Patent Application
20250020212
This disclosure relates to a sealing device and an electric motor.
There is known a conventional sealing device that seals an annular space between a housing with an opening and a shaft disposed in the opening. For example, the device disclosed in Patent Document 1 includes an electrically conductive seal that electrically connects a housing to a shaft.
Rotation of an electric motor induces a current in a shaft of the motor. Electromagnetic waves generated by the induced current cause noise in devices such as AM (Amplitude Modulation) radio receivers.
In the device disclosed in Patent Document 1, electrical continuity between the housing and the shaft is unstable because a contact area between the seal and the shaft is small and prone to variation. Room remains for improving reduction of noise generated by the device disclosed in Patent Document 1.
To solve the foregoing problems, a sealing device according to one aspect of this disclosure is a sealing device for disposed between a housing with an opening and a shaft within the opening, and that seals a gap between an inner peripheral surface of the housing and an outer peripheral surface of the shaft. The sealing device includes (i) an annular reinforcing ring fixed to the housing, (ii) an annular elastic member including a fixing portion fixed to the reinforcing ring, and a lip that protrudes from the fixed portion and that is slidable contact with an outer peripheral surface of the shaft, and (iii) at least one annular spring that presses the lip against the outer peripheral surface of the shaft. The lip is between the outer peripheral surface of the shaft and the at least one spring. The elastic member is made of an electrically conductive elastic material. The lip includes a contact surface in contact with the outer peripheral surface of the shaft. The contact surface is straight in a natural state when viewed in a cross section defined by a plane that includes a central axis of the elastic member.
An electric motor according to another aspect of this disclosure includes the sealing device, the housing, and the shaft.
According to this disclosure, stable electrical continuity between the housing and the shaft is ensured.
Preferred embodiments of this disclosure will now be described below with reference to the accompanying drawings. In the drawings, depicted dimensions and scales of respective parts differ from their counterparts in practice, and some parts are depicted schematically for ease of understanding. The scope of this disclosure is not limited to these depictions unless otherwise specifically stated in the following description.
The electric motor 1 shown in
The electric motor 1 is configured to reduce induction of an electric current in a shaft 120. As shown in
The sealing device 10 in the electric motor 1 ensures electrical continuity between the housing 110 and the shaft 120, thereby ensuring transfer of induced current generated in the shaft 120 to the housing 110. As a result, noise caused by the induced current is reduced in a device such as an AM radio receiver. As is described below, a size of the electric motor 1 can be reduced since an installation space for the sealing device 10 can be readily secured, and a cost of installing the sealing device 10 can be reduced. First, description will be given of each part of the electric motor 1 with reference to
For convenience of explanation, in some cases, a direction along the axis AX of the shaft 120 is referred to as an “axial direction.” In some cases, a direction around the axis AX is referred to as a “circumferential direction.” In some cases, a direction perpendicular to the axis AX is referred to as a “radial direction.” In
The housing 110 with the opening H is a conductive structure. It is preferable that the housing 110 be grounded to transfer an induced current from the shaft 120. The housing 110 is made of a metal material, such as iron, stainless steel, or an aluminum alloy.
The housing 110 includes a main body 110a and a cover 110b. The main body 110a is a bottomed cylinder and has a space for accommodating the stator 150 and the rotor 160. The opening H is at the bottom of the main body 110a. The opening H communicates with the space and is surrounded by an inner peripheral surface 111 along the axis AX. A bearing 130, such as a ball bearing, is fitted in the opening H.
In the example shown in
The cover 110b is a plate member used to close the opening of the main body 110a. There is a recessed portion R on a surface of the cover 110b facing in the direction X2. The recessed portion R communicates with the space in the main body 110a and includes an inner peripheral surface 112 along the axis AX. The recessed portion R includes an inner peripheral surface 112 into which an outer peripheral surface of a bearing 140, such as a ball bearing, is fitted.
