Method and system for operating a driveline disconnect clutch

Abstract

Systems and methods for operating a hybrid powertrain including an engine, a motor / generator, and a driveline disconnect clutch are described. The systems and methods can improve vehicle efficiency while providing expected vehicle operation and performance. In one example, driveline pressure is regulated to match driveline disconnect clutch torque capacity with driver demand torque.

Description

TECHNICAL FIELD

[0001] The present specification relates to methods and systems for operating a powertrain system of a hybrid vehicle. The methods and systems are particularly useful for hybrid vehicles that include a driveline disconnect clutch.

[0002] BACKGROUND AND SUMMARY

[0003] A driveline of a hybrid vehicle can include a driveline disconnect clutch. The driveline disconnect clutch can be located in the driveline between an engine and an integrated starter / generator. The driveline disconnect clutch can be closed when the driver demand torque request level is high or when an electrical energy storage device is being charged. The driveline disconnect clutch can be disengaged when the driver demand torque request level is low and when the integrated starter / generator is propelling the hybrid vehicle alone. The driveline disconnect clutch can be hydraulically applied and released, and a transmission pump can supply pressure to apply the driveline disconnect clutch. However, operating the transmission pump to maintain the driveline disconnect clutch in a closed state can increase the energy used to operate the driveline. Therefore, it can be desirable to develop an operating approach to operate the driveline disconnect clutch in a manner that can improve driveline efficiency.

[0004] The inventors herein have recognized the above-referenced problems and have developed a driveline operating method that includes receiving a driver demand torque to a controller and adjusting, by the controller, a torque capacity of a driveline disconnect clutch in response to the driver demand torque and a compensation torque.

[0005] By adjusting the torque capacity of the driveline disconnect clutch in response to the driver demand torque, it can be possible to improve driveline efficiency while providing the intended driveline disconnect clutch operation. In particular, the transmission line pressure (e.g., the hydraulic output of the transmission pump, which can be adjusted by a pressure regulator or by adjusting the transmission pump efficiency) can be adjusted to provide a driveline disconnect clutch torque capacity that is a function of the driver demand torque and a torque compensation. In one example, the disconnect clutch torque capacity is the greater of a requested engine torque and an actual engine torque plus the compensation torque, and the requested engine torque is the driver demand torque minus an energy management torque. In this manner, the transmission line pressure can be controlled to close the driveline disconnect clutch and maintain the driveline disconnect clutch closed without slipping, while not necessarily operating at a maximum transmission line pressure. In other words, the transmission line pressure can be adjusted to keep the driveline disconnect clutch closed, such that little additional force is needed to keep the driveline disconnect clutch closed.

[0006] The present description can provide several advantages. In particular, the approach can provide increased driveline efficiency. Additionally, the approach can extend the duration of the life cycle of the driveline components. Additionally, the approach keeps the driveline disconnect clutch closed during static and dynamic driver demand torque conditions.

[0007] The above advantages and other advantages and features of the present description will be apparent from the following "DETAILED DESCRIPTION," which should be understood to provide illustrations of various concepts and embodiments of the present description. It will be apparent to those skilled in the art that modifications can be made to the specific implementation described without departing from the scope of the claimed subject matter.

[0008] It should be understood that the foregoing general description of the disclosure has been presented for the purposes of illustration and description only. It is not intended to be exhaustive or to limit the claimed subject matter to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the claimed subject matter be limited not with this detailed description, but rather determined with reference to the claims. BRIEF DESCRIPTION OF DRAWINGS

[0009] The advantages described herein will be more fully understood from the following, taken in conjunction with the accompanying 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 illustrating an exemplary predicted driveline operation sequence;

[0013] Figure 4 exemplary method for operating the system shown in Figure 1 and Figure 2 is a flowchart of an exemplary method for operating the system shown in DETAILED DESCRIPTION

[0014] The present description relates to improving driveline efficiency of a hybrid vehicle while providing desired functionality. Driveline hydraulic line pressure can be regulated to keep the driveline disconnect clutch closed while matching the torque capacity of the driveline disconnect clutch to the engine output torque. In one example, the engine can be of the type shown in Figure 1 . The engine and integrated starter / generator can be incorporated into a driveline as shown in Figure 2 . The driveline can be operated as shown in Figure 3 and according to the method of Figure 4 to provide desired driveline disconnect clutch operation while improving driveline efficiency.

[0015] Reference is made to Figure 1 An internal combustion engine 10 comprising a plurality of cylinders is controlled by an electronic engine controller 12, one of which is shown in Figure 1 The engine 10 is comprised of a cylinder head 35 and a cylinder block 33, which includes combustion chambers 30 and cylinder walls 32. A piston 36 is located therein and reciprocates by connection to a crankshaft 40. A flywheel 97 and ring gear 99 are coupled to the crankshaft 40. A starter 96 (e.g., a low voltage (operates at less than 30 volts) electric motor) includes a pinion shaft 98 and pinion gear 95. The pinion shaft 98 can selectively advance the pinion gear 95 to engage the ring gear 99. The starter 96 can be mounted directly to the front of the engine or to the rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a belt or chain. In one example, the starter 96 is in a quiescent state when not engaged to the engine crankshaft. The combustion chambers 30 are shown in communication with an intake manifold 44 and an exhaust manifold 48 via intake valves 52 and exhaust valves 54, respectively. Each intake 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 positioned to inject fuel directly into the cylinder 30, which is known in the art as direct injection. The fuel injector 66 delivers liquid fuel in proportion to a pulse width from the controller 12. The fuel is delivered to the fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail (not shown). In one example, a high pressure two-stage fuel system can be used to generate higher fuel pressures.

