GB2564845A

GB2564845A - A method for removing contamination from within a valve

Info

Publication number: GB2564845A
Application number: GB1711463.8A
Authority: GB
Inventors: Van Gordon Michael; Inglis Rob; Nesbitt David; Leek Chris; Hateley Adam
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-07-17
Filing date: 2017-07-17
Publication date: 2019-01-30
Anticipated expiration: 2037-07-17
Also published as: DE102018210384A1; GB201711463D0; GB2564845B

Abstract

A method for controlling a vehicle air conditioning system comprises: receiving a signal indicative of a vehicle operating parameter 800; determining, based on the signal, whether a predetermined condition is met 810; and if the condition is met, outputting a control signal to a control valve of a compressor of the system to cause the valve to perform a valve unblocking operation 840. A corresponding control module includes an input for receiving the signal and an output for outputting the control signal. The valve member may be a direct pressure sensing (DPS) solenoid valve, and the unblocking or flushing operation may involve dislodging contaminants from a groove in the valve by cyclically moving the valve between two positions. The predetermined condition may be that the ignition status of the vehicle has changed from on to off, that the compressors rotational speed is zero, or that the temperature of an evaporator is outside a desired range.

Description

TECHNICAL FIELD

The present disclosure relates to a method for removing contamination from within a valve and particularly, but not exclusively, to a method for removing contamination from within a valve in a vehicle air-conditioning system. Aspects of the invention relate to a control module, to a system, to a vehicle and to a method.

BACKGROUND

Air-conditioning systems are typically provided within vehicles, such as passenger cars, trucks, buses etc., in order to help regulate the temperature and humidity of air within a vehicle cabin so as to improve comfort for the vehicle occupants. Such airconditioning systems typically include a compressor for circulating a refrigerant around components of the system, such as heat exchangers, etc. For a vehicle in which drive power is provided by an internal combustion engine, such as a compression-ignition or spark-ignition combustion engine, the compressor of the air-conditioning system is typically driven by the combustion engine. In a typical implementation, the compressor has at least one inlet for receiving refrigerant at a relatively low pressure and at least one outlet for outputting refrigerant at a higher pressure. An example of a known implementation of an air-conditioning system comprising is described in United States patent number 6,622,500 assigned to Delphi Technologies Inc., in which the enginedriven compressor comprises one or more pistons coupled to a swash plate. The pistons are arranged for reciprocating movement in a bore so as to define respective pumping chambers in which refrigerant fluid is compressed and expelled through the high pressure outlet of the compressor. The angle of the swash plate may be controlled to vary the displacement of the compressor, i.e. by varying the effective volume of the pumping chamber. A control valve, such as Direct Pressure Sensing (DPS) valve, controls a pressure differential between a crankside port and a suction port on the compressor to vary the angle of the swash plate and thus the displacement of the compressor. The control valve may be pneumatically or electromagnetically controlled by a control module to vary the position of a valve member therein, and thereby alter the swash plate angle, and thus the displacement of the compressor.

Movement of the control valve member may be affected by contaminants within the refrigeration fluid becoming lodged between the valve member and the surrounding valve housing or other parts of the control valve assembly, thereby inhibiting movement of valve member. If this happens operation of the control valve may be compromised meaning that the performance of the air-conditioning system is impaired, adversely affecting the comfort of the vehicle occupants.

It is an aim of the present invention to provide an improved air-conditioning system and to overcome and/or at least substantially mitigate the above mentioned problems of known air-conditioning systems.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a control module for a vehicle airconditioning system, a system, a vehicle and a method.

According to an aspect of the present invention there is provided a control module for a vehicle air-conditioning system comprising an input for receiving a signal indicative of a vehicle operating parameter and an output for outputting a control signal to a control valve of a compressor of the air-conditioning system, wherein the control module is configured to determine whether a predetermined condition for performing a control valve unblocking operation is met in dependence on a signal received at the input and, when it is determined that the condition is met, the control is configured to output a control signal to the control valve to cause the control valve to perform the unblocking operation.

