GB2534387A

GB2534387A - A method and system of cleaning a control valve

Info

Publication number: GB2534387A
Application number: GB1501022.6A
Authority: GB
Inventors: David Eves Brian; Keilthy Shane; Leroy Tom; Acton Mike
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2015-01-21
Filing date: 2015-01-21
Publication date: 2016-07-27
Anticipated expiration: 2035-01-21
Also published as: RU2016100896A3; GB201501022D0; GB2534387B; MX2016000813A; DE102016100482A1; RU2016100896A; RU2712537C2

Abstract

A method and system of cleaning a turbocharger bypass control valve 30, the control valve being operable to vary position of a bypass valve 26 (known as a wastegate valve) and thereby vary the amount of flow bypass across a turbine [Fig 1 22] and/or compressor 24 of a turbocharger for an engine, wherein the control valve is in fluidic communication with a vacuum source associated with the engine. The control valve is configured to selectively output the vacuum source pressure to modulate the output pressure of the control valve. The method further comprises determining when the control valve requires cleaning, whether the vacuum source is below a threshold value and increasing the flow through the control valve to clean the control valve. The method may also determine whether the vacuum source pressure is expected to be below the threshold and predicting a vacuum requirement for the vacuum source and may also monitor the performance of the control valve, bypass valve, turbocharger and engine, and determine length of time since previous clean of the control valve. The method may also sense whether contaminants have built up within the control valve. The vacuum source may comprise a vacuum reservoir.

Description

A METHOD AND SYSTEM OF CLEANING A CONTROL VALVE

The present disclosure relates to a method and system for cleaning a control valve and particularly but not exclusively relates to a method and system of cleaning a turbocharger bypass control valve.

Background

With reference to Figure 1, it is well known to provide an internal combustion engine 10 with a turbocharger 20 to improve its power output and reduce emissions. Typically, the turbocharger 20 is arranged with an exhaust gas driven turbine 22 driving a compressor 24 mounted on the same shaft. In addition, such turbochargers 20 often incorporate a bypass valve, known as a wastegate valve 26, which is used to control the flow of exhaust gas in a bypass passage 28 arranged in parallel to the turbine 22 of the turbocharger. The wastegate valve 26 may be used to modulate the amount of exhaust gas flowing through the turbine 22 and thereby change the power available to drive the compressor 24. Accordingly, the performance boost provided by the turbocharger 20 may be controlled by the position of the wastegate valve 26. Typically, an aim of the boosting by the turbocharger 20 is to run the engine 10 with the lowest possible level of throttling by the throttle 12, thereby reducing the pumping losses.

With reference to Figure 2, the position of the wastegate valve 26 may be controlled by a control valve 30. The control valve 30 is in fluidic communication with first and second reference pressures via first and second inlets 32, 34 respectively. For example, one of the first and second inlets 32, 34 may be in fluidic communication with a vacuum source, for example an engine driven pump or a super aspirator, and the other of the inlets 32, 34 may be open to atmosphere. The control valve 30 modulates the first and second reference pressures by virtue of a reciprocating shuttle 36, which is configured to selectively transmit the first or second reference pressures to an outlet 38 of the control valve. In this way, the control valve 30 provides an output pressure signal, which may be between the first and second reference pressures, and which may be varied by changing the duty cycle of the reciprocating shuttle. The shuttle 36 may be selectively moved by a solenoid, such that that the control valve 30 may comprise a pulse width modulated solenoid driven valve.

The output pressure signal from the control valve is in turn in fluidic communication 5 with a wastegate capsule 40. The wastegate capsule 40 comprises a diaphragm 41 behind which there is a piston 42 acting against a spring 43. A connecting rod 44 attached to the piston 42 is configured to move the wastegate valve 26 via a linkage 45. The linkage 45 may comprise a rotatable portion 46, which may rotate about an axis 46' to move the wastegate valve 26 away from or towards a corresponding valve seat. The modulated output pressure from the control valve 30 acts on the diaphragm 42 so as to selectively move the piston 44 against the spring 46 and thus open or close the wastegate valve 26.

The air drawn into the system from the atmosphere may be contaminated, for example with oil from the engine, dirt or any other contaminants. Additionally, and especially if the vacuum source is an engine driven pump, contaminants such as oil, water and other combustion products may be introduced from the vacuum source into the control valve 30. Hence, under certain conditions, the control valve 30 may become contaminated by a build up of deposits, resulting in a loss of functionality of the control valve. The responsiveness of the wastegate valve may suffer as a result.

