the opening 108 in the braking surface 104, across the braking surface 104 where brake dust is collected, down the channels 1 12 and into the perimeter void 1 18. The fluid containing the brake dust is then removed from the perimeter void 1 18 through the spigot 1 14 (and possibly spigot 1 16) via the opening 1 12 in the skirt 1 10.

Under braking conditions, fluid (e.g. air) may or may not be provided to the opening 108 in the braking surface 104. As discussed above in relation to other embodiments, if fluid is provided to the opening 108 in the braking surface 104, then it is preferably at a pressure and/or flow rate which is insufficient to separate the braking surface 104 of the brake pad 102 from the brake rotor 124.

Fluid containing brake dust is also removed from the perimeter void 1 18 through the spigot 1 14 via the opening 1 12 in the skirt 1 10. Fluid containing brake dust may also be removed from the perimeter void 1 18 through the opening in the spigot 1 16.

Thus, under braking conditions, brake dust which is generated under braking and which migrates across the braking surface 104 can be extracted down the channels 122 and into the perimeter void 1 18. The fluid containing the brake dust can then be removed from the perimeter void 1 18 through the spigot 1 14 (and possibly spigot 1 16) via the opening 1 12 in the perimeter wall 1 10.

Alternatively, in some embodiments, under braking conditions, fluid containing brake dust may be removed through the first spigot 1 14 via the first opening 1 12 in the perimeter wall but fluid (e.g. air) may be provided to the perimeter void 1 18 through the second spigot 1 16 via the second opening in the skirt 1 10. Fluid may be provided, for example, using the pressurised fluid supply (e.g. the pump or compressor output). This alternative arrangement can help to provide a flow of fluid through the perimeter void 1 18 under braking conditions. Although preferred embodiments of the present invention have been described, it will be apparent to the skilled person that various features of those embodiments can be altered, removed or substituted without departing from the scope of the invention as defined by the appended claims.

Fig. 7 shows a diaphragm gas pump 60 having four separate pump heads 62a, 62b, 62c, 62d. Each head is identical in construction, so only a single head 62a will be described. The heads are powered by a single motor 61 , such as a brushless DC motor. The motor 61 drives first and second co-axial drive shafts 71 . Bearings 70 are provided between the drive shaft 71 and the pump housing 72. The shafts 71 are each connected to an eccentric cam 69, which in turn is connected to upper and lower connecting rods 68. The connecting rods 68 are each connected to a diaphragm support 67 and a diaphragm 66.

The diaphragm 66 is positioned below a plate 73 and together they define a pumping plenum 63. The plate 73 of each head 62a - 62d comprises an inlet 65 and outlet 64. The inlet 65 comprises a non-return valve (not shown) that permits fluid flow in one direction 75 only. Similarly, the outlet 64 comprises a non-return valve (not shown) that permits fluid flow in one direction 74 only.

Rotating the drive shaft 71 causes the eccentric cam 69 to push the connecting rods in a reciprocating manner, which in turn pushes the diaphragms 66 towards and away from the plate 73. When the diaphragm 66 is moved away from the plate 73 the pumping plenum increases in size and fluid is sucked through the inlet 65 (in direction 75). Head 62a shows the diaphragm 66 in its furthest position away from the top plate 73. In this position, the pumping plenum 63 will be full of fluid, such as air.

When the diaphragm 66 is moved towards plate 73, the size of the plenum 63 is reduced and fluid is pumped out until the diaphragm 66 contacts plate 73, as shown by head 62b. Heads 62c and 62d show the diaphragms 66 in mid-positions, where the diaphragms 66 are on the way to the positions shown by heads 62a and 62b.

The four outlets 64 of heads 62a - 62d can be connected to separate piping to provide four independent gas supplies.

The use of a multi-headed diaphragm reduces vibrations and noise due to the offset of the different heads at any point in time.

Fig. 8 shows a car 80 having the diaphragm pump 60 of Fig. 7. The pump 60 may be positioned at any suitable location, preferably one close to a centre of the car. The pump 60 may source air from an engine bay (not shown) so that warm ambient air can be used. As can be seen, the car 80 has four brake discs 46, each having a hub 48 for connection to a wheel (not shown).

The pump 60 supplies pressurised air to the brake pads of each disc 4 via four separate (and independent) gas supply lines 83a, 83b, 83c, 83d. Each line is connected to an inlet 74 of a head 62a - 62d (Fig. 7) of the pump 60. The pump 60 may provide the same pressure air to each line 83a - 83d. The lines are not in fluid communication with each other, so a change in pressure in one line (for example due to a problem in one brake pad/caliper) will not affect the pressure in any other line.

