Vehicle drive device

Abstract

The invention provides a vehicle drive device capable of suppressing complexity of the structure and preventing excessive torque from being input into a power transmission path even when a brake mechanism is in an engaged state. The engine is connected to the first rotation element via a torque limiter that limits torque transmitted between the first drive shaft and the engine, and the brake mechanism is provided in a power transmission path between the torque limiter and the engine. Thus, even if excessive torque is input from the first drive shaft in the engaged state of the brake mechanism, it is possible to prevent an excessive input load from being applied to a rotating member, such as a gear, a shaft, or the like, in the power transmission path by means of the one torque limiter. Thus, it is possible to suppress the complexity of the structure, and to prevent excessive torque from being input into the power transmission path even when the brake mechanism is in the engaged state.

Description

Technical Field

[0001] The present invention relates to a vehicle drive system comprising an engine, two electric motors, a planetary gear system, and a drive shaft that drives one of the front or rear wheels. Background Technology

[0002] A known vehicle drive system includes an engine, a first electric motor, a second electric motor, a planetary gear assembly having three rotating elements (a first rotating element, a second rotating element, and a third rotating element), and a first drive shaft that drives one of the front wheels or the rear wheels. For example, the vehicle power transmission device described in Patent Document 1 is such a device. Patent Document 1 also discloses a braking mechanism that stops the engine's rotation and a first torque limiter that limits the torque transmitted between the first drive shaft and the engine. Furthermore, Patent Document 1 discloses that by also including a second torque limiter that limits the torque transmitted between the first drive shaft and the braking mechanism, excessive torque is prevented from being input to gears, shafts, etc., in the power transmission path when the braking mechanism is engaged.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-35991

[0004] To achieve multiple driving modes, a configuration could be considered as follows: The engine and a first electric motor are connected to the rotating elements of the planetary gear unit at 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 driving mode could be, for example, a BEV (Battery Electric Vehicle) mode where the engine is stopped and the first and second electric motors generate torque. To enable motor-driven operation (BEV driving) in this BEV mode, where the second electric motor is used as the power source instead of generating torque from the first electric motor, a configuration could also include a braking mechanism to stop the rotation of the first rotating element. In such a vehicle drive system, it is desirable to prevent excessive torque from being input to gears, shafts, etc., in the power transmission path when the braking mechanism is engaged. Therefore, in such a vehicle drive system, in addition to a first torque limiter that limits the torque transmitted between the first drive shaft and the engine, a second torque limiter that limits the torque transmitted between the first drive shaft and the braking mechanism could also be considered. However, in this case, two torque limiters are required, thus complicating the construction. Summary of the Invention

[0005] The present invention was made against the background of the above situation, and its object is to provide a vehicle drive device that can suppress the complexity of the structure and prevent excessive torque input into the power transmission path even when the braking mechanism is in an engaged state.

[0006] The subject of the first invention is a drive device for a vehicle, (a) comprising: an engine; a first electric motor; a second electric motor; a planetary gear assembly having three rotating elements: a first rotating element, a second rotating element, and a third rotating element; and a first drive shaft for driving one of the front wheels and the rear wheels, wherein, (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) further comprising: a braking mechanism that stops the rotation of the first rotating element by engaging; and a torque limiter that limits the torque transmitted between the first drive shaft and the engine, (d) the engine is connected to the first rotating element via the torque limiter, and (e) the braking mechanism is disposed in the power transmission path between the torque limiter and the engine.

[0007] According to the first invention described above, the planetary gear assembly connects an engine and a first electric motor to a first rotating element, a second electric motor to a second rotating element, and a first drive shaft to a third rotating element. The vehicle drive unit also includes a braking mechanism that stops the rotation of the first rotating element. Thus, in the vehicle drive unit, multiple driving modes can be realized, including a BEV driving mode, in which the second electric motor is used as the power source when the engine is stopped. Furthermore, the engine is connected to the first rotating element via a torque limiter that limits the torque transmitted between the first drive shaft and the engine, and the braking mechanism is provided in the power transmission path between the torque limiter and the engine. Therefore, even if excessive torque is input from the first drive shaft when the braking mechanism is engaged, an excessive input load can be prevented from being applied to rotating components such as gears and shafts in the power transmission path by a torque limiter. Here, the power transmission path is the power transmission path from the first drive shaft to the braking mechanism, and is synonymous with the power transmission path from the first drive shaft to the engine. Therefore, it can suppress the complexity of the structure and prevent excessive torque input into the power transmission path even when the braking mechanism is engaged. Attached Figure Description

[0008] Figure 1 This diagram illustrates a simplified configuration of a vehicle equipped with the drive system of the present invention.

[0009] Figure 2 It is a diagram that uses collinearity to represent the configuration of a vehicle's drive system.

