Conductive Device

Abstract

To provide a conductive device which releases electromagnetic noise from a rotary shaft to a housing and achieves high reliability.SOLUTION: A conductive device 40 is disposed at a periphery of a metallic rotary shaft 20 and arranged over an entire gap between a metallic housing 38 and the rotary shaft. The conductive device has: a cylindrical part 41 in which the rotary shaft is fitted; a circular disc part 42 extending from the cylindrical part to the radial outer side; and at least one lip 44 which further extends from the circular disc part to the radial outer side and slidably contacts with an inner peripheral surface of a shaft hole of the housing. The cylindrical part and the circular disc part are formed of at least one of metal and conductive rubber. The lip is formed of conductive rubber.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrically conductive device. [Background technology]

[0002] In electric vehicles (EVs) or hybrid electric vehicles (xHEVs), electromagnetic noise is generated by the induced current in the motor, which can affect electronic devices (e.g., car radios or in-vehicle wireless devices). Electromagnetic noise is caused, for example, by the on / off operation of switching elements in an inverter that controls the current supplied to the stator.

[0003] Patent Document 1 discloses a technology for electrically connecting a motor's rotating shaft to a metal motor housing and dissipating electromagnetic noise induced in the rotating shaft to the motor housing. In particular, Figure 4 of Patent Document 1 discloses that a sealing device, which is an oil seal disposed between the motor's rotating shaft and housing, is made from conductive rubber.

[0004] Patent Document 2 discloses that a sealing device, which is an oil seal disposed between a rotating shaft and a housing of a motor, is manufactured from a metal reinforcing ring and conductive rubber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-244180 [Patent Document 2] Japanese Patent Application Publication No. 2020-63792 Summary of the Invention [Problem to be solved by the invention]

[0006] When placing a conductive device around a motor's rotating shaft to allow electromagnetic noise to escape from the rotating shaft to the housing, it is desirable to ensure contact between the conductive device and the metal rotating shaft, and between the conductive device and the metal housing. The same applies when placing a conductive device around a generator's rotating shaft. The same also applies to the rotating shaft that is rotated by the motor's rotating shaft and the rotating shaft that rotates the generator's rotating shaft.

[0007] The present invention provides a reliable conductive arrangement for conducting electromagnetic noise away from a rotating shaft to a housing. [Means for solving the problem]

[0008] One aspect of the present invention provides a conductive device that is disposed around a metallic rotating shaft and that is disposed over the entire gap between the rotating shaft and the inner circumferential surface of a shaft hole in a metallic housing, the conductive device having a cylindrical portion into which the rotating shaft is fitted, a disk portion that extends radially outward from the cylindrical portion, and at least one lip that extends further radially outward from the disk portion and is in slidable contact with the inner circumferential surface of the shaft hole in the housing. The cylindrical portion and the disk portion are formed from at least one of metal and conductive rubber, and the lip is formed from conductive rubber.

[0009] In this embodiment, the conductive device is formed from a conductive material over the entire radial direction. Because the lip, made of conductive rubber, extends radially outward, it is subjected to centrifugal force when the rotating shaft rotates and is pressed toward the inner circumferential surface of the housing's axial hole. This prevents an oil film from forming between the lip and the housing, and even if an oil film does form, its thickness is small. This reduces the electrical resistance of the oil film, resulting in high reliability in dissipating electromagnetic noise from the rotating shaft to the housing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a power transmission system of an electric vehicle equipped with a conductive device according to an embodiment of the present invention; [Figure 2]1 is a cross-sectional view showing a portion of a conductive device according to an embodiment of the present invention. [Figure 3] 10 is a cross-sectional view showing a portion of a conductive device according to another embodiment of the present invention. [Figure 4] 3 is a cross-sectional view showing another application of the conductive device of FIG. 2. [Figure 5] 4 is a cross-sectional view showing another application of the conductive device of FIG. 3. [Figure 6] FIG. 10 is a diagram showing a power transmission system of another electric vehicle equipped with a conductive device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings, in which the drawings are not necessarily to scale and some features may be exaggerated or omitted.

[0012] As shown in FIG. 1, the power transmission system of an electric vehicle equipped with a power transmission device according to the embodiment includes an electric motor 2, a gear train 4, a differential gear device 6, a left axle structure 8, a right axle structure 10, a left drive wheel 12, and a right drive wheel 14.

[0013] The motor 2 has a stator 16 and a rotor 18, and a rotating shaft 20 is fixed to the rotor 18. The rotating shaft 20 is made of metal such as cast iron, steel, or an aluminum alloy, and is rotatably supported by bearings 21 to 24. The rotation of the rotating shaft 20 is transmitted to a differential gear device 6 by a gear train 4, i.e., a gear reducer. The differential gear device 6 rotates the left and right axle structures 8, 10 while distributing torque to the left and right axle structures 8, 10 in accordance with the load acting on the left and right drive wheels 12, 14.

