GB2269144A

GB2269144A - Vehicle brake temperature control.

Info

Publication number: GB2269144A
Application number: GB9314599A
Authority: GB
Inventors: Ian Gordon Murray
Original assignee: McLaren Cars NV
Current assignee: McLaren Cars NV
Priority date: 1992-07-28
Filing date: 1993-07-14
Publication date: 1994-02-02
Anticipated expiration: 2013-07-14
Also published as: GB9215966D0; GB2269144B; GB9314599D0

Abstract

An active system for providing cooling air to car brakes ensures that the flow of air is not directed at the braking assembly continuously. An air duct (10) directs air to the calliper area (4) of a brake assembly (2, 4). The air duct (10) is fitted with a valve (12) which is normally closed, to prevent the flow of air therealong. An electronic control unit (16) receives information from sensors (18, 20) as to the brake line pressure and the speed of the car. If the electronic control unit (16) determines from the information received that the driver of the car is making a heavy braking manoeuvre, it controls a motor (14) to open the valve (12) so that air flow to cool the brake assemblies is directed thereto. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO VEHICLE BRAKE TEMPERATURE CONTROL The present invention relates to a method and system of controlling the temperature of brakes of a vehicle.

High performance and high mass vehicles have an inherent brake cooling problem due to the total energy which has to be dissipated from the brakes when they are subjected to extreme loads or braking at extremely high speeds. Clearly, the braking system must be capable of dissipating the total energy generated when a fully laden vehicle is heavily braked from its maximum velocity to a full stop. Moreover, the braking system should be capable of performing safely even when subjected to repeated stops involving maximum energy.

Most high performance cars use a flow of air to help dissipate the energy. In this respect, air ducts are provided in the front end of the vehicle to allow air to flow across the brake disc. However, as the air is supplied to the area of the brakes at all times when the vehicles is in motion, the cooling air lowers the base or starting temperature of the brake discs and pads. This can increase the response time of the braking system as the pad/disc interface has an optimum operational temperature range for the coefficient of friction.

It is an object of the present invention to reduce the disadvantages identified above.

According to a first aspect of the present invention there is provided a method of controlling the temperature of brakes of a vehicle, said method comprising the steps of sensing at least one parameter related to the vehicle and/or its brakes, and, if the, one or more of, or each parameter is outside predetermined limits, causing a flow of air to be directed to brakes of the vehicle.

The method of the invention is an active system for controlling the temperature of the brakes and accordingly does not suffer from the disadvantages of the previously known passive systems. In particular, the flow of air is preferably not directed to the brakes when the or each parameter is within the predetermined limits. In a preferred embodiment, the method comprises preventing a flow of air to brakes of the vehicle when the parameter(s) are within the predetermined limits.

It would be possible to generate a flow of cool air and to flow that air to brakes of the vehicle. For example, a fan or other air flow generating means may be arranged to generate a flow of cool air when required and direct it at brakes of the vehicle.

Preferably, the flow of air is generated by the motion of the vehicle and is arranged to be flowed along appropriate ducts provided which direct the air to brakes of the vehicle. If the or each parameter is within the predetermined limits, the ducts are closed to prevent a flow of air to the brakes.

The parameters which are sensed and which determine if a flow of air is to be caused may be selected as required.

For example, the parameters may be one or more of the speed of the vehicle, its braking force, the temperature of the brakes, and/or the ambient temperature. The braking force may be determined by the pressure applied to the brakes, for example, and/or by reaction forces of the vehicle. In a preferred embodiment, the method comprises sensing the speed of the vehicle and/or the braking force.

Furthermore, a flow of air is caused if the speed and/or the braking force is above a predetermined limit, whereas the flow of air is prevented if the speed and/or the braking force is below the predetermined limit.

The method further comprises applying additional braking forces to a vehicle when the flow of air is caused to be directed to the brakes.

For example, the means for opening the air ducts may also be arranged to provide for air braking of the vehicle.

