JP2010246180A - Electric drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent seizure of differential gears, while reducing the amount of lubricating oil. <P>SOLUTION: An electric drive system includes a resolver 38 for detecting the rotational speed of a motor shaft 34; an MR sensor 63 for detecting the rotational speed of a first output shaft 58; a rotational speed difference calculating section 74a for calculating the difference in the rotational speed between respective output shafts 58, 59, based on a rotation speed Mn of a motor from the resolver 38 and a rotational speed Rn of the first output shaft from the MR sensor 63; and a driving force control section 74b for controlling the driving force of the motor shaft 34 to restrain the increase in the difference in the rotational speed, when the difference in the rotation speed is not less than a rotational speed difference threshold, thus suppressing high-speed operation of the differential gear 50, where the difference in the rotational speed between the respective output shafts 58, 59 becomes not less than the rotational speed difference threshold, and preventing the seizure of the differential gear 50, even if the amount of lubricating oil is reduced, while adopting an arrangement structure, where the motor shaft 34 and the respective output shafts 58, 59 are disposed coaxially. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric drive system that includes a drive unit that is mounted on an electric vehicle or the like and particularly includes an electric motor and a differential device.

  2. Description of the Related Art Conventionally, as an electric drive system mounted on an electric vehicle or the like, one having a drive unit including an electric motor and a differential device is known. The driving force of the electric motor is transmitted to the respective drive wheels provided on the left and right sides of the vehicle via the differential device, and the differential device generates a speed difference between the left and right drive wheels during cornering of the vehicle ( The inner ring difference) is absorbed.

  The drive unit is provided between the drive wheels, and the electric motor and the differential device are laid out according to the arrangement space on the vehicle side. For example, the technique described in Patent Document 1 employs an arrangement structure in which the motor shaft of the electric motor and the left and right output shafts connected to the differential device are provided on different axes so as to be parallel to each other. (Type A). Further, in the techniques described in Patent Documents 2 and 3, an arrangement structure is employed in which the motor shaft of the electric motor and the left and right output shafts connected to the differential device are provided coaxially ( Type B).

JP-A-10-175455 (FIG. 3) Japanese Patent Laid-Open No. 08-048164 (FIG. 1) Japanese Patent Laying-Open No. 2005-125920 (FIG. 2)

  When the arrangement structure is type A (Patent Document 1), the electric motor and the differential device can be arranged apart from each other in the vertical direction of the vehicle so that only the differential device is immersed in the lubricating oil. As a result, seizure of the differential device can be prevented. On the other hand, since a relatively large arrangement space is required in the vertical direction of the vehicle, problems such as deterioration in the design of the vehicle may occur.

  When the arrangement structure is type B (Patent Documents 2 and 3), it is possible to reduce the arrangement space in the vertical direction of the vehicle and improve the design of the vehicle. On the other hand, since the electric motor and the differential device are arranged at the same height with respect to the vertical direction of the vehicle, both the differential device and the electric motor are immersed in the lubricating oil. When the electric motor is used in a lubricating oil atmosphere, problems such as an increase in rotational resistance of the electric motor due to the stirring resistance of the lubricating oil and early deterioration of the lubricating oil due to an increase in the oil temperature may occur.

  Accordingly, it is conceivable to reduce the amount of lubricating oil in the type B arrangement structure so that the electric motor is not immersed in the lubricating oil. However, in this case, since the differential unit is also not immersed in the lubricant, the lubricant drops from the differential unit while the vehicle is stopped, and the amount of lubricant to be held by the differential unit is insufficient. It becomes a state. If the differential is operated at high speed, that is, the difference between the rotation speeds of the left and right output shafts is increased under such a shortage of lubricating oil, the differential may be burned.

  An object of the present invention is to provide an electric drive system capable of preventing seizure of a differential device while reducing the amount of lubricating oil.

