GB2560573B

GB2560573B - An apparatus, method and computer program for controlling an engine within a vehicle

Info

Publication number: GB2560573B
Application number: GB1704243.3A
Authority: GB
Inventors: 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: 2019-09-25
Anticipated expiration: 2037-03-17
Also published as: GB201704243D0; GB2560573A

Description

AN APPARATUS, METHOD AND COMPUTER PROGRAM FOR CONTROLLING AN ENGINE WITHIN A VEHICLE

TECHNICAL FIELD

The present disclosure relates to an apparatus, method, computer program and non-transitory computer readable medium for controlling an engine within a vehicle. In particular, but not exclusively it relates to an apparatus, method, computer program and non-transitory computer readable medium for controlling an engine within a vehicle to reduce risk of damage to the engine.

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

BACKGROUND

If pressure levels within an exhaust system are too high this can cause damage to the engine.

It is an aim of the present invention to provide improved control of an engine to prevent pressure levels within an exhaust system from getting too high and so preventing damage to the engine, and to minimise any driver perception that the engine is being so controlled.

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 controlling an engine within a vehicle, the method comprising: obtaining a value indicative of exhaust pressure within an exhaust system of the vehicle; obtaining a value indicative of volumetric flow rate within the exhaust system; using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded; and restricting an output torque of the engine dependent +1-·»Ζ·Χ +ζ·\*»Ζ·ΜΙ I I + » A · 1“» + L·» I + Ι/ΛΐΊΖΛΛ » A 1 + L"! Λ 41/Λ I /Λ I + l·"! ΖΜ*ΊΛΐηΖΛ Λ Z“J the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

Using this method, an engine torque limit which varies with the rotational speed of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded can be determined when the engine is operating at a low torque value, at which point the pressure within the exhaust system is substantially below the exhaust pressure threshold. Following application of this torque limit to the engine, the engine torque will increase with engine speed at a steady rate up to a maximum torque at which the exhaust pressure threshold is not exceeded. This provides the advantage that the driver of an associated vehicle will have a reduced perception of the engine torque being controlled to prevent an exhaust pressure threshold from being exceeded, as opposed to conventional methods which impose an instantaneous torque limit on the engine when it has been determined that the threshold exhaust pressure has been reached.

It is to be understood that although embodiments of the invention relate to determining a torque limit of the engine, and restricting an output torque of the engine dependent upon the torque limit, the same result would be achieved by determining a power limit of the engine and subsequently restricting an output power of the engine dependent on this power limit. The power output of the engine is equal to the torque output of the engine multiplied by the rotational speed of the engine multiplied by a constant. The relevant skilled person would therefore consider restricting an output torque of the engine and restricting an output power of the engine to be functionally the same. A mapping between pressure, volumetric flow rate and torque may be used to determine the torque limit. This mapping may be predetermined by any suitable means.

The method may comprise using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a flow resistance of the exhaust system, and using the flow resistance to determine the torque limit.

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 an 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. By determining the flow resistance of the exhaust system when the exhaust pressure is below the threshold exhaust pressure, the relationship between exhaust pressure and volumetric flow rate can be extrapolated to give the value of volumetric flow rate at which the threshold exhaust pressure will be met. This value of volumetric flow rate can then be used to determine, by any suitable means, a torque limit of the engine that will prevent the exhaust pressure threshold from being exceeded. A mapping between flow resistance and torque may be used to determine the torque limit. This mapping may be predetermined by any suitable means. A mapping between pressure, volumetric flow rate and flow resistance may be used to determine the flow resistance. This mapping may be predetermined by any suitable means.

An equation relating flow resistance, pressure and/or volumetric flow rate may be used to determine the flow resistance. Any suitable equation may be used.

The method may comprise using one or more air mass flow sensors to obtain the value indicative of volumetric flow rate within the exhaust system.

The method may comprise using a value for fuel mass flow to obtain the value indicative of volumetric flow rate within the exhaust system.