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

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

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

[0020] The controller 12 controls the engine 10 by adjusting the position of the throttle plate 64, the throttle 62, the intake valve 52, the exhaust valve 54, the wastegate 163, and the compressor recirculation valve 47. Figure 1The controller 12 is shown as a conventional microcomputer, including a microprocessor unit 102, input / output ports 104, read only memory 106 (e.g., non-transitory memory), random access memory 108, keep-alive memory 110, and a conventional data bus. In addition to those signals previously discussed, the controller 12 is shown receiving various signals from sensors coupled to the engine 10, including engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling jacket 114, a position sensor 134 coupled to an accelerator pedal 130 for sensing force applied by a human foot 132, a position sensor 154 coupled to a brake pedal 150 for sensing force applied by the human foot 132, engine manifold pressure (MAP) measurements from a pressure sensor 122 coupled to the intake manifold 44, an engine position sensor from a Hall effect sensor 118 that senses the position of the crankshaft 40, measurements of mass of air entering the engine from a sensor 120, and throttle position measurements from a sensor 68. Atmospheric pressure can also be sensed (sensor not shown) for processing by the controller 12. In one preferred aspect of the present description, the engine position sensor 118 produces a predetermined number of equally spaced pulses for each rotation of the crankshaft, from which engine revolutions per minute (RPM) can be determined.

[0021] During operation, each cylinder within the engine 10 typically undergoes a four stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Typically, during the intake stroke, 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 to increase the volume within the combustion chamber 30. The position of the piston 36 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 commonly referred to by those skilled in the art as the bottom dead center (BDC).

[0022] During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30. The position of the piston 36 at the end of its stroke and nearest the cylinder head (e.g., when the combustion chamber 30 is at its minimum volume) is commonly referred to by those skilled in the art as the 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 the spark plug 92, 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 rotational shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to the exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is shown by way of example only, and the intake and exhaust valve opening and / or closing timing can vary, for example to provide positive or negative valve overlap, intake valve late 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 includes Figure 1 The engine 10 shown in. The driveline 200 is shown to include a vehicle system controller 255, an engine controller 12, an electric machine controller 252, a transmission controller 254, an energy storage device controller 253, and a brake controller 250. The controllers can communicate over a controller area network (CAN) 299. Each of the controllers can provide information to the other controllers, such as: torque output limits (e.g., torque outputs of devices or components that are controlled not to be exceeded), torque input limits (e.g., torque inputs of devices or components that are controlled not to be exceeded), sensor and actuator data, diagnostic information (e.g., information about a deteriorating transmission, information about a deteriorating engine, information about a deteriorating electric machine, information about a deteriorating brake). Additionally, the vehicle system controller can provide commands to the engine controller 12, the electric machine 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 display).

[0025] For example, in response to the driver releasing the accelerator pedal and the 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 that requests a first brake torque from the electric machine controller 252 and a second brake torque from the brake controller 250 that provide a desired brake torque at the wheels 216.

[0026] In other examples, the powertrain control devices can be partitioned in a manner different from that shown in. For example, a single controller can replace the vehicle system controller 255, the engine controller 12, the electric machine controller 252, the transmission controller 254, and the brake controller 250. Figure 2

[0027] ​In this example, the powertrain 200 can be powered by an engine 10 and an electric machine 240. The engine 10 can be started using the engine starting system shown in FIG. 1 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 regulated via torque actuators 204 such as fuel injectors, throttle, etc. Figure 1

[0028] The engine output torque can be transmitted to an input side or first side of a powertrain disconnect clutch 235 via a dual mass flywheel 215. The disconnect clutch 236 can be electrically or hydraulically actuated. A downstream side or second side 234 of the disconnect clutch 236 is shown mechanically coupled to an ISG input shaft 237. In this example, the disconnect clutch 236 can be hydraulically actuated by hydraulic fluid supplied by a mechanically driven transmission pump 230. Alternatively, hydraulic fluid can be supplied to the disconnect clutch 236 via an electric pump 242. The mechanical transmission pump 230 or the electric pump 242 supplies hydraulic fluid at a line pressure via a conduit 239. The line pressure delivered via the electric pump 242 can be controlled by regulating the voltage and / or current supplied to the electric pump 242. The line pressure delivered via the mechanical transmission pump 230 can be controlled via a pump efficiency control device or actuator 231 (e.g., swash plate, vane position regulation device, gear position regulation device, etc.) or an optional regulator 232. The conduit 239 can also supply hydraulic fluid at a line pressure to the gear transmission clutch 211.

