GB2506674A

GB2506674A - Method of producing an adaptive dataset of disengaged clutch pedal positions

Info

Publication number: GB2506674A
Application number: GB1217946.1A
Authority: GB
Inventors: Themi Philemon Petridis; Ian Halleron; David Hesketh; Urs Christen
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2012-10-08
Filing date: 2012-10-08
Publication date: 2014-04-09
Anticipated expiration: 2032-10-08
Also published as: CN104002789A; GB201217946D0; RU2658238C2; DE102013111071A1; CN104002789B; RU2013144947A; GB2506674B

Abstract

A method is disclosed in which a dataset of clutch pedal positions expected to result in a disengaged clutch state is produced that adapts itself to changes in a bite point, of a clutch (8, fig 1). The method adds the current clutch pedal position P, to the dataset when the clutch engagement state is inferred to be disengaged and removes clutch pedal positions P, that are more engaged than the current clutch pedal position P, from the dataset when the clutch engagement state is inferred to be not disengaged. A method for stopping and starting an engine (10, fig 1) that utilises the dataset to determine whether or not to start the engine (10, fig 1) in response to a driver engine start request is also disclosed.

Description

A Method for Producing an Adaptive Inferred Clutch engagement state This invention relates to a motor vehicle having an internal combustion engine and, in particular, to a method of producing an adaptive inferred clutch engagement state of a clutch drivingly connecting the engine to a manual transmission.

It is known to provide a motor vehicle having a manual transmission with a stop-start system for automatically stopping and starting an internal combustion engine used to provide motive power for the motor vehiole.

A stop-start system automatically stops the engine whenever it is determined that there is an opportunity to do so in order to improve fuel consumption and reduce emissions from the engine.

A vehicle equipped with stop-start functionality needs to know when torque is being transmitted from the engine to one or more driven road wheels. Some implementations of stop-start will only stop and re-start the engine when a neutral gear is selected (SIN) and others also allow stopping and re-starting when a driving gear is selected provided that the clutch is depressed (SIG) It is important for the stop-start control system to know that no torque will be transmitted (transmission is in neutral or clutch is disengaged) before the engine is re-started, especially if the engine re-start is automatically reguested by the stop-start system (e.g. due to low battery or a/c demand) and therefore not expected by the driver.

For a manual transmission start-stop application, a clutch pedal pressed/clutch pedal released' threshold is normally used to indicate the driver's intention to drive away when the clutch is pressed, so that the start-stop system can trigger an engine start. The same threshold can also be used tc indicate when the driver has released the clutch pedal and is intending to remain stationary long enough that the start-stop system can switch the engine off to conserve fuel.

Starting the engine with the transmission engaged could result in the vehicle moving unexpectedly, causing a hazard.

For a manual transmission Stop-in-Neutral (SIN) application, a method of determining that the transmission is in neutral and therefore no torque will be transmitted is to use a Gear Neutral Sensor (GNS) , which indicates to the stop-start controller that the neutral gear is selected or is not selected. Failure of the GNS to correctly indicate the state of the transmission is of particular concern as it could lead to an engine re-start with the transmission engaged, resulting in unintended vehicle movement.

For manual transmission Stop-in-Gear (SIG) start-stop applications, it is necessary to rely on an indication that the driveline is disengaged. This is a non-trivial task and is one of the main reasons that all manual transmission stop-start systems in production to date have been SIN systems.

For SIC applications it has been proposed to use a Concentric Slave Cylinder (CSC) sensor in combination with a Clutch Master Cylinder (CMC) sensor or clutch pedal position sensor in order to provide an indication that the clutch is disengaged. However, vehicles do not typically have both a CSC sensor and a CMC sensor or clutch pedal position sensor and so there is an added expense to such a solution.

Furthermore, a predetermined clutch disengagement point CSC threshold is difficult to determine and potentially highly conservative due to the piece to piece tolerances and clutch wear. In addition, movement in the bite-point of the clutch over time means that it is even more difficult to specify a single fixed threshold on the 050 to indicate that the clutch is disengaged and also be reached during normal driving conditions (i.e. requires the driver to press the clutch pedal to or very close to full pedal travel) If both 0F40 and 050 sensors are fitted it is possible to detect a failure such as hydraulic leakage but a catastrophic failure of the clutch resulting in engagement cannot be detected. Such a catastrophic failure could result in an unintended vehicle movement and action would have to be taken based on sensing the vehicle movement.

There is a need for a low cost, reliable method for establishing clutch engagement state so as to enable 510 to be enabled in an economic but safe manner.

It is an object of the invention to provide a method of inferring clutch engagement state in a cost effective manner that can adapt to compensate for clutch wear.

It is a further object of the invention to enable the use of a STG system in a cost effective and reliable manner.

According to a first aspect of the invention there is provided a method for producing an adaptive inferred clutch engagement state of a clutch drivingly connecting an engine of a motor vehicle to a manual multi-speed transmission and for which the engagement state of the clutch is controlled by movement of a clutch pedal wherein the method comprises monitoring the position of the clutch pedal, producing an inferred clutch engagement state when the current speed of the vehicle is substantially equal to zero, a gear in a transmission of the vehicle is selected and the engine is running, saving a current measured clutch pedal position when the inferred clutch engagement state is disengaged and, when the inferred clutch engagement state is not disengaged, removing saved clutch pedal positions that are more engaged than the current measured clutch pedal position.

The saving and removing of saved clutch pedal positions may produce an adaptive dataset of clutch pedal positions expected to produce a disengaged clutch engagement state.

Saving a current measured clutch pedal position may comprise updating the dataset of clutch pedal positions with a current measured clutch pedal position.

The dataset may have a predefined number of saved clutch pedal positions and, when the dataset is full, updating the dataset may comprise overwriting the oldest saved clutch pedal position with the latest clutch pedal position.

Removing saved clutch pedal positions may comprise removing from the dataset all saved clutch pedal positions that are more engaged than the current measured clutch pedal position.

If the torgue being transmitted by the clutch is substantially zero, the method may comprise inferring that the clutch engagement state is disengaged and otherwise inferring that the clutch engagement state is not disengaged.

