GB2561386A

GB2561386A - A method of controlling fuelling of an engine

Info

Publication number: GB2561386A
Application number: GB1705966.8A
Authority: GB
Inventors: Richard Skilling Mark; Lineham Owen; Lonut Palamariu Catalin
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2017-04-13
Filing date: 2017-04-13
Publication date: 2018-10-17
Anticipated expiration: 2037-04-13
Also published as: GB201705966D0; DE102018105275A1; GB2561386B

Abstract

A method is disclosed for controlling the fuel injection of a direct injection spark ignited gasoline engine 11 based upon a comparison of a current engine temperature (t) with a minimum temperature limit (TLim) based upon an expected steady state temperature (T) and a predefined temperature difference (ΔT). If the current engine temperature (t) is below the minimum temperature limit (TLim) then the use of a transient split injection mode of fuelling using two or more injections of fuel per intake cycle is used otherwise a normal single injection mode of fuelling may be used. An associated apparatus is also disclosed. The method minimises particulate emissions during engine warm up by minimising spray of fuel on to an inside of a cold engine cylinder during engine warm up.

Description

(71) Applicant(s):

Ford Global Technologies, LLC Suite 800, 330 Town Center Drive,

Fairlane Plaza South, Dearborn 48126, Michigan, United States of America (72) Inventor(s):

Mark Richard Skilling Owen Lineham Catalin lonut Palamariu (56) Documents Cited:

EP 0982489 A2 EP 0919709 A2 WO 2006/070259 A1 US 20150057911 A1 (58) Field of Search:

INT CL F02B, F02D Other: WPI, EPODOC

EP 0947684 A2 WO 2014/057825 A1 US 6330796 B1 (74) Agent and/or Address for Service:

Ivan Rogers

Room 1/445 Eagle Way, Warley, BRENTWOOD, Essex, CM13 3BW, United Kingdom (54) Title of the Invention: A method of controlling fuelling of an engine

Abstract Title: A method and apparatus for controlling fuel injection in an engine (57) A method is disclosed for controlling the fuel injection of a direct injection spark ignited gasoline engine 11 based upon a comparison of a current engine temperature (t) with a minimum temperature limit (TLim) based upon an expected steady state temperature (T) and a predefined temperature difference (ΔΤ). If the current engine temperature (t) is below the minimum temperature limit (TLim) then the use of a transient split injection mode of fuelling using two or more injections of fuel per intake cycle is used otherwise a normal single injection mode of fuelling may be used. An associated apparatus is also disclosed. The method minimises particulate emissions during engine warm up by minimising spray of fuel on to an inside of a cold engine cylinder during engine warm up.

10

190

Fig.2

Yes

/2

Fig.1

2/2

Fig.2

A Method of Controlling Fuelling of an Engine

This invention relates to the control of an internal combustion engine and in particular to the control of fuelling of a direct injection spark ignited engine.

Engine out particulates emissions from a direct injection spark ignited engine during transient operation in which the temperature of a combustion chamber of an engine increases from a relatively low level to a higher level are a significant contributor to overall particulate generation on most emission drive cycles and in real-world driving.

When operating in a low load condition, surface temperatures within an internal combustion engine are relatively low and any significant fuel spray surface impingement will create pool fires which generate particulate emissions.

Transient temperature events are events in which the temperature increases from a relatively low level to a higher level and result in an increase in fuel spray impingement particulate production particularly at the lower temperature end of such an event. Transient temperature events are therefore high particulate forming events and it is desirable to minimise surface impingement during such transient temperature events.

It is an object of this invention to provide a method of controlling fuelling of a direct injection spark ignited engine to reduce the particulate emissions during a transient temperature event.

According to the invention there is provided a method of controlling the fuel supply to a direct injection spark ignited engine comprising comparing a current engine temperature with a predefined temperature limit and, if the current engine temperature is below the predefined temperature limit, operating the engine in a transient split injection mode of operation in which at least two injections of fuel are provided to each cylinder of the engine wherein the predefined temperature limit is set to an expected steady state engine temperature for the engine when operating at the same load and the same engine speed minus a predefined temperature difference from the steady state temperature .

This has the advantage that particulate emissions from the engine are reduced during a transient temperature event.

