System and method for starting a vehicle hybrid powertrain

Abstract

The present disclosure relates to a system and method for starting a hybrid powertrain of a vehicle. The vehicle includes a disconnect clutch that selectively connects an engine and an electric motor. The vehicle also includes a mechanical pump driven by the electric motor and operable to pressurize the fluid of the clutch. The vehicle includes a controller configured to: in response to the electric motor being inoperable, enable an auxiliary starter to start the engine, enable an electric pump operable to pressurize the fluid of the clutch, and operate the engine to drive the mechanical pump.

Description

Technical Field

[0001] The present application generally relates to operating a hybrid vehicle when a high voltage electric machine is unavailable. Background Art

[0002] A hybrid vehicle includes an electric motor powered by a high voltage power source. The electric motor is capable of providing propulsion torque for the vehicle. The electric motor is also used to crank the engine to start it. In the event that the high voltage electric motor is not available, the engine cannot be started. Summary of the invention

[0003] A control system for a hybrid powertrain system includes a controller configured to: in response to an electric motor configured to drive a mechanical pump operable to pressurize fluid in a clutch between an engine and an electric motor being inoperable, (i) enable an auxiliary starter to start the engine, (ii) enable an electric pump configured to pressurize fluid, (iii) actuate a valve to enable fluid to flow to the clutch, and (iv) operate the engine to drive the mechanical pump.

[0004] The mechanical pump is operable to pressurize the fluid of the clutch to a certain fluid pressure, which is higher than the predetermined locking pressure that causes the clutch to lock when the valve is actuated. The electric pump is operable to pressurize the fluid of the clutch to a certain fluid pressure level, which is lower than or equal to a predetermined electric pump maximum pressure, which is lower than the predetermined locking pressure. The controller can also be configured to command a transmission shift clutch to a closed state to maximize the pressure of the clutch, and the transmission shift clutch is connected to the same fluid circuit as the clutch. The controller can also be configured to operate the engine at a speed of at least a predetermined engine speed, and the predetermined engine speed is configured to rotate the mechanical pump at a predetermined pump speed, at which the fluid pressure exceeds the predetermined locking pressure of the clutch. The controller can also be configured to increase the engine torque in response to the activation of the electric pump to prevent the engine speed from decreasing. The controller can also be configured to disable the engine automatic stop in response to the motor being inoperable.

[0005] A vehicle includes a clutch that selectively connects an engine to an electric motor and a mechanical pump that is driven by the electric motor and is operable to pressurize the fluid of the clutch. The vehicle also includes a controller that is configured to: in response to the electric motor being inoperable, enable the electric pump that is operable to pressurize the fluid of the clutch, and enable an auxiliary starter to start the engine to drive the mechanical pump.

[0006] The controller may also be configured to disable automatic engine stop in response to the motor being inoperable. The controller may also be configured to increase engine torque in response to the activation of the electric pump to prevent the engine speed from decreasing. The controller may also be configured to operate the engine at a speed of at least a predetermined engine speed, the predetermined engine speed being configured to rotate the mechanical pump at a predetermined pump speed, at which the fluid pressure exceeds a predetermined locking pressure of the clutch. The controller may be configured to command a transmission shift clutch to a closed state to maximize the pressure of the clutch, the transmission shift clutch being connected to the same fluid circuit as the clutch. The mechanical pump may be operable to generate a fluid pressure higher than a predetermined locking pressure that locks the clutch. The electric pump may be operable to cause the fluid pressure to not exceed a predetermined electric pump maximum pressure, the predetermined electric pump maximum pressure being lower than the predetermined locking pressure.

[0007] A method includes: in response to an electric machine failing to drive a mechanical pump configured to pressurize a clutch disposed between an engine and the electric machine, activating an electric pump to pressurize the clutch, and starting and operating the engine to drive the mechanical pump to achieve a lockup pressure of the clutch.

[0008] The method may also include: operating a transmission shift clutch to a closed state to maximize clutch pressure, the transmission shift clutch being connected to the same fluid circuit as the clutch. The method may also include: operating the engine at a speed of at least a predetermined engine speed, the predetermined engine speed being configured to rotate the mechanical pump at a predetermined pump speed, at which the fluid pressure reaches or exceeds the locking pressure of the clutch. The method may also include: increasing the engine torque in response to the activation of the electric pump to prevent the engine speed from decreasing. The method may also include: disabling engine automatic stop in response to the motor being inoperable. The method may also include: operating the engine to meet the torque demand for propulsion in response to the clutch being fully boosted. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A block diagram of a vehicle having a hybrid powertrain is shown.

[0010] Figure 2 A block diagram of a hybrid powertrain system including a hydraulic control system is shown.

[0011] Figure 3 A flow chart of a possible operating sequence for controlling a hybrid powertrain system is shown. DETAILED DESCRIPTION

[0012] Embodiments of the present disclosure are described herein. However, it will be understood that the disclosed embodiments are examples only, and other embodiments may take various and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but only as a representative basis for teaching those skilled in the art to use the embodiments in various ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any of the figures may be combined with the features shown in one or more other figures to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments for typical applications. However, various combinations and variations of features consistent with the teachings of the present disclosure may be desired for specific applications or implementations.

