Hybrid vehicle

Abstract

To more reliably crank an engine by generating sufficient drag torque in a first motor when causing three phases of a first inverter to be in an ON state.SOLUTION: A hybrid vehicle comprises an engine, a first motor, a planetary gear mechanism, a second motor, a first inverter, a second inverter, a battery, and a control device. When the control device causes a vehicle to travel by causing the second inverter to drive the second motor, and performs three-phase ON control of the first inverter to crank the engine by drag torque generated in the first motor, thereby starting the engine, the control device sets a limit rotation speed of the second motor on the basis of a rotation speed of the engine so that rotation of the first motor is maintained in a rotation speed range where the drag torque at a level capable of cranking the engine is generated, and controls the second inverter so that the second motor is driven at the limit rotation speed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to hybrid vehicles. [Background technology]

[0002] A conventional hybrid vehicle of this type includes an engine, a first rotating electric machine having a rotor equipped with a permanent magnet, a planetary gear mechanism mechanically coupled to the engine, the first rotating electric machine, and an output shaft connected to the drive wheels, a second rotating electric machine connected to the output shaft, a battery, a first inverter electrically connected between the battery and the first rotating electric machine, and a second inverter electrically connected between the battery and the second rotating electric machine (see, for example, Patent Document 1). In this hybrid vehicle, when starting the engine in a state where the first inverter cannot be normally PWM controlled, three-phase ON control of the first inverter is performed, and the engine is cranked by the drag torque generated by the three-phase ON control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-114222 Summary of the Invention [Problem to be solved by the invention]

[0004] To crank the engine, the first rotating electric machine needs to generate a drag torque that exceeds the engine friction. However, due to a decrease in the amount of magnets resulting from a reduction in the use of rare earths in recent years, the rotation speed range in which sufficient drag torque can be generated when the inverter's three phases are on has been significantly reduced, which could result in engine cranking failure.

[0005] The hybrid vehicle of the present disclosure has a main object to generate sufficient drag torque in the first motor when the three phases of the first inverter are on, thereby cranking the engine more reliably. [Means for solving the problem]

[0006] The hybrid vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The hybrid vehicle disclosed herein is a hybrid vehicle including an engine, a first motor capable of generating electricity and having a rotor with a permanent magnet, a planetary gear mechanism connected to an output shaft of the engine, a rotating shaft of the first motor, and a drive shaft connected to drive wheels, a second motor capable of outputting power to the drive shaft, a first inverter that drives the first motor, a second inverter that drives the second motor, a battery connected to the first inverter and the second inverter via power lines, and a control device that controls the engine, the first inverter, and the second inverter, wherein the control device drives the second motor using the second inverter to run the hybrid vehicle, and when cranking and starting the engine using drag torque generated in the first motor by controlling the first inverter to be three-phase on, sets a limit rotation speed of the second motor based on the engine speed so that rotation of the first motor is maintained in a rotation speed range where drag torque of a magnitude sufficient to crank the engine is generated, and controls the second inverter so that the second motor is driven at the set limit rotation speed.

[0008] In the hybrid vehicle disclosed herein, even if the first motor cannot crank the engine normally, sufficient drag torque can be generated in the first motor when the three phases are on, allowing the engine to be cranked and started more reliably. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a hybrid vehicle according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of an electric drive system including motors MG1 and MG2. [Figure 3] 10 is a flowchart showing an example of an engine start process when the motor MG1 is abnormal. [Figure 4] 1 is an explanatory diagram showing the relationship between the rotation speed Nm1 of the motor MG1 and the drag torque when the three phases are on, and an explanatory diagram showing the limit rotation speed Nm2lim of the motor MG2 when cranking the engine using the drag torque of the motor MG1 when the three phases are on. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present disclosure will be described. Fig. 1 is a schematic diagram of a hybrid vehicle 20 according to this embodiment, and Fig. 2 is a schematic diagram of an electric drive system including motors MG1 and MG2. As shown in Fig. 1, the hybrid vehicle 20 according to this embodiment includes an engine 22, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery 50, and a hybrid electronic control unit (hereinafter referred to as HVECU) 70.

