Sealing material, electric motor including the same, and method for manufacturing sealing material

Abstract

To provide a sealing material with a simple structure that can discharge (divert) current flowing through a rotation axis such as a shaft due to shaft voltage to the outside, and that also exhibits excellent wear resistance.SOLUTION: The invention provides a sealing material made of a fluororesin base material and including at least an annular base portion. The base portion has a low-conductivity portion with a volume resistivity of 1.0×104 Ω cm, and a high-conductivity portion having a lower volume resistivity than the low-conductivity portion. The high-conductivity portion is formed at least at one location in the circumferential direction of the base portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sealant arranged to seal a gap between a rotating shaft and a housing of an electric motor for an automobile or the like, an electric motor including the sealant, and a method for manufacturing the sealant. [Background technology]

[0002] In recent years, electric vehicles (EVs) and hybrid vehicles (HVs) have become increasingly popular in place of automobiles with internal combustion engines.

[0003] These electric vehicles (EVs) and hybrid vehicles (HVs) use electric motors as their power source, but as the electric motor rotates, a voltage is generated on the shaft (rotating axis), and there are concerns that electrolytic corrosion will occur when current from the shaft voltage passes through the inside of the bearings that support the electric motor.If electrolytic corrosion occurs in the bearings, it will leave marks on the bearing raceways, causing abnormal noise and vibration when the vehicle is running, and may lead to early damage to the bearings.

[0004] Grease is usually used in the bearings of the shaft, and because grease has insulating properties, the occurrence of electrolytic corrosion can be suppressed to some extent by this grease.

[0005] However, if the insulation provided by the grease breaks down, electrolytic corrosion can occur.Furthermore, as the power output of electric vehicles increases in the future, the potential difference between the inner and outer rings of the bearings will increase, raising concerns about electrolytic corrosion due to insulation breakdown in the grease.

[0006] To deal with induced currents generated in electric motors, Patent Document 1 discloses a sealing device that includes a reinforcing ring, an elastic body made of conductive rubber, and conductive grease. This sealing device forms a conductive path between the output shaft of the drive motor and the casing via the elastic body made of conductive rubber, thereby reducing noise caused by induced currents.

[0007] Patent Document 2 discloses an electromagnetic noise suppression device in which a conductive means (oil seal made of conductive rubber) connected to a casing is attached to a shaft (rotating shaft). Electromagnetic noise induced in the shaft flows to the casing via the conductive means, preventing leakage of the electromagnetic noise to the external axle.

[0008] Patent Document 3 discloses a sealing device that includes a core metal, a seal lip member made of a conductive rubber material, and a rubber portion made of a non-conductive rubber material. This sealing device makes it difficult for a potential difference to occur between the hub wheel and the outer ring, thereby suppressing the occurrence of sparks caused by static electricity building up on the outer ring. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6967087 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-244180 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-14296 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the sealing device of Patent Document 1 requires conductive grease, which can cause problems in terms of securing installation space and durability. The electromagnetic noise suppression device of Patent Document 2 requires a separate conducting means, and if the rotating shaft becomes eccentric, there is a risk that the rotating shaft and the conducting means will become separated and lose electrical continuity, and there is also a risk that the mechanical strength of the entire seal will be reduced. In the sealing device of Patent Document 3, the three lip portions of the seal lip member are in contact with the hub wheel, which further increases sliding resistance. Furthermore, as wear progresses, there is a risk that the lip portions and the hub wheel will separate, resulting in an inability to conduct electricity.

[0011] Therefore, in electric motors, a sealing material is used to seal the gap between the rotating shaft and the housing (casing). Because this sealing material comes into contact with the rotating shaft and the housing, if this sealing material could be given both conductivity and durability, it would be possible to achieve both the ability to channel (escape) the current flowing through the rotating shaft to the outside and excellent durability with a simple structure.

[0012] However, in electric vehicles (EVs) and hybrid vehicles (HVs), motors are becoming smaller and faster, so high durability against wear caused by sliding of the rotating shaft is required. However, since the addition of conductive fillers generally tends to reduce wear resistance, it has been difficult to impart both conductivity and wear resistance to sealing materials at the high level required for electric vehicles (EVs) and hybrid vehicles (HVs).

[0013] Therefore, an object of the present invention is to provide a sealing material with a simple structure that can direct the current flowing in a rotating shaft or other such axis due to axial voltage to the outside, and that has good wear resistance, an electric motor equipped with the same, and a method for manufacturing the sealing material. [Means for solving the problem]

[0014] The above problem is solved as follows. That is, the present invention (1) is a sealing material made of a fluororesin substrate and having at least an annular base portion, The base has a volume resistivity of 1.0×10 4 a low-conductivity portion having a volume resistivity of Ω·cm or more and a high-conductivity portion having a volume resistivity lower than that of the low-conductivity portion, the highly conductive portion is formed at least at one location in the circumferential direction of the base portion; The present invention provides a sealing material characterized by the above.

[0015] The present invention (2) also provides the sealing material of (1), characterized in that the high-conductivity portion contains a conductive filler, and the low-conductivity portion contains a reinforcing filler.

[0016] The present invention (3) also provides the sealing material according to (1) or (2), wherein the conductive filler is a carbon material and / or metal fiber.

[0017] In addition, the present invention (4) is characterized in that the volume resistivity of the highly conductive part is 1.0 × 10 -1 ~1.0×10 2 The present invention provides a sealing material according to any one of (1) to (3), characterized in that the resistance is Ω·cm.

[0018] The present invention (5) also provides a sealing material according to any one of (1) to (4), wherein the fluororesin is at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride.

[0019] The present invention (6) also provides a sealing material according to any one of (1) to (5), characterized in that the highly conductive portions are formed at four equally spaced locations in the circumferential direction of the base.

[0020] The present invention (7) also provides a sealing material according to any one of (1) to (6), characterized in that the width of the outer diameter side of the highly conductive portion is wider than the width of the inner diameter side of the highly conductive portion.

[0021] Furthermore, the present invention (8) is a bearing having an inner lip portion formed cylindrically on the inner circumferential side along an axial direction intersecting the circumferential direction of the base, and an annular flat plate portion extending from the outer circumferential side of the inner lip portion to the outer diameter side, The present invention provides a sealing material according to any one of (1) to (7), characterized in that the highly conductive portion is formed at least at one location in the circumferential direction of the inner lip portion and the annular flat plate portion.

[0022] The present invention (9) provides the sealing material according to any one of (1) to (8), characterized in that the sealing material is a shaping material.