Statements of Invention

According to an aspect of the present disclosure, there is provided a method of cleaning a turbocharger bypass control valve, the control valve being operable to vary the position of a bypass valve and thereby vary the amount of flow bypass across a turbine and/or compressor of a turbocharger for an engine, wherein the control valve is in fluidic communication with a vacuum source associated with the engine, the control valve being configured to selectively output the vacuum source pressure so as to modulate an output pressure of the control valve, the position of the bypass valve being determined by the output pressure of the control valve, wherein the method comprises: determining whether the control valve may require cleaning; determining whether the vacuum source pressure is below a threshold value; and increasing a flow of fluid through the control valve to clean the control valve.

The method may further comprise determining whether the vacuum source pressure is expected to be below the threshold value during a cleaning cycle. Determining whether the vacuum source pressure is expected to be below the threshold value may comprise predicting a vacuum requirement for the vacuum source.

If the vacuum source is above and/or is expected to be above the threshold pressure, cleaning of the control valve may be delayed by the method, for example, for a set period of time.

Additionally or alternatively, the method may further comprise monitoring the pressure of the vacuum source if the vacuum source pressure is above or is expected to be above the threshold value. The method may further comprise cleaning the control valve when the vacuum source pressure is no longer above and/or no longer expected to be above the threshold value.

The method may further comprise determining whether the engine torque requirement is below a threshold value. If the engine torque requirement is above a threshold value, cleaning of the control valve may be delayed by the method.

The method may further comprise maintaining a substantially constant engine torque output. This may be achieved, for example, by adjusting the throttle position of the engine so as to reduce or increase the engine torque output.

Cleaning of the control valve may be performed during a deceleration event of the engine and/or a vehicle comprising the engine, for example when the engine throttle is closed, and/or the torque requirement of the engine is zero or negative. In this case adjustment of the throttle to compensate for changes in boost level may not be required.

The control valve may comprise a movable shuttle con figured to selectively transmit the vacuum source pressure or a reference pressure such that a duty cycle of the shuttle determines the output pressure of the control valve.

The method may further comprise adjusting the duty cycle of the shuttle so as to increase or reduce the amount of boost provided by the turbocharger. The duty cycle of the shuttle may be adjusted such that the duty cycle is closer to a substantially 50% ratio.

The control valve may comprise an electronic vacuum regulator valve (EVRV) comprising an electromagnetic coil, wherein the strength of electromagnetic field generated by the coil determines the outlet pressure provided by the EVRV.

The method may further comprise adjusting the duty cycle of a pulse width modulated (PWM) control signal provided to the electromagnetic coil so as to increase or reduce the amount of boost provided by the turbocharger.

The method may comprise alternating the duty cycle between low and high values to clean the control valve. The method may further comprise adjusting the duty cycle of the PWM signal to a ratio of 80% or higher, e.g. 85%, for a set period. The method may further comprise adjusting the duty cycle of the PWM signal to a ratio of 20% or lower, e.g. 15%, for a set period.

Determining whether the control valve may require cleaning may comprise monitoring 25 the performance of one or more of the control valve, bypass valve, turbocharger and engine and determining if the performance is below a predetermined performance threshold.

Additionally or alternatively, determining whether the control valve may require 30 cleaning may comprise determining the length of time the control valve has been operating since a previous clean of the control valve.

Again additionally or alternatively, determining whether the control valve may require cleaning may comprise sensing whether contaminants have built up within the control valve.

The vacuum source may comprise a vacuum reservoir. Monitoring/predicting vacuum source pressure may comprise monitoring/predicting vacuum reservoir pressure. The vacuum source may further comprise a pump, an aspirator, a venturi etc. According to another aspect of the present disclosure, there is provided a system for cleaning a turbocharger bypass control valve, the control valve being operable to vary the position of a bypass valve and thereby vary the amount of flow bypass across a turbine and/or compressor of a turbocharger for an engine, wherein the control valve is in fluidic communication with a vacuum source associated with the engine, the control valve being configured to selectively output the vacuum source pressure so as to modulate an output pressure of the control valve, the position of the bypass valve being determined by the output pressure of the control valve, wherein the system comprises one or more controllers configured to: determine whether the control valve may require cleaning; determine whether the vacuum source pressure is below a threshold value; and increase a flow of fluid through the control valve to clean the control valve.

The one or more controllers may be further configured to determine whether the vacuum source pressure is expected to be below a threshold value during a cleaning cycle.

The one or more controllers may be further configured to predict a vacuum requirement for the vacuum source.

The one or more controllers may be further configured to delay cleaning the control valve if the vacuum source pressure is above and/or is expected to be above the threshold value.

Additionally or alternatively, the one or more controller may be further configured to monitor the pressure of the vacuum source if the vacuum source pressure is above or is expected to be above the threshold value; and clean the control valve when the vacuum source pressure is no longer above and/or expected to be above the threshold value.

The vacuum source comprises a vacuum reservoir.