[0010] Figure 3 This is a collinear diagram illustrating an example of a drive mode based on electric motor drive.

[0011] Figure 4 This is a collinear diagram illustrating an example of an engine-driven drive mode.

[0012] Figure 5 This diagram illustrates an example of the effect when a braking mechanism is installed in the power transmission path between the torque limiter and the engine.

[0013] Figure 6 This diagram illustrates the simplified configuration of a vehicle equipped with a comparative example vehicle drive system.

[0014] Explanation of reference numerals in the attached figures

[0015] 10…Vehicle drive unit; 12f…Front wheel; 12r…Rear wheel; 14f…Front drive shaft (first drive shaft); 14r…Rear drive shaft (second drive shaft); 18…Engine; 24…Differential mechanism (planetary gear assembly); S…Sun gear (second rotating element); C…Planet carrier (first rotating element); R…Ring gear (third rotating element); BR…Brake (brake mechanism); MG1…First electric motor; MG2…Second electric motor; MG3…Third electric motor; RE1…First rotating element; RE2…Second rotating element; RE3…Third rotating element; TLdp…Damper torque limiter (torque limiter). Detailed Implementation

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] [Example]

[0018] Figure 1 This diagram illustrates a simplified configuration of a vehicle 8 equipped with the vehicle drive unit 10 to which the present invention is applied. Figure 1In this vehicle 8, there are drive wheels 12 and a vehicle drive unit 10 for driving 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 unit 10 includes a front drive unit 10f for driving the front wheels 12f and a rear drive unit 10r for driving the rear wheels 12r. The vehicle drive unit 10 includes a drive shaft 14 for driving the drive wheels 12 and a drive unit 16 for driving the drive shaft 14. The drive shaft 14 includes left and right front drive shafts 14f and left and right rear drive shafts 14r. The drive unit 16 includes a front drive unit 16f and a rear drive unit 16r. Furthermore, the term "left and right" refers to left and right relative to the forward direction of the vehicle 8.

[0019] The front drive unit 10f includes an engine 18, a front drive shaft 14f, and a front drive unit 16f. The rear drive unit 10r includes a rear drive shaft 14r and a rear drive unit 16r. The front drive shaft 14f is a first drive shaft that drives the front wheel 12f, which is one of the front wheel 12f and the rear wheel 12r. The rear drive shaft 14r is a second drive shaft that drives the rear wheel 12r, which is the other of the front wheel 12f and the rear wheel 12r. The front drive unit 16f is a first drive unit that drives the front drive shaft 14f. The rear drive unit 16r is a second drive unit that drives the rear drive shaft 14r.

[0020] The front drive unit 16f includes a first motor MG1, a second motor MG2, a front power transmission mechanism 20, an input shaft 22, and a differential mechanism 24. The rear drive unit 16r includes a third motor MG3 and a rear power transmission mechanism 50.

[0021] Vehicle 8 is a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV). Furthermore, vehicle 8 is an all-wheel drive vehicle capable of independently driving the front wheels 12f and the rear wheels 12r. All-wheel drive (AWD) is synonymous with four-wheel drive (4WD). The vehicle drive unit 10 is capable of front-wheel drive that transmits torque only to the front wheels 12f, and rear-wheel drive that transmits torque only to the rear wheels 12r.

[0022] Engine 18 is, for example, a known internal combustion engine. Engine 18 controls engine torque Te, which is the torque of engine 18, by means of engine control unit 60 controlled by electronic control unit 70 (described later). Engine control unit 60 is located in front drive unit 10f and includes throttle actuator, fuel injection device, and ignition device, etc.

[0023] The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are rotating electric machines that function as prime movers to generate mechanical power from electricity and as generators to generate electricity from mechanical power, respectively; they are so-called electric generators. The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each connected to a battery 64 included in the vehicle drive unit 10 via an inverter 62. The torque of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 is controlled by the inverter 62 controlled by an electronic control device 70 (described later). The torque of the first electric motor MG1 is the first electric motor torque Tmg1, the torque of the second electric motor MG2 is the second electric motor torque Tmg2, and the torque of the third electric motor MG3 is the third electric motor torque Tmg3. The torque of the electric motor is the operating torque when the motor functions as a prime mover, and the regenerative torque when the motor functions as a generator. The battery 64 is an energy storage device that receives and supplies electricity to the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3. The first motor MG1, the second motor MG2, and the third motor MG3 are controlled to simultaneously receive and receive power via inverter 62. "Simultaneously" means, for example, that the first motor MG1, the second motor MG2, and the third motor MG3 can each independently operate or regenerate power at the same time.

[0024] The front power transmission mechanism 20 is the first power transmission mechanism located in the power transmission path between the differential mechanism 24 and the front drive shaft 14f, i.e., the front wheel 12f. The front power transmission mechanism 20 includes a reverse gear pair 26, an intermediate driven shaft 28, an end drive gear pair 30, and a front differential gear 32.

