Method and system for operating a powertrain during recuperation braking

Abstract

Powertrain operating procedures that include the following: Predictions of a gearbox input shaft speed from a Transmission output shaft speed; and Adjusting an actuator in response to an actual Transmission input shaft speed minus the predicted speed Transmission input shaft speed; and Determining a negative drivetrain wheel torque limit based on the actual transmission input shaft speed minus the predicted transmission input shaft speed.

Description

Technical area

[0001] This description relates to a method and a system for operating the powertrain of a hybrid vehicle during regenerative braking. The methods and systems can be particularly useful for hybrid vehicles in which a transmission can be powered by an electric motor.

[0002] The patent application US 2008 / 0288145A1 describes a powertrain control device and a method for doing so, as well as a program to implement this control method.

[0003] The patent application US 2014 / 0207324A1 discloses a system for starting an engine. Background and brief presentation

[0004] A hybrid vehicle can purposefully enter or exit a regenerative braking mode, where the vehicle's kinetic energy is converted into electrical energy and stored for later use. The vehicle may enter regenerative braking mode at times when driver demand is low, such as when the hybrid vehicle is traveling on a road with a negative gradient. An electric machine provides negative torque to the hybrid vehicle's powertrain during regenerative braking. The negative torque assists vehicle braking, but vehicle braking can also be provided by friction brakes. If the negative torque provided by the electric machine is not applied to the vehicle's wheels due to transmission degradation, the vehicle may not decelerate at a desired rate.Furthermore, a delay may occur that is longer than might be desired in order to increase the applied braking force through friction brakes in order to provide a desired amount of vehicle braking.

[0005] The inventors recognized the problems mentioned above and developed a powertrain operating method that includes: predicting a transmission input shaft speed from a transmission output shaft speed; and adjusting an actuator in response to an actual transmission input shaft speed minus the predicted transmission input shaft speed.

[0006] By predicting a transmission input speed based on a transmission output speed, it may be possible to provide the technical result of determining transmission deterioration, thus enabling earlier initiation of automatic friction braking. Furthermore, it may be possible to reduce the negative torque applied to a transmission input shaft earlier, so that the transmission input shaft speed can be maintained above a threshold speed at which a transmission pump provides a desired amount of transmission fluid flow or pressure.

[0007] The present description can offer several advantages. In particular, the approach can provide improved vehicle performance under conditions of transmission deterioration. Additionally, the approach can improve vehicle braking under conditions of transmission deterioration. Furthermore, the approach can reduce the time required to determine deterioration, allowing corrective actions to be implemented earlier.

[0008] The above advantages, as well as further advantages and features of the present description, will become clear from the following detailed description alone or in conjunction with the accompanying drawings.

[0009] It is understood that the above summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to reveal any key or essential features of the claimed invention, the scope of which is defined solely by the claims following the full description. Furthermore, the claimed invention is not limited to implementations that resolve the disadvantages mentioned above or in any other part of this disclosure. Brief description of the drawings

[0010] The advantages described herein will be better understood upon reading an example of an embodiment, called the detailed description here, alone or with reference to the drawings, in which: Fig. 1 is a schematic representation of a power machine; Fig. 2 is a schematic representation of a hybrid vehicle powertrain; Fig. 3-6 different exemplary conditions for monitoring a gearbox and taking mitigation measures in response to an indication of deterioration are shown; and Fig. Figure 7 shows an exemplary method for operating a vehicle powertrain. Detailed description

[0011] This description concerns the monitoring of a hybrid vehicle's powertrain during recuperation. The hybrid vehicle may include a power unit, as shown in Fig. 1 is shown. The power engine of the Fig. 1 can be included in a powertrain, as in Fig. 2 is shown. The powertrain can be monitored during operating conditions such as those found in Fig. Figures 3-6 are shown. The powertrain can be configured according to the diagram in Fig. The 7 procedures shown are monitored and controlled.

[0012] Referring to Fig. 1 is an internal combustion engine 10 comprising several cylinders, one of which is in Fig. The engine 10, as shown in Figure 1, is controlled by an electronic engine control unit 12. The engine 10 comprises a cylinder head 35 and a block 33, which contain a combustion chamber 30 and cylinder walls 32. A piston 36 is positioned within the cylinder and moves back and forth via a connection to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. The starter 96 (e.g., a low-voltage electric motor (operated at less than 30 volts)) comprises a pinion shaft 98 and a pinion 95. The pinion shaft 98 can selectively advance the pinion 95 to engage with the ring gear 99. The starter 96 can be mounted directly on the front or 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 resting state when it is not engaged with the engine crankshaft. The combustion chamber 30 is connected to an intake manifold 44 and an exhaust manifold 48 via an intake valve 52 and an exhaust valve 54, respectively. Each intake and exhaust valve can be actuated 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 valve 52 can be selectively activated and deactivated by a valve activation device 59. The exhaust valve 54 can be selectively activated and deactivated by a valve activation device 58. The valve activation devices 58 and 59 can be electromechanical devices.

[0013] The fuel injector 66 shown is positioned to inject fuel directly into cylinder 30, a process known to those skilled in the art as direct injection. The fuel injector 66 delivers liquid fuel proportional to the pulse width from the controller 12. Fuel is supplied to the fuel injector 66 by a fuel system (not shown) comprising a fuel reservoir, a fuel pump, and a fuel distribution line (not shown). In one example, a two-stage high-pressure fuel system can be used to generate higher fuel pressures.

[0014] Additionally, intake manifold 44 is shown communicating with a turbocharger compressor 162 and an engine air intake 42. In other examples, compressor 162 may be a supercharger compressor. Shaft 161 mechanically couples turbocharger turbine 164 to turbocharger compressor 162. An optional electronic throttle 62 adjusts a position of a throttle plate 64 to control airflow from compressor 162 to intake manifold 44. A pressure within a boost chamber 45 may be referred to as a throttle inlet pressure because the inlet of throttle 62 is located within boost chamber 45. The throttle outlet is located in the intake manifold 44. In some examples, the throttle valve 62 and the throttle plate 64 may be positioned between the intake valve 52 and the intake manifold 44 such that the throttle valve 62 is an intake port throttle valve.A compressor return valve 47 can be selectively adjusted to several positions between fully open and fully closed. A wastegate 163 can be adjusted via the control unit 12 to allow exhaust gases to bypass the turbine 164 in a controlled manner, thus controlling the speed of the compressor 162. An air filter 43 cleans the air entering the engine air intake 42.

[0015] A distributorless ignition system 88 provides a spark to the combustion chamber 30 via a spark plug 92 in response to the control unit 12. A wideband lambda sensor (UEGO - Universal Exhaust Gas Oxygen) 126 is shown coupled to the exhaust manifold 48 upstream of a catalytic converter 70. Alternatively, a dual-state lambda sensor can be used instead of the UEGO sensor 126.

