WO2019112057A1

WO2019112057A1 - Fluid dynamic bearing device

Info

Publication number: WO2019112057A1
Application number: PCT/JP2018/045171
Authority: WO
Inventors: 和慶原田; 慎治小松原; 翔平岡; 淳平出
Original assignee: Ntn株式会社
Priority date: 2017-12-08
Filing date: 2018-12-07
Publication date: 2019-06-13
Also published as: CN111433472B; CN111433472A

Abstract

A fluid dynamic bearing device 1 comprising: a shaft member 2; a bearing sleeve 8 having the shaft member 2 inserted into the inner circumference thereof; a floored cylindrical housing 7 holding the bearing sleeve 8 in the inner circumference thereof and having an opening in an end section on one side in the axial direction; and a seal member 9 provided in the opening of the housing 7. The seal member 9 has: a disc 9a arranged on one side of the bearing sleeve 8 in the axial direction; and a protruding section (tubular section 9b) protruding to the other side in the axial direction, from an outer radial end of the disc 9a. An outer circumferential surface 9c of the seal member 9 is fixed to an inner circumferential surface 7a1 of the housing 7.

Description

Fluid dynamic bearing device

The present invention relates to a fluid dynamic bearing device.

In the fluid dynamic bearing device, the pressure of the oil film generated in the radial bearing gap between the outer peripheral surface of the shaft and the inner peripheral surface of the bearing sleeve is increased with the rotation of the shaft, and this pressure supports the shaft in a noncontact manner It is a thing. Since the fluid dynamic bearing device has features such as high speed rotation, high rotation accuracy, low noise, etc., it is mounted on the motor of various electric devices including information devices, and is a spindle incorporated in disk drive devices such as HDD. It is mounted on a motor, a cooling fan motor incorporated in a PC or the like, or a polygon scanner motor incorporated in a laser beam printer or the like.

For example, in Patent Document 1 below, a bottomed cylindrical housing, a bearing sleeve fixed on the inner periphery of the housing, a shaft member inserted on the inner periphery of the bearing sleeve, and a housing opening fixed A fluid dynamic bearing device with a seal member (seal washer) is shown. By covering the opening of the housing with the seal member, the oil in the housing is prevented from leaking out.

Patent Document 2 below shows that the bearing sleeve is fixed to the inner periphery of the housing by being sandwiched from both sides in the axial direction by the seal member (annular member) and the bottom of the housing. As a result, compared to, for example, fixing the bearing sleeve to the inner periphery of the housing by press fitting, it is possible to reduce the time required for assembly and reduce the width accuracy of the radial bearing gap due to the deformation of the bearing sleeve accompanying the press fitting. Can be prevented.

Japanese Patent Application Laid-Open No. 2002-61658 JP, 2014-59014, A

In the fluid dynamic bearing device, in order to increase the bearing rigidity and stably support the rotating shaft, the axial dimension of the bearing sleeve is made as large as possible, and the bearing span {radial bearings provided at two axial locations It is desirable to secure the axial spacing of the parts (high pressure generating parts). However, since there is a restriction on the axial dimension of the motor in which the fluid dynamic bearing device is incorporated, in order to ensure the axial dimension of the bearing sleeve at maximum, the seal member disposed axially in line with the bearing sleeve It is necessary to reduce the axial dimension as much as possible.

When the axial dimension of the seal member is reduced as described above, the area of the fastening portion between the outer peripheral surface of the seal member and the inner peripheral surface of the housing decreases, so that the fixing strength between the both is insufficient. When an impact load or vibration is applied, the fixing position of the seal member with respect to the housing may be shifted. In particular, in the case of a structure in which the bearing sleeve is sandwiched and fixed from both sides in the axial direction by the seal member and the housing as in Patent Document 2 described above, the fixing position of the bearing sleeve with respect to the housing when the seal member is displaced. Also, there is a concern that the bearing performance will significantly decrease.

From the above circumstances, it is an object of the present invention to secure the fixing strength between the seal member and the housing even when the axial dimension of the seal member is reduced.

