Method and system for detecting engine stall

Abstract

The present disclosure provides "Methods and systems for detecting engine stall". Systems and methods for operating a hybrid powertrain are described, the hybrid powertrain including an engine and a motor / generator. The systems and methods provide a way to determine whether the engine has stalled when the vehicle can be propelled via the motor / generator. In one example, an engine stall can be indicated in response to a first estimated engine torque and a second estimated engine torque.

Description

Technical Field

[0001] This specification relates to methods and systems for operating a powertrain of a hybrid vehicle. The methods and systems may be particularly useful for hybrid vehicles including a torque converter and a driveline disconnect clutch.

[0002] Background Art and Summary of the Invention

[0003] Sometimes, the engine of a hybrid vehicle may stall during engine start-up. Engine stalling may be attributed to poor air-fuel mixture preparation, fuel properties, or other engine operating conditions during engine start-up. One way to determine whether the engine has stalled during engine start-up is to monitor the engine speed. If the engine speed drops below a threshold speed, it can be determined that the engine has stalled and the engine can be restarted. However, if the engine is coupled to an electric motor that propels the vehicle, the electric motor can cause the engine to rotate such that engine stalling may not be detected by monitoring only the engine speed. For example, the engine can be started by closing a driveline disconnect clutch that connects the engine to the electric motor that propels the vehicle. When the torque provided by the electric motor accelerates the engine to the speed of the electric motor, the engine may stall. Due to the torque provided by the electric motor, the engine speed may continue to increase. Thus, the engine speed may not indicate an engine stalling condition. However, the amount of energy consumed by the electric motor can be increased without performing useful work to maintain the engine speed. Therefore, it may be desirable to provide a way to determine whether the engine has stalled when the engine is coupled to an electric motor that propels the vehicle.

[0004] The inventors herein have recognized the above-mentioned problems and have developed a vehicle operation method that includes: indicating engine stall when a first engine torque is less than a second engine torque in response to a request to determine the presence or absence of engine stall, the first engine torque being based on torque converter impeller torque and motor torque; and disconnecting the driveline disconnect clutch in response to indicating engine stall.

[0005] By indicating an engine stalling condition in response to the first engine torque being less than the second engine torque, it is possible to determine an engine stalling condition when the engine speed may not indicate an engine stalling condition. For example, if an attempt is made to start the engine with torque generated by an electric motor that propels the vehicle, it can be determined that the engine has stalled even if the engine speed may be increasing. In one example, engine stall can be based on comparing an estimated first engine torque with a second torque estimate. Thus, an engine stalling condition can be determined independently of the engine speed. If an engine stalling condition is indicated, mitigation measures can be taken via the engine controller.

[0006] This specification can provide several advantages. In particular, even if the engine rotates at the same speed as the electric motor that propels the vehicle, the method can determine whether the engine has stalled. Additionally, the method can operate without the need for additional engine sensors or actuators. Moreover, if an engine stall occurs, the method can reduce energy consumption.

[0007] When viewed alone or in conjunction with the drawings, the above and other advantages and features of this specification will be readily apparent from the following detailed description.

[0008] It should be understood that the above summary is provided to introduce in a simplified form selected concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The advantages described herein will be more fully understood by reading examples of embodiments referred to herein as the detailed description, when viewed alone or in reference to the drawings, in which:

[0010] Figure 1 is a schematic diagram of an engine.

[0011] Figure 2 is a schematic diagram of a hybrid vehicle powertrain.

[0012] Figure 3 is a graph showing an example vehicle operation sequence.

[0013] Figure 4 shows an example flowchart of a method of operating a vehicle. DETAILED DESCRIPTION

[0014] This specification relates to determining whether an engine stall occurs after an attempt to start the engine. The engine start can be attempted when the vehicle in which the engine is located is stationary or moving. The engine can be Figure 1 of the type shown, or alternatively, the engine can be a diesel engine. The engine and the electric motor can be incorporated into a powertrain such as Figure 2 shown. The engine and the electric motor can be operated according to Figure 3 the method shown in Figure 4 . Figure 4 The method of Figure 1 can be incorporated into Figure 2 and

[0015] systems. Figure 1, an internal combustion engine 10 is controlled by an electronic engine controller 12, the internal combustion engine 10 including a plurality of cylinders, one of which is shown in Figure 1 . The engine 10 includes a cylinder head 35 and a cylinder block 33, the cylinder head 35 and the cylinder block 33 including a combustion chamber 30 and a cylinder wall 32. A piston 36 is positioned within the combustion chamber and reciprocates via a connection coupled to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. A starter 96 (e.g., a low voltage (operating at less than 30 volts) electric motor) includes a pinion shaft 98 and a pinion 95. The pinion shaft 98 can selectively advance the pinion 95 to engage the ring gear 99. The starter 96 can be directly mounted to the front or the rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a belt or a chain. In one example, the starter 96 is in a basic state when not engaged to the engine crankshaft. The combustion chamber 30 is shown as being in communication with an intake manifold 44 and an exhaust manifold 48 via respective intake valves 52 and exhaust valves 54. Each intake valve and exhaust valve can be operated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57. The intake valves 52 can be selectively activated and deactivated by a valve activation device 59. The exhaust valves 54 can be selectively activated and deactivated by a valve activation device 58. The valve activation devices 58 and 59 can be electromechanical devices.

[0016] A fuel injector 66 is shown as being positioned to inject fuel directly into the cylinder 30, which is known to those skilled in the art as direct injection. The fuel injector 66 delivers liquid fuel in proportion to a pulse width from the controller 12. Fuel is delivered to the fuel injector 66 via a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail (not shown). In one example, a high pressure dual stage fuel system can be used to generate a higher fuel pressure.