[0023] The present invention (10) also provides a sealing material according to (1) or (2), a housing that contacts an outer peripheral surface of the sealing material; a rotary shaft that contacts an inner peripheral surface of the sealing material and is supported rotatably relative to the housing along an axial direction that intersects the circumferential direction; a bearing that rotatably supports the rotary shaft; The present invention provides an electric motor comprising:

[0024] The present invention (11) also provides a first step of molding a material for a low conductive portion, which is a mixture of at least a reinforcing filler and a fluororesin, and a material for a high conductive portion, which is a mixture of at least a conductive filler and a fluororesin, to obtain an annular flat plate-shaped molded body; a second step of shaping the annular flat plate-shaped body to obtain a sealing material having at least an annular base portion and including a highly conductive portion at at least one location in the circumferential direction of the base portion; The present invention provides a method for producing a sealing material, which comprises the steps of: [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a sealing material with a simple structure that can direct (escape) the current that flows in a rotating axis such as a shaft due to axial voltage to the outside, and that has good wear resistance, an electric motor equipped with the same, and a method for manufacturing the sealing material. [Brief explanation of the drawings]

[0026] [Figure 1]FIG. 1 is a front view schematically showing an example of the sealing material of the present invention. [Figure 2] FIG. 2 is a side view schematically showing an example of the sealing material of the present invention. [Figure 3] FIG. 3 is a view showing an end face taken along line AA in FIG. [Figure 4] FIG. 4 is a diagram for explaining discharge and grounding by the sealing material of the present invention. [Figure 5] FIG. 5 is a schematic end view showing an example of how the sealing material of the present invention is used. [Figure 6] FIG. 6 is a front view schematically showing an example of the sealing material of the first embodiment of the present invention. [Figure 7] FIG. 7 is a view showing an end face taken along line AA in FIG. [Figure 8] FIG. 8 is a front view schematically showing an example of the sealing material according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a view showing an end face taken along line AA in FIG. [Figure 10] FIG. 10 is a front view schematically showing an example of a sealing material according to the third embodiment of the present invention. [Figure 11] FIG. 11 is a view showing an end face taken along line AA in FIG. [Figure 12] FIG. 12 is a front view schematically showing an example of a sealing material according to the fourth embodiment of the present invention. [Figure 13] FIG. 13 is a view showing an end face taken along line AA in FIG. [Figure 14] FIG. 14 is a diagram showing an example of the sealing material of the present invention. [Figure 15] FIG. 15 is a diagram showing an example of the sealing material of the present invention. [Figure 16] FIG. 16 is a diagram showing an example of the sealing material of the present invention. [Figure 17] FIG. 17 is a diagram showing an example of a material produced by the method of producing a raw material for processing a sealing material of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The sealing material of the present invention is A sealing material made of a fluororesin base material and having at least an annular base portion, The base has a volume resistivity of 1.0×10 4 a low-conductivity portion having a volume resistivity of Ω·cm or more and a high-conductivity portion having a volume resistivity lower than that of the low-conductivity portion, the highly conductive portion is formed at least at one location in the circumferential direction of the base portion; The sealing material is characterized by the above.

[0028] 1 to 3 are diagrams showing an example of a sealing material 1 of the present invention. The sealing material 1 is an annular sealing material. The annular sealing material 1 is a member having a substantially circular opening 2 in the center of the sealing material.

[0029] The sealing material 1 includes at least an annular base portion. The base portion has, for example, an inner lip portion 5 and an annular flat portion 6 on the inner circumferential side (rotation shaft side), and an outer lip portion 7 on the outer circumferential side, and has a U-shaped cross section. As shown in FIGS. 1 and 3 , the base portion of the sealing material 1 having a U-shaped cross section can include the annular flat portion 6, the inner lip portion 5 formed cylindrically on the inner circumferential side along an axial direction intersecting the circumferential direction of the base, and the outer lip portion 7 formed cylindrically on the outer circumferential side along an axial direction intersecting the circumferential direction of the base. The inner lip portion 5 extends, for example, approximately perpendicularly from the annular flat portion 6 toward the inner circumferential side. The outer lip portion 7 extends, for example, approximately perpendicularly from the annular flat portion 6 toward the outer circumferential side. As shown in FIG. 3 , the base portion of the sealing material 1 can have an annular recess 8 formed by the inner lip portion 5, the outer lip portion 7, and the annular flat portion 6.

[0030] As described above, the sealing material 1 is an annular sealing material having at least a base portion. The inner peripheral surface of the annular flat portion 6 and the inner peripheral surface of the inner lip portion 5 constitute a rotating shaft contact surface 12 that contacts the rotating shaft (FIG. 5). In the embodiment shown in FIGS. 1 to 5, the entire inner peripheral surface of the annular flat portion 6 and the inner peripheral surface of the inner lip portion 5 contact the rotating shaft 3. However, in other embodiments, when the sealing material 1 includes the inner lip portion 5, a part of the inner peripheral surface of the annular flat portion 6 and the inner peripheral surface of the inner lip portion 5 may contact the rotating shaft 3, or only the inner peripheral surface of the inner lip portion 5 may contact the rotating shaft 3 (i.e., the inner peripheral surface of the annular flat portion 6 does not contact the rotating shaft 3). The surface of the annular flat portion 6 facing the housing constitutes a housing contact surface 13 (FIG. 5).

[0031] The sealing material 1 has a low conductive portion 11 and a high conductive portion 9, and the high conductive portions 9 are formed at four locations in the circumferential direction of the annular sealing material 1 (at least in the circumferential direction of the annular flat plate portion 6, preferably at least in the circumferential direction of the inner lip portion 5 and the annular flat plate portion 6). In other words, the sealing material 1 has a low conductive portion 11 (a portion other than the high conductive portion) and a high conductive portion 9 having a volume resistivity lower than that of the low conductive portion 11.

[0032] The electrical continuity and grounding of the sealing material 1 when it is in use will be described with reference to FIGS.

[0033] FIG. 4 is a diagram illustrating electrical continuity and grounding provided by the sealing material 1, and FIG. 5 is a diagram schematically illustrating an example of a state in which the sealing material 1 is used. As shown schematically in FIG. 4 , the rotating shaft contact surface 12 of the sealing material 1 (the inner peripheral surface of the inner lip portion 5 and the inner peripheral surface of the annular flat plate portion 6) is disposed in contact with the rotating shaft (shaft) 3, and the housing contact surface 13 (the housing-facing surface of the annular flat plate portion 6) and the outer peripheral surface of the outer lip portion 7 are disposed in contact with the housing 4. Therefore, the highly conductive portions 9 formed in the circumferential direction of the inner lip portion 5 and the annular flat plate portion 6 are also disposed in contact with the rotating shaft (shaft) 3, and the highly conductive portions 9 formed in the circumferential direction of the annular flat plate portion 6 and the outer lip portion 7 are disposed in contact with the housing 4. Each highly conductive portion 9 is formed from the inner lip portion 5 through the annular flat plate portion 6 to the outer lip portion 7. Therefore, the rotating shaft 3 is grounded to the housing 4 via the sealing material 1. The current generated inside the seal material 1 due to the shaft voltage generated by the electric motor flows from the rotating shaft 3 through the highly conductive part 9 of the seal material 1 to the housing 4. This prevents electrolytic corrosion.

