GB2428995A

GB2428995A - Tyre pressure modulation with valve actuator

Info

Publication number: GB2428995A
Application number: GB0516644A
Authority: GB
Inventors: Laurence John Potter
Original assignee: Haldex Brake Products Ltd
Current assignee: Haldex Brake Products Ltd
Priority date: 2005-08-13
Filing date: 2005-08-13
Publication date: 2007-02-14
Also published as: GB0516644D0

Abstract

A valve actuator assembly (10, 100) including a inlet (12, 120) which is adapted to be connected to a source of pressurised fluid, an outlet (18, 180) which is adapted to be connected to a tyre valve (20, 200), and an actuator part (26, 260) which, when the outlet (18,180) is connected to a tyre valve (20, 200) may bear on a valve member (22,220) of the tyre valve (20, 200) wherein the valve actuator assembly (10, 100) is adapted to permit flow of fluid through the outlet (18, 180) both to and from the tyre valve (20, 200) except when the fluid pressure at the tyre valve (20, 200) exceeds the fluid pressure at the tyre valve actuator assembly inlet (12, 120) by a predetermined amount. Tyre pressure modulation may also be used in a vehicle including a source of pressurised fluid connected to a tyre and a controller.

Description

1 2428995 Title: Tyre Pressure Modulation System and Valve Actuator

Assembly The refor

Description of Invention

The present invention relates to a system for modulating the pressure in a vehicle tyre, and a valve actuator assembly suitable for use in such a system.

It is known to provide means for automatically pumping air into a vehicle tyre whilst in use, should the vehicle tyre pressure decrease below a predetermined minimum pressure. In such systems, it is known to pump air into each tyre by means of a centrifugal or inertial pump in which the energy for pressurising the air is provided by a hub-mounted weight which rotates with the wheel on which the tyre is mounted. It is also possible to connect each tyre to an existing source of pressurised air such as a compressor or air tank from which compressed air is provided for brake actuation. The source of pressurised air can be connected to a conventional Schrader valve, as such a valve is configured to move to an open position to allow air into the tyre when pressurised air is supplied to the valve inlet, but to move to a closed position in which flow of air to or from the tyre is substantially prevented, when the tyre pressure exceeds the air pressure at the valve inlet.

Such known systems only provide for inflation of the tyres, however.

According to a first aspect of the present invention we provide a valve actuator assembly including an inlet which is adapted to be connected to a source of pressurised fluid, an outlet which is adapted to be connected to a tyre valve, and an actuator part which, when the outlet is connected to a tyre valve may bear on a valve member of the tyre valve wherein the valve actuator assembly is adapted to permit flow of fluid through the outlet both to and from the tyre valve except when the fluid pressure at the tyre valve exceeds the fluid pressure at the tyre valve actuator assembly inlet by a predetermined amount.

By virtue of the provision of such a valve actuator assembly, controlled deflation of the tyre is permitted, but rapid deflation of the tyre, such as could occur if the connection between the source of pressurised fluid and the tyre valve actuator assembly were severed, is substantially prevented.

In one embodiment of the invention, the actuator part may be movable between an open position in which it bears on the valve member of a valve to which the outlet of the valve actuator assembly is connected to bring the valve member out of engagement with its valve seat, and a closed position in which the actuator part retracts and the valve member is permitted to engage with the valve seat.

In this case, preferably the actuator part moves frOm the open position to the closed position when fluid pressure in the valve exceeds the fluid pressure at the tyre valve actuator assembly inlet by a predetermined amount.

Preferably the actuator is a piston mounted in a cylinder which extends between the inlet and the outlet of the valve actuator.

The tyre valve actuator assembly is preferably provided with resilient biasing means which biases the actuator part to the closed position.

In an alternative embodiment of the invention, the actuator part may be fixed such that when the tyre valve actuator assembly outlet is connected to a tyre valve, the actuator part bears on the valve member of the tyre valve and moves the valve member out of engagement with its valve seat.

In this case, the tyre valve actuator assembly may include a valve member which is movable to engage with a valve seat substantially to prevent flow of fluid from the inlet to the outlet of the valve actuator assembly. Preferably the valve member moves to engage with the valve seat when fluid pressure in the valve exceeds the fluid pressure at the valve actuator assembly inlet by a predetermined amount.

Preferably, the valve member is moved by means of an electrically or electronically operated actuator and is adapted to engage with the valve seat when supply of electrical power to the actuator is removed, and to move away from the valve seat so that flow of fluid between the inlet and outlet of the valve actuator assembly is permitted, when electrical power is supplied to the actuator.

This embodiment of valve actuator assembly may also include an exhaust port which vents to the atmosphere or any other low pressure fluid reservoir, and a second valve member which is movable to engage with a second valve seat substantially to prevent flow of fluid through the exhaust port. The second valve member may also be moved by means of an electrically or electronically operated actuator and engage with the second valve seat when supply of electrical power to the actuator is removed, and move away from the valve seat so that flow of fluid through the exhaust port is permitted, when electrical power is supplied to the actuator.

