Drive system, vehicle

Abstract

To prevent or suppress electric corrosion more effectively.SOLUTION: A motor shaft 1 of a driving device 100 extends along a first axis of rotation J1 extending in an axial direction. A gear part 3 is connected to one side D1 of a motor shaft 1 in the axial direction. A housing cylindrical part extends in the axial direction and holds a stator 22 on an inner surface in a radial direction. A first lid part is attached to another end part of the housing cylindrical part in the axial direction. A first bearing of motor bearings 4311, 4211, 4221, and 4611 for rotatably supporting the motor shaft 1 is a rolling bearing arranged in the first lid part, and rotatably supports the motor shaft 1 in another side of the axial direction with respect to a rotor 21. The motor shaft 1 and the first lid part are electrically insulated by the first bearing.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, a technique for discharging electricity from a motor shaft of an electric motor has been known. For example, a charge dissipation assembly as a charge removal device is in contact with the outer surface in the radial direction of the motor shaft. Thereby, the shaft voltage of the motor shaft is grounded (see, for example, Japanese Patent Application Laid-Open No. 2005-124391).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there is a risk that the charge of the motor shaft cannot be sufficiently discharged only by forming a conductive path in the motor shaft. In particular, in a drive device mounted on an electric vehicle, a rotor, a stator, and a gear part are housed in a housing, and control of potential fluctuations occurring in this housing becomes important. For example, potential fluctuations occur in the motor shaft due to control of an inverter with respect to the drive current of the stator, and thus electrolytic corrosion is likely to occur. Electrolytic corrosion is a phenomenon in which the inner peripheral surfaces of the outer ring and the inner ring of a rolling bearing are damaged in a wavy shape. Electrolytic corrosion occurs when a current flowing from the shaft to the rolling bearing discharges within the rolling bearing. Therefore, suppression and prevention of electrolytic corrosion are important issues.

[0005] An object of the present invention is to more effectively suppress or prevent electrolytic corrosion.

Means for Solving the Problems

[0006] An exemplary drive system of the present invention comprises a motor shaft, a rotor, a stator, a gear section, and a housing. The motor shaft extends along a first rotation axis that extends axially and is rotatable about the first rotation axis. The rotor is rotatable with the motor shaft. The stator is positioned radially outward from the rotor. The gear section is connected to one axial side of the motor shaft. The housing accommodates the rotor, the stator, and the gear section. The housing has a housing cylinder, a first cover, a second cover, and a motor bearing. The housing cylinder extends axially and holds the stator on its radially inner surface. The first cover is attached to the other axial end of the housing cylinder. The second cover is positioned axially to the side of the housing cylinder and extends in a direction intersecting the first rotation axis. The motor bearing rotatably supports the motor shaft. The motor bearing has a first bearing and a second bearing. The first bearing is a rolling bearing located in the first cover portion and rotatably supports the motor shaft in the axial direction other than that of the rotor. The second bearing is located in the second cover portion and rotatably supports the motor shaft in the axial direction other than that of the rotor. The motor shaft and the first cover portion are electrically insulated by the first bearing.

[0007] An exemplary vehicle of the present invention is equipped with the above-described drive system. [Effects of the Invention]

[0008] According to exemplary drive systems and vehicles of the present invention, electrolytic corrosion can be more effectively suppressed or prevented. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a conceptual diagram showing an example of the configuration of a drive unit. [Figure 2] Figure 2 is a conceptual diagram illustrating the static elimination path of the drive device in the embodiment. [Figure 3]Figure 3 is a schematic diagram showing an example of a vehicle equipped with a drive system. [Figure 4A] Figure 4A is a cross-sectional view showing an example of a motor bearing configuration. [Figure 4B] Figure 4B is a cross-sectional view showing a first modified example of the motor bearing configuration. [Figure 4C] Figure 4C is a cross-sectional view showing a second modified example of the motor bearing configuration. [Figure 5] Figure 5 is a cross-sectional view showing an example configuration of the first drive bearing and the second drive bearing. [Figure 6] Figure 6 is a cross-sectional view showing an example configuration of the first intermediate bearing and the second intermediate bearing. [Figure 7] Figure 7 is a schematic diagram of the drive device according to a modified example. [Figure 8] Figure 8 is a conceptual diagram illustrating the static elimination path of the drive unit in a modified example. [Modes for carrying out the invention]

[0010] An exemplary embodiment will be described below with reference to the drawings.

[0011] In this specification, the direction parallel to the first rotation axis J1 of the motor 2 is defined as the "axial direction" of the drive device 100. With respect to the axial direction, as shown in Figure 1, the gear section 3 side is defined as one axial direction D1, and the motor 2 side is defined as the other axial direction D2. Furthermore, the radial direction perpendicular to a predetermined axis such as the first rotation axis J1 is simply referred to as the "radial direction," and the circumferential direction centered on a predetermined axis such as the first rotation axis J1 is simply referred to as the "circumferential direction."

[0012] Furthermore, in this specification, in relation to any of the orientations, lines, and planes, "parallel" includes not only a state in which they never intersect no matter how far they are extended, but also a state in which they are substantially parallel. Similarly, "perpendicular" includes not only a state in which they intersect at a 90-degree angle, but also a state in which they are substantially perpendicular. In other words, "parallel" and "perpendicular" each include a state in which there is an angle difference between the two in their positional relationship that does not depart from the spirit of the present invention.

[0013] In addition, in this specification, "annular" includes, in addition to a shape that is continuously connected without a break over the entire circumferential direction centered on a predetermined axis such as the first rotation axis J1, a shape having one or more breaks in a part of the entire area centered on the predetermined axis. Also included is a shape that draws a closed curve on a curved surface that intersects the predetermined axis around the predetermined axis.

[0014] In addition, in this specification, "extending" in a predetermined direction includes, in addition to a configuration in which the extending direction extends strictly in the predetermined direction, a configuration that extends substantially in the predetermined direction. That is, "extending" in a predetermined direction includes a configuration in which there is a deviation in direction to such an extent that the gist of the present invention is not deviated from the predetermined direction. The same applies to "spreading" in a predetermined direction.

[0015] <1. Embodiment> FIG. 1 is a conceptual diagram showing a configuration example of the drive device 100. FIG. 2 is a conceptual diagram illustrating a charge removal path of the drive device 100 in the embodiment. FIG. 3 is a schematic diagram showing an example of a vehicle 300 equipped with the drive device 100. Note that FIGS. 1 and 2 are merely conceptual diagrams, and the arrangement and dimensions of each part are not necessarily exactly the same as those of the actual drive device 100. Also, in FIG. 2, a thick solid line with an arrow indicates the charge removal path. FIG. 3 conceptually illustrates the vehicle 300.

[0016] In this embodiment, as shown in FIG. 3, the drive device 100 is mounted on a vehicle 300 having at least a motor as a power source. The vehicle 300 is a hybrid vehicle (HV), a plug-in hybrid vehicle (PHV), or an electric vehicle (EV). The vehicle 300 includes the drive device 100. In the vehicle 300, the occurrence of electric corrosion at the motor bearings 4311, 4211, 4221, 4611 (particularly the first rotor bearing 4311) that support the motor shaft 1 (specifically, the rotor shaft 11 described later) of the drive device 100 can be more effectively suppressed or prevented. In FIG. 3, the drive device 100 drives the front wheels of the vehicle 300. However, the drive device 100 is not limited to the example shown in FIG. 3, and the drive device 100 may drive at least any one of the wheels. Further, the vehicle 300 further has a battery 200. The battery 200 stores electric power for supplying to the drive device 100.

[0017] As shown in FIGS. 1 to 3, the drive device 100 includes a motor shaft 1, a motor 2, a gear unit 3, a housing 4, a fluid circulation unit 5, and an earth connection unit 6.

[0018] <1-1. Motor shaft 1> The motor shaft 1 extends in the axial direction along the first rotation axis J1. The first rotation axis J1 extends in the axial direction. As described above, the drive device 100 includes the motor shaft 1. The motor shaft 1 is rotatable about the first rotation axis J1. As shown in FIG. 1, the motor shaft 1 is rotatably supported by the housing 4 via the first rotor bearing 4311 and the second rotor bearing 4211 and the first gear bearing 4221 and the second gear bearing 4611.

[0019] Hereinafter, the first rotor bearing 4311 and the second rotor bearing 4211 may be collectively referred to as "rotor bearings 4211, 4311". The rotor bearings 4211, 4311 rotatably support the rotor shaft 11. The housing 4 has the rotor bearings 4211, 4311.

[0020] Furthermore, the first gear bearing 4221 and the second gear bearing 4611 are sometimes collectively referred to as "gear bearings 4221, 4611". The gear bearings 4221, 4611, together with the rotor bearings 4211, 4311, rotatably support the motor shaft 1. The housing 4 has the gear bearings 4221, 4611.

[0021] Furthermore, the first rotor bearing 4311, the second rotor bearing 4211, the first gear bearing 4221, and the second gear bearing 4611 are sometimes collectively referred to as "motor bearings 4311, 4211, 4221, and 4611". The motor bearings 4311, 4211, 4221, and 4611 rotatably support the motor shaft 1. The housing 4 has the motor bearings 4311, 4211, 4221, and 4611.

[0022] The motor shaft 1 is cylindrical and extends in the axial direction. The motor shaft 1 is conductive and, in this embodiment, is made of metal. A fluid F flows inside the motor shaft 1. The fluid F flow path, including the inside of the motor shaft 1, is an example of the "fluid flow path" of the present invention. The drive unit 100 further includes this fluid F. In this embodiment, the fluid F is a lubricant that lubricates the gear section 3 and the bearings of the drive unit 100, and is, for example, ATF (automatic transmission fluid). The fluid F is also used as a coolant to cool the motor 2 and the like. In accordance with the rotation of the motor shaft 1, the fluid F flowing inside the motor shaft 1 can be supplied to the motor 2, the first rotor bearing 4311, and the second rotor bearing 4211 through the shaft through hole 111, which will be described later. Therefore, the stator 22 (especially the coil end 2221, which will be described later) and the rotor bearings 4211, 4311, etc. can be cooled by the fluid F.