According to a second aspect of the invention there is provided a method for stopping and starting an engine of a motor vehicle driving a multispeed manual transmission via a clutch, the engagement state of which is controlled by a clutch pedal wherein the method comprises determining whether a request for an engine start is a driver generated reguest or a system generated reguest and, if the start request is a driver generated request, determining whether to start the engine based upon a oomparlson of a current measured olutoh pedal position with a number of stored inferred disengaged olutoh pedal positions produoed by a method in aocordanoe with said first aspeot of the invention.

If the current olutoh pedal position is one of equal to and greater than the least disengaged saved clutch pedal position, the method may comprise starting the engine.

Alternatively, if the current clutoh pedal position is less than the least disengaged saved clutch pedal position, the method may comprise not starting the engine.

If the engine start request is a system generated request, the method may oompr±se determining whether to start the engine based upon a comparison of the current clutch pedal position with a clutch pedal position when the engine was stopped.

If the clutch pedal position is equal to or more disengaged than it was when the engine was stopped, the method may comprise starting the engine.

Alternatively, if the clutch pedal position more engaged than it was when the engine was stopped, the method may comprises not starting the engine.

In response to a driver generated engine stop request when the transmission is in gear and the motor vehicle is stationary, the method may further comprise determining whether to permit the engine stop based upon an inferred clutch engagement state.

If the inferred clutch engagement state is disengaged, the engine may be stopped and otherwise it may remain running.

The clutch engagement state may be inferred to be disengaged if the torque being transmitted by the clutoh is substantially zero.

According to a third aspect of the invention there is provided an apparatus for stopping and starting an engine of a motor vehicle driving a multispeed manual transmission via a clutch, the engagement state of which is controlled by a clutch pedal wherein the apparatus comprises an electronic control unit operable to determine whether a request for an engine start is a driver generated reguest or a system generated reguest and, if the start reguest is a driver generated request, the electronic control unit is operable to determine whether to start the engine based upon a comparison of a current measured clutch pedal position measured by a clutch position sensor with a number of inferred disengaged clutch pedal positions stored in a memory of the electronic control unit.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1A is a schematic representation of a motor vehicle having a SIG stop-start system according to the invention; Fig.1B is a schematic representation of a clutch actuation system forming part of the stop-start system of Fig.1; Fig.2 is a schematic representation of the operational range of movement of a clutch pedal showing three predefined zones; Fig.3P. is a flow chart showing a first embodiment of a method for inferring clutch engagement state; Fig.33 is a flow chart showing a second embodiment of a method for inferring clutch engagement state; Figs.4A to 40 are a schematic flow chart showing a method of controlling a SIG stop-start system using an inferred clutch engagement state in accordanoe with a second aspect of the invention; Fig.5A is a diagram showing three possible clutch pedal positions when an engine stop occurs; Fig.5B is a diagram showing a number of clutch pedal positions resulting from disengagement tests; Fig.6 is a diagram illustrating a rapid change in clutch bite point during an engine stop; and Fig.7 is a flow chart of a method for adaptively inferring disengaged clutch pedal position.

With reference to Figs.1A and 18 there is shown a motor vehicle 5 having an engine 10 driving a multi-speed manual transmission 11. The transmission 11 is driveably connected to the engine 10 by a clutch 8 (not shown on Fig.1A) which is manually engaged or released by a driver of the motor vehicle 5 and has a gear selector (not shown) . The gear selector is manually moveable between several positions including at least one position where a gear forming part of the multi-speed transmission is selected and a neutral position in which no gears of the multi-speed transmission are selected. When the gear selector is moved to the neutral position the multi-speed manual transmission 11 is said to be in a neutral state in which drive cannot be transmitted by the multi-speed transmission and when the gear selector is moved to an in gear position the multi-speed transmission 11 is said to be in an in-gear' state in which drive can be transmitted by the multi-speed transmission.

An engine starter in the form of an integrated starter-generator 13 is driveably connected to the engine 10 and in this case is connected by a flexible drive in the form of a drive belt or chain drive 14 to a crankshaft of the engine 10. The starter-generator 13 is connected to a source of electrical energy in the form of a battery 15 and is used to start the engine 10 and which is recharged by the starter-generator when it is operating as an electrical generator.

The invention is not limited to the use of a starter-generator 13 and the starter-generator 13 could be replaced by a starter motor for starting the engine 10.

It will be appreciated that, during starting of the engine 10, the starter-generator 13 drives the crankshaft of the engine 10 and that at other times the starter-generator is driven by the engine 10 to generate electrical power.

A driver operable on/ off device in the form of a key operable ignition switch 17 is used to control the overall operation of the engine 10. That is to say, when the engine is running the ignition switch 17 is in a key-on' position and when the ignition switch 17 is in a key-off' position the engine 10 is not able to run. The ignition switch 17 also includes a third momentary position used to manually start the engine 10. It will be appreciated that other devices may be used to provide this functionality and that the invention is not limited to the use of an ignition switch.

An electronic control unit 16 is connected to the starter-generator 13, to the engine 10, to a gear selector sensor 12 used to monitor whether the transmission 11 is in neutral or in gear, to a road speed sensor 21 used to measure the rotational speed of a road wheel 20, to a brake pedal position sensor 24 used to monitor the position of a brake pedal 23, to a clutch pedal position sensing system used to monitor the position of a clutch pedal 25 and to an accelerator pedal position sensor 19 used to monitor the position of an accelerator pedal 18. The accelerator pedal 18 provides a driver input of reguired power output from the engine 10. If the accelerator pedal 18 has been moved from a rest position it is said to be in a pressed position or in a pressed state. It will be appreciated that instead of monitoring accelerator pedal position the position of a throttle valve could be monitored and used to infer accelerator pedal position.

The electronic control unit 16 may include the functionality of or be connected to an engine management system of the motor vehiole 5 capable of determining the fuel supplied to the engine 10 and be operable to control the engine 10 torque output and operation of the engine 10 at idle speed via an engine idle speed governor.

Although the measurement of motor vehicle speed is described above with reference to the use of a road wheel sensor 21 because such sensors are often already present on a motor vehicle as part of a brake anti-lock system it will be appreciated that other suitable means can be used to determine the speed of the motor vehicle 5 such as, for example, a sensor measuring the rotational speed of an output shaft from the transmission 11.