By virtue of the unblocking operation embodiments of the invention can reduce the likelihood and/ or substantially prevent contaminants, such as particles in a refrigerant fluid from blocking or obstructing the control valve. Accordingly, reliable operation of the control valve can be achieved.

In an embodiment of the invention the unblocking operation may comprise actuating the control valve while the compressor is not being driven. By performing the unblocking operation when the compressor is not being driven the risk of damage to the control valve can be reduced and/ or prevented.

In another embodiment of the invention the unblocking operation may comprise actuating the control valve for a predetermined length of time and/or for a predetermined number of times. Following a determination that the predetermined condition is met, the control module may be configured to delay outputting the control signal for a prescribed amount of time. Advantageously, in embodiments where the unblocking operation comprises a delay before which the control valve is actuated the compressor has time to come to rest before movement of the control valve takes place thus reducing the risk of the control valve being damaged.

In another embodiment of the invention the signal indicative of a vehicle operating parameter may be indicative of a change of ignition status of an engine of the vehicle. In a further embodiment of the invention determining that the predetermined condition is met may comprise determining that the ignition status of the engine has changed from an ON state to an OFF state.

By waiting until the engine is off before performing the unblocking operation it may be performed when the compressor is not being driven and/ or when other elements of the air-conditioning system are not operable. Alternatively, the unblocking operation may be inhibited when the change in status from an on state to an off state is a result of an Eco-stop of an engine stop/start system. Thus there is less risk of actuating the valve when the compressor may need to be restarted quickly as it is likely when in an eco-stop mode the engine may be required to start quickly.

In an embodiment of the invention the signal being indicative of a vehicle operating parameter may be indicative of a compressor rotational speed. In another embodiment of the invention determining that the predetermined condition is met may comprise determining that the compressor rotational speed is zero or substantially equal to zero.

In another embodiment of the invention the signal indicative of a vehicle operating parameter may be indicative of the temperature of a component of the air-conditioning system. Determining that the predetermined condition is met may comprise determining that the temperature of an evaporator of the air-conditioning system is outside a predetermined temperature range.

In embodiments of the invention, if the temperature of the evaporator is below a predetermined temperature this may be indicative of the control valve being in a stuck open state. Similarly, if the temperature of the evaporator is above a predetermined threshold this may be an indication that the control valve is stuck in a closed state.

In a further embodiment of the invention the control signal is a cyclical control signal.

According to an aspect of the invention there is provided a system comprising a compressor for a vehicle air-conditioning system and a control module according to various embodiments of the invention, the compressor comprising a control valve having a valve member movable between first and second positions, the displacement of the compressor being dependent on the position of the valve member.

In an embodiment of the invention the valve member may be arranged for reciprocating movement within a valve bore between the first position in which the control valve is in a closed state and the second position in which the control valve is in at least a partially open state.

By repeatedly moving the valve member backwards and forwards this can serve to dislodge particles from between the valve member and an adjacent valve seat and/ or prevent build-up of contaminant particles in the vicinity of the valve member. In particular, where the valve member comprises one or more grooves to permit or restrict flow of a control fluid therepast reciprocating the valve can serve to dislodge particles from the groove/s.

In a further embodiment of the invention the position of the valve member may be controlled by an actuator, optionally a solenoid. In another embodiment of the invention the compressor may be arranged so as to be driven by a combustion engine of the vehicle.

In an embodiment of the invention there may be a clutch means for decoupling the compressor from the engine, wherein determining that said predetermined condition has been met comprises determining that the clutch means is in an open state.

Conveniently, by ensuring that the clutch is open when the unblocking operation is performed actuation of the valve only occurs when the compressor is not being directly driven and is preferably stationary.

According to another aspect of the invention there is provided a vehicle comprising a control module or a system according to embodiments of the invention.

According to another embodiment of the invention there is provided a method for controlling a vehicle air-conditioning system comprising: receiving a signal indicative of a vehicle operating parameter; determining whether a predetermined condition for performing a control valve unblocking operation is met in dependence on the received signal, and in dependence on a positive determination that the condition is met, outputting a control signal to a control valve of a compressor of the air-conditioning system to cause the control valve to perform the unblocking operation.

