Hybrid electric vehicle control device

Abstract

To make it possible to start an engine by outputting torque required for cranking from an electric motor when detecting an abnormality while suppressing damage of the electric motor or the like when detecting the abnormality.SOLUTION: Start advance control is executed when a detected abnormality is a low risk abnormality; engine start control for starting an engine by cranking the engine is performed before limit control of an MG torque upper limit value Tmgmax is started; and the MG torque upper limit value Tmgmax is lowered after starting the engine. Therefore, the occurrence of driving force insufficiency caused by cranking can be avoided like a case where the engine is started by cranking the engine during evacuation travel in which The MG torque upper limit value Tmgmax is limited while suppressing damage of a rotary machine MG or the like caused by an abnormality. Furthermore, since the engine is started before the MG torque upper limit value Tmgmax is limited, the evacuation travel using the engine is made possible; a travel distance during the evacuation travel becomes longer; and driving force performance is improved.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a control device for a hybrid electric vehicle, and more particularly to a control device for a hybrid electric vehicle in which motor torque is limited when an abnormality related to an electric motor is detected. [Background technology]

[0002] There is known a control device for a hybrid electric vehicle, which is (a) equipped with an engine and an electric motor and capable of starting the engine by outputting a torque required for cranking the engine from the electric motor when the engine is stopped and the electric motor is used as a driving force source, (b) has an abnormality detection unit that detects an abnormality related to the electric motor, and (c) has a torque limiting unit that, when the abnormality is detected by the abnormality detection unit, limits an upper limit value of the motor torque, which is the torque of the electric motor, to a predetermined limit torque at which the vehicle can run with the motor torque. The control device for a hybrid electric vehicle described in Patent Document 1 is one example, and in the case of a relatively minor abnormality, the electric motor is operated within the limit torque range to perform evacuation running. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-75293 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when starting the engine due to low battery power during evacuation travel, if the electric motor is to output the torque required for cranking, the upper limit of the motor torque is limited, which may result in insufficient driving force when the vehicle is under high load, such as on an uphill road. In addition, if the limit torque is lower than the cranking torque required for cranking the engine, the engine may not be able to start depending on the travel condition, and evacuation travel or power generation using the engine may not be possible, which may limit the travel distance during evacuation travel. In response to this, it is possible to crank the engine to start it before limiting the motor torque, but there is a risk of damage to the electric motor and its related parts due to the delayed limiting of the motor torque.

[0005] The present invention has been made against the background of the above circumstances, and its object is to suppress damage to the electric motor, etc. when an abnormality is detected, while enabling the engine to be started by outputting the torque required for cranking from the electric motor when the abnormality is detected. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention is applied to a hybrid electric vehicle having an engine and an electric motor, and capable of starting the engine by outputting a torque required for cranking the engine from the electric motor during running with the engine stopped and the electric motor used as a driving force source, and Coil temperature sensor, oil temperature sensor, or communication bus abnormality, and inverter temperature sensor abnormality A control device for a hybrid electric vehicle having (c) an abnormality detection unit that detects an abnormality, and (d) a torque limiting unit that, when the abnormality is detected by the abnormality detection unit, limits an upper limit value of a motor torque, which is a torque of the electric motor, to a predetermined limit torque at which the vehicle can run with the motor torque. Coil temperature sensor, oil temperature sensor, or communication bus A predetermined low-risk abnormality that, when an abnormality is detected, has a low urgency for limiting the motor torque. and Judge ,before The torque limiting unit limits the motor torque. is limited to the first torque limit.A torque required for cranking the engine is output from the electric motor before limit control is started to start the engine. While executing the start-advance control, if the abnormality detection unit detects an abnormality in the inverter temperature sensor, the abnormality is determined to be a predetermined high-risk abnormality that requires high urgency to limit the motor torque, and a limit control is started by the torque limiting unit to limit the motor torque to a second limit torque that is set higher than the first limit torque, and at the same time, a simultaneous start control is executed to start the engine by outputting a torque required for cranking the engine from the electric motor. Evacuation control unit 、 The present invention is characterized by having the following. Effect of the Invention

