Method for controlling the stopping and starting of a power machine

Abstract

A method for controlling the stopping and starting of a motor vehicle engine connected to a transmission by a manually operated clutch while the transmission remains in gear, comprising: setting a first clutch release threshold for use when the clutch is disengaged; setting a second clutch release threshold for use when the clutch is engaged; using the first release threshold to decide whether to allow the engine to stop; and using the second clutch release threshold to decide whether to allow the engine to restart from the stopped state, wherein the second clutch release threshold is set at a less disengaged state of the clutch than the first clutch release threshold, and wherein the first clutch release threshold is set such that the clutch will be sufficiently disengaged.that no torque is transmitted through the clutch, and the second clutch disengagement threshold of the clutch is set at a certain point during the range of motion of a clutch release bearing, at which the state of the clutch changes from a disengaged state, in which substantially no torque is transmitted through the clutch from the engine to the transmission, to a partially engaged state, in which, in particular, a small amount of torque can be transmitted, such that any torque transmitted by the clutch is insufficient to move the motor vehicle equipped with the engine.

Description

[0001] This procedure relates to motor vehicles and in particular a procedure for controlling the stopping and starting of a motor vehicle's engine in order to improve fuel consumption and reduce emissions.

[0002] For vehicles with manual transmissions equipped with automatic engine stop / start control, it is desirable to minimize fuel consumption by initiating automatic engine shutdowns and restarts whenever possible. Stop-in-Idle Stop / Start systems (SIN Stop / Start systems) are currently available, but these systems do not minimize fuel consumption because many drivers wait in a stationary vehicle with the engine in gear. Stop-in-Idle stops are not triggered under these conditions, and a Stop-in-Gear (SIG) strategy is required.

[0003] The publication EP 2 440 773 B1 discloses a method for controlling the stopping and starting of an internal combustion engine of a vehicle having a manual transmission and a clutch pedal, in which actuation of the clutch pedal is detected. The depressing or releasing of the clutch pedal is detected depending on the position of the clutch pedal with respect to the direction of depressing the pedal in relation to at least two predetermined depress threshold positions.

[0004] German patent application DE 10 2013 205 315 A1 also discloses a clutch position detection system for motor vehicles and a method for generating a control output from the clutch position detection system, which includes monitoring the position of a motor vehicle's clutch pedal. A control output is changed from a current state to an alternative state when a movable threshold is exceeded, which is offset from a clutch pedal starting position.

[0005] To employ a stop-in-gear stop / start strategy (SIG stop / start strategy), it is necessary to ensure that the drivetrain is disengaged to prevent accidents or unwanted vehicle movements. Stop-in-gear stops and starts can typically be initiated when both the clutch and brake pedals are depressed with a gear engaged. However, to ensure the safety of such a strategy when a restart request is received from the driver, for example, by releasing the brake pedal, the stop-start logic must only engage the engine when the drivetrain is disengaged. This prevents the vehicle from jerking or moving at all during the start-up process.Therefore, current practice is to use a very cautious clutch pedal position threshold for the clutch pedal position that must be reached if stopping the engine is to be permitted.

[0006] There are two disadvantages to using such a cautious clutch pedal position threshold.

[0007] Firstly, if the driver allows the clutch pedal to move back into a clutch engagement direction while the engine is stopped (pedal wander), in some cases the engine cannot be restarted because the clutch pedal position will have exceeded the clutch pedal position threshold and it is therefore considered unsafe to allow the engine to be restarted.

[0008] Secondly, when starting from a standstill, it is common practice for the driver to begin engaging the clutch at the same time as releasing the brake pedal and pressing the accelerator pedal. If the timing of these events is slightly out of sync, the driver may inadvertently allow the clutch pedal to move too quickly into the engagement position, causing it to exceed the clutch pedal position threshold before the engine has started to engage, thus preventing the engine from restarting.

[0009] In both cases, opportunities to start the engine are omitted, and the driver may be so dissatisfied with the operation of the stop / start system that he will switch it off.

[0010] It is an object of this invention to provide a method for controlling the stopping and starting of a power machine that reduces the number of missed opportunities to restart the power machine.

[0011] Based on this prior art, a method for controlling the stopping and starting of a motor vehicle engine with the features of independent claim 1 and a motor vehicle with the features of independent claim 11 are provided. Advantageous embodiments are described in the dependent claims.

[0012] According to a first aspect of the invention, a method for controlling the stopping and starting of a motor vehicle engine, which is in drive connection with a transmission by means of a manually operated clutch while the transmission remains in gear, is provided, wherein the method comprises: setting a first clutch release threshold for use when the clutch is disengaged, setting a second clutch release threshold for use when the clutch is engaged, using the first release threshold to decide whether to allow the engine to be stopped, and using the second clutch release threshold to decide whether to allow the engine to be restarted from the stopped state, wherein the second clutch release threshold is set at a less disengaged state of the clutch than the first clutch release threshold.wherein the first clutch release threshold is set such that the clutch is sufficiently disengaged so that no torque is transmitted through the clutch, and the second clutch release threshold is set near a friction point of the clutch so that any torque transmitted by the clutch is insufficient to move the motor vehicle equipped with the engine.

[0013] If the clutch is disengaged beyond the first clutch release threshold, the engine can be stopped if at least one engine stop trigger is present.

[0014] If the clutch is disengaged less than the first clutch release threshold, stopping the engine can be prevented even if the engine stop trigger is present.

[0015] The motor stop trigger can be present if it is detected that a brake pedal of the motor vehicle is pressed.

