GB2427443A

GB2427443A - Automatically stopping and starting the i.c. engine of a vehicle having a manual transmission

Info

Publication number: GB2427443A
Application number: GB0512465A
Authority: GB
Inventors: Themi Petridis; Don Kees; Steve Mcgonigle
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-06-20
Filing date: 2005-06-20
Publication date: 2006-12-27
Anticipated expiration: 2025-06-20
Also published as: DE102006028340B4; DE102006028340A1; GB2427443B; GB0512465D0

Abstract

A method for starting and stopping an engine 10 driveably connected to a manual transmission 11 by a clutch is disclosed in which the engine 10 is operable in a first mode 200 in which the engine 10 is automatically stopped and started and in a second mode 100 in which the engine 10 is run continuously. When the engine 10 is being operated in the first mode 200 the method includes the step 900, 902, 408 of automatically starting the engine 10 from an engine stopped state 700, 702 when it is determined that the clutch is disengaged, the transmission 11 is in gear and a brake pedal 23 is released.

Description

A Method for Starting and Stopping an Engine. This invention relates to a motor vehicle having an internal combustion engine and in particular to a motor vehicle having a system to automatically stop and start the internal combustion engine. It is known to provide a motor vehicle having an automatic transmission with a stop-start system for automatically stopping and starting an internal combustion engine used to provide motive power for the motor vehicle. 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. It is an object of this invention to provide a method and apparatus for controlling the stop-start operation of an engine fitted to a motor vehicle having a manual transmission. According to a first aspect of the invention there is provided a method for starting and stopping an internal combustion engine of a motor vehicle, the motor vehicle having a clutch to driveably connect the engine to a manual multi-speed transmission having a neutral state in which drive cannot be transmitted by the multi-speed transmission and an in gear state in which drive can be transmitted by the multi-speed transmission, a driver operable clutch pedal to control engagement and disengagement of the clutch and a brake pedal to selectively apply one or more vehicle brakes wherein the method comprises the steps of operating the engine in a first mode of operation in which the engine is automatically switched between an engine stopped state and engine running state, determining, when the engine is in the stopped state, the state of the transmission,whether the brake pedal is being pressed and whether the clutch pedal is being pressed and, if it is determined that the brake pedal is being pressed, the clutch pedal is being pressed and the transmission is in the in gear state, switching the engine from the engine stopped state to the engine running state if the brake pedal is released. The method may further comprise determining the speed of the motor vehicle and operating the engine in a second mode in which the engine is run continuously when the speed of the vehicle is determined to be above a predetermined speed. The predetermined speed may be zero. The method may further comprise switching the engine from the engine running state to the engine stopped state when a predetermined engine secondary stop condition is determined to exist. The predetermined engine secondary stop condition may be a determination that the clutch pedal is in a pressed position, the brake pedal is in a pressed position and the transmission is in the in gear state. The predetermined engine secondary stop condition may further comprise a determination that the clutch pedal has remained in the pressed position, the brake pedal has remained in the pressed position and the transmission has remained in the in gear state for a predetermined period of time. Alternatively, the predetermined secondary stop condition may be a determination that the transmission is in the neutral state and remains in the neutral state for the duration of a predetermined period of time and that there has been no change in the position of the clutch pedal during the predetermined period of time. According to a second aspect of the invention there is provided a motor vehicle having an internal combustion engine operable in a first mode in which it is automatically stopped and started, a manual multi-speed transmission driveably connected to the engine by a clutch, a driver operable clutch pedal to control engagement and disengagement of the clutch, a brake pedal to selectively apply one or more vehicle brakes, a gear selector moveable between 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 and an electronic control unit connected to a number of sensors including at least one clutch pedal sensor the or each of which provides a signal indicative of the position of the clutch pedal,a brake pedal sensor which provides a signal indicative of whether the brake pedal is being pressed and a gear selector sensor providing a signal indicative of the state of the transmission wherein, when the engine is operating in the first mode, the electronic control unit is operable to automatically start the engine from an engine stopped state in which the clutch pedal is in a pressed position, the brake pedal is in a pressed position and the transmission is in gear when the signal from the brake pedal sensor indicates that the brake pedal has been released from the pressed position. The motor vehicle may further comprise at least one vehicle speed sensor to supply a signal indicative of the speed of the motor vehicle to the electronic control unit and the electronic control unit is operable to determine the speed of the motor vehicle from the signal received from the at least one vehicle speed sensor and operate the engine in a second mode in which the engine is run continuously when the signal from the or each vehicle speed sensor indicates that the motor vehicle is moving above a predetermined speed. The predetermined speed may be zero. The electronic control unit may be further operable to stop the engine when a predetermined engine secondary stop condition is determined to exist. The predetermined engine secondary stop condition may be a determination based upon the signals received