JP2022036593A - Control device of hybrid vehicle - Google Patents

Abstract

To start an internal combustion engine when detecting an abnormal state that an inverter cannot operate normally.SOLUTION: A hybrid vehicle comprises: a converter that boosts an output voltage of a battery and outputs the voltage; a capacitor that stores the voltage outputted by the converter; a first inverter connected between the capacitor and a first motor generator; and a second inverter connected between the capacitor and a second motor generator. A control device, when detecting an abnormal state that the first inverter does not operate normally under a situation where the second motor generator is driven and an internal combustion engine is not driven, stops the converter as processing for reducing charging voltages of the capacitor (a step S20). The control device, when a vehicle speed SP rises above a prescribed vehicle speed SP (a step S30:YES) and when power consumption Pm of the second motor generator rises above a predetermined power value PmC (a step S40:YES), starts the internal combustion engine (a step S50).SELECTED DRAWING: Figure 5

Description

The present invention relates to a control device for a hybrid vehicle.

The hybrid vehicle disclosed in Patent Document 1 includes an internal combustion engine, a first motor generator, a second motor generator, a planetary gear mechanism, a battery, and a drive wheel. The planetary gear mechanism has a sun gear, a ring gear, a pinion gear, and a carrier. A first motor generator is connected to the sun gear. An internal combustion engine is connected to the carrier. A second motor generator is connected to the ring gear. The internal combustion engine and the first motor generator can transmit power to each other via the planetary gear mechanism. The first motor generator receives the power of the internal combustion engine to generate electricity, or transmits the power to the internal combustion engine to start the internal combustion engine.

The second motor generator is connected to the drive wheels. The second motor generator is supplied with electric power from the battery and electric power generated by the first motor generator. The second motor generator operates in response to the supply of these electric powers to transmit power to the drive wheels.

The hybrid vehicle is equipped with a control device. The control device controls the drive of the internal combustion engine and both motor generators. When an abnormality occurs in the drive control of the first motor generator, the control device does not use the first motor generator and supplies the electric power of the battery to the second motor generator to evacuate the hybrid vehicle.

Japanese Unexamined Patent Publication No. 2016-03510

When only the electric power of the battery is used when an abnormality occurs in the drive control of the first motor generator as in the technique of Patent Document 1, the evacuation travelable distance may be shortened. In order to extend the evacuation running distance, it is preferable to use the power of the internal combustion engine to generate electricity in the first motor generator and supply the electric power to the second motor generator. In order to realize this aspect, when the internal combustion engine is stopped when the above abnormality occurs, it is necessary to first drive the internal combustion engine. However, if the above abnormality occurs, it is not possible to supply electric power to the first motor generator to drive the first motor generator. Therefore, the internal combustion engine cannot be started by the power of the first motor generator.

The control device for the hybrid vehicle for solving the above problems is a drive connection of an internal combustion engine, a first motor generator, a second motor generator, the internal combustion engine, the first motor generator, and the second motor generator. The planetary gear mechanism, the battery that transfers power between the first motor generator and the second motor generator, the converter that boosts and outputs the output voltage of the battery, and the voltage output by the converter. A capacitor to be smoothed, a first inverter connected between the capacitor and the first motor generator to perform DC AC power conversion, and a DC AC power connected between the capacitor and the second motor generator. The planetary gear mechanism includes a second inverter that performs conversion, and the planetary gear mechanism is interposed between the rotating sun gear, the ring gear that rotates coaxially with the sun gear, and the sun gear and the ring gear, and revolves around the sun gear. The pinion gear has a carrier that rotates coaxially with the sun gear according to the revolution of the pinion gear, the carrier is connected to the output shaft of the internal combustion engine, and the sun gear is connected to the rotation shaft of the first motor generator. The ring gear is applied to a hybrid vehicle connected to the rotating shaft of the second motor generator, and the second motor generator is driven and the internal combustion engine is not driven. 1 When an abnormal state in which the inverter does not operate normally is detected, the process of lowering the charging voltage of the capacitor and the power supplied from the first motor generator to the capacitor exceed a predetermined specified power value. When this happens, the process of starting the internal combustion engine is executed.

When the second motor generator is driven and the internal combustion engine is stopped, the rotating shaft of the first motor generator rotates without receiving power supply from the battery. Therefore, a counter electromotive force is generated in the first motor generator. Then, when the electric power is supplied from the first motor generator to the capacitor, the first motor generator has done the work, so that the rotation speed of the rotation axis of the first motor generator approaches zero. At this time, if the rotation speed of the second motor generator does not change, the rotation speed of the output shaft of the internal combustion engine increases in the forward rotation direction.

According to the above configuration, when an abnormal state in which the first inverter does not operate normally is detected, the charging voltage of the capacitor is lowered. Therefore, the electric power supplied from the first motor generator to the capacitor increases, and the fluctuation range of the rotation speed of the rotation axis of the first motor generator increases accordingly. As a result, the rotation speed of the output shaft of the internal combustion engine is also greatly increased, and a rotation speed sufficient for starting the internal combustion engine can be obtained.

Schematic block diagram of the vehicle. Schematic diagram of the electrical system of the vehicle. A collinear diagram showing the relationship between the rotation speeds of each rotating element of the power distribution integrated mechanism. The figure which shows the relationship between the rotation speed of the 1st motor generator and the drag torque. The flowchart which showed the processing procedure of the internal combustion engine start processing of 1st Embodiment. A time chart showing an example of time change of each variable related to the internal combustion engine starting process of the first embodiment. The flowchart which showed the processing procedure of the internal combustion engine start processing of 2nd Embodiment. A time chart showing an example of time change of each variable related to the internal combustion engine starting process of the second embodiment.

Hereinafter, the first embodiment of the control device for the hybrid vehicle will be described with reference to the drawings.
First, the schematic configuration of the vehicle will be described.
As shown in FIG. 1, the hybrid vehicle (hereinafter referred to as a vehicle) 500 includes an internal combustion engine 10, a first motor generator (hereinafter referred to as a first MG) 71, and a second motor generator (hereinafter referred to as a second MG). It has 72, a power distribution integrated mechanism 40, a reduction gear 50, a reduction mechanism 60, a differential 61, and a drive wheel 62.

The internal combustion engine 10, the first MG71, and the second MG72 are drive sources for the vehicle 500. The internal combustion engine 10 has a fuel injection valve for injecting fuel, a spark plug for igniting a mixture of fuel and intake air, a crank shaft 14 rotated by combustion of the mixture, and the like. The first MG71 and the second MG72 are generator motors having a rotor in which a permanent magnet is embedded and a stator in which a three-phase coil is wound.

A power distribution integration mechanism 40 is connected to a crank shaft 14 which is an output shaft of the internal combustion engine 10. The first MG71 is connected to the power distribution integration mechanism 40. A second MG 72 is connected to the power distribution integration mechanism 40 via a reduction gear 50. A drive wheel 62 is connected to the power distribution integrated mechanism 40 via a deceleration mechanism 60 and a differential 61.

The power distribution integrated mechanism 40 is a planetary gear mechanism. The power distribution integrated mechanism 40 has a sun gear 41, a ring gear 42, a pinion gear 43, and a carrier 44. The sun gear 41 is an external gear. The sun gear 41 rotates on its axis. The ring gear 42 is an internal gear. The ring gear 42 rotates coaxially with the sun gear 41. A plurality of pinion gears 43 are interposed between the sun gear 41 and the ring gear 42. Each pinion gear 43 meshes with both the sun gear 41 and the ring gear 42. Each pinion gear 43 can revolve around the sun gear 41. Specifically, each pinion gear 43 is supported by the carrier 44 in a state where it can rotate and revolve around the sun gear 41. The carrier 44 rotates coaxially with the sun gear 41 according to the revolution of each pinion gear 43. The rotation shaft of the first MG 71 is connected to the sun gear 41. That is, the first MG 71 is interlocked with the sun gear 41. A crank shaft 14 is connected to the carrier 44. That is, the carrier 44 is interlocked with the crank shaft 14. A ring gear shaft 45 is connected to the ring gear 42. Both the reduction gear 50 and the reduction mechanism 60 are connected to the ring gear shaft 45.

