Sealing device and electric motor

Abstract

This sealing device comprises: an annular reinforcing ring fixed to a housing; an annular elastic member having a fixed part which is fixed to the reinforcing ring, and a lip which protrudes from the fixed part and is in sliding contact with the outer peripheral surface of a shaft; and at least one annular spring which is disposed so as to sandwich the lip together with the outer peripheral surface of the shaft and presses the lip against the outer peripheral surface of the shaft. The elastic member is composed of a conductive elastic material. The lip surface contacting the outer peripheral surface of the shaft has a linear shape in a natural state when viewed in a cross-section defined by a plane including the center axis of the elastic member. The entire width of the at least one spring is greater than the thickness of the at least one spring.

Description

[Technical Field]

[0001] The present disclosure relates to a sealing device and an electric motor. [Background technology]

[0002] Conventionally, there have been known sealing devices that seal an annular space formed between a housing having a hole and a shaft inserted into the hole. For example, the device described in Patent Document 1 includes a conductive seal ring that electrically connects the housing and the shaft to each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-142065 Summary of the Invention [Problem to be solved by the invention]

[0004] In an electric motor, an induced current is generated in the shaft as it rotates. The electromagnetic waves caused by this induced current can cause noise in devices such as AM (Amplitude Modulation) radio receivers.

[0005] However, in the device described in Patent Document 1, the contact area between the seal ring and the shaft is small or fluctuates, resulting in unstable electrical conduction between the housing and the shaft. Therefore, the device described in Patent Document 1 has room for improvement in terms of its ability to reduce the aforementioned noise. [Means for solving the problem]

[0006] In order to solve the above problems, a sealing device according to one embodiment of the present disclosure is a sealing device that is arranged between a housing having a hole and a shaft inserted into the hole, and seals a gap between the inner surface of the housing and the outer surface of the shaft, and includes: an annular reinforcing ring fixed to the housing, a fixed portion fixed to the reinforcing ring, and an annular elastic member having a lip protruding from the fixed portion and in slidable contact with the outer surface of the shaft; and at least one annular spring that presses the lip against the outer surface of the shaft, wherein the lip is sandwiched between the outer surface of the shaft and the at least one spring, the elastic member is made of an electrically conductive elastic material, and the lip has a contact surface that contacts the outer surface of the shaft, and the contact surface is linear in its natural state when viewed in a cross section cut along a plane including the central axis of the elastic member.

[0007] An electric motor according to one aspect of the present disclosure includes the sealing device of the above aspect, the housing, and the shaft. [Effects of the Invention]

[0008] In the present disclosure, electrical conduction between the housing and the shaft can be stably ensured. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an electric motor according to a first embodiment. [Figure 2] 1 is a cross-sectional view showing a sealing device according to a first embodiment. [Figure 3] FIG. 2 is a perspective view showing a part of the sealing device according to the first embodiment. [Figure 4] FIG. 6 is a cross-sectional view showing a sealing device according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing a sealing device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0011] 1. First embodiment 1-1. Overview of electric motors Fig. 1 is a cross-sectional view showing an electric motor 1 according to a first embodiment. Fig. 1 shows a part of a cross section of the electric motor 1 cut along a plane including an axis line AX. The electric motor 1 is configured to be substantially rotationally symmetric with the axis line AX as the rotation axis.

[0012] The electric motor 1 shown in Fig. 1 is a rotary electric motor that is rotationally driven by Lorentz force. The electric motor 1 is used as a prime mover mounted on automobiles such as EVs (Electric Vehicles), HVs (Hybrid Vehicles), PHVs (Plug-in Hybrid Vehicles), and FCVs (Fuel Cell Vehicles). Note that the use of the electric motor 1 is not limited to prime movers mounted on automobiles, and may be, for example, prime movers mounted on vehicles other than automobiles, prime movers mounted on moving bodies other than vehicles, or prime movers mounted on general industrial machinery such as construction machinery, agricultural machinery, machine tools, and woodworking machinery.

[0013] The electric motor 1 is configured to reduce an induced current generated in the shaft 120. Specifically, as shown in FIG. 1 , the electric motor 1 includes a sealing device 10, a housing 110, a shaft 120, bearings 130 and 140, a stator 150, and a rotor 160.

[0014] In the electric motor 1, electrical continuity between the housing 110 and the shaft 120 is ensured by the sealing device 10. Therefore, induced current generated in the shaft 120 can be released to the housing 110. As a result, it is possible to reduce noise caused by the induced current in equipment such as an AM radio receiver. Furthermore, as will be described later, it is easy to ensure installation space for the sealing device 10, and the cost associated with installing the sealing device 10 is reduced, which allows for the miniaturization and cost reduction of the electric motor 1. First, each part of the electric motor 1 will be described in order below based on FIG. 1.

[0015] For ease of explanation, the direction along the axis AX of the shaft 120 may be referred to as the "axial direction." The direction around the axis AX may be referred to as the "circumferential direction." The direction perpendicular to the axis AX may be referred to as the "radial direction." FIG. 1 shows the X1 and X2 directions, which indicate axial directions. The X1 direction is the direction along the axis AX from the outside of the housing 110 toward the inside of the housing 110 through a hole H, which will be described later. The X2 direction is the opposite direction to the X1 direction.