[0007] In such a control device for a hybrid electric vehicle, when an abnormality is detected by the abnormality detection unit and the abnormality is a predetermined low-risk abnormality, the torque required for cranking is output from the electric motor to start the engine before the torque limiting unit starts limiting control of the motor torque, so that it is possible to suppress damage to the electric motor, etc., caused by an abnormality, while avoiding a lack of driving force caused by cranking, as occurs when the engine is cranked to start during evacuation running where the motor torque is limited to the limit torque. Also, because the engine can be reliably started before the motor torque is limited, evacuation running and power generation, etc., are possible using the engine depending on the hybrid configuration, and the driving distance during evacuation running can be extended. In addition, when the abnormality is a predetermined high-risk abnormality, a limit control is immediately performed to limit the motor torque to a second limit torque set higher than the first limit torque, and a simultaneous start control is performed to output the torque required for engine cranking from the electric motor to start the engine, thereby appropriately suppressing damage to the electric motor, enabling evacuation running using the engine, increasing the travel distance during evacuation running, and improving the driving force performance. In addition, the second limit torque at which the torque of the electric motor is limited is higher than the first limit torque during start-advance control, suppressing fluctuations in driving force due to insufficient torque of the electric motor during engine cranking. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram for explaining a drive system of a hybrid electric vehicle having a control device according to an embodiment of the present invention, and also shows control functions for various controls and main parts of the control system. [Diagram 2] 4 is a flowchart specifically illustrating an operation of an evacuation travel control unit that is functionally provided in the electronic control device of FIG. 1 when starting the engine when an abnormality occurs. [Diagram 3] 2 is a diagram for explaining a plurality of types of abnormalities detected by an abnormality detection unit functionally provided in the electronic control device in FIG. 1. [Figure 4] 3 is an example of a time chart illustrating changes in the operating state of each part when start advance control is performed in accordance with steps S4 to S6 of the flowchart in FIG. 2. [Diagram 5]3 is an example of a time chart illustrating changes in the operating state of each part when the simultaneous start control is performed in accordance with steps S7 to S8 of the flowchart in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention is applied to a hybrid electric vehicle equipped with an engine and an electric motor. The hybrid electric vehicle may be a parallel type in which both the engine and the electric motor are used as a driving force source for traveling, or a series type in which only the electric motor is used as a driving force source for traveling and the engine is connected to a generator and used exclusively for generating electricity. The engine and the electric motor are connected to each other via a disconnecting device such as a clutch, but may also be connected via a differential gear mechanism such as a planetary gear device, and various modes are possible in which the torque required for cranking the engine can be output from the electric motor. In the case of a parallel type, the electric motor does not necessarily need to be connected to the engine, and the engine may be cranked by the inertia of the vehicle and the torque of the electric motor may be increased by the amount of cranking torque so that the driving force change is suppressed.

[0010] The engine is an internal combustion engine such as a gasoline engine or a diesel engine that generates power by burning fuel. As the electric motor, a motor generator that can also be used as a generator is preferably used, but an electric motor that does not function as a generator may also be used. Abnormalities related to the electric motor include not only failures of the electric motor itself, but also failures of control circuits such as an inverter, a DC / DC converter, or a battery, failures of various sensors used to control the electric motor, such as temperature sensors, rotational speed sensors, and torque sensors of each part, or abnormalities in communication circuits that transmit various information necessary for control.

[0011] The evacuation travel control unit is configured to, for example, stop starting the engine when the low-risk abnormality is not present, but may perform simultaneous start control in which the torque required for cranking is output from the electric motor to start the engine at the same time that the torque limiting unit starts limiting control of the motor torque in response to detection of the abnormality. By lowering the upper limit value of the motor torque at a predetermined gradient, the engine can be cranked and started during the decrease process. If the limit torque is higher than the cranking torque of the engine, the engine can be cranked and started even in the simultaneous start control. The torque limiting unit is configured to limit the torque to a certain limit torque, for example, a limit torque lower than the cranking torque of the engine, regardless of whether or not the low-risk abnormality is present, but various embodiments are possible, such as limiting the torque of the electric motor to a first limit torque lower than the cranking torque of the engine when the low-risk abnormality is present, and limiting the torque of the electric motor to a second limit torque higher than the cranking torque when the low-risk abnormality is not present. EXAMPLES

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified for the purpose of explanation, and the dimensional ratios, angles, shapes, etc. of each part are not necessarily drawn accurately.

[0013] Fig. 1 is a schematic diagram of a drive system of a hybrid electric vehicle 10 (hereinafter simply referred to as electric vehicle 10) having a control device according to one embodiment of the present invention, and also shows the control functions and main parts of the control system for various controls in electric vehicle 10. In Fig. 1, electric vehicle 10 is a parallel-type hybrid electric vehicle equipped with an engine 12 and a rotary machine MG as a driving force source for traveling. Electric vehicle 10 also includes a power transmission device 16 provided in a power transmission path between engine 12 and drive wheels 14.

[0014] The engine 12 is a known internal combustion engine such as a gasoline engine or a diesel engine. An electronic control device 90, which will be described later, controls an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, and the like, to control an engine torque Te, which is an output torque of the engine 12. The rotating machine MG is a so-called motor generator having a function as an electric motor that generates mechanical power from electric power and a function as a generator that generates electric power from mechanical power, and is, for example, a three-phase AC synchronous motor using a permanent magnet in the rotor, and is connected to a battery 54 via an inverter 52. The electronic control device 90 controls the inverter 52 of the rotating machine MG, and thus an MG torque Tmg, which is the torque of the rotating machine MG, is controlled. The rotating machine MG generates power for traveling by electric power supplied from the battery 54 via the inverter 52 instead of or in addition to the engine 12. The rotating machine MG also generates power by being rotated and driven by the power of the engine 12 or a driven force input from the driving wheels 14 side. Electric power generated by the rotating machine MG is stored in the battery 54 via the inverter 52. The battery 54 is an electricity storage device that supplies electric power to the rotating machine MG. The rotating machine MG corresponds to an electric motor, and the MG torque Tmg corresponds to the motor torque.

