GB2614035A

GB2614035A - Apparatus and method for controlling a combustion engine

Info

Publication number: GB2614035A
Application number: GB2115249.1A
Authority: GB
Inventors: Kiyanni Jahaazeb; Mcallister Matthew
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2021-10-22
Filing date: 2021-10-22
Publication date: 2023-06-28
Anticipated expiration: 2041-10-22
Also published as: GB202115249D0; GB2614035B

Abstract

A method of controlling a combustion engine comprising receiving a request for heating of an exhaust system of the engine, controlling, in dependence on the request, an injection of fuel to a cylinder of the engine whilst one or more exhaust valves of the cylinder are at least partially open simultaneous with one or more inlet valves, wherein the injection of fuel is controlled to provide first and second post-injections of fuel 430, 440 to the cylinder after a piston of the cylinder passes through top dead centre (TDC) 420. A control system for carrying out the method comprises input means to receive the request, output means to control the fuel injection and processing means to control the output means. The first post-injection may commence at or before 5° after TDC, for example at around 4°. The second post-injection may commence at or before 20° or 15° after TDC, for example at around 13°. The second post-injection may commence on completion of the first post-injection, or they may be separated by a period of rotation. A system may include the control system and a Diesel combustion engine of a vehicle.

Description

APPARATUS AND METHOD FOR CONTROLLING A COMBUSTION ENGINE

TECHNICAL FIELD

The present disclosure relates to a controlling a combustion engine, in particular to controlling injection of fuel to cylinders of the combustion engine. Aspects of the invention relate to a control system, to a system, to a vehicle, to a method and to computer software.

BACKGROUND

It is known to provide aftertreatment devices associated with an exhaust of a combustion engine, such as a diesel engine, for treating or capturing harmful emissions from the engine.

The aftertreatment devices may be provided to reduce one or both of particulate emissions and emission of oxides of nitrogen such as NOx. The aftertreatment devices may include one or more of a diesel particulate filter (DPF), Diesel Oxidation Catalyst (DOC), a lean NOx trap (LNT), a reductant injection system and a selective catalyst reduction (SCR) system, for example. Often such after treatment devices are operative at or above an operating temperature threshold, or their efficiency improves with increasing temperature. Therefore heating of the exhaust is useful to either reach the operating temperature threshold, particularly after a cold start, or to maintain temperature, to thereby improve efficiency. However it is simultaneously desired to increase the fuel efficiency of combustion engines.

It is known to use variable valve train systems with internal Exhaust Gas Recirculation (iEGR) via Secondary Exhaust Valve Lift (SEVL) for exhaust temperature management. However, further improvements are desired. In particular, it is desired to improve heating of the exhaust system, to thereby improve operation of an aftertreatment device, such as a catalyst, without increasing and, if possible, whilst reducing fuel consumption of the engine.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a control system, a system, a vehicle, a method and computer software as claimed in the appended claims.

According to an aspect of the present invention there is provided a control system for a combustion engine, the control system formed of one or more controller, the control system comprising output means arranged to output a control signal to control fuel injection to a cylinder of the combustion engine, and processing means arranged to control the output means to output the control signal to control the injection of fuel to the cylinder of the combustion engine whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves being at least partially open, the control signal being indicative of a plurality of fuel injections to the cylinder after a piston associated with the cylinder passes through top dead centre, the fuel injections being for increasing a temperature of a catalyst associated with the engine. Advantageously a temperature associated with an exhaust system of the engine is increased, which may promote heating of one or more aftertreatment devices associated with the exhaust. Advantageously, the heating may be achieved efficiently with respect to fuel consumption.

The processing means may be arranged to control the output means to output the control signal indicative of one or more subsequent fuel injections to the cylinder for increasing a temperature of a particulate filter associated with the engine.

According to a further aspect of the present invention there is provided a control system for a combustion engine, the control system formed of one or more controller, the control system comprising input means arranged to receive a request signal indicative of a request for heating of an exhaust system of the combustion engine, output means arranged to output a control signal to control fuel injection to a cylinder of the combustion engine, and processing means arranged to control the output means, in dependence on the request signal, to output the control signal to control the injection of fuel to the cylinder of the combustion engine whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves at least partially open, the control signal being indicative of first and second injections of fuel to the cylinder after a piston associated with the cylinder passes through top dead centre. Advantageously a temperature associated with an exhaust system of the engine is increased, which may promote heating of one or more aftertreatment devices associated with the exhaust. Advantageously, the heating may be achieved efficiently with respect to fuel consumption.