In an embodiment of the invention performing the unblocking operation may only occur when a rotational speed of the compressor is zero or substantially equal to zero. In another embodiment of the invention the unblocking operation may comprise moving a valve member of the control valve between first and second positions a predetermined number of times or for a predetermined amount of time.

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 invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a vehicle comprising an air-conditioning system suitable for use with embodiments of the present invention;

Figure 2 is a schematic showing the air-conditioning system of the vehicle of Figure 1;

Figure 3 is a partial cross-sectional view of a compressor of the air-conditioning system of the embodiment of Figures 1 and 2

Figure 4 is a cross-sectional view of the control valve of the compressor of Figure 3 in a closed state;

Figure 5 is a cross-sectional view of the control valve of the compressor of Figure 3 in a partially open state;

Figure 6 is a cross-sectional view of the control valve of the compressor of Figure 3 in a fully open state;

Figure 7 is a cross-sectional view of the control valve of the compressor of Figure 3 in an obstructed state;

Figure 8 is a flow chart showing an embodiment of a method for controlling the control valve of Figures 3 in accordance with the present invention; and

Figure 9 is a flow chart showing another embodiment of a method for controlling the control valve of Figures 3 in accordance with the present invention.

DETAILED DESCRIPTION

In general terms, embodiments of the invention relate to a control module for controlling a valve located within a compressor of an air-conditioning system on a vehicle. The control module is configured to monitor valve movement and detect if displacement of the compressor is likely to be insufficient. When required, the control module will initiate a flushing cycle or a valve unblocking operation on the valve. The unblocking operation involves applying an actuation force on the valve via an actuator to actuate movement of the valve to dislodge any contaminants held within the valve that may otherwise inhibit valve movement.

This provides the advantage of helping to prevent contaminants building up within the valve that may inhibit movement of the valve by the actuator. The contaminants trapped within the valve may be particles, such as PTFE, due to wear of components from within the air-conditioning system or particles of silica glass and other debris particles that are left over from the manufacturing and assembly of the air-conditioning system. The contaminants are carried through the air-conditioning system via the refrigerant fluid and can become trapped within the control valve within the compressor of the system.

To place embodiments of the invention in a suitable context, reference will now be made to Figure 1 which shows a vehicle 10 including a control module 12 and an airconditioning system 14. The air-conditioning system 14 is controlled by the control module 12 to adjust the temperature inside of the vehicle 10. The air-conditioning system 14 may form part of a heating, ventilation and air-conditioning system controlled by the control module 12 within the vehicle 10.

An example of the air-conditioning system 14 is shown in Figure 2. The skilled person would understand the operation of the air-conditioning system 14 and as such only an overview of the system is described herein. A description of such an air-conditioning system may be found, for example, in United States patent number 6,622,500 as mentioned previously by way of the background.

The air-conditioning system 14 includes a compressor 20 coupled to an engine 22. The engine 22 provides a drive force to the compressor 20. The engine 22 may be an internal combustion engine or an electric motor. In an embodiment of the invention, the engine 20 includes a clutch means (not shown) which is selectively engaged or disengaged to selectively turn the compressor 20 on or off.

The compressor 20 includes a control valve 26 which is configured to vary the displacement and thus effective capacity of the compressor 20. The compressor 20 receives refrigerant fluid at a relatively low pressure and outputs the refrigerant fluid at a higher pressure to the air-conditioning components 24 within the air-conditioning system 14. The control module 12 receives an input 28 indicative of a vehicle users desired vehicle temperature and an input indicative of a vehicle operating parameter such as an engine status or compressor speed and the control module 12 outputs a control signal 29 to the control valve 26 to control the capacity of the compressor 20.

