Vehicle drive systems

Abstract

The present invention provides a vehicle drive system that can suppress an increase in the size of the drive unit while suppressing an increase in the cost of the electric motor, when viewed in the direction of the rotation axis of the input and output shafts of the drive unit. [Solution] (a) The engine 12, first electric motor MG1, second electric motor MG2, and front drive shaft 28 are connected to the carrier CA, sun gear S, and ring gear R of the planetary gear system 40, respectively; (b) The second electric motor MG2 is positioned on the first axis C1 on the opposite side from the engine 12 as viewed from the planetary gear system 40; (c) The front drive shaft 28 is connected to the carrier CA via the output shaft 46 and gear pair 44 on the second axis C2; (d) The first electric motor MG1 is positioned on the third axis C3 on the engine 12 side as viewed from the planetary gear system 40 and is connected to the carrier CA via gear pair 54; (e) In view of the first axis C1, the second axis C2 is in a position that overlaps with the first electric motor MG1.

Description

Technical Field

[0001] The present invention relates to a vehicle drive device including an engine, a drive unit including a first electric motor, a second electric motor, and a planetary gear device having three rotating elements, and a drive shaft for driving one of a front wheel and a rear wheel.

Background Art

[0002] A vehicle drive device including an engine and a drive unit including an electric motor MG1, an electric motor MG2, and a differential mechanism having three rotating elements is known. For example, the vehicle drive device described in Patent Document 1 is such a device. For example, in such a vehicle drive device, when the engine is arranged longitudinally, generally, the differential mechanism is a planetary gear device as disclosed in Patent Document 1. Then, by arranging the electric motor MG1, the electric motor MG2, and the planetary gear device coaxially, the size of the drive unit in the direction of the rotation axis center of the input / output shaft of the drive unit is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when arranging the electric motor MG1, the electric motor MG2, and the planetary gear device coaxially, it is necessary to insert another rotating shaft inside the rotating shaft connecting the electric motor MG1 and the planetary gear device and inside the rotating shaft connecting the electric motor MG2 and the planetary gear device. As a result, there is a problem that the size of the electric motor MG1 and the electric motor MG2 increases and the cost of the electric motor increases. Therefore, it is desired to suppress an increase in the size of the drive unit in the direction of the rotation axis center of the input / output shaft of the drive unit and to suppress an increase in the cost of the electric motor due to an increase in the size of the electric motor.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle drive system that can suppress an increase in the size of the drive unit when viewed in the direction of the rotation axis of the input and output shafts of the drive unit, while suppressing an increase in the cost of the electric motor. [Means for solving the problem]

[0006] The gist of the present invention is a vehicle drive system comprising an engine, a first drive unit including a first electric motor, a second electric motor, and a planetary gear system having three rotating elements, and a first drive shaft that drives either the front wheel or the rear wheel, wherein (a) the planetary gear system has three rotating elements, a first rotating element, a second rotating element, and a third rotating element, and functions as a differential mechanism, (b) 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, and (c) the second electric motor is located on the first axis, which is the rotation axis of the planetary gear system, as seen from the planetary gear system. (d) The first drive shaft is connected to the third rotating element without passing through the inside of the connecting shaft that connects the second motor and the second rotating element, via an output shaft having a second axis parallel to the first axis as its rotation axis and a first power transmission mechanism that transmits power between the output shaft and the third rotating element, (e) the first motor is located on the third axis parallel to the first axis, on the engine side as seen from the planetary gear system, and is connected to the first rotating element via the second power transmission mechanism, and (f) in view in the direction of the first axis, the second axis is in a position that overlaps with the first motor. [Effects of the Invention]