The reduction gear 50 is a planetary gear mechanism. The reduction gear 50 has a sun gear 51, a ring gear 52, and a pinion gear 53. The sun gear 51 is an external gear. The sun gear 51 rotates on its axis. The ring gear 52 is an internal gear. The ring gear 52 rotates coaxially with the sun gear 51. A plurality of pinion gears 53 are interposed between the sun gear 51 and the ring gear 52. Each pinion gear 53 meshes with both the sun gear 51 and the ring gear 52. While each pinion gear 53 can rotate, it is supported around the sun gear 51 in a non-revolving state. The rotation shaft of the second MG 72 is connected to the sun gear 51. A ring gear shaft 45 is connected to the ring gear 52. The second MG 2 is connected to the ring gear 42 via the reduction gear 50 and interlocks with the ring gear 42.

When the torque from the internal combustion engine 10 is input to the carrier 44 of the power distribution integration mechanism 40, the torque is distributed to the sun gear 41 side and the ring gear 42 side. When the first MG 71 is rotated by the torque distributed to the sun gear 41 side, the first MG 71 can function as a generator.

On the other hand, when the first MG 71 is made to function as an electric motor, the torque from the first MG 71 is input to the sun gear 41. The torque of the first MG 71 input to the sun gear 41 is distributed to the carrier 44 side and the ring gear 42 side. Then, the torque from the first MG 71 is input to the crank shaft 14 via the carrier 44, so that the crank shaft 14 rotates.

The torque of the internal combustion engine 10 distributed to the ring gear 42 side and the torque of the first MG 71 are input to the drive wheels 62 via the ring gear shaft 45, the reduction mechanism 60, and the differential 61.

Further, when the vehicle 500 decelerates, the second MG 72 functions as a generator, so that a regenerative braking force corresponding to the amount of power generated by the second MG 72 is generated in the vehicle 500. On the other hand, when the second MG 72 is made to function as an electric motor, the output torque of the second MG 72 is input to the drive wheels 62 via the reduction gear 50, the ring gear shaft 45, the reduction mechanism 60 and the differential 61.

As shown in FIG. 2, the vehicle 500 has a power supply circuit 20. The power supply circuit 20 includes a battery 77, a positive electrode relay 35, a negative electrode relay 36, a first capacitor 39, a converter 80, a first positive electrode line 31, and a first negative electrode line 32. Further, the power supply circuit 20 has a second capacitor 25, a first inverter 90, a second inverter 91, a second positive electrode line 71, and a second negative electrode line 72. Note that FIG. 1 shows only the battery 77, the first inverter 90, and the second inverter 91 among the power supply circuits 20, and the configurations of the other power supply circuits 20 are not shown.

As shown in FIG. 2, the battery 77 is composed of a secondary battery. The battery 77 supplies electric power to the first MG 71 and the second MG 2, and stores electric power from the first MG 71 and the second MG 2.

The terminal on the high potential side of the battery 77 is connected to the converter 80 via the first positive electrode line 31. Further, the terminal on the low potential side of the battery 77 is connected to the converter 80 via the first negative electrode line 32. A positive electrode relay 35 is attached in the middle of the first positive electrode line 31. Further, a negative electrode relay 36 is attached in the middle of the first negative electrode line 32. The positive electrode relay 35 and the negative electrode relay 36 turn on and off the electrical connection between the battery 77 and the converter 80.

A first capacitor 39 is connected to the first positive electrode line 31 and the first negative electrode line 32. The first terminal of the first capacitor 39 is connected to a portion of the first positive electrode line 31 on the converter 80 side of the positive electrode relay 35. The second terminal of the first capacitor 39 is connected to a portion of the first negative electrode line 32 on the converter 80 side of the negative electrode relay 36. The first capacitor 39 smoothes the voltages of the first positive electrode line 31 and the first negative electrode line 32.

The converter 80 includes a first transistor 81, a second transistor 82, a first diode 85, a second diode 86, and a reactor 88. The first transistor 81 and the second transistor 82, which are switching elements, are both composed of npn type transistors. The first transistor 81 and the second transistor 82 are connected in series. A first diode 85 is connected in parallel to the first transistor 81. The first diode 85 returns a current from the emitter side of the first transistor 81 to the collector side. A second diode 86 is connected in parallel to the second transistor 82. The second diode 86 returns a current from the emitter side of the second transistor 82 to the collector side.

The first positive electrode line 31 is connected to the connection point between the emitter terminal of the first transistor 81 and the collector terminal of the second transistor 82 via the reactor 88. The first inverter 90 and the second inverter 91 are connected to the collector terminal of the first transistor 81 via the second positive electrode line 71. The first negative electrode line 32 is connected to the emitter terminal of the second transistor 82, and the first inverter 90 and the second inverter 91 are connected via the second negative electrode line 72. The first inverter 90 and the second inverter 91 are connected in parallel to the converter 80.

The converter 80 configured as described above boosts the output voltage VB of the battery 77 and outputs it to the first inverter 90 and the second inverter 91. Further, the converter 80 steps down the voltage output by the first inverter 90 and the second inverter 91 and outputs the voltage to the battery 77.

Although not shown, the first inverter 90 has 6 transistors and 6 diodes. The six transistors are switching elements, and all of them are composed of npn type transistors. The six transistors are paired with two each. That is, the six transistors are divided into three pairs of a U-phase arm, a V-phase arm, and a W-phase arm. The two transistors constituting the U-phase arm are connected in series with each other. The same applies to the V-phase arm and the W-phase arm. The coils of each phase of the first MG71 are connected to the connection points of the transistors of each phase in the arm. The U-phase arm, the V-phase arm, and the W-phase arm are connected in parallel with each other. In the arm of each phase, a diode is connected in parallel for each transistor. The diode recirculates the current from the emitter side of the transistor to the collector side. The first inverter 90 converts DC power and AC power between the converter 80 and the first MG 71.

Since the configuration of the second inverter 91 is the same as the configuration of the first inverter 90, the description thereof is omitted. The coils of each phase of the second MG 72 are connected to the second inverter 91. The second inverter 91 converts DC power and AC power between the converter 80 and the second MG 72.

The first terminal of the second capacitor 25 is connected to the second positive electrode line 71. The second terminal of the second capacitor 25 is connected to the second negative electrode line 72. The second capacitor 25 smoothes the voltages of the second positive electrode line 71 and the second negative electrode line 72.

In this specification, regarding relays and transistors, a state in which the duty ratio is 100% is referred to as an on state, and a state in which the duty ratio is 0% is referred to as an off state. Duty cycle is the ratio of the period during which these are turned on in the switching cycle of relays and transistors.

As shown in FIG. 1, the vehicle 500 is equipped with a crank angle sensor 95, an accelerator sensor 96, a vehicle speed sensor 97, a first rotation angle sensor 93, and a second rotation angle sensor 94. Although not shown, the vehicle 500 is equipped with a first current sensor, a second current sensor, a battery sensor, a first capacitor sensor, and a second capacitor sensor. The crank angle sensor 95 detects the rotation angle Scr of the crank shaft 14. The accelerator sensor 96 detects the operation amount ACC of the accelerator pedal operated by the driver. The vehicle speed sensor 97 detects the vehicle speed SP, which is the traveling speed of the vehicle 500. The first rotation angle sensor 93 detects the rotation angle Sm1 of the rotation axis of the first MG71. The second rotation angle sensor 94 detects the rotation angle Sm2 of the rotation axis of the second MG 72. The first current sensor detects the current flowing through the coil of the first MG71. The second current sensor detects the current flowing through the coil of the second MG72. The battery sensor detects battery information such as current, output voltage VB, and temperature of the battery 77. The first capacitor sensor detects the charge voltage VL of the first capacitor 39. The second capacitor sensor detects the charge voltage VH of the second capacitor 25.

Next, the control configuration of the vehicle will be described.
First, the outline of the control device and the basic control contents will be described.
The vehicle 500 has a control device 100. The control device 100 may be configured as one or more processors that execute various processes according to a computer program (software). The control device 100 is a circuit (cyclery) including one or more dedicated hardware circuits such as an application specific integrated circuit (ASIC) that executes at least a part of various processes, or a combination thereof. It may be configured as. The processor includes a CPU 101 and a memory such as a RAM and a ROM 102. The memory stores a program code or a command configured to cause the CPU 101 to execute the process. Memory or computer readable media includes any available medium accessible by a general purpose or dedicated computer.

Detection signals from various sensors mounted on the vehicle 500 are input to the control device 100. Specifically, a detection signal for each of the following parameters is input to the control device 100.