[0017] In addition, the intake manifold 44 is shown as being in communication with the turbocharger compressor 162 and the engine intake port 42. In other examples, the compressor 162 can be a supercharger compressor. The shaft 161 mechanically couples the turbocharger turbine 164 to the turbocharger compressor 162. The optional electronic throttle 62 adjusts the position of the throttle plate 64 to control the airflow from the compressor 162 to the intake manifold 44. The pressure in the plenum chamber 45 can be referred to as the throttle inlet pressure because the inlet of the throttle 62 is within the plenum chamber 45. The throttle outlet is within the intake manifold 44. In some examples, the throttle 62 and the throttle plate 64 can be positioned between the intake valve 52 and the intake manifold 44 such that the throttle 62 is an intake passage throttle. The compressor recirculation valve 47 can be selectively adjusted to multiple positions between fully open and fully closed. The wastegate 163 can be adjusted via the controller 12 to allow the exhaust gas to selectively bypass the turbine 164 to control the speed of the compressor 162. The air cleaner 43 cleans the air entering the engine intake port 42.

[0018] The distributorless ignition system 88 provides an ignition spark to the combustion chamber 30 via the spark plug 92 in response to the controller 12. The universal exhaust gas oxygen (UEGO) sensor 126 is shown as being coupled to the exhaust manifold 48 upstream of the catalytic converter 70. Alternatively, a two-state exhaust gas oxygen sensor can replace the UEGO sensor 126.

[0019] In one example, the converter 70 can include multiple catalyst bricks. In another example, multiple emission control devices each having multiple bricks can be used. In one example, the converter 70 can be a three-way type catalyst.

[0020] The controller 12 is in Figure 1shown as a conventional microcomputer, the microcomputer including: a microprocessor unit 102, an input / output port 104, a read-only memory 106 (e.g., non-transitory memory), a random access memory 108, a keep-alive memory 110, and a conventional data bus. In addition to the signals discussed previously, the controller 12 is also shown as receiving various signals from sensors coupled to the engine 10, including: engine coolant temperature (ECT) from a temperature sensor 112 coupled to the coolant jacket 114; a position sensor 134 coupled to the accelerator pedal 130 for sensing the force applied by a human foot 132; a position sensor 154 coupled to the brake pedal 150 for sensing the force applied by the foot 152; a measurement of the engine manifold pressure (MAP) from a pressure sensor 122 coupled to the intake manifold 44; an engine position sensor from a Hall effect sensor 118 sensing the position of the crankshaft 40; a measurement of the air mass entering the engine from a sensor 120; and a measurement of the throttle position from a sensor 68. Atmospheric pressure (sensor not shown) may also be sensed for processing by the controller 12. In a preferred aspect of the present specification, the engine position sensor 118 generates a predetermined number of equally spaced pulses during each revolution of the crankshaft, whereby the engine speed (RPM) can be determined.

[0021] During operation, each cylinder within the engine 10 typically undergoes a four-stroke cycle: the cycle including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, typically, the exhaust valve 54 is closed and the intake valve 52 is open. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves to the bottom of the cylinder in order to increase the volume within the combustion chamber 30. The position where the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its maximum volume) is typically referred to by those skilled in the art as bottom dead center (BDC).

[0022] During the compression stroke, both the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head in order to compress the air within the combustion chamber 30. The point where the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 is at its minimum volume) is typically referred to by those skilled in the art as top dead center (TDC). During a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. During a process hereinafter referred to as ignition, the injected fuel is ignited by a known ignition device such as a spark plug 92, thereby causing combustion.

[0023] During the expansion stroke, the expanding gas pushes the piston 36 back to BDC. The crankshaft 40 converts the piston motion into rotational torque of the rotating shaft. Eventually, during the exhaust stroke, the exhaust valve 54 opens to release the burned air-fuel mixture into the exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is shown only as an example, and the intake and exhaust valve opening and / or closing timings can vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0024] Figure 2 is a block diagram of a vehicle 225 including a powertrain or driveline 200. Figure 2 The powertrain of Figure 1 includes the engine 10 shown. The powertrain 200 is shown as including a vehicle system controller 255, an engine controller 12, a motor controller 252, a transmission controller 254, an energy storage device controller 253, and a brake controller 250. The controllers can communicate via a Controller Area Network (CAN) 299. Each of the controllers can provide information to the other controllers, such as torque output limits (e.g., the torque output of a controlled device or component that will not be exceeded), torque input limits (e.g., the torque input of a controlled device or component that will not be exceeded), sensor and actuator data, diagnostic information (e.g., information about a degraded transmission, information about a degraded engine, information about a degraded motor, information about a degraded brake). Additionally, the vehicle system controller can provide commands to the engine controller 12, the motor controller 252, the transmission controller 254, and the brake controller 250 to implement driver input requests and other requests based on vehicle operating conditions. Status information can be provided to the driver via a human / machine interface 256 (e.g., a keyboard and a display).

[0025] For example, in response to the driver releasing the accelerator pedal and vehicle speed, the vehicle system controller 255 can request a desired wheel torque or wheel power level to provide a desired vehicle deceleration rate. The desired wheel torque can be provided by the vehicle system controller 255, which requests a first braking torque from the motor controller 252 and a second braking torque from the brake controller 250, the first torque and the second torque providing the desired braking torque at the wheel 216.