The valve actuator assembly may include a pressure sensor which is adapted to provide a signal indicative of the tyre fluid pressure.

The valve actuator assembly may also include an electrical or electronic controller which controls operation of the or each electrical or electronic actuator according to the signal output of the pressure sensor.

According to a second aspect of the invention we provide a tyre pressure modulation system for a vehicle including a source of pressurised fluid connected to a tyre and a controller, the source of pressurised fluid being controllable by the controller to pump fluid into the tyre, to reduce the pressure of fluid in the tyre and to maintain the pressure of fluid in the tyre at a desired value.

Every tyre has an ideal pressure for optimum wear and safety performance which depends on local conditions such as vehicle speed, temperature and vehicle loading. By providing a tyre pressure modulation system which allows for inflation and deflation of a tyre, it is possible to ensure that the tyre pressure is closer to its ideal pressure than would be possible if no modulation or if a modulation system accommodating tyre inflation only were provided.

The source of pressurised fluid may include a fluid pump or pressurised fluid reservoir. In this case, the source of pressurised fluid may further include a control valve which is connected between the pump or reservoir and a tyre, the controller controlling operation of the control valve, wherein the control valve can be operated to adopt one of three states, namely an inflate state in which flow of pressurised fluid from the source of pressurised fluid into the tyre is permitted, a deflate state in which flow of pressurised fluid out of the tyre to an exhaust port is permitted, and a hold state in which flow of pressurised fluid into or out of the tyre is substantially prevented.

Where the source of pressurised fluid includes a fluid pump, the controller may be adapted to control operation of the pump to increase, decrease or maintain the pressure of pumped fluid according to whether it is desired to increase, decrease or maintain the pressure of fluid in the tyre.

Preferably the system includes a pressure sensor which is adapted to sense the pressure of fluid within the tyre and transmit a signal indicative of the tyre pressure to the controller, the controller being adapted to control operation of the control valve in accordance with the signal supplied by the pressure sensor.

Preferably the controller is provided with a memory in which is stored data specifying an ideal tyre pressure over a range of tyre conditions, and the controller is adapted to determine the actual tyre pressure from the signal supplied by the pressure sensor, access the data in the memory to determine the ideal tyre pressure specified for the prevailing tyre conditions, and control operation of the control valve to bring the actual tyre pressure closer to the ideal tyre pressure.

In this case, the system may further include a temperature sensor which is adapted to sense the temperature of or within the tyre and transmit a signal indicative of the tyre temperature to the controller, the data in the controller memory specifying the ideal tyre pressure over a range of tyre temperatures, and the controller being adapted to determine the ideal tyre pressure specified for the prevailing tyre temperature.

Additionally or alternatively, the system may further include a load sensor which is adapted to sense the weight carried by the tyre, and transmit a signal indicative of the weight to the controller, the data in the controller memory specifying the ideal tyre pressure over a range of tyre load weights, and the controller being adapted to determine the ideal tyre pressure specified for the prevailing tyre load weight.

Additionally or alternatively, the system may further include a vehicle speed determining device which is adapted to sense or calculate the speed of the vehicle and transmit a signal indicative of the vehicle speed to the controller, the data in the controller memory specifying the ideal tyre pressure over a range of vehicle speeds, and the controller being adapted to determine the ideal tyre pressure specified for the prevailing vehicle speed.

Preferably the system further includes a safety valve assembly which has an inlet port which is connected to the source of pressurised fluid and an outlet which is connected to the tyre, the safety valve assembly being adapted to substantially prevent flow of fluid out of the tyre if the pressure of fluid at the safety valve assembly outlet exceeds the pressure of fluid at the safety valve assembly inlet by a predetermined amount.

By virtue of the safety valve assembly being adapted substantially to prevent flow of fluid out of the tyre if the pressure of fluid at the safety valve assembly outlet exceeds the pressure of fluid at the safety valve assembly inlet by a predetermined amount, controlled deflation of the tyre is permitted, but if the system malfunctions or is damaged, for example if the connection between the source of pressurised fluid and the tyre is severed, rapid deflation of the tyres is prevented.

In this case, the safety valve assembly may include a valve member which is movable to engage with a valve seat substantially to prevent flow of fluid out of the tyre and a valve actuator in accordance with the first aspect of the invention.

Embodiments of the invention will now be described with reference to the accompanying drawings of which, FIGURE 1 is an illustration of a longitudinal cross-section through a valve and first embodiment of valve actuator assembly according to the first aspect of the invention, the valve and valve actuator assembly being in a closed configuration, FIGURE 2 is an illustration of a longitudinal cross-section through the valve and valve actuator assembly shown in Figure 1 in an open configuration, FIGURE 3 is a schematic illustration of a second embodiment of valve actuator assembly according to the first aspect of the invention, FIGURE 4 is a schematic illustration of a first embodiment of tyre pressure modulation system according to the second aspect of the invention, and FIGURE 5 is a schematic illustration of a second embodiment of tyre pressure modulation system according to the second aspect of the invention.

