Conductive resin composition, conductive sliding body, and conductive structure

Abstract

A conductive structure (1) comprises: an annular conductive member (10) formed from a conductive resin composition; and an annular holding member (20) having conductivity. The conductive member (10) is held by the holding member (20). The conductive resin member contains a fluororesin, a conductive material, and a wear-resistant material having conductivity. The fluororesin is polytetrafluoroethylene.

Description

Conductive Resin Composition, Conductive Sliding Body, and Conductive Structure

[0001] The present invention relates to a conductive resin composition, a conductive sliding body, and a conductive structure, and particularly to a conductive resin composition, a conductive sliding body, and a conductive structure for forming a conductive path on a rotating shaft.

[0002] For example, in a vehicle equipped with an electric motor such as an electric vehicle (EV: Electric Vehicle), electromagnetic wave noise may be generated by an induced current or the like generated from the motor. Such electromagnetic wave noise may cause communication disorders in AM radios and other wireless communication devices. In addition, such electromagnetic wave noise may cause electrolytic corrosion in metal parts such as bearings. Therefore, conventionally, measures have been taken to remove such electromagnetic wave noise, and conductive structures and conductive devices for forming a conductive path on a rotating shaft have been proposed. For example, a technique is disclosed in which a conductive structure is attached to the housing of a motor, and a disk-shaped conductive member made of a conductive material is brought into contact with the rotating shaft of the motor to form a conductive path between the rotating shaft and the housing, and the electromagnetic wave noise is released from the rotating shaft to the housing (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2019-509007

[0004] Since the conductive member of the conductive structure slides with respect to the rotating shaft, conventionally, a configuration having conductivity and durability has been required for the conductive member. For example, in Patent Document 1, it is proposed that the conductive member be made of conductive PTFE, which is a conductive resin. However, there is a need to further improve the conductivity and durability of conventional conductive structures.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a conductive resin composition, a conductive sliding body, and a conductive structure that can improve durability while improving conductivity.

[0006] In order to achieve the above object, the conductive resin composition according to the present invention contains a fluororesin, a conductive material, and a wear-resistant material having conductivity, and the fluororesin is polytetrafluoroethylene.

[0007] In a conductive resin composition according to one aspect of the present invention, the wear-resistant material is coke.

[0008] In a conductive resin composition according to one aspect of the present invention, the conductive material is carbon particles.

[0009] In a conductive resin composition according to one aspect of the present invention, the conductive material is carbon black.

[0010] To achieve the above objective, the conductive sliding body according to the present invention is annular around an axis x and is formed from a conductive resin composition, wherein the conductive resin composition contains a fluororesin, a conductive material, and a conductive wear-resistant material, and the fluororesin is polytetrafluoroethylene.

[0011] In a conductive structure according to one aspect of the present invention, the wear-resistant material is coke.

[0012] In a conductive structure according to one aspect of the present invention, the conductive material is carbon particles.

[0013] In a conductive structure according to one aspect of the present invention, the conductive material is carbon black.

[0014] In a conductive structure according to one aspect of the present invention, a shaft that rotates about the axis is inserted.

[0015] To achieve the above objective, the conductive structure according to the present invention is a conductive structure installed between a shaft and a hole through which the shaft passes, comprising a conductive sliding body which is an annular member about an axis x, and a support member which is an annular member about the axis and supports the conductive sliding body, wherein the conductive sliding body is formed from a conductive resin composition, the conductive resin composition contains a fluororesin, a conductive material, and a conductive wear-resistant material, and the fluororesin is polytetrafluoroethylene.

[0016] In a conductive structure according to one aspect of the present invention, the wear-resistant material is coke.

[0017] In a conductive structure according to one aspect of the present invention, the conductive material is carbon particles.

[0018] In a conductive structure according to one aspect of the present invention, the conductive material is carbon black.

[0019] According to the conductive resin composition, conductive sliding body, and conductive structure of the present invention, it is possible to improve durability while improving conductivity.

[0020] This is a cross-sectional view showing a plane containing the axis, illustrating the schematic configuration of a conductive structure according to the first embodiment of the present invention. This is a cross-sectional view showing one side of the conductive structure with respect to the axis shown in Figure 1. This is a conceptual diagram to show an example of an application target for the conductive structure. This is a cross-sectional view showing an example of the usage state of the conductive structure in the application target shown in Figure 4. This is a cross-sectional view showing one side of the axis of a plane containing the axis of a conductive sealing device, illustrating the schematic configuration of a conductive sealing device according to an embodiment of the present invention. This is a conceptual diagram to show an example of an application target for the conductive sealing device. This is a cross-sectional view showing an example of the usage state of the conductive sealing device in the application target shown in Figure 6. This is a diagram schematically illustrating a method for measuring surface resistivity using the four-probe method.

[0021] Embodiments of the present invention will be described below with reference to the drawings. In the drawings, not all of the components are assigned reference numerals, and some of the reference numerals for components may be omitted.

[0022] As a result of diligent research, the inventors have newly discovered that by incorporating a conductive material and a conductive wear-resistant material into the fluororesin, it is possible to improve the conductivity and durability of the fluororesin. This invention was completed by further research based on this finding.

[0023] The conductive resin composition according to the present invention forms, for example, a conductive sliding body into which a shaft is inserted and which the shaft slides. The conductive sliding body forms a conductive passage on a rotating shaft, specifically, for example, a conductive passage between the shaft and the hole through which the shaft is inserted. The conductive resin composition according to the present invention will be described below using a conductive sliding body formed by the conductive resin composition according to the present invention as an example. However, the application of the conductive resin composition according to the present invention is not limited to this.

