Conductive ring

Abstract

A conductive ring (1) forms a conductive path between a rotating shaft and a hole through which the shaft is inserted. The conductive ring (1) comprises: a holding member (10) that has conductivity and is annular around an axis x; a conductive member (20) that has conductivity and extends around the axis x; and a spring member (30) that extends around the axis x. The conductive member (20) is brought into contact with the shaft and the hole, and generates a tension force to the shaft in cooperation with the spring member (30). When the sliding distance D of the shaft with respect to the conductive member (20) is a predetermined required sliding distance D1, the impedance Z between the shaft and the hole of the conductive member (20) is an impedance Z1 of a predetermined value.

Description

Conductive ring

[0001] The present invention relates to a conductive ring, and more particularly to a conductive ring that forms a conductive passage on a rotating shaft.

[0002] For example, in vehicles equipped with electric motors, such as electric vehicles (EVs), the rotating shaft can become charged due to induced currents generated during inverter operation, resulting in electromagnetic noise. Such electromagnetic noise can cause communication interference to AM radios and other wireless communication devices. Furthermore, this charging of the rotating shaft can cause electrolytic corrosion in metal parts such as bearings. For this reason, various measures have been taken to remove the voltage charged on such rotating shafts, and conductive rings that form a conductive passage on the rotating shaft have been proposed. For example, a technique has been disclosed in which a conductive ring is attached to the motor housing, and a disc-shaped conductive member made of a conductive material is brought into contact with the motor's rotating shaft to form a conductive passage between the rotating shaft and the housing, thereby dissipating the charged voltage from the rotating shaft to the housing (see, for example, Patent Document 1).

[0003] Special table 2019-509007 publication

[0004] Since the conductive member of a conductive ring slides against the rotating shaft, there has been a conventional need for a conductive member that is both conductive and resistant to wear. For example, Patent Document 1 proposes using conductive PTFE for the conductive member. Due to the properties of PTFE, the tension force of a conductive PTFE member against the rotating shaft is strong at the beginning of use and decreases significantly over time. As a result, the tension force of a conventional conductive PTFE member against the rotating shaft decreases significantly after the desired period of use, and in many cases, it almost disappears. Consequently, the conductivity of a conventional conductive PTFE member decreases significantly after the desired period of use. Thus, there is a need for a configuration in conventional conductive rings that can prevent a decrease in the tension force against the rotating shaft.

[0005] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a conductive ring that can suppress a decrease in tension force on the shaft.

[0006] To achieve the above objective, the conductive ring according to the present invention is a conductive ring that forms a conductive passage between a rotating shaft and a hole through which the shaft is inserted, comprising a holding member which is an annular conductive member around the axis, a conductive member which is a conductive member extending around the axis, and a spring member which extends around the axis, wherein the conductive member is in contact with the shaft and the outer member, and cooperates with the spring member to generate a tensioning force on the shaft, and when the sliding distance of the shaft with respect to the conductive member is a predetermined distance, the impedance of the conductive member between the shaft and the hole becomes a predetermined value.

[0007] In a conductive ring according to one aspect of the present invention, the required sliding distance is a value corresponding to the diameter of the shaft.

[0008] In a conductive ring according to one aspect of the present invention, the required sliding distance is 175 × 10 of the diameter of the shaft. ７ When doubled, the impedance is 80 ohms or less.

[0009] In a conductive ring according to one aspect of the present invention, the required sliding distance is 175 × 10 of the diameter of the shaft. ７ When doubled, the impedance is 50 ohms or less.

[0010] In a conductive ring according to one aspect of the present invention, the conductive member has a plurality of end pieces arranged in the circumferential direction at its inner end, the spring member has a plurality of end pieces arranged in the circumferential direction at its inner end, each of the plurality of end pieces of the spring member is elastically deformable along the axis and is in contact with the plurality of end pieces of the conductive member, and the holding member holds the conductive member and the spring member aligned in the axial direction.

[0011] In a conductive ring according to one aspect of the present invention, the number of end pieces of the conductive member and the number of end pieces of the spring member are set based on a predetermined value of the tightening allowance.

[0012] In a conductive ring according to one aspect of the present invention, the shape of each end piece of the conductive member and the shape of each end piece of the spring member are set based on a predetermined value of the tightening allowance.

[0013] In a conductive ring according to one aspect of the present invention, the form of the end piece of the conductive member is at least one of the thickness in the axial direction, the width in the circumferential direction about the axis, and the length in the radial direction, and the form of the end piece of the spring member is at least one of the thickness in the axial direction, the width in the circumferential direction about the axis, and the length in the radial direction.

[0014] In a conductive ring according to one aspect of the present invention, the plurality of end pieces of the spring member are arranged with a gap between them in the circumferential direction.

[0015] In a conductive ring according to one aspect of the present invention, the circumferential width of the end piece of the spring member is less than or equal to the circumferential width of the end piece of the conductive member.

[0016] In a conductive ring according to one aspect of the present invention, the outer peripheral ends of the plurality of end pieces of the spring member are located further outward than the outer peripheral ends of the plurality of end pieces of the conductive member.

[0017] In a conductive ring according to one aspect of the present invention, the spring member has a base which is an annular portion, and the plurality of end pieces of the spring member extend inward from the inner circumference end of the base of the spring member.

[0018] In a conductive ring according to one aspect of the present invention, the plurality of end pieces of the conductive member are arranged with a gap between them in the circumferential direction.

[0019] In a conductive ring according to one aspect of the present invention, the conductive member has a base which is an annular portion, and the plurality of end pieces of the conductive member extend inward from the inner circumference end of the base of the conductive member.

[0020] In a conductive ring according to one aspect of the present invention, the number of the plurality of end pieces of the spring member is the same as the number of the plurality of end pieces of the conductive member.

[0021] In a conductive ring according to one aspect of the present invention, the holding member is configured to hold the conductive member and the spring member on the outer circumference.

[0022] In a conductive ring according to one aspect of the present invention, the conductive member is formed from conductive PTFE having electrical conductivity.

[0023] The conductive ring according to the present invention can suppress a decrease in tension on the shaft.

[0024] This is a perspective view showing the schematic configuration of a conductive ring according to an embodiment of the present invention. This is an exploded perspective view of a conductive ring according to an embodiment of the present invention. This is a front view of a conductive ring. This is a rear view of a conductive ring. This is a cross-sectional view showing a cross-section of a conductive ring with respect to the axis of the conductive ring. This is a cross-sectional view showing one side of the axis of the conductive ring shown in Figure 6. This is a partially enlarged front view showing an enlarged portion of a conductive member. This is a partially enlarged front view showing an enlarged portion of a spring member. This is a conceptual diagram to show an example of an application target for the conductive ring. This is a cross-sectional view showing an example of the usage state of the conductive ring in the application target shown in Figure 10. This is a diagram showing the results of a durability test. This is a front view of an example of a modified conductive member. This is a front view of another example of a modified conductive member. This is a front view of an example of a modified spring member. This is a front view of another example of a modified spring member.

[0025] 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.

[0026] The conductive ring according to an embodiment of the present invention forms a conductive passage on a rotating shaft, for example, between the shaft and a hole through which the shaft is inserted. Specifically, the conductive ring according to an embodiment of the present invention forms a conductive passage between the shaft and a member having a hole through which the shaft is inserted. The applications to which the conductive ring according to an embodiment of the present invention is applied are not limited to these. Figures 1 and 2 are perspective views showing a schematic configuration of the conductive ring 1 according to an embodiment of the present invention, and Figure 3 is an exploded perspective view of the conductive ring 1. Figure 4 is a front view of the conductive ring 1, and Figure 5 is a rear view of the conductive ring 1. Figure 6 is a cross-sectional view showing a plane containing the axis x of the conductive ring 1, and Figure 7 is a cross-sectional view showing one side of the conductive ring 1 with respect to the axis x shown in Figure 6. Figure 1 is a perspective view of the conductive ring 1 viewed from the front, and Figure 2 is a perspective view of the conductive ring 1 viewed from the rear.

[0027] As shown in Figures 1 to 7, the conductive ring 1 comprises a retaining member 10 which is an annular conductive member around an axis x, a conductive member 20 which is a conductive member extending around the axis x, and a spring member 30 which extends around the axis x. The conductive member 20 is in contact with the shaft and the hole, and works in cooperation with the spring member 30 to generate tension on the shaft. When the sliding distance D of the shaft relative to the conductive member 20 is a predetermined distance, the impedance Z between the shaft and the hole of the conductive member 20 becomes a predetermined impedance Z1. The configuration of the conductive ring 1 will be described in detail below.

[0028] Specifically, as shown in Figures 1 to 7, the conductive member 20 has a plurality of conductive pieces 21 arranged in the circumferential direction at its inner circumference end 20a. The spring member 30 also has a plurality of spring pieces 31 arranged in the circumferential direction at its inner circumference end 30a. Each of the spring pieces 31 of the spring member 30 is designed to elastically deform along the axis x and to contact the plurality of conductive pieces 21 of the conductive member 20. As a result, the conductive member 20 works in cooperation with the spring member 30 to generate tension on the axis. The holding member 10 holds the conductive member 20 and the spring member 30 side by side in the direction of the axis x. The inner circumference side is the side that approaches the axis x in the direction perpendicular to the axis x (hereinafter also referred to as the radial direction), and the outer circumference side is the side that moves away from the axis x in the radial direction.

[0029] The conductive member 20 is, for example, an annular plate-shaped member around an axis x, as shown in Figures 1 to 7, and has a pair of annular surfaces facing away from each other in the direction of the axis x, namely a contact surface 24 and a pressed surface 25. As shown in Figures 6 and 7, the contact surface 24 faces one side (front side) in the direction of the axis x, and the pressed surface 25 faces the other side (back side) in the direction of the axis x. As described above, the conductive member 20 has a plurality of conductive pieces 21 at the inner circumference end 20a, which is the inner circumference end, and also has an annular base portion 22. As shown in Figures 6 and 7, the base portion 22 is the outer circumference portion of the conductive member 20, relative to the conductive pieces 21. From the inner circumference end 22a, which is the inner circumference end of the base portion 22, the plurality of conductive pieces 21 extend toward the inner circumference. The base portion 22 is, for example, an annular plate-shaped portion around an axis x, as shown in Figures 3, 6, and 7, and the inner circumferential end 22a extends, for example, along a cylindrical surface with axis x as its central axis. Specifically, for example, the inner circumferential end 22a extends on a cylindrical surface or a substantially cylindrical surface with axis x as its central axis. The outer circumferential end 22b also extends, for example, along a cylindrical surface with axis x as its central axis, and specifically, for example, the outer circumferential end 22b extends on a cylindrical surface or a substantially cylindrical surface with axis x as its central axis. The outer circumferential end 22b is the outer-circumferential end of the base portion 22, and specifically, it is the end face facing the outer circumference of the base portion 22.