[0023] The motor shaft 1 includes a rotor shaft 11 and a gear shaft 12. The rotor shaft 11 is an example of the "first shaft" of the present invention and holds the rotor 21. The gear shaft 12 is an example of the "second shaft" of the present invention and is connected to one axial end D1 of the rotor shaft 11. A gear section 3 is connected to the gear shaft 12. The rotor shaft 11 and the gear shaft 12 are cylindrical in shape and extend in the axial direction, along the first rotation axis J1.

[0024] In this embodiment, the two are spline-fitted. When the rotor shaft 11 and the gear shaft 12 are spline-fitted, the external teeth formed on the gear shaft 12 side and the internal teeth formed on the rotor shaft 11 side come into contact when the drive unit 100 is in the powering state and the regenerative state.

[0025] However, the rotor shaft 11 and the gear shaft 12 may be connected by a screw coupling using male and female threads, or they may be joined by fixing methods such as press-fitting and welding. When fixing methods such as press-fitting and welding are used, serrations combining recesses and protrusions extending in the axial direction may be used. With such a configuration, rotation can be reliably transmitted. However, the motor shaft 1 may be a single component, and is not limited to the examples of this embodiment.

[0026] Rotor bearings 4211 and 4311 are positioned at both axial ends of the rotor shaft 11. The rotor bearings 4211 and 4311 rotatably support both axial ends of the rotor shaft 11.

[0027] Motor bearings 4311, 4211, 4221, and 4611 include a first rotor bearing 4311. The first rotor bearing 4311 is an example of the "first bearing" of the present invention. The first rotor bearing 4311 is a rolling bearing positioned in the housing cover portion 43, which will be described later, and rotatably supports the motor shaft 1 in the other axial direction D2 relative to the rotor 21. The first rotor bearing 4311 has an insulating portion (see Figures 4A to 4C, which will be described later). As a result, the motor shaft 1 (i.e., the rotor shaft 11) and the housing cover portion 43 are electrically insulated by the first rotor bearing 4311.

[0028] As shown in Figure 1 and other figures, the first housing cylindrical portion 41 and the housing lid portion 43 are separate components. Therefore, due to cumulative tolerances when assembling the housing 4, which includes these components, with the motor shaft 1, the end of the motor shaft 1 on the other axial side D2 may wobble around the first rotation axis J1. As a result, an imbalance in the fluid F, such as lubricating oil, is likely to occur in the rolling bearing (i.e., the first rotor bearing 4311) on the other axial side D2 of the motor shaft 1, and there is a risk that an increase or decrease in the fluid F due to local imbalance will occur around the first rotation axis J1.

[0029] Furthermore, the motor bearings 4311, 4211, 4221, and 4611 are supplied with fluid F cooled by the cooler unit 53. Here, the first rotor bearing 4311 is located in the housing cover 43 and is therefore close to the outside of the drive unit 100. Moreover, the first rotor bearing 4311 is less likely to be supplied with fluid F whose temperature has risen due to heat sources such as the stator 22 and gear section 3, compared to the fluid F supplied to the other motor bearings 4211, 4221, and 4611. As a result, the fluid F inside the first rotor bearing 4311 is more likely to viscous in proportion to its temperature. Consequently, localized increases and decreases in the fluid F in the first rotor bearing 4311 are more likely to occur in the direction around the first rotation axis J1.

[0030] Generally, in rolling bearings, the more fluid F, such as lubricating oil, there is between a pair of raceways (see, for example, Figures 4A to 6), the higher the potential difference between the raceways. Therefore, in areas with a high fluid content, the potential difference is more likely to exceed the dielectric breakdown voltage.

[0031] Therefore, electrolytic corrosion is more likely to occur in the first rotor bearing 4311 than in the other motor bearings 4211, 4221, and 4611.

[0032] Therefore, the electrical insulation at the first rotor bearing 4311 provides electrical isolation between the axial end of the motor shaft 1 (especially the rotor shaft 11) on the other axial side D2 and the housing cover 43. Consequently, electrolytic corrosion of the first rotor bearing 4311, which is most susceptible to electrolytic corrosion, can be suppressed or prevented. In other words, electrolytic corrosion can be suppressed or prevented more effectively.

[0033] Furthermore, by connecting the gear shaft 12 to the axial end D1 of the rotor shaft 11, the cumulative tolerance described above tends to increase even further. As a result, the runout at the other axial end D2 of the rotor shaft 11 tends to increase, and localized increases and decreases in the fluid F within the first rotor bearing 4311 tend to occur even more easily. Even with this configuration, since the rotor shaft 11 and the housing cover 43 are electrically insulated by the first rotor bearing 4311, electrolytic corrosion of the first rotor bearing 4311 can be suppressed or prevented.

[0034] Furthermore, the drive unit 100 is further equipped with a fluid passage, as will be described later. The fluid passage supplies fluid F to lubricate the rotor bearings 4211 and 4311. For example, in this embodiment, the fluid passage includes a receiving tray portion 465, a passage 464, and a passage composed of the inside of the motor shaft 1, the shaft through hole 111, and the rotor through hole 2111, which will be described later. The fluid passage also includes a fluid circulation section 5. This prevents or suppresses the decrease or depletion of the lubricating fluid F in the rotor bearings 4211 and 4311, thereby preventing or suppressing seizure of the rotor bearings 4211 and 4311.

[0035] Furthermore, motor bearings 4311, 4211, 4221, and 4611 have a second rotor bearing 4211. The second rotor bearing 4211 is an example of the "second bearing" of the present invention. The second rotor bearing 4211 is a rolling bearing disposed in the side plate portion 42 of the housing 4, which will be described later, and rotatably supports the motor shaft 1 in one axial direction D1 relative to the rotor 21. In detail, the second rotor bearing 4211 rotatably supports the end of the rotor shaft 11 on the axial direction D1 side. The second rotor bearing 4211 has an insulating portion, as will be described later. The motor shaft 1 and the side plate portion 42 are electrically insulated by the second rotor bearing 4211. In this way, the motor shaft 1 (especially the end of the rotor shaft 11 on the axial direction D1 side) and the side plate portion 42 can be electrically insulated by the second rotor bearing 4211, thereby suppressing or preventing electrolytic corrosion of the second rotor bearing 4211.

[0036] Furthermore, on the axial side D1 of the motor shaft 1, the charge generated by potential fluctuations flows to and disperses through the gear section 3 and other components. Therefore, the likelihood and extent of electrolytic corrosion occurring in the second rotor bearing 4211 are lower than in the first rotor bearing 4311. Consequently, the electrical resistance in the first rotor bearing 4311 is greater than that in the second rotor bearing 4211. This configuration allows for more effective suppression or prevention of electrolytic corrosion in the first rotor bearing 4311, which is prone to it. However, this example does not exclude configurations where the electrical resistance in the first rotor bearing 4311 is less than or equal to that of the second rotor bearing 4211.

[0037] Furthermore, gear bearings 4221 and 4611 are positioned at both axial ends of the gear shaft 12. The gear bearings 4221 and 4611 rotatably support both axial ends of the gear shaft 12.

[0038] Next, the motor shaft 1 has shaft through holes 111. The shaft through holes 111 are located in the rotor shaft 11 and penetrate the cylindrical rotor shaft 11 radially. The number of shaft through holes 111 may be one or more. When the motor shaft 1 rotates, the fluid F inside it flows out of the rotor shaft 11 through the shaft through holes 111 due to centrifugal force. In this embodiment, as shown in Figure 1, the shaft through holes 111 are located axially D2 to one axial end D1 of the rotor 21, and axially D1 to the other axial end D2 of the rotor 21. The shaft through holes 111 are connected to rotor through holes 2111, which will be described later. However, the shaft through-hole 111 may be located axially D1 further than the axial end D1 of the rotor 21 and axially on the other D2 further than the second rotor bearing 4211, or axially on the other D2 further than the axial end D2 of the rotor 21 and axially on the first rotor bearing 4311. Note that the above examples do not exclude configurations in which the shaft through-hole 111 and rotor through-hole 2111 are omitted.

[0039] Furthermore, the motor shaft 1 has an inlet 121. The inlet 121 is an opening at one axial end D1 side of the motor shaft 1, and in this embodiment, it is an opening at one axial end D1 side of the gear shaft 12, which will be described later. The inlet 121 is connected to the flow path 464 of the gear cover portion 46, which will be described later. Fluid F flows into the inside of the motor shaft 1 from the flow path 464 through the inlet 121.

[0040] Furthermore, the motor shaft 1 has a shaft wall portion 13. The shaft wall portion 13 is located inside the rotor shaft 11 on the other axial side D2 and extends radially. The shaft wall portion 13 is also located on the other axial side D2 beyond the shaft through hole 111. In other words, the shaft wall portion 13 closes the opening at the end of the rotor shaft 11 on the other axial side D2. The radial outer end of the shaft wall portion 13 is connected to the inner surface of the rotor shaft 11. The shaft wall portion 13 may be integrated with the rotor shaft 11 or may be a separate part from the rotor shaft 11.

[0041] <1-2. Motor 2> Motor 2 is a DC brushless motor. Motor 2 is the drive source for the drive unit 100 and is driven by power supplied from the inverter 4031 (see Figure 3). Motor 2 is an inner rotor type in which the rotor 21 is rotatably arranged radially inward of the stator 22. As shown in Figure 1, motor 2 has a rotor 21 and a stator 22.

[0042] <1-2-1. Rotor 21> The rotor 21 is rotatable together with the motor shaft 1. The drive unit 100 includes the rotor 21. The rotor 21 is fixed to the motor shaft 1 and rotatable about a first rotation axis J1. The rotor 21 rotates when power is supplied to the stator 22 from the inverter 4031 of the drive unit 100. The rotor 21 has a rotor core 211 and magnets 212. The rotor core 211 is a magnetic material and is formed, for example, by stacking thin sheets of electromagnetic steel in the axial direction. The rotor core 211 is fixed to the radially outer surface of the rotor shaft 11. Multiple magnets 212 are fixed to the rotor core 211. The multiple magnets 212 are arranged along the circumferential direction with their magnetic poles alternating.