[0029] The ISG 240 can be operated to provide torque to the powertrain 200 or to convert powertrain torque to electrical energy in a regenerative mode, which will be stored in an electrical energy storage device 275. The ISG 240 has a higher output torque capacity than the starter 96 shown in FIG. 1. Additionally, the ISG 240 directly drives the powertrain 200 or is directly driven by the powertrain 200. There are no belts, gears, or chains coupling the ISG 240 to the powertrain 200. Rather, 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 supply) can be a battery, a capacitor, or an inductor. A downstream side of the ISG 240 is mechanically coupled to a pump pulley 285 of a torque converter 206 via a shaft 241. An upstream side of the ISG 240 is mechanically coupled to the disconnect clutch 236. By operating as a motor or a generator as instructed by a motor controller 252, the ISG 240 can provide positive or negative torque to the powertrain 200. Figure 1

[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 transferred from the pump 285 directly 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 transfers engine torque to the automatic transmission 208 via fluid transfer between the torque converter turbine 286 and the torque converter pump 285, enabling torque multiplication. Conversely, when the torque converter lock-up clutch 212 is fully engaged, engine output torque is transferred directly 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, enabling the amount of torque transferred directly to the transmission to be adjusted. The controller 12 can be configured to adjust the amount of torque transferred by the torque converter 212 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or according to engine operating requests based on the driver.

[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 the shift control solenoids 209. Torque output from the automatic transmission 208 can also be transferred to the wheels 216 via the output shaft 260 to propel the vehicle. In particular, the automatic transmission 208 can transfer input drive torque at the input shaft 270 in response to vehicle travel conditions before transmitting output drive torque to the wheels 216. 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] In addition, a frictional force can be applied to the wheels 216 by engaging the friction wheel brakes 218. In one example, the friction wheel brakes 218 can be engaged in response to a driver pressing his foot on a brake pedal (not shown) and / or in response to an instruction within the brake controller 250. In addition, the brake controller 250 can apply the brakes 218 in response to information and / or requests given by the vehicle system controller 255. In the same manner, the frictional force on the wheels 216 can be reduced by disengaging the wheel brakes 218 in response to a human driver releasing his / her 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 a frictional force to the wheels 216 via the controller 250.

[0034] In response to a request to accelerate the vehicle 225, the vehicle system controller can 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 a transmission input torque limit (e.g., a threshold that should not be exceeded), the torque is delivered to the torque converter 206, which in turn transmits at least a portion of the requested torque to the transmission input shaft 270. The transmission controller 254 selectively locks the torque converter clutch 212 and engages a gear through the gear clutch 211 in response to shift schedules and TCC lock schedules that can be based on input shaft torque and vehicle speed. In some cases, a charging torque (e.g., a negative ISG torque) can be requested while there is a non-zero driver demand torque when it can be desirable to charge the electrical energy storage device 275. The vehicle system controller 255 can request increased engine torque to overcome the charging torque to satisfy the driver demand torque.

[0035] In response to a request to slow the vehicle 225 and provide regenerative braking, the vehicle system controller can provide a negative desired wheel torque based on vehicle speed and brake pedal position. The vehicle system controller 255 then allocates a portion of the negative desired wheel torque to the ISG 240 (e.g., a desired powertrain wheel torque) and the remainder to the friction brakes 218 (e.g., a desired friction brake wheel torque). Additionally, the vehicle system controller can inform the transmission controller 254 that the vehicle is in regenerative braking mode so that the transmission controller 254 shifts gears 211 based on a unique shift schedule to improve regenerative efficiency. While the ISG 240 supplies a negative torque to the transmission input shaft 270, the negative torque provided by the ISG 240 can be limited by the transmission controller 254, which outputs a transmission input shaft negative torque limit (e.g., a threshold value that should not be exceeded). Additionally, based on operating conditions of the electrical energy storage device 275, the vehicle system controller 255 or the motor controller 252 can limit the negative torque of the ISG 240 (e.g., to less than a threshold negative threshold torque). Any portion of the desired negative wheel torque that can not be provided by the ISG 240 due to transmission or ISG limitations can be allocated to the friction brakes 218 so that the desired wheel torque is provided by the combination of negative wheel torque from the friction brakes 218 and the ISG 240.

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

[0037] As one example, engine torque output can be controlled by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and / or intake air by controlling throttle opening and / or valve timing, valve lift, and turbo or supercharger boost for a turbocharged or supercharged engine. 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 intake air. In all cases, engine control can be performed cylinder-by-cylinder to control engine torque output.

[0038] The motor controller 252 can control torque output and electrical energy production from the ISG 240 by adjusting current flow into and out of the field and / or armature windings of the ISG, as is known in the art.

[0039] The transmission controller 254 receives transmission input shaft position via a position sensor 271. The transmission controller 254 can convert the transmission input shaft position to input shaft rotational speed by differentiating the signal from the position sensor 271 or counting a number of known angular distance pulses over a predetermined time interval. The transmission controller 254 can receive transmission output shaft torque from a 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 shaft position pulses over a predetermined time interval to determine transmission output shaft speed. The transmission controller 254 can also differentiate the transmission output shaft speed to determine transmission output shaft acceleration.

