Method and system for controlling a starter motor

Abstract

The present disclosure relates to methods and systems for controlling a starter motor. Methods and systems are provided for handling a change of mind event during engine auto-stop, in which the speed at which the starter motor for restarting the engine is disengaged is based on a comparison of the current engine speed (N) and a starting rotation speed limit (S LIM ). In one example, during engine restart when the engine is decelerating, the starter motor can rotate the engine to a threshold starting rotation engine speed, and the threshold starting rotation engine speed is adjusted based on the position of the gear.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to UK Patent Application No. 1713367.9 filed on August 21, 2017. The entire contents of the above-referenced application are hereby incorporated by reference in their entirety for all purposes. Technical Field

[0003] The present application generally relates to automatic stopping and starting of an internal combustion engine in the event of a change of mind following an engine shutdown request. Background Art

[0004] In current motor vehicles equipped with "automatic start-stop" systems, the engine automatically shuts down whenever possible to save fuel and reduce emissions. Once the engine has started to shut down, it must be restarted, which is a problem, in what is often referred to as a "Change of Mind Event" (CoM), when the state of the powertrain is not always in a fully open state.

[0005] CoM occurs when the driver interrupts an automatic engine stop due to a change in circumstances, before the engine has actually stopped. CoM can occur at any time during the engine stop process, because, for example, a set of traffic lights turns green as the engine begins to spin down or when the engine is in the process of stopping due to vehicle spacing allowing the driver to enter traffic at a roundabout or intersection.

[0006] In order to minimize driver dissatisfaction and feelings of unresponsiveness, it is desirable to return the engine to its normal operating conditions as quickly as possible under such circumstances. In some cases, when CoM occurs early in the engine shutdown, this can be achieved by simply increasing the air and fuel supply and, in the case of a spark ignition engine, providing ignition to the engine in what is commonly referred to as a "passive restart," but at other times, when the engine speed and resulting kinetic energy are insufficient for a successful restart, it is necessary to engage the starter motor to crank the engine.

[0007] In some cases, the starter motor can be engaged even when the engine is still spinning at a so-called "early engaged active CoM", but in other cases the engine speed is so low that it is necessary to wait for the engine to come to a complete stop before engaging the starter motor.

[0008] In any case, once the starter motor is engaged, the control system must decide when to turn it off again, that is, when to disengage the starter motor. If the starter motor is disengaged too early, the engine may not be successfully started due to insufficient engine rotation speed, causing the engine to stall and resulting in a vehicle launch failure. Conversely, if the starter motor is disengaged too late, the starter motor internal components will experience excessive wear due to the higher than normal rotation speed and the duration of the starting cranking, and the NVH experienced by the driver will be degraded.

[0009] The current approach is to employ a single speed limit for starter motor disengagement that balances the robustness of the start (guarantee of a successful start) with the adverse NVH caused by engaging the starter motor for too long and is based on the assumption that the driveline is open.

[0010] However, the inventors herein have recognized potential issues with such a system. The existing trade-off between launch robustness and NVH is not necessarily appropriate for a partially closed powertrain condition that can occur after a CoM event. It is not possible to select a single calibration for starter motor disengagement, when the driver is not attempting to launch the vehicle, that has the best NVH for an open powertrain condition, but that is also robust enough to support an aggressive vehicle launch. Summary of the invention

[0011] In one example, the problems described above can be at least partially solved by a method of controlling a starter motor of a powertrain having an engine and a transmission including a gearbox driven by the engine via a friction clutch, the method comprising: when it is desired to use the starter motor to restart the engine after a change of mind during an automatic engine stop, cranking the engine using the starter motor and disengaging the starter motor when a cranking speed limit is reached, the cranking speed limit being based on whether the powertrain is confirmed to be fully open. In this way, engine restart during engine deceleration can be improved by cranking the engine until the engine speed reaches an adjustable threshold speed.

[0012] In one example, according to a first aspect of the present disclosure, a method of controlling a starter motor of a powertrain system is provided, the powertrain system having an engine and a transmission including a gearbox driven by the engine via a friction clutch. The method includes, when it is necessary to use the starter motor to restart the engine after changing one's mind during an automatic engine stop, using the starter motor to crank the engine and disengaging the starter motor when a cranking speed limit is reached, wherein the cranking speed limit is based on whether the powertrain is confirmed to be fully open.

[0013] The first starting rotation speed limit may be used when the transmission is confirmed to be fully open, and the second starting rotation speed limit may be used when the transmission is not confirmed to be fully open. The method may also include checking whether the state of the transmission is fully open, if the state of the transmission is confirmed to be fully open, setting the starting rotation speed limit to the first starter motor disengagement speed limit, otherwise setting the starting rotation speed limit to the second starter motor disengagement speed limit, and using the set starting rotation speed limit to determine when to disengage the starter motor. Checking whether the state of the transmission is open may include checking whether the transmission is in one of an in-gear state and a neutral state.

[0014] The first and second starter motor disengagement speed limits may be based on respective predefined relationships between engine speed and an engine operating parameter that affects engine starting. The engine operating parameter that affects engine starting may be a temperature of the engine. The temperature of the engine may be an engine coolant temperature. Whenever the engine temperature is above a threshold positive temperature, the second starter motor disengagement speed limit may be higher than the first starter motor disengagement speed limit.

[0015] According to another aspect of the present disclosure, there is provided a powertrain system comprising: an engine, a starter motor for starting the engine, a transmission including a gearbox driven by the engine via a friction clutch, and an electronic controller, wherein the electronic controller is arranged to, at least when it is desired to restart the engine using the starter motor after a change of mind during an automatic engine stop, disengage the starter motor when a cranking speed limit is reached. The cranking speed limit is set based on whether the transmission is confirmed to be fully open.

[0016] A first launch rotational speed limit may be used when the powertrain is confirmed to be fully open, and a second launch rotational speed limit may be used when the powertrain is not confirmed to be fully open.

[0017] The electronic controller may also be arranged to check whether the state of the transmission system is fully open, and if the state of the transmission system is confirmed to be fully open, the electronic controller may also be arranged to set the starting rotation speed limit to the first starter motor disengagement speed limit, otherwise the starting rotation speed limit is set to the second starter motor disengagement speed limit. The set starting rotation speed limit is used to decide when to disengage the starter motor.