The rotation angle Scr of the crank shaft 14 detected by the crank angle sensor 95.
-Accelerator pedal operation amount ACC detected by the accelerator sensor 96
-Vehicle speed SP detected by the vehicle speed sensor 97
The rotation angle Sm1 of the rotation axis of the first MG71 detected by the first rotation angle sensor 93.
The rotation angle Sm2 of the rotation axis of the second MG72 detected by the second rotation angle sensor 94.
-Current flowing through the coil of the first MG71 detected by the first current sensor-Current flowing through the coil of the second MG72 detected by the second current sensor-Battery information detected by the battery sensor-First capacitor 39 detected by the first capacitor sensor Charging voltage VL
-Charging voltage VH of the second capacitor 25 detected by the second capacitor sensor
The CPU 101 calculates the engine rotation speed Ne, which is the rotation speed of the crank shaft 14 per unit time, based on the rotation angle Scr of the crank shaft 14. The CPU 101 calculates the rotation speed Nm1 of the rotation axis per unit time based on the rotation angle Sm1 of the rotation axis of the first MG 71. The CPU 101 calculates the rotation speed Nm2 of the rotation axis per unit time based on the rotation angle Sm2 of the rotation axis of the second MG 72. The storage amount SOC of the battery 77 is calculated based on the CPU 101 and the battery information.

The CPU 101 controls the internal combustion engine 10, the first MG71, the second MG72, and the like by executing various programs stored in the ROM 102. Specifically, the CPU 101 calculates a vehicle required output, which is a required value of the output required for the vehicle 500 to travel, based on the operation amount ACC of the accelerator pedal and the vehicle speed SP. The CPU 101 determines the torque distribution of the internal combustion engine 10, the first MG71, and the second MG72 based on the vehicle required output and the battery storage amount SOC. The CPU 101 controls the output of the internal combustion engine 10 and the power running and regeneration of the first MG 71 and the second MG 72 based on the torque distribution of the internal combustion engine 10, the first MG 71, and the second MG 72. For example, regarding the control of the second MG 72, the CPU 101 calculates the second MG required torque MG2 *, which is a required value of the power running torque or the regenerative torque of the second MG 72. Then, the CPU 101 controls the converter 80, the second inverter 91, and the like in order to realize the second MG required torque MG2 *.

In normal travel control, the CPU 101 drives the vehicle 500 in a hybrid travel mode (HV mode), an electric vehicle mode (EV mode), or the like. The hybrid driving mode is a control mode in which the vehicle 500 is driven with the operation of the internal combustion engine 10. The electric traveling mode is a control mode in which the vehicle 500 is driven with the internal combustion engine 10 stopped.

Next, the control contents performed by the CPU 101 when an abnormality related to the first inverter 90 occurs will be described.
The CPU 101 monitors the presence or absence of an inverter abnormal state, which is an abnormal state in which the first inverter 90 does not operate normally. In particular, the inverter abnormal state is a state in which each transistor constituting the first inverter 90 cannot be appropriately turned on and off. When an inverter abnormality state occurs in the first inverter 90, the CPU 101 stops outputting a signal to the base terminal of each transistor constituting the first inverter 90. As a result, each transistor constituting the first inverter 90 is turned off, and the first inverter 90 is stopped. However, as described above, the first inverter 90 has a freewheeling diode connected in parallel to each transistor. Therefore, even when the first inverter 90 is stopped, the current from the first MG71 side can flow.

For example, the following can be mentioned as factors that cause an abnormal state of the inverter.
-Transistor failure in the first inverter 90-Failure of the circuit related to the control of the first inverter 90 in the control device 100-Failure of various sensors required to control the first inverter 90 The above-mentioned various sensors are The first rotation angle sensor 93, the first current sensor, the second condenser sensor and the like. Even if an abnormal state of the inverter occurs, there is no abnormality in the first MG71 itself, and operation such as power generation is possible.

When the CPU 101 detects an abnormal state of the inverter, the CPU 101 cancels the normal traveling control and executes the evacuation traveling control to evacuate the vehicle 500. The evacuation running control includes a battery running mode (MD mode) and an internal combustion engine combined running mode (MDE mode). In the battery drive mode, the CPU 101 does not use the generated power of the first MG 71, but drives the second MG 72 only by the power of the battery 77. That is, the CPU 101 puts the internal combustion engine 10 and the first inverter 90 into a stopped state.

In the internal combustion engine combined operation mode, the CPU 101 causes the first MG 71 to generate electricity by the power of the internal combustion engine 10 in a state where the first inverter 90 is stopped. Then, the CPU 101 drives the second MG 72 by using the generated power Pm1 of the first MG 71 in place of or in addition to the electric power of the battery 77. Specifically, when the first MG 71 is rotationally driven by the internal combustion engine 10 with the first inverter 90 stopped, a counter electromotive voltage R is generated in the first MG 71. When the countercurrent voltage R is higher than the charge voltage VH of the second capacitor 25, the generated power Pm1 caused by the countercurrent voltage R is supplied to the second positive electrode line 71 and the second negative electrode line 72. Then, this generated power Pm1 is supplied to the second MG 72. When the first MG 71 generates power, that is, when the counter electromotive voltage R is higher than the charge voltage VH of the second capacitor 25, the first MG 71 has done the work, so that torque is generated in the first MG 71. Hereinafter, the torque caused by the counter electromotive voltage R is referred to as a drag torque T.

In the above-mentioned internal combustion engine combined driving mode, the distance that the vehicle 500 can evacuate can be made longer than that in the battery driving mode by the amount of using the generated power Pm1 of the first MG71. Therefore, when the CPU 101 detects an abnormal state of the inverter, it basically selects an internal combustion engine combined traveling mode. On the other hand, if the internal combustion engine 10 is stopped when the inverter abnormal state is detected, the power of the internal combustion engine 10 cannot cause the first MG 71 to generate electricity. Therefore, when the CPU 101 detects an inverter abnormal state when the internal combustion engine 10 is not driven, the CPU 101 selects a battery running mode and performs an internal combustion engine starting process for starting the internal combustion engine 10.

In the internal combustion engine starting process, the CPU 101 generally drives the crank shaft 14 to rotate by generating electricity from the first MG 71 around the rotation of the second MG 72. Specifically, the CPU 101 performs a process of lowering the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77 in order to promote the power generation of the first MG 71. Then, the CPU 101 performs a process of starting the internal combustion engine 10 when the generated power Pm1 of the first MG 71 becomes equal to or higher than a predetermined predetermined power value PmB. During the execution of the internal combustion engine starting process, the positive electrode relay 35 and the negative electrode relay 36 are maintained in the ON state because the control is performed by the battery running mode. Further, when the internal combustion engine start process is started and during the execution of the internal combustion engine start process, the vehicle 500 is driven by the output of the second MG 72, so that the second MG 72 is in a driven state and consumes electric power. .. Hereinafter, the contents of each of the above processes and the principle behind each process will be described in detail.

(A) Principle of rotationally driving the crank shaft 14 by the power generation of the first MG 71 First, the principle of rotationally driving the crank shaft 14 by the power generation of the first MG 71 will be described. It should be noted that, substantially, the crank shaft 14 is rotated by the drag torque T when the first MG 71 generates electricity.

As a premise for explaining the principle of rotationally driving the crank shaft 14, first, the relationship between the operation of the rotary shaft of the first MG 71, the crank shaft 14, and the rotary shaft of the second MG 72 will be described. In the power distribution integrated mechanism 40, the rotation shaft of the first MG 71, the crank shaft 14, and the rotation shaft of the second MG 72 are connected to each other at a predetermined gear ratio. Therefore, if the number of rotations of two of these three rotation elements is determined, the number of rotations of the remaining one is naturally determined. Specifically, the rotation speed Nm1 of the first MG71, the engine rotation speed Ne, and the rotation speed Nm2 of the second MG72 can be defined on a collinear diagram showing the relationship between the rotation speeds of these three rotation elements. As shown in FIG. 3, in the collinear diagram, the S-axis, the C-axis, and the R-axis are arranged in this order. The S-axis shows the rotation speed of the sun gear 41, which is the rotation speed Nm1 of the first MG 71. The C axis indicates the rotation speed of the carrier 44, which is the engine rotation speed Ne. The R axis indicates the rotation speed of the ring gear 42 obtained by dividing the rotation speed Nm2 of the second MG 72 by the gear ratio of the reduction gear 50. In this specification, regarding the forward and reverse rotation of each rotating element, the rotation speed when each rotating element is rotating forward is described as positive, and the rotation speed when each rotating element is rotating in the reverse direction is described as negative. In the above collinear diagram, the rotation speed Nm1 of the first MG71, the engine rotation speed Ne, and the rotation speed Nm2 of the second MG72 are connected in a straight line. Under this relationship, the crank shaft 14 is rotationally driven as follows.