Preferably, the at least two injections of fuel may be provided to each cylinder of the engine during a respective intake stroke of the engine.

If the current engine temperature is one of equal to and greater than the predefined temperature limit, the method may further comprise operating the engine in a normal single injection mode of operation in which a single injection of fuel is provided to each cylinder of the engine .

The single injection of fuel may be provided to each cylinder during a respective intake stroke of the engine.

The total volume of fuel injected into a cylinder for each intake stroke of the engine when operating in the transient split injection mode may be the same as the volume of fuel that would be injected into the respective cylinder when using the normal injection mode of operation for the same speed and load conditions.

When operating in the transient split injection mode, each injection may be comprised of substantially the same volume of fuel.

If the speed of the engine is greater than a predefined upper speed limit, then use of the transient split injection mode may be prevented.

This has the advantage that transient split injection is not used when it is unlikely to have any significant beneficial effect so far as reducing particulate emissions is concerned.

If engine load is less than a predefined minimum load limit, then use of the transient split injection mode may be prevented.

The method may further comprise producing a value of current engine temperature by one of direct temperature measurement and temperature modelling.

The current engine temperature may be one of piston crown temperature and cylinder wall temperature.

According to a second aspect of the invention there is provided an engine system comprising a direct injection spark ignited gasoline engine, a fuel supply system for the engine having at least one fuel injector each arranged to inject fuel directly into a respective cylinder of the engine, an ignition system having at least one spark plug to ignite the fuel in each cylinder of the engine and an electronic controller to control the operation of the fuel supply system and the ignition system, the electronic controller being arranged to compare a current engine temperature with a predefined temperature limit and, if the current engine temperature is below the predefined temperature limit, operate the engine in a transient split injection mode of operation in which at least two injections of fuel are provided to each cylinder of the engine wherein the predefined temperature limit is set to an expected steady state engine temperature for the engine when operating at the same load and the same engine speed minus a predefined temperature difference from the steady state temperature .

The at least two injections of fuel may be provided to each cylinder of the engine during a respective intake stroke of the engine.

If the current engine temperature is one of equal to and greater than the predefined temperature limit, the electronic controller may be arranged to operate the engine in a normal single injection mode of operation in which a single injection of fuel is provided to each cylinder of the engine .

Preferably, the single injection of fuel may be provided to each cylinder during a respective intake stroke of the engine.

The electronic controller may be operable to control the fuel supply system so that the total volume of fuel injected into a cylinder for each intake stroke of the engine when operating in the transient split injection mode is the same as the volume of fuel that would be injected into the respective cylinder when using the normal single injection mode of operation for the same speed and load conditions .

When operating in the transient split injection mode, the electronic controller may be operable to ensure that each injection is comprised of substantially the same volume of fuel.

The electronic controller may be arranged to receive a signal indicative of current engine speed and, if the current speed of the engine is greater than a predefined upper speed limit, the electronic controller may be arranged to prevent the use of the transient split injection mode.

The electronic controller may be arranged to estimate a current engine load and, if current engine load is less than a predefined minimum load limit, the electronic controller may be arranged to prevent the use of the transient split injection mode.

The electronic controller may be further arranged to produce a value of current engine temperature by one of direct temperature measurement using an associated temperature sensor and modelling using a temperature model stored in the electronic controller.

According to a third aspect of the invention there is provided a motor vehicle having an engine system constructed in accordance with said second aspect of the invention.

The invention will now be described by way of example with reference to the accompanying drawing of which:Fig.l is a schematic diagram of a motor vehicle constructed in accordance with a third aspect of the invention having an engine system constructed in accordance with a second aspect of the invention; and

Fig.2 is a high level flow chart of a method of controlling fuelling of a direct injection spark ignited engine in accordance with a first aspect of the invention.

With reference to Fig.l there is shown a motor vehicle 5 having an engine system 10. The engine system 10 includes an engine in the form of a three cylinder direct injection spark ignited gasoline engine 11. It will be appreciated that the direct injection spark ignited gasoline engine 11 could have more than or less than three cylinders and that the invention is not limited to use with three cylinders and that the invention is not limited to the use of gasoline as the fuel, other suitable fuels could be used.