[0018] Checking whether the state of the transmission system is fully open may include using one of a neutral gear sensor and an in-gear sensor to check whether the transmission is in one of an in-gear state and a neutral state.

[0019] In this way, by adjusting the threshold engine speed for engine cranking after an engine idle-stop based on the position of the gear, delays in vehicle response time can be reduced. By adjusting the threshold engine speed to an engine speed at which the engine can be cranked via a starter motor based on whether the gear is in a neutral position, noise, vibration and harshness (NVH) during engine restart can be reduced. A technical effect of cranking the engine to different engine speeds based on gear position is that starter motor wear can be reduced. By adjusting different engine restart speeds based on engine temperature, engine operation can be improved.

[0020] It should be understood that the above summary is provided to introduce some concepts that are further described in the detailed description in a simplified form. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the appended claims. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above and in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A block diagram of a motor vehicle having an engine control system is shown.

[0022] FIG. 2 shows a flow chart illustrating an example method that may be implemented to control stopping and restarting of an engine during engine deceleration.

[0023] Figure 3 is a flow chart showing the relationship between the starter motor disengage speed limit with respect to engine speed and coolant temperature for open and non-open powertrain conditions.

[0024] Figure 4 Example operation of a starter motor based on gear position during an engine restart is shown. DETAILED DESCRIPTION

[0025] The following description relates to systems and methods for restarting an engine after an engine idle-stop. As described with reference to an example engine system coupled to a motor vehicle system, Figure 1 As shown, the operation of the starter motor can be adjusted based on the engine operating parameters and the position of the transmission system gear. The engine controller can be configured to execute a control routine, such as the example routine of FIG. 2 , to adjust the operation of the starter motor during an engine restart after an idle-stop. Figure 3 The relationship between starter motor operation and engine temperature is shown. Figure 4 Example operation of the starter motor during an engine restart while the engine is still decelerating is shown.

[0026] Figure 1 A motor vehicle 5 is shown having a powertrain 30 with an internal combustion engine 6 which in this case may be a direct injection spark ignition engine, but in other cases may be a diesel engine.

[0027] The engine 6 may have an intake manifold 9 through which air flows to cylinders (not shown) of the engine 6. Air flow into the manifold 9 may be controlled by a throttle valve 10. Exhaust gas flows out of the engine 6 via an exhaust manifold and an exhaust system (not shown) that may include one or more emission control devices.

[0028] The engine 6 can drive the primary load via a flywheel and friction clutch assembly 8. The multi-speed manual transmission 7 can drive a final drive assembly (not shown) via an output shaft 13. As is well known in the art, the friction clutch is engaged or disengaged by the driver of the motor vehicle 1 operating a driver-operable clutch pedal (not shown).

[0029] The gear selection mechanism 12 is used by an operator of the motor vehicle 5 to select an appropriate one of several speed ratios within the transmission 7 .

[0030] As is well known in the art, the engine 6 has a starter motor 11 that is selectively drivably connected to the engine 6 via a pinion gear that meshes with a ring gear of a flywheel secured to the engine 6 when the starter motor is turned on. The starter motor 11 can provide a power source for starting the engine 6. A power source such as a battery (not shown) can be coupled to the starter motor to provide energy during engine cranking.

[0031] The motor vehicle 5 may include an electronic controller 20 (also referred to herein as an electronic control unit or ECU) that forms part of a powertrain system 30 for controlling the operation of the engine 6. The controller 20 is shown as receiving information from a plurality of sensors 15 and 18 (different examples of which are described herein) and sending control signals to a plurality of actuators 17 (different examples of which are described herein). The electronic controller 20 receives information from a plurality of engine sensors 15 regarding the current operating state of the engine 6, such as the rotational speed of the engine 6, the coolant temperature of the engine 6, the engine oil temperature, the mass air flow entering the engine 6, and may also receive other information regarding, for example, the state of charge of a battery (not shown) used to power the starter motor 11 of the engine 6.

[0032] The electronic controller 20 also receives information from one or more driver input sensors regarding the current operating status of various driver control devices, such as, but not limited to, the position of a driver-operated clutch pedal, the engagement state of a clutch forming part of the flywheel and clutch assembly 8, the brake pedal state, and the accelerator pedal state.

[0033] Electronic controller 20 controls actuator 17 including throttle valve 10 via a closed-loop feedback system in the present example. Controller 20 may receive input data from various sensors, process the input data, and trigger various actuators in response to the processed input data based on instructions or code programmed therein corresponding to one or more routines.

[0034] However, it should be understood that the electronic controller 20 can be replaced by a plurality of decentralized electronic controllers, each having a specific task, which are connected to each other to provide the desired functionality.

[0035] The electronic controller 20 also receives an indication of the engagement state of the manual transmission 7 from the transmission engagement state sensor 16. The transmission engagement state sensor 16 may be one of a neutral state sensor and an in-gear state sensor, and in either case provides an output indicating whether a drive gear or neutral is selected in the manual transmission 7. The purpose of this is to confirm whether there is a fully open driveline.

[0036] Electronic controller 20 uses inputs from engine sensors 15 and driver input sensors 18 and (in some cases) transmission state sensors 16 to decide when to automatically stop and start engine 6 .

[0037] During operation of the powertrain 30 , the electronic controller 20 can determine when the engine 6 can be automatically stopped. The controller 20 can then take appropriate action to stop the engine 6 and continue to monitor the current rotational speed of the engine 6 .

[0038] Once an engine idle-stop is initiated, when the engine is decelerating, when the driver interrupts an automatic engine stop due to a change in circumstances and a request to increase engine speed (increase torque output), a change of mind (CoM) can occur. A CoM can occur at any time during the engine stop process. If a CoM event occurs during a shutdown of the engine 6, the electronic controller 20 can respond in a variety of ways depending on the current speed (N) of the engine 6, the current coolant temperature, and whether the manual transmission 7 is in neutral as sensed by the transmission state sensor 16.

