Vehicle drive systems

Abstract

To suppress gear rattle.SOLUTION: A vehicular driving device has an electric motor with a rotor provided to be movable in an axis direction with respect to a rotor shaft. The vehicular driving device has a first gear provided to be movable in the axis direction with respect to the rotor shaft and arranged to oppose to an end face of the rotor. The vehicular driving device has a power transmission path which has a second gear that engages with the first gear and through which the first gear and wheels are connected to each other. The vehicular driving device has an actuator that moves the rotor to a first position where the rotor is arranged on a radially inner side of a stator and a second position where the rotor is made closer to the first gear than the first position. The vehicular driving device makes the actuator move the rotor to the second position, energizes the first gear in the axis direction by magnetic force acting between the rotor and the first gear, and presses a tooth surface of the first gear against a tooth surface of the second gear.SELECTED DRAWING: Figure 6

Description

Technical Field

[0004] ,

[0006] , , , , , , , , , , , , ,

[0003] , , , , , ,

[0005]

[0001] The present invention relates to a vehicle drive device provided in a vehicle.

Background Art

[0002] Vehicles such as electric vehicles and hybrid vehicles are equipped with an electric motor for driving wheels (see Patent Documents 1 to 3). In addition, various gear trains, rotating shafts, etc. are incorporated in the power transmission path that connects the electric motor and the wheels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

[0007] According to one aspect of the present invention, the rotor is moved to a second position by an actuator, and the first gear is biased axially by a magnetic force acting between the rotor and the first gear, pressing the tooth surface of the first gear against the tooth surface of the second gear. This makes it possible to suppress the sound of gear rattling. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a vehicle equipped with a vehicle drive system, which is one embodiment of the present invention. [Figure 2] This is a diagram showing an example of the internal structure of a power unit. [Figure 3] This figure shows an example of a control system included in a vehicle's drivetrain. [Figure 4] This is a diagram showing an example of the basic structure of a control unit. [Figure 5] This figure shows an example of a motor generator and planetary gear train. [Figure 6] This figure shows an example of a motor generator and planetary gear train. [Figure 7] This diagram shows the planetary gear train from an axial view. [Figure 8] This figure shows how the minute rotation of the pinion is transmitted to each power transmission path. [Figure 9] This figure shows an example of the timing for executing backlash reduction control. [Figure 10] This figure shows an example of the timing for executing backlash reduction control. [Figure 11] This figure shows modified examples of the sun gear, pinion, and rotor shaft. [Figure 12] This figure shows an example of a power unit included in a vehicle drive system, which is another embodiment of the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, identical or substantially identical components and elements will be denoted by the same reference numerals, and repeated descriptions will be omitted.

[0010] [Power Unit] Figure 1 shows a vehicle 11 equipped with a vehicle drive system 10, which is one embodiment of the present invention. As shown in Figure 1, the vehicle 11 is mounted on a power unit 13 that includes an engine 12 and motor generators MG1 and MG2. The rear wheels 17 are connected to the rear wheel output shaft 14 of the power unit 13 via a propeller shaft 15 and a rear differential mechanism 16. The power unit 13 also incorporates a front differential mechanism 18, to which the front wheels 19 are connected. The power unit 13 shown is a power unit for all-wheel drive, but is not limited to this, and may also be a power unit for front-wheel drive or rear-wheel drive.

[0011] Figure 2 shows an example of the internal structure of the power unit 13. As shown in Figure 2, the power unit 13 has a first drive system 21 consisting of an engine 12 and a motor generator MG1, and a second drive system 22 consisting of a motor generator MG2.

[0012] The first drive system 21 has an engine 12 and a motor generator MG1 as power sources. A transmission shaft 25 is connected to the crankshaft 23 of the engine 12 via a damper mechanism 24, and a drive gear 26a is fixed to the transmission shaft 25. A driven gear 26b meshing with the drive gear 26a has a transmission shaft 27 fixed thereto, and a rotor 31 of the motor generator MG1 is connected to the transmission shaft 27 via a planetary gear train 30. Note that the gear train 26 is constituted by the drive gear 26a and the driven gear 26b.