from the clutch pedal sensor, the brake pedal sensor and the gear selector sensor that the clutch pedal is in a pressed position, the brake pedal is in a pressed position and the transmission is in an in gear state. The electronic control unit may includes a timer for measuring a predetermined period of time and the predetermined engine secondary stop condition may further comprise a determination that the clutch pedal has remained in the pressed position, the brake pedal has remained in the pressed position and the transmission has remained in the in gear state for the duration of the predetermined period of time. The electronic control unit may include a timer for measuring a predetermined period of time and the predetermined secondary stop condition may alternatively be a determination based upon the signals received from the gear selector sensor and the clutch pedal sensor that the transmission is in a neutral state and that there has been no change in the state of the transmission or in the position of the clutch pedal for the duration of the predetermined period of time. The invention will now be described by way of example with reference to the accompanying drawing of which:- Fig.l is a schematic representation of a motor vehicle having a stop-start system according to the invention; Fig.2 is a high level flow chart showing the actions used in a method in accordance with the invention for controlling the operation of an internal combustion engine; and Figs.2a to 2c show in greater detail the various steps and actions taken to control the running of the engine while it is in a stop-start mode of operation. With reference to Fig.l there is shown a motor vehicle 5 having an engine 10 driving a multi-speed transmission 11. The transmission 11 is driveably connected to the engine 10 by a clutch (not shown) 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 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 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 startergenerator 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 startergenerator when it is operating as an electrical generator. The invention is not limited to the use of a startergenerator 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 10 is running the ignition switch 17 is in an 'on' position and when the ignition switch 17 is in an '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 an clutch pedal position sensor 26 used to monitor the position of a clutch pedal 25 and to a throttle position sensor 19 used to monitor the position of an accelerator pedal 18. The accelerator pedal 18 provides a driver input of required 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 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 or in neutral. 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 of 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 position. In this case the clutch pedal position sensor comprises of first and second switches (not shown) which are arranged to give an indication when the clutch pedal 25 is towards either end of its travel. This is achieved by opening or closing the switches when the clutch pedal 25 reaches certain positions. If the travel of the clutch pedal 25 is said to be zero percent when it is not being operated that is to say when it is an un-pressed state and one hundred percent when it is pressed to the limit of its travel that is to say when it is in a pressed state then the switch positions may correspond in one example to travel percentages of 10% for the first switch and 75% for the second switch.When the clutch pedal 25 is at 10% or less than 10% of its travel the first switch will be closed and a high side signal will be sent to the electronic control unit 16 confirming this and when the clutch pedal 25 is at 75% or more than 75% of its travel the second switch will be closed and a low side signal will be sent to the electronic control unit 16 confirming this. When the clutch pedal 25 is between 10% and 75% of its travel no signal will be sent by either switch. When the clutch pedal is in the pressed state it is said to be in a pressed position and the clutch is disengaged and when it is in the un-pressed state it is said to be released or in an un-pressed position and the clutch is engaged. Note that when the signal is sent from the first switch the clutch will definitely be engaged and when the signal is sent from the second switch the clutch will definitely be disengaged. As an alternative to this arrangement the actual position of the clutch pedal can be monitored using a single sensor such as a rotary potentiometer and the determination of when the clutch is engaged or disengaged can then be performed by the electronic control unit 16 using the signal received from the position sensor. In this case the high and low side clutch signals representing positions of the clutch pedal 25 where it is known the clutch will be engaged or disengaged would be determined by the electronic control unit 16 based upon the signal received from the clutch pedal position sensor. 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. During normal engine running the electronic control unit 16 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 torque. The electronic control unit 16 controls the operation of the engine 10 which is operable in two modes, a first or 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 primary factor used to determine whether the engine 10 is operated in the second mode or in the first mode is whether the motor vehicle 5 is moving. If the motor vehicle 5 is moving the engine is operated in the second mode and the engine 10 will be run continuously and, if the motor vehicle 5 is not moving, the engine 10 will normally be run in the first mode in which automatic stop-start operation of the engine will occur. However, 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 include the engine coolant temperature, whether any catalytic converters associated with the engine are lit-off and whether the engine is rotating within a predetermined speed range. For example, if the coolant temperature is less than say 65[deg]C or the catalytic converter is not lit-off or the engine speed is greater than say 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 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 default condition is to place the