[0043] Furthermore, the rotor core 211 has a rotor through-hole 2111. The rotor through-hole 2111 penetrates the rotor core 211 axially and connects to the shaft through-hole 111. The rotor through-hole 2111 is used as a flow path for fluid F, which also functions as a coolant. When the rotor 21 rotates, the fluid F flowing inside the motor shaft 1 can flow into the rotor through-hole 2111 via the shaft through-hole 111. The fluid F that has flowed into the rotor through-hole 2111 can also flow out to the outside from both axial ends of the rotor through-hole 2111. The flowing fluid F is ejected towards the stator 22, cooling, for example, the coil section 222 (especially the coil end 2221), which will be described later. The flowing fluid F is also ejected towards the rotor bearings 4211, 4311, etc., which rotatably support the motor shaft 1, lubricating and cooling them.

[0044] <1-2-2.Status 22> The stator 22 is positioned radially outward from the rotor 21. The drive unit 100 includes the stator 22. The stator 22 faces the rotor 21 with a radial gap between them. The stator 22 has a stator core 221 and a coil section 222. The stator 22 is held in a first housing cylindrical section 41, which will be described later, and fixed to its inner surface. The stator core 221 has a plurality of magnetic pole teeth (not shown) extending radially inward from the inner surface of an annular yoke (not shown). The coil section 222 is formed by winding a conductor around the magnetic pole teeth via an insulator (not shown). The coil section 222 has coil ends 2221 that protrude from the axial end face of the stator core 221.

[0045] <1-3. Gear section 3> Next, the gear section 3 is connected to the axial side D1 of the motor shaft 1. As described above, the drive device 100 includes the gear section 3. The gear section 3 is a power transmission device that transmits power from the motor 2 to the drive shaft Ds, which will be described later. The gear section 3 has a reduction gear 31 and a differential gear 32.

[0046] <1-3-1. Reduction device 31> The reduction gear 31 is connected to the gear shaft 12. The reduction gear 31 reduces the rotational speed of the motor 2 and increases the torque output from the motor 2 according to its reduction ratio. The reduction gear 31 transmits the torque output from the motor 2 to the differential gear 32. The reduction gear 31 includes a first gear 311, a second gear 312, a third gear 313, and an intermediate shaft 314.

[0047] The first gear 311 is fixed to the radially outer surface of the motor shaft 1 on one axial side D1 of the motor shaft 1. The gear section 3 has the first gear 311. For example, the first gear 311 is positioned on the radially outer surface of the gear shaft 12. The first gear 311 may be integrated with the gear shaft 12, or it may be separate from the gear shaft 12 and firmly fixed to the radially outer surface of the gear shaft 12. The first gear 311 is rotatable together with the motor shaft 1 around the first rotation axis J1.

[0048] The intermediate shaft 314 extends along the second rotation axis J2 and is rotatable about the second rotation axis J2. The second rotation axis J2 extends in the axial direction. The gear section 3 has the intermediate shaft 314. Both ends of the intermediate shaft 314 are supported by the first intermediate bearing 4231 and the second intermediate bearing 4621 so as to be rotatable about the second rotation axis J2. Hereafter, the first intermediate bearing 4231 and the second intermediate bearing 4621 may be collectively referred to as "intermediate bearings 4231, 4621".

[0049] The second gear 312 is fixed to the radially outer surface of the intermediate shaft 314 and meshes with the first gear 311. The third gear 313 is fixed to the radially outer surface of the intermediate shaft 314. The gear section 3 has the second gear 312 and the third gear 313. The third gear 313 is positioned axially on the other side D2 from the second gear and meshes with the fourth gear 321 of the differential 32. The second gear 312 and the third gear 313 may be integrated with the intermediate shaft 314, or they may be separate from the intermediate shaft 314 and firmly fixed to the radially outer surface of the intermediate shaft 314. The second gear 312 and the third gear 313 are rotatable together with the intermediate shaft 314 around the second rotation axis J2.

[0050] The torque from the motor shaft 1 is transmitted from the first gear 311 to the second gear 312. The torque transmitted to the second gear 312 is then transmitted to the third gear 313 via the intermediate shaft 314. Furthermore, the torque is transmitted from the third gear 313 to the fourth gear 321.

[0051] <1-3-2. Differential device 32> The differential 32 is attached to the drive shaft Ds and transmits torque transmitted from the reduction gear 31 to the drive shaft Ds. As described above, the gear section 3 has a differential 32. The differential 32 has a fourth gear 321 that meshes with the third gear 313 and outputs torque from the fourth gear 321 to the drive shaft Ds. The fourth gear 321 is a so-called ring gear. The drive shaft Ds has a first drive shaft Ds1 and a second drive shaft Ds2. The first drive shaft Ds1 is attached to the other axial side D2 of the differential 32. The second drive shaft Ds2 is attached to the other axial side D1 of the differential 32. For example, when the vehicle 300 turns, the differential 32 transmits torque to the drive shafts Ds1 and Ds2 on both axial sides while absorbing the difference in rotational speed between the drive shafts Ds1 and Ds2 on both axial sides.

[0052] <1-4. Housing 4> The housing 4 houses the motor shaft 1, the motor 2 (particularly the rotor 21 and stator 22), and the gear section 3. As described above, the drive unit 100 includes the housing 4. The housing 4 has a first housing cylindrical section 41, a side plate section 42, a housing lid section 43, a cover member 44, a second housing cylindrical section 45, and a gear lid section 46. The first housing cylindrical section 41, the side plate section 42, the housing lid section 43, the cover member 44, the second housing cylindrical section 45, and the gear lid section 46 are formed using, for example, a conductive material, and in this embodiment, they are formed using metallic materials such as iron, aluminum, or alloys thereof. Furthermore, in order to suppress galvanic corrosion at the contact points, these are preferably formed using the same material. However, this is not limited to this example, and these may be formed using materials other than metallic materials, and at least some of these may be formed using different materials.

[0053] Furthermore, housing 4 further comprises a motor housing 401 and a gear housing 402. The motor housing 401 and gear housing 402 will be described later. Housing 4 further comprises an inverter housing 403. The inverter housing 403 houses an inverter 4031 that supplies drive current to the stator 22.

[0054] <1-4-1. First housing cylindrical section 41> The first housing cylindrical portion 41 is cylindrical in shape and extends in the axial direction, and is an example of the "housing cylindrical portion" of the present invention. As described above, the housing 4 has the first housing cylindrical portion 41. The stator 22 is fixed to the inner surface of the first housing cylindrical portion 41. Inside the first housing cylindrical portion 41, the motor 2, including the rotor 21 and stator 22, and a fluid reservoir 54, which will be described later, are arranged.

[0055] <1-4-2. Side plate part 42> The side plate portion 42 is positioned axially on one side D1 from the first housing cylindrical portion 41 and extends in a direction intersecting the first rotation axis J1. As described above, the housing 4 has a side plate portion 42. The side plate portion 42 is an example of the "second lid portion" of the present invention. The side plate portion 42 is positioned at the end of the first housing cylindrical portion 41 on the axial side D1 and covers the end of the first housing cylindrical portion 41 on the axial side D1. The side plate portion 42 also covers the end of the second housing cylindrical portion 45 on the other axial side D2. The side plate portion 42 extends in a direction intersecting the first rotation axis J1 and separates the first housing cylindrical portion 41 and the second housing cylindrical portion 45. In this embodiment, the first housing cylindrical portion 41 and the side plate portion 42 are integrated. This increases their rigidity. However, the invention is not limited to this example, and the two may be separate parts.

[0056] The side plate portion 42 has a side plate through hole 4201 and a first drive shaft through hole 4202. The side plate through hole 4201 and the first drive shaft through hole 4202 penetrate the side plate portion 42 in the axial direction. The center of the side plate through hole 4201 coincides with the first rotation axis J1. The motor shaft 1 is inserted through the side plate through hole 4201. The center of the first drive shaft through hole 4202 coincides with the third rotation axis J3. The first drive shaft Ds1 is inserted through the first drive shaft through hole 4202. An oil seal (not shown) is placed in the gap between the first drive shaft Ds1 and the first drive shaft through hole 4202 to seal the space between them.

[0057] The side plate portion 42 further includes a second rotor bearing holder 421, a first gear bearing holder 422, a first intermediate bearing holder 423, and a first drive bearing holder 424. The second rotor bearing holder 421 is located on the inner surface of the side plate through hole 4201 on the other axial D2 side and holds the second rotor bearing 4211. The second rotor bearing 4211 rotatably supports the end of the rotor shaft 11 on the axial D1 side. The first gear bearing holder 422 is located on the inner surface of the side plate through hole 4201 on the axial D1 side and holds the first gear bearing 4221. The first gear bearing 4221 is another example of the "second bearing" of the present invention and rotatably supports the end of the gear shaft 12 on the axial D2 side. The first intermediate bearing holder 423 is located on the end face of the side plate portion 42 on the axial D1 side and holds the first intermediate bearing 4231. The first intermediate bearing 4231 rotatably supports the other axial end D2 of the intermediate shaft 314. The first drive bearing holder 424 is positioned on the inner surface of the first drive shaft through hole 4202 and holds the first drive bearing 4241. The first drive bearing 4241 rotatably supports the first drive shaft Ds1.

[0058] <1-4-3. Housing cover 43> The housing cover portion 43 extends in a direction intersecting the first rotation axis J1 and covers the other axial end D2 of the first housing cylinder portion 41. As described above, the housing 4 is equipped with the housing cover portion 43. The housing cover portion 43 is an example of the "first cover portion" of the present invention and is attached to the other axial end D2 of the first housing cylinder portion 41. Fixation of the housing cover portion 43 to the first housing cylinder portion 41 can be, for example, by screwing, but is not limited to this, and a wide range of methods that can firmly fix the housing cover portion 43 to the first housing cylinder portion 41 can be employed, such as screwing or press-fitting. As a result, the housing cover portion 43 can be tightly fitted to the other axial end D2 of the first housing cylinder portion 41. Tight fit refers to having a degree of airtightness such that the fluid F inside the member does not leak to the outside and foreign matter such as water, dust, and dirt from the outside does not enter. The same applies to tight fit hereafter.