[0015] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, and an automatic transmission 24 in series from the engine 12 side in a case 18 that is a non-rotating member attached to the vehicle body, and a rotary machine MG is connected to the power transmission path between the K0 clutch 20 and the torque converter 22. The K0 clutch 20 is a clutch provided between the engine 12 and the rotary machine MG in the power transmission path between the engine 12 and the drive wheels 14, and is an engine disconnecting device that connects and disconnects the rotary machine MG and the engine 12. The torque converter 22 is a fluid type power transmission device provided between the rotary machine MG and the automatic transmission 24, and is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22 and is interposed in the power transmission path between the torque converter 22 and the drive wheels 14. The power transmission device 16 includes a propeller shaft 28 connected to a transmission output shaft 26 which is an output rotating member of the automatic transmission 24, a differential gear 30 connected to the propeller shaft 28, a pair of drive shafts 32 connected to the differential gear 30, etc. The power transmission device 16 also includes an engine connecting shaft 34 which connects the engine 12 and the K0 clutch 20, an MG connecting shaft 36 which connects the K0 clutch 20 and the torque converter 22, etc.

[0016] The K0 clutch 20 is a wet or dry friction engagement device constituted by, for example, a multi-plate or single-plate clutch pressed by an actuator. The K0 clutch 20 switches between control states such as an engaged state and a disengaged state by changing a K0 torque Tk0, which is a torque capacity of the K0 clutch 20, by a regulated K0 oil pressure PRk0 supplied from a hydraulic control circuit 56. An input member of the K0 clutch 20 is connected to the engine connecting shaft 34 and rotated integrally with the engine connecting shaft 34. An output member of the K0 clutch 20 is connected to the MG connecting shaft 36 and rotated integrally with the MG connecting shaft 36. When the K0 clutch 20 is in an engaged state, the pump impeller 22a and the engine 12 are rotated integrally via the engine connecting shaft 34. On the other hand, when the K0 clutch 20 is in a disengaged state, power transmission between the engine 12 and the pump impeller 22a is interrupted.

[0017] The rotary machine MG is connected to the MG connecting shaft 36 in the case 18 so as to be capable of transmitting power. The rotary machine MG is connected to a power transmission path between the engine 12 and the drive wheels 14, in particular to a power transmission path between the K0 clutch 20 and the torque converter 22. In other words, the rotary machine MG is connected to the torque converter 22 and the automatic transmission 24 so as to be capable of transmitting power without passing through the K0 clutch 20. The torque converter 22 and the automatic transmission 24 transmit driving force from each of the drive force sources of the engine 12 and the rotary machine MG to the drive wheels 14, respectively.

[0018] The torque converter 22 includes a pump wheel 22a connected to an MG connecting shaft 36, and a turbine wheel 22b connected to a transmission input shaft 38 that is an input rotating member of the automatic transmission 24. The pump wheel 22a is connected to the engine 12 via the K0 clutch 20, and is also directly connected to the rotary machine MG. The pump wheel 22a is an input member of the torque converter 22, and the turbine wheel 22b is an output member of the torque converter 22. The MG connecting shaft 36 is also an input rotating member of the torque converter 22. The transmission input shaft 38 is also an output rotating member of the torque converter 22 that is formed integrally with a turbine shaft that is driven to rotate by the turbine wheel 22b. The torque converter 22 includes an LU clutch 40 that connects the pump wheel 22a and the turbine wheel 22b. The LU clutch 40 is a direct clutch that connects the input and output rotating members of the torque converter 22, that is, a known lock-up clutch.

[0019] The LU clutch 40 switches between operating states, i.e., control states, by changing the LU clutch torque Tlu, which is the torque capacity of the LU clutch 40, with the regulated LU oil pressure PRlu supplied from the hydraulic control circuit 56. The control states of the LU clutch 40 include a fully released state in which the LU clutch 40 is released, a slip state in which the LU clutch 40 is engaged with slipping, and a fully engaged state in which the LU clutch 40 is engaged. By placing the LU clutch 40 in the fully released state, the torque converter 22 is placed in a torque converter state in which a torque amplification effect is obtained. Also, by placing the LU clutch 40 in the fully engaged state, the torque converter 22 is placed in a lock-up state in which the pump wheel 22a and the turbine wheel 22b are rotated together.

[0020] The automatic transmission 24 is a known planetary gear type automatic transmission including, for example, one or more planetary gear devices and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices including, for example, a multi-plate or single-plate clutch or brake pressed by a hydraulic actuator, or a band brake tightened by a hydraulic actuator. The engagement devices CB have their respective torque capacities, or CB torques Tcb, changed by the regulated CB hydraulic pressure PRcb supplied from the hydraulic control circuit 56, thereby switching between control states such as an engaged state and a disengaged state.

