Method for cleaning a valve

A method and system for cleaning a brake booster aspirator shut-off valve are provided. The shut-off valve is operable to selectively permit flow of intake air through an aspirator; the aspirator bypasses a throttle of an engine and provides a vacuum source for a brake booster. The method comprises determining whether the shut-off valve may require cleaning, opening the shut-off valve so as to permit a flow of air through the shut-off valve and clean the shut-off valve and adjusting the throttle position of the engine to compensate for the additional flow of intake air through the aspirator.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Great Britain Patent Application No. 1501281.8, filed Jan. 27, 2015, the entire contents of which are hereby incorporated by reference for all purposes.

FIELD

The present disclosure relates to a method for cleaning a valve within the air intake system of a motor vehicle and is particularly, although not exclusively, concerned with a method for cleaning a super aspirator shut off valve.

Most modern vehicles are fitted with a brake booster which uses a vacuum chamber to increase the braking force supplied from the brake pedal to the brake master cylinder. The brake booster prevents the brake pedal from feeling heavy to the driver.

The brake booster requires a source of vacuum pressure in order to operate, which, in naturally aspirated engines, is often delivered exclusively by the inlet manifold. In some circumstances the vacuum supplied by the inlet manifold may be insufficient. This may be due to a large amount of torque being supplied by the engine, either for mechanical drive or to power auxiliary electrical systems in the vehicle. In this case the inlet throttle may be fully open and hence inlet manifold vacuum may be low.

In order to maintain the brake booster vacuum under conditions of low inlet manifold vacuum, an additional vacuum source may be used, such as a super aspirator. A super aspirator may take the form of a venturi duct connected between the intake duct and inlet manifold across the inlet throttle, e.g. bypassing the inlet throttle. The pressure difference across the throttle drives a flow through the venturi allowing a lower pressure to be generated within the venturi. This can in turn be used to provide a lower pressure (higher vacuum) in the brake booster vacuum chamber than could be supplied by the inlet manifold.

A shut-off valve may control the operation of the super aspirator, e.g. by selectively permitting flow to the super aspirator. The shut-off valve may be opened when insufficient vacuum is present in the brake booster and/or inlet manifold. The shut-off valve may be controlled by the engine's power-train control module and may normally be in a closed position unless activated.

If the super aspirator is not required for long periods of time and hence the shut-off valve remains closed, contaminants within the air such as oil, dirt, fuel or other deposits may build up on the shut-off valve and impair its performance or prevent it opening when the super aspirator is required.

According to an aspect of the present disclosure, there is provided a method of cleaning a brake booster aspirator shut-off valve, the shut-off valve being operable to selectively permit flow of intake air through an aspirator, the aspirator bypassing a throttle of an engine and providing a vacuum source for a brake booster, wherein the method comprises: determining whether the shut-off valve may require cleaning; and at least partially opening the shut-off valve so as to permit a flow of air through the shut-off valve and clean the shut-off valve. The method may further comprise adjusting the throttle position of the engine to compensate for the additional flow of intake air through the aspirator.

The method may further comprise shutting the shut-off valve and returning the throttle to its unadjusted position. The opening and closing of the shut-off valve, together with the corresponding adjustments to the throttle position may be repeated, e.g. immediately repeated in a particular cleaning cycle, e.g. a predetermined number of times.

The throttle position may be adjusted to compensate for the additional flow of intake air through the aspirator in order to maintain a constant inlet manifold pressure. Additionally or alternatively, the throttle position may be adjusted to compensate for the additional flow of intake air through the aspirator in order to maintain a constant engine torque.

The method may further comprise: determining whether a possible change in throttle position can compensate for the additional flow of intake air through the aspirator. If a change in throttle position cannot compensate for the additional flow of intake air through the aspirator, cleaning of the shut-off valve may be delayed, e.g. for a set period of time or until the throttle position can compensate for the additional flow of intake air. Additionally or alternatively, the throttle position may be monitored and the shut-off valve may be cleaned when a change in throttle position can compensate for the additional flow of intake air through the aspirator.