[0040] The brake controller 250 receives wheel speed information via wheel speed sensors 221 and brake requests from the vehicle system controller 255. The brake controller 250 can also receive brake pedal position information from the brake pedal sensor 154 shown in FIG. 1 directly or through the CAN 299. The brake controller 250 can provide braking in response to wheel torque commands from the vehicle system controller 255. The brake controller 250 can also provide antilock and vehicle stability braking to improve vehicle braking and stability. To this end, the brake controller 250 can provide wheel torque limits (e.g., threshold negative wheel torque that should not be exceeded) to the vehicle system controller 255 so that negative ISG torque does not result in exceeding the wheel torque limit. For example, if the controller 250 gives a negative wheel torque limit of 50 Nm, the ISG torque is adjusted to provide less than 50 Nm (e.g., 49 Nm) negative torque at the wheel, including accounting for transmission gearing. Figure 1

[0041] Figure 1 The system of Figure 2 provides a driveline system including an engine, an integrated starter / generator, a driveline disconnect clutch located in the driveline between the engine and the integrated starter / generator, a transmission including a pump, and a controller including executable instructions stored in non-transitory memory to adjust an outlet pressure of the pump in response to a driver demand torque and a first compensation torque. The system further includes additional instructions to apply the outlet pressure of the pump to the driveline disconnect clutch. The system includes where the outlet pressure of the pump adjusts a torque capacity of the driveline disconnect clutch. The system includes where the outlet pressure is controlled by a pressure regulator. The system includes where the outlet pressure is controlled by adjusting an efficiency of the pump. The system includes where the outlet pressure is controlled by a voltage or current supplied to the pump.

[0042] ​​​Referring now to Figure 3 , an exemplary plot of a powertrain operating sequence is shown in accordance with Figure 4 Figure 3 A manner in which the torque capacity of the powertrain disconnect clutch is regulated (e.g., an upper threshold (e.g., maximum) amount of torque that the powertrain disconnect clutch can transfer when the transmission line pressure is applied to close the powertrain disconnect clutch) is shown. The vertical lines TO-T3 represent times of interest during the operating sequence. The plots are aligned in time and occur simultaneously.

[0043] The first plot from the top number of Figure 3 is a plot of driver demand torque as a function of time. The horizontal axis represents time and an increase in time from the left side of the plot to the right side of the plot. The vertical axis represents driver demand torque and an increase in driver demand torque in the direction of the vertical axis arrow. In one example, the driver demand torque is based on accelerator pedal position and vehicle speed. For example, the accelerator pedal position and vehicle speed from sensors can be referenced to a table or function of empirically determined driver demand torque values and the table or function outputs a driver demand value. The driver demand torque can be a wheel torque, an input torque of a transmission, or a desired torque or torque request at another location along the powertrain. Trace 302 represents the driver demand torque.

[0044] The second plot from the top number of Figure 3 is a plot of energy management torque as a function of time. The horizontal axis represents time and an increase in time from the left side of the plot to the right side of the plot. The vertical axis represents energy management torque. Positive energy management torque is requested when trace 304 is above the horizontal axis. Negative energy management torque is requested when trace 304 is below the horizontal axis. When trace 304 is not visible, the value of trace 304 is zero. The energy management torque is a torque that can be provided to or supplied by the powertrain by an electrical energy storage device (e.g., 275). For example, negative energy management torque can be requested if the electrical energy storage device is low on charge and a request is made to charge the electrical energy storage device. Conversely, positive energy management torque can be requested if the electrical energy storage device is high on charge and a request is made to discharge the electrical energy storage device. Trace 304 represents the engine management torque.

[0045] The third plot from the top number of Figure 3 is a plot of powertrain disconnect clutch torque capacity as a function of time. The vertical axis represents powertrain disconnect clutch torque capacity and an increase in powertrain disconnect clutch torque capacity in the direction of the vertical axis arrow. The horizontal axis represents time and an increase in time from the left side of the plot to the right side of the plot. Trace 306 represents the powertrain disconnect clutch torque capacity.

[0046] The fourth plot from the top number of Figure 3 ​The fourth graph from the top is a plot of transmission line pressure as a function of time. The vertical axis represents transmission line pressure and an increase in transmission line pressure in the direction of the vertical axis arrow. The horizontal axis represents time and an increase in time from the left side of the graph to the right side of the graph. Trace 308 represents transmission line pressure.

[0047] From Figure 3 The fifth graph from the top is a plot of actual engine torque (e.g., torque generated by the engine) as a function of time. The horizontal axis represents time and an increase in time from the left side of the graph to the right side of the graph. The vertical axis represents actual engine torque and an increase in actual engine torque in the direction of the vertical axis arrow. Trace 310 represents actual engine torque.