According to a further aspect of the invention, there is provided a control system for a combustion engine, the control system formed of one or more controller, the control system comprising input means arranged to receive a request signal indicative of a request for heating of an exhaust system of the combustion engine, output means arranged to output a control signal to control fuel injection to a cylinder of the combustion engine, processing means arranged to control the output means, in dependence on the request signal, to output the control signal to control the injection of fuel to the cylinder of the combustion engine whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves at least partially open, the control signal being indicative of first and second post injections of fuel to the cylinder after a piston associated with the cylinder passes through top dead centre. Advantageously a temperature associated with an exhaust system of the engine is increased, which may promote heating of one or more aftertreatment devices associated with the exhaust. Advantageously, the heating may be achieved efficiently with respect to fuel consumption.

Top dead centre may be of a combustion cycle of the engine i.e. top dead centre firing.

The request may be a request to heat a catalyst associated with the exhaust system.

Advantageously heating of the catalyst may be requested to reduce emissions of the engine.

The processing means may be arranged to output the control signal indicative of a third post injection of fuel to the cylinder. The third post injection may be for heating a filter, such as a particulate filter associated with the exhaust system. Advantageously the filter may be heated to regenerate the filter.

The processing means may be arranged to output the control signal to cause the first post injection of fuel to commence at or before 10 degrees after the piston associated with the cylinder passes through top dead centre. Advantageously, the first post injection particularly improves heating and efficiency.

The processing means may be arranged to output the control signal to cause the first post injection of fuel to commence at or before 5 degrees after the piston associated with the cylinder passes through top dead centre. Advantageously, the first post injection particularly improves heating and efficiency.

The processing means is optionally arranged to output the control signal to cause the first post injection of fuel to commence at around 4 degrees after the piston associated with the cylinder passes through top dead centre. Advantageously, the first post injection particularly improves heating and efficiency.

The processing means may be arranged to output the control signal to cause the second post injection of fuel to commence at or before 20 degrees after the piston associated with the cylinder passes through top dead centre. Advantageously, the first post injection particularly improves heating and efficiency.

The processing means is optionally arranged to output the control signal to cause the second post injection of fuel to commence at or before 15 degrees after the piston associated with the cylinder passes through top dead centre. Advantageously, the first post injection particularly improves heating and efficiency.

Optionally the processing means is arranged to output the control signal to cause the first post injection of fuel to commence at around 13 degrees after the piston associated with the cylinder passes through top dead centre. Advantageously, the first post injection particularly improves heating and efficiency.

The processing means may be arranged to output the control signal to cause the second post injection of fuel to commence at or after completion of the first post injection of fuel. Advantageously, the first and second post injections particularly improves heating and efficiency.

The processing means may be arranged to output the control signal to cause the first and second post injections of fuel to be separated by a period of rotation of the piston associated with the cylinder. Advantageously, the first post injection particularly improves heating and efficiency. The period of rotation may be around 10 degrees.

Optionally, the first and second post injections of fuel are at least 0.25mg of fuel. Optionally, the first and second post injections of fuel are at least 0. 5mg of fuel. Optionally, the first and second post injections of fuel are less than or equal to 2mg of fuel. The first and second post injections of fuel may be of an equal mass of fuel. The first and second post injections of fuel may be of an unequal mass of fuel. The first post injection of fuel is optionally larger than the second injection of fuel. Advantageously, the arrangement of first and second post injections particularly improves heating and efficiency.

The first and second post injections of fuel may have a mass ratio of at least 1.3:1.

The processing means may be arranged to control the output means to output the control signal to control the injection of fuel to the cylinder of combustion engine whilst a first exhaust valve of the one or more exhaust vales is open a first amount and a second exhaust valve is open a second amount larger than the first amount. Advantageously the different opening amounts improves control over an internal residual quantity of the engine.

The processing means is optionally arranged to control the output means to output the control signal to control the injection of fuel to the cylinder of combustion engine whilst a negative pressure is applied to the one or more inlet valves. Advantageously the negative pressure may improve efficiency.

According to a further aspect of the invention, there is provided a system, comprising a combustion engine having an injector associated with a respective cylinder, and a control system according to any preceding claim, wherein a control signal output by the control system is arranged to control the injector to inject fuel to the cylinder of the engine.

The combustion engine may be a diesel combustion engine.

According to yet another aspect of the invention, there is provided a vehicle comprising a control system according to one of the aspects above or a system according to one of the aspects above.