[0016] In one example, a catalyst 70 can contain several catalyst modules. In another example, several exhaust gas purification devices, each with multiple modules, can be used. In another example, the catalyst 70 can be a three-way catalyst.

[0017] The control 12 is in Fig. 1 shown as a conventional microcomputer, comprising: a microprocessor unit 102, input / output ports 104, a read-only memory 106 (e.g. non-volatile memory), a read / write memory 108, a persistence memory 110 and a conventional data bus.In the illustration, the controller 12 receives various signals from sensors coupled to the engine 10, in addition to the signals previously discussed, including: an engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 for sensing a force applied by a foot 132; a position sensor 154 coupled to a brake pedal 150 for sensing a force applied by a foot 152; an intake manifold pressure (MAP) measurement 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; a measurement of mass air entering the engine from a sensor 120; and a measurement of throttle position from a sensor 68.Barometric pressure may also be sensed for processing by controller 12 (sensor not shown). In a preferred aspect of the present description, engine position sensor 118 generates a predetermined number of evenly spaced pulses at each revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0018] In operation, each cylinder in the engine 10 typically goes through a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes, and the intake valve 52 opens. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder to increase the volume in the combustion chamber 30. The position in which the piston 36 is near the bottom of the cylinder and at the end of its stroke (for example, when the combustion chamber 30 has reached its maximum volume) is generally referred to by those skilled in the art as bottom dead center (BDC).

[0019] During the compression stroke, the intake valve 52 and exhaust valve 54 are closed. The piston 36 moves towards the cylinder head to compress the air in the combustion chamber 30. The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 has its smallest volume) is generally referred to by those skilled in the art as top dead center (TDC). In a process referred to below as injection, fuel is introduced into the combustion chamber. In a process referred to below as ignition, the injected fuel is ignited by known ignition means, such as a spark plug 92, resulting in combustion.

[0020] During the power stroke, the expanding gases push the piston 36 back to BDC. The crankshaft 40 converts the piston motion into rotational torque of the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to discharge 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 only as an example, and that the timing of intake and exhaust valve opening and / or closing may vary to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0021] Fig. Figure 2 is a block diagram of a vehicle 225, which includes a powertrain 200. The powertrain of the Fig. 2 includes the one in Fig. Figure 1 shows a power unit 10. In the illustration, the powertrain 200 includes a vehicle system controller 255, a power unit controller 12, an electric machine controller 252, a transmission controller 254, and a brake controller 250. The controllers can communicate via a Controller Area Network (CAN) 299. Each of the controllers can provide information to other controllers, such as torque output limits (e.g., a maximum torque output of the controlled device or component), torque input limits (e.g., a maximum torque input of the controlled device or component), sensor and actuator data, and diagnostic information (e.g., information regarding a deteriorated transmission, a deteriorated power unit, a deteriorated electric machine, or deteriorated brakes).Further, the vehicle system controller may provide commands to the engine controller 12, the electric machine controller 252, the transmission controller 254, and the brake controller 250 to achieve driver input requests and other requests based on the vehicle operating conditions.

[0022] For example, in response to a driver releasing the accelerator pedal and a vehicle speed, the vehicle control unit 255 can request a desired wheel torque to provide a desired rate of deceleration. The desired wheel torque can be provided by the vehicle control unit, which requests a first braking torque from the electric motor control unit 252 and a second braking torque from the brake control unit 250, with the first and second torques providing the desired braking torque at the vehicle wheels 216.

[0023] In other examples, the division of control of the powertrain devices may differ from that in Fig. 2 shown, it can be divided. For example, the vehicle system control 255, the power machine control 12, the electrical machine control 252, the transmission control 254 and the brake control 250 can be replaced by a single control.

[0024] In this example, the drive train 200 can be driven by the power machine 10 and the electric machine 240. In other examples, the power machine 10 can be omitted. The power machine 10 can be powered by a Fig. 1 or via an integrated starter / generator (ISG) 240. The ISG 240 (e.g., a high-voltage electrical machine (operating at more than 30 volts)) may also be referred to as an electric machine, a motor, and / or a generator. Furthermore, torque of the engine 10 may be adjusted via a torque actuator 204, such as a fuel injector, a throttle valve, etc.

[0025] A power engine output torque can be transmitted via a dual-mass flywheel 215 to the input side of a drivetrain disconnect clutch 236. The disconnect clutch 236 can be electrically or hydraulically actuated. The downstream side of the disconnect clutch 236 is shown mechanically coupled to an ISG input shaft 237.

[0026] The ISG 240 may be actuated to provide torque to the powertrain 200 or to convert powertrain torque during a regenerative braking mode into electrical energy to be stored in the electrical energy storage device 275. The ISG 240 has a higher output torque capacity than the Fig. The starter 96 shown in Figure 1. Furthermore, the ISG 240 directly drives the drive train 200 or is directly driven by the drive train 200. There are no belts, gears, or chains for coupling the ISG 240 to the drive train 200. Instead, the ISG 240 rotates at the same rate as the drive train 200. The electrical energy storage device 275 (e.g., high-voltage battery or power source) can be a battery, a capacitor, or an inductor. The downstream end of the ISG 240 is mechanically coupled via a shaft 241 to a drive wheel 285 of a torque converter 206. The upstream end of the ISG 240 is mechanically coupled to the disconnect clutch 236. The ISG 240 can provide positive or negative torque to the drive train 200 by operating as a motor or generator according to the instructions of the electrical machine control 252.

[0027] The torque converter 206 includes a turbine 286 for delivering torque to an 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 transmitted directly from the drive gear 285 to the turbine 286. The TCC is electrically actuated by the control unit 12. Alternatively, the TCC can be locked hydraulically. In this example, the torque converter can be considered a component of the transmission.

[0028] When the torque converter clutch 212 is fully disengaged, the torque converter 206 transmits engine torque to the automatic transmission 208 via fluid communication between the torque converter turbine 286 and the torque converter gear 285, enabling torque boosting. Conversely, when the torque converter clutch 212 is fully engaged, the engine output torque is transmitted directly to an input shaft (not shown) of the transmission 208 via the torque converter clutch. Alternatively, the torque converter clutch 212 may be partially engaged, allowing adjustment of the amount of torque transmitted directly to the transmission.The controller 12 may be configured to adjust the amount of torque passed through the torque converter 212 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or based on a driver-based engine operating request.

[0029] 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 an actual total number of revolutions of the input shaft 270 to an actual total number of 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 solenoid valves 209. The torque output from the automatic transmission 208 can also be transmitted to the wheels 216 to drive the vehicle via the output shaft 260. In particular, the automatic transmission 208 can, in response to a vehicle driving condition, transfer an input drive torque to the input shaft 270 before passing on an output drive torque to the wheels 216.The transmission control unit 254 selectively activates or engages the TCC 212, the gear clutches 211, and the forward clutch 210. The transmission control unit also selectively deactivates or disengages the TCC 212, the gear clutches 211, and the forward clutch 210.