[0016] The housing 110 is a conductive structure having a hole H. Here, the housing 110 is preferably grounded to allow induced current from the shaft 120 to escape. The housing 110 is made of a metal material such as iron, stainless steel, or an aluminum alloy.

[0017] The housing 110 is composed of a main body 110a and a lid 110b. The main body 110a is cylindrical with a bottom and has a space for accommodating the stator 150 and the rotor 160. A hole H is provided at the bottom of the main body 110a. The hole H is in communication with the space and is a space surrounded by an inner circumferential surface 111 that extends around the axis AX. The outer circumferential surface of a bearing 130, such as a ball bearing, is fitted into the inner circumferential surface 111 of the hole H.

[0018] 1, a water jacket 114 is provided on the cylindrical portion of the main body 110a. Cooling water flows through the water jacket 114. The water jacket 114 is provided as needed, and may be omitted.

[0019] The lid 110b is a plate-like member that closes the opening of the main body 110a. A recess R is provided on the surface of the lid 110b facing the X2 direction. The recess R communicates with the space inside the main body 110a and has an inner circumferential surface 112 that extends around the axis AX. The inner circumferential surface 112 of the recess R is fitted with the outer circumferential surface of a bearing 140, such as a ball bearing.

[0020] The shape of the housing 110 is not limited to the example shown in Fig. 1 and may be any shape. The material constituting the housing 110 is not limited to a metal material as long as it is capable of providing the housing 110 with the necessary rigidity and conductivity. For example, the material constituting the housing 110 may be a material in which a conductive material such as a metal material and an insulating material such as a resin material or a ceramic material are combined in a laminated or mixed form.

[0021] The shaft 120 is a conductive rod-shaped member having an outer circumferential surface 121 that extends around the axis AX. The shaft 120 is inserted into a hole H in the housing 110 and is supported by bearings 130 and 140 relative to the housing 110 so as to be rotatable about the axis AX. The shaft 120 is made of a metal material such as iron, stainless steel, or an aluminum alloy. The outer circumferential surface 121 has a smaller diameter than the inner circumferential surface 111 of the hole H in the housing 110. Therefore, an annular space S is formed between the outer circumferential surface 121 and the inner circumferential surface 111. In the example shown in FIG. 1, the outer diameter of the shaft 120 is constant throughout the axial direction.

[0022] The material constituting shaft 120 is not limited to metal materials as long as it can provide shaft 120 with the necessary rigidity and conductivity. The shape of shaft 120 is not limited to the example shown in Fig. 1 and may have, for example, multiple portions with different outer diameters. Shaft 120 may be a solid shaft or a hollow shaft.

[0023] The stator 150 is fixed to the housing 110 by an appropriate method such as fitting or with an adhesive. The stator 150 is, for example, a coil arranged along the circumferential direction of the main body 110a. On the other hand, the rotor 160 is fixed to the shaft 120 by an appropriate method such as fitting or with an adhesive. The rotor 160 is, for example, a permanent magnet. The stator 150 and the rotor 160 generate a rotational moment around the axis line AX on the shaft 120 due to the Lorentz force.

[0024] The sealing device 10 is an annular structure disposed in the space S between the inner peripheral surface 111 of the hole H of the housing 110 and the outer peripheral surface 121 of the shaft 120. Here, the sealing device 10 has a sealing function of sealing the space S between the housing 110 and the shaft 120, and a conductive function of ensuring electrical conduction between the housing 110 and the shaft 120.

[0025] The sealing device 10 is electrically conductive and contacts both the housing 110 and the shaft 120. In this manner, the sealing device 10 is disposed between the housing 110 and the shaft 120, electrically connecting the housing 110 and the shaft 120. This allows the induced current generated in the shaft 120 to escape to the housing via the sealing device 10. As a result, the induced current generated in the shaft 120 can be reduced. This reduces noise from devices such as AM radio receivers installed around the electric motor 1. Furthermore, reducing the induced current reduces the potential difference between the housing 110 and the shaft 120. Therefore, for example, if the shaft 120 is supported by a bearing, damage to the bearing or deterioration of the grease in the bearing due to the potential difference can be reduced.

[0026] 1-2. Parts of the sealing device Fig. 2 is a cross-sectional view showing the sealing device 10 according to the first embodiment. Fig. 3 is a perspective view showing a part of the sealing device 10 according to the first embodiment. As shown in Fig. 2, the sealing device 10 has a reinforcing ring 20, an elastic member 30, and a spring 40.

[0027] The reinforcing ring 20 is an annular member that reinforces the elastic member 30 around the axis AX. The reinforcing ring 20 is disposed along the inner circumferential surface 111 of the hole H of the housing 110. The reinforcing ring 20 is made of a material with a higher Young's modulus than the material constituting the elastic member 30, in order to ensure the rigidity or strength required for the reinforcing ring 20. Specifically, the reinforcing ring 20 is made of a metal material such as stainless steel or SPCC (cold rolled steel). When the reinforcing ring 20 is made of a metal material, the reinforcing ring 20 is manufactured by, for example, pressing or forging.

[0028] Here, the reinforcing ring 20 is conductive, and therefore the electrical resistance of the sealing device 10 can be made lower than in a configuration in which an insulating reinforcing ring 20 is used.

