Vehicle drive apparatus

Abstract

To provide a vehicle drive apparatus which can prevent vibration of a vehicle body when a vehicle is caused to travel with an engine being operated, and in addition, which can prevent a deterioration in engine starting performance during traveling and can appropriately start the engine.SOLUTION: A differential mechanism includes three rotary elements consisting of a first rotary element, a second rotary element, and a third rotary element. An engine and a first electric motor are connected to the first rotary element, a second electric motor is connected to the second rotary element, and a first drive shaft for driving one of front and rear wheels is connected to the third rotary element. Further, a third electric motor is connected to a second drive shaft for driving the other of the front and rear wheels. When performing an on-traveling engine start to start the engine while a vehicle is traveling, an electronic controller causes the first electric motor to generate engine starting torque and causes the second electric motor to generate torque in such a direction as to resist inertia torque generated in the second rotary element due to a rotational speed change.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present invention relates to a vehicle drive system that includes an engine, three electric motors, a differential mechanism, drive shafts that drive front and rear wheels, and a control device. [Background technology]

[0002] A well-known vehicle drive system includes an engine, a first electric motor, a second electric motor, a third electric motor, a differential mechanism, a first drive shaft that drives one of the front and rear wheels, a second drive shaft that drives the other of the front and rear wheels, and a control device. For example, Patent Document 1 discloses such a vehicle drive system. Patent Document 1 discloses that the differential mechanism has four rotating elements: a first rotating element, a second rotating element, a third rotating element, and a fourth rotating element. Patent Document 1 also discloses that the engine is connected to the first rotating element, the first electric motor is connected to the second rotating element, the second electric motor is connected to the third rotating element, and the first drive shaft is connected to the fourth rotating element. Patent Document 1 also discloses that the third electric motor is connected to the second drive shaft. The vehicle drive device of Patent Document 1 also discloses that when starting the engine while the vehicle is running with the engine stopped, the first electric motor and the second electric motor are controlled so that they output torque in a direction that increases the engine rotation speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-149917 Summary of the Invention [Problem to be solved by the invention]

[0004] The vehicle drive system of Patent Document 1 realizes a compound split mode in which, while the engine is running, one of the first and second electric motors is operated as a generator and the other is operated as a prime mover to drive the first drive shaft. The vehicle drive system of Patent Document 1 also realizes an input split mode in which, while the engine is running, one of the first and second electric motors is operated as a generator and the third electric motor is operated as a prime mover to drive the second drive shaft. However, when the vehicle is running with the engine running, the first or second electric motor generates a reaction torque against the engine torque, and the torque vibration of the engine is transmitted to the first drive shaft, which may cause the vehicle body to vibrate.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle drive device that is configured to make it difficult for the vehicle body to vibrate when the vehicle is driven with the engine running, and that is capable of preventing deterioration of engine starting while the vehicle is in motion and of ensuring proper engine starting. [Means for solving the problem]

[0006] The gist of a first invention is a vehicle drive device including: (a) an engine, a first electric motor, a second electric motor, a third electric motor, a differential mechanism, a first drive shaft that drives one of front wheels and rear wheels, a second drive shaft that drives the other of the front wheels and the rear wheels, and a control device; (b) the differential mechanism has three rotation elements: a first rotation element, a second rotation element, and a third rotation element; (c) the engine and the first electric motor are connected to the first rotation element, and the second rotation element is connected to the third rotation element; (d) the second electric motor is connected to the first rotating element, and the first drive shaft is connected to the third rotating element; (d) the third electric motor is connected to the second drive shaft; and (e) the control device is configured to, when starting the engine while the vehicle is running, generate an engine starting torque in the first electric motor and generate a torque in the second electric motor in a direction that resists the inertia torque generated in the second rotating element due to a change in rotational speed.

[0007] The gist of the second invention is that in the vehicle drive device described in the first invention, the control device is configured to cause the second electric motor to generate a torque that offsets the inertia torque when starting the engine while the vehicle is traveling.

[0008] The gist of the third invention is that in the vehicle drive device described in the first invention, the control device is configured to cause the second electric motor to generate an engine start acceleration torque that is oriented against the inertia torque and is greater than the inertia torque when starting the engine while the vehicle is traveling.

[0009] The gist of the fourth invention is that in the vehicle drive device described in the third invention, the control device is further configured to cause the third electric motor to generate a torque that offsets the fluctuating torque generated in the first drive shaft by the engine start acceleration torque when starting the engine while the vehicle is traveling. [Effects of the Invention]

[0010] According to the first aspect of the present invention, the differential mechanism has three rotating elements: a first rotating element, a second rotating element, and a third rotating element. The engine and the first electric motor are connected to the first rotating element, the second electric motor is connected to the second rotating element, and the first drive shaft is connected to the third rotating element. The third electric motor is connected to the second drive shaft. This allows so-called series running, in which, when the vehicle is running with the engine running, the first electric motor, which is connected to the same rotating element as the engine, is operated as a generator, and the third electric motor is operated as a prime mover using the generated power to drive the second drive shaft. In series running, torque vibration of the engine is prevented from being transmitted to the first drive shaft, thereby reducing the likelihood of vibration of the vehicle body when the vehicle is running with the engine running. Furthermore, when starting the engine while the vehicle is running with the engine stopped, the rotational speed of the second electric motor connected via the differential mechanism changes as the engine rotational speed increases, and inertial torque generated by the change in rotational speed is transmitted to the crankshaft of the engine, acting as a load for starting the engine and potentially deteriorating the startability of the engine. The control device is configured, when performing an in-motion engine start to start the engine while the vehicle is running, to cause the first electric motor to generate an engine start torque and cause the second electric motor to generate a torque in a direction that counteracts the inertial torque generated in the second rotating element due to the change in rotational speed. As a result, when performing the in-motion engine start, in addition to causing the first electric motor to generate the engine start torque, the second electric motor can generate a torque in a direction that counteracts the inertial torque. This prevents the inertial torque generated in the second rotating element from deteriorating the startability of the engine, and allows the engine to be started appropriately while the vehicle is running.

[0011] According to the second aspect of the present invention, when starting the engine while the vehicle is running, the control device is configured to cause the second electric motor to generate a torque that offsets the inertia torque, thereby allowing the engine starting torque of the first electric motor to be used for starting the engine without being reduced.

[0012] According to the third aspect of the present invention, when starting the engine while the vehicle is traveling, the control device is configured to cause the second electric motor to generate an engine start acceleration torque that is oriented in a direction that resists the inertia torque and is greater than the inertia torque, thereby making it possible to increase the engine start torque by the engine start acceleration torque generated by the second electric motor and improve the startability of the engine.

[0013] According to the fourth aspect of the present invention, when starting the engine while the vehicle is running, the control device is further configured to cause the third electric motor to generate a torque that offsets the torque fluctuations generated in the first drive shaft by the engine start acceleration torque, thereby making it possible to suppress acceleration of the vehicle caused by the engine start acceleration torque generated by the second electric motor. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle equipped with a vehicle drive device (single pinion U / D type) to which the present invention is applied. [Figure 2] FIG. 2 is a nomographic diagram illustrating the configuration of the vehicle drive device. [Figure 3] FIG. 2 is a diagram illustrating a main part of a control system for various controls in the vehicle drive device. [Figure 4] FIG. 4 is a collinear diagram illustrating a BEV mode in which torque is generated in the first electric motor and the second electric motor. [Figure 5] FIG. 10 is a collinear diagram illustrating a BEV mode in which torque is generated by the second electric motor with the brake engaged. [Figure 6]FIG. 10 is a collinear diagram illustrating a BEV mode in which torque is generated by the third electric motor with the brakes engaged. [Figure 7] 1A and 1B are nomographic diagrams illustrating a first HEV mode (series mode) in which the engine is driven to rotate and power is exchanged between the first electric motor and the third electric motor. (a) is a nomographic diagram illustrating a case in which torque is generated in the third electric motor by the electric power generated by the first electric motor. (b) is a nomographic diagram illustrating a case in which the electric power generated by the third electric motor is consumed by the power running of the first electric motor to apply engine braking. [Figure 8] 10A and 10B are nomographic diagrams illustrating a second HEV mode (input split mode) in which the engine is operated and power is exchanged between the second electric motor and the third electric motor. (a) is a nomographic diagram illustrating a case in which torque is generated in the third electric motor by the electric power generated by the second electric motor. (b) is a nomographic diagram illustrating a case in which torque is generated in the second electric motor by the electric power generated by the third electric motor. [Figure 9] 10A and 10B are nomographic diagrams illustrating a third HEV mode (output split mode) in which the engine is operated and power is exchanged between the first and second electric motors. (a) is a nomographic diagram illustrating a case in which torque is generated in the second electric motor by the power generated by the first electric motor. (b) is a nomographic diagram illustrating a case in which torque is generated in the first electric motor by the power generated by the second electric motor. [Figure 10] FIG. 10 is a diagram showing an example of a drive mode switching map used for drive mode switching control, which is used in charge consumption running. [Figure 11] FIG. 10 is a diagram showing an example of a drive mode switching map used for drive mode switching control, which is used in charge-maintenance running. [Figure 12] 11 is a diagram showing an example of a drive mode switching map used for drive mode switching control, which is used in charge consumption running, and in which the drive force in FIG. 10 is replaced with the accelerator opening. [Figure 13] FIG. 12 is a diagram showing an example of a drive mode switching map used for drive mode switching control, which is used in charge-maintenance running, and in which the drive force in FIG. 11 is replaced with the accelerator opening. [Figure 14] FIG. 4 is a nomographic diagram illustrating the operation of each rotary element in a comparative example in the control of engine start while traveling. [Figure 15] 10 is a nomographic diagram illustrating the operation of each rotating element when a torque in a direction counteracting the inertia torque is generated in the second electric motor during engine start control while the vehicle is traveling. FIG. [Figure 16] 10 is a nomographic diagram illustrating the operation of each rotating element when an engine start acceleration torque greater than an inertia torque is generated in the second electric motor during control of engine start while the vehicle is traveling. FIG. [Figure 17] 1 is an example of a flowchart illustrating a main part of the control operation of an electronic control device, and is a flowchart illustrating the control operation of starting the engine while traveling. [Figure 18] FIG. 10 is a diagram showing an example of a time chart for starting the engine while the vehicle is running, which is performed by the electronic control device, and is a time chart for the case where a torque that offsets the inertia torque is generated in the second electric motor. [Figure 19] This is a time chart in the case where the torque that cancels out the inertia torque in the time chart of FIG. 18 is set to an engine start acceleration torque that is greater than the inertia torque. [Figure 20] 1 is a diagram illustrating a schematic configuration of a vehicle equipped with a vehicle drive device (single pinion O / D type) to which the present invention is applied, and is a diagram illustrating a vehicle different from the vehicle of FIG. [Figure 21] 21 is a nomographic diagram showing the configuration of the vehicle drive device of FIG. 20. FIG. [Figure 22] FIG. 21 is a nomographic diagram illustrating the operation of each rotating element when a torque in a direction opposing inertia torque is generated in the second electric motor in the control of engine start during travel performed by the electronic control device provided in the vehicle drive device of FIG. 20. [Figure 23] FIG. 21 is a nomographic diagram illustrating the operation of each rotating element when an engine start acceleration torque greater than an inertia torque is generated in the second electric motor in the control of engine start during travel performed by the electronic control device provided in the vehicle drive device of FIG. [Figure 24]1 is a diagram illustrating a schematic configuration of a vehicle equipped with a vehicle drive device (double pinion U / D type) to which the present invention is applied, the diagram illustrating a vehicle different from the vehicle of FIG. [Figure 25] 25 is a nomographic diagram illustrating the configuration of the vehicle drive device of FIG. 24. FIG. [Figure 26] FIG. 25 is a nomographic diagram illustrating the operation of each rotating element when a torque in a direction opposing inertia torque is generated in the second electric motor in the control of engine start during travel performed by the electronic control device provided in the vehicle drive device of FIG. [Figure 27] FIG. 25 is a nomographic diagram illustrating the operation of each rotating element when an engine start acceleration torque greater than an inertia torque is generated in the second electric motor in the control of engine start during travel performed by the electronic control device provided in the vehicle drive device of FIG. [Figure 28] 1 is a diagram illustrating a schematic configuration of a vehicle equipped with a vehicle drive device (double pinion O / D type) to which the present invention is applied, the diagram illustrating a vehicle different from the vehicle of FIG. [Figure 29] FIG. 29 is a nomographic diagram illustrating the configuration of the vehicle drive device of FIG. 28. [Figure 30] FIG. 29 is a nomographic diagram illustrating the operation of each rotating element when a torque in a direction opposing inertia torque is generated in the second electric motor in the control of engine start during travel performed by the electronic control device provided in the vehicle drive device of FIG. [Figure 31] FIG. 29 is a nomographic diagram illustrating the operation of each rotating element when an engine start acceleration torque greater than an inertia torque is generated in the second electric motor in the control of engine start during travel performed by the electronic control device provided in the vehicle drive device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0016] FIG. 1 is a diagram illustrating the schematic configuration of a vehicle 8 equipped with a vehicle drive system 10 to which the present invention is applied. In FIG. 1, the vehicle 8 is equipped with drive wheels 12 and a vehicle drive system 10 that drives the drive wheels 12. The drive wheels 12 include left and right front wheels 12f and left and right rear wheels 12r. The vehicle drive system 10 includes a front drive unit 10f that drives the front wheels 12f and a rear drive unit 10r that drives the rear wheels 12r. Note that the above "left and right" refer to left and right relative to the forward direction of the vehicle 8.