In order to solve the above-mentioned subject, the present invention holds a shaft member, a bearing sleeve in which the shaft member is inserted in the inner circumference, and holds the bearing sleeve in the inner circumference, and an opening at one end in the axial direction A bottomed cylindrical housing having a bottom, a seal member provided at an opening of the housing, and an oil film formed in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve A fluid dynamic bearing device comprising: a radial bearing portion for supporting the members in a relatively rotatable manner, wherein the seal member is a disc portion disposed on one side in the axial direction of the bearing sleeve, and the outside of the disc portion A fluid dynamic pressure bearing device is provided, which has a convex portion projecting from the radial end to the other side in the axial direction, and the outer peripheral surface of the seal member is fixed to the inner peripheral surface of the housing.

As described above, the seal member is provided with a convex portion (for example, a cylindrical portion) protruding in the axial direction from the outer diameter end of the disk portion, and the seal member has an L-shaped cross section Even when the dimension (D) is reduced, the area can be expanded by axially extending the outer peripheral surface of the seal member by the amount of provision of the convex portion. Thereby, a sufficient fixed area of the outer peripheral surface of the seal member and the inner peripheral surface of the housing can be secured, and the fixing strength of both can be secured.

In the above fluid dynamic bearing device, when the end face of the disk portion of the seal member abuts on the end face of the bearing sleeve, the seal member can prevent the bearing sleeve from coming off the housing. In this case, by enhancing the fixing strength between the seal member and the housing as described above, the positional deviation of the bearing sleeve relative to the housing can be reliably prevented.

By the way, in the fluid dynamic pressure bearing device described in Patent Document 2, when oil that has expanded at high temperature reaches a radial gap between the seal member and the shaft member, the risk of oil leaking out increases. In particular, when the axial dimension of the seal member is reduced as described above, the oil that has reached the radial gap between the seal member and the shaft member tends to leak out.

Therefore, in the fluid dynamic bearing described above, it is preferable to provide a first oil reservoir between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve. The first oil reservoir serving as a buffer function absorbing the volume change of the oil makes it difficult for the expanded oil to reach the radial gap between the seal member and the shaft member, thereby reducing the risk of oil leakage. . In addition, the first oil reservoir is provided on the outer periphery of the bearing sleeve so as to be separated from the radial gap between the seal member and the shaft member, so the oil surface held in the first oil reservoir is the above It becomes difficult to reach the radial clearance, and oil leakage can be reliably prevented.

The first oil reservoir may have, for example, a bowl-like cross-sectional shape in which the radial width is gradually reduced toward one axial side (the closed side of the housing). In this case, since the oil held in the first oil reservoir is drawn to the closed side of the housing by capillary force, the leakage of the oil from the first oil reservoir can be more reliably prevented.

In the above fluid dynamic bearing device, the oil leaks to the outside when the oil in the housing greatly expands at high temperature and overflows from the first oil reservoir and reaches the radial gap between the seal member and the shaft member. It will be easier. Therefore, if a recess is provided at the inner diameter end of the end face of the disk portion of the seal member, and a second oil reservoir is formed by the recess, the end surface of the bearing sleeve and the outer peripheral surface of the shaft member, it overflows from the first oil reservoir Since the oil that has reached the radial gap between the seal member and the shaft member can be held by the second oil reservoir, oil leakage can be prevented.

In the above fluid dynamic bearing device, the bearing sleeve can be held in the axial direction with respect to the housing by holding the bearing sleeve from both sides in the axial direction by the disk portion of the seal member and the housing. In this case, the convex portion of the seal member is press-fit into the gap between the inner circumferential surface of the housing and the outer circumferential surface of the bearing sleeve, and the outer circumferential surface of the convex portion and the inner circumferential surface of the housing and the inner circumferential surface of the convex portion The outer peripheral surface of the bearing sleeve may be fitted with an interference, respectively. Thereby, since the bearing sleeve is tightened from the outer periphery by the seal member and the housing, the bearing sleeve can be firmly held in the radial direction with respect to the housing, and the fastening force between the housing and the bearing sleeve is enhanced.

When the outer peripheral surface of the seal member and the inner peripheral surface of the housing are fitted with an interference as described above, it is preferable to make the linear expansion coefficient of the seal member larger than the linear expansion coefficient of the housing. In this case, since the seal member tends to expand in diameter more than the housing when the temperature rises, the fastening force between the seal member and the housing is not impaired even at high temperatures.

