Vehicle drive device

Abstract

To provide a vehicle drive device capable of suppressing generation of rattling noise.SOLUTION: According to the vehicle drive device 10: (a) The differential mechanism 32 includes three rotary elements, namely, the ring gear R, the sun gear S, and the carrier C; (b) the engine 20 and the first motor MG1 are coupled to the ring gear R, the second motor MG2 is coupled to the sun gear S, and the front drive shaft 38 is coupled to the career C; (c) the third motor MG3 is coupled to the rear drive shaft 58; (d) The electronic control device 70 is configured to cause the first motor Tmg1 to output the backlash elimination torque Tgata for eliminating the backlash G in the power transmission path Tmg1_th between the ring gear R and the first motor MG1, when the engine 20 is in operation and the required amount of the first motor torque PTmg1 for generating the drive force Fr in the vehicle 8 is less than the torque amount MG1.SELECTED DRAWING: Figure 6

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 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 wheels and the rear wheels, a second drive shaft that drives the other of the front wheels and the 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 second drive shaft is connected to the third electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 8,512,189 Summary of the Invention [Problem to be solved by the invention]

[0004] In a differential mechanism having three rotating elements, in which 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, the first drive shaft is connected to the third rotating element, and the second drive shaft is connected to the third electric motor, for example, a portion of the power from the engine is transmitted to the first electric motor via the first rotating element. If backlash (= backlash) exists in the power transmission path between the first rotating element and the first electric motor, when the engine is running and the absolute value of the required output torque of the first electric motor to generate driving force for the vehicle is less than a predetermined torque value, explosive vibrations from the engine may act on the backlash, causing a rattling noise.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a vehicle drive device that can suppress the generation of rattle noise. [Means for solving the problem]

[0006] The gist of the present invention is 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 the front wheels and the rear wheels, a second drive shaft that drives the other of the front wheels and the rear wheels, and a control device, wherein (a) the differential mechanism has three rotation elements: a first rotation element, a second rotation element, and a third rotation element, (b) the engine and the first electric motor are connected to the first rotation element, and the second rotation element is connected to the second electric motor. (c) the second drive shaft is connected to the third rotating element, and the first drive shaft is connected to the third electric motor; and (d) the control device is configured to cause the first electric motor to output a clearance-reducing torque that reduces clearance in the power transmission path between the first rotating element and the first electric motor when the engine is in operation and the absolute value of the required output torque of the first electric motor to generate driving force for the vehicle is less than a predetermined torque value. [Effects of the Invention]

[0007] According to the vehicle drive system of the present invention, (a) the differential mechanism has three rotating elements: a first rotating element, a second rotating element, and a third rotating element, (b) the engine and the first electric motor are connected to the first rotating element, the second rotating element is connected to the second electric motor, and the third rotating element is connected to the first drive shaft, (c) the second drive shaft is connected to the third electric motor, and (d) the control device is configured to, when the engine is in an operating state and the absolute value of the output torque required by the first electric motor to generate driving force for the vehicle is less than a predetermined torque value, cause the first electric motor to output a clearance-reducing torque that reduces clearance in the power transmission path between the first rotating element and the first electric motor. When the engine is in an operating state and the absolute value of the output torque required by the first electric motor to generate driving force for the vehicle is less than the predetermined torque value, explosive vibrations of the operating engine may act on the clearance in the power transmission path between the first rotating element and the first electric motor, causing rattle noise. However, even in such a case, the backlash is eliminated by the backlash elimination torque output from the first electric motor, thereby suppressing rattle noise that occurs when the engine's explosive vibration acts on the backlash. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle equipped with a vehicle drive device to which the present invention is applied; [Figure 2] FIG. 10 is a nomographic diagram illustrating a BEV_MG3 mode in which the brake is engaged, the engine is stopped, and a positive third electric motor torque is output from the third electric motor to generate driving force for the vehicle. [Figure 3] FIG. 10 is a nomographic diagram illustrating a series mode in which the brake is released, the engine is operating, and a positive third electric motor torque is output from the third electric motor by the power generated by the first electric motor. [Figure 4]FIG. 10 is a nomographic diagram illustrating an input split mode in which the brake is released, the engine is in operation, the first electric motor is in a non-driving state, and a positive third electric motor torque is output from the third electric motor using the power generated by the second electric motor. [Figure 5] FIG. 10 is a nomographic diagram illustrating an output split mode in which the brake is released, the engine is running, and the states of the first electric motor and the second electric motor are controlled so that the power balance between the first electric motor and the second electric motor is balanced. [Figure 6] 3 is a flowchart illustrating a main part of the control operation of the electronic control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] 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. The vehicle 8 is equipped with left and right front wheels 12f, a front drive unit 10f that drives the left and right front wheels 12f, left and right rear wheels 12r, and a rear drive unit 10r that drives the left and right rear wheels 12r. Note that the above "left and right" refer to the left and right with respect to the forward direction of the vehicle 8.