[0013] Reference Figure 1 , a schematic diagram of a hybrid electric vehicle (HEV) 110 is shown according to an embodiment of the present disclosure. Figure 1 1 and 2. Representative relationships between components are shown. The physical location and orientation of the components in the vehicle may vary. The HEV 110 includes a powertrain 112. The powertrain 112 includes an engine 114 that drives a transmission 116, which may be referred to as a modular hybrid transmission (MHT). As will be described in further detail below, the transmission 116 includes an electric machine (such as an electric motor / generator (M / G)) 118, an associated traction battery 120, a torque converter 122, and a multi-step ratio automatic transmission or gearbox 124.

[0014] Both the engine 114 and the M / G 118 are the driving sources of the HEV 110. The engine 114 generally represents a power source that may include an internal combustion engine (such as a gasoline, diesel, or natural gas powered engine) or a fuel cell. The engine 114 generates engine power and corresponding engine torque, which are supplied to the M / G 118 when a separation clutch 126 between the engine 114 and the M / G 118 is at least partially engaged. The M / G 118 may be implemented by any of a variety of types of motors. For example, the M / G 118 may be a permanent magnet synchronous motor. As will be described below, the power electronics 156 adjusts the direct current (DC) electricity provided by the traction battery 120 to what is required by the M / G 118. For example, the power electronics may provide three-phase alternating current (AC) electricity to the M / G 118.

[0015] When the disconnect clutch 126 is at least partially engaged, power can flow from the engine 114 to the M / G 118 or from the M / G 118 to the engine 114. For example, the disconnect clutch 126 can be engaged and the M / G 118 can be operated as a generator to convert rotational energy provided by the crankshaft 128 and the M / G shaft 130 into electrical energy stored in the traction battery 120. The disconnect clutch 126 can also be disengaged to isolate the engine 114 from the rest of the powertrain 112 so that the M / G 118 can be used as the sole drive source for the HEV 110. The M / G shaft 130 extends through the M / G 118. The M / G 118 is continuously drivably connected to the M / G shaft 130, while the engine 114 is drivably connected to the M / G shaft 130 only when the disconnect clutch 126 is at least partially engaged.

[0016] The M / G 118 is connected to the torque converter 122 via the M / G shaft 130. Thus, when the disconnect clutch 126 is at least partially engaged, the torque converter 122 is connected to the engine 114. The torque converter 122 includes a pump wheel fixed to the M / G shaft 130 and a turbine fixed to the transmission input shaft 132. Thus, the torque converter 122 provides a fluid coupling between the shaft 130 and the transmission input shaft 132. When the pump wheel rotates faster than the turbine, the torque converter 122 transmits power from the pump wheel to the turbine. The magnitude of the turbine torque and the pump wheel torque generally depends on the relative speed. When the ratio of the pump wheel speed to the turbine speed is high enough, the turbine torque is several times the pump wheel torque. A torque converter bypass clutch 134 can also be provided, which frictionally or mechanically combines the pump wheel and the turbine of the torque converter 122 when engaged to allow more efficient power transmission. The torque converter bypass clutch 134 can be operated as a starting clutch to provide a smooth vehicle start. Alternatively or in combination, for applications that do not include a torque converter 122 or a torque converter bypass clutch 134, a launch clutch similar to the disconnect clutch 126 may be provided between the M / G 118 and the gearbox 124. In some applications, the disconnect clutch 126 is generally referred to as the upstream clutch and the launch clutch 134 (which may be a torque converter bypass clutch) is generally referred to as the downstream clutch.

[0017] The gearbox 124 may include a gear set (not shown) that is selectively placed in different gear ratios through the selective engagement of friction elements, such as clutches and brakes (not shown), to establish a desired plurality of discrete or stepped gear ratios. The gearbox 124 may provide a predetermined number of gear ratios from a low gear (e.g., first gear) to a highest gear (e.g., N gear). An upshift of the gearbox 124 is a shift to a higher gear. A downshift of the gearbox 124 is a shift to a lower gear. The friction elements may be controlled according to a shift schedule that sequentially connects and disconnects specific elements of the gear set to control the gear ratio between the transmission output shaft 136 and the transmission input shaft 132. The gearbox 124 automatically shifts from one gear ratio to another gear ratio based on various vehicle and environmental conditions through an associated controller 150, such as a powertrain control unit (PCU). The gearbox 124 then provides a powertrain output torque to the output shaft 136.

[0018] It should be understood that the hydraulically controlled gearbox 124 used with the torque converter 122 is only one example of a gearbox or transmission arrangement; any multi-speed ratio transmission that receives input torque from an engine and / or electric motor and then provides torque to an output shaft at different gear ratios is acceptable for use in embodiments of the present disclosure. For example, the gearbox 124 can be implemented by an automatic mechanical (or manual) transmission (AMT), which includes one or more servo motors for translating / rotating a shift fork along a shift rail to select a desired gear ratio. As is generally understood by those of ordinary skill in the art, for example, an AMT can be used in applications with higher torque requirements.

[0019] like Figure 1 As shown in the representative embodiment of FIG. 1 , the output shaft 136 is connected to a differential 140. The differential 140 drives a pair of wheels 142 via corresponding axles 144 connected to the differential 140. The differential 140 transmits approximately equal torque to each wheel 142 while allowing slight speed differences (for example, when the vehicle turns). Different types of differentials or similar devices can be used to distribute torque from the powertrain to one or more wheels. For example, in some applications, the torque distribution can be changed according to a specific operating mode or condition.