According to a still further aspect of the invention, there is provided a method of controlling a combustion engine, comprising receiving a request signal indicative of a request for heating of an exhaust system of the combustion engine, controlling, in dependence on the request signal, an injection of fuel to a cylinder of the combustion engine whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves, wherein the injection of fuel is controlled to provide first and second injections of fuel to the cylinder after a piston associated with the cylinder passes through top dead centre.

The controlling may comprise causing the first injection of fuel to commence at or before 10 degrees after the piston associated with the cylinder passes through top dead centre.

The controlling optionally comprises causing the second injection of fuel to commence at or before 20 degrees after the piston associated with the cylinder passes through top dead centre.

According to a still further aspect of the invention, there is provided a computer software which, when executed by a computer, is arranged to control a combustion engine according to a method as described above.

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

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a vehicle according to an embodiment of the present invention; Figure 2 shows a system according to an embodiment of the present invention; Figure 3 illustrates effectiveness of embodiments of the present invention; Figure 4 illustrates fuel injection timing according to an embodiment of the present invention; Figure 5 shows a method according to an embodiment of the present invention; Figures 6(a) and 6(b) illustrate exhaust temperature against crank angle according to an embodiment of the present invention; and Figure 7 illustrates valve openings in a Secondary Exhaust Valve Lift (SEVL) system.

DETAILED DESCRIPTION

A vehicle 100 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 1. The vehicle 100 is a wheeled land-going vehicle having a combustion engine. The engine may be used, at least at points in time, to directly power i.e. provide traction torque to one or more wheels of the vehicle or may act as an electrical generator for one or more traction electric machines of the vehicle. The engine may be a diesel engine, a petrol engine, or use another combustible fuel, such as hydrogen, for example. The engine has an associated exhaust system which is used to direct exhaust gasses from the engine. In order to control or reduce emissions from the engine the exhaust system comprises one or more aftertreatment devices. The one or more aftertreatment devices are arranged to, in use, to reduce one or both of particulate emissions and emission of oxides of nitrogen such as NOx. The aftertreatment devices may include one or more of a diesel particulate filter (DPF), Diesel Oxidation Catalyst (DOC), a lean NOx trap (LNT), a reductant injection system and a selective catalyst reduction (SCR) system, for example. In particular, embodiments of the invention are useful for heating a catalyst associated with the exhaust system of the engine.

Associated with the combustion engine of the vehicle 100 of Figure 1, particularly with diesel engines, it is known to use an Exhaust Gas Recirculation (EGR) system which recirculates a portion of exhaust gas back to an inlet of the engine. Use of an EGR system is useful to reduce oxides of nitrogen, such as NON, in the exhaust gas from the engine. An internal EGR (iEGR) has also been proposed by means of Secondary Exhaust Valve Lift (SEVL) system for increasing a temperature of exhaust gasses from the engine to aid heating of exhaust gas aftertreatment devices, without significantly increasing fuel consumption. In the SEVL system, valve lifts on both intake and exhaust sides of engine cylinders is controlled, such as using an electromechanical arrangement, to partially open one or more exhaust valves of a cylinder whilst one or more intake valves are at least partially open. For example, one or more exhaust valves may be opened between 0.9 and 2.0mm in comparison to a normal valve lift in the region of 8.0mm i.e. between 10 and 25% of the full valve lift whilst the intake valve is at least partially open. It has also been proposed that, for an engine cylinder having two or more exhaust valves, the plurality of exhaust valves may be opened by different amounts. In one example, for an engine cylinder having two exhaust valves, one valve may be opened by a relatively amount e.g. 0.9mm and another exhaust valve by a larger amount e.g. 1.5mm, although it will be appreciated that other exhaust valve lifts may be used.

The SEVL system may be used particularly to achieve initial heating i.e. when the engine is cold, such as at or below 20°C engine temperature, and also to maintain temperature e.g. when the engine has a temperature of above 70°C. It will be appreciated that SEVL may be used at other times and engine temperatures.

Figure 2 illustrates a system 200 according to an embodiment of the invention. The vehicle 100 comprises the system 200.

The system 200 comprises a control system 210 for at least partially controlling a combustion engine 280 of the vehicle 100. The control system 210 is formed of one or more controller 210, only one of which is shown in Figure 1 with it being understood that this is not restrictive.

The control system 210 is for controlling fuel injection to the combustion engine in combination with the SEVL system (not shown) to heat a catalyst associated with the engine 280.

The controller 210 comprises processing means 220 and memory means 230. The processing means 220 may be one or more electronic processing device 220 or processor 220 which operably executes computer-readable instructions. The memory means 230 may be one or more memory device 230. The memory means 230 is electrically coupled to the processing means 220. The memory means 230 is configured to store instructions, and the processing means 220 is configured to access the memory means 230 and execute the instructions stored thereon. The memory means 230 may be formed by one or memory devices. Each of the controller 210 forming the control system may comprise a respective processor 220 and memory 230.