stop-start system in the first mode of operation when the motor vehicle is stationary and in the second mode of operation when it is moving. In the first or stop-start mode the engine 10 is selectively stopped and started by the electronic control unit 16 without driver intervention when one or more predetermined engine stop and start conditions exist. These stop and start conditions are based upon the signals received by the electronic control unit 16 from the throttle sensor 19, the brake sensor 24, the clutch sensor 26 and the gear selector sensor 12. The position or state of the clutch pedal 25, the accelerator pedal 18, the brake pedal 23 and the transmission 11 are all different motor vehicle variables which are used to control the operation of the engine 10. The specific conditions used will are described in greater detail later with reference to the method used to control the operation of the engine 10.One of the features of the electronic control unit 16 is that it is programmed to react to more than one stop condition and more than one start condition and so is able to interface efficiently with drivers having different driving techniques. A further feature of the electronic control unit 16 is that it is programmed to recognise during an engine shutdown in the first mode of operation that one or more conditions have changed and then abort the engine shut down. This is useful in the situation where a driver of a vehicle determines that they need to move off at the same time that the electronic control unit 16 has determined that the engine 10 should be shutdown to save fuel and so is in the process of shutting down the engine 10. Without this extra functionality the electronic control unit 16 would shut down the engine 10 and then would have to immediately restart the engine 10.This unnecessary shut down has no significant fuel economy benefits and can be annoying to a driver of the motor vehicle 5 even if the extra time to restart the engine 10 is minimal. When the engine 10 is operating in the second mode it is run continuously so long as the ignition switch 17 remains in the 'on' position. 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. The method of operation of the engine control system will now be described with reference to Figs.2 to 2c. It will be appreciated that the electronic control unit 16 is programmed to control the engine 10 in accordance with this method. With reference first to Fig.2, the method starts at step 30 which is a normal key-off event and then advances to step 31 when the ignition switch 17 is moved to an 'on' position and then following a momentary movement of the ignition switch 17 to a start position advances to step 32 in which the engine 10 is started. From step 32 the method then advances to step 33 where the engine operating parameters for stop-start operation are checked. As previously described, these parameters comprise whether the engine 10 is operating below a predetermined rotational speed, whether the engine coolant is above a predetermined temperature and whether any exhaust gas treatment devices fitted to the engine 10 such as a catalytic converter or a NOx trap are operating efficiently. If all of the engine operating parameters for stop-start operation have been met then the method advances to step 35. If all of the engine operating parameters for stop-start operation have not been met then the method moves to step 34 where the engine 10 is run continuously in a warm up mode until all the engine operating parameters for stop-start operation are met. At step 35 the electronic control unit 16 is operable to determine whether the motor vehicle 5 is moving by using the signal from the speed sensor 21. If the motor vehicle 5 is determined to be moving, the method advances to step 100 where the engine 10 is operated according to the second mode of operation and is run continuously and, if the motor vehicle 5 is determined not to be moving, the method advances to step 200 in which the engine 10 is run in the first mode of operation. The determination of whether the motor vehicle 5 is moving may comprise a comparison of the measured vehicle speed with zero or may comprise the comparison of the measured vehicle speed with a target or predetermined speed very close to zero such as 1 kph. This will depend upon the accuracy of the speed sensor 21 used to measure vehicle speed. If the vehicle speed is determined to be zero or below the target speed then the motor vehicle 5 will be determined to be stationary otherwise it will be determined to be moving. Whenever the ignition switch 17 is in an 'on' position and the conditions for stop-start running have been met the electronic control unit 16 is operable to continuously check at step 35 the vehicle speed irrespective of whether the vehicle is in the first mode indicated as step 200 or the second mode indicated as step 100 and select the appropriate mode of operation as indicated by the double headed arrows linking steps 35, 100 and 200. Therefore, if the engine 10 is being operated in the first mode and the motor vehicle 5 suddenly starts to move then the mode of operation is immediately switched to the second mode and vice-versa. Operation in the first mode as indicated by step 200 comprises of a number of separate further steps which automatically control the stopping and starting of the engine 10. Upon entry to the first mode of operation the engine 10 will be running as indicated by step 400, the first action that is taken is to determine whether specific predetermined engine stop conditions have been met. These predetermined engine stop conditions are described in greater detail hereinafter with reference to Figs.2A to 2C. If the predetermined engine stop conditions are not met the engine 10 remains running and the method returns to step 400 but if one of the conditions for stopping the engine 10 has been met then the method advances to step 600 where the engine 10 is stopped or switched to a stopped state. In this case the engine 10 is stopped by shutting off the fuel supply and switching off the ignition supply to the engine 10 so that no sparks are produced by the spark plugs of the engine 10. From step 600 the method advances to step 700 where the engine 10 is in a stopped state in which it will remain until one or more specific predetermined engine start conditions set forth in step 