Now, it is assumed that the vehicle 500 is traveling forward with the internal combustion engine 10 stopped. As shown by the two-dot chain line U1 in FIG. 3, the rotation speed Nm2 of the second MG 72 at this time is a positive value in consideration of the rotation direction of the second MG 72 accompanying the forward traveling of the vehicle 500. Further, since the internal combustion engine 10 is stopped, the engine speed Ne is zero. From the balance between the rotation speed Nm2 of the second MG72 and the engine rotation speed Ne, the rotation speed Nm1 of the first MG71 is a negative value. When the vehicle speed SP increases in this state, the rotation speed Nm2 of the second MG 72 increases, as shown by the dotted line U2 in FIG. At this time, if the drag torque T does not occur, that is, if the first MG 71 does not generate electricity, as shown by the dotted line U2 in FIG. 3, the rotation speed Nm1 of the first MG 71 remains a negative value and the absolute value becomes large.

On the other hand, when the first MG 71 generates electricity and a drag torque T is generated when the rotation speed Nm2 of the second MG 72 increases, the drag torque T acts to bring the rotation speed Nm1 of the first MG 71 closer to zero. That is, the drag torque T prevents the absolute value of the rotation speed Nm1 of the first MG 71 from increasing in the negative direction. Along with this, as shown by the solid line U3 in FIG. 3, the inclination of the straight line connecting the three rotating elements becomes smaller than in the case where the drag torque T is not generated (dotted line U2 in FIG. 3). Then, the engine speed Ne increases. That is, the drag torque T can raise the engine rotation speed Ne to the rotation speed required for starting the internal combustion engine 10. By injecting fuel or the like with the internal combustion engine 10 in this state, the internal combustion engine 10 can be operated independently.

In the above description, the case where the crank shaft 14 is rotationally driven when the rotation speed Nm2 of the second MG72 rises is taken as an example, but even when the rotation speed Nm2 of the second MG 72 is constant, the first MG 71 generates power. If the drag torque T is generated, the crank shaft 14 can be rotationally driven to start the internal combustion engine 10 by the same principle.

(B) Regarding the specified power value PmB When the crank shaft 14 is rotationally driven by the principle described in (A), the drag torque T capable of raising the engine rotation speed Ne to the rotation speed required for starting the internal combustion engine 10. That is, it is necessary to generate a drag torque T of a size necessary for starting the internal combustion engine 10. In the internal combustion engine starting process, a drag torque T of a size required for starting the internal combustion engine 10 is generated by determining whether or not the generated power Pm1 of the first MG71 is equal to or higher than the specified power value PmB. To figure out that. The specified power value PmB, which is the reference value for this determination, will be described in detail below.

First, as a premise, the relationship between the drag torque T, the rotation speed Nm1 of the first MG71, and the charging voltage VH of the second capacitor 25 will be described. As described above, in the internal combustion engine starting process, the crank shaft 14 is rotationally driven by the drag torque T generated under the condition that the rotation speed Nm1 of the first MG 71 is a negative value. Therefore, in the following description, the drag torque T generated when the rotation speed Nm1 of the first MG71 is negative will be dealt with.

As shown in FIG. 4, in a Cartesian coordinate system having the drag torque T and the rotation speed Nm1 of the first MG71 as coordinate axes, the relationship between the drag torque T and the rotation speed Nm1 of the first MG71 is the charging voltage of the second capacitor 25. It is specified for each size of VH. Now, it is assumed that the charging voltage VH of the second capacitor 25 does not fluctuate at a constant value VH1. As shown by the solid line in FIG. 4, the drag torque T is generated when the absolute value of the rotation speed Nm1 of the first MG71 is larger than the absolute value of the limit rotation speed A1. The limit rotation speed A1 is the rotation speed Nm1 of the first MG 71 when the counter electromotive voltage R generated by the rotation of the first MG 71 becomes equal to the charge voltage VH of the second capacitor 25. The drag torque T increases once as the absolute value of the rotation speed Nm1 of the first MG71 increases, that is, as the counter electromotive voltage R increases, and when it reaches the maximum value, the rotation speed Nm1 of the first MG71 becomes high. It gradually decreases with the absolute value. The counter electromotive voltage R increases as the absolute value of the rotation speed Nm1 of the first MG 71 increases.

The limit rotation speed changes according to the charging voltage VH of the second capacitor 25. Specifically, the higher the charging voltage VH of the second capacitor 25, the larger the absolute value of the limit rotation speed. For example, as shown by the alternate long and short dash line in FIG. 4, when the charging voltage VH of the second capacitor 25 is VH2 larger than the above VH1, the absolute value of the limit rotation speed A2 is the limit rotation when the charging voltage VH is VH1. It is larger than the absolute value of the number A1. Further, when the charging voltage VH of the second capacitor 25 is VH2, the absolute value of the rotation speed Nm1 of the first MG71 at which the drag torque T becomes maximum also becomes large. That is, as the charging voltage VH of the second capacitor 25 increases, the absolute value of the rotation speed Nm1 of the first MG71 increases in the characteristic curve showing the relationship between the drag torque T and the rotation speed Nm1 of the first MG71. Shift to the side.

Based on the above relationship, the specified power value PmB will be described. When the drag torque T required for starting the internal combustion engine 10 is the cranking torque TK, the charging voltage of the second capacitor 25 is based on the relationship between the drag torque T described above and the rotation speed Nm1 of the first MG 71. If VH is fixed to a certain value, the rotation speed Nm1 of the first MG71 corresponding to the cranking torque TK is uniquely determined. When the rotation speed Nm1 of the first MG71 corresponding to the cranking torque TK is set to the cranking rotation speed NK, the specified power value PmB is the cranking rotation speed NK and the cranking torque TK as shown in the following equation (1). It is defined as the product of. The generated power and power consumption of the motor generator are calculated as the product of the rotation speed of the motor generator and the torque.
PmB = NK x TK ... (1)
As described above, in the internal combustion engine starting process, the charging voltage VH of the second capacitor 25 is lowered to the output voltage VB of the battery 77. In relation to this, the specified power value PmB is determined as the product of the cranking rotation speed NK and the cranking torque TK when the charging voltage VH of the second capacitor 25 is the output voltage VB of the battery 77. That is, if the generated power Pm1 of the first MG 71 is equal to or higher than the specified power value PmB, it can be seen that the drag torque T required for starting the internal combustion engine 10 is generated. Strictly speaking, the output voltage VB of the battery 77 is increased or decreased according to the storage amount SOC of the battery 77. The output voltage VB of the battery 77 for determining the specified power value PmB and the specified vehicle speed SPD described later may be the rated voltage of the battery 77.

(C) Relationship between the generated power Pm1 of the first MG71 and the vehicle speed SP In the internal combustion engine starting process, the generated power of the first MG71 is actually determined as to whether or not the generated power Pm1 of the first MG71 is equal to or higher than the specified power value PmB. Instead of determining the magnitude of Pm1, it is determined whether or not the vehicle speed SP is equal to or higher than the specified vehicle speed SPD. This is because, when an abnormal state of the inverter occurs, the detection signals of various sensors necessary for calculating the generated power Pm1 of the first MG 71 may not be input to the control device 100. The various sensors include a first rotation angle sensor 93, a first current sensor, and the like. On the other hand, the detection signal of the vehicle speed sensor 97 is input to the control device 100 without being influenced by the occurrence of the inverter abnormal state. Therefore, if the vehicle speed SP detected by the vehicle speed sensor 97 is used, an appropriate determination result can be obtained.