[0016] If the clutch is disengaged beyond the second clutch release threshold, starting the engine can then be enabled if at least one engine start trigger is present.

[0017] If the clutch is disengaged less than the second clutch release threshold, starting the engine may be prevented even if the engine start trigger is present.

[0018] The engine start trigger can be present when it is detected that a vehicle's brake pedal is either released or being released. Alternatively, the engine start trigger can be present when it is detected that a vehicle's brake pedal is released and it is detected that an accelerator pedal is depressed.

[0019] The clutch can be actuated by a clutch actuation system comprising a slave cylinder whose piston is arranged to move a clutch release bearing, and a slave cylinder piston position sensor to provide an output signal indicating the position of the slave cylinder piston, wherein the first clutch disengagement threshold can be a first associated value of the output signal from the slave cylinder piston position sensor, and then, when the magnitude of the output signal from the slave cylinder piston position sensor is not less than the first associated value of the output signal from the slave cylinder piston position sensor, the clutch can be considered sufficiently disengaged to allow the power engine to be switched off.

[0020] The clutch can be actuated by a clutch actuation system comprising a slave cylinder whose piston is arranged to move a clutch release bearing, and a slave cylinder piston position sensor to provide an output signal indicating the position of the slave cylinder piston. The second clutch disengagement threshold can be a second associated value of the output signal from the slave cylinder piston position sensor, and then, when the magnitude of the output signal from the slave cylinder piston position sensor is not less than the second associated value of the output signal from the slave cylinder piston position sensor, the clutch can be considered sufficiently disengaged to allow the engine to be started.

[0021] According to a second aspect of the invention, a motor vehicle is provided which comprises: a power engine connected to a transmission by a manually operated clutch, an electronic controller for controlling the stopping and starting of the power engine in response to inputs from a sensor designed to provide a power engine stop trigger signal, a sensor designed to provide a power engine start trigger signal, and a sensor designed to provide a signal indicating the engagement state of the clutch, wherein the electronic controller is operable to set a first clutch disengagement threshold for use when the clutch is disengaged, a second clutch disengagement threshold for use when the clutch is engaged, and the first disengagement threshold to be used to decide whether to allowthat the engine is switched off, and to use the second clutch release threshold to decide whether to allow the engine to be restarted, and to set the second clutch release threshold to a less disengaged clutch state than the first clutch release threshold, the first clutch release threshold being set so that the clutch is sufficiently disengaged so that no torque is transmitted through the clutch, and the second clutch release threshold being set near a clutch friction point so that any torque transmitted by the clutch is insufficient to move the motor vehicle.

[0022] The clutch can be actuated by a clutch actuation system comprising a slave cylinder whose piston is designed to move a clutch release bearing, and a slave cylinder piston position sensor to provide an output signal indicating the position of the slave cylinder piston.

[0023] The first clutch disengagement threshold can be a first assigned value of an output signal from the slave cylinder piston position sensor, and then, if the magnitude of the output signal from the slave cylinder piston position sensor, when checked by the electronic controller, is not less than the first assigned value of the output signal from the slave cylinder piston position sensor, the electronic controller can be operated to deduce that the clutch is sufficiently disengaged to allow the power engine to stop.

[0024] If a stop trigger is present and the clutch is sufficiently disengaged to allow the engine to be switched off, then the engine can be stopped.

[0025] The second clutch release threshold can be a second assigned value of the output signal from the slave cylinder piston position sensor, and then, if the magnitude of the output signal from the slave cylinder piston position sensor, when checked by the electronic controller, is not less than the second assigned value of the output signal from the slave cylinder piston position sensor, the electronic controller can be operated to deduce that the clutch is sufficiently disengaged to allow the engine to start.

[0026] If a start trigger is present and the clutch is sufficiently disengaged to allow the engine to start, then the engine can be started.

[0027] The sensor designed to provide a power machine stop trigger signal can be a brake pedal sensor used to monitor the position of a brake pedal, and the electronic controller can be configured to use the depressing of the brake pedal as a power machine stop trigger. The sensor designed to provide a power machine start trigger signal can be a brake pedal sensor used to monitor the position of a brake pedal, and the electronic controller can be configured to use the release of the brake pedal as a power machine start trigger.

[0028] The invention is described below by way of example with reference to the accompanying drawings, wherein Fig. 1 a schematic representation of a motor vehicle that has a stop / start system; Fig. 2 a schematic representation of a clutch and a clutch actuation system, which is located in the Fig. The vehicle shown in section 1 is used; Fig. 3 a high-level flowchart showing the actions used to control the operation of an internal combustion engine, which is part of the in Fig. The vehicle shown in section 1 is; Fig. 4 a high-level flowchart that describes a procedure for controlling the starting and stopping of the in Fig. The power machine shown in section 1 is shown; Fig. 5 is a representation showing different clutch pedal positions and their relationships to three clutch engagement zones; Fig. 6a is a representation showing the three coupling engagement zones of Fig. 5 in relation to the size of the output signal of a slave cylinder piston displacement sensor indicates when the clutch pedal is adjusted, and shows a first threshold to use then when the clutch is disengaged; Fig. 6b is a representation showing the three coupling engagement zones of Fig. 5 in relation to the size of the output signal of a slave cylinder piston displacement sensor shows when the clutch pedal is adjusted, and a second threshold for use then shows when the clutch is engaged; Fig. 7a is a graphical representation showing the relationship between the output signal of the slave cylinder piston position sensor 63 and a time for a power engine restart; and Fig. 7b is a graphical representation showing the relationship between a brake pedal sensor output and a time for the in Fig. Figure 7a shows the power engine restart.