[0011] 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 or a plug-in hybrid vehicle. The engine 20 is, for example, a well-known internal combustion engine. The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each rotating electric machines that function as prime movers that generate mechanical power from electric power and as generators that generate electric power from mechanical power, and are so-called motor generators. For example, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each synchronous electric motors. The vehicle 8 is an all-wheel drive vehicle (=four-wheel drive vehicle) that can drive the front wheels 12f and the rear wheels 12r independently.

[0012] The front power transmission device 30 is provided in a power transmission path PTf between the engine 20, the first electric motor MG1, and the second electric motor MG2, and the front wheels 12f. In the front power transmission device 30, a differential mechanism 32, a front counter gear 34, a front differential gear 36, a front drive shaft 38, a power transmission member 40, and a brake BR are connected as shown in FIG. 1, and these components have a well-known configuration. The differential mechanism 32 is formed by a single-pinion planetary gear set, and a sun gear S, a ring gear R, and a carrier C are respectively connected to the second electric motor MG2, the engine 20, the first electric motor MG1, and the front drive shaft 38. The first electric motor MG1 is connected to the ring gear R via the power transmission member 40. The ring gear R is provided on both the inner and outer peripheries of the internal gear in the planetary gear set, and the inner periphery side meshes with the pinion P, and the outer periphery side is connected to the power transmission member 40. The ring gear R, the sun gear S, and the carrier C in the differential mechanism 32 correspond to the "first rotating element," the "second rotating element," and the "third rotating element," respectively, in the present invention.

[0013] The power transmission member 40 is provided in a power transmission path PTmg1 between the ring gear R and the rotor of the first electric motor MG1. The power transmission path PTmg1 corresponds to the "power transmission path" in this invention. The power transmission member 40 includes, for example, an intermediate gear 40a fixedly mounted on the rotor shaft MG1rs of the first electric motor MG1 so as not to rotate relative to the rotor shaft MG1rs, and a chain 40b connecting the intermediate gear 40a and the ring gear R. The intermediate gear 40a and the ring gear R connected to the chain 40b function as sprockets. 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. A backlash G exists in the power transmission path PTmg1. For example, a backlash G exists in the rotational direction between the intermediate gear 40a and the chain 40b, and a backlash G exists in the rotational direction between the chain 40b and the ring gear R.

[0014] The brake BR is a well-known engagement device in which one end is connected to the ring gear R and the other end is connected to a non-rotating member (not shown), and both ends of the brake BR are selectively connected. The front drive shaft 38 is a first drive shaft that drives the front wheel 12f, which is one of the front wheels 12f and the rear wheels 12r.

[0015] The rear power transmission device 50 is provided in the power transmission path PTr between the third electric motor MG3 and the rear wheels 12r. In the rear power transmission device 50, an output gear 52, a rear counter gear 54, a rear differential gear 56, and a rear drive shaft 58 are connected as shown in FIG. 1, and these are well-known configurations. The output gear 52 is a gear fixed to the rotor shaft MG3rs of the third electric motor MG3 so as not to rotate relative to it. The output gear 52 has a smaller diameter than the rear counter gear 54, and these gears function as, for example, a reduction mechanism. The rear drive shaft 58 is a second drive shaft that drives the other of the front wheels 12f and the rear wheels 12r, i.e., the rear wheel 12r. The third electric motor MG3 is connected to the rear drive shaft 58.