The shape of the housing 110 is not limited to the example shown in
The shaft 120 is a conductive rod member that includes an outer peripheral surface 121 along the axis AX. The shaft 120 is within the opening H of the housing 110 and is rotatably supported around the axis AX relative to the housing 110 via the bearings 130 and 140. The shaft 120 is made of a metal material, such as iron, stainless steel, or an aluminum alloy. The outer peripheral surface 121 has a smaller diameter than the inner peripheral surface 111 of the opening H of the housing 110, resulting in an annular space S between the outer peripheral surface 121 and the inner peripheral surface 111. In the example shown in
The material of the shaft 120 is not limited to a metal material as long as the shaft 120 is conductive and has sufficient rigidity. The shape of the shaft 120 is not limited to the example shown in
The stator 150 may be fitted to the housing 110 or may be fixed to the housing 110 by an appropriate medium, for example, by an adhesive. The stator 150 is a coil disposed in the direction of the circumference of the main body 110a, for example. The rotor 160 may be fitted to the shaft 120 or may be fixed to the shaft 120 by an appropriate medium, for example, by an adhesive. For example, the rotor 160 is a permanent magnet. The stator 150 and the rotor 160 generate a rotational moment around the axis AX of the shaft 120 by Lorentz force.
The sealing device 10 is an annular structure and is disposed in the space S between the inner peripheral surface 111 of the opening H of the housing 110 and the outer peripheral surface 121 of the shaft 120. The sealing device 10 seals the space S between the housing 110 and the shaft 120, and ensures electrical continuity between the housing 110 and the shaft 120.
The sealing device 10 is electrically conductive and is in contact with the housing 110 and the shaft 120. The sealing device 10 is disposed between the housing 110 and the shaft 120, thereby electrically connecting the housing 110 to the shaft 120. By the electrical connection induced current generated in the shaft 120 is transferred to the housing via the sealing device 10, and an induced current generated in the shaft 120 is reduced. As a result, noise in a device, such as an AM radio receiver in the vicinity of the electric motor 1 is reduced. Further, reduction of the induced current can reduce a potential difference between the housing 110 and the shaft 120. For example, damage to the bearing that supports the shaft 120 can be reduced by the reduction in potential difference, and a deterioration of grease in the bearing can also be reduced.
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 peripheral surface 111 of the opening H of the housing 110. The reinforcing ring 20 is made of a material with Young's modulus higher than the elastic member 30 in terms of securing the rigidity, strength, etc., necessary for the reinforcing ring 20. Specifically, the reinforcing ring 20 is made of a metal material, such as stainless steel or Steel Plate Cold Commercial (SPCC). In this case, the reinforcing ring 20 is manufactured by, for example, press working or forging.
The reinforcing ring 20 is electrically conductive, and reduces an electrical resistance of the sealing device 10 compared with an insulating reinforcing ring 20.
The material of the reinforcing ring 20 is not limited to a metal material, and may be a conductive ceramic or resin material, as long as the reinforcing ring 20 is electrically conductive. Alternatively, the reinforcing ring 20 may be made of an insulating material that is not electrically conductive. In such a case, the electrical conductivity of the sealing device 10 can still be ensured because the elastic member 30 is electrically conductive, as will be described below. Examples of the insulating material include resinous materials, such as polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE). However, the insulating material is not limited thereto. The resin material may contain a fiber base material, such as glass fiber, organic fiber, metal fiber, carbon fiber, or mineral fiber, as needed. Alternatively, the resin material may contain particulate fillers composed of (i) a metal oxide, such as alumina (ii) a metal hydroxide, such as aluminum hydroxide, or (iii) a nitride, such as boron nitride, as appropriate. If the reinforcing ring 20 is made of a resin material, the reinforcing ring 20 is formed by, for example, injection molding.
