GB2422688A

GB2422688A - Four stroke engine sychronisation

Info

Publication number: GB2422688A
Application number: GB0501717A
Authority: GB
Inventors: Jon Dixon; Adam Christian Webb; Clive Oliver Neal Harrison
Original assignee: Visteon Global Technologies Inc
Current assignee: Visteon Global Technologies Inc
Priority date: 2005-01-28
Filing date: 2005-01-28
Publication date: 2006-08-02
Anticipated expiration: 2025-01-28
Also published as: GB0501717D0; GB2422688B

Abstract

This invention relates to an engine management system capable of determining engine phase of a four-stroke spark ignition internal combustion engine that comprises a number of cylinders that have a charge phase (36) and a power phase (37) in one complete cycle of the engine, an air inlet conduit, one or more engine operating condition sensors for sensing when a cylinder has misfired, an indirect fuel injection system for injecting fuel (38,138), and an engine management system for controlling the operation of the engine. The engine operating condition sensor(s) are used to detect when a cylinder has misfired. A test is conducted to determine the phase of a cylinder by temporarily advancing (38',138') the fuel injection into the inlet conduit for said test cylinder by one phase and then subsequently delaying (38'',138'') the fuel injection into said conduit by one phase so that said test cylinder reverts to fuel injection into said conduit on alternate cylinder phases. It is determined whether or not there has been a misfire correlated with the delay of fuel injection, and from the detected presence or absence of said misfire in said test cylinder the correct cylinder phase for fuelling of the or each cylinder is determined.

Description

Motor Vehicle Engine Synchronisation

Introduction

1. Field of the Invention

This invention relates to an engine management system capable of determining engine phase of a four-stroke spark ignition internal combustion engine.

2. Related Art When a four-stroke engine is running, it is desirable to verify that the fuel is being injected into the cylinder during the correct stroke. If the fuel is injected on the wrong stroke, the engine may still run, but engine emissions will increase and engine efficiency will drop.

Internal combustion engines normally have a crankshaft sensor that provides a rotation signal that can be used to verify piston position over one complete revolution of the engine. However, as the engine takes two full revolutions to complete one cycle of the four strokes, this type of engine sensor cannot distinguish between the two halves of the cycle for a particular cylinder. These two halves of the engine cycle for a particular cylinder are sometimes referred to as the charge phase in which the cylinder is charged with air and fuel, and the power phase in which the air-fuel mixture is ignited and expelled as exhaust gas. These two halves of the cylinder cycle will therefore be referred to herein as the two "phases" of the four-stroke cylinder cycle.

454 1a4 26 January 2005 Currently, the most common method of verifying the cylinder phase is through the use of a camshaft position sensor. However, a camshaft sensor with associated wiring and engine machining adds cost to the engine.

It is possible to achieve cylinder phase verification without the use of a camshaft position sensor, for example as described in patent document EP 0 990 787 A. This document describes a method of determining cylinder phase in which one cylinder of the engine is made to run for one cycle at non-optimal conditions. This causes a sharp change in the operating conditions for that cylinder, which can then be detected by measuring a momentary change in the composition of the exhaust gas. The time at which the exhaust gas composition changes can then be used to determine the cylinder stroke on which exhaust gas is expelled by the affected cylinder.

This method suffers from a number of problems, primarily the need to run the engine in a non-optimal mode that can result in noticeably uneven running, and the need to detect slight and momentary variations in exhaust gas composition.

Summary of the Invention

The present invention seeks to provide an improved system for engine injection stroke verification.

454]a4 26 January 2005 According to the invention there is provided a method of correctly fuelling a four-stroke internal combustion engine that comprises a number of cylinders, an inlet conduit leading to the or each cylinder, an indirect fuel injection system, and at least one engine operating condition sensor, wherein the method comprises the steps: i) running the engine so that the or each cylinder moves through a charge phase and a power phase in one complete cycle of the engine; ii) using the indirect fuel injection system to inject fuel into the or each inlet conduit on alternate cylinder phases; and then iii) temporarily advancing the phasing of the fuel injection into the inlet conduit for at least one test cylinder; iv) subsequently delaying the phasing of the fuel injection into said conduit for said test cylinder; and then v) continuing to inject fuel into the or each inlet conduit on alternate cylinder phases; vi) detecting from said at least one sensor whether or not there has been a misfire coincident with said delay of fuel injection; vii) determining from the detected presence or absence of said misfire in said at least one test cylinder the correct cylinder phase for fuelling of the or each test cylinder; and viii) using the indirect fuel injection system to inject fuel into the or each inlet conduit on the correct alternate cylinder phases in accordance with said determination of said correct cylinder phases.

