JP4762757B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device in which a shaft member is rotatably supported by a lubricating film formed in a bearing gap.

  The hydrodynamic bearing device takes advantage of its excellent rotational accuracy, high-speed rotational performance, quietness, etc., for example, magnetic disk drive devices such as HDD, optical disks such as CD-ROM, CD-R / RW, DVD-ROM / RAM, etc. Compact motors such as drive motors, spindle motors for magneto-optical disk drive devices such as MD and MO, polygon scanner motors for laser beam printers (LBP), color wheel motors for projectors, and fan motors used for cooling fans for information equipment, etc. Used for motors.

For example, a hydrodynamic bearing device disclosed in Patent Document 1 includes a shaft member, a bearing member (bearing sleeve) in which the shaft member is inserted on the inner periphery, a housing in which the bearing member is fixed on the inner periphery, and one end is open. And a seal member provided at the opening of the housing. When the shaft member rotates, a lubricating film is formed in the radial bearing gap between the radial bearing surface formed on the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member, whereby the shaft member is rotatably supported. The At the same time, a seal space is formed between the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member to prevent leakage of the lubricating oil filled in the bearing. At this time, the radial bearing surface and the seal space are arranged side by side in the axial direction. In addition, a dynamic pressure groove is formed as a dynamic pressure generating portion on the radial bearing surface of the bearing member of the fluid dynamic bearing device, and the “bearing surface” means a portion facing the bearing gap. It does not matter whether or not the dynamic pressure generating portion is formed (the same applies hereinafter).
JP 2003-172336 A JP 2005-155912 A

  Incidentally, in recent years, the demand for small information devices has increased, and accordingly, the drive devices for HDDs and the like, as well as the bearing devices used therefor, have been required to be small and thin. However, in the bearing device as described above, the seal space requires a volume that allows a volume change accompanying a change in the temperature of the lubricating oil, and therefore requires a certain axial dimension. Further, it is desirable that the radial bearing surface be provided with a span as large as possible in the axial direction in order to increase bearing rigidity. By arranging the seal space and the radial bearing surface side by side in the axial direction, the required space in the axial direction of the bearing device is increased.

  On the other hand, for example, Patent Document 2 discloses that a first taper seal portion provided in the axial direction of the radial bearing gap and a second taper seal provided on the sleeve side surface are provided at the housing opening side end portion of the sleeve. A bearing device with a section is shown. In this bearing device, since the volume change of the lubricating liquid due to thermal expansion or the like is absorbed by the second taper seal portion provided on the side surface of the sleeve, the first taper seal portion provided side by side with the radial bearing gap in the axial direction. Does not require an axial dimension like a conventional seal member, and the axial dimension of the bearing device can be reduced.

  However, in the bearing device of Patent Document 2, since the lubricating oil inside the bearing is opened to the atmosphere at the two taper seal portions, compared to the bearing device of Patent Document 1 in which the taper seal portion is provided only at one location, There is a high risk of the lubricant leaking out of the bearing device due to impact load or the like. Leakage of lubricating oil may cause contamination of the surrounding environment and poor lubrication due to lack of lubricating oil.

  An object of the present invention is to provide a hydrodynamic bearing device that can be reduced in size and thickness, and can reliably prevent leakage of lubricating fluid such as lubricating oil.

In order to solve the above problems, the present invention provides a bearing member having a radial bearing surface on the inner peripheral surface, a shaft member inserted into the inner periphery of the bearing member, having a shaft portion and a flange portion, and fixed to the shaft member . A seal member having a disk part, a cylindrical part extending from the disk part to the other axial end side, a seal space formed by an outer peripheral surface of the cylindrical part of the seal member, an outer peripheral surface of the shaft member, and a bearing member A radial bearing gap formed between the radial bearing surface, a first thrust bearing gap formed between an end surface on one end side in the axial direction of the bearing member and an end surface of the disk portion of the seal member; A second thrust bearing gap formed between the end face on the other end side in the axial direction and the end face of the flange portion of the shaft member, and a radial bearing gap, a first thrust bearing gap, and a second thrust bearing gap. The shaft film can be freely rotated by the lubricating film formed on In the fluid bearing apparatus for supporting at least a portion of the seal space, characterized in that arranged outside diameter region of the radial bearing surface.