[0039] It will be understood that the engine 6 can be stopped in a variety of ways in which the torque is reduced sufficient to produce an engine shutdown, including one or more of cutting off the fuel supply to the engine 6, cutting off the ignition system in the case of a spark-ignition engine, adjusting spark timing, adjusting ignition, adjusting injection timing, adjusting fuel injection, and shutting off fuel injectors.

[0040] An example of a CoM event is when, during a shutdown of the engine 6, the driver performs some action indicating that the engine 6 should remain running. For example, in the case of a manual transmission 7, if the driver has removed their foot from the accelerator pedal, released the clutch pedal and placed the transmission 7 in neutral and then, during a shutdown (deceleration) of the engine 6, the driver again depresses the clutch pedal and places the manual transmission 7 back into gear, a CoM will be constituted.

[0041] In response to the CoM event, the ECU 20 checks the current engine speed (N) and, if it finds that the current engine speed is above the upper speed limit (NUL), then the engine can be passively restarted because the rotational speed of the engine 6 is high enough to allow the restart to occur without the use of the starter motor 11. In this case, the demand for engine operation is restored, such as restarting the fuel supply of the engine 6, and in the case of a spark-ignition engine, restoring normal ignition of the engine 6 can automatically return to an operating state (e.g., a requested engine speed that can meet the torque demand). Based on the engine size and configuration, the upper speed limit (NUL) can vary from engine to engine. In one example, the upper speed limit (NUL) can be 600RPM.

[0042] However, if the speed of the engine 6 is below the upper speed limit (NUL) when CoM occurs, it may be necessary to restart the engine 6 using the starter motor 11 .

[0043] However, engagement of the starter motor at high speeds may result in damage to various drive components (eg, flywheel ring gear and starter motor pinion) and may therefore delay engagement of the starter motor until the speed of the engine 6 drops below the upper starting speed limit (NUSL).

[0044] In addition, the starting speed lower limit (NLSL) can be used to prevent engagement of the starter motor 11 when the engine speed approaches zero. This is because the engine may rotate slightly backward before stopping, and engagement of the starter motor with the reverse engine can be avoided to reduce the possibility of damage to the starter motor. If the engine speed (N) is less than the starting speed lower limit (NLSL), the engine 6 is allowed to stop completely before the starter motor 11 is engaged to restart it.

[0045] The upper starting speed limit (NUSL) and the lower starting speed limit (NLSL) may depend on the actual configuration of the starter motor 11 and associated components. In one example, the upper starting speed limit (NUSL) may be 200-250RPM and the lower starting speed limit (NLSL) may be 50RPM. These values ​​may be pre-calibrated and stored in the electronic controller 20 as pre-calibrated values ​​to be used by the electronic controller 20 to determine whether the current engine speed (N) is within the starter motor restart zone.

[0046] In the event that the engine speed (N) is within the starter motor restart region defined by the upper cranking speed limit (NUSL) and the lower cranking speed limit (NLSL), the starter motor 11 is immediately engaged to crank the engine 6 to restart it.

[0047] In some cases the ignition may remain active and unchanged during an autostop and only the fuel may be cut or modified to produce the stop and may be resupplied to produce a restart, in other cases both the fuel and the ignition may be cut or modified to produce the stop.

[0048] During cranking of the engine via the starter motor 11, the engine speed (N) at which the starter motor 11 may be engaged may be based on a comparison of the current engine speed (N) with a cranking speed limit (SLIM). The cranking speed limit (SLIM) may be a maximum engine speed that allows cranking of the engine 6. In one example, the cranking speed limit (SLIM) may be an actual rotational speed of the starter motor 11. However, by directly comparing the engine speed to the cranking speed limit (SLIM), no additional software or hardware may be required to determine the disengagement of the starter motor.

[0049] If the engine speed (N) is equal to or greater than the set starting rotation speed limit SLIM, the starting rotation can be terminated and the starter motor 11 can be disengaged. The starting rotation speed limit SLIM may not be a fixed value, but may be based on whether the transmission 7 is in neutral. That is, whether it can be confirmed that the motor vehicle 1 is running with a fully open powertrain.

[0050] The starting rotation speed limit (SLIM) can be calibrated differently for different powertrain states. In the case where it can be confirmed that the motor vehicle 1 is running in an open powertrain state by using the transmission engagement state sensor 16 (the transmission 7 is in neutral or the gear is not engaged), the starting rotation speed limit (SLIM) can be set to a first starter motor disengagement speed limit S1 mapped as a function of the engine coolant temperature (first disengagement speed map), and the starter motor disengagement decision can be based on whether the current engine speed (N) exceeds the starting rotation speed limit (SLIM).

[0051] In general, the powertrain may be on when starting from zero engine speed.The starter motor disengagement logic is extended to add a second starter motor speed limit S2 which is also mapped as a function of the engine coolant temperature (second disengagement speed map).

[0052] Therefore, in a case where it cannot be confirmed that the motor vehicle 1 is operating in an open conventional transmission state, the starting rotation speed limit (SLIM) can be set to the second starter motor separation speed limit S2 obtained from the second separation speed map, and the starter motor separation decision can be based on whether the current engine speed (N) exceeds the starting rotation speed limit (SLIM).

[0053] The second split speed map provides a starting cranking speed limit (SLIM) that is higher than the starting cranking speed limit (SLIM) derived from the first split speed map for a majority of engine coolant temperatures.

[0054] This allows the first split speed map to be used for open powertrain starts where NVH can be fully optimized, and the second split speed map provides a higher start rotation speed limit (SLIM) which can be used at any time the driver might start the vehicle (closed powertrain).

[0055] It should be appreciated that the first and second split speed maps may be generated using calibration tests run at a manufacturing facility or using test results during vehicle service of a particular engine and may be digitally stored within the electronic controller 20 .

[0056] Figure 3 An example graph 300 depicting the difference between a first disengagement speed map 302 and a second disengagement speed map 304 with respect to engine coolant temperature for a single test engine is shown. The first map 302 may be used to determine a first starter motor speed limit (S1) at which the starter motor may be disengaged, while the second map 304 may be used to determine a second starter motor speed limit (S2).