[0030] Further, a frictional force may be applied to the wheels 216 by engaging the friction wheel brakes 218. In one example, the friction wheel brakes 218 may be engaged in response to the driver's foot pressing a brake pedal (not shown) and / or in response to instructions in the brake controller 250. Further, the brake controller 250 may apply the brakes 218 in response to information and / or requests from the vehicle system controller 255. In the same way, a frictional force on the wheels 216 may be reduced by disengaging the wheel brakes 218 in response to the driver's foot releasing the brake pedal, instructions from the brake controller, and / or instructions and / or information from the vehicle system controller. For example, the vehicle brakes may apply a frictional force to the wheels 216 via the controller 250 as part of an automated procedure for stopping an engine.

[0031] In response to a request to accelerate the vehicle 225, the vehicle control unit can receive a driver request torque from an accelerator pedal or other device. The vehicle control unit 255 then assigns a portion of the requested driver request torque to the engine and the remainder to the ISG (Integrated Starter Generator). The vehicle control unit 255 requests the engine torque from the engine control unit 12 and the ISG torque from the electric motor control unit 252. If the ISG torque plus the engine torque is less than a transmission input torque limit (e.g., a threshold value that must not 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.The transmission controller 254 selectively locks the torque converter clutch 212 and engages gears via the gear clutches 211 in response to shift schedules and TCC lock schedules, which may be based on input shaft torque and vehicle speed. Under some conditions, when it may be desired to charge an electric energy storage device 275, charging torque (e.g., negative ISG torque) may be requested while a non-zero driver demand torque is present. The vehicle system controller 255 may request increased engine torque to overcome the charging torque to achieve the driver demand torque.

[0032] In response to a request to decelerate the vehicle 225 and provide regenerative braking, the vehicle system controller may provide a desired negative wheel torque based on the vehicle speed and the brake pedal position. The vehicle system controller 255 then allocates a portion of the desired negative wheel torque to the ISG 240 (e.g., desired powertrain wheel torque) and the remaining portion to the friction brakes 218 (e.g., desired friction brake wheel torque). Further, the vehicle system controller may notify the transmission controller 254 that the vehicle is in regenerative braking mode, so that the transmission controller 254 shifts the gears 211 based on a customized shift schedule to increase regenerative braking efficiency.The ISG 240 supplies negative torque to the transmission input shaft 270. However, the negative torque provided by the ISG 240 may be limited by the transmission control unit 254, which outputs a negative transmission input shaft torque limit (e.g., a threshold value that must not be exceeded). Furthermore, the negative torque of the ISG 240 may be limited by the vehicle system control unit 255 or the electrical machine control unit 252 based on operating conditions of the electrical energy storage device 275 (e.g., restricted to below a threshold value for negative threshold torque). Any portion of the desired negative wheel torque that may 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 a combination of negative wheel torque from the friction brakes 218 and the ISG 240.

[0033] Accordingly, the torque control of the various powertrain components can be supervised by the vehicle system control with local torque control for the power machine 10, the transmission 208, the electric machine 240 and the brakes 218 provided via the power machine control 12, the electric machine control 252, the transmission control 254 and the brake control 250.

[0034] For example, in turbocharged or mechanically supercharged internal combustion engines, engine torque output can be controlled by adjusting a combination of ignition timing, fuel pulse width, fuel pulse timing, and / or air charge by controlling the throttle opening and / or valve timing, valve lift, and boost pressure. In the case of a diesel engine, the control unit 12 can control the 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 cylinder by cylinder to control the engine torque output.

[0035] The electrical machine control 252 can control the torque output and the generation of electrical energy from the ISG 240 by adjusting the current flowing to and from the field and / or armature windings of the ISG, as is known in the art.

[0036] The transmission controller 254 receives the transmission input shaft position via position sensor 271. The transmission controller 254 may convert the transmission input shaft position into an input shaft speed by deriving a signal from the position sensor 271. The transmission controller 254 may receive the transmission output shaft torque from the torque sensor 272. Alternatively, the sensor 272 may be a position sensor or both torque and position sensors. If the sensor 272 is a position sensor, the controller 254 derives a position signal to determine the transmission output shaft speed. The transmission controller 254 may also derive the transmission output shaft speed to determine the transmission output shaft acceleration.

[0037] The brake control unit 250 receives wheel speed information via the wheel speed sensor 221 and brake requests from the vehicle system control unit 255. The brake control unit 250 can also receive brake pedal position information from the [unclear text] in Fig. The brake pedal sensor 154 shown in Figure 1 receives the signal directly or via CAN 299. 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. For example, the brake controller 250 can provide the vehicle system controller 255 with a wheel torque limit (e.g., a threshold for negative wheel torque that must not be exceeded) so that negative ISG torque does not cause the wheel torque limit to be exceeded. For example, if the controller 250 outputs 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 wheels, taking the transmission ratio into account.

[0038] Thus, the system displays Fig. 1 and Fig. 2. A system comprising: a power unit; an engine / generator; a disconnect clutch positioned in a drivetrain between the power unit and the engine; a transmission coupled to the engine / generator; and a control unit comprising executable instructions stored in non-volatile memory for setting a clutch pressure in response to an actual transmission input shaft speed minus a predicted transmission input shaft speed. The system includes the fact that the predicted transmission input shaft speed is provided by multiplying a transmission output shaft speed by a currently selected gear ratio. The system further includes additional instructions for setting a friction braking torque in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed.The system further includes additional instructions for operating the system in a regenerative braking mode while adjusting clutch pressure. The system further includes additional instructions for reducing negative motor / generator torque to near zero torque in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed. The system further includes additional instructions for reducing a negative wheel torque limit toward zero in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed. The predicted transmission input speed is lower than the actual transmission input speed during nominal operation where no transmission degradation has occurred.In one example, the predicted transmission input speed is the transmission output shaft speed multiplied by the currently selected gear, minus a compensation. This compensation provides a speed margin to reduce the possibility of a false indication of transmission deterioration, and the compensation can vary depending on operating conditions. For example, the compensation can vary with the transmission fluid temperature.

[0039] Now referring to Fig. 3 shows an exemplary sequence which is carried out according to the method of Fig. 7 is carried out. The sequence of Fig. 3 can be achieved through the system of Fig. 1 and Fig. 2. The various graphs of the Fig. 3 are temporally aligned and occur simultaneously. The vertical lines at times T1 - T3 represent points in time that are of particular interest in the sequence. Fig. The prophetic sequence shown in point 3 represents a condition of gear coupling deterioration during recuperation mode.