The or each controller 210 may comprise one or more electrical input(s) 240, 260 for receiving one or more input signals 245, 265 and one or more electrical output(s) 250 for outputting one or more output signals 255. The input signal(s) 245, 265 may be electrical signals 245, 265 at least some of which may be indicative of one or more parameters. In the illustrated embodiment, the signal 245 is a crank angle or position signal 245 indicative of a position of a crank of the engine 280 such that a position of one or more pistons of the engine may be determined therefrom. The crank angle or position signal 245 may be provided by one or more crank angle or position sensing devices associated with the engine 280. It will be realised that in other embodiments a position of the one or more pistons may be determined or inferred from other signals. The input signal 265 is a heating request signal 265 indicative of a request for heating of the exhaust system. The heating request signal 265 requests that the controller 210 controls fuel injection to the engine 280 as will be explained to increase an exhaust temperature associated with the engine 280, which may beneficially improve operation of one or more aftertreatment devices, such as a catalyst, associated with the exhaust system.

The heating request signal 265 may be provided by another controller or module associated with the vehicle 100. The heating request signal 265 may be provided simultaneous with operation of a SEVL system of the vehicle 100. The SEVL system is arranged to control one or more exhaust valves of the engine 280 to be at least partially open simultaneous to one or more inlet valves being partially open. A brief illustration of the valve openings is provided below with respect to Figure 7.

The output signal 255 is an injector control signal 255. The injector control signal 255 is associated with an injector 270 for injecting fuel to a cylinder of the engine 280. The injector control signal 255 is arranged to control the injector 270 to inject fuel to the respective cylinder of the engine 280, as will be explained particularly with reference to Figure 4. It will be appreciated that the controller may comprise a plurality of injector control signals 255, each corresponding to one of the cylinders of the engine 280. However, for ease of explanation, only one cylinder will be described with it being appreciated that this is for clarity rather than being limiting.

In some embodiments, the input(s) 245, 265 and output(s) 255 of the controller 210 may be combined such as in a network interface which is arranged to couple the controller 210 to a communications network of the vehicle 100 to send and receive data.

The, or each, electronic processor 210 may comprise any suitable electronic processor (e.g., a microprocessor, a microcontroller, an ASIC, etc.) that is configured to execute electronic instructions. The, or each, electronic memory device 230 may comprise any suitable memory device and may store a variety of data, information, threshold value(s), lookup tables or other data structures, and/or instructions therein or thereon. In an embodiment, the memory device 230 has information and instructions for software, firmware, programs, algorithms, scripts, applications, etc. stored therein or thereon that may govern all or part of the methodology described herein. The processor, or each, electronic processor 230 may access the memory device 230 and execute and/or use that or those instructions and information to carry out or perform some or all of the functionality and methodology describe herein.

Figure 3 illustrates plots of exhaust temperature against various parameters for various configurations of valve lift and fuel injection. The exhaust temperature T4 is measured at a position in front of the catalyst in the exhaust system. In particular, T4 is measured around 25mm from a front face of the catalyst, such as the DOC or LNT. Illustrated are plots of the exhaust temperature against air mass in mg per piston stroke, lambda (air fuel ratio) and Brake Specific Fuel Consumption (BSFC) as a measure of fuel efficiency (lower BSFC in g/kWh being indicative of less fuel per unit of power).

In Figure 3 a single point 310 is provided as a base reference and 340 indicates operation of the known SEVL arrangement with relatively large i.e. 2mm valve lift opening of the exhaust valve whilst an inlet valve of the cylinder is at least partially open. As a further reference, 320 and 330 are indicative of an effect of two post-injections (as will be explained below) of fuel to an engine cylinder with conventional valve opening i.e. separate (non-overlapping) intake and exhaust valve openings under different conditions, in particular 330 includes use of Intake Air Throttle (IAT) control. The IAT is control of a throttle position to reduce air pressure, i.e. to apply a negative pressure, at an intake side of the intake calves of the engine, which advantageously encourages gasses to be drawn into the cylinder through the exhaust valves. The negative pressure may be between 100 and 200mb of negative pressure in some embodiments. The processor 210 may output a signal to cause the throttle control to apply the negative pressure.