454 1a4 26 January 2005 Also according to the invention, there is provided four- stroke internal combustion engine, comprising a number of cylinders, the or each cylinder containing a reciprocating piston that moves through a charge phase and a power phase in one complete cycle of the engine, an air inlet conduit leading to the or each cylinder, one or more engine operating condition sensors for sensing when a cylinder has misfired, an indirect fuel injection system for injecting fuel into the or each inlet conduit, and an engine management system for controlling the operation of the engine including controlling the indirect fuel injection system, wherein the engine management system is arranged to: - monitor the engine operating condition sensor(s) and to detect therefrom when a cylinder has misfired; - control the indirect fuel injection system to inject fuel into the or each inlet conduit on alternate cylinder phases; - use at least one cylinder as a test cylinder to determine the phase of said cylinder by temporarily advancing the phasing of the fuel injection into the inlet conduit for said test cylinder and then subsequently delaying the phasing of the fuel injection into said conduit so that said test cylinder reverts to fuel injection into said conduit on alternate cylinder phases; determine whether or not there has been a misfire correlated with said delay of fuel injection; and - determine from the detected presence or absence of said misfire in said test cylinder the correct cylinder phase for fuelling of the or each cylinder.

It may be convenient, as in the preferred embodiment of 454 1a4 26 January 2005 the invention described below, to temporarily advance the phasing of the fuel injection by 3600 into the alternate phase, and then to subsequently delay the phasing of the fuel injection also by 360 SO that the engine reverts to the original phase. In this case, the temporary advancement and subsequent delay of the fuel injection is by exactly one phase.

It may also be convenient to temporarily advance the phasing of the fuel injection into the alternate engine phase, but by an amount differing from 360 and then to subsequently delay the phasing of the fuel injection also by an amount differing from 360 so that the engine reverts to the original engine phase. In this case, the temporary advancement and subsequent delay of the fuel injection is still effectively by "one" phase.

It may, however, not be necessary for the change in fuel injection phasing to advance the fuel injection into the alternate engine phase, so long as it is the case, when the initial engine fuelling is on the incorrect engine phase, that the advanced fuel injection ends before closure of the inlet valve, so that no or insufficient fuel is drawn past that inlet valve for the subsequent cylinder firing to be normal. In this case, when the cylinder is initially fuelled on the incorrect engine phasing, the phasing advancement is effectively by "one" phase because the cylinder effectively misses one fuelling event.

Therefore, in all cases, the advancement of the phasing of the fuel injection and subsequent delay of the phasing of 454 1a4 26 January 2005 the fuel injection is effectively by "one" phase as regards the fuelling of the cylinder via the opening and closing inlet valve, even though the change in phasing may not be exactly by one 360 phase, or even by changed to the alternate engine phase.

The invention provides the advantage that there is no need for a camshaft position sensor, and the engine is no longer required to operate in a manner which will always result in noticeably uneven running in order to provide the engine management with the signals required to verify whether or not the engine is being fuelled on the correct stroke or cylinder phase.

The term "engine management system" (EMS) will be understood to mean any electronic system capable of controlling or influencing the operation of the engine.

The engine will normally have a crank shaft that rotates once in each cylinder phase. Therefore, in a preferred embodiment of the invention, the engine has an engine rotation sensor for measuring the engine angle of the crankshaft. Then, once the engine has been turned off, the engine rotation sensor continues to be used by the EMS to monitor the change in engine angle and hence continues to track the or each correct cylinder phase for fuelling as the engine comes to a stop. When the engine has stopped, these final monitored values (which may be combined mathematically, for example as a single angle value falling in a range 0 to 720 that covers both cylinder phases) may be stored in a memory, such as a non-volatile memory chip in the EMS.