[0029] The material constituting the reinforcing ring 20 is not limited to a metal material. For example, the reinforcing ring 20 may be made of a conductive ceramic material or a resin material. Even in this case, the reinforcing ring 20 is conductive. Alternatively, the reinforcing ring 20 may be made of an insulating material and not be conductive. Even in this case, as described below, the conductivity of the elastic member 30 ensures the conductivity of the sealing device 10. The insulating material is not particularly limited, but examples include resin materials such as polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE). The resin material may contain, as necessary, a fiber base material such as glass fiber, organic fiber, metal fiber, carbon fiber, or mineral fiber, or a particulate filler composed of a metal oxide such as alumina, a metal hydroxide such as aluminum hydroxide, or a nitride such as boron nitride. When the reinforcing ring 20 is made of a resin material, it is manufactured by, for example, injection molding.

[0030] The reinforcing ring 20 has an L-shape when viewed in cross section cut along a plane including the axis AX. That is, as shown in FIG. 2, the reinforcing ring 20 has a first portion 21 and a second portion 22. The first portion 21 has a cylindrical shape that fits along the inner circumferential surface 111 of the hole H of the housing 110. The second portion 22 has a plate shape that protrudes radially inward from one axial end of the first portion 21 around the entire circumference. In the example shown in FIG. 2, the second portion 22 is connected to the end of the first portion 21 in the X2 direction and extends in a direction perpendicular to the axis AX.

[0031] When viewed in a cross section cut on a plane including the axis line AX, the extending directions of the first portion 21 and the second portion 22 are not limited to the example shown in Fig. 2, and may intersect with each other. However, from the viewpoint of suitably increasing the rigidity of the reinforcing ring 20, it is preferable that the extending directions of the first portion 21 and the second portion 22 are perpendicular to each other when viewed in a cross section cut on a plane including the axis line AX. Furthermore, the cross-sectional shape of the reinforcing ring 20 is not limited to the example shown in Fig. 2, and may be, for example, a shape in which one of the first portion 21 and the second portion 22 is omitted.

[0032] In such a reinforcing ring 20, the first portion 21 extends in the axial direction, thereby making it possible to stabilize the installation posture of the reinforcing ring 20 compared to a configuration in which the first portion 21 is omitted. Here, since the reinforcing ring 20 is conductive as described above, from the viewpoint of improving electrical conduction between the reinforcing ring 20 and the housing 110, it is preferable that the first portion 21 overlaps at least a part of the contact area between the housing 110 and the elastic member 30 when viewed in the radial direction.

[0033] 2, the axial width of the reinforcing ring 20 or the first portion 21 is longer than the axial length of the contact area. The first portion 21 encompasses the contact area between the housing 110 and the elastic member 30 in the radial direction. This allows for better electrical conduction between the contact area and the reinforcing ring 20 than in a configuration in which the first portion 21 overlaps a portion of the contact area in the radial direction.

[0034] Furthermore, in the reinforcing ring 20, the radial extension of the second portion 22, coupled with the effect of stabilizing the installation posture of the reinforcing ring 20 by the above-mentioned first portion 21, makes it possible to stabilize the installation posture of the elastic member 30 compared to a configuration in which the second portion 22 is omitted. Furthermore, since the reinforcing ring 20 is conductive as described above, the radial extension of the second portion 22 can also increase the conductivity of the sealing device 10 in the radial direction.

[0035] Here, when WD is the width of the reinforcing ring 20 or the second portion 22 in the radial direction of the shaft 120 and ΔD is the distance between the inner circumferential surface 111 of the housing 110 and the outer circumferential surface 121 of the shaft 120, WD / ΔD is preferably in the range of 0.5 to 0.9, more preferably 0.6 to 0.8. Having WD / ΔD within this range allows for stable contact of the elastic member 30 with the outer circumferential surface 121 of the shaft 120 while reducing the electrical resistance of the sealing device 10 in the radial direction. On the other hand, if WD / ΔD is too small, not only is the effect of reducing the electrical resistance of the sealing device 10 in the radial direction by the conductive reinforcing ring 20 insufficient, but also, depending on the shape of the elastic member 30, the elastic member 30 is more likely to fluctuate in position. On the other hand, if WD / ΔD is too large, the sliding resistance of the sealing device 10 relative to the shaft 120 may increase or fluctuate depending on the eccentricity of the shaft 120, etc.

[0036] The elastic member 30 is an annular elastic member that is fixed to the reinforcing ring 20 and that contacts both the inner circumferential surface 111 of the housing 110 and the outer circumferential surface 121 of the shaft 120. Here, the elastic member 30 is fixed to the inner circumferential surface 111 together with the reinforcing ring 20 by press-fitting. The shaft 120 is inserted inside the elastic member 30.

[0037] The elastic member 30 is made of an elastic material such as a conductive rubber composition. The volume resistivity of the elastic material is not particularly limited, but is preferably 100 Ω·cm or less. The elastic material includes, for example, a rubber material and a conductivity imparting agent. The elastic member 30 is formed, for example, by insert molding using the reinforcing ring 20 as an insert component. This insert molding results in the elastic member 30 being bonded to the reinforcing ring 20 by vulcanization adhesion.

[0038] The rubber material is not particularly limited, but examples thereof include synthetic rubbers such as nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber (ACM), fluororubber (FKM), and silicone rubber. One of these may be used alone, or two or more may be used in combination as a copolymer or blend.