  An electric drive system of the present invention includes an electric motor having a stator and a rotor, a motor shaft provided integrally with the rotor, a pair of output shafts provided coaxially with the motor shaft, and a driving force of the motor shaft. An electric drive system comprising a drive unit having a differential device distributed to each output shaft, and a controller for controlling the drive unit, wherein the first rotational speed detection detects the rotational speed of the motor shaft. Means, a second rotational speed detecting means for detecting the rotational speed of any one of the output shafts, and a detected rotational speed of the first rotational speed detecting means and the second rotational speed provided in the controller. A rotational speed difference calculating means for calculating a rotational speed difference between the output shafts based on a detected rotational speed of the detecting means; and the controller, wherein the motor is provided when the rotational speed difference is a predetermined value or more. And having a driving force control means for controlling the driving force suppressing the increase of the rotational speed difference.

  In the electric drive system according to the present invention, the differential device includes a casing to which a driving force of the motor shaft is transmitted, a gear shaft provided in the casing and orthogonal to the motor shaft, and rotating to the gear shaft. A first gear that is freely provided, and a pair of second gears that are provided on the output shafts and mesh with the first gear, are provided.

  In the electric drive system of the present invention, the motor shaft has a hollow structure, and any one of the output shafts is provided so as to penetrate through a hollow portion of the motor shaft, and the second rotation speed detecting means is the motor The number of rotations of the output shaft passing through the shaft is detected.

  According to the electric drive system of the present invention, the first rotational speed detecting means for detecting the rotational speed of the motor shaft, the second rotational speed detecting means for detecting the rotational speed of any one of the output shafts, A rotational speed difference calculating means for calculating the rotational speed difference of each output shaft based on the detected rotational speed of the first rotational speed detecting means and the detected rotational speed of the second rotational speed detecting means; and when the rotational speed difference is a predetermined value or more And a driving force control means for controlling the driving force of the motor shaft to suppress an increase in the rotational speed difference.

  Therefore, it is possible to suppress high-speed operation of the differential device in which the rotational speed difference of each output shaft becomes larger than a predetermined value, and adopting an arrangement structure in which the motor shaft and each output shaft are provided on the same axis. Even if the amount of lubricating oil is reduced, seizure of the differential can be prevented. As a result, the drive unit can be reduced in size and improved in durability.

It is a schematic diagram of the electric vehicle carrying the electric drive system which concerns on this invention. It is sectional drawing which shows the detailed structure of the drive unit of FIG. FIG. 3 is a partially enlarged cross-sectional view showing an enlarged lower side of the drive unit of FIG. 2. It is a flowchart which shows the control content of an electric drive system. It is explanatory drawing explaining the flow of the lubricating oil in a gear mechanism accommodation chamber.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  1 is a schematic view of an electric vehicle equipped with an electric drive system according to the present invention, FIG. 2 is a cross-sectional view showing a detailed structure of the drive unit of FIG. 1, and FIG. 3 is an enlarged view of the lower side of the drive unit of FIG. The partial expanded sectional views shown are shown respectively.

  As shown in FIG. 1, an electric drive system 11 is mounted on the electric vehicle 10, and the electric drive system 11 includes a drive unit 20. The drive unit 20 is provided in front of the vehicle body of the electric vehicle 10, and is disposed between the right front wheel 12a and the left front wheel 12b as drive wheels. As described above, the electric vehicle 10 according to the present embodiment employs a front wheel drive system in which the front wheels 12 a and 12 b are driven by the drive unit 20.

  One end side of the right drive shaft 13a is connected to the right front wheel 12a via a universal joint (not shown) so as to be integrally rotatable, and the other end side of the left drive shaft (the other output shaft) 13b is connected to the left front wheel 12b. It is connected via a universal joint so that it can rotate integrally. The drive shafts 13a and 13b are coaxially arranged, and the drive unit 20 is connected to the other end side of the right drive shaft 13a and one end side of the left drive shaft 13b.

  As shown in FIG. 2, the drive unit 20 includes an electric motor 30 and a gear mechanism 40, and both the electric motor 30 and the gear mechanism 40 are accommodated in a common unit case 21. The unit case 21 includes a first wall portion 22 provided on the right drive shaft 13a side, a second wall portion 23 provided on the left drive shaft 13b side, and between the first wall portion 22 and the second wall portion 23. And a central wall portion 24 provided. The central wall 24 defines the inside of the unit case 21 into an electric motor storage chamber 21a and a gear mechanism storage chamber 21b.