The reinforcing ring 20 is L-shaped when viewed in a cross section defined by a plane including the axis AX. As shown in
When viewed in the cross section defined by the plane including the axis AX, the direction of extension of the first portion 21 and the direction of extension of the second portion 22 are not limited to the example shown in
Stable installation of the reinforcing ring 20 is attained by a configuration in which the first portion 21 extends axially, in contrast to a configuration in which the first portion 21 is omitted. It is preferable that when viewed radially, the first portion 21 overlap at least a part of a contact area between the housing 110 and the elastic member 30. This is because the reinforcing ring 20 is electrically conductive and electrical continuity between the reinforcing ring 20 and the housing 110 is thereby improved.
In the example shown in
In the reinforcing ring 20, the second portion 22 extends radially. Thus, in addition to stable installation of the reinforcing ring 20 by way of the first portion 21, stable installation of the elastic member 30 is also attained as compared to a configuration in which the second portion 22 is omitted. Further, the reinforcing ring 20 is electrically conductive, and the second portion 22 extends radially. As a result, electrical conductivity is enhanced in the radial direction of the sealing device 10.
Preferably, WD/ΔD is 0.5 or more and 0.9 or less. More preferably, the WD/ΔD is 0.6 or more and 0.8 or less. Where WD is a width of the reinforcing ring 20 or the second portion 22 in the radial direction of the shaft 120, and ΔD is a distance between the inner peripheral surface 111 of the housing 110 and the outer peripheral surface 121 of the shaft 120. Since the WD/ΔD is within such a range, it is possible to stabilize a contact of the elastic member 30 relative to the outer peripheral surface 121 of the shaft 120, as well as to reduce the electrical resistance in the radial direction of the sealing device 10. If the WD/ΔD is too small, it is difficult to sufficiently reduce electrical resistance in the radial direction of the sealing device 10 by the conductive reinforcing ring 20. In addition, variation in the posture of the elastic member 30 tends to occur depending on a shape or the like of the elastic member 30. In contrast, if the WD/ΔD is too great, a sliding resistance of the sealing device 10 relative to the shaft 120 may increase or vary depending on the eccentricity of the shaft 120 or the like.
The elastic member 30 is an annular elastic member that is fixed to the reinforcing ring 20 and is in contact with the inner peripheral surface 111 of the housing 110 and the outer peripheral surface 121 of the shaft 120. The elastic member 30 is fixed to the inner peripheral surface 111 by press-fitting together with the reinforcing ring 20. The shaft 120 is inserted inside the elastic member 30.
The elastic member 30 is made of an elastic material, such as an electrically conductive rubber composition. A volume resistivity of the elastic material is not particularly limited but is preferably 100 Ωcm or less. The elastic material includes a rubber material and a conductivity-imparting agent. For example, the elastic member 30 is formed by insert molding with the reinforcing ring 20 being an insert article. By the insert molding, the elastic member 30 is bonded to the reinforcing ring 20 by vulcanization adhesion.
Examples of the rubber material include a synthetic rubber, such as nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber (ACM), fluororubber (FKM), and silicone rubber. From among these, one may be used alone, or more than one may be combined as a copolymer or a blend. However, the rubber material is not limited thereto.
The rubber material is not limited to synthetic rubber and may be a thermoplastic elastomer. An additive, such as a crosslinking agent or a crosslinking aid, is added to the rubber material as appropriate. Examples of the crosslinking agent include sulfur and a peroxide vulcanizing agent. However, the crosslinking agent is not particularly limited thereto. Examples of the crosslinking aid include inorganic zinc oxide, magnesium oxide, organic stearic acid, and amines.
Examples of the conductivity-imparting agent include an electron conductivity-imparting agent and an ion conductivity-imparting agent. From among these, more than one may be combined by, for example, mixing. However, the conductivity-imparting agent is not limited thereto. Examples of the electron conductivity-imparting agent include conductive particles, such as carbon black and metal powder. From among these, one agent may be used alone, or more than one agent may be combined. However, the electron conductivity-imparting agent is not particularly limited thereto. Examples of the ionic conductivity-imparting agent include organic salt, inorganic salt, metal complex, and ionic liquid. However, the ionic conductivity-imparting agent is not limited thereto. Examples of the organic salts include sodium trifluoride acetate. Examples of the inorganic salts include lithium perchlorate and quaternary ammonium salts. Examples of the metal complex include ferric halide-ethylene glycol as recited in Japanese Patent No. 3655364. The ionic liquid is molten salt, which is liquid at room temperature and has a melting point of 70° C. or less, as recited in Japanese Patent Application Laid-Open Publication No. 2003-202722. It is preferred that the melting point be 30° C. or less.