  Thus, in the hydrodynamic bearing device of the present invention, at least a part of the seal space that requires a certain axial dimension is arranged in the outer diameter region of the radial bearing surface. As a result, at least a part of the seal space can be arranged so as to overlap with the radial bearing gap in the radial direction, so that the required space in the axial direction of the bearing device is suppressed by providing the seal space, and the necessary seal space While maintaining the volume, the bearing device can be reduced in size and thickness.

  Further, since the seal space is formed only at one place, it is possible to more reliably avoid the leakage of the lubricating oil filled in the bearing as compared with the case where a plurality of seal spaces are provided.

In addition, as described above , by providing the thrust bearing gap on both end surfaces of the bearing member, it is possible to increase the axial span of the two thrust bearing gaps, so that the moment rigidity of the bearing device is improved. Can do.

  The seal space as described above can be formed, for example, between the inner peripheral surface of the housing in which the bearing member is fixed on the inner periphery and the outer peripheral surface of the seal member.

  As described above, according to the present invention, it is possible to obtain a hydrodynamic bearing device that can be reduced in size and thickness and can reliably prevent leakage of the lubricating fluid.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 as an example of a hydrodynamic bearing device according to the present invention. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports the shaft member 2 in a non-contact manner, a rotor (disk hub) 3 mounted on the shaft member 2, For example, a stator coil 4 and a rotor magnet 5 that are opposed to each other via a radial gap are provided. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or more disks D such as a magnetic disk. When the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows an embodiment of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a bottomed cylindrical housing 7, a bearing member 8 fixed to the inner periphery of the housing 7, a shaft member 2 inserted into the inner periphery of the bearing member 8, and an opening of the housing 7. A seal member 9 for sealing the portion is provided as a main component. For convenience of explanation, the description will proceed with the opening side of the housing 7 as the upper side and the opposite side in the axial direction as the lower side.

  The shaft member 2 has a shaft portion 2a and a flange portion 2b projecting to the outer diameter side at the lower end of the shaft portion 2a, either integrally or separately. The outer peripheral surface of the shaft portion 2a is formed in a substantially cylindrical shape, an annular groove 2a1 is formed in a region where the seal member 9 is fixed, and other regions in the regions corresponding to the radial bearing portions R1 and R2 An escape portion 2a2 having a slightly smaller diameter than the portion is formed. The shaft member 2 may be entirely formed of a metal material such as stainless steel, or may have a metal-resin hybrid structure in which the shaft portion 2a is made of metal and the flange portion 2b is made of resin, for example.

  The bearing member 8 is formed in a cylindrical shape with a sintered metal mainly composed of copper, for example. The sintered metal is impregnated with lubricating oil. In addition, the bearing member 8 can be formed of a solid metal material, for example, a soft metal such as brass.

  On the inner peripheral surface 8a of the bearing member 8, two upper and lower regions serving as radial bearing surfaces are provided apart in the axial direction (shown by cross-hatching in FIG. 2). In these two regions, as shown in FIG. 3, a plurality of dynamic pressure grooves G arranged in a herringbone shape, for example, are formed as dynamic pressure generating portions. The dynamic pressure groove G in the upper region is formed asymmetrically in the axial direction. In this region, the axial length X1 of the upper dynamic pressure groove is slightly longer than the axial length X2 of the lower dynamic pressure groove. It is larger (X1> X2). On the other hand, the dynamic pressure grooves G in the lower region are formed in the axial direction, and the axial lengths of the upper and lower dynamic pressure grooves G are equal in the region.