The method may further comprise: determining whether the engine speed and/or torque is within a range in which cleaning of the shut-off valve is permitted. Cleaning of the shut-off valve may only be permitted if engine conditions are suitable. If the engine speed and/or torque is not within a range in which cleaning of the shut-off valve is permitted, cleaning of the shut-off valve may be delayed, e.g., for a set period of time. Additionally or alternatively, the engine speed and/or torque may be monitored, and the shut-off valve may be cleaned when the engine speed and/or torque is suitable.

Determining whether the shut-off valve may require cleaning may comprise determining an interval of: engine running time; engine revolutions; and/or engine or vehicle mileage; since the shut-off valve was previously opened and comparing the result to a predetermined threshold value. Additionally or alternatively, determining whether the shut-off valve may require cleaning may comprise determining an interval of time since the shut-off valve was previously cleaned and comparing the result to a predetermined threshold value. Again additionally or alternatively, determining whether the shut-off valve may require cleaning may comprise: sensing whether contaminants have built up within the aspirator shut-off valve. According to another aspect of the present disclosure, there is provided a method of cleaning a throttle, the throttle being operable to selectively permit flow of intake air into an inlet manifold of an engine, wherein the method comprises: determining whether the throttle may require cleaning; adjusting the position of the throttle so as to disturb any contaminants which have settled on the throttle; and adjusting the position of a super aspirator shut-off valve to compensate for the change in flow of intake air through the throttle, the super aspirator shut-off valve selectively permitting the flow of intake air through an aspirator bypassing the throttle.

According to another aspect of the present disclosure, there is provided a system for cleaning a brake booster aspirator shut-off valve or a throttle of an engine, the shut-off valve being operable to selectively permit flow of intake air through an aspirator, the aspirator bypassing the throttle of the engine and providing a vacuum source for a brake booster, wherein the system comprises one or more controllers, including executable instructions stored in memory, configured to perform the method according to any of the previously mentioned aspects of the disclosure.

The system may further comprise one or more sensors configured to sense whether contaminants have built up within the brake booster aspirator shut-off valve and/or throttle.

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

According to another aspect of the present invention, there is provided a vehicle or engine comprising the system for cleaning a brake booster aspirator shut-off valve or throttle of an engine according to any of the previously mentioned aspects of the disclosure.

DETAILED DESCRIPTION

With reference toFIG. 1, a typical motor vehicle including a brake booster is described. The vehicle may comprise an engine10and a brake assembly50.

The engine10may comprise a plurality of cylinders12and corresponding pistons28. Air flow into and out of each of the cylinders12may be controlled through the use of inlet and outlet valves14,16respectively.

The engine10may comprise an inlet20which allows air to be drawn into the engine. The engine10may further comprise a turbocharger22. Typically, the turbocharger comprises a compressor22awhich is arranged with an exhaust driven turbine22bdriving the compressor22aon the same shaft. The turbocharger22may improve the engine power output and emissions. Air may enter the engine10through inlet20and be passed through the compressor22a. Air which has been compressed by the turbocharger compressor22amay be throttled by an inlet throttle19before being delivered to an inlet manifold18.

Due to the presence of the inlet throttle valve19, and also through the action of the engine pistons28drawing air from the inlet manifold into the engine cylinders12, the inlet manifold18may be at a lower pressure than air entering via the inlet20, i.e. there may be a vacuum present within the inlet manifold18. The level of manifold vacuum may be reduced as the throttle is opened, and/or power is supplied to the turbocharger compressor22afrom the turbocharger turbine22b, boosting the pressure of the inlet air.

The inlet manifold18may be disposed about the inlet valves14, such that air within the inlet manifold18may be drawn into the cylinders12when each of their respective inlet valves14is open. In the cylinders12, fuel is mixed with the air and combusted.

Combustion gases are exhausted from the cylinders12via outlet valves16into an exhaust manifold24. Exhaust gases within the manifold24may then pass though the turbocharger turbine22bbefore being exhausted through an exhaust pipe26.