[0014] The left axle structure 8 has a shaft 8a, a universal joint 8b, a shaft 8c, a universal joint 8d, and an axle 8e. The differential gear device 6 rotates the shaft 8a, and the rotation is transmitted via the universal joint 8b, the shaft 8c, and the universal joint 8d to the axle 8e to which the left driving wheel 12 is fixed. The left axle structure 8 is supported by bearings 26 and 27 that rotatably support the shaft 8a, and by a suspension mechanism 28 that rotatably supports the axle 8e.

[0015] The right axle structure 10 has a shaft 10a, a universal joint 10b, a shaft 10c, a universal joint 10d, and an axle 10e. The differential gear device 6 rotates the shaft 10a, and the rotation is transmitted via the universal joint 10b, a shaft 10c, and a universal joint 10d to the axle 10e to which the right drive wheel 14 is fixed. The right axle structure 10 is supported by a bearing 32 that rotatably supports the shaft 10a and a suspension mechanism 34 that rotatably supports the axle 10e.

[0016] The motor 2, gear train 4, differential gear 6, and shafts 8a and 10a are disposed within a common housing 38. The housing 38 is made of metal such as cast iron, steel, or an aluminum alloy.

[0017] An annular conductive device 40 is disposed around one end of the rotating shaft 20 of the motor 2, spanning the entire gap between the end 38a of the metal housing 38 and the rotating shaft 20. The conductive device 40 is fixed to the rotating shaft 20 and contacts the inner circumferential surface of the shaft hole in the end 38a of the housing 38.

[0018] 2 shows only the cylindrical rotating shaft 20, the annular conductive device 40, and the upper half of the cylindrical end portion 38a of the housing 38. In this embodiment, the conductive device 40 is a sealing device (oil seal) that seals the gap between the inner circumferential surface of the shaft hole 38b in the end portion 38a of the housing 38 and the rotating shaft 20. The conductive device 40 has a cylindrical portion 41, a flange 42, an annular portion 43, a seal lip 44, and a dust lip 45.

[0019] The rotating shaft 20 of the motor 2 is fitted into the cylindrical portion 41 by an interference fit. Therefore, the electrical conduction device 40 is fixed to the rotating shaft 20 and rotates together with the rotating shaft 20. The flange 42 is a disk extending radially outward from the cylindrical portion 41. The annular portion 43 is formed on the outer edge of the flange 42.

[0020] The seal lip 44 extends further radially outward from the annular portion 43 and comes into slidable contact with the inner circumferential surface of the shaft hole 38b in the end portion 38a of the housing 38. The seal lip 44 prevents the lubricating oil that lubricates the motor 2 arranged inside the housing 38 from leaking to the outside of the housing 38.

[0021] Although not essential, a garter spring 46 is disposed radially inward of the seal lip 44. The garter spring 46 presses the seal lip 44 against the inner peripheral surface of the axial hole 38b of the end 38a of the housing 38.

[0022] The dust lip 45 also extends radially outward from the annular portion 43 and is in slidable contact with the inner circumferential surface of the axial hole 38b in the end portion 38a of the housing 38. The dust lip 45 prevents foreign matter from entering the housing 38 from the outside to the inside.

[0023] The conductive device 40 includes an elastic ring 50 and a rigid ring 52 made of a rigid material, such as metal. The rigid ring 52 has a substantially L-shaped cross section and is embedded in the elastic ring 50 to reinforce the elastic ring 50.

[0024] The cylindrical portion 41 and the flange 42 are composed of an elastic ring 50 and a rigid ring 52, while the annular portion 43, the seal lip 44 and the dust lip 45 are composed of the elastic ring 50 only.

[0025] The elastic ring 50 is made of conductive rubber, which includes a rubber material such as nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber (ACM), or fluorocarbon rubber (FKM), and conductive powder, such as conductive carbon black powder or metal powder, dispersed in the rubber material.

[0026] Therefore, the conductive device 40 is formed from a conductive material over the entire radial direction and electrically connects the rotating shaft 20 to the housing 38. This allows electromagnetic noise induced in the rotating shaft 20 to escape to the housing 38. Particularly in this embodiment, the conductive device 40 is fixed to the rotating shaft 20 and rotates together with the rotating shaft 20. Because the seal lip 44 and the dust lip 45 extend radially outward, when the rotating shaft 20 rotates, they are subjected to centrifugal force F and are pressed against the inner circumferential surface of the shaft hole 38b of the housing 38.