[0016] The first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are each connected to a battery 64 via an inverter 62, and the torque is controlled by controlling the inverter 62 by an electronic control device 70 (described later). Here, the output torques of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are referred to as first electric motor torque Tmg1 [N·m], second electric motor torque Tmg2 [N·m], and third electric motor torque Tmg3 [N·m], respectively. The battery 64 is a well-known power 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. Unless otherwise specified, the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 are controlled via the inverter 62 so as to supply and receive electric power simultaneously. In other words, the power balance between the power generated by any one of the first electric motor MG1, the second electric motor MG2, and the third electric motor MG3 and the power consumed when that generated power is supplied to drive the other electric motors is balanced.

[0017] For example, the rear drive unit 10r is a main unit that is used for traveling with priority over the front drive unit 10f, in which case the front drive unit 10f is used as an auxiliary unit.

[0018] 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. By controlling the first electric motor MG1, the second electric motor MG2, and the 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.

[0019] The electronic control unit 70 is configured to include, for example, a so-called microcomputer, and performs various controls of the vehicle 8 by performing signal processing in accordance with a pre-stored program. The electronic control unit 70 corresponds to the "control unit" in the present invention.

[0020] The electronic control device 70 receives various signals based on detected values ​​from various sensors provided in the vehicle 8 (for example, an accelerator opening sensor 80, a vehicle speed sensor 82, a battery sensor 84, a shift position sensor 86, a first electric motor rotation sensor 88, a second electric motor rotation sensor 90, a third electric motor rotation sensor 92, an engine rotation speed sensor 94, etc.) (for example, an accelerator opening θacc [%] which is the amount of accelerator operation by the driver indicating the magnitude of the driver's acceleration operation, a vehicle speed V [km / h], a state of charge value (=predetermined The following signals are input: a calculation signal for SOC [%] (the ratio of the amount of charge actually stored to the fully charged capacity of the battery 64); a shift operation position POSop; a first motor rotation speed Nmg1 [rpm] which is the rotation speed of the first electric motor MG1; a second motor rotation speed Nmg2 [rpm] which is the rotation speed of the second electric motor MG2; a third electric motor rotation speed Nmg3 [rpm] which is the rotation speed of the third electric motor MG3; an engine rotation speed Ne [rpm] which is the rotation speed of the engine 20; etc.

[0021] The electronic control device 70 outputs various command signals (such as an engine control signal Se that controls the operating state of the engine 20, a first motor control signal Smg1, a second motor control signal Smg2, and a third motor control signal Smg3 that control the operating states of the first electric motor MG1 to the third electric motor MG3 via the inverter 62, and a brake control signal Sbr that controls the engagement and disengagement state of the brake BR) to each device of the vehicle 8 (such as the engine 20, the inverter 62, and the actuator that controls the brake BR).

[0022] The electronic control unit 70 is configured to be able to switch the drive mode to one of a plurality of modes by controlling the engine 20, 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 70 controls the brake BR to be engaged as necessary. For example, the plurality of drive modes include a BEV_MG3 mode, a series mode, an input split mode, and an output split mode.

[0023] Here, the multiple modes into which the drive mode of the vehicle 8 can be switched will be described with reference to FIGS. 2 to 5. FIGS. 2 to 5 are diagrams showing the relative rotational speeds of the rotational elements RE1 to RE3 of the differential mechanism 32. In these nomographic diagrams, vertical lines Y1 to Y3 represent the rotational elements of the sun gear S, carrier C, and ring gear R of the differential mechanism 32, respectively. In FIGS. 2 to 5, "ENG" represents the engine 20, "FrOUT" represents the front wheels 12f, and "RrOUT" represents the rear wheels 12r. Each arrow indicates the magnitude and direction of torque. Solid arrows indicate torque output from each actuator, and dashed arrows indicate transmitted torque. In FIGS. 2 to 5, the rotational speeds (Nmg1, Nmg3) and torques (Tmg1, Tmg3) of the first electric motor MG1 and the third electric motor MG3 are shown as converted values ​​at the ring gear R and the carrier C, respectively.