The vehicle speed SP and the generated power Pm1 of the first MG71 are related as follows. Due to the collinear diagram, when the internal combustion engine 10 is stopped, the absolute value of the rotation speed Nm1 of the first MG71 basically increases according to the rotation speed Nm2 of the second MG72, that is, the vehicle speed SP. That is, there is a one-to-one relationship between the rotation speed Nm1 of the first MG71 and the vehicle speed SP, and if the absolute value of the rotation speed Nm1 of the first MG71 is determined, the vehicle speed SP corresponding to the absolute value is also uniquely determined.

The specified vehicle speed SPD is defined as a vehicle speed SP corresponding to a cranking rotation speed NK when the charging voltage VH of the second capacitor 25 is the output voltage VB of the battery 77. On the flip side, if the charging voltage VH of the second capacitor 25 reaches the output voltage VB of the battery 77, cranking torque TK will be generated when the vehicle speed SP reaches the specified vehicle speed SPD. The generated power of the first MG 71 at this time is the specified power value PmB represented by the equation (1). Utilizing such a relationship, in the internal combustion engine starting process, the magnitude of the vehicle speed SP is determined instead of the generated power Pm1 of the first MG71.

(D) Reason for lowering the charge voltage VH of the second capacitor 25 to the output voltage VB of the battery 77 Next, the reason for lowering the charge voltage VH of the second capacitor 25 to the output voltage VB of the battery 77 will be described.

As shown in FIG. 4, the relationship between the drag torque T and the rotation speed Nm1 of the first MG 71 is defined for each magnitude of the charging voltage VH of the second capacitor 25. Then, as the charging voltage VH of the second capacitor 25 is higher, the characteristic curve showing the relationship between the drag torque T and the rotation speed Nm1 of the first MG71 shifts to the side where the absolute value of the rotation speed Nm1 of the first MG71 becomes larger. .. Therefore, the higher the charging voltage VH of the second capacitor 25, the larger the cranking rotation speed NK, which is the rotation speed Nm1 of the first MG 71 corresponding to the cranking torque TK. Therefore, in order to make the specified vehicle speed SPD determined from the correspondence with the cranking rotation speed NK as small as possible, it is necessary to make the charging voltage VH of the second capacitor 25 as small as possible. As described above, in the internal combustion engine starting process, the positive electrode relay 35 and the negative electrode relay 36 are kept in the ON state. In this case, the second capacitor 25 can be energized with the first capacitor 39 and the battery 77 through the first diode 85 even when the converter 80 is stopped. Therefore, the minimum value that the charging voltage VH of the second capacitor 25 can take during the execution of the internal combustion engine starting process is the output voltage VB of the battery 77. Therefore, in the present embodiment, the charging voltage VH of the second capacitor 25 is lowered to the output voltage VB of the battery 77, which is the minimum value that the charging voltage VH can take. As a result, the specified vehicle speed SPD can be made as small as possible.

(E) About the method of lowering the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77 In the internal combustion engine starting process, the charging voltage VH of the second capacitor 25 is lowered to the output voltage VB of the battery 77. Substantially, the converter 80 is stopped. That is, both the first transistor 81 and the second transistor 82 are turned off. In addition to this, the second MG 72 is driven during the execution of the internal combustion engine starting process. The combination of turning off the converter 80 and driving the second MG 72 can reduce the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77. The principle will be described in detail below.

Now, it is assumed that the charging voltage VH of the second capacitor 25 is larger than the counter electromotive voltage R of the first MG 71. That is, the first MG 71 cannot supply electric power to the second capacitor 25. When the converter 80 is stopped in this state, the electric charge stored in the second capacitor 25 is consumed by the second MG2 as the second MG 72 is driven. Then, as the electric charge is consumed by the second MG 72, the charging voltage VH of the second capacitor 25 drops rapidly. Then, the charging voltage VH of the second capacitor 25 reaches the output voltage VB of the battery 77, which is the minimum value that the charging voltage VH can take during the execution of the internal combustion engine starting process.

When the charge voltage VH of the second capacitor 25 drops to the output voltage VB of the battery 77 and the countercurrent voltage R of the first MG 71 becomes larger than the charge voltage VH, the first MG 71 can supply power to the second capacitor 25. become. When the second MG 72 consumes the electric power in this state, the generated electric power Pm1 of the first MG 71 covers the electric power Pm2 of the second MG 72. At this time, since the first MG 71 generates only the electric power consumed by the second MG 72, the charging voltage VH of the second capacitor 25 is maintained at the output voltage VB of the battery 77.

In this way, the combination of turning off the converter 80 and driving the second MG 72 can reduce the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77. The contents described here are based on the premise that the power consumption Pm2 of the second MG 72 is correspondingly large. The power consumption Pm2 of the second capacitor 25 depends on the magnitude of the driving force required by the occupant for the vehicle 500. If the power consumption Pm2 of the second MG 72 is relatively small, the second MG 72 cannot completely consume the charge voltage VH of the second capacitor 25, and the charge voltage VH of the second capacitor 25 cannot be reduced to the output voltage VB of the battery 77. do not have.

(F) Understanding that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77 As described above, depending on the magnitude of the driving force required by the occupant for the vehicle 500, the first The power consumption Pm2 of 2MG72 may be relatively small. In this case, the charging voltage VH of the second capacitor 25 may not drop to the output voltage VB of the battery 77. The specified vehicle speed SPD described in (C) is specified on the premise that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77. Therefore, even if the vehicle speed SP becomes equal to or higher than the specified vehicle speed SPD, the cranking torque TK does not occur unless the charging voltage VH of the second capacitor 25 drops to the output voltage VB of the battery 77. Therefore, it is necessary to know that the charging voltage VH is surely lowered to the output voltage VB of the battery 77.

In the internal combustion engine starting process, the fact that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77 is not determined by the value of the charging voltage VH of the second capacitor 25 itself, but by the second MG 72. Judgment is made using the power consumption Pm2. This is because, when an abnormal state of the inverter occurs, the detection signal of the second capacitor sensor that detects the charge voltage VH of the second capacitor 25 may not be input to the control device 100. The CPU 101 can acquire the parameters required for calculating the power consumption Pm2 of the second MG 72 without being affected by the occurrence of the inverter abnormal state. Therefore, the CPU 101 can make an appropriate determination by using the power consumption Pm2 of the second MG 72.

In the internal combustion engine starting process, the power consumption Pm2 of the second MG 72 is determined as a predetermined power value as a process for grasping that the charge voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77. It is determined whether or not it is PmC or more. The determined power value PmC is set as a value slightly larger than the specified power value PmB.

Now, it is assumed that the power consumption Pm2 of the second MG 72 is the determination power value PmC. As described in (E) above, the power consumption Pm2 of the second MG 72 is covered by either the second capacitor 25 or the first MG 71. However, since the determined power value PmC is correspondingly large, it has been found in experiments and the like that it is difficult for the second capacitor 25 to cover the power consumption Pm2 having the size of the determined power value PmC when the converter 80 is stopped. ing. Therefore, when the power consumption Pm2 of the second MG 72 is the determined power value PmC, it can be considered that the first MG 71 covers the power consumption Pm2 and the generated power Pm1 of the first MG 71 is the determined power value PmC.

When the power consumption Pm2 of the second MG 72 is too large to be covered by the second capacitor 25, the output voltage VB of the second capacitor 25 immediately drops to the output voltage VB of the battery 77 after the converter 80 is stopped. Expected to be. Therefore, in a situation where the power consumption Pm2 of the second MG 72 is covered by the generated power Pm1 of the first MG 71, it can be considered that the output voltage VB of the second capacitor 25 reaches the output voltage VB of the battery 77. From this point of view, by determining the magnitude of the power consumption Pm2 of the second MG 72, it can be understood that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77.

When the generated power Pm1 of the first MG71 is the determination power value PmC, the first MG71 has the cranking torque TK and the cranking rotation speed when the charging voltage VH of the second capacitor 25 is the output voltage VB of the battery 77. This means that the amount of power generated is greater than the product of NK. Therefore, it can be grasped that the first MG71 generates enough power to generate the cranking torque TK.

Summarizing the above (A) to (F), in the internal combustion engine starting process, the CPU 101 performs a process of stopping the converter 80 as a process of lowering the charge voltage VH of the second capacitor 25 to the output voltage VB of the battery 77. conduct. Further, the CPU 101 performs a process of determining whether or not the vehicle speed SP is equal to or higher than the specified vehicle speed SPD as a process of determining whether or not the generated power Pm1 of the first MG 71 is equal to or higher than the specified power value PmB. Further, the CPU 101 performs a process of grasping that the charging voltage VH of the second capacitor 25 is surely lowered to the output voltage VB of the battery 77. After performing these processes, the CPU 101 performs a process of starting the internal combustion engine 10.

