GB2538971A

GB2538971A - Central tyre inflation system and method

Info

Publication number: GB2538971A
Application number: GB1509437.8A
Authority: GB
Inventors: King Paul
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-06-01
Filing date: 2015-06-01
Publication date: 2016-12-07
Anticipated expiration: 2035-06-01
Also published as: GB2538971B; GB201509437D0

Abstract

A controller (15, Fig.1B) for controlling a pneumatic control valve (PCV, Fig.1A) in a central tyre inflation system (CTIS) where the controller includes an electronic processor having an electrical input for receiving a supply-side pressure signal and the electronic processor is electrically coupled an electronic memory device having instructions stored therein; where the electronic processor is configured to control a first control valve (VINSS) to generate a pneumatic control signal for changing an operating state of a pneumatic control valve and the electronic processor also monitors the supply-side pressure signal and identifies a change in the operating state of the pneumatic control valve in dependence on a change in the supply-side pressure; wherein the electronic processor is configured to output a first valve close signal upon determining that the pneumatic control valve has changed operating state. The present disclosure also relates to a CTIS incorporating a controller; to a vehicle comprising the CTIS; and to a method of controlling a pneumatic control valve.

Description

CENTRAL TYRE INFLATION SYSTEM AND METHOD

TECHNICAL FIELD

The present disclosure relates to a central tyre inflation system (CTIS) and to a related method. More particularly, but not exclusively, the present disclosure relates to a controller for controlling operation of a pneumatic control valve in a CTIS.

BACKGROUND

A CTIS typically comprises a compressed air source located on-board the vehicle and connected to one or more tyres. Tyre pressure can therefore be adjusted by operating the CTIS. The CTIS delivers compressed air to tyre supply lines. In some examples, the supply lines are integrated into the vehicle axles. Various valves are provided in the CTIS to control flow of compressed air. In one example of a CTIS system to avoid the need to include an additional electrical control to each wheel, the valve at each wheel controlling flow of air into and out of the tyre may be a pneumatically controlled valve, i.e. the state of the valve is changed by a pneumatic signal as opposed to a n electrical signal.

The present invention relates to a revised control strategy for controlling operation of the pneumatic controlled valve.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a controller for controlling a pneumatic control valve; to a central tyre inflation system comprising a controller; to a vehicle; and to a related method.

According to a further aspect of the present invention there is provided a controller for controlling a pneumatic control valve, the controller comprising: an electronic processor having an electrical input for receiving a supply-side pressure signal; and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein; the electronic processor being configured to control a first control valve to generate a pneumatic control signal for changing an operating state of a pneumatic control valve, the electronic processor being configured to output a first valve open signal to open the first control valve to initiate the pneumatic control signal, and to output a first valve close signal to close the first control valve to terminate said pneumatic control signal; wherein the electronic processor is configured to monitor the supply-side pressure signal and to identify a change in the operating state of the pneumatic control valve in dependence on a change in the supply-side pressure; the electronic processor being configured to output said first valve close signal upon determining that the pneumatic control valve has changed operating state. At least in certain embodiments, the present invention may reduce the duration of the pneumatic control signal required to actuate the pneumatic control valve.

The first valve close signal can be output if the change in the operating state of the pneumatic control valve is not detected within a predefined time period. The predefined time period can, for example, be defined with reference to output of the first valve open signal.

By controlling the first control valve to initiate and terminate the pneumatic control signal as described herein, the electronic processor can reduce the duration of the pneumatic control signal. The supply of compressed air required to generate the pneumatic control signal can be reduced. In certain implementations, the pneumatic control signal can be generated by supplying compressed air from a reservoir. By reducing the duration of the pneumatic control signal, the reduction in pressure in the reservoir can be reduced. Thus, the need to operate a compressor to replenish the reservoir can be reduced.

The first control valve can comprise an inlet valve for controlling the supply of compressed air from said first compressed air source. For example, the inlet valve can control the supply of compressed air to a gallery in communication with a supply line connected to the pneumatic control valve.

The change in the supply-side pressure can comprise one or more of the following: a change which is greater than or equal to a defined threshold; a change which is greater than or equal to a defined proportional change; and a change in a rate of change of the supply-side pressure.

The electronic processor can be configured to detect the change in the supply-side pressure within a prescribed time period.

The pneumatic control valve can change from a closed state to an open state. The pneumatic control valve can be latched in said closed state and/or said open state. The pneumatic control signal can unlatch the pneumatic control valve. The electronic processor can be configured to identify when the pneumatic control valve changes operating state in dependence on detection of a decrease in the supply-side pressure. The decrease in the supply-side pressure can be measured with respect to a pressure peak. A decrease in the supply-side pressure can indicate that the pneumatic control valve has changed from a closed state to an open state. Alternatively, the electronic processor can be configured to identify when the pneumatic control valve changes operating state in dependence on detection of an increase in the supply-side pressure. The increase in the supply-side pressure can be measured with respect to a pressure trough. An increase in the supply-side pressure can indicate that the pneumatic control valve has changed from an open state to a closed state.

The electronic processor can be configured to control a second compressed air source in dependence on identification of the change in the operating state of the pneumatic control valve. For example, the second compressed air source can be controlled to inflate a tyre.

The pneumatic control valves can be controlled individually. The controller can be configured to control an operating state of a plurality of said pneumatic control valves sequentially.

