GB2560574B

GB2560574B - An apparatus, method and computer program for monitoring an exhaust flap within a vehicle

Info

Publication number: GB2560574B
Application number: GB1704244.1A
Authority: GB
Inventors: Anthony Varney Brian
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-03-17
Filing date: 2017-03-17
Publication date: 2019-08-21
Anticipated expiration: 2037-03-17
Also published as: GB201704244D0; GB2560574A

Description

AN APPARATUS, METHOD AND COMPUTER PROGRAM FOR MONITORING AN

EXHAUST FLAP WITHIN A VEHICLE

TECHNICAL FIELD

The present disclosure relates to an apparatus, method, computer program and non-transitory computer readable medium for monitoring an exhaust flap within a vehicle. In particular, but not exclusively it relates to an apparatus, method, computer program and non-transitory computer readable medium for monitoring an exhaust flap within a vehicle to identify whether or not the exhaust flap is opening correctly.

Aspects of the invention relate to an apparatus, method, computer program and non-transitory computer readable medium.

BACKGROUND

Exhaust flaps may be provided within exhaust systems to control the noise produced by the systems. If the exhaust flap is not opened correctly this may lead to high pressures within the exhaust system which may cause damage to the engine.

It is useful to be able to identify that the exhaust flap has not opened correctly so that problems caused by the high pressure within the exhaust system can be attributed to the malfunctioning of the exhaust flap.

It is an aim of the present invention to enable an assessment to be made of whether or not an exhaust flap is opening correctly.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an apparatus, method, computer program and non-transitory computer readable medium as claimed in the appended claims.

According to an aspect of the invention there is provided a method of monitoring an exhaust flap of an exhaust system of a vehicle comprising: determining a first flow resistance of the exhaust system when the exhaust flap is indicated to be in a first position, determining a second flow resistance of the exhaust system when the exhaust flap is indicated to be in a second position and determining if the indicated positions of the exhaust flap are correct using the first flow resistance and the second flow resistance, wherein determining the first and second flow resistances and determining if the indicated positions of the exhaust flap are correct is inhibited if a soot oxidation rate of a particulate filter of the exhaust system is above a predetermined limit.

The pressure within the exhaust system for a given volumetric flow rate may vary with the amount of soot loading on a particulate filter of the exhaust system. The flow resistance of the exhaust system is therefore dependent on the amount of soot loading on the particulate filter. If the amount of soot loading is changing, for example through soot oxidation during a filter regeneration process, the reliability of a determined value of flow resistance of the exhaust system may be affected. By inhibiting the determination of the first and second flow resistances and the determination of whether the indicated positions of the exhaust flap are correct if a soot oxidation rate of a particulate filter of the exhaust system is above a predetermined limit, the reliability of the overall method may be improved. This predetermined limit may be a soot oxidation rate of zero or any suitable limit below which the reliability of the method is not affected.

According to another aspect of the invention there is provided a method of monitoring an exhaust flap of an exhaust system of a vehicle comprising: determining a first flow resistance of the exhaust system when the exhaust flap is indicated to be in a first position, determining a second flow resistance of the exhaust system when the exhaust flap is indicated to be in a second position and determining if the indicated positions of the exhaust flap are correct using the first flow resistance and the second flow resistance, wherein determining if the indicated positions of the exhaust flap are correct is inhibited if soot oxidation of a particulate filter of the exhaust system is detected after determining the first flow resistance and before determining the second flow resistance.

As described above, the flow resistance of the exhaust system is dependent on the amount of soot loading on a particulate filter of the exhaust system as well as the degree of opening of the exhaust flap. This is because each of these variables affects the pressure within the exhaust system for a given volumetric flow rate. The difference between flow resistances of the exhaust system when the exhaust flap is indicated to be in each of a first and second position is used to determine whether or not the indicated position of the exhaust flap is correct. If the oxidation of the particulate filter occurs between determining the first flow resistance and determining the second flow resistance, the effect of the oxidation of the particulate filter on the second flow resistance could result in an incorrect determination of whether or not the indicated positions of the exhaust flap are correct. For example, the first flow resistance could be determined when the exhaust flap is indicated to be closed and the second flow resistance could be determined when the exhaust flap is indicated to be open. If the exhaust flap was malfunctioning, the indication that the exhaust flap is in the open position could be incorrect, i.e. the flap had failed to move from the closed position to the open position. This would be reflected by no or little difference between the first and second flow resistances. However, if particulate filter oxidation had occurred between the first and second flow resistances being determined then this could result in a significant difference between the two flow resistances. This could be misinterpreted to mean that the exhaust flap was functioning correctly when in fact it wasn’t. As such, determining if the indicated positions of the exhaust flap are correct is inhibited if soot oxidation of a particulate filter of the exhaust system is detected after determining the first flow resistance and before determining the second flow resistance. This may reduce the likelihood of incorrect determinations of whether or not the positions of the exhaust flap are as indicated.

The flow resistance of the exhaust system may be any suitable indicator of the relationship between exhaust pressure and volumetric flow rate within the exhaust system. This relationship, and thereby flow resistance, may be effected by a number of variables within the exhaust system, such as the amount by which a particulate filter is blocked or the degree of opening of the exhaust flap. A higher value of flow resistance may indicate a higher exhaust pressure for a given volumetric flow rate compared to a lower value of flow resistance. As such, the flow resistance should vary with the degree of opening of the exhaust flap. If there is no difference in the flow resistance determined when the exhaust flap is in a first position compared to the flow resistance determined when the exhaust flap is in a second position, then this could be an indication the exhaust flap is not moving between positions correctly.