According to a further aspect of the present invention there is provided a system for controlling the temperature of brakes of a vehicle by way of the method defined above.

The present invention also extends to a system for controlling the temperature of brakes of a vehicle, said system comprising sensor means for sensing at least one parameter related to the vehicle and/or its brakes, flow means arranged to enable a flow of air to be directed to brakes of the vehicle, and control means responsive to said sensor means and arranged to actuate said flow means such that a flow of air is directed to brakes of the vehicle if the, one or more of, or each parameter is outside predetermined limits.

The flow means may comprise a fan or other air flow generating means arranged, upon actuation, to direct cooling air to brakes of a vehicle.

In a presently preferred embodiment, said flow means comprises ducting communicating brakes of a vehicle with an air supply, and valve means for selectively opening and closing the ducting. For example, ducts may be permanently fitted into a vehicle to communicate its brakes with the exterior of the vehicle. The valve means may comprise a valve or throttle plate mounted in the or each said duct, the valve means being normally closed. Said flow means may also comprise a drive motor for the valve means or for means arranged to be actuated by said control means.

In an embodiment, said drive means is additionally arranged to actuate an air foil. For example, in one embodiment, the valve means comprises one or more throttle plates arranged upon opening to form an air foil.

The control means may comprise an electronic control unit coupled to receive information from said sensor means and to actuate said flow means in dependence upon the parameters sensed. The control unit may comprise processor means controlled by appropriate software. The provision of such software is within the competence of anyone skilled in the art and is not further described herein.

The information applied to the control unit may be related to any parameters of the vehicle and the brakes.

In a preferred embodiment, the information relates to the speed of the vehicle and the braking force applied thereto.

The control unit is arranged to actuate the flow means if both the speed of the vehicle and its braking force are above a predetermined limit. Alternatively, the control unit may be arranged to actuate the flow means whenever one of the parameters is above the predetermined limit there for.

The method and system defined above may be arranged to cause a flow of cooling air to selected ones only of the brakes of a vehicle. Preferably, however, a flow of cooling air is to be arranged to flow to all the brakes of the vehicle.

The present invention also extends to a vehicle incorporating a system as defined above.

Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a known brake cooling system of a high performance car, Figure 2 shows a known brake cooling system of a racing car, Figure 3 shows schematically a brake cooling system of the present invention, and Figure 4 shows schematically part of a further embodiment of a brake cooling system of the invention.

In the description given below, the invention is particularly described with respect to the cooling of disc brakes of cars. However, this is for convenience only and it should be appreciated that the invention is equally applicable to any type of braking system and to any type of vehicle.

Figure 1 illustrates part of the front end of a high performance car and shows a currently available brake cooling system. As is known, the braking assembly comprises a brake disc 2 and a calliper 4 associated with a front wheel 6 of the car. Brake pads (not shown) are carried by the calliper 4 and are arranged to squeeze the disc 2 therebetween on braking. The front bodywork of the car is generally indicated at 8 and it will be seen that a duct 10 is formed therein. It will also be appreciated that as the car moves forward as indicated by the arrow F, cooling air, indicated by the arrow A will enter the wheel arch cavity and flow generally across the general area of the brake assembly.

Figure 2 shows a similar, but more sophisticated system, as used on racing cars. In this respect, in Figure 2 parts thereof which are generally the same or similar to those of Figure 1 have been given the same reference numerals.

In the arrangement shown in Figure 2, a cooling air duct 10 is formed which extends to the brake calliper 4.

In this arrangement, therefore, the cooling air is directed more efficiently to the area of the braking assembly where it is required.

Of course, and as is explained above, the known systems for providing cooling air to the brakes of the cars can lead to degradation in the braking performance as they lower the temperature of the discs and pads of the braking assembly at all times.