[0021] The automatic transmission 24 is a stepped transmission in which one of a plurality of gear stages with different gear ratios γat (=AT input rotation speed Ni / AT output rotation speed No ) is formed by engaging one of the engagement devices CB. The automatic transmission 24 selectively forms a plurality of gear stages by switching the gear stages formed according to the accelerator operation of the driver (=operator) and the vehicle speed V, etc., by the electronic control device 90. In addition, when all of the engagement devices CB are released, the automatic transmission 24 is in neutral, which cuts off the power transmission. The AT input rotation speed Ni is the rotation speed of the transmission input shaft 38, and is the input rotation speed of the automatic transmission 24. The AT input rotation speed Ni is also the rotation speed of the output rotating member of the torque converter 22, and is equal to the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT output rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0022] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the driving wheels 14 via the K0 clutch 20, MG connecting shaft 36, torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, drive shaft 32, etc. in this order. Moreover, the power output from the rotating machine MG is transmitted from the MG connecting shaft 36 to the driving wheels 14 via the torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, drive shaft 32, etc. in this order, regardless of the control state of the K0 clutch 20.

[0023] The electric vehicle 10 includes the MOP 58, which is a mechanical oil pump, the EOP 60, which is an electric oil pump, and a pump motor 62. The MOP 58 is connected to the pump impeller 22a, and is rotated and driven by a driving force source (the engine 12, the rotary machine MG) to discharge hydraulic oil OIL used in the power transmission device 16. The pump motor 62 is a motor dedicated to the EOP 60 for rotating and driving the EOP 60. The EOP 60 is rotated and driven by the pump motor 62 to discharge hydraulic oil OIL. The hydraulic oil OIL discharged by the MOP 58 and the EOP 60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the CB hydraulic pressure PRcb, the K0 hydraulic pressure PRk0, the LU hydraulic pressure PRlu, and the like, which are adjusted based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60. The hydraulic oil OIL is also used for lubrication and cooling of each part.

[0024] The electric vehicle 10 further includes an electronic control device 90 as a control device that executes various controls. The electronic control device 90 includes, for example, a so-called microcomputer equipped with a CPU, RAM, ROM, an input / output interface, and the like, and the CPU executes various controls of the electric vehicle 10 by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The electronic control device 90 can be configured using a single computer, but in this embodiment, it is configured to include an HEV-ECU 92, an MG-ECU 94, an engine-ECU 96, and an ECT-ECU 98. "HEV" is the abbreviation for Hybrid Electric Vehicle, "MG" is the abbreviation for Motor Generator, "ECT" is the abbreviation for Electronic Controlled Transmission, and "ECU" is the abbreviation for Electronic Control Unit. The HEV-ECU 92, MG-ECU 94, engine-ECU 96, and ECT-ECU 98 are connected to each other via a communication bus, and are capable of transmitting and receiving various information required for control.

[0025] The electronic control device 90 receives various signals based on detection values ​​from various sensors (for example, an engine rotation speed sensor 70, a turbine rotation speed sensor 72, an output rotation speed sensor 74, a MG rotation speed sensor 76, an accelerator opening sensor 78, a throttle valve opening sensor 80, a coil temperature sensor 82, an inverter temperature sensor 84, an oil temperature sensor 86, a battery sensor 88, etc.) provided in the electric vehicle 10. The signals include, for example, an engine rotation speed Ne which is the rotation speed of the engine 12, a turbine rotation speed Nt which is the same value as the AT input rotation speed Ni, an AT output rotation speed No corresponding to the vehicle speed V, an MG rotation speed Nmg which is the rotation speed of the rotating machine MG, an accelerator opening θacc which is an accelerator operation amount (for example, an accelerator pedal depression operation amount) which represents an acceleration request amount by the driver, a throttle valve opening θth which is an opening amount of the electronic throttle valve, a stator coil temperature THcoil of the rotating machine MG, an inverter temperature THinv which is the temperature of the inverter 52, an oil temperature THoil which is the temperature of the hydraulic oil OIL used in the hydraulic control circuit 56, and a torque meter 90 which is a torque meter. , battery temperature THbat of the battery 54, battery charge / discharge current Ibat, battery voltage Vbat, etc. are supplied to the oil pressure sensor 86. The MG rotation speed Nmg corresponds to the input rotation speed of the torque converter 22, which is a fluid transmission device, and the turbine rotation speed Nt corresponds to the output rotation speed of the torque converter 22, which is a fluid transmission device. The hydraulic oil OIL of the hydraulic control circuit 56 is also used to cool the rotating machine MG, and the oil temperature THoil reflects the temperature of the magnets provided in the rotor of the rotating machine MG. In other words, the oil temperature sensor 86 is disposed near the rotor so as to detect the temperature of the hydraulic oil OIL used to cool the rotor of the rotating machine MG.

[0026] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Smg for controlling the rotating machine MG, a CB hydraulic control command signal Sbc for controlling the engagement device CB, a K0 hydraulic control command signal Sk0 for controlling the K0 clutch 20, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, etc.) to each device (e.g., the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, etc.) provided in the electric vehicle 10. The hydraulic control circuit 56 is provided with a plurality of solenoid valves that switch oil paths and control hydraulic pressure in accordance with the CB hydraulic control command signal Sbc.