[0030] Figure 8 is a partially enlarged front view showing an enlarged portion of the conductive member 20. As shown in Figures 4, 5, and 8, the multiple conductive pieces 21 are arranged at intervals from each other in the circumferential direction. As shown in Figure 8, the conductive pieces 21 have, for example, a rectangular or substantially rectangular plate shape and have an inner circumferential end 21a, which is the inner circumferential end, a pair of circumferential ends 21b and 21c, and an outer circumferential end 21d, which is the outer circumferential end. Specifically, the inner circumferential end 21a is an end face facing the inner circumferential side, and the circumferential ends 21b and 21c are specifically end faces facing the circumferential direction. The side faces 21b and 21c are facing away from each other in the circumferential direction. The outer circumferential end 21d is specifically the boundary between the conductive piece 21 and the base 22, and the conductive piece 21 is connected to the inner circumferential end 22a of the base 22 at the outer circumferential end 21d. The outer peripheral end 21d of the conductive piece 21 and the inner peripheral end 22a of the base portion 22 are located at a predetermined distance R1 in the radial direction from the axis x.

[0031] The inner circumferential end 21a of the conductive piece 21 extends, for example, along a plane perpendicular to the radial direction. Specifically, the inner circumferential end 21a of the conductive piece 21 extends, for example, along a plane perpendicular to the radial direction or a substantially plane. The inner circumferential end 21a is located at a predetermined distance R2 in the radial direction from the axis x. The sides 21b and 21c of the conductive piece 21 each extend, for example, along the radial direction. Specifically, the side ends 21b and 21c of the conductive piece 21 each extend, for example, along a plane containing the axis x or a substantially plane. The width W1 of the conductive piece 21, which is the circumferential width, is a predetermined size. Note that the width W1 of the conductive piece 21 is the distance between the side 21b and the side 21c. Also, the length L1 of the conductive piece 21 is a predetermined length. Note that the length L1 of the conductive piece 21 is the length in the radial direction, and is the radial distance between the inner circumferential end 21a and the outer circumferential end 21d.

[0032] As described above, the multiple conductive pieces 21 are arranged in the circumferential direction, and as shown in Figures 4, 5, and 8, a gap 23 is formed between two conductive pieces 21 that are adjacent to each other in the circumferential direction. The gap 23 extends to the inner circumferential end 22a of the base portion 22. In other words, between two conductive pieces 21 that are adjacent to each other in the circumferential direction, the side end 21b of one conductive piece 21 and the side end 21c of the other conductive piece 21 face each other through the gap 23. The width W2 of the gap 23 is a predetermined size. The width W2 of the gap 23 is the distance between the side end 21b of one conductive piece 21 and the side end 21c of the other conductive piece 21 between two adjacent conductive pieces 21. The width W2 of the gap 23 is, for example, narrow.

[0033] As an example, as shown in Figure 8, the side ends 21b and 21c of the conductive piece 21 each extend along a plane containing the axis x, and the width W1 of the conductive piece 21 widens radially from the inner circumferential end 21a to the outer circumferential end 21d. In this case, the width W2 of the gap 23 is constant radially. Note that this configuration of the conductive piece 21 is just an example, and the width W1 of the conductive piece 21 does not have to widen radially from the inner circumferential end 21a to the outer circumferential end 21d, nor does the width W2 of the gap 23 have to be constant radially. For example, the conductive piece 21 may have a configuration in which the width W1 of the conductive piece 21 is constant radially, and correspondingly, the width W2 of the gap 23 may narrow radially from the inner side to the outer side. Furthermore, for example, the conductive piece 21 may have a shape that narrows in the radial direction from the inner circumferential end 21a to the outer circumferential end 21d, and correspondingly, the width W2 of the gap 23 may widen in the radial direction from the inner circumferential side to the outer circumferential side.

[0034] The widths W1 of the multiple conductive pieces 21 are all the same or approximately the same, and the widths W2 of the multiple gaps 23 are all the same or approximately the same. Therefore, in the conductive member 20, the multiple conductive pieces 21 are arranged at equal or approximately equal angular intervals around the axis x, and the multiple gaps 23 are arranged at equal or approximately equal angular intervals around the axis x. Note that the widths W1 of the multiple conductive pieces 21 do not have to be the same, and the widths W2 of the multiple gaps 23 do not have to be the same. Also, in the conductive member 20, the multiple conductive pieces 21 do not have to be arranged at equal angular intervals around the axis x, and the multiple gaps 23 do not have to be arranged at equal angular intervals around the axis x.

[0035] Furthermore, as shown in Figures 4 and 5, the inner circumferential ends 21a of the multiple conductive pieces 21 are, for example, aligned along a circle centered on axis x when viewed in the direction of axis x. Specifically, for example, the inner circumferential ends 21a of the multiple conductive pieces 21 are located on a circle or approximately circle centered on axis x when viewed in the direction of axis x, and the distance R2 from axis x to each of the inner circumferential ends 21a of the multiple conductive pieces 21 is the same or approximately the same. In other words, the inner circumferential ends 21a of the multiple conductive pieces 21 are located on a circle with radius R2 or approximately radius R2 centered on axis x when viewed in the direction of axis x. The inner circumferential ends 21a of the multiple conductive pieces 21 form the inner circumferential ends of the conductive member 20, defining a circular or approximately circular space (through hole) 20b that penetrates the conductive member 20 in the direction of axis x when viewed in the direction of axis x.

[0036] A shaft for forming a conductive passage is inserted into the through-hole 20b. In the usage state described later, the shaft is passed through the through-hole 20b, and each of the conductive pieces 21 contacts the outer surface of the shaft. In this way, each conductive piece 21 has a clearance δ between itself and the shaft in the usage state. Specifically, the distance R2 from the axis x to the inner circumferential end 21a of each conductive piece 21 is larger than the radius R0 of the shaft by the clearance δ.

[0037] As shown in Figures 6 and 7, the contact surface 24 of the conductive member 20 extends, for example, along a plane perpendicular to the axis x. Specifically, the contact surface 24 extends, for example, along a plane perpendicular to the axis x or a substantially plane. Also, as shown in Figures 6 and 7, the pressed surface 25 of the conductive member 20 extends, for example, along a plane perpendicular to the axis x. Specifically, the pressed surface 25 extends, for example, along a plane perpendicular to the axis x or a substantially plane. Each of the multiple conductive pieces 21 and the base 22 has a part of the contact surface 23 and the pressed surface 25, and the multiple conductive pieces 21 and the base 22 are connected flush. The thickness T1 of the conductive member 20 is a predetermined size. The thickness T1 of the conductive member 20 is, for example, constant or substantially constant throughout the entire conductive member 20. Note that the thickness T1 of the conductive member 20 is the distance between the contact surface 23 and the pressed surface 25.

[0038] As described above, the conductive member 20 has a plurality of conductive pieces 21 arranged in the circumferential direction at its inner circumferential end 20a, with a gap 23 formed between two adjacent conductive pieces 21. In this way, the inner circumferential end 20a of the conductive member 20 is divided into multiple parts along the circumferential direction. This reduces the tension force that the conductive member 20 exerts on the shaft even when the shaft is passed through the inside of the conductive member 20 and the conductive member 20 deforms during use, as described later. The tension force is the force that tightens the shaft 110. The magnitude of the tension force that the conductive member 20 exerts on the shaft corresponds to the number of conductive pieces 21. Therefore, the number of conductive pieces 21 corresponds, for example, to the magnitude of the tension force that the conductive member 20 exerts on the shaft.

[0039] Furthermore, the magnitude of the tension force that the conductive member 20 itself exerts on the shaft can be adjusted by adjusting the width W1, length L1, and thickness T2 of each conductive piece 21. For this reason, the width W1, length L1, and thickness T2 of each conductive piece 21 are set to values ​​such that, for example, the magnitude of the tension force that the conductive member 20 itself exerts on the shaft becomes a predetermined magnitude when the conductive ring 1 is in use.

[0040] The conductive member 20 has the configuration described above and is integrally formed from a conductive material. That is, the plurality of conductive pieces 21 and the base portion 22 are parts of the integrally formed conductive member 20, and the plurality of conductive pieces 21 and the base portion 22 are integrated with each other. The conductive material forming the conductive member 20 is, for example, a material obtained by adding a conductive material to a base material that forms the conductive member 20, specifically, conductive PTFE (polytetrafluoroethylene) having conductivity. Conductive PTFE is obtained by adding a conductive material to PTFE (polytetrafluoroethylene) serving as a base material. Note that the base material of the conductive member 20 is not limited to PTFE. The base material of the conductive member 20 may be, for example, other resins, rubber, fibers such as non-woven fabric, etc., and the material of the conductive member 20 may be obtained by adding a conductive material to these base materials. Examples of the conductive material added to the base material include conductive particles such as carbon and metal powder.

[0041] The spring member 30 is provided side by side with the conductive member 20 in the axial x direction in the conductive ring 1. Further, the spring piece 31 of the spring member 30 is elastically deformed along the axis x, and generates an elastic force in a direction toward the axis x. Note that the direction toward the axis x is not limited to a direction toward the inner circumferential side in the radial direction, and may be any direction having a component in the direction toward the inner circumferential side in the radial direction. The spring member 30 is, for example, annular around the axis x. Specifically, the spring member 30 is an annular leaf spring. In the use state of the conductive ring 1 described later, when the plurality of spring pieces 31 are elastically deformed, the plurality of conductive pieces 21 of the conductive member 20 are pressed against the outer peripheral surface 110a (see FIG. 10) of the shaft 110, so that the plurality of conductive pieces 21 can generate an elastic force that provides a predetermined tightening force to the shaft 110. In this way, the plurality of spring pieces 31 cooperate with the plurality of conductive pieces 21, so that the plurality of conductive pieces 21 generate a predetermined tightening force on the shaft 110.

[0042] The spring member 30 is, for example, an annular plate-shaped member around an axis x, as shown in Figures 1 to 7, and has a pair of annular surfaces, a pressing side 34 and a back surface 35, which are opposite to each other in the direction of the axis x, as shown in Figures 3, 6, and 7. The pressing side 34 faces the front side, and the back surface 35 faces the back side. As described above, the spring member 30 has a plurality of spring pieces 31 at the inner circumference end 30a, which is the inner circumference end, and also has an annular base portion 32. The base portion 32 is the part of the spring member 30 that is on the outer circumference side of the spring pieces 31, as shown in Figures 3, 6, and 7. A plurality of spring pieces 31 extend inward from the inner circumference end 32a, which is the inner circumference end of the base portion 32. The base portion 32 is, for example, an annular plate-shaped portion around an axis x, as shown in Figures 3, 6, and 7, and the inner circumferential end 32a extends, for example, along a cylindrical surface with axis x as its central axis. Specifically, for example, the inner circumferential end 32a extends on a cylindrical surface or a substantially cylindrical surface with axis x as its central axis. The outer circumferential end 32b also extends, for example, along a cylindrical surface with axis x as its central axis, and specifically, for example, the outer circumferential end 32b extends on a cylindrical surface or a substantially cylindrical surface with axis x as its central axis. The outer circumferential end 32b is the outer-circumferential end of the base portion 32, and specifically, it is the end face facing the outer circumference of the base portion 32.