[0040] The first graph from the top in Fig. Figure 3 is a graph of a selected gear ratio over time. The vertical axis represents the selected gear ratio, and the selected gear ratios are labeled along the vertical axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0041] The second graph from the top in the Fig. Figure 3 is a graph of a gearbox output shaft speed over time. The vertical axis represents the gearbox output shaft speed, which increases in the direction of the arrow on the vertical axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0042] The third graph from the top in the Fig. Figure 3 is a graph of a transmission input shaft speed over time. The vertical axis represents the transmission input shaft speed, and the transmission input shaft speed increases in the direction of the arrow on the vertical axis. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right. Curve 302 represents the actual transmission input shaft speed under conditions where no transmission deterioration is indicated. Curve 304 represents a predicted transmission input shaft speed minus a predetermined compensation for an allowable transmission input shaft speed variation. Curve 306 represents a transmission input shaft speed under a transmission clutch deterioration condition, where the method from Fig. 7 mitigation measures are provided. Transmission deterioration is not indicated if curve 306 matches curve 302. Line 310 represents a transmission input shaft speed below which the transmission pump output flow or pressure is less than a desired amount to maintain the desired transmission clutch pressures.

[0043] The fourth graph from the top in Fig. Figure 3 is a graph of drivetrain wheel torque over time. The vertical axis represents the drivetrain wheel torque, and negative drivetrain wheel torque increases in the direction of the arrow on the vertical axis below the horizontal axis. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right. Line 320 represents a desired drivetrain wheel torque (e.g., wheel torque supplied by the ISG and transmission). Line 322 represents a drivetrain wheel torque limit (e.g., a drivetrain wheel torque that must not be exceeded).

[0044] The fifth graph from the top in Fig. Figure 3 is a graph of a friction braking torque over time. The vertical axis represents a friction braking torque command, and the friction braking torque command increases (e.g., requirements for additional friction braking torque) in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0045] The sixth graph from the top in Fig. Figure 3 is a graph of wheel torque over time. The vertical axis represents the wheel torque, and the negative wheel torque increases in the direction of the arrow on the vertical axis below the horizontal axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right. The wheel torque shown in the sixth graph is the drivetrain wheel torque plus the friction braking torque.

[0046] At time T0, the transmission is in fifth gear and the vehicle is decelerating in response to a low driver demand torque (not shown). The vehicle is in regenerative braking mode. The transmission output shaft speed decreases as the vehicle speed decreases. The actual transmission input shaft speed decreases, and the predicted transmission input shaft speed also decreases. Transmission degradation is not indicated because the transmission input shaft speed during degradation is equal to the actual transmission input shaft speed. The actual transmission input speed is greater than level 310, so the transmission pump is operating as desired. The desired driveline wheel torque is negative, indicating driveline braking.The drivetrain wheel torque limit is greater than the desired drivetrain wheel torque; therefore, the drivetrain wheel torque is not limited. The friction brakes are applied at a low level.

[0047] At time T1, the transmission downshifts, and the actual transmission input shaft speed and the predicted transmission input shaft speed begin to increase in response to the downshift. The transmission output shaft speed continues to decrease as the vehicle continues to decelerate in regenerative braking mode. The desired drivetrain wheel torque and the drivetrain wheel torque remain at the same level. The friction braking torque also remains at the same level or amount. The wheel torque has a constant negative value.

[0048] Shortly before time T2, the transmission input shaft speed begins to decrease under a condition of transmission clutch deterioration in response to the transmission deterioration. The deterioration may originate from clutch deterioration of the fourth gear clutch.

[0049] At time T2, under a transmission clutch deterioration condition (curve 306), the transmission input shaft speed is reduced to a value lower than the predicted transmission input shaft speed. This condition initiates mitigation measures to reduce the possibility of the transmission pump output being lower than desired. If the transmission were not deteriorated, the transmission input shaft speed would continue to be as shown by curve 302. Because the transmission input shaft speed representing the transmission deterioration (curve 306) is lower than the predicted transmission input shaft speed (curve 304), the strength of the drivetrain wheel torque limiter (curve 322) is reduced to zero.The magnitude of the desired driveline wheel torque (curve 320) is reduced by reducing the magnitude of the negative ISG torque to the same level as the driveline wheel torque limit in response to decreasing the driveline wheel torque limit. Reducing the magnitude of the ISG torque allows the transmission input shaft speed to remain at a level greater than 310. As a result, the hydraulically actuated transmission components can remain active. Additionally, the friction braking torque command is increased to replenish or provide the braking torque that was reduced by reducing the magnitude of the negative driveline wheel torque limit. The wheel torque remains essentially constant (e.g., changes less than 10%) even when the driveline wheel torque is reduced because the friction braking torque is increased.

[0050] Between time T2 and time T3, the transmission is downshifted to third gear, and the third gear clutch holds third gear. The transmission input shaft speed, representing transmission degradation (plot 306), increases to a value greater than the predicted transmission speed, eventually reaching the transmission input shaft speed when no degradation is present. The driveline wheel torque limit is increased in response to the transmission input shaft speed being greater than the predicted transmission input shaft speed. The desired driveline wheel torque increases in response to the driveline wheel torque increasing. Friction brake torque is decreased to increase the electrical power output by the ISG in response to increasing the increased driveline wheel torque limit. The wheel torque remains essentially constant.

[0051] In this way, it may be possible to compensate for the deterioration of one or more transmission components, such as a clutch. The compensation provides rapid increases and decreases in friction braking torque, allowing the wheel torque to remain essentially constant, even during transmission deterioration while the vehicle is in regenerative braking mode.

[0052] Now referring to Fig. Figure 4 shows an exemplary sequence for adjusting the drivetrain wheel torque control according to the procedure of Fig. 7 shows the sequence of Fig. 4 can be made by the system Fig. 1 and Fig. 2 will be provided. The various graphs from Fig. Four events are chronologically aligned and occur simultaneously. The vertical lines at times T11–T13 represent points in time that are of particular interest in the sequence. The Fig. The prophetic sequence shown in Figure 4 represents a condition for deterioration of the control valve of the transmission clutch during recuperation mode.

[0053] The first graph from the top in Fig. Figure 4 is a graph of a selected gear ratio over time. The vertical axis represents the selected gear ratio, and the selected gear ratios are labeled along the vertical axis. Time starts on the left side of the figure and increases towards the right.

[0054] The second graph from the top in the Fig. Figure 4 is a graph of drivetrain wheel torque over time. The vertical axis represents the drivetrain wheel torque, and negative drivetrain wheel torque increases in the direction of the arrow on the vertical axis below the horizontal axis. Time starts on the left side of the figure and increases toward the right. Line 402 represents drivetrain wheel torque (e.g., wheel torque supplied via the ISG and transmission) for degraded transmission conditions. Line 404 represents a drivetrain wheel torque limit (e.g., a drivetrain wheel torque that must not be exceeded). Line 406 represents drivetrain wheel torque (e.g., wheel torque supplied via the ISG and transmission) for transmission conditions that are not degraded.