As shown in
The fixed portion 31 is an annular portion of the elastic member 30 that is fixed to the reinforcing ring 20 around its entire circumference. The fixed portion 31 is bonded to the reinforcing ring 20 by, for example, vulcanization bonding.
In the example shown in
The protruding portion 32 is a part of the elastic member 30 and protrudes radially inward from the fixed portion 31. The protruding portion 32 slidably contacts the outer peripheral surface 121 of the shaft 120. The contact ensures electrical continuity between the shaft 120 and the elastic member 30. It is preferable that the protruding portion 32 is in contact with the outer peripheral surface 121 of the shaft 120 over the entire circumference. In this case, conductivity between the shaft 120 and the elastic member 30 can be increased as compared with a configuration in which the protruding portion 32 is in partial contact with the outer peripheral surface 121 of the shaft 120. Further, as compared with the configuration, in which the protruding portion 32 is in partial contact with the outer peripheral surface 121 of the shaft 120, leakage of a lubricant G disposed in the recessed portion 33a, which will be described below is reduced. In addition, entry of foreign matter between the lip 33 and the outer peripheral surface 121 of the shaft 120 is reduced.
In the example shown in
The shape of the protruding portion 32 is not limited to the example shown in
The lip 33 is a part of the elastic member 30 that is entirely circumferential and that protrudes from the fixed portion 31 in the X1 direction. The lip 33 is in slidable contact with the outer peripheral surface 121 of the shaft 120 at a different axial position from the protruding portion 32. The contact ensures electrical continuity between the shaft 120 and the elastic member 30. The lip 33 is in contact over the entire circumference of the outer peripheral surface 121 of the shaft 120. As a result, conductivity between the shaft 120 and the elastic member 30 can be increased as compared with a configuration in which the lip 33 is in partial contact with the outer peripheral surface 121 of the shaft 120. Further, leakage of the lubricant G disposed in the recessed portion 33a described below can be reduced, as compared with the configuration, in which the lip 33 is in partial contact with the outer peripheral surface 121 of the shaft 120.
The lip 33 is provided with a contact surface CR on an inner peripheral surface of the lip 33. The contact surface CR is in contact with the outer peripheral surface 121 of the shaft 120. As shown in
As shown in
As shown in
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 (i) a soap, such as calcium soap, calcium complex soap, sodium soap, aluminum soap, lithium soap, and lithium complex soap, and (ii) a non-soap, such as polyurea, sodium terephthalate, polytetrafluoroethylene (PTFE), organic bentonite, and silica gel. From among these, one alone may be used, or more than one in combination may be used. Examples of the base oil include (i) a mineral oil (refined mineral oil), such as paraffinic and naphthenic oil, and (ii) synthetic oil, such as polyolefin, ester, and silicone. From among these, one alone may be used, or more than one in combination may be used. Examples of the conductivity-imparting agent include conductive particles, such as carbon black, metal powder, and metal oxide powder. For example, the carbon black used for the lubricant G is a colloidal fine powder of carbon, which is obtained by incomplete combustion or thermal decomposition of hydrocarbons, and functions as a thickener for the lubricant G. For example, the metal powder used for the lubricant G is a powder composed of a metal, such as silver or nickel. For example, the metal oxide powder used for the lubricant G is powder composed of a metal oxide, such as titanium oxide, tin oxide, or indium oxide. The foregoing conductive particles may be used alone or in a combination of two or more.