[0048] At time TO, the driver demand torque is at a low level and the energy management torque is zero. The transmission line pressure is adjusted to provide the transmission line pressure that provides the transmission disconnect clutch torque capacity. The actual engine torque is nearly equal to the driver demand torque.

[0049] Between time TO and time Tl, the driver demand torque changes in response to changes in accelerator pedal position and vehicle speed (not shown). The transmission disconnect clutch torque capacity follows the changes in the driver demand torque and also includes the torque compensation. The transmission line pressure is adjusted so that the transmission disconnect clutch torque capacity follows the driver demand torque plus the compensation torque. The actual engine torque follows the driver demand torque.

[0050] At time Tl, a negative energy management torque is requested so that the electrical energy storage device of the vehicle can be charged. The energy management torque is negative because torque is being absorbed from the driveline to charge the electrical energy storage device. The transmission disconnect clutch torque capacity is increased to equal the driver demand torque minus the negative energy management torque, which increases the transmission disconnect clutch torque capacity. The compensation torque is also added to the transmission disconnect clutch torque capacity. The transmission line pressure is adjusted by adjusting the transmission pump output or line pressure regulator output so that the transmission disconnect clutch torque follows the driver demand torque minus the negative energy management torque plus the compensation torque. The actual engine torque follows the driver demand torque minus the negative energy management torque. The compensation torque is delivered by the engine so that the transmission disconnect clutch is greater than the actual engine torque so that the transmission disconnect clutch does not slip.

[0051] At time T2, the driver reduces the driver demand torque while the energy management torque is requested. In response to the reduction in the driver demand torque, the transmission line pressure and the transmission disconnect clutch torque capacity begin to decrease. The actual engine torque is equal to the driver demand torque minus the energy management torque when the driver demand torque is reduced.

[0052] Between time T2 and time T3, the driver demand torque decreases rapidly, but the actual engine torque does not decrease as rapidly as the driver demand torque. The lag in the actual engine torque can be due to the engine consuming air from the engine intake manifold. The transmission disconnect clutch torque follows the actual engine torque plus the compensation torque, not the driver demand torque minus the energy management torque plus the compensation torque. The transmission disconnect clutch torque follows the actual engine torque plus the compensation torque because it is greater than the driver demand torque minus the energy management torque plus the compensation torque. This allows the transmission disconnect clutch torque capacity to decrease without the transmission disconnect clutch slipping. The transmission line pressure is regulated to a pressure that provides a transmission disconnect clutch torque capacity equal to the actual engine torque plus the compensation torque.

[0053] At time T3, the energy management torque is reduced to zero, and the transmission disconnect clutch torque capacity is decreased by a corresponding amount of torque capacity. The transmission line pressure is also decreased so that the transmission disconnect clutch torque capacity is equal to the driver demand torque plus the compensation torque. The actual engine torque follows the driver demand torque. At time T3, the driver demand torque changes in response to the accelerator pedal position and vehicle speed. The transmission disconnect clutch torque capacity and the transmission line pressure are regulated to follow the driver demand torque plus the compensation torque. The actual engine torque follows the driver demand torque.

[0054] Referring now to Figure 4 , an example flow diagram for operating a driveline of a hybrid vehicle is shown. Figure 4 At least some portions of the method of Figure 1 may be incorporated as executable instructions stored in the non-transitory memory of the system shown in Figure 2 Additionally, Figure 4 Some portions of the method of Figure 4 may occur in the physical world as an operation or action performed by a controller executing executable instructions to transform the state of one or more machines. Figure 3 The method of may also provide the sequence of operations shown in

[0055] At 402, the method 400 determines whether the engine of the hybrid vehicle is running. In one example, the engine is determined to be running (e.g., combusting air and fuel) if the engine speed is greater than a threshold value and fuel is being supplied to the engine. If the method 400 determines that the engine of the vehicle is running, the answer is "yes" and the method 400 proceeds to 404. Otherwise, the answer is "no" and the method 400 proceeds to 420.

[0056] At 420, the method 400 adjusts the transmission line pressure to provide a torque capacity of the transmission gear clutch that keeps the transmission clutch closed when the transmission clutch is commanded to be closed. In one example, the torque capacity of the engaged transmission clutch is equal to the absolute value of the motor torque output plus the second compensation torque multiplied by the torque converter torque multiplication factor multiplied by any transmission ratio between the torque converter and the engaged gear clutch. For example, if the output torque of the motor is 100 Nm, the second compensation value is 10 Nm, the torque converter torque multiplication factor is 1, and there is no gear between the engaged gear clutch and the torque converter, the torque capacity of the engaged transmission clutch is adjusted to 110 Nm. The method 400 then exits.