Referring now to the figures, there is shown a first embodiment of valve actuator assembly 10 including an inlet 12 which is adapted to be connected to a source of pressurised fluid (not shown). In this example, the inlet 12 is a generally cylindrical tube and is connected to the source of pressurised fluid by means of a generally cylindrical tube 14 which is mounted around the inlet tube 12. The outer tube 14 is retained on the inlet tube 12, and a substantially fluid tight seal provided between the two tubes by means of a connector 16 which is mounted around both tubes 12, 14.

The valve actuator assembly 10 further includes an outlet 18 which is connected to a tyre valve 20. It will be appreciated that the tyre valve 20 is mounted on a tyre (not shown) and connects the interior of the tyre (or tyre inner tube where provided) with the exterior of the tyre so that the tyre may be inflated or deflated via the tyre valve 20. The tyre valve 20 includes a valve member 22 which is movable into and out of engagement with a valve seat 24.

When the valve member 22 is engaged with the valve seat 24, as illustrated in Figure 1, flow of fluid into or out of the tyre through the tyre valve 20, is substantially prevented. In this example, the outlet 18 of the valve actuator assembly 10 is connected to the tyre valve 20 by means of an internal screw thread 18a which engages with an external screw thread 20a provided around a free end of the valve 20. The valve 20 in this example is a Schrader valve, but it should be appreciated that any other type of valve including a movable valve member may be used.

The valve actuator assembly 10 also includes an actuator part 26 which is movable between an open position in which the actuator part 26 bears on the valve member 22 of the tyre valve 20 to move the valve member 22 out of engagement with the valve seat 24, as illustrated in Figure 2, and a closed position in which the valve member 22 of the tyre valve 20 is permitted to move into engagement with the valve seat 24, as illustrated in Figure 1.

The actuator part 26 includes a piston portion 26a which is mounted in a generally cylindrical body portion 28 of the valve actuator assembly 10, and an actuator rod portion 26b which extends from the piston portion 26a towards the outlet 18, to bear on the valve member 22 of the tyre valve 20 when the valve actuator assembly 10 is in the open position. Whilst a substantially fluid tight seal is provided between the body portion 28 and the body portion 28, sliding movement of the piston portion 26a, and hence the entire actuator part 26, within the body portion 28 is permitted. To assist in providing the substantially fluid-tight seal, a first 0-ring 30 is mounted in a generally circumferentially extending groove around the piston portion 26a.

The internal diameter of the body portion 28 decreases in two steps from the portion nearest the inlet 12 to the portion nearest the outlet 18. The piston portion 26a and first 0-ring 30 engage with the largest diameter portion, whilst a second 0-ring 32 mounted around the actuator rod portion 26b of the actuator part 26 engages with the intermediate diameter portion, and provides a substantially fluid tight seal between the actuator rod portion 26b and the body portion 28 whilst permitting sliding of the actuator rod portion 26b in the body portion 28.

The outer diameter of the actuator part 26 decreases in two steps from the piston portion 26a to the actuator rod portion 26b and towards the free end of the actuator rod portion 26b. The second 0-ring 32 is mounted around the smallest outer diameter portion, and when the valve actuator assembly 10 is in the open position, further movement of the actuator part 26 towards the valve 20 is prevented by engagement of the second 0-ring 32 with the smallest diameter portion of the body portion 28.

*The. valve actuator assembly 10 is further provided with resilient biasing means 34 which biases the actuator part 26 to the closed position. In this example, the resilient biasing means 34 is a helical spring which extends around the intermediate diameter portion of the actuator part 26 between the first 30 and second 32 0-rings, a first end of the spring 34 bearing on the piston part 26a and a second end of the spring 34 bearing on the step between the largest and intermediate diameter portions of the boy portion 28.

Movement of the actuating part 26 towards the outlet 18 causes the spring 34 to be compressed, and thus the spring 34 exerts a force on the actuating part 26 biasing it away from the outlet 18. There is an aperture 36 provided in the body portion 26 of the valve actuator assembly 10 which ensures that the chamber in which the spring 34 is located is vented to the atmosphere, and therefore expansion and contraction of this chamber during movement of the actuator part 26 between the closed and open positions is permitted.

The actuator part 26 is provided with a longitudinal bore 38 via which, fluid may pass between the inlet 12 of the valve actuator assembly 10 and the outlet 18.

As the outer diameter of the piston part 26a of the actuator part 26 is greater than the internal diameter of the inlet 12, in order to permit insertion of the actuator part 26 into the body portion 28 of the valve actuator assembly 10, the inlet 12 is not integral with the body portion 28. Instead, during manufacture of the valve actuator assembly 10, the inlet 12 is connected to the body portion 28 by means of a screw thread after the actuator part 26 is placed in the body portion 28. A third 0ring 40 is provided to ensure that the seal between the inlet 12 and the body portion 28 is substantially fluid tight.

