Electric vehicle driving device

Abstract

To provide an electric vehicle driving device that can prevent the generation of electromagnetic noise.SOLUTION: An electric vehicle driving device 1 comprises a motor 10, and a gearbox 20 that is connected to the motor 10 and changes the speed of rotation of the motor 10 and outputs the changed rotation. The motor 10 comprises a motor housing 11 and a rotor shaft 15, and the rotor shaft 15 projects in an axial direction from the motor housing 11. A speed reducer 20 comprises a speed reducer housing 21 and an input shaft 25, the speed reducer housing 21 is fixed to the motor housing 11 in the axial direction, and the input shaft 25 is coaxially connected to the rotor shaft 15. A conductive plate 51 is fixed to the rotor shaft 15 or the input shaft 25 and extends to the outside in the radial direction of the shaft, and is provided between the motor housing 11 and the speed reducer housing 21. The motor housing 11 is provided with a conductive brush 52 that is in contact with an end face of the conductive plate 51 and electrically connects the motor housing 11 and the conductive plate 51 to each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a drive device for an electric vehicle. [Background technology]

[0002] The drive system of an electric vehicle uses high-frequency, high-voltage power for its inverter and drive motor. In a drive system using such power, electromagnetic noise is emitted into the surrounding area from the transmission, drive shaft, and other components connected to the motor, which may affect the electrical equipment installed in the vehicle.

[0003] Patent Document 1 discloses a configuration in which the rotating shaft of a differential device connected to a rotor shaft is grounded to the case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-310296 Summary of the Invention

[0005] In conventional configurations, grounding is performed at the differential device, which is distant from the motor. As a result, there is a possibility that the motor may not be adequately grounded due to the capacitive components of the rotating shaft, gears, etc. that are interposed between the motor and the differential device. Furthermore, because the rotating shaft and gears are covered with lubricating oil, there is a risk of sparks occurring when power is conducted, which could become a further source of electromagnetic noise.

[0006] In view of the above problems, the present invention has an object to provide a drive device for an electric vehicle that can suppress the generation of electromagnetic noise by grounding the motor at a position close to the motor.

[0007] According to one embodiment of the present invention, the present invention is applied to a drive device for an electric vehicle including a motor and a transmission connected to the motor for varying the speed of rotation of the motor and outputting the rotation. The motor includes a motor housing and a rotor shaft, the rotor shaft protruding in the axial direction from the motor housing. The transmission includes a transmission housing and an input shaft, the transmission housing being axially fixed to the motor housing. The input shaft is coaxially connected to the rotor shaft. A conductive plate is provided between the motor housing and the transmission housing, fixed to the rotor shaft or the input shaft and extending radially outward from the shaft, and the motor housing includes a conductive brush that abuts against an end face of the conductive plate to electrically connect the motor housing and the conductive plate.

[0008] According to the present invention, a conductive plate provided on the rotor shaft or input shaft is electrically connected to the motor housing via a conductive brush provided on the motor housing between the motor housing and the transmission housing. This configuration allows the rotor shaft to be grounded in close proximity to the motor, which is a source of electromagnetic noise, reducing capacitance, thereby minimizing electromagnetic noise generated by the motor, etc. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of the drive device of this embodiment. [Figure 2] FIG. 2 is an explanatory diagram of the intermediate chamber. [Figure 3] FIG. 3 is an explanatory perspective cross-sectional view of the drive device. [Figure 4] FIG. 4 is an explanatory diagram of a conductive brush. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0011] FIG. 1 is an explanatory diagram of a drive device 1 for an electric vehicle according to this embodiment, and is an axial cross-sectional view of the drive device 1. FIG. 2 is an explanatory diagram focusing on an intermediate chamber 40 of the drive device 1. FIG. 3 is a perspective cross-sectional view of the drive device 1. FIG. 4 is an explanatory diagram of a conductive brush 52.

[0012] As shown in Fig. 1, the drive device 1 is configured to include a motor 10, a reducer 20, and an inverter device 30. The motor 10 and the reducer 20 are connected in the direction of the rotation axis. The inverter device 30 is placed on the motor 10.

[0013] The drive unit 1 is mounted on an electric vehicle. The electric vehicle runs by driving the motor 10 by an inverter unit 30 supplying power from a battery (not shown) to the motor 10, and the rotation of the motor 10 is reduced by a reducer 20 and transmitted to drive wheels (not shown). When the electric vehicle decelerates, the regenerative power of the motor 10 is charged into the battery via the inverter unit 30.