[0039] The rubber material is not limited to synthetic rubber and may be a thermoplastic elastomer. Furthermore, a cross-linking agent, a cross-linking aid, or other additives may be added to the rubber material as needed. Examples of the cross-linking agent include, but are not limited to, sulfur and peroxide vulcanizing agents. Examples of the cross-linking aid include inorganic zinc oxide and magnesium oxide, and organic stearic acid and amines.

[0040] The conductivity-imparting agent is not particularly limited, but examples thereof include electronic conductivity-imparting agents and ionic conductivity-imparting agents. These may be used in combination of two or more types, such as by mixing. The electronic conductivity-imparting agent is not particularly limited, but examples thereof include conductive particles such as carbon black and metal powder. One of these may be used alone, or two or more may be used in combination. The ionic conductivity-imparting agent is not particularly limited, but examples thereof include organic salts, inorganic salts, metal complexes, and ionic liquids. Examples of the organic salt include sodium trifluoroacetate. Examples of the inorganic salt include lithium perchlorate and quaternary ammonium salts. Examples of the metal complex include ferric halide-ethylene glycol, as exemplified in Japanese Patent No. 3655364. The ionic liquid is a molten salt that is liquid at room temperature and has a melting point of 70°C or less, as described in Japanese Patent Publication No. 2003-202722. The melting point is preferably 30°C or less.

[0041] 2, the elastic member 30 has a fixing portion 31, a protruding portion 32, and a lip 33. These are integrally formed from the above-mentioned elastic material.

[0042] The fixing portion 31 is an annular portion of the elastic member 30 that is fixed over the entire periphery to the reinforcing ring 20. The fixing portion 31 is joined to the reinforcing ring 20 by vulcanization adhesion or the like.

[0043] In the example shown in FIG. 2 , the fixing portion 31 is provided along the reinforcing ring 20 and encompasses the reinforcing ring 20. In this manner, the reinforcing ring 20 is embedded in the fixing portion 31. Here, the fixing portion 31 has a portion that is disposed on the outer peripheral surface of the first portion 21 of the reinforcing ring 20. Therefore, this portion contacts the inner peripheral surface 111 of the housing 110. Such a fixing portion 31 is inserted into the hole H of the housing 110 with a predetermined interference. Therefore, the outer diameter of the fixing portion 31 is slightly larger than the inner diameter of the hole H of the housing 110 when the fixing portion 31 is not inserted into the hole H (in its natural state). When the fixing portion 31 is inserted into the hole H, it elastically deforms between the inner peripheral surface 111 and the reinforcing ring 20. As a result, the fixing portion 31 is fixed to the housing 110 in a state of intimate contact with the inner peripheral surface 111. This stabilizes the contact state between the housing 110 and the elastic member 30.

[0044] The protruding portion 32 is a portion of the elastic member 30 that protrudes radially inward from the fixed portion 31 and is in slidable contact with the outer circumferential surface 121 of the shaft 120. This contact ensures electrical conduction between the shaft 120 and the elastic member 30. Here, it is preferable that the protruding portion 32 be in contact with the outer circumferential surface 121 of the shaft 120 over the entire circumference. In this case, the conductivity between the shaft 120 and the elastic member 30 can be improved compared to a configuration in which the protruding portion 32 is in partial contact with the outer circumferential surface 121 of the shaft 120. Furthermore, in this case, compared to a configuration in which the protruding portion 32 is in partial contact with the outer circumferential surface 121 of the shaft 120, leakage of the lubricant G disposed in the recess 33a (described later) and intrusion of foreign matter between the lip 33 and the outer circumferential surface 121 of the shaft 120 can be reduced.

[0045] 2, the protrusion 32 has a shape whose width decreases toward the tip. The tip of the protrusion 32 comes into slidable contact with the outer peripheral surface 121 of the shaft 120. This has the advantage that the protrusion 32 is more likely to deform to follow the outer peripheral surface 121 as the shaft 120 becomes eccentric, compared to a configuration in which the width of the protrusion 32 is constant. This advantage has the effect of making it easier to maintain contact between the protrusion 32 and the outer peripheral surface 121 of the shaft 120 over the entire circumference.

[0046] 2, the shape of the protrusion 32 may be, for example, a shape of a constant width or a shape extending in a direction inclined relative to the radial direction. Furthermore, as will be described later, electrical conduction between the elastic member 30 and the shaft 120 is ensured by contact between a lip 33 (described later) and the outer circumferential surface 121. Therefore, the protrusion 32 is provided as needed, and may be configured to contact a portion of the outer circumferential surface 121 of the shaft 120 in the circumferential direction, or may be omitted.

[0047] The lip 33 is a portion of the elastic member 30 that protrudes from the fixed portion 31 in the X1 direction over its entire circumference, and is in slidable contact with the outer circumferential surface 121 of the shaft 120 at a position in the axial direction that is different from the protruding portion 32. This contact ensures electrical conduction between the shaft 120 and the elastic member 30. Here, the lip 33 is in contact with the outer circumferential surface 121 of the shaft 120 over its entire circumference. Therefore, compared to a configuration in which the lip 33 is in partial contact with the outer circumferential surface 121 of the shaft 120, it is possible to improve the conductivity between the shaft 120 and the elastic member 30. Furthermore, compared to a configuration in which the lip 33 is in partial contact with the outer circumferential surface 121 of the shaft 120, it is also possible to reduce leakage of the lubricant G disposed in a recess 33a (described later).