Figure 3 shows a cross-sectional view of a compressor 20 that is suitable for use with embodiments of the invention. The compressor 20 has a plurality of pistons 32a, 32b which are moveable to vary the effective capacity of the compressor 20. The pistons 32a, 32b are connected to a drive shaft 34 via a swash plate 30. The drive shaft 34 is connected to the engine 22. The compressor 20 has three main portions, namely a suction portion 35, a discharge portion 31 and a crankcase portion 33. The displacement of the compressor 20 is controlled by the control valve 26. In an embodiment of the invention, the control valve 26 is a Direct Pressure Sensing (DPS) valve which senses the pressure in each portion of the compressor 20 and alters the pressure differential between the crankcase portion and the suction portion. By altering the pressure differential between the crankcase portion and the suction portion the control valve 26 alters the angle of a swash plate 30 within the compressor 20 which in turn alters the displacement of the pistons 32a, 32b thus varying the capacity of the compressor 20.

An example of the control valve 26, suitable for use with embodiments of the invention, is shown in Figure 4. The valve member 44 is arranged for reciprocating movement within a valve bore 48 between a first position and a second position. The control valve 26 is operable to move between a first position, in which the valve 26 is in a closed position as is shown in Figure 4 and a second position, in which the valve 26 is in a fully open position. The control valve 26 includes an actuator such as a solenoid 40, a valve spring 42, a valve member 44, a passage 49 or bore and a valve casing 47. The control valve 26 has three ports 41, 43, 45 that are respectively positioned in communication with the discharge portion, crankcase portion and suction portion of the compressor 20. The control valve 26 is operable to open and close a passage 49 between the suction port 45 and the crankcase port 43 to vary the pressure differential and thus control the displacement of the compressor 20.

The valve member 44 has a cylindrical body positioned within the valve casing 47. The valve member 44 is operable by the solenoid 40 to move between the closed position and the open position. The valve member 44 includes a plurality of grooves 401 running round an outer cylindrical surface of the valve member 44. The grooves 401 provide a path for controlled leakage or bleed of the refrigerant fluid across the valve member 44 from the crankcase port 41 to the suction port 45. The grooves 401 may form part of a helical thread around the valve member 44 or may be discrete annular grooves. The diameter of the valve member 44 is approximately 20pm smaller than the diameter of the valve casing 47 such that there is approximately a 10pm gap between the edge of the valve member 44 and the internal surface of the valve casing 47.

Figure 5 shows the control valve 26 in a partially open position. The valve member 44 is actuated by the solenoid 40 to move linearly toward the fully open position (shown in Figure 6). When the control valve 26 is in the partially open position, at least one groove 401 is positioned within the passage 49. Fluid from the crankcase port 41 may bleed through to the suction port 45 via a path provided by the grooves 401 .This increases the pressure at the suction port 45 thereby reducing the pressure differential between the crankcase port 41 and the suction port 45. This in turn causes the angle of the swash plate 30 to increase thus increasing the capacity of the compressor 20.

Figure 6 shows the control valve 26 in the fully open position. The valve member 44 is further actuated by the solenoid 40 such that more of the grooves 401 are positioned within the passage 49. Increasing the number of grooves 401 positioned within the passage 49 increases the flow path available to the fluid thereby reducing the pressure differential between the crankcase port 41 and the suction port 45.

The valve member 44 is actuated by the solenoid 40 to vary the position of the valve member 44 within the valve casing 47. The control module 12 varies the control signal applied to the solenoid 40 thereby varying the actuation force applied to the valve member 44 by way of electromechanical repulsion. The control module 12 may use pulse width modulation to vary the control signal applied to the solenoid 40 or may directly modulate the current applied to the solenoid 40. The actuation force applied by the solenoid 40 is opposed by a returning force from the valve spring 42. In use, the returning force from the valve spring 42 increases as it is compressed by the valve member 44 being moved towards it by the actuation force applied by the solenoid 40. In this manner, the control module 12 is able to control the position of the valve member 44 by varying the control signal 29 applied to the solenoid 40 to in turn vary the actuation force applied by the solenoid 40 to the valve member 44; the resulting position of the valve member 44 being generally at the point of equilibrium between the actuation force and return force applied thereto.