The method may comprise using one or more pressure sensors positioned within the exhaust system to obtain the value indicative of the exhaust pressure in the exhaust system.

The method may comprise filtering the output from the one or more pressure sensors. The method may comprise filtering the output from one or more sensors that provide values indicative of volumetric flow rate.

This provides the advantage that it enables unwanted components to be removed from the output signal of the one or more sensors. For instance, this may enable high frequency components which may be caused by noise and vibrations of the engine, or other unwanted noise, to be removed from the signal obtained by the pressure sensors.

If the filtering removes high frequency components this may also reduce the sampling rate needed to obtain an accurate reading from the one or more sensors. This may reduce the processing requirements and provide for a more efficient method.

Filtering the output from the one or more pressure sensors may enable a measurement of the exhaust pressure close to the engine to be obtained. This may be the most useful place to measure the pressure in order to avoid damage being caused to the engine by any high pressures. This reduces the need to take into account any changes in the exhaust pressure as the exhaust gases flow through the exhaust system when the value of the exhaust pressure is being obtained.

At least one of the one or more pressure sensors may be positioned close to the engine.

The method may comprise synchronizing the pressure measured by the one or more pressure sensors and the obtained value for volumetric flow rate before obtaining a value for flow resistance within the exhaust system.

This may enable any delays in calculating the volumetric flow rate or measuring the pressure to be taken into account. For example, the values from the pressure sensor may be read immediately from the sensor outputs but there may be some processing delay in obtaining a value for the volumetric flow rate. In some examples there may be a delay in the time it takes for an exhaust system to fill with air and reach the pressure level associated with a volumetric flow rate. This delay may be dependent upon the size of the engine and/or the size of the exhaust system. This synchronization may enable a more reliable determination of whether or not the flow resistance is above a threshold to be obtained.

In embodiments of the invention in which the exhaust system has an exhaust flap, for example to manipulate the acoustic characteristics of the exhaust system, the degree of opening of the exhaust flap will affect the pressure within the exhaust system for a given volumetric flow rate, i.e. for a given volumetric flow rate, the pressure within the exhaust system will be higher when the exhaust flap is closed compared to when the exhaust flap is open. As a result, the flow resistance determined at a given volumetric flow rate will vary depending on the degree of opening of the exhaust flap. The exhaust flap may operate automatically in dependence of the volumetric flow rate within the exhaust system. The exhaust flap may remain closed below a predetermined volumetric flow rate and may begin opening once the volumetric flow rate in the exhaust system reaches this predetermined value. The exhaust flap may continue to open until the volumetric flow rate reaches a second predetermined value at which the exhaust flap is fully open.

If the flow resistance is calculated when the volumetric flow rate within the exhaust system is below the predetermined value at which the exhaust flap opens, i.e. when the exhaust flap is closed, this may result in a torque limit being determined based on this flow resistance which would not be appropriate when the volumetric flow rate increases and the exhaust flap subsequently opens. Alternatively, if a first torque limit was applied to the engine based on a first flow resistance calculated when the exhaust flap was closed and a second torque limit was applied to the engine based on a second flow resistance calculated when the exhaust flap subsequently opened, the driver of the associated vehicle would perceive this change in torque limit and hence experience poor driveability. For these reasons at least, the flow resistance of the exhaust system may be determined using a value indicative of a degree of opening of the exhaust flap.

The method of the invention may comprise using a value indicative of a degree of opening of an exhaust flap of the exhaust system to determine the flow resistance of the exhaust system. The value indicative of a degree of opening of the exhaust flap may be used to generate a scaling factor which is used to determine the flow resistance of the exhaust system from a first flow resistance based on the exhaust flap being in a fully open position and a second flow resistance based on the exhaust flap being in a fully closed position.

The first 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 open position, and the second 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 closed position. The flow resistance of the exhaust system may then be determined from an intermediate flow resistance between the first and second flow resistances determined using the scaling factor.