[0020] The powertrain system 112 may further include an associated powertrain control unit (PCU) 150. Although shown as one controller, the PCU may be part of a larger control system and may be controlled by various other controllers throughout the vehicle 110, such as a vehicle system controller (VSC). Therefore, it should be understood that the powertrain control unit 150 and one or more other controllers may be collectively referred to as a "controller" that controls various actuators in response to signals from various sensors to control various functions such as starting / stopping the engine 114, operating the M / G 118 to provide wheel torque or charging the traction battery 120, selecting or planning transmission shifts, etc. The controller 150 may include a microprocessor or central processing unit (CPU) that communicates with various types of computer-readable storage devices or media. For example, the computer-readable storage device or media may include volatile and non-volatile storage in a read-only memory (ROM), a random access memory (RAM), and a keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables when the CPU loses power. The computer readable storage device or medium may be implemented using any of a number of known storage devices, such as a PROM (programmable read-only memory), EPROM (electrically programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), flash memory, or any other electrical, magnetic, optical, or combination thereof storage device capable of storing data, some of which represents executable instructions used by the controller to control the engine or vehicle.

[0021] The controller 150 communicates with various engine / vehicle sensors and actuators via an input / output (I / O) interface, which may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing and / or conversion, short circuit protection, etc. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process specific signals before providing them to the CPU. Figure 1As generally shown in the representative embodiment of FIG. 1 , the controller (PCU) 150 can send signals to and / or receive signals from the engine 114, the disconnect clutch 126, the M / G 118, the launch clutch 134, the transmission gearbox 124, and the power electronics 156. Although not explicitly shown, one of ordinary skill in the art will recognize the various functions or components within each of the above-mentioned subsystems that can be controlled by the controller (PCU) 150. Representative examples of parameters, systems and / or components that may be directly or indirectly actuated using control logic executed by the controller include fuel injection timing, rate and duration, throttle position, spark plug firing timing (for spark-ignition engines), intake / exhaust valve timing and duration, front end accessory drive (FEAD) components (such as an alternator), air conditioning compressor, battery charging, regenerative braking, M / G operation, clutch pressures for the disconnect clutch 126, the start clutch 134, and the transmission gearbox 124, etc. Sensors communicating input via the I / O interface may be used to indicate, for example, turbocharger boost pressure, crankshaft position (PIP), engine speed (RPM), wheel speed (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT), intake manifold pressure (MAP), accelerator pedal position (PPS), ignition switch position (IGN), throttle position (TP), air temperature (TMP), exhaust gas oxygen (EGO) or other exhaust gas constituent concentration or presence, intake air flow (MAF), transmission gear, ratio or mode, transmission oil temperature (TOT), transmission turbine speed (TS), torque converter bypass clutch 134 state (TCC), deceleration or shift mode (MDE).

[0022] The control logic or functions performed by the controller (PCU) 150 can be represented by a flowchart or similar diagram in one or more of the accompanying drawings. These drawings provide representative control strategies and / or logic, which can be implemented using one or more processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). As such, the various steps or functions shown can be performed in the sequence shown, performed in parallel, or omitted in some cases. Although not always explicitly stated, a person of ordinary skill in the art will recognize that one or more of the steps or functions described can be repeated according to the specific processing strategy used. Similarly, the order of processing is not necessary to obtain the features and advantages described herein, but is provided for ease of illustration and description. The control logic can be implemented primarily in software executed by a microprocessor-based vehicle, engine and / or powertrain controller (such as PCU 150). Of course, depending on the specific application, the control logic can be implemented in software, hardware, or a combination of software and hardware in one or more controllers. When the control logic is implemented in software, the control logic may be provided in one or more computer-readable storage devices or media having stored data representing code or instructions executed by a computer to control the vehicle or its subsystems. The computer-readable storage devices or media may include one or more of several known physical devices that utilize electrical, magnetic, and / or optical memory to hold executable instructions and associated calibration information, operating variables, etc.

[0023] The vehicle driver uses an accelerator pedal 152 to provide a demanded torque, power, or drive command to propel the vehicle 110. In general, depressing and releasing the accelerator pedal 152 generates an accelerator pedal position signal that can be interpreted by the controller 150 as a demand for increased power or decreased power, respectively. Based at least on the input from the pedal, the controller 150 commands torque from the engine 114 and / or the M / G 118. The controller 150 also controls the timing of shifts within the gearbox 124 and the engagement or disengagement of the disconnect clutch 126 and the torque converter bypass clutch 134. Similar to the disconnect clutch 126, the torque converter bypass clutch 134 can be adjusted within a range between an engaged position and a disengaged position. This also generates variable slip in the torque converter 122 in addition to the variable slip generated by the fluid coupling between the impeller and the turbine. Alternatively, the torque converter bypass clutch 134 can be operated in a locked or disconnected operating mode without using regulation, depending on the specific application.

[0024] To drive the vehicle 110 via the engine 114, the disconnect clutch 126 is at least partially engaged to transfer at least a portion of the engine torque through the disconnect clutch 126 to the M / G 118 and then from the M / G 118 through the torque converter 122 and the gearbox 124. The M / G 118 can assist the engine 114 in rotating the shaft 130 by providing additional power. This operating mode may be referred to as a "hybrid mode" or an "electric assist mode."