The engine 11 has an inlet manifold 12 through which air enters the cylinders of the engine 11 as indicated by the arrow Ά' on Fig.l and an exhaust manifold 13 from which exhaust gasses flow out of the engine 11 as indicated by the arrow Έ' on Fig.l.

It will be appreciated that the engine 11 could be normally aspirated or be a forced induction engine having a supercharger or turbocharger to increase the pressure of the air flowing to the engine 11.

It will be further appreciated that one or more exhaust gas aftertreatment devices will normally be present downstream from the exhaust manifold 13 to reduce the level of exhaust gas emissions entering the atmosphere from the engine 11.

Fuel is supplied to the engine via a fuel supply system including a fuel rail 14 which supplies fuel at high pressure to, in the case of this example, three fuel injectors 15a, 15b and 15c. Each of the fuel injectors 15a, 15b and 15c is arranged to inject fuel directly into a respective cylinder of the engine 11 with which it is associated. The operation of the fuel injectors 15a, 15b and 15c are controlled by an electronic controller 20. As is well known in the art, the electronic controller 20 controls the timing of the injection of fuel as well as the quantity of fuel injected.

Ignition for the engine 11 is provided in the case of this example by three spark plugs 16a, 16b and 16c each of which is arranged to provide a spark in a respective cylinder of the engine 11 with which it is associated. The operation of the spark plugs 16a, 16b and 16c are controlled by the electronic controller 20. As is well known in the art, the electronic controller 20 controls the timing of the sparks provided by the spark plugs 16a, 16b and 16c that is to say, the ignition timing of the engine 11.

It will be appreciated that although in the case of this example both fuel injection control and ignition timing control are both included as part of a single electronic controller in other examples there could be separate electronic controllers for controlling fuel injection and ignition that are interlinked to provide the necessary control of the engine 11.

A torque demand from a user of the motor vehicle 5 is provided by means of an accelerator pedal 17 that has a position sensor 19 arranged to send a signal indicative of the position of the accelerator pedal to the electronic controller 20.

Although not shown the electronic controller 20 is arranged to receive information from a number of other inputs required to control the operation of the engine 11. For example, the mass of air entering the engine can be provided from MAF sensor, the rotational position of a crankshaft of the engine 11 can be provided from a crank sensor and the crank sensor can be used to provide a value indicative of the rotational speed of the engine.

- 8 Such inputs are well known in the art and will not be described in further detail herein.

Operation of the electronic controller 20 so far as this invention is concerned is as follows.

When the engine 11 is operating normally the control of the engine 11 is conventional with the timing of the ignition for each cylinder and the timing and quantity of a single injection of fuel into each cylinder being controlled to produce a desired combination of torque and emissions. That is to say the fuelling of the engine 11 is provided in a 'normal injection mode' of operation using a single injection of fuel at a predetermined rotational position of the crankshaft for each cylinder of the engine 11.

However, when the engine 11 is operating in a transient temperature state in which the temperature is increasing from a relatively low level to a higher level the timing of the ignition for each cylinder is substantially the same as for the normal injection mode of operation but instead of providing a single injection of fuel into each cylinder two or more smaller injections of fuel are provided to each cylinder so as to reduce the risk of surface impingement of fuel during such events in what is referred to herein as a 'transient split injection mode' of operation.

A transient temperature state so far as this invention is concerned is when components located in a combustion chamber of an engine such as a combustion chamber wall or crown of a piston are operating below an expected steady state temperature for the current load more than a predefined amount and there has been an increase in engine load that will result in the temperature of the engine increasing.

When a transient temperature state is determined to be present the electronic controller 20 is operable to use the transient split injection mode of operation to provide the required fuel to the engine 11 to meet the current load.

When operating in the transient split injection mode of engine fuelling the same quantity of fuel (a standard injection quantity) is supplied to the engine 11 as would normally be supplied to meet the current load using a single injection but it is supplied in two or more separate inj ections.

That is to say, if there are two injections of fuel used then each of the injections provides one half of the standard injection quantity and if there are three injections of fuel each injection provides approximately one third of the standard quantity of fuel.