  The electric motor housing chamber 21a is provided with a stator (stator) 31 formed in a substantially cylindrical shape by laminating a plurality of steel plates (not shown), and the stator 31 is coiled with a predetermined number of turns and a winding method. 32 is wound. A rotor (movable element) 33 made of steel or the like is rotatably provided inside the stator 31 through a predetermined gap. A hollow structure motor shaft 34 is integrally provided at the rotation center of the rotor 33. Yes. One end side (right side in the figure) of the motor shaft 34 is rotatably supported by a radial bearing 35 attached to the boss portion 22a of the first wall portion 22, and the other end side (left side in the figure) of the motor shaft 34 is The radial bearing 36 mounted on the boss 24a of the central wall 24 is rotatably supported.

  A small-diameter gear 37 is integrally provided at the other end of the motor shaft 34, and the first gear 42 of the gear member 41 is engaged with the small-diameter gear 37. Between the small-diameter gear 37 of the motor shaft 34 and the rotor 33, there is provided a resolver (first rotational speed detecting means) 38 for detecting the rotational speed of the motor shaft 34 (rotor 33). Is electrically connected to the inverter 72 (see FIG. 1).

  A gear member 41 including a first gear 42 and a second gear 43 is rotatably provided in the gear mechanism accommodation chamber 21b. The gear member 41 is disposed above the vehicle body with a predetermined distance offset from the motor shaft 34, and one end side of the gear member 41 is rotatably supported by a radial bearing 44 mounted on the central wall portion 24. The other end of is supported rotatably on a radial bearing 45 mounted on the second wall portion 23. The diameter dimension of the second gear 43 is set to be smaller than the diameter dimension of the first gear 42, and is set to be approximately the same as the diameter dimension of the small diameter gear 37 of the motor shaft 34.

  In addition to the gear member 41, the differential device 50 is rotatably accommodated in the gear mechanism accommodation chamber 21b. The differential device 50 transmits the driving force of the motor shaft 34 to the first output shaft 58 and the second output shaft 59. Is to be distributed to. The differential device 50 includes a casing 51 formed in a substantially spherical shape, and the casing 51 is provided with a plurality of case windows (not shown) communicating between the inside and the outside of the casing 51. One end side of the casing 51 is rotatably supported by a radial bearing 52 attached to the boss portion 24 a of the central wall portion 24, and the other end side of the casing 51 is attached to the boss portion 23 a of the second wall portion 23. Further, it is rotatably supported by the radial bearing 53.

  A differential gear 54 that meshes with the second gear 43 of the gear member 41 is fixed to one end side of the casing 51, whereby the casing 51 is connected to the motor shaft via the small diameter gear 37, the gear member 41, and the differential gear 54. 34 driving force is transmitted. The diameter of the differential gear 54 is set to be approximately the same as the diameter of the first gear 42 of the gear member 41, and the rotation of the motor shaft 34 is caused by the small-diameter gear 37, the first gear 42, the second gear 43, and the like. The torque is reduced by the differential gear 54 to increase the torque. That is, the small diameter gear 37, the first gear 42, the second gear 43, and the differential gear 54 form a reduction mechanism.

  A cylindrical gear shaft 55 extending in a direction orthogonal to the axial direction of the motor shaft 34 is provided in the casing 51. A pair of first bevel gears (first gears) 56 are rotatably provided at both end sides of the gear shaft 55, and the tooth portions of the first bevel gears 56 each have an inclination angle of approximately 45 °. 51 is directed. A spherical surface portion 56 a having a predetermined radius of curvature is provided on the back surface of each first bevel gear 56, and each spherical surface portion 56 a slides on the spherical surface portion 51 a provided at a location facing each spherical surface portion 56 a of the casing 51. It is supported freely. The radius of curvature of each spherical portion 51a is set to the same radius of curvature as that of each spherical portion 56a.