According to another aspect of the present disclosure, there is provided software, which when executed by a computing apparatus causes the computing apparatus to perform the method of a previously mentioned aspect of the present disclosure.

According to another aspect of the present disclosure, there is provided a vehicle or engine comprising the system for cleaning a turbocharger bypass control valve according to a previously mentioned aspect of the present disclosure.

Brief Description of the Drawings

For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic view of a previously-proposed engine and turbocharger arrangement with a wastegate; Figure 2 shows a schematic view of a previously-proposed wastegate assembly for controlling the position of a turbocharger wastegate; Figure 3 shows a schematic view of an engine and turbocharger arrangement with a wastegate according to an example of the present disclosure; Figure 4a shows a schematic view of a vacuum control valve in a neutral position; Figure 4b shows a schematic view of a vacuum control valve in a configuration open to vacuum pressure; Figure 4c shows a schematic view of a vacuum control valve in a configuration open to a control air pressure; Figure 5 shows a method of cleaning a control valve according to an example of the

present disclosure; and

Figure 6 shows a system for cleaning a control valve according to an example of the present disclosure.

Detailed Description

With reference to Figures 3, 5 & 6, the present disclosure relates to a method of and/or system for cleaning the control valve 30 described above with reference to Figures 1 and 2. As mentioned above, the control valve 30 may control the position of the wastegate valve 26 via the wastegate capsule 40 and, for the sake of brevity, the details of their operation is not included here.

With reference to Figure 3, the engine 10, as described with reference to Figure 1 above, may be associated with a vacuum pump 14 which may be mechanically coupled to the output shaft of the engine and may be mechanically driven by the engine. Alternatively, the vacuum pump 14 may be driven electrically or a vacuum may be generated by any other vacuum source, such as a venturi device which does not require power directly from the engine to operate. The vacuum source, e.g. vacuum pump 14 may provide a vacuum source to systems associated with a vehicle, such as a motor vehicle, which is powered by the engine 10. Such systems, for example a brake boost system, may require vacuum pressure for their operation.

The vacuum pump 14 may also be used to provide a first reference pressure to the control valve 30. A vacuum reservoir 16 may be provided to ensure a stable pressure is available from the vacuum source 14. Although in the example shown in Figure 3, the vacuum pump 14 is shown in fluidic communication with the vacuum reservoir 16 and the vacuum reservoir 16 is shown in fluidic communication with the control valve 30, it will be appreciated that alternative arrangements are also possible. For example, the control valve may be in fluidic communication with both the vacuum reservoir and the vacuum pump.

Referring to Figure 5, the method 100 according to the present disclosure comprises: a first step 120, which determines whether the control valve 30 may require cleaning; a second step 140, which determines whether the pressure of the vacuum source 14 is below a threshold pressure; and a third step 160, which increases a flow of fluid through the control valve to clean the control valve.

The method 100 may comprise an optional step, which determines whether engine torque is below a threshold value. This step may be performed between the first and second steps 120, 140.

The method may further comprise an additional optional step, which adjusts a throttle 12 position of the engine 10 and thus the engine torque output to compensate for the adjustment in the amount of boost provided by the turbocharger 20. This step may occur at substantially the same time as the third step 160.

Referring to Figure 6, the system 200 according to the present disclosure comprises one or more controllers 200 comprising a first module 220 configured to determine whether the control valve 30 may require cleaning; a second module 240 configured to determine whether the pressure of the vacuum source is below a threshold value; and a third module 260 configured to increase a flow of fluid through the control valve to clean the control valve.

The system 200 may comprise an optional module configured to determine whether the engine torque is below a threshold value.

The system 200 may further comprise an additional optional module configured to adjust a throttle 12 position of the engine 10 and thus the engine torque output to compensate for the adjustment in the amount of boost provided by the turbocharger 20.

Throughout the present disclosure, pressure is considered relative to a perfect vacuum. Therefore, describing a pressure of a vacuum source as being "above" a threshold pressure means that the absolute pressure of the vacuum source is greater than the absolute threshold pressure and vice versa. Accordingly, it will be appreciated that when the vacuum source is at a "lower pressure" it is considered to be providing a better vacuum source and vice versa.

The control valve 30 may comprise a first inlet 32 for the first reference pressure and a second inlet 34 for the second reference pressure. The shuttle 36, or any other valve element may move, e.g. reciprocate, within the control valve so that it may alternatingly block the first and second inlets 32, 34. In this way the control valve 30 may modulate the first and second reference pressures such that the control valve output pressure may be equal to either, or between, the first and second reference pressures. As mentioned above, the first reference pressure may correspond to the pressure of a vacuum source.

The second reference pressure may be atmospheric pressure.