[0059] Furthermore, the housing cover 43 has a first rotor bearing holder 431. The first rotor bearing holder 431 holds the first rotor bearing 4311. The first rotor bearing 4311 rotatably supports the other axial end D2 of the rotor shaft 11. The first rotor bearing holder 431 has an opening 4312 through which the rotor shaft 11 is inserted. The opening 4312 penetrates the housing cover 43 axially and surrounds the first rotation axis J1 when viewed from the axial direction.

[0060] <1-4-4. Cover component 44> The cover member 44 is positioned on the other axial end D2 side of the housing lid 43 and covers the opening 4312 and the other axial end D2 side of the motor shaft 1. The cover member 44 can be attached to the housing lid 43 by, for example, screws, but is not limited to this; a wide range of methods that can firmly fix the cover member 44 to the housing lid 43, such as screwing or press-fitting, can be employed. A rotation detector (e.g., a resolver) for detecting the rotation angle of the rotor can be housed in the space enclosed by the cover member 44 and the housing lid 43. Furthermore, a static eliminator that electrically connects the motor shaft 1 and the housing 4 may be placed in this space.

[0061] <1-4-5. Second housing cylindrical section 45> The second housing cylinder portion 45 is cylindrical, surrounding the first rotation axis J1, and extends in the axial direction. The other axial end D2 of the second housing cylinder portion 45 is connected to the side plate portion 42 and covered by the side plate portion 42. In this embodiment, the second housing cylinder portion 45 is detachably attached to the axial end D1 of the side plate portion 42. The attachment of the second housing cylinder portion 45 to the side plate portion 42 can be, for example, fixed with screws, but is not limited to this, and a wide range of methods that can firmly fix the second housing cylinder portion 45 to the side plate portion 42 can be employed, such as screwing or press-fitting. As a result, the second housing cylinder portion 45 can be in close contact with the axial end D1 of the side plate portion 42.

[0062] <1-4-6. Gear cover section 46> The gear cover portion 46 is positioned at one axial end D1 of the second housing cylindrical portion 45 and covers that end. The gear cover portion 46 is positioned axially D1 further than the first housing cylindrical portion 41 and extends in a direction intersecting the first rotation axis J1. The gear cover portion 46 is another example of the "second cover portion" of the present invention. As described above, the housing 4 includes the gear cover portion 46. In this embodiment, the second housing cylindrical portion 45 and the gear cover portion 46 are integrated. However, the embodiment is not limited to this example, and the two may be separate parts.

[0063] The gear cover portion 46 has a second drive shaft through hole 460. The second drive shaft through hole 460 penetrates the gear cover portion 46 in the axial direction. The center of the second drive shaft through hole 460 coincides with the third rotation axis J3. The second drive shaft Ds2 is inserted through the second drive shaft through hole 460. An oil seal (not shown) is placed in the gap between the second drive shaft Ds2 and the second drive shaft through hole 460.

[0064] Furthermore, the gear cover portion 46 further includes a second gear bearing holder 461, a second intermediate bearing holder 462, and a second drive bearing holder 463. The second gear bearing holder 461 and the second intermediate bearing holder 462 are positioned on the other axial end face D2 side of the gear cover portion 46. The second gear bearing holder 461 holds the second gear bearing 4611. In the following, the first gear bearing holder 42 2 And the second gear bearing holder 461 is replaced with the gear bearing holder 42 2 It is sometimes collectively referred to as "461". Housing 4 is the gear bearing holder 42 2 It has 461. Gear bearing holder 42 2 461 holds the gear bearings 4221 and 4611.

[0065] The second gear bearing 4611 is another example of the "second bearing" of the present invention, and rotatably supports one axial end D1 of the gear shaft 12. The second intermediate bearing holder 462 holds the second intermediate bearing 4621. The second intermediate bearing 4621 rotatably supports one axial end D1 of the intermediate shaft 314. The second drive bearing holder 463 is located on the inner surface of the second drive shaft through hole 460 and holds the second drive bearing 4631. The second drive bearing 4631 rotatably supports the second drive shaft Ds2.

[0066] Furthermore, the gear cover portion 46 has a flow path 464. The flow path 464 is a passage for fluid F and connects the receiving tray portion 465 to the inlet 121 of the motor shaft 1. The receiving tray portion 465 has a recess that is recessed vertically downward. The receiving tray portion 465 can store fluid F that has been scraped up by the gears of the gear portion 3 (for example, the fourth gear 321). In this embodiment, the gear cover portion 46 has a receiving tray portion 465. The receiving tray portion 465 is located on the other axial side D2 end face of the gear cover portion 46 and extends in the other axial side D2. The fluid F stored in the receiving tray portion 465 is supplied to the flow path 464 and flows into the interior of the motor shaft 1 from the inlet 121 at the end of the motor shaft 1 on the other axial side D1.

[0067] <1-4-7. Motor Housing 401> Next, the motor housing 401 houses the rotor 21 and the stator 22. As described above, the housing 4 has the motor housing 401. In this embodiment, the motor housing 401 is composed of a first housing cylindrical portion 41, a side plate portion 42, and a housing lid portion 43.

[0068] <1-4-7-1. Rotor bearings 4211, 4311> The motor housing 401 is equipped with a first rotor bearing holder 431 and a second rotor bearing holder 421. Hereafter, the first rotor bearing holder 431 and the second rotor bearing holder 421 may be collectively referred to as "rotor bearing holders 421, 431". The housing 4 has rotor bearing holders 421, 431. The rotor bearing holders 421, 431 hold rotor bearings 4211, 4311.

[0069] Furthermore, the following describes the first rotor bearing holder 431, the second rotor bearing holder 421, and the first gear bearing holder 42 2 , and the second gear bearing holder 461 is replaced with the motor bearing holder 42 2 They are sometimes collectively referred to as "431, 421, 461". Housing 4 has motor bearing holders 421, 431, 421, 461. Motor bearing holders 421, 431, 42 2 , 461 is motor bearing 4 2 11,4 3 It holds 11, 4221,4611.

[0070] Furthermore, rotor bearings 4211 and 4311 are arranged in the motor housing 401. The rotor bearings 4211 and 4311 rotatably support the motor shaft 1 on both axial sides of the rotor 21. The housing 4 has the rotor bearings 4211 and 4311. In this embodiment, the rotor bearings 4211 and 4311 are ball bearings. The motor shaft 1 and the motor housing 401 are electrically insulated by the rotor bearings 4211 and 4311. However, the examples in this embodiment do not exclude a configuration in which at least one of the first rotor bearing 4311 and the second rotor bearing 4211 is a rolling bearing other than a ball bearing.

[0071] In this embodiment, the rotor bearings 4211 and 4311 rotatably support both axial ends of the rotor shaft 11. This allows the electric charge flowing from the rotor shaft 11 due to potential fluctuations within the rotor shaft 11 to be discharged to the housing 4 via the gear shaft 12 and gear section 3, as shown in Figure 2. In particular, in this embodiment, when the drive unit 100 is in the powering and regenerative states, the internal teeth of the rotor shaft 11 and the external teeth of the gear shaft 12 make metallic contact, and the rotor shaft 11 becomes electrically connected to the gear shaft 12. Therefore, the electric charge from the rotor shaft 11 is discharged to the housing 4 via the above-described path, and further discharged to an external object (such as the vehicle body 301) via the ground connection section 6 connected to the gear housing 402 and inverter housing 403 (see Figures 2 and 3). Thus, even if the motor shaft 1 is divided, the occurrence of electrolytic corrosion in the motor bearings 4311, 4211, 4221, and 4611 can be effectively suppressed or prevented.

[0072] Figure 4A is a cross-sectional view showing an example configuration of motor bearings 4311, 4211, 4221, and 4611. Figure 4B is a cross-sectional view showing a first modified configuration of motor bearings 4311, 4211, 4221, and 4611. Figure 4C is a cross-sectional view showing a second modified configuration of motor bearings 4311, 4211, 4221, and 4611. Figures 4A to 4C show the cross-section of motor bearings 4311, 4211, 4221, and 4611 viewed radially with reference to the first rotation axis J1.

[0073] For example, as shown in Figures 4A to 4C, the motor bearings 4311, 4211, 4221, and 4611 each have a pair of raceway rings 71 and rolling elements 72. The pair of raceway rings 71 are arranged concentrically. The rolling elements 72 are arranged to roll between the pair of raceway rings 71.

[0074] The pair of raceways 71 includes an inner raceway 711 and an outer raceway 712 positioned radially outward from the inner raceway 711. The inner raceway 711 and the outer raceway 712 are, for example, made of metal and are annular in shape, surrounding the first rotation axis J1. In Figure 4A, the inner raceway 711 is fixed to the radially outer surface of the rotor shaft 11, and the outer raceway 712 is fixed to the motor housing 401. The rolling elements 72 are numerous and are arranged circumferentially between the inner raceway 711 and the outer raceway 712.

[0075] Preferably, at least one of the following is electrically insulating: at least the surface of the rolling element 72, the first opposing surface 7110 of the inner raceway 711 facing the rolling element 72, and the second opposing surface 7120 of the outer raceway 712 facing the rolling element 72. With this configuration, discharge between the pair of raceway 71 and the rolling element 72 can be suppressed or prevented in the motor bearings 4311, 4211, 4221, and 4611. Therefore, electrolytic corrosion of the motor bearings 4311, 4211, 4221, and 4611 can be effectively suppressed or prevented.

[0076] For example, in Figure 4A, the rolling element 72 is an electrically insulating sphere. This suppresses or prevents discharge between the pair of raceway rings 71 and the rolling element 72 in the motor bearings 4311, 4211, 4221, and 4611. Therefore, electrolytic corrosion of the motor bearings 4311, 4211, 4221, and 4611 can be effectively suppressed or prevented.

[0077] As an example, an electrical insulating layer formed by anodizing or the like may be placed on the surface of the rolling element 72. In other words, the rolling element 72 may have a metal sphere and an electrical insulating layer covering the surface of the sphere. However, the material and method of forming the electrical insulating layer of the rolling element 72 are not limited to this example.

[0078] Alternatively, in Figure 4A, the rolling element 72 may be a ceramic ball. In this case, the rolling element 72 can more reliably suppress or prevent discharge between the pair of raceway rings 71. However, the example is not limited to this, and in Figure 4A, the rolling element 72 may be an electrically insulating sphere other than a ceramic ball.