The position of the exhaust flap may be indicated by any suitable means such via a signal generated by an electro-mechanical actuator configured to operate the exhaust flap.

The flow resistance of the exhaust system may be previously determined in order to obtain a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded. The value of flow resistance obtained for this purpose can therefore also be used to determine if the indicated positions of the exhaust flap are correct. This may advantageously reduce computing time and computing power demand.

The first position may be a closed position and the second position may be an open position.

There may be a larger expected difference in the flow resistance values between an open position and a closed position than between a partially open and a closed position. Therefore this may provide an accurate determination of whether the indicated position of the exhaust flap is correct.

Determining if the indicated positions of the exhaust flap are correct may comprise determining a difference between absolute values of the first flow resistance and the second flow resistance. The difference then may be compared to a predetermined limit. If the difference is below the predetermined limit, the indicated positions of the exhaust flap may be determined to be incorrect.

This may provide a reliable method of monitoring the position of the exhaust flap with minimal increase in the processing requirements.

Determining if the indicated positions of the exhaust flap are correct may comprise determining a difference between average values of the first flow resistance and the second flow resistance. The difference then may be compared to a predetermined limit. If the difference is below the predetermined limit, the indicated positions of the exhaust flap may be determined to be incorrect.

This may provide a reliable method of monitoring the position of the exhaust flap.

Determining the first flow resistance may comprise obtaining a first value indicative of exhaust pressure within the exhaust system and obtaining a first value indicative of volumetric flow rate within the exhaust system, and determining the second flow resistance comprises obtaining a second value indicative of exhaust pressure within the exhaust system and obtaining a second value indicative of volumetric flow rate within the exhaust system. A mapping between pressure, volumetric flow rate and flow resistance may be used to determine the flow resistance. Alternatively, an equation relating flow resistance, pressure and/or volumetric flow rate may be used.

One or more air mass flow sensors may be used to obtain the first and second values indicative of volumetric flow rate within the exhaust system. Alternatively, a value for fuel mass flow is may be used.

The first and second values indicative of exhaust pressure within the exhaust system may be obtained from one or more pressure sensors positioned within the exhaust system. The output from the one or more pressure sensors may be filtered prior to determining the first and second flow resistances. At least one of the one or more pressure sensors may be positioned close to the engine and may additionally be positioned downstream of a turbocharger turbine of the exhaust system.

The first values indicative of exhaust pressure and volumetric flow rate within the exhaust system may be synchronised before determining the first flow resistance. Alternatively or additionally, the second values indicative of exhaust pressure and volumetric flow rate within the exhaust system may be synchronised before determining the second flow resistance.

The use of the sensors described above may enable the method to be implemented without requiring any additional components to be added to the exhaust system.

The method may comprise recording information indicative of when the indicated position of the exhaust flap is incorrect.

This provides the benefit that it enables a log of times when the indicated position of the exhaust flap is incorrect to be maintained. This information may be used during maintenance of the vehicle to enable any problems with the exhaust flap to be identified and addressed.

According to an aspect of the invention there is provided an apparatus for monitoring an exhaust flap of an exhaust system of a vehicle comprising means for carrying out the method as described above.

The respective means may be provided by one or more controllers.

According to an aspect of the invention there is provided a vehicle comprising an apparatus as described above.

According to an aspect of the invention there is provided a computer program for controlling an engine within a vehicle, the computer program comprising instructions that, when executed by one or more processors, cause an apparatus to perform, at least a method as described above.

According to an aspect of the invention there is provided a non-transitory computer readable medium comprising a computer program as described above.

Within the scope of the claims 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:

Fig 1 illustrates a vehicle;

Fig 2 illustrates an apparatus;

Fig 3 illustrates a system;

Fig 4 illustrates an example plot of pressure within an exhaust system;

Fig 5 illustrates a method;

Fig 6 illustrates a method;

Fig 7 illustrates a mapping;

Fig 8 illustrates a method; and Fig 9 illustrates a method.

DETAILED DESCRIPTION

The Figures illustrate an apparatus 11, method, computer program 27 and non-transitory computer readable medium for monitoring an exhaust flap 39 within a vehicle 1, the method comprising determining a first flow resistance of the exhaust system 31 when the exhaust flap 39 is indicated to be in a first position; determining a second flow resistance of the exhaust system 31 when the exhaust flap 39 is indicated to be in a second position; and determining if the indicated positions of the exhaust flap 39 are correct using the first flow resistance and the second flow resistance.

Fig 1 illustrates an example vehicle 1 which may comprise an apparatus 11 according to embodiments of the invention. The vehicle 1 may comprise an engine and an exhaust system 31 where the exhaust system 31 is arranged to enable exhaust gases to be removed from the engine 33. The engine 33 may comprise any suitable type of engine 33. In some examples the engine 33 may be a petrol engine. In other examples the engine 33 may be a diesel engine 33 or any other suitable type of engine 33.

Fig 2 illustrates an apparatus 11 which may be provided within the vehicle 1. The apparatus 11 may be arranged to enable an exhaust flap 39 within the exhaust system 31 to be monitored. This may help to ensure that any problems caused by high pressure within the exhaust system 31 can be correctly attributed to the malfunctioning of the exhaust flap 39.