[0057] When the engine coolant temperature is below a threshold positive temperature (a temperature close to but above 0° C., such as +5 to +25° C.), in the example case of 10° C., the first and second starter motor speed limits S1 and S2 are substantially the same.

[0058] However, when the engine coolant temperature is higher than the threshold temperature, there is a significant difference between the first starter motor speed limit S1 and the second starter motor speed limit S2, wherein the second starter motor speed limit S2 is always higher than the first starter motor speed limit S1.

[0059] Above a threshold second engine coolant temperature (e.g., 95° C.), the difference between the first starter motor speed limit S1 and the second starter motor speed limit S2 remains substantially equal (e.g., within 5%), the first starter motor speed limit S1 being approximately 400 RPM and the second starter motor speed limit S2 being approximately 500 RPM. The first threshold temperature and the second threshold temperature may be pre-calibrated at a manufacturing plant or service station based on engine characteristics.

[0060] Therefore, if the coolant temperature is above the second threshold when the starter motor 11 is in use, the starting rotation speed limit (SLIM) can be set to 400RPM, otherwise the starting rotation speed limit (SLIM) can be set to 500RPM if it can be confirmed that the transmission system is fully open.

[0061] return Figure 1 After the acceleration of the engine 6 is completed, the control of the throttle 10, the fuel supply of the engine and the ignition timing of the engine 6 in this example case return to the required control strategy to provide the user-demanded torque of the engine 6.

[0062] In this example, the relationship between engine coolant temperature and engine speed is used as a reference for setting the starter motor disengagement speed limit, and it will be understood that other engine temperature relationships that affect the speed when it is necessary to disengage the starter motor may also be used, such as, for example, the relationship between engine speed and cylinder block temperature or the relationship between engine speed and engine oil temperature.

[0063] In this way, Figure 1A system is implemented by a component of an engine, a transmission system, and a controller with computer readable instructions stored in a non-transitory memory to: in response to an engine restart request during engine deceleration, in a first condition, start rotating the engine via a starter motor until the engine speed increases to a first starting rotational speed; in a second condition, start rotating the engine via a starter motor until the engine speed increases to a second starting rotational speed, in a third condition, start rotating the engine via a starter motor until the engine speed increases to a third starting rotational speed, and in a fourth condition, start rotating the engine via a starter motor until the engine speed increases to a fourth starting rotational speed, the fourth starting rotational speed being higher than each of the third starting rotational speed, the second starting rotational speed, and the first starting rotational speed. The first condition may include each of a first engine temperature and a neutral position of a gear of the transmission system, and the second condition may include each of the first engine temperature and a non-neutral position of the gear. The third condition may include each of a second engine temperature and a neutral position of the gear, and the fourth condition may include each of the second engine temperature and a non-neutral position of the gear, the first engine temperature being higher than the second engine temperature.

[0064] FIG. 2 shows an example method 200 that can be implemented to adjust engine operation during an engine idle stop and subsequent restart. Instructions for executing method 200 and other methods included herein may be generated by a controller based on instructions stored in a memory of the controller and in combination with sensors from the engine system (e.g., as described above with reference to FIG. Figure 1 The controller may utilize an engine actuator of the engine system to adjust the engine operation according to the method described below.

[0065] At 202, the routine includes determining whether a vehicle key-on request has been made. A key-on request may include an operator using a key to initiate vehicle operation. For a remote start, a vehicle key-on signal may be received from a signal source external to the vehicle. The vehicle may be communicatively coupled to an external signal source such as a key fob, a mobile phone, or a smart phone for remotely starting the engine via wireless communication. Based on the signal received from the remote signal source, the controller may schedule an engine start at a requested time.

[0066] If the vehicle switch-on request is not made, at 204, the engine may remain disabled. Thus, fuel injection and spark may not be initiated for engine start. If the vehicle switch-on request is confirmed, then at 206, engine operation may be initiated. In one example, the engine may be started via a starter motor (e.g., Figure 1The starter motor 11 in the engine 6 is started and rotated while opening the throttle valve 10 and providing spark and fuel to the engine 6. It should be understood that the end of the start rotation can be based on a fixed engine speed, or the engine speed at which the start rotation is terminated can depend on whether the powertrain of the motor vehicle can be confirmed to be fully open. In one example (described later), if the powertrain is fully open (such as when the gear is in the neutral position), the starter motor can run until the engine speed reaches a first threshold speed. In another example, if the powertrain is not fully open (such as when the gear is not in the neutral position), the starter motor can run until the engine speed reaches a second threshold speed, which is higher than the first threshold speed.

[0067] At 208, the routine includes determining whether an engine stop has been requested. Various sensor inputs may be used to determine whether engine idle-stop conditions are met and the engine may be stopped to save fuel. In the case of this example, the automatic stop decision (engine stop request) is made by a start-stop controller that forms part of the electronic controller.

[0068] The condition of engine idle-stop can include engine idling longer than a threshold duration. For example, when the vehicle is stopped in traffic, when the engine load is below a threshold (e.g., when the vehicle is stationary), engine idling can occur. Running the engine at idle speed for more than a threshold duration can result in increased fuel use and increased exhaust emission levels. Likewise, the threshold duration can be based on the fuel level in the fuel tank. In one example, if the fuel level in the fuel tank is below a threshold level, the threshold duration can be reduced so that additional fuel is not consumed by engine idling.

[0069] The driver requested torque may be estimated and confirmation of an engine idle-stop may be initiated in response to a torque below a threshold driver request. The vehicle speed may be determined and estimated to be below a predetermined threshold. For example, if the vehicle speed is below a threshold (e.g., 3 mph), an engine idle-stop may be requested even if the vehicle is not at rest. Also, an emission control device coupled to the exhaust manifold of the engine may be analyzed to determine that no engine restart request has been made.

[0070] If it is determined that no engine stop request has been made, at 210, the current engine operation may be maintained. Fuel injection and spark may be implemented to continue combustion in the engine cylinders. The throttle opening may be adjusted based on the torque demand. The driveline may be shut down and the engine torque may be transmitted to the wheels via the transmission system, and the gear of the transmission system may not be in a neutral position.