[0013] The planetary gear train 30 connecting the transmission shaft 27 and the rotor 31 has a carrier 30c that rotatably supports a pinion 30p, a sun gear 30s that meshes with the pinion 30p, and a ring gear 30r also called an internal gear that meshes with the pinion 30p. The transmission shaft 27 is connected to the carrier 30c of the planetary gear train 30, and the rotor 31 of the motor generator MG1 is connected to the sun gear 30s of the planetary gear train 30. Further, a first output shaft 32 is connected to the ring gear 30r of the planetary gear train 30 as an output shaft for outputting engine torque and motor torque.

[0014] The second drive system 22 has a motor generator MG2 as a power source. A second output shaft 34 is connected to the rotor 33 of the motor generator MG2 via a planetary gear train 40. The planetary gear train 40 connecting the rotor 33 and the second output shaft 34 has a carrier 40c that rotatably supports a pinion 40p, a sun gear 40s that meshes with the pinion 40p, and a ring gear 40r also called an internal gear that meshes with the pinion 40p. The second output shaft 34 is connected to the carrier 40c of the planetary gear train 40, and the rotor 33 of the motor generator MG2 is connected to the sun gear 40s of the planetary gear train 40. Note that the ring gear 40r of the planetary gear train 40 is fixed to the housing 35 of the power unit 13.

[0015] Further, the first output shaft 32 of the first drive system 21 is connected to the second output shaft 34 of the second drive system 22 via a gear train 36. Also, a front wheel output shaft 38 is connected to one end of the second output shaft 34 via a gear train 37, and a rear wheel output shaft 14 is connected to the other end of the second output shaft 34 via a coupling 39. The front wheel output shaft 38 is connected to the front wheels 19 via the front differential mechanism 18 described above, and the rear wheel output shaft 14 is connected to the rear wheels 17 via the rear differential mechanism 16 described above.

[0016] As shown in FIG. 2, a sun gear (first gear) 40s of a planetary gear train 40 is connected to a rotor 33 of a motor generator (electric motor) MG2. Also, the sun gear 40s and the front wheels (wheels) 19 are connected to each other via a power transmission path 41 including a pinion (second gear) 40p that meshes with the sun gear 40s. In the illustrated example, the power transmission path 41 is constituted by a pinion 40p, a carrier 40c, a second output shaft 34, a gear train 37, a front wheel output shaft 38, a front differential mechanism 18, and the like. Also, as shown in FIGS. 1 and 2, the sun gear 40s of the planetary gear train 40 and the rear wheels (wheels) 17 are connected to each other via a power transmission path 42 including a pinion 40p that meshes with the sun gear 40s. In the illustrated example, the power transmission path 42 is constituted by a pinion 40p, a carrier 40c, a second output shaft 34, a coupling 39, a rear wheel output shaft 14, a propeller shaft 15, a rear differential mechanism 16, and the like.

[0017] Furthermore, the second output shaft 34 and the first output shaft 32 are connected to each other via a gear train 36. In other words, the power transmission paths 41 and 42 that constitute the second drive system 22 are connected to the power transmission path 43 that constitutes the first drive system 21 and the engine 12 via the gear train 36. In the illustrated example, the power transmission path 43 that connects the power transmission paths 41, 42 to the engine 12 is composed of the first output shaft 32, a ring gear 30r, a pinion 30p, a carrier 30c, a transmission shaft 27, a gear train 26, a transmission shaft 25, and a damper mechanism 24, etc. Thus, the engine 12 is connected to the power transmission paths 41 and 42 via the power transmission path 43.

[0018] [Control System] Figure 3 shows an example of a control system 80 provided in a vehicle drive unit 10. As shown in Figure 3, the intake manifold 50 of the engine 12 is equipped with a throttle valve 51 for adjusting the amount of intake air. The engine 12 is also equipped with injectors 52 for injecting fuel into the intake ports and cylinders, and an ignition device 53 consisting of an ignition coil and spark plug. An engine control unit 54 is connected to the throttle valve 51, injectors 52, and ignition device 53, etc., in order to control engine torque and engine speed.