[0024] Figure 1 is a cross-sectional view showing a schematic configuration of a conductive structure 1 according to a first embodiment of the present invention, which includes a conductive member 10 as a conductive sliding body according to an embodiment of the present invention, with respect to a plane containing axis x. Figure 2 is a cross-sectional view showing one side of the conductive structure 1 shown in Figure 1 with respect to axis x.

[0025] As shown in Figures 1 and 2, the conductive structure 1 comprises a conductive member 10, which is an annular conductive resin composition formed around an axis x, and a holding member 20, which is an annular conductive member around an axis x. The conductive member 10 is held by the holding member 20. The conductive resin composition contains a fluororesin, a conductive material, and a conductive wear-resistant material. The fluororesin is polytetrafluoroethylene (PTFE). The conductive resin composition will be described in detail later. The configuration of the conductive structure 1 will be described in detail below. The inner circumference is the side that approaches the axis x in the direction perpendicular to the axis x (hereinafter also referred to as the radial direction) (see arrow c in Figure 1), and the outer circumference is the side that moves away from the axis x in the radial direction (see arrow d in Figure 1).

[0026] The conductive member 10 is an annular plate-shaped member with an axis x, as shown in Figures 1 and 2, and has a pair of annular surfaces, a contact side 11 and a back side 12, which are opposite each other in the direction of the axis x. As shown in Figures 1 and 2, the contact side 11 faces one side in the direction of the axis x (the side in the direction of arrow a in Figure 1) (hereinafter also referred to as the front side), and the back side 12 faces the other side in the direction of the axis x (the side in the direction of arrow b in Figure 1) (hereinafter also referred to as the back side). The conductive member 10 has an annular inner end 10a at the inner circumference and an annular outer end 10b at the outer circumference. The inner end 10a defines a space (through hole) that penetrates the conductive member 10 in the direction of the axis x on the inner circumference side. The inner end 10a extends, for example, along a circle centered on the axis x. Similarly, the outer edge 10b extends along a circle centered on axis x, for example.

[0027] The conductive member 10 has an inner circumference end 13 which is the annular inner circumference end around the axis x, and the inner circumference end 13 of the conductive member 10 extends along a plane perpendicular to the axis x, as shown in Figures 1 and 2. However, the inner circumference end 13 of the conductive member 10 does not have to be along a plane. The inner circumference end 13 of the conductive member 10 may have other shapes, for example, it may curve and extend toward the back side, or it may be bent toward the back side.

[0028] As shown in Figures 1 and 2, the holding member 20 specifically includes an inner holding member 21 located on the inside and an outer holding member 25 located on the outside. The inner holding member 21 and the outer holding member 25 are annular members around an axis x, and are configured to hold the conductive member 10 between them.

[0029] As shown in Figure 2, the internal retaining member 21 has, for example, a fitting portion 22 which is an annular portion around axis x, and a retaining portion 23 which is an annular portion around axis x. The fitting portion 22 is a cylindrical portion extending along axis x, and the retaining portion 23 is an annular portion extending inward from the front end of the fitting portion 22. The fitting portion 22 is, for example, cylindrical or substantially cylindrical with axis x as its central axis or substantially its central axis.

[0030] As shown in Figure 2, the outer retaining member 25 has, for example, a fitting portion 26 which is an annular portion around axis x, and a retaining portion 27 which is an annular portion around axis x. The fitting portion 26 is a cylindrical portion extending along axis x, and the retaining portion 27 is an annular portion extending inward from the front end of the fitting portion 26. The fitting portion 26 is, for example, cylindrical or substantially cylindrical with axis x as its central axis or substantially its central axis.

[0031] As shown in Figures 1 and 2, the inner retaining member 21 and the outer retaining member 25 are fitted together. Specifically, for example, the diameter of the outer peripheral surface 22a of the fitting portion 22 of the inner retaining member 21 is larger than the diameter of the inner peripheral surface 26a of the fitting portion 26 of the outer retaining member 25, and the fitting portion 22 of the inner retaining member 21 is press-fitted into the inner peripheral side of the fitting portion 26 of the outer retaining member 25, so that the fitting portion 22 of the inner retaining member 21 and the fitting portion 26 of the outer retaining member 25 are fitted together. The outer peripheral surface 22a of the fitting portion 22 is an annular surface facing the outer peripheral side of the fitting portion 22, and the inner peripheral surface 26a of the fitting portion 26 is an annular surface facing the inner peripheral side of the fitting portion 26. Furthermore, as shown in Figures 1 and 2, when the fitting portion 22 of the inner retaining member 21 and the fitting portion 26 of the outer retaining member 25 are fitted together, the retaining portion 23 of the inner retaining member 21 and the retaining portion 27 of the outer retaining member 25 have portions that face each other in the axial x direction.

[0032] Furthermore, as shown in Figures 1 and 2, when the inner retaining member 21 and the outer retaining member 25 are fitted together, the retaining portion 23 of the inner retaining member 21 and the retaining portion 27 of the outer retaining member 25 face the conductive member 10 in the axial x direction. Specifically, the back surface 12 of the outer peripheral end 14 of the conductive member 10 faces the retaining portion 23 of the inner retaining member 21, and the contact surface 11 of the outer peripheral end 14 of the conductive member 20 faces the retaining portion 27 of the outer retaining member 25. The outer peripheral end 14 is the outer peripheral end of the conductive member 10. As shown in Figures 1 and 2, the inner peripheral end 13 of the conductive member 10 is located on the inner circumference side of the retaining portion 23 of the inner retaining member 21, and also on the inner circumference side of the retaining portion 27 of the outer retaining member 25.