According to a further aspect of the present invention there is provided a central tyre inflation system (CTIS) for a vehicle, the CTIS comprising: a supply line for supplying compressed air to a tyre; a pneumatic control valve operable in at least first and second operating states to control the supply of compressed air from the supply line to the tyre; a first control valve connected to a first compressed air source; and a controller having an electronic processor as claimed in any one of the preceding 25 claims wherein the electronic processor is configured to control the first control valve to generate the pneumatic control signal for changing the operating state of a pneumatic control valve, the electronic processor being configured to output a first valve open signal to open the first control valve to initiate the pneumatic control signal; and to output a first valve close signal to the first control valve to terminate the pneumatic control signal; wherein the electronic processor is configured to output the first valve close signal upon determining that the pneumatic control valve has changed operating state.

The CTIS can comprise a pressure sensor for generating said supply-side pressure signal.

The pressure sensor can be disposed in the supply line; or in a gallery in fluid communication with the supply line. The CTIS can comprise more than one pressure sensor. For example, a separate pressure sensor can be provided in each tyre supply line.

The pneumatic control valve can be in an open state in said first operating state and in a closed state in said second operating state. Alternatively, the pneumatic control valve can be in a closed state in said first operating state and in an open state in said second operating state. The pneumatic control valve can be latched in said first operating state and/or said second operating state.

The CTIS can comprise a second compressed air source. The CTIS can comprise a second control valve connected to the second compressed air source. The electronic processor can be configured to output a second valve open signal to open the second control valve to supply compressed air from the second compressed air source to the tyre. The second valve open signal can be output in dependence on identification of the change from said first operating state to said second operating state.

The first compressed air source can supply compressed air to control said at least one pneumatic control valve. The CTIS can comprise a second compressed air source for supplying compressed air to inflate the tyre. At least in certain embodiments, the first and second compressed air sources can have different operating parameters suitable for performing the respective functions of inflating the tyre(s) and generating the pneumatic control signal. The first compressed air source can operate at a higher pressure than the second compressed air source. The second compressed air source can have a higher flow rate than the first compressed air source. The first compressed air source can comprise a reservoir which can be charged by a first compressor. The second compressed air source can comprise a second compressor for supplying compressed air to inflate the tyres of the vehicle. The first and second compressors may be one and the same compressor.

The CTIS can comprise a plurality of said pneumatic control valves each configured to control the supply of compressed air to a respective tyre. The controller can be configured to control two or more of said pneumatic control valves simultaneously; or to control two or more of said pneumatic control valves sequentially.

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

According to a yet further aspect of the present invention there is provided a method of controlling an operating state of a pneumatic control valve disposed in a supply line, the method comprising: generating a pneumatic control signal for changing an operating state of the pneumatic control valve; monitoring a supply-side pressure; and determining that the pneumatic control valve has changed operating state in dependence on detection of a change in the supply-side pressure; wherein the pneumatic control signal is terminated upon determining that the pneumatic control valve has changed operating state.

The method can comprise opening the first control valve to initiate the pneumatic control signal. The method can comprise closing the first control valve to terminate said pneumatic control signal. The first control valve can be closed upon determining that the pneumatic control valve has changed operating state. Alternatively, or in addition, the method can comprise closing the first control valve if the change in the operating state of the pneumatic control valve is not detected within a predefined time period.

The change in the supply-side pressure can comprise one or more of the following: a change which is greater than or equal to a defined threshold; a change which is greater than or equal to a defined proportional change; and a change in a rate of change of the supply-side pressure. The method can comprise detecting the change in the supply-side pressure within a prescribed time period.

The method can comprise identifying a change in the operating state of the pneumatic control valve in dependence on detection of a decrease in the supply-side pressure.

The method can comprise performing the method for a plurality of said pneumatic control valves. The method can comprise controlling a plurality of said pneumatic control valves sequentially.

According to a yet further aspect of the present invention there is provided a non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more electronic processors to carry out the method described herein.

As used throughout the application, the singular form of "a", "an" and "the" may include plural referents unless the context clearly dictates otherwise.

References herein to a "supply side" of the pneumatic control valve are to the side of the pneumatic control valve closest to the pressure source which supplies the compressed air to generate the pneumatic control signal. The supply side could also be referred to as a vehicle side (as opposed to a wheel side) of the pneumatic control valve.

For the avoidance of doubt, references herein to a central tyre inflation system (CTIS) are to an apparatus for controlling the pressure of one or more tyres.

Any controller or controllers described herein may suitably comprise a control unit or computational device having one or more electronic processors. Thus the system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term "controller" or "control unit" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide any stated control functionality. To configure a controller, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said controller to be executed on said computational device. A first controller may be implemented in software run on one or more processors. One or more other controllers may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller. Other suitable arrangements may also be used.

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

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying Figures, in which: Figure 1A is a schematic representation of a central tyre inflation system (CTIS) according to an embodiment of the invention; Figure 1B is a schematic representation of a valve arrangement of the CTIS shown in Figure 1A; Figure 1C is a vehicle system boundary diagram representing the CTIS shown in Figures 1A and 1B; Figures 2A-D illustrate operation of a pneumatic control valve incorporated into the CTIS; Figure 3 shows a first graph for operation of a pneumatic control valve in dependence on a pneumatic control signal having a fixed duration; Figure 4 shows a second graph for operation of a pneumatic control valve in dependence on a pneumatic control signal generated in dependence on a detected pressure change; Figure 5 shows a third graph for operation of a pneumatic control valve in dependence on a pneumatic control signal generated in dependence on a detected pressure change; and Figure 6 shows a fourth graph illustrating operation of a pneumatic control valve in dependence on a pneumatic control signal generated in dependence on a detected pressure change.