[0019] The motor generator MG1 has a stator 61 around which stator coils 60 are wound, and a rotor 31 housed in the cylindrical stator 61. An inverter 62 is connected to the stator 61, and a battery pack 63 is connected to the inverter 62. In addition, a first motor control unit 64 is connected to the inverter 62 in order to control the motor generator MG1 via the inverter 62. The first motor control unit 64 controls the motor torque and motor speed of the motor generator MG1 by controlling the inverter 62, which consists of multiple switching elements, etc. The motor generator MG1 can be controlled to a powering state in which powering torque is generated to increase the motor speed, and a regenerative state in which regenerative torque is generated to decrease the motor speed. The regenerative state of the motor generator MG1 is also called the power generation state.

[0020] The motor generator MG2 has a stator 71 around which stator coils 60 are wound, and a rotor 33 housed in the cylindrical stator 71. An inverter 72 is connected to the stator 71, and a battery pack 63 is connected to the inverter 72. A second motor control unit 73 is connected to the inverter 72 in order to control the motor generator MG2 via the inverter 72. The second motor control unit 73 controls the motor torque and motor speed of the motor generator MG2 by controlling the inverter 72, which consists of multiple switching elements. The motor generator MG2 can be controlled to either a powering state, which generates powering torque to increase the motor speed, or a regenerative state, which generates regenerative torque to decrease the motor speed. The regenerative state of the motor generator MG2 is also called the power generation state.

[0021] The vehicle drive system 10 is equipped with a control system 80 consisting of multiple electronic control units for controlling the power unit 13. The control system 80 is equipped with the aforementioned engine control unit 54 and motor control units 64 and 73 as electronic control units, and a vehicle control unit 81 that outputs control signals to these control units 54, 64 and 73. These control units 54, 64, 73 and 81 are connected to each other so as to be able to communicate with each other via an in-vehicle network 82 such as CAN. The vehicle control unit 81 sets operating targets for the engine 12 and motor generators MG1 and MG2 based on input information from various control units and various sensors described later. It then generates control signals according to the operating targets for the engine 12 and motor generators MG1 and MG2, and outputs these control signals to the engine control unit 54 and motor control units 64 and 73, etc.

[0022] The vehicle control unit 81 is connected to an accelerator sensor 83 that detects the amount of operation of the accelerator pedal, and a brake sensor 84 that detects the amount of operation of the brake pedal. It is also connected to a vehicle speed sensor 85 that detects the vehicle speed from the rotational speed of the front wheel output shaft 38 and the rear wheel output shaft 14, and an engine speed sensor 86 that detects the engine speed, which is the rotational speed of the crankshaft 23. Furthermore, it is connected to a first motor speed sensor 87 that detects the motor speed, which is the rotor rotational speed of the motor generator MG1, and a second motor speed sensor 88 that detects the motor speed, which is the rotor rotational speed of the motor generator MG2. In addition, the vehicle control unit 81 is connected to a start switch 89 that is operated by the driver when the control system 80 is started, and to a position switch 91 that detects the driver's position of the select lever 90.

[0023] Figure 4 shows an example of the basic structure of control units 54, 64, 73, and 81. As shown in Figure 3, the electronic control units 54, 64, 73, and 81 have a microcontroller 102 that incorporates a processor 100 and main memory (memory) 101, etc. A predetermined program is stored in the main memory 101, and the program is executed by the processor 100. The processor 100 and the main memory 101 are connected to each other so as to be able to communicate with each other. Note that the microcontroller 102 may incorporate multiple processors 100, and the microcontroller 102 may also incorporate multiple main memory 101.

[0024] Furthermore, control units 54, 64, 73, and 81 are equipped with an input circuit 103, a drive circuit 104, a communication circuit 105, an external memory 106, and a power supply circuit 107, etc. The input circuit 103 converts signals input from various sensors into signals that can be input to the microcontroller 102. The drive circuit 104 generates drive signals for various devices such as the inverters 62 and 72 mentioned above, based on signals output from the microcontroller 102. The communication circuit 105 converts signals output from the microcontroller 102 into communication signals for other control units. The communication circuit 105 also converts communication signals received from other control units into signals that can be input to the microcontroller 102. In addition, the power supply circuit 107 supplies a stable power voltage to the microcontroller 102, input circuit 103, drive circuit 104, communication circuit 105, and external memory 106, etc. Furthermore, the external memory 106, which consists of non-volatile memory, stores programs and various data.