[0007] According to the vehicle drive system of the present invention, (a) the planetary gear system has three rotating elements, a first rotating element, a second rotating element, and a third rotating element, and functions as a differential mechanism; (b) 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; (c) the second electric motor is positioned on the first axis, which is the rotation axis of the planetary gear system, on the opposite side from the engine as seen from the planetary gear system; and (d) the second axis, which is parallel to the first axis, is the rotation axis. (e) The first drive shaft is connected to the third rotating element via an output shaft and a first power transmission mechanism that transmits power between the output shaft and the third rotating element, without passing through the inside of the connecting shaft that connects the second motor and the second rotating element; (f) In view of the first axis, the second axis is in a position that overlaps with the first motor. This suppresses an increase in the size of the first drive unit in view of the first axis, while also suppressing an increase in the size of the first and second motors and the resulting increase in the cost of the first and second motors. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the schematic configuration of a vehicle equipped with a vehicle drive system according to Example 1. [Figure 2] This is a collinear diagram explaining the BEV_MG3 mode. [Figure 3] This is a collinear diagram illustrating the series mode. [Figure 4] This is a collinear diagram illustrating the input split mode. [Figure 5] This is a collinear diagram illustrating the output split mode. [Figure 6] This diagram illustrates the schematic configuration of a vehicle equipped with a vehicle drive system according to Embodiment 2. [Figure 7]This is a collinear diagram illustrating the input split mode. [Modes for carrying out the invention]

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. Unless otherwise specified, the drawings in each embodiment have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0010] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 90 equipped with a vehicle drive unit 10 according to Embodiment 1.

[0011] Vehicle 90 is a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV). Furthermore, vehicle 90 is an all-wheel-drive vehicle capable of independently driving the left and right front wheels 14f and the left and right rear wheels 14r. All-wheel drive (AWD) and four-wheel drive (4WD) are synonymous. Note that "left and right" above refers to the left and right sides of vehicle 90 in the forward direction. Hereafter, "left and right front wheels 14f" and "left and right rear wheels 14r" will be simply referred to as "front wheels 14f" and "rear wheels 14r," respectively.

[0012] The vehicle 90 comprises an engine 12, wheels 14 including front wheels 14f and rear wheels 14r, a first power transmission path between the engine 12 and the front wheels 14f, and a second power transmission path between the engine 12 and the rear wheels 14r. The vehicle 90 also includes an inverter 70, a battery 72, and an electronic control unit 80.

[0013] The engine 12 is a power source for driving and is a well-known internal combustion engine. The engine torque Te [N·m], which is the output torque of the engine 12, is controlled by the electronic control unit 80. In this specification, unless otherwise specified, torque, driving force, power, and force (=power) are synonymous. In two-wheel drive driving (=2WD driving), either the front wheels 14f or the rear wheels 14r are the drive wheels. In four-wheel drive driving (=4WD driving), both the front wheels 14f and the rear wheels 14r are the drive wheels.

[0014] The first power transmission path includes, in order from the engine 12 side, a front drive unit 20, a transfer case 22, a front propeller shaft 24, a front differential gear 26, and left and right front drive shafts 28, and the configuration is well known except for the front drive unit 20. Hereinafter, the left and right front drive shafts 28 will be simply referred to as "front drive shafts 28". The transfer case 22 is a front and rear wheel power distribution device capable of distributing the input power to the front wheels 14f and rear wheels 14r. The front drive unit 20 is a unit that drives at least the front wheel 14f of the front wheel 14f and rear wheel 14r, and corresponds to the "first drive unit" in the present invention. The front drive shafts 28 correspond to the "first drive shaft" in the present invention.

[0015] The front drive unit 20 includes a first motor MG1, a second motor MG2, and a planetary gear system 40 having three rotating elements. The first motor MG1 and the second motor MG2 are rotating electric machines, so-called motor generators, that have the functions of a prime mover and a generator, respectively, and are, for example, three-phase synchronous motors. The configuration of the front drive unit 20 will be described later.

[0016] The second power transmission path includes, in order from the engine 12 side, a front drive unit 20, a transfer case 22, a rear propeller shaft 30 that transmits power distributed by the transfer case 22 to the rear wheels 14r in the front-to-rear wheel distribution mode described later, an electronically controlled coupling device 32, a transmission shaft 34, a rear differential gear 36, and left and right rear drive shafts 38, all of which are well-known components. A third electric motor MG3 is connected to the transmission shaft 34. The third electric motor MG3 is a rotating electric machine, a so-called motor generator, that has both prime mover and generator functions, and is, for example, a three-phase synchronous motor. Hereinafter, the left and right rear drive shafts 38 will simply be referred to as "rear drive shafts 38". The electronically controlled coupling device 32 can adjust the torque transmitted from the transfer case 22 to the rear differential gear 36 by controlling its transmission torque capacity (also called the fastening torque). The transmission shaft 34 and the third electric motor MG3 constitute the rear drive unit 60. The configuration of the rear drive unit 60 will be described later. The rear drive unit 60 is a unit that drives the rear wheel 14r of the front wheel 14f and rear wheel 14r, and corresponds to the "second drive unit" in the present invention. The rear drive shaft 38 corresponds to the "second drive shaft" in the present invention.