[0048] The inner peripheral surface of the lip 33 is provided with a contact surface CR that contacts the outer peripheral surface 121 of the shaft 120. As shown in FIG. 3 , the contact surface CR has a shape that follows a straight line in its natural state when viewed in a cross section cut along a plane including the axis AX. Here, the "natural state of the contact surface CR" refers to a state in which the sealing device 10 is not incorporated into the electric motor 1, the spring 40 is not attached to the elastic member 30, and no external force is applied to the contact surface CR. Furthermore, the "straight line" refers to a roughly straight line and may include minute concave or convex shapes. Preferably, the contact surface CR is a surface that extends in a direction along the axis AX in its natural state, i.e., a surface in which the straight line is parallel to the axis AX.

[0049] As shown in FIG. 3, the contact surface CR is provided with a plurality of grooves 33c extending in the circumferential direction. A lubricant G is held in each groove 33c. In the example shown in FIG. 3, each groove 33c is provided over the entire circumferential area. The grooves 33c may be provided intermittently in the circumferential direction. The number of grooves 33c is not limited to the example shown in FIG. 3 and may be one, two, four or more. The shape of each groove 33c is not limited to the example shown in FIG. 3. For example, the widths of the plurality of grooves 33c may be different from one another, or each groove 33c may have a plurality of portions with different widths. The grooves 33c may be provided as needed or may be omitted.

[0050] 2 and 3, a recess 33a is provided on the inner peripheral surface of the lip 33 over the entire circumferential area between the contact surface CR and the protrusion 32. Therefore, a space is formed by the recess 33a between the elastic member 30 and the outer peripheral surface 121 of the shaft 120. In the example shown in FIG. 2, a lubricant G is contained in the recess 33a.

[0051] The lubricant G is, for example, a conductive grease, and includes a base oil, a thickener, and a conductivity-imparting agent. Examples of the thickener include soap-based agents such as calcium soap, calcium complex soap, sodium soap, aluminum soap, lithium soap, and lithium complex soap, as well as non-soap-based agents such as polyurea, sodium terephthalate, polytetrafluoroethylene (PTFE), organic bentonite, and silica gel. These agents can be used alone or in combination. Examples of the base oil include mineral oils (refined mineral oils) such as paraffinic and naphthenic oils, and synthetic oils such as polyolefins, esters, and silicones. These agents can be used alone or in combination. Examples of the conductivity-imparting agent include conductive particles such as carbon black, metal powder, or metal oxide powder. The carbon black used in the lubricant G is a colloidal fine powder of carbon obtained, for example, by incomplete combustion or thermal decomposition of hydrocarbons, and also functions as a thickener for the lubricant G. The metal powder used in the lubricant G is, for example, a powder made of a metal such as silver or nickel. The metal oxide powder used in the lubricant G is, for example, a powder made of a metal oxide such as titanium oxide, tin oxide or indium oxide. The above conductive particles may be used alone or in combination of two or more.

[0052] The lubricant G contains a base oil, a thickener, a conductivity imparting agent, and various additives as needed. The lubricant G is not limited to grease, but may be, for example, a lubricating oil or a solid lubricant. When the lubricant G is a lubricating oil, it contains, for example, a base oil and a conductivity imparting agent without the aforementioned thickener. When the lubricant G is a solid lubricant, it is composed of, for example, conductive particles such as carbon black, metal powder, or metal oxide powder. However, the lubricant G is preferably a grease, since it is more likely to remain in the required locations on the elastic member 30.

[0053] On one side, a recess 33b in which a spring 40 is disposed is provided on the outer peripheral surface of the lip 33. The recess 33b is a groove extending over the entire circumferential direction and restricts the axial movement of the spring 40.

[0054] Here, when the width of the contact surface CR in the axial direction of the shaft 120 is W1 and the width of the spring 40 in the axial direction of the shaft 120 is W2, the relationship W1 > W2 is satisfied. For this reason, compared with a configuration that satisfies the relationship W1 < W2, since the area of the contact surface CR is large, the electrical resistance between the shaft 120 and the lip 33 can be reduced. As a result, the induced current generated in the shaft 120 can be suitably dissipated to the lip 33.

[0055] Also, when the thickness of the portion of the lip 33 sandwiched between the spring 40 and the outer peripheral surface 121 of the shaft 120 is t and the width of the contact surface CR in the axial direction of the shaft 120 is W1, the relationship t < W1 is satisfied, and preferably, the relationship 2 × t < W1 is satisfied. When the thickness t and the width W1 satisfy such a relationship, the conductivity between the sealing device 10 and the shaft 12 can be enhanced compared with a configuration that does not satisfy the relationship. This is because as the thickness t becomes smaller, the tightening force by the spring 40 is more easily transmitted to the contact surface CR, and the adhesion between the lip 33 and the shaft 120 increases, resulting in a lower electrical resistance between the lip 33 and the shaft 120.

[0056] Furthermore, the relationship t < W2 is satisfied. For this reason, compared with a configuration that satisfies the relationship t > W2, there is an advantage that the tightening force by the spring 40 is more easily transmitted to the contact surface CR.