  A pair of second bevel gears (second gears) 57 are provided in the casing 51 so as to sandwich the gear shaft 55. The tooth portion of each second bevel gear 57 is directed into the casing 51 with an inclination angle of approximately 45 °, and meshed with the tooth portion of each first bevel gear 56. At the rotation center of each second bevel gear 57, the other end of a first output shaft (output shaft) 58 and one end of a second output shaft (output shaft) 59 provided coaxially with the motor shaft 34 are respectively provided. It is connected so that it can rotate integrally.

  The length of the first output shaft 58 is set to be longer than the length of the second output shaft 59, and the first output shaft 58 passes through the hollow portion 34 a of the motor shaft 34. One end side of the first output shaft 58 extends out of the unit case 21 through the boss portion 22a of the first wall portion 22, and the right drive shaft 13a (see FIG. 1) is provided at one end side of the first output shaft 58. Are concatenated. A seal member 60 is provided between the first output shaft 58 and the boss portion 22a to seal the space between the electric motor housing chamber 21a and the outside, and the hollow portion 34a of the motor shaft 34 and the first output shaft 58 are connected to each other. A radial bearing 61 that smoothes the relative rotation between the motor shaft 34 and the first output shaft 58 is provided therebetween.

  The other end side of the second output shaft 59 extends out of the unit case 21 via the boss portion 23a of the second wall portion 23, and the left drive shaft 13b (FIG. 1) extends to the other end side of the second output shaft 59. Are linked). A seal member 62 is provided between the second output shaft 59 and the boss portion 23a to seal between the gear mechanism accommodation chamber 21b and the outside.

  The first wall portion 22 of the unit case 21 is provided with an MR sensor (second rotational speed detection means) 63 that detects the rotational speed of the first output shaft 58. The MR sensor 63 is connected to the EVCU 74 via a conducting wire 63a. (See FIG. 1). The MR sensor 63 is provided so as to enter the inside of the coil 32 wound around the stator 31, thereby reducing the length of the drive unit 20. A multi-pole magnetized portion 58 a that is multi-pole magnetized along the circumferential direction of the first output shaft 58 is integrally provided at a location facing the MR sensor 63 of the first output shaft 58. Generates a rectangular pulse as the first output shaft 58 rotates.

  A predetermined amount of lubricating oil LO is contained below the vehicle body of the unit case 21 as shown in FIG. 3, and the lubricating oil LO has the same composition as that of a generally used automatic transmission fluid (ATF). Used. The lubricating oil LO can go back and forth between the electric motor accommodation chamber 21a and the gear mechanism accommodation chamber 21b through a communication hole 24b provided below the vehicle body of the central wall portion 24.

  In the present embodiment, the amount of the lubricating oil LO to be put into the unit case 21 (broken arrow A in the figure) is such that the lubricating oil LO touches the tooth tip of the differential gear 54 set to the diameter dimension d1 and has a diameter. The amount of the lubricant LO is not in contact with the rotor 33 set to the dimension d2 (d1> d2). By setting the amount of the lubricating oil LO in this way, an increase in the rotational resistance of the rotor 33 is suppressed by the stirring resistance of the lubricating oil LO. In addition, the stator 31 and the coil 32 can be partially cooled (oil-cooled) by immersing the lower portion of the stator 31 in the lubricating oil LO. However, the amount of the lubricating oil LO is not limited to the above, and may be an amount that a part of the rotor 33 touches in a range that does not affect the increase in the rotational resistance of the rotor 33.

  As shown in FIG. 1, in addition to the drive unit 20, the electric drive system 11 includes a high voltage battery 70, a BCU (battery control unit) 71, an inverter 72, a DC / DC converter 73, and an EVCU (electric vehicle control unit) 74. It has. The BCU 71, the inverter 72, the DC / DC converter 73, and the EVCU 74 are each electrically connected to a communication network 75 such as a CAN provided in the electric vehicle 10, and thereby various signals (running state signals, etc.) between them. Communication is possible.