An embodiment of a cooling system of the present invention is shown in Figure 3. In Figure 3, the same reference numerals as used in Figures 1 and 2 are employed for the same or similar parts. The embodiment of Figure 3 has an air duct 10 which is designed to direct air to the calliper area 4 of the brake assembly for maximum efficiency. However, this air duct 10 is fitted with a valve 12 which is normally closed, and which when it is closed prevents the flow of air along the duct 10 to the brake assembly 2,4. A control motor 14 is provided and when actuated is able to open the valve 12.The mechanism is chosen so that the response time is low, for example, so that the valve 12 can be opened in less than 0.3 seconds The control motor 14 is controlled and actuated by way of an electronic control unit 16 which includes processor means and which is connected to receive information from sensors 18 and 20. In the embodiment illustrated, the sensor 18 provides information as to the brake line pressure, whilst the sensor 20 provides information as to the speed of the car. The electronic control unit 16 uses the information received from the sensors 18,20 to determine if the driver of the car is making a sufficiently heavy braking manoeuvre to require the valve 12 to be opened so that air flow to cool the brake assemblies is directed thereto.In this respect, in a preferred embodiment, actuation of the control motor 14 to open the valve 12 occurs when both the speed as sensed by the sensor 20, and the brake line pressure, as sensed by the sensor 18 are above predetermined values. In this respect, the brake line pressure is proportional to brake pedal effort. Of course, these predetermined values may be adjusted and it is also possible, if required, for the control motor 14 to be actuated if only one of the parameters is above the respective predetermined value. Similarly, the control unit 16 is arranged to turn off the control motor 14 so that the valve 12 returns to its normally closed position when either or both of the sensed parameters falls below the associated predetermined value.

It will be appreciated that the system as illustrated in Figure 3 is an active system which only produces a cooling effect for the brakes when this is needed. In addition, as the air flow through the ducts 10 is prevented when not required, the system also improves the aerodynamic efficiency of the car. In this respect, where cooling air ducts are provided and are open all the time, there is an induced aerodynamic drag which acts on the car.

It would be possible to provide for cooling of only some of the brakes of the car. However, it is preferred that the brakes associated with each wheel should be provided with an associated air duct and means, as the valve 12 and its associated motor 14, to control the flow of air thereto. A single control unit 16 is generally provided to control all of the motors 14 and in most cases only a single sensor 18 and a single sensor 20 are provided.

Figure 4 shows a part of an alternative embodiment of a cooling system of the invention and illustrates a rear wheel 6 of a car and part of the rear bodywork 8 thereof.

A cooling air duct 10 is provided in the rear bodywork 8 and is arranged, when open, to enable a flow of air to be directed to the brake assembly adjacent to the brake calliper 4. However, in the embodiment shown in Figure 4, the flow control means comprises a valve plate 22 which in its normally closed position (not shown) extends across the duct 10 to close it. However, when its associated control motor (not visible) is actuated to open the duct 10, the valve plate 22 assumes the position shown in Figure 4 in which it defines a foil to act as an air brake for the vehicle by increasing the drag coefficient.

In the embodiment shown in Figure 4, it is the valve plate 22 itself which defines the foil on opening of the air duct. However, it is alternatively possible for the associated control motor to be arranged when opening an air duct to deploy a separate foil. It is also alternatively possible for the control unit 16 to be arranged to actuate a separate foil deploying system simultaneously with the actuation of the brake cooling means.

It will be appreciated that other modifications and variations may be made to the embodiments as described and illustrated within the scope of this application.

Claims

1. A method of controlling the temperature of brakes of a vehicle, said method comprising the steps of sensing at least one parameter related to the vehicle and/or its brakes, and if the, one or more of, or each parameter is outside predetermined limits, causing a flow of air to be directed to brakes of the vehicle.

2. A method of controlling brakes temperature as claimed in Claim 1, further comprising the steps of preventing a flow of air to brakes of the vehicle when the parameter(s) are within the predetermined limits.