  The upper end surface 8b and the lower end surface 8c of the bearing member 8 are formed with regions to be thrust bearing surfaces (shown by cross-hatching in FIG. 2), and in these regions, for example, FIG. 5, a plurality of dynamic pressure grooves 8b1 and 8c1 arranged in a spiral shape are formed.

  A circulation groove 8d for circulating the lubricating oil is formed in the axial direction at one place on the outer peripheral surface of the bearing member 8 or at a plurality of places equally arranged in the circumferential direction. Both ends of the circulation groove 8d are open to both end faces 8b, 8c of the bearing member 8.

  The housing 7 includes a cylindrical portion 7a and a bottom portion 7b that seals the lower end opening of the cylindrical portion 7a. The inner peripheral surface of the cylindrical portion 7a includes a small-diameter inner peripheral surface 7a1, a large-diameter inner peripheral surface 7a2, and a boundary surface 7a3 between the inner peripheral surfaces 7a1 and 7a2, and the boundary surface 7a3 is in a direction orthogonal to the axial direction. A flat surface is formed. The outer peripheral surface of the cylindrical portion 7a is fixed to the inner peripheral surface of the bracket 6 shown in FIG. 1 by appropriate means such as press-fitting, bonding, and press-fitting adhesion.

  The housing 7 is made of a soft metal material such as brass or an aluminum alloy, or other metal material. As the processing method, appropriate machining can be adopted, but forging is preferably performed from the viewpoint of workability and cost.

  The housing 7 and the bearing member 8 can be fixed by press-fitting, bonding, or press-fitting (press-fitting with an adhesive interposed). The fixed area between the housing 7 and the bearing member 8 is narrower than the inner peripheral surface 7a2 formed on the inner peripheral surface of the housing 7, compared with the case where the inner peripheral surface is formed in a cylindrical shape. It is desirable to fix with as strong a fixing force as possible. As described above, when the housing 7 is made of metal, the adhesiveness by the adhesive is excellent. Therefore, when the housing 7 is fixed by adhesion, the metal housing 7 can be firmly fixed to the bearing member 8.

  The seal member 9 is formed in an inverted L-shaped cross section by a disc portion 9a and a seal portion 9b extending downward in the axial direction from the outer diameter end of the disc portion 9a. In the present embodiment, the inner peripheral surface 9a2 of the disk portion 9a, the inner peripheral surface 9b1 and the outer peripheral surface 9b2 of the seal portion 9b are all formed in a cylindrical surface shape.

  The seal member 9 is formed of various metal materials or resin materials. As the metal material, for example, a soft metal material such as brass or an aluminum alloy can be used. As the resin material, for example, when the seal member 9 is formed by injection molding, any resin material that can be injection molded can be used regardless of whether it is an amorphous resin or a crystalline resin. For example, an amorphous resin As a crystalline resin such as polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), liquid crystal polymer (LCP), polyetheretherketone (PEEK), Polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or the like can be used. Of course, these are only examples, and other resin materials suitable for the application and use environment of the bearing can also be used. Moreover, what is necessary is just to use the resin material suitable for the processing method, when forming by processing methods other than injection molding. One or more kinds of various fillers such as a reinforcing material (fibrous, powdery form, etc.), a lubricant, and a conductive material are blended in the resin material as necessary.

  The seal member 9 is fixed to the outer peripheral surface of the shaft portion 2a of the shaft member 2 by, for example, press-fitting, bonding, or press-fitting adhesion. When the seal member 9 is fixed via an adhesive, the annular groove 2a1 formed in the shaft portion 2a acts as an adhesive reservoir, thereby obtaining a stronger fixing force. When the seal member 9 is fixed without using an adhesive, the annular groove 2a1 of the shaft portion 2a may not be provided.