[0057] The spring 40 is an annular or endless coil spring that presses the lip 33 against the outer peripheral surface 121. The lip 33 is sandwiched between the spring 40 and the outer peripheral surface 121. In the examples shown in FIGS. 2 and 3, the spring 40 has a shape with equal widths in the axial and radial directions when viewed in cross section, more specifically, a circular shape.

[0058] Here, the spring 40 is disposed in the recess 33b described above. Therefore, the axial movement of the spring 40 is restricted by the recess 33b. The spring 40 is disposed in the recess 33b in a state in which it is elastically deformed so as to expand in diameter. The spring 40 presses the lip 33 against the outer circumferential surface 121 of the shaft 120 due to the restoring force resulting from this elastic deformation. The spring 40 is made of spring steel, such as stainless steel.

[0059] Here, the spring 40 is conductive, and therefore the electrical resistance of the sealing device 10 can be made lower than in a configuration using an insulating spring 40.

[0060] As described above, the sealing device 10 is disposed between the housing 110 having the hole H and the shaft 120 inserted into the hole H, and electrically connects the housing 110 and the shaft 120. Here, as described above, the sealing device 10 includes the annular reinforcing ring 20, the annular elastic member 30, and at least one annular spring 40.

[0061] The reinforcing ring 20 is fixed to the housing 110. The elastic member 30 has a fixed portion 31 fixed to the reinforcing ring 20, and a lip 33 protruding from the fixed portion 31 and in slidable contact with the outer peripheral surface 121 of the shaft 120. The spring 40 presses the lip 33 against the outer peripheral surface 121 of the shaft 120. The lip 33 is sandwiched between the spring 40 and the outer peripheral surface 121 of the shaft 120.

[0062] In particular, the elastic member 30 is made of a conductive elastic material. Moreover, the contact surface CR of the lip 33 that contacts the outer peripheral surface 121 of the shaft 120 is linear in its natural state when viewed in a cross section cut along a plane including the axis AX, which is the central axis of the elastic member 30.

[0063] In the sealing device 10 described above, the elastic member 30 is made of a conductive elastic material, thereby ensuring electrical continuity between the housing 110 and the shaft 120 via the elastic member 30. Furthermore, the contact surface CR of the lip 33 with the outer circumferential surface 121 of the shaft 120 has a cross-sectional shape that is linear in its natural state, allowing the area of ​​the contact surface CR to be increased. This increases the conductivity between the shaft 120 and the elastic member 30, i.e., reduces the electrical resistance between the shaft 120 and the elastic member 30. As a result, sufficient electrical continuity between the housing 110 and the shaft 120 can be ensured. Here, because the lip 33 is pressed against the outer circumferential surface 121 of the shaft 120, fluctuations in the area of ​​the contact surface CR can be reduced. This allows for stable electrical continuity between the housing 110 and the shaft 120.

[0064] Furthermore, in the sealing device 10, the elastic member 30 is fixed to the housing 110 via the reinforcing ring 20, so the configuration for fixing to the housing 110 is simpler than the configuration using a conductive brush as disclosed in Patent Document 1. Therefore, it is easy to ensure installation space for the sealing device 10, and the cost associated with installing the sealing device 10 is reduced.

[0065] In this embodiment, as described above, the contact surface CR is provided with at least one groove 33c extending along the circumferential direction of the shaft 120. Furthermore, a conductive lubricant G is held in each of the at least one grooves 33c. Therefore, the sliding resistance of the lip 33 against the outer circumferential surface 121 of the shaft 120 can be reduced by the lubricant G. Furthermore, because the lubricant G is held in the grooves 33c provided in the contact surface CR, even if the width W1 of the contact surface CR of the lip 33 with the outer circumferential surface 121 of the shaft 120 is large, the sliding resistance of the lip 33 against the outer circumferential surface 121 of the shaft 120 can be suitably reduced by the lubricant G. Furthermore, because the lubricant G is conductive, even if the lubricant G is interposed between the lip 33 and the shaft 120, the conductivity between the lip 33 and the shaft 120 can be improved compared to a configuration using an insulating lubricant.

[0066] As described above, the elastic member 30 further has a protruding portion 32 that protrudes from the fixed portion 31 in a direction different from that of the lip 33. The protruding portion 32 contacts the outer peripheral surface 121 of the shaft 120 at a position in the axial direction of the shaft 120 that is different from that of the lip 33. Therefore, electrical continuity between the shaft 120 and the elastic member 30 can be ensured even by the contact between the protruding portion 32 and the shaft 120. As a result, the electrical resistance between the shaft 120 and the elastic member 30 can be lowered compared to a configuration in which the protruding portion 32 is omitted.

[0067] Furthermore, as described above, the elastic member 30 is provided with a recess 33a for forming a space surrounded by the outer circumferential surface 121 of the shaft 120, the lip 33, and the protrusion 32. The recess 33a contains a conductive lubricant G. This allows the lubricant G to be supplied from within the recess 33a to both the contact surface with the outer circumferential surface 121 of the shaft 120 and the contact surface CR. As a result, the effects of the lubricant G can be obtained over a long period of time.

[0068] 2. Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements whose actions or functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions of each element will be omitted where appropriate.