DETAILED DESCRIPTION OF AN EMBODIMENT

In the following description and in the drawings, reference letters are used to collectively or un-specifically identify equivalent or essentially equivalent components. Where necessary, a specific component in a collection of equivalent or essentially equivalent components is identified by suffixing a reference letter in subscript format.

A central tyre inflation system (CTIS) 1 in accordance with an embodiment of the present invention will now be described with reference to the accompanying Figures. As shown schematically in Figure 1A, the CTIS 1 is installed in a vehicle VH having four wheels W each having a tyre T mounted on a wheel hub (not shown). The wheels W (and the tyres T) are identified herein based on their relative position on the vehicle VH, namely: front left (FL), front right (FR), rear left (RL) and rear right (RR). This nomenclature is employed to identify the components of the CTIS 1 associated with the respective tyres T. The front tyres TFR, TFL are mounted on a front axle and the rear wheels TRR, TRH are mounted on a rear axle of the vehicle.

The CTIS 1 comprises four pneumatic control valves PCV fixedly mounted to the wheel hubs and arranged to control the supply of compressed air to and from a respective tyre cavity. The pneumatic control valves PCV are pneumatically operated in response to changes in the pressure in the associated tyre supply line TSL. Specifically, the pneumatic control valves PCV are operable to cycle sequentially (i.e. to toggle) between an open state and a closed state in dependence on application of a pressure exceeding a valve activation pressure. The pneumatic control valves PCV are stable in both the open and closed state via a latching mechanism, i.e. they can each be considered as a pressure actuated bi-stable valve. Herein the application of air at a pressure and time sufficient to switch the valve from one state to its other state, i.e. from open to closed or from closed to open, is referred to as "toggling" the valve, and the application of said air in this manner is referred to as a high pressure (pneumatic) control signal. A suitable pneumatic control valve PCV for this application is available in the form of a pneumatic latching valve from Norgren Limited of PO Box 22, Eastern Avenue, Lichfield, Staffordshire, WS13 6SB, United Kingdom. It will be appreciated that each pneumatic control valve could have additional operating states which are cycled through sequentially in dependence on said pneumatic control signal.

The CTIS 1 further comprises a valve block 3 for controlling the supply of compressed air to each of the pneumatic control valves PCV. The valve block 3 is fluidly coupled to a first compressed air source 5 and a second compressed air source 7. The first compressed air source 5 provides air at a high flow rate and low pressure (HF/LP); and the second compressed air source 7 is operable to provide air at a higher pressure. As described herein, the first and second compressed air sources 5, 7 are distinct from each other. In the present embodiment, the first compressed air source 5 comprises a first compressor 9; and the second compressed air source 7 comprises a reservoir 13 supplied by the first compressor 9. Alternatively, the first and second compressed air sources 5, 7 can comprise separate compressors which are operable independently of each other. By way of illustration, a second compressor 11 for charging the reservoir 13 is shown in phantom in Figure 1C.

The activation pressure of each said pneumatic control valve PCV is below the pressure of the second compressed air source 7. In this manner the second compressed air source 7 can be applied for a short duration to switch one or more selected pneumatic control valves PCV from a closed state to an open state, and vice versa.

An ECU 15 is provided to control operation of the CTIS 1. Specifically, the ECU 15 is configured to control operation of the valve block 3 and the first compressor 9. The ECU 15 comprises at least one electronic processor which is electrically coupled to an electronic memory device having instructions stored thereon.

A tyre supply line TSL is provided to supply compressed air from the valve block 3 to each tyre T. Specifically, the CTIS 1 comprises a front left tyre supply line TSLFL, a front right tyre supply line TSLFR, a rear left tyre supply line TSLRL and a rear right tyre supply line TSLRR. The pneumatic control valves PCV are provided at the ends of the tyre supply lines TSL to control the supply of compressed air to the respective tyres T. A section of each tyre supply line TSL extends along the respective vehicle axles to supply compressed air to the pneumatic control valves PCV mounted in each wheel hub. A rotary air coupling (RAC) is provided in each tyre supply line TSL to provide a fluid coupling to supply compressed air from the valve block 3 to the section of each tyre supply line TSL disposed in the vehicle axle.

The valve block 3 will now be described in more detail with reference to Figure 1B. The valve block 3 comprises first and second inlet valves VINc,Nss. The first inlet valve VINO operatively controls the supply of compressed air from the first compressed air source 5 which is connected to the valve block 3 by a first supply line 17. The second inlet valve ViNss operatively controls the supply of compressed air from the second compressed air source 7 which is connected to the valve block 3 by a second supply line 19.

The valve block 3 comprises four outlet valves (collectively referenced as Vo) for controlling the supply of compressed air to the respective tyre supply lines TSL. In particular, the valve block 3 comprises: a front left outlet valve VFLo for controlling the supply of compressed air to the front left tyre supply line TSLFL; a rear left outlet valve VRLo for controlling the supply of compressed air to the rear left tyre supply line TSLRL; a front right outlet valve VFRO for controlling the supply of compressed air to the front right tyre supply line TSLFR; and a rear right outlet valve VRRO for controlling the supply of compressed air to the rear right air supply line TSLRR. The outlet valves Vo are operable independently of each other to enable the selective supply of compressed air to one or more of the tyre supply lines TSL.

The valve block 3 also comprises first and second exhaust valves E1, E2 coupled to an exhaust line 21. The exhaust line 21 terminates with an exhaust outlet 23 which is open to atmosphere to vent exhaust air from the CTIS 1. The first and second exhaust valves E 1, E2 are operable to control the flow of exhaust air to the exhaust line 21, for example during tyre deflation. A safety valve VsAFE is also provided in the valve block 3. The safety valve VsAFE is operable to vent to atmosphere any excess air which might accumulate in the valve block 3 due, for example, to malfunction of any of the components of the CTIS 1.