The first injection of fuel, in the case of this example, is provided at substantially the same crank position in the intake stroke as used for a single injection when operating in the normal mode of operation and the second or subsequent injections follow later at timings that are dependent upon both the separation time possible using the installed injectors 15a, 15b and 15c and the rotational speed of the engine 11. It will be appreciated that when using the transient split injection mode the timing of the first injection could be adjusted as well as providing more than one injection of fuel.

For example and without limitation in the case of a dual injection arrangement, the first injection of fuel can be made at circa 300°BTDC and the second injection be made at circa 260°BTDC.

In order to achieve the required functionality the electronic controller 20 has stored therein relationships between engine operating state and the steady state temperature when the engine is operating in that state for a wide range of operating conditions (load/ speed). The relationship for steady state temperature for a particular engine are obtained by carrying out dynamometer testing on one or more exemplar engines and the values are stored in the electronic controller 20 in any convenient manner.

The electronic controller 20 is further arranged to deduce, either from a model of exhaust gas temperature stored in a memory of the electronic controller 20 or from direct temperature measurement using one or more temperature sensors, the temperature of the exhaust gas exiting the engine or the temperature of critical components of the engine 11 so far as particulate generation is concerned such as the temperature of the piston crowns and/or cylinder walls of the engine. In the case that the deduced temperature is that of exhaust gas it will be appreciated that there is a verifiable relationship between this temperature and the temperature of the critical components of the engine 11. The electronic controller 20 is therefore continuously provided with an indication of the current engine temperature for use in deciding whether to use the normal injection mode or the transient split injection mode for fuelling the engine 11.

In addition to the above a predefined temperature difference (ΔΤ) from the steady state temperature (T) is stored in the electronic controller 20.

During operation of the engine 10 the electronic controller 20 is continually monitoring the current engine temperature (t) and comparing it to the steady state temperature (T) for the current operating conditions in terms of engine speed and torque demand or load to evaluate whether the current temperature (t) is lower than a minimum temperature limit (T_Lim) based upon the steady state temperature (T) for the current operating conditions and the required temperature difference (ΔΤ).

That is to say a test such as: Is t < T_Lim ? (EQ1)

Where : T_Lim = Τ-ΔΤ;

t is the current engine temperature;

T is the steady state engine temperature; and

ΔΤ is the required predefined temperature difference from the steady state temperature.

If the answer to the test is 'Yes' then the electronic controller 20 is operable to enable the transient split injection mode of operation whereas if the answer is 'No' the electronic controller 20 is operable to use the normal (single) injection mode of operation.

For example, assuming that the steady state temperature T for the current engine operating conditions is 750°C and ΔΤ = 200°C then, if the current engine temperature is equal to or greater than 550°C (the minimum temperature limit T_Li_min this case), the normal single injection mode is used by the electronic controller 20 and, if the current engine temperature (t) is less than 550°C, the transient split injection mode is used by the electronic controller 20.

Therefore, if the engine has been operating in a low load state causing its temperature to drop and there is a request for more output from the engine then it is likely that the current engine temperature (t) will be more than ΔΤ degrees cooler than the steady state temperature (T) for the desired engine output and so transient split injection will be activated by the electronic controller 20 until the temperature of the engine 11 reaches or exceeds the minimum temperature limit (T_Li_m) whereupon the normal single injection mode of fuelling will be activated by the electronic controller 20.

In this way the production of particulate matter from the engine 11 will be reduced as the volume of fuel impinging against relatively cold engine components such as the upper surface of the pistons (piston crowns) and the cylinder walls will be reduced.

It will be appreciated that there may be physical constraints on the use of the transient split injection mode such as engine speed and load.

For example, it will be appreciated that as engine speed increases the amount of time per degree of crankshaft rotation decreases and so there will be a limit whereupon the fuel injectors are unable to produce accurately the desired number of injections in the required time. This will depend upon the type of fuel injectors used and the injection timing required. Therefore as a refinement to the above there may be an upper speed limit (N_max) above which the transient split fuelling mode is not permitted due to fuel injection physical limitations. In such a case the logic equation EQ1 could be replaced by the logic equation EQ2 below.

Is (t < (Τ-ΔΤ) AND N < N_max? (EQ2)

Where:- N is the current rotational speed of the engine 11 and T, T and ΔΤ have the same meaning as per logic equation EQ1.