Next, a specific processing procedure of the internal combustion engine starting process will be described.
When the CPU 101 detects an abnormal inverter state when the internal combustion engine 10 is not driven while the ignition switch of the vehicle 500 is turned on, the CPU 101 starts the internal combustion engine starting process. The CPU 101 realizes each process of the internal combustion engine start process by executing various programs stored in the ROM 102. As described above, the second MG 72 is inevitably driven when the internal combustion engine start process is performed. If the ignition switch is turned off during the execution of the internal combustion engine start process, the CPU 101 forcibly terminates the internal combustion engine start process.

As shown in FIG. 5, when the internal combustion engine start process is started, the CPU 101 first executes the process of step S10. In step S10, the CPU 101 stops the first inverter 90 and starts the control in the battery running mode. As described above, stopping the first inverter 90 means turning off each transistor of the first inverter 90. Further, since the control is performed in the battery running mode, the CPU 101 keeps the positive electrode relay 35 and the negative electrode relay 36 in the ON state. When the CPU 101 finishes executing the process of step S10, the CPU 101 advances the process to step S20.

In step S20, the CPU 101 stops the converter 80. That is, both the first transistor 81 and the second transistor 82 are turned off. When the CPU 101 finishes executing the process of step S20, the CPU 101 proceeds to step S30.

In step S30, the CPU 101 determines whether or not the vehicle speed SP is equal to or higher than the specified vehicle speed SPD. Specifically, the CPU 101 acquires the latest vehicle speed SP and determines the magnitude relationship between the vehicle speed SP and the specified vehicle speed SPD. When the vehicle speed SP is less than the specified vehicle speed SPD (step S30: NO), the CPU 101 executes the process of step S30 again. When the vehicle speed SP becomes equal to or higher than the specified vehicle speed SPD (step S30: YES), the CPU 101 advances the process to step S40. If the determination in step S30 is YES, the cranking torque TK is generated if the charging voltage VH of the second capacitor 25 is lowered to the output voltage VB of the battery 77.

In step S40, the CPU 101 determines whether or not the power consumption Pm2 of the second MG 72 is equal to or greater than the determination power value PmC. Specifically, the CPU 101 acquires the latest value of the rotation speed Nm2 of the second MG 72. Further, the CPU 101 acquires the latest value of the second MG required torque MG2 *. Then, the CPU 101 calculates the power consumption Pm2 of the second MG72 by multiplying the rotation speed Nm2 of the second MG72 and the second MG required torque MG2 *. Then, the CPU 101 determines the magnitude relationship between the power consumption Pm2 of the second MG 72 and the determination power value PmC. When the power consumption Pm2 of the second MG 72 is less than the determination power value PmC (step S40: NO), the CPU 101 returns to the process of step S30.

On the other hand, when the power consumption Pm2 of the second MG 72 is equal to or greater than the determination power value PmC (step S40: YES), the CPU 101 advances the process to step S50. If the determination in step S40 is YES, the CPU 101 can grasp that the charging voltage VH of the second capacitor 25 is surely lowered to the output voltage VB of the battery 77. Then, when the determination in both steps S30 and S40 is YES, the CPU 101 can grasp that the cranking torque TK is surely generated.

In step S50, the CPU 101 performs a process of starting the internal combustion engine 10. Specifically, the CPU 101 controls the internal combustion engine 10 so as to perform fuel injection by the fuel injection valve and ignition by the spark plug. When the CPU 101 finishes executing the process of step S50, the CPU 101 advances the process to step S60. In addition, by the process of step S50, the crank shaft 14 is in a state of independently rotating even without the rotation drive by the first MG71.

In step S60, the CPU 101 cancels the control in the battery running mode and starts the control in the internal combustion engine combined mode. When the CPU 101 finishes executing the process of step S60, the CPU 101 ends a series of processes of the internal combustion engine start process.

Next, the operation of this embodiment will be described.
Now, it is assumed that the vehicle 500 is running with the internal combustion engine 10 stopped and the second MG 72 driven. Then, it is assumed that the CPU 101 detects the inverter abnormality processing at the time ta1. Along with this, the CPU 101 starts the internal combustion engine start process. As shown in FIG. 6A, the vehicle speed SP is assumed to gradually increase after the time ta1. Further, as shown in FIG. 6B, it is assumed that the power consumption Pm2 of the second MG 72 gradually increases as the vehicle speed SP increases after the time ta1.

When the CPU 101 starts the internal combustion engine start process, it first starts the control in the battery running mode and stops the first inverter 90 (step S10). Further, as shown in FIG. 6 (e), the CPU 101 stops the converter 80 at the time ta1 (step S20). As shown in FIG. 6 (f), when the CPU 101 stops the converter 80, the second MG 72 consumes the electric charge stored in the second capacitor 25, so that the charging voltage VH of the second capacitor 25 drops rapidly. do. Then, the charging voltage VH of the second capacitor 25 reaches the output voltage VB of the battery 77, which is the minimum value that the charging voltage VH of the second capacitor 25 can take during the execution of the internal combustion engine starting process. After that, the charge voltage VH of the second capacitor 25 is maintained at the output voltage VB of the battery 77.

As shown in FIG. 6 (g), at the time of time ta1, the rotation speed Nm1 of the first MG 71 is a negative value. As already explained, this is due to the balance between the rotation speed Nm2 of the second MG72 and the engine rotation speed Ne. After the time ta1, the absolute value of the rotation speed Nm1 of the first MG71 increases as the vehicle speed SP increases. Along with this, as shown in FIG. 6 (f), the counter electromotive voltage R of the first MG 71 increases. Then, at time ta2, the counter electromotive voltage R of the first MG 71 exceeds the charge voltage VH of the second capacitor 25.

After the time ta2 when the counter electromotive voltage R of the first MG 71 exceeds the charge voltage VH of the second capacitor 25, the electric power generated by the first MG 71 is supplied to the second capacitor 25. Along with this, as shown in FIG. 6 (c), a drag torque T is generated after the time ta2. This drag torque T acts so as to prevent an increase in the number of rotations of the first MG 71 in the negative direction. Therefore, as shown in FIG. 6 (g), the rotation speed Nm1 of the first MG 71 remains a substantially constant value after the time ta3. While the increase in the negative rotation speed of the first MG71 is hindered, as the positive rotation speed of the second MG 72 increases, as shown in FIG. 6D, the engine rotation speed Ne after the time ta2. Begins to lift. The reason why the engine speed Ne rises is due to the relationship of the collinear diagram already explained.

After that, the vehicle speed SP increases, and as shown in FIG. 6A, the vehicle speed SP reaches the specified vehicle speed SPD at time ta4 (step S30: YES). That is, if the charging voltage VH of the second capacitor 25 drops to the output voltage VB of the battery 77, the cranking torque TK is generated. As shown in FIG. 6B, at the time of time ta4, the power consumption Pm2 of the second MG 72 has not yet reached the determination power value PmC. Therefore, the CPU 101 cannot grasp that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77.

After that, as shown in FIG. 6B, the power consumption Pm2 of the second MG72 increases, and the power consumption Pm2 of the second MG72 reaches the determination power value PmC at time ta5 (step S40: YES). At this point, the CPU 101 grasps that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77. Therefore, at this point, the CPU 101 can surely grasp that the cranking torque TK is generated. Therefore, as shown in FIG. 6H, the CPU 101 starts fuel injection and ignition of the internal combustion engine 10 at time ta5. As a result, the crank shaft 14 will rotate independently. After that, the CPU 101 drives the vehicle 500 under the control of the internal combustion engine combined traveling mode.

In addition, in FIG. 6H, whether or not fuel injection or ignition control for the internal combustion engine 10 is performed is indicated by ON / OFF. Further, in FIG. 6, in order to show the relationship of the change with time of each variable in an easy-to-understand manner, the change with time of each variable is shown schematically. Therefore, the change with time of each variable shown in FIG. 6 does not necessarily match the actual change with time of each variable.

Next, the effect of this embodiment will be described.
(1-1) In the internal combustion engine starting process, the first MG 71 creates a situation in which electric power can be supplied to the second capacitor 25 by lowering the charging voltage VH of the second capacitor 25. As a result, cranking torque TK can be generated. Therefore, the internal combustion engine 10 can be started by using the cranking torque TK even in a situation where an abnormal state of the inverter occurs.