The inlet valves VINO, VINSS, the outlet valves Vo and the exhaust valves El, E2 are solenoid valves having a normally-closed configuration (illustrated by a filled symbol in Figure 1B).

The inlet valves VINO, ViNss, the outlet valves Vo and the exhaust valves E1, E2 are operable independently of each other and are actuated by control signals received from the ECU 15. The safety valve VSAFE is also a solenoid valve but has a normally-open configuration (illustrated by an open symbol in Figure 1B). The safety valve VSAFE is closed by receiving a control signal from the ECU 15.

The first and second compressed air sources 5, 7 are controlled, directly or indirectly, by the ECU 15. The first compressor 9 comprises an electric motor 27 and has an operating pressure of approximately 9 bar. A dryer unit 29 is coupled to the first compressor 9 partway through a first compressed air supply line 31 connecting the first compressor 9 to the valve block 3. The second compressed air source 7 comprises the reservoir 13 which is connected to, and charged by the first compressor 9. In use, the operating pressure of the reservoir 13 can be up to 20 bar.

A fluid gallery 33 is provided in the valve block 3. The gallery 33 is open to each of: the outlet valves Vo, the inlet valves VINO, VINSS, the exhaust valves El, E2, and the safety valve VSAFE. The valve block 3 houses a pressure sensor 35 arranged to measure the pressure in a gallery 33. The gallery 33 can be selectively placed in fluid communication with one or more of the tyre supply lines TSL by opening one or more of the outlet valves Vo. In the present embodiment, the pressure sensor 35 measures the pressure in the individual tyre supply lines TSL by placing the tyre supply line TSL in fluid communication with the gallery 33. By opening the pneumatic control valve PCV associated with that tyre supply line TSL, the pressure sensor 35 can measure the air pressure in the tyre cavity (hereinafter referred to, for simplicity, as the tyre pressure). The pressure sensor 35 measures the pressure on a supply-side of the pneumatic control valve PCV (i.e. the pressure on the side in communication with the second compressed air source 10, rather than the tyre T). The pressure sensor 35 outputs a supply-side pressure signal to the ECU 15.

The gallery 33 receives compressed air from each of said first and second compressed air sources 9, 11 via the respective first and second inlet valves ViNc, Wigs. The first inlet valve ViNc is operable to control the supply of compressed air from the first compressed air source 5 to the gallery 33. The second inlet valve VINSS is operable to control the supply of compressed air from the second compressed air source 7 to the gallery 33. In use, the first compressed air source 5 is the primary source of compressed air for inflating the tyres T. One or more of the tyre supply lines TSL can be placed in communication with the first compressed air source 5 by opening the first inlet valve Virys and the appropriate outlet valves Vo.

The second compressed air source 7 provides a higher pressure supply which is controlled by the second inlet valve Viryss to generate a pneumatic control signal as described above for controlling operation of one or more of said pneumatic control valves PCV to tyres for which the respective outlet valves Vo are open, i.e. to toggle the valves from one stable state to the other stable state. Specifically, the second inlet valve Viryss is operated to generate the pneumatic control signal to cycle the pneumatic control valve(s) PCV in communication with the gallery 33. The pneumatic control valve(s) PCV cycle through their respective operating states in response to the pneumatic control signal and, therefore, can be operated to control the supply of compressed air to and from the respective tyres T. By opening the pneumatic control valve(s) PCV, one or more of the tyres T can be placed in communication with the respective tyre supply lines TSL.

The valve block 3 can be operated to place the tyre supply lines TSL in communication with the first compressed air source 5 to inflate one or more of said tyres T; or in communication with the exhaust line 21 to deflate one or more of said tyres T. Furthermore, the valve block 3 can be operated to measure the pressure of the air in the tyres T. The CTIS 1 according to the present embodiment uses a single pressure sensor 35 for measuring the pressure in the gallery 33. It will be appreciated that more than one pressure sensor 35 could be provided. For example, a pressure sensor 35 could be provided in communication with each tyre supply line TSL. Equally, a separate valve block 3 could be provided for each tyre T or for each axle.

The ECU 15 is programmed to control the overall operation of the CTIS 1. Figure 1C illustrates the relationship between the main mechanical components of the CTIS 1 described herein (which incorporates the valve block 3 illustrated in Figure 1B) and a vehicle control system 41. The vehicle control system 41 comprises the ECU 15. The ECU 15 is programmed to implement the control strategies and procedures described herein. In this embodiment, the ECU 15 receives from a tyre pressure monitoring system (TPMS) 43, via a vehicle controller area network (CAN) 45, real-time information relating to the current tyre pressures for the four tyres T of the vehicle VH. The pressure sensor communicates directly with the ECU 15 via electric signals representative of the pressure measured by the pressure sensor 35 in the gallery 33 of the valve block 3. As described earlier, the pneumatic control valves PCV and the various valves V, I, E of the valve block 3 can be configured such that the pressure sensor 35 measures a pressure which is representative of the pressure inside each of the tyres T. The TPMS 43 also monitors the temperature inside the tyres T so that the tyre pressures can be referred to a nominal temperature of 25 degrees C using appropriate algorithms, for example a thermocouple or other thermal sensor may be located in or through the hub of each wheel.