[0034] As shown in FIG. 5 , when the rotating shaft contact surface 12 (the inner peripheral surface of the annular plate portion 6 and the inner peripheral surface of the inner lip portion 5) of the seal material 1 contacts the rotating shaft 3 and the outer lip portion 7 and housing contact surface 13 (the housing-facing surface of the annular plate portion 6) contact the housing 4, the pressure outside the housing 4 is lower than the pressure inside the housing 4, and the pressure inside the housing 4 is higher than the pressure outside the housing 4. In the seal material 1 having a U-shaped cross section, the inner lip portion 5 and the outer lip portion 7 extending from the annular plate portion 6 are positioned on the high-pressure side, so a force F acts to expand the inner lip portion 5 toward the rotating shaft 3 and the outer lip portion 7 toward the housing 4. This strengthens the adhesion of the inner lip portion 5 to the rotating shaft 3 and the outer lip portion 7 to the housing 4. This improves the sealing performance of the seal material 1 and prevents leakage of liquids such as oil.

[0035] The sealing material of the present invention is used in electric motors that receive and convert electrical energy into motive energy and are used as power sources for automobiles such as electric vehicles (EVs) and hybrid vehicles (HVs), electric compressors, dehumidifying rotors, etc. It is placed inside the housing, coming into contact with the rotating shaft (shaft) and the housing, and is used to seal and block the gap between the rotating shaft and the housing, thereby preventing leakage of oil and other liquids inside the housing.

[0036] The sealing material of the present invention is made of a fluororesin substrate. In other words, the sealing material of the present invention is formed of a fluororesin. Examples of fluororesins include one or more selected from the group consisting of polytetrafluoroethylene (PTFE), polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. Because fluororesins have a low coefficient of friction, high strength, and high abrasion resistance, the sealing material of the present invention made of a fluororesin substrate is suitable as a material with which a rotating shaft comes into contact and slides. As the fluororesin used in the sealing material of the present invention, polytetrafluoroethylene (PTFE) is particularly preferred in terms of its heat resistance, chemical stability, electrical properties, low coefficient of friction, and other properties. The sealing material of the present invention may also have a base material made of one or more fluororesins. In this case, a sealing material using a resin such as that described in Japanese Patent No. 3837266 may be used as the base material, from the viewpoint of providing better lubricity, high sliding properties, and high strength.

[0037] The dynamic friction coefficient of the fluororesin substrate for the sealing material of the present invention is preferably 0.04 to 0.50, more preferably 0.04 to 0.40, and particularly preferably 0.04 to 0.30. In the present invention, the dynamic friction coefficient of the substrate containing a fluororesin is measured in accordance with JIS K7125.

[0038] The sealing material of the present invention has at least an annular base. The sealing material of the present invention has a substantially circular opening formed in the center of the base for inserting a rotating shaft. The base of the sealing material of the present invention may have at least an inner lip portion formed cylindrically on the inner periphery along the axial direction of the rotating shaft, which intersects the circumferential direction of the base, and an annular flat plate portion extending from the outer periphery of the inner lip portion to the outer diameter. In this case, a substantially circular opening for inserting the rotating shaft is formed inside the annular flat plate portion and the inner lip portion. The base of the sealing material of the present invention may also have an outer lip portion extending from the outer periphery of the annular flat plate portion. When the sealing material of the present invention has an inner lip portion and an outer lip portion, the inner lip portion, the annular flat plate portion, and the outer lip portion form an annular recess. In other words, the sealing material of the present invention may have a base having only an annular flat plate portion; a base having an annular flat plate portion and an inner lip portion; a base having an annular flat plate portion and an outer lip portion; or a base having an annular flat plate portion, an inner lip portion, and an outer lip portion. Therefore, the cross-sectional shape of the sealing material when cut on a plane parallel to the central axis of the rotating shaft can be I-shaped (for sealing material having only an annular flat portion), L-shaped (for sealing material having an inner lip portion and an annular flat portion, or for sealing material having an annular flat portion and an outer lip portion), T-shaped (for sealing material having an inner lip portion and annular flat portion), or U-shaped (for sealing material having an inner lip portion, annular flat portion, and an outer lip portion).

[0039] The base portion of the sealing material of the present invention can have a housing contact surface that contacts the housing and a rotating shaft contact surface that contacts the rotating shaft when the sealing material is in use.

[0040] In the sealing material of the present invention, when the base has an inner lip portion, the inner lip portion may be formed cylindrically along the axial direction of the rotation shaft that intersects the circumferential direction of the base. The inner lip portion is formed with an inclination with respect to the axial direction of the rotation shaft in a cross-sectional view, and the degree of inclination of the inner lip portion with respect to the axial direction of the rotation shaft is appropriately selected within a range that produces the effects of the present invention.

[0041] In the sealing material of the present invention, when the base has an outer lip portion, the outer lip portion may be formed cylindrically along the axial direction of the rotation shaft that intersects the circumferential direction of the base. The outer lip portion is formed with an inclination with respect to the axial direction of the rotation shaft in a cross-sectional view, and the degree of inclination of the outer lip portion with respect to the axial direction of the rotation shaft is appropriately selected within a range that achieves the effects of the present invention.

[0042] A sealing material according to a first embodiment of the present invention, as shown in FIGS. 6 and 7 as a sealing material 1a, has a base that includes only an annular flat plate portion 6 (without an inner lip portion). In the sealing material according to the first embodiment of the present invention, the base is annular, and the cross-sectional shape of the sealing material when cut along a plane parallel to the central axis of the rotating shaft is I-shaped. In the sealing material according to the first embodiment of the present invention, the inner peripheral surface of the annular flat plate portion 6 of the base serves as a rotating shaft contact surface that contacts the rotating shaft, and the rotating shaft slides on this rotating shaft contact surface on the inner peripheral side of the annular flat plate portion 6. The sealing material according to the first embodiment of the present invention also has a housing contact surface on the housing side of the annular flat plate portion 6 that contacts the housing. The housing contact surface on the housing side of the annular flat plate portion 6 and the rotating shaft contact surface on the inner peripheral side of the annular flat plate portion 6 are installed in contact with the housing and the rotating shaft, whereby the sealing material according to the first embodiment of the present invention seals the gap between the rotating shaft and the housing.