Plots 350, 360 and 370 are illustrative of configurations according to embodiments of the invention. In particular, as can be observed from the lower left graph indicative of Brake Specific Fuel Consumption (BSFC), embodiments of the invention achieve an increase in exhaust temperature whilst also lowering BSFC i.e. greater exhaust temperature with lower fuel consumption per kWh power output. Advantageously, the increase in exhaust temperature improves operating conditions for aftertreatment devices associated with the engine, thereby reducing or improving emissions. As can be observed from Figure 3, the increase in exhaust temperature is up to 30°C accompanied by a reduction in BSFC of up to around 40 g/kWh. It will be noted that changes in temperature shown in Figure 3 are illustrated in Kelvin (K) with it being appreciated that degrees Celsius equal degrees Kelvin, albeit with an offset temperature of 273. The configurations associated with plots 350, 360, 370 of Figure 3 will now be explained with reference to Figures 4 to 7 as described below.

For clarity, embodiments of the present invention will be explained with reference to a single cylinder of the engine 280. However, it will be appreciated that most engines comprise a plurality of cylinders, such as often (although not exclusively) 4, 6 or 8 cylinders. Embodiments of the present invention may be used with such multi-cylinder engines by appropriate control of the fuel injection to each respective according to the position of the piston associated therewith.

In embodiments of the invention, an injection of fuel to a cylinder of the engine 280 is controlled whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves being at least partially open. The injection of fuel to the cylinder is controlled to provide first and second injections of fuel to the cylinder after a piston associated with the cylinder passes through top dead centre. The first and second injections of fuel to the cylinder are separate i.e. distinct from a main fuel injection i.e. the fuel injected into the cylinder for the purpose of combustion to provide torque output from the engine 280.

Figure 4 illustrates periods of fuel injection to a cylinder of the engine 280 over a period of time, or an angle of rotation of a crank associated with the piston of the cylinder. In Figure 4, a main fuel injection 410 is indicated as occurring mainly over a period of time or rotation of the crank before the cylinder passes through top-dead centre (TDC) 420. The TDC, representing a 0° point, illustrated in Figure 4 is a combustion or firing TDC. The main fuel injection 410 is a largest amount of fuel delivered to the cylinder during the combustion cycle of the injection. The main fuel injection 410 begins prior to the piston reaching TDC such that the fuel is compressed by movement of the piston responsive to rotation of the crank. However, as illustrated in Figure 4, a portion of the main fuel injection 410 occurs after TDC in some embodiments. The portion of the main fuel injection 410 occurring after TDC is a minor portion of the main fuel injection 410 in some embodiments. It has been found that a combination of two or more separate injections of fuel 430, 440 after the piston associated with the cylinder passes through TDC 420 provide increased exhaust temperature in combination with one or more exhaust valves associated with the cylinder being at least partially open simultaneous with one or more inlet valves being at least partially open.

As illustrated in Figure 4, one or more further injections 450 of fuel i.e. a third fuel injection 450 may be provided, which are useful for heating a particulate filter associated with the exhaust of the engine during a regeneration process. In some embodiments, a separation between an end of a second fuel injection 440 and a third fuel injection may be at least 5° rotation of the crank of the engine 280.

In particular, in embodiments of the invention, the first and second post injections 430, 440 of fuel (i.e. post combustion TDC) occur between TDC (0°) and 45° of crank rotation, as will be explained. It is noted that the TDC value corresponds to the combustion TDC.

Furthermore, in some embodiments of the invention the first and second injections of fuel are at least 0.1, 0.2, 0.25 or 0.5 mg of fuel. In some embodiments, the first and second injections 430, 440 of fuel are less than or equal to 2mg or less than or equal to 1.5mg of fuel. It will be appreciated that the fuel masses are given with respect to a 2.01 four cylinder injection engine 280. Thus, as mass per cylinder, the fuel quantities may be scaled appropriately for other engine capacities, fuel types or cylinder volumes.

Figure 5 illustrates a method 500 according to an embodiment of the invention. The method 500 is a method of controlling a combustion engine 280. The method 500 may be performed by the system described above with reference to Figure 2.

The method comprises a block 510 of determining whether a request signal 265 indicative of a request for heating of an exhaust system of the combustion engine 280 is received. The request signal may be the heating request signal 265 received at the input 260 of the controller 210. The heating request signal 265 may be received at a time when the SEVL system of the engine 280 is activated, such that one or more exhaust valves of cylinders of the engine 280 are at least partially open simultaneous with one or more inlet valves of the cylinders.

If the heating request signal 265 is not received, the method 500 loops or waits at block 510. If, or when, the heating request signal 265 is received, the method moves to block 520 such that the following blocks 520, 530 are performed in dependence on the heating request signal 265 being received.