[0026] In other examples, the powertrain control devices can be divided differently than Figure 2 shown. For example, a single controller can replace the vehicle system controller 255, the engine controller 12, the motor controller 252, the transmission controller 254, and the brake controller 250.

[0027] In this example, the powertrain 200 can be powered by the engine 10 and the electric machine 240. The engine 10 can be started with the Figure 1 engine starting system shown or via an integrated starter / generator (ISG) 240. The ISG 240 (e.g., a high voltage (operating at greater than 30 volts) electric machine) can also be referred to as an electric machine, a motor, and / or a generator. Additionally, the torque of the engine 10 can be adjusted via torque actuators 204 such as fuel injectors, throttle valves, etc.

[0028] The engine output torque can be transmitted through the dual mass flywheel 215 to the input side or the first side of the powertrain disconnect clutch 235. The disconnect clutch 236 can be electrically actuated or hydraulically actuated. The downstream side or the second side 234 of the disconnect clutch 236 is shown to be mechanically coupled to the ISG input shaft 237.

[0029] The ISG 240 can be operated to provide torque to the powertrain 200 or to convert powertrain torque into electrical energy in a regenerative mode for storage in the electrical energy storage device 275. The ISG 240 has a higher output torque capacity than the Figure 1 starter 96 shown. Additionally, the ISG 240 directly drives the powertrain 200 or is directly driven by the powertrain 200. There are no belts, gears, or chains to couple the ISG 240 to the powertrain 200. Instead, the ISG 240 rotates at the same rate as the powertrain 200. The electrical energy storage device 275 (e.g., a high voltage battery or power source) can be a battery, a capacitor, or an inductor. The downstream side of the ISG 240 is mechanically coupled to the impeller 285 of the torque converter 206 via the shaft 241. The speed sensor 273 senses the torque converter impeller speed. The upstream side of the ISG 240 is mechanically coupled to the disconnect clutch 236. The ISG 240 can provide positive or negative torque to the powertrain 200 by operating as a motor or a generator as indicated by the motor controller 252.

[0030] The torque converter 206 includes a turbine 286 to output torque to the input shaft 270. The input shaft 270 mechanically couples the torque converter 206 to the automatic transmission 208. The torque converter 206 also includes a torque converter bypass lock-up clutch 212 (TCC). When the TCC is locked, torque is directly transmitted from the impeller 285 to the turbine 286. The TCC is electrically operated by the controller 12. Alternatively, the TCC can be hydraulically locked. In one example, the torque converter can be referred to as a component of the transmission.

[0031] When the torque converter lock-up clutch 212 is fully disengaged, the torque converter 206 transmits engine torque to the automatic transmission 208 via fluid transfer between the torque converter turbine 286 and the torque converter pump impeller 285, thereby achieving torque multiplication. In contrast, when the torque converter lock-up clutch 212 is fully engaged, the engine output torque is directly transmitted to the input shaft (not shown) of the transmission 208 via the torque converter clutch. Alternatively, the torque converter lock-up clutch 212 can be partially engaged, such that the amount of torque directly transmitted to the transmission can be adjusted. The controller 12 can be configured to adjust the amount of torque transmitted by the torque converter 212 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or based on a driver's engine operation request.

[0032] The automatic transmission 208 includes gear clutches (e.g., gears 1-10) 211 and a forward clutch 210. The automatic transmission 208 is a fixed-ratio transmission. The gear clutches 211 and the forward clutch 210 can be selectively engaged to change the ratio of the actual total revolutions of the input shaft 270 to the actual total revolutions of the wheels 216. The gear clutches 211 can be engaged or disengaged by adjusting the fluid supplied to the clutches via shift control solenoids 209. The torque output from the automatic transmission 208 can also be transmitted to the wheels 216 to propel the vehicle via the output shaft 260. In particular, prior to transmitting the output drive torque to the wheels 216, the automatic transmission 208 can transmit the input drive torque to the input shaft 270 in response to vehicle driving conditions. The transmission controller 254 selectively activates or engages the TCC 212, the gear clutches 211, and the forward clutch 210. The transmission controller also selectively deactivates or disengages the TCC 212, the gear clutches 211, and the forward clutch 210.

[0033] Additionally, frictional force can be applied to the wheels 216 by engaging the wheel brakes 218. In one example, the wheel brakes 218 can be engaged in response to the driver depressing his foot on the brake pedal (not shown) and / or in response to an instruction within the brake controller 250. Additionally, the brake controller 250 can apply the brakes 218 in response to information and / or requests issued by the vehicle system controller 255. In the same manner, the frictional force applied to the wheels 216 can be reduced by disengaging the wheel brakes 218 in response to the driver releasing his foot from the brake pedal, brake controller instructions, and / or vehicle system controller instructions and / or information. For example, as part of an automated engine stop procedure, the vehicle brakes can apply frictional force to the wheels 216 via the controller 250.

[0034] In response to a request to accelerate vehicle 225, the vehicle system controller may obtain a driver demand torque or power request from an accelerator pedal or other device. The vehicle system controller 255 then allocates a portion of the requested driver demand torque to the engine and the remainder to the ISG. The vehicle system controller 255 requests engine torque from the engine controller 12 and ISG torque from the motor controller 252. If the ISG torque plus the engine torque is less than the transmission input torque limit (e.g., a threshold that is not to be exceeded), the torque is delivered to the torque converter 206, which then transmits at least a portion of the requested torque to the transmission input shaft 270. In response to shift and TCC lockup schedules that may be based on input shaft torque and vehicle speed, the transmission controller 254 selectively locks the torque converter clutch 212 and engages gears via the gear clutch 211. In some cases where it may be desirable to charge the electrical energy storage device 275, a charging torque (e.g., negative ISG torque) may be requested when there is non-zero driver demand torque. The vehicle system controller 255 may request increased engine torque to overcome the charging torque to meet the driver demand torque.

