JP2008174069A - Wheel driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wheel driving device capable of improving the flexibility in setting an oil pump rotation frequency while keeping the certainty of action of an oil pump. <P>SOLUTION: The wheel driving device 1 comprises a case 3 attached to a vehicle through a suspension device 130, a traction motor 20 provided in the case 3 and including a stator 21 and a rotor 22, a rotor shaft 25 to which the rotor 22 is fixed, an oil 11 injected into the case 3, an oil cooler cooling the oil 11, and an oil pump 50 supplying the oil 11 cooled by the oil cooler to the stator 21. The wheel driving device 1 also comprises a pump driving shaft 52 driving the oil pump 40, an oil pump driving motor 51 driving the pump driving shaft 52, and a one-way clutch 70 interposed between the rotor shaft 25 and the pump driving shaft 52, and capable of transmitting torque in one direction from the rotor shaft 25 to the pump driving shaft 52. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a wheel drive device that drives a wheel by a traction motor including a stator and a rotor and includes an oil pump, and particularly relates to a device that is characterized by a drive mode of the oil pump.

  Conventionally, a case attached to a vehicle via a suspension device, a traction motor provided in the case and including a stator and a rotor, a rotor shaft on which the rotor is fixed, and oil injected into the case There is known a wheel drive device that includes an oil cooler that cools the oil, and an oil pump that supplies at least the oil cooled by the oil cooler to the stator.

  In general, the efficiency of the traction motor varies depending on the temperature, so it is desirable to maintain the temperature near the most efficient temperature. However, since the traction motor used in the wheel drive device generates heat when a current flows through a stator coil provided in the stator, cooling is required to maintain the temperature.

  Usually, the traction motor is cooled by lubricating oil. Effective cooling can be achieved by supplying the oil cooled by the oil cooler to the stator by the oil pump.

Patent Document 1 discloses a wheel drive device (in-wheel motor) in which the cooling efficiency of the motor is improved by devising the oil circulation path.
JP 2005-73364 A

  However, in the conventional wheel drive device, as disclosed in Patent Document 1, the rotor shaft of the traction motor and the pump drive shaft of the oil pump are directly connected. According to this structure, when the traction motor is operated, the oil pump is mechanically interlocked with the oil pump, so that there is an advantage that high operation reliability can be obtained. However, the oil pump rotation speed always matches the traction motor rotation speed. Therefore, the degree of freedom in setting the number of revolutions of the oil pump is low, and the following inconveniences are likely to occur.

  For example, in the conventional structure, when the traction motor is stopped, the oil pump is also stopped. Therefore, it is difficult to cope with the case where the stator needs to be cooled even when the traction motor is stopped. Further, when high cooling performance is required in a relatively low rotation region, a large-sized and large-capacity cooling system (oil pump or oil cooler) is required to meet the demand. If such a cooling system is adopted, since the discharge flow rate is higher than necessary in the high rotation region, the oil pump driving torque is increased. Therefore, useless energy consumption by the oil pump increases, resulting in a decrease in fuel consumption.

  In view of the circumstances as described above, an object of the present invention is to provide a wheel drive device that can increase the degree of freedom in setting the number of revolutions of the oil pump while maintaining the operational reliability of the oil pump.

  The invention according to claim 1 for solving the above-described problem is a case in which a case attached to a vehicle via a suspension device, a traction motor provided in the case and including a stator and a rotor, and the rotor are fixedly provided. A rotor shaft, oil injected into the case, an oil cooler that cools the oil, and an oil pump that supplies at least the oil cooled by the oil cooler to the stator. In the wheel drive device that drives the wheel by the output torque of the pump, the pump drive shaft that drives the oil pump, the oil pump drive motor that drives the pump drive shaft, and the rotor shaft and the pump drive shaft A one-way clutch that can transmit torque in one direction from the rotor shaft to the pump drive shaft. Characterized in that it obtain.

  According to a second aspect of the present invention, in the wheel drive device according to the first aspect, a reduction gear is provided between the rotor shaft and the wheel, and the oil pump and the oil pump drive motor are coaxial with the rotor shaft. Further, it is provided on the opposite side of the speed reducer across the rotor.

  According to a third aspect of the present invention, in the wheel drive device according to the second aspect, the pump drive shaft is provided coaxially with the rotor shaft at an end portion of the rotor shaft and is opposed to the rotor shaft. The one-way clutch is interposed between the outer peripheral surface of the end portion of the rotor shaft and the inner peripheral surface of the concave portion.

  The invention according to claim 4 is the wheel drive device according to claim 2 or 3, wherein the oil pump drive motor is disposed on the opposite side of the rotor shaft across the oil pump, and the oil pump drive motor The rotor is fixed to the pump drive shaft.

  According to the first aspect of the present invention, as will be described below, the degree of freedom in setting the number of revolutions of the oil pump can be increased while maintaining the operational reliability of the oil pump.