[0024] FIG. 2 is a nomographic diagram illustrating the BEV_MG3 mode in which the brake BR is engaged, the engine 20 is stopped, and a positive third motor torque Tmg3 is output from the third electric motor MG3 to generate a driving force Fr [N] for the vehicle 8. The "positive torque" is a torque that acts in the same direction as the engine torque Te [N·m], which is the output torque of the engine 20, if the engine 20 is operating, and also acts in a direction that moves the vehicle 8 forward. The "negative torque" is a torque that acts in the opposite direction to the positive torque. The BEV_MG3 mode is a mode in which the vehicle is driven as a BEV (Battery Electric Vehicle). In the BEV_MG3 mode, the first electric motor MG1 is in a non-driving state. The "non-driving state" refers to a state in which the first electric motor MG1 is not operating as either a prime mover or a generator. In the BEV_MG3 mode, the third electric motor MG3 is driven by power supplied from the battery 64, without being controlled to balance the power generated and consumed.

[0025] 3 is a nomographic diagram illustrating the series mode in which the brake BR is released, the engine 20 is operating, and a positive third electric motor torque Tmg3 is output from the third electric motor MG3 due to the power generated by the first electric motor MG1. The series mode is a mode in which HEV (Hybrid Electric Vehicle) running is possible, and in which series running using the engine 20 as a power source is possible. In the series mode, the first electric motor torque Tmg1 is set to negative torque, and the first electric motor MG1 is operated as a generator by the power of the engine 20, and the third electric motor MG3 is operated as a prime mover. In the series mode, explosive vibrations of the engine 20 are not transmitted to the front drive shaft 38, which is advantageous in reducing booming noise, etc.

[0026] FIG. 4 is a nomographic diagram illustrating an input split mode in which the brake BR is released, the engine 20 is operating, the first electric motor MG1 is non-driven, and the third electric motor torque Tmg3, which is a positive torque, is output from the third electric motor MG3 using the power generated by the second electric motor MG2. The input split mode is a mode enabling hybrid driving and input split driving using the engine 20 as a power source. In the input split mode, the required output torque of the first electric motor torque Tmg1 for generating the driving force Fr of the vehicle 8 is zero. In the input split mode, the second electric motor MG2 rotates in the negative direction and the second electric motor torque Tmg2 is positive torque, so that the second electric motor MG2 operates as a generator and the third electric motor MG3 operates as a prime mover. The differential mechanism 32 is in a differential state, and the second electric motor MG2 absorbs the reaction force of the engine torque Te, mechanically transmitting positive torque to the carrier C. In addition, 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 output a positive third electric motor torque Tmg3.

[0027] 5 is a nomographic diagram illustrating the output split mode in which the brake BR is released, the engine 20 is operating, and the states of the first electric motor MG1 and the second electric motor MG2 are controlled so that the power balance between the first electric motor MG1 and the second electric motor MG2 is balanced. In the output split mode, one of the first electric motor MG1 and the second electric motor MG2 is operated as a prime mover, and the other is operated as a generator. The first electric motor torque Tmg1, which is controlled so that the power balance between the first electric motor MG1 and the second electric motor MG2 is balanced, is the required amount of the first electric motor torque Tmg1. The output split mode is a mode in which hybrid driving is possible, and in which output split driving using the engine 20 as a power source is possible. As shown in FIG. 5(a), when the second motor MG2 rotates in the forward direction in the output split mode, the second motor torque Tmg2 is set to positive torque, thereby controlling the second motor MG2 to operate as a prime mover, and the first motor torque Tmg1 is set to negative torque, thereby controlling the first motor MG1 to operate as a generator. As shown in FIG. 5(c), when the second motor MG2 rotates in the reverse direction in the output split mode, the second motor torque Tmg2 is set to positive torque, thereby controlling the second motor MG2 to operate as a generator, and the first motor torque Tmg1 is set to positive torque, thereby controlling the first motor MG1 to operate as a prime mover. FIG. 5(b) is a nomographic diagram for the case in which the second motor rotation speed Nmg2 is zero in the output split mode, and details will be described later. In the output split mode, the generated power of one of the first motor MG1 and the second motor MG2 is supplied to the other and consumed as power to drive the other motor. The differential mechanism 32 is in a differential state, and the second electric motor MG2 takes up the reaction force of the combined torque Tsum (=Te+Tmg1) of the engine torque Te and the first electric motor torque Tmg1, thereby mechanically transmitting torque to the carrier C. The third electric motor MG3 is in a non-driven state.