[0033] As shown in Figure 2, the inner retaining member 21 and the outer retaining member 25 are fitted together, and the conductive member 10 is sandwiched between the retaining portion 23 of the inner retaining member 21 and the retaining portion 27 of the outer retaining member 25 at its outer peripheral end 14, and pressed in the axial x direction. A pressing portion 28 is formed on the fitting portion 26 of the outer retaining member 25, and the inner retaining member 21 is fixed to the outer retaining member 25. The pressing portion 28 of the outer retaining member 25 is the part that contacts the fitting portion 22 of the inner retaining member 21 and fixes the fitting portion 22 in the axial x direction. In this way, the conductive member 10 is fixed between the inner retaining member 21 and the outer retaining member 25 (hereinafter also referred to as the "assembled state").

[0034] The inner retaining member 21 and the outer retaining member 25 are made of a conductive metal. However, the inner retaining member 21 and the outer retaining member 25 may be formed from other conductive materials.

[0035] Each component of the conductive structure 1 has the configuration described above, and when assembled, it becomes the conductive structure 1 shown in Figures 1 and 2. In the conductive structure 1, the fitting portion 22 of the inner holding member 21 is fitted into the fitting portion 26 of the outer holding member 25, and the fitting portion 22 of the inner holding member 21 is pushed toward the front by the pressing portion 28 of the fitting portion 26 of the outer holding member 25. The conductive member 10 is sandwiched between the holding portion 23 of the inner holding member 21 and the holding portion 27 of the outer holding member 25. The conductive member 10 is held by the inner holding member 21 and the outer holding member 25 at its outer peripheral end 14. Thus, the inner holding member 21 is fixed to the outer holding member 25, and the conductive member 10 is fixed between the inner holding member 21 and the outer holding member 25. Furthermore, the conductive member 10 is attached to the inner holding member 21 and the outer holding member 25 such that the contact surface 11 of the conductive member 10 contacts the shaft in the usage state described later. As shown in Figures 1 and 2, the conductive member 10 is attached to the inner retaining member 21 and the outer retaining member 25 such that the contact surface 11 of the conductive member 10 faces the front side. However, the conductive member 10 may also be attached to the inner retaining member 21 and the outer retaining member 25 such that the contact surface 11 of the conductive member 10 faces the back side.

[0036] Before reaching the assembled state shown in Figures 1 and 2, the fitting portion 26 of the outer retaining member 25 does not necessarily have a pressing portion 28. For example, the conductive member 10 may be attached to the outer retaining member 25, which does not have a pressing portion 28 formed on its fitting portion 26, and then the fitting portion 22 of the inner retaining member 21 may be attached to the fitting portion 26 of the outer retaining member 25, after which the pressing portion 28 may be formed on the fitting portion 26. In other words, by forming the pressing portion 28, the fitting portion 22 and the fitting portion 26 are crimped together, and the end of the fitting portion 22 is pressed toward the front by the pressing portion 28, thereby assembling the conductive member 10, the inner retaining member 21, and the outer retaining member 25 as shown in Figures 1 and 2.

[0037] Next, the operation of the conductive structure 1 will be explained. Figure 3 is a conceptual diagram showing an example of an application target of the conductive structure 1. Figure 4 is a cross-sectional view showing an example of the usage state of the conductive structure 1 in the application target shown in Figure 3. As an example, the conductive structure 1 is applied to the drive unit 100 of a battery electric vehicle (BEV), as shown in Figure 3. The drive unit 100 includes, for example, an electric motor 101, a reduction gear 102, an inverter 103 that controls the electric motor 101, and a battery 104 as a power source, as shown in Figure 3. In the electric motor 101, the shaft 110 is rotatably supported by a bearing 112 supported within the housing 111, and also exits the housing 111 through a shaft hole 113 in the housing 111. The shaft 110 of the electric motor 101 enters the housing 120 of the reduction gear 102 through a shaft hole 124 in the housing 120, and is rotatably supported by a bearing 123 supported within the housing 120. Furthermore, the shaft 110 is connected to a reduction gear stage 121 inside the housing 120. The reducer 102 is also provided with a shaft 122 that outputs the rotational driving force reduced by the reduction gear stage 121. The shaft 122 is rotatably supported by a bearing 123 supported inside the housing 120 and is also connected to a wheel 105 so that it can transmit rotational driving force to the wheel 105. An oil seal 125 is installed in the shaft hole 124 of the housing 120 of the reducer 102 to seal the gap between the shaft hole 124 and the shaft 110 of the electric motor 101. An oil seal 127 is installed in the shaft hole 126 of the housing 120 through which the shaft 122 of the reducer 102 passes to seal the gap between the shaft hole 126 and the shaft 122. Note that the shaft 110 and housing 111 of the electric motor 101 are made of metal, and the housing 120 and shaft 122 of the reducer 102 are made of metal.

[0038] As an example, the conductive structure 1 is installed between the housing 111 and the shaft 110 of an electric motor 101 to enter a working state. Specifically, as shown in Figure 4, the fitting portion 26 of the outer holding member 25 of the holding member 20 is fitted into the shaft hole 113 of the housing 111, fixing the conductive structure 1 in the shaft hole 113, and the shaft 110 is inserted into the conductive member 10, so that the conductive structure 1 is in a working state. In the working state, the contact surface 11 at the inner circumferential end 13 of the conductive member 10 is in contact with the outer circumferential surface 110a of the shaft 110, and the inner circumferential end 13 of the conductive member 10 is deformed by being pushed outward by the shaft 110. As shown in Figure 4, the inner circumferential end 13 of the conductive member 10 has a width in the axial x direction and is in contact with the outer circumferential surface 110a of the shaft 110. Furthermore, the retaining members 20 (inner retaining member 21 and outer retaining member 25) to which the conductive member 10 is attached are made of a conductive metal and are in contact with the inner circumferential surface 113a of the shaft hole 113 of the housing 111. In this way, the conductive member 10 and the retaining members 20 form a conductive passage that allows electricity to flow between the shaft 110 of the electric motor 101 and the housing 111 when in use.