[0017] The front drive unit 10f includes an engine 20, a first electric motor MG1, a second electric motor MG2, and a front power transmission device 30. The rear drive unit 10r includes a third electric motor MG3 and a rear power transmission device 50. The vehicle 8 is a hybrid vehicle (HEV (Hybrid Electric Vehicle)) or a plug-in hybrid vehicle (PHEV (Plug-in Hybrid Electric Vehicle)). The vehicle 8 is also an all-wheel drive vehicle capable of independently driving the front wheels 12f and the rear wheels 12r. All-wheel drive (AWD) and four-wheel drive (4WD) are synonymous. The vehicle drive system 10 is capable of front-wheel drive, in which torque is transmitted only to the front wheels 12f, and rear-wheel drive, in which torque is transmitted only to the rear wheels 12r.

[0018] The engine 20 is, for example, a known internal combustion engine. An electronic control unit 70 (described later) controls an engine control device 60, thereby controlling the engine torque Te of the engine 20. The engine control device 60 is provided in the front drive unit 10f and includes a throttle actuator, a fuel injection device, an ignition device, etc.

[0019] The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are rotating electric machines, so-called motor generators, that function as a prime mover that generates mechanical power from electric power and as a generator that generates electric power from mechanical power. The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each connected to a battery 64 provided in the vehicle drive system 10 via an inverter 62 provided in the vehicle drive system 10. The torque of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 is controlled by an electronic control device 70 (described later) controlling the inverter 62. The torque of the first electric motor MG1 is first electric motor torque Tmg1, the torque of the second electric motor MG2 is second electric motor torque Tmg2, and the torque of the third electric motor MG3 is third electric motor torque Tmg3. The torque of the electric motors is power running torque when the electric motors function as prime movers, and is regenerative torque when the electric motors function as generators. The battery 64 is an electricity storage device that supplies and receives electric power to and from each of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3. The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are controlled via the inverter 62 so that electric power is supplied and received simultaneously. "Simultaneously" means, for example, that the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each capable of power running or regenerating independently and simultaneously.

[0020] The front power transmission device 30 is provided in a power transmission path between the engine 20, the first electric motor MG1, and the second electric motor MG2, and the front wheels 12f. The front power transmission device 30 includes a differential mechanism 32, a front counter gear 34, a front differential gear 36, and left and right front drive shafts 38. The differential mechanism 32 and the front differential gear 36 are connected via the front counter gear 34. The front drive shaft 38 is connected to the front differential gear 36. The front power transmission device 30 transmits power from the engine 20, the second electric motor MG2, and the like to the front wheels 12f. The front drive shaft 38 is a first drive shaft that drives the front wheels 12f, which are one of the front wheels 12f and the rear wheels 12r.

[0021] The differential mechanism 32 is a single-pinion planetary gear device having a sun gear S, a pinion P, a carrier C that supports the pinion P so that it can rotate and revolve, and a ring gear R that meshes with the sun gear S via the pinion P. A second electric motor MG2 is connected to the sun gear S. The engine 20 and a first electric motor MG1 are connected to the ring gear R. The carrier C meshes with a front counter gear 34. A front drive shaft 38 is connected to the carrier C.

[0022] The engine 20 and the second electric motor MG2 are each disposed on a first axis CS1, which is the rotation axis of the differential mechanism 32. The first electric motor MG1 is disposed on a second axis CS2. The second axis CS2 is a rotation axis different from the first axis CS1 and is parallel to the first axis CS1. Therefore, the front power transmission device 30 further includes a power transmission member 40. The first electric motor MG1 is connected to a ring gear R of the differential mechanism 32 via the power transmission member 40. The power transmission member 40 includes, for example, an intermediate gear 40a fixed to the rotor shaft MG1rs of the first electric motor MG1 so as not to rotate relative to it, and a belt 40b connecting the intermediate gear 40a and the ring gear R. The intermediate gear 40a has a smaller diameter than the ring gear R, and the power transmission member 40 functions as, for example, a reduction mechanism. By arranging the first electric motor MG1 on the second axis CS2, the size of the front drive unit 10f in the direction of the first axis CS1 is reduced compared to when the first electric motor MG1 is arranged on the first axis CS1.

[0023] The front power transmission device 30 further includes a brake BR. One end of the brake BR is connected to the ring gear R of the differential mechanism 32, and the other end is connected to a non-rotating member (not shown). The non-rotating member to which the brake BR is connected is, for example, a case that houses the front power transmission device 30, etc. The brake BR is an engagement device that is operated by, for example, an electric or hydraulic actuator to selectively connect members at both ends. The brake BR functions as a brake mechanism that selectively stops rotation of the ring gear R of the differential mechanism 32. The ring gear R is selectively made rotatable or non-rotatable by the brake BR.

[0024] The rear power transmission device 50 is provided in a power transmission path between the third electric motor MG3 and the rear wheels 12r. The rear power transmission device 50 includes an output gear 52, a rear counter gear 54, a rear differential gear 56, and left and right rear drive shafts 58. The output gear 52 is fixed to the rotor shaft MG3rs of the third electric motor MG3 so as not to rotate relative to the rotor shaft MG3rs, and is in mesh with the rear counter gear 54. The output gear 52 and the rear differential gear 56 are connected via the rear counter gear 54. The rear drive shaft 58 is connected to the rear differential gear 56. The output gear 52 has a smaller diameter than the rear counter gear 54, and the output gear 52 and the rear counter gear 54 function as, for example, a reduction mechanism. The rear power transmission device 50 transmits power from the third electric motor MG3 to the rear wheels 12r. The rear drive shaft 58 is a second drive shaft that drives the other of the front wheels 12f and the rear wheels 12r, 12r. A third electric motor MG3 is connected to the rear drive shaft 58.

[0025] The rear power transmission device 50 further includes a parking mechanism PLC. One end of the parking mechanism PLC is connected to a non-rotating member (not shown). The parking mechanism PLC is operated by, for example, an electric actuator or a manually operated mechanical actuator, and the other end of the parking mechanism PLC is engaged with or disengaged from the output gear 52. The non-rotating member to which the parking mechanism PLC is connected is, for example, a case that houses the rear power transmission device 50. The parking mechanism PLC is a known parking lock device that switches between a parking lock state in which the output gear 52 is mechanically fixed so as to be non-rotatable, and a non-parking lock state in which the output gear 52 is rotatable. The output gear 52 is a rotating member that rotates together with the rear drive shaft 58. The output gear 52 and the rear drive shaft 58 are selectively non-rotatable or rotatable by the parking mechanism PLC.

[0026] FIG. 2 is a nomographic diagram showing the configuration of the vehicle drive system 10. In FIG. 2, the rear drive unit 10r is a main unit that is used for driving with priority over, for example, the front drive unit 10f. In this case, the front drive unit 10f is considered an auxiliary unit. "FrOUT" in FIG. 2 indicates the front wheels 12f, and "RrOUT" in FIG. 2 indicates the rear wheels 12r.