454 1a4 26 January 2005 Later, the engine rotation sensor is again used to monitor the change in engine angle from the moment the engine is restarted. The stored final engine angle and the or each correct cylinder phase are then recalled from memory and used together with the monitored change in engine angle to determine the correct alternate cylinder phases for fuelling the or each cylinder.

If the engine angle has been correctly monitored during stopping of the engine, and if the engine has not been turned off due to some other reason, the newly determined alternate cylinder phases for fuelling the or each cylinder should indeed be the correct cylinder phases.

There may be, however, a need to verify this, and so the method preferably includes, after engine start up the step of verifying that the determined correct alternate cylinder phases for fuelling the or each cylinder are indeed the correct phases by repeating steps iii) to vii) If, after repeating steps iii) to viii), the determined correct alternate cylinder phases for fuelling the or each cylinder are indeed the correct phases, then there is no need to repeat steps iii) to viii) starting from the incorrect alternate cylinder phases. As a result, once the correct cylinder phases are known, and as long as the determination of the stopped engine angle and stopped cylinder phases is reliable, the method does not require that the engine be run in a condition that will inevitably result in a misfire, and hence uneven running, in order to verify the correct fuel injection phasing following restarting of the engine.

454 1a4 26 January 2005 One way in which misfires can be detected is by monitoring the engine speed for perturbations and deducing therefrom the presence or absence of a misfire.

The method may comprise conducting steps ii) and iv) during steady state engine running conditions. This helps in the detection of any engine misfires.

Most preferably, these steady state running conditions are engine idle conditions. Engine idle speed will normally be between about 500 rpm and 1000 rpm. At such a low engine speeds, the time window for fuel injection is relatively short compared with the time window during one cylinder phase. This is also due to the fact only a relatively small quantity of fuel is needed at low engine powers.

Consequently, and as will be explained in greater detail below, if the engine fuelling was correctly timed to occur immediately before inlet valve opening, the two injections of fuel that occur in subsequent cylinder cycles when fuel injection is initially advanced will both fall between subsequent periods defined by the time of inlet valve closing and subsequent opening. As a result, there will normally be no misfire from either the initial advance or subsequent delay in the injection fuelling for the or each test cylinder.

On the other hand, if the engine fuelling was incorrectly timed so that this occurs immediately after inlet valve closing, then the two injections of fuel that occur in subsequent cylinder cycles when fuel injection is initially advanced will both fall in the same period 4541a4 26 January 2005 defined by the time of inlet valve closing and subsequent opening. As a result, there will be no injected fuel in the next period prior to inlet valve opening when the fuel injection timing is subsequently delayed, with the result that there will be a misfire coincident with this subsequent delay in the injection fuelling for the or each test cylinder.

In this case, because of the double fuelling during the period prior to inlet valve opening, it may be desirable to provide between steps iii) and iv) one or more cycles of fuelling on alternate cylinder phases so that any excess fuel in the inlet is fully consumed prior to delaying the injected fuel and causing the cylinder misfire. This is also advantageous in minimizing any uneven running of the engine, because in this case, the advanced fuelling phase is in fact also the correct fuelling phase.

Alternatively, in the case in which injection timing was initially correct, it may be desirable for step iii) to proceed directly to step iv) so that between steps iii) and iv) there are two sequential phases during which no fuel is injected into the inlet conduit for the test cylinder. In this case, there will be only one cylinder phase during which the test cylinder is incorrectly fuelled at a time immediately following closing of the inlet valve, thereby also helping to minimize any disturbance to the running of the engine.

Therefore, if the engine was initially being correctly fuelled, as should normally be the case, the invention 454 1a4 26 January 2005 - 10 - should not cause any noticeable roughness in engine operation as the test is being conducted.

One way to ensure that the test occurs during steady state conditions is by monitoring the engine speed, and then using this monitored engine speed in the determination of steady state conditions. Alternatively or additionally, the engine management system may be arranged to use the monitored presence of misfires (which may be present for other reasons) in the determination of steady state conditions.