[0039] The conductive structure 1 may also be provided between the housing 120 and the shaft 122 of the reduction gear 102. Specifically, as shown in Figure 3, the conductive structure 1 may be provided outside the oil seal 127 in the gap between the shaft hole 126 of the housing 120 and the shaft 122. In this case as well, similar to the conductive structure 1 attached to the electric motor 101, the conductive member 10 and the holding member 20 of the conductive structure 1 form a conductive passage for electricity to flow between the shaft 122 of the reduction gear 102 and the housing 120.

[0040] The above-described drive unit 100 is just one example of an application target for the conductive structure 1, and the application targets for the conductive structure 1 are not limited to this. The conductive structure 1 can be used, for example, in drive units of electric vehicles (EVs) other than battery electric vehicles (BEVs), such as hybrid vehicles (HVs) and fuel cell vehicles (FCVs). In vehicles equipped with electric motors such as electric vehicles (EVs), electromagnetic noise may be generated by induced currents from the motor. In addition, electromagnetic noise may be generated by the on / off operation of inverters for current control supplied to electric motors, or by the induced voltage of the electric motor itself. As described above, the conductive structure 1 forms a conductive passage and allows electromagnetic noise transmitted to the shafts 110 and 122 to flow to the housings 111 and 120. This prevents communication failures and malfunctions in electronic equipment, and prevents electrolytic corrosion in metal parts such as bearings.

[0041] The conductive structure 1 may also have a support member, which is an annular member made of an elastic material that is superimposed on the back surface 12 of the conductive member 10. In the conductive structure 1 in use, the support member presses the inner circumferential end 13 of the conductive member 10 against the outer circumferential surface 110a of the shaft 110. This improves the stability of the contact between the conductive member 10 and the shaft 110. Furthermore, the shape of the conductive member 10 is not limited to the shape described above. For example, the conductive member 10 may be divided into multiple parts. Also, the conductive member 10 may have a slit extending in the radial direction, and its shape when viewed in the axial x direction may be arc-shaped or circular arc-shaped.

[0042] Next, a conductive sealing device 2 as a conductive structure according to a second embodiment of the present invention will be described. Figure 5 is a cross-sectional view showing one side of a cross-section of the conductive sealing device 2 with respect to the axis x, in a plane containing the axis x of the conductive sealing device 2, illustrating the schematic configuration of the conductive sealing device 2. The conductive sealing device 2 is a sealing device for sealing between an axis of an object to which the axis passes and a hole through which the axis passes, and is also a conductive structure that forms a conductive passage between the axis and the hole through which the axis passes.

[0043] As shown in Fig. 5, the conductive sealing device 2 includes a reinforcing ring 30 which is an annular member around the axis x, an elastic body part 40 formed from an annular elastic body attached to the reinforcing ring 30 around the axis x, and a conductive structure part 3 which is annular around the axis x. The elastic body part 40 has a seal lip 41 that contacts the shaft. The conductive structure part 3 has a holding member 50 which is an annular member around the axis x and the above-described conductive member 10. The conductive member 10 is held by the holding member 50. Hereinafter, the configuration of the conductive sealing device 2 will be specifically described.

[0044] As shown in Fig. 5, the conductive sealing device 2 has, for example, a reinforcing ring 30 and an elastic body part 40 similar to a known oil seal. The reinforcing ring 30 has a cylindrical part 31 and an annular part 32. Further, the elastic body part 40 has, in addition to the seal lip 41, a base part 42, a gasket part 43, and a cover part 44. The seal lip 41 extends from the base part 42 toward the object to be sealed. The gasket part 43 is a part that covers the cylindrical part 31 of the reinforcing ring 30 from the outer peripheral side and is a part that is press-fitted into the hole of the applicable object. The outer peripheral surface 43a of the gasket part 43 has a diameter such that it is pressed against the hole of the applicable object. The cover part 44 is a part that covers the annular part 32 of the reinforcing ring 30 from the side opposite to the object to be sealed.

[0045] As shown in Fig. 5, a fitting surface 45 which is an annular surface facing the outer peripheral side is formed at the outer peripheral side end (outer peripheral end 44a) of the cover part 44. The fitting surface 45 is, for example, a cylindrical surface that extends along a cylindrical surface having the axis x as the central axis. Specifically, the fitting surface 45 is, for example, a cylindrical surface or a substantially cylindrical surface having the axis x as the central axis or a substantially central axis. As shown in Fig. 5 for example, the fitting surface 45 is located more on the outer peripheral side than other parts of the outer peripheral end 44a, and an annular recess 46 that is recessed inward in the inner peripheral side is formed between the fitting surface 45 and the gasket part 43. The fitting surface 45 of the cover part 44 is located on the inner peripheral side in the radial direction compared to the outer peripheral surface 43a of the gasket part 43.

[0046] Further, the cover portion 44 has a holding surface 47 which is an annular surface facing the side opposite to the object to be sealed. The holding surface 47 is, for example, a surface extending along a plane orthogonal to the axis x. Specifically, the holding surface 47 is, for example, a surface extending on a surface parallel or substantially parallel to the plane orthogonal to the axis x.