[0027] The HEV-ECU 92 of the electronic control device 90 functions as a hybrid control unit that controls the operation of the rotary machine MG and the engine 12 in a coordinated manner. That is, the HEV-ECU 92 executes hybrid drive control by the engine 12 and the rotary machine MG using an MG-ECU 94 that controls the operation of the rotary machine MG via the inverter 52, and an engine-ECU 96 that controls the operation of the engine 12. The HEV-ECU 92 calculates a drive demand amount for the electric vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a drive demand amount map. The drive demand amount is, for example, a required drive torque Trdem at the drive wheels 14. The HEV-ECU 92 determines, for example, a required input torque Tindem, which is the input torque of the torque converter 22 required to realize the required drive torque Trdem, taking into consideration transmission loss, auxiliary load, the speed ratio γat of the automatic transmission 24, the torque ratio of the torque converter 22, the chargeable power Win and dischargeable power Wout of the battery 54, etc., and outputs an MG control command signal Smg for controlling the rotating machine MG via the MG-ECU 94 and an engine control command signal Se for controlling the engine 12 via the engine-ECU 96 so that the required input torque Tindem is obtained.

[0028] The chargeable power Win of the battery 54 is the maximum power that can be input, which specifies the limit on the input power of the battery 54, and indicates the input limit of the battery 54. The dischargeable power Wout of the battery 54 is the maximum power that can be output, which specifies the limit on the output power of the battery 54, and indicates the output limit of the battery 54. The chargeable power Win and dischargeable power Wout of the battery 54 are calculated by the electronic control device 90, for example, based on the battery temperature THbat and the state of charge value SOC [%] of the battery 54. The state of charge value SOC of the battery 54 is a value that indicates the state of charge of the battery 54, i.e., the remaining amount of stored power, and can be calculated, for example, based on the battery charge / discharge current Ibat and the battery voltage Vbat.

[0029] When the required input torque Tindem can be satisfied only by the output of the rotary machine MG, the HEV-ECU 92 selects a BEV (Battery Electric Vehicle) driving mode, which is a motor driving mode in which the rotary machine MG is driven only by the electric power from the battery 54 to drive the vehicle. In the BEV driving mode, the K0 clutch 20 is opened to stop the engine 12, and the vehicle is driven in a BEV driving mode in which the vehicle is driven only by the rotary machine MG as a driving force source. In the BEV driving mode, the MG torque Tmg is controlled so as to realize the required input torque Tindem. On the other hand, when the required input torque Tindem cannot be satisfied without using at least the output of the engine 12, the HEV-ECU 92 selects an HEV (Hybrid Electric Vehicle) driving mode, which is an engine driving mode. In the HEV driving mode, the K0 clutch 20 is engaged to drive the vehicle using at least the engine 12 as a driving force source, i.e., the vehicle is driven in an engine driving mode, i.e., an HEV driving mode. In the HEV driving mode, the engine torque Te is controlled so as to realize all or a part of the required input torque Tindem, and the MG torque Tmg is controlled so as to compensate for the torque that is insufficient in the engine torque Te with respect to the required input torque Tindem. On the other hand, even if the required input torque Tindem can be satisfied only by the output of the rotary machine MG, the HEV-ECU 92 establishes the HEV driving mode when the engine 12 or the like needs to be warmed up. In this way, the HEV-ECU 92 switches between the BEV driving mode and the HEV driving mode by automatically stopping the engine 12 during HEV driving, restarting the engine 12 after the engine is stopped, starting the engine 12 during BEV driving, automatically stopping the engine 12 while the vehicle is stopped, and starting the engine 12, based on the required input torque Tindem, etc. Automatic stopping and restarting of the engine 12 are also expressed as intermittent operation of the engine 12.

[0030] When it is necessary to start the stopped engine 12, such as when switching from the BEV driving mode to the HEV driving mode, the HEV-ECU 92 has an engine start control unit 92a that engages the K0 clutch 20 to crank the engine 12 and executes fuel injection and ignition timing control by the engine control device 50 via the engine-ECU 96. The engine start control unit 92a increases the MG torque Tmg by the cranking torque Tcrk via the MG-ECU 94 so that the cranking torque Tcrk required for cranking is provided by the rotary machine MG. Even when the vehicle is stopped, the engine start control unit 92a can crank and start the engine 12 by the rotary machine MG while preventing a change in driving force by putting the automatic transmission 24 into neutral.

[0031] The ECT-ECU 98 has a function of a shift control section that executes shift control of the automatic transmission 24. That is, the ECT-ECU 98 performs shift determination of the automatic transmission 24 using, for example, a shift map, which is a predetermined relationship, and outputs a CB hydraulic control command signal Scb to the hydraulic control circuit 56 as necessary for executing shift control of the automatic transmission 24. The shift map is a predetermined relationship having shift lines for determining shifts of the automatic transmission 24 on a two-dimensional coordinate system having, for example, vehicle speed V and required drive torque Trdem as variables.