[0028] Next, we will explain the control operation of the electronic control device 70 that can suppress the generation of rattle noise. "Rattle noise" is an abnormal noise that occurs when the contact surface of one member of the rattle G and the contact surface of the other member repeatedly separate and collide in the rotational direction when the first electric motor torque Tmg1 is zero or close to zero. The rattle noise is generated when the explosive vibration of the engine 20 acts on the rattle G.

[0029] The electronic control unit 70 determines whether the vehicle is in input split running or not, and also determines whether the vehicle is in output split running or not.

[0030] When the electronic control device 70 determines that the vehicle is in input split driving, it determines whether the ring gear rotation speed Nr [rpm] (= engine rotation speed Ne), which is the rotation speed of the ring gear R, is increasing or decreasing. A determination that the vehicle is in input split driving corresponds to the case in the present invention where "the engine is operating and the absolute value of the required amount of output torque of the first electric motor for generating driving force for the vehicle is less than a predetermined torque value." For example, on a flat road, the engine rotation speed Ne is increased to accelerate the vehicle 8, thereby increasing the ring gear rotation speed Nr. On a downhill road, the ring gear rotation speed Nr can be increased by the driven force input from the front wheels 12f. On a flat road, the engine rotation speed Ne is decreased to decelerate the vehicle 8, thereby decreasing the ring gear rotation speed Nr. On an uphill road, the ring gear rotation speed Nr can be decreased by the deceleration of the front wheels 12f, which are decelerated by the driving load.

[0031] When the electronic control device 70 determines that the vehicle is in input split running and the ring gear rotation speed Nr is increasing, it causes the first electric motor MG1 to output a first electric motor torque Tmg1 (<0), which is a negative torque, as the backlash-removing torque Tgata [N·m]. When the electronic control device 70 determines that the vehicle is in input split running and the ring gear rotation speed Nr is decreasing, it causes the first electric motor MG1 to output a first electric motor torque Tmg1 (>0), which is a positive torque, as the backlash-removing torque Tgata. When the electronic control device 70 determines that the vehicle is in input split running and the ring gear rotation speed Nr is neither increasing nor decreasing, it causes the first electric motor MG1 to output a first electric motor torque Tmg1, which is a positive torque or a negative torque, as the backlash-removing torque Tgata. Preferably, when the backlash-reducing torque Tgata has already been output, the first electric motor torque Tmg1, which is a positive torque or a negative torque and which has already been output as the backlash-reducing torque Tgata, is maintained. The "backlash-reducing torque Tgata" is a predetermined torque determined experimentally or by design, which is necessary to reduce the backlash G, and is a positive torque or a negative torque having a magnitude close to zero.

[0032] When the electronic control device 70 determines that the vehicle is in output split driving, it determines whether the absolute value of the second electric motor rotation speed Nmg2 is less than a judgment rotation speed Nmg2_jdg (>0). The "criterion rotation speed Nmg2_jdg" is an upper limit value of the absolute value of the second electric motor rotation speed Nmg2, determined experimentally or by design, at which the absolute value of the first electric motor torque Tmg1 becomes less than the torque value Tmg1_th and the rattle noise falls outside the allowable range. For example, it is a predetermined rotation speed near zero. The torque value Tmg1_th is a lower limit value of the absolute value of the first electric motor torque Tmg1, determined experimentally or by design, at which the backlash G can be eliminated. For example, it is a predetermined torque value near zero. The torque value Tmg1_th is equal to or less than the backlash-eliminating torque Tgata. The torque value Tmg1_th corresponds to the "predetermined torque value" in this invention. The judgment rotation speed Nmg2_jdg corresponds to the "predetermined judgment rotation speed" in this invention. When the electronic control device 70 determines that the vehicle is in output split traveling mode and the absolute value of the second electric motor rotation speed Nmg2 is less than the reference rotation speed Nmg2_jdg, the electronic control device 70 causes the first electric motor MG1 to output a backlash-reducing torque Tgata in addition to the normal control torque (zero or near-zero torque) during output split traveling. The backlash-reducing torque Tgata may be either positive or negative.