The apparatus 11 comprises a controller 21. The controller 21 may be a chip or a chip set. The controller 21 may form part of one or more systems comprised in the vehicle 1. The controller 21 may be arranged to control any suitable functions or applications within the vehicle 1.

The controller 21 comprises at least one processor 23, at least one memory 25 and at least one computer program 27.

Implementation of a controller 21 may be as controller circuitry. The controller 21 may be implemented in hardware alone, may have certain aspects in software including firmware alone or may be a combination of hardware and software (including firmware).

As illustrated in Fig 2 the controller 21 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 27 in a general-purpose or special-purpose processor 23 that may be stored on a computer readable storage medium (disk, memory etc) to be executed by such a processor 23.

The processor 23 may be arranged to read from and write to the memory 25. The processor 23 may also comprise an output interface via which data and/or commands are output by the processor 23 and an input interface via which data and/or commands are input to the processor 23.

The memory 25 may be arranged to store a computer program 27 comprising computer program instructions 29 (computer program code) that controls the operation of the controller 21 when loaded into the processor 23. The computer program instructions 29, of the computer program 27, provide the logic and routines that enables the controller 21 to control the torque limit of an engine 33 based on values of flow resistance within the exhaust system. The processor 23 by reading the memory 25 is able to load and execute the computer program 27.

The controller 21 may be arranged to determine a first flow resistance for an exhaust system 31 when the exhaust flap 39 is indicated to be in a first position and determine a second flow resistance for the exhaust system 31 when the exhaust flap 39 is indicated to be in a second position. The controller may also be arranged to determine if the indicated positions of the exhaust flap 39 are correct using the first flow resistance and the second flow resistance.

As illustrated in Fig 2, the computer program 27 may arrive at the controller 21 via any suitable delivery mechanism 30. The delivery mechanism 30 may be, for example, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a compact disc read-only memory (CD-ROM) or digital versatile disc (DVD), an article of manufacture that tangibly embodies the computer program 27. The delivery mechanism may be a signal arranged to reliably transfer the computer program 27. The controller 21 may propagate or transmit the computer program 27 as a computer data signal.

Although the memory 25 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent, dynamic/cached storage.

Although the processor 23 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor 23 may be a single core or multi-core processor.

Fig. 3 schematically illustrates an example exhaust system 31 and engine 33 that may be provided within a vehicle 1 and used in embodiments of the invention. The exhaust system 31 and the engine 33 are arranged to be controlled by an apparatus 11. The apparatus 11 may comprise a controller 21 as described above. Corresponding reference numerals are used for corresponding features.

The apparatus 11 may be arranged to control the exhaust system 31 and engine 33 to prevent high pressures within the exhaust system. The apparatus 11 may be arranged to calculate a flow resistance for the exhaust system 31 and use the calculated flow resistance to limit the torque levels of the engine 33.

The engine 33 may comprise any suitable torque provider which produces exhaust gases. The engine 33 may be a petrol engine, a diesel engine or any other suitable type of engine 33.

The engine 33 is coupled to the exhaust system 31 so that, when the engine 33 is in use, exhaust gases produced by the engine 33 are removed via the exhaust system 31.

The exhaust system 31 comprises a channel 35 having an inlet 36 and an outlet 37. The exhaust gases enter the exhaust system 31 from the engine 33 at the inlet 36. The exhaust gases have the highest pressure at the inlet 36. The exhaust gases flow along the channel 35 are expelled from the exhaust system 31 into the atmosphere at the outlet 37. At the outlet 37 the pressure of the gases matches atmospheric pressure. The pressure of the exhaust gases drops as the exhaust gases travel through the exhaust system 31. Fig 4 schematically illustrates how the pressure of the exhaust gases may change as the exhaust gases travel through the exhaust system 31.

In embodiments of the invention the exhaust system 31 may comprise one or more components which are positioned between the inlet 36 and the outlet 37. In the example of Fig 3 the exhaust system 31 comprises a filter 38 and an exhaust flap 39.

The filter 38 is positioned within the channel 35. The filter 38 may be arranged to remove particulate material such as soot from the exhaust gases before the gases are expelled into the atmosphere. The filter 38 may become blocked or partially blocked during use due to the build of particulate material on the filter 38. The blockage or partial blockage of the filter 38 may increase the resistance to flow for the exhaust gases as they travel through the exhaust system 31. This may increase the pressure of the exhaust gases within the exhaust system 31.

The exhaust flap 39 may comprise a valve or other means which may be arranged to be opened or closed. In some examples the exhaust flap 39 may be arranged to be partially open. The exhaust flap 39 may be arranged to control noise provided by the exhaust system 31. The exhaust flap 39 is positioned within the channel 35. The exhaust flap 39 may be positioned close to the outlet 37 of the exhaust system 31.

The exhaust flap 39 may also affect the pressure of the exhaust gases within the exhaust system 31. When the exhaust flap 39 is closed this provides a higher flow resistance than when it is open. The exhaust flap 39 may be controlled so that the exhaust flap 39 is closed when the engine 33 is operating at low power levels and may be open when the engine 33 is operating a high power levels. This may cause a change in the pressure of the exhaust gases within the exhaust system 31 as the exhaust flap 39 is moved between open and closed positions.

In the example of Fig 3 the exhaust system also comprises a pressure sensor 40. In the example of Fig 3 the exhaust system 31 comprises one pressure sensor 40. In other examples the exhaust system 31 may comprise more than one pressure sensor 40.