[0055] The third graph from the top in Fig. Figure 4 is a graph of a friction braking torque over time. The vertical axis represents a friction braking torque command, and the friction braking torque command increases (e.g., requirements for additional friction braking torque) in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0056] The fourth graph from the top in the Fig. Figure 4 is a graph of wheel torque over time. The vertical axis represents the wheel torque, and the negative wheel torque increases in the direction of the arrow on the vertical axis below the horizontal axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right. The wheel torque shown in the fourth graph is the drivetrain wheel torque plus the friction braking torque.

[0057] At time T10, the transmission is in third gear and decelerating in response to a low driver request torque (not shown). The vehicle is not in regenerative braking mode. There is no transmission degradation, and the degraded drivetrain torque is zero. The non-degraded drivetrain wheel torque is also zero, and the drivetrain wheel torque limit is a large negative value, indicating that it is possible to induce a large negative torque in the drivetrain via the ISG. The friction brakes are not applied, as indicated by the friction brake torque command of zero. Wheel torque is also at a low level.

[0058] At time T11, the vehicle switches to recuperation mode and begins to apply a negative drivetrain wheel torque, as indicated by the drivetrain wheel torque for deteriorated conditions (curve 402) and drivetrain wheel torque for non-deteriorated conditions (curve 406). The drivetrain wheel torque limit remains at a large negative value.

[0059] At time T12, degradation is indicated because the actual transmission input shaft speed is less than the predicted transmission input shaft speed (not shown). The driveline wheel torque limit is reduced in response to the actual transmission input shaft speed being less than the predicted transmission input shaft speed. The driveline wheel torque for degraded conditions is reduced to a value equal to the driveline wheel torque limit. If degradation had not been present, the driveline wheel torque would have been at the level of the driveline wheel torque for non-degraded conditions. Because the driveline wheel torque is reduced in response to an unexpected transmission input shaft speed, the desired braking level is provided by increasing the friction braking torque request and the friction braking torque.The negative ISG torque is reduced in response to the reduced powertrain wheel torque limit (curve 404). As a result, the transmission input shaft speed (not shown) is maintained at a higher level than if the powertrain wheel torque limit had not been reduced. The negative wheel torque increases in response to the increased friction braking torque and the initial increase in powertrain wheel torque.

[0060] Between time T12 and time T13, the transmission downshifts from third gear to second gear. The second-gear shift solenoid is activated, engaging second gear. As time T13 approaches, the engagement of second gear causes the actual transmission input shaft speed to increase to a value greater than the predicted transmission input shaft speed. In response to the actual transmission input shaft speed being greater than the predicted transmission input shaft speed (not shown), the transmission wheel torque limit is increased. The transmission wheel torque for deteriorated conditions is also increased in response to this increased limit. Furthermore, the friction brake torque command is reduced in response to the increased transmission wheel torque for deteriorated conditions.The wheel torque continues to have a nearly constant negative value in order to brake the vehicle.

[0061] At time T13, the friction braking torque command is reduced to zero in response to the fact that the drivetrain wheel torque for deteriorating conditions provides a desired amount of drivetrain braking, as indicated by the drivetrain wheel torque for non-deteriorating conditions. Furthermore, the friction braking torque command is reduced to zero, allowing the drivetrain to recover more energy from the vehicle.

[0062] In this way, the operation of the friction brakes can be coordinated with the drivetrain wheel torque generation to provide a desired amount of vehicle braking even under conditions of transmission deterioration. Furthermore, friction braking can be reduced after the deteriorating vehicle conditions have been eliminated.

[0063] Now referring to Fig. 5 shows an exemplary sequence which is carried out according to the method of Fig. 7 is carried out. The sequence of Fig. 5 can be achieved through the system of Fig. 1 and Fig. 2. The various graphs of the Fig. 5 are temporally aligned and occur simultaneously. The vertical lines at times T21 - T26 represent points in time that are of particular interest in the sequence. Fig. The prophetic sequence shown in Figure 5 represents a transmission clutch capacity degradation condition during regenerative braking mode.

[0064] The first graph from the top in Fig. Figure 5 is a graph of a selected transmission gear over time. The vertical axis represents the selected transmission gear, and the selected gears are labeled along the vertical axis. The horizontal axis represents time. Time begins on the left side of the figure and increases toward the right side of the figure.

[0065] The second graph from the top in the Fig. Figure 5 is a graph of a transmission input shaft speed over time. The vertical axis represents the transmission input shaft speed, and the transmission input shaft speed increases in the direction of the arrow on the vertical axis. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right. Curve 502 represents a transmission input shaft speed for non-deteriorated conditions. Curve 504 represents a predicted transmission input shaft speed minus a predetermined compensation for an expected transmission input shaft speed variation. Curve 506 represents a transmission input shaft speed under a transmission clutch capacity deterioration condition, where the procedure of Fig. 7 mitigation measures. Transmission degradation is not indicated when curve 506 corresponds to curve 502. Line 510 represents a transmission input shaft speed below which the transmission pump output is less than a desired amount to maintain the desired transmission clutch pressures.

[0066] The third graph from the top in FIG. 5 is a graph of a load-supplying clutch pressure over time. The vertical axis represents the load-supplying clutch pressure, which increases in the direction of the arrow on the vertical axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0067] The fourth graph from the top in Fig. Figure 5 is a graph of incoming clutch pressure over time. The vertical axis represents incoming clutch pressure, and the incoming clutch pressure increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time begins on the left side of the figure and increases toward the right side.

[0068] At time T20, the transmission is in third gear, and the transmission input shaft speed for deteriorated and non-deteriorated conditions is the same, both being higher than the predicted transmission input shaft speed to indicate that there is no transmission clutch capacity deterioration. The load-sending clutch pressure is higher to indicate that third gear is engaged. The incoming clutch pressure is lower to indicate that the second gear clutch is not engaged. Second gear is selected shortly before time T21.

[0069] At time T21, the system switches to the shift support phase to pre-position the incoming clutch surfaces (e.g., second gear clutch) before switching to the torque phase and to reduce the pressure in the load-emitting clutch (e.g., third gear clutch) before the load-emitting clutch begins to slip. Pressure in the load-emitting clutch is released, and the volume in the incoming clutch begins to fill with fluid. The transmission input shaft speed for degraded and non-degraded conditions is the same, with both being higher than the predicted transmission input shaft speed, thus indicating no transmission clutch capacity degradation.

[0070] At time T22, the system switches to the shift-start phase. Pressure in the disengaging clutch is maintained while pressure in the incoming clutch is increased to boost the pressure delivered to it. The transmission input shaft speed for degraded and non-degraded conditions is the same, with both being higher than the predicted transmission input shaft speed, indicating no transmission clutch capacity degradation.

[0071] At time T23, the shifter enters the torque phase, with the negative ISG torque being split between the path through third gear and the path through second gear. The load-sensing clutch pressure is reduced, while the incoming clutch pressure is increased.