  The wheel drive device of the present invention has an oil pump drive motor that drives a pump drive shaft. That is, this oil pump functions as an electric oil pump. However, this oil pump is not a simple electric oil pump, and its pump drive shaft is connected to the rotor shaft of the traction motor via a one-way clutch. Therefore, it has the following effects.

  First, the oil pump drive motor can increase the oil pump speed more than the traction motor speed. At this time, since the torque is not transmitted from the pump drive shaft to the rotor shaft due to the action of the one-way clutch, for example, overrun (also referred to as idling), the operation (rotation) of the oil pump does not affect the operation (rotation) of the traction motor. Absent. Accordingly, the oil pump rotational speed can be set to an appropriate rotational speed corresponding to the required discharge flow rate within a range equal to or higher than the traction motor rotational speed. That is, the degree of freedom in setting the oil pump speed is increased.

  On the other hand, when the oil pump drive motor is stopped or when its rotational speed is going to be lower than the traction motor rotational speed, torque is transmitted from the rotor shaft to the pump drive shaft by the action of the one-way clutch, for example, lock. That is, the oil pump is driven by the rotor shaft as in the conventional structure. Therefore, even if a failure occurs in which the output of the oil pump drive motor decreases due to some cause, such as disconnection or a decrease in supply power, the operation of the oil pump at the rotational speed of the traction motor or more is ensured. That is, a discharge flow rate (cooling performance) of a certain level or more can be ensured even during a failure, and a significant decrease in cooling performance can be suppressed.

  According to the invention of claim 2, it becomes easy to arrange the traction motor and the oil pump at positions close to each other in terms of layout. Therefore, a cooling oil passage from the oil pump to the traction motor (particularly the stator) can be easily arranged, and the distance can be shortened.

  According to the invention of claim 3, as described below, the structure around the rotor shaft can be easily made compact.

  According to the structure of the present invention, the inner peripheral side of the one-way clutch comes into contact with the outer peripheral surface of the end portion of the rotor shaft. Therefore, it is easy to reduce the diameter of the end of the rotor shaft. A drive shaft such as a rotor shaft is generally tapered (medium thick) in consideration of assembly. By reducing the diameter of the tip of the rotor shaft, it becomes easier to reduce the diameter of the entire rotor shaft, so that the structure around the rotor shaft can be easily made compact.

  According to the invention of claim 4, the oil pump drive motor is easily assembled. Moreover, when the presence or absence of the oil pump drive motor is provided depending on the model, it becomes easy to additionally install the motor. That is, the assembly property of the oil pump drive motor can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a wheel driving device 1 according to an embodiment of the present invention. FIG. 2 is a right side view of FIG. 1 and 2, the upper part of the figure shows the upper part of the vehicle, and in FIG. 2, the right side of the figure shows the front part of the vehicle. 1 and 2 show the left front wheel, the same configuration is provided for all the drive wheels.

  The wheel drive device 1 includes a case 3 attached to a vehicle via a suspension device 130 (an upper strut assembly 131 and a lower lower arm 132 shown in FIG. 1), a stator 21 and a rotor 22 provided in the case 3. Including the traction motor 20, the rotor shaft 25 fixed to and supported by the rotor 22, the oil 11 injected into the case 3, an oil cooler 63 (shown in FIG. 2) for cooling the oil 11, and the oil And an oil pump 50 that supplies the oil 11 cooled by the cooler 63 to each part including the stator 21, and is configured to drive the wheel 120 by the output torque from the rotor shaft 25.

  Furthermore, the wheel drive device 1 includes a pump drive shaft 52 that drives the oil pump 50 and an oil pump drive motor 51 that drives the pump drive shaft 52. A one-way clutch (hereinafter abbreviated as OWC) 70 is interposed between the rotor shaft 25 and the pump drive shaft 52. As will be described in detail later, the OWC 70 is configured such that torque can be transmitted only in one direction from the rotor shaft 25 to the pump drive shaft 52.

  The wheel drive device 1 includes an output shaft 80 that is rotatably provided in the case 3. The output shaft 80 transmits the output from the rotor shaft 25 to the wheel 120 via the planetary gear 30 (reduction gear).

  The oil pump drive motor 51, the oil pump 50, the traction motor 20, the planetary gear 30 and the output shaft 80 are arranged in this order from the inner side in the vehicle width direction (the right side in FIG. 1). The rotor 53 of the oil pump drive motor 51, the pump drive shaft 52 of the oil pump 50, the rotor shaft 25 of the traction motor 20, the sun gear 31 of the planetary gear 30, and the output shaft 80 are arranged coaxially.

  The traction motor 20 mainly includes a stator 21 and a rotor 22. The stator 21 is formed by winding a coil around a substantially cylindrical stator core, and is fixed to the case 3. The rotor 22 is a substantially cylindrical member provided on the inner peripheral side of the stator 21. The rotor shaft 25 is rotatably supported by the case 3 and is inserted through and connected to the inner peripheral side of the rotor 22. A rotor shaft oil passage 27 penetrating in the axial direction is formed in the axial center portion of the rotor shaft 25. By passing a predetermined current through the coil of the stator 21, the rotor 22 is rotated by electromagnetic force, and the driving force is output from the rotor shaft 25.