Another aspect of engine operation that may be monitored is in-cylinder ionization, which can be measured using an ionization detection circuit. In this case, the monitored in-cylinder ionization can alternatively or additionally be used in the determination of steady state conditions.

The more cylinders an engine has the more difficult it becomes to detect engine misfires using engine speed alone as an indicator. Therefore if there is any doubt about the accuracy of the determination of the correct cylinder phase for fuelling, then the method may comprise repeating at different times (and optionally also with different cylinders) steps iii) to vii) . Furthermore, the test may be performed with two or more cylinders simultaneously if it is difficult to detect engine misfires.

454 1.i4 26 January 2005 - 11 -

Brief Description of the Drawings

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a partial schematic view of a four-stroke internal combustion engine according to the invention having a crank shaft sensor that provides an engine speed signal to an engine management system that uses the signal from the engine speed sensor together with advancement subsequent delay of fuel injection to deduce the correct engine phasing for fuel injection; Figures 2A and 2B show, respectively time lines during operation of the engine of Figure 1, divided into a repeating sequence of four strokes of engine operation and showing times of advancement and delay for fuel injection; Figure 3 is a plot of real data from a four-stroke, fourcylinder internal combustion engine according to the invention showing engine speed, a calculated misfire index and the times of delay for the fuel injection; and Figure 4 is a flowchart illustrating some of the main steps of the invention in which the engine management system uses the signal from the engine speed sensor together with advancement and subsequent delay of fuel injection to deduce the correct engine phasing for fuel injection.

454 1a4 26 January 2005 - 12 -

Detailed Description

Figure 1 shows a schematic view of a four-stroke internal combustion engine 2 having a cylinder 16 with an associated piston 18 and an indirect fuel injector 20.

Although in this drawing only one cylinder is shown, it should be understood that there will usually be more than one cylinder, and in this example there are four in-line cylinders 16 with associated air inlets 22 for supplying inlet air 12 and fuel injectors 20 for injecting a fine mist of fuel 6 into each inlet conduit 22.

The inlet air 12 is mixed with the injected fuel 6 in a ratio defined by the engine management system (EMS) 14.

This air/fuel mixture is then drawn into the cylinder 16, compressed by the piston 18 and ignited by a spark plug 24. The ignited air/fuel mixture expands and forces the piston down giving power to a crankshaft 26. Exhaust gases 27 created by this combustion event are expelled from the cylinder via an exhaust conduit 8.

The EMS 14 will be connected electronically to the fuel injectors 20 and spark plugs 24 in a manner well-known to those skilled in the art, and which will therefore not be further described.

The engine has a conventional crank shaft rotation sensor 4 and toothed wheel 28 mounted to the crankshaft 26. The toothed wheel 28 has one or more missing teeth (not shown) so that a signal 10 from the rotation sensor 4 gives a repeating signal every full 3600 rotation of the crankshaft 26. The EMS 14 receives the signal 10 from the 454 1a4 26 January 2005 - 13 - crankshaft sensor 4, which enables the EMS 14 to calculate the angular position of the crankshaft 26, which is directly related to the vertical position and cycle of each piston 18.

However, because the engine is a four-stroke engine with a full cycle extending over 7200 crankshaft rotation, it is not possible to determine only from the signal 10 if a particular cylinder 16 is in the charging phase during which air 12 and fuel 6 are drawn into the cylinder 16, or in the power phase when the air/fuel mixture is ignited by the spark plug 24 and expelled as exhaust gas 27 through the exhaust gas outlet 8.

Reference is now made also to Figures 2A and 2B, which show, respectively time lines 30, 31 for two different cases of engine operation in which the invention may be employed. Each time line 30, 31 is divided into a repeating sequence of four piston strokes, namely the inlet stoke 32, compression stroke 33, power stroke 34 and exhaust stroke 35. The inlet and compression strokes 32, 33 form the charge phase 36. The power and exhaust strokes 34, 35 form the power phase 37.

Also shown on the timelines 30, 31 are timings of fuel injection events 38, 138 inlet valve opening events 39, 139 and spark events 40, 140.