  In assembling the hydrodynamic bearing device 1, the shaft member 2 is accommodated in the housing 7, and then the bearing member 8 is fixed to the inner peripheral surface of the housing 7. It is done by fixing. Thereafter, when the internal space of the housing 7 is filled with lubricating oil, the fluid dynamic bearing device 1 shown in FIG. 2 is obtained. After assembly, the lower end surface 9a1 of the disk portion 9a of the seal member 9 abuts on the upper end surface 8b of the bearing member 8, and the lower end surface of the seal portion 9b of the seal member 9 contacts the boundary surface 7a3 on the inner periphery of the housing 7. It is opposed via an axial gap 11.

  When the shaft member 2 rotates, the two upper and lower dynamic pressure groove regions formed on the radial bearing surface of the inner peripheral surface 8a of the bearing member 8 face the outer peripheral surface of the shaft portion 2a via the radial bearing gap. Further, the dynamic pressure groove region formed on the thrust bearing surface of the upper end surface 8b of the bearing member 8 faces the lower end surface 9a1 of the disk portion 9a of the seal member 9 via the first thrust bearing gap, and the bearing member 8 The dynamic pressure groove region formed on the thrust bearing surface of the lower end surface 8c faces the upper end surface of the flange portion 2b via the second thrust bearing gap. As the shaft member 2 rotates, dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the radial direction by the oil film of the lubricating oil formed in the radial bearing gap. Is done. Thus, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are configured. At the same time, the dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the thrust direction by the oil film of the lubricating oil formed in the first and second thrust bearing gaps. . Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which non-contact-support the shaft member 2 rotatably in a thrust direction are comprised.

  The outer peripheral surface 9b2 of the seal portion 9b of the seal member 9 forms a seal space S having a predetermined volume with the large-diameter inner peripheral surface 7a2 of the housing 7. At this time, at least a part of the seal space S is located in the outer diameter region of the radial bearing surface of the first radial bearing portion R1. In this embodiment, the large-diameter inner peripheral surface 7a2 of the housing 7 is formed in a tapered surface shape that gradually increases in diameter upward, so that the seal space S exhibits a tapered shape that gradually decreases in the downward direction. Accordingly, the lubricating oil in the seal space S is drawn in the direction in which the seal space S becomes narrow due to the drawing action by the capillary force, and the opening of the housing 7 is thereby sealed. The seal space S also has a buffer function for absorbing a volume change amount associated with a temperature change of the lubricating oil filled in the internal space of the housing 7, and the oil level is always in the seal space S.

  As described above, by disposing at least a part of the seal space S in the outer diameter region of the radial bearing surface, at least a part of the seal space S and the formation region of the radial bearing surface can be overlapped in the radial direction. Therefore, by providing the seal space S, the axial dimension of the first radial bearing part R1 and the axial distance between the two radial bearing parts R1 and R2 can be suppressed, so that the bearing rigidity is reduced. Therefore, the bearing device can be made thinner. Thereby, it is possible to cope with the downsizing and thinning of the HDD device.

  Or according to said structure, since the axial direction dimension of the bearing member 8 can be increased, without increasing the axial direction dimension of a bearing apparatus, by increasing the space | interval between two radial bearing part R1, R2. The bearing rigidity (especially moment rigidity) can be improved. As a result, it is possible to cope with a plurality of disks in the HDD device.

  Further, since the seal portion in which the lubricating oil inside the bearing comes into contact with the atmosphere is formed only at one place, there is less risk of leakage of the lubricating oil, for example, compared to a case where a plurality of seal portions are formed. As a result, contamination of the surrounding environment and poor lubricating oil can be avoided.

  Further, since the first and second thrust bearing gaps are provided on both end surfaces of the bearing member 8, the axial span of each thrust bearing gap can be increased, thereby improving the moment rigidity of the bearing device. Can be made.

  In addition, while the large-diameter inner peripheral surface 7a2 of the housing 7 is a cylindrical surface, the outer peripheral surface 9b2 of the seal portion 9b of the seal member 9 opposed to the cylindrical surface may be formed into a tapered surface. Since the function as a centrifugal force seal can be given to S, the sealing effect is further enhanced.