[0017] The inverter 70 is a well-known power circuit that converts direct current to alternating current or alternating current to direct current. The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each connected to the battery 72 via the inverter 70. The torque of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 is controlled by the inverter 70 being controlled by an electronic control unit 80 described later. The output torque of the first electric motor MG1 is the first electric motor torque Tmg1 [N·m], the output torque of the second electric motor MG2 is the second electric motor torque Tmg2 [N·m], and the output torque of the third electric motor MG3 is the third electric motor torque Tmg3 [N·m]. The torque of the electric motor becomes a driving torque when the electric motor functions as a prime mover, and becomes a regenerative torque when the electric motor functions as a generator. The battery 72 is a power storage device that exchanges power with each of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3. For example, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are controlled so that power is exchanged simultaneously via the inverter 70. "Simultaneously" means, for example, in a state where each of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 can independently perform driving or regeneration at the same time.

[0018] As described above, the vehicle drive device 10 includes the engine 12, the front drive unit 20, the front drive shaft 28, the rear drive unit 60, and the rear drive shaft 38. The vehicle drive device 10 is capable of front-wheel drive that transmits torque only to the front wheels 14f and rear-wheel drive that transmits torque only to the rear wheels 14r.

[0019] In the front drive unit 20, the planetary gear device 40 and the second electric motor MG2 are arranged coaxially, and their rotation axes are the first axis C1. Both the first electric motor MG1 and the second electric motor MG2 are supported by the case 18. The case 18 is a non-rotating member, for example, a case that houses the front drive unit 20 and the like.

[0020] In the direction of the first axis C1, the second electric motor MG2 is positioned on the opposite side from the engine 12 when viewed from the planetary gear set 40. The planetary gear set 40 is a well-known double pinion type having a sun gear S, a carrier CA, and a ring gear R. The engine 12 is connected to the carrier CA via the engine connecting shaft 50, and the first electric motor MG1 is connected to it via a gear pair 54, as will be described later. The engine connecting shaft 50 is the input shaft from the engine 12 to the front drive unit 20. The second electric motor MG2 is connected to the sun gear S. The transfer case 22 is connected to the ring gear R via a gear pair 44 and an output shaft 46. The gear pair 44 consists of a gear 44a that meshes with each other and is not rotatable relative to the ring gear R, and a gear 44b that is fixed to the output shaft 46 and not rotatable relative to it. The output shaft 46 is the output shaft from the front drive unit 20 to the transfer case 22. The rotational axis of the output shaft 46 is the second axis C2, which is parallel to the first axis C1. In this way, the front drive shaft 28 is connected to the ring gear R via the output shaft 46, which has the second axis C2 as its rotational axis, and the gear pair 44, without passing through the inside of the rotor shaft MG2r of the second motor MG2, which connects the second motor MG2 and the sun gear S. The gear pair 44 corresponds to the "first power transmission mechanism" in this invention. The rotor shaft MG2r is the rotational shaft that connects the second motor MG2 and the sun gear S, and corresponds to the "connecting shaft" in this invention.

[0021] The carrier CA, sun gear S, and ring gear R correspond to the "first rotating element RE1," "second rotating element RE2," and "third rotating element RE3" in the present invention, respectively. The planetary gear system 40 functions as a differential mechanism that puts the carrier CA, sun gear S, and ring gear R into a differential state. For example, the planetary gear system 40 mechanically divides the power input to the carrier CA between the sun gear S and the ring gear R.

[0022] For example, the second motor MG2 is rotationally driven by the power divided amongst itself by the planetary gear system 40. The second motor MG2 generates electricity using the power divided amongst itself. The planetary gear system 40 functions as an electrically operated continuously variable transmission, in which the differential state of the planetary gear system 40 is controlled by controlling the operating state of the second motor MG2. The electricity generated by the second motor MG2 is used to charge the battery 72 or to drive the first motor MG1 and the third motor MG3.