800 have been met. These predetermined engine start conditions are described in greater detail hereinafter with reference to Figs.2A to 2C. If one of the predetermined engine start conditions has been met then the method advances to step 900 where the engine is restarted or switched to a restarted state by, in this case, energising the starter-generator 13. The method then advances to step 950 where the engine is once more running. So far as the state of the engine 10 is concerned this is the same in step 950 as it is in step 400 but it is different from a control viewpoint as there is a different path from step 950 back to step 600 than there is from step 400 to step 600. The method then advances from step 950 to step 1000 where it is determined using predetermined secondary stop conditions whether the engine 10 should be kept running or should be shut down. If the predetermined secondary stop conditions at step 1000 are not met the engine 10 will be kept running and the method will continuously cycle around a control loop from step 950 to step 1000 and back to step 950 until the conditions at step 1000 are met. When the predetermined secondary stop conditions are met the method moves back to step 600 and the engine 10 will be stopped or switched to a stopped state. The conditions of step 1000 to maintain the engine 10 running after a restart are described hereinafter with reference to Figs.2A to 2C.However, one of the features of these conditions is that they take into account a possible driver change of mind during the process of shutting down the engine 10. Operation in the first mode identified on Fig.2 as step 200 will now be described in greater detail with reference to figures 2A to 2C which in combination form the totality of the operation of the engine 10 in the first mode. That is to say they are all part of a single method of control for the engine 10 and the steps 400 and 950 are common steps on all of Figs.2 to 2C. As Figs.2A to 2C are merely a more detailed explanation of the first mode of operation shown on Fig.2 it will be appreciated that steps on Figs.2A to 2C correspond to the steps shown on Fig.2 and that the steps 500, 600, 700, 800, 900 and 1000 on Fig.2 have equivalent steps on Figs.2A to 2C indicated by the reference numbers 501, 502, 503; 601, 602, 603; 701, 702, 703; 801, 802, 803; 901, 902, 903; 1001, 1002 and 1003. Referring first to Fig.2A, the operation in the first mode starts at step 400 with the engine running. There are three groups of predetermined engine stop conditions for escape from the engine running state at step 400. One of these is shown on Fig.2A as step 502 and the others are shown on Figs.2B and 2C as steps 501 and 503. Continuing with Fig.2A step 502 includes sub-steps 402 and 404. At step 402 it is determined from the clutch sensor 26 whether the clutch pedal 25 is being pressed, from the brake pedal sensor 24 whether the brake pedal 23 is being pressed and from the gear sensor 12 whether the transmission 11 is in gear. If one or more of these conditions does not exist then the engine 10 remains running and the method remains at step 400 as indicated by the 'Else' step 403. This determination is run in parallel with the similar determinations shown on Figs. 2B and 2C as steps 501 and 503. If at step 402 it is determined that the clutch pedal 25 is being pressed, the brake pedal 23 is being pressed and the transmission 11 is in gear then a one second timer referred to as timer 1 is started in the electronic control unit 16 and the method advances to step 404. At step 404 it is determined whether, when the one second counted by timer 1 has elapsed, the clutch pedal 25 is still being pressed, the brake pedal 23 is still being pressed and the transmission 11 is still in gear. If all of these conditions are present then the method advances to step 602 but if one or more of these conditions no longer exists then the method returns via step 403 to step 400. It will be appreciated that the predetermined engine stop conditions forming step 502 comprise the selection of certain motor vehicle variables and then determining whether there is any change in these during a predetermined time period. If there is no change in any of the motor vehicle variables during the predetermined time period then the engine 10 is shut down but if one of the variables changes during the predetermined time period the engine 10 is kept running. At step 602 the engine 10 is stopped and the method advances to a second engine stopped state at step 702. The second engine stopped state is characterised by the clutch pedal 25 being pressed so that the clutch is disengaged, the brake pedal 23 being pressed and the transmission 11 being in one of the numerous available gears that is to say, it is not in neutral. The method then advances to step 802 where three separate predetermined engine start conditions are used to determine whether the engine 10 should be restarted. If none of these predetermined engine start conditions is met the method remains at step 702 with the engine stopped. The first of these predetermined engine start conditions is indicated on Fig.2A as step 405 and comprises a determination of whether the brake pedal 23 has been released while the clutch pedal 25 remains pressed and the transmission 11 remains in gear. If it is determined by the electronic control unit 16 using the signals received from the gear selection, brake and clutch sensors 12, 24 and 26 connected to it that this is the case then the method advances to step 408 which is a sub-step of step 902 otherwise the method remains at step 702 until this or one of the other release conditions is met. The second of the predetermined engine start conditions is indicated on Fig.2A as step 406 and comprises a determination of whether the accelerator pedal 18 has been pressed while the brake and clutch pedals 23 and 25 remain pressed and the transmission 11 remains in gear. If it is determined by the electronic control unit 16 using the signals received from the accelerator pedal, gear selection, brake and clutch sensors 19, 12,24 and 26 connected to it that this is the case then the method advances to step 409 which is a sub-step of step 902 otherwise the method remains at step 702 until this or one of the other release conditions is met. The third of these predetermined engine start conditions is