It should be appreciated that, in order to overcome the biasing force of the spring 34 and move the actuator part 26 towards the outlet 18 so that it bears on the valve member 22 and moves the valve member 22 out of engagement with the valve seat 24, the force exerted on the piston part 26a by fluid pressure at the inlet 12 must exceed the combination of the biasing force of the spring 34 and the force exerted on the valve member 22 by the fluid pressure in the tyre valve, i.e. the tyre pressure. The diameter of the piston part 26a is selected so that it is larger than the diameter of the valve member 22 and therefore when the fluid pressure at the inlet 12 equals the tyre pressure, the force exerted on the piston part 26a is greater than the force exerted on the valve member 22 by a degree that is sufficient to overcome the biasing force of the spring 34, and move the actuator part 26 to the open position. Moreover, the diameter of the piston part 26a is selected so that it is so much larger than the diameter of the valve member 22 that if the fluid pressure at the inlet 12 drops below the tyre pressure, the force exerted on the piston part 26a is still greater than the force exerted on the valve member 22 by a degree that is sufficient to overcome the biasing force of the spring 34, and retain the actuator part 26 in the open position. Thus, pressurised fluid may be drawn from the tyre to deflate the tyre.

The strength of the spring 34 and the relative diameters of the piston part 26a and the valve member 22 are selected such that the force exerted on the piston part 26a is no longer sufficient to overcome the force exerted on the valve member 22 and the biasing force of the spring 34, when the tyre pressure exceeds the inlet pressure by a predetermined amount. Thus, the actuator part 26 moves from the open position to the closed position when fluid pressure in the tyre valve 20 exceeds the fluid pressure at the tyre valve actuator assembly inlet 12 by the predetermined amount.

In other words, the valve actuator assembly 10 is adapted to permit flow of fluid between the tyre valve 20 and the inlet 12 of the valve actuator assembly both to and from the tyre valve 20 except when the fluid pressure at the tyre valve 20 exceeds the fluid pressure at the valve actuator assembly inlet 12 by a predetermined amount. In this example, this occurs if the pressure differential exceeds 4.3 bar. Thus, if there is sudden loss of pressure at the inlet 12, for example if the tube 14 is severed and vents to atmosphere, rapid and complete deflation of the tyre is prevented.

The same effect may be achieved by means of an electronic control system, and an alternative embodiment of valve actuator assembly 100 is illustrated in Figure 3. This valve actuator assembly 100 also includes an inlet 120 which is connected to a source of pressurised fluid (not shown) by means of a tube 140, and an outlet 180 which is connected to a tyre valve 200 by means of a screw thread arrangement. The tyre valve 200 is of the same configuration as the tyre valve described above with reference to Figures 1 and 2, and includes a valve member 220 which is movable into and out of engagement with a valve seat 240.

The valve actuator assembly 100 also includes an actuator part 260, but in this embodiment of the invention, the actuator part 260 is fixed such that when the valve actuator assembly outlet 180 is connected to the tyre valve 200, the actuator part 260 bears on the valve member 220 of the tyre valve 200 and moves the valve member 220 out of engagement with the valve seat 240. In other words, when this embodiment of the invention is employed, the tyre valve 200 is permanently open to allow flow of fluid into and out of the tyre.

In this case, the valve actuator assembly 100 also includes a first valve member 410 which is movable to engage with a first valve seat 420 substantially to prevent flow of fluid through the inlet 12. The first valve member 410 is moved by means of an electrically or electronically operated actuator 440 such as a piezoelectric element or a solenoid. The actuator 440 is biased to the closed position in which the valve member 410 engages with the valve seat 240, and therefore substantially prevents flow of fluid through the inlet 120, when the supply of electrical power to the actuator is removed, the valve member 410 moving away from the valve seat 420 so that flow of fluid through the inlet 120 is permitted when electrical power is supplied to the actuator 440.

This embodiment of valve actuator assembly 100 also includes an exhaust port 460 which vents to the atmosphere or any other low pressure fluid reservoir, and a second valve member 480 which is movable to engage with a second valve seat 500 substantially to prevent flow of fluid through the exhaust port 460. The second valve member 480 is also moved by means of an electrically or electronically operated actuator 520, such as a piezoelectric element or a solenoid, and engages with the second valve seat 500 when supply of electrical power to the actuator 520 is removed, and moves away from the valve seat 500 so that flow of fluid through the exhaust port 460 is permitted when electrical power is supplied to the actuator 520.

Both the first and second valve members 410, 480 are arranged relative to their respect valve seats 420, 500 such that when the fluid pressure inside the valve actuator assembly 100 exceeds the pressure outside the valve actuator assembly 100, the pressure differential urges the valve members 410, 480 into engagement with their valve seat 420, 500.

The valve actuator assembly 100 further includes a first pressure sensor 540 of conventional construction, which is adapted to provide a signal indicative of the fluid pressure within the valve actuator assembly 100. As the interior of the valve actuator assembly 100 is in open communication with the tyre valve which is maintained in an open configuration, fluid pressure within the valve actuator assembly 100 corresponds to the pressure of fluid in the tyre.