The exhaust flap 39 operates in a harsh environment where the exhaust flap 39 is exposed to dirt and high temperatures from the exhaust gases. In some vehicles 1 the exhaust flap 39 may be positioned adjacent to the outlet 37 of the exhaust system 31 and in such examples the exhaust flap 39 may be exposed to dirt and other contaminants from the road and external atmosphere. This can cause the exhaust flap 39 to stick or to be prevented from opening and closing properly. If the exhaust flap 39 remains closed when it is required to open, unacceptably high levels of back pressure may occur in the exhaust system which may result in damage to exhaust system or engine components upstream of the exhaust flap 39.

The pressure sensor 40 is positioned within the channel 35 between the inlet 36 and the filter 38. This may enable the pressure sensor 40 to detect any changes in pressure caused by a blockage or partial blockage of the filter 38. This may also enable the pressure sensor 40 to detect changes in pressure caused by moving the exhaust flap 39 between an open and closed configuration or to a partially open configuration.

In some examples the pressure sensor 40 may be positioned close to the engine 33. For example the pressure sensor 40 may be positioned close to the inlet 36 of the channel 35. This may enable the pressure of the exhaust gases to be measured as they are expelled from the engine 33. This may be a suitable place to obtain the pressure measurements in order to prevent high pressure from causing damage to the engine 33.

The pressure sensor 40 may comprise any means which may be arranged to enable a value indicative of exhaust pressure within the exhaust system 31 to be obtained. In some examples the pressure sensor 40 may comprise a differential pressure sensor 40. In such examples the differential pressure sensor may be open to the atmosphere such as a gauge sensor or relative sensor. The differential pressure sensor may enable the difference between the pressure with the exhaust system 31 and the atmospheric pressure to be measured. In other examples an absolute pressure sensor 40 may be used however the differential pressure sensor may provide more accurate measurements as this obtains measurements over a smaller range.

The pressure sensor 40 is arranged so that an output signal 41 from the pressure sensor 40 is provided to the apparatus 11. The apparatus 11 is arranged to use the output signal 41 from the pressure sensor 40 to obtain a value of flow resistance within the exhaust system 31. The value of the flow resistance may provide an indication of whether or not a threshold exhaust pressure will be exceeded when the power level of the engine 33 is increased.

The output signal 41 from the pressure sensor 40 may be a digital or an analogue signal. In some examples a chip or other means may be arranged to convert an analogue output of the pressure sensor 40 into a digital output.

The output signal 41 from the pressure sensor 40 may be filtered. In some examples the output signal 41 from the pressure sensor 40 may be filtered before it is provided to the apparatus 11. In other examples the apparatus 11 may be arranged to filter the signals that are received from the pressure sensor 40.

The filtering may be arranged to remove any unwanted components from the output signal 41 from the pressure sensor 40. In some examples the filtering may be arranged to remove high frequency components. The high frequency components could be caused by noise and vibrations from the engine 33 or from any other components of the vehicle 1.

In some examples the pressure sensor 40 may be positioned so that it is not located within the channel 35. For instance, in some examples the pressure sensor 40 may be located at the end of a pipe which is connected to the channel 35. The pipe may separate the pressure sensor 40 from the exhaust gases so as to protect the pressure sensor 40 from the high temperatures of the exhaust gases. The pipe may comprise steel, rubber or any other suitable material. In such examples the pipe may introduce noise into the output signal 41 from the pressure sensor 40. The noise may be removed by filtering the output signal 41. In such examples the length of the pipe may be kept short to avoid standing waves with a low frequency being creating noise in the output of the pressure sensor 40. The noise caused by standing waves with a low frequency would not be removed from the filter which is arranged to remove the high frequencies.

In the example of Fig 3 the exhaust system 31 also comprises one or more sensors 42 which may be arranged to obtain a value of volumetric flow rate within the exhaust system. The one or more sensors 42 could comprise any suitable sensors. In some examples the sensors may comprise an air intake sensor which is arranged to measure air intake into the engine 33. In some examples the one or more sensor 42 could comprise a lambda sensor within the exhaust system 31 which can be used to adjust measurements obtained by the air intake sensor,

The sensors 42 for obtaining a value of volumetric flow rate may be arranged to provide an output signal 45 to the apparatus 11. The apparatus 11 is arranged to use the output signal 45 from the sensors 42 to obtain a value of flow resistance within the exhaust system 31.

The output signal 45 from the sensors 42 may be a digital or an analogue signal. In some examples a chip or other means may be arranged to convert an analogue output of the sensors 42 into a digital output.

The output signal 45 from the sensors 42 may be filtered. The filtering may be arranged to remove any unwanted components from the output signal 45. In some examples the filtering may be arranged to remove high frequency components.

It is to be appreciated that the exhaust system 31 may also comprise other components that are not illustrated in Fig 3. For instance the exhaust system 31 may comprise a turbo, baffles or any other suitable components. Also in the schematic illustration of Fig 3 only one channel 35 and inlet 36 are shown. It is to be appreciated that the exhaust system 31 may comprises a plurality of inlets channels 35 and inlets 36 in other embodiments.

In the example of Fig 3 the apparatus 11 is coupled to both the engine 33 and the exhaust system 31. The apparatus 11 is coupled to the exhaust system 31 to enable the apparatus 11 to receive input signals 41 from the exhaust system 31. In embodiments of the invention the input signals 41 that are received from the exhaust system 31 may comprise input signals 41 comprising a value indicative of the exhaust pressure within the exhaust system31 and/or input signal 45 indicating a value of volumetric flow rate. The input signals 41 may be obtained by the pressure sensors 40 and/or any other suitable sensors 42 within the exhaust system 31.