  The traction motor 20 acts as a generator during reverse driving (when the rotor shaft 25 is driven from the output shaft 80 side). That is, it has an energy regeneration function. The generated electricity can be stored in the high voltage battery 91 or the low voltage battery 93 (see FIG. 4).

  The oil pump 50 sucks up the oil 11 stored in the case 3 from the oil reservoir 10, pressurizes it, and discharges it to the oil passage for lubrication / cooling (details will be described later). As described above, the pump drive shaft 52 that drives the oil pump 50 is disposed coaxially with the rotor shaft 25 and on the inner side in the vehicle width direction. A recess 52 a that includes the end of the rotor shaft 25 is formed at a position of the pump drive shaft 52 that faces the rotor shaft 25. An OWC 70 is interposed between the outer peripheral surface of the end portion of the rotor shaft 25 and the inner peripheral surface of the recess 52a.

  3A and 3B are views showing the vicinity of the OWC 70 in particular in the cross-sectional view taken along the line III-III in FIG. 1, wherein FIG. 3A shows the locked state of the OWC 70 and FIG. 3B shows the overrun state of the OWC 70.

  In FIG. 3, arrow A1 shows the rotation direction of the rotor shaft 25 when the vehicle moves forward. The OWC 70 of this embodiment is generally called a roller type, and mainly includes an outer ring 71, a roller 72, a spring 73, and a cage 74. The outer ring 71 is a substantially annular member, and the outer peripheral surface is fitted on the inner circumferential side of the recess 52a of the pump drive shaft 52 (may be spline fitting or the like). Accordingly, the outer ring 71 rotates integrally with the pump drive shaft 52. A predetermined cam surface is formed on the inner peripheral surface of the outer ring 71. An annular gap is provided between the outer peripheral surface of the rotor shaft 25 and the inner peripheral surface (cam surface) of the outer ring 71, and a plurality of sets of rollers 72 and springs 73 are disposed therein (this embodiment). Then 6 sets). These are held by the holder 74. Each spring 73 biases each roller 72 to one side in the circumferential direction (the same direction as the arrow A1).

  With this structure, as shown in FIG. 3A, when the pump drive shaft 52 attempts to rotate relative to the rotor shaft 25 in the direction opposite to the arrow A1 direction (indicated by the arrow A2), that is, the rotor shaft. When trying to rotate at a lower speed than 25, trying to stop, or trying to rotate in the opposite direction, a locked state (also simply referred to as a lock) is entered. At the time of locking, the roller 72 moves in the urging direction of the spring 73 and engages between the outer peripheral surface of the rotor shaft 25 and the inner peripheral surface (cam surface) of the outer ring 71 to prevent its relative rotation (indicated by a cross). Show). Therefore, such rotation of the pump drive shaft 52 is prohibited, and the pump drive shaft 52 rotates integrally with the rotor shaft 25 (indicated by an arrow A1). At that time, torque can be transmitted from the rotor shaft 25 to the pump drive shaft 52.

  On the other hand, when the pump drive shaft 52 tries to rotate relative to the rotor shaft 25 in the same direction as the arrow A1 (indicated by the arrow A3), that is, when it tries to rotate at a higher speed than the rotor shaft 25, the overrun state (simply Also called overrun). At the time of overrun, a slight gap is generated between the cam surface of the outer ring 71 and the roller 72, so that the engagement of the roller 72 is released and the roller 72 rolls smoothly. Accordingly, such rotation of the pump drive shaft 52 is allowed (indicated by a circle). At that time, torque is not transmitted from the pump drive shaft 52 to the rotor shaft 25.

  Eventually, the OWC 70 is locked, thereby prohibiting the pump drive shaft 52 from rotating at a lower speed than the rotor shaft 25 (including stop and reverse rotation). By entering the overrun state, the OWC 70 52 is allowed to rotate independently at a higher speed than the rotor shaft 25. Further, torque can be transmitted from the rotor shaft 25 to the pump drive shaft 52 in the locked state, and torque cannot be transmitted from the pump drive shaft 52 to the rotor shaft 25 in the overrun state.

  Returning to FIG. 1, the description will be continued. An oil pump drive motor 51 is provided on the side opposite to the traction motor 20 (inner side in the vehicle width direction) with the oil pump 50 interposed therebetween. The oil pump drive motor 51 is an electric motor having a structure similar to that of the traction motor 20, and the rotor 53 is fixed to the pump drive shaft 52. Therefore, the pump drive shaft 52 is directly connected to the output shaft of the oil pump drive motor 51. When operating, the oil pump drive motor 51 drives the pump drive shaft 52 in the same direction as the rotation direction of the rotor shaft 25 when the vehicle moves forward (the direction of arrow A3 in FIG. 3B).