[0025] [Motor Generators and Sun Gears] Next, the structure of the motor generator MG2 and the sun gear 40s will be described in detail. Figures 5 and 6 show an example of the motor generator MG2 and the planetary gear train 40. As shown in Figure 5, the motor generator MG2 has a cylindrical rotor 33 and a stator 71 positioned radially outward from the rotor 33. The rotor 33 of the motor generator MG2 has a rotor core 110 made of multiple stacked electromagnetic steel sheets and multiple permanent magnets 111 provided on the rotor core 110. The stator 71, which is fixed to the housing 35, has a stator core 112 made of multiple stacked electromagnetic steel sheets and a stator coil 70 wound around the stator core 112.

[0026] To support the rotor 33 of the motor generator MG2, a hollow rotor shaft 113 is provided on the radially outer side of the second output shaft 34. An internal spline tooth 114 is formed in a through hole 116 that penetrates the rotation center of the rotor 33, and external spline teeth 115 are formed on the outer circumferential surface of the rotor shaft 113. The rotor shaft 113 is inserted into the through hole 116 of the rotor 33, and the internal spline tooth 114 and the external spline tooth 115 are slidably engaged with each other. In other words, the rotor 33 of the motor generator MG2 is provided so as to be movable in the axial direction relative to the rotor shaft 113.

[0027] Furthermore, the motor generator MG2 has a slide mechanism 120 that moves the rotor 33 in the axial direction. The slide mechanism 120 includes a bearing 121 attached to the rotor 33, a lever member 122 tiltably supported by the housing 35, and an electric actuator (actuator) 124 equipped with a push rod 123. One end of the lever member 122 is connected to the bearing 121, and the other end of the lever member 122 is connected to the push rod 123. A second motor control unit 73 is connected to the electric actuator 124, and the electric actuator 124 is controlled based on a control signal from the second motor control unit 73. In addition, the electric actuator 124 is operable in a first state in which the push rod 123 is pushed out and a second state in which the push rod 123 is retracted.

[0028] As shown in Figure 5, by retracting the push rod 123 of the electric actuator 124, the lever member 122 can be rotated in the direction of arrow a1, and the rotor 33 can be moved to a first position where it is positioned radially inward of the stator 71. By moving the rotor 33 to this first position, almost the entire outer surface of the rotor 33 can be brought into contact with the inner surface of the stator 71, thereby maximizing the effective magnetic flux of the motor generator MG2.

[0029] On the other hand, as shown in Figure 6, by pushing out the push rod 123 of the electric actuator 124, the lever member 122 can be rotated in the direction of arrow a2, and the rotor 33 can be moved to a second position, which is closer to the sun gear 40s than the first position. By moving the rotor 33 to the second position in this way, a part of the rotor 33 can be made to protrude from the inside of the stator 71, thereby reducing the effective magnetic flux and lowering the back electromotive force during rotation. The control system 80 increases the motor speed of the motor generator MG2 by moving the rotor 33 to the second position and lowering the back electromotive force within the preset operating range of the motor generator MG2. The motor generator MG2 is also called a variable field motor.