[0035] In response to a request to decelerate vehicle 225 and provide regenerative braking, the vehicle system controller may provide the required negative wheel torque based on vehicle speed and brake pedal position. The vehicle system controller 255 then allocates a portion of the required negative wheel torque to the ISG 240 (e.g., the required powertrain wheel torque) and the remainder to the friction brake 218 (e.g., the required friction brake wheel torque). Additionally, the vehicle system controller may notify the transmission controller 254 that the vehicle is in regenerative braking mode, such that the transmission controller 254 shifts the gears 211 based on a unique shift schedule to improve regenerative efficiency. The ISG 240 supplies negative torque to the transmission input shaft 270, but the negative torque provided by the ISG 240 may be limited by the transmission controller 254 to an output transmission input shaft negative torque limit (e.g., a threshold that is not to be exceeded). Additionally, the negative torque of the ISG 240 may be limited (e.g., constrained to be less than a threshold negative threshold torque) by the vehicle system controller 255 or the motor controller 252 based on the operating condition of the electrical energy storage device 275. Any portion of the required negative wheel torque that cannot be provided by the ISG 240 due to transmission or ISG limits may be allocated to the friction brake 218, such that the required wheel torque is provided by a combination of negative wheel torque from the friction brake 218 and the ISG 240.

[0036] Accordingly, torque control of various powertrain components can be supervised by the vehicle system controller 255, where local torque control of the engine 10, transmission 208, electric machine 240, and brakes 218 is provided via the engine controller 12, electric machine controller 252, transmission controller 254, and brake controller 250, respectively.

[0037] As an example, engine torque output can be controlled by controlling throttle opening and / or valve timing, valve lift, and supercharging for turbocharged or supercharged engines, by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and / or air charge. In the case of a diesel engine, the controller 12 can control engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge. In all cases, engine control can be performed on a cylinder-by-cylinder basis to control engine torque output.

[0038] The electric machine controller 252 can control torque output and electrical energy generation from the ISG 240 by adjusting the current flowing to and from the field winding and / or armature winding of the ISG, as is known in the art.

[0039] The transmission controller 254 receives transmission input shaft position or torque converter turbine speed via the position sensor 271. The transmission controller 254 can convert the transmission input shaft position to input shaft speed by differentiating the signal from the position sensor 271 or by counting the number of known angular displacement pulses over a predetermined time interval. The transmission controller 254 can receive transmission output shaft torque from the torque sensor 272. Alternatively, the sensor 272 can be a position sensor or a torque and position sensor. If the sensor 272 is a position sensor, the controller 254 can count the shaft position pulses over a predetermined time interval to determine the transmission output shaft speed. The transmission controller 254 can also differentiate the transmission output shaft speed to determine the transmission output shaft acceleration.

[0040] The brake controller 250 receives wheel speed information via the wheel speed sensors 221 and receives a brake request from the vehicle system controller 255. The brake controller 250 can also receive directly or via CAN 299 from Figure 1The illustrated brake pedal sensor 154 receives brake pedal position information. The brake controller 250 can provide braking in response to a wheel torque command from the vehicle system controller 255. The brake controller 250 can also provide anti-skid and vehicle stability braking to improve vehicle braking and stability. Thus, the brake controller 250 can provide a wheel torque limit (e.g., a threshold negative wheel torque that is not to be exceeded) to the vehicle system controller 255 such that negative ISG torque does not cause the wheel torque limit to be exceeded. For example, if the controller 250 issues a negative wheel torque limit of 50 Nm, the ISG torque is adjusted to provide less than 50 Nm (e.g., 49 Nm) of negative torque at the wheel, which includes consideration of the transmission gearing.

[0041] Thus, Figure 1 and Figure 2 The system of provides a vehicle system that includes: an electric motor; an engine; a driveline disconnect clutch that is mechanically coupled to the engine and the electric motor; and one or more controllers that include executable instructions stored in a non-transitory memory for indicating an engine stall in response to a first engine torque being less than a second engine torque, the first engine torque being based on a torque converter impeller torque and a torque of the electric motor, the second engine torque being based on engine operating conditions. The system includes where the engine operating conditions are engine air flow and engine fuel flow. The system further includes additional instructions for incrementing a counter in response to the first engine torque being less than the second engine torque. The system further includes additional instructions for indicating an engine stall in response to a value of the counter exceeding a threshold. The system further includes additional instructions for stopping the incrementing of the value of the counter in response to the torque converter clutch being locked. The system further includes additional instructions for automatically restarting the engine in response to an engine stall indication.

[0042] Now referring to Figure 3 , an example vehicle operation sequence is shown. Figure 3 The vehicle operation sequence of can be provided via Figure 1 and Figure 2 The system of according to Figure 4 The method of. Figure 3 The graphs of are time-aligned and they occur simultaneously. The vertical lines at times t0 - t7 represent times of interest in the sequence.

[0043] From Figure 3The first graph at the top is a graph of the powertrain disengaging clutch operating state versus time. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph. The vertical axis represents the powertrain disengaging clutch operating state, and when the trace 302 is at a lower level near the horizontal axis, the powertrain disengaging clutch is disengaged and does not transmit torque. When the trace 302 is at a higher level near the vertical axis arrow, the powertrain disengaging clutch is engaged. The trace 302 represents the powertrain disengaging clutch operating state.