[0079] Furthermore, in Figure 4A, an electrically insulating layer 7111 formed by anodizing or the like is placed on the first opposing surface 7110 of the inner raceway 711. In other words, the inner raceway 711 may have an electrically insulating layer 7111 and a metal ring portion 7112. The electrically insulating layer 7111 covers the surface of the ring portion 7112 on the outer raceway 712 side. However, the materials of the ring portion 7112 and the electrically insulating layer 7111, and the method of forming the electrically insulating layer 7111 are not limited to the examples given above.

[0080] Furthermore, in Figure 4A, an electrical insulating layer 7121 formed by anodizing or the like is placed on the second opposing surface 7120 of the outer raceway 712. In other words, the outer raceway 712 may have an electrical insulating layer 7121 and a metal ring portion 7122. The electrical insulating layer 7121 covers the surface of the ring portion 7122 on the inner raceway 711 side. However, the materials of the ring portion 7122 and the electrical insulating layer 7121, and the method of forming the electrical insulating layer 7121 are not limited to the examples given above.

[0081] In Figure 4A, at least the surface of the rolling element 72, the first opposing surface 7110, and the second opposing surface 7120 are all electrically insulating. However, this example does not exclude configurations in which at least two of these surfaces are not electrically insulating.

[0082] For example, preferably, the rolling elements 72 of the second rotor bearing 4211, the first gear bearing 4221, and the second gear bearing 4611 are ceramic balls. Furthermore, the first opposing surface 7110 and the second opposing surface 7120 of these bearings do not have an electrical insulating layer 7111. However, the first opposing surface 7110 of the inner raceway 711 of the first rotor bearing 4311 may have electrical insulating properties, for example, an electrical insulating layer 7111 may be provided. Also, the second opposing surface 7120 of the outer raceway 712 of the first rotor bearing 4311 may have electrical insulating properties, for example, an electrical insulating layer 7111 may be provided.

[0083] This way, the motor shaft is more prone to runout due to cumulative tolerances. 1 In the first rotor bearing 4311, which rotatably supports the other axial side D2, electrical insulation can be ensured while improving the wear resistance of the first opposing surface 7110 and other surfaces. Furthermore, in the motor bearings 4211, 4221, and 4611, electrical insulation can be ensured with a simple configuration by using ceramic balls for the rolling elements 72.

[0084] Furthermore, if the motor bearings 4311, 4211, 4221, and 4611 are electrically insulated from at least one of the rotor shaft 11 and the motor housing 401, the rolling elements 72, the inner raceway 711, and the outer raceway 712 may be made of electrically conductive material.

[0085] For example, in Figure 4B, the motor bearings 4311, 4211, 4221, and 4611 further have a first insulating member 73. The first insulating member 73 is positioned between the outer raceway 712 and the motor bearing holders 421, 431, 422, and 461. In this embodiment, the first insulating member 73 is axially extending and cylindrical, and has electrical insulating properties. The material of the first insulating member 73 is, for example, anodized aluminum. The outer raceway 712 of the motor bearings 4311, 4211, 4221, and 4611 is fixed to the motor bearing holders 421, 431, 422, and 461 via the first insulating member 73. This allows the first insulating member 73 to electrically insulate the outer raceway 712 from the motor bearing holders 421, 431, 422, and 461 of the motor housing 401. For example, the electrical path from the inner raceway 711 of the first rotor bearing 4311 to the housing cover 43 can be insulated. Similarly, the electrical path from the inner raceway 711 of the second rotor bearing 4211 to the side plate 42 can be insulated. The same applies to the other motor bearings 4221 and 4611. Consequently, discharge becomes less likely to occur within the motor bearings 4311, 4211, 4221, and 4611. Therefore, electrolytic corrosion of the motor bearings 4311, 4211, 4221, and 4611 can be effectively suppressed or prevented.

[0086] Furthermore, in Figure 4C, the motor bearings 4311, 4211, 4221, and 4611 further have a second insulating member 74. The second insulating member 74 is positioned between the inner raceway 711 and the motor shaft 1 (specifically the rotor shaft 11). In this embodiment, the second insulating member 74 is cylindrical and extends axially, and has electrical insulating properties. The material of the second insulating member 74 is, for example, anodized aluminum. The inner raceway 711 of the motor bearings 4311, 4211, 4221, and 4611 is fixed to the motor shaft 1 (specifically the rotor shaft 11) via the second insulating member 74. This allows the second insulating member 74 to electrically insulate the space between the inner raceway 711 and the rotor shaft 11. The electrical path from the outer raceway 712 of the motor bearings 4311, 4211, 4221, and 4611 to the rotor shaft 11 can be insulated. Therefore, discharge is less likely to occur within the motor bearings 4311, 4211, 4221, and 4611. Thus, electrolytic corrosion of the motor bearings 4311, 4211, 4221, and 4611 can be effectively suppressed or prevented.

[0087] Furthermore, since the second insulating member 74 is pre-positioned on the inner raceway 711, unlike the case where the second insulating member 74 is pre-positioned on the rotor shaft 11, it is not necessary to precisely determine the position of the motor bearings 4311, 4211, 4221, and 4611 relative to the rotor shaft 11. Therefore, the placement of the motor bearings 4311, 4211, 4221, and 4611 becomes easier. In addition, when press-fitting the outer raceway 712 of the motor bearings 4311, 4211, 4221, and 4611 into the motor bearing holders 421, 431, 422, and 461, the lifespan of the insulating member can be improved by not placing the insulating member on the outer raceway 712 side.

[0088] Furthermore, the motor bearings 4311, 4211, 4221, and 4611 may have both the first insulating member 73 and the second insulating member 74, and are not limited to the examples in Figures 4B and 4C. In addition, the above configurations can be combined in any way, as long as no particular contradictions arise. This will allow for even more effective suppression or prevention of electrolytic corrosion of the motor bearings 4311, 4211, 4221, and 4611.

[0089] <1-4-8. Gear Housing 402> The gear housing 402 houses the gear section 3. As described above, the housing 4 has the gear housing 402. In this embodiment, the gear housing 402 consists of a side plate section 42, a second housing cylindrical section 45, and a gear cover section 46, and houses the reduction gear 31, the differential gear 32, and the like.

[0090] A fluid reservoir P is located in the lower part of the gear housing 402, where fluid F accumulates. A portion of the gear section 3 (for example, the fourth gear 321) is immersed in the fluid reservoir P. The fluid F accumulated in the fluid reservoir P is scraped up by the operation of the gear section 3 and supplied to the inside of the gear housing 402. For example, when the fourth gear 321 of the differential 32 rotates, the fluid F is scraped up by the tooth surface of the fourth gear 321. A portion of the scraped-up fluid F is supplied to the gears and bearings of the reduction gear 31 and the differential 32 within the gear housing 402 and used for lubrication. Another portion of the scraped-up fluid F is supplied to the inside of the motor shaft 1 and supplied to the rotor 21 and stator 22 of the motor 2 and the bearings within the gear housing 402, and used for cooling and lubrication.

[0091] <1-4-8-1. Gear bearings 4221, 4611> The gear housing 402 houses a first gear bearing holder 422 and a second gear bearing holder 461, as well as gear bearings 4221 and 4611. In this embodiment, the gear bearings 4221 and 4611 rotatably support both axial ends of the gear shaft 12.

[0092] <1-4-8-2. Drive bearings 4241, 4631> Furthermore, the gear housing 402 is equipped with a first drive bearing holder 424 and a second drive bearing holder 463, and a first drive bearing 4241 and a second drive bearing 4631. In the following description, the first drive bearing 4241 and the second drive bearing 4631 may be collectively referred to as "drive bearings 4241, 4631". The drive bearings 4241, 4631 rotatably support both axial ends of the drive shaft Ds. The housing 4 has the drive bearings 4241, 4631.

[0093] The drive bearings 4241 and 4631 are roller bearings. Figure 5 is a cross-sectional view showing an example configuration of the first drive bearing 4241 and the second drive bearing 4631. Note that Figure 5 shows the cross-section of the drive bearings 4241 and 4631 viewed from the radial direction with reference to the third rotation axis J3.

[0094] For example, as shown in Figure 5, the drive bearings 4241 and 4631 each have a pair of raceway rings 81 and rolling elements 82. The pair of raceway rings 81 are arranged concentrically. The rolling elements 82 are arranged to roll between the pair of raceway rings 81 and have a longitudinal shape in the axial direction. The pair of raceway rings 81 includes an inner raceway ring 811 and an outer raceway ring 812 arranged radially outward from the inner raceway ring 811. The inner raceway ring 811 and the outer raceway ring 812 are made of metal, for example, and 3 Rotation axis J 3 It is an annular shape surrounding the drive shaft Ds. In Figure 5, the inner raceway 811 is fixed to the radially outer surface of the drive shaft Ds, and the outer raceway 812 is fixed to the gear housing 402. There are multiple rolling elements 82, which are arranged circumferentially between the inner raceway 811 and the outer raceway 812. The rolling elements 82 are electrically conductive and are made of metal, for example. Therefore, the electrical resistance of the drive bearings 4241 and 4631 is lower than that of the motor bearings 4311, 4211, 4221, and 4611.

[0095] As described above, the rolling elements 82 of the drive bearings 4241 and 4631, which are roller bearings, have a shape that has a longitudinal direction in the axial direction, so that the contact area with the pair of raceway rings 81 can be made larger compared to, for example, ball bearings. Furthermore, the drive bearings 4241 and 4631 have lower electrical resistance than the motor bearings 4311, 4211, 4221, and 4611. In other words, the drive bearings 4241 and 4631 have higher electrical conductivity. On the other hand, as mentioned above, the motor bearings 4311, 4211, 4221, and 4611 that support the motor shaft 1 within the motor housing 401 are electrically insulated from the motor housing 401. Therefore, as shown in Figure 2, the charge flowing from the rotor shaft 11 due to potential fluctuations within the motor shaft 1 (especially the rotor shaft) is discharged to the gear housing 402 through the gear shaft 12, the differential 32 including the first gear 311, the second gear 312, the third gear 313, the intermediate shaft 314, and the fourth gear 321, the drive shaft Ds, and the drive bearings 4241 and 4631 when the drive unit 100 is in the powering and regenerating states. Furthermore, this charge is discharged through the ground connection 6 connected to the gear housing 402, inverter housing 403, etc. of the housing 4, to, for example, the vehicle body 301 (see Figure 3) of the vehicle 300 on which the drive unit 100 is mounted. Thus, the occurrence of electrolytic corrosion in the motor bearings 4311, 4211, 4221, and 4611 can be more effectively suppressed or prevented.