[0043] Figure 9 is a partially enlarged front view showing an enlarged portion of the spring member 20. As shown in Figures 2, 5, and 9, the multiple spring pieces 31 are arranged at intervals from each other in the circumferential direction. As shown in Figure 9, the spring piece 31 has, for example, a rectangular or substantially rectangular plate shape and has an inner circumferential end 31a, which is the inner circumferential end, a pair of circumferential ends 31b and 31c, and an outer circumferential end 31d, which is the outer circumferential end. Specifically, the inner circumferential end 31a is an end face facing the inner circumferential side, and specifically, the circumferential ends 31b and 31c are end faces facing the circumferential direction. The circumferential ends 31b and 31c face away from each other in the circumferential direction. Specifically, the outer circumferential end 31d is the boundary between the spring piece 31 and the base 32, and the spring piece 31 is connected to the inner circumferential end 32a of the base 32 at the outer circumferential end 31d. The outer peripheral end 31d of the spring piece 31 and the inner peripheral end 32a of the base portion 32 are located at a predetermined distance R3 in the radial direction from the axis x.

[0044] An inner circumferential end 31a of the spring piece 31 extends along, for example, a plane orthogonal to the radial direction, and the inner circumferential end 31a is located at a position separated by a distance R4, which is a predetermined distance in the radial direction from the axis x. Side ends 31b and 31c of the spring piece 31 extend along the radial direction, for example. Specifically, the side ends 31b and 31c of the spring piece 31 extend on a plane or substantially plane including the axis x, for example. A width W3, which is the circumferential width of the spring piece 31, has a predetermined dimension. Note that the width W3 of the spring piece 31 is the distance between the side surface 31b and the side surface 31c. The width W3 of the spring piece 31 is equal to or less than the width W1 of the conductive piece 21 (W3 ≤ W1). As an example, as shown in Fig. 5, the width W3 of the spring piece 31 is smaller than the width W1 of the conductive piece 21. Specifically, for example, the width W3 of the spring piece 31 is smaller than the width W1 of the entire conductive piece 21. Further, as shown in Fig. 9, a length L2, which is the length of the spring piece 31, is a predetermined length. Note that the length L2 of the spring piece 31 is the radial distance between the inner circumferential end 31a and an outer circumferential end 31d. Further, a thickness T2, which is the thickness of the spring piece 31 (see Fig. 3), has a predetermined dimension. The thickness T2 of the spring piece is, for example, constant or substantially constant over the entire spring piece 31. Note that the thickness T2 of the spring piece 31 is the distance between a pressing side surface 34 and a back surface 35 of the spring piece 31.

[0045] As described above, the spring piece 31 is configured to elastically deform along the axis x, and specifically, as described later, in a usage state of the conductive ring 1, the spring piece 31 presses the deformed conductive piece 21 toward the axis x. The width W3, length L2, and thickness T2 of the spring piece 31 are set to values such that, for example, the deformed conductive piece 21 is pressed toward the axis x with a predetermined force in the usage state of the conductive ring 1.

[0046] As described above, the multiple spring pieces 31 are arranged in the circumferential direction, and as shown in Figures 5 and 9, a space 33 is formed between two adjacent spring pieces 31 in the circumferential direction. The space 33 is defined between two adjacent spring pieces 31 in the circumferential direction by the side end 31b of one spring piece 31, the side end 31c of the other spring piece 31, and the inner circumferential end 32a of the base portion 32 extending between these two spring pieces 31. As shown in Figure 9, the width W4 of the space 33 in the circumferential direction is a predetermined size. The width W4 of the space 33 is the distance between the side end 31b of one spring piece 31 and the side end 31c of the other spring piece 31 between two adjacent spring pieces 31. The width W4 of the space 33 is wider than the width W2 of the gap 23 of the conductive member 20.

[0047] The widths W3 of the multiple spring pieces 31 are all the same or approximately the same, and the widths W4 of the multiple spaces 33 are all the same or approximately the same. Therefore, in the spring member 30, the multiple spring pieces 31 are arranged at equal or approximately equal angular intervals around the axis x, and the multiple spaces 33 are arranged at equal or approximately equal angular intervals around the axis x. Note that the widths W3 of the multiple spring pieces 31 do not have to be the same, and the widths W4 of the multiple spaces 33 do not have to be the same. Also, in the spring member 30, the multiple spring pieces 31 do not have to be arranged at equal angular intervals around the axis x, and the multiple spaces 33 do not have to be arranged at equal angular intervals around the axis x.

[0048] Furthermore, as shown in Figure 7, in the conductive ring 1, the outer peripheral ends 31d of the multiple spring pieces 31 are located further outward than the outer peripheral ends 21d of the multiple conductive end pieces 21. In other words, the radius R3 of the inner peripheral end 32a of the base 32 of the spring member 30 is larger than the radius R1 of the inner peripheral end 22a of the base 22 of the conductive member 20.

[0049] As shown in Figure 5, the inner ends 31a of the multiple spring pieces 31 are aligned along a circle centered on axis x, for example, when viewed in the direction of axis x. Specifically, for example, the inner ends 31a of the multiple spring pieces 31 are located on a circle or approximately a circle centered on axis x, and the distance R4 from axis x to each of the inner ends 31a of the multiple spring pieces 31 is the same or approximately the same. In other words, the inner ends 31a of the multiple spring pieces 31 are located on a circle with radius R4 or approximately a circle with radius R4 centered on axis x, when viewed in the direction of axis x.

[0050] As shown in Figures 6 and 7, the pressing surface 34 of the spring member 30 is, for example, aligned with a plane perpendicular to the axis x. Specifically, the pressing surface 34 extends on a plane perpendicular to the axis x or a substantially flat plane. Also, as shown in Figures 6 and 7, the back surface 35 of the spring member 30 is, for example, aligned with a plane perpendicular to the axis x. Specifically, the back surface 35 extends on a plane perpendicular to the axis x or a substantially flat plane. Each of the multiple spring pieces 31 and the base 32 has a portion of the pressing surface 34 and the back surface 35, and the multiple spring pieces 31 and the base 32 are connected flush with each other.

[0051] As shown in Figures 6 and 7, the spring member 30 is shaped to overlap the conductive member 20 in the axial x direction. For example, the base 32 of the spring member 30 is the same or approximately the same shape and size as the portion of the base 22 of the conductive member 20 from the outer peripheral end 22b to the vicinity of the inner peripheral end 22a, so that the outer peripheral end 32b of the base 32 of the spring member 30 and the outer peripheral end 22b of the base 22 of the conductive member 20 coincide or approximately coincide with each other, so that the spring member 30 and the conductive member 20 overlap.

[0052] Furthermore, as shown in Figures 5 to 7, in the conductive member 1, each of the multiple spring pieces 31 is in contact with each of the multiple conductive pieces 21. Specifically, the number of multiple spring pieces 31 is equal to the number of multiple conductive pieces 21, and one of the multiple spring pieces 31 corresponds to one of the multiple conductive pieces 21. Each spring piece 31 is in contact with the corresponding conductive piece 21, and specifically, the pressing surface 34 of each spring piece 31 is in contact with the pressed surface 25 of the corresponding conductive piece 21. The distance R4 from the axis x of the inner circumferential end 31a of the spring piece 31, the length L2 of the spring piece 31, and the width W4 of the space 33, which is the width between two adjacent spring pieces 31 in the circumferential direction, are set so that each spring piece 31 is in contact with the corresponding conductive piece 21.

[0053] As described above, in the conductive ring 1, the outer peripheral end 31d of the spring piece 31 is located further outward than the outer peripheral end 21d of the conductive piece 21, and the spring piece 31 extends from near the inner peripheral end 22a of the base portion 22 of the conductive member 20, beyond the inner peripheral end 22a, to the conductive piece 21. For example, the spring piece 31 extends to a position closer to the outer peripheral end 22d than the radial center of the conductive piece 21, and the inner peripheral end 31a of the spring piece 31 is located closer to the outer peripheral end 22d than the radial center of the conductive piece 21. Note that the spring piece 31 is not limited to extending to a position closer to the outer peripheral end 22d than the radial center of the conductive piece 21. For example, the spring piece 31 may extend to the radial center or near the center of the conductive piece 21, or it may extend to a position closer to the inner peripheral end 21a than the radial center of the conductive piece 21. Thus, the radius R4 of the inner circumferential end 31a of the spring piece 31 is larger than the radius R2 of the inner circumferential end 21a of the conductive piece 21, and smaller than the radius R1 of the outer circumferential end 21d of the conductive piece 21. However, the radius R4 of the inner circumferential end 31a of the spring piece 31 may be the same as, or smaller than, the radius R2 of the inner circumferential end 21a of the conductive piece 21. For example, in the usage state of the conductive ring 1 described later, the radius R4 of the inner circumferential end 31a of the spring piece 31 may be smaller than the radius R2 of the inner circumferential end 21a of the conductive piece 21, in the range where the spring piece 31 does not contact the shaft.

[0054] Furthermore, as shown in Figure 5, the spring piece 31 is positioned to contact, for example, the center or approximate center of the conductive piece 21 in the circumferential direction, and the spring piece 31 is positioned to contact the conductive piece 21 on the inside of the side ends 21b and 21c in the circumferential direction. In other words, the width W2 of the spring piece 31 is smaller than the width W1 of the conductive piece 21 (W2 < W1). Note that the position in the circumferential direction where the spring piece 31 contacts the conductive piece 21 is not limited to the position described above. Also, the width W2 of the spring piece 31 is not limited to being smaller than the width W1 of the conductive piece 21.

[0055] The spring member 30 has the configuration described above, and its inner circumferential end 30a is comb-shaped by a plurality of spring pieces 31. The spring member 30 is integrally formed from an elastic material. That is, the plurality of spring pieces 31 and the base 32 are part of the integrally formed spring member 31, and the plurality of spring pieces 31 and the base 32 are integral. The elastic material forming the spring member 30 is, for example, a metal. The metal forming the spring member 30 is, for example, stainless steel. However, the elastic material forming the spring member 30 is not limited to a metal, and may be, for example, a polymer material.

[0056] As shown in Figures 1 to 7, the holding member 10 specifically includes an inner holding member 11 located on the inside and an outer holding member 15 located on the outside. The inner holding member 11 and the outer holding member 15 are annular members around an axis x, and are configured to hold the conductive member 20 and the spring member 30 stacked between them.