[0032] Here, the MG-ECU 94 functionally includes an abnormality detection unit 94a and a torque limiting unit 94b. The abnormality detection unit 94a detects abnormalities related to the rotating machine MG in order to prevent damage to the rotating machine MG and motor-related components such as the inverter 52, and specifically detects abnormalities in the coil temperature sensor 82, the oil temperature sensor 86, the communication bus, and the inverter temperature sensor 84, as shown in Fig. 3. In other words, if an abnormality occurs in which the stator coil temperature THcoil cannot be accurately detected due to a failure of the coil temperature sensor 82, etc., and the rotating machine MG is continued to be used in a normal manner, the stator coil may overheat and damage the rotating machine MG. If an abnormality occurs in which the oil temperature THoil cannot be detected accurately due to a failure of the oil temperature sensor 86 or the like, the oil temperature THoil reflects the temperature of the rotor of the rotating machine MG, and the temperature of the magnet embedded in the rotor cannot be accurately grasped. Therefore, if the rotating machine MG is continued to be used in the normal manner, the magnet may overheat and the rotating machine MG may be damaged or the specified MG torque Tmg may not be obtained. If an abnormality occurs in which the inverter temperature sensor 84 cannot accurately detect the inverter temperature THinv, the inverter 52 may overheat and be damaged if the rotating machine MG is continued to be used in the normal manner. Furthermore, since an abnormality in the oil temperature sensor 86 is detected by the ECT-ECU 98 and the information is transmitted to the MG-ECU 94 via the communication bus, if an abnormality occurs in the communication bus, the abnormality in the oil temperature sensor 86 cannot be detected. Therefore, similar to the case of an abnormality in the oil temperature sensor 86, if the rotating machine MG is continued to be used in the normal manner, the magnet may overheat and the rotating machine MG may be damaged or the specified MG torque Tmg may not be obtained. Abnormalities other than those of the oil temperature sensor 86, i.e., abnormalities of the coil temperature sensor 82, abnormalities of the communication bus, and abnormalities of the inverter temperature sensor 84, are not affected by abnormalities in the communication bus because they are all detected by the MG-ECU 94. The presence or absence of these abnormalities can be detected, for example, by the trend of changes in the stator coil temperature THcoil, the oil temperature THoil, and the inverter temperature THinv, the presence or absence of signals, and comparison with other information.

[0033] When an abnormality is detected by the abnormality detection unit 94a, the torque limiting unit 94b limits an MG torque upper limit value Tmgmax, which is an upper limit value of the MG torque Tmg, to a predetermined limit torque Tlim at which the electric vehicle 10 can run with the MG torque Tmg, in order to prevent damage caused by the abnormality to the rotating machine MG and motor-related components such as the inverter 52. The limit torque Tlim may be a constant value regardless of the type of abnormality, but in this embodiment, in the case of an abnormality in the coil temperature sensor 82, an abnormality in the oil temperature sensor 86, or an abnormality in the communication bus, the limit torque Tlim is limited to a first limit torque Tlim1 that is lower than the cranking torque Tcrk when starting the engine 12, and in the case of an abnormality in the inverter temperature sensor 84, the limit torque Tlim is limited to a second limit torque Tlim2 that is higher than the cranking torque Tcrk. The torque limiting unit 94b also reduces the MG torque upper limit value Tmgmax to the limit torques Tlim1 and Tlim2 at a constant rate of change in order to prevent a sudden change in the driving force when, for example, the rotating machine MG generates a high torque close to the MG torque upper limit value Tmgmax. This rate of change may be constant regardless of the type of abnormality, but different rates of change may be determined depending on the type of abnormality.

[0034] The HEV-ECU 92 is functionally equipped with an evacuation travel control unit 92b in relation to the abnormality detection by the abnormality detection unit 94a. When an abnormality is detected by the abnormality detection unit 94a, the evacuation travel control unit 92b judges whether or not the abnormality is a predetermined low-risk abnormality that has a low urgency for limiting the MG torque upper limit value Tmgmax, and if it is a low-risk abnormality, executes start-up advance control to output a torque required for cranking from the rotating machine MG before the motor torque is limited by the torque limiting unit 94b, to start the engine 12, and to permit the torque limiting unit 94b to limit the MG torque upper limit value Tmgmax after confirming the start of the engine 12. FIG. 2 is a flowchart specifically explaining the control by the evacuation travel control unit 92b, and executes signal processing according to steps S1 to S8 (hereinafter, steps are omitted and simply referred to as S1 to S8).

[0035] In S1 of FIG. 2, it is determined whether the engine 12 is stopped, such as when driving in the BEV driving mode. If the engine is not stopped, the process ends as it is, but if the engine is stopped, S2 is executed. In S2, it is determined whether the abnormality detection unit 94a has detected an abnormality, and if no abnormality is detected, the process ends as it is, but if an abnormality is detected, S3 is executed. In S3, it is determined whether the abnormality is a predetermined low-risk abnormality with low urgency for limiting the MG torque upper limit value Tmgmax. In this embodiment, an abnormality in the coil temperature sensor 82, an abnormality in the oil temperature sensor 86, and an abnormality in the communication bus are set as a low-risk abnormality, and an abnormality in the inverter temperature sensor 84 is set as a high-risk abnormality. Then, in the case of a low-risk abnormality, the start-precedence control in S4 and thereafter is executed, and in the case of a high-risk abnormality, the simultaneous start control in S7 and thereafter is executed.