indicated on Fig.2A as step 407 and comprises a determination of whether the transmission 11 has been placed into neutral while the brake and clutch pedals 23 and 25 have remained pressed. If it is determined by the electronic control unit 16 using the signals received from the gear selection, brake and clutch sensors 12, 24 and 26 connected to it that this is the case then the method advances to step 414 which is a link to step 703 shown on Fig.2C otherwise the method remains at step 702 until this or one of the other release conditions is met. At step 902 the engine 10 is restarted and steps 408 and 409 show the triggers used to cause the engine 10 to be restarted. That is to say comparing the state of the various motor vehicle variables (driver inputs) at step 702 with those at step 902 the only difference is that either the brake pedal 23 has been released as indicated by step 408 or the accelerator pedal 18 has been pressed as indicated by the step 409 and these are therefore the triggers used to restart the engine 10. From step 902 the method advances to step 950 in which the engine 10 is running again after a restart. It will stay in this state until one of a number of predetermined engine secondary stop conditions have been met of which one is shown on Fig.2A as step 1002 and others of which are shown on Figs.2B and 2C as steps 1001 and 1003. Continuing with Fig.2A step 1002 comprises of two substeps 410 and 412. The first of these steps is step 410 which is used to release the method from step 950 and the second of these steps is step 412 which is used to confirm that an engine stop should be continued. That is to say, step 412 is used to determine if there has been a change of mind during the shut down of the engine 10. As indicated at step 410 the method will advance from step 950 if the electronic control unit 16 determined based upon the sensor inputs that it receives that the brake and clutch pedals 23 and 25 are pressed, the transmission 11 is in gear and the accelerator pedal 18 has not been pressed and the method will otherwise remain at step 950 as indicated by the 'Else' step 411 unless one or more other predetermined secondary engine stop conditions shown on Figs.2B and 2C are met. If the predetermined engine secondary stop condition is met in step 410 then a 6 second timer referred to as timer 3 is started in the electronic control unit 16 and the method advances to step 412. At step 412 it is determined whether the 6 seconds measured by timer 3 have elapsed and when the time has elapsed the electronic control unit 16 rechecks whether there has been any change in the motor vehicle variables used to form the predetermined engine secondary stop condition. If it is determined by the electronic control unit 16 that the brake and clutch pedals 23 and 25 remain pressed, the transmission 11 is in gear and the accelerator pedal 18 remains not pressed, it is assumed that an engine stop or shut down is appropriate and the method returns to step 602 but if any of these motor vehicle variables (gear selection, clutch pedal position, brake pedal position accelerator pedal position) have changed during the predetermined time period then the method returns to step 950 and the engine 10 is kept running. Step 412 therefore provides a check to prevent the engine 10 being shut down prematurely for if there are any changes within the 6 seconds provide by timer 3 the engine shut down is aborted. It will be appreciated that 6 seconds is the predetermined time used in this example but the invention is not limited to the use of 6 seconds and other predetermined time periods could be used without departing from the scope of the invention. Referring now to Fig.2B, the operation in the first mode starts at step 400 with the engine running. As previously mentioned there are three groups of predetermined engine stop conditions for escape from the engine running state at step 400 a second of which one is shown as step 501 on Fig.2B having a single sub-step 420. At step 420 it is determined by the electronic control unit 16 using the signal received from the clutch sensor 26 whether the clutch pedal 25 is being pressed. If the electronic control unit 16 determines from the clutch pedal sensor 26 that the clutch pedal 25 is not depressed and in this case a signal is being received from the high side or first switch the engine 10 is stopped as indicated by step 601 otherwise the engine remains running and the method remains at step 400 as indicated by the 'Else' step 421. After the engine has been stopped at step 601 the method advances to a first engine stopped state at step 701. The first engine stopped state is characterised by the clutch pedal 25 not being pressed so that the clutch is engaged. Step 701 can also be entered as indicated by the box 430 from step 444 as will be described hereinafter. The method then advances from step 701 to step 801 where two separate predetermined engine start conditions indicated as steps 422, 423 are used to determine whether the engine 10 should be restarted. If neither of these predetermined engine start conditions is met then the method remains at step 701 with the engine stopped. The first of these predetermined engine start conditions is indicated on Fig.2B as the step 422 and comprises a determination by the electronic control unit 16 based upon the signals it receives from the connected sensors of whether the clutch pedal 25 is pressed and the transmission 11 is in neutral. If the clutch pedal 25 is pressed and the transmission 11 is in neutral the method advances to step 424 which is a sub-step of step 901 otherwise the method remains at step 701 until this or the other predetermined engine start condition is met. The second of the predetermined engine start conditions is indicated on Fig.2B as step 423 and comprises a determination by the electronic control unit 16 based upon the signals it receives from the sensors of whether the clutch pedal 25 is pressed and the transmission 11 has remained in gear. If the electronic control unit 16 determines that the clutch pedal 25 is pressed and the transmission 11 has remained in gear the method advances to step 425 which is a sub-step of step 901 otherwise the method remains at step 701 until this or the other predetermined engine start condition is met. At step 901 the engine 10 is restarted and boxes 424 and 