  The output shaft 80 is provided coaxially with the rotor shaft 25 and on the opposite side (outside in the vehicle width direction) of the pump drive shaft 52 with the output shaft 80 interposed therebetween. One end side (the vehicle width direction outer side) of the output shaft 80 is connected to the wheel 120 via the wheel hub 85 and the brake rotor disk 87, and the other end (the vehicle width direction inner side) is connected to the planetary gear 30 (reduction gear). The rotor shaft 25 is in communication. The end of the output shaft 80 on the rotor shaft 25 side is enlarged in diameter, and a concave portion 80a that opens to the rotor shaft 25 side is formed on the end surface. And the front-end | tip of the rotor shaft 25 enters into the recessed part 80a, and it arrange | positions so that the exit of the rotor shaft oil path 27 may be located in the inner peripheral side of the recessed part 80a.

  The front end side (the vehicle width direction outer side) of the output shaft 80 protrudes from the case 3 and is connected to the wheel 120. Specifically, the distal end side of the output shaft 80 is fitted into a substantially cylindrical wheel hub 85 having a flange portion, and is fixed by a nut 81. A wheel disc 121 is fixed to a flange portion of the wheel hub 85 by a bolt / nut 103 together with a substantially disc-shaped brake rotor disc 87. The outer periphery of the wheel disc 121 is fitted into the inner peripheral surface of the tire 122. The wheel disc 121 and the tire 122 are integrated to form the wheel 120. With the above configuration, the output shaft 80, the wheel hub 85, the brake rotor disk 87, and the wheel 120 rotate integrally.

  The planetary gear 30 is a speed reducer that reduces the rotation of the rotor shaft 25 and transmits it to the output shaft 80, and is provided on the opposite side of the oil pump 50 and the oil pump drive motor 51 with the traction motor 20 interposed therebetween. The main structure of the planetary gear 30 includes a sun gear 31 provided at the center, pinion gears 32 meshed with the sun gear 31 and arranged at a plurality of radial equidistant positions from the sun gear 31, and a ring-shaped member coaxial with the sun gear 31. The ring gear 33 meshes with the pinion gears 32 on the inner peripheral surface thereof, and the carrier 34 that supports the pinion gears 32 while maintaining their relative positions.

  The sun gear 31 is connected to the rotor shaft 25. The carrier 34 is connected to the output shaft 80. The ring gear 33 is fixed to the case 3.

  FIG. 4 is a block diagram of the power transmission system of the wheel drive device 1. The vehicle is equipped with a high voltage battery 91 for driving the traction motor 20 and a low voltage battery 93 for driving the oil pump drive motor 51. The high voltage battery 91 and the traction motor 20 are connected via a first inverter / converter 92. The low voltage battery 93 and the oil pump drive motor 51 are connected via a second inverter / converter 94. Further, a high voltage battery 91 and a low voltage battery 93 are connected, and power can be supplied from the high voltage battery 91 to the low voltage battery 93 as necessary.

  Next, the lubrication and cooling system of the wheel drive device 1 will be described with reference to FIGS. An oil passage 57 extending downward in the case 3 is connected to the suction port 58 of the oil pump 50, and an oil strainer 55 that opens near the bottom of the oil reservoir 10 is attached to the lower end of the oil passage 57. .

  As shown in FIG. 2, one end of an oil passage 62 (pipe) led out of the case 3 is connected to the discharge port 61 of the oil pump 50, and an oil cooler 63 is introduced to the other end of the oil passage 62. The port 63a is connected. The oil cooler 63 is a device for cooling the oil 11 by heat exchange, and a thin tube is disposed between the inlet port 63a and the outlet port 63b of the oil 11. While the oil 11 passes through the narrow tube, heat exchange between the oil 11 and the outside air is performed on the narrow tube wall surface. The oil cooler 63 is disposed in front of the case 3 where the traveling wind W when the vehicle moves forward is easily hit so that the heat exchange is effectively promoted.

  One end of an oil passage 64 (pipe) is connected to the outlet 63 b of the oil cooler 63, and the other end of the oil passage 64 is connected to the case 3. The oil passage branches off in the case 3. One of the branched oil passages is connected to an oil passage 66 at the top of the case 3 via an oil passage 65 (pipe). As shown in FIG. 1, the oil passage 66 extends inside the case 3 in the axial direction above the stator 21. The case 3 is formed with oil holes 67 and 68 having one end opened to the oil passage 66 and the other end opened to the inside of the case 3. The oil hole 67 allows communication between the oil passage 66 and the upper portion of the stator core of the stator 21, and the oil hole 68 allows communication between the oil passage 66 and the upper portion of the coil of the stator 21. The oil passage 62 from the discharge port 61 of the oil pump 50 to the stator 21, the oil cooler 63, the oil passage 64, the oil passages 65 and 66, and the oil holes 67 and 68 form a stator cooling oil passage 69 as a whole. The stator cooling oil passage 69 is an oil supply oil passage that preferentially cools the stator 21.