[0096] Furthermore, by discharging charge through the drive bearings 4241 and 4631, the static elimination path between the gear shaft 12 and the gear housing 402 passes through the differential 32, which includes the first gear 311, second gear 312, third gear 313, intermediate shaft 314, and fourth gear 321, the drive shaft Ds, and the drive bearings 4241 and 4631. Therefore, the static elimination path from the motor shaft 1 to the housing 4 can be made longer. Consequently, the potential difference between the motor shaft 1 and the drive bearing holders 424 and 463 that hold the drive bearings 4241 and 4631 in the housing 4 can be made larger. Thus, it becomes easier to discharge charge from the motor shaft 1 (especially the rotor shaft) to the housing 4.

[0097] The pair of raceway rings 81 of the drive bearings 4241 and 4631 are lubricated by a lubricant 83. Preferably, the electrical conductivity of the lubricant 83 is higher than that of the fluid F. For example, conductive grease can be used as the lubricant 83. In conductive grease, conductive materials such as copper powder and carbon powder are added to the lubricant such as grease. Improving the electrical conductivity of the lubricant 83 can contribute to suppressing or preventing the occurrence of electrolytic corrosion. However, this example does not exclude configurations in which the lubricant 83 is not provided, nor does it exclude configurations in which the electrical conductivity of the lubricant 83 is not higher than that of the fluid F.

[0098] <1-4-8-3. Intermediate bearings 4231, 4621> Furthermore, the gear housing 402 is equipped with a first intermediate bearing holder 423 and a second intermediate bearing holder 462, and intermediate bearings 4231 and 4621. The intermediate bearings 4231 and 4621 rotatably support both axial ends of the intermediate shaft 314. The housing 4 has intermediate bearings 4231 and 4621.

[0099] In this embodiment, the intermediate bearings 4231 and 4621 are roller bearings. Figure 6 is a cross-sectional view showing an example of the configuration of the first intermediate bearing 4231 and the second intermediate bearing 4621. Note that Figure 6 shows the cross-section of the intermediate bearings 4231 and 4621 viewed from the radial direction with reference to the second rotation axis J2.

[0100] For example, as shown in Figure 6, the intermediate bearings 4231 and 4621 each have a pair of raceway rings 91 and rolling elements 92. The pair of raceway rings 91 are arranged concentrically. The rolling elements 92 are rotatably arranged between the pair of raceway rings 91 and have a longitudinal shape in the axial direction. The pair of raceway rings 91 includes an inner raceway ring 911 and an outer raceway ring 912 arranged radially outward from the inner raceway ring 911. The inner raceway ring 911 and the outer raceway ring 912 are, for example, made of metal and are annular in shape surrounding the second rotation axis J2. In Figure 6, the inner raceway ring 911 is fixed to the radially outer surface of the intermediate shaft 314, and the outer raceway ring 912 is fixed to the gear housing 402. The rolling elements 92 are plurality and are arranged circumferentially between the inner raceway rings 911 and the outer raceway rings 912. The rolling elements 92 are electrically conductive and are, for example, made of metal. Therefore, the electrical resistance of the intermediate bearings 4231 and 4621 is lower than that of the motor bearings 4311, 4211, 4221, and 4611.

[0101] As shown in Figure 2, the electric charge flowing from the rotor shaft 11 due to potential fluctuations within the rotor shaft 11 can flow to the intermediate shaft 314 via the gear shaft 12, the first gear 311, and the second gear 312 when the drive unit 100 is in the powering and regenerative states. Therefore, the charge can be further discharged to the gear housing 402 through the intermediate shaft 314 and intermediate bearings 4231 and 4621. Furthermore, this charge can be discharged to, for example, the vehicle body 301 (see Figure 3) of the vehicle 300 on which the drive unit 100 is mounted, through the ground connection 6 connected to the gear housing 402, inverter housing 403, etc. of the housing 4. Thus, the occurrence of electrolytic corrosion in the motor bearings 4311, 4211, 4221, and 4611 can be more reliably suppressed or prevented.

[0102] Furthermore, the space between the pair of raceway rings 91 of the intermediate bearings 4231 and 4621 is lubricated by a lubricant 93. Preferably, the electrical conductivity of the lubricant 93 is higher than that of, for example, the fluid F. For example, conductive grease can be used as the lubricant 93. In conductive grease, conductive materials such as copper powder and carbon powder are added to the lubricant such as grease. Improving the electrical conductivity of the lubricant 93 can contribute to suppressing or preventing the occurrence of electrolytic corrosion. However, this example does not exclude configurations in which the lubricant 93 is not provided, nor does it exclude configurations in which the electrical conductivity of the lubricant 93 is not higher than that of, for example, the fluid F.

[0103] It should be noted that the examples in this embodiment do not exclude configurations in which the intermediate bearings 4231 and 4621 are not roller bearings. For example, it does not exclude configurations in which the intermediate bearings 4231 and 4621 are ball bearings or sliding bearings.

[0104] <1-5. Fluid circulation section 5> Next, the fluid circulation unit 5 will be described. The fluid circulation unit 5 includes a piping section 51, a pump 52, a cooler unit 53, and a fluid reservoir 54.

[0105] The piping section 51 connects the pump 52 to the fluid reservoir 54 located inside the first housing cylindrical section 41. The pump 52 draws in the fluid F stored in the fluid storage section P and supplies the fluid F to the fluid reservoir 54. In this embodiment, the pump 52 is an electric pump.

[0106] The cooler unit 53 is positioned in the piping section 51 between the pump 52 and the fluid reservoir 54. In other words, the fluid F drawn in by the pump 52 passes through the cooler unit 53 via the piping section 51 and is then sent to the fluid reservoir 54. The cooler unit 53 is supplied with a refrigerant, such as water supplied from an external source. The cooler unit 53 exchanges heat between the refrigerant and the fluid F to lower the temperature of the fluid F.

[0107] The fluid reservoir 54 is a tray located inside the motor housing 401, vertically above the stator 22. A drip hole (not shown) is formed at the bottom of the fluid reservoir 54, and the motor 2 is cooled by dripping fluid F from the drip hole. The drip hole is formed, for example, above the coil end 2221 of the coil portion 222 of the stator 22, so that the coil portion 222 is cooled by the fluid F.

[0108] <1-6. Ground connection part 6> The grounding connection 6 grounds the housing 4 to an external object. As described above, the drive unit 100 further includes the grounding connection 6. In this embodiment, the grounding connection 6 is a conductive cable with an insulated conductor. One end of the conductive cable is electrically connected to the housing 4, and the other end is electrically connected to, for example, the body 301 of the vehicle 300 (see Figure 3). In this way, the housing 4 can be grounded to an external object (for example, the body 301 of the vehicle 300) via the grounding connection 6. Therefore, the charge released from the motor shaft 1 (especially the rotor shaft 11) to the housing 4 can be released to the external object, thereby suppressing or preventing a potential rise in the housing 4. This further reliably suppresses or prevents the occurrence of electrolytic corrosion in the motor bearings 4311, 4211, 4221, and 4611.

[0109] Preferably, as shown in Figure 3, the ground connection 6 is located in the inverter housing 403. For example, one end of the conductive cable described above is electrically connected to the inverter housing 403. In this way, the ground connection 6 can further ground the inverter housing 403 to an object outside the housing 4 (for example, the vehicle body 301 of the vehicle 300). Therefore, it is possible to further suppress or prevent an increase in the ground potential of the inverter 4031 housed in the inverter housing 403. However, this example does not exclude configurations in which the ground connection 6 is located in a part of the housing 4 other than the inverter housing 403. For example, the ground connection 6 may be connected to the motor housing 401, the gear housing 402 (see Figure 2), etc.

[0110] <1-7. Modified Examples of Embodiments> Next, a modified example of the embodiment will be described with reference to Figures 7 and 8. Figure 7 is a schematic diagram of the drive device 100 according to the modified example. Figure 8 is a conceptual diagram illustrating the static elimination path of the drive device 100 in the modified example. Note that Figures 7 and 8 are merely conceptual diagrams, and the arrangement and dimensions of each part may not be the same as those of the actual drive device 100. Also, in Figure 8, the thick solid line with an arrow indicates the static elimination path. Below, a configuration different from the embodiment described above will be described. Also, components similar to those in the embodiment described above will be denoted by the same reference numerals, and their descriptions may be omitted.

[0111] In this modified example, the motor shaft 1 is cylindrical and extends in the axial direction. The drive shafts Ds are inserted inside the cylindrical motor shaft 1 that extends in the axial direction and extend along the first rotation axis J1. This eliminates the need to secure space for the drive shafts Ds to be positioned radially outward from the motor shaft 1. Therefore, the size of the drive unit 100 in the direction perpendicular to the axial direction can be reduced. Thus, the drive unit 100 can be miniaturized. In addition, the gap between the drive shafts Ds and the motor shaft 1 can be used as a passage for the fluid F that functions as a coolant.

[0112] The drive shaft Ds is rotatable around the first rotation axis J1. In other words, the axis of rotation of the drive shaft Ds coincides with the first rotation axis J1. By having the rotation centers of the drive shaft Ds and the motor shaft 1 coincide, the gap between them in the radial direction relative to the first rotation axis J1 can be kept constant. Therefore, fluid F can flow through this gap without fluctuating the flow rate and flow resistance in the circumferential direction relative to the first rotation axis J1.

[0113] In detail, a portion of the first drive shaft Ds1 (i.e., the central portion in the axial direction) is located inside the motor shaft 1. Viewed from the axial direction, the first drive shaft Ds1 is positioned concentrically with the motor shaft 20. The other axial end D2 of the first drive shaft Ds1 is positioned further axially D2 than the motor shaft 1.