The ECU 15 controls the various mechanical components of the CTIS 1. As seen in Figure 1C, the ECU 15 is configured to control the outlet valves Vo via a pulse width modulation (PWM) control network 47. Via the same PWM control network 47, the ECU 15 also controls the purging function of the dryer unit 29, the electric motor 27 which drives the first compressor 9, the first and second inlet valves Viryc, Viryss, the exhaust valves El, E2 and the safety valve VsAFE. As an alternative to PWM control full cycle on/off solenoid valves could be used. The ECU 15 outputs open and close signals to open and close the first and second inlet valves VINC, VINSS.

The pneumatic control valve is disposed in a hub of the vehicle wheel. In the present embodiment, the pneumatic control valve PCV is a pneumatic latching valve which can be selectively opened and closed in response to the application of a pneumatic control signal. With reference to Figures 2A-D, the pneumatic control valve PCV has an axial inlet port 49 and a radial outlet port 51. The outlet port 51 is connected to a transfer line (not shown) formed in a spoke of the wheel to establish fluid communication with the tyre T. As described herein, the pneumatic control valve PCV can be selectively opened and closed to control the flow of compressed air between the inlet port 49 and the outlet port 51.

The pneumatic control valve PCV comprises a valve member 53 and a latch mechanism 55 disposed within a valve chamber 57. The valve member 53 and the latch mechanism 55 are movable axially within the valve chamber 57 to control the operating state of the pneumatic control valve PCV. The valve member 53 is arranged to cooperate with a first valve seat 59 formed at the inlet port 49; and a second valve seat 61 formed on the latch mechanism 55. A valve spring 63 is provided for loading the valve member 53. The latch mechanism 55 comprises a latching member 65 and a latch spring 67. In response to a pneumatic control signal supplied to the pneumatic control valve PCV through the tyre supply line TSL, the latching member 61 is disposed sequentially in first, second, third and fourth positions.

With reference to Figure 2A, during a normal running mode the valve member 53 is displaced to its closed position under the action of the valve spring 63 and the fluid pressure from the tyre side. The pneumatic control valve PCV is in a closed operating state in which the pressure of the tyre 3 is maintained. The latching member 65 is in a first position when the pneumatic control valve PCV is operating in the normal running mode, as shown in Figure 2A. To change the operating state of the pneumatic control valve PCV to an open state for inflating the tyre T, a pneumatic control signal is supplied to the inlet port 49 of the pneumatic control valve PCV. As shown in Figure 2B, the valve member 53 is displaced against the action of the valve spring 63 (to the right in the illustrated arrangement). The latching member 65 is displaced to a second position against the action of the latch spring 67. The valve member 53 is thereby lifted from the first and second valve seats 59, 61 allowing compressed air to flow through the pneumatic control valve PCV (as illustrated by the arrow overlaid onto Figure 2B). The tyre 3 can be inflated to a required pressure with the pneumatic control valve PCV in this configuration. The axial displacement of the latching member 65 causes it to rotate. When the pressure in the tyre supply line TSL is reduced, for example when the pneumatic control signal is terminated or inflation of the tyre is completed, the latching member 65 is displaced to a third position under the action of the latch spring 67, as shown in Figure 2C. In this configuration, air can be vented from the tyre T through the tyre supply line TSL (as illustrated by the arrow overlaid onto Figure 2C) by reducing the pressure in the tyre supply line TSL, for example by venting the gallery 33 to atmosphere. In this configuration, the tyre T can be deflated or the tyre pressure measured by the pressure sensor 35. To reset the pneumatic control valve PCV, a pneumatic control signal is supplied to the inlet port 49 (as illustrated by the arrow overlaid onto Figure 2D). The valve member 53 and the latching member 65 are displaced against the action of the valve spring 63 and the latch spring 67 (to the right in the illustrated arrangement). When the valve member 53 and the latching member 65 are displaced by the pneumatic control signal, the tyre T can be inflated by continuing the supply of compressed air to the inlet port 49. When the pneumatic control signal terminates, the valve member 53 and the latching member 65 are displaced to their starting position under the action of the valve spring 63 and the latch spring 67. The operating state of the pneumatic control valve PCV is thereby changed to a closed state, as shown in Figure 2A.

As outlined above, the second compressed air source 7 generates the pneumatic control signal(s) for controlling operation of one or more of said pneumatic control valves PCV. In particular, an operating state of the pneumatic control valve PCV can change in dependence on the pneumatic control signal. For example, the pneumatic control valve PCV can change from a closed state to an open state and vice versa. The pneumatic control valve PCV can be latched in said closed state to provide a normal operating mode in which the tyre T is sealed. The pneumatic control valve PCV can change from the latched closed state to an open state. Once the pneumatic control valve PCV is unlatched from said closed state, the tyre T can be inflated by supplying compressed air through the tyre supply line TSL. When the pneumatic control signal ends, the reduction in the pressure in the tyre supply line TSL causes the pneumatic control valve PCV to latch in the open state. The tyre T can be deflated and/or the tyre pressure measured when the pneumatic control valve PCV is latched in said open state. The pneumatic control valve PCV can be returned to the closed state by applying a further pneumatic control signal. The pneumatic control signal resets the pneumatic control valve PCV and latches the pneumatic control valve PCV in the closed state to allow operation in the normal operating mode.

The pressure required to change the operating state of the pneumatic control valves PCV depends on the pressure in the associated tyre T. For example, when changing from a closed state to an open state, the pneumatic control signal must increase the pressure in the tyre supply line TSL to overcome the pressure in the tyre. The pneumatic control valve PCV may optionally comprise a spring mechanism acting on the valve member and the pneumatic control signal will also have to overcome a spring bias applied by the spring mechanism. Thus, a high tyre pressure will require that a higher pressure is established in the tyre supply line TSL to actuate the pneumatic control valves PCV. The pressure in the reservoir 13 will determine the time taken to establish a sufficient pressure differential across the pneumatic control valve PCV (i.e. between the tyre supply line TSL and the pressure in the tyre) to actuate the pneumatic control valves PCV. A relatively low pressure in the reservoir 13 will result in a slower increase in the pressure in the tyre supply line TSL, thereby extending the time taken to actuate the pneumatic control valves PCV.