It will be appreciated that the term gear selector sensor is not limited to a sensor that monitors the position of the gear selector but rather is any device which can provide a feedback of whether the transmission 11 is in gear -10 -or in neutral that is to say, it can be a gear neutral sensor or a gear seleoted sensor.

Similarly, the term brake pedal sensor is not limited to a sensor that monitors the position of the brake pedal but rather is any device that provides feedback cf whether an operator of the motor vehicle 5 has applied pressure to the brake pedal 23 to apply the brakes of the motor vehicle 5. For example the brake pedal sensor could monitor the pressure of the fluid in one or more brake lines. When the brake pedal 23 has been pressed sufficiently to apply the brakes it is said to be in a pressed state or in a pressed pcsition.

In this case the clutch pedal position sensing system comprises a clutch pedal position sensor 26 used to monitor the position of the clutch pedal 25 operatively connected to a clutch hydraulic master cylinder 27 and an electronic clutch pedal pcsition prccesscr (EC3P) 16C used to process the pcsition signal frcm the clutch pedal positicn sensor 26 into a control output for use by the electronic control unit 16 using logic stored in the EC3P 160. It will however be appreciated that, instead of monitoring the position of the clutch pedal 25, the position of a master cylinder piston could be monitored by a position sensor or a number of switches could be used as indicators of clutch pedal position.

The determinaticn of the state of the clutch pedal 25 as pressed or released is performed by the EO3P 160 forming part of the electronic control unit 16 using the clutch position signal received from the position sensor 26. The clutch position signal represents the current position (Rr) of the clutch pedal 25.

As shown in Fig.lB a clutch actuation system is formed in this case by the clutch pedal 25, the hydraulic master -11 -cylinder 27, a hydraulic slave cylinder 28 and a clutch release lever 29 which engages and releases the clutch 8 via a release bearing 9. It will however be appreciated that other means could be used for converting movement of the clutch pedal 25 into engagement or disengagement of the clutch 8 and that the invention is not limited to the use of a hydraulic clutch actuation system.

It will also be appreciated that the electronic clutch pedal position processor (FC3P) 160 could be a separate unit and may not be formed as part of the main stop-start electronic control unit 16.

The electronic control unit 16 receives several signals from the engine 10 including a signal indicative of the rotational speed of the engine 10 from a speed sensor (not shown) and sends signals to the engine used to control shutdown and start-up of the engine 10. In this case the engine 10 is a spark ignited engine 10 and the signals sent from the electronic control unit 16 are used to control a fuel supply system (not shown) for the engine 10 and an ignition system (not shown) for the engine 10. If the engine 10 were to be a diesel engine then only the fuel supply to the engine would be controlled. The electronic control unit 16 comprises of various components including a central processing unit, memory devices, timers and signal processing devices to convert the signals from the sensors connected to the electronic control unit 16 into data which is used by the electronic control unit 16 to control the operation and, in particular, the automatic stopping and starting of the engine 10. One of the memory devices of the electronic control unit 16 is a clutch pedal position memory 16M. The clutch pedal position memory 1604 stores an adaptive dataset of clutch pedal positions expected to produce a disengaged clutch engagement state as described in more detail hereinafter.

-12 -During normal engine running the electronic control unit 16 which in this case includes an engine management system and idle speed controller is operable to control the fuel supplied to the engine 10 and to adjust the ignition system so that sparks are supplied to the engine 10 from spark plugs at the correct timing to produce the desired engine torgue.

The electronic control unit 16 controls the operation of the engine 10 which is operable in two modes, a first or automatic stop-start running mode and a second or continuous running mode. However, it will be appreciated that one or more separate electronic controllers could be used to control the normal running of the engine 10 and the electronic controller 16 may only control the switching of the engine 10 between the two modes of operation and the automatic stopping and starting of the engine 10.

The electronic control unit 16 is further operable to determine whether it is appropriate to run the engine 10 in the first mode by checking one or more engine operating parameters before permitting operation in the first mode.

These engine operating parameters may include the engine coolant temperature, whether any catalytic converters associated with the engine are lit-off, whether the engine is rotating within a predetermined speed range, the state of charge of a battery of the motor vehicle 5 and the current electric power consumption of the motor vehicle 5.

For example, if the coolant temperature is less than say 65°C or the catalytic converter is not lit-off or the engine speed is greater than approximately 1100 revolutions per minute (RPM) then entry to the first mode is barred and the electronic control unit 16 is operable to operate the engine 10 in a warm up mode in which the engine 10 is run -13 -continuously irrespective of whether the motor vehicle 5 is moving or is stationary.

As soon as it is determined that the engine operating conditions have been met then the stop-start system is placed in the first mode of operation when one or more predetermined engine stop and start conditions exist.

These engine stop and start conditions are for a stop in gear system (STG) based upon the signals received by the electronic control unit 16 from various sensors and systems.

For example to initiate a SIG engine stop the following factors have to be considered: 1/ is the vehicle speed equal to zero as indicated by the vehicle speed sensor 21; 2/ is a gear currently selected, as indicated by the gear selector sensor 12; 3/ is the accelerator pedal 18 not being pressed as indicated by the accelerator pedal position sensor 19; 4/ is the brake pedal 23 being pressed as indicated by the brake pedal sensor 24; 5/ is the inferred state of the clutch disengaged; and 6/ are there no engine stop inhibitors present such as heavy electrical demand from an air conditioning unit, a low state of charge of the battery and or a system fault.

-14 -If all of these requirements are met then the engine 10 is stopped otherwise it remains running.

To restart the engine 10 in gear the following oonditions have to be present: 1/ a gear is currently selected; and 2a/ the brake pedal 23 moves from pressed to released; or 2b/ the accelerator pedal moves from released to pressed; and 3/ the inferred state of the clutch is disengaged; and 4/ there are no engine start inhibitors present such as a system fault.

If these requirements are met then the engine 10 is started otherwise it remains stopped.

With reference to conditions 2a and 2b above it will be appreciated that it will depend upon the configuration of the vehicle and the restart triggers enabled which of these conditions is relevant.