If the answer to the test EQ2 is 'Yes' then the electronic controller 20 is operable to enable the transient split injection mode of operation whereas if the answer is 'No' the electronic controller 20 is operable to use the

- 13 normal single injection mode. Therefore normal fuelling will be used whenever the engine speed N is greater than N_maxeven if the current engine temperature t would indicate that use of the transient split injection mode would reduce particulate emissions. This is because even if the transient split injection mode were to be used the inability of the fuel injectors to respond guickly or accurately enough would likely result in higher particulate emissions than the use of a well timed single injection as provided by use of the normal single injection mode.

In the case of load, it will be appreciated that if the load is below a certain level it may not be possible to provide accurately such small volumes of fuel from the fuel injectors if the volume of fuel is split using multiple injections. Therefore in some cases a lower load limit may be applied below which the transient split injection mode cannot be used.

In such a case the logic eguation EQ1 could be replaced by logic eguation EQ3 below.

Is (t < (Τ-ΔΤ) AND L > L_min? (EQ3)

Where:- L is the current load, L_mi_n is the minimum load for which accurate dosing of fuel can be provided by the fuel injectors and t, T and ΔΤ have the same meaning as per logic eguation EQ1.

If the answer to the test EQ3 is 'Yes' then the electronic controller 20 is operable to enable the transient split injection mode of operation whereas if the answer is 'No' the electronic controller 20 is operable to use the normal single injection mode.

It will be appreciated that logic eguations EQ2 and EQ3 could be combined to produce a fourth logic eguation EQ4 : 14

Is (t < (Τ-ΔΤ) AND N < N_max AND L > L_min?

If the answer to the test EQ4 is 'Yes' then the electronic controller 20 is operable to enable the transient split injection mode of operation whereas if the answer is 'No' the electronic controller 20 is operable to use the normal single injection mode.

However, it will be appreciated that the primary controlling factor is engine temperature and the other factors are constraints due to the physical capabilities of the fuel supply system and in particular the fuel injectors.

Referring now to Fig.2 there is shown a high level flow chart of a method (100) of controlling fuelling of a direct injection spark ignited gasoline engine such as the engine 11.

The method 100 starts in box 110 which is a Key-On event or an eguivalent event that will result in the starting of an engine of a motor vehicle such as the engine 11 of the motor vehicle 5.

The method advances from box 110 to box 120 where the engine is running and then on to box 130 where it is checked whether the conditions for a transient split injection mode are present.

The primary condition for the use of the transient split injection mode is that the current temperature of the engine is more than a predefined amount lower than an expected steady state temperature for the engine given the current operating conditions (Load/ Speed).

The temperature of the engine (engine temperature) is a temperature of a component or region that is known to have a real effect on the production of particulate matter when it is operating at a relatively low temperature. Non limiting examples of such components are the cylinder walls of the engine and upper surfaces of the pistons of the engine (piston crown temperature). However, it will be appreciated that the temperature of these components can be inferred from, for example, the temperature of the exhaust gas exiting the engine.

It will appreciated that as the current temperature (t) of the engine approaches the expected steady state temperature (T) the reduction in particulate matter produced by the use of split multiple injections diminishes rapidly and the use of split multiple injections can in some cases have a negative effect on overall engine out emissions. Therefore, in order to maximise the gains in terms of reduced particulate emissions while minimising any adverse effects on other exhaust gas emissions, the use of split multiple injections is terminated before the current temperature of the engine has reached the expected steady state temperature.

That is to say, a minimum temperature limit (T_Li_m) for the use of split multiple injections is set below the steady state temperature (T). The predefined temperature difference between the temperature limit (TLim) and the steady state temperature (T) is referred to as Delta T (ΔΤ) and in the case of this example is a predefined fixed quantity but could be a variable quantity based upon other engine operating factors such as load or the magnitude of the steady state temperature. The value of Delta T (ΔΤ) is set based upon experimental data from an engine of the same type from which it can be deduced when the benefit gained by the use of the transient split injection mode is minimal and potential disadvantages have begun to become significant.

Therefore, referring back to box 130, if the current temperature (t) of the engine is less than (T_Lim) then the transient split injection mode utilising multiple injections of fuel is enabled and the method advances to box 140 and otherwise it is not enabled and the method advances to box 150 .