In the first case of operation, shown in Figure 2A, the fuel injection 38 initially takes place towards the end of the exhaust stroke 35 and prior to opening 39 of the inlet valve 23. This is the correct phasing of the fuel 454 1a4 26 January 2005 - 14 - injection. In this example, the engine 2 is operating at about 800 rpm while idling. At this speed, each piston stroke 32-35 takes 37.5 ms to complete, and each cylinder phase 36,37 takes 75 ms to complete.

Because the engine is idling, the fuel demand is low, and so each fuel injector 20 injects fuel 6 for about 10 ms.

This is a relatively short time compared with the time between valve openings, which is about 90 to 100 ms.

The inlet valve 23 closes shortly after the beginning of the compression stroke 33. About 5 ms before the piston 18 reaches the top or end of the compression stroke 33, the spark plug 24 fires, and the inlet fuel 6 and air 12 ignite and burn inside the cylinder 16 during the power stroke 34. The cycle would then normally repeat itself, as shown in the second fuel injection event 38.

During stable idling operation, the EMS 14 may call for a test to verify the cylinder phases. This is shown in Figure 2A, where the third fuel injection event 38' is advanced by one full phase so that this occurs shortly after the closing of the inlet valve 23. The fuel injected 6 into the inlet port 22 therefore remains in the inlet until the inlet valve 23 opens 39' on the subsequent charge phase 36. Although some fuel 6 may remain within the inlet port 22 owing to the delay 42 between fuel injection 38 and the subsequent inlet valve opening 39', there will normally be sufficient fuel drawn into the cylinder 16 such that the cylinder 16 will fire when the next spark event 40' occurs. There should therefore be no misfire following this spark event 40' 454 1a4 26 January 2005 - 15 - As indicated by the double dashed lines cutting the time line 30, in either the next or a later engine cycle, the injection timing is delayed 38" by one full engine phase, so that the fuel 6 is again injected shortly before the inlet valve opening 39". The engine 2 therefore continues to run normally, in this case with the correct phasing of fuel injection. As will be explained below, because this test did not result in a cylinder misfire, it is possible to deduce that the initial and final injection of fuel occurred during the correct engine phase, namely towards the end of the power phase 37.

Figure 2B illustrates the alternative case in which the injection of fuel 138 occurs during the wrong engine phase, namely towards the end of the charge phase 36, shortly after the inlet valve opening 139 has ended. At least during idle conditions, the engine 2 should still run normally because fuel 6 in the inlet conduit 22 will be drawn into the cylinder 16 during the subsequent valve opening 139.

A test may then be conducted under the control of the EMS 14 to determine if the cylinder fuel injection phasing is indeed correct. In the same manner as described above, the fuel injection is first advanced 138' by one full phase of the engine. In this case, the result is that there will be two fuel injection events 138, 138' prior to the next valve opening 139' . This will result in an overly rich mixture of fuel 6 and air 12 being drawn into the cylinder 16. This may adversely affect the combustion process after the next firing 140' of the spark plug 24, resulting in a 4541a4 26 January 2005 - 16 - drop in power or even a misfire in that cylinder 16.

It should be noted that in this case the advanced fuel injection event 138' is correctly phased. As indicated by the diagonal dashed lines cutting the time line 31, the test procedure may continue to run the engine with one or more fuel injection events with the same correct phasing.

This provides the advantage that any excess fuel remaining in the inlet conduit 22 will be consumed prior to the next step of the test process, which is to delay the fuel injection event 138" by one full phase, so that the fuel injection returns to the original, incorrect phasing.

As shown, this results in no fuel injection event between two sequential inlet valve openings 139', 139", which will reliably result in a misfire after the next firing 140' of the spark plug 24. After the misfire, the cylinder 16 will again be fuelled 138" once prior to each opening of the inlet valve 23 and so the engine 2 will revert to normal running, at least at relatively low engine speeds and/or low engine power demand.