[0029] With particular reference to Fig. 1 and Fig. Figure 2 shows a motor vehicle 5 comprising a motor engine 10 that drives a manual multi-speed transmission 11. The transmission 11 is connected to the motor engine 10 by a clutch system 50, which is manually engaged or disengaged by a driver of the motor vehicle 5 using a clutch pedal 25.

[0030] The transmission 11 has a gear selector (not shown) that is movable between several positions, including at least one position in which a gear-forming part of the multi-speed transmission is selected and a neutral position in which no gear of the multi-speed transmission is selected. When the gear selector is moved to the neutral position, the multi-speed transmission 11 is, so to speak, in a “neutral” state in which no drive can be transmitted through the multi-speed transmission, and when the gear selector is moved to a gear position, the multi-speed transmission 11 is, so to speak, in an “in-gear” state in which the drive can be transmitted through the multi-speed transmission.

[0031] A motor starter, in this case an integrated starter-generator (ISG) 13, is connected to the motor 10 via a drive connection, specifically a drive belt or chain drive 14, to the motor 10's crankshaft. The ISG 13 is connected to an electrical energy source, a battery 15, and acts as a motor to start the motor 10. The battery 15 is charged by the ISG 13 when it operates as an electric generator. It is understood that the ISG 13 could be replaced by a separate starter motor to start the motor 10.

[0032] A driver-operated on / off device in the form of a human-machine interface (HMI), in this case embodied in the form of a key-operated ignition switch 17, is used to control the overall operation of the engine 10. This means that when the engine 10 is running, the ignition switch 17 is in an 'on' position (ignition on), and when the ignition switch 17 is in an 'off' position (ignition off), the engine 10 cannot run. The ignition switch 17 also includes a third momentary position, which is used to start the engine 10 manually. It is understood that other HMI devices can be used to provide this functionality, and that the invention is not limited to the use of a key-operated ignition switch.

[0033] An electronic controller 16 is connected to the starter-generator 13, the power unit 10, a gear selector sensor 12 that monitors whether the transmission 11 is in neutral or in gear, a vehicle speed sensor 21 that is used to measure the rotational speed of a road wheel 20, a brake pedal position sensor 24 that is used to monitor the position of a brake pedal 23, a clutch master cylinder position sensor 53 that is used to monitor the position of a master cylinder piston 53 and indirectly the position of the clutch pedal 25 to which the master cylinder piston is mechanically connected, a clutch slave cylinder position sensor 53 that is used to monitor the position of a slave cylinder piston 62, and a throttle position sensor 19 that is used to monitor the position of an accelerator pedal 18.

[0034] The position of the master and slave cylinder pistons 52 and 62 can be measured by the sensors 53, 63 using any number of position sensor technologies, such as PLCD and Hall effect, without limitation.

[0035] The accelerator pedal 18 provides a driver input of the required output power from the motor 10. When the accelerator pedal 18 has been moved from a rest position, it is, as it is said, in a "depressed position" or in a "pressed state".

[0036] It is understood that the term gear selector sensor is not limited to a sensor that monitors the position of the gear selector, but can be any device that can provide feedback as to whether the transmission 11 is in the engaged state or in the neutral state.

[0037] Similarly, the term brake pedal sensor is not limited to a sensor that monitors the position of the brake pedal, but can be any device that provides feedback as to whether a driver of the motor vehicle 5 has applied pressure to the brake pedal 23 to apply the brakes of the motor vehicle 5. The brake pedal sensor could, for example, 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, as it is said, in a pressed state or in a pressed position.

[0038] Especially with reference to Fig. As can be seen from Figure 2, the clutch system 50 comprises a clutch 2 and a hydraulic actuation system that connects the clutch 2 to the clutch pedal 25. The hydraulic actuation system includes a mechanical linkage 54 that connects the clutch pedal 25 to the master cylinder piston 52 of a master cylinder 51, a hydraulic connection or line 55 that connects an outlet of the master cylinder 51 to one end of a slave cylinder 61 in which the slave cylinder piston 62 is slidably mounted, and a mechanical linkage 65 from the slave cylinder piston 62 to a release bearing 6, which is used to selectively disengage and engage the clutch 2.

[0039] It is understood that a displacement of the clutch pedal 25 in the direction of the arrow “clutch pedal travel” in Fig. 2 corresponding shifts D master and D slave of the master piston 52 or the slave piston 62 in a clutch release direction.

[0040] The coupling 2 is therefore, in this case, a pressure-release type of friction coupling. However, it is understood that the invention could also be applied to a pull-release type coupling.

[0041] The clutch 2 comprises a cover and spring assembly 3, a pressure plate 4, and a driven plate 7, which is arranged between the pressure plate 4 and a flywheel 8 attached to a crankshaft (not shown) of the engine 10. The clutch 2 is of conventional design and is not described in detail; it is only necessary to know that movement of the release bearing 6 in the direction of arrow D clutch through the slave cylinder piston 62 a movement in a clutch release direction and that a movement of the release bearing 6 in a opposite direction is a movement in a clutch engagement direction.

[0042] At a certain point during the range of motion of the release bearing 6, the state of the clutch 2 will change from a disengaged state, in which essentially no torque is transmitted through the clutch from the power unit 10 to the transmission 11, to a partially engaged state, in which a small amount of torque can be transmitted. This position of clutch engagement is often referred to as the 'friction point'. The value of the torque transmitted at the friction point varies from vehicle to vehicle depending on many factors, including the mechanical gear ratio between the power unit 10 and the driven wheels (not shown), the friction between the clutch discs and in the drivetrain, and the friction between the road wheels and the road surface.However, the magnitude of the torque transmitted at the friction point may be sufficient for a driver to feel a slight jolt, but not sufficient to cause the vehicle to move. The magnitude of the transmissible torque at the friction point is typically in the range of 3 to 10 Nm.