[0044] from Figure 3 The second graph at the top is a graph of the engine torque estimated from the torque converter model versus time. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph. The vertical axis represents the engine torque estimated from the torque converter model, and the engine torque increases in the direction of the vertical axis arrow. The trace 304 represents the engine torque.

[0045] from Figure 3 The third graph at the top is a graph of the engine torque estimated from the engine condition versus time. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph. The vertical axis represents the engine torque estimated from the engine condition, and the engine torque increases in the direction of the vertical axis arrow. The trace 306 represents the engine torque.

[0046] from Figure 3 The fourth graph at the top is a graph of the count of the engine stall counter versus time. The vertical axis represents the value of the engine stall counter, and the value of the engine stall counter increases in the direction of the vertical axis arrow. The trace 308 represents the value stored in the engine stall counter. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph.

[0047] from Figure 3 The fifth graph at the top is a graph of the torque converter clutch (TCC) operating state versus time. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph. The vertical axis represents the TCC state, and when the trace 310 is at a higher level near the vertical axis arrow, the TCC is engaged and locked. The trace 310 represents the TCC state. When the trace 310 is at a lower level near the horizontal axis, the TCC is disengaged.

[0048] from Figure 3The sixth graph at the top is a graph of engine stall indication status versus time. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph. The vertical axis represents the engine stall indication status, and the engine stall indication is asserted or enabled when the trace 312 is at a higher level near the vertical axis arrow. When the trace 312 is at a low level near the horizontal axis, the engine stall indication is not asserted. The trace 312 represents the engine stall indication status.

[0049] from Figure 3 The seventh graph at the top is a graph of engine stall diagnosis status versus time. The horizontal axis represents time, and time increases from the left side of the graph toward the right side of the graph. The vertical axis represents the engine stall diagnosis status, and the engine stall diagnosis is asserted or enabled when the trace 314 is at a higher level near the vertical axis arrow. When the trace 314 is at a low level near the horizontal axis, the engine stall diagnosis is not asserted. When the trace 314 is at a higher level, the engine stall diagnosis is activated. The trace 314 represents the engine stall diagnosis status.

[0050] At time t0, the driveline disconnect clutch is disengaged, separating the engine from the electric motor. The engine torque estimated from the torque converter is zero, and the engine torque estimated from the engine condition is zero, indicating that the engine is not running (e.g., burning air and fuel). The engine stall counter value is zero, and the TCC is closed. The engine stall indication is not asserted and the engine stall diagnosis is not activated. Such a condition can indicate when the electric motor is propelling the vehicle and when the engine is stopped to save fuel.

[0051] Between time t0 and time t1, the TCC is disengaged. The TCC can disengage in response to a request to start the engine or in response to other vehicle operating conditions such as an increase in driver demand torque. The remaining operating conditions remain at their previous levels.

[0052] At time t1, the driveline disconnect clutch is engaged to rotate the engine using torque from the electric motor. Additionally, an attempt is made to start the engine and the engine speed accelerates toward the electric motor speed (not shown). The engine starts and the engine torque estimated from the torque converter model is zero because the diagnosis is not activated. Since the diagnosis is not activated, the engine torque estimated from the engine condition is also zero. However, in other examples, the engine torque estimate based on the engine condition can continue to be determined. The TCC remains disengaged, and no engine stall is indicated.

[0053] Between time t1 and time t2, the engine stall diagnosis is activated and no engine stall is indicated. In response to the engine diagnosis being activated, the engine torque estimated from the torque converter model increases. In response to the engine stall diagnosis being activated, the engine torque estimated from the engine condition also increases. The driveline disconnect clutch remains closed and the TCC status remains open. Since the engine torque estimated from the torque converter model is not less than the engine torque estimated from the engine condition, the engine stall counter value remains zero.

[0054] At time t2, the TCC closes in response to the vehicle operating condition. The engine stall diagnosis ends in response to the TCC closing. No engine stall is indicated and the engine stall counter value remains zero. The engine torque estimated from the torque converter model transitions to zero, and the engine torque estimated from the engine condition transitions to zero. The driveline disconnect clutch remains closed.

[0055] At time t3, the TCC disconnects for the second time in response to the vehicle condition. In response to the TCC disconnecting, the engine stall diagnosis is activated shortly after time t3. No engine stall is indicated and the engine stall counter value remains zero. In response to the engine stall diagnosis being activated, the engine torque estimated from the torque converter model increases together with the engine torque estimated from the engine condition. The driveline disconnect clutch remains closed.

[0056] At time t4, the driveline disconnect clutch disconnects to separate the engine from the motor. The TCC remains open and the engine stall counter value remains zero. The engine torque estimated from the torque converter model is zero, and the engine torque estimated from the engine condition is also zero. The engine stall diagnosis stops in response to the driveline disconnect clutch disconnecting.

[0057] Between time t4 and time t5, the driveline disconnect clutch remains open and the engine stall diagnosis is not asserted. No engine stall is indicated and the engine stall counter value is zero. The TCC opens and closes, and the engine torque is estimated to be zero.

[0058] At time t5, the driveline disconnect clutch closes in response to the vehicle operating condition, such as a low battery state or an increase in driver demand torque. An engine start is attempted while the TCC is open. Since the engine stall diagnosis is not activated, the engine torque estimated from the torque converter model remains zero. Similarly, since the engine stall diagnosis is not activated, the engine torque estimated from the engine condition is zero. No engine stall is indicated and the engine stall counter value is zero.