[0057] At 404, the method 400 determines the driver demand torque. In one example, the driver demand torque is determined by receiving the position of the accelerator pedal and the vehicle speed into the controller. The controller then references a table or function stored in the controller memory that is empirically determined and outputs the driver demand torque. Additionally, in some examples, the driver demand torque can also be based on the brake pedal position. For example, the driver demand torque can be represented by the following equation:

[0058] τ dd = τ acc_ped + τ brk_ped

[0059] where τ dd is the driver demand torque, τ acc_ped is the torque requested by the accelerator pedal, and τ brk_ped is the torque requested by the brake pedal (negative value). Thus, if the accelerator pedal position is applied and indicates a positive requested torque of 300 Nm, and the brake pedal is applied simultaneously with the accelerator pedal and indicates a negative request of 50 Nm, the driver demand torque is 250 Nm. The driver demand torque can be a requested wheel torque, a transmission input torque, or a torque at another location in the driveline. The method 400 proceeds to 406.

[0060] At 406, the method 400 determines an energy management torque. The energy management torque is determined by logic responsive to the driver demand torque, the battery state of charge, the battery temperature, and other vehicle operating conditions. The energy management torque determination is an amount of torque delivered to or absorbed from the driveline by the ISG and the electrical energy storage device. Torque absorbed from the driveline by the electric machine and stored as electrical energy in the electrical energy storage device can be referred to as negative torque. Torque supplied to the driveline by the electric machine and the electrical energy storage device can be referred to as positive torque. In one example, if the driver demand torque is 300 Nm and the engine has a capacity to output 250 Nm, the energy management torque can be 50 Nm supplied to the driveline by the electric machine. If the battery state of charge is low, a negative torque of 25 Nm can be applied to the driveline by the electric machine. The electric machine can convert the torque to electrical energy, which is stored in the electrical energy storage device. The method 400 proceeds to 408.

[0061] At 408, the method 400 determines a desired engine torque. In one example, the desired engine torque can be determined by the following equation:

[0062] τ des_eng = τ dd - τ EM

[0063] where τ des_eng is the desired engine torque, τ dd is the driver demand torque, and τ EM is the energy management torque. After determining the desired engine torque, the method 400 proceeds to 410.

[0064] At 410, the method 400 determines a desired driveline disconnect clutch torque capacity (e.g., an upper threshold amount of torque that the driveline disconnect clutch can transfer when transmission line pressure is applied to the driveline disconnect clutch). In one example, the method 400 determines the desired driveline disconnect clutch torque capacity by the following equation:

[0065] τ des_ddc = max(τ des_eng , τ act_eng ) + compensation torque

[0066] where τ des_ddc is the desired driveline disconnect clutch torque capacity, max is a function that returns the larger of the arguments τ des_eng and τ act_eng , τ des_eng is the desired engine torque, τ act_eng is the actual engine torque (e.g., the torque that the engine is currently outputting), and compensation torque is a first compensation torque.

[0067] In one example, the first compensation torque can be based on an upper threshold (e.g., maximum) rate of positive torque change on the driveline disconnect clutch. For example, if the motor is off and the maximum engine torque change rate is 100 Nm per second, the compensation value can be selected to be 50 Nm such that the engine will take at least 0.5 seconds to reach the condition that the rate of torque change on the driveline disconnect clutch overcomes the compensation value and the driveline disconnect clutch begins to slip. Thus, the compensation torque can be a torque that allows the input side of the driveline disconnect clutch to subtract the torque on the output side of the driveline disconnect clutch to increase the torque difference without causing the driveline disconnect clutch to slip in a predetermined amount of time.

[0068] In another example, the first compensation can be a predetermined value (e.g., 40 Nm) and the driveline disconnect clutch torque capacity can increase at an upper threshold rate (e.g., maximum rate) of 50 Nm per second, but the engine torque can increase at a rate of 100 Nm per second. The engine machine torque can then be allowed to increase at a rate of 100 Nm per second for 0.2 seconds while the driveline disconnect clutch torque capacity increases at a rate of 50 Nm per second in response to the driver demand torque increasing 100 Nm per second. Thereafter, the engine torque can be limited to the threshold rate of 50 Nm per second, or the maximum rate of increase of the torque capacity of the driveline disconnect clutch. The engine torque can be limited by limiting the throttle opening and / or the amount of fuel injection. This allows the engine torque to increase 20 Nm while the driveline disconnect clutch torque capacity increases 10 Nm, but the disconnect clutch torque capacity is still greater than the engine torque output by 30 Nm such that the driveline disconnect clutch does not slip. In this way, the torque change on the driveline disconnect clutch can be limited to reduce the likelihood of the driveline disconnect clutch slipping when the rate of torque increase on the driveline disconnect clutch exceeds the rate at which the torque capacity of the driveline disconnect clutch can increase. The method 400 proceeds to 412.