In some embodiments only brake pedal position is used as a restart trigger, in other embodiments only accelerator -15 -pedal position is used as a restart trigger but in the described embodiment, if either brake pedal position changes from pressed to released or the accelerator pedal position changes from released to pressed, this is used as a restart trigger.

Figure 2 depiots three clutch states, Released, Pressed and Depressed, and the transition thresholds between the states. These three states are typically used in start-stop applications today.

In the zone "P" a clutch pedal 25 is considered to be released that is to say the clutch 8 will definitely be engaged, in the zone "D" the clutch pedal 25 is considered to be depressed and the clutch 8 will definitely be disengaged and in the zone "P" the clutch pedal 25 is considered to be pressed and the clutch 8 could be disengaged or engaged depending upon the location of the clutch pedal in the zone P" relative to a bite point te* The boundary between the pressed "P" and depressed "D" zones corresponds to a clutch pedal travel of approximately 70% in this case.

Referring now to Fig.3P. there is shown a first embodiment of a method for inferring clutch engagement state that is suitable for use by a SIG system.

The method starts at box 105 which corresponds to a key-on event for the motor vehicle 5. The method then advances to box 110 where it is checked whether the motor vehicle is stationary as indicated by the vehicle speed sensor 21. If the vehicle speed is not substantially zero then the clutch engagement state cannot be inferred to be disengaged and the method advances to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

-16 -The method then advanoes from box HO to box 190 to oheck whether a key-off event has occurred, if it has occurred, the method terminates at box 199 and otherwise it returns to box 110 to start the next cycle.

If the vehicle 5 is stationary then the method advances from box 110 to box 111 to determine whether a gear is selected. This is done by using the signal from the gear selector sensor 12. This condition is required since if transmission 11 is in neutral, the torque produced at the clutch 8 will always be zero, irrespective of clutch pedal position. Hence without this condition the inferred disengagement test could erroneously infer that the clutch pedal position is past the clutch bite point, when in fact th±s would not be the case.

If a gear is not selected the clutch engagement state cannot be inferred to be disengaged and the method advances from box 111 to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 1O.

The method then advances from box 140 to box 190 to check whether a key-off event has occurred, if it has occurred, the method terminates at box 199 and otherwise it returns to box 110 to start the next cycle.

If a gear is currently selected, then the method advances from box 111 to box 112 to determine whether the engine is running. This test is to ensure that the engine is running because without a running engine it is not possible to infer that the clutch 8 is disengaged using clutch torque. This is because with a stationary engine 10, the clutch torque would be zero whether or not the clutch 8 is engaged.

-17 -Therefore, if the engine is not running the clutch engagement state cannot be inferred to be disengaged and the method advances from box 112 to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

If in box 112 the engine is determined to be running, the method advances from box 112 to box 113 to determine whether an engine idle speed governor is active. This condition is included to restrict the clutch torque calculation to idle speed. This avoids engine transients and deceleration fuel shutoff conditions that add unnecessary complications. However this condition is not essential and its use should not be considered as the only way to implement the inferred disengagement strategy.

However, in this case, if the engine idle speed governor is not active the clutch engagement state cannot be inferred to be disengaged and the method advances from box 113 to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

However in box 113, if the engine idle speed governor is found to be active, the method advances from box 113 to box 114 to check whether the clutch torque is substantially equal to zero. The clutch torque is based on calculations -18 -performed in the engine management system of the motor vehicle 5 relating to how muoh fuel is being injected into the engine 10 to meet idle speed torgue demands taking into account electrical loading and mechanical loading on the engine 10.

If the clutch torgue is not substantially equal to zero the clutch engagement state cannot be inferred to be disengaged and the method advances from box 114 to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

However, if in box 114 the clutch torque is found to be substantially equal to zero, the method advances from box 114 to box 118 to check whether a stabilisation time period such as one second has elapsed. This condition is included as a robustness measure to ensure that signal noise or signal spikes do not inadvertently cause other conditions to erroneously be met only momentarily. A stabilisation time period of one second is normally sufficient for such conditions to subside.

If the stabilisation time period has not elapsed the clutch engagement state cannot be inferred to be disengaged and the method advances from box 118 to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

-19 -If in box 118 the required time stabilisation period has elapsed then the method advances to box 120 where it is confirmed that the inferred engaqement state of the clutch 8 is "disengaged" and the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

The method then advances from box 120 to box 190 to check whether a key-off event has occurred, if it has occurred, the method terminates at box 199 and otherwise it returns to box 110 to start the next cycle.

Therefore the method provides a convenient and low cost way of producing an indication of the engagement state of the clutch 8 without the need for an expensive or complicated clutch engagement sensor system. That is to say, no significant additional hardware or associated costs are required.

Referring now to Fig.3B there is shown a second embodiment of a method of inferring clutch engagement state that is suitable for use by a SIG system.

The method is in most respects identical to that previously described and for which like numbered boxes have the same functionality. The second embodiment adds three additional conditions indicated in boxes 115, 166 and 177 between the boxes 114 and 118 already discussed with respect to the first embodiment shown in Fig.3P.

In this case, if in box 114 the engine torque is found to be substantially equal to zero, the method advances from box 114 to box 115 to check whether the clutch pedal is depressed. That is to say the output erjK from the clutch pedal position sensor in the form of the clutch master -20 -cylinder sensor 26 indicates that the clutch pedal has been pressed more than a predetermined threshold amount P!1ee.

For example, if the threshold 1Thres is a signal level equal to 70% of clutch pedal 25 travel, then the test would be -Is P-> P!Itre;? or Is Sers > 70% If Yes' then the clutch pedal 25 is depressed if No' then the clutch pedal 25 is not depressed.

This condition is included to add an additional layer of protection to prevent a disengagement being successfully inferred when there exists an obviously wrong OMO sensor signal P30rs. For example, if the OMO sensor position signal Sc:is indicates that the clutch pedal 25 is only 10% pressed and all other clutch test conditions infer that clutch disengagement is confirmed, this implies that there is a fault relating to the CMC sensor signal Sefls or a there is fault or failure in the clutch system itself. In such circumstances the inferred disengagement tests should not be passed so that an engine stop event is not allowed.