(1-2) The positive electrode relay 35 and the negative electrode relay 36 are kept on during the execution of the internal combustion engine starting process. Therefore, the minimum value that the charge voltage VH of the second capacitor 25 can take during the execution of the internal combustion engine starting process is the output voltage VB of the battery 77. In the above configuration, the specified vehicle speed SPD can be made as small as possible by lowering the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77. Therefore, the internal combustion engine 10 can be started without extremely increasing the vehicle speed SP.

(1-3) When an abnormal inverter state occurs, the detection signals from various sensors that detect the state of the first MG71 and the second capacitor sensor that detects the charging voltage VH of the second capacitor 25 are not input to the control device 100. It is possible. In the internal combustion engine starting process, various judgments are made by using variables such as the vehicle speed SP, which are not affected by the occurrence of the inverter abnormality state, without using the information from these sensors. Therefore, the internal combustion engine 10 can be reliably started even in a situation where the inverter is in an abnormal state.

(1-4) In the internal combustion engine start process, the process substantially performed by the CPU 101 in generating the cranking torque TK determines the timing for stopping the converter 80 and starting the fuel injection and ignition of the internal combustion engine 10. It is a process to do. Therefore, it is possible to reduce the processing load on the CPU 101 when starting the internal combustion engine 10.

Next, a second embodiment of the control device for the hybrid vehicle will be described.
The content of the second embodiment differs from that of the first embodiment only in the content of the internal combustion engine starting process. Therefore, the internal combustion engine starting process will be described below, and duplicated description will be omitted for other parts.

First, an outline of the internal combustion engine starting process in the present embodiment will be described.
Similar to the first embodiment, in the internal combustion engine starting process of the present embodiment, the CPU 101 performs a process of reducing the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77, and the generated power Pm1 of the first MG 71 is a specified power. When the value becomes PmB or more, the process of starting the internal combustion engine 10 is performed.

The CPU 101 controls to turn on the first transistor 81 of the converter 80 as a process of lowering the charging voltage VH of the second capacitor 25 to the output voltage VB of the battery 77. Specifically, the CPU 101 gradually increases the duty ratio DY of the first transistor 81 to reach 100%. The principle that the charge voltage VH of the second capacitor 25 is lowered by this will be described later. The CPU 101 reduces the duty ratio of the second transistor 82 to 0% in accordance with the control of shifting the first transistor 81 to the on state.

The CPU 101 performs a process of determining whether or not the vehicle speed SP has reached the specified vehicle speed SPD, as in the first embodiment, as a process of determining whether or not the generated power Pm1 of the first MG71 has reached the specified power value PmB or more. .. It should be noted that the CPU 101 controls the duty ratio of the first transistor 81 to 100%, and thus considers that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77.

Next, the relationship between the control of shifting the first transistor 81 to the ON state and lowering the charging voltage VH of the second capacitor 25 will be described. As a premise, as in the case of the first embodiment, the positive electrode relay 35 and the negative electrode relay 36 are maintained in the ON state during the execution of the internal combustion engine starting process. Therefore, the charge voltage VL of the first capacitor 39 is maintained at the output voltage VB of the battery 77. As shown by the alternate long and short dash line Q in FIG. 2, when the first transistor 81 is turned on, a current is generated from the second capacitor 25 to the first capacitor 39, and the electric charge stored in the second capacitor 25 is the first capacitor 39. Taken out to. Since the positive electrode relay 35 and the negative electrode relay 36 are in the ON state, the battery 77 is charged when the charging voltage VL of the first capacitor 39 increases. In this way, the electric charge stored in the second capacitor 25 is taken out to the first capacitor 39 and the battery 77. Since the charge capacity of the battery 77 is larger than the charge capacity of the second capacitor 25, the charge voltage VH of the second capacitor 25 drops rapidly. As described above, if the duty ratio of the first transistor 81 is 100% and the first transistor 81 is always on, the charging voltage VH of the second capacitor 25 is surely the same as the charging voltage VL of the first capacitor 39. The value, that is, the output voltage VB of the battery 77 will be reached. Based on these characteristics, in the present embodiment, control is performed to shift the first transistor 81 to the on state as a process of lowering the charge voltage VH of the second capacitor 25 to the output voltage VB of the battery 77.

Next, the specific processing contents of the internal combustion engine starting process will be described.
Since the start conditions and the like of the internal combustion engine starting process are the same as those in the first embodiment, duplicated description will be omitted. As shown in FIG. 7, when the internal combustion engine start process is started, the CPU 101 executes the process of step S110. In step S110, the CPU 101 starts the control in the battery running mode. The content of the process of step S110 is the same as the process of step S10 of the internal combustion engine starting process of the first embodiment. When the CPU 101 finishes executing the process of step S110, the CPU 101 advances the process to step S120.

In step S120, the CPU 101 starts control to shift the first transistor 81 of the converter 80 to the ON state. Specifically, the CPU 101 starts a process of increasing the duty ratio DY of the first transistor 81. The CPU 101 increases the duty ratio DY of the first transistor 81 at a predetermined rate of change. The CPU 101 starts a process of lowering the duty ratio of the second transistor 82 in accordance with the process of the first transistor 81. Regarding the rate of change of the duty ratio of the second transistor 82, the duty ratio of the second transistor 82 becomes 0% at the same timing as or before the duty ratio DY of the first transistor 81 reaches 100%. It may be determined as appropriate. The CPU 101 considers that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77 when the duty ratio DY of the first transistor 81 reaches 100%. When the CPU 101 finishes executing the process of step S120, the CPU 101 proceeds to step S130.

In step S130, the CPU 101 determines whether or not the vehicle speed SP is equal to or higher than the specified vehicle speed SPD. The content of the process of step S130 is the same as the process of step S30 of the internal combustion engine starting process of the first embodiment. When the vehicle speed SP is less than the specified vehicle speed SPD (step S130: NO), the CPU 101 executes the process of step S130 again. When the vehicle speed SP becomes equal to or higher than the specified vehicle speed SPD (step S130: YES), the CPU 101 advances the process to step S140. If the determination in step S130 is YES, the cranking torque TK is generated if the charging voltage VH of the second capacitor 25 is lowered to the output voltage VB of the battery 77. After starting the process of increasing the duty ratio DY of the first transistor 81 by the process of step S120, the determination of step S130 may be YES before the duty ratio DY reaches 100%. In this case, the CPU 101 waits until the duty ratio DY reaches 100% after the determination in step S130 becomes YES. Then, when the duty ratio DY reaches 100%, the CPU 101 advances the process to step S140. If the duty ratio DY reaches 100% before the determination in step S130 becomes YES, the CPU 101 advances the process to step S140 when the determination in step S130 becomes YES.

In step S140, the CPU 101 performs a process of starting the internal combustion engine 10. The content of the process of step S140 is the same as the process of step S50 of the internal combustion engine starting process of the first embodiment. When the CPU 101 finishes executing the process of step S140, the CPU 101 advances the process to step S150.

In step S150, the CPU 101 starts control in the internal combustion engine combined mode. The content of the process of step S150 is the same as the process of step S60 of the internal combustion engine starting process of the first embodiment. When the CPU 101 finishes executing the process of step S150, the CPU 101 ends a series of processes of the internal combustion engine start process.

Next, the operation of this embodiment will be described.
Now, it is assumed that the vehicle 500 is running with the internal combustion engine 10 stopped and the second MG 72 driven. Then, it is assumed that the CPU 101 detects the inverter abnormality processing at the time tb1. Along with this, the CPU 101 starts the internal combustion engine start process. As shown in FIG. 8A, the vehicle speed SP is assumed to gradually increase after the time tb1. Further, as shown in FIG. 8C, it is assumed that the duty ratio DY of the first transistor 81 is, for example, 50% at the time tb1.

When the CPU 101 starts the internal combustion engine start process, it first starts the control in the battery running mode and stops the first inverter 90 (step S110). Further, as shown in FIG. 8B, the CPU 101 starts the control to shift the converter 80 to the on state at the time tb1 (step S120). Along with this, as shown in FIG. 8C, the duty ratio DY of the first transistor 81 gradually increases after the time tb1. Along with this, as shown in FIG. 8 (f), the charging voltage VH of the second capacitor 25 gradually decreases after the time tb1.