[0025] In order to drive the vehicle 110 using the M / G 118 as the sole power source, the power flow remains unchanged except that the disconnect clutch 126 is operated to isolate the engine 114 from the rest of the powertrain 112. During this time, combustion in the engine 114 may be disabled or otherwise shut down to save fuel. The traction battery 120 transmits the stored electrical energy to a power electronics module 156, which may include, for example, an inverter, via a high voltage (HV) bus 154. The high voltage bus 154 includes lines and conductors for conducting current between modules and may include positive side conductors and negative (or return) side conductors. The power electronics 156 converts the DC voltage from the traction battery 120 into an AC voltage for use by the M / G 118. The controller 150 commands the power electronics 156 to convert the voltage from the traction battery 120 into an AC voltage provided to the M / G 118 to provide positive or negative torque to the shaft 130. This operating mode may be referred to as a "pure electric" operating mode.

[0026] In any operating mode, the M / G 118 may function as a motor and provide motive force to the powertrain 112. Alternatively, the M / G 118 may function as a generator and convert kinetic energy from the powertrain 112 into electrical energy for storage in the traction battery 120. For example, the M / G 118 may function as a generator when the engine 114 is providing propulsion power for the vehicle 110. The M / G 118 may also function as a generator during regenerative braking, in which rotational energy from the rotating wheels 142 is transferred back through the gearbox 124 and converted into electrical energy for storage in the traction battery 120.

[0027] It should be understood that Figure 1 The schematic diagrams shown in are merely exemplary and are not meant to be limiting. Other configurations that utilize selective engagement of both the engine and the electric motor to transfer torque through the transmission are contemplated. For example, the M / G 118 may be offset from the crankshaft 128, an additional electric motor may be provided to start the engine 114, and / or the M / G 118 may be disposed between the torque converter 122 and the gearbox 124. Other configurations are contemplated without departing from the scope of the present disclosure. Other hybrid vehicle configurations are possible (e.g., power split configurations), and the innovative aspects disclosed herein are applicable to these other configurations.

[0028] The vehicle 110 may utilize the M / G 118 to start the engine 114. The controller 150 may command the disconnect clutch 126 to close and request torque from the M / G 118 via the power electronics 156. The torque from the M / G 118 rotates the engine 114 so that the engine speed increases above a predetermined speed, at which time the engine 114 may be commanded to provide fuel and ignite to maintain continued engine rotation. During engine cranking and initial startup, the torque converter 122 may provide some torsional isolation. In certain vehicle configurations, an auxiliary starter 168 may also be connected to the engine 114 to provide an auxiliary or backup means of starting the engine 114. The auxiliary starter 168 may be a belt-integrated starter generator (BISG) system in which an electric motor is connected to the engine 114 via a belt drive assembly. The auxiliary starter 168 may be an electric motor having a ring gear that interacts with a flywheel that is connected to the engine 114. The electric machine associated with the auxiliary starter 168 may be operated using a low voltage power source (eg, provided by a 12V power system) or a high voltage power source (eg, provided by the traction battery 120).

[0029] The vehicle 110 may also include a power converter module 158 and an auxiliary battery 160. The auxiliary battery 160 may be a low voltage battery (such as a 12V battery) commonly used in automobiles. The terminals of the auxiliary battery 160 may be electrically connected to a low voltage bus 166. The low voltage bus 166 includes lines and conductors for conducting current between connected modules. The power converter 158 may be electrically connected between the high voltage bus 154 and the low voltage bus 166. The power converter module 158 may be a DC / DC converter configured to convert the voltage from the high voltage bus 154 to a voltage level compatible with the low voltage bus 166. The power converter 158 may also be configured to convert the voltage from the low voltage bus 166 to a voltage compatible with the high voltage bus 154. For example, the power converter 158 may be configured to provide a bidirectional flow of current between the high voltage bus 154 and the low voltage bus 166.

[0030] The vehicle 110 may include a display. For example, the display may be part of an instrument panel. The display may include a lamp, light, and / or other indicator for alerting an operator to the status of the vehicle. The display may be a liquid crystal display (LCD) module. The display may communicate with a controller (e.g., PCU 150) connected to a communication bus.

[0031] Figure 2Depicted are further aspects of a hybrid powertrain. The hybrid powertrain and / or transmission 116 may include a hydraulic system 170. The hydraulic system 170 may be configured to direct and deliver fluid to various components within the transmission 116. The hydraulic system 170 may include a reservoir for hydraulic fluid. The hydraulic system 170 may provide fluid to the disconnect clutch 126, the torque converter 122, and the gearbox 124. The hydraulic system 170 may include valves and hydraulic actuators to control the flow of fluid within the hybrid powertrain. The hydraulic actuator may be configured to engage / disengage the clutch and for shifting gears. Solenoids may be connected to the valves and actuators to provide an interface for controlling the valves and actuators to the controller 150.