[0059] At time t6, the engine stall diagnosis is activated, but since the engine is not started, the engine torque estimate from the torque converter model is zero. The engine torque estimate from the engine condition increases such that the engine torque estimate from the engine condition is greater than the engine torque estimate from the torque converter model. The engine stall counter value starts to increase in response to the engine torque estimate from the engine condition being greater than the engine torque estimate from the torque converter model. The driveline disconnect clutch remains closed and the TCC remains disengaged. No engine stall is indicated.

[0060] At time t7, the engine stall counter value has increased to exceed the threshold of 320. Accordingly, an engine stall is indicated and the driveline disconnect clutch is disengaged shortly thereafter. The engine torque estimate is zero and the TCC remains disengaged. The engine stall diagnosis is deactivated in response to the engine stall counter value.

[0061] In this way, an engine stall can be indicated in response to two estimated engine torque values. Additionally, the driveline disconnect clutch is disengaged to reduce the load on the motor. In some examples, an engine restart can be attempted and adjustments to other engine actuators can be performed in response to the engine stall indication.

[0062] Now referring Figure 4 , an example flowchart for operating a hybrid vehicle is shown. Figure 4 At least part of the method of Figure 1 and Figure 2 can be incorporated as executable instructions stored in the non-transitory memory of the system shown in Figure 4 . Additionally, part of the method of Figure 4 can occur in the real world as operations or actions performed by a controller to cause a change in the operating state of one or more devices. Figure 3 The method of

[0063] can also provide the sequence of operations shown in

[0064] At 402, method 400 determines whether the vehicle in which the engine is located is activated. The vehicle can be activated in response to the driver being within a threshold distance of the vehicle. In some examples, the vehicle can be activated in response to the driver requesting activation of the vehicle via a button, key switch, or other type of human / machine interface. If method 400 determines that the vehicle is activated, the answer is yes and method 400 proceeds to 404. Activating the vehicle can include supplying electrical or chemical energy to the vehicle propulsion source. If method 400 determines that the vehicle is not activated, the answer is no and method 400 proceeds to 420.

[0064] At 420, method 400 sets the value of the stall counter to zero. By adjusting the value of the stall counter to zero, the possibility of indicating an engine stall after a very short period of time following low engine torque can be avoided. The engine stall counter can be configured in the controller hardware or as a value in the controller memory. Method 400 proceeds to exit.

[0065] At 404, method 400 determines whether the torque converter clutch is disengaged and whether the driveline disconnect clutch is engaged. Method 400 can determine that the torque converter clutch is disengaged in the case of commanding the torque converter to disengage via the controller. Alternatively, the torque converter clutch position can be sensed to determine whether the torque converter clutch is disengaged. Method 400 can determine that the driveline disconnect clutch is engaged in the case of commanding the driveline disconnect clutch to engage via the controller. Alternatively, method 400 can determine that the driveline disconnect clutch is engaged via a sensor. If method 400 determines that the driveline disconnect clutch is engaged and the torque converter clutch is disengaged, the answer is yes and method 400 proceeds to 406. Otherwise, the answer is no, and method 400 proceeds to 430. When the driveline disconnect clutch is engaged and the torque converter clutch is disengaged, engine torque may be estimated via a torque converter model. However, if the torque converter clutch is engaged, the torque converter model may be an inadequate basis for estimating engine torque, and thus engine stall diagnosis can be delayed. Additionally, if the driveline disconnect clutch is disengaged, engine torque cannot be transmitted to the torque converter impeller, such that estimating engine torque may be futile. Thus, engine stall diagnosis can be delayed.

[0066] At 430, method 400 deactivates the engine stall diagnosis for determining engine stall, and method 400 also maintains the current value of the engine stall count. For example, if the engine stall count value is 2, method 400 maintains the value 2 in the engine stall counter. Method 400 proceeds to exit.

[0067] At 406, method 400 estimates the torque converter impeller torque load. In one example, method 400 estimates the torque converter impeller load via the following equation:

[0068]

[0069]

[0070] where is the torque converter impeller torque load, ω 泵轮 is the torque converter impeller speed, K is the torque converter capacity factor curve that varies with the torque converter ratio SR, and where ω 涡轮is the converter pump speed. The converter pump speed and the converter turbine speed are determined via a speed sensor. Method 300 proceeds to 408.

[0071] At 408, method 400 estimates the engine torque via the converter pump load. In one example, method 400 estimates the engine torque via the following equation:

[0072]

[0073] where is the estimated engine torque, and is the estimated motor or engine torque. As is known in the art, the motor torque can be estimated from the motor current and the motor speed. After estimating the engine torque via the converter model, method 400 proceeds to 410.

[0074] At 410, method 400 estimates the engine torque in response to the engine condition. Additionally, method 400 increments an engine stall counter value in response to the engine torque estimated from the converter model being less than a threshold torque amount than the engine torque estimated from the engine condition. The engine torque can be estimated from the engine speed, the engine air amount, the engine spark timing, and the fuel amount supplied to the engine. In one example, the engine speed, the engine air amount, and the fuel amount supplied to the engine are referenced to a table or function of empirically determined torque values, and the table or function outputs an estimate of the engine torque. The values in the table or function can be empirically determined. If the engine is a spark ignition engine, the engine torque value retrieved from the table or function can be modified in response to the engine spark timing. In one example, the torque output from the table or function can be modified in response to the amount of spark timing delay relative to the minimum spark timing for the best engine torque. The torque modification can be empirically determined and stored in the table or function. If the engine torque estimated from the converter model plus an offset torque amount is less than the engine torque estimated from the engine condition, method 400 increments the engine stall counter value. Each time method 400 is executed in the case where the engine torque estimated from the converter model plus the offset torque amount is less than the engine torque estimated from the engine condition, the engine stall counter value can be incremented. If the engine torque estimated from the converter model plus the offset torque amount is not less than the engine torque estimated from the engine condition, the engine stall counter value is not incremented. Method 400 proceeds to 412.