As the shuttle reciprocates there may be a net flow of fluid from the second inlet 34 to the first inlet 32 or vice versa. It will be appreciated that a very low or a very high duty cycle will limit such a net flow since one of the first and second inlets will be predominantly blocked with such a duty cycle. On the other hand the net flow will be increased at duty cycles away from these extremes since the first and second inlets are not blocked for as long. Therefore by varying the duty cycle of the shuttle valve the flow of fluid through the control valve may be increased. The increased flow of fluid through the control valve may carry with it any contaminants that have built up in the control valve and the control valve may thus be cleaned.

It will be appreciated that the duty cycle of the shuttle may be adjusted (whether by decrease or increase) such that the duty cycle is closer to a substantially 50% ratio at which the net flow through the control valve may be at a maximum. The duty cycle is a ratio of the time the shuttle spends at one end of the control valve relative to the time period for one oscillation of the shuttle. Accordingly, a 50% duty cycle ratio may correspond to the shuttle blocking the first and second control valve inlets for equal lengths of time.

As described above, when the first and second inlets 32, 34 are connected to the vacuum source 14 and left open to atmospheric pressure respectively, adjusting the duty cycle of the control valve 30 and increasing the net flow through the control valve results in the wastegate capsule being rapidly vented and then evacuated though the control valve.

This may flush any accumulated contaminants from the wastegate control system through to the vacuum source 14.

Alternatively, with reference to Figure 4a to 4c, the control valve 30 may instead comprise an electronic vacuum regulating valve (EVRV) 50. The EVRV 50 may receive a supply of vacuum pressure via vacuum inlet 52. Air at a reference pressure, for example atmospheric air, may he supplied via reference air input 54. The control pressure for the wastegate may be output via control outlet 64. A plunger 56 may be provided within the EVRV 50 which may be supported by a resilient clement, such as a diaphragm 58. The diaphragm 58 may be configured to bias the plunger 56 downwards against a bellows 62. The force acting on the plunger 56 may be the combination of the force applied by the diaphragm 58 and a force resulting from the pressure difference between the control outlet pressure at outlet 64 and the reference air pressure from inlet 54, i.e. the pressure difference across the plunger 56. A first end of the bellows 62 may selectively abut the vacuum inlet 52, e.g. so as to selectively block the vacuum inlet 52.

A second end of the bellows 62 may he operatively connected to an electromagnetic coil 60. The coil may receive a pulse width modulated (PWM) control signal, the duty cycle of which varies the strength of the magnetic field produced by the coil, and hence the force applied by the first end of the bellows against the vacuum inlet 52.

In a neutral position, as depicted in Figure 4a, an abutment surface 56a of the plunger may rest against the bellows 62, blocking the flow of reference air from the inlet 54 to the outlet 64. The bellows may in turn be positioned against the vacuum inlet 52, blocking the flow of air through the valve to the vacuum source 14. The pressure of control outlet 64 may therefore be substantially constant.

With reference to Figure 4b, if the duty cycle applied to the coil 60 is reduced, the force acting on the plunger may exceed the force applied by the bellows 62 against the vacuum inlet 52. Hence, the bellows may be compressed and may no longer block the vacuum inlet 52. Pressure within the control valve may therefore be reduced by the vacuum source 14 until the pressure difference across the plunger 56 balances the change in force provided by the coil 60 through the bellows 62. Once the force is balanced, the valve may return to the neutral configuration depicted in Figure 4a, the pressure output by the valve from outlet 64 may now be reduced.

With reference to Figure 4c, if the duty cycle applied to the coil 60 is instead increased, the force balance on the plunger 56 may be sufficient to move the plunger abutment surface 56a away from the bellows (e.g. if the pressure at outlet 64 becomes too low), producing a gap through which reference air from inlet 54 may flow. The pressure within the EVRV may therefore be increased until the pressure difference across the plunger 56 balances other forces acting on the plunger. Once the force is balanced, the control valve may return to the neutral position depicted in Figure 4a, with the pressure output by the valve from outlet 64 now increased.

The EVRV 50 may be cleaned by encouraging a flow through the EVRV, e.g. by alternating the duty cycle between low and high values so as to alternate between the modes depicted in Figures 4b and 4c. By way of example, the duty cycle may be held initially at a low value, for example a value less than 20%, such as 15%, for a period of time, before being held at a high value, for example a value greater than 80%, such as 85%, for a period of time. This process may be repeated a set number of times.

If the amount of boost provided by the turbocharger is increased through a change made to the duty cycle of the control valve during a cleaning cycle, the throttle position of the engine may then be adjusted to reduce the engine torque output. Once the cleaning has finished, the duty cycle of the control valve may be adjusted to reduce the amount of boost provided by the turbocharger and the throttle position of the engine may be adjusted to increase the engine torque output. During this process a substantially constant engine torque output may be maintained, e.g. by controlling the throttle position, so that the driver does not perceive a difference in the performance of the vehicle.