[0033] For example, when the vehicle is in output split driving mode and the second electric motor rotation speed Nmg2 is zero, as shown in Fig. 5(b), neither the first electric motor MG1 nor the second electric motor MG2 operates as a prime mover or a generator. That is, the first electric motor MG1 and the second electric motor MG2 are controlled to be in a non-driving state so that the electric power balance between the first electric motor MG1 and the second electric motor MG2 is balanced. The first electric motor torque Tmg1 becomes zero.

[0034] For example, when the vehicle is in output split traveling mode and the absolute value of the second electric motor rotation speed Nmg2 is less than the reference rotation speed Nmg2_jdg and is not zero, one of the first electric motor MG1 and the second electric motor MG2 is operated as a prime mover, and the other is operated as a generator. For example, the second electric motor MG2 is operated as a generator, and the first electric motor MG1 is operated as a prime mover. In this case, the first electric motor torque Tmg1 is less than the torque value Tmg1_th, and the first electric motor MG1 is controlled to be in a substantially non-driven state, i.e., to be in a very low first electric motor torque Tmg1. When it is determined that the vehicle is in output split traveling mode and the absolute value of the second electric motor rotation speed Nmg2 is less than the reference rotation speed Nmg2_jdg, this corresponds to "when the engine is operating and the absolute value of the required amount of output torque of the first electric motor for generating driving force for the vehicle is less than a predetermined torque value" in the present invention. The "normal control torque" means that, during output split traveling, when the second electric motor MG2 is rotating in the forward direction, negative torque (see FIG. 5(a)) is output from the first electric motor torque Tmg1 to operate the first electric motor MG1 as a generator, and when the second electric motor MG2 is rotating in the reverse direction, positive torque (see FIG. 5(c)) is output from the first electric motor torque Tmg1 to operate the first electric motor MG1 as a prime mover. When the electronic control device 70 determines that output split traveling is in progress and that the absolute value of the second electric motor rotation speed Nmg2 is equal to or greater than the judgment rotation speed Nmg2_jdg, the electronic control device 70 outputs the normal control torque that is used during output split traveling.

[0035] When the electronic control device 70 determines that the vehicle is not in input split driving or output split driving, it does not cause the first electric motor MG1 to output the backlash-reducing torque Tgata. Note that, as necessary, the first electric motor MG1 outputs a normal control torque for controlling the differential state of the differential mechanism 32. For example, during driving in the BEV_MG3 mode, the first electric motor MG1 is in a non-driving state, and therefore the "normal control torque" is zero. For example, during series driving, the reaction torque (= power generation torque) output from the first electric motor MG1 is the "normal control torque."

[0036] Fig. 6 is a flowchart illustrating the main control operations of the electronic control unit 70. The flowchart in Fig. 6 is repeatedly executed.

[0037] First, in step (hereinafter, step will be omitted) S10, it is determined whether or not input split running is in progress. If the determination in S10 is YES, it is determined in S20 whether or not ring gear rotation speed Nr is increasing. If the determination in S20 is YES, in S30, first electric motor torque Tmg1, which is a negative torque, is output as backlash-removing torque Tgata from the first electric motor MG1. By outputting first electric motor torque Tmg1, which is a negative torque, as backlash-removing torque Tgata while ring gear rotation speed Nr is increasing, the absolute value of backlash-removing torque Tgata can be made lower compared to when first electric motor torque Tmg1, which is a positive torque, is output as backlash-removing torque Tgata. This reduces the power consumed to output backlash-removing torque Tgata.

[0038] If the determination in S20 is NO, then in S40 it is determined whether the ring gear rotation speed Nr is decreasing. If the determination in S40 is YES, then in S50, the first electric motor MG1 outputs a positive first electric motor torque Tmg1 as the backlash-reducing torque Tgata. By outputting a positive first electric motor torque Tmg1 as the backlash-reducing torque Tgata while the ring gear rotation speed Nr is decreasing, the absolute value of the backlash-reducing torque Tgata can be lowered compared to when a negative first electric motor torque Tmg1 is output as the backlash-reducing torque Tgata. This reduces the power consumed to output the backlash-reducing torque Tgata.