The apparatus 11 is coupled to the engine 33 to enable a control signal 43 to be provided from the apparatus 11 to control the limits of the power levels provided by the engine 33. The apparatus 11 may be arranged to provide the control signal 43 in response to a determination that a flow resistance is above a threshold. In some examples the apparatus 11 may be arranged to provide the control signal 43 to another controller such as power control module. In other examples the apparatus 11 may be arranged to provide the control signal 43 may be provided directly to the engine 33.

The apparatus 11 may be arranged to use values indicative of the exhaust pressure within the exhaust system 31 and the volumetric flow rate within the exhaust system 31 to calculate values of flow resistance. In embodiments of the invention the apparatus 11 may use calculated values of the flow resistance to determine a torque limit of the engine which varies with a rotational speed of the engine and which will prevent a threshold exhaust pressure from being exceeded.

Fig 4 illustrates an example plot of pressure within the exhaust system 31. Fig 4 illustrates how the pressure of the exhaust system 31 decreases from high pressure at the inlet 36 to atmospheric pressure at the outlet 37.

Fig 4 is a plot of pressure P against distance d along the channel 35 of the exhaust system 31. The pressure P starts at a high level at the inlet 36 and drops to atmospheric pressure Pa at the outlet 37.

In the example of Fig 4 the distance x corresponds to the position of the filter 38 within the channel 35. The filter 38 creates a resistance to the flow of the exhaust gases as the flow through the channel. The resistance provided by the filter 38 will depend on whether the filter 38 is blocked or partially blocked and the volumetric flow rate of the exhaust gases. This may produce a large increase in the pressure of the gases within the exhaust system 31. The plots of Fig 4 show a large pressure difference across the position where the filter 38 is located. This indicates that a filter 38 provides a large flow resistance within the exhaust system 31. It is to be appreciated that other components within the exhaust system 31 may also provide a resistance to flow of the exhaust gases however the effect of these components may be much smaller than the effect of the filter 38.

Fig 4 shows a first plot A which represents the pressure when the exhaust flap 39 is open and plot B which represents the pressure when the exhaust flap 39 is closed. Closing the exhaust flap 39 increases the flow resistance and so increases the exhaust pressure within the exhaust system 31. Therefore the plot B has a higher pressure than the plot A.

Fig 5 illustrates an method in which values indicative of exhaust pressure and volumetric flow rate within the exhaust system are used to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded. The method may be implemented using the apparatus 11 and exhaust system 31 as described above. Corresponding reference numbers are used for corresponding features.

The method comprises obtaining, at block 51, a value indicative of exhaust pressure within an exhaust system 31. The value indicative of the exhaust pressure may be obtained using any suitable means. In some examples the value indicative of the exhaust pressure may be obtained using one or more pressure sensors 40 that are positioned within the exhaust system 31.

The method comprises obtaining, also at block 51, a value indicative of volumetric flow rate within the exhaust system. The value indicative of volumetric flow rate may be obtained using any suitable means. In some examples the value indicative of volumetric flow rate may be obtained using one or more sensors 42 such as air mass flow sensors arranged to measure the air intake into the engine 33.

The method comprises, at block 52, determining a torque limit of the engine which varies with a rotational speed of the engine and which will prevent a threshold exhaust pressure from being exceeded. In some examples a mapping may be used to determine the torque limit. The mapping may comprise a plot, look up table or any other suitable means which may enable a torque limit of the engine 33 which will prevent the threshold exhaust pressure from being exceeded to be determined based, at least in part, on pressure and volumetric flow rate, or a determined flow resistance.

In some, but not necessarily all examples, the mapping may comprise a plot, look up table or any other suitable means which may enable values of exhaust pressure at low torque to be referenced to values of exhaust pressure at higher torque. In some examples the mapping may use values of flow resistance.

In examples where the mapping comprises a plurality of measured values and/or derived values the different values may be synchronized before the mapping is used. For instance, in examples where the mapping uses the exhaust pressure and an obtained value of volumetric flow rate, the pressure measured by the one or more pressure sensors 40 and the obtained value for volumetric flow rate may be synchronized before determining a torque limit.

The method comprises, at block 53, restricting an output torque of the engine dependent upon the torque limit determined at block 52. The output torque of the engine 33 is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

The apparatus 11 may be arranged to provide a control signal 43 to the engine 33 or other control means such as a torque control module to control the torque limit of the engine 33.

In some, but not necessarily all examples, the method is performed in closed loop, correcting the torque limit if necessary to prevent the threshold exhaust pressure from being exceeded.

Fig 6 illustrates a method in which a value of flow resistance and an indicated exhaust flap position are used to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded. The flow resistance is calculated using values of exhaust pressure obtained by a sensor 40 in the exhaust system 31 and values of the volumetric flow rate.

The method of Fig 6 may be implemented using an apparatus 11 as described above. In some examples some blocks of the method may be performed by the controller 21 in the apparatus 11 and other blocks may be performed by other controllers that may be positioned elsewhere within the vehicle 1. For instance, some blocks may be performed by a power control module or any other suitable component.

In the example of Fig 6 the pressure sensor 40 provides an output signal 41. The output signal 41 comprises a value 60 indicative of the pressure within the exhaust system 31. The value 60 may be a measured value which is measured by the one or more pressure sensors 40 positioned within the exhaust system 31. This therefore enables the controller 21 to obtain a value 60 indicative of the pressure within the exhaust system 31.