Therefore the pressure sensor 540 provides a signal indicative of the tyre pressure.

A second pressure sensor 560 is provided in the tube 140 connecting the inlet to the source of pressurised fluid, directly adjacent to the inlet 120, and is adapted to provide a signal indicative of the fluid pressure within the tube 140 Operation of the valve actuator assembly 100 is controlled by an electrical or electronic controller (not shown in Figure 3) which is connected to the pressure sensors 540, 560 and which controls operation of the electrical or electronic actuators 440, 520 according to the signal output by the pressure sensors 540, 560. Operation of the valve actuator assembly 100 will be described in more detail below.

Referring to figure 4 there is illustrated a tyre pressure modulation system 50 for a vehicle (not shown) including a source of pressurised fluid 52 connected to a tyre 54. The source of pressurised fluid 52 may include a fluid pump or pressurised fluid reservoir and is controllable, in this example by means of a control valve 56,' to pump fluid into the tyre 54, to reduce the pressure of fluid in the tyre 54 or to maintain the pressure of fluid in the tyre 54 at a desired value.

The control valve 56 is connected between the source of pressurised fluid 52 and the tyre 54, and a controller 58 is provided to control operation of the control valve 56. In this example, the control valve 56 is of the type which can be operated to adopt one of three states, namely an inflate state in which flow of fluid through the control valve 56 between the source of pressurised fluid 52 and the tyre 54 is permitted, a deflate state in which flow of pressurised fluid out of the tyre 54 to an exhaust port 57 provided in the control valve 56 is permitted, and a hold state in which flow of pressurised fluid through the control valve 56 is substantially prevented. A suitable configuration of control valve is described in our International patent application W003/031855.

The system 50 also includes a pressure sensor 60 which is adapted to sense the pressure of fluid within the tyre 54 and transmit a signal indicative of the tyre pressure to the controller 58, the controller 58 being adapted to control operation of the control valve 56 in accordance with the signal supplied by the pressure sensor 60 as will be described in more detail below.

The pressure sensor 60 may be mounted within the tyre and connected to the controller 58 via a radio link. In this embodiment, however, the pressure sensor 60 is mounted in the conduit between the control valve 56 and the valve actuator assembly 10. As will be appreciated, under normal circumstances, the conduit between the control valve 56 and the valve actuator assembly is in open fluid communication with the interior of the tyre because the Schrader valve is retained in an open position. Thus, the pressure sensor 60 will, under normal operating conditions provide an indication of the pressure within the tyre.

The controller 58 is a conventional electronic processor and is provided with a memory in which is stored data specifying an ideal tyre pressure over a range of tyre conditions. Every tyre has an ideal pressure for optimum wear and safety performance which depends on local conditions such as vehicle speed, temperature and vehicle loading, and such data can be obtained from the manufacturer of a tyre. Alternatively, the controller 58 may be programmed with an algorithm which enables it to calculate the ideal tyre pressure using one or more inputs representing the prevailing conditions.

In this example, the system includes a temperature sensor 62 which is adapted to sense the temperature of or within the tyre and transmit a signal indicative of the tyre temperature to the controller 58, a load sensor 64 which is adapted to sense the weight carried by the tyre 54, and transmit a signal indicative of the weight to the controller 58, and a vehicle speed determining device 66 which is adapted to sense or calculate the speed of the vehicle and transmit a signal indicative of the vehicle speed to the controller 58. The data stored in the controller memory specifies the ideal tyre pressure over a range of tyre temperatures, loads and speeds, and the controller 58 is programmed to determine the ideal tyre pressure specified for the prevailing tyre temperature, load and speed.

It will be appreciated that the system need not include all of the above measuring devices 62, 64, 66, and the data stored in the controller memory may specify the ideal tyre pressure over a range of alternative conditions.

It should also be appreciated that the system need not include the measuring devices 62, 64, 66 themselves, as the necessary inputs temperature, speed, load etc. may be obtained from other vehicle control systems via an appropriate data bus. For example, the vehicle speed may be determined from a wheel speed signal generated in a vehicle ABS system. Similarly, the vehicle loading may be determined from the load measurement in a brake apportioning algorithm.

Moreover, the inputs may be determined directly or indirectly. For example, rather than providing aload sensor 64, the vehicle loading may bedetermined using a measurement of engine torque and wheel slip, or the vehicle speed may be determined from the rotational speed of the wheels and wheel diameter.

The tyre temperature may be determined by means of a temperature sensor mounted in or on the tyre itself. Alternatively, the tyre temperature may be measuring using a temperature sensor integral with or adjacent the pressure sensor 60. In the latter case, in order to measure the tyre temperature, the control valve 56 is operated to allow a small volume of fluid out of the tyre, the temperature of the fluid from the tyre being sensed as it passes over the temperature sensor in or adjacent the pressure sensor 60. Once the tyre temperature has been determined, the control valve 56 is operated to re- inflate the tyre to the desire tyre pressure. It will be appreciated that this may not be a satisfactory method of measuring the tyre temperature in a very low profile vehicle, but in a high profile vehicle such as a truck, the necessary slight deflation of the tyres required to measure the tyre temperature in this way can readily be accommodated without adversely affecting the vehicle operation.