One control strategy to ensure that the pneumatic control valve PCV changes from a closed state to an open state would be to generate a pneumatic control signal sufficient to actuate the pneumatic control valve PCV assuming a relatively high tyre pressure and a relatively low pressure in the reservoir 13 (i.e. a worst-case scenario). The second inlet valve VINss could be controlled to generate a pneumatic control signal having a predefined duration, for example a time of 0.5 seconds. With reference to Figure 3, a first graph 100 represents the pressure in the gallery 33 when the operating state of the pneumatic control valve PCV changes from a closed stated to an open state. The second inlet valve ViNss is opened to initiate a pneumatic control signal at a first time t1; and is closed to terminate the pneumatic control signal at a second time t2. The duration of the pneumatic control signal is fixed at 0.5 seconds irrespective of the status of the pneumatic control valve PCV. The pneumatic control signal results in a progressive increase in the pressure in the gallery 33 until a sufficient pressure differential is established to actuate the pneumatic control valve PCV. In the operating cycle illustrated in Figure 3, the pneumatic control valve PCV changes from the closed state to the open state at a third time t3, as indicated by a drop in the pressure in the gallery 33. It will be appreciated that the pneumatic control signal continues after the pneumatic control valve PCV changes to said open state. A potential disadvantage of this control strategy is that the pressure in the reservoir 13 can be reduced unnecessarily.

Furthermore, it has been recognised that the compressed air supplied from the reservoir 13 to generate the pneumatic control signals to change the operating state of the pneumatic control valve PCV depends on the nature of the change. During a transition from an open operating state to a closed operating state, the pneumatic control valve PCV closes in dependence on the pneumatic control signal and inhibits the continued supply of air from the reservoir 13 to the tyre T. However, during the transition from a closed operating state to an open operating state, for example to inflate the tyres T, the pneumatic control valve PCV opens to establish a fluid connection between the tyre supply line TSL and the tyre T. The compressed air supplied by the reservoir 13 in the form of the pneumatic control signal can then flow into the tyre T. It will be appreciated, therefore, that the change from a closed operating state to an open operating state tends to result in a larger drop in pressure in the reservoir 13.

The ECU 15 in accordance with the present embodiment is configured to control operation of the pneumatic control valves PCV to help reduce the duration of the pneumatic control signals, thereby reducing the drop in pressure in the reservoir 13 and potentially reducing operation of the first compressor 9 (or a second compressor if the second compressed air source 7 utilises a separate compressor to replenish pressure in the reservoir 13). In particular, the ECU 15 is configured to identify a change in the operating state of the pneumatic control valve(s) PCV and to control operation of the second inlet valve ViNss in dependence on the identified change in operating state. The ECU 15 receives a pressure measurement signal from the pressure sensor 35. The pressure sensor 35 measures the pressure in the gallery 33 which corresponds to the pressure on a supply side of the pneumatic control valve PCV (i.e. the pressure on the side of the pneumatic control valve PCV closest to the second pressure source 13 which supplies the compressed air to generate the pneumatic control signal). As outlined above, a change in the operating state of the pneumatic control valve(s) PCV results in a change in the pressure in the tyre supply lines TSL. When the pneumatic control valve PCV changes from a closed state to an open state, there is an identifiable drop in the pressure in the associated tyre supply line TSL (and in the gallery 33). Conversely, when the pneumatic control valve PCV changes from an open state to a closed state, there is an identifiable increase in the pressure in the associated tyre supply line TSL (and in the gallery 33). By monitoring the pressure in the gallery 33, the ECU 15 can identify a change in pressure indicative of a change in the operating state of the pneumatic control valve(s) PCV. The ECU 15 can thereby identify when the operating state of the pneumatic control valve(s) PCV changes.

In the present embodiment, the ECU 15 is configured to identify the peak pressure measured by the pressure sensor 35 in the gallery 33. If the peak pressure decreases by a predetermined pressure, the ECU15 determines that the pneumatic control valve PCV has changed from a closed state to an open state. The predetermined pressure in the present embodiment is set as 0.25 bar, but this value can be calibrated for different systems. Thus, in the scenario illustrated in Figure 3, the ECU 15 would determine at a fourth time t4 that the pneumatic control valve PCV has changed from said closed state to said open state.

Alternatively, or in addition, the predetermined pressure may vary depending on whether the pneumatic control valve PCV is associated with the front axle or the rear axle of the vehicle.

The ECU 15 is configured to control operation of the second inlet valve ViNss in dependence on the identification of a change in the operating state of the pneumatic control valve(s) PCV. Specifically, upon identifying that the operating state of the pneumatic control valve(s) PCV has changed, the ECU 15 outputs a control signal to close the second inlet valve VINSS, thereby terminating the pneumatic control signal.

The ECU 15 can also implement a failsafe strategy. For example, if the predetermined pressure decrease is not detected within a predefined cut-off time period (measured from opening the second inlet valve VINSS to initiate the pneumatic control signal), the ECU 15 can output a control signal to close the second inlet valve ViNss. By way of example, the cut-off time period could be set as 0.6 seconds. If the ECU 15 determines that the operating state of the pneumatic control valve PCV has not changed, the procedure can be repeated. If the pneumatic control valve PCV does not respond in the expected manner, the ECU 15 can be configured to output a fault signal. For example, the process could be repeated five (5) times and then a fault signal output.