[0043] The electronic controller 16 receives several signals from the engine 10, including a signal from a speed sensor (not shown) indicating the engine speed 10, and sends signals to the engine that are used to control the shutdown and start-up of the engine 10. In this case, the engine 10 is a spark-ignition internal combustion engine, and the signals sent by the electronic control unit 16 are used to control a fuel supply system (not shown) and an ignition system (not shown) for the engine 10. If the engine 10 were a diesel engine, then only the fuel supply to the engine would be controlled.The electronic controller 16 can comprise various components, including a central processing unit, storage devices, timers, and signal processing devices, to convert the signals from the sensors connected to the electronic controller 16 into data that the electronic controller 16 uses to control the operation, and in particular the automatic stopping and starting, of the power machine 10. It should be noted that the electronic controller 16 can be composed of several discrete electronic control units that communicate with each other to achieve the desired functionality.

[0044] During normal engine operation, the electronic controller 16 can be operated to control the fuel supplied to the engine 10 and to adjust the ignition system so that the sparks are supplied to the engine 10 by the spark plugs at the correct time to generate the desired engine torque.

[0045] The electronic controller 16 controls the operation of the power machine 10, which can be operated in two modes: a first or start-stop mode and a second or manual mode.

[0046] The primary factor used in this example to determine whether the engine 10 operates in the second or first operating mode is whether the vehicle 5 is moving. If the vehicle 5 is moving, the engine 10 will operate in the second operating mode and will run continuously until it is manually switched off by the driver. If the vehicle 5 is not moving, the engine 10 will operate in the first operating mode, in which the engine's automatic start-stop operation will occur, provided other factors, as described below, indicate that start-stop operation is possible.It is understood that the invention could also be applied to a motor vehicle in which the engine is switched off with the transmission remaining in the engaged gear while the motor vehicle is still moving, which is sometimes referred to as a vehicle with rolling start-stop.

[0047] In addition to the requirement that the vehicle 5 be stationary, other factors can be used to decide whether operation in the first operating mode is possible. For example, the state of charge of the battery 15 may need to be above a predetermined level, the temperature of the power unit 10 may need to be above a predetermined level, the ambient temperature may need to be above a predetermined value, or an aftertreatment system may need to be at a certain temperature (start-up temperature).

[0048] In the first or start-stop operating mode, the engine 10 is selectively stopped and started by the electronic controller 16 without driver intervention when one or more predetermined engine stop and start conditions, known as "triggers," are present. These stop and start triggers are based on signals received by the electronic controller 16 from the throttle sensor 19, brake sensor 24, clutch system 50, and gear selector sensor 12. The position or state of the clutch 2, accelerator pedal 18, brake pedal 23, and transmission 11 are all various vehicle parameters used to control the operation of the engine 10. It is understood that many other variables can also be used, including, but not limited to, the state of a parking brake and whether a manual stop-start preventer switch is activated by the driver.

[0049] When the engine 10 is operated in the second operating mode, it will operate continuously as long as the ignition lock 17 remains in the "On" position, and the engine 10 is stopped and started by the driver manually operating the ignition switch 17.

[0050] Although the measurement of the motor vehicle speed is described above with reference to the use of a road wheel sensor 21, because such sensors are often already present in a motor vehicle as part of a brake anti-lock system, it should be noted that other suitable means can be used to determine the speed of the motor vehicle 5, such as a sensor that measures the rotational speed of an output shaft of the transmission 11.

[0051] Motor vehicle 5 will operate in the following manner.

[0052] If the conditions for start-stop operation are not met, the engine will continue to run while the HMI 17 remains in an "ignition-on" state, and will then be stopped when the state of the HMI 17 changes to an ignition-off state.

[0053] When start-stop operation is possible, i.e., the speed of the vehicle 5, as detected by the vehicle speed sensor 21, is essentially zero and all other conditions are met, the electronic controller 16 controls the stopping and starting of the engine 10 as follows.

[0054] With the engine 10 running and the transmission 11 in gear, it is checked whether the current engagement state of the clutch 2 is such that it is safe to stop the engine 10.

[0055] This is done by comparing the output signal (OS) from the slave cylinder piston position sensor 63 with a predefined and fixed first threshold D_P.

[0056] The first threshold D_P is a very conservative threshold. This means that, taking tolerances and noise factors into account, it can be ensured that clutch 2 is disengaged when OS ≥ D_P.

[0057] It is understood that the slave cylinder piston position sensor 63 could include internal signal processing and that the output signal (OS) from the slave cylinder piston position sensor 63 could be an analog or a digital signal. It is also understood that the output signal (OS) from the slave cylinder piston position sensor 63 could drop when the clutch pedal 25 is pressed, in which case the above test would be replaced with "Is OS ≤ D_P?"

[0058] In any case, once it has been confirmed that the clutch 2 is disengaged, the electronic controller 16 checks whether at least one engine stop trigger is present. For example, if the output from the brake pedal sensor 24 indicates that the brake pedal is being pressed, this would be an engine stop trigger, and stopping engine 10 is desirable to save fuel and reduce engine 10 emissions.

[0059] Therefore, if a power machine stop trigger is present, power machine 10 is stopped, and otherwise power machine 10 is left in the running state.