Alternatively, if the amount of boost provided by the turbocharger is reduced through a change made to the duty cycle of the control valve during a cleaning cycle, the throttle position of the engine may then be adjusted to increase the engine torque output. Once the cleaning has finished, the duty cycle of the control valve may be adjusted to increase the amount of boost provided by the turbocharger and the throttle position of the engine may be adjusted to reduce the engine torque output. Again, during this process a substantially constant engine torque output may be maintained, e.g. by controlling the throttle position, so that the driver does not perceive a difference in the performance of the vehicle.

If the control valve comprises the EVRV 50 and the duty cycle of the control valve is varied in an alternating fashion. The throttle position of the engine may be adjusted accordingly to maintain the engine torque output.

The amount of turbocharger boost (i.e. the position of the wastegate valve) may be returned to pre-adjustment levels, e.g. once it is determined that the control valve is clean or after a set amount of time of cleaning.

The throttle position may be adjusted by a throttle controller, such as a Powertrain Control Module (PCM). The throttle controller may adjust the throttle position so as to maintain a constant torque output of the engine whilst the duty cycle of the shuttle (and thus the turbocharger boost) is being varied. The throttle controller may refer to a stored look-up table to determine how much adjustment of the throttle is required to compensate for the change in turbocharger boost. The data in the stored look-up table may be obtained from the known characteristics of the turbocharger and engine.

Alternatively or additionally, a sensor may sense the engine torque output and the controller may adjust the throttle position, for example in a feedback loop.

During cleaning of the control valve, the flow of air through the control valve to the vacuum source 14 may be at its greatest. The power required by the vacuum source 14, to maintain the level of vacuum pressure supplied, may therefore be increased compared to when the control valve 30 is operating normally. Under normal operation of the wastegate valve, the reservoir 16 may reduce the impact of this effect on other vehicle systems. However, during a cleaning cycle, when the duty cycle of the control valve is adjusted as necessary to increase the flow of air through the control valve, significant demand may be place on the vacuum source 14 to maintain vacuum pressure within the reservoir 16, and hence to the control valve 30. In order to prevent this affecting or being affected by other systems which require the vacuum source 14, the system 200 may determine, before initiating a cleaning cycle, whether vacuum pressure is below a threshold pressure.

The cleaning of the control valve may be carried out at an appropriate point in the drive cycle of the engine. For example, if a high torque is required or likely to be required from the engine and high levels of boost from the turbocharger are thus required, it may be inappropriate to reduce the boost level to clean the control valve. On the other hand, if it is determined that the engine is in a low torque point in the drive cycle, then it may be appropriate to clean the control valve for example by increasing the boost level and throttling the engine. It may also be appropriate to clean the control valve during a deceleration event. During such an event, the throttle may be fully closed and/or the engine torque requirement may be zero or negative. Additionally the vacuum supply may still be below the threshold pressure. When cleaning the control valve under these conditions there may be no requirement to adjust the throttle, as described above, to compensate for the change in boost provided.

The controller may determine whether it is an appropriate time to clean the control valve. The controller may base such a decision on a proposed vehicle route and knowledge of the likely engine torque requirements along that route. If it is determined that the control valve may require cleaning, the actual cleaning may be delayed until the controller determines it is an appropriate point in the drive cycle to carry out the cleaning.

Considering the torque requirement of the engine, may be beneficial when the first and/or second reference pressure of the control valve is supplied by the vacuum source 14 provided on the engine. When a high mechanical torque is required from the engine, a venturi device such as a super-aspirator may be operating across a reduced pressure difference and a mechanically or electrically driven vacuum pump may be driven less effectively by the engine. This may compound the issue of reduced vacuum pressure being available to other systems, if cleaning is carried out whilst a. high torque is required from the engine.

If the vacuum source pressure is above a threshold value, cleaning of the control valve may be ineffective. Attempting to clean the control valve when the vacuum source pressure is high may prevent it from returning below the threshold value; additionally it may further increase the pressure of the vacuum source. This may affect the performance of other systems which require vacuum pressure from the vacuum source, such as the brake boost system.

If the vacuum source pressure is above the threshold value, the controller may delay the cleaning of the control valve until the vacuum source pressure has returned below the threshold pressure. Additionally, it may be desirable to consider whether the vacuum source pressure is expected to be above the threshold pressure during a planned cleaning cycle. The controller may consider the likely demand on the vacuum source from other systems on the vehicle to determine whether the pressure of the vacuum source may rise above the threshold value during a cleaning cycle. In this case the controller may similarly delay the cleaning cycle until the vacuum source is expected to remain below the threshold pressure throughout.