[0027] Lubricating oil for the motor 2 is present inside the housing 38, and the lubricating oil may form an oil film between the seal lip 44 and the inner circumferential surface of the axial bore 38b of the housing 38. In some cases, the lubricating oil may also form an oil film between the dust lip 45 and the inner circumferential surface of the axial bore 38b of the housing 38. However, because the seal lip 44 and the dust lip 45 are pressed against the inner circumferential surface of the axial bore 38b of the housing 38 by centrifugal force F, an oil film is unlikely to form between the lip and the housing 38, and even if an oil film does form, its thickness is small. This reduces the electrical resistance of the oil film, resulting in a reliable escape of electromagnetic noise from the rotating shaft 20 to the housing 38. As described above, because the seal lip 44 is pressed against the inner circumferential surface of the axial bore 38b of the housing 38 by centrifugal force F, the garter spring 46 may be omitted.

[0028] As shown in Fig. 3, the conductive device 60 may have other shapes. In this embodiment, the conductive device 60 is a sealing device (oil seal) that seals the gap between the inner circumferential surface of the shaft hole 38b in the end 38a of the housing 38 and the rotating shaft 20. Fig. 3 shows only the cylindrical rotating shaft 20, the annular conductive device 60, and the upper half of the cylindrical end 38a of the housing 38. The conductive device 60 has a cylindrical portion 61, a flange 62, a seal lip 64, and a dust lip 65.

[0029] The rotating shaft 20 of the motor 2 is fitted into the cylindrical portion 61 by an interference fit. Therefore, the electrical conduction device 60 is fixed to the rotating shaft 20 and rotates together with the rotating shaft 20. The flange 62 is a disk extending radially outward from the cylindrical portion 61.

[0030] The seal lip 64 extends radially outward from the outer edge of the flange 62 and comes into slidable contact with the inner circumferential surface of the shaft hole 38b in the end portion 38a of the housing 38. The seal lip 64 prevents the lubricating oil that lubricates the motor 2 arranged inside the housing 38 from leaking to the outside of the housing 38.

[0031] The dust lip 65 also extends radially outward from the outer edge of the flange 62 and slidably contacts the inner circumferential surface of the axial hole 38b in the end portion 38a of the housing 38. The dust lip 65 prevents foreign matter from entering the housing 38 from the outside to the inside.

[0032] The conductive device 60 has an elastic ring 70 and a rigid ring 72 made of a rigid material, for example, metal. The rigid ring 72 has a substantially L-shaped cross section and fits tightly against the elastic ring 70 to reinforce the elastic ring 70.

[0033] The cylindrical portion 61 and the flange 62 are composed of an elastic ring 70 and a rigid ring 72, and the seal lip 64 and the dust lip 65 are composed of only the elastic ring 70.

[0034] The elastic ring 70 is made of conductive rubber, similar to the elastic ring 50 (see FIG. 2).

[0035] Therefore, the conductive device 60 is formed from a conductive material over the entire radial direction and electrically connects the rotating shaft 20 to the housing 38. This allows electromagnetic noise induced in the rotating shaft 20 to escape to the housing 38. Particularly in this embodiment, the conductive device 60 is fixed to the rotating shaft 20 and rotates together with the rotating shaft 20. Because the seal lip 64 and the dust lip 65 extend radially outward, when the rotating shaft 20 rotates, they are subjected to centrifugal force F and are pressed against the inner circumferential surface of the shaft hole 38b of the housing 38.

[0036] Lubricating oil that lubricates the motor 2 is present inside the housing 38, and the lubricating oil may form an oil film between the seal lip 64 and the inner circumferential surface of the axial hole 38b of the housing 38. In some cases, the lubricating oil may also form an oil film between the dust lip 65 and the inner circumferential surface of the axial hole 38b of the housing 38. However, because the seal lip 64 and the dust lip 65 are subjected to centrifugal force F and pressed against the inner circumferential surface of the axial hole 38b of the housing 38, an oil film is unlikely to form between the lip and the housing 38, and even if an oil film does form, its thickness is small. As a result, the electrical resistance of the oil film is small, making it highly reliable at dissipating electromagnetic noise from the rotating shaft 20 to the housing 38.

[0037] In this embodiment, the metallic rigid ring 72 is in surface contact with the outer circumferential surface of the rotary shaft 20 in the cylindrical portion 61. Therefore, the reliability of dissipating electromagnetic noise from the rotary shaft 20 to the housing 38 is further increased.

[0038] 4 shows another application of the electrical conductor 40 of FIG. 2. Here, a sealing device (oil seal) 80 is provided on the more internal side of the housing 38 than the electrical conductor 40. Therefore, the electrical conductor 40 is either an auxiliary sealing device (dust seal device) for the sealing device 80 or does not function as a sealing device at all. In either case, the electrical conductor 40 functions to allow electromagnetic noise to escape from the rotating shaft 20 to the housing 38.

[0039] Preferably, grease is disposed as a lubricant in the space 48 between the sealing lip 44 and the dust lip 45 of the conductive device 40. This grease preferably has high electrical conductivity.