[0043] A sealing material according to a second embodiment of the present invention, as shown in FIGS. 8 and 9 as sealing material 1b, has a base including an annular flat plate portion 6 and an inner lip portion 5. In the sealing material according to the second embodiment of the present invention, the base is annular, and the cross section of the sealing material when cut along a plane parallel to the central axis of the rotating shaft is L-shaped. In the sealing material according to the second embodiment of the present invention, the inner lip portion 5 is cylindrically formed along an axial direction intersecting the circumferential direction of the base on the inner periphery, and the annular flat plate portion 6 extends from the outer periphery of the inner lip portion 5 to the outer diameter side. In the sealing material according to the second embodiment of the present invention, the inner periphery of the inner lip portion 5, or the inner periphery of the annular flat plate portion 6 and the inner periphery of the inner lip portion 5, constitutes a rotating shaft contact surface that contacts the rotating shaft, and the rotating shaft slides on this rotating shaft contact surface. Furthermore, the sealing material according to the second embodiment of the present invention has a housing contact surface on the housing side of the annular flat plate portion 6 that contacts the housing. The housing contact surface on the housing side of the annular flat portion 6 contacts the housing, and the rotating shaft contact surface on the inner side of the inner lip portion 5, or the rotating shaft contact surfaces on the inner side of the annular flat portion 6 and the inner side of the inner lip portion 5, are installed in contact with the rotating shaft, thereby sealing the gap between the rotating shaft and the housing with the sealing material of the second form of the present invention.

[0044] A sealing material according to a third embodiment of the present invention, as shown in FIGS. 10 and 11 as a sealing material 1c, has a base including an annular flat plate portion 6 and an inner lip portion 5. In the sealing material according to the third embodiment of the present invention, the base is annular, and the cross-sectional shape of the sealing material when cut along a plane parallel to the central axis of the rotating shaft is T-shaped. In the sealing material according to the third embodiment of the present invention, the inner lip portion 5 is formed cylindrically on the inner periphery along an axial direction intersecting the circumferential direction of the base, and the annular flat plate portion 6 extends from the outer periphery of the inner lip portion 5 to the outer diameter side. In the sealing material according to the third embodiment of the present invention, the inner periphery of the inner lip portion 5, or the inner periphery of the annular flat plate portion 6 and the inner periphery of the inner lip portion 5, constitutes a rotating shaft contact surface that contacts the rotating shaft, and the rotating shaft slides on this rotating shaft contact surface. Furthermore, the sealing material according to the third embodiment of the present invention has a housing contact surface on the housing side of the annular flat plate portion 6 that contacts the housing. The housing contact surface on the housing side of the annular flat portion 6 contacts the housing, and the rotating shaft contact surface on the inner side of the inner lip portion 5, or the rotating shaft contact surfaces on the inner side of the annular flat portion 6 and the inner side of the inner lip portion 5, are installed in contact with the rotating shaft, thereby sealing the gap between the rotating shaft and the housing with the sealing material of the third form of the present invention.

[0045] A sealing material according to a fourth embodiment of the present invention, as shown in FIGS. 12 and 13 as a sealing material 1d, has a base including an annular flat plate portion 6 and an outer lip portion 7. In the sealing material according to the fourth embodiment of the present invention, the base is annular, and the cross-sectional shape of the sealing material when cut along a plane parallel to the central axis of the rotating shaft is L-shaped. In the sealing material according to the fourth embodiment of the present invention, the outer lip portion 7 is cylindrically formed on the outer periphery along an axial direction intersecting the circumferential direction of the base, and the annular flat plate portion 6 extends from the inner periphery of the outer lip portion 7 toward the inner diameter. In the sealing material according to the fourth embodiment of the present invention, the inner periphery of the annular flat plate portion 6 serves as a rotating shaft contact surface that contacts the rotating shaft, and the rotating shaft slides on this rotating shaft contact surface. Furthermore, in the sealing material according to the fourth embodiment of the present invention, the housing-side of the annular flat plate portion 6 and the housing-side of the outer lip portion 7 have housing contact surfaces that contact the housing. The housing contact surfaces on the housing side of the annular flat portion 6 and the housing side of the outer lip portion 7 contact the housing, and the rotating shaft contact surface on the inner side of the annular flat portion 6 is installed in contact with the rotating shaft, thereby sealing the gap between the rotating shaft and the housing by the sealing material of the fourth form of the present invention.

[0046] As described with reference to FIGS. 1 to 3 , the sealing material of the fifth embodiment of the present invention has a base portion including an annular flat plate portion 6, an inner lip portion 5, and an outer lip portion 7. In the sealing material of the fifth embodiment of the present invention, the base portion is annular, and the cross-sectional shape when the sealing material is cut along a plane parallel to the central axis of the rotating shaft is U-shaped. In the sealing material of the fifth embodiment of the present invention, the inner lip portion 5 is formed cylindrically along an axial direction intersecting the circumferential direction of the base on the inner peripheral side, and the annular flat plate portion 6 extends from the outer peripheral side of the inner lip portion 5 to the outer diameter side. Furthermore, the outer lip portion 7 is formed cylindrically along an axial direction intersecting the circumferential direction of the base on the outer peripheral side, and the annular flat plate portion 6 extends from the inner peripheral side of the outer lip portion 7 to the inner diameter side. The housing-side surface of the annular flat plate portion 6 and the outer peripheral surface of the outer lip portion 7 have housing contact surfaces that come into contact with the housing on the housing side of the annular flat plate portion 6 and the housing side of the outer lip portion 7. The outer peripheral surface of the outer lip portion 7, or the outer peripheral surface of the annular flat portion 6 and the outer peripheral surface of the outer lip portion 7, come into contact with the housing, thereby improving the sealing of the gap between the rotating shaft and the housing. The housing contact surface on the housing side of the annular flat portion 6 comes into contact with the housing, and the rotating shaft contact surface on the inner peripheral side of the inner lip portion 5, or the rotating shaft contact surfaces on the inner peripheral side of the annular flat portion 6 and the inner peripheral side of the inner lip portion 5, are installed in contact with the rotating shaft, so that the sealing material of the fifth form of the present invention seals the gap between the rotating shaft and the housing.

[0047] In addition, among the sealing materials of the present invention, in forms in which the base has an inner lip portion (the sealing material of the second form of the present invention, the sealing material of the third form of the present invention, and the sealing material of the fifth form of the present invention), the rotating shaft contact surface may be formed so that the entire inner surface of the annular flat plate portion and the inner surface of the inner lip portion contact the rotating shaft, or the rotating shaft contact surface may be formed so that a portion of the inner surface of the annular flat plate portion and the inner surface of the inner lip portion contact the rotating shaft, or the rotating shaft contact surface may be formed so that only the inner surface of the inner lip portion contacts the rotating shaft.