[0025] Input shaft 22 is a rotating component connecting engine 18 and differential mechanism 24. Reverse gear pair 26 is a first gear pair having a reverse drive gear 34 and a reverse driven gear 36 meshing with the reverse drive gear 34. End-drive gear pair 30 is a second gear pair having a final stage gear 38 and a final stage driven gear 32r meshing with the final stage gear 38. Intermediate driven shaft 28 is a rotating shaft arranged parallel to front drive shaft 14f. On intermediate driven shaft 28, reverse driven gear 36 and final stage gear 38 are respectively arranged in a manner that prevents relative rotation. Reverse driven gear 36 and final stage gear 38 are arranged on intermediate driven shaft 28. The diameter of final stage gear 38 is smaller than the diameter of reverse driven gear 36. Final stage driven gear 32r is the ring gear of front differential gear 32 and functions as an input rotating component of front differential gear 32. The front differential gear 32 is a differential gear connected to the front drive shaft 14f. The differential mechanism 24 is connected to the front drive shaft 14f via the front power transmission mechanism 20, etc.

[0026] The differential mechanism 24 is a double-pinion planetary gear system, comprising a sun gear S, pinions Pa and Pb, a planet carrier C supporting the pinions Pa and Pb for rotation and revolution, and a ring gear R meshing with the sun gear S via the pinions Pa and Pb. The pinions Pa and Pb are multiple meshing pairs of pinions. A second electric motor MG2 is connected to the sun gear S. An engine 18 and a first electric motor MG1 are connected to the planet carrier C. The front drive shaft 14f is connected to the ring gear R via a reverse gear pair 26 and a final drive gear pair 30.

[0027] The engine 18, the second electric motor MG2, the differential mechanism 24, and the reversing drive gear 34 are respectively mounted on a first shaft CS1, which serves as the rotation axis of the differential mechanism 24. The first shaft CS1 is a rotation axis parallel to the intermediate driven shaft 28. The first electric motor MG1 is mounted on a second shaft CS2. The second shaft CS2 is a rotation axis parallel to the first shaft CS1. The reversing driven gear 36 and the final stage gear 38 are respectively mounted on a third shaft CS3, which serves as the rotation axis of the intermediate driven shaft 28. The front differential gear 32 and the front drive shaft 14f are respectively mounted on a fourth shaft CS4, which serves as the rotation axis of the front drive shaft 14f. By mounting the first electric motor MG1 on the second shaft CS2, the size of the front drive unit 10f in the direction of the first shaft CS1 is reduced compared to mounting the first electric motor MG1 on the first shaft CS1. That is, the axial dimension of the front drive unit 16f is reduced.

[0028] Engine 18 is connected to planetary carrier C of differential mechanism 24 via input shaft 22. First electric motor MG1 is disposed on second shaft CS2, which is different from first shaft CS1. Therefore, front drive unit 16f also includes power transmission component 40. First electric motor MG1 is connected to planetary carrier C via power transmission component 40. Part or all of first electric motor MG1 is disposed at a position that overlaps with the range of first shaft CS1 from the position of engine 18 to the position of second electric motor MG2 when viewed radially from first shaft CS1.

[0029] The power transmission component 40 is configured to include, for example, a motor drive gear 40a, a motor driven gear 40b, an idler gear 40c, a motor drive shaft 40d, and an idler gear shaft 40e. The motor drive shaft 40d is a rotating shaft mounted on the second axis CS2, integrally connected to the rotor shaft MG1rs of the first electric motor MG1 via spline engagement in a manner that prevents relative rotation. The motor drive shaft 40d is the rotating shaft on which the motor drive gear 40a is mounted in a manner that prevents relative rotation. The idler gear shaft 40e is a rotating shaft mounted on the fifth axis CS5, which is a rotating axis parallel to the first axis CS1. The idler gear shaft 40e is the rotating shaft on which the idler gear 40c is mounted in a manner that prevents relative rotation. The motor drive gear 40a is a gear mounted on the second axis CS2 and connected to the first electric motor MG1. The motor driven gear 40b is a gear mounted on the first axis CS1 and connected to the planetary carrier C. The idler gear 40c is a gear mounted on a fifth shaft CS5, different from the first shaft CS1 and the second shaft CS2, and meshes with the motor drive gear 40a and the motor driven gear 40b, respectively. Compared with the motor driven gear 40b, both the motor drive gear 40a and the idler gear 40c have smaller diameters and fewer teeth. The power transmission component 40 functions, for example, as a speed reduction mechanism.