[0072] Between time T23 and time T24, the incoming clutch does not transmit the expected amount of torque. Therefore, the transmission input shaft speed is reduced to a speed lower than the predicted transmission input shaft speed, as indicated because the transmission input shaft speed for deteriorated conditions is lower than the predicted transmission input shaft speed. The transmission input shaft speed is reduced because negative ISG torque is delivered to the drivetrain. The transmission speed for non-deteriorated conditions is at a level higher than the predicted transmission input shaft speed.

[0073] The disengaging clutch pressure is increased, and the incoming clutch pressure is decreased, in response to the transmission input shaft speed being lower than the predicted input shaft speed for re-engaging third gear. Re-engaging third gear via the disengaging clutch increases the transmission input shaft speed, as indicated by the input shaft speed for deteriorated conditions. The transmission input shaft speed is increased while kinetic energy from the vehicle is delivered to the ISG. Therefore, the transmission input shaft speed remains above 510, allowing the transmission pump pressure to be maintained at the desired level. Thus, re-engaging third gear via the disengaging clutch reduces the possibility of the transmission pump delivering lower than desired pressure.

[0074] At time T24, the transmission enters the inertia phase, where the slip of the oncoming clutch would have been reduced. However, as the pressure to the off-loading clutch increases, the slip of third gear, or previously the off-loading clutch, is reduced. The pressure in the oncoming clutch (e.g., second gear clutch) remains at a low level, so both gears are not engaged.

[0075] Between time T25 and time T26, the transmission shifts into the final phase, with the third gear clutch (previously the power-releasing clutch) fully locked and slippage eliminated. When the transmission input shaft speed is reduced to approximately 510, the transmission can be downshifted to first gear instead of second gear.

[0076] In this way, the pressure in the discharge and input clutches can be controlled to reduce the possibility of the transmission input shaft speed dropping below a threshold level, with the transmission pump output being less than a threshold. Since the vehicle is in regenerative braking mode, the negative ISG torque tends to increase the deceleration of the transmission input shaft during a downshift unless the input clutch is able to fully engage. The sequence of Fig. 5 can reduce the possibility that the transmission input shaft speed is reduced to a speed below a threshold speed, with the transmission output being lower than a desired threshold output (e.g. lower than a desired flow rate and / or pressure).

[0077] Now referring to Fig. Figure 6 shows an exemplary sequence, which is carried out according to the procedure of Fig. 7 is carried out. The sequence of Fig. 6 can be achieved through the system of Fig. 1 and Fig. 2. The various graphs of the Fig. Six events are chronologically aligned and occur simultaneously. The vertical lines at times T31–T33 represent points in time that are of particular interest in the sequence. The Fig. The prophetic sequence shown in Figure 6 represents a condition of transmission clutch capacity deterioration during recuperation mode.

[0078] The first graph from the top in Fig. Figure 6 is a graph of a selected transmission gear over time. The vertical axis represents the selected transmission gear, and the selected gears are labeled along the vertical axis. The horizontal axis represents time. Time begins on the left side of the figure and increases toward the right side of the figure.

[0079] The second graph from the top in the Fig. Figure 6 is a graph of a transmission input shaft speed over time. The vertical axis represents the transmission input shaft speed, and the transmission input shaft speed increases in the direction of the arrow on the vertical axis. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right. Curve 602 represents a transmission input shaft speed for non-deteriorated conditions. Curve 604 represents a predicted transmission input shaft speed minus a predetermined compensation for an allowable transmission input shaft speed variation. Curve 606 represents a transmission input shaft speed under a transmission clutch capacity deterioration condition, where the method of Fig. 7 mitigating measures. Transmission degradation is not indicated when curve 606 corresponds to curve 602. Curve 608 represents a transmission input shaft speed when no mitigating measures are taken to maintain the transmission input shaft speed above the speed of line 610. Line 610 represents a transmission input shaft speed below which the transmission pump output is less than a desired amount to maintain the desired transmission clutch pressures.

[0080] The third graph from the top in FIG. 6 is a graph of active gear coupling capacity over time. The vertical axis represents active gear coupling capacity (e.g., the amount of torque the coupling can transmit), and the active gear coupling capacity increases in one direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right.

[0081] At time T30, the transmission is in third gear, and the transmission input shaft speed for degraded and non-degraded conditions is the same, with both being higher than the predicted transmission input shaft speed, indicating that there is no transmission clutch capacity degradation. The active gear clutch capacity is at a higher level, indicating that the active gear clutch capacity is high.

[0082] At time T31, the active clutch capacity decreases. This decrease could be a result of a line leak, clutch seal deterioration, or shift magnet deterioration. Because the vehicle is in recuperation mode, the negative ISG torque would slow the transmission input shaft speed, as shown by curve 608, if no mitigation measures were taken. The procedure of Fig. However, step 7 recognizes that the transmission input shaft speed is lower than the predicted transmission input shaft speed. Therefore, the strength of the drivetrain wheel torque limit is reduced from a large negative torque value to near zero. As a result, the transmission input shaft speed follows the trajectory of curve 606 instead of curve 608. If the clutch capacity had not been reduced, the transmission input shaft speed would have followed the trajectory of curve 602 and fallen below level 610.

[0083] In the context of the description of Fig. 3-6 reduces the strength of the drivetrain wheel torque when setting from -200 Nm to -100 Nm, because at -100 Nm a lower negative drivetrain wheel torque is applied to the wheels than at -200 Nm.

[0084] Now referring to Fig. Figure 7 describes a method for operating a vehicle powertrain. At least parts of the method 700 can be implemented as executable control instructions stored in non-volatile memory. Additionally, parts of the method 700 can be actions taken in the physical world to change an operating state of an actuator or device.

[0085] In procedure 702, procedure 700 determines vehicle operating conditions. Vehicle operating conditions can include, among other things, vehicle speed, driver input torque, transmission input shaft speed, battery charge level, and brake pedal position. Vehicle operating conditions can be determined via a controller that requests inputs. After determining the operating conditions, procedure 700 proceeds to 704.

[0086] At 704, procedure 700 assesses whether the vehicle is in regenerative braking mode. During regenerative braking, the vehicle's kinetic energy is converted into electrical energy and stored in an energy storage device. The vehicle's integrated starter generator (ISG) provides negative torque to the drivetrain and wheels when the vehicle is operating in regenerative braking mode. The vehicle can enter regenerative braking mode when a set of conditions is met. For example, the vehicle can enter regenerative braking mode if the battery state of charge is less than a threshold, a driver request torque is less than a threshold, the torque converter clutch is locked, and the vehicle speed is greater than a threshold. If procedure 700 determines that the vehicle is in regenerative braking mode, the answer is yes, and procedure 700 proceeds to 706.Otherwise, the answer is no, and procedure 700 proceeds to 767.

[0087] At 767, procedure 700 disables transmission ratio monitoring (e.g., comparing the predicted transmission input shaft speed with the actual transmission input shaft speed) and operates the ISG and the power unit based on vehicle operating conditions, including driver request torque, battery charge level, and vehicle speed. Procedure 700 terminates after the transmission ratio monitoring is disabled.