  On the other hand, the other of the oil passages branched downstream of the oil passage 64 is connected to the oil passage 78 of the case 3. As shown in FIG. 1, the oil passage 78 is connected to the rotor shaft oil passage 27 provided in the axial center portion of the rotor shaft 25. The front end side (downstream side) of the rotor shaft oil passage 27 is open near the recess 80 a of the output shaft 80. The oil passage 62, the oil cooler 63, the oil passage 64, the oil passage 78, and the rotor shaft oil passage 27 extending from the discharge port 61 of the oil pump 50 to the vicinity of the recess 80 a of the output shaft 80, as a whole, includes an output shaft cooling oil passage 79. Form. The output shaft cooling oil passage 79 is an oil supply oil passage that preferentially cools the output shaft 80. Of the output shaft cooling oil passage 79, the passage from the discharge port 61 of the oil pump 50 to the oil passage 64 is shared with the stator cooling oil passage 69.

  The structure of the wheel drive device 1 has been described above. As described above, the wheel drive device 1 includes the planetary gear 30 (reduction gear) between the rotor shaft 25 and the wheel 120, and the oil pump 50 and the oil pump drive motor 51 are provided. It is provided coaxially with the rotor shaft 25 and on the opposite side of the planetary gear 30 across the rotor 22.

  With such a structure, the traction motor 20 and the oil pump 50 are arranged at positions close to each other. Therefore, the arrangement of the cooling oil passage (stator cooling oil passage 69) from the oil pump 50 to the traction motor 20 is facilitated, and the distance is shortened.

  The pump drive shaft 52 is provided coaxially with the rotor shaft 25 at the end of the rotor shaft 25 and has a recess 52 a that includes the end of the rotor shaft 25 at a position facing the rotor shaft 25. Is interposed between the outer peripheral surface of the end of the rotor shaft 25 and the inner peripheral surface of the recess 52a.

  With this structure, the inner peripheral side of the OWC 70 comes into contact with the outer peripheral surface of the end portion of the rotor shaft 25. Therefore, the end of the rotor shaft 25 has a relatively small diameter. A drive shaft such as the rotor shaft 25 is generally tapered (medium thick) in consideration of assembly. By reducing the diameter of the tip of the rotor shaft 25, the entire diameter of the rotor shaft 25 can be reduced, and the structure around the rotor shaft 25 is compact.

  An oil pump drive motor 51 is disposed on the opposite side of the rotor shaft 25 across the oil pump 50, and a rotor 53 of the oil pump drive motor 51 is fixed to the pump drive shaft 52.

  With such a structure, the oil pump drive motor 51 can be easily assembled. Moreover, when the presence or absence of the oil pump drive motor 51 is provided depending on the model, it becomes easy to additionally install the motor. That is, the assembling property of the oil pump drive motor 51 is improved.

  Next, the operation of the wheel drive device 1 will be described. First, at the time of forward drive, the first inverter / converter 92 shown in FIG. 4 converts the electric power from the high-voltage battery 91 into a predetermined voltage and current, and supplies them to the traction motor 20.

  The rotor shaft 25 of the traction motor 20 rotates clockwise (in the direction of arrow A1 in FIG. 3) when viewed from the oil pump drive motor 51 side when moving forward. The sun gear 31 of the planetary gear 30 connected to the rotor shaft 25 also rotates clockwise. Since the pinion gear 32 meshes with the sun gear 31, the pinion gear 32 rotates counterclockwise. However, since the ring gear 33 is fixed to the case 3, the shaft position rotates clockwise. That is, the carrier 34 rotates clockwise. At this time, the rotation speed of the carrier 34 is lower than the rotation speed of the rotor shaft 25, and the torque is amplified (deceleration action). The output shaft 80 and the wheel 120 integrated with the carrier 34 also rotate clockwise, and the vehicle is driven forward.

  At the time of reverse drive, the first inverter / converter 92 converts the electric power from the high voltage battery 91 into a predetermined voltage and current (current opposite to that at the time of forward drive) and supplies the traction motor 20 with the electric power. As a result, the rotor shaft 25 rotates in the direction opposite to that when the vehicle is moving forward (counterclockwise when viewed from the oil pump drive motor 51 side). As a result, the wheel 120 also rotates counterclockwise, and the vehicle is driven backward.

  Further, during forward travel, the traction motor 20 acts as a generator during reverse driving in which the rotor shaft 25 is driven from the wheel 120 side, such as during braking and traveling downhill. The generated electricity is converted into charging voltage / current by the first inverter / converter 92 and stored in the high voltage battery 91 (energy regeneration). FIG. 4 shows the flow of energy at this time by paths C1, C2, and C3.

  Next, the operation of the oil pump 50 and the oil pump drive motor 51 and the flow of the oil 11 and the lubrication / cooling of each part by the operation will be described. The oil pump drive motor 51 converts the electric power from the low voltage battery 93 into a predetermined voltage and current by the second inverter / converter 94 shown in FIG. To supply. FIG. 4 shows the flow of energy at this time by paths B2 and B3 (and B1 if necessary). By driving the oil pump drive motor 51, the pump drive shaft 52 rotates in the same direction as the rotation direction of the rotor shaft 25 when the vehicle moves forward (the direction indicated by the arrow A3 in FIG. 3B). As a result, the oil pump 50 sucks up the oil 11 from the oil reservoir 10, boosts it, and discharges it to the stator cooling oil passage 69 and the output shaft cooling oil passage 79.