The lubricant G includes a base oil, a thickener, and a conductivity-imparting agent, as well as a variety of additives, as appropriate. The lubricant G is not limited to a grease and may be a lubricant oil or a solid lubricant. As a lubricating oil, the lubricant G includes a base oil and a conductivity-imparting agent without a thickener. As a solid lubricant, the lubricant G includes conductive particles, such as carbon black, metal powder or metal oxide powder. Preferably, the lubricant G is a grease, since it remains largely at a desired position on the elastic member 30.
The lip 33 is provided with a recessed portion 33b on the outer peripheral surface of the lip 33. The spring 40 is disposed on the recessed portion 33b. The recessed portion 33b is a groove that extends over the entire circumference. The recessed portion 33b prevents the spring 40 from shifting axially.
Where W1 is a width of the contact surface CR in the axial direction of the shaft 120, and W2 is a width of the spring 40 in the axial direction of the shaft 120, a relationship of W1>W2 is met. If an area of the contact surface CR is greater than that in a case of the relationship of W1<W2 being met, an electrical resistance between the shaft 120 and the lip 33 may be reduced. The induced current generated in the shaft 120 is transferred to the lip 33.
Where t is a thickness of a part of the lip 33 between the spring 40 and the outer peripheral surface 121 of the shaft 120, and W1 is a width of the contact surface CR in the axial direction of the shaft 120, a relationship of t<W1 is met, and preferably, a relationship of 2×t<W1 is met. When such relationships of the thickness t and the width W1 are met, the electrical conductivity between the sealing device 10 and the shaft 120 can be increased in contrast to when the relationships are not met. This is because as the thickness t decreases, a tightening force of the spring 40 is more likely to be transmitted to the contact surface CR, and the adhesiveness between the lip 33 and the shaft 120 increases. As a result, an electrical resistance between the lip 33 and the shaft 120 decreases.
Further, when a relationship of t<W2 is met, a tightening force by the spring 40 is transmitted to the contact surface CR with ease as compared to when a relationship of t>W2 is met.
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 between the spring 40 and the outer peripheral surface 121. In the example shown in
The spring 40 is disposed in the recessed portion 33b, which prevents the spring 40 from shifting axially. Further, the spring 40 is disposed in the recessed portion 33b in an elastically deformed state such that its diameter expands. Due to a restoring force caused by the elastic deformation, the lip 33 is pressed by the spring 40 against the outer peripheral surface 121 of the shaft 120. The spring 40 is made of a steel material, such as stainless steel, for example.
The spring 40 is electrically conductive, thereby reducing an electrical resistance of the sealing device 10 as compared with an insulating spring 40.
The sealing device 10 is disposed between the housing 110 with the opening H and the shaft 120 disposed in the opening H. The sealing device 10 electrically connects the housing 110 and the shaft 120. As described above, the sealing device 10 includes the annular reinforcing ring 20, an annular elastic member 30, and at least one annular spring 40.
The reinforcing ring 20 is fixed to the housing 110. The elastic member 30 includes the fixed portion 31 that is fixed to the reinforcing ring 20, and the lip 33 that protrudes from the fixed portion 31 and that is 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 between the spring 40 and the outer peripheral surface 121 of the shaft 120.
The elastic member 30 is made of an electrically conductive elastic material. Moreover, the contact surface CR, which is a part of the lip 33 and is in contact with the outer peripheral surface 121 of the shaft 120, is straight in its natural state when viewed in the cross section defined by the plane including the axis AX that is the central axis of the elastic member 30.
Since the elastic member 30 is made of an electrically conductive elastic material, the sealing device 10 ensures electrical continuity between the housing 110 and the shaft 120 via the elastic member 30. Moreover, the cross-sectional shape of the contact surface CR, which is a part of the lip 33 and is in contact with the outer peripheral surface 121 of the shaft 120, is straight in its natural state. By this configuration, the area of the contact surface CR is increased, thereby increasing the electrical conductivity between the shaft 120 and the elastic member 30. That is, electrical resistance between the shaft 120 and the elastic member 30 is decreased. As a result, the electrical continuity between the housing 110 and the shaft 120 is sufficiently ensured. Since the lip 33 is pressed against the outer peripheral surface 121 of the shaft 120, variations in the contact surface CR are reduced, and the electrical continuity between the housing 110 and the shaft 120 is kept stable.