[0057] As shown in Figures 1, 3, 4, 6, and 7, the internal retaining member 11 has, for example, a fitting portion 12 which is an annular portion around axis x, and a retaining portion 13 which is an annular portion around axis x. The fitting portion 12 is a cylindrical portion extending along axis x, and the retaining portion 13 is an annular portion extending inward from the front end of the fitting portion 12. The fitting portion 12 is, for example, cylindrical or substantially cylindrical with axis x as its central axis or substantially its central axis.

[0058] As shown in Figures 2, 3, 5 to 7, the outer retaining member 15 has, for example, a fitting portion 16 which is an annular portion around axis x, and a retaining portion 17 which is an annular portion around axis x. The fitting portion 16 is a cylindrical portion extending along axis x, and the retaining portion 17 is an annular portion extending inward from the front end of the fitting portion 16. The fitting portion 16 is, for example, cylindrical or substantially cylindrical with axis x as its central axis or substantially its central axis.

[0059] As shown in Figures 6 and 7, the inner retaining member 11 and the outer retaining member 15 are designed to be fitted together. Specifically, for example, the diameter of the outer peripheral surface 12a of the fitting portion 12 of the inner retaining member 11 is smaller than the diameter of the inner peripheral surface 16a of the fitting portion 16 of the outer retaining member 15. The fitting portion 12 of the inner retaining member 11 is inserted into the inner peripheral side of the fitting portion 16 of the outer retaining member 15, so that the fitting portion 12 of the inner retaining member 11 and the fitting portion 16 of the outer retaining member 15 are fitted together in a clearance fit. The outer peripheral surface 12a of the fitting portion 12 is an annular surface facing the outer peripheral side of the fitting portion 12, and the inner peripheral surface 16a of the fitting portion 16 is an annular surface facing the inner peripheral side of the fitting portion 16. Furthermore, as shown in Figures 6 and 7, when the fitting portion 12 of the inner retaining member 11 and the fitting portion 16 of the outer retaining member 15 are assembled together, the retaining portion 13 of the inner retaining member 11 and the retaining portion 17 of the outer retaining member 15 have portions that face each other in the axial x direction. The diameter of the outer circumferential surface 12a of the fitting portion 12 of the inner retaining member 11 may be larger than the diameter of the inner circumferential surface 16a of the fitting portion 16 of the outer retaining member 15, and the fitting portion 12 and the fitting portion 16 may be fitted together in an interference fit. Also, the diameter of the outer circumferential surface 12a of the fitting portion 12 and the diameter of the inner circumferential surface 16a of the fitting portion 16 may be the same.

[0060] Furthermore, as shown in Figures 6 and 7, when the inner retaining member 11 and the outer retaining member 15 are assembled together, the retaining portion 13 of the inner retaining member 11 and the retaining portion 17 of the outer retaining member 15 face the conductive member 20 and the spring member 30 which are stacked on top of each other in the axial x direction. Specifically, the entire back surface 35 of the base portion 32 of the spring member 30 faces the retaining portion 13 of the inner retaining member 11, and the entire contact surface 21 of the base portion 22 of the conductive member 20 faces the retaining portion 17 of the outer retaining member 15. Furthermore, in the conductive ring 1, as shown in Figures 6 and 7, the portion of each conductive piece 21 of the conductive member 20 from a position on the inner circumference side of the outer circumference end 21d to the inner circumference end 21a is located on the inner circumference side of the holding portion 17 of the outer holding member 15. Similarly, the portion of each spring piece 31 of the spring member 30 from a position on the inner circumference side of the outer circumference end 31d to the inner circumference end 31a is located on the inner circumference side of the holding portion 13 of the inner holding member 11. In other words, the inner circumference end 17a of the holding portion 17 is located on the inner circumference side of the inner circumference end 22a of the base portion 22 of the conductive member 20 in the radial direction, and the distance R5 of the inner circumference end 17a of the holding portion 17 from the axis x is smaller than the distance R1 of the inner circumference end 22a of the base portion 22 of the conductive member 20 (R5 < R1). Furthermore, the inner circumference end 13a of the retaining portion 13 is located radially further inward than the inner circumference end 32a of the base portion 32 of the spring member 30. The distance R6 of the inner circumference end 13a of the retaining portion 13 from the axis x is smaller than the distance R3 of the inner circumference end 32a of the base portion 32 of the spring member 30 (R6 < R3).

[0061] The radial position of the inner circumferential end 13a of the retaining portion 13 relative to the conductive piece 21, that is, the relationship between distance R6 and distance R2, is related to the magnitude of the pressing force toward the axis x generated by the deformed conductive piece 21 when the conductive ring 1 is in use. For this reason, the distance R6 of the inner circumferential end 13a of the retaining portion 13 is set to a value such that the pressing force generated by the deformed conductive piece 21 is of a predetermined magnitude when the conductive ring 1 is in use.

[0062] Furthermore, the radial position of the inner circumferential end 13a of the retaining portion 13 relative to the spring piece 31, that is, the relationship between distance R6 and distance R4, is related to the magnitude of the pressing force toward the axis x generated by the deformed spring piece 31 when the conductive ring 1 is in use. For this reason, the distance R6 of the inner circumferential end 13a of the retaining portion 13 is set to a value such that the pressing force generated by the deformed spring piece 31 is of a predetermined magnitude when the conductive ring 1 is in use.

[0063] The inner circumferential end 17a of the retaining portion 17 may be located at the same position in the radial direction as the inner circumferential end 22a of the base portion 22 of the conductive member 20 (R5 = R1). Alternatively, the inner circumferential end 17a of the retaining portion 17 may be located on the outer circumference side of the inner circumferential end 22a in the radial direction (R5 > R1). In this case, a part of the contact surface 21 of the base portion 22 of the conductive member 20 faces the retaining portion 17. Similarly, the inner circumferential end 13a of the retaining portion 13 may be located at the same position in the radial direction as the inner circumferential end 32a of the base portion 32 of the spring member 30 (R6 = R3). Alternatively, the inner circumferential end 13a of the retaining portion 13 may be located on the outer circumference side of the inner circumferential end 32a in the radial direction (R6 > R3). In this case, a part of the back surface 35 of the base portion 32 of the spring member 30 faces the retaining portion 13.

[0064] As shown in Figures 6 and 7, the inner retaining member 11 and the outer retaining member 15 are assembled, and the conductive member 20 and the spring member 30, which are stacked on top of each other, are sandwiched between the retaining portion 13 of the inner retaining member 11 and the retaining portion 17 of the outer retaining member 15 at their respective base portions 22 and 32, and pressed in the axial x direction. A pressing portion 18 is formed on the fitting portion 16 of the outer retaining member 15, and the inner retaining member 11 is fixed to the outer retaining member 15. The pressing portion 18 of the outer retaining member 15 is the part that contacts the fitting portion 12 of the inner retaining member 11 and fixes the fitting portion 12 to the fitting portion 16 in the axial x direction. In this way, the conductive member 20 and the spring member 30, which are stacked on top of each other, are fixed between the inner retaining member 11 and the outer retaining member 15 (hereinafter also referred to as the "assembled state").

[0065] The inner retaining member 11 and the outer retaining member 15 are made of a conductive metal. However, the inner retaining member 11 and the outer retaining member 15 may be made of other conductive materials.

[0066] Each component of the conductive ring 1 has the configuration described above, and when assembled, it becomes the conductive ring 1 shown in Figures 1, 2, 4 to 7. In the conductive ring 1, the fitting portion 12 of the inner holding member 11 is fitted into the fitting portion 16 of the outer holding member 15, and the fitting portion 12 of the inner holding member 11 is pressed toward the front by the pressing portion 18 of the fitting portion 16 of the outer holding member 15. The conductive member 20 and the spring member 30, which are stacked on top of each other, are sandwiched between the holding portion 13 of the inner holding member 11 and the holding portion 17 of the outer holding member 15. The conductive member 20 and the spring member 30 are stacked on top of each other such that the pressed side surface 25 of the conductive member 20 is in contact with the pressing side surface 35 of the spring member 30. The conductive member 20 and the spring member 30 are held by the inner holding member 11 and the outer holding member 15 at the base portion 22 and base portion 32, respectively. As described above, the inner retaining member 11 is fixed to the outer retaining member 15, and the conductive member 20 and the spring member 30 are fixed between the inner retaining member 11 and the outer retaining member 15. Furthermore, the conductive member 20 and the spring member 30 are attached to the inner retaining member 11 and the outer retaining member 15, respectively, so that the contact surface 21 of the conductive member 20 contacts the shaft in the usage state described later. As shown in Figures 1 to 7, the conductive member 20 and the spring member 30 are attached to the inner retaining member 11 and the outer retaining member 15, respectively, so that the contact surface 21 of the conductive member 20 faces the front side. However, the conductive member 20 and the spring member 30 may also be attached to the inner retaining member 11 and the outer retaining member 15, respectively, so that the contact surface 21 of the conductive member 20 faces the back side.

[0067] Furthermore, in the assembled conductive ring 1, as described above, each spring piece 31 is in contact with the corresponding conductive piece 21. Specifically, the pressing surface 34 of each spring piece 31 is in contact with the pressed surface 25 of the corresponding conductive piece 21. Each spring piece 31 extends from the vicinity of the inner circumferential end 22a of the base portion 22 of the conductive member 20, beyond the inner circumferential end 22a, to the corresponding conductive piece 21. As an example, as shown in Figures 1 to 7, the spring piece 31 extends to the vicinity of the outer circumferential end 22d of the conductive piece 21, and the inner circumferential end 31a of the spring piece 31 is located near the outer circumferential end 22d of the conductive piece 21, and is located to the vicinity of the radial center of the conductive piece 21. Also, the spring piece 31 is located at or approximately at the circumferential center of the conductive piece 21 and is in contact with or approximately at the circumferential center of the conductive piece 21.

[0068] Before reaching the assembled state shown in Figures 1, 2, 4 to 7, the fitting portion 16 of the outer retaining member 15 does not necessarily have a pressing portion 18. For example, the conductive member 20 and the spring member 30, which are superimposed on each other, may be attached to the outer retaining member 15, which does not have a pressing portion 18 formed on the fitting portion 16. After that, the fitting portion 12 of the inner retaining member 11 may be attached to the fitting portion 16 of the outer retaining member 15, and then the pressing portion 18 may be formed on the fitting portion 16. In other words, by forming the pressing portion 18, the fitting portion 12 and the fitting portion 16 are crimped together, and the end of the fitting portion 12 is pressed to the front by the pressing portion 18, thereby assembling the conductive member 20, the spring member 30, the inner retaining member 11, and the outer retaining member 15 as shown in Figures 1 to 7.