According to an aspect of the invention there is provided an apparatus for controlling an engine within a vehicle, the apparatus comprising: means for obtaining a value indicative of exhaust pressure within an exhaust system of the vehicle; means for obtaining a value indicative of volumetric flow rate within the exhaust system; means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded; and means for restricting an output torque of the engine dependent upon the torque limit; wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

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: obtaining a value indicative of exhaust pressure within an exhaust system of the vehicle; obtaining a value indicative of volumetric flow rate within the exhaust system; using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded; and restricting an output torque of the engine dependent upon the torque limit; wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

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

According to an aspect of the invention there is provided a system for controlling an engine within a vehicle, the system comprising: means for receiving one or more signals each indicative of a value of exhaust pressure within an exhaust system; means for receiving one or more signals each indicative of a value of volumetric flow rate within the exhaust system; means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded; and means for restricting an output torque of the engine dependent upon the torque limit; wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

According to an aspect of the invention there is provided a system for controlling an engine within a vehicle as described above, wherein: said means for receiving one or more signals each indicative of a value of exhaust pressure within an exhaust system and said means for receiving one or more signals each indicative of a value of volumetric flow rate within the exhaust system comprises an electronic processor having an electrical input for receiving said signals; and said means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded and said means for restricting an output torque of the engine dependent upon the torque limit, wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure, comprises an electronic memory device having instructions stored thereon.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig 1 illustrates a vehicle;

Fig 2 illustrates an apparatus;

Fig 3 illustrates a system;

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

Fig 5 illustrates a method;

Fig 6 illustrates another method; and

Fig 7 illustrates a mapping.

DETAILED DESCRIPTION

The Figures illustrate an apparatus 11, method, computer program 27 and non-transitory computer readable medium for controlling an engine 33 within a vehicle 1, the method comprising: obtaining 51 a value indicative of exhaust pressure within an exhaust system 31 of the vehicle 1, obtaining 51 a value indicative of volumetric flow rate within the exhaust system 31, using the obtained values indicative of exhaust pressure and volumetric flow rate to determine 52 a torque limit of the engine 33 such that a threshold exhaust pressure of the exhaust system 31 is not exceeded; and restricting 53 an output torque of the engine dependent upon the torque limit; wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine 33 is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

Figs 1 to 3 illustrate an example vehicle 1 which comprises an apparatus 11 according to embodiments of the invention. The vehicle 1 comprises 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 comprises 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 provided within the vehicle 1. The apparatus 11 is arranged to enable the torque limit of the engine 33 to be controlled. This may help to prevent any damage to the engine 33 which might be caused by high exhaust pressures.

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. In embodiments of the invention the controller 21 is arranged to control a torque limit of the engine 33.

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. The processor 23 by reading the memory 25 is able to load and execute the computer program 27.

The controller 21 is arranged to obtain a value indicative of exhaust pressure within an exhaust system 31. The controller 21 is arranged to obtain a value indicative of volumetric flow rate within the exhaust system 31. The controller 21 is also arranged to use the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine 33 such that a threshold exhaust pressure of the exhaust system 31 is not exceeded. The controller 21 is also arranged to restrict an output torque of the engine 33 to maintain the exhaust pressure below the threshold exhaust pressure.

As illustrated in Fig 2, the computer program 27 may arrive at the controller 21 via any suitable delivery mechanism 31. The delivery mechanism 31 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 which may be arranged to be controlled by an apparatus 11 as described above. The apparatus 11 may comprise a controller 21 as described above. Corresponding reference numerals are used for corresponding features. The exhaust system 31 and engine 33 may be provided within a vehicle 1.

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.

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 configurations.

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 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.

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.

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. In other examples the differential pressure sensor may be arranged to measure the pressure difference across the filter 38 within the channel 35. 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 determine a torque limit of the engine 33 such that a threshold exhaust pressure of the exhaust system 31 is not exceeded.