The ECU 15 can be configured to change the operating states of the pneumatic control 35 valves PCV associated with each of the tyres T in sequence. By way of example, the ECU 15 can be configured to change the pneumatic control valves PCV from a closed state to an open state in the following sequence: front left (FL), front right (FR), rear left (RL) and rear right (RR).

With reference to Figure 4, the operation of the CTIS 1 based on a tyre pressure of 0.8 bar is represented in a second graph 200. The ECU 15 is configured to change the operating state of the pneumatic control valves PCV sequentially in this embodiment. A first plot 201 represents the pressure in the reservoir 13; and a second plot 202 represents the pressure in the gallery 33. The operating state of the outlet valves VFL, VFR, VRL, VRR are represented by third, fourth, fifth and sixth plots 203, 204, 205, 206 respectively (a "1" indicating that the valve is open and a "0" indicating that the valve is closed). A seventh plot 207 represents the operating state of the second inlet valve ViNss controlled by the ECU 15 in accordance with the strategy described herein. In particular, the ECU 15 identifies a pressure drop of at least 0.25 bar from a peak pressure measured in the gallery 33 and determines that the pneumatic control valve has changed from a closed state to an open state. The ECU 15 outputs a control signal to close the second inlet valve ViNss, thereby inhibiting the supply of compressed air from the reservoir 13 after the operating state of the pneumatic control valve PCV has changed. As the pneumatic control valve PCV is changed to an open state, the pressure in the gallery 33 increases to match the tyre pressure. The corresponding outlet valve Vc, is closed and the process is repeated for the next pneumatic control valve PCV in the sequence. In the example illustrated in Figure 4, the duration of the pneumatic control signals to change the operating state of each pneumatic control valve PCV is as follows: front left (FL) 0.279 seconds, front right (FR) 0.289 seconds, rear left (RL) 0.15 seconds and rear right (RR) 0.17 seconds. The progressive decrease in the pressure of the reservoir 13 is represented by the first plot 201.

With reference to Figure 5, the operation of the CTIS 1 based on a tyre pressure of 1.4 bar is represented in a third graph 300. A first plot 301 represents the pressure in the reservoir 13; and a second plot 302 represents the pressure in the gallery 33. The operating state of the outlet valves VFL, VFR, VRL, VRR are represented by third, fourth, fifth and sixth plots 303, 304, 305, 306 respectively. A seventh plot 307 represents the operating state of the second inlet valve VIRas controlled by the ECU 15 in accordance with the strategy described herein. In particular, the ECU 15 identifies a pressure drop of at least 0.25 bar from a peak pressure measured in the gallery 33 and determines that the pneumatic control valve has changed from a closed state to an open state. The ECU 15 outputs a control signal to close the second inlet valve ViNss, thereby inhibiting the supply of compressed air from the reservoir 13 after the operating state of the pneumatic control valve PCV has changed. As the pneumatic control valve PCV is changed to an open state, the pressure in the gallery 33 increases to match the tyre pressure. The corresponding outlet valve Vo is closed and the process is repeated for the next pneumatic control valve PCV in the sequence. In the example illustrated in Figure 5, the duration of the pneumatic control signals to change the operating state of each pneumatic control valve PCV is as follows: front left (FL) 0.32 seconds, front right (FR) 0.31 seconds, rear left (RL) 0.22 seconds and rear right (RR) 0.23 seconds. The progressive decrease in the pressure of the reservoir 13 is represented by the first plot 301.

With reference to Figure 6, the operation of the CTIS 1 based on a front tyre pressure of 2.3 bar and a rear tyre pressure of 2.5 bar is represented in a fourth graph 400. A first plot 401 represents the pressure in the reservoir 13; and a second plot 402 represents the pressure in the gallery 33. The operating state of the outlet valves VFL, VAR, VRL, VRR are represented by third, fourth, fifth and sixth plots 403, 404, 405, 406 respectively. A seventh plot 407 represents the operating state of the second inlet valve VINSS controlled by the ECU 15 in accordance with the strategy described herein. In particular, the ECU 15 identifies a pressure drop of at least 0.25 bar from a peak pressure measured in the gallery 33 and determines that the pneumatic control valve has changed from a closed state to an open state. The ECU 15 outputs a control signal to close the second inlet valve ViNss, thereby inhibiting the supply of compressed air from the reservoir 13 after the operating state of the pneumatic control valve PCV has changed. As the pneumatic control valve PCV is changed to an open state, the pressure in the gallery 33 increases to match the tyre pressure. The corresponding outlet valve Vo is closed and the process is repeated for the next pneumatic control valve PCV in the sequence. In the example illustrated in Figure 6, the duration of the pneumatic control signals to change the operating state of each pneumatic control valve PCV is as follows: front left (FL) 0.43 seconds, front right (FR) 0.45 seconds, rear left (RL) 0.36 seconds and rear right (RR) 0.34 seconds. The progressive decrease in the pressure of the reservoir 13 is represented by the first plot 401.

It will be appreciated that the operation of the ECU 15 can account for variations in the configuration of the CTIS 1. The control strategy described herein automatically allows for differences in the length of the tyre supply lines for each tyre T, or for the tyres on each axle. For example, in the CTIS 1 described herein with reference to Figures 4, 5 and 6, the tyre supply lines TSL for the rear tyres TRL, TRR are shorter than the tyre supply lines TSL for the front tyres TFL, TFR due to the location of the valve block 3. The ECU 15 allows for these variations without the need for separate calibration steps.