[0023] The first electric motor MG1 is located on a third axis C3 parallel to the first axis C1, on the engine 12 side as viewed from the planetary gear set 40. Preferably, in the direction of the first axis C1, the first electric motor MG1 is located between the engine 12 and the planetary gear set 40. The first electric motor MG1 is connected to the carrier CA via a gear pair 54. The gear pair 54 consists of a gear 54a fixed to the engine connecting shaft 50 so as not to rotate relative to it, and a gear 54b fixed to the rotor shaft MG1r of the first electric motor MG1 so as not to rotate relative to it. The gear pair 54 corresponds to the "second power transmission mechanism" in the present invention.

[0024] For example, the gear pair 54 functions as a reduction mechanism that connects the first electric motor MG1 to the engine 12 in a way that allows power to be transmitted while reducing its rotational speed to that of the first electric motor MG1. When the first electric motor MG1 functions as a prime mover, the gear pair 54 reduces its rotational speed to that of the first electric motor Nmg1 [rpm], while the torque of the first electric motor Tmg1 is added to the engine torque Te. When the first electric motor MG1 functions as a generator, the gear pair 54 increases the rotational speed of the first electric motor Nmg1 to that of the engine rotational speed Ne [rpm], while the engine torque Te rotates the first electric motor MG1. The engine rotational speed Ne and the rotational speed Nmg1 are the rotational speed of the engine 12 and the rotational speed of the first electric motor MG1, respectively.

[0025] In a view in the direction of the first axis C1, the second axis C2 is in a position that overlaps with the first motor MG1. As a result, in the circumferential direction centered on the first axis C1, the gear pair 44, particularly the gear 44b, and the first motor MG1 overlap. Therefore, in a view in the direction of the first axis C1, the gear pair 44 and the first motor MG1 are in an overlapping position. Preferably, in the circumferential direction centered on the first axis C1, the second axis C2 and the third axis C3 are in the same direction. This maximizes the region in which the gear pair 44 and the first motor MG1 overlap in a view in the direction of the first axis C1.

[0026] The engine connecting shaft 50 is equipped with a brake BR. One end of the brake BR is connected to the engine connecting shaft 50, and the other end is connected to the case 18. The brake BR is an engagement device in which the members at both ends are selectively connected by an actuator, such as an electric or hydraulic actuator. The brake BR functions as a braking mechanism that selectively stops the rotation of the engine connecting shaft 50.

[0027] The rear drive unit 60 comprises a transmission shaft 34 and a third electric motor MG3. The third electric motor MG3 is supported, for example, by the vehicle body 62, which is a non-rotating member. When the transfer case 22 is in the front-wheel distribution mode described later, the rear drive unit 60 inputs the power of the third electric motor MG3 to the rear differential gear 36. When the transfer case 22 is in the front-to-rear wheel distribution mode described later, the rear drive unit 60 adds the power of the third electric motor MG3 to the power transmitted from the rear propeller shaft 30 to the transmission shaft 34 and inputs it to the rear differential gear 36.

[0028] For example, the rear drive unit 60 is the primary engine used for propulsion, with priority given to it over the front drive unit 20. In this case, the front drive unit 20 is considered a secondary engine.

[0029] Since the third electric motor MG3 of the rear drive unit 60 is connected to the rear wheel 14r, it can be considered to be connected to the front wheel 14f via the ground. By controlling the power of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 to be transmitted and received simultaneously, it is possible to drive as if the third electric motor MG3 were connected to the front wheel 14f.

[0030] The electronic control unit 80 is configured to include, for example, a so-called microcomputer, and performs various controls on the vehicle 90 by performing signal processing according to a pre-stored program.

[0031] The electronic control unit 80 receives various signals based on detection signals from various sensors and other devices installed in the vehicle 90. These signals include, for example, engine speed Ne, vehicle speed V [km / h], first motor rotation speed Nmg1, second motor rotation speed Nmg2 [rpm], third motor rotation speed Nmg3 [rpm], accelerator opening θacc [%], shift position POSop, and charge state value SOC [%]. The second motor rotation speed Nmg2 and third motor rotation speed Nmg3 are the rotation speeds of the second motor MG2 and the third motor MG3, respectively. The accelerator opening θacc is the amount of accelerator operation by the driver, representing the magnitude of the driver's acceleration operation. The shift position POSop is the lever position of a shift operation device (not shown), such as "P", "R", "N", or "D". The State of Charge (SOC) is the ratio of the actual amount of charge stored in the battery 72 to its predetermined full charge capacity, calculated based on factors such as the battery charge / discharge current and battery voltage.