  The high voltage battery 70 is formed of, for example, a 400 V lithium ion secondary battery, and is provided on the rear side of the electric vehicle 10 so as to be positioned between the right rear wheel 14a and the left rear wheel 14b. By arranging the high-voltage battery 70 in the rear of the vehicle body in this way, the front-rear weight distribution is optimized particularly in the front-wheel drive electric vehicle 10 in which the weight in front of the vehicle body is increased. The BCU 71 is provided in the vicinity of the high voltage battery 70 and controls charging / discharging of the high voltage battery 70.

  The inverter 72 is electrically connected to the high voltage battery 70 via energization lines 76 and 77. When the electric motor 30 is driven as an electric motor, the inverter 72 converts a direct current from the high voltage battery 70 into an alternating current and supplies the alternating current to the electric motor 30. On the other hand, when driving the electric motor 30 as a generator, the inverter 72 converts an alternating current from the electric motor 30 into a direct current and supplies the direct current to the high voltage battery 70. The inverter 72 controls the driving force and the rotational speed of the electric motor 30 by controlling the current value and frequency of the alternating current based on the rotational speed signal of the motor shaft 34 from the resolver 38. A pair of main relays 78 is provided in the middle of the energization wires 76 and 77.

  A low voltage battery 79 is electrically connected to the high voltage battery 70 via a DC / DC converter 73. As the low voltage battery 79, for example, a 12V lead acid battery is used. The low voltage battery 79 is used as a power source for driving the inverter 72, the DC / DC converter 73, the BCU 71, the EVCU 74, and the like, and is a power source for driving other air conditioners, headlights, etc. (none of which are shown). Also used as

  The EVCU 74 is electrically connected to an accelerator sensor 15a and an MR sensor 63 that detect the operation amount of the accelerator pedal 15. In addition to this, the EVCU 74 is electrically equipped with a plurality of sensors that can detect the running state of the electric vehicle 10, such as a brake sensor that detects the amount of operation of the brake pedal, a vehicle speed sensor that detects the vehicle speed (none of which are shown), and the like. It is connected. Thus, the EVCU 74 controls the electric vehicle 10 including the drive unit 20 in an integrated manner. Here, the EVCU 74 constitutes a controller in the present invention.

  The EVCU 74 is provided with a rotation speed difference calculation section (rotation speed difference calculation means) 74a and a driving force control section (driving force control means) 74b.

  The rotational speed difference calculation unit 74a receives the motor rotational speed Mn (detected rotational speed) from the resolver 38 via the inverter 72 and the communication network 75, and the first output shaft rotational speed Rn (detected rotational speed) from the MR sensor 63. Number) is entered. The rotational speed difference calculation unit 74a calculates the rotational speed difference | Rn−Ln | between the first output shaft 58 and the second output shaft 59 based on the motor rotational speed Mn and the first output shaft rotational speed Rn. It has become. Here, Ln represents the second output shaft rotational speed, and the second output shaft rotational speed Ln is the motor rotational speed Mn, the first output shaft rotational speed Rn, the small diameter gear 37, the first gear 42, and the second gear 43. , And the gear ratio of the differential gear 54 and the first and second bevel gears 56 and 57 (see FIG. 2). The gear ratio data is stored in advance in the rotational speed difference calculation unit 74a.

  The driving force control unit 74b receives the rotation speed difference | Rn−Ln | calculated by the rotation speed difference calculation unit 74a, and the driving force control unit 74b receives the input rotation speed difference | Rn−Ln | The rotational speed difference threshold value (predetermined value) N stored in advance is compared. Then, when the rotational speed difference | Rn−Ln | is equal to or larger than the rotational speed difference threshold N, the driving force control unit 74b controls the driving force of the motor shaft 34 to suppress an increase in the rotational speed difference | Rn−Ln |. It has become.

  Next, the operation of the electric drive system 11 configured as described above will be described in detail with reference to the drawings. FIG. 4 is a flowchart showing the control contents of the electric drive system, and FIG. 5 is an explanatory diagram for explaining the flow of the lubricating oil in the gear mechanism housing chamber.

  As shown in FIG. 4, in step S <b> 1, control of the electric drive system 11 is started with an ignition switch on operation or the like as a trigger. Here, as a trigger for starting step S1, in addition to turning on the ignition switch, even when the operation amount of the accelerator pedal 15 is large (when the output from the accelerator sensor 15a suddenly rises), etc. good.