[0071] If it is determined that an engine stop has been requested, at 212, engine operation may be stopped. In one example, engine shutdown includes cutting off or adjusting the fuel supply to the engine and closing the throttle valve. In another example, ignition may also be shut down or adjusted / changed. In yet another example, both fuel supply and ignition may be suspended while keeping the valve at least partially open.

[0072] At 214, the routine includes determining whether an engine restart has been requested due to a change of mind (CoM). CoM can occur during engine deceleration (when the engine speed has not yet decreased to zero) when the operator requests engine torque. Therefore, an engine restart can be requested to meet the torque demand even before the engine is completely shut down.

[0073] If it is determined that no engine restart is requested during the engine shutdown, engine deceleration can be completed. At 216, the engine can remain in a shutdown state without fuel injection.

[0074] During a subsequent engine restart, for example when idle-start conditions are met, engine operation can be restarted by cranking the engine (as previously described in step 206). In one example, engine restart conditions after an engine idle-stop can include an increase in engine load.

[0075] If it is determined that an engine restart has been requested before the engine was stopped (due to the CoM), at 224, the routine includes determining whether the current engine speed (N) is above an upper speed limit (NUL), above which the engine may rotate fast enough to restart it without using a starter motor, a so-called "passive start". The controller may determine the engine speed via a crankshaft position sensor and compare the speed to the upper speed limit (NUL). The upper speed limit (NUL) may be pre-calibrated based on engine characteristics (such as weight).

[0076] If it is determined that the engine speed (N) is higher than the upper speed limit (NUL), at 226, a passive engine start can be achieved. Passive starting technology can utilize the inertia of a rotating part of the engine (such as a flywheel). During the passive start of the engine, at 227, the fuel injection and throttle valve opening can be adjusted to promote engine acceleration. The throttle opening can be increased to provide air to the engine, and the fuel supply to the engine can be turned on or re-enabled. Similarly, the ignition can be restarted. For example, the controller can send a signal to each of the actuators coupled to the throttle valve to increase the valve opening, coupled to one or more fuel injectors to start fuel injection to the engine cylinders, and send a signal to the actuator coupled to the spark plug to start the ignition.

[0077] If it is determined that the engine speed is not higher than the speed upper limit (NUL), the program includes determining whether the engine speed is within the engine speed region suitable for starting the engine using the starter motor. The current engine speed (N) can be compared with a predetermined starting speed upper limit (NUSL) and a starting speed lower limit (NLSL) to determine whether the engine speed is higher than the starting speed lower limit (NLSL) but lower than the starting speed upper limit (NUSL) (NLSL < N < NUSL). In one example, NUL can be approximately 600 RPM and NUSL can be approximately 250 RPM.

[0078] If it is determined that the engine speed is within the engine speed region suitable for starting the engine using the starter motor (e.g., N is less than NUSL but greater than NLSL), the program proceeds as Figure 2B to step 236. If it is determined that the engine speed is not within NLSL and NUSL, the program includes determining whether the engine speed is lower than the starting speed lower limit (NLSL). If it is determined that during deceleration, the engine has decelerated to below NLSL, at 232, the controller can wait for the engine to come to a complete stop (N = 0) before engaging the starter motor. The program can then proceed as Figure 2B to step 236.

[0079] If it is determined that the engine speed is not lower than the starting speed lower limit (NLSL) and it has previously been determined that the engine speed is not lower than the starting speed upper limit (NUSL), it can be inferred that the engine speed is higher than NUSL. In one example, the engine speed can be between the speed upper limit (NUL) and the starting speed upper limit (NUSL). At 234, the controller can wait for the engine speed to drop below the starting speed upper limit (NUSL) before engaging the starter motor. If the starter motor is engaged at a speed higher than NUSL, degradation due to mechanical wear may occur in the starter motor. Once the engine speed decreases to below NUSL, as described in step 236 ( Figure 2B ) the starter motor can be used to start rotating the engine.

[0080] Continue Figure 2B , at 236, the starter motor can be engaged to start rotating the engine. The controller can send a signal to the actuator coupled to the starter motor to start the operation of the starter motor using the energy from the vehicle battery.

[0081] At 238, the engagement state of the manual transmission can be judged via a transmission engagement state sensor (such as the sensor 16 in Figure 1 ). The gear position can be adjusted by the operator using the gear selection mechanism. The gear can be in the neutral position, which indicates an open driveline, or the gear can be in a non-neutral position (such as drive, reverse, etc.) when the driveline is closed.

[0082] At 240, the routine includes determining whether neutral has been selected. If it is determined that neutral has been selected during the engine restart, it can be inferred that the powertrain is on. At 244, a threshold engine speed (also referred to herein as a starter cranking speed limit, SLIM) can be set at a first starter motor disengagement speed limit S1. The controller can use a first mapping of engine speed to engine coolant temperature ( Figure 3 S1 can be determined by the curve line 302 of the graph 300 in FIG. As previously described, S1 can be a function of the engine coolant temperature. The different thresholds described herein can be set by vehicle test development, including calibration operation at appropriate levels, which follows the guidance provided herein regarding the relative relationship between the thresholds.

[0083] If it is determined that neutral has not been selected during the engine restart, it can be inferred that the powertrain is off. At 242, the starting rotation speed limit (SLIM) can be set at the second starter motor disconnect speed limit S2. The controller can use a second map of engine speed to engine coolant temperature ( Figure 3 S2 is determined based on line 304 of graph 300. Similar to S1, S2 may be a function of the engine coolant temperature.

[0084] Thus, the map used to determine SLIM may be selected based on whether an open powertrain state can be confirmed to exist, with a first map being used to confirm a fully open powertrain and a second map being selected if it cannot be determined that the powertrain is fully open.

[0085] The S1 value obtained from the first map for most engine operating temperature conditions is lower than the value S2 obtained from the second map for the same engine temperature operating conditions so that when it is possible to start the vehicle, the starter motor can be allowed to start the engine to a higher rotational speed (N) than when vehicle starting is not expected to occur during the engine starting rotation.

[0086] Therefore, according to the present disclosure, the starting rotation speed limit SLIM may not be a fixed value but may be based on whether the transmission is in the neutral position and a predetermined relationship between the starter motor disengagement speed based on the engine speed and the engine coolant temperature.