[0060] The power machine 10 is started from the stopped state if, secondly, at least one existing power machine start trigger is detected, as verified by the electronic controller 16, and secondly, the engagement state of the clutch 2 is such that the power machine 10 can be started safely. Regarding this second requirement, the output signal (OS) from the slave cylinder piston position sensor 63 is compared with the second predefined threshold D_R. The second threshold D_R is set to correspond approximately to the friction point of the clutch 2 and is therefore a relatively aggressive threshold.

[0061] If OS ≥ D_R, restarting the engine 10 is enabled and the ISG 13 is used to start the engine 10. If the output signal (OS) from the slave cylinder piston position sensor 63 drops when the clutch pedal 25 is depressed, then the above test would be replaced by the following: Is OS ≤ D_R?

[0062] In any case, if it has been confirmed that the clutch 2 is not sufficiently engaged to cause a problem if the engine 10 were to be started, the electronic controller 16 uses the ISG 13 to start the engine 10.

[0063] Therefore, in summary, two different thresholds are defined for use in determining when the power machine 10 should be started and stopped. The first threshold D_P is effective when clutch 2 is disengaged, and the second threshold D_R is used when clutch 2 is engaged.

[0064] Because the first threshold D_P is more cautious than the second threshold D_R, the driver can easily release the clutch pedal 25 while the engine 10 is stopped without affecting the ability of the electronic controller 16 to restart the engine 10 when an engine start trigger occurs. Additionally, the difference between the first and second thresholds D_P and D_R provides the driver with a greater margin of error regarding the synchronization of releasing the clutch pedal 25 with the restart trigger.

[0065] Fig. 7a and Fig. Figure 7b shows the release of the clutch pedal 25 and the release of the brake pedal 23 respectively during an attempt by a driver to start moving after a power engine has stopped.

[0066] In this example, a force machine start trigger is provided when the output from the brake pedal sensor 24 falls to zero at time "T". It is understood that other start triggers could be used and that the invention is not limited to the use of a trigger with the brake pedal sensor at zero. For example, and without limitation, it would be possible to use a strategy to detect an intention to release the brake pedal early, before it has been fully released, by detecting a rapid movement in the release direction from a brake-held position.

[0067] As in Fig. Figure 7a shows that the output signal (OS) from the slave cylinder piston position sensor 63 has already fallen below the level D_P at time "T" because the driver begins to release the clutch pedal 25. Therefore, if only one threshold value were provided, the engine 10 would not restart, as it would be assumed that the clutch 2 is too engaged to allow an engine restart. However, since the value of the output signal (OS) at time "T" is greater than the second threshold D_R, the engine is allowed to start.

[0068] Therefore, if the same cautious threshold D_P (a threshold similar to the threshold that would be set if there were only a single threshold) were used for both engaging and disengaging clutch 2, then in this example, the power machine 10 would be prevented from starting because the output signal (OS) at time T is smaller than the first threshold D_P. However, since a more aggressive second threshold D_R is used, when clutch 2 is engaged (the clutch pedal is released), the output signal (OS) is larger than the second threshold D_R at time T, thus enabling the power machine 10 to start.

[0069] Therefore, by using two thresholds D_P and D_R in accordance with this invention, a possibility of starting the power machine is not lost.

[0070] With reference to Fig. Figure 3 shows a high-level flowchart of the methodology used to determine whether the motor vehicle should be operated in the first operating mode or the second operating mode.

[0071] The procedure begins at box 110 with the ignition key 17 being in a "Off" position (ignition off) and remaining in this state until in box 115 the ignition key 17 is moved to a "On" position (ignition on), which will start the engine 10, as indicated at box 120.

[0072] Box 130 then determines whether the conditions for stop-start operation are met. This means that Box 130 decides whether to use the first or second operating mode. One of the conditions used for this decision in this example is whether the vehicle 5 is moving at more than a predetermined speed. As far as the invention is concerned, it is assumed that if the vehicle is moving at more than a predetermined speed, the manual or second operating mode is used. This is because this example is intended for use in controlling the start-stop operation of the motor 10 when the vehicle 5 is stationary.However, it is understood that, as mentioned above, the invention could be applied to a motor vehicle in which the engine is switched off with the transmission remaining in a gear engaged while the motor vehicle is still moving (a vehicle with rolling start-stop).

[0073] Other conditions that could be used to make this decision regarding the first or second operating mode include whether the ambient temperature is higher than a predetermined temperature, whether a predefined level of passenger cabin comfort has been reached, whether the current accessory power requirement is lower than a predefined level, or whether sensor plausibility checks have been completed.

[0074] Provided that all the necessary conditions are met when checked in Box 130, the procedure will proceed from Box 130 to Box 135, where the first operating mode is selected, and then on to Box 205. However, if none of the necessary conditions are met when checked in Box 130, the procedure will proceed to Box 134, where the second or normal operating mode is selected. After Box 134, the procedure proceeds to Box 140 to determine whether the ignition key 17 is still in the "On" position. If the ignition key 17 is still in the "On" position (ignition-on), the procedure returns to Box 130 with the engine running. However, if it is determined that the ignition key 17 is in the "Off" position (ignition-off), the procedure ends at Box 199.

[0075] It is understood that the process will always end when an ignition-off event occurs.

[0076] With reference to Fig. In steps 4 to 6b, the procedure progresses from box 135 to box 205, where clutch engagement state thresholds are set. The clutch engagement state thresholds are set based on the output signal from the slave cylinder piston position sensor 63, which measures the position of the slave cylinder piston 62.