[0048] The sealing material of the present invention has a low conductive portion (a portion other than the high conductive portion) and a high conductive portion having a volume resistivity lower than that of the low conductive portion.

[0049] The low-conductivity portion of the sealing material of the present invention is a portion having a higher volume resistivity than the high-conductivity portion, and the volume resistivity is 1.0×10 4 Ω·cm or more. In other words, the low-conductivity part has a volume resistivity of 1.0×10 4 The volume resistivity of the low conductive part is preferably 1.0×10 5 Ω·cm or more.

[0050] In the sealing material of the present invention, a highly conductive portion is formed at at least one location in the circumferential direction of the base, i.e., a highly conductive portion extending from the inner peripheral surface to the outer peripheral surface of the base. In the sealing material of the present invention, the base of the sealing material preferably has an inner lip portion, and a highly conductive portion is formed at at least one location in the circumferential direction of the inner lip portion and the annular plate portion, extending from the inner lip portion to the annular plate portion, i.e., a highly conductive portion that is conductive from the inner lip portion to the annular plate portion. Each highly conductive portion is conductive at least from the inner peripheral surface to the outer peripheral surface of the annular plate portion, preferably at least from the inner lip portion to the annular plate portion, so that the highly conductive portion contacts both the rotating shaft and the housing and electrically connects the rotating shaft and the housing, thereby forming a grounding path for conducting current generated in the rotating shaft due to shaft voltage to the outside via the highly conductive portion and the housing.

[0051] Furthermore, when the sealing material of the present invention has an outer lip portion, the outer lip portion may also have a highly conductive portion formed therein that is electrically connected to the highly conductive portion of the annular flat plate portion, or the outer lip portion may not have a highly conductive portion formed therein. When a highly conductive portion is formed in at least one circumferential location on the inner lip portion and the annular flat plate portion, extending from the inner lip portion through the annular flat plate portion to the outer lip portion, each highly conductive portion is conductive from the inner lip portion through the annular flat plate portion to the outer lip portion, and therefore the highly conductive portion comes into contact with both the rotating shaft and the housing, electrically connecting the rotating shaft and the housing, thereby forming a ground path for flowing current generated in the rotating shaft due to the shaft voltage to the outside via the highly conductive portion and the housing.

[0052] The highly conductive portion of the sealing material of the present invention has a volume resistivity lower than that of the low conductive portion. The volume resistivity of the highly conductive portion is preferably 1.0×10 2 Ω·cm or less, preferably 1.0×10 1 Ω·cm or less, preferably 1.0×10 0 The lower limit of the volume resistivity of the highly conductive portion is not particularly limited, but is preferably 1.0×10 -1 Ω·cm, and the volume resistivity of the highly conductive part is preferably 1.0×10 -1 ~1.0×10 2 Ω·cm, more preferably 1.0×10 -1 ~1.0×10 1 Ω·cm, more preferably 1.0×10 -1 ~1.0×10 0 When the volume resistivity of the highly conductive portion is within the above range, the current resulting from the axial voltage can be conducted by the sealing material of the present invention and can be grounded.

[0053] The highly conductive portion of the sealing material of the present invention contains a conductive filler. That is, the highly conductive portion is a fluororesin to which a conductive filler has been added. Examples of conductive fillers include carbon-based materials, metal fibers, metal oxides such as zinc oxide, tin oxide, and indium tin oxide (ITO), and metal sulfides such as copper sulfide and zinc sulfide. The highly conductive portion preferably contains a carbon-based material and / or metal fibers as the conductive filler. Examples of carbon-based materials include graphite, carbon fibers, carbon black, ketjen black, and carbon nanotubes. Examples of metal fibers include stainless steel and copper.

[0054] The low-conductivity part of the sealing material of the present invention may contain a reinforcing filler. Furthermore, the low-conductivity part of the sealing material of the present invention may not contain a reinforcing filler, that is, may be made of a fluororesin base material that does not contain a reinforcing filler, as long as the low-conductivity part has durability against abrasion caused by sliding of a rotating shaft that meets or exceeds the required performance.

[0055] When the low-conductivity portion of the sealing material of the present invention contains a reinforcing filler, the low-conductivity portion is obtained by adding the reinforcing filler to a fluororesin substrate. The reinforcing filler is a filler that, when contained in the fluororesin, improves durability against wear caused by sliding of the rotating shaft. The reinforcing filler is not particularly limited as long as it can improve durability against wear caused by sliding of the rotating shaft and can achieve a predetermined volume resistivity value, and examples thereof include metal fiber and carbon fiber. It is particularly preferable for the low-conductivity portion to contain carbon fiber as the reinforcing filler, as this increases friction and wear resistance.

[0056] In the sealing material of the present invention, the volume resistivity of the high conductive portion can be adjusted by adjusting the type of fluororesin, the type and content of the conductive filler, etc. Furthermore, in the sealing material of the present invention, the volume resistivity of the low conductive portion can be adjusted by adjusting the type of fluororesin, the type and content of the reinforcing filler, etc. Furthermore, in the sealing material of the present invention, the content of the conductive filler in the high conductive portion is appropriately selected depending on the type of conductive filler and the set volume resistivity of the high conductive portion, etc. Furthermore, in the sealing material of the present invention, the content of the reinforcing filler in the low conductive portion is appropriately selected depending on the type of reinforcing filler, the target friction and wear resistance, the set volume resistivity, etc. Note that, by selecting the content of conductive materials such as metal fibers and carbon fibers in the fluororesin substrate, they can be used as a conductive filler to be contained in the high conductive portion or as a reinforcing filler to be contained in the low conductive portion.

[0057] When a fluororesin is used as the base resin of a sealing material and the entire sealing material is made of a resin material with the same filler composition, adding a conductive filler to the base resin to impart conductivity reduces durability against wear caused by sliding of the rotating shaft. In this case, adding a reinforcing filler to improve durability reduces conductivity. Furthermore, adding a conductive filler to an amount that does not reduce durability against wear caused by sliding of the rotating shaft does not provide sufficient conductivity.

[0058] In contrast to when the entire sealing material is made of a resin material of the same composition, the sealing material of the present invention forms high conductivity portions and low conductivity portions in the circumferential direction, so that the high conductivity portions are responsible for conducting and grounding the current resulting from the shaft voltage, and the low conductivity portions are responsible for providing durability against wear due to sliding of the rotating shaft. This makes it possible to increase both the conductivity of the sealing material and its durability against wear due to sliding of the rotating shaft.

[0059] Furthermore, the high conductivity portion and the low conductivity portion may contain a solid lubricant such as aromatic polyamide, a reinforcing fiber such as glass fiber, carbon fiber, or aromatic polyamide fiber, for the purpose of improving sliding characteristics, within a range that does not impair the effects of the present invention.