[0030] The front drive unit 16f also includes a brake BR. The brake BR is an engagement device that operates via an actuator, such as an electric or hydraulic one, to selectively engage components at both ends. The brake BR functions as a braking mechanism that selectively stops the rotation of the planet carrier C. The planet carrier C is selectively prevented from rotating or allowed to rotate by the brake BR.

[0031] The rear power transmission mechanism 50 is a second power transmission mechanism located in the power transmission path between the third electric motor MG3 and the rear drive shaft 14r, i.e., the rear wheel 12r. The rear power transmission mechanism 50 includes an output gear 52, a rear reverse gear 54, and a rear differential gear 56. The output gear 52 is fixed to the rotor shaft MG3rs of the third electric motor MG3 in a non-rotatable manner and meshes with the rear reverse gear 54. The output gear 52 and the rear differential gear 56 are connected via the rear reverse gear 54. The rear differential gear 56 is a differential gear connected to the rear drive shaft 14r. The third electric motor MG3 is connected to the rear drive shaft 14r via the rear power transmission mechanism 50, etc. The diameter of the output gear 52 is smaller than the diameter of the rear reverse gear 54, and the output gear 52 and the rear reverse gear 54 function, for example, as a reduction mechanism.

[0032] The rear drive unit 16r also includes a parking mechanism PLC. The parking mechanism PLC is a known parking locking device that switches between a parking lock state in which the output gear 52 is mechanically fixed in a non-rotatable state and a non-park lock state in which the output gear 52 can rotate.

[0033] The vehicle drive unit 10 also includes an electronic control unit 70 as a controller, which includes control devices associated with the control of the vehicle drive unit 10, etc. The electronic control unit 70 is configured, for example, as a so-called microcomputer including a CPU, RAM, ROM, input / output interfaces, etc. The CPU processes signals according to a program pre-stored in the ROM, thereby executing various controls of the vehicle 8. For example, the electronic control unit 70 executes output control of the engine 18, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3, and performs drive mode switching control as described later.

[0034] The electronic control unit 70 inputs various signals based on detection signals from various sensors present in the vehicle 8. These signals include, for example, engine speed Ne, vehicle speed V, first electric motor speed Nmg1, second electric motor speed Nmg2, third electric motor speed Nmg3, accelerator opening θacc, and state of charge (SOC). The SOC [%] is, for example, the remaining charge of the battery 64 calculated based on the battery charging / discharging current and battery voltage.

[0035] The electronic control unit 70 outputs various command signals to various devices (such as the engine control unit 60, inverter 62, brake BR, etc.) of the vehicle 8. These command signals include, for example, the engine control command signal Se, the first electric motor control command signal Smg1, the second electric motor control command signal Smg2, the third electric motor control command signal Smg3, and the brake control command signal Sbr. The engine control command signal Se is used to control the intake air volume, ignition timing, and fuel injection quantity of the engine 18. The first electric motor control command signal Smg1 is used to control the current of the first electric motor MG1. The second electric motor control command signal Smg2 is used to control the current of the second electric motor MG2. The third electric motor control command signal Smg3 is used to control the current of the third electric motor MG3. The brake control command signal Sbr is a request signal used to control the brake BR to be in an engaged or disengaged state. Furthermore, in the engagement device, the engaged state is synonymous with the engaged state (=connected state), and the disengaged state is synonymous with the released state (=disengaged state).

[0036] Figure 2 This is a diagram using a collinear diagram to represent the configuration of the vehicle drive unit 10. Figure 2 In this configuration, the rear drive unit 10r is, for example, the primary unit that takes priority for driving compared to the front drive unit 10f. In this case, the front drive unit 10f becomes the secondary unit. Figure 2 In this context, "FrOUT" indicates that the front wheel is 12f. Figure 2 In this context, "RrOUT" indicates that the rear wheel is 12r.

[0037] The differential mechanism 24 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. Each of the rotating elements RE1-RE3 in the differential mechanism 24 is connected to an actuator. Figure 2 The collinear diagram is a diagram in which the three rotating elements of the differential mechanism 24 are arranged on a straight line. If expressed using a collinear diagram, the first rotating element RE1 is the planet carrier C. The engine 18 and the first electric motor MG1 are connected to the first rotating element RE1. The second rotating element RE2 is the sun gear S. The second electric motor MG2 is connected to the second rotating element RE2. The third rotating element RE3 is the ring gear R. The front drive shaft 14f, i.e., the front wheel 12f, is connected to the third rotating element RE3. The brake BR is a braking mechanism that stops the rotation of the first rotating element RE1 by engaging it.

[0038] The third electric motor MG3 of the rear drive unit 10r is connected to the rear wheel 12r, and can therefore be considered to be connected to the front wheel 12f via the ground (refer to the dotted line). By controlling the operation in a manner that simultaneously supplies power to the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3, it is possible to drive as if the third electric motor MG3 is connected to the front wheel 12f.