One way in which the EMS 14 may sense the cylinder misfire of the second time line case 31, is by monitoring the engine speed for perturbations using the signal 10 from the engine speed and position sensor 4. This is illustrated in Figure 3, which shows a plot 45 of data collected from a 4cylinder, 1.8 litre engine. The top line 41 is a plot of engine speed during idle conditions at about 700 rpm. The bottom plot shows a misfire index 43 calculated by the EMS 14 using data from the engine speed sensor 4. Because the engine speed may also be affected by 454 1a4 26 January 2005 - 17 - road roughness, optionally, inputs from accelerometers (not shown) may also be used in order to compensate for changes in engine speed correlated with road roughness.

For the sake of illustration, Figure 3 shows the test procedure run at three times indicated by arrows labelled 44 when the fuel injection is on the incorrect engine phase, and then at three times indicated by arrows 46 when the fuel injection is on the correct engine phase. At each occurrence 44 of the test during incorrect phasing of the fuel injection, the misfire index 43 produces an unambiguous spike 48, which can be detected by the EMS 14 against a suitable threshold value 49. In contrast, there are no noticeable spikes in the misfire index 43 when the engine phasing test is run 46 with the fuel injection initially on the correct engine phase.

Figure 4 shows a flowchart 50 that illustrates the main steps taken by the invention. The engine management system (EMS) 14 checks 51 engine operating conditions to determine if the engine 2 is operating in a stable condition, and on a smooth road. If so 52, then the EMS 14 selects 53 a new cylinder 16 for testing. The EMS then advances 54 the phasing of the fuel injection for that cylinder 16 and then waits for n cycles, where n = 1.

Following this, the EMS returns 55 to the original fuel phasing and then checks 56 to see if there has been a misfire. If not 57, then the initial fuel phasing is deemed to have been correct, and no change is made 58 to the timing of the fuel injection. If there has been a misfire 59, then the initial fuel phasing is deemed to 454].a4 26 January 2005 - 18 - have been incorrect, and 3600 of crank angle is added 60 to the fuel injection phasing for that cylinder, 16 and any other cylinders that were similarly mis-synchronised.

Again, the EMS checks 61 for stable engine operating conditions, and when conditions are suitable 62, the test as described above is repeated 63, 64, 65 to see if there has been a misfire. If there has been an unexpected misfire 66, then there may have been an error in the original determination 56, 57, 58 that the fuel phasing was initially correct. A counter (not illustrated) in software running in the EMS 14 is incremented and a test made 68 to see how many times there has been an unexpected misfire 66. If a limit has been exceeded 69, then a flag is set 70 indicating that there has been a failure in the process to determine correct phasing of cylinder fuelling.

If the retest limit has not been exceeded 71, then the test sequence 5070 is repeated using a different cylinder 16.

On the other hand, if the second test 63-65 results in no misfire 72, then the fuel injection phasing has been confirmed as being correct, and the test procedure 50 comes to an end 73.

The invention described above works best in conjunction with a scheme which tracks the engine angle as it comes to rest when keyed off, and then stores the engine angle in non-volatile memory, for example flash memory within the engine control unit 14. Therefore, once cylinder phasing has been identified using the techniques described above, 454 1a4 26 January 2005 - 19 - the engine can be started using the known final engine angle to phase the fuel injection with a high degree of confidence that this will in fact be the correct engine phasing. The engine phasing test that may then be conducted is very likely to be the first case shown in Figure 2A, which will not cause any misfire or result in any unevenness in engine running noticeable to a driver of the vehicle or such as to cause an increase in engine exhaust emissions.

Furthermore, because the initial engine phasing is very likely to be correct, the phasing confirmation test does not necessarily need to be run immediately the engine starts, but can take place at some convenient later time.

This provides the benefit that the engine phasing test can be scheduled when engine misfires or other irregularities have not been detected for some period of time, and when the engine speed is reliably predictable and when the time for fuel injection is about 20% or less, or preferably 10% or less, than the time between subsequent inlet valve openings. This may be, for example, when the vehicle is stopped with the engine idling.