[0077] The slave cylinder piston position sensor 63 is calibrated such that when the clutch pedal 25 is not touched, the output signal (OS) from the slave cylinder piston position sensor 63 is equal to S Min is and then, when the clutch pedal 25 is fully depressed, the signal from the slave cylinder piston position sensor 63 is equal to S max Three zones of clutch engagement, known as Released (R), Depressed (P), and Extended (D), are described in Fig. 5 as shown, how they relate to the position of the clutch pedal 25, and corresponding slave cylinder piston zones are based on a relationship between the clutch pedal position and the slave cylinder displacement (D Slave ) defined. The corresponding values ​​of the output signal (OS) from the slave cylinder piston position sensor 63 for zones “R”, “P” and “D” are in Fig. 6a and Fig. 6b shown.

[0078] When the clutch pedal 25 is in the released zone (R), the clutch 2 is always fully engaged.

[0079] When the clutch pedal 25 is in the depressed zone (P), it has been moved from its rest position, any slippage or free play in the clutch actuation system has been absorbed, and the disengagement or engagement of the clutch 2 begins. The friction point of the clutch 2 is located in the depressed zone "P" and, in this example, is near the boundary between the depressed zone "P" and the fully depressed zone "D".

[0080] When the clutch pedal 25 is in the depressed zone (D), it has been significantly displaced from its rest position and is approaching a fully disengaged position. Therefore, in the depressed zone, the clutch 2 is disengaged and is unable to transmit torque.

[0081] In the case of this invention, two control thresholds D_P and D_R are used, depending on whether the movement of the clutch pedal 25 is towards the fully depressed position or towards the fully released position. That is, there is a first threshold D_P when the clutch 2 is disengaged (the clutch pedal 25 is pressed downwards), and a second threshold D_R when the clutch 2 is engaged (the clutch pedal 25 is released).

[0082] When the clutch pedal 25 moves towards the fully depressed position, causing the clutch 2 to disengage, a very cautious threshold, the first threshold D_P, is used. The equivalent slave cylinder piston displacement (D Slave) from the fully released position with respect to the output signal (OS) from the slave cylinder piston position sensor 63, which is defined as the first threshold D_P, is in Fig. Figure 6a shows that when the output signal (OS) from the slave cylinder piston position sensor 63 is equal to, but preferably greater than, the first threshold (D_P), it is ensured that the clutch 2 is disengaged and no torque can be transmitted from the clutch 2. The first threshold D_P therefore defines the extent of the depressed zone “D”.

[0083] When the clutch pedal 25 moves towards the fully released position to engage the clutch 2, i.e., away from the fully depressed position, a less cautious threshold, the second threshold D_R, is used, which in this example corresponds approximately to the friction point of clutch 2. D_R is the last guaranteed point at which it is not possible to transmit sufficient torque via the clutch to cause unsafe vehicle movement in the worst case scenario due to tolerance accumulation.

[0084] The equivalent slave cylinder piston displacement (D Slave ) from the fully released position with respect to the output signal (OS) from the slave cylinder piston position sensor 63, which is defined as threshold D_R, is in Fig. Figure 6b shows that the exact location of this threshold D_R will depend on how close the friction point is to the junction between the depressed and the forced-through zones “P” and “D”.

[0085] When the output signal (OS) from the slave cylinder piston position sensor 63 is equal to, but preferably greater than, this second threshold D_R, it is assumed that the clutch 2 is sufficiently disengaged so that no significant torque can be transmitted through the clutch 2. At or near the threshold D_R, the state of the clutch 2 changes from a disengaged to a partially engaged state due to the proximity of the threshold D_R to the clutch 2's friction point. Therefore, it is possible that some torque can be transmitted by the clutch 2 if the detected displacement of the slave cylinder piston 62 reaches the second threshold D_R. This will depend on tolerances in the clutch system of a particular vehicle, such as manufacturing tolerances, as well as the wear condition of the clutch system and the operating temperatures of the various components of the clutch system.The calibration of the second threshold D_R is such that the magnitude of any torque transmitted when OS = D_R is insufficient to produce an undesired movement of the motor vehicle 5.

[0086] It is understood that there is a calibrated relationship between the actual shift D Slave of the slave cylinder piston 62 and the equivalent sensor output (OS) from the slave cylinder piston position sensor 63. The calibration of the slave cylinder piston position sensor 63 must therefore take this relationship into account, along with all the various tolerances and noise factors for the clutch 2 and the clutch 2 actuation system.

[0087] It is also understood that the specific values ​​selected for the first and second thresholds D_P and D_R may not be fixed values, but can be varied to account for or compensate for wear of the clutch 2, such as wear of the driven disc 7, as well as changes in the clutch release mechanism itself. Therefore, when the stop-start or first operating mode is selected, the first and second thresholds D_P and D_R in Box 205 are set in such a way as to allow for adjustment of these values ​​over time if such a compensation technique is used.

[0088] The clutch pedal positions CP_P and CP_R equivalent to the first and second thresholds D_P and D_R are in Fig. 5 shown as dashed outlines.

[0089] Referring back to box 205, the procedure proceeds to box 210, where the engine 10 is running and a gear is engaged in the transmission 11. It can be seen that the sequence of boxes 205 and 210 could be reversed.