[0039] The electronic control unit 70 can control the engine 18, the first electric motor MG1, the second electric motor MG2 and the third electric motor MG3, and switch the drive mode to any one of the multiple modes.

[0040] use Figure 3 , Figure 4 The various modes that enable switching the drive mode of vehicle 8 are explained. Figure 3 , Figure 4 They are in Figure 2The collinear diagram shows the rotational speeds of the rotating elements RE1-RE3 of the differential mechanism 24. In this collinear diagram, with respect to the vertical lines Y1-Y3, they are arranged sequentially from left to right in the attached diagram in the order of Y1, Y2, Y3. Vertical line Y1 represents the rotational speed of the second rotating element RE2, i.e., the sun gear S, which is connected to the second electric motor MG2. Vertical line Y2 represents the rotational speed of the third rotating element RE3, i.e., the ring gear R, which is connected to the front wheel 12f (refer to "FrOUT" in the diagram). Vertical line Y3 represents the rotational speed of the first rotating element RE1, i.e., the planetary carrier C, which is connected to the engine 18 (refer to "ENG" in the diagram) and the first electric motor MG1. In addition, the third electric motor MG3, which is connected to the rear wheel 12r (refer to "RrOUT" in the diagram), is connected to the front wheel 12f via the ground. Furthermore, each arrow indicates the magnitude and direction of the torque converted on the shaft of each rotating element RE1-RE3. Solid arrows represent the torque output from each actuator, while dashed arrows represent the torque transmitted mechanically.

[0041] Figure 3 This is a collinear diagram illustrating an example of a motor-driven drive mode (BEV mode, series mode). Figure 3 (a) is a collinear diagram illustrating BEV mode 1, which is capable of BEV driving, even when the second electric motor MG2 generates torque. Figure 3 (b) is a collinear diagram illustrating mode 2, which enables series driving, i.e., the series mode in which the engine 18 is driven to rotate and power is transferred between the first electric motor MG1 and the third electric motor MG3.

[0042] exist Figure 3 In (a), mode 1 is a mode in which the engine 18 is stopped, and the second electric motor MG2 generates torque to perform BEV driving while the brake BR is engaged. In mode 1, since the brake BR is engaged and the rotational speed of the first rotating element RE1 is fixed at zero, the first electric motor MG1 does not generate torque, and BEV driving based on the forward and reverse movement of the second electric motor MG2 can be achieved using the power of the battery 64. In mode 1, the differential mechanism 24 is set to a non-differential state, and torque is mechanically transmitted to the third rotating element RE3, which is the output element, by generating torque in the second electric motor MG2.

[0043] In Mode 1, the third motor MG3 can generate torque to produce drive torque Tr, either in place of the second motor MG2 or based on the second motor MG2. When only the third motor MG3 generates torque for BEV driving, the brake BR can be left unengaged. Alternatively, in Mode 1, the first motor MG1 and the second motor MG2 generate mutual torque in such a way that the torque around the third rotating element RE3 is zero while receiving power from the battery 64, thereby enabling BEV driving with the brake BR released. In this case, for example, the first motor torque Tmg1 is controlled in such a way that there is no drag from the engine 18, i.e., the rotational speed of the first rotating element RE1 is zero.

[0044] exist Figure 3 In (b), Mode 2 is a hybrid electric vehicle (HEV) mode, which is a series mode capable of driving with engine 18 as the power source. Mode 2 operates engine 18 and uses the first electric motor MG1 as a generator, and uses the generated electricity from the first electric motor MG1 to power the third electric motor MG3 as a prime mover. Mode 2 is an electric continuously variable transmission (EV) function that sets the input to engine 18 and the output to the rear wheels 12r when the brake BR is released, enabling series mode operation. In Mode 2, the burst vibration torque of engine 18 is not transmitted to the front drive shaft 14f, thus Mode 2 is beneficial for NV suppression. "NV" is a general term for noise and vibration, such as rumbling, generated in vehicle 8, representing at least one of the noise and vibration in vehicle 8. Therefore, using Mode 2 is useful, for example, in low-speed, low-load areas where quietness is required.

[0045] Figure 4 This is a collinear diagram illustrating an example of an engine-driven drive mode (input split mode, output split mode). Figure 4 (a) is a collinear diagram illustrating mode 3, which operates engine 18 and performs power transfer between the second electric motor MG2 and the third electric motor MG3. Figure 4 (b) is a collinear diagram illustrating mode 4, which operates engine 18 and performs power transfer between the first electric motor MG1 and the second electric motor MG2.