[0011] The engine 22 is configured as an internal combustion engine that outputs power using fuel such as gasoline or diesel. The operation of the engine 22 is controlled by an engine electronic control unit (hereinafter referred to as engine ECU) 24. The engine ECU 24 receives detection signals from various sensors, such as a crank angle θcr from a crank position sensor 23a that detects the rotational position of a crankshaft 23 of the engine 22. The engine ECU 24 calculates the rotation speed Ne of the engine 22 based on the crank angle θcr. The engine ECU 24 also outputs control signals to intake valves, fuel injection valves, and spark plugs.

[0012] The planetary gear 30 is configured as a single-pinion planetary gear mechanism and includes a sun gear 31 that is an external gear, a ring gear 32 that is an internal gear, a plurality of pinion gears 33 that mesh with the sun gear 31 and the ring gear 32, respectively, and a carrier 34 that supports the plurality of pinion gears 33 so that they can rotate and revolve freely. A rotor of a motor MG1 is connected to the sun gear 31. A drive shaft 36 that is connected to drive wheels 39a, 39b via a differential gear 38 is connected to the ring gear 32. The crankshaft 23 of the engine 22 is connected to the carrier 34.

[0013] Both motors MG1 and MG2 are configured as synchronous generator motors having a rotor with a permanent magnet embedded in the rotor core and a stator with a three-phase coil wound around the stator core. The rotor of motor MG2 is connected to drive shaft 36.

[0014] As shown in FIG. 2, the inverters 41 and 42 are connected to a power line 54 to which a battery 50 is connected. The inverters 41 and 42 include six transistors T11 to T16 and T21 to T26 and six diodes D11 to D16 and D21 to D26 connected in anti-parallel to the corresponding transistors. The transistors T11 to T16 and T21 to T26 are arranged in pairs, two on the source side and two on the sink side of a positive line 54a and a negative line 54b of the power line 54. The coils of each phase (U-phase, V-phase, and W-phase) of the motors MG1 and MG2 are connected to the connection points between corresponding transistors T11 to T16 and T21 to T26, respectively. The motors MG1 and MG2 are driven and rotated by a motor electronic control unit (hereinafter referred to as "motor ECU") 40, which controls the switching of the transistors T11 to T16 and T21 to T26. The motors MG1 and MG2 are configured as generator motors, and the electric power generated by the motors MG1 and MG2 is rectified by diodes D11 to D16 and D21 to D26 and supplied to the electric power line .

[0015] The motor ECU 40 receives signals from various sensors via input ports. For example, the motor ECU 40 receives rotational positions θm1 and θm2 from rotational position sensors 43 and 44 that detect the rotational positions of the rotors of the motors MG1 and MG2, and phase currents from current sensors that detect the phase currents of the respective phases of the motors MG1 and MG2. The motor ECU 40 calculates rotational speeds Nm1 and Nm2 of the motors MG1 and MG2 based on the rotational positions θm1 and θm2.

[0016] The battery 50 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The battery 50 is connected to a power line 54 via a system main relay 55. The battery 50 is managed by a battery electronic control unit (hereinafter referred to as "battery ECU") 52. The battery ECU 52 receives inputs such as a voltage Vb of the battery 50 from a voltage sensor 51a attached between the terminals of the battery 50 (battery voltage) and a current Ib of the battery 50 from a current sensor 51b attached to the output terminals of the battery 50. The battery ECU 52 calculates a state of charge (SOC) of the battery 50 based on an integrated value of the battery current Ib.

[0017] The HVECU 70 receives inputs such as an ignition signal from a start switch 80, a shift position SP from a shift position sensor 82 that detects the operating position of a shift lever 81, an accelerator opening Acc from an accelerator pedal position sensor 84 that detects the amount of depression of an accelerator pedal 83, a brake pedal position BP from a brake pedal position sensor 86 that detects the amount of depression of a brake pedal 85, and a vehicle speed V from a vehicle speed sensor 87. The HVECU 70 communicates with the engine ECU 24, the motor ECU 40, and the battery ECU 52.

[0018] In the hybrid vehicle 20 of this embodiment, the engine 22 and the motors MG1 and MG2 are controlled to travel in a hybrid driving mode (HV driving mode) or an electric driving mode (EV driving mode). The HV driving mode is a mode in which the vehicle travels with the engine 22 operating, and the EV driving mode is a mode in which the vehicle travels with the engine 22 stopped.