[0027] The differential mechanism 32 of the front drive unit 10f has three rotating elements: a first rotating element RE1, a second rotating element RE2, and a third rotating element RE3. An actuator is connected to each of the rotating elements RE1-RE3 of the differential mechanism 32. The nomographic diagram of FIG. 2 illustrates the three rotating elements of the differential mechanism 32 arranged in a straight line. Expressed using the nomographic diagram, the first rotating element RE1 is a ring gear R. The engine 20 and the first electric motor MG1 are connected to the first rotating element RE1. The second rotating element RE2 is a sun gear S. The second electric motor MG2 is connected to the second rotating element RE2. The third rotating element RE3 is a carrier C. The front drive shaft 38, i.e., the front wheels 12f, are connected to the third rotating element RE3. The brake BR is a brake mechanism that stops rotation of the first rotating element RE1 when engaged.

[0028] The third electric motor MG3 of the rear drive unit 10r is connected to the rear wheels 12r, and can therefore be considered to be connected to the front wheels 12f via the ground (see dashed lines). By controlling the first electric motor MG1, second electric motor MG2, and third electric motor MG3 so that electric power is exchanged simultaneously, it is possible to travel as if the third electric motor MG3 were connected to the front wheels 12f.

[0029] FIG. 3 is a diagram illustrating essential parts of a control system for various controls in the vehicle drive system 10. In FIGS. 1 and 3, the vehicle drive system 10 further includes an electronic control unit 70 as a controller including control devices related to the control of the vehicle drive system 10 and the like. The electronic control unit 70 includes, for example, a so-called microcomputer equipped with a CPU, RAM, ROM, an input / output interface, and the like. The CPU performs various controls of the vehicle 8 by, for example, performing signal processing according to a program pre-stored in the ROM. For example, the electronic control unit 70 controls the outputs of the engine 20, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3, and performs drive mode switching control, which will be described later. The electronic control unit 70 is divided into a hybrid control ECU 72 (see "PHEV-ECU" in FIG. 3), an engine control ECU 74 (see "ENG-ECU" in FIG. 3), an electric motor control ECU 76 (see "MG-ECU" in FIG. 3), and the like, as needed.

[0030] The hybrid control ECU 72 receives various signals based on detection signals from various sensors provided in the vehicle 8. The various sensors include, for example, an accelerator pedal position sensor 80, a vehicle speed sensor 81, a battery sensor 82, a BEV switch 83, and a shift position sensor 84. The various sensors also include, for example, a first electric motor rotation sensor 85, a second electric motor rotation sensor 86, and a third electric motor rotation sensor 87, each of which may be a resolver. The various sensors also include, for example, an engine rotation speed sensor 88, a brake switch 89, a brake operation amount sensor 90, a crawl switch 91, and a traction switch 92. The various signals also include, for example, an accelerator pedal position θacc, a vehicle speed V, a signal for calculating the charge state of charge (SOC), a BEV-on signal BEVon, and a shift operation position POSop. The various signals also include, for example, a first electric motor rotation speed Nmg1, a second electric motor rotation speed Nmg2, and a third electric motor rotation speed Nmg3. The various signals include, for example, an engine rotation speed Ne, a brake-on signal BPon, a brake operation amount θbp, a crawl-on signal CRon, a traction-on signal TRon, and the like.

[0031] The BEV switch 83 is a switch operated by the driver when BEV driving is required. When the BEV switch 83 is operated, the engine 20 is not started, and the vehicle is driven in BEV mode using only the power of the battery 64. The crawl switch 91 is a switch operated by the driver when a situation is anticipated in which the vehicle will be driven at an extremely low speed and with a high load on a rocky road, for example. The towing switch 92 is a switch operated by the driver when the vehicle 8 is driven with a towed vehicle coupled to the rear of the vehicle.

[0032] The accelerator opening θacc is the amount of accelerator operation by the driver, which indicates the magnitude of the driver's acceleration operation. The vehicle speed V is the speed of the vehicle 8. The signals for calculating the state of charge SOC are the battery charge / discharge current and battery voltage detected by the battery sensor 82. The state of charge SOC is the remaining charge of the battery 64 and is calculated by the electronic control unit 70 based on the battery charge / discharge current and battery voltage. The battery sensor 82 also detects the battery temperature. The BEV-on signal BEVon is a signal indicating that the BEV switch 83 has been operated by the driver. The shift operation position POSop is the lever position of the shift operation device, such as "P," "R," "N," or "D." The first electric motor rotation speed Nmg1 is the rotation speed of the first electric motor MG1. The second electric motor rotation speed Nmg2 is the rotation speed of the second electric motor MG2. The third electric motor rotation speed Nmg3 is the rotation speed of the third electric motor MG3. The engine rotation speed Ne is the rotation speed of the engine 20. The brake-on signal BPon is a signal indicating that the brake pedal for applying the wheel brakes is being operated by the driver. The brake operation amount θbp is a signal indicating the magnitude of the brake pedal depression operation by the driver, i.e., the magnitude of the brake operation, and is synonymous with the brake pedal depression force. The crawl-on signal CRon is a signal indicating that the crawl switch 91 has been operated by the driver. The tow-on signal TRon is a signal indicating that the tow switch 92 has been operated by the driver.

[0033] The engine control ECU 74 receives input of an air-fuel ratio A / F and the like based on detection signals from an air-fuel ratio sensor 93 and the like provided on the vehicle 8. The motor control ECU 76 receives input of a first electric motor rotation angle θmg1, a second electric motor rotation angle θmg2, a third electric motor rotation angle θmg3 and the like based on detection signals from a first electric motor rotation sensor 85, a second electric motor rotation sensor 86, a third electric motor rotation sensor 87, and the like.

[0034] The air-fuel ratio A / F is a signal that represents the state of the air-fuel ratio in the exhaust gas. The first electric motor rotation angle θmg1 is a signal that represents the rotational position, which is the rotational angle of the rotor of the first electric motor MG1 from a predetermined reference position. The second electric motor rotation angle θmg2 is a signal that represents the rotational position, which is the rotational angle of the rotor of the second electric motor MG2 from a predetermined reference position. The third electric motor rotation angle θmg3 is a signal that represents the rotational position, which is the rotational angle of the rotor of the third electric motor MG3 from a predetermined reference position.

[0035] The hybrid control ECU 72 outputs various command signals to the engine control ECU 74. The various command signals to the engine control ECU 74 include, for example, a command signal for a target engine torque Tetgt, a fuel cut request signal FCreq for requesting a fuel cut operation, etc. The hybrid control ECU 72 also outputs various command signals to the electric motor control ECU 76. The various command signals to the electric motor control ECU 76 include, for example, a command signal for a target first electric motor torque Tmg1tgt, a command signal for a target second electric motor torque Tmg2tgt, and a command signal for a target third electric motor torque Tmg3tgt, etc. The hybrid control ECU 72 also outputs a brake control command signal Sbr to the brake BR, etc.

[0036] The target engine torque Tetgt is a target value of the engine torque Te. The fuel cut operation is a control operation that cuts off the supply of fuel to the engine 20. The target first electric motor torque Tmg1tgt is a target value of the first electric motor torque Tmg1. The target second electric motor torque Tmg2tgt is a target value of the second electric motor torque Tmg2. The target third electric motor torque Tmg3tgt is a target value of the third electric motor torque Tmg3. The brake control command signal Sbr is a request signal for controlling the brake BR to an on state or an off state. Note that in an engagement device, the on state is synonymous with an engaged state (= connected state), and the off state is synonymous with a released state (= disconnected state).

[0037] The engine control ECU 74 outputs engine control command signals Se and the like to the engine control device 60 and the like. The engine control command signals Se are command signals for controlling the engine 20, and include command signals for the intake air amount Qair, the ignition timing TMig, the fuel injection amount Qfi, and the like.

[0038] The motor control ECU 76 outputs a first motor control command signal Smg1, a second motor control command signal Smg2, a third motor control command signal Smg3, etc. to the inverter 62, etc. The first motor control command signal Smg1 is a command signal for controlling the first motor MG1 and includes command signals such as a first motor current Img1. The second motor control command signal Smg2 is a command signal for controlling the second motor MG2 and includes command signals such as a second motor current Img2. The third motor control command signal Smg3 is a command signal for controlling the third motor MG3 and includes command signals such as a third motor current Img3. The first motor current Img1 is a drive current for the first motor MG1. The second motor current Img2 is a drive current for the second motor MG2. The third motor current Img3 is a drive current for the third motor MG3.

[0039] The hybrid control ECU 72 determines various command signals based on the driver's intentions, such as the accelerator opening θacc and the brake operation amount θbp, the first electric motor rotation speed Nmg1, the second electric motor rotation speed Nmg2, the third electric motor rotation speed Nmg3, and the engine rotation speed Ne. For example, the hybrid control ECU 72 determines a brake control command signal Sbr to control the engagement and release states of the brake BR. The engine control ECU 74 determines an engine control command signal Se based on a command signal for a target engine torque Tetgt, a fuel cut request signal FCreq requesting a fuel cut operation, and the like. The engine control ECU 74 outputs the engine control command signal Se to control the engine 20. The electric motor control ECU 76 determines electric motor control command signals Smg1, Smg2, and Smg3 based on a target first electric motor torque Tmg1tgt, a target second electric motor torque Tmg2tgt, and a target third electric motor torque Tmg3tgt, etc. The electric motor control ECU 76 outputs electric motor control command signals Smg1, Smg2, Smg3 to control the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3.

[0040] As a result, the electronic control unit 70 is configured to control the engine 20, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3, and to switch the drive mode to one of a plurality of modes. Furthermore, when switching the drive mode, the electronic control unit 70 controls the brake BR to be engaged as necessary.