  After cooling the stator 21, the oil 11 guided to the stator cooling oil passage 69 falls while lubricating and cooling the planetary gear 30 and the bearings, and finally returns to the oil reservoir 10. The oil 11 guided to the output shaft cooling oil passage 79 cools the traction motor 20 from the inside by passing through the rotor shaft oil passage 27. The oil 11 is cooled by being ejected from the tip of the rotor shaft oil passage 27 and hitting the recess 80 a of the output shaft 80. The output shaft 80 is connected to a brake rotor disk 87 via a wheel hub 85. The brake rotor disk 87 becomes high temperature due to friction with a brake pad (not shown) during braking. By cooling the output shaft 80, it is possible to effectively suppress the heat during braking from the brake rotor disk 87 to the traction motor 20 via the output shaft 80. The oil 11 ejected from the tip of the rotor shaft oil passage 27 to cool the output shaft 80 falls while lubricating and cooling the planetary gear 30 and the bearings, and finally returns to the oil reservoir 10.

  When the oil pump 50 is driven by the oil pump drive motor 51, the oil pump speed Np is set to be equal to or higher than the traction motor speed Nm. At this time, the OWC 70 is in an overrun state, and torque is not transmitted from the pump drive shaft 52 to the rotor shaft 25. Therefore, the operation (rotation) of the oil pump 50 does not affect the operation (rotation) of the traction motor 20. Therefore, the oil pump rotational speed Np can be set with a high degree of freedom according to the required discharge flow rate.

  The operation and effect will be described with reference to FIG. FIG. 5 is a diagram illustrating characteristics relating to the heat balance of the wheel driving device 1. The horizontal axis represents the traction motor rotation speed Nm (rpm) or a vehicle speed V (km / h) proportional thereto, and the vertical axis represents the heat quantity Q (heat generation amount or heat release amount). Reference sign Q3max indicates a heat generation amount (maximum value) at the maximum load among the heat generation amount Q3 of the traction motor 20. The maximum load output of the traction motor 20 is proportional to the traction motor rotation speed Nm in a relatively low speed range, and becomes a constant value (maximum output) in a high speed range equal to or higher than a predetermined value. The maximum calorific value Q3max indicates a characteristic substantially in line with the maximum load output characteristic. In other words, in a relatively low speed range, it increases at a relatively large increase rate that is approximately proportional to the traction motor rotational speed Nm, and the increase rate decreases gradually from the vicinity of the vehicle speed where the maximum load output is constant (near the bending point of the characteristic). To increase.

  In order to appropriately suppress the temperature rise of the traction motor 20, particularly the stator 21, it is required that the maximum heat dissipation amount by the cooling system be equal to or greater than the maximum heat generation amount Q3max.

  On the other hand, the symbol Q <b> 1 indicates the amount of heat released by other than the oil cooler 63. For example, this is the amount of heat that propagates through the case 3 or the like and is dissipated into the outside air. The heat dissipation amount Q1 increases as the vehicle speed increases because the relative speed of the traveling wind W that strikes the case 3 increases as the vehicle speed increases. However, the overall value is relatively low and the rate of increase with respect to the vehicle speed V is also small.

  Reference sign Q2L indicates a heat release amount of the heat release amount Q2 from the oil cooler 63 when the OWC 70 is in a locked state, that is, when the oil pump rotation speed Np = the traction motor rotation speed Nm. The higher the vehicle speed, the higher the relative speed of the traveling wind W and the higher the cooling capacity of the oil cooler 63, and the discharge flow rate of the oil pump 50 (the oil flow rate supplied to the oil cooler 63) is the traction motor rotational speed Nm. Since it increases in proportion to (= oil pump rotation speed Np), the heat radiation amount Q2L increases as the vehicle speed increases. The heat dissipation amount Q2L is relatively large with respect to the heat dissipation amount Q1, and occupies most of the total heat dissipation amount, particularly at high vehicle speeds.

  When the OWC 70 is in the locked state, the total heat radiation amount is a heat radiation amount Q1 + a heat radiation amount Q2L. In this case, at the maximum load, the maximum heat generation amount Q3max− (heat radiation amount Q1 + heat radiation amount Q2L), that is, the heat radiation amount in the hatched portion in FIG. 5 is insufficient. In this embodiment, such a shortage of heat dissipation is eliminated by setting the oil pump rotation speed Np> the traction motor rotation speed Nm. This is because when the oil pump rotation speed Np is increased as described above, the discharge flow rate of the oil pump 50 is increased, the cooling performance is improved, and the heat radiation amount Q2 can be increased more than the heat radiation amount Q2L. In order to solve the above shortage of heat dissipation amount, specifically, the oil pump rotation speed Np is set to (rotation amount Q1 + heat dissipation amount Q2) = rotation speed at which a discharge flow rate is obtained such that the heat dissipation amount Q2 satisfies the heat generation amount Q3. (> Traction motor rotation speed Nm).