[0060] In the sealing material of the present invention, the substrate of both the high-conductivity portion and the low-conductivity portion is a fluororesin, and the high-conductivity portion and the low-conductivity portion are integrated. In the sealing material of the present invention, the fluororesin of the fluororesin substrate constituting the high-conductivity portion and the fluororesin of the fluororesin substrate constituting the low-conductivity portion may be the same or different, but it is preferable that they are the same fluororesin from the viewpoint of not reducing the strength of the boundary portion.

[0061] In this way, the sealing material of the present invention has a high conductivity and slidability in the high conductivity portion, and a low conductivity portion that has high strength and durability against abrasion due to sliding of the rotating shaft, so that it is possible to improve both the conductivity and abrasion resistance of the sealing material overall. In the sealing material of the present invention, the low conductivity portion, which has high abrasion resistance, prevents the entire inner periphery of the sealing material (at least the inner periphery surface of the annular flat plate portion, preferably the inner periphery surface of the annular flat plate portion and the inner lip portion) from wearing out due to sliding of the inner periphery with the rotating shaft, so that wear of the high conductivity portion also becomes less likely to progress, and the abrasion resistance of the sealing material as a whole is improved. The sealing material of the present invention can increase both the conductivity of the sealing material and its durability against wear caused by sliding of the rotating shaft by forming a high-conductivity portion having high conductivity and slidability and a low-conductivity portion having high strength and high wear resistance in the circumferential direction, so that both the conductivity of the sealing material and its durability against wear caused by sliding of the rotating shaft can be increased with a simple configuration without employing means such as processing the sealing material into a complex shape or making it into a special seal structure. In other words, the sealing material of the present invention has a good balance of functions such as prevention of electrolytic corrosion, slidability, strength, and wear resistance, can channel current flowing in a rotating body such as a shaft due to axial voltage to the outside, and has a simple structure and good durability.

[0062] In the sealing material of the present invention, the highly conductive portion may be formed in at least one location in the circumferential direction. The number of locations in the circumferential direction where the highly conductive portion is formed may be, for example, four locations, as in the embodiments shown in FIGS. 1 to 3, 15, and 16, or two locations, as in the embodiment shown in FIG. 14. In the sealing material of the present invention, forming two or more highly conductive portions in the circumferential direction is preferable because, even if a portion of the sealing material loses contact with a rotating shaft or a part of the housing due to a gap scratch, dust, or the like, other portions can still make contact, thereby preventing electrolytic corrosion. Furthermore, when two or more highly conductive portions are formed in the circumferential direction, forming the highly conductive portions at equal intervals is preferable because it reduces the difference in surface wear due to friction. Furthermore, forming the highly conductive portions radially distributes the overall frictional resistance between the inner and outer sides. In the sealing material of the present invention, forming four highly conductive portions at equal intervals in the circumferential direction, as in the embodiments shown in FIGS. 1 to 3, 15, and 16, is particularly preferable from the viewpoint of formability.

[0063] As described with reference to the embodiment shown in FIG. 5 , the pressure inside the housing of an electric motor is higher than the pressure outside the housing. Therefore, when the base of the sealing material of the present invention has an inner lip portion, a force is applied in a direction pressing the inner lip portion toward the rotating shaft, thereby strengthening the adhesion of the inner lip portion to the rotating shaft. Furthermore, when an outer lip portion is further provided, a force is applied in a direction pressing the outer lip portion toward the housing, thereby strengthening the adhesion of the outer lip portion to the housing. In other words, the pressure of the sealed fluid in the housing strengthens the adhesion between the inner lip portion of the sealing material of the present invention and the rotating body shaft. This improves the sealing performance of the sealing material of the present invention and prevents leakage of liquids such as oil. Furthermore, the pressure of the sealed fluid in the housing strengthens the adhesion between the outer lip portion of the sealing material of the present invention and the housing. This further improves the sealing performance of the sealing material of the present invention and enhances its effectiveness in preventing leakage of liquids such as oil.

[0064] The inner lip portion and the outer lip portion of the sealing material of the present invention may be provided, for example, by shaping a processed raw material made of a fluororesin substrate in a flat, annular shape and having a highly conductive portion formed in a predetermined position. That is, the sealing material of the present invention may be a shaped material, specifically a shaped material of a processed raw material made of a fluororesin substrate in a flat, annular shape and having a highly conductive portion formed in a predetermined position.

[0065] When the sealing material of the present invention is a shaped material made of a raw material that is made of a flat, annular fluororesin substrate and has highly conductive portions formed in predetermined locations, the ambient temperature and frictional heat caused by the sliding of the rotating shaft act as a restoring force that attempts to return the material to its original shape before shaping. This further improves the sealing performance between the inner lip portion of the sealing material of the present invention and the rotating shaft, and, if an outer lip portion is also provided, further improves the sealing performance between the outer lip portion and the housing.

[0066] The inner lip portion and the outer lip portion of the sealing material of the present invention may be formed, for example, by cutting a processed raw material made of an annular fluororesin substrate having a thickness equal to or greater than the height of the inner lip portion and the outer lip portion, and having highly conductive portions formed in predetermined positions. That is, the sealing material of the present invention may be a machined material, more specifically, a machined material made of a processed raw material made of an annular fluororesin substrate having a thickness equal to or greater than the height of the inner lip portion and the outer lip portion, and having highly conductive portions formed in predetermined positions.

[0067] 17, a cylindrical pipe mold with a hole in the center is filled with four equal partition plates, and 30 g of a mixture of conductive filler and fluororesin as the high-conductivity material 21 and a mixture of reinforcing filler and fluororesin as the low-conductivity material 22 are poured into the predetermined positions. The partition plates are then removed, and the molded body is then molded at a molding pressure of 50 MPa to remove the molded body. The removed molded body is then fired at 365°C for 5 hours to produce a cylindrical material with a diameter of 32 mm and a height of 120 mm. Next, this cylindrical material is turned on a lathe to form a washer shape with an outer diameter of 30 mm, an inner diameter of 18.5 mm, and a thickness of 1 mm, which is then hot pressed under conditions of a pressure of 20 MPa and a temperature of 300°C to form the desired shape, thereby obtaining a sealing material.

[0068] The shapes and arrangements of the high conductivity portion and low conductivity portion of the sealing material of the present invention are not limited as long as electrical conduction is established from the rotating shaft to the housing via the high conductivity portion.

[0069] The width (circumferential length) of the high conductive portion of the sealing material of the present invention may be narrower than the width of the low conductive portion. This allows the high conductive portion to be produced inexpensively, and also maintains low friction, increasing durability against wear due to sliding of the rotating shaft of the product. Examples of embodiments in which the width (circumferential length) of the high conductive portion of the sealing material of the present invention is narrower than the width of the low conductive portion include the embodiments shown in Figures 1 to 3, 15, and 16.