Specifically, for example, when the housing and the seal member are formed of a resin material containing reinforcing fibers, the compounding ratio of the reinforcing fibers in the resin material of the housing is determined by the compounding ratio of the reinforcing fibers in the resin material of the seal member The linear expansion coefficient of the seal member can be made larger than the linear expansion coefficient of the housing.

Alternatively, the linear expansion coefficient of the seal member can be made larger than the linear expansion coefficient of the housing by forming the housing by brass and forming the seal member by a resin material.

As described above, when the seal member is press-fit into the inner periphery of the housing, the effect of the press-fit causes the outer peripheral surface of the housing to expand, which may cause trouble in attaching the fluid dynamic bearing device to another member (for example, motor bracket). is there. Therefore, it is preferable to provide the housing with a large diameter outer peripheral surface and a small diameter outer peripheral surface, and fit the seal member with an interference to the axial region of the small diameter outer peripheral surface. As described above, by forming the portion of the outer peripheral surface of the housing which is expanded by the press-fitting of the seal member to a small diameter in advance, it is possible to avoid the situation where this portion interferes with other members.

As described above, in the present invention, even when the axial dimension of the seal member is reduced, the fixing strength between the seal member and the housing can be secured, and the positional deviation between the seal member and the housing can be prevented.

It is a sectional view of a fan motor. It is a sectional view of a fluid dynamic pressure bearing device concerning one embodiment of the present invention. It is a sectional view of a bearing sleeve. It is an enlarged view of FIG. It is sectional drawing of the fluid hydrodynamic bearing apparatus which concerns on other embodiment. It is sectional drawing of the fluid hydrodynamic bearing apparatus which concerns on other embodiment. It is sectional drawing of the fluid hydrodynamic bearing apparatus which concerns on other embodiment.

Hereinafter, embodiments of the present invention will be described based on the drawings.

The fan motor shown in FIG. 1 includes a fluid dynamic pressure bearing device 1 according to an embodiment of the present invention, a motor base 6 to which a housing 7 of the fluid dynamic pressure bearing device 1 is fixed, and a shaft of the fluid dynamic pressure bearing device 1 And a rotor 3 fixed to the member 2. A stator coil 5 is attached to the motor base 6, and a rotor magnet 4 opposed to the stator coil 5 via a gap in the radial direction is attached to the rotor 3. When the stator coil 5 is energized, the electromagnetic force generated between the stator coil 5 and the rotor magnet 4 causes the rotor 3 and the shaft member 2 to rotate integrally, and the vanes (not shown) provided on the rotor axially or radially Air flow occurs.

As shown in FIG. 2, the fluid dynamic bearing device 1 holds the shaft member 2, the bearing sleeve 8 in which the shaft member 2 is inserted in the inner periphery, and the bearing sleeve 8 in the inner periphery. A bottomed cylindrical housing 7 having an opening at its end and a seal member 9 provided at the opening of the housing 7 are provided as main components. The internal space of the housing 7 is filled with a predetermined amount of lubricating oil (indicated by a scattering point in FIG. 2). The fluid dynamic bearing device 1 of the present embodiment is mainly used in the posture shown in FIG. 2, that is, in the state where the opening side of the housing 7 is on the upper side in the axial direction. However, the fluid dynamic bearing device 1 is not limited to the above, and may be used, for example, in a state in which the axial direction is horizontal or in a state in which the opening side of the housing 7 is on the lower side.

The shaft member 2 is formed of a metal material such as stainless steel. The outer peripheral surface 2a of the shaft member 2 is a smooth cylindrical surface without unevenness, and the outer diameter is constant throughout the axial direction. The outer diameter of the shaft member 2 is smaller than the inner diameters of the bearing sleeve 8 and the seal member 9. A convex spherical surface 2 b is provided at the lower end of the shaft member 2. The rotor 3 is fixed to the upper end of the shaft member 2 (see FIG. 1).