[0087] The relationship between the first starter motor disconnection speed limit S1 and the second starter motor disconnection speed limit S2 and the engine coolant temperature (in Figure 3 An example of the relationship is shown in FIG. 1 ) is stored as a map in a memory of the electronic controller.

[0088] With the transmission on, the decision as to when to disengage the starter motor may be based on whether the current engine speed (N) exceeds a starting rotation speed limit (SLIM) based on a first mapping diagram consisting of a first starter motor disengagement speed limit S1 mapped as a function of the engine coolant temperature.

[0089] Without confirming that the transmission is open, the decision as to when to disengage the starter motor can be based on whether the current engine speed (N) exceeds a starting rotation speed limit (SLIM), which is based on a second mapping diagram consisting of a second starter motor disengagement speed limit S2 mapped as a function of the engine coolant temperature.

[0090] This allows a first map to be used for an open powertrain start, where NVH can be fully optimized, and a second map providing a higher start rotation speed limit (SLIM) which can be used at any time when the driver may restart the vehicle with a closed powertrain. The proposed solution thus provides flexibility by calibrating the start rotation speed limit (SLIM) differently for open and unconfirmed open powertrain states.

[0091] At 246, the routine includes determining whether the engine speed is greater than or equal to the start cranking speed limit (SLIM). As described above, SLIM can be set to S1 or S2 based on the gear position. The starter motor can be disengaged based on a comparison between the current engine speed (N) and the start cranking speed limit (SLIM). If it is determined that the engine speed (N) is lower than the set start cranking speed limit (SLIM), at 248, the starter motor can continue to operate to crank the engine.

[0092] If it is determined that the engine speed (N) is equal to or greater than the set cranking speed limit (SLIM), at 250, the engine cranking can be terminated and the starter motor can be disengaged. The controller can send a signal to an actuator coupled to the starter motor to stop the starter motor. In one example, the total cranking time can be 400 milliseconds.

[0093] Therefore, according to the present disclosure, the starting rotation limit (SLIM) may not be a fixed value but may be based on whether it can be determined that the transmission is open, in which case the open state of the transmission is tested by using a transmission engagement state sensor to provide an indication of whether the transmission is confirmed to be in neutral or not confirmed to be in neutral. Generally, the transmission is always open, and when the start is a restart process starting from zero engine speed, (SLIM) may be set to the first starter motor speed limit S1. It should be understood that the present disclosure can be used for any automatic stop situation.

[0094] In this way, in response to a request to restart the engine after an engine idle-stop, the position of the gear can be determined and the engine can be selectively cranked via a starter motor to a threshold cranking engine speed that is adjustable based on the gear position. The request to restart the engine can be made during engine deceleration after an engine idle-stop.

[0095] Figure 4 An example timeline 400 illustrating starter motor operation is shown. The horizontal axis (x-axis) represents time and vertical markers t1-t9 identify significant moments in the sequence of engine operation.

[0096] The first graph, line 402, shows the change of torque demand over time. The torque demand is estimated based on the input from the pedal position sensor. Line 403 identifies the threshold torque demand. If the torque demand remains below the threshold torque demand 403 for longer than the threshold duration, the engine is shut down. The threshold torque demand 403 and the threshold duration are pre-calibrated to improve fuel efficiency. The second graph, line 404, shows the engine speed estimated via the crankshaft position sensor. Line Nul represents the upper engine speed limit, above which the starter motor is not engaged to crank the engine, and the engine is restarted by adjusting the fuel supply and throttle opening (while the engine is still decelerating). Line Nlsl represents the lower engine start speed limit, below which the starter motor is engaged to crank the engine after the engine speed drops to zero. Curve Nusl represents the upper engine start speed limit, and if the engine speed is between Nlsl and Nusl, the starter motor is engaged to crank the engine during the engine restart. S1 represents a first starter motor disengagement speed limit and S2 represents a second starter motor disengagement speed limit. During engine cranking, S1 is the engine speed at which the starter motor is engaged if the transmission is in a neutral position, and S2 is the engine speed at which the starter motor is engaged if the transmission is not in a neutral position. A third graph, line 406, illustrates fuel injection to one or more engine cylinders. A fourth graph, line 408, illustrates a gear position determined via a transmission state sensor. A fifth graph, line 410, illustrates operation of the starter motor.

[0097] Prior to time t1, the engine is spinning by burning fuel and air to meet the torque demand. Since engine cranking is not desired, the starter motor is not engaged. The gear is set to a non-neutral position (such as in drive gear) by the vehicle operator. At time t1, the torque demand drops below the threshold torque demand 403, and correspondingly, the engine speed drops. Furthermore, the operator shifts the gear to a neutral position.

[0098] At time t2, after a threshold duration (the time difference between times t1 and t2) has elapsed since the engine torque started to drop, the engine is shut down. To shut down the engine, at time t2, fuel injection to the engine cylinders is suspended. The engine remains shut down between times t2 and t3.

[0099] At time t3, even before the engine speed has decreased to zero, in response to an increase in torque demand, it is still desired to restart the engine. Since the engine speed is between Nls1 and Nus1 at this moment, the starter motor is engaged by the controller to start the engine. When the gear is in the neutral position, the engine is started to the first starter motor disengagement S1. In addition, the controller sends a signal to the fuel injector to start fuel injection to the engine cylinder.

[0100] At time t4, in response to the engine speed increasing to S1, the controller sends a signal to the actuator coupled to the starter motor to disengage the starter motor. Also, at time t4, the gear is shifted from the neutral position. Between time t4 and time t5, the engine is operated to meet the torque demand.

[0101] At time t5, the torque demand decreases below the threshold torque demand 403, and correspondingly, the engine speed also decreases. At time t6, after a threshold duration has elapsed since the engine torque decrease (the time difference between times t6 and t5 is equal to the time difference between times t2 and t1), the engine is shut down. To shut down the engine, at time t6, fuel injection to the engine cylinders is suspended. The engine remains shut down between times t6 and t7.