The lines 83a - 83d may comprise flexible plastic tubing. Each line may be split proximate the brake disc into a pipe for each brake pad on that disc (e.g. two pipes) (not shown).

Figs. 9 and 10 show part of a pressurised gas supply line for an air bearing system. The air bearing system comprises one or more air bearings, an air pump, a variable timer controller (VTC) 90, a number of dump valves 92, an actuator (such as a footbrake) and pipework 94, 96, 98. Each air bearing comprises a brake pad and a brake disc.

In use, the air pump supplies pressurised air via pipe 94 to each brake pad, a pair of pads being associated with each wheel of the automobile (e.g. four wheels). The pipework includes a plurality of dump valves 92 (e.g. four), one located proximal to each pair of brake pads. As the dump valves 92 are normally closed, they are provided in a separate pipe 96 extending from the pipe 98 between the air pump and the air bearing, as shown in Figs. 13 and 14. As such, when the compressor is on, the air supply to the brake pad does not flow through dump valves 92.

The dump valves 92 are solenoid valves, which are normally closed. As such, energy is required to open the dump valves 92 and to maintain them in an open condition, whereas closing the dump valves 92 and maintaining them in a closed condition does not require any energy.

When the footbrake is not applied, for example when the car is in motion, the air pump is on so that air is constantly supplied to the brake pads, and the dump valves 92 are closed, as shown in Fig 9. When the footbrake is applied, the air pump is turned off, the dump valves 92 are opened and the timer is started, as shown in Fig 10. These three events occur simultaneously. Turning the air pump off saves energy. Opening the dump valves 92 allows the pressurised air in the pipes 94 and in the air-bearing (i.e. between the brake pad and the brake disc) to be discharged, through the brake pad and pipework to atmosphere, until the pressure drops to that of the surroundings, i.e. atmospheric pressure.

After the timer reaches a pre-set time, the dump valves 92 are closed. The time elapsed since the timer was started is sufficient to allow the air to be discharged fully. For example, this time may be 1 to 5 seconds. As such, closing the valves 92 at this time does not prevent the air from discharging. Closing the valves 92 at this time saves energy as the valves no longer need to be open (i.e. powered).

When the footbrake is released, the air pump is turned back on, supplying air to the brake pads. The dump valves 92 remain closed so that pressurised air in the air bearing pushes the brake pads away from the disc.

Fig 1 1 is a schematic circuit diagram of an apparatus for providing a variable voltage output to a pressurised fluid supply, according to an embodiment of the present invention.

The apparatus comprises a step-up/step-down converter board, as is known in the art, except that a variable resistor has been removed to expose contacts a, b, c. In order to provide three different voltage outputs from the converter board (to the pressurised fluid supply via wires F, G), the contacts a, b, c are connected to an IC board, via wires A, B, C.

The IC board has an IC chip, two relays and three variable resistors R1 , R2, R3. The three resistors are connected to wires A, B, C, as shown in Fig 12b. The circuitry shown in Fig 12b, replaces the prior art variable resistor R4 circuit of Fig 12a, which has been removed from the converter board of Fig 1 1.

Relays 1 , 2 are each arranged to be selectively and independently energised, upon receipt of a (mA) signal from the IC chip.

As shown in Figure 12b, Relays 1 , 2 are normally open (i.e. de-energised), with resistor R2 being selected. This gives a low voltage output to converter board and to pressurised fluid supply.

When Relay 1 is energised (and Relay 2 is not), resistor R3 is selected and a medium voltage is outputted.

When Relay 2 is energised (and Relay 1 is not), resistor R1 is selected a high voltage is outputted.

The IC chip provides a signal to Relay 1 or 2, or no signal, depending on pre-set or measured time periods. For example, the IC chip comprises a timer function to record the duration of a braking period, via a wired connection M to brake switch, which is normally open (until braking commences). The brake switch also turns off converter board via wire D when braking commences. The brake switch also opens a fluid removal means, such as a solenoid valve, via fluid removal valve switch and wire L, to remove pressurised air from the brake pad surface, when braking commences. The IC chip also has an input (via wire K) from a driver-operated manual override switch, so that the driver can select a particular output voltage mode, such as medium voltage, to provide extra cooling and brake dust removal in a sports mode.

The IC chip may also be programmed to energise Relay 2 to provide a high voltage output when the vehicle's ignition is turned on, for example, upon initial power-up of the IC chip board by power supply.

In an alternative embodiment (not shown), three resistors having three different fixed resistances could be used instead of variable resistors.