Use of the sealing device 10 provides a structure for fixing the elastic member 30 to the housing 110 that is simpler than that provided by use of the conductive brush recited in Patent Document 1. This is because the elastic member 30 is fixed to the housing 110 via the reinforcing ring 20. Thus, an installation space for the sealing device 10 can be readily secured, and a cost for installation of the sealing device 10 can be reduced.
In this embodiment, as described above, the contact surface CR is provided with at least one groove 33c that extends in the circumferential direction of the shaft 120. The groove 33c holds the conductive lubricant G. The lubricant G reduces sliding resistance of the lip 33 relative to the outer peripheral surface 121 of the shaft 120. Further the lubricant G is held in the groove 33c provided on the contact surface CR. The lubricant G reduces the sliding resistance of the lip 33 relative to the outer peripheral surface 121 of the shaft 120, even if the width W1 of the contact surface CR, which is a part of the lip 33 and is in contact with the outer peripheral surface 121 of the shaft 120, is large. Further, the lubricant G is electrically conductive. Even if the lubricant G is interposed between the lip 33 and the shaft 120, higher conductivity between the lip 33 and the shaft 120 can be attained as compared with use of an insulating lubricant.
As described above, the elastic member 30 further includes the protruding portion 32 that protrudes from the fixed portion 31 in a direction that differs from the lip 33. The protruding portion 32 is in contact with the outer peripheral surface 121 of the shaft 120 at a different position from the lip 33 in the axial direction of the shaft 120. Such contact between the protruding portion 32 and the shaft 120 ensures electrical continuity between the shaft 120 and the elastic member 30. Thus, electrical resistance between the shaft 120 and the elastic member 30 is reduced compared to a configuration in which the protruding portion 32 is omitted.
As described above, the elastic member 30 is provided with the recessed portion 33a to define a space surrounded by the outer peripheral surface 121 of the shaft 120, the lip 33, and the protruding portion 32. The recessed portion 33a holds the electrically conductive lubricant G. The lubricant G can be supplied from the inside of the recessed portion 33a to (i) the contact surface of the shaft 120 relative to the outer peripheral surface 121 and (ii) the contact surface CR. As a result, the effect of supply of the lubricant G can be maintained over a long period of time.
The second embodiment according to this disclosure will now be described below. In the following embodiment, elements having the same operations or functions as in the first embodiment will be referred to by the same reference signs used in the first embodiment and detailed description thereof will be omitted, as appropriate.
A configuration of the elastic member 30A is the same as that of the elastic member 30 except that a lip 33A is provided instead of the lip 33. A configuration of the lip 33A is the same as that of the lip 33 except that (i) a recessed portion 33d is provided instead of the recessed portion 33b, and (ii) the width W1 of the contact surface CR is greater than that of the lip 33. The recessed portion 33d has an axial width greater than the recessed portion 33b. The spring 40A is disposed in the recessed portion 33d.
The spring 40A is an annular or endless coiled spring that presses the lip 33A against the outer peripheral surface 121. The lip 33A is between the spring 40A and the outer peripheral surface 121. In the example shown in
According to the second embodiment, the sealing device 10A ensures the electrical continuity between the housing 110 and the shaft 120. As in the first embodiment, an installation space for the sealing device 10A can be readily secured, and a cost of installation of the sealing device 10A can be reduced. In this embodiment, as described above, the sealing device 10A includes the spring 40A. The spring 40A is flat in the radial direction of the shaft 120. As compared with a circular cross-sectional spring 40, even if an area of the contact surface CR of the lip 33A relative to the outer peripheral surface 121 of the shaft 120 is increased, an axial tightening force caused by the spring 40A can be efficiently transmitted to the contact surface CR in wide range. By increasing adherence between the lip 33A and the shaft 120, electrical resistance between the lip 33A and the shaft 120 is reduced, and as a result, an induced current generated in the shaft 120 can be transferred to the lip 33A.