[0041] Here, the multiple modes into which the drive mode of the vehicle 8 can be switched will be described with reference to FIGS. 4 to 9. FIGS. 4 to 9 each show the relative rotational speeds of the rotational elements RE1-RE3 of the differential mechanism 32 in the alignment chart of FIG. 2. In this alignment chart, vertical lines Y1-Y3 are arranged in the order of Y1, Y2, and Y3 from the left side of the drawing. The vertical line Y1 represents the rotational speed of the sun gear S, which is the second rotational element RE2 connected to the second electric motor MG2. The vertical line Y2 represents the rotational speed of the carrier C, which is the third rotational element RE3 connected to the front wheels 12f (see "FrOUT" in the drawing). The vertical line Y3 represents the rotational speed of the ring gear R, which is the first rotational element RE1 connected to the engine 20 (see "ENG" in the drawing) and the first electric motor MG1. Furthermore, this indicates that the third electric motor MG3 connected to the rear wheels 12r (see "RrOUT" in the drawing) is connected to the front wheels 12f via the ground. Each arrow indicates the magnitude and direction of torque converted onto the axis of each rotating element RE1-RE3. The solid arrow indicates the torque output from each actuator, and the dashed arrow indicates the mechanically transmitted torque.

[0042] FIG. 4 is a nomographic diagram illustrating Mode1_MG2, a BEV mode in which torque is generated in the first electric motor MG1 and the second electric motor MG2, which is one of Mode1 modes that enables BEV driving. In FIG. 4, Mode1_MG2 is included in multiple modes that allow switching of the drive mode. Mode1_MG2 is a mode in which the engine 20 is stopped and torque is generated in the first electric motor MG1 and the second electric motor MG2 to perform BEV driving. In Mode1_MG2, the first electric motor MG1 and the second electric motor MG2 exchange power with the battery 64 and generate mutual torque so that the moment around the third rotating element RE3 becomes zero, thereby enabling BEV driving. At this time, the first electric motor torque Tmg1 is controlled, for example, so as not to cause drag of the engine 20, i.e., so that the rotational speed of the first rotating element RE1 becomes zero. In Mode1_MG2, the differential mechanism 32 is in a differential state, and torque is generated in the first electric motor MG1 and the second electric motor MG2, and the torque is mechanically transmitted to the third rotating element RE3, which is the output element. Note that in Mode1_MG2, it is also possible to increase the drive torque by generating torque in the third electric motor MG3.

[0043] FIG. 5 is a nomographic diagram illustrating Mode1_MG2_BRon, a BEV mode in which torque is generated by the second electric motor MG2 with the brake BR engaged, which is another mode of Mode1 that enables BEV driving. In FIG. 5, Mode1_MG2_BRon is included in multiple modes that allow switching of the drive mode. Mode1_MG2_BRon is a mode in which BEV driving is performed by stopping the engine 20 and causing the second electric motor MG2 to generate torque with the brake BR engaged. In Mode1_MG2_BRon, the brake BR is engaged and the rotational speed of the first rotating element RE1 is fixed to zero. Therefore, forward and reverse BEV driving is possible with the second electric motor MG2 using power from the battery 64 without generating torque in the first electric motor MG1. In this case, BEV driving is possible with maximum torque from the second electric motor MG2. In Mode1_MG2_BRon, the differential mechanism 32 is in a non-differential state, and torque is generated in the second electric motor MG2, which mechanically transmits the torque to the third rotating element RE3, which is the output element. Note that in Mode1_MG2_BRon, it is also possible to increase the drive torque by generating torque in the third electric motor MG3.

[0044] FIG. 6 is a nomographic diagram illustrating Mode1_MG3, a BEV mode in which the third electric motor MG3 generates torque with the brake BR engaged, which is yet another mode within Mode1 that enables BEV driving. In FIG. 6, Mode1_MG3 is included in multiple modes that allow switching of the drive mode. Mode1_MG3 is a mode in which the engine 20 is stopped and the third electric motor MG3 generates torque with the brake BR engaged, thereby achieving BEV driving. In Mode1_MG3, the brake BR is engaged and the rotational speed of the first rotating element RE1 is fixed to zero. This prevents drag from occurring in the engine 20 or the first electric motor MG1, and enables forward and reverse BEV driving by the third electric motor MG3 using the power of the battery 64.

[0045] In Mode1_MG3, it is also possible to increase the drive torque by causing the second electric motor MG2 to generate torque. Also, in Mode1_MG3, it is possible to perform BEV running by causing the third electric motor MG3 to generate torque even if the brake BR is not engaged. In other words, Mode1_MG3 may be a mode in which the engine 20 is stopped and the third electric motor MG3 is caused to generate torque to perform BEV running.

[0046] FIG. 7 is a nomographic diagram illustrating a first HEV mode, or Mode 2, in which the engine 20 is rotationally driven and power is exchanged between the first electric motor MG1 and the third electric motor MG3. FIG. 7(a) is a nomographic diagram when torque is generated in the third electric motor MG3 by the electric power generated by the first electric motor MG1. FIG. 7(b) is a nomographic diagram when engine braking is applied by consuming the electric power generated by the third electric motor MG3 through the power running of the first electric motor MG1. In FIG. 7, Mode 2 is included in multiple modes that allow switching of the drive mode. Mode 2 is a mode in which hybrid driving, or HEV driving, is possible, and is a series mode in which series driving using the engine 20 as a power source is possible.

[0047] In FIG. 7A, Mode 2 includes a mode in which the engine 20 is running to operate the first electric motor MG1 as a generator while the third electric motor MG3 is operated as a prime mover using the generated power of the first electric motor MG1. Mode 2 is a mode in which, with the brake BR disengaged, an electric continuously variable transmission function can be realized, with the input from the engine 20 and the output from the rear wheels 12r, performing series mode operation. In Mode 2, power is converted between the engine 20 and the first electric motor MG1, and between the first electric motor MG1 and the third electric motor MG3. The power conversion is between mechanical and electrical power. In Mode 2, explosive vibration torque of the engine 20 is not transmitted to the front drive shaft 38, which is advantageous for suppressing NV. "NV" is a general term for noise and vibration, such as booming noise, generated in the vehicle 8, and represents at least one of the noise and vibration in the vehicle 8. Therefore, Mode 2 is useful when used, for example, at low vehicle speeds and low loads where quietness is required. Furthermore, in Mode 2, for example, the setting of the operating point of the engine 20 is less subject to restrictions such as muffled noise, so the engine 20 can be operated at an operating point that provides good fuel efficiency.

[0048] In FIG. 7(b), Mode 2 includes a mode in which the third electric motor MG3 is operated as a generator, and the first electric motor MG1 is powered by the electric power generated by the third electric motor MG3 to rotate and drive the engine 20. In Mode 2, the electric power consumed by the power running of the first electric motor MG1 is covered by the regenerative electric power of the third electric motor MG3 generated by the kinetic energy of the vehicle 8, and the engine rotation speed Ne is increased by the power running of the first electric motor MG1. The rotation speed of the engine 20 is increased by the first electric motor torque Tmg1 in a fuel-cut state, and the torque converted onto the shaft of the first rotating element RE1 is negative torque. Note that even when the engine 20 is operated by injecting fuel, if the engine rotation speed Ne is increased by the first electric motor torque Tmg1 to a speed higher than that in the autonomous operation state, the torque converted onto the shaft of the first rotating element RE1 is negative torque. The positive direction of torque is the direction of torque when the engine 20 is operating. The case where the engine 20 is operating is synonymous with the case where the engine 20 alone generates positive torque. In Mode 2 of FIG. 7(b), power is converted between the kinetic energy of the vehicle 8 and the third electric motor MG3, and power is converted between the third electric motor MG3 and the first electric motor MG1. In this way, engine braking can be applied in Mode 2. Even when engine braking is applied in Mode 2, the explosive vibration torque of the engine 20 is not transmitted to the front drive shaft 38, which is advantageous for suppressing NV.

[0049] FIG. 8 is a nomographic diagram illustrating a second HEV mode, i.e., Mode 3, in which the engine 20 is operated and power is exchanged between the second electric motor MG2 and the third electric motor MG3. (a) of FIG. 8 is a nomographic diagram illustrating a case in which torque is generated in the third electric motor MG3 by the electric power generated by the second electric motor MG2. (b) of FIG. 8 is a nomographic diagram illustrating a case in which torque is generated in the second electric motor MG2 by the electric power generated by the third electric motor MG3. In FIG. 8, Mode 3 is included in a plurality of modes that enable switching of the drive mode. Mode 3 is a mode that enables hybrid driving, i.e., HEV driving, and is an input split mode that enables input split driving using the engine 20 as a power source. In Mode 3, the differential mechanism 32 is in a differential state, and the second electric motor MG2 takes up the reaction force of the engine torque Te, thereby mechanically transmitting torque to the third rotating element RE3. Mode 3 is a mode in which, with the brake BR released, an electric continuously variable transmission function can be realized, performing input split mode operation with the engine 20 as input and the front wheels 12f and rear wheels 12r as output. In Mode 3, engine braking can be applied. Expressed using a nomographic diagram, input split refers to a type in which two electric motors (MG2, MG3) and one engine are connected to three rotating elements of a differential mechanism, and the electric motor (MG3) is located as the output element (RE3).

[0050] The two-dot chain line A in FIG. 8(a) indicates a state in which a mechanical point is formed in the differential mechanism 32 where no electrical work is performed by setting the rotational speed of the second rotating element RE2 (second electric motor rotational speed Nmg2) to zero and the power of the second electric motor MG2 to zero. At this mechanical point in the differential mechanism 32, the rotational speed of the third rotating element RE3, which is the output element, is on the deceleration side, i.e., the underdrive (U / D) side, relative to the engine rotational speed Ne. In other words, the mechanical point of the differential mechanism 32 is set by the reduction ratio. In FIG. 8, Mode 3 is the U / D input split mode.

[0051] In (a) of Figure 8, Mode 3 includes at least a mode in which the engine 20 is operated to operate the second electric motor MG2 as a generator, while the third electric motor MG3 is operated as a prime mover by the electric power generated by the second electric motor MG2. In Mode 3, torque is mechanically transmitted to the third rotating element RE3, and the electric power generated by the second electric motor MG2 is supplied to the third electric motor MG3, causing the third electric motor MG3 to generate torque. In Mode 3, power is converted between the engine 20 and the second electric motor MG2, and between the second electric motor MG2 and the third electric motor MG3. Mode 3 has high transmission efficiency in the low vehicle speed and high load range, and is therefore useful for use in the low vehicle speed and high load range, for example.