[0032] The electronic control unit 80 outputs various control signals to each device of the vehicle 90 (engine 12, inverter 70, brake BR, transfer case 22, electronically controlled coupling device 32, etc.). These signals include an engine control signal Se that controls the operating state of the engine 12, first motor control signals Smg1, second motor control signals Smg2, and third motor control signals Smg3 that control the operating states of the first motor MG1 to the third motor MG3 via the inverter 70, respectively, a brake control signal Sbr that controls the disconnection state of the brake BR, a transfer control signal Str that selectively selects the distribution mode of the transfer case 22, and a torque control signal Sc that controls the transmission torque capacity of the electronically controlled coupling device 32. The transfer case 22 has two distribution modes: a front wheel distribution mode that distributes all the input power to the front wheels 14f, and a front and rear wheel distribution mode that distributes the input power to both the front wheels 14f and the rear wheels 14r.

[0033] The electronic control unit 80 is configured to switch the drive mode to one of several modes by controlling the engine 12, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3. When switching the drive mode, the electronic control unit 80 controls the brake BR to engage as needed. For example, the multiple drive modes include BEV_MG3 mode, series mode, input split mode, and output split mode.

[0034] Here, when the transfer case 22 is in front-wheel distribution mode, several modes for switching the drive mode of the vehicle 90 will be explained using Figures 2 to 5. Figures 2 to 5 are diagrams that relatively show the rotational speeds of each rotating element RE1 to RE3 of the planetary gear system 40. In these collinear diagrams, the vertical lines Y1 to Y3 represent the sun gear S, ring gear R, and carrier CA of the planetary gear system 40, respectively. In Figures 2 to 5, "ENG" represents the engine 12, "FrOUT" represents the front wheel 14f, and "RrOUT" represents the rear wheel 14r. Each arrow indicates the magnitude and direction of the torque. Solid arrows indicate the torque output from each actuator, and dashed arrows indicate the transmitted torque. In Figures 2 to 5, the rotational speeds (Nmg1, Nmg3) and torques (Tmg1, Tmg3) of the first motor MG1 and third motor MG3 are shown as converted values ​​for carrier CA and ring gear R, respectively.

[0035] Figure 2 is a collinear diagram illustrating the BEV_MG3 mode. The BEV_MG3 mode is a mode in which the brake BR is engaged, the engine 12 is stopped, and a positive torque third motor torque Tmg3 is output from the third motor MG3 to generate the driving force Fr[N] of the vehicle 90. "Positive torque" is a torque that acts in the same direction as the engine torque Te, which is the output torque of the engine 12 if the engine 12 were running, and is also a torque that acts in the direction that moves the vehicle 90 forward. "Negative torque" is a torque that acts in the opposite direction to positive torque. The BEV_MG3 mode is a mode for BEV (Battery Electric Vehicle) driving. In the BEV_MG3 mode, the first motor MG1 is in a non-driven state. "Non-driven state" means that it is not operating as either a prime mover or a generator. In the BEV_MG3 mode, the power balance between generated power and consumed power is not controlled, and the third motor MG3 is driven by power supplied from the battery 72.

[0036] Figure 3 is a collinear diagram illustrating the series mode. The series mode is a mode in which the brake BR is released, the engine 12 is running, and the third motor MG3 outputs a positive torque Tmg3 from the third motor MG3 due to the power generated by the first motor MG1. The series mode is a mode in which HEV (Hybrid Electric Vehicle) driving is possible, and it is a mode in which series driving with the engine 12 as the power source is possible. In the series mode, the first motor torque Tmg1 is a negative torque, the first motor MG1 is operated as a generator by the power of the engine 12, and the third motor MG3 is operated as the prime mover. In the series mode, the explosion vibration of the engine 12 is not transmitted to the front drive shaft 28, which is advantageous in terms of reducing booming noise, etc.