The housing 7 has a cylindrical side 7a and a bottom 7b closing the lower end opening of the side 7a. In the present embodiment, the side portion 7 a and the bottom portion 7 b of the housing 7 are integrally formed of metal or resin. On the inner peripheral surface of the side portion 7a, a large-diameter inner peripheral surface 7a1 provided at the upper end, a small-diameter inner peripheral surface 7a2 provided below the upper end, and a flat surface 7a3 continuous with these are formed. The outer peripheral surface of the side portion 7a is a straight cylindrical surface. As a result, the thickness (radial dimension) of the axial region of the large diameter inner circumferential surface 7a1 in the side portion 7a is smaller than the thickness of the axial region of the small diameter inner circumferential surface 7a2. At the upper end face of the bottom 7b, a bottom surface 7b1 provided at the axial center and a shoulder surface 7b2 provided at the outer periphery of the bottom surface 7b1 are formed. Shoulder surface 7b2 is arranged above bottom surface 7b1. In the present embodiment, the thrust plate 10 made of resin is disposed on the bottom surface 7b1 of the housing 7, and the upper surface of the thrust plate 10 functions as a thrust bearing surface that contacts and supports the convex spherical surface 2b at the lower end of the shaft member 2. However, the thrust plate 10 is not necessarily provided, and may be omitted. In this case, the bottom surface 7b1 of the housing 7 functions as a thrust bearing surface.

The bearing sleeve 8 has a cylindrical shape, and is formed of, for example, a metal, particularly a sintered metal, specifically, a copper-iron-based sintered metal containing copper and iron as main components. The inner hole of the bearing sleeve 8 is impregnated with lubricating oil. The material of the bearing sleeve 8 is not limited to the above, and for example, a metal melting material such as a copper alloy or an iron alloy, or a resin may be used.

A radial bearing surface is provided on the inner circumferential surface 8 a of the bearing sleeve 8. In the present embodiment, as shown in FIG. 3, radial bearing surfaces A1 and A2 are provided at two locations separated in the axial direction of the inner peripheral surface 8a of the bearing sleeve 8. A radial dynamic pressure generating portion is formed on each of the radial bearing surfaces A1 and A2. In the present embodiment, herringbone-shaped dynamic pressure grooves G1, G2 are formed as the radial dynamic pressure generating portion. In the illustrated example, each of the hydrodynamic grooves G1, G2 has an axially symmetrical shape. The area indicated by cross hatching indicates a hill portion raised to the inner diameter side than the other areas. The form of the radial dynamic pressure generating portion is not limited to the above, and, for example, a spiral dynamic groove, a multi-arc bearing, or a step bearing may be adopted. Alternatively, the radial bearing surfaces A1 and A2 of the bearing sleeve 8 may be smooth cylindrical surfaces, and a radial dynamic pressure generating portion may be formed on the outer peripheral surface 2a of the opposing shaft member 2.

A plurality of axial grooves 8d1 are formed on the outer peripheral surface 8d of the bearing sleeve 8 at equal intervals in the circumferential direction. A plurality of radial grooves 8c1 and 8b1 are formed on the upper end surface 8c and the lower end surface 8b of the bearing sleeve 8 at equal intervals in the circumferential direction, respectively. An annular groove 8 c 2 is formed on the upper end surface 8 c of the bearing sleeve 8. The lower end surface 8 b of the bearing sleeve 8 abuts on a shoulder surface 7 b 2 provided on the bottom 7 b of the housing 7.

As shown in FIG. 4, the seal member 9 has a disk portion 9 a having an inner hole through which the shaft member 2 is inserted, and a convex portion protruding downward from the outer diameter end of the disk portion 9 a. In the example of illustration, a convex part is comprised by the cylindrical part 9b provided cyclically | annularly. The seal member 9 is fixed to the opening of the housing 7, and in the present embodiment, the outer peripheral surface 9 c of the seal member 9 is fixed to the large diameter inner peripheral surface 7 a 1 provided on the upper end of the side portion 7 a of the housing 7. The means for fixing the sealing member 9 and the housing 7 is not limited. For example, press fit, adhesion after gap fitting between both, press fit adhesion (combination of press fit and adhesion), or both of the same resin (base resin is the same Ultrasonic welding or the like after forming it with the resin of At this time, as described above, the seal member 9 has an L-shaped cross section having the disc portion 9a and the cylindrical portion 9b, so that the cylindrical portion 9b is extended downward even if the disc portion 9a is thinned. The area of the outer peripheral surface 9c of the member can be enlarged. Thereby, the fixed area of the outer peripheral surface 9c of the seal member 9 and the large diameter inner peripheral surface 7a1 of the housing 7 is sufficiently secured, and the fixing strength of both members can be secured.