  As described above, the dynamic pressure groove G of the first radial bearing portion R1 is formed asymmetrically in the axial direction, and the axial dimension X1 of the upper region is larger than the axial dimension X2 of the lower region. Therefore, when the shaft member 2 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove G is relatively larger in the upper region than in the lower region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the radial bearing gap between the inner circumferential surface 8a of the bearing member 8 and the outer circumferential surface of the shaft portion 2a flows downward, and the second thrust bearing gap It circulates through the path of (second thrust bearing portion T2) → circulation groove 8d in the axial direction → first thrust bearing gap (first thrust bearing portion T1), and is drawn into the radial bearing gap again.

  In this way, the configuration in which the lubricating oil flows and circulates in the housing 7 prevents the pressure of the lubricating oil filled in the housing 7 from being locally reduced to a negative pressure. Problems such as generation of bubbles accompanying the generation, leakage of lubricating oil and generation of vibration due to the generation of bubbles can be solved. Since the seal space S communicates with the lubricating oil circulation path via the axial gap 11, even when bubbles are mixed in the lubricating oil for some reason, the bubbles are circulated along with the lubricating oil. In addition, the lubricating oil in these seal spaces S is discharged from the oil surface (gas-liquid interface) to the outside air, and adverse effects on the bubbles are more effectively prevented. The axial circulation groove 8 d can also be formed on the inner peripheral surface of the housing 7.

  Such a flow circulation of the lubricating oil can be reversed in the reverse direction by adjusting the lengths of the dynamic pressure grooves of the radial bearing portions R1 and R2. Alternatively, when the differential pressure of the pulling force due to the dynamic pressure groove G is not particularly required, any of the dynamic pressure grooves of the radial bearing portions R1 and R2 may have a symmetrical shape with respect to the respective axial centers.

  In the above description, the dynamic pressure generating portions of the first and second radial bearing portions R1, R2 are formed on the inner peripheral surface of the bearing member 8, and the dynamic pressure generating portions of the first and second thrust bearing portions T1, T2 are formed. The case where it forms in the upper end surface 8b and the lower end surface 8c of the bearing member 8 is illustrated. In order to form the dynamic pressure generating portion in the bearing member 8 in this manner, for example, a shape corresponding to the dynamic pressure groove or the like of the dynamic pressure generating portion is formed in a mold used for compression molding of the bearing member 8. This is done by transferring this shape to the bearing member 8 simultaneously with compression molding. According to this processing method, the dynamic pressure generating portion can be formed relatively easily and with high accuracy as compared with other machining processes, so that costs can be reduced and productivity can be improved.

  The present invention is not limited to the above. For example, as shown in FIG. 6, when a fixed portion 9 c extending in the axial direction is provided at the inner diameter end of the disk portion 9 a of the seal member 9, the fixed area between the seal member 9 and the shaft portion 2 a of the shaft member 2 is increased. It is possible to expand and improve these fixing forces. At this time, if the axial dimension of the annular groove 2a1 of the shaft portion 2a is enlarged, more adhesive can be retained, and further improvement in fixing force can be achieved.

  Further, the position of the first thrust bearing portion T1 is not limited to the above. For example, the first thrust bearing portion T1 may be configured by the lower end surface 2b2 of the flange portion 2b and the inner bottom surface 7b1 of the housing 7 (not shown). ). At this time, the shaft member 2 is supported in the thrust direction by the dynamic pressure action of the oil film in the thrust bearing gap formed between the lower end surface 2b2 of the flange portion 2b and the inner bottom surface 7b1 of the housing 7. In this case, the gap between the upper end surface 8b of the bearing member 8 and the end surface 9a1 of the seal member 9 facing the upper end surface 8b constitutes the above-described lubricating oil circulation path. When the width of the gap is too small to prevent the circulation of the lubricating oil, a radial groove may be provided in the upper end surface 8b of the bearing member 8 or the end surface 9a1 of the seal member 9 in order to promote the circulation.