The brake assembly50may comprise a brake pedal54, a brake booster56and a brake master cylinder59. The brake booster56may be configured to amplify the force provided by a foot52on the brake pedal54.

Amplification of the applied braking force may be achieved through the use of a negatively pressurized brake booster chamber58provided within the brake booster56. A diaphragm (not shown) may be provided within the brake booster chamber58. When the brake pedal54is pushed by a driver, the diaphragm may be exposed to atmospheric air on one side, whilst the other side of the diaphragm may be exposed to the vacuum pressure within the brake booster chamber. The pressure difference across the diaphragm may be used to provide additional braking force to the brake master cylinder59.

Using a brake booster to amplify the supplied braking force in this way has the effect of a lighter feeling brake pedal, as the driver need not push as hard to achieve the desired level of braking.

The brake booster chamber58may be connected via a vacuum line60to the inlet manifold18and may thereby be charged with vacuum pressure from the inlet manifold. A check valve62may be provided in the vacuum line60to ensure the flow is from the brake booster chamber58to the inlet manifold18only. This allows vacuum pressure in the brake booster chamber58to be maintained through conditions when inlet manifold vacuum is low.

When the turbocharger22is operating, and/or the inlet throttle19is open, the inlet manifold pressure may be close to or above atmospheric levels and hence an additional vacuum source64may be provided for the brake booster56. InFIG. 1, the additional vacuum source comprises an electrically driven vacuum pump.

With reference now toFIG. 2, the vehicle may comprise an engine210, a super aspirator201and a system200according to an example of the present disclosure. In the example shown inFIG. 2, the engine210comprises a naturally aspirated petrol engine, however it is equally envisaged that the present disclosure could apply to a diesel engine. Additionally or alternatively, the engine could comprise a turbocharger or supercharger. In some embodiments, the vehicle may additionally comprise an electric motor and the engine210may be part of a hybrid drive system.

The naturally aspirated engine210shown inFIG. 2also comprises the inlet20, the throttle19and the intake manifold18described above.

In the example shown inFIG. 2, the additional vacuum source64comprises the super aspirator201. The super aspirator is a venturi device and comprises an inlet side201a, an outlet side201band a narrowing or throat201ctherebetween. The inlet side201ais connected to the inlet20of the engine210via inlet line206. An outlet line208connects the outlet side201bto the inlet manifold18of the engine210.

As described above, when the engine210is operating, there may be a reduced pressure within the inlet manifold18relative to the inlet20. Air may therefore be drawn through the super aspirator from the higher pressure inlet20to the lower pressure inlet manifold18. When a flow of air is present through the super aspirator, the pressure within the venturi of the super aspirator201may be lower than at either the inlet side201aor the outlet side201b.

A vacuum pipe220may be connected to the super aspirator201, e.g. at the throat201c, between the inlet end201aand the outlet end201b. The vacuum pipe may be in fluidic communication with the flow through the super aspirator venturi. The vacuum pipe220may be connected at the location where the pressure in the venturi is lowest.

The vacuum pipe220may also be connected (directly or indirectly) to the brake booster chamber58. When the super aspirator is operating, the brake booster chamber may thus be charged with a higher level of vacuum than the inlet manifold18. A super aspirator check valve216may be provided between the brake booster56and the super aspirator201to allow the vacuum to be retained within brake booster56when the super aspirator201is not operating.

Operation of the super aspirator may be controlled by a shut-off valve202. The shut off valve may comprise a ball valve, or a butterfly valve, or any other valve capable of selectively permitting flow through the super aspirator. The shut-off valve may be positioned within the super aspirator and may be positioned at the inlet or the outlet of the super aspirator. Alternatively, the shut-off valve may be positioned between the inlet and the outlet of the super aspirator, for example at the throat201c. Alternatively, the shut-off valve may be positioned upstream of the super aspirator, e.g. on the inlet line206or downstream of the super aspirator, e.g. on the outlet line208. The shut-off valve202may close to prevent the flow of air through the super aspirator when additional vacuum is not required. For example, when a sufficient level of vacuum is available from the inlet manifold18and the super aspirator is not required.