[0069] The clamping allowance δ of the conductive piece 21 is, as shown in Figure 7, the radial width of the conductive piece 21 of the conductive member 20 of the conductive ring 1 in its assembled state, that is, in a free state where no external force is applied to the conductive member 20 and the spring member 30, from the inner circumferential end 21a to a position radially away from the axis x by a distance of radius R0 of the axis 110. When the conductive piece 21 deteriorates due to use in the usage state described later, the conductive piece 21 undergoes plastic deformation, and in a free state where no external force is applied to the conductive member 20 and the spring member 30, the conductive piece 21 becomes curved so that the inner circumferential end 21a is displaced in the axis x direction, and the position of the inner circumferential end 21a of the conductive piece 21 is displaced radially toward the outer circumference. For this reason, when the conductive piece 21 deteriorates and deforms, the clamping allowance δ of the conductive piece 21 decreases.

[0070] As described later, the conductive ring 1 is installed between the shaft and the hole through which the shaft is inserted when in use. Specifically, the conductive ring 1 is installed in the annular gap formed in the hole through which the shaft is inserted. When in use, the conductive member 20 forms a conductive path between the shaft and the outer member, which is the member through which the shaft is inserted. The impedance Z of the conductive path between the shaft and the outer member formed by the conductive member 20 is related to the clamping allowance δ of the conductive piece 21. When the clamping allowance δ of the conductive piece 21 decreases, the conductive path becomes an unstable path, and the impedance Z increases. Also, the tensioning force of the conductive member 20 on the shaft is related to the clamping allowance δ. Therefore, the impedance Z is related to the tensioning force of the conductive member 20 on the shaft. When the pressing force of the conductive piece 21 decreases, the tensioning force of the conductive member 20 on the shaft decreases, the clamping allowance δ decreases, and the impedance Z increases. Therefore, when the conductive piece 21 deteriorates and deforms, the impedance Z of the conductive member 20 increases.

[0071] As described above, in the conductive ring 1, when the sliding distance D of the shaft 110 relative to the conductive member 20 reaches a predetermined required sliding distance D1, the impedance Z becomes a predetermined impedance Z1. The required sliding distance D1 is, for example, a value corresponding to the diameter of the shaft 110. Specifically, the required sliding distance D1 is a predetermined multiple of the diameter Φ0 of the shaft 110. Specifically, for example, the required sliding distance D1 is 175 × 10⁻¹⁰ of the diameter Φ0 of the shaft 110.７ The conductive ring 1 is configured such that when the shaft 110 slides over the required sliding distance D1, the impedance Z1 of the conductive member 20 is 80Ω or less (Z1 ≤ 80Ω). Specifically, for example, the required sliding distance D1 is 175 × 10 of the diameter Φ0 of the shaft 110. ７ The conductive ring 1 is configured such that when the shaft 110 slides along the required sliding distance D1, the impedance Z1 of the conductive member 20 is 50Ω or less (Z1 ≤ 50Ω).

[0072] For example, the number of conductive pieces 21 in the conductive member 20 and the number of spring pieces 31 in the spring member 30 are set based on the impedance Z1 when the sliding distance D of the shaft 110 relative to the conductive member 20 becomes a predetermined required sliding distance D1. In other words, by setting the number of conductive pieces 21 in the conductive member 20 and the number of spring pieces 31 in the spring member 30 to a predetermined number, the impedance Z1 when the required sliding distance D1 is reached can be set to a predetermined value.

[0073] Furthermore, for example, the shape of each conductive piece 21 of the conductive member 20 and the shape of each spring piece 31 of the spring member 30 are set based on the impedance Z1 when the sliding distance D of the shaft 110 relative to the conductive member 20 becomes a predetermined required sliding distance D1. In other words, by setting the shape of each conductive piece 21 and the shape of each spring piece 31 to a predetermined shape, the impedance Z1 when the required sliding distance D1 is reached can be set to a predetermined value.

[0074] The form of the conductive piece 21 for setting the impedance Z1 is, for example, at least one of the thickness T1, width W1, and length L1 of the conductive piece 21, and the form of the spring piece 31 for adjusting the interference fit δ1 is, for example, at least one of the thickness T2, width W2, and length L2 of the spring piece 31.

[0075] Furthermore, as described above, the radial position of the inner circumferential end 13a of the retaining portion 13 relative to the conductive piece 21 is related to the magnitude of the pressing force generated on the deformed conductive piece 21. For this reason, for example, the distance R6 of the inner circumferential end 13a of the retaining portion 13 relative to the distance R1 of the outer circumferential end 21d of the conductive piece 21 is set based on the impedance Z when the sliding distance D of the shaft 110 relative to the conductive member 20 becomes a predetermined required sliding distance D1. In other words, by setting the distance R6 of the inner circumferential end 13a of the retaining portion 13 relative to the distance R1 of the outer circumferential end 21d of the conductive piece 21 to a predetermined value, the impedance Z1 when the required sliding distance D1 is reached can be set to a predetermined value.

[0076] Furthermore, as described above, the radial position of the inner circumferential end 13a of the retaining portion 13 relative to the spring piece 31 is related to the magnitude of the pressing force generated on the deformed spring piece 31. For this reason, for example, the distance R6 of the inner circumferential end 13a of the retaining portion 13 relative to the distance R3 of the outer circumferential end 31d of the spring piece 31 is set based on the impedance Z1 when the sliding distance D of the shaft 110 relative to the conductive member 20 becomes a predetermined required sliding distance D1. In other words, by setting the distance R6 of the inner circumferential end 13a of the retaining portion 13 relative to the distance R3 of the outer circumferential end 31d of the spring piece 31 to a predetermined value, the impedance Z1 when the required sliding distance D1 is reached can be set to a predetermined value.

[0077] As described above, by adjusting at least one of the following: the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive pieces 21, the width W1 of the conductive pieces 21, the length L1 of the conductive pieces 21, the thickness T2 of the spring pieces 31, the width W2 of the spring pieces 31, the length L2 of the spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining portion 13, the impedance Z1 when the required sliding distance D1 is reached can be adjusted to a predetermined value. In the conductive ring 1, the impedance Z1 when the required sliding distance D1 is reached is a predetermined value, and the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive pieces 21, the width W1 of the conductive pieces 21, the length L1 of the conductive pieces 21, the thickness T2 of the spring pieces 31, the width W2 of the spring pieces 31, the length L2 of the spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining portion 13 are set to predetermined values ​​so that the impedance Z1 when the required sliding distance D1 is reached is a predetermined value.

[0078] The required sliding distance D1 is set, for example, based on the durability required of the conductive ring 1. Specifically, for example, the required sliding distance D1 is set, for example, based on the required lifespan of the conductive ring 1. The lifespan of the conductive ring 1 can be converted to the sliding distance of the shaft using various conversion methods. For example, by calculating the average rotational speed of the shaft during the operating time of the conductive ring 1, the lifespan can be converted to the sliding distance of the shaft based on this average rotational speed.

[0079] Furthermore, the setting of the impedance Z1 when the required sliding distance D1 is reached is, for example, based on the impedance between the conductive piece 21 and the shaft 110 so that the conductive performance of the conductive passage formed by the conductive ring 1 is maintained at the desired conductive performance when the required sliding distance D1 is reached. The impedance Z that allows the conductive performance of the conductive passage formed by the conductive ring 1 to be maintained at the desired conductive performance is, for example, 80 Ω or less (Z ≤ 80 Ω) and also 50 Ω or less (Z ≤ 50 Ω).

[0080] Furthermore, in order to set the impedance Z to impedance Z1 when the required sliding distance D1 is reached, the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of conductive pieces 21, the width W2 of conductive pieces 31, the length L2 of spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining part 13 are set to predetermined values ​​by adjusting at least one of the following: the length L1 of conductive pieces 21, the thickness T1 of spring pieces 21, the width W1 of conductive pieces 21, the length L1 of conductive pieces 21, the thickness T2 of spring pieces 31, the width W2 of spring pieces 31, the length L2 of spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining part 13.

[0081] For example, a conductive ring 1 is created in which the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive piece 21, the width W1 of the conductive piece 21, the length L1 of the conductive piece 21, the thickness T2 of the spring piece 31, the width W2 of the spring piece 31, the length L2 of the spring piece 31, and the distance R6 of the inner circumference end 13a of the holding part 13 are set to predetermined values. A durability test is then performed on this ring until the sliding distance D becomes the required sliding distance D1, and the impedance Z is measured when the required sliding distance D1 is reached. If the impedance Z is not impedance Z1 when the required sliding distance D1 is reached, at least one of the following is changed: the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive piece 21, the width W1 of the conductive piece 21, the length L1 of the conductive piece 21, the thickness T2 of the spring piece 31, the width W2 of the spring piece 31, the length L2 of the spring piece 31, and the distance R6 of the inner circumference end 13a of the retaining part 13. A conductive ring 1 is then created with one of these values ​​changed, and a durability test is performed on it until the sliding distance D becomes the required sliding distance D1. The impedance Z is then measured when the required sliding distance D1 is reached. The number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive pieces 21, the width W1 of the conductive pieces 21, the length L1 of the conductive pieces 21, the thickness T2 of the spring pieces 31, the width W2 of the spring pieces 31, the length L2 of the spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining part 13 are adjusted until the impedance Z1 at the required sliding distance D1 becomes impedance Z1. This process is repeated, the adjusted conductive ring 1 is created, and the created conductive ring 1 is subjected to durability testing. Through this process, the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive pieces 21, the width W1 of the conductive pieces 21, the length L1 of the conductive pieces 21, the thickness T2 of the spring pieces 31, the width W2 of the spring pieces 31, the length L2 of the spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining part 13 are set so that the impedance Z1 at the required sliding distance D1 becomes a predetermined value.

[0082] Furthermore, the setting of the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive piece 21, the width W1 of the conductive piece 21, the length L1 of the conductive piece 21, the thickness T2 of the spring piece 31, the width W2 of the spring piece 31, the length L2 of the spring piece 31, and the distance R6 of the inner circumference end 13a of the holding part 13 is not limited to actually creating the conductive ring 1 and conducting durability tests as described above. These values ​​may also be set using computer analysis or simulation without actually creating the conductive ring 1 or conducting durability tests. In this case, various data such as data obtained from recalled products may be used. Also, impedance Z can be measured by various methods. For example, impedance Z can be measured using the automatic balanced bridge method.