A radial gap S is formed between the inner peripheral surface 9 a 1 of the disk portion 9 a of the seal member 9 and the outer peripheral surface 2 a of the shaft member 2. The gap width of the radial gap S is set as small as possible in order to prevent oil leakage and prevent entry of foreign matter from the outside. For example, in the case of a fluid dynamic pressure bearing device having a shaft diameter of about 2 to 4 mm, the gap width of the radial gap S is set to about 0.3 mm or less. Further, the gap width of the radial gap S is larger than the gap width of the radial bearing gap formed between the inner peripheral surface 8 a of the bearing sleeve 8 and the outer peripheral surface 2 a of the shaft member 2.

The lower end surface 9 a 2 of the disk portion 9 a of the seal member 9 is in contact with the upper end surface 8 c of the bearing sleeve 8. Thereby, the upward movement of the bearing sleeve 8 with respect to the housing 7 is restricted. In the present embodiment, the bearing sleeve 8 is fixed to the inner periphery of the housing 7 by sandwiching the sealing sleeve 9 and the housing 7 from both sides in the axial direction. Specifically, after the outer peripheral surface 8d of the bearing sleeve 8 and the small diameter inner peripheral surface 7a2 of the housing 7 are fitted with a gap, the lower end surface 9a2 of the disk 9a of the seal member 9 and the bottom of the housing 7 The bearing sleeve 8 is fixed to the housing 7 by holding the bearing sleeve 8 from both sides in the axial direction with the shoulder surface 7b2 provided on 7b. As a result, compared with the case where the bearing sleeve 8 is fixed to the housing 7 by press fitting, the time and effort of fixing operation can be reduced and deformation of the bearing sleeve 8 accompanying the press fitting can be avoided. In the illustrated example, an axial gap is formed between the lower end of the cylindrical portion 9 b of the seal member 9 and the flat surface 7 a 3 of the inner peripheral surface of the housing 7. Thereby, the lower end surface 9a2 of the disk portion 9a of the seal member 9 and the upper end surface 8c of the bearing sleeve 8 can be reliably brought into contact with each other.

The lubricating oil is at least in the radial bearing gap between the outer peripheral surface 2a of the shaft member 2 and the radial bearing surfaces A1 and A2 of the inner peripheral surface 8a of the bearing sleeve 8 in the inside of the housing 7, and The sliding portion between the lower end convex spherical surface 2 b and the thrust plate 10 is interposed. In the present embodiment, the entire area of the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft member 2, and the space D on the closed side facing the convex spherical surface 2b of the shaft member 2 (see FIG. 2) The whole area of) is filled with lubricating oil. As the lubricating oil, it is preferable to use a fluorine-based, ether-based or silicone-based oil which is stable in a high temperature environment without deterioration and stable in lubricity.

The fluid dynamic bearing device 1 is provided with a communication passage that communicates the space D on the closed side and the radial gap S between the shaft member 2 and the seal member 9 without interposing the radial bearing gap. In the present embodiment, the communication passage is between the lower end surface 8b of the bearing sleeve 8 and the shoulder surface 7b2 of the housing 7, between the outer peripheral surface 8d of the bearing sleeve and the small diameter inner peripheral surface 7a2 of the housing 7, and the bearing sleeve It is formed between the upper end surface 8 c of the second and third, and the lower end surface 9 a 2 of the disc portion 9 a of the seal member 9. In the illustrated example, the communication passage is constituted by the radial groove 8b1 of the lower end surface 8b of the bearing sleeve 8, the axial groove 8d1 of the outer peripheral surface 8d, and the radial groove 8c1 of the upper end surface 8c.

The fluid dynamic bearing device 1 of the present embodiment is an internal space of the housing 7, more specifically, a space provided between the shaft member 2 and the seal member 9 on the inner side of the radial gap S adjacent to the outside air. However, not all the lubricant oil is filled, it has a so-called partial fill structure having a void portion not filled with the lubricant oil. Specifically, as shown in FIG. 4, an oil reservoir P1 (first oil reservoir) is formed between the large diameter inner peripheral surface 7a1 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8, and this temperature is normal. An oil surface is formed in the oil reservoir P1. In the illustrated example, an oil reservoir P1 is formed between the inner peripheral surface 9b1 of the cylindrical portion 9b of the seal member 9 and the outer peripheral surface 8d of the bearing sleeve 8. On the other hand, the gap between the outer peripheral surface 2a of the shaft member 2 and the inner peripheral surface 8a of the bearing sleeve 8 is filled with lubricating oil over its entire area by capillary force, and the oil surface provided on the upper end of the lubricating oil is a bearing The clearance between the chamfer 8e at the upper end of the inner peripheral surface 8a of the sleeve 8 and the outer peripheral surface 2a of the shaft member 2 is reached. As described above, in the internal space of the housing 7, a part of the oil reservoir P1, a part of the axial groove 8d1 of the outer peripheral surface 8d of the bearing sleeve 8, a radial groove 8c1 of the upper end surface 8c of the bearing sleeve 8, A part of the space facing the upper end chamfer 8e of the inner peripheral surface 8a of the bearing sleeve 8 constitutes a gap not filled with the lubricating oil.