[0032] The hydraulic system 170 may include one or more disconnect clutch control valves 176, which may be configured to enable and disable the flow of fluid to the disconnect clutch 126. The disconnect clutch control valve 176 may include a solenoid that interacts with the controller 150. In some configurations, a single disconnect clutch control valve 176 may be implemented. When enabled, the disconnect clutch control valve 176 may allow fluid to flow to the disconnect clutch 126 to engage the disconnect clutch 126. When deactivated, fluid may be released from the disconnect clutch 126 to disengage the disconnect clutch 126. In some configurations, the disconnect clutch control valve 176 may include multiple valves configured to establish, maintain, and release fluid pressure of the disconnect clutch 126 depending on the activation of the valve.

[0033] The hydraulic system 170 may include one or more gearbox control valves 178 having associated solenoids that interact with the controller 150. When actuated, the gearbox control valves 178 may allow fluid to flow to the associated actuators, and when deactivated, the gearbox control valves 178 may allow fluid to be released from the associated actuators. The gearbox control valves 178 may be configured to control a selected gear of the gearbox 124. By activating various combinations of the gearbox control valves 178, different gear ratios may be selected. In addition, by activating selected combinations of the gearbox control valves 178, neutral and park gears may be selected.

[0034] The hydraulic system may include one or more torque converter control valves 180 having associated solenoids that interact with the controller 150. The torque converter control valves 180 may be configured to engage and disengage the bypass clutch 134. When actuated, the torque converter control valves 180 may allow fluid to flow to the associated actuator, and when deactivated, the torque converter control valves 180 may allow fluid to be released from the associated actuator.

[0035] The operation of the hydraulic system 170 may depend on the fluid pressure in the hydraulic system 170. Each of the components operated by the valve and the hydraulic actuator may be characterized by a pressure, wherein, under the pressure, appropriate operation may be expected. For example, the disconnect clutch 126 may be characterized by a predetermined full pressure level for the full engagement of the disconnect clutch 126. When the fluid pressure reaches or exceeds the predetermined full pressure level, the disconnect clutch 126 may be fully engaged or locked. When the fluid pressure exceeds the predetermined full pressure level, the disconnect clutch 126 may be fully engaged. That is, the crankshaft 128 and the M / G shaft 130 may be connected and may rotate together without slipping at both ends of the disconnect clutch 126. In this mode, the engine torque may be fully transmitted to the M / G shaft 130. When the fluid pressure is lower than the predetermined full pressure level, the disconnect clutch 126 may not be fully engaged. In this case, the crankshaft 128 and the M / G shaft 130 may not rotate at the same speed and there may be slipping at both ends of the disconnect clutch 126. The amount of slipping may depend on the pressure level of the fluid. In this mode, engine torque may only be partially transferred to the M / G shaft 130 .

[0036] The transmission 116 may also include a mechanically driven transmission pump 174. The transmission pump 174 may be configured to pressurize the fluid within the hydraulic system 170. The transmission pump 174 may be connected to the M / G shaft 130. The rotation of the M / G shaft 130 may cause the transmission pump 174 to pressurize the fluid. When rotating at a predetermined speed or above a predetermined speed, the transmission pump 174 may pressurize the hydraulic fluid to at least a predetermined full pressure level (e.g., fully pressurized). When rotating at a speed below the predetermined speed, the transmission pump 174 may pressurize the hydraulic fluid to a pressure below the predetermined full pressure level (e.g., partially pressurized). The hydraulic fluid pressure may be a function of the rotation speed of the transmission pump 174. During time intervals when the M / G shaft 130 is not rotating, the transmission pump 174 cannot increase the pressure within the hydraulic system 170. The M / G 118 may be powered by the traction battery 120 and may be controlled to cause the rotation of the M / G shaft 130 and the transmission pump 174.

[0037] The movement of fluid in the hydraulic system 170 depends on the fluid being pressurized. In normal operation, the transmission pump 174 builds fluid pressure when the M / G shaft 130 is rotating. In addition, by operating the M / G 118, the speed of the transmission pump 174 can be maintained above a predetermined speed. There may be a situation where the M / G 118 cannot provide torque to rotate the transmission pump 174. For example, the loss of traction battery power (e.g., caused by diagnostic conditions, consumption, low battery discharge limits) may cause the M / G 118 to be unable to be driven and provide torque for rotating the M / G shaft 130. Diagnostic conditions involving power electronics 156 may cause the M / G 118 to be unable to operate. If the transmission pump 174 stops rotating, the fluid pressurization may be missing. The lack of fluid pressurization may cause the disconnect clutch 126 to be unable to engage or the gearbox 124 to be unable to shift. Without the ability to operate the M / G 118 or engage the disconnect clutch 126, the vehicle cannot be propelled. If the M / G 118 is unable to spin the transmission pump 174, an alternative method of pressurizing the fluid may be beneficial.

[0038] The hybrid powertrain system may include an auxiliary pump 172 that is electrically driven. The auxiliary pump 172 may be configured to pressurize the fluid within the hydraulic system 170. The auxiliary pump 172 may receive power from the low voltage bus 166 and / or the auxiliary battery 160. The auxiliary pump 172 may include an electric motor that is configured to drive a pumping mechanism. The auxiliary pump 172 may be operated by a controller such as the PCU 150. The controller 150 may include a drive circuit configured to enable and disable the auxiliary pump 172. Since the auxiliary pump 172 is powered by the low voltage bus 166, it is able to operate under conditions where the transmission pump 174 is inoperable due to problems involving high voltage components. The capacity of the auxiliary pump 172 to pressurize the fluid may be lower than the capacity of the transmission pump 174. The auxiliary pump 172 may have a capacity to increase the pressure to a first predetermined pressure limit. The transmission pump 174 may have a capacity to increase the pressure to a second predetermined pressure limit, which is higher than the first predetermined pressure limit. In certain configurations, the auxiliary pump 172 may not be able to pressurize the hydraulic system 170 to a predetermined full pressure level for locking the disconnect clutch 126. That is, the auxiliary pump 172 may only be able to partially pressurize the fluid in the hydraulic system 170.