When the additional vacuum source64comprises the super aspirator201, as shown inFIG. 2, the vacuum line60may still be provided to enable the brake booster chamber56to be charged with vacuum pressure from the inlet manifold when desirable, i.e. when a sufficient level of vacuum is available from the inlet manifold18. If the vacuum line60is provided, the check valve62may also be provided as described above.

The shut-off valve202may be exposed to contaminants present in the air from the inlet20and the inlet manifold18as well as in the air which is drawn from the brake booster chamber58. This air may contain traces of oil, dirt, fuel or other particles which may settle on the shut-off valve and may build up as a deposit on the valve. Exposure to contaminants may occur even when the shut-off valve202is closed.

In some vehicle configurations and driving conditions, the shut-off valve202may be opened regularly which may dislodge any built up contaminants. Dislodged contaminants may be drawn into the engine210and combusted.

In some circumstances, the shut-off valve202may remain closed for long periods, for example if the engine210is configured such that the inlet manifold vacuum remains high during normal operation, and/or the brakes are not regularly operated. In these cases, contaminants may not be regularly removed from the shut-off valve202.

If contaminants are allowed to build up on the shut-off valve202, the performance of the shut-off valve may be affected. In some cases, the build up of contaminants may lead to the shut-off valve being completely blocked, or unable to open, such that the super aspirator201can no longer be used to provide a vacuum source for the brake booster56.

With reference toFIG. 3, in order to prevent a loss of performance of the shut-off valve202, a monitoring and cleaning process300according to the present disclosure may be carried out. The process300may comprise a first step310, which determines whether the shut-off valve may require cleaning; a second step320, which performs a cleaning cycle on the shut-off valve; and a third step330, which adjusts the position of the throttle19of the engine210to compensate for the change in flow through the super aspirator201, which by-passes the throttle19, during the cleaning cycle. The second and third steps320,330may occur substantially at the same time.

Referring toFIG. 4, a system according to the present disclosure may comprise one or more controllers100comprising a first module110configured to determine whether the super aspirator shut off valve202may require cleaning; a second module120configured to perform the shut-off valve cleaning cycle; and a third module130configured to adjust the throttle19to compensate for the change in flow through the super aspirator201.

During a valve cleaning cycle in step320, the shut-off valve may be opened and shut a number of times, which may allow air to flow through the shut-off valve and may dislodge and remove any contaminants from the valve. The number of times the valve is opened may be 5, 10, 20 or more times. The number of times the valve is opened may be configured, for example the number of times the valve is opened may be set according to the predicted amount of contaminant build up. The time period the shut-off valve is open and the time period the shut-off valve is closed may be calibrated to maximize contaminant removal. Additionally or alternatively other considerations may be used.

The shut-off valve may open and close rapidly. Furthermore, when opening or closing the shut-off valve during cleaning, the rate of movement of the shut-off valve may be greater than during normal operation. This may help to dislodge any contaminants on the shut-off valve. Additionally or alternatively to opening and closing the shut-off valve, the shut-off valve may be opened, partially or fully, for a set period of time to allow a flow of air over the valve to carry away any dislodged contaminants. When the shut-off valve is partially opened, the velocity of the air flowing through the shut-off valve may be higher than when the shut-off valve is fully open. The flow of air through the partially opened shut-off valve may therefore be more likely to dislodge and/or carry away any contaminants present. The period over which the valve is opened may be set according the predicted amount of contaminant build up.

When the super aspirator201is operating, a portion of the inlet air passes through the super aspirator rather than through the inlet throttle19and hence more air may be allowed to flow from the inlet20to the inlet manifold18than would usually flow past the throttle19if the super aspirator was not operating. To compensate for the fluctuations in air flow to the inlet manifold18during a shut-off valve cleaning cycle, in step330the controller100may close, e.g., partially or fully, the inlet throttle19at the same time as opening the shut-off valve202, in order to maintain substantially the same flow of air into the inlet manifold18.