It will be appreciated that various changes and modifications can be made to the method and apparatus described herein without departing from the scope of the present application.

Claims

CLAIMS: 1. A controller for controlling a pneumatic control valve, the controller comprising: an electronic processor having an electrical input for receiving a supply-side pressure signal; and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein; the electronic processor being configured to control a first control valve to generate a pneumatic control signal for changing an operating state of a pneumatic control valve, the electronic processor being configured to output a first valve open signal to open the first control valve to initiate the pneumatic control signal, and to output a first valve close signal to close the first control valve to terminate said pneumatic control signal; wherein the electronic processor is configured to monitor the supply-side pressure signal and to identify a change in the operating state of the pneumatic control valve in dependence on a change in the supply-side pressure; the electronic processor being configured to output said first valve close signal upon determining that the pneumatic control valve has changed operating state.
2. A controller as claimed in claim 1, wherein the first valve close signal is output if the change in the operating state of the pneumatic control valve is not detected within a predefined time period.
3. A controller as claimed in claim 1 or claim 2, wherein the change in the supply-side pressure comprises: a change which is greater than or equal to a defined threshold; or a change which is greater than or equal to a defined proportional change; or change in the rate of change of the supply-side pressure.
4. A controller as claimed in claim 3, wherein the electronic processor is configured to detect the change in the supply-side pressure within a prescribed time period.
5. A controller as claimed in any one of the preceding claims, wherein the electronic processor is configured to identify when the pneumatic control valve changes operating state in dependence on detection of a decrease in the supply-side pressure.
6. A controller as claimed in any one of the preceding claims configured to control an operating state of a plurality of said pneumatic control valves.
7. A controller as claimed in claim 6, wherein the controller is configured to control two or more of said pneumatic control valves simultaneously; or to control two or more of said pneumatic control valves sequentially.
8. A central tyre inflation system (CTIS) for a vehicle, the CTIS comprising: a supply line for supplying compressed air to a tyre; a pneumatic control valve operable in at least first and second operating states to control the supply of compressed air from the supply line to the tyre; a first control valve connected to a first compressed air source; and a controller having an electronic processor as claimed in any one of the preceding claims: wherein the electronic processor is configured to control the first control valve to generate the pneumatic control signal for changing the operating state of a pneumatic control valve, the electronic processor being configured to output a first valve open signal to open the first control valve to initiate the pneumatic control signal; and to output a first valve close signal to the first control valve to terminate the pneumatic control signal; wherein the electronic processor is configured to output the first valve close signal upon determining that the pneumatic control valve has changed operating state.
9. A CTIS as claimed in claim 8 comprising a pressure sensor for generating said supply-side pressure signal.
10. A CTIS as claimed in claim 8 or claim 9, wherein the pneumatic control valve is in a closed state in said first operating state and in an open state in said second operating state.
11. A CTIS as claimed in any one of claims 8, 9 or 10 comprising a second control valve connected to a second compressed air source; wherein the electronic processor is configured to output a second valve open signal to open the second control valve to supply compressed air from the second compressed air source to the tyre.
12. A CTIS as claimed in claim 11, wherein the second valve open signal is output in dependence on identification of the change from said first operating state to said second operating state.
13. A CTIS as claimed in any one of claims 8 to 12 comprising a plurality of said pneumatic control valves each configured to control the supply of compressed air to a respective tyre.
14. A CTIS as claimed in claim 13, wherein the controller is configured to control two or more of said pneumatic control valves simultaneously; or to control two or more of said pneumatic control valves sequentially.
15. A vehicle comprising a CTIS as claimed in any one of claims 8 to 14.
16. A method of controlling an operating state of a pneumatic control valve disposed in a supply line, the method comprising: generating a pneumatic control signal for changing an operating state of the pneumatic control valve; monitoring a supply-side pressure; and determining that the pneumatic control valve has changed operating state in dependence on detection of a change in the supply-side pressure; wherein the pneumatic control signal is terminated upon determining that the pneumatic control valve has changed operating state.
17. A method as claimed in claim 16 comprising opening a first control valve to initiate the pneumatic control signal; and closing the first control valve to terminate said pneumatic control signal.
18. A method as claimed in claim 17 comprising closing the first control valve upon determining that the pneumatic control valve has changed operating state.
19. A method as claimed in claim 17 or claim 18 comprising closing the first control valve if the change in the operating state of the pneumatic control valve is not detected within a predefined time period.
20. A method as claimed in any one of claims 16 to 19, wherein the change in the supply-side pressure comprises: a change which is greater than or equal to a defined threshold; or a change which is greater than or equal to a defined proportional change; or a change in a rate of change of the supply-side pressure.
21. A method as claimed in claim 20 comprising detecting the change in the supply-side pressure within a prescribed time period.
22. A method as claimed in any one of claims 16 to 21 comprising identifying a change in the operating state of the pneumatic control valve in dependence on detection of a decrease in the supply-side pressure.
23. A method as claimed in any one of claims 16 to 22 comprising performing the method for a plurality of said pneumatic control valves.
24. A method as claimed in claim 23 comprising controlling two or more of said pneumatic control valves simultaneously; or controlling two or more of said pneumatic control valves sequentially.
25. A non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more electronic processors to carry out the method of any one of claims 16 to 24.
26. A controller substantially as herein described with reference to the accompanying figures.
27. A central tyre inflation system (CTIS) substantially as herein described with reference to the accompanying figures.
28. A method substantially as herein described with reference to the accompanying figures.