425 show the triggers used to cause the engine 10 to be restarted. The object of steps 422 and 423 is to differentiate between a situation when the transmission 11 is in neutral and a situation when the transmission 11 is in gear. From step 701 if the transmission 11 is in neutral and the driver presses the clutch pedal 25 a start is triggered at step 424 from the high side clutch pedal position switch. That is to say, when the signal from the first switch changes, which will occur when a clutch pedal travel of 10% is reached, the engine 10 is restarted so as to provide the maximum amount of time in which to restart the engine 10. It will be appreciated that at the 10% travel position of the clutch pedal 25 the clutch will remain engaged. However, if this approach is used when the transmission 11 is in gear it would at best cause an undesirable lurch of the motor vehicle 5 and is potentially dangerous if the engine 10 were to start because the motor vehicle 5 would then move and could run into another object. Therefore, when the transmission 11 is determined at step 423 to be in gear, an alternative trigger is used at step 425 in which the engine 10 is not restarted until a low side clutch signal is received from the second switch confirming that the clutch pedal has reached 75% of is travel and so the clutch is known to be fully disengaged. Because the clutch is fully disengaged there is no lurching of the motor vehicle 5 and there is no risk of the motor vehicle 5 moving. From step 901 the method advances to step 950 in which the engine 10 is running again after a restart. It will stay in this state until one of a number of predetermined engine secondary stop conditions have been met of which one is shown on Fig.2B as step 1001. Step 1001 comprises of two sub-steps 426 and 428. Step 426 is a release step from step 950 and the method will advance from step 950 if the electronic control unit 16 determines from the signals it receives from the sensors connected to it that the transmission 11 is in neutral and the clutch pedal 25 has not been pressed but will otherwise remain at step 950 unless one or more other predetermined secondary engine stop conditions shown on Figs.2A and 2C as steps 1002, 1003 are met. If the electronic control unit 16 determines that the transmission 11 is in neutral and the clutch pedal 25 has not been pressed in step 426 then a 6 second timer referred to as timer 4 is started in the electronic control unit 16 and the method advances to step 428 otherwise the method stays at step 950 as indicated by the 'Else' step 427. At step 428 it is determined by the electronic control unit 16 at the end of the predetermined time period of 6 seconds measured by timer 4 using the signal it receives from the clutch pedal sensor 26 whether the clutch pedal 25 remains not pressed. That is to say, if a signal is being received from the first switch indicating that the clutch pedal 25 is within 10% of its travel the clutch pedal 25 can be assumed to be not pressed. If the electronic control unit 16 determines that the clutch pedal 25 is still not pressed and so no change has occurred it is assumed that an engine stop is appropriate and the method returns to step 601 but if the electronic control unit 16 determines that the clutch pedal 25 has been pressed within the predetermined time period then the method returns to step 950 and the engine 10 is kept running. Step 428 therefore provides a check to prevent the engine 10 being shut down prematurely and if there are any changes to the clutch position with the 6 seconds the shut down is aborted. It will be appreciated that 6 seconds is the predetermined time used in this example but the invention is not limited to the use of 6 seconds and other predetermined time periods could be used without departing from the scope of the invention. Referring now to Fig.2C, the operation in the first mode starts at step 400 with the engine running. As previously referred to there are three groups of predetermined engine stop conditions for escape from the engine running state at step 400 of which one is shown as step 503 on Fig.2C and the others are shown as steps 502 and 501 on Figs.2A and 2B respectively. Continuing with Fig.2C the step 503 comprises of two sub-steps 440 and 441. At step 440 it is determined by the electronic control unit 16 from the signal received from the clutch sensor 26 whether the clutch pedal 25 is being pressed and from the signal received from the gear sensor 12 whether the transmission 11 is in neutral. If the electronic control unit 16 determines that one or more of these conditions does not exist then the engine 10 remains running and the method remains at step 400 as indicated by the 'Else' step 450. This determination is run in parallel with the similar processes shown and previously described on Figs.2A and 2B. If however, at step 440 it is determined by the electronic control unit 16 that the clutch pedal 25 is being pressed and the transmission 11 is in neutral then a one second timer referred to as timer 2 is started in the electronic control unit 16 and the method advances to step 441. At step 441 it is determined by the electronic control unit 16 when the one second counted by timer 1 has elapsed whether the clutch pedal 25 is still being pressed and the transmission 11 is still in neutral. If the electronic control unit 16 determines that the clutch pedal 25 is still being pressed and the transmission 11 is still in neutral the method advances to step 603 but if one or more of these conditions no longer exists then the method returns via the 'Else' step 450 to step 400. At step 603 the engine 10 is stopped and the method advances to a third engine stopped state at step 703. The third engine stopped state is characterised by the clutch pedal 25 being pressed so that the clutch is disengaged and by the transmission 11 being in neutral. The method can also reach step 703 from step 407 on Fig.2A as indicated by the link step 414. There are two escapes from the third engine stopped state at step 703, the first of these is indicated as step 444 and comprises determining whether the clutch pedal 25 has been released and if it has moving to step 430 which is a link step to step 701 on Fig.2B. If the clutch pedal 25 has not been released the method moves to step 803 where a predetermined engine start condition is