[0040] The sealing device 80 has a cylindrical portion 81 , a disk portion 82 , an annular portion 83 , a seal lip 84 , and a dust lip 85 .

[0041] The cylindrical portion 81 is fitted into the axial hole 38b of the housing 38 by an interference fit. Thus, the sealing device 80 is fixed to the housing 38. The disk portion 82 extends radially inward from the cylindrical portion 81. The annular portion 83 is formed on the inner edge of the disk portion 82.

[0042] The seal lip 84 extends further radially inward from the annular portion 83 and comes into slidable contact with the outer peripheral surface of the rotating shaft 20 of the motor 2. The seal lip 84 prevents the lubricating oil that lubricates the motor 2 arranged inside the housing 38 from leaking to the outside of the housing 38.

[0043] Although not essential, a garter spring 86 is disposed radially inward of the seal lip 84. The garter spring 86 presses the seal lip 84 against the outer peripheral surface of the rotary shaft 20.

[0044] The dust lip 85 also extends radially inward from the annular portion 83 and is in slidable contact with the outer circumferential surface of the rotary shaft 20. The dust lip 85 prevents foreign matter from entering the housing 38 from the outside to the inside.

[0045] The sealing device 80 includes an elastic ring 90 and a rigid ring 92 made of a rigid material, such as metal. The rigid ring 92 has a substantially L-shaped cross section and is embedded in the elastic ring 90 to reinforce the elastic ring 90.

[0046] The cylindrical portion 81 and the disk portion 82 are composed of an elastic ring 90 and a rigid ring 92, while the annular portion 83, the seal lip 84 and the dust lip 85 are composed of the elastic ring 90 only.

[0047] The elastic ring 90 is made of a rubber material. The elastic ring 90 may be made of conductive rubber, similar to the elastic ring 50 of the conductive device 40.

[0048] 5 shows another application of the electrical conductor 60 of FIG. 3. Here, a sealing device (oil seal) 80 is provided on the more internal side of the housing 38 than the electrical conductor 60. Therefore, the electrical conductor 60 is either an auxiliary sealing device (dust seal device) for the sealing device 80 or does not function as a sealing device at all. In either case, the electrical conductor 60 functions to allow electromagnetic noise to escape from the rotating shaft 20 to the housing 38.

[0049] Preferably, grease is disposed as a lubricant in the space 68 between the sealing lip 64 and the dust lip 65 of the conductive device 60. The grease preferably has high electrical conductivity.

[0050] Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be included within the scope of the invention.

[0051] For example, the shape of the lip is not limited to the above embodiment.

[0052] Furthermore, the electrical conduction devices 40 and 60 according to the above embodiments are disposed around the rotating shaft 20 of the motor 2. However, the electrical conduction devices 40 and 60 may also be disposed around a rotating shaft (shaft 8a or 10a) that is rotated by the rotating shaft 20 of the motor 2 via a power transmission mechanism (for example, the gear train 4 and the differential gear device 6). For example, as shown in FIG. 6 , the electrical conduction devices 40 and 60 may be disposed in the gap between the housing 38 and the shaft 8a, or in the gap between the housing 38 and the shaft 10a. Furthermore, the electrical conduction devices 40 and 60 may be disposed in the gap between the rotating shaft 4A of the intermediate gear of the gear train 4 and the housing 38. A sealing device 80 may also be disposed near the electrical conduction devices 40 and 60.

[0053] Alternatively, the electrical conduction device 40 or 60 may be disposed in a gap between the rotating shaft of a generator in which lubricating oil is used and the housing of the rotating shaft. Alternatively, the electrical conduction device 40 or 60 may be disposed in a gap between the rotating shaft that rotates the rotating shaft of a generator and the housing. [Explanation of symbols]

[0054] 2. Electric motor 8a, 10a shaft (rotating shaft) 20 Rotation axis 38 Housing 38b shaft hole 40,60 Sealing device (conducting device) 41,61 Cylindrical part 42,62 flange 43 Annular part 44,64 Seal lip 45,65 Dust Trip 50,70 Elastic ring 52,72 rigid ring

Claims

1. A conductive device is disposed around a metallic rotating shaft and is disposed over the entire gap between an inner circumferential surface of a shaft hole of a metallic housing and the rotating shaft, a cylindrical portion into which the rotating shaft is fitted; a disk portion extending radially outward from the cylindrical portion; at least one lip extending radially outward from the disk portion and slidably contacting the inner circumferential surface of the axial hole of the housing; The cylindrical portion and the disk portion are made of at least one of metal and conductive rubber, and the lip is made of conductive rubber. A conductive device characterized by:

2. a sealing device that seals the gap between the inner circumferential surface of the shaft hole and the rotating shaft; The conductive device according to claim 1 .

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