Block 520 comprises controlling an injection of fuel to the cylinder of the engine 280 associated with the injector 270 to provide a first injection 430 of fuel to the cylinder after a piston associated with the cylinder passes through top dead 420 centre, whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves. The injection of fuel is controlled by the controller 210 outputting an the injector control signal 255 appropriately to control the injector 270.

Figure 6(a) illustrates a crank angle in degrees and Figures 6(b) illustrates injected fuel mass in mg/stroke against exhaust temperature for different configurations. Three configurations according to embodiments of the invention are specifically labelled with reference numerals 350, 360, 370 corresponding to those used in Figure 3. However the same symbols are used for all traces between Figures 3 and 6(a)/(b) to aid comparison. The lower Figures in (a) and (b) labelled InjCrv_phiPol3Des in °Crs illustrates crank angle and InjCrvphiPol3Des mp in mg/stroke fuel mass for the first fuel injection 420 commencing after TDC whilst the upper Figures labelled InjCrv_phiPol2Des in °Crs illustrates crank angle and IniCry phiPol2Des mp in mg/stroke fuel mass for the second fuel injection 430.

As can be appreciated, referring to the lower part of Figure 6(a) for the three configurations of the first fuel post injections 410 according to embodiments of the invention, higher exhaust temperatures may be achieved than for other configurations used with closed exhaust valves of the cylinder. The first fuel injection 410 according to an embodiment of the invention is performed after TDC (0°) at least 2.5° after the piston associated with the cylinder passes through.

In particular, as can be appreciated from plot 350 in Figure 6(a) the first injection 430 of fuel in block 520 is arranged to commence at around 4 degrees after the piston associated with the cylinder passes through TDC. It will be appreciated that in some embodiments, the first post injection 430 of fuel in block 520 is arranged to commence at least 5 degrees after the piston associated with the cylinder passes through TDC. It will be appreciated that in some embodiments, the first injection 430 of fuel in block 520 is arranged to commence at least 10 or 12 degrees after the piston associated with the cylinder passes through TDC. It will be appreciated that in some embodiments, the first post injection 430 of fuel in block 520 is arranged to commence at around 13 or 14 degrees after the piston associated with the cylinder passes through top dead centre.

In particular, as can be appreciated from plot 350 in Figure 6(b) the first post injection 430 of fuel in block 520 is arranged to comprise at least 0.25mg of fuel. In particular, in some embodiments, as can be appreciated from plot 350 in Figure 6(b) the first post injection 430 of fuel in block 520 is arranged to comprise at least 0.5mg of fuel.

In particular, as can be appreciated from plot 350 in Figure 6(b) the first post injection 430 of fuel in block 520 is arranged to comprise less than or equal to 2mg of fuel. In some embodiments the first post injection 430 of fuel in block 520 is arranged to comprise less than or equal to 1.5mg of fuel.

In particular, as can be appreciated, it has been found that increased exhaust temperature is provided by increasing the angle after TDC at which the first fuel post injection 430 commences, as illustrated by plot 350 which illustrates, for a fixed fuel mass such as an example 1mg/stroke, that increasing angle after TDC increases exhaust temperature. The first post injection 430 of fuel in block 520 is arranged to commence at up to 35 degrees, up to 25 degrees or up to 20 degrees after the piston associated with the cylinder passes through TDC.

Plot 360 illustrates that increasing the angle of the first fuel post injection 430 and increasing the mass i.e. from 0.5 to 1.5mg/stroke of fuel further increases the exhaust temperature.

However, as shown in Figure 3, increasing the mass of fuel for the first post injection may eventually result in increased BSFC.

It is observed from a comparison of Figures 3 and 6(a)/6(b) that an optimum for the first post injection 430 of fuel is observed at which commences at an angle of between 5-10° after TDC and comprises less than 1.5mg/stroke of fuel. In particular, the angle after TDC may be between 5-10° after TDC and comprise at least 0.5mg/stroke of fuel, or at least 1.0mg/stroke of fuel. In one embodiment, the first post injection 430 comprises between 1.1mg/stroke and 1.4mg/stroke of fuel, or between 1.2mg/stroke and 1.3mg/stroke of fuel. The first post injection 430 comprises around 1.3mg/stroke, where around may be understood to mean ±10%.

Block 530 comprises controlling an injection of fuel to the cylinder of the engine 280 associated with the injector 270 to provide a second post injection 440 of fuel to the cylinder after a piston associated with the cylinder passes through top dead centre 420, and after the first post injection 430, whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves. The injection of fuel is controlled by the controller 210 outputting an the injector control signal 255 appropriately to control the injector 270.