[0052] In (b) of Fig. 8, Mode 3 may include a mode in which the second electric motor MG2 is operated as a prime mover by electric power generated by the third electric motor MG3 while the engine 20 is running. In Mode 3, the second electric motor MG2 is rotated in the forward direction when torque is mechanically transmitted to the third rotating element RE3, and therefore the electric power consumed in the power running of the second electric motor MG2 is covered by regenerative electric power of the third electric motor MG3 that is generated by the kinetic energy of the vehicle 8. In Mode 3 of (b) of Fig. 8, power conversion is performed between the kinetic energy of the vehicle 8 and the third electric motor MG3, and power conversion is performed between the third electric motor MG3 and the second electric motor MG2.

[0053] The vehicle drive device 10 is controlled to perform Mode 3 shown in (a) of Fig. 8 during normal driving where the drive mode is switched with emphasis on energy efficiency, for example. On the other hand, when the drive mode is switched with emphasis on power performance, for example, and Mode 3 shown in (a) of Fig. 8 is not executed, the vehicle drive device 10 is controlled to perform Mode 3 shown in (b) of Fig. 8.

[0054] FIG. 9 is a nomographic diagram illustrating a third HEV mode, i.e., Mode 4, in which the engine 20 is operated and power is exchanged between the first electric motor MG1 and the second electric motor MG2. (a) of FIG. 9 is a nomographic diagram illustrating a case in which torque is generated in the second electric motor MG2 by the electric power generated by the first electric motor MG1. (b) of FIG. 9 is a nomographic diagram illustrating a case in which torque is generated in the first electric motor MG1 by the electric power generated by the second electric motor MG2. In FIG. 9, Mode 4 is included in a plurality of modes that allow switching of the drive mode. Mode 4 is a mode that allows hybrid driving, i.e., HEV driving, and is an output split mode that allows output split driving using the engine 20 as a power source. In Mode 4, the differential mechanism 32 is in a differential state, and the second electric motor MG2 takes up the reaction force of the engine torque Te, thereby mechanically transmitting torque to the third rotating element RE3. Mode 4 is a mode in which, with the brake BR released, an electric continuously variable transmission function can be realized, in which the input is the engine 20 and the output is the front wheels 12f, performing output split mode operation. In Mode 4, engine braking can be applied. Since the mechanical point of the differential mechanism 32 is set by the reduction ratio, Mode 4 in FIG. 9 is U / D output split mode. Expressed using a collinear diagram, output split refers to a type in which, when two electric motors (MG1, MG2) and one engine are connected to three rotating elements of the differential mechanism, the electric motor (MG1) is located at the input element (RE1) to which the engine is connected.

[0055] In (a) of Fig. 9, Mode 4 includes at least a mode in which the engine 20 is operated to operate the first electric motor MG1 as a generator, while the second electric motor MG2 is operated as a prime mover by the electric power generated by the first electric motor MG1. In Mode 4, when torque is mechanically transmitted to the third rotating element RE3, the second electric motor MG2 is rotated in the forward direction. Therefore, the electric power consumed by the power running of the second electric motor MG2 is covered by the electric power generated by the first electric motor MG1 using the power of the engine 20. In Mode 4, power conversion is performed between the engine 20 and the first electric motor MG1, and power conversion is performed between the first electric motor MG1 and the second electric motor MG2. Mode 4 has high transmission efficiency at high vehicle speeds, and is therefore useful for use at high vehicle speeds, for example.

[0056] 9(b), Mode 4 may include a mode in which the first electric motor MG1 is operated as a prime mover by the electric power generated by the second electric motor MG2 while the engine 20 is running. In Mode 4, the second electric motor MG2 is rotated in the negative direction when torque is mechanically transmitted to the third rotating element RE3. Therefore, the electric power generated by the second electric motor MG2 is supplied to the first electric motor MG1, causing the first electric motor MG1 to generate torque. In Mode 4 in FIG. 9(b), power conversion is performed between the engine 20 and the second electric motor MG2, and power conversion is performed between the second electric motor MG2 and the first electric motor MG1.

[0057] The vehicle drive device 10 is controlled to perform Mode 4 shown in (a) of Fig. 9 during normal driving where the drive mode is switched with emphasis on energy efficiency, for example. On the other hand, when the drive mode is switched with emphasis on power performance, for example, and Mode 4 shown in (a) of Fig. 9 is not executed, the vehicle drive device 10 is controlled to perform Mode 4 shown in (b) of Fig. 9.

[0058] The electronic control unit 70 is configured to switch the drive mode based on the vehicle speed V and the road load. The road load is, for example, the accelerator opening θacc. Alternatively, the road load is, for example, the required value of the driving force Fr based on the accelerator opening θacc and the vehicle speed V, or the actual value of the driving force Fr. For example, in the low vehicle speed / low load range, the first HEV mode, or Mode 2, is set as the drive mode (see Mode 2 shown in FIG. 7). In the low vehicle speed / high load range, the second HEV mode, or Mode 3, is set as the drive mode (see Mode 3 shown in FIG. 8). In the high vehicle speed range, the third HEV mode, or Mode 4, is set as the drive mode (see Mode 4 shown in FIG. 9).

[0059] Figures 10, 11, 12, and 13 each show an example of a drive mode switching map used for drive mode switching control. Each of these drive mode switching maps is a predetermined relationship on a two-dimensional coordinate system with vehicle speed V on the horizontal axis and road load on the vertical axis, with boundaries defining an area corresponding to one of a plurality of modes. In other words, each of these drive mode switching maps is a predetermined relationship for determining which drive mode to set.

[0060] Figures 10 and 11 show the case where the road load is set to driving force Fr, and Figures 12 and 13 show the case where the road load is set to accelerator pedal position θacc. Figure 12 shows the case where the driving force Fr in Figure 10 is replaced with accelerator pedal position θacc, and Figure 13 shows the case where the driving force Fr in Figure 11 is replaced with accelerator pedal position θacc. Figures 10 and 12 are drive mode switching maps used in CD (Charge Depleting) driving, in which the vehicle drives while consuming the state of charge SOC. Figures 11 and 13 are drive mode switching maps used in CS (Charge Sustain) driving, in which the vehicle drives to maintain the state of charge SOC.

[0061] 10 and 12 are used, for example, in a PHEV or the like equipped with a battery 64 of a relatively large capacity, when a CD mode is set for CD running, i.e., running while consuming the charged amount. In an HEV or the like equipped with a battery 64 of a smaller capacity than a PHEV, FIGS. 10 and 12 may not be used. FIGS. 11 and 13 are used, for example, in a PHEV or the like, when a CS mode is set for CS running, i.e., running while maintaining the charged amount. Alternatively, FIGS. 11 and 13 are used, for example, in an HEV or the like.

[0062] When the CD mode is set and the SOC is sufficient, FIG. 10 or FIG. 12 is selected, and Mode 1 is set across the entire range. When the CD mode is set but the SOC is low, or when the CS mode is set, FIG. 11 or FIG. 13 is selected. In FIG. 11 or FIG. 13, Mode 2 is set in the low-speed, low-load range where muffled noise is likely to be a problem. Mode 3 is set in the high-load range because it has high transmission efficiency in the high-load range. Mode 4 is set in the high-speed range because it has good transmission efficiency at the overdrive gear ratio, which is frequently used at high vehicle speeds. Even when the SOC is low and the usable range of the SOC is narrow, Mode 1 may be set in the range where the output of power from the battery 64 is small if consumption of the SOC is acceptable. Alternatively, Mode 1 may be set when the operating efficiency of the engine 20 is poor. In FIG. 11 or FIG. 13, Mode 1 is set in the low-speed, low-load range depending on the SOC.

[0063] 11 or 13, it can be seen that in the low vehicle speed / high load range, Mode 3 is set as the drive mode, and in the high vehicle speed range, Mode 4 is set as the drive mode. Or, looking at it from another perspective, it can be seen that in the high load range, Mode 3 is set as the drive mode, and in the high vehicle speed / low load range, Mode 4 is set as the drive mode.

[0064] Incidentally, when starting the engine 20 while the vehicle 8 is traveling with the engine stopped (hereinafter referred to as starting the engine while traveling), as the engine rotation speed Ne increases, the rotation speed of the second electric motor MG2 connected via the differential mechanism 32 also changes, and the inertia torque I2×dω2 / dt generated by the change in rotation speed is transmitted to the crankshaft of the engine 20, becoming a load for starting the engine and potentially deteriorating the startability of the engine.

[0065] 14 is a nomographic diagram illustrating the operation of each rotating element in a comparative example of engine start control performed by the electronic control unit 70 while the vehicle is moving, i.e., when inertia torque I2×dω2 / dt is transmitted to the crankshaft of the engine 20 and becomes a load. In the following explanation, parts that are common to the nomographic diagrams of FIGS. 4 to 9 are assigned the same reference numerals and will not be described again. Furthermore, the torque that is mechanically transmitted from the inertia torque I2×dω2 / dt is indicated by an outlined arrow.

[0066] To start the engine while traveling, the crankshaft of the engine 20 is rotated (hereinafter referred to as motoring) with the engine starting torque Tg of the first electric motor MG1, and when the engine rotation speed Ne rises to a predetermined startable rotation speed Ne1, for example 600 rpm, fuel injection and ignition are performed in that order. Figure 14 shows the state during motoring when starting the engine while traveling. The motoring angular acceleration dωe / dt, which indicates the startability of motoring, is given by the following equation (1), and the engine starting torque Tg output by the first electric motor MG1 is set so that this becomes a predetermined value, i.e., so that the angular acceleration becomes such that motoring can be performed without any problems. dωe / dt=(Tg-Tex) / (Ie+I1) ···(1) Here, Tex represents the resisting torque generated by the engine 20 against the rotation of the motor ring, Ie represents the moment of inertia of the engine 20, and I1 represents the moment of inertia of the first electric motor MG1 toward the ring gear, each of which is a value determined in advance by design or experiment.