As described above, by providing the oil surface in the oil reservoir P1 formed inside the housing 7, the volume change of the lubricating oil in the housing 7 can be absorbed by the oil reservoir P1, so the expanded lubricating oil is adjacent to the outside air It is difficult to reach the radial gap S, and oil leakage can be prevented. In particular, in the case where the fluid dynamic bearing device 1 has the partial fill structure as described above, the position of the oil surface is likely to fluctuate, so oil leakage is likely to occur. Even in this case, in the illustrated example, since the oil reservoir P1 is provided on the outer periphery of the bearing sleeve 8 and is separated from the radial gap S adjacent to the outside air, the lubricating oil in the oil reservoir P1 is separated by the radial gap S It becomes even harder to reach, and oil leakage can be reliably prevented. The oil surface provided on the outer peripheral side of the bearing sleeve 8 may be provided below the oil reservoir P1. For example, an oil surface may be provided in a communication passage formed by the axial groove 8 d 1 of the outer peripheral surface 8 d of the bearing sleeve 8 and the small diameter inner peripheral surface 7 a 2 of the housing 7.

On the other hand, since the lubricating oil in the space facing the upper end chamfer 8e of the inner peripheral surface 8a of the bearing sleeve 8 is always drawn into the radial bearing clearance side where the clearance width is extremely small, there is a risk of this lubricating oil leaking out. Low. Therefore, as described above, the oil reservoir P1 functioning as a buffer is provided on the outer peripheral side of the bearing sleeve 8 so that the oil surface is held in the oil reservoir P1 within the working temperature range of the fluid dynamic bearing device 1. By setting the amount of oil to be injected into the housing 7 and the volume of the oil reservoir P1, oil leakage to the outside can be reliably prevented.

Although illustration is omitted, in order to more effectively prevent oil leakage through the radial gap S, of the outer peripheral surface 2a of the shaft member 2, the inner peripheral surface 9a1 of the disc portion 9a of the seal member 9 An oil repellent film may be formed on the opposite region or the upper end surface of the seal member 9.

The fluid dynamic bearing device 1 having the above configuration is assembled in the following procedure.

First, the bearing sleeve 8 is inserted into the inner periphery of the housing 7 with a clearance fit, and the lower end surface 8b of the bearing sleeve 8 is brought into contact with the shoulder surface 7b2 of the bottom 7b of the housing 7. Next, the seal member 9 is inserted into the side portion 7a of the housing 7 from above, and the lower end surface 9a2 of the disk portion 9a of the seal member 9 is brought into contact with the upper end surface 8c of the bearing sleeve 8. The outer peripheral surface 9c of the second embodiment and the large diameter inner peripheral surface 7a1 of the housing 7 are fixed. As a result, the bearing sleeve 8 is nipped from both sides in the axial direction by the seal member 9 and the shoulder surface 7 b 2 of the housing 7, and is fixed to the inner periphery of the housing 7.

Then, a predetermined amount of lubricating oil is injected into the internal space of the housing 7 (for example, the inner periphery of the bearing sleeve 8). Thereafter, the shaft member 2 is inserted from above into the inner periphery of the seal member 9 and the bearing sleeve 8. At this time, the housing 7 is formed via the communication passage (radial groove 8b1 of lower end surface 8b of bearing sleeve 8, axial groove 8d1 of outer peripheral surface 8d, radial groove 8c1 of upper end surface 8c) and radial gap S. Since the air inside is discharged to the outside, the shaft member 2 can be smoothly inserted into the inner periphery of the bearing sleeve 8 and oil leakage accompanying the insertion of the shaft member 2 can be prevented. Then, by bringing the convex spherical surface 2b at the lower end of the shaft member 2 into contact with the end face of the thrust plate 10, the fluid dynamic bearing 1 shown in FIG. 2 is completed.