[0039] When M / G 118 is operable, M / G 118 can be controlled to rotate transmission pump 174. M / G 118 can be controlled at a speed of at least a predetermined speed to ensure that full pressurization of hydraulic system 170 is available. In this case, by directing pressurized fluid to disconnect clutch 126 (e.g., enabling disconnect clutch control valve 176), disconnect clutch 126 can be fully engaged. When M / G 118 is inoperable, M / G 118 cannot drive transmission pump 174 to pressurize fluid. In addition, if M / G 118 is inoperable, propulsion by M / G 118 is hindered. Engine 114 is the remaining source of propulsion torque for the vehicle. However, when disconnect clutch 126 is disengaged, engine 114 cannot provide propulsion torque to move the vehicle.

[0040] If the M / G 118 becomes inoperable, it may be necessary to start the engine 114 if the engine 114 is currently stopped. Obviously, in this case, the M / G 118 cannot crank the engine 114 to start it. In this case, the auxiliary starter 168 may be activated to crank the engine 114. The controller 150 may command activation of the auxiliary starter 168. The auxiliary starter 168 may crank the engine 114 so that the engine 114 can be started. The controller 150 may then control the fuel and ignition during the starting process to achieve the start of the engine 114. The engine 114 may run at idle speed after starting.

[0041] If the M / G 118 becomes inoperable to drive the transmission pump 174, other methods of engaging the disconnect clutch 126 must be developed or the vehicle cannot be propelled. The auxiliary pump 172 can be used to pressurize the fluid to a level sufficient to partially transfer the engine torque to the M / G shaft 130. The controller 150 can be configured to energize the auxiliary pump 172 or enable the auxiliary pump 172. The auxiliary pump 172 can increase the fluid pressure in the hydraulic system 170 to a predetermined pressure. The predetermined pressure can be sufficient to partially engage the disconnect clutch 126.

[0042] There may be other hydraulic actuators that rely on pressurized fluid to operate. When the auxiliary pump 172 is enabled, it may be necessary to disable other hydraulic actuators within the hydraulic system 170. Any additional hydraulic actuators that are active can reduce the fluid pressure available to the disconnect clutch 126. When the auxiliary pump 172 is enabled, the controller 150 can command the deactivation of other hydraulic actuators and valves. For example, when the auxiliary pump 172 is enabled, the gearbox control valve 178 can be disabled (e.g., operated to be in a closed state).

[0043] The disconnect clutch 126 may be partially engaged when the engine 114 is running and fluid is pressurized by the auxiliary pump 172. The controller 150 may enable the disconnect clutch control valve 176 to allow fluid to flow to the disconnect clutch 126 to partially engage the disconnect clutch 126. Since the fluid pressure established by the auxiliary pump 172 may be lower than the predetermined full pressure level, the disconnect clutch 126 may only be partially engaged, so that only a portion of the engine torque passes through the disconnect clutch 126.

[0044] The controller 150 may operate the engine 114 to increase engine torque when or before the disconnect clutch 126 is partially engaged. Increasing engine torque before the disconnect clutch 126 is partially engaged may avoid stalling or sagging of the engine 114 when additional load is added. The controller 150 may also control the engine speed to a value above the normal idle speed to prevent the engine speed from becoming too low when the disconnect clutch 126 is partially engaged.

[0045] Before the disconnect clutch 126 is partially engaged, the controller 150 can operate the gearbox control valve 178 to select a non-driving gear to reduce the load. For example, the gearbox control valve 178 can be commanded to select a neutral gear or a park gear so that torque is not transmitted to the drive wheels. Operating the gearbox 124 in a non-driving gear prevents the engine speed from decreasing and allows the mechanical pump 174 to increase speed in less time.

[0046] When the disconnect clutch 126 is partially engaged, the M / G shaft 130 will begin to rotate, causing rotation of the transmission pump 174. As the speed of the transmission pump 174 increases, the fluid pressure in the hydraulic system 170 will increase. As the fluid pressure in the hydraulic system 170 builds, the torque transmitted through the disconnect clutch 126 increases, which can further increase the speed of the transmission pump 174. When the transmission pump 174 reaches a predetermined full pressure speed, the hydraulic system 170 can be pressurized to a predetermined full pressure level. When the fluid is pressurized to or above the predetermined full pressure level, the disconnect clutch 126 can be fully engaged or locked.

[0047] When the disconnect clutch 126 is engaged, the engine 114 may be used for vehicle propulsion. When the disconnect clutch 126 is fully engaged, full engine power is available for propulsion. The hybrid powertrain system may be operated as a conventional, engine-driven vehicle. In this mode, the engine 114 may optionally remain in operation as long as the M / G 118 is not operable. For example, auto-stop and auto-start may be disabled. Note that if the engine auto-stop / start function remains enabled, the response time may be increased compared to full operation with the M / G 118 operable. For example, the engine 114 may take longer to start and more time may be required before vehicle propulsion is available.