[0067] In FIG. 14, as engine rotation speed Ne increases due to motoring, a rotational speed change dω2 / dt occurs in the rotational speed of sun gear S. Accordingly, an inertia torque I2×dω2 / dt that resists the rotational speed change dω2 / dt is generated in the sun gear S. I2 represents the moment of inertia of the second electric motor MG2 with respect to the sun gear S, and is a value determined in advance through design or experimentation. The moment of inertia of carrier C (first drive shaft FrOUT), which is connected to the ground via the vehicle body, is larger than the moment of inertia of sun gear S (= I2) and the moment of inertia of ring gear R (= Ie + I1), and therefore serves as a reaction element for the generated inertia torque I2×dω2 / dt. Therefore, the inertia torque I2×dω2 / dt is transmitted to ring gear R, generating reaction torque RT (I2×dω2 / dt) (see the white arrows in the figure). When a reaction torque RT (I2 × dω2 / dt) occurs, the motoring angular acceleration dωe / dt is given by the following equation (2). dωe / dt=(Tg-Tex-RT(I2×dω2 / dt)) / (Ie+I1) ···(2) Compared to the previous equation (1), the torque acting on the crankshaft of the engine 20 is reduced by the reaction torque RT (I2 × dω2 / dt), so the motoring angular acceleration dωe / dt is reduced. As a result, the timing when the engine rotation speed Ne reaches an ignition speed is delayed, and the startability of the engine 20 is deteriorated.

[0068] FIG. 15 is a nomographic diagram that explains the operation of each rotating element when the second electric motor MG2 generates a torque that opposes the inertia torque I2×dω2 / dt in the control of engine start while traveling performed by the electronic control device 70.

[0069] 15, in starting the engine while traveling, the electronic control device 70 motors the first electric motor MG1 with the engine starting torque Tg, and simultaneously causes the second electric motor MG2 to generate a torque T2r in a direction that resists the inertia torque I2×dω2 / dt generated in the sun gear S. This reduces the reaction torque RT (I2×dω2 / dt) transmitted to the ring gear R, thereby reducing the decrease in the motoring angular acceleration dωe / dt and preventing a deterioration in the startability of the engine 20.

[0070] Furthermore, if torque T2r is set to an inertia cancellation torque T2r1 that cancels out inertia torque I2×dω2 / dt, that is, if torque T2r1=-I2×dω2 / dt, then no reaction torque RT (I2×dω2 / dt) is generated on ring gear R (see the area enclosed by dashed lines in the figure). As a result, motoring angular acceleration dωe / dt is given by equation (1) above, and engine starting torque Tg of first electric motor MG1 is not reduced, so engine rotation speed Ne increases at the desired motoring angular acceleration dωe / dt, and can be made to reach a rotation speed at which ignition is possible at the desired timing.

[0071] FIG. 16 is a nomographic diagram that explains the operation of each rotating element when the electronic control device 70 controls engine start-up while the vehicle is moving and causes the second electric motor MG2 to generate an engine start-up acceleration torque greater than the inertia torque I2×dω2 / dt.

[0072] 16, in starting the engine while traveling, the electronic control device 70 motors the first electric motor MG1 with the engine starting torque Tg, and simultaneously causes the second electric motor MG2 to generate an engine starting acceleration torque T2r2 that is greater than the inertia torque I2×dω2 / dt and that acts in a direction that resists the inertia torque I2×dω2 / dt generated in the sun gear S. As a result, a differential torque (=I2×dω2 / dt−T2r2) between the inertia torque I2×dω2 / dt and the engine starting acceleration torque T2r2 is generated in the sun gear S, and this differential torque generates a reaction torque RTa (I2×dω2 / dt−T2r2) in the ring gear R (first rotating element) and a fluctuation torque RTb (I2×dω2 / dt−T2r2) in the carrier C (third rotating element) (see the outline arrows in the figure). Due to the generation of reaction torque RTa (I2 × dω2 / dt - T2r2), the motoring angular acceleration dωe / dt is given by the following equation (3). dωe / dt=(Tg-Tex+RTa(I2×dω2 / dt-T2r2)) / (Ie+I1) ···(3) Compared to the previous equation (1), the torque acting on the crankshaft of the engine 20 increases by the reaction torque RTa (I2 × dω2 / dt - T2r2), so the motoring angular acceleration dωe / dt increases. As a result, the timing at which the engine rotation speed Ne reaches an ignition-enabling rotation speed is advanced, improving the startability of the engine 20. The control for engine start while traveling shown in Figure 16 is performed when it is desired to accelerate the start of the engine 20 or when the engine start torque Tg of the first electric motor MG1 is insufficient.

[0073] Furthermore, since the generation of the fluctuation torque RTb (I2×dω2 / dt-T2r2) in the carrier C causes deceleration and acceleration in the vehicle 8, the electronic control device 70 causes the third electric motor MG3 to generate a vehicle acceleration cancellation torque ΔTm3 that cancels out the fluctuation torque RTb (I2×dω2 / dt-T2r2), i.e., a vehicle acceleration cancellation torque ΔTm3 such that ΔTm3=-RTb(I2×dω2 / dt-T2r2). This prevents deceleration and acceleration from being caused in the vehicle 8 by the engine start acceleration torque T2r2. The vehicle acceleration cancellation torque ΔTm3 corresponds to the "torque that cancels out the fluctuation torque generated in the first drive shaft" in this invention.

[0074] 17 is an example of a flowchart illustrating the main control operations of the electronic control unit 70, and is a flowchart illustrating the control operations for starting the engine while the vehicle is running. This flowchart is executed repeatedly, for example, while the vehicle is running.

[0075] First, in step (hereinafter, "step" will be omitted) S10, it is determined whether the engine 20 is motoring. If the determination in S10 is negative, in S20, torque generation by the second electric motor MG2 and the third electric motor MG3 described in FIG. 15 or 16 is not performed, and this routine is terminated.

[0076] If the determination in S10 is positive, then in S30 it is determined whether or not there is a request for early start of the engine 20. If the determination in S30 is negative, then in S40 the second electric motor MG2 generates an inertia cancellation torque T2r1 (see FIG. 15), and this routine is terminated.

[0077] If the determination in S30 is affirmative, in S50, the second electric motor MG2 generates the engine start acceleration torque T2r2 and the third electric motor MG3 generates the vehicle acceleration offset torque ΔTm3 (see FIG. 16), and this routine is then terminated.

[0078] Figure 18 is a time chart that explains the control operation when the inertia cancellation torque T2r1 of Figure 15 is generated during engine start while the vehicle 8 is moving when the drive mode of the vehicle 8 is switched from Mode1_MG3 to Mode2, i.e., when S40 of Figure 17 is implemented.

[0079] First, at time t0, the accelerator is turned ON (accelerator opening θacc is changed to θ1), and the third electric motor MG3 outputs a traveling torque Tm3s, starting the vehicle in Mode1_MG3 drive mode. Next, at time t1, the vehicle speed V reaches a target vehicle speed V1 for switching to Mode2, and motoring of the engine 20 is started to switch to Mode2. The first electric motor MG1 generates an engine starting torque Tg for motoring, and the second electric motor MG2 generates an inertia cancellation torque T2r1 that cancels out the inertia torque I2×dω2 / dt generated in the sun gear S. Next, at time t2, the engine rotation speed Ne reaches a startable rotation speed Ne1, fuel injection and ignition are performed, and the generation of the inertia cancellation torque T2r1 by the second electric motor MG2 is stopped. Furthermore, the engine starting torque Tg by the first electric motor MG1 is changed to a torque Tgs, and torque support is provided until the engine rotation speed Ne stabilizes. Then, at time t3 when the engine 20 has completed ignition and the engine rotation speed Ne has stabilized, the mode is switched to Mode 2.

[0080] FIG. 19 is a time chart for explaining the control operation when the inertia canceling torque T2r1 in the time chart of FIG. 18 is set to the engine start acceleration torque T2r2, that is, when S50 in FIG. 17 is carried out.

[0081] First, as in the case of FIG. 18 , at time t0, the vehicle starts traveling in drive mode Mode1_MG3. Next, at time t1, the vehicle speed V reaches the target vehicle speed V1 for switching to Mode2, and motoring of the engine 20 is started to switch to Mode2. The first electric motor MG1 generates an engine starting torque Tg for motoring, and the second electric motor MG2 generates an engine starting acceleration torque T2r2 that is greater than the inertia cancellation torque T2r1 that cancels out the inertia torque I2×dω2 / dt generated in the sun gear S. At the same time, the third electric motor MG3 generates a vehicle acceleration cancellation torque ΔTm3 that cancels out the fluctuation torque RTb (I2×dω2 / dt−T2r2) generated by the engine starting acceleration torque T2r2. FIG. 19 shows the generation of torque Tm3c, which is the traveling torque Tm3s plus the vehicle acceleration cancellation torque ΔTm3. Next, at time t2, the engine rotation speed Ne reaches the startable rotation speed Ne1, fuel injection and ignition are performed, and the generation of the engine start acceleration torque T2r2 by the second electric motor MG2 and the vehicle acceleration offset torque ΔTm3 by the third electric motor MG3 are stopped. Furthermore, the engine start torque Tg by the first electric motor MG1 is changed to torque Tgs, and torque support is provided until the engine rotation speed Ne stabilizes. Then, at time t3, when the engine 20 has completed ignition and the engine rotation speed Ne has stabilized, the operation mode is switched to Mode 2.

[0082] As described above, according to this embodiment, the differential mechanism 32 has three rotating elements: the first rotating element RE1, the second rotating element RE2, and the third rotating element RE3. The engine 20 and the first electric motor MG1 are connected to the first rotating element RE1, the second electric motor MG2 is connected to the second rotating element RE2, and the front drive shaft 38 is connected to the third rotating element RE3. The third electric motor MG3 is also connected to the rear drive shaft 58. This allows for so-called series running, in which the first electric motor MG1, which is connected to the same rotating elements as the engine 20, is operated as a generator, and the third electric motor MG3 is operated as a prime mover using the generated power to drive the rear drive shaft 58. In series running, torque vibrations of the engine 20 are prevented from being transmitted to the front drive shaft 38, thereby reducing the likelihood of the vehicle body vibrating when the vehicle 8 is running with the engine 20 running. Furthermore, when starting the engine while the vehicle 8 is traveling, the electronic control device 70 is configured to cause the first electric motor MG1 to generate an engine starting torque Tg, and to cause the second electric motor MG2 to generate a torque T2r in a direction that resists the inertia torque I2×dω2 / dt that is generated in the second rotating element RE2 (sun gear S) due to a change in rotation speed. As a result, when starting the engine while the vehicle 8 is traveling, in addition to causing the first electric motor MG1 to generate the engine starting torque Tg, the second electric motor MG2 can generate the torque T2r that resists the inertia torque I2×dω2 / dt. This makes it possible to prevent the startability of the engine 20 from being deteriorated by the inertia torque I2×dω2 / dt that is generated in the second rotating element RE2, and enables the engine 20 to be started appropriately while the vehicle 8 is traveling.