In the case that the controller delays the cleaning cycle, the controller may continue to monitor the pressure of the vacuum source and the vacuum requirements of other systems on the vehicle until an appropriate point is reached to clean the control valve.

To determine whether the control valve may require cleaning, the performance of one or more of the control valve, bypass valve, turbocharger and engine may be monitored. For example, if the performance is below a predetermined performance threshold, it may be determined that the control valve may require cleaning.

Alternatively or additionally, the control valve may be cleaned at periodic intervals. Accordingly, the length of time the control valve has been operating since a previous clean of the control valve may be calculated and stored.

Again, alternatively or additionally, determining whether the control valve may require cleaning may comprise determining the length of time the control valve output pressure, bypass valve position or duty cycle is above an upper threshold value and/or below a lower threshold value. Accordingly, when this length of time reaches a predetermined threshold, it may be determined that the control valve may require cleaning. For example if the control valve comprises a valve with a reciprocating shuttle, the length of time that the control valve operates with a shuttle duty cycle above 80% and/or below 20% may be calculated and when this length of time reaches a predetermined threshold it may be determined that the control valve may require cleaning. The longer the control valve operates at a high or low duty cycle, the more likely contaminants are to build up since there is less flow through the control valve. Therefore calculating and storing the time spent at these extremes may serve as a useful measure of whether the control valve may need cleaning.

Building on the previously-mentioned way of determining whether the control valve may require cleaning, a function dependent on a variable, such as the control valve output pressure, shuttle duty cycle and/or bypass valve position, may be integrated with respect to time and the result of the integration may be compared with a predetermined threshold value to decide whether cleaning is required. The function may be an absolute difference between the variable and a value of the variable which results in the minimum accrual of contaminants in the control valve. For example in the case where the control valve comprises a valve with a reciprocating shuttle, the absolute difference between the shuttle duty cycle D (expressed as a %) and a 50% duty cycle may be integrated with respect to time and compared against a threshold value T. As mentioned above, a 50% duty cycle may provide the maximum flow through the control valve and thus the cleanest mode of operation. The integration of duty cycle values away from this optimum may provide a measure of how contaminated the control valve may have become. When the result of the integration exceeds the threshold value T, the control valve may be cleaned. In other words the control valve may be cleaned when the expression below is satisfied: -50%ldt > T This integration may be carried out by a controller, e.g. an onboard computer, and the result of the integration may be stored in memory. It will be appreciated that the integration may be performed since a previous clean of the control valve, e.g. once the control valve has been cleaned the value resulting from the integration may be reset to zero. The duty cycle may be a convenient variable to integrate since a controller will have determined the desired duty cycle of the shuttle and as such will be readily available. However, the control valve output pressure and/or bypass valve position may instead be measured and may also be integrated in a manner similar to that described above, i.e. integrating the absolute difference between the variable and an optimum value (e.g. a value of the variable which results in the minimum accrual of contaminants in the control valve).

it will be appreciated that when it is determined that the control valve may require cleaning, the control valve may not actually require cleaning. The control valve may be cleaned as a precaution, for example to avoid a drop in the performance of the control valve that might otherwise occur. Alternatively, or as a further way of determining that the control valve requires cleaning, one or more sensors may be provided to sense whether contaminants have built up within the control valve and the control valve may then be cleaned when a build up of contaminants is sensed.

It will be appreciated by those skilled in the art that although the invention has been described by way of example, with reference to one or more examples, it is not limited to the disclosed examples and that alternative examples could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