[0046] exist Figure 4In (a), mode 3 is a mode capable of HEV driving, specifically an input split mode capable of input split driving powered by engine 18. In mode 3, the differential mechanism 24 is set to differential mode, and torque is mechanically transmitted to the third rotating element RE3 by obtaining the reaction force of engine torque Te from the second electric motor MG2. Mode 3 is an electric continuously variable transmission (EV) mode that enables input split operation by setting the input to engine 18 and the output to the front wheels 12f and rear wheels 12r when the brake BR is released. Input split refers to the configuration of electric motor (MG3) at the output element (RE3) when two electric motors (MG2, MG3) and one engine are connected to the three rotating elements of the differential mechanism, using a collinear diagram.

[0047] like Figure 4 As shown in (a), mode 3 includes at least a mode in which the engine 18 is operated and the second electric motor MG2 operates as a generator, and the generated electricity from the second electric motor MG2 is used to operate the third electric motor MG3 as a prime mover. In mode 3, in addition to mechanically transmitting torque to the third rotating element RE3, the generated electricity from the second electric motor MG2 is also supplied to the third electric motor MG3, thereby causing the third electric motor MG3 to generate torque. For mode 3, the transmission efficiency is higher in the high-load region, so it is useful, for example, in the high-load region. Furthermore, mode 3 may also include a mode in which the engine 18 is operated and the generated electricity from the third electric motor MG3 is used to operate the second electric motor MG2 as a prime mover. In this case of mode 3, when transmitting torque mechanically to the third rotating element RE3, the second electric motor MG2 is rotated forward. The electricity consumed by the power operation of the second electric motor MG2 is supplied by the regenerative power of the third electric motor MG3 based on the kinetic energy of the vehicle 8.

[0048] Figure 4 The double-dotted line A in (a) indicates that in the differential mechanism 24, by making the rotational speed of the second rotating element RE2 (the rotational speed of the second motor Nmg2) zero, the power of the second motor MG2 is reduced to zero, thus creating a mechanical point where no electrical operation is performed. For the differential mechanism 24, at this mechanical point, the rotational speed of the third rotating element RE3, which is the output element, is on the deceleration side relative to the engine speed Ne, i.e., the low-speed drive (U / D) side. That is, the mechanical point of the differential mechanism 24 is set according to the reduction ratio. Figure 4 In (a), mode 3 is the U / D input split mode.

[0049] exist Figure 4In (b), mode 4 is a mode capable of HEV driving, specifically an output split mode that enables output split driving powered by engine 18. In mode 4, the differential mechanism 24 is in a differential state, and torque is mechanically transmitted to the third rotating element RE3 by obtaining the reaction force of the engine torque Te from the second electric motor MG2. Mode 4 is an electric continuously variable transmission (EV) mode that enables output split operation by setting the input to engine 18 and the output to the front wheels 12f when the brake BR is released. Output split refers to the configuration of the electric motor (MG1) at the input element (RE1) connected to the engine, when the two electric motors (MG1, MG2) and one engine are connected to the three rotating elements of the differential mechanism, using a collinear diagram. Since the mechanical point of the differential mechanism 24 is set by the reduction ratio, therefore Figure 4 Mode 4 in (b) is the U / D output split mode.

[0050] like Figure 4 As shown in (b), mode 4 includes at least a mode in which the engine 18 is operated and the first electric motor MG1 operates as a generator, and the generated electricity from the first electric motor MG1 powers the second electric motor MG2 as a prime mover. In mode 4, when torque is mechanically transmitted to the third rotating element RE3, the second electric motor MG2 rotates positively, so the electricity consumed by the operation of the second electric motor MG2 is supplied by the generated electricity from the first electric motor MG1, which is powered by the engine 18. Mode 4 has higher transmission efficiency in high-speed regions, so it is useful, for example, in high-speed regions. Alternatively, mode 4 may also include a mode in which the engine 18 is operated and the generated electricity from the second electric motor MG2 powers the first electric motor MG1 as a prime mover. In this case, in mode 4, when torque is mechanically transmitted to the third rotating element RE3, the second electric motor MG2 rotates negatively. By supplying the generated electricity from the second electric motor MG2 to the first electric motor MG1, the first electric motor MG1 generates torque.

[0051] return Figure 1The vehicle drive unit 10 also includes a damping mechanism DP and a damping torque limiter TLdp. The front drive unit 16f has a damping mechanism DP in the power transmission path between the engine 18 and the input shaft 22. The damping mechanism DP is, for example, a known damper that absorbs torque fluctuations of the engine 18. The front drive unit 16f has a damping torque limiter TLdp in the power transmission path between the engine 18 and the damping mechanism DP. The damping torque limiter TLdp is a torque limiter that limits the torque transmitted between the front drive shaft 14f (also synonymous with the front wheel 12f) and the input shaft 22 (also synonymous with the engine 18). The front drive unit 16f also includes an engine connecting shaft 19, which is a rotating component, connecting the damping torque limiter TLdp to the engine 18.