[0083] Furthermore, according to this embodiment, when starting the engine while the vehicle is running, the electronic control device 70 is configured to cause the second electric motor MG2 to generate an inertia cancellation torque T2r1 that cancels out the inertia torque I2×dω2 / dt, thereby enabling the engine starting torque Tg of the first electric motor MG1 to be used for engine starting without being reduced.

[0084] Furthermore, according to this embodiment, when starting the engine while the vehicle is traveling, the electronic control device 70 causes the second electric motor MG2 to generate an engine start acceleration torque T2r2 that is oriented in a direction that resists the inertia torque I2×dω2 / dt and is greater than the inertia torque I2×dω2 / dt. As a result, the torque that starts the engine 20 can be increased by the engine start acceleration torque T2r2 generated by the second electric motor MG2, and the startability of the engine 20 can be improved.

[0085] Furthermore, according to this embodiment, when starting the engine while the vehicle is traveling, the electronic control device 70 causes the third electric motor MG3 to generate a vehicle acceleration cancellation torque ΔTm3 that cancels out the fluctuation torque RTb (I2×dω2 / dt−T2r2) that is generated on the front drive shaft 38 by the engine start acceleration torque T2r2. This makes it possible to suppress acceleration of the vehicle 8 that is caused by the engine start acceleration torque T2r2 generated by the second electric motor MG2. [Example]

[0086] 20 is a diagram illustrating a schematic configuration of a vehicle 300 equipped with a vehicle drive system 310 (including a front drive unit 310f and a rear drive unit 310r) to which the present invention is applied. In FIG. 20, a front power transmission device 330 of the front drive unit 310f includes a differential mechanism 332. The differential mechanism 332 and a front differential gear 36 are connected via a front counter gear 34, similar to the front power transmission device 30 of the first embodiment described above.

[0087] The differential mechanism 332 is a single-pinion planetary gear device having a sun gear S, a pinion P, a carrier C, and a ring gear R. A second electric motor MG2 is connected to the sun gear S. The engine 20 and a first electric motor MG1 are connected to the carrier C. The first electric motor MG1 is connected to the carrier C via a power transmission member 40. The ring gear R is in mesh with a front counter gear 34. A front drive shaft 38 is connected to the ring gear R. One end of a brake BR is connected to the output shaft of the engine 20 or the carrier C, and the other end is connected to a non-rotating member (not shown) such as a case.

[0088] FIG. 21 is a nomographic diagram illustrating the configuration of the vehicle drive device 310. In FIG. 21, the differential mechanism 332 of the front drive unit 310f has three rotating elements: a first rotating element RE1, a second rotating element RE2, and a third rotating element RE3. Each of the rotating elements RE1-RE3 of the differential mechanism 332 is coupled to an actuator. Expressed using the nomographic diagram, the first rotating element RE1 is the carrier C. The engine 20 and the first electric motor MG1 are coupled to the first rotating element RE1. The second rotating element RE2 is the sun gear S. The second rotating element RE2 is coupled to the second electric motor MG2. The third rotating element RE3 is the ring gear R. The front drive shaft 38, i.e., the front wheels 12f, are coupled to the third rotating element RE3. The brake BR is a brake mechanism that stops rotation of the first rotating element RE1 when engaged. The rear drive unit 310r is the same as the rear drive unit 10r in the first embodiment described above, and therefore a description thereof will be omitted.

[0089] Similar to the vehicle driving device 10 of the first embodiment, the vehicle driving device 310 is capable of switching between a plurality of driving modes by controlling the engine 20, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 by the electronic control device 70. Furthermore, when switching between driving modes, the vehicle driving device 310 is controlled by the electronic control device 70 to engage the brake BR as necessary.

[0090] In the differential mechanism 332, the rotational speed of the third rotating element RE3, which is the output element, is set to the speed-increasing side, or overdrive (O / D) side, relative to the engine rotational speed Ne at the mechanical point. That is, in the differential mechanism 332, the mechanical point is set by the speed-increasing ratio. Therefore, in the vehicle drive device 310, Mode 3 is the O / D input split mode, and Mode 4 is the O / D output split mode.

[0091] Figure 22 is a nomographic diagram that explains the operation of each rotating element when a torque that resists the inertia torque I2×dω2 / dt is generated in the second electric motor MG2 during engine start control performed by the electronic control device 70, and Figure 23 is a nomographic diagram that explains the operation of each rotating element when an engine start acceleration torque greater than the inertia torque I2×dω2 / dt is generated in the second electric motor MG2.

[0092] As shown in Figures 22 and 23, in this embodiment, the directions of the inertia torque I2×dω2 / dt, torque T2r, inertia-cancelling torque T2r1, engine start acceleration torque T2r2, fluctuation torque RTb (I2×dω2 / dt-T2r2), and vehicle acceleration-cancelling torque ΔTm3 are reversed compared to Figures 15 and 16 of the first embodiment. However, even in this embodiment, the torque T2r, inertia-cancelling torque T2r1, engine start acceleration torque T2r2, etc. are generated by the second electric motor MG2, thereby suppressing or increasing torque loss for engine start. Furthermore, preferably, when the engine start acceleration torque T2r2 is generated, the vehicle acceleration-cancelling torque ΔTm3 is generated by the third electric motor MG3, thereby suppressing acceleration of the vehicle 300.

[0093] 17 of the first embodiment can be similarly implemented in this embodiment. The time charts shown in Fig. 18 and Fig. 19 of the first embodiment can also be similarly implemented in this embodiment by reversing the directions of the torques described above.

[0094] As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained. [Example]

[0095] 24 is a diagram illustrating a schematic configuration of a vehicle 400 equipped with a vehicle drive system 410 (including a front drive unit 410f and a rear drive unit 410r) to which the present invention is applied. In FIG. 24, a front power transmission device 430 of the front drive unit 410f includes a differential mechanism 432. The differential mechanism 432 and the front differential gear 36 are connected via the front counter gear 34, similar to the front power transmission device 30 of the first embodiment described above.

[0096] The differential mechanism 432 is a double-pinion planetary gear device having a sun gear S, pinions Pa and Pb, a carrier C, and a ring gear R. The pinions Pa and Pb are pairs of pinions that mesh with each other. A second electric motor MG2 is connected to the sun gear S. The engine 20 and a first electric motor MG1 are connected to the carrier C. The first electric motor MG1 is connected to the carrier C via a power transmission member 40. The ring gear R meshes with the front counter gear 34. A front drive shaft 38 is connected to the ring gear R. One end of the brake BR is connected to the output shaft of the engine 20 or the carrier C, and the other end is connected to a non-rotating member (not shown) such as a case.

[0097] FIG. 25 is a nomographic diagram illustrating the configuration of the vehicle drive device 410. In FIG. 25, the differential mechanism 432 of the front drive unit 410f has three rotating elements: a first rotating element RE1, a second rotating element RE2, and a third rotating element RE3. Each of the rotating elements RE1-RE3 of the differential mechanism 432 is coupled to an actuator. Expressed using the nomographic diagram, the first rotating element RE1 is the carrier C. The engine 20 and the first electric motor MG1 are coupled to the first rotating element RE1. The second rotating element RE2 is the sun gear S. The second rotating element RE2 is coupled to the second electric motor MG2. The third rotating element RE3 is the ring gear R. The front drive shaft 38, i.e., the front wheel 12f, is coupled to the third rotating element RE3. The brake BR is a brake mechanism that stops rotation of the first rotating element RE1 when engaged. The rear drive unit 410r is the same as the rear drive unit 10r in the first embodiment described above, and therefore a description thereof will be omitted.

[0098] Similar to the vehicle driving device 10 of the first embodiment, the vehicle driving device 410 is capable of switching between a plurality of driving modes by controlling the engine 20, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 by the electronic control device 70. Furthermore, when switching between driving modes, the vehicle driving device 410 is controlled by the electronic control device 70 to engage the brake BR as necessary.

[0099] In differential mechanism 432, the rotational speed of third rotating element RE3, which is the output element, is on the deceleration side, i.e., underdrive (U / D) side, relative to engine rotational speed Ne at the mechanical point. That is, in differential mechanism 432, the mechanical point is set by the reduction ratio. Therefore, in vehicle drive device 410, Mode 3 is U / D input split mode, and Mode 4 is U / D output split mode.

[0100] Figure 26 is a nomographic diagram that explains the operation of each rotating element when the electronic control device 70 controls engine start-up while driving, and when the second electric motor MG2 generates a torque that resists the inertia torque I2×dω2 / dt. Figure 27 is a nomographic diagram that explains the operation of each rotating element when the second electric motor MG2 generates an engine start-up acceleration torque that is greater than the inertia torque I2×dω2 / dt.

[0101] As shown in FIGS. 26 and 27 , in this embodiment, unlike the first embodiment, the first rotating element RE1 changes from the ring gear R to the carrier C, and the third rotating element RE3 changes from the carrier C to the ring gear R. However, as in the first embodiment, the torque T2r, the inertia cancellation torque T2r1, the engine start acceleration torque T2r2, etc. are generated by the second electric motor MG2, thereby suppressing or increasing the torque decrease required for starting the engine. Preferably, when the engine start acceleration torque T2r2 is generated, the vehicle acceleration cancellation torque ΔTm3 is generated by the third electric motor MG3, thereby suppressing the generation of acceleration in the vehicle 400. That is, in this embodiment, the first rotating element RE1 is changed to the carrier C and the third rotating element RE3 is changed to the ring gear R, and thus the same control operation as in the first embodiment is performed.