In some embodiments, the control signal 29 applied to the solenoid 40 may be in the form of a control current. When the control current applied to the solenoid 40 by the control module 12 is at 0mA the valve spring 42 applies an actuation force to move the valve member 44 to the closed position. As the control current is increased by the control module 12, the actuation force applied to the valve member 44 increases, thereby overcoming the return force applied by the valve spring 42 thus moving the valve member 44 toward the fully open position until equilibrium between the actuation force and the return force is generally achieved. The control current controls the position of the valve member 44 such that the valve member 44 is operable between the closed position and the fully open position. When the control current is at a maximum, for example at 800mA, the valve member 44 is located in the fully open position.

Figure 7 shows the control valve 26 in an obstructed state. Over time the grooves 401 may collect contaminants 70 and particles carried within the refrigerant fluid. If the contaminants 70 become lodged in the gap between the valve member 44 and the valve casing 47 then actuation of the valve member 44 within the passage 49 may be inhibited. If this occurs, the displacement of the valve member 44, and thus compressor 20, is no longer controllable, meaning a user of the vehicle 10 may experience reduced performance of the air-conditioning system 14.

To prevent the build-up of contaminants 70 between the valve member 44 and the valve casing 47, the control module 12 is arranged to control the solenoid 40 to actuate a valve flush or unblocking operation on the control valve 26 The valve unblocking operation may be a flush cycle where the solenoid 40 is controlled by the control module 12 to apply a cyclical actuation force on the valve member 44. For example, the solenoid 40 may be intermittently actuated to urge the valve member 44 to cyclically move between a fully open and closed position to prevent and/ or dislodge contaminants 70 that may obstruct and inhibit movement of the valve member 44. Such an unblocking operation not only inhibits the build-up of contaminants 70 but also may dislodge contaminants 70 when a contaminant 70 becomes lodged within the valve 26.

In an embodiment of the invention, the valve unblocking operation involves intermittently actuating the control valve 26 by applying maximum allowable current to the solenoid 40 at a low frequency of < 5Hz for a sufficient time period to dislodge contaminants obstructing the control valve 26. The time period may be in the region of 5, 10, 20, 30 or 60 seconds depending on the amount of contaminants 70 obstructing the control valve 26.

If the valve member 44 has no contaminants lodged in the gap between the valve member 44 and the valve casing 47 then the valve member 44 would move between the fully open position and the fully closed position freely. If however a contaminant 70 was lodged between the valve member 44 and the valve casing 47, thereby inhibiting movement of the valve member 44, then the cyclical application of an actuation force applied to the valve member 44 would encourage movement of the valve member 44 to dislodge and flush out any particles trapped on the valve member 44 without necessarily actuating movement of the valve member 44 whilst such contaminants were present. In scenarios where the standard flush cycle is not successful in dislodging the contaminant 70 the control module 12 may increase the frequency to, for example, 10Hz or 20Hz, to help dislodge the contaminant 70.

The control module 12 is configured to initiate the valve unblocking operation when a predetermined condition is satisfied. For example, if the control module 12 detects that a contaminant 70 is inhibiting movement of the valve member 44 or if, for example, the vehicle ignition is turned to an OFF” state meaning the vehicle engine 22 is turned off.

Figure 8 shows a flow chart outlining the steps carried out by the control module 12 in one embodiment of the invention. As the first step 800 the control module 12 receives an input signal 28 indicating that the vehicle engine 22 running status has changed. For example, the engine 22 has been switched from an on to an off state or the compressor 20 has been switched from an off to an on state. The input signal may be indicative of a vehicle “key off” meaning the user of the vehicle 10 has turned the vehicle ignition from an ON” state to an OFF” state and has thus ended their journey or alternatively the input signal may be indicative of the compressor 20 speed.