  In step S2, the resolver 38 detects the motor rotational speed Mn and the MR sensor 63 detects the first output shaft rotational speed Rn. Thereafter, the detected motor rotation speed Mn and the first output shaft rotation speed Rn are respectively input to the rotation speed difference calculation unit 74a.

  In step S3, the rotation speed difference calculation unit 74a calculates the second output shaft rotation speed Ln from the motor rotation speed Mn and the first output shaft rotation speed Rn input based on a predetermined arithmetic expression. Further, a rotational speed difference | Rn−Ln |, which is a difference value between the first output shaft rotational speed Rn and the second output shaft rotational speed Ln, is calculated, and then the rotational speed difference | Rn−Ln | 74b.

  In step S4, the driving force control unit 74b determines whether or not the rotational speed difference | Rn−Ln | is larger than the rotational speed difference threshold N. When the rotational speed difference | Rn−Ln | is equal to or smaller than the rotational speed difference threshold N (no determination), a return process is executed that proceeds to step S6 and returns to step S2. On the other hand, if the rotational speed difference | Rn−Ln | is larger than the rotational speed difference threshold N (yes determination), the process proceeds to step S5.

  In step S5, assuming that the differential device 50 operates at a high speed and the difference in rotational speed between the first output shaft 58 and the second output shaft 59 is large, control (limit control) is performed to suppress the driving force Mout of the motor shaft 34. Here, the control of the motor shaft 34 in step S5 will be specifically described.

  When the rotational speed difference | Rn−Ln | between the first output shaft 58 and the second output shaft 59 exceeds the rotational speed difference threshold N as indicated by arrows (1) and (2) in FIG. The bevel gears 56 rotate at high speeds around the gear shaft 55. For example, when the electric vehicle 10 is changed from the stopped state to the start state, the lubricating oil LO between the spherical surface portion 56a and the spherical surface portion 51a is insufficient, and therefore, the sliding contact portion CP between the spherical surface portions 56a and 51a (see FIG. The middle black circle) may be seized by frictional heat. Therefore, in step S5, control for reducing the supply current to the electric motor 30 to zero, control for generating reverse rotation driving force on the motor shaft 34, and the like are performed so as to suppress the driving force Mout of the motor shaft 34. As a result, high-speed operation of the differential device 50 is suppressed, and an increase in the rotational speed difference | Rn−Ln | Accordingly, high-speed rotation of each first bevel gear 56 within the casing 51 can be suppressed, and seizure of the sliding contact portion CP can be prevented.

  During straight traveling where the difference in rotational speed | Rn−Ln | is small, the lubricating oil LO adhering to the differential gear 54 causes the gear member in the gear mechanism housing chamber 21 b to be subjected to centrifugal force due to the rotation of the differential gear 54. It is pumped up and sprayed to the 41 side. Thereafter, as indicated by a two-dot chain line arrow in the figure, the lubricating oil LO reaches the meshing portion of the second gear 43 and the differential gear 54, the meshing portion of the first gear 42 and the small diameter gear 37, and the like. Further, the lubricating oil LO enters the casing 51 through a plurality of case windows (not shown) provided in the casing 51, as indicated by the two-dot chain arrows in the figure, and between the spherical portions 56a, 51a. It reaches the sliding contact part CP, the meshing part of each first bevel gear 56 and each second bevel gear 57, and the like.

  As described above in detail, according to the electric drive system 11 according to the present embodiment, the resolver 38 that detects the rotational speed of the motor shaft 34, the MR sensor 63 that detects the rotational speed of the first output shaft 58, Based on the motor rotational speed Mn from the resolver 38 and the first output shaft rotational speed Rn from the MR sensor 63, a rotational speed difference calculating unit 74a that calculates a rotational speed difference | Rn−Ln | between the output shafts 58 and 59; When the rotational speed difference | Rn−Ln | is equal to or greater than the rotational speed difference threshold N, the driving force control unit 74b that controls the driving force Mout of the motor shaft 34 to suppress the increase in the rotational speed difference | Rn−Ln | I have.