[0088] In 706, the procedure 700 determines a lower transmission input shaft speed threshold, which is also referred to as a predicted transmission input shaft speed, as in Fig. 3-6 described, can be designated. In an example, the lower transmission input shaft speed threshold can be determined by the following equation: NIS_threshold=(OSS⋅SR)−Offset(Tinput,NIS,OilT) where M IS_threshold the lower transmission input shaft speed threshold (e.g. curve 304 of the Fig. 3) OSS is the transmission output shaft speed, SR is the gear ratio of transmission output shaft speed to input shaft speed or the transmission ratio from the output shaft to the input shaft, Offset (compensation) is a compensating speed that takes clutch slippage into account during shifting, T input the transmission input shaft torque is N IS the input shaft speed is and oil T The transmission oil temperature is...

[0089] Additionally, in some examples, the speed threshold N IS_thresholdbased on a per-gear calibration. The calibration can also be linked to a transmission shift pattern. For example, if the downshift points for each downshift from 4th gear (4-3, 4-2, 4-1) are always greater than 1200 RPM, then the RPM threshold for 4th gear can be set at 1000 RPM. The transmission input shaft speed should not fall below 1000 RPM in the absence of degradation. If the transmission input shaft speed is less than the 1000 RPM threshold, then the minimum input shaft torque is reduced from a larger negative torque to a torque approaching zero, with the reduction occurring in the same manner as described above. Fig. 3-6 is used. Method 700 proceeds to 708 after the lower transmission input shaft speed threshold is determined.

[0090] At 708, method 700 determines a speed difference between the lower transmission input shaft speed threshold and the transmission input shaft speed. The speed difference may be determined by the following equation: Ndiff=NIS−NIS_threshold where Ndiff is the speed difference. Procedure 700 transitions to 710 after the speed difference has been determined.

[0091] At 710, procedure 700 determines a negative drivetrain wheel torque limit (e.g., curve 322 of the Fig. 3) The negative powertrain wheel torque limit is a maximum threshold for negative wheel torque generated at the vehicle wheels via the ISG (Integrated Starter Generator). For example, if the negative powertrain wheel torque limit is -100 Nm, the ISG torque generated at the wheels must not exceed -100 Nm. Therefore, the ISG can generate -99 Nm at the wheels without exceeding a negative powertrain wheel torque limit of -100 Nm. As an example, the negative powertrain wheel torque limit can be determined using the following equation: TPW_LIM=TLIM(Ndiff,NIS) where T PW_LIM is the negative driveline wheel torque limit, T LIM is a function of empirically determined wheel torque limiting values ​​based on or indexed by N diff and M ISThe table or function may contain values ​​such as that for large positive speed differences (e.g., Ndiff=NIS−NIS_threshold ) the negative drivetrain wheel torque allows a larger negative wheel torque (e.g. -100 Nm); at small positive speed differences the negative drivetrain wheel torque allows smaller, non-limiting negative wheel torques (e.g. -20 Nm); at small negative speed differences a small amount of negative drivetrain wheel torque limitation is provided (e.g. a reduction of 20 Nm to maximum negative drivetrain wheel torque), at large negative speed differences a larger amount of negative drivetrain wheel torque limitation is provided (e.g. a reduction of 80 Nm to maximum negative drivetrain wheel torque).

[0092] In some examples, the negative drivetrain wheel torque limit can also be dynamically adjusted using integral control based on the speed difference. With this approach, the negative drivetrain wheel torque limit can be driven towards zero until the input speed exceeds the speed threshold N. IS_threshold increases. The rate at which the speed increases depends on a speed difference magnitude. The wheel torque magnitude limit may also be set for the duration of the event that the transmission shaft speed is below the threshold speed (e.g., until other mitigation measures are taken). Once a new gear is selected (or similar), the negative powertrain wheel torque magnitude limit may be removed. Method 700 proceeds to 712 after the negative powertrain wheel torque limit is determined.

[0093] At 712, method 700 decides the negative powertrain wheel torque magnitude limit T PW_LIM and a negative powertrain torque limiter. As with the Fig. 2, a desired negative wheel torque may be requested during regenerative braking based on operating conditions such as brake pedal position and vehicle speed. The desired negative wheel torque is equal to the desired friction braking torque plus the desired negative powertrain wheel torque. In one example, the brake controller provides the desired friction braking torque request based on the desired negative powertrain wheel torque minus the desired negative powertrain wheel torque. The desired negative powertrain wheel torque and the desired negative wheel torque may be sent to the friction braking controller by the vehicle system controller so that the brake controller may determine the desired friction braking torque.The desired negative driveline wheel torque magnitude can be reduced to a level equal to the negative driveline wheel torque magnitude limit or a negative driveline torque magnitude limit set for the currently selected transmission ratio and final drive ratio. In one example, the desired negative driveline wheel torque magnitude cannot exceed a lower value of the negative driveline wheel torque magnitude limit or the negative driveline torque magnitude limit set for the currently selected transmission ratio.For example, if the desired negative wheel torque is -35 Nm and the negative drivetrain wheel torque limit is -20 Nm, the desired negative drivetrain wheel torque is -30 Nm, and the negative drivetrain torque limit set for the currently selected gear ratio is -25 Nm, where -20 Nm of negative drivetrain wheel torque is provided by the drivetrain and -15 Nm is provided by the friction brakes. Thus, the sum of the braking torque and the negative drivetrain wheel torque is the desired negative wheel torque. The friction brakes are set at 712 based on the negative drivetrain wheel torque limit, the desired negative drivetrain wheel torque, the desired negative wheel torque, and the negative drivetrain torque limit.If the desired negative drivetrain wheel torque is less than the lower value of the negative drivetrain wheel torque limit and the negative drivetrain torque limit set for the currently selected gear ratio, the desired negative drivetrain wheel torque is not set. Procedure 700 proceeds to 714 after the negative drivetrain wheel torque limit T. PW_LIM and a negative powertrain torque limit has been decided upon.

[0094] In case 714, the procedure 700 determines the negative drivetrain wheel torque limit T. PW_LIMto a transmission input shaft torque requirement. The negative drivetrain wheel torque limit can be converted into a negative drivetrain input shaft torque limit by multiplying the negative drivetrain wheel torque limit by the currently selected transmission ratio, including the final drive ratio (e.g., axle ratio). Likewise, the negative drivetrain wheel torque can be converted into a negative drivetrain input shaft torque by multiplying the negative drivetrain wheel torque by the currently selected transmission ratio and the final drive ratio.The desired or requested transmission input shaft torque must not exceed the lower of the negative drivetrain wheel torque limit multiplied by the currently selected gear ratio, or the desired negative drivetrain wheel torque multiplied by the currently selected gear ratio. On model 714, the transmission input shaft torque is set to the desired transmission input shaft torque by adjusting the ISG torque setting.If the desired transmission input shaft torque is less than the lower value of the negative driveline wheel torque magnitude limit multiplied by the currently selected transmission ratio, including the final drive ratio, or the desired negative driveline wheel torque multiplied by the currently selected transmission ratio, including the final drive ratio, the desired transmission input shaft torque is not set. Method 700 proceeds to 716 after the transmission input shaft torque is set.