[0052] The damping torque limiter TLdp is a torque limiting mechanism that prevents the transmission of torque exceeding a predetermined limit torque Tlim, i.e., it limits the transmission of torque greater than the limit torque Tlim. In the damping torque limiter TLdp, for example, if a torque exceeding the limit torque Tlim is input, slippage is generated to prevent the transmission of torque exceeding the limit torque Tlim. For example, even if the front drive shaft input torque Tfds is an excessive torque exceeding the limit torque Tlim, the damping torque limiter TLdp reduces the input shaft input torque Tin to below the limit torque Tlim. The front drive shaft input torque Tfds is the input torque to the front drive shaft 14f. The input shaft input torque Tin is the input torque to the input shaft 22. Excessive torque in the front drive shaft input torque Tfds is, for example, the torque input from the front wheel 12f side generated when the front wheel 12f repeatedly slips and grips on a wavy road.

[0053] In the vehicle drive unit 10, the engine 18 is connected to the first rotating element RE1 of the differential mechanism 24 via the damping torque limiter TLdp. The position of the brake BR, which stops the rotation of the first rotating element RE1, will be explained.

[0054] Figure 6 This diagram illustrates a simplified configuration of a vehicle 100 equipped with a comparative example vehicle drive unit 110 (including a front drive unit 110f and a rear drive unit 110r). Figure 6In the vehicle drive unit 110, the connection relationships of the components in the drive unit 116 (including the front drive unit 116f and the rear drive unit 116r) are the same as those in the drive unit 16 of the vehicle drive unit 10. In the front drive unit 110f, the brake BR is disposed on the idler shaft 40e. One end of the brake BR is connected to the idler shaft 40e, and the other end is connected to a non-rotating component (not shown). The non-rotating component connected to the brake BR is, for example, a housing that houses the front drive unit 116f. However, if the brake BR is engaged, the torque limiter in the damping torque limiter TLdp does not function because the first rotating element RE1, i.e., the input shaft 22, is fixed and cannot rotate. If the input torque Tfds of the front drive shaft is set to an excessive torque while the brake BR is engaged, it is possible to apply an excessive input load to the rotating components, such as gears and shafts, in the power transmission path between the brake BR and the input shaft 22 and the front wheel 12f. Therefore, the front drive unit 116f also includes a brake torque limiter TLbr, which limits the torque transmitted between the front drive shaft 14f and the brake BR. The brake torque limiter TLbr, like the damping torque limiter TLdp, functions to prevent torque transmission exceeding the limit torque Tlim. The brake torque limiter TLbr is provided in, for example, the power transmission path between the idler wheel 40c in the idler shaft 40e where the brake BR is located, and the brake BR. In the front drive unit 110f, both the damping torque limiter TLdp and the brake torque limiter TLbr are required, thus complicating the construction. Furthermore, the rear drive unit 110r is the same as the rear drive unit 10r, so its description is omitted.

[0055] return Figure 1 In the front drive unit 10f of this embodiment, the brake BR is disposed in the power transmission path between the damping torque limiter TLdp and the engine 18. The brake BR is disposed, for example, on the engine connecting shaft 19. One end of the brake BR is connected to the engine connecting shaft 19, and the other end is connected to a non-rotating component (not shown). The non-rotating component connected to the brake BR is, for example, a housing that houses the front drive unit 16f. By disposing the brake BR on the engine connecting shaft 19, the damping torque limiter TLdp also functions as the brake torque limiter TLbr, that is, limiting the torque transmitted between the front drive shaft 14f and the brake BR.

[0056] Figure 5 This diagram illustrates an example of the effect when a brake BR is installed in the power transmission path between the damper torque limiter TLdp and the engine 18. Figure 5Even when the front drive shaft input torque Tfds exceeds the limit torque Tlim when the brake BR is engaged, the input shaft input torque Tin is reduced to below the limit torque Tlim through the function of the damping torque limiter TLdp.

[0057] As described above, according to this embodiment, the differential mechanism 24 connects the engine 18 and the first electric motor MG1 to the first rotating element RE1, the second electric motor MG2 to the second rotating element RE2, and the front drive shaft 14f to the third rotating element RE3. The vehicle drive unit 10 also includes a brake BR that stops the rotation of the first rotating element. Thus, the vehicle drive unit 10 can achieve multiple driving modes, including a BEV driving mode, in which the engine 18 is stopped and the second electric motor MG2 is used as the power source. Furthermore, the engine 18 is connected to the first rotating element RE1 via a damping torque limiter TLdp, and the brake BR is provided in the power transmission path between the damping torque limiter TLdp and the engine 18. Therefore, even when excessive torque is input from the front drive shaft 14f while the brake BR is engaged, a torque limiter can prevent excessive input load from being applied to rotating components such as gears and shafts in the power transmission path. The power transmission path here is the power transmission path from the front drive shaft 14f to the brake BR, which is synonymous with the power transmission path from the front drive shaft 14f to the engine 18. Therefore, it is possible to suppress structural complexity and prevent excessive torque input into the power transmission path even when the brake BR is engaged.