Third embodiment according to this disclosure will now be described below. In the following embodiment elements having the same operations or functions in this embodiment as in the first embodiment will be referred to by the same reference signs used in the first embodiment and detailed description thereof will be omitted, as appropriate.
A configuration of the elastic member 30B is the same as that of the elastic member 30 except that a lip 33B is provided instead of the lip 33. A configuration of the lip 33B is the same as that of the lip 33 expect that (i) more than one recessed portion 33e is provided instead of the recessed portion 33b, and (ii) a width W1 of the contact surface CR is greater than that of the lip 33. The recessed portions 33e are arranged axially. The springs 40B are disposed in the respective recessed portions 33e.
Each spring 40B is an annular or endless coiled spring that presses the lip 33B against the outer peripheral surface 121. The lip 33B is between the spring 40B and the outer peripheral surface 121. In the example shown in
According to the third embodiment, the sealing device 10B ensures electrical continuity between the housing 110 and the shaft 120. As in the first embodiment, an installation space for the sealing device 10B can be readily secured, and a cost of installation of the sealing device 10B can be reduced. In this embodiment, as described above, the sealing device 10B includes more than one spring 40B that is arranged along the axial direction of the shaft 120. As compared with a single spring 40, even if an area of the contact surface CR of the lip 33B relative to the outer peripheral surface 121 of the shaft 120 is increased, an axial tightening force caused by the spring 40B can be efficiently transmitted to the contact surface CR over a wide range. Increasing adherence between the lip 33B and the shaft 120 enables electrical resistance between the lip 33B and the shaft 120 to be reduced, and, as a result, an induced current generated in the shaft 120 can be transferred to the lip 33B.
The foregoing embodiments exemplified above may be modified. Specific modes of modification applicable to the embodiments will be exemplified below. More than one mode freely selected from the following examples may be combined, as appropriate, as long as such combination does not give rise to any conflict.
The foregoing embodiments provide an example of a configuration in which the reinforcing ring 20 is embedded in the elastic member 30, 30A, or 30B, but are not limited thereto. A part of the reinforcing ring 20 may be exposed from the elastic member 30, 30A, or 30B. In this case, the elastic member 30, 30A, or 30B may be composed of two members spaced apart from each other. An electrical continuity between the two members is ensured via the reinforcing ring 20.
The foregoing embodiments provide an example of a configuration in which the elastic member 30, 30A, or 30B is in contact with the housing 110, but are not limited thereto. The elastic member 30, 30A, or 30B may not be in contact with the housing 110. In this case, the reinforcing ring 20 may include a part exposed from the elastic member 30, 30A, or 30B such that the reinforcing ring 20 is in contact with the housing 110. As an electrically conductive reinforcing ring 20, the reinforcing ring 20 is in contact with the housing 110, thereby substantially reducing electrical resistance between the housing 110 and the sealing device 10, 10A or 10B. If the elastic member 30, 30A, or 30B is in contact with the housing 110 as in the foregoing embodiments, electric resistivity between the housing 110 and the sealing device 10A or 10B is more easily stabilized as compared with a configuration in which the reinforcing ring 20 is in contact with the housing 110.
The foregoing embodiments provide an example of a configuration in which the sealing device 10, 10A, or 10B is directly fixed to the housing 110, but are not limited thereto. A member, such as a spacer, may be interposed between the housing 110 and the sealing device 10, 10A, or 10B. The member may be regarded as a part of the housing 110 because the member is fixed to the housing 110.
The foregoing embodiments provide an example of a configuration in which the sealing device 10, 10A, or 10B is in direct contact with the housing 110 and the outer peripheral surface of the shaft 120 but are not limited thereto. The sealing device 10, 10A, or 10B may be in contact with a member, such as a sleeve fixed to the shaft 120. The member may be regarded as a part of the shaft 120 because the member is fixed to the shaft 120.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-193933 | Nov 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/037858 | 10/11/2022 | WO |