[0047] As shown in FIG. 5, the holding member 50 of the conductive structure portion 3 has the same form as the outer holding member 25 of the holding member 20 of the above-described conductive structure 1. The holding member 50 is made of the same conductive material as the outer holding member 25. As shown in FIG. 5, the holding member 50 has, for example, a fitting portion 51 which is an annular portion around the axis x and a holding portion 52 which is an annular portion around the axis x. The fitting portion 51 is a cylindrical portion extending along the axis x, and the holding portion 52 is an annular portion extending from the front end portion of the fitting portion 51 to the inner peripheral side. As shown in FIG. 5, the fitting portion 51 has, for example, an outer peripheral surface 51a and an inner peripheral surface 51b which are surfaces facing away from each other in the radial direction. The outer peripheral surface 51a is an annular surface facing the outer peripheral side, and the inner peripheral surface 51b is an annular surface facing the inner peripheral side. The inner peripheral surface 51b is a cylindrical surface extending along the axis x, and is, for example, a cylindrical surface or a substantially cylindrical surface having the axis x as the central axis or the substantially central axis. Further, as shown in FIG. 5, the holding portion 52 has, for example, side surfaces 52a, 52b which are surfaces facing away from each other in the direction of the axis x. The side surface 52b connected to the inner peripheral surface 51b of the fitting portion 51 extends along a plane orthogonal to the axis x, and extends, for example, on a surface parallel or substantially parallel to the plane orthogonal to the axis x.

[0048] The fitting portion 51 of the holding member 50 is capable of fitting to the outer peripheral end portion 44a of the cover portion 44 of the elastic body portion 40. Specifically, for example, the diameter of the inner peripheral surface 51b of the fitting portion 51 is smaller than the diameter of the fitting surface 45 of the outer peripheral end portion 44a of the cover portion 44. Thereby, the cover portion 44 of the elastic body portion 40 is press-fitted into the fitting portion 51 of the holding member 50, and the holding member 50 is fixed to the elastic body portion 40.

[0049] As shown in Figure 5, the conductive member 10 is held between the holding portion 52 of the holding member 50 and the holding surface 47 of the cover portion 44 of the elastic body portion 40. Specifically, the side surface 52b of the holding member 50 contacts the back surface 12 of the outer peripheral end 14 of the conductive member 10, pressing the outer peripheral end 14 of the conductive member 10 against the holding surface 47 of the cover portion 44. As described above, the fitting portion 51 of the holding member 50 is fitted onto the outer peripheral end 44a of the cover portion 44 of the elastic body portion 40, and the holding member 50 is fixed to the elastic body portion 40 with the holding portion 52 pressing the conductive member 10 against the holding surface 47 of the cover portion 44. Note that a protrusion 53 that fits into the recess 46 of the cover portion 44 may be provided at the end 51c of the fitting portion 51 of the holding member 50 (see Figure 5). As described above, when the fitting portion 51 of the retaining member 50 is fitted onto the outer peripheral end 44a of the cover portion 44 of the elastic body portion 40, the convex portion 53 is accommodated in the recess 46. This allows the retaining member 50 to be more firmly fixed to the elastic body portion 40 while the retaining portion 52 presses the conductive member 10 against the retaining surface 47 of the cover portion 44.

[0050] In the conductive sealing device 2, similar to the conductive member 10 in the conductive structure 1 described above, the contact surface 11 at the inner circumferential end 13 of the conductive member 10 is in contact with the outer circumferential surface of the shaft to be applied.

[0051] Each component of the conductive sealing device 2 has the configuration described above, and when assembled, it becomes the conductive sealing device 2 shown in Figure 5. In the conductive sealing device 2, the fitting portion 51 of the holding member 50 is fitted to the outer peripheral end 44a of the cover portion 44 of the elastic body portion 40, and the conductive member 10 is sandwiched between the holding portion 52 of the holding member 50 and the cover portion 44 of the elastic body portion 40. In this way, the holding member 50 is fixed to the elastic body portion 40, and the conductive member 10 is fixed between the holding member 50 and the elastic body portion 40.

[0052] Figure 6 is a conceptual diagram illustrating an example of an application target for the conductive sealing device 2. Figure 7 is a cross-sectional view showing an example of the usage state of the conductive sealing device 2 in the application target shown in Figure 6. As an example, the conductive sealing device 2 is applied to the drive unit 200 of a battery electric vehicle (BEV), as shown in Figure 6. The drive unit 200 has a similar configuration to the drive unit 100 (see Figures 3 and 4) described above, but differs in that the conductive structure 1 is not attached to the drive unit 100. In addition, the conductive sealing device 2 is attached to the drive unit 200 in place of the oil seal 127 of the drive unit 100. As an example, the conductive sealing device 2 is installed between the housing 120 and the shaft 122 of the reduction gear 102 and is in use. Specifically, the gasket portion 43 of the elastic portion 40 is fitted into the shaft hole 126 of the housing 120, fixing the conductive sealing device 2 to the shaft hole 126. The shaft 122 is then inserted into the seal lip 41 and the conductive member 10, putting the conductive sealing device 2 into operation. In operation, the seal lip 41 contacts the outer circumferential surface 122a of the shaft 122, sealing the object to be sealed. Also in operation, the contact surface 11 at the inner circumferential end 13 of the conductive member 10 contacts the outer circumferential surface 122a of the shaft 122. Furthermore, the retaining member 50 that holds the conductive member 10 is made of a conductive metal and contacts the inner circumferential surface 126a of the shaft hole 126 of the housing 120. In this way, the conductive member 10 and the retaining member 50 form a conductive passage between the shaft 122 and the housing 120 for electricity to flow in operation.

[0053] The above-mentioned drive unit 200 is just one example of an application target for the conductive sealing device 2, and the application target of the conductive sealing device 2 is not limited to this. The conductive sealing device 2 is used, for example, in drive units of electric vehicles (EVs) such as battery electric vehicles (BEVs), hybrid vehicles (HVs), and fuel cell vehicles (FCVs). In vehicles equipped with electric motors such as electric vehicles (EVs), electromagnetic noise may be generated by induced currents from the motor. In addition, electromagnetic noise may be generated by the on / off operation of the inverter for current control supplied to the electric motor, or by the induced voltage of the electric motor itself. As described above, the conductive sealing device 2 forms a conductive passage and allows the electromagnetic noise transmitted to the shafts 110 and 122 to flow into the housing 120. This prevents communication failures and malfunctions in electronic equipment, and prevents electrolytic corrosion in metal parts such as bearings.