[0102] At t7, during engine deceleration, in response to an increase in torque demand, the engine is expected to restart. However, the engine speed at this moment is higher than Nus1 but lower than Nu1. Therefore, the starter motor cannot be engaged by the controller to start the engine. Between t7 and t8, the engine gradually decelerates to Nus1.

[0103] At time t8, in response to the engine speed reaching Nus1, the starter motor is engaged to start the engine. However, at this time, the gear is not in the neutral position. Therefore, the engine is started to the second starter motor disengagement S2. In addition, the controller sends a signal to the fuel injector to start fuel injection to the engine cylinder.

[0104] At time t9, in response to the engine speed increasing to S9, the controller sends a signal to the actuator coupled to the starter motor to disengage the starter motor. After time t9, the engine runs (without assistance from the starter motor) to provide the required torque.

[0105] In this way, by adjusting the threshold engine speed for engine cranking during engine deceleration based on gear position, engine deceleration time can be improved. A technical effect of using different starter motor disengagement speeds is that noise, vibration and harshness (NVH) during engine restart can be reduced. Overall, by adjusting different engine restart speeds based on engine temperature and gear ratio, engine restart can be improved and starter motor degradation can be mitigated.

[0106] It should be understood that other techniques may be used to determine whether the driveline is fully open, such as a transmission torque sensor or a clutch engagement state sensor associated with a friction clutch connecting the engine to the gearbox. It should also be understood that the present disclosure can also be used for a clutched automatic transmission, where the main drive clutch is not necessarily fully disengaged when the start is initiated.

[0107] It will be understood by those skilled in the art that, although the present disclosure has been described in the form of examples with reference to one or more embodiments, it is not limited to the disclosed embodiments and that one or more variations or alternative embodiments of the disclosed embodiments can be constructed without departing from the scope of the invention as defined by the appended claims.

[0108] An example method for controlling a starter motor of a powertrain having an engine and a transmission including a gearbox driven by the engine via a friction clutch, the method comprising: when a request to use the starter motor to restart the engine is made after a change of mind during an automatic engine stop, using the starter motor to crank the engine and disengaging the starter motor when a cranking speed limit is reached, wherein the cranking speed limit is based on confirming whether the powertrain is fully open. In any of the foregoing examples, additionally or alternatively, the cranking speed limit is a first cranking speed limit when the powertrain is confirmed to be fully open, and wherein the cranking speed limit is a second cranking speed limit when the powertrain is not confirmed to be fully open. In any or all of the foregoing examples, the method further comprises, additionally or alternatively, determining a state of the powertrain and, in response to the state of the powertrain being fully open, setting the cranking speed limit to a first cranking speed limit, and in response to the state of the powertrain being not open, setting the cranking speed limit to a second cranking speed limit. In any or all of the foregoing examples, additionally or alternatively, determining the state of the transmission includes determining whether the transmission is in a neutral position via a transmission engagement state sensor. In any or all of the foregoing examples, additionally or alternatively, in response to the transmission being in the neutral position, the state of the transmission is determined to be fully open, and in response to the transmission not being in the neutral position, the state of the transmission is determined to be not open. In any or all of the foregoing examples, additionally or alternatively, each of the first start-up rotation speed limit and the second start-up rotation speed limit is based on each of an engine speed and an engine temperature. In any or all of the foregoing examples, additionally or alternatively, the second start-up rotation speed limit is higher than the first start-up rotation speed limit when the engine temperature is higher than a threshold temperature.

[0109] Another example method of an engine includes: in response to a request to restart the engine after an engine idle-stop, determining the position of the gear, and selectively cranking the engine via a starter motor to a threshold cranking engine speed, the threshold cranking engine speed being adjusted based on the position of the gear. In any of the foregoing examples, additionally or alternatively, the request to restart the engine is during engine deceleration. In any or all of the foregoing examples, additionally or alternatively, selectively cranking the engine includes deactivating the starter motor in response to the engine speed increasing to a threshold cranking speed. In any or all of the foregoing examples, additionally or alternatively, the threshold cranking speed is a first cranking speed when the gear is in a neutral position, and wherein the threshold cranking speed is a second cranking speed when the gear position is not in a neutral position. In any or all of the foregoing examples, additionally or alternatively, the second threshold cranking speed is higher than the first cranking speed. In any or all of the foregoing examples, additionally or alternatively, each of the first threshold cranking speed and the second threshold cranking speed is a function of the engine coolant temperature. In any or all of the foregoing examples, additionally or alternatively, selectively cranking the engine includes, in response to receiving a request to restart the engine before engine deceleration, cranking the engine via a starter motor when the engine speed is between a first threshold engine speed and a second threshold engine speed, the second threshold engine speed being higher than the first threshold engine speed. In any or all of the foregoing examples, the method further includes, additionally or alternatively, in response to the engine speed being lower than the first threshold engine speed, cranking the engine via a starter motor after engine deceleration is complete. In any or all of the foregoing examples, the method further includes, additionally or alternatively, in response to the engine speed being higher than a third threshold engine speed, increasing the throttle opening without cranking the engine via a starter motor, the third threshold engine speed being higher than the second threshold engine speed, and in response to the engine speed being lower than the third threshold engine speed and higher than the second threshold engine speed, cranking the engine via a starter motor as soon as the engine speed drops to the second threshold engine speed.

[0110] In yet another example, a vehicle system includes: an engine, a transmission system, and a controller with computer readable instructions stored in a non-transitory memory, the instructions being used to: in response to an engine restart request during engine deceleration, in a first condition, crank the engine via a starter motor until the engine speed increases to a first cranking speed, in a second condition, crank the engine via a starter motor until the engine speed increases to a second cranking speed, in a third condition, crank the engine via a starter motor until the engine speed increases to a third cranking speed, and in a fourth condition, crank the engine via a starter motor until the engine speed increases to a fourth cranking speed, the fourth cranking speed being higher than each of the third cranking speed, the second cranking speed, and the first cranking speed. In any of the foregoing examples, additionally or alternatively, the first condition includes each of a first engine temperature and a neutral position of a gear of the transmission system, and wherein the second condition includes each of the first engine temperature and a non-neutral position of the gear, the neutral position of the gear being determined via a gear position sensor coupled to a gearbox of the transmission system. In any or all of the foregoing examples, additionally or alternatively, the third condition includes each of a second engine temperature and a neutral position of a gear, and wherein the fourth condition includes each of the second engine temperature and a non-neutral position of a gear, the first engine temperature being higher than the second engine temperature. In any or all of the foregoing examples, additionally or alternatively, the third starting rotational speed is lower than the fourth starting rotational speed and higher than each of the second starting rotational speed and the first starting rotational speed, and wherein the second starting rotational speed is lower than the third starting rotational speed and higher than the first starting rotational speed.