The measurements of the exhaust pressure are obtained when the engine 33 is operating at a first torque level. The first torque level may be a low torque level. The first torque level may be a level at which the exhaust pressure is well below the threshold exhaust pressure so as to reduce the risk of damage being caused to the engine 33.

The controller 21 also obtains a value 61 of the volumetric flow rate of the exhaust gas within the exhaust system 31. The value 61 indicative of volumetric flow rate within the exhaust system 31 may be obtained while the engine 33 is operating at the first torque level, and/or within the order of milliseconds before or after obtaining the value indicative of exhaust pressure.

In the example of Fig 6 the value 61 of the volumetric flow rate is obtained from one or more sensors 42 such as air mass flow sensors. The air mass flow sensors may be arranged to measure the air intake into the engine 33. The air mass flow may be calibrated using measure values of pressure and temperature within the exhaust system to obtain a value 61 for the volumetric flow rate within the exhaust system 31.

In some, but not necessarily all examples, the volumetric flow rate may be calculated by combining the air mass flow with calculated fuel mass flow. Fuel mass flow may be calculated using one or more of fuel injection timing, fuel manifold pressure, and temperature. Calculated fuel mass flow may be corrected by the use of an exhaust oxygen sensor.

In the example of Fig 6 a power control module may be arranged to calculate the volumetric flow rate. The power control module may also be arranged to control the torque limit of the engine 33.

At block 63 the obtained signals comprising the value 60 of the exhaust pressure and the signal comprising the obtained value 61 for the volumetric flow rate are synchronized. This may enable any delay in obtaining the calculated value 61 of the volumetric flow rate to be taken into account or delays due to the time it takes for the exhaust system 31 to fill with air and reach the pressure level associated with a volumetric flow rate. The synchronization may comprise adding a time delay to the one or both of the signals. This enables the two values 60, 61 to be correlated to each other.

In some examples the signals may also be filtered at block 63. The filtering may comprise removing any unwanted components from one or both of the signals. In some examples the filtering may be arranged to remove high frequency components from the signals. In some examples the filtering may assist with the correlation of the two values 60, 61.

After block 63 a synchronized and filtered pressure signal 64 and a synchronized and filtered volumetric signal 65 are provided. These signals 64, 65 are used to determine the current flow resistance of the exhaust system. The value of the flow resistance of the exhaust system may vary as the filter 38 gets blocked or as the exhaust flap 39 is opened and closed, or for any other reason.

In some examples the method may comprise block 66 in which it is determined whether or not the volumetric flow rate exceeds a threshold value. If the volumetric flow rate does not exceed a threshold value then no determination of the flow resistance is made. If the volumetric flow rate does exceed the threshold value then a determination of the flow resistance may be made.

At lower volumetric flow rates the measurements and/or calculations may be less accurate than at higher flow rates. Therefore by ensuring that the volumetric flow rate is above a minimum threshold this helps to ensure that reliable values of the flow resistance within the exhaust system 31 are obtained and that the torque of the engine 33 is not limited unnecessarily.

At block 67 the flow resistance of the exhaust system 31 is determined. The flow resistance may provide a measurement of how the components within the exhaust system 31 obstruct the flow of gases within the exhaust system 31. In particular it may provide an indication of whether the filter 38 is blocked or partially blocked.

The flow resistance may be determined using the synchronized and filtered pressure signal 64 and the synchronized and filtered volumetric signal 65. The flow resistance may be determined using any suitable means. The flow resistance may be determined from a predetermined relationship between the flow resistance, exhaust pressure and the volumetric flow rate. In such examples the relationships between the flow resistance, exhaust pressure and the volumetric flow rate may be provided on a mapping. The mapping may be stored in memory circuitry of the apparatus 11.

An input signal 68 comprising a value indicative of the exhaust flap 39 is also provided. This may provide an indication of whether the exhaust flap 39 is open or closed or provided in an intermediate position. As shown in Fig 4 the position of the exhaust flap 39 affects the pressure within the exhaust system 31. Therefore this information is used to determine the flow resistance within the exhaust system 31. In the example of Fig 6 the signal 68 indicating whether or not the exhaust flap 39 is open is obtained from the power control module.

At block 67 a flow resistance signal 69 is obtained. The flow resistance signal 69 comprises values indicative of the flow resistance of the exhaust system 31.

At block 70 the flow resistance signal 69 is filtered to provide a filtered flow resistance signal 71. The filtering may remove unwanted components from the flow resistance signal 69 and may enable a stable value of the flow resistance to be obtained.

At block 72, the filtered flow resistance signal is used to determine a torque limit to be applied to the engine 33 such that a threshold exhaust pressure of the exhaust system 31 is not exceeded.

Once the required torque limit has been determined, a control signal 73 is provided to a power control module so that at block 74 the power control module can control the torque limit of the engine 33.

At block 75 the measured value 60 of the exhaust pressure is compared to the defined threshold pressure (or maximum pressure limit). This exhaust pressure may be greater than the threshold pressure when operating at the power limit due to piece to piece variation in the engine 33. This variation in manufacturing tolerance may therefore lead to an increased volumetric flow rate generated by the engine 33 at a given power level and hence an increased exhaust pressure. The comparison of the measured value to the threshold value may enable an adjustment in the torque limit 73 of the engine 33 to be made to take into account these piece to piece differences.