[0030] As shown in Figure 5, a sun gear 40s is positioned near the rotor 33 of the motor generator MG2, facing the end face 33a of the rotor 33. An internal spline tooth 125 is formed in a through-hole 129 that penetrates the rotation center of the sun gear 40s, and an external spline tooth 126 is formed on the outer circumferential surface of the rotor shaft 113. Furthermore, the rotor shaft 113 is inserted into the through-hole 129 of the sun gear 40s, and the internal spline tooth 125 and the external spline tooth 126 are slidably engaged with each other. In other words, the sun gear 40s of the planetary gear train 40 is provided to be axially movable relative to the rotor shaft 113. Additionally, a permanent magnet 128 is provided on the side surface 127 of the sun gear 40s facing the end face 33a of the rotor 33, and the magnetic poles of this permanent magnet 128 are set to repel the rotor 33. In other words, the magnetic poles that appear on the side surface 127 of the sun gear 40s due to the permanent magnet 128 and the magnetic poles that appear on the end surface 33a of the rotor 33 are set to the same pole. Furthermore, as shown in the enlarged portion of Figure 5, the sun gear 40s and pinion 40p of the planetary gear train 40 are helical gears whose tooth traces are inclined with respect to the axial direction.

[0031] [Backlash Reduction Control] Backlash reduction control using the electric actuator 124 will now be explained. As shown in Figure 6, by pushing out the push rod 123 of the electric actuator 124 and bringing the rotor 33 closer to the sun gear 40s, the magnetic force acting between the rotor 33 and the sun gear 40s can be increased, thereby biasing the sun gear 40s in the axial direction. In other words, by bringing the rotor 33 closer to the sun gear 40s, the sun gear 40s can be biased in the direction of arrow b1 by magnetic force. Here, Figure 7 is a diagram showing the planetary gear train 40 from the axial direction. As mentioned above, since the axially biased sun gear 40s is a helical gear with inclined tooth traces, the tooth surface 130 of the sun gear 40s can be moved toward the tooth surface 131 of the pinion 40p, as shown by arrow c1 in Figure 7. Then, the tooth surface 130 of the sun gear 40s is pressed against the tooth surface 131 of the pinion 40p, and the pinion 40p can be rotated slightly in the direction of arrow c2. In other words, it is possible to reduce the backlash between the 40s sun gear and the 40p pinion.

[0032] Such minute rotations of the pinion 40p are transmitted to the aforementioned power transmission paths 41 to 43. Figure 8 shows the transmission of the minute rotations of the pinion 40p to each power transmission path 41 to 43. As indicated by arrow X1 in Figure 8, the minute rotations of the pinion 40p are transmitted to the power transmission path 41 while reducing the backlash of each mechanical element. In other words, the minute rotations of the pinion 40p are transmitted to the carrier, second output shaft 34, gear train 37, front wheel output shaft 38, and front differential mechanism 18, etc., while reducing the backlash of each mechanical element.

[0033] Furthermore, as shown by arrow X2 in Figure 8, the minute rotation of pinion 40p is transmitted to the power transmission path 42 while reducing the backlash of each mechanical element. In other words, the minute rotation of pinion 40p is transmitted to the carrier, second output shaft 34, coupling 39, and rear wheel output shaft 14, etc., while reducing the backlash of each mechanical element. Moreover, as shown by arrow X3 in Figure 8, the minute rotation of pinion 40p is transmitted to the power transmission path 43 while reducing the backlash of each mechanical element. In other words, the minute rotation of pinion 40p is transmitted to the carrier 40c, second output shaft 34, gear train 36, first output shaft 32, ring gear 30r, pinion 30p, carrier 30c, transmission shaft 27, gear train 26, transmission shaft 28, and damper mechanism 24, etc., while reducing the backlash of each mechanical element.

[0034] As explained above, by pushing out the push rod 123 of the electric actuator 124 and bringing the rotor 33 closer to the sun gear 40s, the sun gear 40s can be biased in the axial direction by magnetic force. This allows the tooth surface 130 of the sun gear 40s to be pressed against the tooth surface 131 of the pinion 40p, causing the pinion 40p to rotate slightly and reducing the backlash in each power transmission path 41 to 43. By reducing the backlash in each power transmission path 41 to 43 in this way, even if the torque flow reverses in each power transmission path 41 to 43, the tooth noise of each gear train constituting each power transmission path 41 to 43 can be suppressed.

[0035] In the illustrated example, in backlash reduction control, the tooth surface 130 of the sun gear 40s is pressed against the tooth surface 131 of the pinion 40p. However, the direction in which the tooth surfaces are pressed can be either the drive side or the coast side. Whether to press the drive-side tooth surface or the coast-side tooth surface is determined by the effect of suppressing tooth noise in each gear train of the power transmission path 41-43. The direction in which the tooth surfaces are pressed can be set by the orientation of the tooth traces in the sun gear 40s and the pinion 40p.