Referring firstly to box 140 two or more injections of fuel are supplied to the engine with the first of these injections being made at substantially the same rotational position of the crankshaft of the engine as is the case when the normal single injection mode of fuelling is used.

The subsequent injection or injections of fuel are later than the initial injection in the combustion cycle with all of the injections occurring in an intake stroke of the engine. It will be appreciated that the initial injection could be at the same timing used for the normal single injection mode or can be adjusted when using the transient split injection mode.

For example and without limitation, in the case of a dual injection arrangement, if the primary timing for a single injection of fuel is 320°BTDC then a subsequent injection could be scheduled for 240°BTDC.

The total volume of fuel injected during the two injections will be the same as that injected if the normal single injection mode were to be used to produce the desired output from the engine. The amount of fuel injected is, in the case of this example, equally split between all of the multiple injections. So, in the case of two injections, each injection provides approximately 50% of the total fuel supplied during the intake stroke of a single cylinder. However, it will be appreciated that other ratios could be used.

From box 140 the method advances to box 160 to check whether there has been Key-Off event and, if there has been a Key-Off event, the method advances to box 190 where it ends otherwise the method returns from box 160 to box 130 where it is checked again whether the conditions for the use of the transient split injection mode are present.

The method will then continue to cycle through the boxes 130, 140 and 160 until a Key-Off event occurs or until the conditions for the use of the transient split injection mode are no longer present.

Referring back to box 130, if the conditions for the use of the transient split injection mode are not present when checked for in box 130, the method advances to box 150 where the engine is operated normally using the normal single injection mode to inject fuel during the intake stroke of each cylinder to meet a current torque demand for the engine .

From box 150 the method advances to box 160 to check whether there has been Key-Off event and, if there has been a Key-Off event, the method advances to box 190 where it ends otherwise the method returns from box 160 to box 130 where it is checked again whether the conditions for the use of the transient split injection mode are present or not.

The method will then continue to cycle through boxes 130, 150 and 160 until a Key-Off event occurs or until the conditions for the use of the transient split fuelling are present at which time it will, as previously described, advance to box 140.

The decision as to whether to use the transient split injection mode or the normal single injection mode is therefore based primarily on the temperature of potential particulate generating engine components referred to as 'engine temperature' and, in particular, whether the temperature of the engine is lower than an expected steady state temperature for the engine when operating in such a state of loading and rotational speed.

Therefore, whenever the engine is cooler by more than a predefined amount than an expected steady state temperature for those load and speed conditions, the transient split injection mode utilising multiple injections of fuel is advantageously used to reduce particulate emissions from the engine .

However, it will be appreciated that the physical constraints of the fuel supply system have to be taken into account and for this reason the test in box 130 may also include limitations on when the transient split injection mode can be used. For example, at higher engine speeds there is less time to inject the fuel because the time taken for the crankshaft to rotate from 360°BTDC to the last available rotational position where fuel can be injected will be less and there is a minimum amount of time required between injections based upon injector functionality. That is to say, there will be a maximum engine speed N_max above which is no real benefit in using multiple injections partly due the physical capabilities of the fuel injectors and control system used and partly due to combustion dynamics.

Similarly, there will be a limitation based upon engine load. Engine load can be estimated in a number of ways including but not limited to the air mass flow rate into the engine, the torque output from the engine, manifold pressure and the volumetric efficiency of the engine based upon the ratio of the volume of air entering a cylinder compared to the actual volume of the cylinder.

It will be appreciated that when the engine load is very low the amount of fuel required will also be low and there will be a level of load below which the fuel injectors are unable to accurately supply the required amount of fuel if multiple injections are used. That is to say, the use of multiple injections can only be used above a predefined load threshold L_min.

Therefore in practice the test in box 130 may require a number of conditions to be met before testing for the use of transient split fuelling is applied.

For example the test in box 130 could comprise three tests : (a) Is L (the current engine load) greater than L_min(the minimum load for which accurate dosing of fuel can be provided by the fuel injectors);

AND (b) Is N (the current engine speed) less than N_max (the maximum engine speed providing sufficient time to effect multiple injections of fuel);

AND c/ If (a) and (b) are passed then Is t < (Τ-ΔΤ)?