[0039] If the determination in S40 is NO, then in S60, the first electric motor MG1 outputs either a positive torque or a negative torque as the backlash-reducing torque Tgata. If either a positive torque or a negative torque is already being output from the first electric motor MG1 as the backlash-reducing torque Tgata, then in S60, the backlash-reducing torque Tgata in the same acting direction is maintained. Maintaining the backlash-reducing torque Tgata in the same acting direction prevents the backlash-reducing torque Tgata from being repeatedly switched from one of the positive torque and the negative torque to the other within a short period of time. If the determination in S10 is NO, then in S100, it is determined whether the vehicle is in out-split running mode. If the determination in S100 is YES, then in S110, it is determined whether the absolute value of the second electric motor rotation speed Nmg2 is less than the determination rotation speed Nmg2_jdg. If the determination in S110 is YES, then in S120, the first electric motor MG1 adds a backlash-reducing torque Tgata to the normal control torque during output split running and outputs the result. If the determination in S110 is NO, then in S130, the first electric motor MG1 outputs the normal control torque during output split running, and does not output the backlash-reducing torque Tgata. If the determination in S100 is NO, then in S140, the backlash-reducing torque Tgata is not output. Note that, if necessary, the first electric motor MG1 outputs a normal control torque for controlling the differential state of the differential mechanism 32.

[0040] According to this embodiment, (a) the differential mechanism 32 has three rotating elements: a ring gear R, a sun gear S, and a carrier C; (b) the engine 20 and the first electric motor MG1 are connected to the ring gear R, the second electric motor MG2 is connected to the sun gear S, and the front drive shaft 38 is connected to the carrier C; (c) the third electric motor MG3 is connected to the rear drive shaft 58; and (d) the electronic control device 70 is configured to output a backlash-eliminating torque Tgata to the first electric motor MG1 to eliminate backlash G in the power transmission path PTmg1 when generating a driving force Fr for the vehicle 8 during input split running in which the engine 20 is operating and the first electric motor MG1 is in a non-driven state. Even during input split running in which the first electric motor MG1 is in a non-driven state, the backlash G in the power transmission path PTmg1 is eliminated by the backlash-eliminating torque Tgata. This suppresses rattle noise caused by the explosive vibration of the engine 20 acting on the rattle G.

[0041] According to this embodiment, (a) the differential mechanism 32 has three rotating elements: a ring gear R, a sun gear S, and a carrier C; (b) the engine 20 and the first electric motor MG1 are connected to the ring gear R, the second electric motor MG2 is connected to the sun gear S, and the front drive shaft 38 is connected to the carrier C; (c) the third electric motor MG3 is connected to the rear drive shaft 58; and (d) the electronic control device 70 is configured to output a backlash-eliminating torque Tgata to the first electric motor MG1 when the engine 20 is in an operating state and the first electric motor MG1 and the second electric motor MG2 are in an output split driving state in which the respective states of the first electric motor MG1 and the second electric motor MG2 are controlled so that the power balance between them is balanced, and when a driving force Fr for the vehicle 8 is generated, and the absolute value of the second electric motor rotation speed Nmg2 is less than the judgment rotation speed Nmg2_jdg, the electronic control device 70 outputs a backlash-eliminating torque Tgata to the first electric motor MG1 to eliminate the backlash G in the power transmission path PTmg1. When the absolute value of the second electric motor rotation speed Nmg2 is less than the reference rotation speed Nmg2_jdg during output split driving, the absolute value of the first electric motor torque Tmg1 is set to be less than the torque value Tmg1_th. Even in such a case, the backlash G in the power transmission path PTmg1 is eliminated by the backlash elimination torque Tgata, thereby suppressing the generation of rattle noise.

[0042] The above-described embodiments of the present invention are merely illustrative, 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 without departing from the spirit of the present invention.