[0069] 4 is a cross-sectional view showing a sealing device 10A according to the second embodiment. The electric motor 1A is configured similarly to the electric motor 1 of the first embodiment, except that it includes the sealing device 10A instead of the sealing device 10. Moreover, the sealing device 10A is configured similarly to the sealing device 10, except that it includes an elastic member 30A and a spring 40A instead of the elastic member 30 and the spring 40.

[0070] The elastic member 30A is configured similarly to the elastic member 30, except that it has a lip 33A instead of the lip 33. The lip 33A has a recess 33d instead of the recess 33b, and is configured similarly to the lip 33, except that the width W1 of the contact surface CR is longer than that of the lip 33. Here, the axial width of the recess 33d is longer than the axial width of the recess 33b. A spring 40A is disposed in the recess 33d.

[0071] Spring 40A is an annular or endless coil spring that presses lip 33A against outer peripheral surface 121. Lip 33A is sandwiched between spring 40A and outer peripheral surface 121. In the example shown in FIG. 4, spring 40A has a radially flattened shape in cross section, more specifically, an outer shape having a pair of axial sides and a pair of convex curves connecting adjacent ends of the pair of sides. Here, the axial width of spring 40A is greater than the radial width of spring 40A, and preferably is within a range of two to four times the radial width of spring 40A.

[0072] According to the second embodiment, the sealing device 10A can also ensure sufficient electrical conduction between the housing 110 and the shaft 120. As with the first embodiment, the installation space for the sealing device 10A can be easily secured, and installation costs for the sealing device 10A can be reduced. In this embodiment, as described above, the sealing device 10A includes the spring 40A. The spring 40A has a flattened shape in the radial direction of the shaft 120. Therefore, compared to a configuration using a spring 40 with a circular cross section, even if the area of ​​the contact surface CR of the lip 33A relative to the outer circumferential surface 121 of the shaft 120 is increased, the tightening force of the spring 40A can be efficiently transmitted to the contact surface CR over a wide axial range. Therefore, by improving the contact between the lip 33A and the shaft 120, the electrical resistance between the lip 33A and the shaft 120 can be reduced, and as a result, induced current generated in the shaft 120 can be suitably released to the lip 33A.

[0073] 3. Third embodiment A third embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements that have the same actions or functions as those in the first embodiment will be designated by the same reference numerals as those in the first embodiment, and detailed descriptions of each element will be omitted where appropriate.

[0074] 5 is a cross-sectional view showing a sealing device 10B according to the third embodiment. The electric motor 1B is configured similarly to the electric motor 1 of the first embodiment, except that it includes a sealing device 10B instead of the sealing device 10. Moreover, the sealing device 10B is configured similarly to the sealing device 10, except that it includes an elastic member 30B and a plurality of springs 40B instead of the elastic member 30 and the spring 40.

[0075] The elastic member 30B is configured similarly to the elastic member 30, except that it has a lip 33B instead of the lip 33. The lip 33B has a plurality of recesses 33e instead of the recess 33b, and is configured similarly to the lip 33, except that the width W1 of the contact surface CR is longer than that of the lip 33. Here, the plurality of recesses 33e are aligned in the axial direction. A spring 40B is disposed in each recess 33e. In the example shown in FIG. 5, there are three recesses 33e. The number of recesses 33e is determined according to the number of springs 40B, and is not limited to the example shown in FIG. 5, and may be two, four or more.

[0076] The spring 40B is an annular or endless coil spring that presses the lip 33B against the outer peripheral surface 121. The lip 33B is sandwiched between the spring 40B and the outer peripheral surface 121. In the example shown in FIG. 5, the spring 40B has a circular shape when viewed in cross section. In the example shown in FIG. 5, there are three springs 40B. The number of springs 40B is not limited to the example shown in FIG. 5, and may be two, four or more. Furthermore, the width W2 is the axial length of a group of multiple springs 40B that the sealing device 10B has. Therefore, in this embodiment, the axial length of a group of three springs 40B is the width W1.

[0077] According to the third embodiment, the sealing device 10B can also ensure sufficient electrical continuity between the housing 110 and the shaft 120. As with the first embodiment, the installation space for the sealing device 10B can be easily secured, and installation costs for the sealing device 10B can be reduced. In this embodiment, as described above, the sealing device 10B includes multiple springs 40B arranged along the axial direction of the shaft 120. Therefore, compared to a configuration using a single spring 40, even if the area of ​​the contact surface CR of the lip 33B with the outer circumferential surface 121 of the shaft 120 is increased, the tightening force of the springs 40B can be efficiently transmitted to the contact surface CR over a wide area in the axial direction. Therefore, by improving the contact between the lip 33B and the shaft 120, the electrical resistance between the lip 33B and the shaft 120 can be reduced, and as a result, induced current generated in the shaft 120 can be suitably released to the lip 33B.

[0078] 4. Variations The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within the scope of not mutually contradictory.

[0079] 4-1. Variation 1 In each of the above-described embodiments, the reinforcing ring 20 is embedded in the elastic member 30, the elastic member 30A, or the elastic member 30B, but is not limited to this configuration. For example, the reinforcing ring 20 may be configured so that a portion thereof is exposed from the elastic member 30, the elastic member 30A, or the elastic member 30B. In this case, the elastic member 30, the elastic member 30A, or the elastic member 30B may be configured as two members spaced apart from each other. Electrical conduction between the two members is ensured via the reinforcing ring 20.