Only if all three of these tests are passed will the transient split fuelling mode be used and if any one of the tests is failed then the normal single injection mode is used.

Experimental testing using an engine in which a value of 0.6 of the maximum load was used for L_mi_n; the value of Nmax was set to 4000RPM and values of ΔΤ in the range of 250 to 200°C were used provided useful reductions in particulate emissions from the engine compared to the use of a single injection mode.

Therefore in summary, whenever an engine is running cooler that an expected steady state temperature for the same load and engine speed by more than a predefined amount (ΔΤ) the use of a transient split injection mode is used to reduce the production of particulate matter provided that the functionality of the fuel supply system allows such use.

Although the invention has been described with respect to embodiments in which the injections of fuel occur within an intake stroke of the engine it will be appreciated that in some case the final injection of fuel could commence in the intake stroke and terminate in the early part of a compression stroke of the engine.

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

Claims

1. A method of controlling the fuel supply to a direct injection spark ignited engine comprising comparing a current engine temperature with a predefined temperature limit and, if the current engine temperature is below the predefined temperature limit, operating the engine in a transient split injection mode of operation in which at least two injections of fuel are provided to each cylinder of the engine wherein the predefined temperature limit is set to an expected steady state engine temperature for the engine when operating at the same load and the same engine speed minus a predefined temperature difference from the steady state temperature.

2. A method as claimed in claim 1 wherein the at least two injections of fuel are provided to each cylinder of the engine during a respective intake stroke of the engine .

3. A method as claimed in claim 1 or in claim 2 wherein if the current engine temperature is one of equal to and greater than the predefined temperature limit, the method further comprises operating the engine in a normal single injection mode of operation in which a single injection of fuel is provided to each cylinder of the engine .

4. A method as claimed in any of claims 1 to 3 wherein the total volume of fuel injected into a cylinder for each intake stroke of the engine when operating in the transient split injection mode is the same as the volume of fuel that would be injected into the respective cylinder when using the normal injection mode of operation for the same speed and load conditions.

5. A method as claimed in claim 4 wherein, when operating in the transient split injection mode, each injection is comprised of substantially the same volume of fuel.

6. A method as claimed in any of claims 1 to 5 wherein, if the speed of the engine is greater than a predefined upper speed limit, then use of the transient split injection mode is prevented.

7. A method as claimed in any of claims 1 to 6 wherein, if engine load is less than a predefined minimum load limit, then use of the transient split injection mode is prevented.

8. A method as claimed in any of claims 1 to 7 wherein the method further comprises producing a value of current engine temperature by one of direct temperature measurement and temperature modelling.

9. A method as claimed in claim 8 wherein the current engine temperature is one of piston crown temperature and cylinder wall temperature.

10. An engine system comprising a direct injection spark ignited gasoline engine, a fuel supply system for the engine having at least one fuel injector each arranged to inject fuel directly into a respective cylinder of the engine, an ignition system having at least one spark plug to ignite the fuel in each cylinder of the engine and an electronic controller to control the operation of the fuel supply system and the ignition system, the electronic controller being arranged to compare a current engine temperature with a predefined temperature limit and, if the current engine temperature is below the predefined temperature limit, operate the engine in a transient split injection mode of operation in which at least two injections of fuel are provided to each cylinder of the engine wherein the predefined temperature limit is set to an expected steady state engine temperature for the engine when operating at the same load and the same engine speed minus a predefined temperature difference from the steady state temperature .

11. A system as claimed in claim 10 wherein the at least two injections of fuel are provided to each cylinder of the engine during a respective intake stroke of the engine .

12. A system as claimed in claim 10 or in claim 11 wherein, if the current engine temperature is one of equal to and greater than the predefined temperature limit, the electronic controller is arranged to operate the engine in a normal single injection mode of operation in which a single injection of fuel is provided to each cylinder of the engine .

13. A system as claimed in any of claims 10 to 12 wherein the electronic controller is operable to control the fuel supply system so that the total volume of fuel injected into a cylinder for each intake stroke of the engine when operating in the transient split injection mode is the same as the volume of fuel that would be injected into the respective cylinder when using the normal single injection mode of operation for the same speed and load conditions.