In the case where the vehicle engine 22 is switched from an on to an off state, as is shown in step 810, when the compressor 20 speed is equal to zero, meaning the compressor is not being driven, the control module 12 may determine it to be appropriate to initiate a flushing cycle. Accordingly, in the example illustrated in Figure 8, when the vehicle engine 22 is switched from an on to an off state, the control module 12 then waits sufficient time for the compressor 20 within the air-conditioning system 14 to stop rotating and for the pressure of the fluid within the air-conditioning system 14 to equalise as part of step 820. When the timer has elapsed 830, meaning the pressure of the fluid has equalised and the compressor 20 has stopped rotating, the control module 12 determines that it is appropriate to initiate a valve flush on the control valve 26. The control module 12 initiates a valve unblocking operation 840 by outputting a control signal to the actuator, for example the solenoid 40. The output signal actuates actuator to apply a cyclical actuation force to the valve member 44 to urge the the valve member 44 between the fully open and closed positions to dislodge contaminants 70 trapped within the control valve 26. When the predetermined cycle time elapses 850, the flushing cycle ends 860 and the valve 26 is operated in its normal operating mode 870.

In an embodiment of the invention, when the control module 12 detects a change in engine running status 800, the control module 12 determines the type of engine running status change associated with said change. For example, if the engine 22 is turned off in an eco-stop mode when the vehicle 10 is stationary in traffic the control module 12 would not deem it appropriate to run the valve unblocking operation. In this scenario, the engine 22 may not be turned off for a sufficient length of time to enable the compressor 20 to stop rotating and to allow the pressure of the fluid to equalise prior to initiating the valve unblocking operation. Initiating the unblocking operation when the compressor is being driven may cause damage to the valve 26 and compressor 20. In this scenario the control module 12 would not initiate a valve unblocking operation.

Alternatively, in hybrid electric vehicles the combustion engine 22 may stop running when the vehicle 10 is running in a full EV mode, however, a vehicle battery may still power the compressor 20. In this scenario, the control module 12 detects that the compressor 12 is still running and as such determines initiating the valve unblocking operation to be inappropriate under those given vehicle parameters. In this scenario the control module 12 would not initiate a valve unblocking operation.

Figure 9 shows the steps carried out by the control module 12 in an alternative embodiment of the invention. In this embodiment, a valve unblocking operation may be carried out when the vehicle engine 22 is still running. In step 900 the control module 12 receives a signal 28 indicative of a vehicle operating parameter, indicating that the air-conditioning system 14 is working abnormally indicating that a contaminant 70 may be obstructing the control valve 26.

The input signal may be indicative of a temperature of a component of the airconditioning system 24. For example, the input signal may be indicative of a temperature of an evaporator within the air-conditioning system 14. If the evaporator temperature is out with a predetermined temperature range, for example if the evaporator has frozen, then this may indicate that a contaminant 70 is obstructing the control valve 26. The input signal may also be indicative of an air temperature at air outlet vents within the vehicle cabin. If the user of the vehicle selects an air temperature of, for example 20^sC, and the air temperature output at the vents is not being output at the same temperature then this may also indicate that a particle is inhibiting operation of the control valve 26.

The control module 12 may also receive an input signal 28 indicative of fluid pressures within the air-conditioning system 14. If the control module 12 outputs a control signal 29 to the control valve 26 to actuate the control valve 26 then the control module 12 may check that the pressure within the air-conditioning system 14 varies as expected. If the pressure of the fluid within the air-conditioning system 14 does not vary following actuation of the control valve 26 then this may indicate that a contaminant 70 is inhibiting movement of the control valve 26 and that a valve unblocking operation is required.

When the control module 12 positively detects an obstruction within the control valve 26 in step 900 the control module 12 then decouples a clutch means as part of step 910. Decoupling the clutch means between the vehicle engine 22 and the compressor 20 enables the valve unblocking operation to be initiated when the vehicle 10 is still moving. Decoupling the clutch means removes the drive force to the compressor 20 meaning that it is not being driven. The control module 12 waits a predetermined amount of time as part of step 920 to ensure that the compressor 20 has time to come to a rest and to allow the pressure within the air-conditioning system to stabilise. In an embodiment of the invention, the control module 12 receives a signal 28 indicative of the speed of the compressor 20 and only initiates the unblocking routine when the speed of the compressor is zero or substantially equal to zero.