[0036] In the above description, a repulsive magnetic force is applied to move the sun gear 40s away from the rotor 33, but this is not the only option; an attractive magnetic force may also be applied to move the sun gear 40s closer to the rotor 33. Also, in the above description, a permanent magnet 128 is attached to the sun gear 40s, but this is not the only option; the permanent magnet 128 may be removed from the sun gear 40s. In this way, even if the permanent magnet 128 is removed from the sun gear 40s, it is still possible to bias the sun gear 40s, which is made of a magnetic material, toward the rotor 33 by an attractive magnetic force.

[0037] [Backlash reduction control: during engine startup] Figure 9 shows an example of the timing of backlash reduction control. The control system 80 performs backlash reduction control using the electric actuator 124 when cranking the engine 12 in, for example, the parking range or driving range. In other words, the control system 80 starts the engine 12 with the rotor 33 moved to the second position by the electric actuator 124. When the engine is started, the engine 12 is cranked by the motor generator MG1.

[0038] As shown in Figure 9, the electric actuator 124 brings the rotor 33 closer to the sun gear 40s, and the magnetic force biases the sun gear 40s in the axial direction, thereby reducing the backlash of the power transmission path 43 (arrow X3). In other words, the tooth surface 132 of the driven gear 26b constituting the power transmission path 43 can be pressed against the tooth surface 133 of the drive gear 26a, thereby reducing the backlash of the gear train 26. As a result, even when torque fluctuations Tf1 associated with the cranking of the engine 12 are input to the gear train 26, the tooth noise of the gear train 26 can be suppressed. Note that the suppression of tooth noise is not limited to the gear train 26, but can be suppressed for each gear train constituting the power transmission path 43.

[0039] [Backlash reduction control: during constant speed driving] Figure 10 shows an example of the execution timing of backlash reduction control. The control system 80, for example, executes backlash reduction control using the electric actuator 124 when driving the vehicle 11 at a constant speed using the motor generator MG2. In other words, with the rotor 33 moved to the second position by the electric actuator 124, the control system 80 alternately switches the motor generator MG2 between the powering state and the regenerative state in order to maintain the vehicle speed at a predetermined speed.

[0040] As shown in Figure 10, the electric actuator 124 brings the rotor 33 closer to the sun gear 40s, and the magnetic force biases the sun gear 40s in the axial direction, thereby reducing the backlash of the power transmission path 43 (arrows X1, X2). In other words, the tooth surfaces of each gear train constituting the power transmission paths 41 and 42 can be pressed against each other, reducing the backlash of these gear trains. As a result, even when the motor generator MG2 alternates between the powering state and the regenerative state to maintain a predetermined speed, and torque fluctuations Tf2 are input to each gear train of the power transmission paths 41 and 42, the tooth noise of each gear train constituting the power transmission paths 41 and 42 can be suppressed.

[0041] [Other Embodiment 1] In the above description, helical gears are used as the sun gear 40s and pinion 40p of the planetary gear train 40, but this is not the only option, and spur gears may also be used as the sun gear 40s and pinion 40p. Here, Figure 11 shows a modified example of the sun gear 40s, pinion 40p and rotor shaft 113. Note that the planetary gear train 140 shown in Figure 11 is a gear train that functions similarly to the planetary gear train 40, but is denoted by reference numeral 140 because the tooth pattern is different. Similarly, the rotor shaft 143 shown in Figure 11 is a rotating shaft that functions similarly to the rotor shaft 113, but is denoted by reference numeral 143 because the spline teeth are different. Also, in Figure 11, components similar to those shown in Figure 6 are given the same reference numerals and their descriptions are omitted.