[0114] In a modified example, the first drive shaft through-hole 432 through which the first drive shaft Ds1 is inserted is located in the housing cover portion 43 instead of the side plate portion 42. The housing cover portion 43 further has the first drive shaft through-hole 432. The first drive shaft through-hole 432 penetrates the housing cover portion 43 axially. The center of the first drive shaft through-hole 432 coincides with the first rotation axis J1. An oil seal (not shown) is placed in the gap between the first drive shaft Ds1 and the first drive shaft through-hole 432 to seal the two.

[0115] The housing cover 43 further includes a first drive bearing holder 433 and a first drive bearing 4331. The first drive bearing holder 433 is positioned on the inner surface of the first drive shaft through hole 432 and holds the first drive bearing 4331. The first drive bearing 4331 rotatably supports the first drive shaft Ds1.

[0116] Furthermore, the first drive bearing holder 433 is connected to the piping section 51. Therefore, the first drive bearing 4331 is lubricated and cooled by a portion of the fluid F flowing through the piping section 51. This fluid F also flows into the motor shaft 1. In other words, in this modified example, the opening at the other axial end D2 of the motor shaft 1 becomes the fluid inlet 112. A portion of the fluid F that flows into the motor shaft 1 from the inlet 112 flows through the shaft through-hole 111 to the rotor through-hole 2111. The remaining portion is discharged from the other axial end D1 of the motor shaft 1 and accumulates in the fluid reservoir P.

[0117] Furthermore, the second drive shaft Ds2 and the differential 32 are positioned axially to one side D1 of the motor shaft 1. The second gear bearing 471, which rotatably holds the axial end of the motor shaft 20 on the axial side D1, is held by the second gear bearing holder 47. In other words, the housing 4 has the second gear bearing holder 47 and the second gear bearing 471 instead of the second gear bearing holder 461 and the second gear bearing 4611. The second gear bearing holder 47 is positioned axially to the other side D2 of the differential 32 and is located in the side plate portion 42 or the second housing cylindrical portion 45.

[0118] In the modified example, similar to the embodiment described above, the motor shaft 1 and the motor housing 401 are electrically insulated by motor bearings 4311, 4211, 4221, and 4611. Furthermore, the first drive bearing 4331 and the second drive bearing 4631 are roller bearings. In this modified example, the first drive bearing 4331 and the second drive bearing 4631 are collectively referred to as "drive bearings 4331, 4631". The electrical resistance of the drive bearings 4331, 4631 is lower than that of the motor bearings 4311, 4211, 4221, and 4611. As described above, the rolling elements 82 of the roller bearings 4331, 4631 have a shape with a longitudinal direction in the axial direction, allowing for a larger contact area with the pair of raceway rings 81 compared to, for example, ball bearings. Therefore, the drive bearings 4331, 4631 have higher electrical conductivity.

[0119] Therefore, as shown in Figure 8, the charge flowing from the rotor shaft 11 due to potential fluctuations within the motor shaft 1 (especially the rotor shaft) is discharged to the differential 32, including the gear shaft 12, the first gear 311, the second gear 312, the intermediate shaft 314, the third gear 313, and the fourth gear 321, and the drive shaft Ds when the drive unit 100 is in the powering and regenerative states. Furthermore, this charge is discharged to the motor housing 401 of the housing 4 through the first drive bearing 4331 and to the gear housing 402 of the housing 4 through the second drive bearing 4631. These charges are then discharged through the ground connection 6 connected to the gear housing 402, inverter housing 403, etc. of the housing 4, to, for example, the vehicle body 301 (see Figure 3) of the vehicle 300 on which the drive unit 100 is mounted. Thus, the occurrence of electrolytic corrosion in the motor bearings 4311, 4211, 4221, and 4611 can be more effectively suppressed or prevented.

[0120] Furthermore, by discharging charge through the drive bearings 4331 and 4631, the static elimination path between the gear shaft 12 and the housing 4 passes through the differential 32, which includes the first gear 311, second gear 312, third gear 313, intermediate shaft 314, and fourth gear 321, the drive shaft Ds, and the drive bearings 4331 and 4631. Therefore, the static elimination path from the motor shaft 1 to the housing 4 can be made longer. Accordingly, the motor shaft 1 and the drive bearing holder 4 that holds the drive bearings 4331 and 4631 of the housing 4 33 The potential difference with 463 can be made larger. Therefore, it becomes easier to discharge charge from the motor shaft 1 (especially the rotor shaft) to the housing 4.

[0121] Furthermore, in the modified configuration, similar to the embodiment described above, the electrical resistance of the intermediate bearings 4231 and 4621 is lower than that of the motor bearings 4311, 4211, 4221, and 4611. Therefore, as shown in Figure 8, the charge flowing from the rotor shaft 11 due to potential fluctuations within the rotor shaft 11 is such that when the drive unit 100 is in the powering state and the regenerative state, the charge flows through the gear shaft 12, the first gear 311, the second gear 312, the intermediate shaft 314, and middle Bearing 42 3 1.46 2 The charge is discharged to the gear housing 402 via 1. Furthermore, this charge can be discharged to, for example, the vehicle body 301 (see Figure 3) of the vehicle 300 on which the drive unit 100 is mounted, through the ground connection 6 connected to the gear housing 402, inverter housing 403, etc. of the housing 4. Therefore, the occurrence of electrolytic corrosion in the motor bearings 4311, 4211, 4221, and 4611 can be more reliably suppressed or prevented.

[0122] <2. Others> Embodiments of the present invention have been described above. However, the scope of the present invention is not limited to the embodiments described above. The present invention can be implemented by making various modifications to the embodiments described above without departing from the spirit of the invention. Furthermore, the matters described in the embodiments described above can be combined as appropriate and arbitrarily as long as they do not create contradictions.

[0123] Furthermore, in this embodiment and its modifications, the present invention is applied to an in-vehicle drive unit 100. However, the present invention is not limited to these examples and can also be applied to drive units and the like used in applications other than in vehicles.

[0124] <3. Summary> The embodiments and their variations described above will be summarized below.

[0125] For example, the drive system disclosed herein is A motor shaft extending along a first rotation axis that extends in the axial direction and rotatable about the first rotation axis, A rotor that can rotate together with the motor shaft, A stator positioned radially outward from the rotor, A gear section connected to one axial side of the motor shaft, A housing that accommodates the rotor, the stator, and the gear section, Equipped with, The aforementioned housing is A housing cylindrical portion extending in the axial direction and holding the stator on its inner surface, A first lid portion is attached to the other end of the axial direction of the housing cylinder portion, A second lid portion is positioned axially to the side of the housing cylindrical portion and extends in a direction intersecting the first rotation axis, A motor bearing that rotatably supports the motor shaft, It has, The motor bearing is A rolling bearing disposed in the first cover portion, the first bearing rotatably supports the motor shaft in the axial direction other than the rotor, A second bearing is positioned in the second cover and rotatably supports the motor shaft in one axial direction relative to the rotor, It has, The motor shaft and the first cover are electrically insulated by a first bearing (first configuration).

[0126] The drive device of the first configuration described above is The motor shaft is The first shaft that holds the rotor, A second shaft connected to one axial end of the first shaft and to which the gear portion is connected, A configuration having the following (second configuration) is also possible.

[0127] Furthermore, the drive device of the first or second configuration described above is The second lid portion is a side plate portion that is positioned at one axial end of the housing cylinder portion and covers the one axial end of the housing cylinder portion, The aforementioned 2 The bearing is a rolling bearing disposed on the side plate portion, which rotatably supports the motor shaft in one axial direction relative to the rotor. The motor shaft and the side plate portion may be electrically insulated by the second bearing (third configuration).

[0128] Furthermore, the drive device of the third configuration described above is The electrical resistance in the first bearing may be greater than that in the second bearing (fourth configuration).

[0129] Furthermore, the drive device having any of the above configurations from the first to the fourth is The motor bearing is A pair of track rings arranged in concentric circles, A rolling element arranged to be able to roll between the pair of raceway wheels, It has, The pair of raceways includes an inner raceway and an outer raceway positioned radially outward from the inner raceway. At least one of the surfaces of the rolling element, the first opposing surface of the inner raceway facing the rolling element, and the second opposing surface of the outer raceway facing the rolling element may be configured to have electrical insulating properties (fifth configuration).

[0130] Furthermore, the drive device of the fifth configuration described above is The rolling element may be configured as a ceramic ball (sixth configuration).

[0131] Furthermore, the drive device of the fifth configuration described above is The aforementioned 1 The first opposing surface of the ring has electrical insulating properties. The aforementioned 2 The rolling element of the ring may be a ceramic ball (seventh configuration).

[0132] Furthermore, the drive device having any of the fifth to seventh configurations described above is The housing further includes a motor bearing holder for holding the motor bearing, The motor bearing further comprises a first insulating member disposed between the outer raceway and the motor bearing holder. The outer raceway may be fixed to the motor bearing holder via the first insulating member (the eighth configuration).

[0133] Furthermore, the drive device having any of the configurations from the 5th to the 8th above is The motor bearing further comprises a second insulating member positioned between the inner raceway and the motor shaft. The inner raceway may be fixed to the motor shaft via the second insulating member (the ninth configuration).

[0134] Furthermore, the drive device having any of the above configurations 1 to 9 is The configuration may further include a fluid passage for supplying a lubricating fluid to the motor bearing (a tenth configuration).

[0135] Furthermore, the drive device having any of the above configurations 1 to 10 is The gear section is, A first gear is fixed to the radially outer surface of the motor shaft on one axial side of the motor shaft, An intermediate shaft extending along a second rotation axis that extends in the axial direction and is rotatable about the second rotation axis, A second gear is fixed to the radially outer surface of the intermediate shaft and meshes with the first gear, A third gear fixed to the radially outer surface of the intermediate shaft, A differential having a fourth gear that meshes with the third gear, and which outputs the torque of the fourth gear to the drive shaft, Yes, The housing further includes drive bearings that rotatably support both axial ends of the drive shaft, The first bearing is a ball bearing, The aforementioned drive bearing is a roller bearing, The electrical resistance of the drive bearing may be lower than that of the first bearing (11th configuration).

[0136] Furthermore, the drive device having any of the above configurations 1 to 11 is The housing further includes intermediate bearings that rotatably support both axial ends of the intermediate shaft, The intermediate bearing may have a configuration with lower electrical resistance than the first bearing (a twelfth configuration).