[0048] Figure 3 A flow chart describing a possible sequence of operations for a control system for a hybrid powertrain system that may be performed by the controller 150 is shown. The sequence of operations may be performed when the vehicle is in a run or ignition key-on mode in which vehicle propulsion is expected to be available. In operation 302, a check may be performed to determine whether the M / G 118 is operable. The controller 150 may monitor parameters associated with the traction battery 120. For example, a discharge limit of the traction battery 120 falling below a minimum discharge limit may cause the M / G 118 to be inoperable. A temperature associated with the traction battery 120 exceeding a maximum temperature may cause the M / G 118 to be inoperable. Additionally, a diagnostic condition associated with the traction battery 120 may cause the M / G 118 to be inoperable. Any condition that causes the traction battery 120 to be unable to deliver power may cause the M / G 118 to be inoperable.

[0049] The controller 150 may monitor parameters associated with the power electronics 156. For example, a temperature associated with the power electronics exceeding a predetermined maximum temperature may cause the M / G 118 to be inoperable. A diagnostic condition indicating that the power electronics 156 are inoperable may also cause the M / G 118 to be inoperable. Any condition that causes the power electronics 156 to be unable to operate and control the M / G 118 may cause the M / G 118 to be considered inoperable.

[0050] The controller 150 may monitor parameters associated with the M / G 118. For example, a temperature associated with the M / G 118 exceeding a predetermined maximum temperature may cause the M / G 118 to be inoperable. A diagnostic condition associated with the M / G 118 may also cause the M / G 118 to be inoperable. For example, a failure of a resolver configured to measure the angular position of the M / G shaft 130 may prevent accurate control and may cause the M / G 118 to be inoperable.

[0051] If the M / G 118 is operational, execution of the operation may be bypassed and normal operation may be performed. If the M / G 118 is not operational, operation 304 may be performed. In operation 304, a check may be performed to determine if the engine 114 is running. For example, a status indication from an engine controller may be monitored for the operating status of the engine 114.

[0052] If the engine 114 is not running, operation 308 may be performed. In operation 308, the engine 114 may be started. The controller 150 may start the engine 114 by enabling the auxiliary starter 168. The controller 150 may further control the spark and fuel applied to the engine 114 to facilitate starting. The controller 150 may also command the gearbox 124 to a non-driving gear such as a neutral gear or a parking gear. After the engine 114 has been started, operation 310 may be performed. In operation 310, the controller 150 may enable the electric pump 172 to partially pressurize the hydraulic system 170. In operation 312, the disconnect clutch 126 may be partially engaged. There may be a delay between operation 310 and operation 312 to allow the pressure to be built up to a predetermined pressure level. In order to partially engage the disconnect clutch 126, the controller 150 may enable the disconnect clutch control valve 176 to allow pressurized fluid to flow to the disconnect clutch 126. In addition to enabling the disconnect clutch control valve 176, the controller 150 may also deactivate valves associated with other fluid consuming parts in the hydraulic system 170 (e.g., operating the gearbox control valve 178 to be in a closed state). Since the fluid is not fully pressurized to the desired operating pressure when the fluid is pressurized by the electric pump 172, the disconnect clutch 126 is partially engaged. In operation 314, the engine 114 may be operated to drive the mechanical transmission pump 174. The controller 150 may control the engine torque and the engine speed so that the transmission pump 174 rotates at a speed at least equal to a predetermined speed. The predetermined speed may be selected to make the fluid pressure higher than a predetermined full pressure level. In operation 316, the engine automatic stop may be disabled to prevent the engine 114 from shutting down when the M / G118 is inoperable.

[0053] At operation 304, if the engine 114 is running, operation 306 may be performed. At operation 306, a check may be performed to determine if the disconnect clutch 126 is currently engaged. The engagement of the disconnect clutch 126 may be checked based on the activation state of the disconnect clutch control valve 176 and / or the fluid pressure in the hydraulic system 170. The hydraulic system 170 may include one or more pressure sensors that interact with the controller 150 and are configured to monitor the fluid pressure at one or more locations within the hydraulic system 170. If the disconnect clutch 126 is not engaged, the operation may proceed to operation 310 to activate the electric pump 172, followed by operation 312 to partially engage the disconnect clutch 126. If the disconnect clutch 126 is engaged, operation 314 may be performed to operate the engine 114 to maintain the disconnect clutch 126 in an engaged state.

[0054] The described systems and methods allow vehicle operation in situations where the M / G is inoperable. By implementing alternative methods of starting the vehicle and pressurizing the hydraulic system, vehicle propulsion can be maintained when the M / G is inoperable. In addition, the method requires only low voltage power to bring the hybrid powertrain system to a state where propulsion is available. This is useful in situations where the high voltage power system is missing or unavailable. By implementing the disclosed systems and methods, the availability of the hybrid propulsion system is improved.