  The heat generation amount Q3 of the traction motor 20 at the time of partial load is smaller than the maximum heat generation amount Q3max. In the present embodiment, the optimum heat radiation amount Q2 corresponding to the heat generation amount Q3 can be achieved by appropriately adjusting the oil pump rotation speed Np even during partial load. Moreover, since it can adjust so that the thermal radiation amount Q2 may not increase more than necessary, useless energy consumption by the oil pump 50 can be suppressed, and a fuel consumption can be improved.

  Further, for example, when the traction motor rotation speed Nm = 0 rpm, such as when stopping on an uphill road, a load is applied to the traction motor 20 (heat generation amount Q3> 0), or immediately after traveling at a high load and high vehicle speed. When there is a possibility that the temperature of the traction motor 20 may increase due to a sudden decrease in the heat dissipation amount Q2, such as when the vehicle is stopped, there is a demand for improving the cooling performance using the oil cooler 63. In this embodiment, even when the vehicle is in a stopped state (traction motor rotation speed Nm = 0 rpm), the oil pump 50 is driven by the oil pump drive motor 51 to meet the demand by obtaining the necessary heat dissipation amount Q2. it can.

  Further, even when the vehicle is moving backward and the rotor shaft 25 is rotating backward with respect to the forward movement, the oil pump 50 is driven by the oil pump drive motor 51 in the normal rotational direction (the rotor shaft 25 is moved forward when the vehicle is moving forward). The required heat radiation amount Q2 can be obtained.

  When the required heat release amount is smaller than the heat release amount Q1 + heat release amount Q2L, such as when the heat generation amount Q3 is small in the low load region, the oil pump drive motor 51 may be stopped. As a result, the OWC 70 is locked, and the oil pump 50 is driven by the rotor shaft 25 as in the conventional structure.

  When the oil pump 50 is driven by the rotor shaft 25 as in the conventional structure (the same applies when the oil pump drive motor 51 is stopped in this embodiment), the oil is consumed by consuming part of the output of the traction motor 20. The pump 50 is driven. Accordingly, the output supplied to the wheel 120 correspondingly decreases (oil pump drive loss). In this embodiment, by driving the oil pump 50 with the oil pump drive motor 51, the oil pump drive loss can be suppressed. Particularly when the load is high, the driver demands a high output. Therefore, it is effective to suppress the oil pump drive loss and increase the supply output to the wheel 120 accordingly.

  As described above, according to this embodiment, the oil pump drive motor 51 makes it easy to set the oil pump rotation speed Np to an appropriate rotation speed according to the running state (required discharge amount or required heat dissipation amount). That is, the degree of freedom in setting the oil pump speed is increased. This is because the cooling system (oil pump 50 and oil cooler 63) is reduced in size and capacity compared to the conventional structure in which the oil pump 50 is directly connected to the rotor shaft 25, and wasteful energy consumption by the oil pump 50 is suppressed. To make a great contribution. For example, in order to obtain a heat release amount equal to or greater than the maximum heat release amount Q3max in the conventional structure, a heat release amount Q1 + a heat release amount Q2 ′ as shown by a two-dot chain line in FIG. 5 is required (the heat release amount Q2 ′ is derived from the oil cooler 63). Heat dissipation). The heat radiation amount Q2 'is considerably larger than the heat radiation amount Q2L, and the rate of increase (characteristic gradient) with respect to the traction motor rotation speed Nm is also large. In order to obtain such a heat radiation amount Q2 ', a large and large capacity cooling system (oil pump 50 and oil cooler 63) is required.

  If such a cooling system is adopted, the heat release amount Q1 + heat release amount Q2 'greatly exceeds the maximum heat release amount Q3max in the high vehicle speed region. This means that the oil pump discharge flow rate is large, and there is a great waste of energy consumption for driving the oil pump 50.

  According to the present embodiment, the heat radiation amount Q2L is significantly reduced from the heat radiation amount Q2 ', so that the cooling system can be reduced in size and capacity, and wasteful energy consumption by the oil pump 50 can be easily suppressed.

  Further, according to the present embodiment, compared to a configuration in which the oil pump 50 is driven only by the oil pump drive motor 51, the oil pump drive efficiency at the time of energy regeneration can be increased, and fuel consumption can be improved. . This point will be described with reference to FIG.

  As described above, when the oil pump 50 is driven by the oil pump drive motor 51, the drive energy is propagated via the paths B1, B2, B3, and B4. On the other hand, when the high voltage battery 91 is charged by energy regeneration, the regenerative energy is propagated via the paths C1, C2, and C3. Therefore, when the oil pump 50 is driven only by the oil pump drive motor 51, in order to drive the oil pump 50 during energy regeneration, it is necessary to propagate (convert) these energy independently. There is.