[0090] From box 210, the procedure proceeds to box 215, where the current output signal (OS) from the slave cylinder piston position sensor 63 is compared with the first clutch disengagement threshold D_P. It is understood that during normal operation of the vehicle 5, the clutch 2 will be fully engaged, while the transmission 11 will be in gear, and thus the driver only has the option of disengaging the clutch 2. Therefore, the relevant threshold will always be the first threshold D_P when the vehicle is brought to a standstill. However, there could be an additional step to determine which threshold to use, and this would be particularly applicable in the case of a vehicle with rolling start-stop.For example, if the signal from the slave cylinder piston position sensor 63 increases, it can be deduced that clutch 2 is disengaged, and conversely, if the signal from the slave cylinder piston position sensor 63 decreases, then clutch 2 is engaged. It is also conceivable that the opposite change in the output signal (OS) could be used: if the magnitude of the signal from the slave cylinder piston position sensor 63 decreases while clutch 2 is disengaged, then clutch 2 is engaged.

[0091] Referring back to Box 215, if the value of the output signal (OS) from the slave cylinder piston position sensor 63 is less than D_P, the clutch 2 is assumed to be engaged, and the procedure returns to Box 210. This means there is currently no way to stop or shut down the power unit 10. However, if the output signal (OS) from the slave cylinder piston position sensor 63 is equal to or preferably greater than D_P, then the clutch 2 is assumed to be disengaged, and thus there is an opportunity to stop or shut down the power unit 10, and the procedure proceeds from Box 215 to Box 220.

[0092] Box 220 checks whether at least one engine stop trigger is present. Examples of engine stop or engine shutdown triggers are that the brake pedal 23 is pressed, that the accelerator pedal 18 is not pressed, or that a parking brake has been applied. If at least one of these triggers is present, the procedure proceeds from Box 220 to Box 225, where the engine 10 is shut down so that it stops as indicated by Box 230. Otherwise, the procedure returns from Box 220 to Box 210, with the engine 10 still running.

[0093] It is understood that boxes 215 and 220 could be combined by requiring that both requirements given in boxes 215 and 220 be met for the procedure to proceed to box 225. If one requirement is not met, the procedure would return to box 210.

[0094] Upon returning to box 230, the procedure continues from box 230 to box 240 with the power engine stopped, in order to check if at least one start trigger is present.

[0095] Examples of these start triggers are that the brake pedal 23 is not pressed, is released, is released faster than a predetermined rate, or has been released; that the accelerator pedal 18 is pressed; or that a parking brake has been released. If at least one of these start triggers is present, the procedure proceeds from box 240 to box 250; otherwise, the procedure returns from box 240 to box 230, with the power unit 10 still stopped.

[0096] If at least one of the restart triggers is present when checked in Box 240, the procedure progresses from Box 240 to Box 250, where the current output signal (OS) from the slave cylinder piston position sensor 63 is compared with the second clutch disengagement threshold D_R. It can be seen that by the time Box 250 is reached, clutch 2 will have been disengaged, and to start moving from a standstill or to restart the engine while it is still rolling, the driver must engage clutch 2. Therefore, the relevant threshold will be the second threshold D_R. However, as mentioned earlier, there could be an additional step to determine which threshold to use.

[0097] If the current output signal (OS) from the slave cylinder piston position sensor 63 is greater than or equal to the second threshold D_R when compared in box 250, the procedure proceeds to block 260, where the engine is restarted, and then returns to box 210 with the engine 10 running and the transmission 11 in gear. However, if the current output signal (OS) from the slave cylinder piston position sensor 63 is less than the second threshold D_R when compared in box 250, the procedure returns to box 230 with the engine 10 still stopped. This is because the clutch 2 might be sufficiently engaged to cause a problem if the engine 10 were restarted.

[0098] It is understood that if an ignition-off event occurs at any time during the execution of the procedure, the procedure will end.

[0099] It goes without saying that the procedure that is in Fig. 3 and Fig. 4 is shown, as executable steps could be encoded in the electronic controller 16.

[0100] In summary, a first, cautious clutch release threshold is used when the clutch is disengaged, and a second, less cautious clutch release threshold is used when the clutch is engaged. By using two different thresholds depending on whether the clutch is engaged or disengaged, the invention provides reliable stopping and starting of the engine while reducing the number of failed restarts.

[0101] Although in the provided example the first and second clutch release thresholds are set as values ​​of an output signal from a slave cylinder piston position sensor associated with a slave cylinder such as a concentric slave cylinder, it is understood that the two thresholds could be set and compared in other ways.

[0102] For example, and without limitation, the movement of the release bearing could be detected by a position sensor and the output signal from the release bearing sensor could be used for comparison with signal values ​​corresponding to the first and second thresholds, or a clutch master cylinder detection, clutch pedal position detection or clutch line pressure detection could be used with the respective output signals, comparing them with signal values ​​corresponding to the first and second thresholds.

[0103] It will be recognized by those skilled in the field 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 one or more modifications to the disclosed embodiments or alternative embodiments could be created without deviating from the scope of the invention as set out in the attached claims.