[0137] Furthermore, the drive device having any of the above configurations 1 to 12 is The housing may also be configured to include an earth connection portion for grounding to an external object (13th configuration).

[0138] Furthermore, the drive device of the 13th configuration described above is The housing further comprises an inverter housing that houses an inverter that supplies drive current to the stator, The ground connection portion may be configured to be located in the inverter housing (configuration 14).

[0139] Furthermore, a drive device having any of the above configurations 1 to 14 is: The motor shaft is cylindrical and extends in the axial direction. The drive shaft may be configured to be inserted inside the motor shaft (configuration 15).

[0140] Furthermore, the vehicles disclosed herein are A configuration comprising a drive device having any of the above configurations 1 to 15 (configuration 16) may also be used. [Industrial applicability]

[0141] The present invention is useful, for example, for devices having a motor in which the motor shaft is rotatably supported by rolling bearings. While the above-mentioned device is useful for automotive applications, it is also useful for non-automotive applications. [Explanation of Symbols]

[0142] 100...Drive unit, 200...Battery, 300...Vehicle, 301...Body, 1...Motor shaft, 11...Rotor shaft, 111...Shaft through hole, 112...Inlet, 12...Gear shaft, 121...Inlet, 13...Shaft wall, 2...Motor, 21...Rotor, 211...Rotor core, 2111...Rotor through hole, 212...Magnet, 22...Stator, 221...Stator core, 222...Coil section, 2221...Coil end, 3...Gear section, 31...Reduction gear, 311... • 1st gear, 312... 2nd gear, 313... 3rd gear, 314... Intermediate shaft, 32... Differential gear, 321... 4th gear, 4... Housing, 401... Motor housing, 402... Gear housing, 403... Inverter housing, 4031... Inverter, 41... 1st housing cylinder section, 42... Side plate section, 4201... Side plate through hole, 4202... 1st drive shaft through hole, 421... 2nd rotor bearing holder, 4211... 2nd rotor bearing, 422... 1st gear bearing holder, 4221... 423···First gear bearing, 423···First intermediate bearing holder, 4231···First intermediate bearing, 424···First drive bearing holder, 4241···First drive bearing, 43···Housing cover, 431···First rotor bearing holder, 4311···First rotor bearing, 4312···Opening, 432···First drive shaft through hole, 433···First drive bearing holder, 4331···First drive bearing, 44···Cover member, 45···Second housing cylinder, 46···Gear cover, 460···Second drive shaft through hole Through hole, 461... Second gear bearing holder, 4611... Second gear bearing, 462... Second intermediate bearing holder, 4621... Second intermediate bearing, 463... Second drive bearing holder, 4631... Second drive bearing, 464... Flow path, 465... Receiving tray section, 47... Second gear bearing holder, 471... Second gear bearing, 5... Fluid circulation section, 51... Piping section, 52... Pump, 53... Cooler unit, 54... Fluid reservoir, 6... Ground connection section, 71... Raceway ring, 711... Inner raceway ring,712...Outer raceway, 72...Rolling element, 73...First insulating member, 74...Second insulating member, 81...Raceway, 811...Inner raceway, 812...Outer raceway, 82...Rolling element, 83...Lubricant, 91...Raceway, 911...Inner raceway, 912...Outer raceway, 92...Rolling element, 93...Lubricant, F...Fluid, P...Fluid reservoir, Ds...Drive shaft, Ds1...First drive shaft, Ds2...Second drive shaft, J1...First rotating shaft, J2...Second rotating shaft, J3...Third rotating shaft,

Claims

1. A motor shaft extending along a first rotation axis that extends in the axial direction and rotatable about the first rotation axis, A rotor that can rotate together with the motor shaft, A stator positioned radially outward from the rotor, A gear section connected to one axial side of the motor shaft, A housing that accommodates the rotor, the stator, and the gear section, Equipped with, The aforementioned housing is A housing cylindrical portion extending in the axial direction and holding the stator on its inner surface, A first lid portion is attached to the other end of the axial direction of the housing cylinder portion, A second lid portion is positioned axially to the side of the housing cylindrical portion and extends in a direction intersecting the first rotation axis, A motor bearing that rotatably supports the motor shaft, It has, The motor bearing is A rolling bearing disposed in the first lid, the first bearing rotatably supports the motor shaft in the axial direction other than the rotor, A second bearing is positioned in the second cover and rotatably supports the motor shaft in one axial direction relative to the rotor, It has, The motor shaft and the first cover are electrically insulated by the first bearing. A drive device in which the electrical resistance in the first bearing is greater than the electrical resistance in the second bearing.

2. A motor shaft extending along a first rotation axis extending in the axial direction and rotatable about the first rotation axis, A rotor that can rotate together with the motor shaft, A stator positioned radially outward from the rotor, A gear section connected to one axial side of the motor shaft, A housing that accommodates the rotor, the stator, and the gear section, Equipped with, The aforementioned housing is A housing cylindrical portion extending in the axial direction and holding the stator on its inner surface, A first lid portion is attached to the other end of the axial direction of the housing cylinder portion, A second lid portion is positioned axially to the side of the housing cylindrical portion and extends in a direction intersecting the first rotation axis, A motor bearing that rotatably supports the motor shaft, It has, The motor bearing is A rolling bearing disposed in the first lid, the first bearing rotatably supports the motor shaft in the axial direction other than the rotor, A second bearing is positioned in the second cover and rotatably supports the motor shaft in one axial direction relative to the rotor, It has, The motor shaft and the first cover are electrically insulated by the first bearing. The gear section is, A first gear is fixed to the radially outer surface of the motor shaft on one axial side of the motor shaft, An intermediate shaft extending along a second rotation axis that extends in the axial direction and is rotatable about the second rotation axis, A second gear is fixed to the radially outer surface of the intermediate shaft and meshes with the first gear, A third gear fixed to the radially outer surface of the intermediate shaft, A differential having a fourth gear that meshes with the third gear, and which outputs the torque of the fourth gear to the drive shaft, It has, The housing further includes drive bearings that rotatably support both axial ends of the drive shaft, The first bearing is a ball bearing, The aforementioned drive bearing is a roller bearing, A drive device wherein the electrical resistance of the drive bearing is lower than that of the first bearing.

3. A motor shaft extending along a first rotation axis extending in the axial direction and rotatable about the first rotation axis, A rotor that can rotate together with the motor shaft, A stator positioned radially outward from the rotor, A gear section connected to one axial side of the motor shaft, A housing that accommodates the rotor, the stator, and the gear section, Equipped with, The aforementioned housing is A housing cylindrical portion extending in the axial direction and holding the stator on its inner surface, A first lid portion is attached to the other end of the axial direction of the housing cylinder portion, A second lid portion is positioned axially to the side of the housing cylindrical portion and extends in a direction intersecting the first rotation axis, A motor bearing that rotatably supports the motor shaft, It has, The motor bearing is A rolling bearing disposed in the first lid, the first bearing rotatably supports the motor shaft in the axial direction other than the rotor, A second bearing is positioned in the second cover and rotatably supports the motor shaft in one axial direction relative to the rotor, It has, The motor shaft and the first cover are electrically insulated by the first bearing. The gear section has an intermediate shaft that extends along a second rotation axis that extends in the axial direction and is rotatable about the second rotation axis. The housing further includes intermediate bearings that rotatably support both axial ends of the intermediate shaft, The intermediate bearing has lower electrical resistance than the first bearing in the drive device.

4. The motor shaft is The first shaft that holds the rotor, A second shaft connected to one axial end of the first shaft and to which the gear portion is connected, A drive device according to any one of claims 1 to 3, having the following features.

5. The second lid portion is a side plate portion that is positioned at one axial end of the housing cylinder portion and covers the one axial end of the housing cylinder portion, The second bearing is a rolling bearing disposed on the side plate portion, which rotatably supports the motor shaft in one axial direction relative to the rotor, The drive device according to any one of claims 1 to 3, wherein the motor shaft and the side plate portion are electrically insulated by the second bearing.

6. The motor bearing is A pair of track rings arranged in concentric circles, A rolling element arranged to be able to roll between the pair of raceway wheels, It has, The pair of raceways includes an inner raceway and an outer raceway positioned radially outward from the inner raceway. The drive device according to any one of claims 1 to 3, wherein at least one of the surfaces of the rolling elements, the first opposing surface of the inner raceway facing the rolling elements, and the second opposing surface of the outer raceway facing the rolling elements are electrically insulating.

7. The drive device according to claim 6, wherein the rolling element is a ceramic ball.

8. The first opposing surface of the first bearing has electrical insulating properties. The drive device according to claim 6, wherein the rolling element of the second bearing is a ceramic ball.

9. The housing further includes a motor bearing holder for holding the motor bearing, The motor bearing further comprises a first insulating member disposed between the outer raceway and the motor bearing holder. The drive device according to claim 6, wherein the outer raceway is fixed to the motor bearing holder via the first insulating member.

10. The motor bearing further comprises a second insulating member positioned between the inner raceway and the motor shaft. The drive device according to claim 6, wherein the inner raceway is fixed to the motor shaft via the second insulating member.

11. The drive device according to any one of claims 1 to 3, further comprising a fluid passage for supplying a fluid for lubricating the motor bearing to the motor bearing.

12. The drive device according to any one of claims 1 to 3, further comprising an earth connection portion for grounding the housing to an external object.

13. The housing further comprises an inverter housing that houses an inverter that supplies drive current to the stator, The drive device according to claim 12, wherein the ground connection portion is located in the inverter housing.

14. The gear section is An intermediate shaft extending along a second rotation axis that extends in the axial direction and is rotatable about the second rotation axis, A third gear fixed to the radially outer surface of the intermediate shaft, A differential having a fourth gear that meshes with the third gear, and which outputs the torque of the fourth gear to the drive shaft, It has, The motor shaft is cylindrical and extends in the axial direction. The drive device according to claim 1 or claim 3, wherein the drive shaft is inserted inside the motor shaft.

15. The motor shaft is cylindrical and extends in the axial direction. The drive device according to claim 2, wherein the drive shaft is inserted inside the motor shaft.

16. A vehicle comprising the drive system described in any one of claims 1 to 3.

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