[0080] 4-2. Variation 2 In each of the above-described embodiments, a configuration in which the elastic member 30, the elastic member 30A, or the elastic member 30B contacts the housing 110 is exemplified, but the present invention is not limited to this configuration, and the elastic member 30, the elastic member 30A, or the elastic member 30B may not contact the housing 110. In this case, for example, the reinforcing ring 20 has a portion exposed from the elastic member 30, 30A, or 30B so as to contact the housing 110. If the reinforcing ring 20 is conductive, contacting the housing 110 in this manner has the advantage of easily reducing the electrical resistance between the housing 110 and the sealing device 10, the sealing device 10A, or the sealing device 10B. Note that a configuration in which the elastic member 30, the elastic member 30A, or the elastic member 30B contacts the housing 110, as in each of the above-described embodiments, has the advantage of easily stabilizing the electrical resistance between the housing 110 and the sealing device 10A or the sealing device 10B, compared to a configuration in which the reinforcing ring 20 contacts the housing 110.

[0081] 4-3. Variation 3 In each of the above-described embodiments, a configuration in which the sealing device 10, the sealing device 10A, or the sealing device 10B is directly fixed to the housing 110 is exemplified, but the present invention is not limited to this configuration. For example, a member such as a spacer may be interposed between the sealing device 10, the sealing device 10A, or the sealing device 10B and the housing 110. Note that, since this member is fixed to the housing 110, it may be considered to be part of the housing 110.

[0082] 4-4. Variation 4 In each of the above-described embodiments, a configuration is exemplified in which the sealing device 10, the sealing device 10A, or the sealing device 10B directly contacts the outer circumferential surface of the shaft 120 with the housing 110, but the present invention is not limited to this configuration. For example, the sealing device 10, the sealing device 10A, or the sealing device 10B may contact a member such as a sleeve fixed to the shaft 120. Note that this member is fixed to the shaft 120, and is therefore considered to be part of the shaft 120. [Explanation of symbols]

[0083] 1...electric motor, 1A...electric motor, 1B...electric motor, 10...sealing device, 10A...sealing device, 10B...sealing device, 20...reinforcing ring, 21...first part, 22...second part, 30...elastic member, 30A...elastic member, 30B...elastic member, 31...fixing part, 32...protrusion, 33...lip, 33A...lip, 33B...lip, 33a...recess, 33b...recess, 33c...groove, 33d...recess, 33e...recess, 40...spring, 40A...spool Spring, 40B...spring, 110...housing, 110a...main body, 110b...lid body, 111...inner surface, 112...inner surface, 114...water jacket, 120...shaft, 130...bearing, 140...bearing, 150...stator, 160...rotor, 121...outer surface, AX...axis, CR...contact surface, G...lubricant, H...hole, S...space, R...recess, W1...width, W2...width, WD...width, t...thickness, ΔD...distance.

Claims

1. A sealing device disposed between a housing having a hole and a shaft inserted into the hole, the sealing device sealing a gap between an inner peripheral surface of the housing and an outer peripheral surface of the shaft, an annular reinforcing ring fixed to the housing; an annular elastic member having a fixed portion fixed to the reinforcing ring and a lip protruding from the fixed portion and in slidable contact with an outer circumferential surface of the shaft; at least one annular spring that presses the lip against the outer circumferential surface of the shaft; the lip is sandwiched between an outer circumferential surface of the shaft and the at least one spring; the elastic member is made of an elastic material having electrical conductivity, the lip has a contact surface that contacts the outer circumferential surface of the shaft, the contact surface is linear in a natural state when viewed in a cross section cut along a plane including a central axis of the elastic member; When the thickness of the lip portion sandwiched between the at least one spring and the outer peripheral surface of the shaft is defined as t, the width of the contact surface in the axial direction of the shaft is defined as W1, and the width of the at least one spring in the axial direction of the shaft is defined as W2, The relationship W1>W2>t is satisfied. Sealing device.

2. The at least one spring includes a plurality of springs arranged along the axial direction of the shaft. The sealing device according to claim 1 .

3. The at least one spring includes a spring having a flattened shape in a radial direction of the shaft. The sealing device according to claim 1 .

4. The contact surface is provided with at least one groove extending along the circumferential direction of the shaft, a conductive lubricant is held in each of the at least one groove; The sealing device according to any one of claims 1 to 3.

5. the elastic member further has a protruding portion protruding from the fixing portion in a direction different from the lip, the protrusion contacts the outer peripheral surface of the shaft at a position different from the lip in the axial direction of the shaft; The sealing device according to any one of claims 1 to 3.

6. the elastic member is provided with a recess for forming a space surrounded by the outer circumferential surface of the shaft, the lip, and the protrusion, A conductive lubricant is contained in the recess. The sealing device according to claim 5 .

7. The reinforcing ring is electrically conductive. The sealing device according to any one of claims 1 to 3.

8. When WD is the width of the reinforcing ring in the radial direction of the shaft, and ΔD is the distance between the inner circumferential surface of the housing and the outer circumferential surface of the shaft, WD / ΔD is in the range of 0.5 or more and 0.9 or less, The sealing device according to claim 7.

9. the at least one spring is electrically conductive; The sealing device according to any one of claims 1 to 3.

10. The sealing device according to any one of claims 1 to 3; the housing; the shaft, Electric motor.

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