[0102] As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained. [Example]

[0103] 28 is a diagram illustrating a schematic configuration of a vehicle 500 equipped with a vehicle drive device 510 (including a front drive unit 510f and a rear drive unit 510r) to which the present invention is applied. In FIG. 28, a front power transmission device 530 of the front drive unit 510f includes a differential mechanism 532. The differential mechanism 532 and the front differential gear 36 are connected via the front counter gear 34, similar to the front power transmission device 30 of the first embodiment described above.

[0104] The differential mechanism 532 is a double-pinion planetary gear device having a sun gear S, pinions Pa and Pb, a carrier C, and a ring gear R. A second electric motor MG2 is connected to the sun gear S. An engine 20 and a first electric motor MG1 are connected to the ring gear R. The first electric motor MG1 is connected to the ring gear R via a power transmission member 40. The carrier C is in mesh with the front counter gear 34. A front drive shaft 38 is connected to the carrier C. One end of the brake BR is connected to the ring gear R, and the other end is connected to a non-rotating member (not shown) such as a case.

[0105] FIG. 29 is a diagram illustrating the configuration of a vehicle drive device 510 using a collinear diagram. In FIG. 29, a differential mechanism 532 of a front drive unit 510f has three rotating elements: a first rotating element RE1, a second rotating element RE2, and a third rotating element RE3. Each of the rotating elements RE1-RE3 of the differential mechanism 532 is coupled to an actuator. Expressed using the collinear diagram, the first rotating element RE1 is a ring gear R. The engine 20 and a first electric motor MG1 are coupled to the first rotating element RE1. The second rotating element RE2 is a sun gear S. The second rotating element RE2 is coupled to a second electric motor MG2. The third rotating element RE3 is a carrier C. The front drive shaft 38, i.e., the front wheel 12f, is coupled to the third rotating element RE3. The brake BR is a brake mechanism that stops rotation of the first rotating element RE1 when engaged. The rear drive unit 510r is the same as the rear drive unit 10r in the first embodiment described above, and therefore a description thereof will be omitted.

[0106] Similar to the vehicle driving device 10 of the first embodiment, the vehicle driving device 510 is capable of switching between a plurality of driving modes by controlling the engine 20, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 by the electronic control device 70. Furthermore, when switching between driving modes, the vehicle driving device 510 is controlled by the electronic control device 70 to engage the brake BR as necessary.

[0107] In differential mechanism 532, the rotational speed of third rotating element RE3, which is the output element, is on the speed-increasing side, or overdrive (O / D) side, relative to engine rotational speed Ne at a mechanical point. That is, in differential mechanism 532, the mechanical point is set by a speed-increasing ratio. Therefore, in vehicle drive device 510, Mode 3 is an O / D input split mode, and Mode 4 is an O / D output split mode.

[0108] Figure 30 is a nomographic diagram that explains the operation of each rotating element when a torque that resists the inertia torque I2×dω2 / dt is generated in the second electric motor MG2 during engine start control while the electronic control device 70 is in motion, and Figure 31 is a nomographic diagram that explains the operation of each rotating element when an engine start acceleration torque greater than the inertia torque I2×dω2 / dt is generated in the second electric motor MG2.

[0109] As shown in FIGS. 30 and 31 , in this embodiment, unlike the second embodiment, the first rotating element RE1 changes from a carrier C to a ring gear R, and the third rotating element RE3 changes from a ring gear to a carrier C. However, as in the second embodiment, torque T2r, inertia cancellation torque T2r1, engine start acceleration torque T2r2, and the like are generated by the second electric motor MG2, thereby suppressing or increasing torque loss for engine start. Preferably, when engine start acceleration torque T2r2 is generated, vehicle acceleration cancellation torque ΔTm3 is generated by the third electric motor MG3, thereby suppressing acceleration of the vehicle 500. That is, in this embodiment, by changing the first rotating element RE1 to a ring gear R and the third rotating element RE3 to a carrier C, control operations similar to those in the second embodiment are performed.

[0110] As described above, according to this embodiment, the same effects as those of the second embodiment, ie, the first embodiment, can be obtained.

[0111] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0112] For example, in the differential mechanism 32 of the first embodiment described above, the first rotating element RE1 may be one of the ring gear R and the sun gear S, and the second rotating element RE2 may be the other of the ring gear R and the sun gear S. When the first rotating element RE1 is the sun gear S and the second rotating element RE2 is the ring gear R, the engine 20 and the first electric motor MG1 are connected to the sun gear S, and the second electric motor MG2 is connected to the ring gear R.

[0113] In the differential mechanism 332 of the second embodiment described above, the second rotating element RE2 may be one of the sun gear S and the ring gear R, and the third rotating element RE3 may be the other of the sun gear S and the ring gear R. When the second rotating element RE2 is the ring gear R and the third rotating element RE3 is the sun gear S, the second electric motor MG2 is connected to the ring gear R, and the front drive shaft 38 is connected to the sun gear S.

[0114] In the differential mechanism 432 of the third embodiment described above, the first rotating element RE1 may be one of the carrier C and the sun gear S, and the second rotating element RE2 may be the other of the carrier C and the sun gear S. When the first rotating element RE1 is the sun gear S and the second rotating element RE2 is the carrier C, the engine 20 and the first electric motor MG1 are connected to the sun gear S, and the second electric motor MG2 is connected to the carrier C.

[0115] In the differential mechanism 532 of the fourth embodiment described above, the second rotating element RE2 may be one of the sun gear S and the carrier C, and the third rotating element RE3 may be the other of the sun gear S and the carrier C. When the second rotating element RE2 is the carrier C and the third rotating element RE3 is the sun gear S, the second electric motor MG2 is connected to the carrier C, and the front drive shaft 38 is connected to the sun gear S.

[0116] Here, as shown in the above-mentioned Examples 1-4, the second rotating element RE2 is a rotating element that is arranged at either end of a nomographic diagram in which the three rotating elements of the differential mechanism are arranged in a straight line.

[0117] In the above-described Examples 1-4, the power transmission member 40 may be, for example, a chain and sprocket, or a gear pair. For example, when the power transmission member 40 is a gear pair, the intermediate gear 40a and the first rotating element RE1 are connected via a counter gear that meshes with both of them.

[0118] In addition, in the above-described Examples 1 to 4, the first electric motor MG1 may be disposed on the same rotational axis as the engine 20 and the second electric motor MG2. In other words, the first electric motor MG1 may be disposed on the first axis CS1, which is the rotational axis of the differential mechanism 32.

[0119] In addition, in the above-described embodiments 1-4, a one-way clutch may be used as the brake mechanism for stopping the rotation of the first rotating element RE1 instead of the brake BR.

[0120] In addition, in the above-described Examples 1-4, the brake BR does not necessarily have to be provided. In this case, mode 1_MG2_BRon of mode 1 is not executed. As described above, in mode 1_MG3, BEV driving is possible even if the brake BR is not engaged, and therefore mode 1_MG3 can be executed even if the brake BR is not provided.

[0121] In addition, in the above-described Examples 1-4, the first drive wheels to which the power of the engine 20 and the second electric motor MG2 is transmitted may be the rear wheels 12r, and the second drive wheels to which the power of the third electric motor MG3 is transmitted may be the front wheels 12f.

[0122] Furthermore, in the above-mentioned Examples 1-4, since it is expected that BEV driving using Mode 1_MG3 will be frequently used in a PHEV, a drive unit equipped with the third electric motor MG3 is used as the main engine, but in an HEV, a drive unit equipped with the engine 20 or the second electric motor MG2 may be used as the main engine.

[0123] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0124] 8: Vehicle 10: Vehicle drive unit 12f: Front wheels (first drive wheels) 12r: Rear wheels (second drive wheels) 20: Engine 32: Differential mechanism S: Sun gear (second rotating element) C: Carrier (third rotating element) R: Ring gear (first rotating element) 38: Front drive shaft (first drive shaft) 58: Rear drive shaft (second drive shaft) 70: Electronic control unit (control unit) 300: Vehicle 310: Vehicle drive unit 332: Differential mechanism S: Sun gear (second rotating element) C: Carrier (first rotating element) R: Ring gear (third rotating element) 400: Vehicle 410: Vehicle drive unit 432: Differential mechanism S: Sun gear (second rotating element) C: Carrier (first rotating element) R: Ring gear (third rotating element) 500: Vehicle 510: Vehicle drive unit 532: Differential mechanism S: Sun gear (second rotating element) C: Carrier (third rotating element) R: Ring gear (first rotating element) MG1: First electric motor MG2: Second electric motor MG3: Third electric motor I2×dω2 / dt: Inertia torque T2r: Torque (torque that resists inertia torque) T2r1: Inertia cancellation torque (torque that cancels out inertia torque) T2r2: Engine starting acceleration torque ΔTm3: Vehicle acceleration cancellation torque (torque that cancels out torque fluctuations that occur in the first drive shaft) RE1: First rotating element RE2: Second rotating element RE3: Third rotating element RTb(I2×dω2 / dt-T2r2): Fluctuation torque

Claims

1. A vehicle drive device including an engine, a first electric motor, a second electric motor, a third electric motor, a differential mechanism, a first drive shaft that drives one of front wheels and rear wheels, a second drive shaft that drives the other of the front wheels and the rear wheels, and a control device, the differential mechanism has three rotation elements: a first rotation element, a second rotation element, and a third rotation element; the engine and the first electric motor are connected to the first rotating element, the second electric motor is connected to the second rotating element, and the first drive shaft is connected to the third rotating element, The third electric motor is connected to the second drive shaft, The control device is configured to, when starting the engine while the vehicle is running, cause the first electric motor to generate an engine starting torque, and cause the second electric motor to generate a torque in a direction that resists an inertia torque generated in the second rotating element due to a change in rotation speed. A vehicle drive device characterized by:

2. The control device is configured to cause the second electric motor to generate a torque that offsets the inertia torque when starting the engine during traveling.

2. The vehicle drive system according to claim 1.

3. The control device is configured to, when starting the engine during traveling, cause the second electric motor to generate an engine start acceleration torque that is oriented in a direction that resists the inertia torque and is greater than the inertia torque.

2. The vehicle drive system according to claim 1.

4. The control device is further configured to, when starting the engine during traveling, cause the third electric motor to generate torque that offsets a fluctuating torque generated in the first drive shaft by the engine start acceleration torque.

4. The vehicle drive system according to claim 3.

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