  In contrast, in the present embodiment, when the oil pump 50 is driven during energy regeneration, the oil pump drive motor 51 is stopped, the OWC 70 is locked, and the oil pump 50 can be driven by the rotor shaft 25. The driving energy of the oil pump 50 at this time is propagated via the paths C1, D1, and B4. This path is used as mechanical energy for driving the pump drive shaft 52 without converting mechanical energy of reverse driving from the wheel 120 into electrical energy, and once converted into electrical energy. After that, the energy loss is smaller than the above path (path C2, C3, B1, B2, B3) that is taken out again as mechanical energy. In other words, the path C2, C3, B1, B2, B3 is bypassed. Therefore, the oil pump drive efficiency can be increased, and fuel consumption can be improved.

  When the reverse driving torque from the wheel 120 is larger than the driving torque of the oil pump 50, the surplus energy may be stored in the high voltage battery 91 via the paths C2 and C3. On the contrary, when the reverse drive torque from the wheel 120 is smaller than the drive torque of the oil pump 50, the insufficient energy may be supplied to the oil pump drive motor 51 via the paths B1, B2, and B3.

  The operation when the wheel drive device 1 is operating normally has been described above. However, as one form of failure (failure), the oil pump 50 should be driven by the oil pump drive motor 51, for example, disconnection or supply A failure may be assumed in which the output of the oil pump drive motor 51 decreases due to some cause such as a decrease in electric power. It is important to deal with such risks as they are considered to be increasing compared to conventional structures. When such a failure occurs, in the structure in which the oil pump 50 is simply driven only by the oil pump drive motor 51, the oil pump 50 stops in the worst case, and a significant cooling performance (heat radiation amount). There is a risk of lowering. However, according to this embodiment, even if the worst situation of stopping the oil pump drive motor 51 occurs, the operation of the oil pump 50 at the traction motor rotational speed Nm is ensured by the OWC 70 being locked. . That is, even during such a failure, a heat dissipation amount equal to or greater than the heat dissipation amount Q1 + the heat dissipation amount Q2L can be secured, so that a significant decrease in cooling performance can be suppressed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said each embodiment, It can change suitably in a claim.

  For example, in the above embodiment, the OWC 70 is a roller type, but this may be another type of one-way clutch. For example, a one-way clutch called a sprag type using a substantially saddle-shaped sprag may be used.

  Further, in the above embodiment, the stator cooling oil passage 69 and the output shaft cooling oil passage 79 are configured to branch downstream of the oil passage 64. However, a switching valve or the like is provided at this branching point, as appropriate. Flow distribution may be performed.

  Moreover, although the separate type oil cooler 63 was provided in the said embodiment, it is not necessarily limited to it. For example, a simple oil cooler that is cooled by the traveling wind W between the oil reservoir 10 of the case 3 and the case wall surface may be used.

It is a longitudinal cross-sectional view of the wheel drive device which concerns on one Embodiment of this invention. It is a right view of FIG. It is a figure which shows the vicinity of a one-way clutch especially among the III-III sectional views of FIG. 1, (a) shows the locked state of a one-way clutch, (b) shows the overrun state of a one-way clutch, respectively. It is a block diagram of the power transmission system of the said wheel drive device. It is a figure which shows the characteristic regarding the heat balance of the said wheel drive device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel drive device 3 Case 11 Oil 20 Traction motor 21 Stator (of traction motor) 22 Rotor (of traction motor) 25 Rotor shaft 30 Planetary gear (reduction gear)
DESCRIPTION OF SYMBOLS 50 Oil pump 51 Oil pump drive motor 52 Pump drive shaft 52a Recessed part (Pump drive shaft) 63 Oil cooler 70 One-way clutch 120 Wheel 130 Suspension device

Claims (4)

A case attached to the vehicle via a suspension,
A traction motor provided in the case and including a stator and a rotor;
A rotor shaft on which the rotor is fixed;
Oil injected into the case,
An oil cooler for cooling the oil;
An oil pump that supplies at least the oil cooled by the oil cooler to the stator,
In the wheel drive device that drives the wheel by the output torque from the rotor shaft,
A pump drive shaft for driving the oil pump;
An oil pump drive motor for driving the pump drive shaft;
A wheel drive device comprising a one-way clutch interposed between the rotor shaft and the pump drive shaft and capable of transmitting torque in one direction from the rotor shaft to the pump drive shaft. A reduction gear is provided between the rotor shaft and the wheel,
2. The wheel drive device according to claim 1, wherein the oil pump and the oil pump drive motor are provided coaxially with the rotor shaft and on the opposite side of the speed reducer with the rotor interposed therebetween. The pump drive shaft is provided coaxially with the rotor shaft at the end of the rotor shaft, and has a recess that encloses the end of the rotor shaft at a position facing the rotor shaft.
The wheel driving device according to claim 2, wherein the one-way clutch is interposed between an outer peripheral surface of an end portion of the rotor shaft and an inner peripheral surface of the concave portion.   3. The oil pump drive motor is disposed on the opposite side of the rotor shaft across the oil pump, and the rotor of the oil pump drive motor is fixed to the pump drive shaft. Or the wheel drive device of 3.

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