[0058] Furthermore, according to this embodiment, a third electric motor MG3 is connected to the rear drive shaft 14r. Therefore, the vehicle drive unit 10 can achieve various driving modes, including a mode capable of so-called series driving. For example, when the vehicle 8 is driven with the engine 18 running, the power from the engine 18 powers the first electric motor MG1 to function as a generator, and the generated electricity powers the third electric motor MG3 to function as a prime mover, thereby driving the rear drive shaft 14r, thus enabling series driving.

[0059] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is also applicable to other methods.

[0060] For example, in the above embodiment, the rear drive unit 10r may not be included. In this case, the present invention, which places the brake BR in the power transmission path between the damper torque limiter TLdp and the engine 18, can also be applied. In addition, as a drive mode, multiple modes such as "Mode 1" and "Mode 4" can be realized, in addition to the mode in which the third electric motor MG3 generates torque for BEV driving.

[0061] Furthermore, in the differential mechanism 24 of the above embodiment, the first rotating element RE1 can be either the planet carrier C or the sun gear S, and the second rotating element RE2 can be the other one of the planet 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 planet carrier C, the engine 18 and the first electric motor MG1 are connected to the sun gear S, and the second electric motor MG2 is connected to the planet carrier C.

[0062] Alternatively, in the differential mechanism 24 of the above embodiment, it can also be configured such that: the first rotating element RE1 is a ring gear R, the second rotating element RE2 is one of the sun gear S and the planet carrier C, and the third rotating element RE3 is the other of the sun gear S and the planet carrier C. In this case, for the differential mechanism 24, at the mechanical point, the rotational speed of the third rotating element RE3, which is the output element, is on the speed-increasing side relative to the engine speed Ne, i.e., the overdrive (O / D) side. That is, the mechanical point of the differential mechanism 24 is set according to the speed-increasing ratio. Therefore, mode 3 is the O / D input split mode, and mode 4 is the O / D output split mode. Alternatively, the differential mechanism 24 can also be a single-pinion type planetary gear device having a sun gear, a pinion, a planet carrier, and a ring gear. Even when the differential mechanism 24 is a single-pinion type planetary gear device, it is possible to configure either the U / D side or the O / D side at the mechanical point. Even so, the same effect as in the above embodiment can be obtained.

[0063] Here, the second rotating element RE2 is a rotating element located at either end in a collinear diagram in which the three rotating elements of the differential mechanism 24 are arranged on a straight line.

[0064] Alternatively, in the above embodiments, the power transmission component 40 may be configured such that it does not have an idler gear 40c, but connects the motor drive gear 40a and the motor driven gear 40b via a connecting component such as a belt. Or, the power transmission component 40 may be configured such that it does not have an idler gear 40c, but the motor drive gear 40a meshes with the motor driven gear 40b.

[0065] Alternatively, in the above embodiments, the brake BR can be replaced with a one-way clutch.

[0066] Alternatively, in the above embodiments, it can be configured such that one of the front wheel 12f and the rear wheel 12r, which transmits power to the engine 18 and the second electric motor MG2, is the rear wheel 12r, and the other of the front wheel 12f and the rear wheel 12r, which transmits power to the third electric motor MG3, is the front wheel 12f. That is, it can also be configured such that the first drive shaft is the rear drive shaft 14r, and the second drive shaft is the front drive shaft 14f.

[0067] In addition, in the above embodiments, it is envisioned that in PHEV, BEV driving based on the third electric motor MG3 is frequently used, so the drive unit equipped with the third electric motor MG3 is the main unit. However, in HEV, the drive unit equipped with the engine 18 and the second electric motor MG2 can also be the main unit.

[0068] Furthermore, the above is merely one implementation method, and the present invention can be implemented in various ways with modifications and improvements based on the knowledge of those skilled in the art.

Claims

1. A vehicle drive unit comprising: an engine; a first electric motor; a second electric motor; a planetary gear assembly having three rotating elements: a first rotating element, a second rotating element, and a third rotating element; and a first drive shaft for driving one of a front wheel and a rear wheel, characterized in that, 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. It also includes: a braking mechanism that stops the rotation of the first rotating element by engaging; and a torque limiter that limits the torque transmitted between the first drive shaft and the engine. The engine is connected to the first rotating element via the torque limiter. The braking mechanism is located in the power transmission path between the torque limiter and the engine.

2. The vehicle drive device according to claim 1, characterized in that, It also includes: a second drive shaft for driving the other of the front wheel and the rear wheel; and a third electric motor connected to the second drive shaft.

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