[0075] At 412, method 400 determines whether the engine stall counter value is greater than (G.T.) a threshold. If so, the answer is yes, and method 400 proceeds to 414. If not, the answer is no, and method 400 returns to 404. Additionally, if the vehicle is deactivated, method 400 can exit.

[0076] At 414, method 400 indicates an engine stall condition and disengages the driveline disconnect clutch. Additionally, in some examples, method 400 may deactivate fuel injection so that an undesired amount of fuel does not accumulate in the engine. Additionally, method 400 may temporarily open the throttle to purge excess fuel from the engine cylinders. Method 400 may also stop supplying spark to the engine cylinders, or method 400 may adjust the spark timing (e.g., advance the spark timing) to attempt to increase engine torque production in the event the engine is cold-started. The engine stall condition may be indicated to the vehicle occupants via a human / machine interface. Additionally, the engine stall condition may be notified to one or more controllers in the vehicle system. For example, the engine stall condition may be notified to the motor controller and may be notified to the engine controller so that mitigation measures may be taken. Method 400 proceeds to 416.

[0077] At 416, method 400 may attempt to restart the engine. If fewer than a threshold number of engine restart attempts have been performed, an engine restart attempt may be performed. Additionally, if the battery charge is less than a threshold amount, or if the motor has a torque output capacity less than that currently requested by the vehicle driver or controller, an engine restart attempt may be performed. In one example, an engine restart attempt may be performed by engaging the starter 96. In another example, an engine restart attempt may be made by closing the driveline disconnect clutch to accelerate the engine with torque provided by the motor 240. Method 400 proceeds to exit.

[0078] In this manner, an engine stall condition may be detected so that power is not consumed by rotating an engine that is not combusting air and fuel. The engine stall condition may indicate that no combustion is occurring within the engine, or that the torque generated via the engine is less than a threshold amount, which may indicate an engine torque production problem. If an engine stall condition is indicated, an attempt may be made to restart the engine.

[0079] Therefore, Figure 4The method provides a vehicle operation method, the vehicle operation method including: indicating engine stall when a first engine torque is less than a second engine torque in response to a request to determine the presence or absence of engine stall, the first engine torque being based on a torque converter impeller torque and a motor torque; and disconnecting a driveline disconnect clutch in response to indicating engine stall. The method further includes: incrementing a counter value in response to the first torque being less than the second engine torque; and disconnecting the driveline disconnect clutch in response to the value of the counter exceeding a threshold. The method further includes starting an automatic engine restart in response to engine stall. The method includes wherein the automatic engine restart includes engaging a starter motor and starting the engine by rotating via a flywheel. The method includes wherein a request to determine the presence or absence of engine stall is generated when a torque converter clutch is disengaged. The method further includes delaying a request to determine the presence or absence of engine stall in response to the torque converter clutch being engaged. The method includes wherein the second engine torque is an engine torque estimate in response to engine air flow and engine fuel flow

[0080] Figure 4 The method also provides a vehicle operation method, the vehicle operation method including: indicating engine stall when a first engine torque is less than a second engine torque in response to a request to determine the presence or absence of engine stall, the first engine torque being based on a torque converter impeller torque and a motor torque; and adjusting an engine actuator in response to the indicated engine stall. The method includes wherein the engine actuator is a fuel injector, and wherein fuel flow through the fuel injector is stopped in response to the indicated engine stall. The method includes wherein the engine actuator is an engine throttle, and wherein the engine throttle is opened in response to the indicated engine stall. The method further includes: incrementing a value of a counter of a controller in response to the first torque being less than the second engine torque; and disconnecting a driveline disconnect clutch in response to the count of the counter exceeding a threshold. The method includes wherein the second engine torque is an engine torque estimate in response to engine air flow and engine fuel flow. The method includes wherein engine stall is the engine producing less than a threshold amount of torque. The method includes wherein the engine actuator is an ignition coil, and wherein the spark timing provided via the ignition coil is adjusted

[0081] It should be noted that the example control and estimation procedures included herein can be used with a variety of 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 including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific procedures described herein can represent any number of processing strategies, such as one or more of event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Accordingly, the various acts, operations, and / or functions shown can be executed in the order shown, in parallel, or in some cases omitted. Similarly, the processing order is not necessarily required to implement the features and advantages of the example embodiments described herein, but is provided for convenience of illustration and description. Depending on the particular strategy being used, one or more of the acts, operations, and / or functions shown can be repeated. Additionally, at least a portion of the acts, operations, and / or functions described can be graphically represented as code in a non-transitory memory of a computer-readable storage medium that would be programmed into a control system. When the described acts are executed by executing instructions in a system including a combination of various engine hardware components and one or more controllers, the control acts can also cause a change in the operating state of one or more sensors or actuators in the real world.

[0082] The description ends here. Many changes and modifications will occur to those skilled in the art upon reading this specification without departing from the spirit and scope of the specification. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating on natural gas, gasoline, diesel, or alternative fuel configurations can advantageously use this specification.