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 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 mass flow intake into the engine 33. In some examples the one or more sensors 42 could comprise a lambda sensor within the exhaust system 31 which can be used to adjust measurements obtained by the air intake sensor. In some examples the one or more sensors 42 may comprise an air intake pressure sensor and/or an air intake temperature sensor and/or a throttle valve position 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 determine a torque limit of the engine 33 such that a threshold exhaust pressure of the exhaust system 31 is not exceeded.

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 comprise a plurality of channels 35 and inlets 36 in other embodiments. In such examples a determination of a flow resistance may be carried out for each channel-inlet combination and the torque limit of the engine 33 may be defined based on a maximum of the determined flow resistances.

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 system 31 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 torque limit of the engine 33. 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.

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 exhaust pressure decrease immediately downstream of the position x 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 exhaust pressure within the exhaust system 31 for a given volumetric flow rate. Therefore the plot B has a higher pressure than the plot A. In the example of Fig 4 the pressure of plot B exceeds the threshold pressure Pt along at least part of the distance d of the channel 35 when the exhaust flap 39 is closed. Therefore in examples where the exhaust system 31 comprises an exhaust flap 39 the position of the exhaust flap 39 (e.g. open or closed) may need to be taken into account when obtaining a value of flow resistance and/or when determining the torque limit of the engine 33 to be applied.

Fig 5 illustrates an example method. 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 another method which may be used in embodiments of the invention. In the example of Fig 6 the torque limit of the engine 33 is determined using a value of the flow resistance for the exhaust system 31. The flow resistance is calculated using values of exhaust pressure obtained by a sensor 40 in the exhaust system 31, values of the volumetric flow rate and a value indicative of a degree of opening of an exhaust flap of the exhaust system.

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.

In examples where the exhaust system 31 comprises an exhaust flap 39 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, the synchronized and filtered pressure signal 64 and the synchronized and filtered volumetric signal 65 may be used to determine a first flow resistance based on the exhaust flap being in a fully open position and a second flow resistance based on the exhaust flap being in a fully closed position. The input signal 68 may then be used to generate a scaling factor, based on the degree of opening of the exhaust flap, which is used to determine the flow resistance of the exhaust system from the first and second flow resistances.

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 Vi. 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.

The blocks illustrated in Figs 5 and 6 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, within the scope of the claims, hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A method of controlling an engine within a vehicle, the method comprising: obtaining a value indicative of exhaust pressure within an exhaust system of the vehicle; obtaining a value indicative of volumetric flow rate within the exhaust system; using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded; and restricting an output torque of the engine dependent upon the torque limit; wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

2. A method as claimed in claim 1 wherein a mapping between pressure, volumetric flow rate and torque limit is used to determine the torque limit.

3. A method as claimed in claim 1 wherein the obtained values indicative of exhaust pressure and volumetric flow rate are used to determine a flow resistance of the exhaust system, and the flow resistance is used to determine the torque limit.

4. A method as claimed in claim 3 wherein a mapping between flow resistance and torque is used to determine the torque limit.

5. A method as claimed in claim 3 wherein a mapping between pressure, volumetric flow rate and flow resistance is used to determine the flow resistance.

6. A method as claimed in claim 3 wherein an equation relating flow resistance, pressure and/or volumetric flow rate is used to determine the flow resistance.

7. A method as claimed in any preceding claim wherein one or more air mass flow sensors are used to obtain the value indicative of volumetric flow rate within the exhaust system.

8. A method as claimed in claim 7 wherein a value for fuel mass flow is used to obtain the value indicative of volumetric flow rate within the exhaust system.

9. A method as claimed in any preceding claim wherein the value indicative of exhaust pressure within the exhaust system is obtained from one or more pressure sensors positioned within the exhaust system.

10. A method as claimed in claim 9 comprising filtering the output from the one or more pressure sensors.

11. A method as claimed in claim 9 or claim 10 wherein at least one of the one or more pressure sensors is positioned downstream of a turbocharger turbine of the exhaust system.