3. A method of controlling brakes temperature as claimed in Claim 2, wherein air flow generating means are arranged to generate a flow of cool air when required and to direct it at brakes of the vehicle.

4. A method of controlling brakes temperature as claimed in any of Claims 1 to 3, wherein the flow of air is generated by the motion of the vehicle and is arranged to be flowed along appropriate ducts provided which direct the air to brakes of the vehicle.

5. A method of controlling brakes temperature as claimed in Claim 4, wherein, if the or each parameter is within the predetermined limits, the ducts are closed to prevent a flow of air to the brakes.

6. A method of controlling brakes temperature as claimed in any preceding claim, wherein said parameters which are sensed are one or more of the speed of the vehicle, its braking force, the temperature of the brakes, and/or the ambient temperature.

7. A method of controlling brakes temperature as claimed in Claim 6, wherein the braking force is determined by the pressure applied to the brakes, for example, and/or by reaction forces of the vehicle.

8. A method of controlling brakes temperature as claimed in any preceding claim, comprising the steps of sensing the speed of the vehicle and/or the braking force, and causing a flow of air if the speed and/or the braking force is above a predetermined limit, whereas the flow of air is prevented if the speed and/or the braking force is below the predetermined limit.

9. A method of controlling brakes temperature as claimed in any preceding claim, further comprising applying additional braking forces to a vehicle when the flow of air is caused to be directed to the brakes.

10. A method of controlling brakes temperature as claimed in Claim 9, wherein the flow of air is arranged to be flowed along appropriate openable and closable ducts, and wherein means are provided to open said ducts to direct the air to brakes of the vehicle, and wherein the means for opening the air ducts may also be arranged to provide for air braking of the vehicle.

11. A system for controlling the temperature of brakes of a vehicle by way of a method as claimed in any preceding claim.

12. A system for controlling the temperature of brakes of a vehicle, said system comprising sensor means for sensing at least one parameter related to the vehicle and/or its brakes, flow means arranged to enable a flow of air to be directed to brakes of the vehicle, and control means responsive to said sensor means and arranged to actuate said flow means such that a flow of air is directed to brakes of the vehicle if the, one or more of, or each parameter is outside predetermined limits.

13. A system as claimed in Claim 12, wherein said flow means comprises a fan or other air flow generating means arranged, upon actuation, to direct cooling air to brakes of a vehicle.

14. A system as claimed in Claim 12 or 13, wherein said flow means comprises ducting communicating brakes of a vehicle with an air supply, and valve means for selectively opening and closing the ducting.

15. A system as claimed in Claim 14, wherein ducts are fitted into a vehicle to communicate its brakes with the exterior of the vehicle, and the valve means comprises a valve or throttle plate mounted in the or each said duct, the valve means being normally closed.

16. A system as claimed in Claim 14 or 15, wherein said flow means also comprises a drive motor for the valve means or for means arranged to be actuated by said control means.

17. A system as claimed in Claim 16, wherein said drive means is additionally arranged to actuate an air foil.

18. A system as claimed in Claim 17, wherein the valve means comprises one or more throttle plates arranged upon opening to form an air foil.

19. A system as claimed in any of Claims 12 to 18, wherein said control means comprises an electronic control unit coupled to receive information from said sensor means and to actuate said flow means in dependence upon the parameters sensed.

20. A system as claimed in Claim 19, wherein the information applied to the control unit relates to the speed of the vehicle and the braking force applied thereto.

21. A system as claimed in Claim 20, wherein said control unit is arranged to actuate the flow means if both the speed of the vehicle and its braking force are above a predetermined limit.

22. A system as claimed in Claim 20, wherein said control unit is arranged to actuate the flow means whenever one of the parameters is above the predetermined limit therefor.

23. A method of controlling the temperature of brakes of a vehicle substantially as hereinbefore described with reference to the accompanying drawings.

24. A system for controlling the temperature of brakes of a vehicle substantially as hereinbefore described with reference to the accompanying drawings.