The controller 58 is adapted to determine the actual tyre pressure from the signal supplied by the pressure sensor 60, access the data in the memory to determine the ideal tyre pressure specified for the prevailing tyre conditions, and control operation of the control valve 56 to bring the actual tyre pressure closer to the ideal tyre pressure. Thus, if the controller 58 determines that the actual tyre pressure is lower than the ideal tyre pressure, the controller 58 sends appropriate signals to the control valve 56 to bring the control valve 56 into the inflate state so that pressurised fluid is pumped into the tyre.

Alternatively, if the controller 58 determines that the actual tyre pressure is higher than the ideal tyre pressure, the controller 58 sends appropriate signals to the control valve 56 to bring the control valve 56 into the deflate state so that pressurised fluid is removed from the tyre 54 in a controlled manner.

When the signal from the pressure sensor 60 indicates that the actual tyre pressure is at or sufficiently close to the ideal tyre pressure, the controller 58 sends a signal to the control valve 56 to bring the control valve 56 to the hold state.

Every tyre has an ideal pressure for optimum wear and safety performance which depends on local conditions such as vehicle speed, temperature and vehicle loading. By providing a tyre pressure modulation system 50 which allows for inflation and deflation of a tyre, it is possible to ensure that the tyre pressure is closer to its ideal pressure than would be possible if no modulation or if a modulation system accommodating tyre inflation only were provided.

It will be appreciated that the control valve 56 may be in open fluid communication with the tyre 54. There is, however, a risk that the conduit between the tyre 54 and control valve 56 is severed or otherwise damaged, and if this occurs, free flow of fluid out of the tyre is permitted, and rapid and complete deflation of the tyre would occur. Obviously this has very significant safety implications, as rapid deflation of a tyre 54 whilst the vehicle is moving at significant speeds could result in a driver losing control of the vehicle and a serious accident occurring. The control valve 56 may advantageously be remote from the tyre 54, for example it may be located adjacent a central fluid pump or reservoir of pressurised fluid and connected to the tyre 54 by means of a long conduit. The risk of damage to the conduit, particularly the portion of the conduit at the vehicle wheel, would be significantly increased in this case.

In order to avoid this problem, in this example, the system 50 further includes a safety valve assembly 68 which is adapted substantially to prevent flow of fluid out of the tyre 54 if the fluid pressure in the tyre exceeds the fluid pressure at the safety valve assembly inlet by a pre-determined amount, such as would occur if the conduit between the control valve 56 and tyre 54 is damaged. In this example, the safety valve assembly 68 includes a valve actuator assembly 10 and tyre valve 20 as described in relation to Figures 1 and 2.

As described above, the valve actuator assembly 10 is adapted to bring the valve member 22 of the tyre valve 20 into engagement with its valve seat 24 to prevent flow of fluid into or out of the tyre when the pressure of fluid in the tyre 54 exceeds the pressure of fluid at the valve actuator assembly inlet 12 by a predetermined amount. Thus, by virtue of the provision of the safety valve assembly 68, controlled deflation of the tyre 54 is permitted, but if the connection between the source of pressurised fluid 53 and the tyre 54 is severed, rapid deflation of the tyre 54 is prevented.

Where the source of pressurised fluid includes a fluid pump, the control valve 56 may be omitted from the system 50, and the controller 58 adapted to control operation of the pump to increase, decrease or maintain the pressure of pumped fluid in the tube 14 according to whether it is desired to increase, decrease or maintain the pressure of fluid in the tyre 54.

An alternative tyre pressure modulation system 50' is illustrated in Figure 5.

This system 50' also includes a source of pressurised fluid 52, which is connected to a tyre 54 via a safety valve assembly 68', and which is controllable using a controller 58' to pump fluid into the tyre 54, to reduce the pressure of fluid in the tyre 54 and to maintain the pressure of fluid in the tyre 54 at a desired value. In this example, however, such control is achieved by means of the safety valve assembly 68', rather than by means of a separate control valve 56.

In this example, the safety valve assembly 68' comprises the valve actuator assembly 100 and tyre valve 200 described above with reference to Figure 3.