[0036] In S4, the K0 clutch 20 is engaged, and engine start control is started by cranking the engine 12. This engine start control is executed by the engine start control unit 92a. Specifically, the MG torque Tmg is increased by the cranking torque Tcrk via the MG-ECU 94 so that the driving force change is suppressed regardless of the cranking of the engine 12 due to the engagement of the K0 clutch 20, and fuel injection and ignition timing control are executed by the engine control device 50 via the engine-ECU 96. In S5, it is determined whether the start of the engine 12 is completed, and the process waits until the start of the engine 12 is completed. Whether the start of the engine 12 is completed can be determined, for example, by a complete combustion determination that the engine 12 can rotate stably under its own power. The complete combustion determination of the engine 12 is performed, for example, by the engine-ECU 96, and specifically, it can be determined by the engine rotation speed Ne becoming equal to or higher than a predetermined determination value (for example, about 400 rpm). Then, when the start of the engine 12 is completed, S6 is executed to limit the MG torque upper limit value Tmgmax. This limitation of the MG torque upper limit value Tmgmax allows the torque limiting unit 94b of the MG-ECU 94 to limit the MG torque upper limit value Tmgmax, and the MG torque upper limit value Tngmax is reduced to the first limit torque Tlim1 at a constant rate of change. The first limit torque Tlim1 is a limit torque in the case of a low-risk abnormality, and the engine 12 is appropriately started while suppressing driving force fluctuations by increasing the MG torque Tmg by a cranking torque Tcrk higher than the first limit torque Tlim1 before the MG torque upper limit value Tmgmax is limited to the first limit torque Tlim1. In addition, during evacuation running upon detection of this abnormality, intermittent operation of the engine 12 is prohibited, and the operating state of the engine 12 is continued regardless of the magnitude of the required input torque Tindem, etc.

[0037] FIG. 4 is an example of a time chart explaining the change in the operating state of each part when an abnormality is detected by the abnormality detection unit 94a during driving in the BEV driving mode and start-precedent control is performed according to steps S4 to S6 of the flowchart in FIG. 2. Time t1 in FIG. 4 is the time when a low-risk abnormality is detected by the abnormality detection unit 94a, and an engine start command is immediately output to start the start control of the engine 12. At time t2, when it is determined that the engine 12 has completely exploded, the limit control of the MG torque Tmg for lowering the MG torque upper limit value Tmgmax is started, and the MG torque upper limit value Tmgmax is smoothly lowered at a constant rate of change to the first limit torque Tlim1. Time t3 is the time when the MG torque upper limit value Tmgmax is lowered to the first limit torque Tlim1. Since the engine 12 is started prior to the limiting of the MG torque Tmg in this way, evacuation driving using the engine 12 is possible, and the driving distance is increased and the driving force performance is improved. Furthermore, since the low-risk abnormality has a relatively low urgency, damage to the rotating machine MG, etc. is suppressed even if the control to limit the MG torque Tmg is started after the start of the engine 12. In other words, an abnormality that suppresses damage to the rotating machine MG, etc. even if the control to limit the MG torque Tmg is started after the start of the engine 12 is set as a low-risk abnormality.

[0038] The dashed line in the column for MG torque upper limit value Tmgmax in Figure 4 represents the conventional case in which the MG torque upper limit value Tmgmax is immediately reduced to the first limit torque Tlim1 upon detection of an abnormality. Although damage to the rotating machine MG, etc. is appropriately suppressed, there is a possibility that the MG torque Tmg will be insufficient when cranking the engine 12. Therefore, no start control of the engine 12 is performed, and evacuation running is performed using only the rotating machine MG.

[0039] When the determination in S3 is NO (negative), that is, when a predetermined high-risk abnormality occurs that requires high urgency to limit the MG torque upper limit value Tmgmax, specifically, when the inverter temperature sensor 84 is abnormal, the simultaneous start control in S7 and S8 is executed. That is, the limit control of the MG torque Tmg is started in S7, and at the same time, the K0 clutch 20 is engaged in S8 to start engine start control. The limit of the MG torque upper limit value Tmgmax is executed by the torque limiting section 94b of the MG-ECU 94, and the MG torque upper limit value Tngmax is reduced to the second limit torque Tlim2 at a constant rate of change. The engine start control is executed by the engine start control section 92a, and specifically, the MG torque Tmg is increased by the cranking torque Tcrk via the MG-ECU 94 so that the driving force change is suppressed regardless of the cranking of the engine 12 due to the engagement of the K0 clutch 20, and the engine control device 50 executes fuel injection, ignition timing control, and the like via the engine-ECU 96. In this case as well, the intermittent operation of the started engine 12 is prohibited, and the operating state of the engine 12 is continued regardless of the magnitude of the required input torque Tindem, etc.