[0014] The motor 10 is composed of a motor housing 11, and a rotor 16 and a stator 17 housed within the motor housing 11. A rotor shaft 15 is fixed to the center of the rotor 16 and is rotatably supported by the motor housing 11. The motor housing 11 is composed of a cylindrical main body 13, a front cover 12 that covers one end (right side in FIG. 1) of the main body 13, and a rear cover 14 that covers the other end (left side in FIG. 1) of the main body 13. The rotor shaft 15 is rotatably supported by the front cover 12 via a motor-side bearing 18. The motor housing 11 is electrically grounded to the body of the electric vehicle.

[0015] The reducer 20 is configured to include a reducer housing 21 and a reduction mechanism 24 housed within the reducer housing 21. The reduction mechanism 24 has a plurality of gears and a rotating shaft. The reduction mechanism 24 includes an input shaft 25 to which the rotation of the motor 10 is input. The rotation of the input shaft 25 is reduced by the reduction mechanism 24 and output to a drive shaft (not shown) to drive the drive wheels. The input shaft 25 is disposed coaxially with the rotor shaft 15 of the motor 10 and is connected to the rotor shaft 15 by spline fitting so that they rotate integrally. The input shaft 25 is rotatably supported by the reducer housing 21 via a reducer-side bearing 28.

[0016] The motor 10 and the reducer 20 are arranged adjacent to each other in the axial direction, but the front cover 12 of the motor housing 11 and the reducer housing 21 are spaced apart from each other near the rotor shaft 15, thereby defining an intermediate chamber 40.

[0017] 2, the front cover 12 of the motor housing 11 has a surface 12a extending in a direction perpendicular to the axial direction of the rotor shaft 15, and the reducer housing 21 has a surface 21a extending in a direction perpendicular to the axial direction of the input shaft 25, with the surfaces 12a and 21a facing each other with a predetermined gap between them. The space between the surfaces 12a and 21a constitutes an intermediate chamber 40.

[0018] A motor-side bearing 18 is fixed to the front cover 12, and the rotor shaft 15 supported by the motor-side bearing 18 protrudes from the surface 12a into the intermediate chamber 40. A reducer-side bearing 28 is fixed to the reducer housing 21, and the input shaft 25 supported by the reducer-side bearing 28 protrudes from the surface 21a into the intermediate chamber 40. A motor-side seal member 19 is fixed to the front cover 12 on the intermediate chamber 40 side of the motor-side bearing 18. A reducer-side seal member 29 is fixed to the reducer housing 21 on the intermediate chamber 40 side of the reducer-side bearing 28. These are oil seals that prevent lubricating oil and the like from leaking from the motor housing 11 and the reducer housing 21 into the intermediate chamber 40.

[0019] A splined tip portion 15a is formed at the tip of the rotor shaft 15, and a splined connecting hole 25a is formed at the tip of the input shaft 25. By inserting the tip portion 15a of the rotor shaft 15 into the connecting hole 25a of the input shaft 25, they are connected together.

[0020] The intermediate chamber 40 is provided with a conductive mechanism 50, as will be described later.

[0021] Next, suppression of electromagnetic noise in the driving device 1 for an electric vehicle configured as described above will be described.

[0022] Conventionally, motors and inverter devices use high-frequency, high-voltage power, which can cause high-frequency electromagnetic noise to be superimposed on the rotating shafts and gears of the motors and reducers. This electromagnetic noise can be radiated from these rotating shafts and gears to the surrounding area, potentially affecting electrical equipment installed in the vehicle.

[0023] Furthermore, because lubricating oil is present between the rotating shaft and gears and the housing of the motor or reducer, the capacitance between them increases, which can cause electrical sparks due to short-term short circuits caused by superimposed electromagnetic noise, which can generate further electromagnetic noise.

[0024] Therefore, in this embodiment, the following configuration is adopted to suppress electromagnetic noise in the drive device 1 of an electric vehicle.

[0025] As shown in FIG. 1, an intermediate chamber 40 formed between the motor 10 and the reducer 20 is provided with a conductive mechanism 50 for electrically connecting the rotor shaft 15 and the front cover 12 of the motor housing 11.

[0026] As shown in FIG. 2, the conductive mechanism 50 is composed of a conductive plate 51 and a conductive brush 52.

[0027] The conductive plate 51 is fixed to the outer periphery of the rotor shaft 15 outside the front cover 12 (on the intermediate chamber 40 side), i.e., outside the motor-side bearing 18 and the motor-side seal member 19. The conductive plate 51 is arranged on the rotor shaft 15 at a position spaced a predetermined distance (for example, several mm) from the front cover 12 so as to extend radially outward from the rotor shaft 15. That is, the conductive plate 51 is arranged so that its end face faces the surface 12a of the front cover 12. As shown in FIG. 3 , the conductive plate 51 is formed in the shape of a thin disk fixed coaxially with the rotor shaft 15.