The controller 58' receives signals from the two pressure sensors 540, 560 in addition to signals from the temperature sensor 62, load sensor 64, and vehicle speed determining device 66. If the controller 58 determines from the signal received from the first pressure sensor 540 that the actual tyre pressure is lower than the ideal tyre pressure, the controller 58 sends an apprOpriate signal to the first actuator 440 to move the first valve member 410 out of engagement with the first valve seat 420 so that pressurised fluid from the pressurised fluid source 52 is permitted to flow through the valve actuator assembly inlet 120 into the tyre 54. Alternatively, if the controller 58' determines that the actual tyre pressure is higher than the ideal tyre pressure, the controller 58 sends an appropriate signal to the second actuator 520 to move the second valve member 480 out of engagement with the second valve seat 500 so that pressurised fluid is permitted to flow through the exhaust port 460 and out of the tyre 54 in a controlled manner. When the signal from the pressure sensor 540 indicates that the actual tyre pressure is at or sufficiently close to the ideal tyre pressure, the controller 58' cuts electrical power supply to both actuators 440, 520 so that both the inlet 120 and exhaust port 460 are closed and flow of fluid into or out of the tyre 54 is substantially prevented.

It will be appreciated that the controller 58' is programmed such that the first and second valve members 410, 480 are never simultaneously out of engagement with their respective valve seats 420, 500.

The controller 58' is also programmed to compare the signals from both the pressure sensors 540, 560, and, if the pressure in the tube 140 adjacent the inlet 120 exceeds the tyre pressure by a predetermined amount, cut power supply to both actuators 440, 520 so that both the inlet 120 and exhaust port 460 are closed and flow of fluid into or out of the tyre 54 is substantially prevented. Thus, as above, by virtue of the provision of the safety valve assembly 68, controlled deflation of the tyre 54 is permitted, but if the connection between the source of pressurised fluid 53 and the tyre 54 is severed, rapid deflation of the tyre 54 is prevented.

In this embodiment of the second aspect of the invention, it will be appreciated that, as removal of fluid from the tyre 54 takes place via the exhaust port 460 in the valve actuator assembly 100, flow of fluid along the tube 140 from the inlet 120 towards the source of pressurised fluid 52 is not required. Thus, the second pressure sensor 560 may be replaced a conventional one-way check valve which is adapted to close the tube 140 if the pressure at the inlet 120 side of the check valve exceeds the pressure at the source of pressurised fluid 52 side of the check valve. Thus, rather than operating electronically by comparing the readings of two pressure sensors 540, 560, rapid deflation of the tyre 54 is prevented by purely mechanical means.

In this embodiment of the second aspect of the invention, if the temperature sensor 62 is not mounted in the tyre itself, and connected to the controller 58' via a radio link, it may be located in or adjacent the first or second pressure sensor 540, 560. If the temperature sensor 62 is located in or adjacent the second pressure sensor 560, slight deflation of the tyre would be required so that fluid from the tyre passes over the temperature sensor, thus permitting the tyre temperature to be measured.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process. for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A valve actuator assembly including a inlet which is adapted to be connected to a source of pressurised fluid, an outlet which is adapted to be connected to a tyre valve, and an actuator part which, when the outlet is connected to a tyre valve may bear on a valve member of the tyre valve wherein the valve actuator assembly is adapted to permit flow of fluid through the outlet both to and from the tyre valve except when the fluid pressure at the tyre valve exceeds the fluid pressure at the tyre valve actuator assembly inlet by a predetermined amount.

2. A valve actuator assembly according to claim I wherein the actuator part is movable between an open position in which it bears on the valve member of a valve to which the outlet of the valve actuator assembly is connected to bring the valve member out of engagement with its valve seat, and a closed position in which the actuator part retracts and the valve member is permitted to engage with the valve seat.

3. A valve actuator assembly according to claim 2 wherein the actuator part moves from the open position to the closed position when fluid pressure in the valve exceeds the fluid pressure at the tyre valve actuator assembly inlet by a predetermined amount.

4. A valve actuator assembly according to claim 2 or 3 wherein the actuator is a piston mounted in a cylinder which extends between the inlet and the outlet of the valve actuator.

5. A valve actuator assembly according to any one of claims 2 to 4 wherein the tyre valve actuator assembly is provided with resilient biasing means which biases the actuator part to the closed position.

6. A valve actuator assembly according to claim I wherein the actuator part is fixed such that when the tyre valve actuator assembly outlet is connected to a tyre valve, the actuator part bears on the valve member of the tyre valve and moves the valve member out of engagement with its valve seat.

7. A valve actuator assembly according to claim 6 wherein the tyre valve actuator assembly includes a valve member which is movable to engage with a valve seat substantially to prevent flow of fluid from the inlet to the outlet of the valve actuator assembly.

8. A valve actuator assembly according to claim 7 wherein the valve member moves to engage with the valve seat when fluid pressure in the valve exceeds the fluid pressure at the valve actuator assembly inlet by a predetermined amount.

9. A valve actuator assembly according to claim 7 or 8 wherein the valve member is moved by means of an electrically or electronically operated actuator and is adapted to engage with the valve seat when supply of electrical power to the actuator is removed, and to move away from the valve seat so that flow of fluid between the inlet and outlet of the valve actuator assembly is permitted, when electrical power is supplied to the actuator.

10. A valve actuator assembly according to any one of claims 6 to 9 wherein the valve actuator assembly further includes an exhaust port which vents to the atmosphere or any other low pressure fluid reservoir, and a second valve member which is movable to engage with a second valve seat substantially to prevent flow of fluid through the exhaust port.