The controller100may refer to a stored look-up table to determine how much adjustment of the throttle is required to compensate for the flow through the super aspirator201. Alternatively or additionally, the adjustment of the throttle may be determined by the current running conditions of the engine210. For example, a sensor may measure the engine torque output, which may be used to determine the throttle adjustment necessary. Additionally or alternatively, the controller100may act to maintain an engine parameter such as manifold air pressure during shut-off valve cleaning, for example using a feedback loop. In this way the controller100may be configured to clean the shut-off valve in a way which is undetectable to the driver.

The controller100may be configured not to trigger a cleaning cycle when the engine is running within a certain speed range and/or when the engine is providing a certain torque. For example, when the engine is running at low speed or is only lightly loaded, the throttle may only be slightly open. Under these conditions, it may not be possible to adequately compensate for the increased air flow to the inlet manifold by closing the throttle. In this case, cleaning of the shut-off valve may be delayed, e.g. for a set period of time. Additionally or alternatively, the controller may continue to monitor the engine speed and/or torque, and a cleaning cycle may be initiated when the engine speed and/or torque is at an appropriate level.

To determine whether the super aspirator shut-off valve may require cleaning, the performance of one or more of the super aspirator, the brake booster, the brake system and the engine may be monitored. For example, if the performance is below a predetermined performance threshold, it may be determined that the super aspirator shut-off valve may require cleaning.

In order to determine the performance of the shut-off valve, the controller100may consider the rate at which the pressure of the brake booster vacuum chamber changes when the shut-off valve is opened, and/or the time taken to reach a desired vacuum level. Additionally or alternatively, the controller100may compare the maximum vacuum level achieved to an expected value.

Alternatively or additionally, the controller100may be configured to determine whether a cleaning cycle is required by recording the interval between shut-off valve openings. The interval may be measured with respect to engine running time, engine or vehicle mileage, or revolutions of the engine210. If the interval between shut-off valve openings exceeds a pre-determined threshold value, the controller100may initiate a valve cleaning cycle.

Alternatively or additionally, the controller100may trigger a cleaning cycle at periodic intervals regardless of how frequently the super aspirator is switched on. Accordingly, the length of time since the shut-off valve has undergone a cleaning cycle may be calculated and stored.

It will be appreciated that when it is determined that the shut-off valve may require cleaning, the shut-off valve may not actually require cleaning. The shut-off valve may be cleaned as a precaution, for example to ensure the shut-off valve will be able to open when required by the brake system and will not restrict air flow through the super aspirator undesirably.

Alternatively, or as a further way of determining that the shut-off valve requires cleaning, one or more sensors may be provided to sense whether contaminants have built up within the shut-off valve. The shut-off valve may then be cleaned when a build up of contaminants is detected.

As another example, the movement of the throttle valve may be based on a determination that the cleaning is about to be initiated, but before the shut-off valve is actually opened (and or repeatedly opened/closed) for cleaning. For example, the throttle may be closed immediately before, but still before, movement of the shut-off valve to compensate for airflow and/or pressure change delays in the air induction system so that the airflow may be controlled accurately at the engine cylinders. Further, spark timing adjustments or fuel injection timing adjustments may also be coordinated with the early throttle movement to decrease any remaining airflow/aircharge errors at the cylinders. For example, the pre-movement of the throttle may be based on anticipated movement estimated for the shut-off valve, but based upon actual movement and/or actual airflow measurements, further adjustments to the throttle may be too slow, and thus adjustments to spark timing may be used to compensate for such transient errors.

Although the description above has been made with reference to the shut-off valve being cleaned and the throttle being adjusted to compensate for the change in flow through the super aspirator, it is equally possible that the method of the present disclosure could be applied to cleaning the throttle by varying the position of the throttle and controlling the shut-off valve to compensate for the change in flow through the throttle. Therefore, features described with respect to the shut-off valve may also apply to the throttle.

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.