[0028] The conductive plate 51 is made of a highly conductive metal such as steel, aluminum, etc. The conductive plate 51 is fixed to the outer periphery of the rotor shaft 15 by press-fitting or the like.

[0029] In the intermediate chamber 40, the front cover 12 is provided with a conductive brush 52 that abuts against an end face of a conductive plate 51 from the front cover 12 side. The conductive brush 52 is fixed upright on the surface 12a of the front cover 12 so as to be parallel to the rotor shaft 15. The conductive brush 52 abuts against the end face of the conductive plate 51. The conductive brush 52 comes into sliding contact with the end face of the conductive plate 51, which rotates as the rotor shaft 15 rotates, electrically connecting the conductive plate 51 to the front cover 12 and the motor housing 11. As a result, the rotor shaft 15 is grounded to the motor housing 11, which is at earth potential.

[0030] FIG. 4 is a cross-sectional view showing the configuration of the conductive brush 52. As shown in FIG.

[0031] The conductive brush 52 includes a brush holder 521 , a brush 522 , a pressure spring 523 , and a lead wire 524 .

[0032] The brush holder 521 is made of a metal such as aluminum and has a cylindrical shape, and holds the brush 522 in an internal hole so that the brush 522 can move back and forth in the axial direction. The brush 522 is formed into a cylindrical shape and is made of a material with excellent conductivity and a high coefficient of friction, such as carbon. The pressure spring 523 urges the brush 522 in the axial direction, causing the brush 522 to abut against the end surface of the conductive plate 51. One end of the lead wire 524 is fixed to the brush 522, and the other end is fixed to the brush holder 521 by soldering or the like. The lead wire 524 provides electrical conductivity between the brush 522 and the brush holder 521.

[0033] The conductive brush 52 configured in this manner is fixed in a conductive brush insertion hole provided in advance in the front cover 12 by a method such as screwing or press-fitting.

[0034] In this way, the conductive plate 51 and the conductive brush 52 are configured to electrically connect the rotor shaft 15 and the front cover 12 of the motor housing 11, so that the rotor shaft 15 is grounded to the motor housing 11 via the conductive plate 51 and the conductive brush 52. This reduces the capacitance component of the rotor shaft 15, making it possible to suppress electromagnetic noise superimposed on the rotor shaft 15.

[0035] The conductive brush 52 is disposed so as to abut against the end face of the conductive plate 51 below the rotor shaft 15. This causes wear powder from the brush 522 of the conductive brush 52 to fall below the rotor shaft 15 in the intermediate chamber 40. This prevents the wear powder from passing through the gap in the motor-side seal member 19 of the rotor shaft 15 or the reducer-side seal member 29 of the input shaft 25. This prevents the wear powder from entering the interior of the motor 10 or the reducer 20.

[0036] As described above, the drive device 1 for an electric vehicle of this embodiment includes the motor 10 and the reducer 20 as a transmission connected to the motor 10 and changing the speed of the rotation of the motor 10 to output the rotation. The motor 10 includes the motor housing 11 and the rotor shaft 15, which protrudes axially from the motor housing 11. The reducer 20 includes the reducer housing 21 as a transmission housing and the input shaft 25. The reducer housing 21 is axially fixed to the motor housing 11, and the input shaft 25 is coaxially connected to the rotor shaft 15. A conductive plate 51 is fixed to the rotor shaft 15 or the input shaft 25 and extends radially outward from the rotor shaft 15 between the motor housing 11 and the reducer housing 21. The motor housing 11 includes a conductive brush 52 that abuts against an end face of the conductive plate 51 to electrically connect the motor housing 11 and the conductive plate 51.

[0037] In this configuration, a conductive plate 51 provided on the rotor shaft 15 or the input shaft 25 between the motor housing 11 and the reducer housing 21 can be electrically connected (grounded) to the motor housing 11 via a conductive brush 52 provided on the motor housing 11. With this configuration, the rotor shaft 15 can be grounded at a position close to the motor 10 and inverter device 30, which are sources of electromagnetic noise, and the capacitive component can be suppressed, thereby suppressing electromagnetic noise generated from the motor 10, etc. as much as possible.

[0038] In addition, in this embodiment, the rotor shaft 15 is supported on the motor housing 11 via the motor side bearing 18, and the conductive plate 51 is provided on the rotor shaft 15 axially outside the motor side bearing 18 (on the reducer 20 side).

[0039] In this configuration, the rotor shaft 15 of the motor 10 is electrically connected to the motor housing 11 by a conductive plate 51 near the end of the rotor shaft 15, thereby appropriately reducing the capacitance component with the rotor shaft 15 and effectively suppressing electromagnetic noise generated from the motor 10, etc.