[0070] The width (circumferential length) of the outer diameter side of the highly conductive portion of the sealing material of the present invention may be wider than the width (circumferential length) of the inner diameter side of the highly conductive portion. By making the width of the outer diameter side of the highly conductive portion wider than the width of the inner diameter side of the highly conductive portion, it is possible to reliably ground the highly conductive portion to the outside, while reducing the width of the inner diameter side of the highly conductive portion to match the size of the inner diameter, which is smaller than the outer diameter, and reducing frictional wear associated with the highly conductive portion.

[0071] The central portion of the conductive portion of the sealing material of the present invention may be narrower than the outer diameter side and / or inner diameter side of the conductive portion. Even if the width of the central portion is narrow, the width of the inner diameter side and / or outer diameter side can be widened to ensure reliable conduction and grounding. Furthermore, by having the central portion of the conductive portion of the sealing material of the present invention narrower than the outer diameter side and / or inner diameter side of the conductive portion, the amount of conductive filler used can be reduced, allowing for inexpensive production. Furthermore, by having the central portion of the conductive portion of the sealing material of the present invention narrower than the outer diameter side and / or inner diameter side of the conductive portion, the conductive portion can be made smaller, and the portions other than the conductive portion become relatively larger, thereby improving the strength of the sealing material after molding. Examples of embodiments in which the central portion is narrower than the outer diameter side and / or inner diameter side of the conductive portion include the embodiments shown in Figures 15 and 16.

[0072] The sealing material of the present invention may be arranged in a plurality of positions in the axial direction, and other materials such as grease may be added to improve the sealing properties.

[0073] The sealing material of the present invention is suitable for use as a sealing material for the rotating shaft of an electric motor that receives and converts electrical energy into motive power, preferably an electric motor that serves as a power source for automobiles such as electric vehicles (EVs) and hybrid vehicles (HVs), electric compressors, dehumidifying rotors, etc. More specifically, it is suitable for use as a sealing material for sealing the gap between the rotating shaft (shaft) and housing (case) of an electric motor that receives and converts electrical energy into motive power, preferably an electric motor that serves as a power source for automobiles such as electric vehicles (EVs) and hybrid vehicles (HVs), electric compressors such as refrigeration compressors, dehumidifying rotors, etc.

[0074] The electric motor of the present invention comprises: The sealing material of the present invention; a housing that contacts an outer peripheral surface of the sealing material; a rotary shaft that contacts an inner peripheral surface of the sealing material and is supported rotatably relative to the housing along an axial direction that intersects the circumferential direction; a bearing that rotatably supports the rotary shaft; The electric motor is characterized by comprising:

[0075] The electric motor of the present invention can be an electric motor that receives electrical energy and converts it into motive energy, preferably an electric motor that is the power source for automobiles such as electric vehicles (EVs) and hybrid vehicles (HVs), electric compressors such as refrigerator compressors, dehumidifying rotors, etc., and more specifically, the electric motor can be an electric motor that is equipped with a sealing material for sealing the gap between the rotating shaft (shaft) and housing (case) of the electric motor that is the power source for automobiles such as electric vehicles (EVs) and hybrid vehicles (HVs), electric compressors such as refrigerator compressors, dehumidifying rotors, etc.

[0076] The housing, rotating shaft, and bearings for the electric motor of the present invention are not particularly limited as long as they are bearings used in an electric motor, a rotating shaft rotatably supported by the bearings, and a housing (case) in which the bearings are housed. Examples of such structures include those described in JP 2017-22319 A, JP 2019-056399 A, JP 2014-142065 A, etc.

[0077] In the electric motor of the present invention, the housing is in contact with the outer peripheral surface of the sealing material of the present invention. Also, in the electric motor of the present invention, the rotating shaft is rotatably supported relative to the housing along an axial direction intersecting the circumferential direction of the sealing material of the present invention. The rotating shaft is in contact with the inner peripheral surface of the sealing material of the present invention and slides against the inner peripheral surface of the sealing material of the present invention during rotation.

[0078] In the electric motor of the present invention, the inner peripheral surface of the sealing material of the present invention contacts the rotating shaft and the outer peripheral surface contacts the housing, thereby sealing the gap between the rotating shaft and the housing. The inner peripheral surface of the sealing material of the present invention that contacts the rotating shaft is the rotating shaft contact surface, and the outer peripheral surface of the sealing material of the present invention that contacts the housing is the housing contact surface.

[0079] In addition, in the electric motor of the present invention, the inner surface of the sealing material of the present invention, which has a highly conductive portion formed from the inner surface of the base to the outer surface, comes into contact with the rotating shaft, and the outer surface comes into contact with the housing, thereby electrically connecting the rotating shaft and the housing, and thereby forming a grounding path for flowing current generated in the rotating shaft due to the shaft voltage to the outside via the highly conductive portion and the housing.

[0080] The method for producing the sealing material of the present invention is not particularly limited, but examples thereof include the production method of the present invention shown below.

[0081] The method for producing a sealing material of the present invention includes the steps of: a first step of molding a material for a low conductive portion, which is a mixture of at least a reinforcing filler and a fluororesin, and a material for a high conductive portion, which is a mixture of at least a conductive filler and a fluororesin, to obtain an annular flat plate-shaped molded body; a second step of shaping the annular flat plate-shaped body to obtain a sealing material having at least an annular base portion and including a highly conductive portion at at least one location in the circumferential direction of the base portion; The present invention provides a method for producing a sealing material, which comprises the steps of:

[0082] The first step in the method for producing a sealing material of the present invention is a step of molding a material for a low-conductivity portion and a material for a high-conductivity portion to obtain an annular, flat-plate-shaped molded body.

[0083] The low-conductivity material comprises a mixture of at least a reinforcing filler and a fluororesin. The reinforcing filler and fluororesin used in the method for producing a sealing material of the present invention are the same as those used in the material for the low-conductivity portion. The amounts of the reinforcing filler and fluororesin mixed in the material for the low-conductivity portion are appropriately adjusted to the amounts required to form the low-conductivity portion of the sealing material of the present invention.

[0084] The high conductivity material is composed of a mixture of at least a conductive filler and a fluororesin. The conductive filler and fluororesin used in the high conductivity material are the same as those used in the sealing material of the present invention. The amounts of the conductivity and fluororesin mixed in the high conductivity material are appropriately adjusted to the amounts required to form the high conductivity portion of the sealing material of the present invention.

[0085] In the first step, the material for the low conductivity portion and the material for the high conductivity portion are used to mold the material for the low conductivity portion and the material for the high conductivity portion so that the low conductivity portion and the high conductivity portion are formed in the desired position and shape of the sealing material of the present invention, thereby obtaining an annular flat molded body.