[0037] Figure 4 is a collinear diagram illustrating the input split mode. The input split mode is a mode in which the brake BR is released, the engine 12 is running, the first motor MG1 is not driven, and the third motor MG3 outputs a positive torque Tmg3 from the third motor MG3 due to the power generated by the second motor MG2. The input split mode is a mode in which hybrid driving is possible, and it is a mode in which input split driving with the engine 12 as the power source is possible. In the input split mode, the second motor MG2 rotates in the negative direction and the second motor torque Tmg2 is a positive torque, so the second motor MG2 is operated as a generator and the third motor MG3 is operated as a prime mover. The planetary gear set 40 is in a differential state, and the reaction force of the engine torque Te is taken by the second motor MG2, so that a positive torque is mechanically transmitted to the ring gear R. In addition, the power generated by the second motor MG2 is supplied to the third motor MG3, causing the third motor MG3 to output a positive torque Tmg3.

[0038] The dashed line A1 in Figure 4 indicates a state in the planetary gear system 40 where a mechanical point is formed in which no electrical work is performed by setting the rotational speed of the second rotating element RE2 (second motor rotational speed Nmg2) to zero and thereby setting the power of the second motor MG2 to zero. At this mechanical point, the planetary gear system 40 has the rotational speed of the output element, the third rotating element RE3, set to the reduction side, or underdrive (U / D), relative to the engine rotational speed Ne. In other words, the mechanical point of the planetary gear system 40 is set to a reduction ratio α (=Nre3 / Ne<1). Note that the rotational speed Nre3 [rpm] is the rotational speed of the third rotating element RE3.

[0039] Figure 5 is a collinear diagram illustrating the output split mode. The output split mode is a mode in which the brake BR is released, the engine 12 is running, and the states of the first motor MG1 and the second motor MG2 are controlled so that the power balance between the two is balanced. In the output split mode, one of the first motor MG1 and the second motor MG2 is operated as a prime mover, and the other is operated as a generator. The output split mode is a mode that enables hybrid driving, and is a mode that enables output split driving with the engine 12 as the power source. As shown in Figure 5(a), in the output split mode, when the second motor MG2 is rotating in the forward direction, the second motor torque Tmg2 is set to a positive torque so that the second motor MG2 operates as a prime mover, and the first motor torque Tmg1 is set to a negative torque so that the first motor MG1 operates as a generator. As shown in Figure 5(b), in output split mode, when the second motor MG2 is rotating in the negative direction, the second motor torque Tmg2 is set to a positive torque so that the second motor MG2 operates as a generator, and the first motor torque Tmg1 is set to a positive torque so that the first motor MG1 operates as a prime mover. The planetary gear set 40 is in a differential state, and the reaction force of the combined torque Tsum (=Te+Tmg1) of the engine torque Te and the first motor torque Tmg1 is taken by the second motor MG2, thereby mechanically transmitting torque to the ring gear R. The third motor MG3 is in a non-driven state.

[0040] As described above using Figures 3 to 5, there are several modes in which the drive mode of the vehicle 90 can be switched when the transfer case 22 is in front-wheel distribution mode. However, the vehicle 90 can also be switched to modes other than those described above. For example, in the above-mentioned modes, different modes can be created by setting the transfer case 22 to front-to-rear wheel distribution mode.

[0041] According to this embodiment, (a) the planetary gear system 40 has three rotating elements, a first rotating element RE1, a second rotating element RE2, and a third rotating element RE3, and functions as a differential mechanism; (b) the engine 12 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 28 is connected to the third rotating element RE3; (b) the second electric motor MG2 is positioned on the first axis C1, on the opposite side from the engine 12 as seen from the planetary gear system 40; and (c) the second axis C2 is parallel to the first axis C1. (d) The output shaft 46 has a rotation axis, and a gear pair 44 transmits power between the output shaft 46 and the third rotating element RE3. The front drive shaft 28 is connected to the third rotating element RE3 without passing through the inside of the rotor shaft MG2r via the gear pair 54. The first electric motor MG1 is located on the third axis C3, which is parallel to the first axis C1, on the engine 12 side as seen from the planetary gear system 40, and is connected to the first rotating element RE1 via the gear pair 54. In view in the direction of the first axis C1, the second axis C2 is in a position that overlaps with the first electric motor MG1. As a result, in view in the direction of the first axis C1, the gear pair 44 and the first electric motor MG1 are in a position that overlaps, so the size of the front drive unit 20 in view in the direction of the first axis C1 is suppressed. In addition, there is no need to insert another rotating shaft inside the rotor shaft MG1r or rotor shaft MG2r. Therefore, an increase in the cost of the first motor MG1 and the second motor MG2 due to their larger size is suppressed. Furthermore, since the first axis C1 and the second axis C2 are parallel to each other, the "view in the direction of the first axis C1" is the same as the view in the direction of the rotation axis of the engine connecting shaft 50, which is the input shaft of the front drive unit 20, and the output shaft 46, which is the output shaft, and is also the view in the direction of the rotation axis of the input and output shafts of the front drive unit 20.