When the timer has elapsed and/ or the control module 12 determines that the compressor is stationary, the control module 12 initiates the valve unblocking operation as part of step 940. The control module 12 then waits a predetermined time to allow the valve unblocking operation to complete as step 950 before ending the valve unblocking operation 960. When the control module 12 ends the valve unblocking operation a signal is sent to the clutch means to engage the clutch means 970 and to resume normal operation of the control valve 26. The control module 12 continues to monitor the operating conditions of the air-conditioning system and if an obstruction is detected or if the original valve unblocking operation did not successfully remove the contaminant 70 then the control module returns to step 900 and follows the steps outlined in Figure 9 again until the contaminant 70 is successfully dislodged from the valve 26.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims

1. A control module for a vehicle air-conditioning system comprising:

an input for receiving a signal indicative of a vehicle operating parameter; and an output for outputting a control signal to a control valve of a compressor of the air-conditioning system;

wherein the control module is configured to determine whether a predetermined condition for performing a control valve unblocking operation is met in dependence on a signal received at the input and, when it is determined that the condition is met, the control module is configured to output a control signal to the control valve to cause the control valve to perform the unblocking operation.

2. A control module according to claim 1, wherein the unblocking operation comprises actuating the control valve while the compressor is not being driven.

3. A control module according to claim 1 or claim 2, wherein the unblocking operation comprises actuating the control valve for a predetermined length of time and/or for a predetermined number of times.

4. A control module according to any preceding claim wherein, following a determination that the predetermined condition is met, the control module is configured to delay outputting the control signal for a prescribed amount of time.

5. A control module according to any preceding claim wherein the signal indicative of a vehicle operating parameter is indicative of a change of ignition status of an engine of the vehicle.

6. A control module according to claim 5, wherein determining that the predetermined condition is met comprises determining that the ignition status of the engine has changed from an ON state to an OFF state.

7. A control module according to any preceding claim wherein the signal indicative of a vehicle operating parameter is indicative of a compressor rotational speed.

8. A control module according to claim 7, wherein determining that the predetermined condition is met comprises determining that the compressor rotational speed is zero or substantially equal to zero.

9. A control module according to any one of the preceding claims wherein the signal indicative of a vehicle operating parameter is indicative of the temperature of a component of the air-conditioning system.

10. A control module according to claim 9, wherein determining that the predetermined condition is met comprises determining that the temperature of an evaporator of the air-conditioning system is outside a predetermined temperature range.

11. A control module according to any preceding claim, wherein the control signal is a cyclical control signal.

12. A system comprising a compressor for a vehicle air-conditioning system and a control module according to any one of claim 1 to 11, the compressor comprising a control valve having a valve member movable between first and second positions, the displacement of the compressor being dependent on the position of the valve member.

13. A system according to claim 12, where the valve member is arranged for reciprocating movement within a valve bore between the first position in which the control valve is in a closed state and the second position in which the control valve is in at least a partially open state.

14. A system according to claim 12 or 13, wherein the position of the valve member is controlled by an actuator, optionally a solenoid.

15. A system according to any one of claims 12 to 14, wherein the compressor is arranged so as to be driven by a combustion engine of the vehicle.

16. A system according to claim 15, comprising clutch means for decoupling the compressor from the engine, wherein determining that said predetermined condition has been met comprises determining that the clutch means is in an open state.

17. A vehicle comprising a control module according to any one or claims 1 to 11 or a system according to any one of claims 12 to 16.

18. A method for controlling a vehicle air-conditioning system comprising: receiving a signal indicative of a vehicle operating parameter;

determining whether a predetermined condition for performing a control valve unblocking operation is met in dependence on the received signal, and in dependence on a positive determination that the condition is met, outputting a control signal to a control valve of a compressor of the air-conditioning system to cause the control valve to perform the unblocking operation.

19. A method according to claim 18, wherein performing the unblocking operation only occurs when a rotational speed of the compressor is zero or substantially equal to zero.

20. A method according to claim 18 or 19, wherein the unblocking operation comprises moving a valve member of the control valve between first and second position a predetermined number of times or for a predetermined amount of time.