[0083] According to the present invention, a vehicle operation method includes: indicating an engine stall when a first engine torque is less than a second engine torque in response to a request to determine the presence or absence of an engine stall, the first engine torque being based on a torque converter pump impeller torque and a motor torque; and disconnecting a driveline disconnect clutch in response to indicating an engine stall.

[0084] According to one embodiment, a further feature of the above invention is that: incrementing a value of a counter in response to the first torque being less than the second engine torque; and disconnecting the driveline disconnect clutch in response to the value of the counter exceeding a threshold.

[0085] According to one embodiment, a further feature of the above invention is that: starting an automatic engine restart in response to an engine stall.

[0086] According to one embodiment, the automatic engine restart includes engaging a starter motor and rotating the engine via a flywheel to start the engine.

[0087] According to one embodiment, when the torque converter clutch is disengaged, a request is generated to determine the presence or absence of engine stall.

[0088] According to one embodiment, a further feature of the above invention is that the request to determine the presence or absence of engine stall is delayed in response to the torque converter clutch being engaged.

[0089] According to one embodiment, the second engine torque is an engine torque estimate in response to engine air flow and engine fuel flow.

[0090] According to the present invention, a vehicle operation method includes: indicating engine stall when a first engine torque is less than a second engine torque in response to a request to determine the presence or absence of engine stall, the first engine torque being based on torque converter impeller torque and motor torque; and adjusting an engine actuator in response to the indicated engine stall.

[0091] According to one embodiment, the engine actuator is a fuel injector, and wherein fuel flow through the fuel injector is stopped in response to the indicated engine stall.

[0092] According to one embodiment, the engine actuator is an engine throttle, and wherein the engine throttle is opened in response to the indicated engine stall.

[0093] According to one embodiment, a further feature of the above invention is that the value of a counter is incremented in response to the first torque being less than the second engine torque; and the driveline disconnect clutch is disengaged in response to the value of the counter exceeding a threshold.

[0094] According to one embodiment, the second engine torque is an engine torque estimate in response to engine air flow and engine fuel flow.

[0095] According to one embodiment, engine stall is the engine producing less than a threshold amount of torque.

[0096] According to one embodiment, the engine actuator is an ignition coil, and wherein the spark timing provided via the ignition coil is adjusted.

[0097] According to the present invention, a vehicle system is provided, the vehicle system having: an electric motor; an engine; a driveline disconnect clutch mechanically coupled to the engine and the electric motor; and one or more controllers including executable instructions stored in a non-transitory memory, the executable instructions for indicating engine stall in response to a first engine torque being less than a second engine torque, the first engine torque being based on torque converter impeller torque and the torque of the electric motor, and the second engine torque being based on engine operating conditions.

[0098] According to one embodiment, the engine operating condition is the engine air flow and the engine fuel flow.

[0099] According to one embodiment, a further feature of the above invention is: an additional instruction for incrementing a counter in response to a first engine torque being less than a second engine torque.

[0100] According to one embodiment, a further feature of the above invention is: an additional instruction for indicating an engine stall in response to a value of the counter exceeding a threshold.

[0101] According to one embodiment, a further feature of the above invention is: an additional instruction for stopping the incrementing of the value of the counter in response to a torque converter clutch being locked.

[0102] According to one embodiment, a further feature of the above invention is: an additional instruction for automatically restarting the engine in response to an engine stall indication.

Claims

1. A vehicle operation method, the vehicle operation method comprising: indicating an engine stall when a first engine torque is less than a second engine torque in response to a request for determining the presence or absence of an engine stall, the first engine torque being based on a torque converter impeller torque and a motor torque, and the second engine torque being based on engine operating conditions; and disconnecting a driveline disconnect clutch in response to indicating the engine stall.

2. The method according to claim 1, the method further comprising: Incrementing a value of a counter in response to the first engine torque being less than the second engine torque; and disconnecting the driveline disconnect clutch in response to the value of the counter exceeding a threshold.

3. The method according to claim 1, the method further comprising initiating an automatic engine restart in response to the engine stall.

4. The method according to claim 3, wherein the automatic engine restart comprises engaging a starter motor and starting the engine by rotating via a flywheel.

5. The method according to claim 1, wherein when a torque converter clutch is disengaged, the request for determining the presence or absence of the engine stall is generated.

6. The method according to claim 1, the method further comprising delaying the request for determining the presence or absence of the engine stall in response to the torque converter clutch being engaged.

7. The method according to claim 1, wherein the second engine torque is an engine torque estimate in response to engine air flow and engine fuel flow.

8. The method according to claim 1, the method further comprising: adjusting an engine actuator in response to the indicated engine stall.

9. A vehicle system, the vehicle system comprising: an electric motor; an engine; a driveline disconnect clutch mechanically coupled to the engine and the electric motor; and one or more controllers including executable instructions stored in a non-transitory memory for indicating an engine stall in response to a first engine torque being less than a second engine torque, the first engine torque being based on a torque converter impeller torque and a torque of the electric motor, and the second engine torque being based on engine operating conditions.

10. The system according to claim 9, wherein the engine operating conditions are engine air flow and engine fuel flow.

11. The system according to claim 9, the system further comprising additional instructions for incrementing a counter in response to the first engine torque being less than the second engine torque.

12. The system according to claim 11, the system further comprising additional instructions for indicating the engine stall in response to the value of the counter exceeding a threshold.

13. The system according to claim 12, the system further comprising additional instructions for stopping the incrementing of the value of the counter in response to a torque converter clutch being locked.

14. The system according to claim 9, the system further comprising additional instructions for automatically restarting the engine in response to the indication of the engine stall.

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