[0054] The conductive sealing device 2 is used in the same manner as the conductive structure 1 described above, operates in the same manner as the conductive structure 1, and produces the same effects.

[0055] Next, the conductive resin composition according to the present invention will be described. As an example, the conductive resin composition forms a conductive member 10 for forming a conductive path in the application object, as described above.

[0056] As described above, the conductive resin composition contains a fluororesin, a conductive material, and a conductive wear-resistant material. The fluororesin is polytetrafluoroethylene (PTFE). The conductive wear-resistant material is, for example, coke. Specifically, the conductive wear-resistant material is powdered coke. The conductive wear-resistant material also includes, for example, graphite, carbon nanotubes, carbon fibers, etc. In other words, the conductive wear-resistant material may be one or more selected from, for example, coke, graphite, carbon nanotubes, carbon fibers, etc. In the conductive resin composition, coke is used as the conductive wear-resistant material. The conductive material is, for example, carbon particles. Specifically, for example, the conductive material is carbon black such as Ketjenblack.

[0057] The content of conductive wear-resistant material is, for example, 10 vol% to 30 vol%. The content of conductive material is 1 wt% to 8 wt%.

[0058] The conductive resin composition uses PTFE as the base resin and contains a conductive wear-resistant material as an additive in addition to the conductive material. As a result, the conductive member 10 formed from the conductive resin composition has improved conductivity and durability. This is because, by blending a conductive wear-resistant material as an additive in addition to the conductive material into the conductive resin composition, it is possible to improve conductivity while also improving the elongation of the conductive member 10 by at least 10%. As a result, in use, the conductive member 10 contacts the outer circumferential surface 110a of the shaft 110 with a lower modulus of elasticity and deforms with lower elasticity according to the eccentricity of the shaft 110. This suppresses wear of the conductive member 10 due to sliding against the shaft 110. As a result, the wear resistance of the conductive member 10 is improved and the durability of the conductive member 10 is improved. Furthermore, because the conductive member 10 formed from the conductive resin composition has improved elongation, it can expand without damage according to the diameter of the outer circumferential surface 110a of the inserted shaft 110, and can deform without damage according to the eccentricity of the shaft 110. In this way, the conductive member 10 formed from the conductive resin composition has improved durability. Furthermore, since the elongation of the conductive member 10 is improved by at least 10%, when molding the conductive member 10 from the conductive resin composition, damage such as cracking of the conductive member 10 can be made less likely to occur during demolding.

[0059] The present invention will be described more specifically below based on examples. However, the present invention is not limited to the following examples.

[0060] (Examples 1-3, Comparative Examples 1-6) Conductive resin compositions were obtained by blending the raw materials shown in Table 1. Then, conductive members were created by molding the kneaded conductive resin compositions. A known PTFE molding method was used for molding. Specifically, the kneaded raw materials were filled into a mold, compressed to pre-form, and the pre-formed pre-molded body was fired to obtain a molded body (material). Then, this molded body was processed to obtain a conductive member. The conductive members in Examples 1-3 are conductive member 10, and the conductive members in Comparative Examples 1-6 are conductive members with the same shape as conductive member 10.

[0061] Details of the raw materials used in Examples 1-3 and Comparative Examples 1-6 are shown below. (PTFE) INOFLON640 (product name) (manufactured by GUJARAT FLUOROCHEMICALS L.T.D.) (wear-resistant material) CMW-350 (manufactured by Chuetsu Graphite Industry Co., Ltd.) (conductive material) VULCAN XC72 (manufactured by Cabot Corporation)

[0062] Furthermore, the surface resistivity was measured and the properties were evaluated for Examples 1-3 and Comparative Examples 1-6. Surface resistivity was measured using the four-probe method. Figure 8 is a schematic diagram showing the surface resistivity measurement method using the four-probe method. In the measurement using the four-probe method, for example, the applied voltage was set to 1, 2, or 5V. In addition, as a property evaluation, the tensile strength and elongation of Examples 1-3 and Comparative Examples 1-6 were measured, and the 10% elongation stress was also measured. The tensile strength and 10% elongation stress were measured at room temperature by a tensile test according to ASTM D638. For this reason, the shapes of Examples 1-3 and Comparative Examples 1-6 were based on the shapes specified in ASTM D638 for the measurement of tensile strength and 10% elongation stress. The 10% elongation stress is the stress generated when Examples 1-3 and Comparative Examples 1-6 are stretched by 10%. Table 1 shows the measurement results of surface resistivity and the property evaluation results for Examples 1-3 and Comparative Examples 1-5. Furthermore, the conductive resin composition of Comparative Example 6 could not be molded into a conductive member. Therefore, there are no measurement results for the surface resistivity or evaluation results for the properties of Comparative Example 6. Also, the surface resistivity of Comparative Example 1 could not be measured.

[0063]

[0064] As shown in Table 1, the surface resistivity measurements for Examples 1-3 and Comparative Examples 2-5 show that the surface resistivity decreases as the conductive material content increases. Therefore, in Comparative Examples 1-6, which do not contain conductive wear-resistant material, it is necessary to increase the conductive material content to lower the surface resistivity. However, the conductive resin composition of Comparative Example 6, which contains 30 wt% conductive material, cannot be molded into a conductive member. Thus, it can be seen that conductive resin compositions that do not contain conductive wear-resistant material (Comparative Examples 1-6) cannot be molded into highly conductive members with a surface resistivity of 10 Ω or less, for example, as measured by the four-probe method.