[0083] As an example, the required sliding distance D1 is 175 × 10 of the diameter Φ0 of the shaft 110. ７ It is set to double, and in the conductive ring 1, when the required sliding distance D1 is reached, the impedance Z1 of the conductive member 20 is 80Ω or less (Z1 ≤ 80Ω). Also, as an example, the required sliding distance D1 is 175 × 10 of the diameter Φ0 of the shaft 110. ７ The impedance is set to double, and in the conductive ring 1, the impedance Z1 of the conductive member 20 when the required sliding distance D1 is reached is 50 Ω or less (Z1 ≤ 50 Ω). For this reason, in the conductive ring 1, the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive piece 21, the width W1 of the conductive piece 21, the length L1 of the conductive piece 21, the thickness T2 of the spring piece 31, the width W2 of the spring piece 31, the length L2 of the spring piece 31, and the distance R6 of the inner circumference end 13a of the holding part 13 are set to predetermined values ​​so that the impedance Z1 when the required sliding distance D1 is reached is 80 Ω or less (Z1 ≤ 80 Ω) or 50 Ω or less (Z1 ≤ 50 Ω).

[0084] Next, the operation of the conductive ring 1 will be explained. Figure 10 is a conceptual diagram showing an example of an application target of the conductive ring 1. Figure 11 is a cross-sectional view showing an example of the usage state of the conductive ring 1 in the application target shown in Figure 10. As an example, the conductive ring 1 is applied to the drive unit 100 of a battery electric vehicle (BEV), as shown in Figure 10. 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 10. 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 of 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 of 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.

[0085] The conductive ring 1 is installed, for example, between the housing 111 and the shaft 110 of an electric motor 101, and is in use. Specifically, as shown in Figure 11, the fitting portion 16 of the outer holding member 15 of the holding member 10 is fitted into the shaft hole 113 of the housing 111, fixing the conductive ring 1 in the shaft hole 113, and the shaft 110 is inserted into the conductive member 20, so that the conductive ring 1 is in use. In use, the contact surfaces 24 of the multiple conductive pieces 21 of the conductive member 20 are in contact with the outer circumferential surface 110a of the shaft 110, and the multiple conductive pieces 21 of the conductive member 20 are deformed by being pushed outward by the shaft 110. As shown in Figure 11, the multiple conductive pieces 21 of the conductive member 20 have a width in the axial x direction corresponding to the overlap δ of the conductive pieces 21 and are in contact with the outer circumferential surface 110a of the shaft 110. Furthermore, the retaining members 10 (inner retaining member 11 and outer retaining member 15) to which the conductive member 20 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 20 and the retaining members 10 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.

[0086] As described above, in the operating state, the multiple conductive pieces 21 of the conductive member 20 are deformed by being pressed outward by the shaft 110. As a result, a reaction force is generated on each of the multiple conductive pieces 21 that presses against the shaft 110, and the multiple conductive pieces 21 generate a tightening force that grips the shaft 110.

[0087] Furthermore, as shown in Figure 10, each of the multiple spring pieces 31 of the spring member 30 overlaps with the multiple conductive pieces 21 of the conductive member 20 from the back side, and the pressing side surface 34 of each spring piece 31 is in contact with the pressed side surface 25 of the corresponding conductive piece 21. As described above, in the operating state, the multiple conductive pieces 21 are deformed by the reaction force from the shaft 110 toward the outer circumference, and each of the multiple spring pieces 31 is also deformed by the force directed toward the outer circumference from the shaft 110 via the corresponding conductive piece 21. As described above, the multiple spring pieces 31 are elastic, so they are elastically deformed, and each spring piece 31 generates a reaction force against the force received from the shaft 110. Due to this reaction force of each spring piece 31, each conductive piece 21 is pressed against the outer circumferential surface 110a of the shaft 110 and pressed toward the shaft 110. In this way, the multiple spring pieces 31 tighten the shaft 110 via the multiple conductive pieces 21, and the multiple spring pieces 31 generate a tightening force that grips the shaft 110.

[0088] Thus, in the operating state, the multiple conductive pieces 21 generate tension, and the multiple spring pieces 31 also generate tension. Therefore, the multiple conductive pieces 21 tighten the shaft 110 not only with the tension they themselves generate, but also with the tension generated by the multiple spring pieces 31. In this way, each of the multiple conductive pieces 21, in cooperation with the spring piece 31 it contacts, generates tension on the shaft 110. As a result, the contact between the multiple conductive pieces 21 and the shaft 110 becomes strong. Furthermore, the conformability of the multiple conductive pieces 21 to the shaft 110 is improved, which also contributes to the strong contact between the multiple conductive pieces 21 and the shaft 110. Therefore, in the conductive structure 1, the contact between the conductive member 20 and the shaft 110 is stable. This makes it possible to maintain or suppress changes in the impedance of the conductive passage formed by the conductive ring 1 between the shaft 110 of the electric motor 101 and the housing 111 over time, thereby making the conductive passage between the shaft 110 of the electric motor 101 and the housing 111 a conductive passage that allows electricity to flow stably.

[0089] Furthermore, the conductive member 20 is made of PTFE resin and is prone to deterioration over time. Therefore, when the conductive ring 1 is in use for the desired usage time, the multiple conductive pieces 21 undergo plastic deformation, and the tension force generated by the reaction force of the multiple conductive pieces 21 decreases. Depending on the length of usage time, the reaction force generated in the multiple conductive pieces 21 may become small, or no reaction force may be generated in the multiple conductive pieces 21 at all. In this case, the tension force generated by the multiple conductive pieces 21 themselves against the shaft 110 becomes small, or the multiple conductive pieces 21 themselves do not generate any tension force against the shaft 110.

[0090] In contrast, the conductive ring 1 has a spring member 30 having multiple spring pieces 31 corresponding to each of the multiple conductive pieces 21. In use, each spring piece 31 presses the corresponding conductive piece 21 against the shaft 110, and the tension generated by the multiple spring pieces 31 tightens the multiple conductive pieces 21 against the shaft 110. Therefore, even if the tension generated by the multiple conductive pieces 21 themselves against the shaft 110 decreases over time in use, or even if the tension generated by the multiple conductive pieces 21 themselves against the shaft 110 disappears, the tension generated by the multiple spring pieces 31 allows the multiple conductive pieces 21 to continue tightening the shaft 110, thus maintaining or suppressing the decrease in tension of the multiple conductive pieces 21 against the shaft 110. Therefore, the impedance Z of the conductive passage formed by the conductive ring 1 can be maintained or its change can be suppressed over time, and the conductive passage formed by the conductive ring 1 can be made into a conductive passage that allows electricity to flow stably.

[0091] Furthermore, in the conductive ring 1, when the sliding distance D of the shaft 110 relative to the conductive member 20 reaches a predetermined required sliding distance D1, the tightening allowance δ becomes a predetermined tightening allowance. Therefore, even when the operating time of the conductive ring 1 reaches the required durability time, the conductive ring 1 can apply a predetermined amount of tension to the shaft, maintaining the impedance Z of the conductive member 20 at a predetermined value, or preventing the impedance Z of the conductive member 20 from exceeding a predetermined value. Therefore, even if the impedance Z of the conductive passage formed by the conductive ring 1 increases over time, the impedance Z of the conductive member 20 is prevented from exceeding a predetermined value, thus maintaining the conductive performance of the conductive passage at the required conductivity. As a result, the conductive passage formed by the conductive ring 1 can be made into a conductive passage that stably conducts electricity.

[0092] As an example, the required sliding distance D1 is 175 × 10 of the diameter Φ0 of the shaft 110. ７ The impedance is doubled, and when the shaft 110 slides along the required sliding distance D1, the impedance Z1 of the conductive member 20 becomes 80Ω or less (Z1 ≤ 80Ω) or 50Ω or less (Z1 ≤ 50Ω). The diameter Φ0 of the shaft 110 is 175 × 10 ７ The doubled sliding distance D is sufficiently long, and the usage time of the conductive ring 1 calculated from this required sliding distance D1 reaches the required durability time of the conductive ring 1. Furthermore, the impedance Z of the conductive member 20, which is 80 Ω or less or 50 Ω or less, is an impedance that can maintain the conductive performance of the conductive passage to the required conductive performance.

[0093] Furthermore, the inner circumferential end portion 20a of the conductive member 20 is made up of a plurality of conductive pieces 21 that are spaced apart from each other in the circumferential direction. Therefore, in the operating state, the plurality of conductive pieces 21 come into contact with the shaft 110, and each of the plurality of conductive pieces 21 deforms. In this way, the circumferential restraining force of each conductive piece 21 is reduced, and the magnitude of the tension force generated by the plurality of conductive pieces 21 themselves can be reduced. As a result, wear of the plurality of conductive pieces 21 caused by the rotation of the shaft 110 can be suppressed.

[0094] Further, the conductive ring 1 may be provided between the housing 120 of the speed reducer 102 and the shaft 122. Specifically, as shown in FIG. 10, the conductive ring 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, similarly to the conductive ring 1 attached to the electric motor 101, the conductive member 20 and the holding member 10 of the conductive ring 1 form a conductive path that allows electricity to flow between the shaft 122 of the speed reducer 102 and the housing 120. The conductive ring 1 may be used in oil, and may be provided inside the oil seal 127.

[0095] Note that the above-described drive device 100 is an example of an application target of the conductive ring 1, and the application target of the conductive ring 1 is not limited thereto. The conductive ring 1 is used, for example, in drive devices for electric vehicles (EV) such as hybrid vehicles (HV), fuel cell vehicles (FCV), other than battery electric vehicles (BEV). In vehicles equipped with an electric motor such as an electric vehicle (EV), the shafts 110 and 120 may be charged by an induced current or the like generated from the motor, which may cause electromagnetic noise. Further, the shafts 110 and 120 may be charged by the on-off operation of an inverter for current control supplied to an electric motor such as an electric motor, or the induced voltage of the electric motor itself, which may cause electromagnetic noise. As described above, the conductive ring 1 forms a conductive path and allows the voltage charged in the shafts 110 and 122 to flow to the housings 111 and 120. This can prevent communication failures and malfunctions of electronic devices, and electrolytic corrosion of metal parts such as bearings.

[0096] As described above, the conductive ring 1 according to the embodiment of the present invention can suppress a decrease in tightening force with respect to the shaft 110.

[0097] Next, examples of the conductive ring 1 will be described.

[0098] The inventor of the present invention produced a conductive ring 1 (hereinafter referred to as Test Example 1) used for the shaft 110 in which the diameter φ0 of the shaft 110 is 40 mm. The required sliding distance D1 is 175×10 of the diameter Φ0 (40 mm) of the shaft 110 ７The required sliding distance D1 was set to double, 70,000 km, and the impedance Z1 of the conductive member 20 when the shaft 110 slides over the required sliding distance D1 was set to 50 Ω or less (Z1 ≤ 50 Ω). Furthermore, in order to ensure that the impedance Z becomes impedance Z1 (Z1 ≤ 50 Ω) when the required sliding distance D1 = 70,000 km, the inventors adjusted the length L1 of the conductive piece 21, the thickness T2 of the spring piece 31, the width W2 of the spring piece 31, the length L2 of the spring piece 31, the distance R5 of the inner circumference end 17a of the holding part 17, and the distance R6 of the inner circumference end 13a of the holding part 13, thereby setting the number of conductive pieces 21, the number of spring pieces 31, the thickness T1 of the conductive piece 21, the width W1 of the conductive piece 21, the length L1 of the conductive piece 21, the thickness T2 of the spring piece 31, the width W2 of the spring piece 31, the length L2 of the spring piece 31, and the distance R6 of the inner circumference end 13a of the holding part 13.