[0042] As shown in Figure 11, the sun gear (first gear) 140s and pinion (second gear) 140p of the planetary gear train 140 are spur gears with tooth traces parallel to the axial direction. Furthermore, internal spline teeth 141 are formed in a through-hole 144 that penetrates the rotation center of the sun gear 140s, and external spline teeth 142 are formed on the outer circumferential surface of the rotor shaft 143. The rotor shaft 143 is inserted into the through-hole 144 of the sun gear 140s, and the internal spline teeth 141 and external spline teeth 142 are slidably engaged with each other. The internal spline teeth 141 and external spline teeth 142 are helical splines with tooth traces inclined with respect to the axial direction. In other words, the sun gear 140s of the planetary gear train 140 is mounted to be axially movable while rotating relative to the rotor shaft 143.

[0043] As shown in Figure 11, by pushing out the push rod 123 of the electric actuator 124 and bringing the rotor 33 closer to the sun gear 140s, the magnetic force acting between the rotor 33 and the sun gear 140s can bias the sun gear 140s in the axial direction. In other words, by bringing the rotor 33 closer to the sun gear 140s, the sun gear 140s can be biased in the direction of arrow b1 by magnetic force. Here, as the sun gear 140s moves in the direction of arrow d1 when it moves in the axial direction, the tooth surface of the sun gear 140s can be moved toward the tooth surface of the pinion 140p. Then, the tooth surface of the sun gear 140s is pressed against the tooth surface of the pinion 140p, causing the pinion 140p to rotate slightly and reducing the backlash in each power transmission path 41 to 43. In this way, by reducing the backlash in each power transmission path 41 to 43, it is possible to suppress the tooth noise of each gear train constituting each power transmission path 41 to 43, even when the torque flow in each power transmission path 41 to 43 is reversed.

[0044] [Another Embodiment 2] In the above description, the vehicle drive system 10 is provided for a hybrid vehicle 11 equipped with an engine 12 and motor generators MG1 and MG2, but it is not limited to this. For example, the vehicle drive system may be provided for an electric vehicle equipped only with a motor generator MG2 as a power source. Here, Figure 12 is a diagram showing an example of a power unit 151 provided for a vehicle drive system 150, which is another embodiment of the present invention. In Figure 12, components similar to those shown in Figure 2 are given the same reference numerals and their descriptions are omitted.

[0045] As shown in Figure 12, the rotor 33 of the motor generator (electric motor) MG2 is connected to the sun gear (first gear) 40s of the planetary gear train 40. The sun gear 40s and the front wheel 19 are connected to each other via a power transmission path 41 consisting of a pinion (second gear) 40p that meshes with the sun gear 40s. In the illustrated example, the power transmission path 41 consists of the pinion 40p, carrier 40c, second output shaft 34, gear train 37, front wheel output shaft 38, and front differential mechanism 18. The motor generator MG2 is also provided with a slide mechanism 120 that moves the rotor 33 in the axial direction.

[0046] Thus, even in an electric vehicle equipped only with a motor generator MG2, for example, when the vehicle is driven at a constant speed using the motor generator MG2, backlash reduction control is performed by the electric actuator 124. In other words, the control system 80 alternately switches the motor generator MG2 between a powering state and a regenerative state in order to maintain the vehicle speed at a predetermined speed, with the rotor 33 moved to the second position by the electric actuator 124. As mentioned above, the electric actuator 124 brings the rotor 33 closer to the sun gear 40s and biases the sun gear 40s axially by magnetic force, thereby reducing the backlash in the power transmission path 41. As a result, even when the powering state and regenerative state of the motor generator MG2 are alternately repeated in order to maintain a predetermined vehicle speed, and torque fluctuations are input to each gear train of the power transmission path 41, the tooth noise of each gear train constituting the power transmission path 41 can be suppressed.

[0047] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. In the above description, two motor generators MG1 and MG2 are provided for the power unit 13, but the invention is not limited to this, and one motor generator may be provided for the power unit 13. Also, in the above description, a slide mechanism 120 is provided for the motor generator MG2, but the invention is not limited to this, and the slide mechanism 120 may be provided only for the motor generator MG1, or for both motor generators MG1 and MG2. Also, in the above description, an electric actuator 124 is used as the actuator to move the rotor 33, but the invention is not limited to this, and a hydraulic actuator may be used. Also, in the above description, the rotor 33 is moved in the axial direction using a lever member 122, but the invention is not limited to this. For example, as a hydraulic actuator, a hydraulic chamber may be formed at the end of the rotor 33, and the rotor 33 may be moved in the axial direction by supplying hydraulic fluid to the hydraulic chamber.