In particular, as can be appreciated from plot 350 in the upper portion of Figure 6(a) the second post injection 440 of fuel in block 530 is arranged to commence at least 10 degrees after the piston associated with the cylinder passes through TDC. It will be appreciated that in some embodiments, the second post injection 440 of fuel in block 530 is arranged to commence at least 15 degrees after the piston associated with the cylinder passes through TDC. It will be appreciated that in some embodiments, the second post injection 440 of fuel in block 530 is arranged to commence at least 20 degrees after the piston associated with the cylinder passes through TDC. It will be appreciated that in some embodiments, the second post injection 440 of fuel in block 530 is arranged to commence at around 25 degrees after the piston associated with the cylinder passes through top dead centre.

In particular, as can be appreciated from plot 350 in Figure 6(b) the second post injection 440 of fuel in block 530 is arranged to comprise at least 0.25mg of fuel. In particular, in some embodiments, as can be appreciated from plot 350 in Figure 6(b) the second post injection 440 of fuel in block 530 is arranged to comprise at least 0.5mg of fuel.

In particular, as can be appreciated from plot 350 in Figure 6(b) the second post injection 440 of fuel in block 530 is arranged to comprise less than or equal to 2mg of fuel. In some embodiments the second post injection 440 of fuel in block 530 is arranged to comprise less than or equal to 1.5mg of fuel.

In particular, as can be appreciated, it has been found that increased exhaust temperature is provided by increasing the angle after TDC at which the second post injection 440 commences, as illustrated by plot 350 which illustrates, for a fixed fuel mass such as an example 1mg/stroke, that increasing angle after TDC increases exhaust temperature. The second post injection 440 of fuel in block 530 is arranged to commence at up to 20 degrees, 35 degrees or 40 degrees after the piston associated with the cylinder passes through top dead centre.

Plot 360 illustrates that increasing the angle of the second post injection 440 and increasing the mass i.e. from 0.5 to 1.5mg/stroke of fuel further increases the exhaust temperature. However, as shown in Figure 3, increasing the mass of fuel may eventually result in increased BSFC.

It is observed from a comparison of Figures 3 and 6(a)/(b) that an optimum for the second post injection 440 of fuel is observed at which commences at an angle of between 20-30° after TDC and comprises less than 1.5mg/stroke of fuel. In particular, the angle after TDC may be between 20-30° after TDC and comprise at least 0.5mg/stroke of fuel. In one embodiment, the second post injection 440 comprises between 0.5mg/stroke and 1mg/stroke of fuel, or between 0.5mg/stroke and 0.8mg/stroke of fuel. The second post injection 440 may comprise around 0.75mg/stroke, where around may be understood to mean ±10%.

It can be appreciated that in some embodiments, the first and second post injections 430, 440 of fuel are of an equal mass of fuel. However, it can be observed that increased exhaust temperature with low BSFC can be achieved with the first and second post injections of fuel being of an unequal mass of fuel. In particular, in some embodiments, the first injection 430 of fuel may be larger than the second post injection 440 of fuel. In some embodiments, The control system according to claim 15, wherein the first and second post injections of fuel have a mass ratio of at least 1.3:1.

It has been further observed that embodiments of the present invention are particularly useful where, for a cylinder associated with two exhaust valves, the exhaust valves may be opened by different amounts simultaneous with one, or in some embodiments two, inlet valves being at least partially open.

Referring to Figure 7, a valve lift in mm of exhaust valve(s) 710 is indicated along with a valve lift of intake valve(s) 720. In Figure 7 a crank angle is illustrated. It will be noted that the crank angle in Figure 7 is with respect to 0° being a top dead centre (TDC) of a gas exchange cycle of the engine 280. Also illustrated in Figure 7 is a SEVL 730, 740 of one or more exhaust valves. A first exhaust valve 730 may be opened by a first amount and a second exhaust valve 740 may be opened by a second, different, amount. The first exhaust valve 730 may be opened by a valve lift of 1.5mm and the second exhaust valve may be opened by a valve lift of 0.9mm. It will be appreciated that the first exhaust valve may be opened by 1mm or more whilst the second exhaust valve is opened by less than 1mm in some embodiments.