[0055] The processes, methods or algorithms disclosed herein may be delivered to / implemented by a processing device, a controller or a computer (which may include any existing programmable electronic control unit or dedicated electronic control unit). Similarly, the processes, methods or algorithms may be stored as data and instructions executable by a controller or a computer in a variety of forms, including but not limited to information permanently stored on non-writable storage media (such as ROM devices) and information variably stored on writable storage media (such as floppy disks, tapes, CDs, RAM devices, and other magnetic and optical media). The processes, methods or algorithms may also be implemented as software executable objects. Alternatively, the processes, methods or algorithms may be implemented in whole or in part using suitable hardware components (such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices) or a combination of hardware, software, and firmware components.

[0056] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are descriptive words rather than limiting, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As described previously, the features of the various embodiments can be combined to form further embodiments of the present invention that may not be explicitly described or shown. Although the various embodiments may have been described as providing advantages or being superior to other embodiments or prior art implementations in one or more desired characteristics, it should be recognized by those of ordinary skill in the art that, depending on the specific application and implementation, one or more features or characteristics may be compromised to achieve the desired overall system properties. These properties may include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as being less desirable than other embodiments or prior art implementations in one or more characteristics are not outside the scope of the present disclosure and can be expected to be used in specific applications.

Claims

1. A control system for a hybrid powertrain system, comprising: a controller configured to: in response to an electric motor configured to drive a mechanical pump operable to pressurize a fluid of a clutch between the engine and the electric motor being inoperable, Activate the auxiliary starter to start the engine, activating an electric pump configured to pressurize the fluid, actuating a valve to allow fluid to flow to the clutch and partially engage the clutch, and The engine is operated to drive the mechanical pump to lock the clutch.

2. The control system of the hybrid powertrain system as claimed in claim 1, wherein: The mechanical pump is operable to pressurize the fluid of the clutch to a fluid pressure that is above a predetermined lockup pressure that causes the clutch to lock when the valve is actuated.

3. The control system of the hybrid powertrain system as claimed in claim 2, wherein: The electric pump is operable to pressurize the fluid of the clutch to a fluid pressure level that is less than or equal to a predetermined electric pump maximum pressure that is less than the predetermined lock-up pressure.

4. The control system of the hybrid powertrain system as claimed in claim 1, wherein: The controller is also configured to disable an automatic engine stop in response to the electric machine being inoperable.

5. The control system of the hybrid powertrain system as claimed in claim 1, wherein: The controller is further configured to, in response to activation of the electric pump, increase engine torque to prevent engine speed from decreasing.

6. The control system of the hybrid powertrain system as claimed in claim 1, wherein: The controller is further configured to operate the engine at at least a predetermined engine speed configured to rotate the mechanical pump at a predetermined pump speed at which the fluid pressure exceeds a predetermined lock-up pressure of the clutch.

7. The control system of the hybrid powertrain system as claimed in claim 1, wherein: A controller is configured to command a transmission shift clutch to a disengaged state to maximize pressure of the clutch, the transmission shift clutch being connected to the same fluid circuit as the clutch.

8. A vehicle comprising: a clutch that selectively connects the engine and the motor; a mechanical pump driven by the motor and operable to pressurize the clutch fluid; A controller configured to: in response to the motor being inoperable, activating an electric pump operable to pressurize clutch fluid to partially engage the clutch, The auxiliary starter is activated to start the engine to drive the mechanical pump to lock the clutch.

9. The vehicle of claim 8, wherein: The controller is also configured to disable an automatic engine stop in response to the electric machine being inoperable.

10. The vehicle of claim 8, wherein: The controller is further configured to, in response to activation of the electric pump, increase engine torque to prevent engine speed from decreasing.

11. The vehicle of claim 8, wherein: The controller is further configured to operate the engine at at least a predetermined engine speed configured to rotate the mechanical pump at a predetermined pump speed at which the fluid pressure exceeds a predetermined lock-up pressure of the clutch.

12. The vehicle of claim 8, wherein: A controller is configured to command a transmission shift clutch to a disengaged state to maximize pressure of the clutch, the transmission shift clutch being connected to the same fluid circuit as the clutch.

13. The vehicle of claim 8, wherein: The mechanical pump is operable to generate a fluid pressure above a predetermined locking pressure that causes the clutch to lock.

14. The vehicle of claim 13, wherein: The electric pump is operable such that the fluid pressure does not exceed a predetermined electric pump maximum pressure, the predetermined electric pump maximum pressure being lower than the predetermined locking pressure.

15. A method for controlling a hybrid powertrain system, comprising: In response to the motor being unable to drive a mechanical pump configured to pressurize a clutch disposed between the engine and the motor, activating an electric pump to pressurize the clutch to a partially engaged state, The engine is started and operated to drive the mechanical pump to achieve the clutch lock-up pressure.

16. The method for controlling a hybrid powertrain system as claimed in claim 15, further comprising: A transmission shift clutch connected to the same fluid circuit as the clutch is operated in a disengaged state to maximize the pressure of the clutch.

17. The method for controlling a hybrid powertrain system as claimed in claim 15, further comprising: The engine is operated at at least a predetermined engine speed configured to rotate the mechanical pump at a predetermined pump speed at which the fluid pressure reaches or exceeds a lockup pressure of the clutch.

18. The method for controlling a hybrid powertrain system of claim 15, further comprising: In response to activation of the electric pump, engine torque is increased to prevent engine speed from decreasing.

19. The method for controlling a hybrid powertrain system of claim 15, further comprising: An engine auto-stop is disabled in response to the electric machine being inoperable.

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