  Therefore, high-speed operation of the differential device 50 in which the rotational speed difference | Rn−Ln | between the output shafts 58 and 59 becomes larger than the rotational speed difference threshold N can be suppressed, and the motor shaft 34 and each output shaft can be suppressed. Even if the amount of the lubricating oil LO is reduced, the seizure of the differential device 50 can be prevented while adopting an arrangement structure in which 58 and 59 are provided on the same axis. As a result, the drive unit 20 can be reduced in size and improved in durability.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the electric drive system 11 that drives the front wheels 12a and 12b of the electric vehicle 10 is shown. However, the present invention is not limited to this, and the rear wheels 14a and 14b of the electric vehicle 10 are driven. The present invention can also be applied to a rear wheel drive type electric vehicle.

  Moreover, in the said embodiment, although what showed the electric drive system 11 applied to the electric vehicle 10 which drives each front wheel 12a, 12b was shown, this invention is not restricted to this, For example, each rear wheel 14a, The present invention can also be applied to a so-called hybrid vehicle in which 14b is driven by the electric drive system 11 and each front wheel 12a, 12b is driven by an internal combustion engine (engine).

  Furthermore, in the above-described embodiment, the MR sensor 63 as the second rotational speed detection means is provided on the first output shaft 58 side. However, the present invention is not limited to this, and the arrangement space for the vehicle is not limited thereto. It can also be provided on the second output shaft 59 side according to the above.

  In the above embodiment, the resolver 38 is used as the first rotation speed detection means and the MR sensor 63 is used as the second rotation speed detection means. However, the present invention is not limited to this, and the motor shaft is used. Other types of rotation sensors (such as optical encoders and Hall sensor encoders) may be used as long as the rotation sensors can detect the rotation speeds of the first output shaft 58 and the first output shaft 58.

DESCRIPTION OF SYMBOLS 10 Electric vehicle 11 Electric drive system 20 Drive unit 30 Electric motor 31 Stator 33 Rotor 34 Motor shaft 34a Hollow part 38 Resolver (1st rotation speed detection means)
50 differential gear 51 casing 55 gear shaft 56 first bevel gear (first gear)
57 Second bevel gear (second gear)
58 First output shaft (output shaft)
59 Second output shaft (output shaft)
63 MR sensor (second rotational speed detection sensor)
74 EVCU (Controller)
74a Rotational speed difference calculation unit (rotational speed difference calculation means)
74b Driving force control unit (driving force control means)
LO Lubricating oil Mn Motor speed (detection speed)
Rn First output shaft speed (detected speed)
N Rotational speed difference threshold (predetermined value)

Claims (3)

An electric motor having a stator and a rotor; a motor shaft provided integrally with the rotor; a pair of output shafts provided coaxially with the motor shaft; and a difference in distributing the driving force of the motor shaft to the output shafts An electric drive system comprising a drive unit comprising a moving device and a controller for controlling the drive unit,
First rotational speed detection means for detecting the rotational speed of the motor shaft;
Second rotational speed detection means for detecting the rotational speed of any one of the output shafts;
A rotational speed difference calculating means provided in the controller for calculating a rotational speed difference between the output shafts based on a detected rotational speed of the first rotational speed detecting means and a detected rotational speed of the second rotational speed detecting means; ,
An electric drive comprising: a driving force control means provided in the controller, for controlling a driving force of the motor shaft to suppress an increase in the rotational speed difference when the rotational speed difference is a predetermined value or more. system.   2. The electric drive system according to claim 1, wherein the differential device includes a casing to which a driving force of the motor shaft is transmitted, a gear shaft provided in the casing and orthogonal to the motor shaft, and the gear shaft. An electric drive system comprising: a first gear that is rotatably provided; and a pair of second gears that are provided on the output shafts and mesh with the first gear.   3. The electric drive system according to claim 1, wherein the motor shaft has a hollow structure, and any one of the output shafts is provided so as to penetrate through a hollow portion of the motor shaft, and the second rotational speed detection means. Detects the number of rotations of the output shaft passing through the motor shaft.

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