Therefore, in this case, if the clutch pedal is determined from the sensor 26 to be not depressed the clutch engagement state cannot be inferred to be disengaged and the method advances from box 115 to box 140 where the result from box 140 is output to the start-stop controller 16 for use in controlling the operation of the engine 10. Although not shown on Fig.3B a driver of the motor vehicle 5 could be alerted if such a condition is established.

-21 -However, if in box 115 the clutch pedal 25 is found to be depressed, the method advanoes to box 116 to determine whether the brake pedal 23 is depressed.

In box 116 it is checked whether the signal from the brake pedal sensor 24 indicates that the brake pedal 23 is being depressed. If the brake pedal is determined to be depressed then the method advances to box 117 to determine the state of the accelerator pedal 18. This condition has been included as an additional layer of protection to confirm that the vehicle 5 is in fact stationary. The accuracy of the vehicle speed signal from the vehicle speed sensor 21 at low speeds is not always sufficient to be certain the vehicle 5 has come to rest. That is to say, it is included as an additional measure to ensure that the vehicle 5 is not creeping at idle drive speed down a gradient which could result in neutral torque at the clutch 8 when in fact the clutch 8 is engaged. The idle drive speed would have to be less than the minimum vehicle speed it is possible to detect with the vehicle speed sensor 21 given that the condition in box 110 requires to see zero vehicle speed for the complete set of conditions to be passed.

If the brake pedal 23 is determined in box 116 not to be depressed, the clutch engagement state cannot be inferred to be disengaged and the method advances from box 116 to box where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

-22 -In box 117 it is ohecked whether the signal from the accelerator pedal sensor 19 indicates that the accelerator pedal 18 is not being pressed.

Continuing with box 117, if the accelerator pedal 18 is from the accelerator pedal position sensor 19 determined to be not pressed, then the method advances from box 117 to box 118. This condition is included because it is only desirable to infer disengagement if the conditions to subseguently shut the engine down are met. If a driver of the motor vehicle is reguesting torque as would be the case if the accelerator pedal 18 is being depressed, then a SIG stop will not be initiated.

If the accelerator pedal 18 is determined in box 117 to be depressed, the clutch engagement state need not be inferred to be disengaged and the method advances from box 117 to box 140 where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

If the method has advanced from box 117 to box 118 then as before a check is made as to whether a stabilisation time period such as one second has elapsed. This condition is, as before, included as a robustness measure to ensure that signal noise or signal spikes do not inadvertently cause other conditions to erroneously be met only momentarily.

As before, if the stabilisation time period has not elapsed, the clutch engagement state cannot be inferred to be disengaged and the method advances from box 118 to box -23 -where the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

However, if in box 118 the reguired time stabilisation period has elapsed, then, as before, the method advances to box 120 where it is confirmed that the inferred engagement state of the clutch 8 is disengaged" and the result is output to the start-stop controller 16 for use in controlling the operation of the engine 10.

This second embodiment also provides a convenient and low cost way of producing an indication of the engagement state of the clutch 8 without the need for an expensive or complicated clutch engagement sensor system and is more robust in operation than that of the first embodiment.

With reference to Figs.4A to 6 there is shown a method for automatically stopping and starting the engine 10 of the motor vehicle 5 while the multispeed manual transmission 11 that is driven by the engine 10 is in gear.

The method starts in box 205 which corresponds to a key-on event resulting in the engine 10 running.

The method then advances to box 210 where it is checked whether the motor vehicle 5 is moving. That is to say, is the motor vehicle speed (VS) greater than zero. If the -24 -answer is "Yes" then the method does not proceed and loops back to check the vehicle speed again. That is to say, a stop in gear is only possible when the vehicle speed is substantially equal to zero and if the vehicle speed is not substantially equal to zero a stop in gear is not permitted.

If the vehiole speed is found not to be greater than zero then the method advances to box 220.

In box 220 it is checked whether the conditions for inferred clutch disengagement are met. These conditions have been previously described with reference to Figs. 3A and 3B and will not be described again in detail. Therefore if the result of this test is that the inferred clutch state is disengaged as per box 120 on Figs. 3A and SB then the method advances from box 220 to box 225 but if the inferred clutch state is that the clutch is not confirmed to be disengaged as per box 140 on Figs. 3A and 3B then the method advances to box 227.

In box 227 previously stored values P of clutch pedal positions expected to produce a disengaged clutch engagement state that occur to the engaged side of the current clutch pedal position P measured by the clutch pedal position sensor 26 or by any other sensor capable of providing an output indicative of clutch pedal position and hence clutch engagement state. For example, if the current clutch pedal position Pr: indicates that the clutch pedal 25 has been pressed to 73% of its maximum travel, then all saved clutch pedal position values Fe. lower than 73% such as 70% will be deleted.

The values of clutch pedal positions P expected to produce a disengaged clutch engagement state are stored as a dataset in the clutch pedal position memory 1614 which in this case is formed as part of the electronic control unit 16 but could be part of another electronic unit or -25 -controller. The clutch pedal positions Ps are therefore deleted from the dataset stored in the clutch pedal position memory 1614.

This technique adapts the system for changes in the clutch bite point by removing from the clutch pedal position memory 1614 clutch pedal positions than can no longer be relied upon to produce a disengaged clutch state.

Continuing with box 227, from box 227 the method advances to box 228 where the engine 10 is not stopped and then returns to box 210 to check once again whether the motor vehicle 5 is moving.

Referring back now to box 220, if the conditions are met, the method advances from box 220 to box 225 where the current clutch pedal position P1, is read from the clutch pedal position sensor 26 and temporarily saved as a clutch pedal position P corresponding to an inferred disengaged clutch state. As an alternative to this the latest value of P saved in step 230 could be used for later comparison purposes.

The method then advances to box 230 where the current clutch pedal position P5 is added to the dataset of the clutch pedal position memory 1614 as the latest saved clutch disengaged value PF. That is to say, because the clutch 8 has been inferred to be disengaged, the current clutch pedal position P5. represents the latest clutch pedal position that relates to a disengaged state of the clutch 8 and will always include n' latest saved clutch pedal positions P. The clutch pedal position memory 1614 is an overwrite memory or rolling register memory. That is to say, there are a fixed number n' of memorised clutch pedal position values P.,, such as, for example and without limitation, fifty positions and when the fifty first clutch pedal position -26 -value P1, is added to the clutch pedal position memory ibM, the oldest memorised clutch pedal position value is overwritten or expunged from the memory so that the clutch pedal position memory 16M is always updated to account for changes in the clutch 8 or in the actuation system such as variations in bite point. Prior to the clutch pedal position memory 16M reaching its limit, the clutch pedal position values are saved in the dataset in the order they are received.