Fig 7 illustrates an example mapping. In the example of Fig 7 the mapping comprises a plot of pressure against volumetric flow rate. The different traces C and D represent different characteristics achieved by the exhaust system 31 when operating with different flow resistances. The mappings may be stored in the memory circuitry 25 of the apparatus 11 and may be retrieved as needed.

Pt represents a threshold exhaust pressure. If the exhaust pressure exceeds Pt there may be a risk of damage to the engine 33.

In embodiments of the invention values of the exhaust pressure may be obtained at a low engine power level and volumetric flow rate. For example they may be obtained when the volumetric flow rate is at level At this level the exhaust pressures for the different flow resistances are all well below the threshold level.

The plots may be used to extrapolate the expected exhaust pressure at higher power levels and volumetric flow rates. Using trace C it can be seen that at volumetric flow rate V2. the threshold exhaust pressure is exceeded for the first flow resistance Ki. Similarly the plot shows that at volumetric flow rate V2 the threshold exhaust pressure is not exceeded for the second flow resistance K2 represented by trace D. If the controller 21 determines that the current flow resistance of the exhaust system 31 corresponds to trace D then a higher volumetric flow rate is permitted before the threshold exhaust pressure is exceeded. Therefore the torque limit of the engine 33 derived from flow resistance K2 may be higher than the torque limit of the engine 33 derived from flow resistance Ki.

Fig 8 illustrates an example method of monitoring the exhaust flap 39 according to embodiments of the invention. The method may be implemented using the apparatus 11 and exhaust system 31 as described above. Corresponding reference numerals are used for corresponding features.

The method comprises, at block 81, determining a first flow resistance for the exhaust system 31 when the exhaust flap 39 is indicated to be in a first position. The first position may be a closed position.

The method also comprises, at block 82, determining a second flow resistance for the exhaust system 31 when the exhaust flap 39 is indicated to be in a second position. The second position is a different position to the first position. The second position may be an open position or a partially open position. It is to be appreciated that different first and second positions may be used in embodiments of the invention.

At block 83 the method comprises determining a difference between the first and second flow resistances and at block 84 the difference is compared to a predetermined limit. If the difference is below the predetermined limit then the indicated positions are determined to be incorrect.

There should be a significant change in the value of the flow resistance between the two different positions of the exhaust flap 39. If the significant change is not detected then it may be determined that the position of the exhaust flap 39 has not changed and therefore that the exhaust flap 39 is malfunctioning.

The apparatus 11 may be arranged to record information indicative of the positions of the exhaust flap 39. In some examples the information that is recorded may comprise an indication of the times when the indicated position of the exhaust flap 39 is incorrect. This information may be stored in the memory circuitry 25. The information may be used during maintenance of the vehicle 1.

Fig 9 illustrates another method which may be used in embodiments of the invention.

At block 90 the exhaust flap 39 is controlled by the power control module. The power control module may control the position of the exhaust flap 39 in dependence on the current power level of the engine 33.

The power control module provides a control signal 91 to the apparatus 11. The control signal 91 comprises information indicating the current position of the exhaust flap 39. The current position may be the position that the power control module has controlled the exhaust flap 39 to be in. This information may be incorrect, for example if the exhaust flap 39 is malfunctioning so that it does not open and close correctly.

At block 92 the apparatus 11 calculates flow resistance values for the exhaust system 31. The flow resistance values may be calculated using obtained values of pressure and volumetric flow rate within the exhaust system. In the example of Fig 9 the apparatus 11 calculates three flow resistance values. A first value is obtained assuming that the exhaust flap 39 is closed, a second value is obtained assuming that the exhaust flap 39 is open and a third value is obtained using the information indicating the current position of the exhaust flap 39 that is received from the power control module. The first value of flow resistance may be determined from a first mapping between pressure, volumetric flow rate and flow resistance based on conditions when the exhaust flap is in a fully closed position, and the second value of flow resistance may be determined from a second mapping between pressure, volumetric flow rate and flow resistance based on conditions when the exhaust flap is in a fully open position. The third value of flow resistance may be determined from an intermediate value between the first and second values of flow resistance. This intermediate value may be obtained using a scaling factor generated using information indicating the current position of the exhaust flap provided by the control signal 91.

At block 93 the calculated values of flow resistance are filtered. The filtering may remove unwanted components from the calculated flow resistances and may enable a stable value of the flow resistance to be obtained.

The different calculated flow resistances may be stored in the memory circuitry 25 of the apparatus 11. At block 94 different flow resistances may be selected for determining average flow resistance values at blocks 95 and 96 (as described below). When the flow resistance is selected it may be retrieved from the memory circuitry 25.

At block 95 an average flow resistance for time periods when the exhaust flap 39 is closed is obtained and at block 96 an average flow resistance for time periods when the exhaust flap 39 is open is obtained. At block 97 the two values are compared to determine if there is any difference between the flow resistance values calculated when the exhaust flap 39 is indicated to be open and when the exhaust flap 39 is indicated to be closed. Information indicative of the position of the exhaust flap 39 may be obtained from the power control modules and used to determine the time periods when the exhaust flap is open and the time periods when the exhaust flap 39 is closed.

At block 98 any determined difference is compared against a limit. If the difference is below a limit then it may be determined that the exhaust flap 39 is not working correctly. If the difference is above a limit then it may be determined that the exhaust flap 39 is working correctly.

At block 99 information indicative of when the exhaust flap 39 is malfunctioning may be recorded. In the example of Fig 9 this information is stored in the power control module. This information may be used during servicing or maintenance of the vehicle 1.