[0065] On the other hand, in Examples 1 to 3, which include a conductive wear-resistant material, it can be seen that even conductive resin compositions that can reduce surface resistivity can be molded into conductive members 10. Furthermore, it can be seen that Examples 1 to 3 can achieve a lower surface resistivity than Comparative Examples 2 to 5. In addition, it can be seen that Examples 2 and 3 can achieve a surface resistivity of 10 Ω or less as measured by the four-probe method. Thus, the conductive resin compositions according to the embodiments of the present invention, which include a conductive wear-resistant material in addition to a conductive material, can reduce surface resistivity while enabling the molding of the conductive member 10, thereby improving the conductivity of the conductive member 10.

[0066] Furthermore, as shown in Table 1, the elongation of Examples 1 to 3 is smaller than that of Comparative Examples 1 to 5, but it is still greater than 10%. In other words, the electrical components 10 of Examples 1 to 3 have elongation characteristics that allow them to stretch by more than 10%. Here, even if it is necessary to deform the molded conductive component 10 during demolding when molding the conductive component 10, it is considered that the molded conductive component 10 can be demolded without damage if a 10% deformation is possible. For this reason, although the elongation characteristics of the conductive components 10 of Examples 1 to 3 are reduced, it can be seen that the conductive components 10 of Examples 1 to 3 maintain elongation characteristics that allow them to be demolded without damage. Also, as shown in Table 1, the 10% elongation stress of Examples 1 to 3 is lower than that of Comparative Examples 1 to 5, and it can be seen that the conductive components 10 of Examples 1 to 3 are more easily deformable than the conductive components of Comparative Examples 1 to 5, at least within the range of 10% deformation. In other words, the conductive components 10 of Examples 1 to 3 are easier to demold than the conductive components of Comparative Examples 1 to 5. Thus, the conductive resin composition according to the embodiment of the present invention can suppress a significant decrease in the elongation characteristics of the molded conductive member 10, maintain the elasticity required for molding, and improve the moldability of the conductive member 10.

[0067] Furthermore, as shown in Table 1, a comparison of the 10% elongation stress of Examples 1 to 3 reveals that the higher the conductive material content, the lower the 10% elongation stress. In other words, in Examples 1 to 3, the easier it is to deform by 10%, the higher the conductivity. Thus, the conductive resin composition according to the embodiment of the present invention can improve moldability while improving the conductivity of the molded conductive member 10.

[0068] Furthermore, as described above, the conductive resin compositions of Examples 1 to 3 can suppress a significant decrease in the elongation characteristics of the molded conductive member 10. Therefore, in use, the conductive member 10 of Examples 1 to 3 elastically deforms to contact the outer circumferential surfaces 110a and 122a of the shafts 110 and 122, and also elastically deforms in accordance with the eccentricity of the shaft 110. In addition, the conductive resin compositions of Examples 1 to 3 can expand without damage in accordance with the diameter of the outer circumferential surfaces 110a and 122a of the inserted shafts 110 and 122, and can deform without damage in accordance with the eccentricity of the shafts 110 and 122.

[0069] Furthermore, as described above, the 10% tensile stress of Examples 1 to 3 is lower than that of Comparative Examples 1 to 5, indicating that, at least within the range of 10% deformation, the conductive members 10 of Examples 1 to 3 have a lower elastic modulus, are softer, and are more easily elastically deformed than the conductive members of Comparative Examples 1 to 5. For this reason, the clamping force of the conductive members 10 of Examples 1 to 3 on the shafts 110 and 122 is lower than that of the conductive members of Comparative Examples 1 to 5 on the shafts 110 and 122. As a result, the amount of wear of the conductive members 10 of Examples 1 to 3 due to sliding on the shafts 110 and 122 can be reduced to less than the amount of wear of the conductive members of Comparative Examples 1 to 5 due to sliding on the shafts 110 and 122. Thus, the conductive resin compositions according to the embodiments of the present invention can improve the wear resistance of the molded conductive members 10 and improve the durability of the molded conductive members 10. Furthermore, the conductive members 10 of Examples 1 to 3 are more easily deformed in response to the eccentricity of the shafts 110 and 122 than the conductive members of Comparative Examples 1 to 5, and are less susceptible to damage due to the eccentricity of the shafts 110 and 122. Thus, the conductive resin compositions according to the embodiments of the present invention can improve the conformability of the molded conductive member 10 to the shafts 110 and 122, and can improve the durability of the molded conductive member 10. In addition, the conductive members 10 of Examples 1 to 3 are more easily expanded when the shafts 110 and 122 are inserted than the conductive members of Comparative Examples 1 to 5, and are less susceptible to damage due to the insertion of the shafts 110 and 122. Thus, the conductive resin compositions according to the embodiments of the present invention can improve the conformability of the molded conductive member 10 to the diameter of the shafts 110 and 122, and can improve the durability of the molded conductive member 10.

[0070] Furthermore, as shown in Table 1, for example, Examples 2 and 3 can achieve a surface resistivity of 10 Ω or less as measured by the four-probe method.

[0071] As described above, the conductive resin compositions and conductive members 10 of Examples 1 to 3 can improve durability, reduce surface resistivity, and improve the conductivity of the conductive member 10.

[0072] Furthermore, the conductive resin compositions of Examples 1 to 3 can provide the conductive member 10 with an appropriate tensile strength and the appropriate tension on the conductive member 10 with respect to the shafts 110 and 122. This suppresses wear and deformation of the conductive member 10. In this respect as well, the conductive resin compositions of Examples 1 to 3 can improve the durability of the conductive member 10. Moreover, since wear and deformation of the conductive member 10 can be suppressed, it is not necessary to provide a conductive lubricant between the conductive member 10 and the shafts 110 and 122. Therefore, there is no lubricant in the conductive passage between the shafts 110 and 122 and the housings 111 and 120 that could act as resistance to the conductive passage, and a decrease in the conductive performance of the conductive structure 1 and the conductive sealing device 2 during use can be suppressed.