[0043] In the above-mentioned embodiment, when it is determined that the vehicle is in input split driving, and when it is determined that the vehicle is in output split driving and the absolute value of the second electric motor rotation speed Nmg2 is less than the judgment rotation speed Nmg2_jdg, these are examples of "when the engine is in operation and the absolute value of the required amount of output torque of the first electric motor to generate driving force for the vehicle is less than a predetermined torque value" in the present invention. For example, (a) a case in which the driving mode is substantially the same as during input split driving, and the third electric motor MG3 is supplied with power generated by the second electric motor MG2 and power from the battery 64, or (b) a case in which the driving mode is substantially the same as during output split driving, and instead of the third electric motor MG3 being in a non-driving state, the third electric motor MG3 outputs a positive third electric motor torque Tmg3 due to power supply from the battery 64, and it is determined that the absolute value of the second electric motor rotation speed Nmg2 is less than the judgment rotation speed Nmg2_jdg, are also included in the ``case in which the engine is in an operating state and the absolute value of the required amount of output torque of the first electric motor to generate driving force for the vehicle is less than a predetermined torque value'' in the present invention.

[0044] In the flowchart of FIG. 6 of the above-described embodiment, the backlash eliminating torque Tgata may be set to a positive torque in S30, or may be set to a negative torque in S50.

[0045] For example, in the differential mechanism 32 of the above-described embodiment, 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.

[0046] For example, in the differential mechanism 32 of the above-described embodiment, the second rotating element RE2 may be one of the sun gear S and the ring gear R, the third rotating element RE3 may be the other of the sun gear S and the ring gear R, and the first rotating element RE1 may be the carrier C. In such an embodiment, the engine 20 and the first electric motor MG1 are connected to the carrier C, the second electric motor MG2 and one of the front drive shaft 38 are connected to the sun gear S, and the ring gear R is connected to the other of the second electric motor MG2 and the front drive shaft 38.

[0047] For example, the differential mechanism 32 may be configured as a double-pinion type planetary gear device.

[0048] Here, as shown in the above-mentioned embodiment, 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 32 are arranged in a straight line.

[0049] For example, the power transmission member 40 may be configured by a gear pair instead of being configured by a sprocket (intermediate gear 40a and ring gear R) and a chain 40b.

[0050] For example, in the above-described embodiment, the brake BR does not necessarily have to be provided.

[0051] For example, in the above-described embodiment, the brake BR may be replaced with a one-way clutch.

[0052] For example, in the above-described embodiment, 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. [Explanation of symbols]

[0053] 8: vehicle, 10: vehicle drive device, 12f: front wheels, 12r: rear wheels, 20: engine, 32: differential mechanism, 38: front drive shaft (first drive shaft), 58: rear drive shaft (second drive shaft), 70: electronic control device (control device), C: carrier (third rotating element), Fr: driving force, G: backlash, MG1: first electric motor, MG2: second electric motor, MG3: third electric motor, Nmg2: second electric motor rotation speed (rotation speed of second electric motor), Nmg2_jdg: judgment rotation speed (predetermined judgment rotation speed), PTmg1: power transmission path (power transmission path), R: ring gear (first rotating element), S: sun gear (second rotating element), Tgata: backlash elimination torque, Tmg1: first electric motor torque (output torque of first electric motor), Tmg1_th: torque value (predetermined torque value)

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 cause the first electric motor to output a backlash-reducing torque that reduces backlash in a power transmission path between the first rotating element and the first electric motor when the engine is in an operating state and an absolute value of a required amount of output torque of the first electric motor for generating a driving force for the vehicle is less than a predetermined torque value. A vehicle drive device characterized by:

2. The case where the absolute value of the required amount of output torque of the first electric motor for generating a driving force of the vehicle is less than the predetermined torque value means a case where the first electric motor is in a non-driving state, the second electric motor is operated as a generator, and the third electric motor is operated as a prime mover while the vehicle is traveling and a driving force of the vehicle is generated.

2. The vehicle drive system according to claim 1.

3. The case where the absolute value of the required amount of output torque of the first electric motor for generating a driving force of the vehicle is less than the predetermined torque value means that, when the driving force of the vehicle is generated during traveling and the states of the first electric motor and the second electric motor are controlled so that the power balance between the first electric motor and the second electric motor is balanced, the absolute value of the rotation speed of the second electric motor is less than a predetermined judgment rotation speed.

2. The vehicle drive system according to claim 1.

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