[0048] As mentioned above, the rotor 33 biases the sun gear 40s in the axial direction, pressing the tooth surface 130 of the sun gear 40s against the tooth surface 131 of the pinion 40p, causing the pinion 40p to rotate slightly. This slight rotation of the pinion 40p reduces the backlash in each power transmission path 41-43, but it is not necessary to eliminate the backlash of all mechanical elements constituting the power transmission paths 41-43; it goes without saying that it is sufficient for at least the tooth surface 130 of the sun gear 40s to be pressed against the tooth surface 131 of the pinion 40p. Furthermore, in the above explanation, the sun gear 40s of the planetary gear train 40 is used as the first gear and the pinion 40p of the planetary gear train 40 is used as the second gear, but it is not limited to the gears that make up the planetary gear train.

[0049] In the above description, a spline structure consisting of internal spline teeth 114 and external spline teeth 115 is used as the support structure between the rotor shaft 113 and the rotor 33, but it is not limited to this. For example, a ball spline structure with rolling elements interposed between the rotor shaft 113 and the rotor 33 may be used as the support structure between the rotor shaft 113 and the rotor 33. Similarly, a spline structure consisting of internal spline teeth 125, 141 and external spline teeth 126, 142 is used as the support structure between the rotor shaft 113 and the sun gear 40s, but it is not limited to this. For example, a ball spline structure with rolling elements interposed between the rotor shaft 113 and the sun gear 40s may be used as the support structure between the rotor shaft 113 and the sun gear 40s. [Explanation of symbols]

[0050] 10. Vehicle drive systems 11 vehicles 12 Engines 17 Rear wheel (wheel) 19 Front wheel 33 Rotors 33a End face 40s Sun gear (1st gear) 40p pinion (2nd gear) 41 Power transmission path 42 Power transmission path 80 Control Systems 100 processors 101 Main memory (memory) 113 Rotor shaft 124 Electric Actuator (Actuator) 128 Permanent Magnets 130 Tooth surface 131 Tooth surface 140s Sun gear (first gear) 140p pinion (2nd gear) 143 Rotor shaft 150 Vehicle drive systems MG2 Motor Generator (Electric Motor)

Claims

1. A vehicle drive system installed in a vehicle, An electric motor comprising a rotor that is axially movable with respect to the rotor shaft, and a stator positioned radially outward of the rotor, A first gear is provided so as to be axially movable with respect to the rotor shaft and is positioned opposite the end face of the rotor, A power transmission path is provided which a second gear meshes with the first gear and connects the first gear and the wheel to each other, An actuator moves the rotor to a first position where it is positioned radially inward of the stator, and to a second position where the rotor is closer to the first gear than to the first position. It has, The actuator moves the rotor to the second position, and the magnetic force acting between the rotor and the first gear biases the first gear in the axial direction, pressing the tooth surface of the first gear against the tooth surface of the second gear. Vehicle drive system.

2. In the vehicle drive system according to claim 1, The first gear is equipped with a permanent magnet. Vehicle drive system.

3. In the vehicle drive system according to claim 1, The first gear and the second gear are helical gears. Vehicle drive system.

4. In the vehicle drive system according to claim 1, An engine connected to the aforementioned power transmission path, A control system comprising a processor and memory connected to each other in a manner that enables communication between them, for controlling the engine and the actuator, It has, The control system starts the engine while the rotor is moved to the second position by the actuator. Vehicle drive system.

5. In the vehicle drive system according to claim 1, A control system comprising a processor and memory connected to each other in a manner that enables communication between them, for controlling the electric motor and the actuator, The control system alternately switches the electric motor between a powering state and a regenerative state while the rotor is moved to the second position by the actuator. Vehicle drive system.

Images