11. A valve actuator assembly according to claim 10 wherein the second valve member is moved by means of an electrically or electronically operated actuator and engage with the second valve seat when supply of electrical power to the actuator is removed, and move away from the valve seat so that flow of fluid through the exhaust port is permitted, when electrical power is supplied to the actuator.

12. A valve actuator assembly according to claim 6 wherein the valve actuator assembly includes a pressure sensor which is adapted to provide a signal indicative of the tyre fluid pressure.

13. A valve actuator assembly according to claim 12 and claims 9 or 11 wherein the valve actuator assembly includes an electrical or electronic controller which controls operation of the or each electrical or electronic actuator according to the signal output of the pressure sensor.

14. A tyre pressure modulation system for a vehicle including a source of pressurised fluid connected to a tyre and a controller, the source of pressurised fluid being controllable by the controller to pump fluid into the tyre, to reduce the pressure of fluid in the tyre and to maintain the pressure of fluid in the tyre at a desired value.

15. A tyre pressure modulation system according to claim 14 wherein the source of pressurised fluid includes a fluid pump or pressurised fluid reservoir.

16. A tyre pressure modulation system according to claim 15 wherein the source of pressurised fluid further includes a control valve which is connected between the pump or reservoir and a tyre, the controller controlling operation of the control valve, the control valve being operable to adopt one of three states, namely an inflate state in which flow of pressurised fluid from the source of pressurised fluid into the tyre is permitted, a deflate state in which flow of pressurised fluid out of the tyre to an exhaust port is permitted, and a hold state in which flow of pressurised fluid into or out of the tyre is substantially prevented.

17. A tyre pressure modulation system according to claim 15 wherein the source of pressurised fluid includes a fluid pump, and the controller controls operation of the pump to increase, decrease or maintain the pressure of pumped fluid according to whether it is desired to increase, decrease c maintain the pressure of fluid in the tyre.

18. A tyre pressure modulation system according to any one of claims 14 to 17 wherein the system includes a pressure sensor which is adapted to sense the pressure of fluid within the tyre and transmit a signal indicative of the tyre pressure to the controller, the controller being adapted to control operation supply of fluid from the source of pressurised fluid to the tyre in accordance with the signal supplied by the pressure sensor.

19. A tyre pressure modulation system according to claim 18 wherein the controller is provided with a memory in which is stored data specifying an ideal tyre pressure over a range of tyre conditions, and the controller is adapted to determine the actual tyre pressure from the signal supplied by the pressure sensor, access the data in the memory to determine the ideal tyre pressure specified for the prevailing tyre conditions, and control operation of the control valve to bring the actual tyre pressure closer to the ideal tyre pressure.

20. A tyre pressure modulation system according to claim 19 wherein the system further includes a temperature sensor which is adapted to sense the temperature of or within the tyre and transmit a signal indicative of the tyre temperature to the controller, the data in the controller memory specifying the ideal tyre pressure over a range of tyre temperatures, and the controller being adapted to determine the ideal tyre pressure specified for the prevailing tyre temperature.

21. A tyre pressure modulation system according to claim 20 wherein the temperature sensor is connected between the source of pressurised fluid and the tyre, so that measurement of the tyre temperature may be achieved by deflating the tyre by a limited degree such that fluid from the tyre passes over the temperature sensor, thus enabling the temperature sensor to determine the temperature of the fluid from the tyre.

22. A tyre pressure modulation system according to claim 19, 20 or 21 wherein the system further includes a load sensor which is adapted to sense the weight carried by the tyre, and transmit a signal indicative of the weight to the controller, the data in the controller memory specifying the ideal tyre pressure over a range of tyre load weights, and the controller being adapted to determine the ideal tyre pressure specified for the prevailing tyre load weight.

23. A tyre pressure modulation system according to any one of claims 19 to 22 wherein the system further includes a vehicle speed determining device which is adapted to sense or calculate the speed of the vehicle and transmit a signal indicative of the vehicle speed to the controller, the data in the controller memory specifying the ideal tyre pressure over a range of vehicle speeds, and the controller being adapted to determine the ideal tyre pressure specified for the prevailing vehicle speed.

24. A tyre pressure modulation system according to any one of claims 14 to 23 wherein the system further includes a safety valve assembly which has an inlet port which is connected to the source of pressurised fluid and an outlet which is connected to the tyre, the safety valve assembly being adapted to substantially prevent flow of fluid out of the tyre if the pressure of fluid at the safety valve assembly outlet exceeds the pressure of fluid at the safety valve assembly inlet by a predetermined amount.

25. A tyre pressure modulation system according to claim 24 wherein the safety valve assembly includes a valve member which is movable to engage with a valve seat substantially to prevent flow of fluid out of the tyre and a valve actuator in accordance with any one of claims 1 to 13.

26. A valve actuator assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

27. A tyre pressure modulation system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

28. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.