[0019] In the HV driving mode, the HVECU 70 first sets a required torque Tr* required of the drive shaft 36 based on the accelerator opening Acc and the vehicle speed V, and then calculates a required power Pr* required of the drive shaft 36 by multiplying the set required torque Tr* by the rotation speed Nd (rotation speed Nm2) of the drive shaft 36. Next, the HVECU 70 calculates a target power Pe* of the engine 22 based on the required power Pr* and a required charging / discharging power Pb* of the battery 50. Next, the HVECU 70 sets a target rotation speed Ne* and target torque Te* of the engine 22 and torque commands Tm1* and Tm2* of the motors MG1 and MG2 so that the target power Pe* is output from the engine 22 and the required torque Tr* is output to the drive shaft 36. The HVECU 70 then transmits the target rotation speed Ne* and target torque Te* of the engine 22 to the engine ECU 24, and transmits torque commands Tm1* and Tm2* of the motors MG1 and MG2 to the motor ECU 40. The engine ECU 24 controls the operation of the engine 22 so that the engine 22 operates at the target rotation speed Ne* and target torque Te*. The motor ECU 40 controls the switching of the transistors T11 to T16 and T21 to T26 of the inverters 41 and 42 so that the motors MG1 and MG2 are driven by the torque commands Tm1* and Tm2*.

[0020] In the EV driving mode, the HVECU 70 sets the required torque Tr* in the same manner as in the HV driving mode, sets the torque command Tm1* of the motor MG1 to a value of 0, and sets the torque command Tm2* of the motor MG2 so that the required torque Tr* is output to the drive shaft 36, and transmits the torque commands Tm1* and Tm2* of the motors MG1 and MG2 to the motor ECU 40.

[0021] In addition, when transitioning from EV driving mode to HV driving mode, the HVECU 70 sets a torque command Tm1* for the motor MG1 so that the engine 22 is cranked using the torque from the motor MG1, and sets a torque command Tm2* for the motor MG2 so that the required torque Tr* is output to the drive shaft 36, and transmits the torque commands Tm1* and Tm2* for the motors MG1 and MG2 to the motor ECU 40.

[0022] Furthermore, when an abnormality occurs in motor MG1, HVECU 70 shuts off the gate of inverter 41 as a fail-safe and uses power from battery 50 to perform electric driving using power from motor MG2. In this embodiment, HVECU 70 operates engine 22 to rotate motor MG1 using power from engine 22, thereby supplying back electromotive force generated in motor MG1 to power line 54 in addition to power from battery 50, thereby securing the power required for electric driving. This enables the cruising distance to be extended compared to when electric driving is performed using only power from battery 50. Here, when engine 22 is stopped, normal cranking of engine 22 by driving motor MG1 cannot be performed. Therefore, HVECU 70 performs three-phase ON control to turn on all transistors T11, T12, and T13 of the upper arm of inverter 41 or all transistors T14, T15, and T16 of the lower arm, thereby cranking engine 22 using drag torque Td generated in motor MG1. The following describes in detail the process of cranking and starting the engine 22 when an abnormality occurs in the motor MG1.

[0023] 3 is a flowchart showing an example of an engine start process when an abnormality in the motor MG1 is detected. This process is executed when an abnormality in the motor MG1 is detected, the engine 22 is stopped, and the vehicle is traveling forward. When an abnormality in the motor MG1 is detected, the EVECU 70, as described above, shuts off the gate of the inverter 41 and drives the motor MG2 to perform electric traveling. Note that abnormalities in the motor MG1 include element abnormalities such as overcurrent or overheating in the transistors T11 to T16 of the inverter 41, and sensor abnormalities such as a failure of the rotational position sensor 43 of the motor MG1 or a failure of the current sensor.

[0024] When the engine start process during MG1 abnormality is executed, the HVECU 70 first inputs the rotation speed Nm1 of the motor MG1 (step S100) and waits until the rotation speed Nm1 approaches the peak drag torque generating rotation speed Nm1td (step S102). The peak drag torque generating rotation speed Nm1td is the rotation speed of the motor MG1 when the drag torque Td generated in the motor MG1 reaches its peak (minimum) when the inverter 41 is in three-phase on mode (see FIG. 4(a)), and is determined in advance through experiments, etc. The motor MG1 of this embodiment has a small amount of permanent magnet, and therefore has a small rotation speed range in which sufficient drag torque can be generated when the inverter 41 is in three-phase on mode.