[0111] Note that the example control and estimation procedures included herein can be used in conjunction with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system that includes a controller combined with various sensors, actuators, and other engine hardware. The specific procedures described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. Similarly, the various actions, operations, and / or functions illustrated can be executed in the order illustrated, executed in parallel, or omitted in some cases. Similarly, the processing order is not required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the illustrated actions, operations, and / or functions can be repeatedly performed. In addition, the described actions, operations, and / or functions can graphically represent the code in the non-transitory memory of a computer-readable storage medium programmed into the engine control system, wherein the described actions are implemented by executing instructions in a system including different engine hardware components combined with an electronic controller.

[0112] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting as many variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4 cylinders, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0113] The following claims specifically point out certain combinations and subcombinations deemed novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. These claims should be understood to include combinations of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, equal to, or different in scope from the original claims, are also deemed to be included in the subject matter of the present disclosure.

Claims

1. A method for controlling a starter motor of a powertrain system having an engine and a transmission including a gearbox driven by the engine via a friction clutch, the method comprising: when it is necessary to use the starter motor to restart the engine after changing one's mind during an automatic engine stop process, using the starter motor to start the engine and disengaging the starter motor when a starting rotation speed limit is reached, wherein the starting rotation speed limit is based on whether the powertrain is confirmed to be fully open.

2. The method of claim 1, wherein the starting rotation speed limit is a first starting rotation speed limit when the transmission system is confirmed to be fully open, and wherein the starting rotation speed limit is a second starting rotation speed limit when the transmission system is not confirmed to be fully open.

3. The method according to claim 2 further comprises: determining the state of the transmission system and, in response to the state of the transmission system being fully open, setting the starting rotation speed limit to the first starting rotation speed limit, and in response to the state of the transmission system being not open, setting the starting rotation speed limit to the second starting rotation speed limit. 4 . The method of claim 3 , wherein determining the state of the powertrain comprises determining whether a transmission is in neutral via a transmission engagement state sensor.

5. The method of claim 4, wherein the state of the powertrain is determined to be fully open in response to the transmission being in a neutral position, and the state of the powertrain is determined to be not open in response to the transmission not being in the neutral position. 6 . The method of claim 2 , wherein each of the first cranking speed limit and the second cranking speed limit is based on each of an engine speed and an engine temperature. 7 . The method of claim 2 , wherein the second startup cranking speed limit is higher than the first startup cranking speed limit when the engine temperature is above a threshold temperature.

8. A method for an engine, comprising: In response to a request to restart the engine after initiating an engine idle stop, Determine the position of the gears in the transmission system, and The engine is selectively cranked via a starter motor to a threshold cranking engine speed, the threshold cranking engine speed being adjusted based on the position of the gear.

9. The method of claim 8, wherein the request to restart the engine is during engine deceleration.

10. The method of claim 8, wherein selectively cranking the engine comprises: The starter motor is deactivated in response to the engine speed increasing to the threshold cranking engine speed.

11. The method of claim 8, wherein the threshold cranking engine speed is a first cranking speed when the position of the gear is neutral, and wherein the threshold cranking engine speed is a second cranking speed when the position of the gear is non-neutral.

12. The method of claim 11, wherein the second starting rotational speed is higher than the first starting rotational speed.

13. The method of claim 11, wherein each of the first starting rotational speed and the second starting rotational speed is a function of engine coolant temperature.

14. The method of claim 8, wherein selectively cranking the engine comprises: In response to receiving a request to restart the engine before engine deceleration, the engine is cranked via the starter motor when the engine speed is between a first threshold engine speed and a second threshold engine speed, the second threshold engine speed being higher than the first threshold engine speed.

15. The method of claim 14, further comprising, in response to the engine speed being less than the first threshold engine speed, cranking the engine via the starter motor after engine deceleration is complete.

16. The method according to claim 15 further comprises: in response to the engine speed being higher than a third threshold engine speed, increasing the throttle opening without starting the engine via the starter motor, the third threshold engine speed being higher than the second threshold engine speed, and in response to the engine speed being lower than the third threshold engine speed and higher than the second threshold engine speed, starting the engine via the starter motor as soon as the engine speed drops to the second threshold engine speed.

17. A vehicle system comprising: engine; Transmission systems; and A controller with computer readable instructions stored in a non-transitory memory, the instructions for: In response to an engine restart request during engine deceleration, Under the first condition, the engine is cranked via the starter motor until the engine speed increases to a first cranking speed, Under the second condition, the engine is started by the starter motor until the engine speed increases to a second starting speed. Under a third condition, the engine is cranked via the starter motor until the engine speed increases to a third cranking speed, and Under a fourth condition, the engine is cranked via the starter motor until the engine speed increases to a fourth cranking speed that is higher than each of the third cranking speed, the second cranking speed, and the first cranking speed.

18. The system of claim 17, wherein the first condition includes each of a first engine temperature and a neutral position of a gear of the transmission system, and wherein the second condition includes each of the first engine temperature and a non-neutral position of the gear, the neutral position of the gear being determined via a gear position sensor coupled to a gearbox of the transmission system, wherein the engine is operated under each of the first, second, third and fourth conditions.

19. The system of claim 18, wherein the third condition includes a second engine temperature and each of the neutral positions of the gears, and wherein the fourth condition includes the second engine temperature and each of the non-neutral positions of the gears, the first engine temperature being higher than the second engine temperature.

20. The system of claim 17, wherein the third starting rotational speed is lower than the fourth starting rotational speed and higher than each of the second starting rotational speed and the first starting rotational speed, and wherein the second starting rotational speed is lower than the third starting rotational speed and higher than the first starting rotational speed.

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