Claims 1. A method of cleaning a turbocharger bypass control valve, the control valve being operable to vary the position of a bypass valve and thereby vary the amount of flow bypass across a turbine and/or compressor of a turbocharger for an engine, wherein the control valve is in fluidic communication with a vacuum source associated with the engine, the control valve being configured to selectively output the vacuum source pressure so as to modulate an output pressure of the control valve, the position of the bypass valve being determined by the output pressure of the control valve, wherein the method comprises: determining whether the control valve may require cleaning; determining whether the vacuum source pressure is below a threshold value; and increasing a flow of fluid through the control valve to clean the control valve.
2. "The method of claim 1, wherein the method further comprises: determining whether the vacuum source pressure is expected to be below the threshold value during a cleaning cycle.
3. The method of claim 2, wherein determining whether the vacuum source pressure is expected to be below the threshold value comprises predicting a vacuum requirement for the vacuum source.
4. The method of any of the preceding claims, wherein the method further comprises: delaying the cleaning of the control valve if the vacuum source pressure is above and/or is expected to be above the threshold value.
5. The method of any of the preceding claims, wherein the method further comprises: monitoring the pressure of the vacuum source if the vacuum source pressure is above or is expected to be above the threshold value; and cleaning the control valve when the vacuum source pressure is no longer above and/or no longer expected to be above the threshold value.
6. The method of any of the preceding claims, wherein the method further comprises: determining whether the engine torque requirement is below a threshold value.
7. The method of any of the preceding claims, wherein the method further comprises: delaying cleaning of the control valve if the engine torque requirement is above a threshold value.
8. The method of any of the preceding claims, wherein the method further comprises: maintaining a substantially constant engine torque output.
9. The method of any of the preceding claims, wherein the method further 20 comprises: adjusting the throttle position of the engine so as to reduce or increase the engine torque output.
10. The method according to any of the preceding claims, wherein the control valve 25 comprises an electronic vacuum regulator valve (EVRV) comprising an electromagnetic coil, wherein the strength of electromagnetic field generated by the coil determines the outlet pressure provided by the EVRV.
11. The method of claim 10, wherein the method further comprises: adjusting the duty cycle of a pulse width modulated (PWM) control signal provided to the electromagnetic coil so as to increase or reduce the amount of boost provided by the turbocharger.
12. The method of claim 11, wherein the method further comprises: adjusting the duty cycle of the PWM signal to a ratio of 80% or higher for a set period; and adjusting the duty cycle of the PWM signal to a ratio of 20% or lower for a set period.
13. The method of any of the preceding claims, wherein determining whether the control valve may require cleaning comprises: monitoring the performance of one or more of the control valve, bypass valve, 10 turbocharger and engine and determining if the performance is below a predetermined performance threshold.
14. The method of any of the preceding claims, wherein determining whether the control valve may require cleaning comprises: determining the length of time the control valve has been operating since a previous clean of the control valve.
15. The method of any of the preceding claims, wherein determining whether the control valve may require cleaning comprises: sensing whether contaminants have built up within the control valve.
16. The method of any of the preceding claims wherein the vacuum source comprises a vacuum reservoir.
17. The method according to any of the preceding claims, wherein cleaning of the control valve is performed during a deceleration event of the engine and/or a vehicle comprising the engine.
18. A system for cleaning a turbocharger bypass control valve, the control valve being 30 operable to vary the position of a bypass valve and thereby vary the amount of flow bypass across a turbine and/or compressor of a turbocharger for an engine, wherein the control valve is in fluidic communication with a vacuum source associated with the engine, the control valve being configured to selectively output the vacuum source pressure so as to modulate an output pressure of the control valve, the position of the bypass valve being determined by the output pressure of the control valve, wherein the system comprises one or more controllers configured to: determine whether the control valve may require cleaning; determine whether the vacuum source pressure is below a threshold value: and increase a flow of fluid through the control valve to clean the control valve.
19. The system of claim 18, wherein the one or more controllers are further configured to: determine whether the vacuum source pressure is expected to be below a threshold value during a cleaning cycle.
20. The system of claim 19, wherein the one or more controllers are further configured to predict a vacuum requirement for the vacuum source.
21. The system of any of claims 18 to 20, wherein the one or more controllers arc further configured to: delay cleaning the control valve if the vacuum source pressure is above and/or is expected to be above the threshold value.
22. The system of any of claims 18 to 21, wherein the one or more controller arc further configured to: monitor the pressure of the vacuum source if the vacuum source pressure is above or s expected to be above the threshold value; and clean the control valve when the vacuum source pressure is no longer above and/or expected to be above the threshold value.
23. The system of any of claims 18 to 22, wherein the vacuum source comprises a vacuum reservoir.
24. Software which when executed by a computing apparatus causes the computing apparatus to perform the method of any of claims 1 to 17.
25. A vehicle or engine comprising the system for cleaning a turbocharger bypass control valve of any of claims 18 to 23.
26. A method of cleaning a turbocharger bypass control valve substantially as described herein with reference to and as shown in Figure 5.