[0025] When the HVECU 70 determines that the rotation speed Nm1 of the motor MG1 has approached the peak drag torque generating rotation speed Nm1td, it performs three-phase ON control of the inverter 41 (step S104). Next, the HVECU 70 inputs the rotation speed Ne of the engine 22 (step S106) and sets the limit rotation speed Nm2lim of the motor MG2 based on the input rotation speed Ne and the peak drag torque generating rotation speed Nm1td (step S108). Because the engine 22, the motor MG1, and the motor MG2 are connected to the planetary gear 30, the limit rotation speed Nm2lim of the motor MG2 can be calculated from the rotation speed Ne of the engine 22 and the peak drag torque generating rotation speed Nm1td using the gear ratio of the planetary gear 30. Then, the HVECU 70 sets a torque command Tm2* for the motor MG2 so that the motor MG2 rotates at the set limit rotation speed Nm2lim, and transmits the set torque command Tm2* to the motor ECU 40 (step S110). Here, the limit rotation speed Nm2lim may be a region for rotating the motor MG1 within a certain rotation speed range including the peak drag torque generating rotation speed Nm1td, and the torque command Tm2* may be set to a torque that limits the required torque Td* so that the motor MG2 rotates within the region of the limit rotation speed Nm2lim.

[0026] In this way, by controlling motor MG2 by setting torque command Tm2* so that motor MG2 rotates at limit rotational speed Nm2lim, which is set based on engine speed Ne of engine 22 and peak drag torque generating rotational speed Nm1td of motor MG1, motor MG1 rotational speed Nm1 is maintained near peak drag torque generating rotational speed Nm1td (see FIG. 4B). As a result, engine 22 is cranked by torque near the peak of drag torque generated by motor MG1, regardless of engine speed Ne. Therefore, even if motor MG1 has a small rotational speed range in which sufficient drag torque can be generated during three-phase ON, sufficient drag torque can be generated to more reliably crank engine 22. Here, torque command Tm2* of motor MG2 is limited to the torque required to rotate motor MG2 at limit rotational speed Nm2lim relative to required torque Td*. However, this torque limitation of motor MG2 is only performed for a short period until cranking of engine 22 is completed, so no major problems arise.

[0027] Next, the HVECU 70 inputs the rotation speed Ne of the engine 22 (step S112) and determines whether the input rotation speed Ne of the engine 22 is equal to or greater than the start-up rotation speed Nefire (step S114). If the HVECU 70 determines that the rotation speed Ne of the engine 22 is less than the start-up rotation speed Nefire, the process returns to step S108 and repeats the processes of steps S108 to S114. On the other hand, if the HVECU 70 determines that the rotation speed Ne of the engine 22 is equal to or greater than the start-up rotation speed Nefire, the HVECU 70 starts intake air amount control, fuel injection control, ignition control, etc. to start the engine 22 (step S116). Then, the EVECU 70 shuts off the gate of the inverter 41 (step S118) and releases the torque limit of the motor MG2 (step S120), and ends the engine start process when MG1 is abnormal. When the engine 22 is started, the power from the engine 22 rotates the motor MG1, and in addition to the power from the battery 50, the back electromotive force generated in the motor MG1 can be supplied to the power line 54, thereby extending the range of electric driving by the motor MG2.

[0028] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be embodied in various forms without departing from the spirit of the present disclosure. [Industrial Applicability]

[0029] The present disclosure is applicable to the hybrid vehicle manufacturing industry and the like. [Explanation of symbols]

[0030] 20 Hybrid vehicle, 22 Engine, 30 Planetary gear, 41, 42 Inverter, 50 Battery, 70 HVECU, MG1, MG2 Motor.

Claims

[Claim 1] A hybrid vehicle comprising: an engine; a first motor capable of generating electricity having a rotor provided with a permanent magnet; a planetary gear mechanism connected to an output shaft of the engine, a rotary shaft of the first motor, and a drive shaft connected to drive wheels; a second motor capable of outputting power to the drive shaft; a first inverter that drives the first motor; a second inverter that drives the second motor; a battery connected to the first inverter and the second inverter via power lines; and a control device that controls the engine, the first inverter, and the second inverter, When the vehicle is driven by the second inverter to drive the second motor and the first inverter is controlled to be three-phase ON to crank and start the engine by a drag torque generated in the first motor, the control device sets a limit rotation speed of the second motor based on the rotation speed of the engine so that the rotation of the first motor is maintained in a rotation speed range in which a drag torque large enough to crank the engine is generated, and controls the second inverter so that the second motor is driven at the set limit rotation speed. Hybrid car.

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