[0042] In this embodiment, (a) the planetary gear unit 40 is of the double pinion type, and (b) the first rotating element RE1 is a carrier CA, the second rotating element RE2 is a sun gear S, and the third rotating element RE3 is a ring gear R. With this double pinion type planetary gear unit 40 connection configuration, the mechanical point can be set to a reduction ratio α.

[0043] In this embodiment, (a) a rear drive shaft 38 is provided, along with a rear drive unit 60 including a third electric motor MG3 connected to the rear drive shaft 38. With this configuration, for example, the drive modes of the vehicle 90 can include so-called series driving. Compared to the case where the rear drive unit 60 is not provided, a wider variety of drive modes can be realized when the rear drive unit 60 is provided. [Examples]

[0044] Figure 6 is a diagram illustrating the schematic configuration of the vehicle drive unit 110 according to Embodiment 2. The vehicle drive unit 110 is mounted on a vehicle 190. The vehicle 190 has substantially the same configuration as the vehicle 90 according to Embodiment 1 described above, but differs in that the front drive unit 20 is replaced by a front drive unit 120. Therefore, in this embodiment, the explanation will focus on the parts that differ from Embodiment 1, and parts that are substantially common in function with Embodiment 1 will be given the same reference numerals and their explanations will be omitted as appropriate.

[0045] The ring gear R is connected to the engine 12 via the engine connecting shaft 50, and the first electric motor MG1 is connected via the gear pair 54. The sun gear S is connected to the second electric motor MG2. The carrier CA is connected to the transfer case 22 via the gear pair 44 and the output shaft 46. Thus, in this embodiment, the connection relationship between the planetary gear system 40 and the engine 12 and the first electric motor MG1, the second electric motor MG2, and the transfer case 22 differs from that of Embodiment 1.

[0046] Figure 7 is a collinear diagram illustrating the input split mode. Figure 7 is a collinear diagram in this embodiment, corresponding to Figure 4(a) in Embodiment 1. The dashed line A2 in Figure 7 indicates the state in which a mechanical point is formed in the planetary gear unit 40. At this mechanical point, the rotational speed of the third rotating element RE3, which is an output element, is set to the overdrive (O / D) side relative to the engine rotational speed Ne. In other words, the mechanical point of the planetary gear unit 40 is set with a speed increase ratio β (=Nre3 / Ne>1).

[0047] According to this embodiment, by having the same configuration as in the aforementioned Embodiment 1, the effects based on that configuration are achieved in the same way.

[0048] In this embodiment, (a) the planetary gear system 40 is of the double pinion type, and (b) the first rotating element RE1 is a ring gear R, the second rotating element RE2 is a sun gear S, and the third rotating element RE3 is a carrier CA. With this double pinion type planetary gear system 40 connection configuration, the mechanical point can be set at a speed increase ratio β.

[0049] Although each embodiment of the present invention has been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0050] In the aforementioned embodiments 1 and 2, the output shaft 46 and the third rotating element RE3 were connected via a gear pair 44, and the first electric motor MG1 and the first rotating element RE1 were connected via a gear pair 54. However, the present invention is not limited to these embodiments. For example, the gear pair 44 and gear pair 54 may be replaced by a chain and sprocket. The replaced chain and sprocket correspond to the "first power transmission mechanism" and "second power transmission mechanism" in the present invention.

[0051] In the aforementioned embodiments 1 and 2, the system was equipped with a transfer case 22, a front propeller shaft 24, a rear propeller shaft 30, and an electronically controlled coupling device 32. However, the present invention is not limited to these embodiments. For example, the present invention is also applicable to embodiments in which these are not provided and the output shaft 46 is connected to the front differential gear 26.