used to determine whether the engine 10 should be restarted. The step 803 comprises a single sub-step 443 which is a test to determine whether the predetermined engine start condition is present. The predetermined engine start condition comprises a determination by the electronic control unit 16 using the signals it receives from the sensors connected to it of whether a gear has been selected in the transmission 11 while the clutch pedal 25 remains pressed. If the electronic control unit 16 determines that a gear has been selected in the transmission 11 and the clutch pedal 25 has remained pressed the predetermined engine start condition is met and the method advances to step 445 which is a sub-step of step 903 otherwise the method remains at step 703 until an escape condition is met. At step 903 the engine 10 is restarted and step 445 shows the trigger used to cause the engine 10 to be restarted. That is to say, comparing the state of the various motor vehicle variables at step 703 with those at step 903 the only difference is that the transmission 11 has been moved from a no gear selected state to a state where a gear has been selected and so the selection of a gear in the transmission 11 is the trigger for restart of the engine 10. From step 903 the method automatically advances to step 950 in which the engine 10 is running again after a restart. It will stay in this state until one of a number of predetermined engine secondary stop conditions have been met of which one is shown on Fig.2C as step 1003 and others of which have been previously described with reference to steps 1002 and 1001 on Figs.2A and 2B respectively. Step 1003 comprises of two sub-steps 446 and 448, the first of which is a release condition and the second of which is a check to ensure that a change of mind has not occurred. As indicated at step 446 the method will advance from step 950 if the electronic control unit 16 determines from the signals it receives from the connected sensors that the transmission 11 is in neutral and the clutch pedal 25 is pressed otherwise the method will remain at step 950 unless one or more of the other predetermined secondary engine stop conditions shown on Figs.2A and 2B are met. If the electronic control unit 16 determines that the transmission 11 is in neutral and the clutch pedal 25 is pressed in step 446 then a 6 second timer referred to as timer 5 is started in the electronic control unit 16 and the method advances to step 448 otherwise it stays at step 950 as indicated by the 'Else' step 447. At step 448 it is determined by the electronic control unit 16 whether at the end of the predetermined 6 second time period measured by timer 5 whether neutral remains selected in the transmission 11 and the clutch pedal 25 remains pressed. If the electronic control unit 16 determines that at the end of the predetermined 6 second time period neutral remains selected in the transmission 11 and the clutch pedal 25 remains pressed it is assumed that an engine stop is appropriate and the method returns to step 603 but if the electronic control unit 16 determines that during the 6 second time period neutral is no longer selected in the transmission 11 or the clutch pedal 25 no longer remains pressed then the method returns to step 950 as indicated by the 'Else' step 449 and the engine 10 is kept running. Step 448 therefore provides a check to prevent the engine 10 being shut down prematurely. If there are any changes within the 6 seconds to the conditions being monitored the shut down is aborted as this indicates a change of mind has occurred. It will be appreciated that 6 seconds is the predetermined time used in this example but the invention is not limited to the use of 6 seconds and other predetermined time periods could be used without departing from the scope of the invention. It will be appreciated that steps 426 and 446 in combination can be replaced by a check to determine based upon the signals received from the gear selector sensor 12 and the clutch pedal sensor 26 that the transmission 11 is in the neutral state and remains in the neutral state and that there has been no change in the position of the clutch pedal 25 for the duration of a predetermined period of time. One of the features of the method set forth above and shown on Figs.2A to 2C is that the predetermined engine stop conditions set out in steps 501, 502 and 503 are the same as or similar to the secondary engine stop conditions set out in steps 1001, 1002 and 1003 respectively. Referring now to Figs.2 to 2C it will be appreciated that if at any time during the time when the engine 10 is being operated in the first mode the motor vehicle 5 begins to move, the electronic controller 16 will immediately switch from operation in the first mode to operation in the second mode which is to say operation will transfer from step 200 on Fig.2 to step 100 on Fig.2. It will be appreciated that this change of operation mode may occur when the engine 10 is not running and so step 100 includes a check to see if the engine 10 is running and, if the engine 10 is not running it is immediately started. However, when the opposite is true that is to say when the motor vehicle 5 is moving and comes to a halt the engine 10 will always be running and so the first mode of operation is always entered with a running engine 10. If at any time during operation in either of the two modes of operation the ignition switch 17 is moved to an 'off' position the method will revert to step 30 shown on Fig.2. Similarly, if the engine 10 is stalled at any time the method with revert to step 30 if, in order to restart the engine 10 from a stall, the driver of the motor vehicle 5 returns the ignition switch 17 to the 'off' position otherwise the process will return to one of the engine stopped conditions 701, 702 and 703 depending upon the state of the various motor vehicle variables. Therefore in summary the invention provides a method for controlling the engine of a motor vehicle that provides automatic stop-start operation of the engine and preferably is able to maximise the fuel economy gains from automatic shut down by providing a number of differing predetermined engine secondary stop condition which account for different driving styles. 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 modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention.