[0073] Furthermore, the conductive structure 1 can be attached around the shaft 110 by fitting the retaining member 20 into the shaft hole 113 of the housing 111, as shown in Figures 4 and 7. In this way, only an annular space surrounding the outer circumferential surface 110a of the shaft 110 is required for the attachment of the conductive structure 1. If there is space to attach the conductive structure 1 between the outer circumferential surface 110a of the shaft 110 and the inner circumferential surface 113a of the shaft hole 113, the conductive structure 1 can be attached to the shaft hole 113, so there is no need to provide additional space in the housing 111 for the attachment of the conductive structure 1. Also, even if there is no space to attach the conductive structure 1 between the outer circumferential surface 110a of the shaft 110 and the inner circumferential surface 113a of the shaft hole 113, since the cross-section of the conductive structure 1 is not large, it is only necessary to provide a small annular space on the inner circumferential surface 113a of the shaft hole 113 for the attachment of the conductive structure 1. In this way, the conductive structure 1 can be attached in a small space, enabling space saving. The same applies to the conductive sealing device 2.

[0074] As described above, the conductive resin composition, conductive sliding body, and conductive structure according to the present invention can improve durability while improving conductivity.

[0075] Although the present invention has been described above through the embodiments described above, the technical scope of the present invention is not limited to the scope described in the embodiments above. It will be obvious to those skilled in the art that various modifications or improvements can be made to the embodiments described above. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0076] The embodiments described above are for the purpose of facilitating understanding of the present invention and are not intended to limit its interpretation. Furthermore, the embodiments described above do not limit the scope of application of the present invention, and the present invention may encompass anything as its target application. The components of the above embodiments, as well as their arrangement, materials, conditions, shapes, and sizes, are not limited to those exemplified and can be modified as appropriate. For example, the present invention includes differences that arise in the implementation of manufacturing tolerances, etc. Furthermore, components shown in different embodiments can be partially substituted or combined to the extent that they do not contradict each other in a technical sense. In addition, each configuration can be selectively combined as appropriate to achieve at least some of the problems and effects described above.

[0077] For example, the shape of the outer peripheral end 10b of the conductive member 10 may be a straight section along a straight line, rather than a circular shape. For example, the shape of the outer peripheral end 10b of the conductive member 10 may be rectangular. Alternatively, the conductive member 10 may be bonded to the holding members 20, 50 and the elastic body portion 40 using an adhesive. In this case, the adhesive should be applied in a way that does not create resistance to the conductive passage. In this case, a conductive adhesive should be used.

[0078] 1 Conductive structure, 2 Conductive sealing device, 3 Conductive structural part, 10 Conductive member, 10a Inner circumferential end, 10b Outer circumferential end, 11 Contact side, 12 Back, 13 Inner circumferential end, 14 Outer circumferential end, 20 Holding member, 21 Inner holding member, 22 Fitting part, 22a Outer circumferential surface, 23 Holding part, 25 Outer holding member, 26 Fitting part, 26a Inner circumferential surface, 27 Holding part, 27a Side, 28 Pressing part, 30 Reinforcing ring, 31 Cylindrical part, 32 Ring part, 40 Elastic body part, 41 Seal lip, 41a Protrusion, 42 Base part, 43 Gasket part, 43a Outer circumferential surface, 44 Cover part, 44a Outer circumferential end, 45 Fitting surface, 46 Recess, 47 Holding surface, 47a Recess, 50 Holding member, 51 Fitting part, 51a outer surface, 51b inner surface, 51c end, 52 holding part, 52a, 52b side, 53 protrusion, 100, 200 drive device, 101 electric motor, 102 reduction gear, 103 inverter, 104 battery, 105 wheel, 110, 122 axle, 110a, 122a outer surface, 111, 120 housing, 121 reduction gear stage, 112, 123 bearing, 113, 124, 126 axle hole, 113a, 124a, 126a inner surface, 125, 127 oil seal, x axis

Claims

1. A conductive resin composition comprising a fluororesin, a conductive material, and a conductive wear-resistant material, wherein the fluororesin is polytetrafluoroethylene.

2. The conductive resin composition according to claim 1, wherein the wear-resistant material is coke.

3. The conductive resin composition according to claim 1 or 2, wherein the conductive material is carbon particles.

4. The conductive resin composition according to claim 3, wherein the conductive material is carbon black.

5. A conductive sliding body that is annular around an axis x and formed from a conductive resin composition, wherein the conductive resin composition contains a fluororesin, a conductive material, and a conductive wear-resistant material, and the fluororesin is polytetrafluoroethylene.

6. The conductive sliding body according to claim 5, wherein the wear-resistant material is coke.

7. The conductive sliding body according to claim 5 or 6, wherein the conductive material is carbon particles.

8. The conductive sliding body according to claim 7, wherein the conductive material is carbon black.

9. The conductive sliding body according to claim 5, wherein a shaft that rotates about the aforementioned axis is inserted.

10. A conductive structure to be installed between a shaft and a hole through which the shaft passes, comprising: a conductive sliding body which is an annular member around an axis; and a support member which is an annular member around the axis and supports the conductive sliding body, wherein the conductive sliding body is formed from a conductive resin composition, the conductive resin composition contains a fluororesin, a conductive material, and a conductive wear-resistant material, and the fluororesin is polytetrafluoroethylene.

11. The conductive structure according to claim 10, wherein the wear-resistant material is coke.

12. The conductive structure according to claim 10 or 11, wherein the conductive material is carbon particles.

13. The conductive structure according to claim 12, wherein the conductive material is carbon black.

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