Advantageously, opening two exhaust valves by different amounts provides improved control of internal residual pressure for a given delta pressure across the engine.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

For purposes of this disclosure, it is to be understood that the controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on one or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

The blocks illustrated in FIG. 5 may represent steps in a method and/or sections of code in the computer program. 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 endeavouring 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 hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A control system for a combustion engine, the control system formed of one or more controller, the control system comprising: input means arranged to receive a request signal indicative of a request for heating of an exhaust system of the combustion engine; output means arranged to output a control signal to control fuel injection to a cylinder of the combustion engine; and processing means arranged to control the output means, in dependence on the request signal, to output the control signal to control the injection of fuel to the cylinder of the combustion engine whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves at least partially open, the control signal being indicative of first and second post injectionsof fuel to the cylinder after a piston associated with the cylinder passes through top dead centre.
2. The control system according to claim 1, wherein the processing means is arranged to output the control signal to cause the first post injection of fuel to commence at or before 10 degrees after the piston associated with the cylinder passes through top dead centre.
3. The control system according to claim 2, wherein the processing means is arranged to output the control signal to cause the first post injection of fuel to commence at or before 5 degrees after the piston associated with the cylinder passes through top dead centre.
4. The control system according to claim 3, wherein the processing means is arranged to output the control signal to cause the first post injection of fuel to commence at around 4 degrees after the piston associated with the cylinder passes through top dead centre.
5. The control system according to any preceding claim, wherein the processing means is arranged to output the control signal to cause the second post injection of fuel to commence at or before 20 degrees after the piston associated with the cylinder passes through top dead centre.
6. The control system according to claim 5, wherein the processing means is arranged to output the control signal to cause the second post injection of fuel to commence at or before 15 degrees after the piston associated with the cylinder passes through top dead centre.
7. The control system according to claim 6, wherein the processing means is arranged to output the control signal to cause the first post injection of fuel to commence at around 13 degrees after the piston associated with the cylinder passes through top dead centre.
8. The control system according to any preceding claim, wherein the processing means is arranged to output the control signal to cause the second post injection of fuel to commence at completion of the first post injection of fuel.
9. The control system according to any preceding claim, wherein the processing means is arranged to output the control signal to cause the first and second post injections of fuel to be separated by a period of rotation of the piston associated with the cylinder.
10. The control system according to any preceding claim, wherein the first and second post injections of fuel are at least 0.25mg of fuel.
11. The control system of claim 10, wherein the first and second post injections of fuel are at least 0. 5mg of fuel.
12. The control system according to any preceding claim, wherein the first and second post injections of fuel are less than or equal to 2mg of fuel.
13. The control system according to any preceding claim, wherein the first and second post injections of fuel are of an equal mass of fuel. 14. 15. 16. 17. 18. 19. 20. 21.
The control system according to any preceding claim, wherein the first and second post injections of fuel are of an unequal mass of fuel.
The control system according to claim 14, wherein the first post injection of fuel is larger than the second injection of fuel.
The control system according to claim 15, wherein the first and second post injections of fuel have a mass ratio of at least 1.3:1.
The control system according to any preceding claim, wherein the processing means is arranged to control the output means to output the control signal to control the injection of fuel to the cylinder of combustion engine whilst a first exhaust valve of the one or more exhaust vales is open a first amount and a second exhaust valve is open a second amount larger than the first amount.
The control system according to any preceding claim, wherein the processing means is arranged to control the output means to output the control signal to control the injection of fuel to the cylinder of combustion engine whilst a negative pressure is applied to the one or more inlet valves.
A system, comprising: a combustion engine having an injector associated with a respective cylinder; and a control system according to any preceding claim, wherein a control signal output by the control system is arranged to control the injector to inject fuel to the cylinder of the engine.
The system of claim 19, wherein the combustion engine is a diesel combustion engine.
A vehicle comprising a control system according to any one of claims 1 to 18 or a system according to claim 19 or 20.
22. A method of controlling a combustion engine, comprising: receiving a request signal indicative of a request for heating of an exhaust system of the combustion engine; controlling, in dependence on the request signal, an injection of fuel to a cylinder of the combustion engine whilst one or more exhaust valves associated with the cylinder are at least partially open simultaneous with one or more inlet valves, wherein the injection of fuel is controlled to provide first and second injections of fuel to the cylinder after a piston associated with the cylinder passes through top dead centre.
23. The method according to claim 22, wherein the controlling comprises causing the first injection of fuel to commence at or before 10 degrees after the piston associated with the cylinder passes through top dead centre.
24. The method according to claim 22 or 23, wherein the controlling comprises causing the second injection of fuel to commence at or before 20 degrees after the piston associated with the cylinder passes through top dead centre.
25. Computer software which, when executed by a computer, is arranged to control a combustion engine according to a method as claimed in any of claims 22 to 24.