[0040] FIG. 5 is an example of a time chart for explaining the change in the operating state of each part when an abnormality is detected by the abnormality detection unit 94a during driving in the BEV driving mode and the simultaneous start control is performed according to steps S7 to S8 of the flowchart in FIG. 2. Time t1 in FIG. 5 is the time when a high-risk abnormality is detected by the abnormality detection unit 94a, and the limit control of the MG torque Tmg is immediately started, and an engine start command is output to start the start control of the engine 12. Time t2 is the time when the MG torque upper limit value Tmgmax is reduced to the second limit torque Tlim2, and the start (complete explosion) of the engine 12 is completed at time t3 after the time t2. By immediately starting the limit control of the MG torque Tmg, damage to the rotating machine MG and the like is appropriately suppressed, while the second limit torque Tlim2 is higher than the cranking torque Tcrk, so that the shortage of the MG torque Tmg during cranking of the engine 12 is suppressed. However, although there is a possibility that a temporary fluctuation in driving force may occur during cranking due to the limit on the MG torque Tmg, the degree of discomfort felt by the driver is low because an abnormality is displayed on the instrument panel, etc. immediately after the abnormality is detected. By setting the rate of change when lowering the MG torque upper limit value Tmgmax in S7 to a relatively small value, it is also possible to crank and start the engine 12 at an early stage in the process of lowering the MG torque upper limit value Tmgmax, thereby suppressing changes in driving force due to cranking.

[0041] In this way, according to the electronic control device 90 of the electric vehicle 10 of this embodiment, when an abnormality is detected by the abnormality detection unit 94a, if the abnormality is a predetermined low-risk abnormality, the start-up advance control of S4 to S6 is executed, and before the torque limiting unit 94b starts the limiting control of the MG torque Tmg, the engine 12 is cranked by engaging the K0 clutch 20 and the MG torque Tmg is increased by the cranking torque Tcrk, and the MG torque Tmg is limited after the start of the engine 12 is confirmed. Therefore, while suppressing damage to the rotating machine MG and the like due to an abnormality, it is possible to avoid a shortage of driving force due to cranking, such as when the engine 12 is cranked and started during evacuation running in which the MG torque Tmg is limited to the first limit torque Tmg1. In addition, since the engine 12 can be reliably started before the MG torque Tmg is limited, evacuation running using the engine 12 is possible, and the running distance during evacuation running is extended and the driving force performance is improved.

[0042] Furthermore, when the abnormality is a predetermined high-risk abnormality, the simultaneous start control of S7 to S8 is executed, and the limit control of the MG torque Tmg and the start control of the engine 12 are immediately performed, so that damage to the rotating machine MG and the like is appropriately suppressed, and evacuation running is possible using the engine 12, so that the running distance during evacuation running is extended and the driving force performance is improved. Furthermore, since the second limit torque Tlim2 of the MG torque Tmg is higher than the cranking torque Tcrk, the driving force fluctuation due to the insufficient MG torque Tmg during cranking of the engine 12 is suppressed.

[0043] Although the embodiment of the present invention has been described in detail above with reference to the drawings, this is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0044] 10: Hybrid electric vehicle 12: Engine 90: Electronic control device (control device) 92b: Evacuation drive control unit 94a: Abnormality detection unit 94b: Torque limiting unit MG: Rotating machine (electric motor) Tmg: MG torque (motor torque) Tmgmax: MG torque upper limit value (upper limit value) Tlim1: First limit torque (limit torque)

Claims

[Claim 1] This invention is applied to a hybrid electric vehicle that includes an engine and an electric motor, and that is capable of starting the engine by outputting a torque required for cranking the engine from the electric motor during running while stopping the engine and using the electric motor as a driving force source, an abnormality detection unit that detects an abnormality in a coil temperature sensor, an oil temperature sensor, or a communication bus related to the electric motor, and an abnormality in an inverter temperature sensor; a torque limiting unit that limits an upper limit value of a motor torque, which is a torque of the electric motor, to a predetermined limit torque at which running is possible using the motor torque when the abnormality is detected by the abnormality detection unit; A control device for a hybrid electric vehicle having an evacuation travel control unit that, when the abnormality detection unit detects an abnormality in the coil temperature sensor, the oil temperature sensor, or the communication bus, determines that the abnormality is a predetermined low-risk abnormality that requires low urgency to limit the motor torque, and executes start-advance control to start the engine by outputting a torque required for cranking the engine from the electric motor before limiting control by the torque limiting unit to limit the motor torque to a first limit torque is started; and, when the abnormality detection unit detects an abnormality in the inverter temperature sensor, determines that the abnormality is a predetermined high-risk abnormality that requires high urgency to limit the motor torque, and starts limiting control by the torque limiting unit to a second limit torque that is set higher than the first limit torque, and at the same time executes simultaneous start control to output a torque required for cranking the engine from the electric motor to start starting the engine. A control device for a hybrid electric vehicle.

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