As shown in figure 9, determining an average flow resistance for time periods when the exhaust flap 39 is closed at block 95 and determining an average flow resistance for time periods when the exhaust flap 39 is open at block 96, and comparing the average flow resistances at block 97 is enabled or inhibited in dependence of a soot oxidation rate of a particulate filter of the exhaust system 31. As described above, this may reduce the likelihood of incorrect determinations of whether or not the positions of the exhaust flap are as indicated.

The blocks illustrated in Figs 5, 6, 8 and 9 may represent steps in a method and/or sections of code in the computer program 27. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features falling within the scope the claims and hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A method of monitoring an exhaust flap of an exhaust system of a vehicle, the method comprising; determining a first flow resistance of the exhaust system when the exhaust flap is indicated to be in a first position; determining a second flow resistance of the exhaust system when the exhaust flap is indicated to be in a second position; and determining if the indicated positions of the exhaust flap are correct using the first flow resistance and the second flow resistance; wherein determining the first and second flow resistances and determining if the indicated positions of the exhaust flap are correct is inhibited if a soot oxidation rate of a particulate filter of the exhaust system is above a predetermined limit.

2. A method of monitoring an exhaust flap of an exhaust system of a vehicle, the method comprising; determining a first flow resistance of the exhaust system when the exhaust flap is indicated to be in a first position; determining a second flow resistance of the exhaust system when the exhaust flap is indicated to be in a second position; and determining if the indicated positions of the exhaust flap are correct using the first flow resistance and the second flow resistance; wherein determining if the indicated positions of the exhaust flap are correct is inhibited if soot oxidation of a particulate filter of the exhaust system is detected after determining the first flow resistance and before determining the second flow resistance.

3. A method as claimed in any preceding claim wherein the first position is a closed position and the second position is an open position.

4. A method as claimed in any preceding claim wherein determining if the indicated positions of the exhaust flap are correct comprises determining a difference between absolute values of the first flow resistance and the second flow resistance.

5. A method as claimed in claim 4 wherein determining if the indicated positions of the exhaust flap are correct further comprises comparing a difference between absolute values of the first flow resistance and the second flow resistance to a predetermined limit.

6. A method as claimed in claim 5 wherein if the difference between absolute values of the first flow resistance and the second flow resistance is below the predetermined limit the indicated positions of the exhaust flap are determined to be incorrect.

7. A method as claimed in any of claims 1 to 3 comprising determining a plurality of values of each of the first and second flow resistances and determining an average value of each of the first and second flow resistances, wherein determining if the indicated positions of the exhaust flap are correct comprises determining a difference between the average values of the first flow resistance and the second flow resistance.

8. A method as claimed in claim 7 wherein determining if the indicated positions of the exhaust flap are correct further comprises comparing the difference between the average values of the first flow resistance and the second flow resistance to a predetermined limit.

9. A method as claimed in claim 8 wherein if the difference between the average values of the first flow resistance and the second flow resistance is below the predetermined limit the indicated positions of the exhaust flap are determined to be incorrect.

10. A method as claimed in any preceding claim wherein determining the first flow resistance comprises obtaining a first value indicative of exhaust pressure within the exhaust system and obtaining a first value indicative of volumetric flow rate within the exhaust system, and determining the second flow resistance comprises obtaining a second value indicative of exhaust pressure within the exhaust system and obtaining a second value indicative of volumetric flow rate within the exhaust system.

11. A method as claimed in claim 10 wherein a mapping between pressure, volumetric flow rate and flow resistance is used to determine the flow resistance.

12. A method as claimed in claim 10 wherein an equation relating flow resistance, pressure and/or volumetric flow rate is used to determine the flow resistance.

13. A method as claimed in any of claims 10 to 12 wherein one or more air mass flow sensors are used to obtain the first and second values indicative of volumetric flow rate within the exhaust system.

14. A method as claimed in any of claims 10 to 12 wherein a value for fuel mass flow is used to obtain the first and second values indicative of volumetric flow rate within the exhaust system.

15. A method as claimed in any of claims 10 to 14 wherein the first and second values indicative of exhaust pressure within the exhaust system are obtained from one or more pressure sensors positioned within the exhaust system.

16. A method as claimed in claim 15 comprising filtering the output from the one or more pressure sensors.

17. A method as claimed in claim 15 or claim 16 wherein at least one of the one or more pressure sensors is positioned close to the engine.

18. A method as claimed in claim 17 wherein at least one of the one or more pressure sensors is positioned downstream of a turbocharger turbine of the exhaust system.

19. A method as claimed in any of claims 10 to 18 comprising synchronizing the first values indicative of exhaust pressure and volumetric flow rate within the exhaust system and/or synchronizing the second values indicative of exhaust pressure and volumetric flow rate within the exhaust system.

20. A method as claimed in any preceding claim comprising recording information indicative of when the indicated positions of the exhaust flap are incorrect.

21. An apparatus for monitoring an exhaust flap of an exhaust system of a vehicle, the apparatus comprising means for carrying out the method of any one of claims 1 to 20.

22. A vehicle comprising an apparatus as claimed in claim 21.

23. A computer program for controlling an engine within a vehicle, the computer program comprising instructions that, when executed by one or more processors, cause an apparatus to perform a method as claimed in any of claims 1 to 20.

24. A non-transitory computer readable medium comprising a computer program as claimed in claim 23.