[0099] The inventors conducted a durability test on Test Example 1. The durability test was performed using a test apparatus that simulates the usage conditions shown in Figure 11. In the test apparatus, the diameter of the shaft corresponding to shaft 110 is 40 mm. The target value of the shaft eccentricity of the shaft corresponding to shaft 110 was set to 0.2 mm TIR. The rotational speed of the shaft corresponding to shaft 110 was set to 9000 rpm. The ambient temperature of the test apparatus was set to 80°C. For Test Example 1, the durability test was performed until the sliding distance D of the shaft reached 70,000 km (required sliding distance D1), and the impedance Z was measured at multiple sliding distances D1. The results of the durability test for Test Example 1 are shown in Figure 12. Figure 12 also shows the relationship between the sliding distance D and the impedance Z.

[0100] Furthermore, the inventors prepared Comparative Example 1, which differs from Test Example 1 in that it does not have a spring member 30, and conducted a durability test in the same manner as for Test Example 1. The results of the durability test for Comparative Example 1 are shown in Figure 12.

[0101] As shown in Figure 12, in Test Example 1, the impedance Z of the conductive member 20 at the required sliding distance D1 (70,000 km) is 27 Ω, satisfying the impedance Z1 (Z1 ≤ 50 Ω). Thus, in Test Example 1, when the sliding distance D of the shaft relative to the conductive member 20 reaches the predetermined required sliding distance D1 (70,000 km), the impedance Z of the conductive member 20 is the predetermined impedance Z1 (Z1 ≤ 50 Ω). Therefore, in Test Example 1, the impedance Z of the conductive member 20 is set to an impedance that can maintain the conductive performance of the conductive passage to the required conductive performance.

[0102] On the other hand, as shown in Figure 12, in Comparative Example 1, the impedance Z of the conductive member 20 at the required sliding distance D1 (70,000 km) reaches approximately 90 Ω. Thus, in Comparative Example 1, when the sliding distance D of the shaft relative to the conductive member 20 reaches the predetermined required sliding distance D1 (70,000 km), the impedance Z of the conductive member 20 does not reach the predetermined impedance Z1 (Z1 ≤ 50 Ω), and the impedance Z of the conductive member 20 is high. For this reason, in Comparative Example 1, the impedance Z of the conductive member 20 is not set to an impedance that can maintain the conductive performance of the conductive passage to the required conductive performance.

[0103] Next, a modified example of the conductive member 20 will be described. Figure 13 is a front view of conductive member 20A, which is an example of a modified example of the conductive member 20.Hereafter, regarding the configuration of conductive member 20A, components that are the same as or have the same function as conductive member 20 described above will be denoted by the same reference numerals and their descriptions will be omitted, while components that differ from conductive member 20 will be described.

[0104] As shown in Figure 13, the conductive member 20A has a gap 27 that extends in at least one radial direction and a conductive member piece 26 that extends around at least one axis x. The conductive member piece 26 has a pair of ends 28a, 28b in the direction of axis x. The gap 26 is connected to the ends 28a, 28b of the conductive member piece 26.

[0105] As shown in Figure 13, the conductive member 20A is an annular plate-shaped structure composed of, for example, two gaps 27 (gaps 27A, 27B) and two conductive member pieces 26 (conductive member pieces 26A, 26B). As shown in Figure 13, the conductive member piece 26A has a pair of ends 28Aa, 28Ab, and the conductive member piece 26B has a pair of ends 28Ba, 28Bb. One of the pair of ends of one conductive member piece 26 (conductive member piece 26A) (end 28Aa) and one of the pair of ends of the other conductive member piece 26 (conductive member piece 26B) (end 28Ba) face each other in the direction around the axis x (circumferential direction). Furthermore, the other end of the pair of conductive member pieces 26A (end 28Ab) and the other end of the pair of conductive member pieces 26B (end 28Bb) face each other in the direction around the axis x (circumferential direction). One side of the gap 27 (gap 27A) is formed between end 28Aa of conductive member piece 26A and end 28Ba of conductive member piece 26B, and the other side of the gap 27 (gap 27B) is formed between end 28Ab of conductive member piece 26A and end 28Bb of conductive member piece 26B.

[0106] The conductive member pieces 26A and 26B are members that correspond to a part of the conductive member 20 of the conductive ring 1 shown in Figures 1 to 9, and coincide with or substantially coincide with a part of the conductive member 20. The conductive member pieces 26A and 26B are formed, for example, by dividing the conductive member 20, as shown in Figures 1 to 9, to form gaps 27A and 27B. Therefore, the cross-sectional shape of the conductive member pieces 26A and 26B in a plane containing the axis x is the same as the cross-sectional shape of the conductive member 20 shown in Figure 13. The conductive member pieces 26A and 26B are, for example, the same. However, the conductive member pieces 26A and 26B do not have to be the same. The conductive member pieces 26A and 26B extend along a circular arc or substantially circular arc centered on the axis x, for example, as shown in Figure 13. Specifically, as shown in Figure 13, for example, the conductive member pieces 26A and 26B extend in the circumferential direction such that their length is shorter than the semicircle of the circle along which they extend.

[0107] In the conductive ring 1, the conductive member 20A is provided in the same manner as the conductive member 20. That is, the conductive member piece 26A is superimposed on the spring member 30 in the same manner as the corresponding part of the conductive member 20 of the conductive member piece 26A. Multiple conductive pieces 21 of the conductive member piece 26A are in contact with multiple corresponding spring pieces 31 of the spring member 30. Similarly, multiple conductive pieces 21 of the conductive member piece 26B are in contact with multiple corresponding spring pieces 31 of the spring member 30. In addition, two gaps 27A and 27B are interposed between the conductive member piece 26A and the conductive member piece 26B superimposed on the spring member 30. Specifically, a gap 27A is interposed between the end 28Aa of the conductive member piece 26A and the end 28Ba of the conductive member piece 26B, and a gap 27B is interposed between the end 28Ab of the conductive member piece 26A and the end 28Bb of the conductive member piece 26B. Thus, the gap 27A is connected to the end 28Aa of the conductive member piece 26A and the end 28Ba of the conductive member piece 26B, and the gap 27B is connected to the end 28Ab of the conductive member piece 26A and the end 28Bb of the conductive member piece 26B.

[0108] The conductive ring 1 having the conductive member 20A according to the modified example is used in the same way as the conductive ring 1 described above to form a conductive passage between the shaft 110 of the electric motor 101 and the housing 111. Furthermore, the conductive member 20A according to the modified example also functions in the same way as the conductive ring 1 described above and produces the same effect.

[0109] Furthermore, in the conductive ring 1 having the conductive member 20A according to the modified example, the conductive member pieces 26A and 26B are arranged in an annular shape with gaps 27A and 27B in between. Therefore, even if an external force is applied to the conductive member pieces 26A and 26B due to the rotation of the shaft 110 during use, the conductive member pieces 26A and 26B can escape into the gaps 27A and 27B. This prevents deformation that would cause stress concentration in the conductive member pieces 26A and 26B, as well as contact with the shaft 110. This prevents wear and deterioration of the conductive member pieces 26A and 26B.

[0110] Furthermore, when fixing the conductive member pieces 26A and 26B to the holding member 10, the conductive member pieces 26A and 26B can escape into the gaps 27A and 27B. This prevents deformation such as wrinkles from occurring in the conductive member pieces 26A and 26B when they are fixed to the holding member 10.

[0111] Next, other modifications of the conductive member 20 will be described. Figure 14 is a front view of conductive member 20B as another example of a modification of conductive member 20. As shown in Figure 10, conductive member 20B according to the other modification has one conductive member piece 26C as conductive member piece 26 and one gap 27C as gap 27. In conductive member 20B, one of the gaps 27A or gap 27B is absent, and conductive member piece 26A or conductive member piece 26B extends into one portion of gap 27A or gap 27B, and conductive member piece 26A and conductive member piece 26B are connected in one portion of gap 27A or gap 27B to form one conductive member piece 26C. The conductive member piece 26C of the conductive member 20B extends, for example, on a circle or approximately circle with axis x as its center or approximate center, as shown in Figure 14, and its ends 28Ca and 28Cb face each other in the circumferential direction, specifically, for example, in a direction perpendicular to axis x. The conductive member piece 26C, like the conductive member pieces 26A and 26B, has a conductive member piece 20C which is a member corresponding to a part of the conductive member 20. The conductive member 20 may have three or more gaps 27 and three or more conductive member pieces 26. In this case as well, the multiple gaps 27 and the multiple conductive member pieces 26 are connected in an annular shape.

[0112] Next, a modified example of the spring member 30 will be described. The spring member 30 may also be modified in the same way as the conductive member 20 described above. Figure 15 is a front view of spring member 30A as an example of a modified example of spring member 30. Hereinafter, regarding the configuration of spring member 30A, the same reference numerals are used for components that have the same configuration or function as spring member 30 described above, and their descriptions are omitted. Components that differ from spring member 30 will be described.

[0113] As shown in Figure 15, the spring member 30A has a gap 37 that extends in at least one radial direction and a spring member piece 36 that extends around at least one axis x. The spring member piece 36 has a pair of ends 38a, 38b in the direction of axis x. The gap 36 is connected to the ends 38a, 38b of the spring member piece 36.

[0114] As shown in Figure 15, the spring member 30A is an annular plate-shaped structure composed of, for example, two gaps 37 (gaps 37A, 37B) and two spring member pieces 36 (spring member pieces 36A, 36B). As shown in Figure 15, the spring member piece 36A has a pair of ends 38Aa, 38Ab, and the spring member piece 36B has a pair of ends 38Ba, 38Bb. One of the pair of ends of one of the spring member pieces 36 (spring member piece 36A) (end 38Aa) and one of the pair of ends of the other spring member piece 36 (spring member piece 36B) (end 38Ba) face each other in the direction around the axis x (circumferential direction). Furthermore, the other end of the pair of ends of spring member piece 36A (end 38Ab) and the other end of the pair of ends of spring member piece 36B (end 38Bb) face each other in the direction around the axis x (circumferential direction). One side of the gap 37 (gap 37A) is formed between end 38Aa of spring member piece 36A and end 38Ba of spring member piece 36B, and the other side of the gap 37 (gap 37B) is formed between end 38Ab of spring member piece 36A and end 38Bb of spring member piece 36B. For example, spring member pieces 36A and 36B extend around the axis x to the same or approximately the same length as conductive member pieces 26A and 26B. In other words, spring member piece 36A and conductive member piece 26A can be superimposed on each other by aligning or approximately aligning their ends 38Aa and 28Aa, and their ends 38Ab and 28Ab, respectively, in the direction of the axis x. Similarly, the spring member piece 36B and the conductive member piece 26B can be superimposed on each other by aligning their ends 38Ba and 28Ba, and their ends 38Bb and 28Bb, respectively, in the x-axis direction.