[0069] At 412, the method 400 adjusts the transmission line pressure to provide a desired driveline disconnect clutch torque capacity. In one example, the output of a pressure regulator can be adjusted to provide a line pressure that provides the desired driveline disconnect clutch torque capacity when the line pressure is applied to the driveline disconnect clutch. In another example, the output pressure of a (mechanically or electrically) transmission pump can be adjusted to provide the desired driveline disconnect clutch torque capacity. In one example, the desired driveline disconnect clutch torque capacity is input to a function of the output transmission line pressure. For example, the desired driveline disconnect clutch torque capacity is input to a function that empirically determines line pressure values that provide the desired driveline disconnect clutch torque capacity, and each line pressure value is associated with a corresponding desired driveline disconnect clutch torque capacity. The function then outputs the desired transmission line pressure, and the transmission line pressure is adjusted by adjusting the output of the transmission pump to provide the desired line pressure. In particular, the controller adjusts the pump output by supplying a voltage or current to adjust the output of the transmission pump. If the transmission pump is an electrically powered pump, the voltage input to the pump is adjusted to change the transmission line pressure. If the pump is mechanically driven, an actuator within the pump adjusts the pump efficiency to change the transmission line pressure. Similarly, if the transmission line pressure is adjusted by a pressure regulator, the desired driveline disconnect clutch torque capacity is input to a function that empirically determines line pressure values that provide the desired driveline disconnect clutch torque capacity, and the function outputs a regulator control voltage or signal duty cycle, and the controller commands the pressure regulator by the voltage or duty cycle signal. The values in the function can be empirically determined and stored in the controller memory. The method 400 then exits.

[0070] In this way, the driveline disconnect clutch torque capacity can be adjusted as the vehicle is driving on the road and the driver demand torque changes. The driveline disconnect clutch torque capacity is adjusted to allow the driver demand torque plus a small amount of additional torque to be transferred across the driveline disconnect clutch. This ensures that the driveline disconnect clutch remains closed and does not slip, while reducing the transmission line pressure to less than the upper threshold transmission line pressure. Therefore, the energy used to operate the driveline can be reduced.

[0071] Accordingly, the method 400 provides a powertrain operating method including receiving a driver demand torque to a controller and adjusting, by the controller, a torque capacity of a powertrain disconnect clutch in response to the driver demand torque and a compensation torque. The method includes where the compensation torque is a torque based on an upper threshold rate of change of engine torque. The method includes where the driver demand torque varies with an accelerator pedal position. The method includes where the driver demand torque also varies with a brake pedal position. The method includes where the powertrain disconnect clutch is located in a powertrain between an engine and an electric machine. The method includes where the electric machine is located in the powertrain between the disconnect clutch and a transmission. The method includes where adjusting, by the controller, a torque capacity of a powertrain disconnect clutch in response to the driver demand torque and a compensation torque occurs when an engine of a powertrain is running, and where the torque capacity of the powertrain disconnect clutch is not adjusted by the controller in response to the driver demand torque and the compensation torque when an integrated starter / generator is running and the engine of the powertrain is not running.

[0072] Figure 4 The method of 400 also provides a powertrain operating method including receiving a driver demand torque to a controller and adjusting, by the controller, a torque capacity of a powertrain disconnect clutch in response to the driver demand torque and a compensation torque. The method includes where the compensation torque is a torque based on an upper threshold rate of change of engine torque. The method includes where the driver demand torque varies with an accelerator pedal position. The method includes where the driver demand torque also varies with a brake pedal position. The method includes where the powertrain disconnect clutch is located in a powertrain between an engine and an electric machine. The method includes where the electric machine is located in the powertrain between the disconnect clutch and a transmission. The method includes where adjusting, by the controller, a torque capacity of a powertrain disconnect clutch in response to the driver demand torque and a compensation torque occurs when an engine of a powertrain is running, and where the torque capacity of the powertrain disconnect clutch is not adjusted by the controller in response to the driver demand torque and the compensation torque when an integrated starter / generator is running and the engine of the powertrain is not running.

[0073] Note 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 non-transitory memory and can be executed by control systems including controllers in combination with various sensors, actuators, and other engine hardware. The particular procedures described herein can represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and so on. As such, the various acts, operations, and / or functions illustrated can be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily restricted to the order of presentation in this document but is adaptable to a variety of other processing strategies. One or more of the acts, operations, and / or functions illustrated can be repeated, regardless of whether they are illustrated as a single function, or repeated within a loop or processing block. Moreover, an aspect can consist of any combination of one or more of the described aspects. Further, to the extent that aspects can be implemented over time and that updated functionally described herein can supersede or augment the functional elements and processes described herein, those new functions and processes can be implemented as described herein or can be implemented as modifications to existing functions and processes.

[0074] The following is a summary of the present specification. Many variations and modifications can be made to the present specification by those skilled in the art upon reading the present specification. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations can utilize the present specification.

[0075] According to the present invention, a powertrain operating method is provided: receiving a driver demand torque to a controller; and adjusting, by the controller, a torque capacity of a powertrain disconnect clutch in response to the driver demand torque and a compensation torque.

[0076] According to one embodiment, the compensation torque is a torque based on an upper threshold rate of change of engine torque.

[0077] According to one embodiment, the driver demand torque varies with an accelerator pedal position.

[0078] According to one embodiment, the driver demand torque also varies with a brake pedal position.

[0079] According to one embodiment, the powertrain disconnect clutch is located in the powertrain between an engine and an electric machine.

[0080] According to one embodiment, the electric machine is located in the powertrain between the disconnect clutch and a transmission.