In the fluid dynamic bearing device 1 configured as described above, when the shaft member 2 rotates, the radial bearing surfaces A1 and A2 of the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft member 2 opposed thereto. A radial bearing gap is formed therebetween. Then, with the rotation of the shaft member 2, the pressure of the oil film formed in the gap between both radial bearings is increased by the dynamic pressure grooves G1, G2, and the radial bearing portions R1, R2 supporting the shaft member 2 in the non-contact manner in the radial direction are formed. Be done. At the same time, a thrust bearing portion T is formed, which contacts and supports the convex spherical surface 2b at the lower end of the shaft member 2 on the thrust bearing surface (upper end surface of the thrust plate 10) provided on the bottom surface 7b1 of the housing 7.

In the fluid dynamic bearing device 1 described above, the axial dimension of the fluid dynamic bearing device 1 as a whole is reduced by reducing the axial dimension of the disk portion 9 a of the seal member 9 or the fluid dynamic bearing device 1 as a whole. The axial dimension of the bearing sleeve 8 can be expanded to increase the bearing rigidity while maintaining the axial dimension of At this time, the sealing member 9 has a cylindrical portion 9b extending downward from the disk portion 9a, so that the area of the outer peripheral surface 9c of the sealing member 9 is reduced even when the axial dimension of the disk portion 9a is reduced as described above. By securing it, the fixed area between the outer peripheral surface 9c of the seal member 9 and the inner peripheral surface 7a1 of the housing 7 and hence the fixed strength of both can be ensured.

The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described, but duplicate explanations will be omitted for the same points as the above embodiments.

The embodiment shown in FIG. 5 differs from the above-described embodiment in that an annular recess 9a3 is provided on the inner diameter end of the lower end surface 9a2 of the disc portion 9a of the seal member 9. A space formed by the recess 9 a 3, the upper end surface 8 c of the bearing sleeve 8, and the outer peripheral surface 2 a of the shaft member 2 functions as a second oil reservoir P 2. The second oil reservoir P2 has a larger radial width and volume than the radial gap S. At normal temperature, the oil surface is held in the first oil reservoir P1, but when the volume of the lubricating oil is greatly expanded at high temperature, the lubricating oil overflowing from the first oil reservoir P1 is the upper end surface 8c of the bearing sleeve 8. Through the radial groove 8c1 of the second oil reservoir P2 (see dotted line in FIG. 5). As described above, by providing the second oil reservoir P2 on the air open side of the first oil reservoir P1, the lubricating oil overflowing from the first oil reservoir P1 is held by the second oil reservoir P2. Oil leakage from the radial gap S can be reliably prevented.

The embodiment shown in FIG. 6 is different from the above embodiment in that a tapered surface 9b10 is provided on the inner peripheral surface 9b1 of the cylindrical portion 9b of the seal member 9. A first oil sump P1 formed between the tapered surface 9b10 and the outer peripheral surface 8d of the bearing sleeve 8 has a cross-sectionally wedge shape whose radial dimension is gradually reduced downward. As a result, a downward pulling force acts on the oil held in the oil reservoir P1, so that oil leakage from the oil reservoir P1 can be further reliably prevented. In this embodiment, as in the embodiment shown in FIG. 5, the lower end surface 9a2 of the disc portion 9a of the seal member 9 is provided with a recess 9a3 to form a second oil reservoir P2. The second oil reservoir P2 may be omitted.

In the embodiment shown in FIG. 7, the convex portion (cylindrical portion 9 b) of the seal member 9 is press-fitted into the gap between the large diameter inner peripheral surface 7 a 1 of the housing 7 and the outer peripheral surface 8 d of the bearing sleeve 8. Specifically, the outer peripheral surface 9c (the outer peripheral surface of the disk portion 9a and the outer peripheral surface of the cylindrical portion 9b) of the seal member 9 and the large diameter inner peripheral surface 7a1 of the housing 7 are fitted with an interference and the seal member An inner peripheral surface 9b1 of the cylindrical portion 9b and an outer peripheral surface 8d of the bearing sleeve 8 are fitted with an interference. In this case, the bearing sleeve 8 is not only held in the axial direction by being pinched from both sides in the axial direction by the lower end face 9a2 of the disk 9a of the seal member 9 and the shoulder surface 7b2 of the housing 7, Since the radial direction is also held via the cylindrical portion 9 b of 9, the fastening strength of the bearing sleeve 8 to the housing 7 is further enhanced.