The engine phasing test described above relies on the principle that aport injected gasoline engine at idle typically operates with an injection duration of a few tens of degrees crank angle and with that injection timed to end shortly before the inlet valve opening event. Under such conditions, the injection timing may be moved significantly earlier in the cycle without any noticeable effect on the operation of the engine. The only restriction on the angle by which this movement can be 454 1a4 26 January 2005 - 20 - made is that the leading edge of the injection must move no earlier than the prior inlet valve closing event, otherwise some of the injected fuel would go into the previous cycle.

In summary, to verify cylinder phase synchronisation, when the engine is at a suitable steady state operating condition, the injection timing is moved earlier in the cycle by an amount which will not move it into the previous inlet event if correctly phased, but would move it entirely into the previous cycle if phase is incorrect, that is off by 3600 of crank angle. One or more engine cycles later, the timing is advanced back to its original position. This may be repeated a number of times until phasing is satisfactorily confirmed.

If the phasing is correct no effect on engine operation will be seen. If, however, the phasing is incorrect, one cycle will have close to twice the required fuel and another will have almost no fuel. This will cause at least one of these cycles to misfire and this misfire event can easily be detected by existing diagnostic systems. If it is determined that the engine is being incorrectly fuelled, the engine management system can then be used to adjust automatically the timing of the fuel injection.

Although the invention has been described above as using an engine speed sensor in the determination of cylinder misfires, other techniques may additionally or alternatively be employed to make this determination. For example, one of the engine operating condition sensors may be an incylinder ionization detection sensor. The engine 454 1a4 26 January 2005 management system may then be arranged to monitor the in- cylinder ionization detection sensor and use a signal output from this in or to detect if the engine is operating in steady state conditions or if a misfire has taken place.

The invention therefore provides a convenient way to sense and correct fuelling on an incorrect stoke of the engine.

454 1a4 26 Januiry 2005

Claims

- 22 - Claims 1. A method of correctly fuelling a four-stroke internal

combustion engine that comprises a number of cylinders, an inlet conduit leading to the or each cylinder, an indirect fuel injection system, and at least one engine operating condition sensor, wherein the method comprises the steps: 1) running the engine so that the or each cylinder moves through a charge phase and a power phase in one complete cycle of the engine; ii) using the indirect fuel injection system to inject fuel into the or each inlet conduit on alternate cylinder phases; and then iii) temporarily advancing the phasing of the fuel injection into the inlet conduit for at least one test cylinder; iv) subsequently delaying the phasing of the fuel injection into said conduit for said test cylinder; and then v) continuing to inject fuel into the or each inlet conduit on alternate cylinder phases;

vi) detecting from said at least one sensor whether or not Lhere has been a misfire coincident with said delay of fuel injection; vii) determining from the detected presence or absence of said misfire in said at least one test cylinder the correct cylinder phase for fuelling of the or each test cylinder; and viii) using the indirect fuel injection system to inject fuel into the or each inlet conduit on the correct alternate cylinder phases in accordance with said determination of said correct cylinder phases.

454 1a4 26 January 2005 - 23 -
2. A method as claimed in Claim 1, in which the engine comprises a crank shaft that rotates once in each cylinder phase, an engine rotation sensor for measuring the engine angle of the crankshaft and a memory, and the method comprises after step viii) ix) turning the engine off and using the engine rotation sensor to monitor the change in engine angle and hence continue to track the or each correct cylinder phase for fuelling as the engine comes to a stop; x) when the engine has stopped, storing the final monitored engine angle together with the or each correct cylinder phase in the memory; xi) restarting the engine and using the engine rotation sensor to monitor the change in engine angle as the engine is started; and xii) recalling from memory the stored final engine angle and the or each correct cylinder phase and using this together with said monitored change in engine angle to determine the correct alternate cylinder phases for fuelling the or each cylinder.
3. A method as claimed in Claim 2, comprising after step xii) the step of verifying that said determined correct alternate cylinder phases for fuelling the or each cylinder are indeed the correct phases by repeating steps iii) to vii)
4. A method as claimed in any preceding claim, in which the method comprises the step of monitoring the engine speed for perturbations and deducing therefrom the presence or absence of said misfire.