Continuing from box 230 the method advances to box 235 to determine whether the conditions for a SIG stop are met.

The full conditions for a SIG stop are:- 1/ the vehicle speed is egual to zero as indicated by the vehicle speed sensor 21; and 2/ the inferred state of the clutch is disengaged; and 3/ a gear is currently selected, as indicated by the gear selector sensor 12; and 4/ the accelerator pedal 18 is not being pressed as indicated by the accelerator pedal position sensor 19; and 5/ the brake pedal 23 is being pressed as indicated by the brake pedal sensor 24; and 6/ there are no engine stop inhibitors present such as a heavy electrical demand from an air conditioning unit, a low state of charge of the battery and or a system fault.

-27 -The conditions 1 and 2 have already been tested in boxes 210 and 220 and so the actual requirement to be met in box 235 is: A gear is currently selected, and the accelerator pedal 18 is not being pressed and the brake pedal 23 is being pressed and there are no engine stop inhibitors present.

If these conditions are not met in box 225 then the method advances to box 228 where the engine 10 is not stcpped and the method returns to box 210 to check once again whether the motor vehicle 5 is moving.

However, if the SIG stop conditions are met in box 235, the method advances to box 237 where the engine 10 is stopped so as to be in an engine-off state as indicated in box 240.

While the engine 10 is in the engine off state the clutch pedal position P is continuously monitored for use in deciding whether to restart the engine 10 as indicated in box 245 and then in box 250 it is determined whether the conditions for a SIG engine start are met.

The conditions for a SIG start are shown in Fig.4C and are now described in detail.

In box 250a it is determined whether the SIG start request is a driver induced request such as for example the releasing of the brake pedal 23 or the pressing of the accelerator pedal 18. Tf the start request is not a driver induced start then the method advances to box 250n which merely confirms that the start is a system induced start request such as a low state of charge of the battery 15 or a request for air conditioning.

-28 -The method then advances to box 250p to check whether the current clutch pedal position Pc is greater than or egual to the clutch pedal position Pp!-corresponding to an inferred disengaged clutch state previously saved. That is to say, has the clutch pedal position changed since the engine 10 was stopped? Fig.5A shows diagrammatically this process. The point a' corresponds to the clutch pedal position P0 saved in box 225 when the engine 10 was stopped in box 237 and the points b' and c' represent two possible current clutch pedal positions P. If the current clutch pedal position P is equal to or to the disengaged side of the point a', as indicated by way of example by the point c', then the test in box 250p will be passed. Conversely, if the current clutch pedal position P is more engaged than the memorised clutch pedal position P, as indicated by of example by the point b', then the test in box 25Op will be failed.

This can be expressed in terms of clutch pedal position magnitudes as:-If P < P3 go to box 250r; else go to box 250y.

It will be appreciated that, provided there are no faults in the clutch actuation system, a clutch pedal position of 0% indicates that the clutch pedal is not being pressed at all and the clutch 8 will definitely be engaged and a clutch pedal position magnitude of 100% indicates that the clutch pedal 25 is fully depressed and the clutch 8 will definitely be disengaged.

Therefore a restart will not be permitted for a system induced restart request if the clutch pedal position P has changed to a more engaged position from the time the engine was stopped.

-29 -In box 250r the conditions for a SIC start are not met because the clutch pedal position test in box 250p has been failed and the method advances from box 250 to box 255 where the driver may be given a request to depress the clutch/ select neutral or a warning that a SIG start is not possible. The method then advances from box 255 to box 240 where the engine 10 remains in the off state.

Returning to box 250p if the current clutch pedal position P is equal to or greater than the stored clutch pedal position P0 when the engine 10 was stopped that is to say, the clutch pedal position P, is the same or more disengaged, then the method advances to box 2SOy and then from box 250 to box 260 where the engine 10 is started. The method then advances from box 260 to box 280 where it is checked whether a key-off event has occurred and, if it has, the method ends at box 290 and otherwise it returns to box 210 to check whether the vehicle speed is substantially equal to zero.

It will be appreciated that, in practice, the system may also include timers or delays to take account of driver changes of mind so as to prevent the enqine 10 from being started and then stopped again immediately thereafter.

Control techniques for dealing with a driver change of mind are described in UK Patent 2427441.

Therefore in the oase of system induced start, provided the clutch disengaged test in box 2SOp is passed the engine 10 is restarted. As an alternative not shown a box between boxes 250p and 250y could check to make sure there are no system faults present. In such a case, if there are no system faults, the method would advance to box 250y but otherwise would advance to box 250r.

Returning now to box 250a on Fig.4C, if the start request is a driver induced start request then the method -30 -advances to box 250b tc check the current clutch position P1, against the clutch pedal positions P stored in the dataset of the clutch pedal position memory 16M. If the current clutch pedal pcsition is equal to or greater than the least disengaged clutch pedal position of any of the clutch pedal positions P5 stored in the clutch pedal position memory 16M then the test in box 250b will be passed and otherwise it will be failed.

If the test is failed the method will advance from box 250b to box 250f and then from box 250 to boxes 255 and 240 as previously described and the engine 10 will remain off.

Fig.5B shows a representative number of clutch pedal positions P saved in the clutch pedal position memory indicated on Fig.5B as Passed Tests' . The upper and lower limits of this range is bounded by the lowest value of clutch pedal position P5::jfl saved in the dataset of the clutch pedal position memory 1614 and the maximum value of clutch pedal position;1tx saved in the clutch pedal position memory 1614. These values are the values stored in box 230. Note that the values indicated on Fig.5B as Failed tests' are earlier saved clutch pedal positions P5 that are deleted in box 227. These are unlearned or deleted because the inferred engagement test has been failed and so it is no longer safe to assume that a corresponding clutch pedal position will now result in a disengaged clutch state.