[0086] The method for carrying out the first step is not particularly limited, but for example, a partition plate is placed in a cylindrical molding pipe mold with a hole in the center so that low conductivity portions and high conductivity portions are formed in predetermined positions, and material for the low conductivity portions and material for the high conductivity portions are poured into the predetermined positions.The partition plate is then removed, and the molded product is then press-molded at a predetermined surface pressure to obtain a cylindrical molded body. The cylindrical compact is then fired to obtain a cylindrical fired product comprising a low-conductivity portion made of the material for the low-conductivity portion and a high-conductivity portion made of the material for the high-conductivity portion. The firing temperature is not particularly limited as long as it is a temperature at which the fluororesins in the material for the low-conductivity portion and the fluororesins in the material for the high-conductivity portion sinter together and become dense enough to ensure sealing performance, but is preferably 320 to 360°C, more preferably 340 to 360°C. The firing atmosphere is preferably air. Next, the cylindrical fired product is processed by lathe processing or the like to obtain an annular plate-shaped molded body.

[0087] The second step in the method for manufacturing the sealing material of the present invention is a step of shaping and processing the annular flat molded body obtained by performing the first step to obtain the sealing material of the present invention, i.e., a sealing material having at least an annular base and including a highly conductive portion in at least one location circumferentially of the base.

[0088] In the second step, the method of shaping is not particularly limited, but examples thereof include a method in which an annular plate-shaped molded body is placed in a processing mold, and then hot-pressed at a pressure of 10 to 100 MPa and a temperature of 150 to 300°C to be shaped into a predetermined shape.

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0090] Examples 1 to 4 PTFE resin (Daikin M392) was dry-blended with conductive carbon black (Ketjenblack EC300J, Lion Specialty Chemicals Co., Ltd.) or SUS chop (Bexhield, Bekaert Japan Co., Ltd.) in a roll mill or Henschel mixer, adjusting the mixing ratio to achieve the desired volume resistivity. The average particle size of the resulting mixture is shown in Table 1. Next, 10 g of the mixture was pressed into a 52 mm diameter mold at a molding pressure of 30 MPa using a press. The mixture was then calcined at 365°C for 5 hours to obtain a test sample. The volume resistivity of the obtained test sample was then measured by the four-probe method. The results are shown in Table 1.

[0091] (Reference example 1) 10 g of PTFE resin (M392 manufactured by Daikin) was pressed into a shape with a diameter of 52 mm at a molding pressure of 30 MPa, and then baked at 365°C for 5 hours to obtain a test sample. The volume resistivity of the obtained test sample was then measured by the four-probe method. The results are shown in Table 1.

[0092] <Method for measuring volume resistivity using the four-probe method> Using the same principle as the four-terminal method (current-voltage method), four needle-shaped electrodes are placed in a straight line on the sample, a constant current is passed between the two outer probes, and the potential difference between the two inner probes is measured to determine the resistance.The volume resistivity is then calculated by multiplying the resistance by the sample thickness and the RCF (Resistivity Correction Factor).

[0093] For the test samples of Examples 1 to 4, the volume resistance was 1.0 × 10 4 Those with a resistivity of less than 1.0×10 Ω·cm were considered to be conductive. 4 Ω·cm or more was considered non-conductive. In the table, the measurement results shown as O / L are 1.0×10 6 Ω·cm or more. Conductive properties are shown as "yes" and non-conductive properties as "no" in Table 1.

[0094] [Table 1]

[0095] As shown in Table 1, Examples 1 to 3 were found to be conductive. Therefore, it was confirmed that Examples 1 to 3 function as the high conductivity part of the sealing material of the present invention. Example 4 and Reference Example 1 were found to be non-conductive. Therefore, it was confirmed that Example 4 functioned as the low conductivity part of the sealing material of the present invention. [Explanation of symbols]

[0096] 1. Sealing material 2 aperture 3 Rotating shaft 4 Housing (case) 5 Inner lip 6 Annular flat plate 7 Outer lip 8 Annular recess 9 Highly conductive part 11 Low conductive part 12 Rotating shaft contact surface 13 Housing contact surface 21 Highly conductive materials 22 Low-conductivity materials

Claims

1. A sealing material made of a fluororesin base material and having at least an annular base portion, The base has a volume resistivity of 1.0×10 ４ a low-conductivity portion having a volume resistivity of Ω cm or more and a high-conductivity portion having a volume resistivity lower than that of the low-conductivity portion; the highly conductive portion is formed at least at one location in the circumferential direction of the base portion; A sealing material characterized by:

2. 2. The sealing material according to claim 1, wherein the high-conductivity portion contains a conductive filler, and the low-conductivity portion contains a reinforcing filler.

3. 3. The sealing material according to claim 2, wherein the conductive filler is a carbon material and / or a metal fiber.

4. The volume resistivity of the highly conductive part is 1.0×10 －１ ~1.0 x 10 ２ 3. The sealing material according to claim 1, wherein the resistance is Ω·cm.

5. The sealing material according to claim 1 or 2, characterized in that the fluororesin is one or more selected from the group consisting of polytetrafluoroethylene (PTFE), polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride.

6. 3. The sealing material according to claim 1, wherein the highly conductive portions are formed at four locations at equal intervals in the circumferential direction of the base portion.

7. 3. The sealing material according to claim 1, wherein the width of the highly conductive portion on the outer diameter side is wider than the width of the highly conductive portion on the inner diameter side.

8. the base portion includes an inner lip portion formed cylindrically on an inner peripheral side along an axial direction intersecting the circumferential direction of the base portion, and an annular flat plate portion extending from an outer peripheral side of the inner lip portion to an outer diameter side, 3. The sealing material according to claim 1, wherein the highly conductive portion is formed at least at one location in the circumferential direction of the inner lip portion and the annular flat plate portion.

9. 3. The sealing material according to claim 1, wherein the sealing material is a shaped material.

10. The sealing material according to claim 1 or 2; a housing that contacts an outer peripheral surface of the sealing material; a rotary shaft that contacts an inner peripheral surface of the sealing material and is supported rotatably relative to the housing along an axial direction that intersects the circumferential direction; a bearing that rotatably supports the rotary shaft; An electric motor comprising:

11. a first step of molding a material for a low conductive portion, which is a mixture of at least a reinforcing filler and a fluororesin, and a material for a high conductive portion, which is a mixture of at least a conductive filler and a fluororesin, to obtain an annular flat plate-shaped molded body; a second step of shaping the annular flat plate-shaped body to obtain a sealing material having at least an annular base portion and including a highly conductive portion at at least one location in the circumferential direction of the base portion; A method for producing a sealing material, comprising:

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