Claims

[1] A method for controlling the stopping and starting of a motor vehicle engine connected to a transmission by a manually operated clutch while the transmission remains in gear, comprising: setting a first clutch release threshold for use when the clutch is disengaged, setting a second clutch release threshold for use when the clutch is engaged, using the first release threshold to decide whether to allow the engine to stop, and using the second clutch release threshold to decide whether to allow the engine to restart from the stopped state, the second clutch release threshold being set at a less disengaged state of the clutch than the first clutch release threshold, and the first clutch release threshold being set such that the clutch will be sufficiently disengaged.that no torque is transmitted through the clutch, and the second clutch disengagement threshold of the clutch is set at a certain point during the range of motion of a clutch release bearing, at which the state of the clutch changes from a disengaged state, in which substantially no torque is transmitted through the clutch from the engine to the transmission, to a partially engaged state, in which, in particular, a small amount of torque can be transmitted, such that any torque transmitted by the clutch is insufficient to move the motor vehicle equipped with the engine. [2] Method according to claim 1, wherein, when the clutch is disengaged further than the first clutch disengagement threshold, it is possible to stop the engine if at least one engine stop trigger is present. [3] Method according to claim 2, wherein, when the clutch state is less disengaged than the first clutch disengagement threshold, stopping the engine is prevented even when the engine stop trigger is present. [4] Method according to claim 2 or claim 3, wherein the motor engine stop trigger is present when it is detected that a brake pedal of the motor vehicle is pressed. [5] Method according to any one of claims 1 to 4, wherein, when the clutch is disengaged further than the second clutch disengagement threshold, starting the engine is enabled if at least one engine start trigger is present. [6] Method according to claim 5, wherein, when the clutch state is less disengaged than the second clutch disengagement threshold, the starting of the engine is prevented even when the engine start trigger is present. [7] Method according to claim 5 or claim 6, wherein the motor start trigger is present when it is detected that a brake pedal of the motor vehicle is either released or is being released. [8] Method according to claim 5 or claim 6, wherein the engine start trigger is present when it is detected that a brake pedal of the motor vehicle is released and it is detected that an accelerator pedal is pressed. [9] Method according to any one of claims 1 to 8, wherein the clutch is actuated by a clutch actuation system comprising a slave cylinder whose piston is designed to move a clutch release bearing, and a slave cylinder piston position sensor for providing an output signal indicating the position of the slave cylinder piston, wherein the first clutch disengagement threshold is a first associated value of the output signal from the slave cylinder piston position sensor, and then, when the magnitude of the output signal from the slave cylinder piston position sensor is not less than the first associated value of the output signal from the slave cylinder piston position sensor, the clutch is considered to be sufficiently disengaged to allow the engine to be switched off. [10] Method according to any one of claims 1 to 9, wherein the clutch is actuated by a clutch actuation system comprising a slave cylinder whose piston is designed to move a clutch release bearing, and a slave cylinder piston position sensor for providing an output signal indicating the position of the slave cylinder piston, wherein the second clutch disengagement threshold is a second associated value of the output signal from the slave cylinder piston position sensor, and then, when the magnitude of the output signal from the slave cylinder piston position sensor is not less than the second associated value of the output signal from the slave cylinder piston position sensor, the clutch is considered to be sufficiently disengaged to allow the engine to be started. [11] Motor vehicle comprising: a power engine connected to a transmission by a manually operated clutch, an electronic controller for controlling the stopping and starting of the power engine in response to inputs from a sensor designed to provide a power engine stop trigger signal, a sensor designed to provide a power engine start trigger signal, and a sensor designed to provide a signal indicating the engagement state of the clutch, wherein the electronic controller is operable to set a first clutch disengagement threshold for use when the clutch is disengaged, to set a second clutch disengagement threshold for use when the clutch is engaged, and to use the first disengagement threshold to decide whether to allow the power engine to be switched off.and to use the second clutch release threshold to decide whether to allow the engine to be restarted, and to set the second clutch release threshold to a less disengaged clutch state than the first clutch release threshold, the first clutch release threshold being set such that the clutch will be sufficiently disengaged that no torque will be transmitted from the clutch, and the second clutch release threshold being set at some point during the range of motion of a clutch release bearing where the state of the clutch changes from a disengaged state in which substantially no torque is transmitted through the clutch from the engine to the transmission, to a partially engaged state in which, in particular, a small amount of torque can be transmitted, so that any torque transmitted by the clutchnot sufficient to move the motor vehicle. [12] Vehicle according to claim 11, wherein the clutch is actuated by a clutch actuation system comprising a slave cylinder whose piston is designed to move a clutch release bearing and a slave cylinder piston position sensor for providing an output signal indicating the position of the piston of the slave cylinder. [13] Vehicle according to claim 12, wherein the first clutch disengagement threshold is a first associated value of an output signal from the slave cylinder piston position sensor and then, when the magnitude of the output signal from the slave cylinder piston position sensor, when checked by the electronic controller, is not less than the first associated value of the output signal from the slave cylinder piston position sensor, the electronic controller is operable to deduce that the clutch is sufficiently disengaged to allow the engine to stop. [14] Vehicle according to claim 13, wherein, when a stop trigger is present and the clutch is sufficiently disengaged to allow the engine to be switched off, the engine is stopped. [15] Vehicle according to one of claims 12 to 14, wherein the second clutch disengagement threshold is a second associated value of an output signal from the slave cylinder piston position sensor and then, when the magnitude of the output signal from the slave cylinder piston position sensor, when checked by the electronic controller, is not less than the second associated value of the output signal from the slave cylinder piston position sensor, the electronic controller can be operated to deduce that the clutch is sufficiently disengaged to allow the engine to be started. [16] Vehicle according to claim 15, wherein, when a start trigger is present and the clutch is sufficiently disengaged to enable the starting of the engine, the engine is started. [17] Vehicle according to any one of claims 11 to 16, wherein the sensor designed to provide a power engine stop trigger signal is a brake pedal sensor used to monitor the position of a brake pedal, and the electronic controller is operable to use the pressing of the brake pedal as a power engine stop trigger. [18] Vehicle according to any one of claims 11 to 17, wherein the sensor designed to provide a power engine start trigger signal is a brake pedal sensor used to monitor the position of a brake pedal, and the electronic controller is operable to use the release of the brake pedal as a power engine start trigger.

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