27. A system for cleaning a turbocharger bypass control valve substantially as described herein with reference to and as shown in Figures 3 and 6.Amendment to the claims have been filed as follows Claims 1. A method of cleaning a turbocharger bypass control valve, the bypass control valve being operable to vary the position of a bypass valve and thereby vary the amount of flow bypass across a turbine and/or compressor of a turbocharger for an engine, wherein the bypass control valve is in fluidic communication with a vacuum source associated with the engine, the bypass control valve being configured to selectively output the vacuum source pressure so as to modulate an output pressure of the bypass control valve, the position of the bypass valve being deter wined by the output pressure of the bypass control valve, wherein the method comprises: determining whether the bypass control valve may require cleaning; determining whether the vacuum source pressure is below a threshold value; and increasing a flow of fluid through the bypass control valve to clean the a) bypass control valve.2. The method of claim I, wherein the method further comprises: C\J determining whether the vacuum source pressure is expected to be below the threshold value during a cleaning cycle.3. The method of claim 2, wherein determining whether the vacuum source pressure is expected to be below the threshold value comprises predicting a vacuum requirement for the vacuum source.4. The method of any of the preceding claims, wherein the method further comprises: delaying the cleaning of the bypass control valve if the vacuum source pressure is above and/or is expected to be above the threshold value.5. The method of any of the preceding claims, wherein the method further comprises: monitoring the pressure of the vacuum source if the vacuum source pressure is above or is.expected to be above the threshold value; and cleaning the bypass control valve when the vacuum source pressure is no longer above and/or no longer expected to be above the threshold value.6. The method of any of the preceding claims, wherein the method further comprises: determining whether the engine torque requirement is below a threshold value.7. The method of any of the preceding claims, wherein the method further comprises: delaying cleaning of the bypass control valve if the engine torque requirement is above a threshold value."1- 15 8. The method of any of the preceding claims, wherein the method further a) comprises: CD maintaining a substantially constant engine torque output.9. The method of any of the preceding claims, wherein the method further comprises: adjusting the throttle position of the engine so as to reduce or increase the engine torque output.10. The method according to any of the preceding claims, wherein the bypass control 25 valve comprises an electronic vacuum regulator valve (EVRV) comprising an electromagnetic coil, wherein the strength of electromagnetic field generated by the coil determines the outlet pressure provided by the EVRV.11. The method of claim 10, wherein the method further comprises: adjusting the duty cycle of a pulse width modulated (PWM) control signal provided to the electromagnetic coil so as to increase or reduce the amount of boost provided by the turbocharger.12. The method of claim 1 1, wherein the method further comprises: adjusting the duty cycle of the PWM signal to a ratio of 80% or higher for a set period; and adjusting the duty cycle of the PWM signal to a ratio of 20% or lower for a set period.13. The method of any of the preceding claims, wherein determining whether the bypass control valve may require cleaning comprises: monitoring the performance of one or more of the bypass control valve, bypass valve, turbocharger and engine and determining if the performance is below a predetermined performance threshold.14. The method of any of the preceding claims, wherein determining whether the bypass control valve may require cleaning comprises: determining the length of time the bypass control valve has been operating since a a) previous clean of the bypass control valve.15. The method of any of the preceding claims, wherein determining whether the C\J bypass control valve may require cleaning comprises: sensing whether contaminants have built up within the bypass control valve.16. The method of any of the preceding claims wherein the vacuum source comprises a vacuum reservoir.17. The method according to any of the preceding claims, wherein cleaning of the bypass control valve is performed during a deceleration event of the engine and/or a vehicle comprising the engine.18. A system for cleaning a turbocharger bypass control valve, the bypass control 30 valve being operable to vary the position of a bypass valve and thereby vary the amount of flow bypass across a turbine and/or compressor of a turbocharger for an engine, wherein the bypass control valve is in fluidic communication with a vacuum source associated with the engine, the bypass control valve being configured to selectively output the vacuum source pressure so as to modulate an output pressure of the bypass control valve, the position of the bypass valve being determined by the output pressure of the bypass control valve, wherein the system comprises one or more controllers configured to: determine whether the bypass control valve may require cleaning; determine whether the vacuum source pressure is below a threshold value; and increase a flow of fluid through the bypass control valve to clean the bypass control valve.19. The system of claim 18, wherein the one or more controllers are further configured to: determine whether the vacuum source pressure is expected to be below a threshold value during a cleaning cycle.a) 20. The system of claim 19, wherein the one or more controllers are further CD configured to predict a vacuum requirement for the vacuum source.21. The system of any of claims 18 to 20, wherein the one or more controllers are further configured to: delay cleaning the bypass control valve if the vacuum source pressure is above and/or is expected to be above the threshold value.22. The system of any of claims 18 to 21, wherein the one or more controllers are further configured to: monitor the pressure of the vacuum source if the vacuum source pressure is above or is expected to be above the threshold value; and clean the bypass control valve when the vacuum source pressure is no longer above and/or expected to be above the threshold value.23. The system of any of claims 18 to 22, wherein the vacuum source comprises a vacuum reservoir.24. Software which when executed by a computing apparatus causes the computing apparatus to perform the method of any of claims 1 to 17.25. A vehicle or engine comprising the system for cleaning a turbocharger bypass control valve of any of claims 18 to 23.26. A method of cleaning a turbocharger bypass control valve substantially as described herein with reference to and as shown in Figure 5.27. A system for cleaning a turbocharger bypass control valve substantially as described herein with reference to and as shown in Figures 3 and 6.