As shown in FIG. 8 (g), at the time tb1, the rotation speed Nm1 of the first MG71 is a negative value due to the balance between the rotation speed Nm2 of the second MG72 and the engine rotation speed Ne. After the time tb1, the absolute value of the rotation speed Nm1 of the first MG71 increases as the vehicle speed SP increases. Along with this, as shown in FIG. 8 (f), the counter electromotive voltage R of the first MG 71 rises. Then, at time tb2, the counter electromotive voltage R of the first MG 71 exceeds the charge voltage VH of the second capacitor 25.

After the time tb2 in which the counter electromotive voltage R of the first MG 71 exceeds the charge voltage VH of the second capacitor 25, the electric power generated by the first MG 71 is supplied to the second capacitor 25. Along with this, as shown in FIG. 8D, a drag torque T is generated after the time tb2. This drag torque T acts so as to prevent an increase in the number of rotations of the first MG 71 in the negative direction. Therefore, as shown in FIG. 8 (g), the rotation speed Nm1 of the first MG 71 remains a substantially constant value after the time tb3. While the increase in the negative rotation speed of the first MG71 is hindered, as the positive rotation speed of the second MG 72 increases, as shown in FIG. 8 (e), the engine rotation speed Ne after the time tb2. Begins to lift.

After that, as shown in FIG. 8C, the duty ratio DY of the first transistor 81 reaches 100% at time tb5 (step S120 is completed). At this point, the CPU 101 grasps that the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77.

In the example shown in FIG. 8, at the time tb4 before the time tb5, the vehicle speed SP has already reached the specified vehicle speed SPD (step S130: YES). That is, at the time tb5, the charging voltage VH of the second capacitor 25 has dropped to the output voltage VB of the battery 77, and the cranking torque TK has been generated. Therefore, as shown in FIG. 8 (h), the CPU 101 starts fuel injection and ignition of the internal combustion engine 10 at time tb5. As a result, the crank shaft 14 will rotate independently. After that, the CPU 101 drives the vehicle 500 under the control of the internal combustion engine combined traveling mode.

Although not shown, if the vehicle speed SP reaches the specified vehicle speed SPD at a time after the time tb5, the fuel injection and ignition of the internal combustion engine 10 are started at that time. That is, the internal combustion engine 10 is started when the two conditions of the duty ratio DY of the first transistor 81 being 100% and the vehicle speed SP being the specified vehicle speed SPD or higher are satisfied.

Similar to FIG. 6, FIG. 8 schematically shows the change with time of each variable in order to show the relationship of the change with time of each variable in an easy-to-understand manner. Therefore, the change with time of each variable shown in FIG. 8 does not necessarily match the actual change with time of each variable.

Next, the effect of this embodiment will be described.
In this embodiment, in addition to the same effects as those of (1-1) to (1-3) of the first embodiment, the following effects can be obtained.

(2-1) In the case of the first embodiment, in order to reduce the charging voltage VH of the second capacitor 25, it is necessary to consume the electric power by the second MG 72. The magnitude of the power consumption of the second MG 72 depends on the magnitude of the driving force required by the occupant. Therefore, depending on the request of the occupant, the charging voltage VH of the second capacitor 25 cannot be lowered to the charging voltage VH of the battery 77.

In this respect, in the present embodiment, the charging voltage VH of the second capacitor 25 is reduced to the charging voltage VH of the battery 77 regardless of the amount of power consumption by the second MG 72 by controlling the converter 80 to be turned on. Can be done. Therefore, the internal combustion engine 10 can be started regardless of the driving force required by the occupant.

The first embodiment and the second embodiment can be modified and implemented as follows. The first embodiment, the second embodiment, and the following modified examples can be implemented in combination with each other within a technically consistent range.

-Regarding the process of step S50 in the internal combustion engine starting process of the first embodiment, the crank shaft 14 may not rotate independently even if fuel injection or ignition is performed. For example, even if the determination in step S30 or step S40 is YES due to a sensor detection error or the like, if the cranking torque TK is not actually generated or the air-fuel mixture is not normally burned, this is the case. There can be something. Therefore, if the crank shaft 14 does not rotate independently even after repeating fuel injection and ignition a plurality of times, the internal combustion engine starting process may be terminated and the control by the battery running mode may be continued. The same applies to step S140 in the internal combustion engine starting process of the second embodiment.

-Regarding the process of step S30 in the internal combustion engine start process of the first embodiment, if the determination is not YES even after performing the process of step S30 a predetermined number of times, the internal combustion engine start process is terminated and the battery runs. Control by mode may be continued. In this case, the processing load of the CPU 101 can be reduced as compared with the case where the processing of step S30 is repeated for a long period of time. The same applies to step S130 in the internal combustion engine starting process of the second embodiment.

-Similar to the above modification example, regarding the process of step S40 in the internal combustion engine start process of the first embodiment, if the determination is not YES even if the process of step S40 is performed a predetermined number of times, the internal combustion engine start process is performed. May be terminated and control by the battery drive mode may be continued.

-If the cause of the inverter abnormality state is not an abnormality of the sensor related to the calculation of the generated power Pm1 of the first MG71, the CPU 101 can calculate the generated power Pm1 of the first MG71. In this case, in the process of step S30 in the internal combustion engine starting process of the first embodiment, the magnitude of the generated power Pm1 of the first MG71 may be determined instead of determining the magnitude of the vehicle speed SP. That is, the generated power Pm1 of the first MG71 may be calculated, and it may be determined whether or not the generated power Pm1 is equal to or higher than the specified power value PmB. The same applies to step S130 in the internal combustion engine starting process of the second embodiment.

When the cause of the inverter abnormality state is not an abnormality of the second capacitor sensor that detects the charge voltage VH of the second capacitor 25, the CPU 101 can acquire the detection signal of the second capacitor sensor. In this case, in the process of step S40 in the internal combustion engine starting process of the first embodiment, the magnitude of the charge voltage VH of the second capacitor 25 itself may be determined instead of determining the magnitude of the power consumption Pm2 of the second MG 72. .. That is, it may be determined whether or not the charging voltage VH of the second capacitor 25 reaches the output voltage VB of the battery 77.

The method for lowering the charging voltage VH of the second capacitor 25 is not limited to the methods shown in the first embodiment and the second embodiment. Any method may be adopted as long as the charging voltage VH of the second capacitor 25 can be lowered.

-To what extent the charging voltage VH of the second capacitor 25 is lowered can be appropriately set. The specified vehicle speed SPD and the specified power value PmB may be appropriately set according to the value at which the charging voltage VH of the second capacitor 25 is reached.

10 ... Internal combustion engine 25 ... Second condenser 40 ... Power distribution integrated mechanism 71 ... First motor generator 72 ... Second motor generator 77 ... Battery 80 ... Converter 90 ... First inverter 91 ... Second inverter 100 ... Control device 101 ... CPU
500 ... Hybrid vehicle

Claims (1)

With an internal combustion engine
With the first motor generator
With the second motor generator
A planetary gear mechanism that drives and connects the internal combustion engine, the first motor generator, and the second motor generator.
A battery that transfers power between the first motor generator and the second motor generator, and
A converter that boosts the output voltage of the battery and outputs it.
A capacitor that smoothes the voltage output by the converter,
A first inverter connected between the capacitor and the first motor generator and performing DC AC power conversion,
It is equipped with a second inverter connected between the capacitor and the second motor generator and performing DC / AC power conversion.
The planetary gear mechanism includes a sun gear that rotates, a ring gear that rotates coaxially with the sun gear, a pinion gear that is interposed between the sun gear and the ring gear and revolves around the sun gear, and a revolvement of the pinion gear. With a carrier that rotates coaxially with the sun gear according to
The carrier is connected to the output shaft of the internal combustion engine, the sun gear is connected to the rotating shaft of the first motor generator, and the ring gear is applied to a hybrid vehicle connected to the rotating shaft of the second motor generator. ,
When the abnormal state in which the first inverter does not operate normally is detected in a situation where the second motor generator is driven and the internal combustion engine is not driven.
The process of lowering the charging voltage of the capacitor
A control device for a hybrid vehicle that executes a process of starting an internal combustion engine when the electric power supplied from the first motor generator to the capacitor exceeds a predetermined predetermined electric power value.

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