[0095] At 716, method 700 takes other mitigating actions if the transmission input shaft speed is less than the threshold speed determined at 706 or based on the difference determined at 708. In particular, method 700 may upshift or downshift the transmission to a different gear than was selected at the time the transmission input shaft speed was determined to be less than the threshold speed or greater than a predetermined difference determined at 708. The transmission may upshift or downshift by adjusting the pressure provided to one or more gear clutches. Further, method 700 may decrease the amount of negative torque output by the ISG (e.g., from a larger negative value toward zero) or provide positive torque via the ISG. Method 700 proceeds to exit after mitigating actions are taken.The mitigation measures can enable the transmission input shaft speed to be kept higher than a threshold speed, while providing a desired transmission pump output.

[0096] Thus, the procedure of Fig. 7. Provide a powertrain operating procedure that includes: predicting a transmission input shaft speed from a transmission output shaft speed; and adjusting an actuator in response to an actual transmission input shaft speed minus the predicted transmission input shaft speed. The procedure involves predicting the transmission input shaft speed by multiplying the transmission output shaft speed by a currently selected gear ratio. The procedure further includes adjusting a friction braking torque in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed.

[0097] In some examples, the method further includes determining a negative drivetrain wheel torque limit based on the actual transmission input shaft speed minus the predicted transmission input shaft speed. The method further includes determining a negative drivetrain torque based on the actual transmission input shaft speed minus the estimated transmission input shaft speed. The method further includes setting the torque of an integrated starter / generator to provide the negative drivetrain torque.

[0098] The procedure of Fig.7 also provides a powertrain operating method comprising: decreasing a negative wheel torque magnitude limit toward a value of zero in response to an actual transmission input shaft speed decreasing below a threshold; and adjusting a motor / generator torque to provide negative wheel torque less than the negative wheel torque limit. The method further includes increasing a friction brake torque to provide a desired wheel brake torque based on an adjustment of the motor / generator negative torque. The method includes increasing the friction brake torque by an amount of torque by which the motor / generator is decreased. The method includes commanding a transmission for a fixed gear ratio while the transmission input shaft speed decreases below a threshold.

[0099] In some examples, the method involves a transmission receiving a command to shift between two gear ratios while the transmission input shaft speed decreases below the threshold. The method involves a powertrain, in which the engine / generator is operating, being in a regenerative braking mode. The method further involves determining a negative powertrain wheel torque limit based on the actual transmission input shaft speed minus a predicted transmission input shaft speed. The method further involves adjusting the engine / generator torque to maintain a transmission input shaft speed greater than the speed at which a transmission pump delivers a threshold flow.

[0100] It should be noted that the example control and estimation routines included herein are usable with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system, including the controller along with the various sensors, actuators, and other engine equipment. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various illustrated actions, operations, and / or functions may be performed in the illustrated sequence, performed in parallel, or in some cases, omitted.Accordingly, the processing sequence is not strictly necessary to achieve the features and advantages of the embodiments described here, but merely serves to facilitate presentation and description. One or more of the described measures, processes, and / or functions can be performed repeatedly, depending on the strategy employed. Furthermore, at least some of the described measures, processes, and / or functions can graphically represent code that is to be programmed into non-volatile memory of the computer-readable storage medium in the control system. The control measures can also change the operating state of one or more sensors or actuators in the physical world when the described measures are carried out by executing the instructions in a system, including the various power machine hardware components in combination with one or more controllers.

[0101] This concludes the description. A reading of it by a person skilled in the art would reveal many changes and modifications without departing from the intent and scope of the description. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating on natural gas, gasoline, diesel, or alternative fuel designs could make advantageous use of the present description.

Claims

[1] Powertrain operating procedure that includes: Predicting a transmission input shaft speed from a Transmission output shaft speed; and Adjusting an actuator in response to an actual Transmission input shaft speed minus the predicted Transmission input shaft speed; and Determining a negative driveline wheel torque limit based on the actual transmission input shaft speed minus the predicted transmission input shaft speed. [2] The method of claim 1, wherein the transmission input speed is predicted by multiplying the transmission output shaft speed by a currently selected transmission ratio and subtracting an offset. [3] The method of claim 1, further comprising adjusting a friction brake torque in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed. [4] The method of claim 1, further comprising determining a negative driveline torque based on the actual transmission input shaft speed minus the predicted transmission input shaft speed. [5] The method of claim 4, further comprising adjusting a torque of an integrated starter / generator to provide the negative driveline torque. [6] Powertrain operating procedure comprising: Decreasing a negative wheel torque magnitude limit toward a value of zero in response to an actual transmission input shaft speed decreasing below a threshold; and Setting a torque of a motor / generator to provide negative wheel torque that is less than the negative wheel torque limit. [7] The method of claim 6, further comprising increasing a friction braking torque to provide a desired wheel braking torque based on adjusting the torque of the motor / generator. [8] The method of claim 7, wherein the friction braking torque is increased by an amount of torque by which the motor / generator is reduced. [9] The method of claim 6, wherein a transmission receives a fixed gear ratio command while the transmission input shaft speed decreases below a threshold. [10] The method of claim 6, wherein a transmission receives a command to shift between two gear ratios while the transmission input shaft speed decreases below the threshold. [11] The method of claim 6, wherein a powertrain in which the motor / generator is operated is in a recuperation mode. [12] The method of claim 6, further comprising determining a negative driveline wheel torque limit based on the actual transmission input shaft speed minus a predicted transmission input shaft speed. [13] The method of claim 6, further comprising adjusting the torque of the motor / generator to maintain a transmission input shaft speed at a speed greater than a speed at which a transmission pump outputs a threshold flow. [14] System comprising: a power machine; a motor / generator; a disconnect clutch positioned in a driveline between the engine and the motor / generator; a transmission coupled to the motor / generator; and a controller that provides executable instructions stored in a non-volatile memory for adjusting a clutch pressure in response to an actual transmission input shaft speed minus a predicted Transmission input shaft speed includes; and further comprising additional instructions for reducing a negative motor / generator torque to near zero torque in response to the actual transmission input shaft speed minus the predicted Transmission input shaft speed. [15] The system of claim 14, wherein the predicted transmission input shaft speed is provided by multiplying a transmission output shaft speed by a currently selected transmission ratio. [16] The system of claim 14, further comprising additional instructions for adjusting a friction brake torque in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed. [17] The system of claim 16, further comprising additional instructions for operating the system in a regenerative mode during the adjustment of the clutch pressure. [18] The system of claim 14, further comprising additional instructions for decreasing a negative torque limit toward a value of zero in response to the actual transmission input shaft speed minus the predicted transmission input shaft speed.

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