[0040] In addition, in this embodiment, the input shaft 25 is supported on the reducer housing 21 via a reducer side bearing 28 which serves as a transmission bearing, and the conductive plate 51 is provided on the input shaft 25 axially outside (on the motor 10 side) the reducer side bearing 28.

[0041] In this configuration, the input shaft 25, which is connected to the rotor shaft 15 by a conductive plate 51 near the end of the input shaft 25 of the reducer 20, is electrically connected to the motor housing 11, thereby appropriately reducing the capacitance component of the rotor shaft 15 and more effectively suppressing electromagnetic noise generated from the motor 10, etc.

[0042] In this embodiment, an intermediate chamber 40 is defined between the motor housing 11 and the reducer housing 21. A motor-side seal member 19 that seals the lubricating oil inside the motor housing 11 is fixed to the front cover 12 of the motor housing 11, closer to the intermediate chamber 40 than the motor-side bearing 18.

[0043] In this configuration, the presence of the motor-side sealing member 19 that seals the lubricating oil prevents wear powder from the brush 522, which is generated when the conductive brush 52 slides against the end surface of the conductive plate 51, from entering the interior of the motor 10 or the reducer 20.

[0044] In this embodiment, the conductive plate 51 is disk-shaped, and the conductive brush 52 is provided below the rotor shaft 15 and comes into contact with the end face of the conductive plate 51 .

[0045] In this configuration, wear powder generated by the brush 522 as the conductive brush 52 slides against the end surface of the conductive plate 51 can be dropped downward inside the intermediate chamber 40. This prevents the wear powder from adhering to the motor-side bearing 18 and the reducer-side bearing 28 of the rotor shaft 15.

[0046] The above describes embodiments of the present invention, but the configurations described in the above embodiments and each modified example only show some of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0047] In the above-described embodiment, the conductive plate 51 may be fixed to the input shaft 25 instead of the rotor shaft 15. That is, the conductive plate 51 may be fixed to the outer periphery of the input shaft 25 outside the reducer housing 21 (on the intermediate chamber 40 side), that is, outside the reducer-side bearing 28 and the reducer-side seal member 29. Even when the conductive plate 51 is fixed to the input shaft 25, the conductive brush 52 fixed to the front cover 12 of the motor housing 11 comes into contact with the end face, as described above, thereby electrically connecting them.

[0048] Furthermore, in the above-described embodiment, the configuration is provided with a reducer 20 that reduces the output of the motor 10, but this is not limited to this, and instead of the reducer 20, the configuration may be provided with a transmission that can change the reduction ratio. [Explanation of symbols]

[0049] 1: drive unit, 10: motor, 11: motor housing, 12: front cover, 15: rotor shaft, 18: motor side bearing, 19: motor side seal member, 20: reducer, 21: reducer housing, 25: input shaft, 28: reducer side bearing, 29: reducer side seal member, 40: intermediate chamber, 51: conductive plate, 52: conductive brush

Claims

1. A drive device for an electric vehicle including a motor and a transmission connected to the motor, which changes the speed of rotation of the motor and outputs the rotation, the motor includes a motor housing and a rotor shaft, the rotor shaft protruding from the motor housing in an axial direction; the transmission includes a transmission housing and an input shaft, the transmission housing is axially fixed to the motor housing, and the input shaft is coaxially connected to the rotor shaft; a conductive plate fixed to the rotor shaft or the input shaft and extending radially outward from the shaft is provided between the motor housing and the transmission housing; The motor housing is provided with a conductive brush that abuts against an end surface of the conductive plate to electrically connect the motor housing and the conductive plate. Drive unit for electric vehicles.

2. The drive device for an electric vehicle according to claim 1, the rotor shaft is supported by the motor housing via a motor-side bearing, the conductive plate is provided on the rotor shaft axially outward of the motor-side bearing; Drive unit for electric vehicles.

3. The drive device for an electric vehicle according to claim 1, the input shaft is supported by the transmission housing via a transmission-side bearing, the conductive plate is provided on the input shaft axially outward of the transmission-side bearing of the input shaft; Drive unit for electric vehicles.

4. The drive device for an electric vehicle according to claim 2, An intermediate chamber is defined between the motor housing and the transmission housing, the conductive plate is disposed in the intermediate chamber; a seal member that seals lubricating oil in the motor housing is fixed to the motor housing on the intermediate chamber side of the motor-side bearing; Drive unit for electric vehicles.

5. 5. A drive device for an electric vehicle according to claim 1, the conductive plate is disk-shaped; the conductive brush is provided below the rotor shaft and contacts an end surface of the conductive plate; Drive unit for electric vehicles.

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