Claims

1. A method for starting and stopping an internal combustion engine of a motor vehicle, the motor vehicle having a clutch to driveably connect the engine to a manual multi-speed transmission having a neutral state in which drive cannot be transmitted by the multi-speed transmission and an in gear state in which drive can be transmitted by the multi-speed transmission, a driver operable clutch pedal to control engagement and disengagement of the clutch and a brake pedal to selectively apply one or more vehicle brakes wherein the method comprises the steps of operating the engine in a first mode of operation in which the engine is automatically switched between an engine stopped state and engine running state, determining, when the engine is in the stopped state, the state of the transmission, whether the brake pedal is being pressed and whether the clutch pedal is being pressed and, if it is determined that the brake pedal is being pressed, the clutch pedal is being pressed and the transmission is in the in gear state, switching the engine from the engine stopped state to the engine running state if the brake pedal is released.

2. A method as claimed in claim 1 wherein the method further comprises determining the speed of the motor vehicle and operating the engine in a second mode in which the engine is run continuously when the speed of the vehicle is determined to be above a predetermined speed.

3. A method as claimed in claim 2 wherein the predetermined speed is zero.

4. A method as claimed in any of claims 1 to 3 wherein the method further comprises switching the engine from the engine running state to the engine stopped state when a predetermined engine secondary stop condition is determined to exist.

5. A method as claimed in claim 4 wherein the predetermined engine secondary stop condition is a determination that the clutch pedal is in a pressed position, the brake pedal is in a pressed position and the transmission is in the in gear state.

6. A method as claimed in claim 5 wherein the predetermined engine secondary stop condition further comprises a determination that the clutch pedal has remained in the pressed position, the brake pedal has remained in the pressed position and the transmission has remained in the in gear state for a predetermined period of time.

7. A method as claimed in claim 4 wherein the predetermined secondary stop condition is a determination that the transmission is in the neutral state and remains in the neutral state for the duration of a predetermined period of time and that there has been no change in the position of the clutch pedal during the predetermined period of time.

8. A motor vehicle having an internal combustion engine operable in a first mode in which it is automatically stopped and started, a manual multi-speed transmission driveably connected to the engine by a clutch, a driver operable clutch pedal to control engagement and disengagement of the clutch, a brake pedal to selectively apply one or more vehicle brakes, a gear selector moveable between 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 and an electronic control unit connected to a number of sensors including at least one clutch pedal sensor the or each of which provides a signal indicative of the position of the clutch pedal, a brake pedal sensor which provides a signal indicative of whether the brake pedal is being pressed and a gear selector sensor providing a signal indicative of the state of the transmission wherein, when the engine is operating in the first mode, the electronic control unit is operable to automatically start the engine from an engine stopped state in which the clutch pedal is in a pressed position, the brake pedal is in a pressed position and the transmission is in gear when the signal from the brake pedal sensor indicates that the brake pedal has been released from the pressed position. 8. A motor vehicle as claimed in claim 7 wherein the motor vehicle further comprises at least one vehicle speed sensor to supply a signal indicative of the speed of the motor vehicle to the electronic control unit and the electronic control unit is operable to determine the speed of the motor vehicle from the signal received from the at least one vehicle speed sensor and operate the engine in a second mode in which the engine is run continuously when the signal from the or each vehicle speed sensor indicates that the motor vehicle is moving above a predetermined speed.

9. A motor vehicle as claimed in claim 8 wherein the predetermined speed is zero.

10. A motor vehicle as claimed in any of claims 7 to 9 wherein the electronic control unit is further operable to stop the engine when a predetermined engine secondary stop condition is determined to exist.

11. A motor vehicle as claimed in claim 10 wherein the predetermined engine secondary stop condition is a determination based upon the signals received from the clutch pedal sensor, the brake pedal sensor and the gear selector sensor that the clutch pedal is in a pressed position, the brake pedal is in a pressed position and the transmission is in an in gear state.

12. A motor vehicle as claimed in claim 11 wherein the electronic control unit includes a timer for measuring a predetermined period of time and the predetermined engine secondary stop condition further comprises a determination that the clutch pedal has remained in the pressed position, the brake pedal has remained in the pressed position and the transmission has remained in the in gear state for the duration of the predetermined period of time.

13. A method as claimed in claim 11 wherein the electronic control unit includes a timer for measuring a predetermined period of time and the predetermined secondary stop condition is a determination based upon the signals received from the gear selector sensor and the clutch pedal sensor that the transmission is in a neutral state and that there has been no change in the state of the transmission or in the position of the clutch pedal for the duration of the predetermined period of time.

14. A method for starting and stopping an engine of to a motor vehicle substantially as described herein with reference to the accompanying drawing.

15. A motor vehicle substantially as described herein with reference to the accompanying drawing.