[0115] The spring member pieces 36A and 36B are members that correspond to a part of the spring member 30 of the conductive ring 1 shown in Figures 1 to 7 and 9, and coincide with or substantially coincide with a part of the spring member 30. The spring member pieces 36A and 36B are formed, for example, by dividing the spring member 30, as shown in Figures 1 to 7 and 9, to form gaps 37A and 37B. Therefore, the cross-sectional shape of the spring member pieces 36A and 36B in a plane containing the axis x is the same as the cross-sectional shape of the spring member 40 shown in Figure 15. The spring member pieces 36A and 36B are, for example, the same. However, the spring member pieces 36A and 36B do not have to be the same. The spring member pieces 36A and 36B extend along a circular arc or substantially circular arc centered on the axis x, for example, as shown in Figure 15. Specifically, as shown in Figure 15, for example, the spring member pieces 36A and 36B extend in the circumferential direction such that they are shorter than the semicircle of the circle along which they extend.

[0116] In the conductive ring 1, the spring member 30A is provided in the same way as the spring member 30. That is, the spring member piece 36A is superimposed on the conductive members 20, 20A, and 20B in the same way as the corresponding part of the spring member 30 of the spring member piece 36A. Multiple spring pieces 31 of the spring member piece 36A are in contact with multiple corresponding conductive pieces 21 of the conductive members 20, 20A, and 20B. Similarly, multiple spring pieces 31 of the spring member piece 36B are in contact with multiple corresponding conductive pieces 21 of the conductive members 20, 20A, and 20B. In addition, two gaps 37A and 37B are interposed between the spring member piece 36A and the spring member piece 36B that are superimposed on the conductive members 20, 20A, and 20B. Specifically, a gap 37A is interposed between the end 38Aa of spring member piece 36A and the end 38Ba of spring member piece 36B, and a gap 37B is interposed between the end 38Ab of spring member piece 36A and the end 38Bb of spring member piece 36B. Thus, gap 37A is connected to the end 38Aa of spring member piece 36A and the end 38Ba of spring member piece 36B, and gap 37B is connected to the end 38Ab of spring member piece 36A and the end 38Bb of spring member piece 36B.

[0117] The conductive ring 1 having the modified spring member 30A is used in the same way as the conductive ring 1 described above to form a conductive passage between the shaft 110 of the electric motor 101 and the housing 111. Furthermore, the modified spring member 30A also acts in the same way as the conductive ring 1 described above and produces the same effect.

[0118] Furthermore, in the conductive ring 1 having a modified spring member 30A, the spring member pieces 36A and 36B are arranged in an annular shape with gaps 37A and 37B in between. Therefore, even if an external force is applied to the spring member pieces 36A and 36B due to the rotation of the shaft 110 during use, the spring member pieces 36A and 36B can escape into the gaps 37A and 37B. This prevents deformation that would cause stress concentration in the spring member pieces 36A and 36B, as well as contact with the shaft 110. As a result, damage to the spring member pieces 36A and 36B can be suppressed.

[0119] Furthermore, when fixing the spring member pieces 36A and 36B to the retaining member 10, the spring member pieces 36A and 36B can escape into the gaps 37A and 37B. This prevents deformation such as wrinkles from occurring in the spring member pieces 36A and 36B when they are fixed to the retaining member 10.

[0120] Next, other modifications of the spring member 30 will be described. Figure 16 is a front view of spring member 30B as another example of a modification of spring member 30. As shown in Figure 16, the spring member 30B according to the other modification has one spring member piece 36C as a spring member piece 36 and one gap 37C as a gap 37. In spring member 30B, one of the gaps 37A or 37B is absent, and the spring member piece 36A or 36B extends into one portion of the gap 37A or 37B, and the spring member piece 36A and the spring member piece 36B are connected in one portion of the gap 37A or 37B to form one spring member piece 36C. As shown in Figure 16, the spring member piece 36C of the spring member 30B extends on a circle or approximately circle with axis x as its center or approximately center, and its ends 38Ca and 38Cb face each other in the circumferential direction, specifically, for example, in a direction perpendicular to axis x. The spring member piece 36C, like the spring member pieces 36A and 36B, has a spring member piece 30C that corresponds to a part of the spring member 30. For example, the spring member piece 36C extends around axis x to the same or approximately the same length as the conductive member piece 26C. In other words, the spring member piece 36C and the conductive member piece 26C can be superimposed on each other by aligning or approximately aligning their ends 38Ca and 28Ca in the direction of axis x. The spring member 30 may have three or more gaps 37 and three or more spring member pieces 36. In this case as well, the multiple gaps 37 and the multiple spring member pieces 36 are connected in an annular shape.

[0121] 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.

[0122] 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.

[0123] For example, the elements adjusted so that the impedance Z becomes impedance Z1 when the required sliding distance D1 is reached are not limited to the number of conductive pieces 21, the shape of the conductive pieces 21, the number of spring pieces 31, the shape of the spring pieces 31, and the distance R6 of the inner circumference end 13a of the retaining portion 13. For example, the elements adjusted so that the impedance Z becomes impedance Z1 when the required sliding distance D1 is reached may include the distance R2 of the conductive pieces 21 and the distance R4 of the spring pieces 31.

[0124] 1 Conductive ring, 10 Holding member, 11 Inner holding member, 12 Fitting portion, 12a Outer surface, 13 Holding portion, 13a Inner end, 15 Outer holding member, 16 Fitting portion, 16a Inner surface, 17 Holding portion, 17a Inner end, 18 Pressing portion, 20, 20A, 20B Conductive member, 20a Inner end, 20b Through hole, 21 Conductive piece (end piece), 21a Inner end, 21b, 21c Side end, 21d Outer end, 22 Base portion, 22a Inner end, 22b Outer end, 23 Gap, 24 Contact side, 25 Pressed side, 26, 26A, 26B, 26C Conductive member piece, 27, 27A, 27B, 27C Gap, 28a, 28Aa, 28Ba, 28Ca, 28b, 28Ab, 28Bb, 28Cb End, 30, 30A, 30B Spring member, 30a Inner circumference end, 31 Spring piece (end piece), 31a Inner circumference end, 31b, 31c Side end, 31d Outer circumference end, 32 Base, 32a Inner circumference end, 32b Outer circumference end, 33 Space, 34 Pressing side, 35 Back, 36, 36A, 36B, 36C Conductive member piece, 37, 37A, 37B, 37C Gap, 38a, 38Aa, 38Ba, 38Ca, 38b, 38Ab, 38Bb, 38Cb End, 100, 200 Drive device, 101 Electric motor, 102 Reducer, 103 Inverter, 104 Battery, 105 Wheels, 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, D Sliding distance, D1 Required sliding distance, L1, L2 Length, R0 Radius, R1, R2, R3, R4, R5, R6 Distance (radius), T1, T2 Thickness, W1, W2, W3, W4 Width, x Axis, Z, Z1 Impedance, δ, δ1 Clamp, φ0 Diameter

Claims

1. A conductive ring that forms a conductive passage between a rotating shaft and a hole through which the shaft is inserted, comprising: a holding member which is an annular conductive member about an axis; a conductive member which is a conductive member extending about the axis; and a spring member which extends about the axis, wherein the conductive member is in contact with the shaft and the hole, and cooperates with the spring member to generate a tensioning force on the shaft, and the impedance of the conductive member between the shaft and the hole is set to a predetermined value when the sliding distance of the shaft with respect to the conductive member is a predetermined distance, i.e., a required sliding distance.

2. The conductive ring according to claim 1, wherein the required sliding distance is a value corresponding to the diameter of the shaft.

3. The required sliding distance is 175 × 10 of the shaft diameter. ７ The conductive ring according to claim 2, wherein the impedance is 80 Ω or less when doubled.

4. The required sliding distance is 175 × 10 of the shaft diameter. ７ The conductive ring according to claim 2, wherein the impedance is 50 Ω or less when doubled.

5. The conductive ring according to claim 1, wherein the conductive member has a plurality of end pieces arranged in the circumferential direction at its inner end, the spring member has a plurality of end pieces arranged in the circumferential direction at its inner end, each of the plurality of end pieces of the spring member is elastically deformable along the axis and is in contact with the plurality of end pieces of the conductive member, and the holding member holds the conductive member and the spring member aligned in the axial direction.

6. The conductive ring according to claim 5, wherein the number of end pieces of the conductive member and the number of end pieces of the spring member are set based on a predetermined value of the impedance.

7. The conductive ring according to claim 5 or 6, wherein the shape of each end piece of the conductive member and the shape of each end piece of the spring member are set based on a predetermined value of the impedance.

8. The conductive ring according to claim 7, wherein the form of the end piece of the conductive member is at least one of the thickness in the axial direction, the width in the circumferential direction about the axis, and the length in the radial direction, and the form of the end piece of the spring member is at least one of the thickness in the axial direction, the width in the circumferential direction about the axis, and the length in the radial direction.

9. The conductive ring according to claim 5, wherein the plurality of end pieces of the spring member are arranged at intervals from one another in the circumferential direction.

10. The conductive ring according to claim 5, wherein the circumferential width of the end piece of the spring member is less than or equal to the circumferential width of the end piece of the conductive member.

11. The conductive ring according to claim 5, wherein the outer peripheral ends of the plurality of end pieces of the spring member are located further outward than the outer peripheral ends of the plurality of end pieces of the conductive member.

12. The conductive ring according to claim 5, wherein the spring member has a base which is an annular portion, and the plurality of end pieces of the spring member extend inward from the inner circumference end of the base of the spring member.

13. The conductive ring according to claim 5, wherein the plurality of end pieces of the conductive member are arranged at intervals from one another in the circumferential direction.

14. The conductive ring according to claim 5, wherein the conductive member has a base which is an annular portion, and the plurality of end pieces of the conductive member extend inward from the inner circumferential end of the base of the conductive member.

15. The conductive ring according to claim 5, wherein the number of the plurality of end pieces of the spring member is the same as the number of the plurality of end pieces of the conductive member.

16. The conductive ring according to claim 1, wherein the holding member is configured to hold the conductive member and the spring member on the outer circumference.

17. The conductive ring according to claim 1, wherein the conductive member is formed from conductive PTFE having electrical conductivity.

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