  The dynamic pressure generating portions shown in the above embodiments are surfaces facing each other, that is, the outer peripheral surface of the shaft portion 2a of the shaft member 2, the lower end surface 9a1 of the disk portion 9a of the seal member 9, or the flange of the shaft member 2. You may form in the upper end surface 2b1 of the part 2b.

  Further, although the herringbone shape and spiral shape dynamic pressure grooves are illustrated as the dynamic pressure generating portions of the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2, the present invention is not limited thereto. For example, so-called step bearings, corrugated bearings, or multi-arc bearings can be employed as the radial bearing portions R1, R2, and step bearings or corrugated bearings can be employed as the thrust bearing portions T1, T2. . Furthermore, what is called a perfect circle bearing which does not have a dynamic-pressure generation | occurrence | production part can also be employ | adopted as radial bearing part R1, R2. At this time, the cylindrical inner peripheral surface 8a of the bearing member 8 becomes a radial bearing surface, and a radial bearing gap is formed between the outer peripheral surface 2a of the opposing shaft member 2. In addition, the thrust bearing portion can be formed of a so-called pivot bearing by using a shaft member that does not have a flange portion but has a spherical lower end portion. Further, only one of the thrust bearing portions T1 and T2 may be formed or both may be omitted.

  In the above description, the housing 7 is formed of a metal material in consideration of the fixing force with the bearing member 8. However, if there is no problem with the fixing force, the housing 7 can be formed of a resin material. In this case, there is an advantage that the cost and weight can be reduced as compared with the metal material. Since the resin material that can be used for the housing 7 is the same as that exemplified as the resin material of the sealing member 9 described above, the description thereof is omitted.

  In the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1. However, other fluids that can generate dynamic pressure in the bearing gaps, for example, gas such as air Alternatively, a magnetic fluid or the like can be used.

It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus (dynamic pressure bearing apparatus 1) which concerns on this invention. 1 is a cross-sectional view showing an embodiment of a hydrodynamic bearing device 1. 3 is a cross-sectional view of a bearing member 8. FIG. It is sectional drawing in the AA line (refer FIG. 5) of the sealing member 9. FIG. FIG. 6 is a plan view of the seal member 9 as viewed from the B direction (see FIG. 4). It is sectional drawing which shows other embodiment of the fluid dynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 7 Housing 8 Bearing member 9 Seal member 9a Disk part 9b Seal part 9c Fixed part G Dynamic pressure groove R1, R2 Radial bearing part T1, T2 Thrust bearing part S Seal space

Claims (2)

A bearing member on the inner circumferential surface having a radial bearing surface, is inserted into the inner periphery of the bearing member, a shaft member having a shaft portion and a flange portion, fixed to the shaft member, the disk portion, and the axial other from the disc portion A seal member having a cylindrical portion extending to the end side, a seal space formed by the outer peripheral surface of the cylindrical portion of the seal member, and a radial formed between the outer peripheral surface of the shaft member and the radial bearing surface of the bearing member A bearing gap , a first thrust bearing gap formed between an end face on one end side in the axial direction of the bearing member and an end face of the disk portion of the seal member; an end face on the other end side in the axial direction of the bearing member; And a second thrust bearing gap formed between the end surface of the flange portion, and the shaft member is rotated by a lubricating film formed in the radial bearing gap, the first thrust bearing gap, and the second thrust bearing gap. In a hydrodynamic bearing device that supports freely,
A hydrodynamic bearing device, wherein at least a part of a seal space is arranged in an outer diameter region of a radial bearing surface. The hydrodynamic bearing device according to claim 1, wherein the bearing member is fixed to the inner peripheral surface of the housing, and the seal space is formed between the outer peripheral surface of the cylindrical portion of the seal member and the inner peripheral surface of the housing.

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