The test in box 25Gb will be passed provided the current clutch position is greater than If the test in box 250b is met, the method advances from box 250b to box 250x. In box 250x it is checked whether all other SIG start conditions are met.

-31 -The other oonditions for a SIG start apart from a disengaged clutch are: 1/ a gear is currently selected; and 2a/ the brake pedal 23 has moved from pressed to released; or 2b/ the accelerator pedal 18 has moved from released to pressed; and 3/ there are no engine start inhibitors present such as a system fault.

In this case, if either the brake pedal is released or the accelerator is pressed, this is interpreted as a restart trIgger.

Therefore in the case of this embodiment, if a gear is currently selected and either the brake pedal 23 has been reeased or the accelerator pedal 18 has been pressed and there are no engine start inhibitors present, the method advances from box 250x to box 25Oy otherwise it advances to box 250f and then from box 250 to boxes 255 and 240 as previously described.

It will be appreciated that the conditions 2a and 2b could have already been met in box 250a and that the engine could be started whether or not the transmission 11 is in -32 -gear but for the specific case of a SIG start the transmission 11 must be in gear.

With reference to conditions 2a and 2b above it will be appreciated that it will depend upon the configuration of the vehicle and the restart triggers enabled which of these ccnditicns is relevant.

In some embodiments only brake pedal position is used as a restart trigger, in other embodiments only accelerator pedal position is used as a restart trigger but in the described embodiment, if either brake pedal position changes from pressed to released or the accelerator pedal position changes from released to pressed, this is used as a restart trigger.

From box 250y the method advances from box 250 to box 260, where the engine 10 is started. The method then advances to box 280 where it is checked whether a key-off event has occurred and, if it has, the method ends at box 290 and otherwise it returns to box 210 to check whether the vehicle speed is substantially equal to zero.

Therefore the disclosed method for controlling STG operation of the engine 10 uses two different clutch position tests depending upon the nature of the reguest for an engine start. If the start is driver induced a less restrictive test is used than if the start is automatically induced by the stop start system due to changes in operation of the motor vehicle 5. This increases the opportunities to start the engine 10 without increasing the risk of inadvertent movement when the driver is not expecting a start. It will be appreciated that with a driver induced request, the driver has to be actively requesting a start by moving the brake pedal or accelerator pedal and so will be aware that a start is imminent.

-33 -Fig.6 shows a situation where the bite point has suddenly changed during the period that the engine 10 has been in the off state from the position BP(l) which is the original bite point when the engine 10 was stopped to BP(2) which is the current bite point. Although such a situation is unlikely to occur and would indicate that a problem has arisen with the clutch 8 or with the clutch actuation system the effect of such a change is significant to clutch engagement state.

The point d' is the clutch position P5 when the engine was stopped and the point e' is the current clutch pedal position Pt.. Note that in this case an engine start will probably result in some vehicle movement because the current clutch pedal position P is now on the engaged side of the clutch bite point BP(2) however because the driver is reguesting the start this is acceptable and does not pose serious safety hazard. However, the next time the box 220 is encountered, the test will likely be failed and so all of the clutch pedal positions to the engaged side of the new bite point BP(2) will probably be deleted.

As described above, the method for stopping and starting the engine 10 while the transmission 11 is in gear uses an adaptive inferred clutch engagement state method in order to provide increased opportunities for restarting the engine 10 after it has been stopped. The basic steps of this method are shown in Fig.7.

The method starts at step 310 which is a key-on event after which it advances to box 320 where the engine 10 is running. The clutch pedal position P is continuously monitored by the clutch pedal position sensor 26 as indicated in box 330 and in box 340 a request to determine inferred clutch state is received. In this case a request to determine inferred clutch engagement state could be a driver induced request for an engine stop while the -34 -transmission ii remains in gear. The inferred clutch engagement state is determined as previously desoribed with referenoe to Fig.3A or Fig.3B.

After determining the inferred clutch engagement state in box 340, the method advances to box 350 where it is decided whether the inferred clutch engagement state is disengaged' . If the inferred clutch engagement state is disengaged' the method advances to box 360 and otherwise it advances to box 370.

In box 360 which corresponds to box 230 on Fig.4A, the current clutch pedal position P is added to the dataset saved in the clutch pedal position memory 1614 so as to update it with the latest clutch pedal position inferred to be disengaged. In this way the clutch pedal position memory 1614 is continuously updated with additional values of clutch pedal position P that are inferred to be disengaged thereby generating a range of saved clutch pedal positions P5 all of which are considered to be clutch pedal positions expected to produce a disengaged clutch state. The clutch pedal positions Ps are inferred positions and not actual positions because the current clutch bite point is not actually known and so these saved clutch pedal positions P cannot be definitively confirmed to represent a clutch disengaged state.

After box 360 the method advances to box 380 to test whether a key-off event has occurred and if it has the method ends in box 390 but otherwise loops back to box 320 to carry out a further cycle.

If in box 350 the inferred clutch engagement state is not disengaged' then the method advances to box 370. In box 370 all of the saved clutch pedal positions s in the dataset of the clutch pedal position memory 1614 that are more engaged than the current clutch pedal position P are -35 -deleted. This is because the current clutch pedal pcsition P has occurred when the inferred clutch pedal position is not disengaged' and so it is not be safe to assume that such a clutch pedal position cr one more engaged would result in a clutch disengaged state. For example, if the current clutch pedal position P is 71%, then all P5 values less than 71% such as 70%; 69% etc. are deleted. It will be appreciated that the values used for this comparison may not be percentages and could be analogue or digital representations of clutch pedal position.

After box 370 the method advances to box 380 to test whether a key-off event has occurred and if it has the method ends in box 390 but otherwise loops back to box 320 to carry out a further cycle.

Therefore in summary, if the clutch position P0 is

located within an Inferred Disengagement Memory Region, as defined by previously saved values P5, a driver induced SIG restart request will be allowed if no start inhibitors are present. If the clutch pedal position P is moved outside the Inferred Disengagement Memory Region, then a SIG restart reguest is not be permitted.