454].a4 26 January 2005 - 24 -
5. A method as claimed in any preceding claim, in which the method comprises conducting steps ii) and iv) during steady state engine running conditions.
6. A method as claimed in Claim 5, in which said steady state running conditions are engine idle conditions.
7. A method as claimed in Claim 5 or Claim 6, in which the method comprises: - monitoring the engine speed; and - using the monitored engine speed in said determination of steady state conditions.
8. A method as claimed in any of Claims 5 to 7, in which the method comprises monitoring the engine for misfires, and using the monitored presence of misfires in said determination of steady state conditions.
9. A method as claimed in any preceding claim, in which the method comprises - monitoring in-cylinder ionization; and - using the monitored in-cylinder ionization in said determination of steady state conditions.
10. A method as claimed in any preceding claim, in which between steps iii) and iv) the method comprises continuing to inject fuel into the or each inlet conduit on alternate cylinder phases at least once.
11. A method as claimed in any of Claims 1 to 9, in which step iii) proceeds directly to iv) so that between steps iii) and iv) there are two sequential phases during which 454 1a4 26 January 2005 - 25 - no fuel is injected into said conduit for said test cylinder.
12. A method as claimed in any preceding claim, in which the engine has a plurality of cylinders, and the method comprises repeating at different times and optionally also with different test cylinders steps iii) to vii)
13. A four-stroke internal combustion engine, comprising a number of cylinders, the or each cylinder containing a reciprocating piston that moves through a charge phase and a power phase in one complete cycle of the engine, an inlet conduit leading to the or each cylinder, one or more engine operating condition sensors for sensing when a cylinder has misfired, an indirect fuel injection system for injecting fuel into the or each inlet conduit, and an engine management system for controlling the operation of the engine including controlling the indirect fuel injection system, wherein the engine management system is arranged to: - monitor the engine operating condition sensor(s) and to detect therefrom when a cylinder has misfired; - control the indirect fuel injection system to inject fuel into the or each inlet conduit on alternate cylinder phases; use at least one cylinder as a test cylinder to determine the phase of said cylinder by temporarily advancing the phasing of the fuel injection into the inlet conduit for said test cylinder and then subsequently delaying the phasing of the fuel injection into said conduit so that said test cylinder reverts to fuel injection into said conduit on alternate cylinder phases; 454 1a4 26 January 2005 - 26 - - determine whether or not there has been a misfire correlated with said delay of fuel injection; and - determine from the detected presence or absence of said misfire in said test cylinder the correct cylinder phase for fuelling of the or each cylinder.
14. A four-stroke internal combustion engine as claimed in Claim 13, in which one engine operating condition sensor is an engine speed sensor, and the engine management system is arranged to: - monitor the engine speed sensor and to detect therefrom engine speed perturbations; and - deduce therefrom the presence or absence of said misfire.
15. A four-stroke internal combustion engine as claimed in Claim 13 or Claim 14, in which the engine management system is arranged to: - monitor the engine operating condition sensor(s) and to determine therefrom when the engine is operating at steady state conditions; and - schedule said advance and delay of fuel injection when the engine is operating at steady state conditions.
16. A four-stroke internal combustion engine as claimed in Claim 15, in which said steady state running conditions are engine idle conditions.
17. A four-stroke internal combustion engine as claimed in any of Claims 13 to 16, in which one engine operating condition sensor is an engine speed sensor, and the engine management system is arranged to: 454 1a4 26 January 2005 - 27 - - monitor the engine speed sensor; and - use the monitored engine speed in said determination of steady state conditions.
18. A four-stroke internal combustion engine as claimed in any of Claims 13 to 17, in which the engine management system is arranged to: - use the monitored presence of misfires in said determination of steady state conditions.
19. A four-stroke internal combustion engine as claimed in any of Claims 13 to 18, in which one engine operating condition sensor is an incylinder ionization detection sensor, and the engine management system is arranged to: - monitor the in-cylinder ionization detection sensor; and use the monitored in-cylinder ionization in said determination of steady state conditions.
20. A method of correctly fuelling a four-stroke internal combustion engine, substantially as herein described, with reference to or as shown in the accompanying drawings.
21. A four-stroke internal combustion engine, substantially as herein described, with reference to or as shown in the accompanying drawings.

454 1a4 26 January 2005