[0081] According to one embodiment, adjusting, by the controller, a torque capacity of a driveline disconnect clutch in response to the driver demand torque and a compensation torque occurs when an engine of a driveline is running, and wherein the torque capacity of the driveline disconnect clutch is not adjusted by the controller in response to the driver demand torque and the compensation torque when an integrated starter / generator is running and the engine of the driveline is not running.

[0082] According to the present invention, there is provided a driveline operating method: receiving a driver demand torque to a controller; and adjusting a torque capacity of a driveline disconnect clutch in response to the driver demand torque and a first compensation torque by adjusting a line pressure output from a driveline pump and the controller.

[0083] According to one embodiment, the above invention features further adjusting the line pressure output from the driveline pump in further response to an energy management torque.

[0084] According to one embodiment, the above invention features further adjusting the line pressure output from the driveline pump in further response to an actual engine torque.

[0085] According to one embodiment, the driveline pump is an electric pump.

[0086] According to one embodiment, the driveline pump is a mechanically driven pump.

[0087] According to one embodiment, the above invention features further adjusting a torque capacity of a transmission range clutch in response to a driver demand torque and a second compensation torque when an integrated starter / generator is running and an engine of a driveline is not running.

[0088] According to one embodiment, the above invention features further constraining a rate of change of torque on the driveline disconnect clutch based on the first compensation torque.

[0089] According to the present invention, there is provided a driveline system having: an engine; an integrated starter / generator; a driveline disconnect clutch located in a driveline between the engine and the integrated starter / generator; a transmission including a pump; and a controller including executable instructions stored in non-transitory memory to adjust an outlet pressure of the pump in response to a driver demand torque and a first compensation torque.

[0090] According to one embodiment, the above invention features further instructions to apply the outlet pressure of the pump to the driveline disconnect clutch.

[0091] According to one embodiment, the outlet pressure of the pump regulates the torque capacity of the driveline disconnect clutch.

[0092] According to one embodiment, the outlet pressure is controlled by a pressure regulator.

[0093] According to one embodiment, the outlet pressure is controlled by regulating the efficiency of the pump.

[0094] According to one embodiment, the outlet pressure is controlled by the voltage or current supplied to the pump.

Claims

1. A driveline operating method, the method comprising: receiving a driver demand torque to a controller, determining a desired engine torque from the demand torque and an energy management torque, wherein the energy management torque is a torque provided to or supplied by a driveline from an electrical energy storage device; and determining a desired torque capacity of a driveline disconnect clutch from the desired engine torque, an actual engine torque, and a compensation torque, adjusting the torque capacity of the driveline disconnect clutch by the controller based on the desired torque capacity of the disconnect clutch.

2. The method of claim 1, wherein the compensation torque is a torque based on an upper threshold rate of change of engine torque.

3. The method of claim 1, wherein the driver demand torque varies with an accelerator pedal position.

4. The method of claim 3, wherein the driver demand torque also varies with a brake pedal position.

5. The method of claim 1, wherein the driveline disconnect clutch is located in a driveline between an engine and an electric machine.

6. The method of claim 5, wherein the electric machine is located in the driveline between the disconnect clutch and a transmission.

7. The method of claim 1, wherein adjusting the torque capacity of the driveline disconnect clutch by the controller in response to the driver demand torque and a compensation torque occurs when an engine of the driveline is operating, and wherein the torque capacity of the driveline disconnect clutch is not adjusted by the controller in response to the driver demand torque and the compensation torque when an integrated starter / generator is operating and the engine of the driveline is not operating.

8. The driveline operating method of claim 1, wherein adjusting the torque capacity of the driveline disconnect clutch includes adjusting a line pressure output from a transmission pump.

9. The method of claim 8, further comprising adjusting the line pressure output from the transmission pump further in response to an energy management torque.

10. The method of claim 8, further comprising adjusting the line pressure output from the transmission pump further in response to an actual engine torque.

11. A driveline system, the driveline system comprising: an engine; an integrated starter / generator; a driveline disconnect clutch located in a driveline between the engine and the integrated starter / generator; a transmission including a pump; and a controller including executable instructions stored in non-transitory memory to adjust an outlet pressure of the pump in response to a driver demand torque and a first compensation torque; the controller receiving a driver demand torque, and determining a desired engine torque from the demand torque and an energy management torque, wherein the energy management torque is a torque provided to or supplied by a driveline from an electrical energy storage device, and the controller adjusting the torque capacity of the driveline disconnect clutch based on the desired torque capacity of the disconnect clutch. A desired torque capacity of a driveline disconnect clutch is determined based on a desired engine torque, an actual engine torque, and a compensation torque, and the torque capacity of the driveline disconnect clutch is adjusted by the controller based on the desired torque capacity of the disconnect clutch.

12. The system of claim 11, further comprising additional instructions to apply the outlet pressure of the pump to the driveline disconnect clutch.

13. The system of claim 11, wherein the outlet pressure of the pump adjusts the torque capacity of the driveline disconnect clutch.

14. The system of claim 11, wherein the outlet pressure is controlled by a pressure regulator.

15. The system of claim 11, wherein the outlet pressure is controlled by adjusting an efficiency of the pump.

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