In the case of a system induced restart, these will only be permitted if the clutch pedal position P is egual to or greater than the clutch pedal position P corresponding to an inferred disengaged clutch state generated when the engine was stopped and no start-inhibitors are present. The reason for not permitting system induced restarts using the whole span of the Inferred Disengagement Memory Region in the case of a system induced start is that the system cannot compensate immediately for a significant movement of the clutch bite point if it occurs rapidly such as that shown in Fig.6. Such a rapid change in bite point could cause the vehicle to move unintentionally. In the case of a driver induced start this is acceptable because it is likely that -36 -it is the driver's intention to drive away at the moment a driver induced restart request is made and hence the driver will be alert and ready to control vehicle movement.

However, in the case of an automatic system induced restart, which could occur at any time durinq a SIG stop event, the driver may not be in a position to control the vehicle if it suddenly jerks.

It will be appreciated that the dataset of memorised inferred clutch disengaqement points P will naturally adapt itself to account for any movement in the actual clutch bite point in either direction over time (e.g. caused by clutch wear, clutch self-adjustment or hydraulic fluid evaporation/degradation) Although in the example given it is proposed that the dataset saved in the clutch pedal position memory l6M will be maintained across vehicle key cycles, this need not be the case and the clutch pedal position memory 1614 could alternatively be cleared every key cycle.

Although the invention has been described by way of example to embodiments that use clutch pedal position as an indication of clutch engagement state because movement of the clutch pedal 25 controls engagement and disengagement of the clutch 8. It will be appreciated that the measurement of the movement of other clutch actuation system components that have a relationship to clutch engagement state could be used and that the term clutch pedal position' is intended to cover such other measurements. For example a sensor measuring of the movement of one of a slave cylinder piston, slave cylinder output rod, master cylinder piston, master cylinder input rod or clutch release lever could produce a signal that has a correlation to clutch engagement state and which equate to clutch pedal position' -37 -It will be appreciated that the clutch pedal could alternatively be a hand operated clutch release device and that the accelerator pedal could likewise be a hand operated driver torque demand device.

It will be 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

-38 -Claims 1. A method for produoing an adaptive inferred clutch engagement state of a olutoh drivingly connecting an engine of a motor vehiole to a manual multi-speed transmission and for whioh the engagement state of the clutch is oontrolled by movement of a clutch pedal wherein the method comprises monitoring the position of the clutch pedal, producing an inferred clutch engagement state when the current speed of the vehicle is substantially equal to zero, a gear in a transmission of the vehicle is selected and the engine is running, saving a current measured clutch pedal position when the inferred clutch engagement state is disengaged and, when the inferred clutch engagement state is not disengaged, removing saved clutch pedal positions that are more engaged than the current measured clutch pedal position.
2. A method as claimed in claim 1 wherein the saving and removing of saved clutch pedal positions produces an adaptive dataset of clutch pedal positions expected to produce a disengaged clutch engagement state.
3. A method as claimed in claim 2 wherein saving a current measured clutch pedal position comprises updating the dataset of clutch pedal positions with a current measured clutch pedal position.
4. A method as claimed in claim 3 wherein the dataset has a predefined number of saved clutch pedal positions and, when the dataset is full, updating the dataset comprises overwriting the oldest saved clutch pedal position with the latest clutch pedal position.
5. A method as claimed in any of claims 2 to 4 wherein removing saved clutch pedal positions comprises removing from the dataset all saved clutch pedal positions -39 -that are more engaged than the current measured clutch pedal position.
6. A method as claimed in any of claims 1 to 5 wherein, if the torque being transmitted by the clutch is substantially zero, the method comprises inferring that the clutch engagement state is disengaged and otherwise inferring that the clutch engagement state is not disengaged.
7. A method for stopping and starting an engine of a motor vehicle driving a multispeed manual transmission via a clutch, the engagement state of which is controlled by a clutch pedal wherein the method comprises determining whether a request for an engine start is a driver generated request or a system generated request and, if the start request is a driver generated request, determining whether to start the engine based upon a comparison of a current measured clutch pedal position with a number of stored inferred disengaged clutch pedal positions produced by a method as claimed in any of claims 1 to 6.
8. A method as claimed in claim 7 wherein, if the current clutch pedal position is one of equal to and greater than the least disengaged saved clutch pedal position, the method comprises starting the engine.
9. A method as claimed in claim 7 or in claim 8 wherein, if the current clutch pedal position is less than the least disengaged saved clutch pedal position, the method comprises not starting the engine.
10. A method as claimed in any of claims 7 to 9 wherein if the engine start request is a system generated request, determining whether to start the engine based upon a comparison of the current clutch pedal position with a clutch pedal position when the engine was stopped.

-40 -
11. A method as claimed in olaim 10 wherein, if the olutoh pedal position is equal to or more disengaged than it was when the engine was stopped, the method oomprises starting the engine.
12. A method as claimed in claim 7 or in claim 8 wherein, if the olutoh pedal position more engaged than it was when the engine was stopped, the method comprises not starting the engine.
13. A method as claimed in any of claims 4 to 9 wherein, in response to a driver generated engine stop request when the transmission is in gear and the motor vehicle is stationary, the method further comprises determining whether to permit the engine stop based upon an inferred clutch engagement state.
14. A method as claimed in claim 13 wherein, if the inferred clutch engagement state is disengaged, the engine is stopped and otherwise it remains running.
15. A method as claimed in claim 14 wherein the clutch engagement state is inferred to be disengaged if the torque being transmitted by the clutch is substantially zero.
16. An apparatus for stopping and starting an engine of a motor vehiole driving a multispeed manual transmission via a clutch, the engagement state of which is controlled by a clutch pedal wherein the apparatus comprises an electronic control unit operable to determine whether a request for an engine start is a driver generated reguest or a system generated request and, if the start request is a driver generated request, the electronic control unit is operable to determine whether to start the engine based upon a comparison of a current measured clutch pedal position measured by a clutch position sensor with a number of -41 -inferred disengaged clutch pedal positicns stored in a memory of the electronic control unit.
17. A method for producing an adaptive inferred clutch engagement state of a clutch substantially as described herein with reference to the accompanying drawing.
18. A method for stopping and starting an engine of a motor vehicle substantially as described herein with reference to the accompanying drawing.
19. An apparatus for stopping and starting an engine of a motor vehicle driving a multispeed manual transmission via a clutch substantially as described herein with reference to the accompanying drawing.