14. A system as claimed in claim 13 wherein, when operating in the transient split injection mode, the electronic controller is operable to ensure that each injection is comprised of substantially the same volume of fuel.

15. A system as claimed in any of claims 10 to 14 wherein, the electronic controller is arranged to receive a signal indicative of current engine speed and, if the current speed of the engine is greater than a predefined upper speed limit, the electronic controller is arranged to prevent the use of the transient split injection mode.

16. A system as claimed in any of claims 10 to 15 wherein, the electronic controller is arranged to estimate a current engine load and, if current engine load is less than a predefined minimum load limit, the electronic controller

10 is arranged to prevent the use of the transient split injection mode.

17. A system as claimed in any of claims 10 to 16 wherein the electronic controller is further arranged to

15 produce a value of current engine temperature by one of direct temperature measurement using an associated temperature sensor and modelling using a temperature model stored in the electronic controller.

20

18. A motor vehicle having an engine system as claimed in any of claims 10 to 17.

Intellectual

Property

Office

Application No: Claims searched:

GB1705966.8

1-18

20 18. A motor vehicle having an engine system as claimed in any of claims 10 to 17.

Amendment to Claims have been filed as follows

Claims co

1. A method of controlling the fuel supply to a direct injection spark ignited engine comprising comparing a

5 current engine temperature with a predefined engine temperature limit and, if the current engine temperature is below the predefined engine temperature limit, operating the engine in a transient split injection mode of operation in which at least two injections of fuel are provided to each

10 cylinder of the engine wherein the predefined engine temperature limit is set to an expected steady state engine temperature for the engine when operating at the same load and the same engine speed minus a predefined temperature difference from the steady state temperature.

3. A method as claimed in claim 1 or in claim 2 wherein if the current engine temperature is one of equal to and greater than the predefined engine temperature limit, the method further comprises operating the engine in a

25 normal single injection mode of operation in which a single injection of fuel is provided to each cylinder of the engine .

4. A method as claimed in any of claims 1 to 3 30 wherein the total volume of fuel injected into a cylinder for each intake stroke of the engine when operating in the transient split injection mode is the same as the volume of fuel that would be injected into the respective cylinder when using the normal injection mode of operation for the

35 same speed and load conditions.

co

25 10. An engine system comprising a direct injection spark ignited gasoline engine, a fuel supply system for the engine having at least one fuel injector each arranged to inject fuel directly into a respective cylinder of the engine, an ignition system having at least one spark plug to

30 ignite the fuel in each cylinder of the engine and an electronic controller to control the operation of the fuel supply system and the ignition system, the electronic controller being arranged to compare a current engine temperature with a predefined engine temperature limit and, if the current engine temperature is below the predefined engine temperature limit, operate the engine in a transient split injection mode of operation in which at least two injections of fuel are provided to each cylinder of the engine wherein the predefined engine temperature limit is set to an expected steady state engine temperature for the engine when operating at the same load and the same engine

5 speed minus a predefined temperature difference from the steady state temperature.

11. A system as claimed in claim 10 wherein the at least two injections of fuel are provided to each cylinder

10 of the engine during a respective intake stroke of the engine .

co

12. A system as claimed in claim 10 or in claim 11 wherein, if the current engine temperature is one of egual

15 to and greater than the predefined engine temperature limit, the electronic controller is arranged to operate the engine in a normal single injection mode of operation in which a single injection of fuel is provided to each cylinder of the engine .

13. A system as claimed in any of claims 10 to 12 wherein the electronic controller is operable to control the fuel supply system so that the total volume of fuel injected into a cylinder for each intake stroke of the engine when

25 operating in the transient split injection mode is the same as the volume of fuel that would be injected into the respective cylinder when using the normal single injection mode of operation for the same speed and load conditions.

30 14. A system as claimed in claim 13 wherein, when operating in the transient split injection mode, the electronic controller is operable to ensure that each injection is comprised of substantially the same volume of fuel.

15. A system as claimed in any of claims 10 to 14 wherein, the electronic controller is arranged to receive a

31 10 17 signal indicative of current engine speed and, if the current speed of the engine is greater than a predefined upper speed limit, the electronic controller is arranged to prevent the use of the transient split injection mode.

10 is arranged to prevent the use of the transient split injection mode.