[0052] In the aforementioned embodiments 1 and 2, the planetary gear system 40 was of the double-pinion type, but the present invention is not limited thereto. For example, the present invention is also applicable to embodiments in which the planetary gear system 40 is of the single-pinion type. When the planetary gear system 40 is of the single-pinion type, and the first rotating element RE1 is a ring gear R, the second rotating element RE2 is a sun gear S, and the third rotating element RE3 is a carrier CA, the mechanical point can be set with a reduction ratio α. When the planetary gear system 40 is of the single-pinion type, and the first rotating element RE1 is a carrier CA, the second rotating element RE2 is a sun gear S, and the third rotating element RE3 is a ring gear R, the mechanical point can be set with a speed increase ratio β.

[0053] In the aforementioned embodiments 1 and 2, a one-way clutch may be used instead of the brake BR to stop the rotation of the first rotating element RE1. Also, in the aforementioned embodiments 1 and 2, the brake BR is not necessarily required.

[0054] In the aforementioned embodiments 1 and 2, the rear drive unit 60 was equipped with a third electric motor MG3, but the present invention is also applicable to embodiments without the third electric motor MG3. In such embodiments, the multiple modes for switching the drive modes of the vehicles 90 and 190 do not include a mode using the third electric motor MG3.

[0055] In the aforementioned embodiments 1 and 2, one of the front wheels 14f and rear wheels 14r to which power from the engine 12 and the second electric motor MG2 is transmitted may be the rear wheel 14r, and the other of the front wheels 14f and rear wheels 14r to which power from the third electric motor MG3 is transmitted may be the front wheel 14f. In other words, the "first drive shaft" may be the rear drive shaft 38 and the "second drive shaft" may be the front drive shaft 28.

[0056] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0057] 10: Vehicle drive unit, 12: Engine, 14f: Front wheel, 14r: Rear wheel, 20: Front drive unit (first drive unit), 28: Front drive shaft (first drive shaft), 38: Rear drive shaft (second drive shaft), 40: Planetary gear system, 44: Gear pair (first power transmission mechanism), 46: Output shaft, 54: Gear pair (second power transmission mechanism), 60: Rear drive unit (second drive unit), C1: First axis, C2: Second axis, C3: Third axis, CA: Carrier, MG1: First motor, MG2: Second motor, MG2r: Rotor shaft (connecting shaft), MG3: Third motor, R: Ring gear, RE1: First rotating element, RE2: Second rotating element, RE3: Third rotating element, S: Sun gear

Claims

1. A vehicle drive system comprising an engine, a first drive unit including a first electric motor, a second electric motor, and a planetary gear system having three rotating elements, and a first drive shaft that drives either the front wheel or the rear wheel, The planetary gear system has three rotating elements: a first rotating element, a second rotating element, and a third rotating element, and functions as a differential mechanism. 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 second electric motor is positioned on the first axis, which is the rotation axis of the planetary gear system, on the opposite side from the engine when viewed from the planetary gear system. The first drive shaft is connected to the third rotating element without passing through the inside of the connecting shaft that connects the second motor and the second rotating element, via an output shaft whose rotation axis is a second axis parallel to the first axis and a first power transmission mechanism that transmits power between the output shaft and the third rotating element. The first electric motor is positioned on a third axis parallel to the first axis, on the engine side as viewed from the planetary gear system, and is connected to the first rotating element via a second power transmission mechanism. In the view along the first axis, the second axis is located in a position that overlaps with the first motor. A vehicle drive system characterized by the following features.

2. The aforementioned planetary gear system has a sun gear, a carrier, and a ring gear. If the planetary gear system is of the single-pinion type, the first rotating element is the ring gear, the second rotating element is the sun gear, and the third rotating element is the carrier. If the planetary gear system is of the double pinion type, the first rotating element is the carrier, the second rotating element is the sun gear, and the third rotating element is the ring gear. The vehicle drive system according to feature 1.

3. The aforementioned planetary gear system has a sun gear, a carrier, and a ring gear. If the planetary gear system is of the single-pinion type, the first rotating element is the carrier, the second rotating element is the sun gear, and the third rotating element is the ring gear. If the planetary gear system is of the double pinion type, the first rotating element is the ring gear, the second rotating element is the sun gear, and the third rotating element is the carrier. The vehicle drive system according to feature 1.

4. The system further comprises a second drive shaft that drives the other of the front wheel and the rear wheel, and a second drive unit that includes a third electric motor connected to the second drive shaft. A vehicle drive system according to any one of claims 1 to 3.

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