12. A method as claimed in any of claims 9 to 11 comprising synchronizing the pressure measured by the one or more pressure sensors and the obtained value for volumetric flow rate.

13. A method as claimed in any of claims 3 to 12 wherein a value indicative of a degree of opening of an exhaust flap of the exhaust system is also used to determine the flow resistance of the exhaust system.

14. A method as claimed in claim 13 wherein the obtained values indicative of exhaust pressure and volumetric flow rate are used to determine a first flow resistance based on the exhaust flap being in a fully open position and a second flow resistance based on the exhaust flap being in a fully closed position, and the value indicative of the degree of opening of the exhaust flap is used to generate a scaling factor which is used to determine the flow resistance of the exhaust system from the first and second flow resistances.

15. An apparatus for controlling an engine within a vehicle, the apparatus comprising: means for obtaining a value indicative of exhaust pressure within an exhaust system of the vehicle; means for obtaining a value indicative of volumetric flow rate within the exhaust system; means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine such that a threshold exhaust pressure of the exhaust system is not exceeded; and means for restricting an output torque of the engine dependent upon the torque limit; wherein the torque limit varies with a rotational speed of the engine and the output torque of the engine is restricted when the obtained value indicative of exhaust pressure is below the threshold exhaust pressure.

16. An apparatus as claimed in claim 15 wherein the means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a torque limit of the engine are arranged to use a mapping between pressure, volumetric flow rate and torque limit to determine the torque limit.

17. An apparatus as claimed in claim 15 comprising means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a flow resistance of the exhaust system, and means for using the flow resistance to determine the torque limit.

18. An apparatus as claimed in claim 17 wherein the means for using the flow resistance to determine the torque limit are arranged to use a mapping between flow resistance and torque to determine the torque limit.

19. An apparatus as claimed in claim 17 wherein the means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a flow resistance of the exhaust system are arranged to use a mapping between pressure, volumetric flow rate and flow resistance to determine the flow resistance.

20. An apparatus as claimed in claim 17 wherein the means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a flow resistance of the exhaust system are arranged to use an equation relating flow resistance, pressure and/or volumetric flow rate to determine the flow resistance.

21. An apparatus as claimed in any of claims 15 to 20 wherein one or more air mass flow sensors are used to obtain the value indicative of volumetric flow rate within the exhaust system.

22. An apparatus as claimed in claim 21 wherein a value for fuel mass flow is used to obtain the value indicative of volumetric flow rate within the exhaust system.

23. An apparatus as claimed in any of claims 15 to 22 wherein the value indicative of exhaust pressure within the exhaust system is obtained from one or more pressure sensors positioned within the exhaust system.

24. An apparatus as claimed in claim 23 comprising means for filtering the output from the one or more pressure sensors.

25. An apparatus as claimed in claim 23 or claim 24 wherein at least one of the one or more pressure sensors is positioned downstream of a turbocharger turbine of the exhaust system.

26. An apparatus as claimed in any of claims 23 to 24 comprising means for synchronizing the pressure measured by the one or more pressure sensors and the obtained value for volumetric flow rate.

27. An apparatus as claimed in any of claims 17 to 26 comprising means for obtaining a value indicative of a degree of opening of an exhaust flap of the exhaust system and means for using this value in addition to the values indicative of exhaust pressure and volumetric flow rate to determine the flow resistance of the exhaust system.

28. An apparatus as claimed in claim 27 comprising means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a first flow resistance based on the exhaust flap being in a fully open position, means for using the obtained values indicative of exhaust pressure and volumetric flow rate to determine a second flow resistance based on the exhaust flap being in a fully closed position, means for using the value indicative of the degree of opening of the exhaust flap to generate a scaling factor and means for using the scaling factor to determine the flow resistance of the exhaust system from the first and second flow resistances.

29. A vehicle comprising an apparatus as claimed in any of claims 15 to 28.

30. 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 the method of any of claims 1 to 14.

31. A non-transitory computer readable medium comprising a computer program as claimed in claim 30.