In this embodiment, a space surrounded by the lower end portion of the cylindrical portion 9b of the seal member 9, the outer peripheral surface 8d of the bearing sleeve 8 and the large-diameter inner peripheral surface 7a1 of the housing 7 serves as a first oil reservoir P1. Function. At normal temperature, (not shown) is held in the first oil reservoir P1, and in particular, the oil level is held below the cylindrical portion 9b of the seal member 9. In this case, the axial dimension (that is, the volume) of the first oil reservoir P1 is determined by the axial dimension of the cylindrical portion 9b of the seal member 9. Therefore, the seal member 9 is (i) capable of securing the necessary volume of the first oil reservoir P1 and (ii) securing the necessary fastening force (fixed area) between the seal member 9 and the housing 7. Designed. The volume of the first oil reservoir P1 can be increased by lowering the flat surface 7a3 of the inner peripheral surface of the housing 7 downward and extending the large diameter inner peripheral surface 7a1 downward. In this case, the housing 7 is used. Since the axial dimension of the thin-walled portion formed by the large-diameter inner peripheral surface 7a1 of the above becomes large, the rigidity is lowered, and the fixing force between the housing 7 and the seal member 9 may be lowered. Therefore, the housing 7 is designed in consideration of (i) the volume of the first oil reservoir P1 and (ii) the fastening force between the seal member 9 and the housing 7 (the rigidity of the thin portion of the housing 7).

Moreover, in this embodiment, both materials are selected so that the linear expansion coefficient of the seal member 9 becomes larger than the linear expansion coefficient of the housing 7. In this case, in the high temperature environment, the outer peripheral surface 9c of the seal member 9 tends to expand in diameter more than the large diameter inner peripheral surface 7a1 of the housing 7, whereby the fastening force (interference margin) between the seal member 9 and the housing 7 is a temperature It is not damaged by the rise, and the fastening strength of both can be secured.

For example, when the seal member 9 is formed of a resin material, it is preferable to use a material having a large deflection temperature under load that can be used in a high temperature environment, for example, PPS, LCP, PBT or the like can be used as the base resin. By adding reinforcing fibers to this base resin, the linear expansion coefficient of the seal member 9, particularly the linear expansion coefficient in the radial direction (direction orthogonal to the resin flow direction during injection molding) is about 2 to 7 × 10 − It is about 5 / ° C.

When the housing 7 is formed of a resin material, PPS, LCP, PBT or the like can be used as the base resin, similarly to the seal member 9. For example, in the case where the housing 7 is formed of the same resin material as the sealing member 9 and the base resin, the linear expansion coefficient of the sealing member 9 is made the housing 7 by slightly increasing the compounding ratio of reinforcing fibers compared with the sealing member 9. It can be larger than the linear expansion coefficient of Further, in this case, if the housing 7 and the seal member 9 are joined by ultrasonic welding, the fastening strength of the both can be further enhanced.

Besides, as the base resin of the resin material of the housing 7, a material having a smaller linear expansion coefficient than that of the base resin of the resin material of the seal member 9 may be used. Alternatively, the housing 7 may be formed of a metal material such as brass, and the seal member 9 may be formed of a resin material having a linear expansion coefficient larger than that of the housing 7.

The linear expansion coefficient of the bearing sleeve 8 is determined by the composition (the mixing ratio of iron and copper), but is usually smaller than that of the seal member 9 and is, for example, about 1.5 × 10 −5 / ° C.

Further, in this embodiment, the large diameter outer peripheral surface 7a4 and the small diameter outer peripheral surface 7a5 are provided on the outer peripheral surface of the housing 7. An outer peripheral surface 9 c of the seal member 9 is fitted with an interference in an axial area of the housing 7 where the small diameter outer peripheral surface 7 a 5 is provided. In the present embodiment, the small diameter outer peripheral surface 7a5 is provided in an axial region including the entire area of the large diameter inner peripheral surface 7a1. Thereby, when the outer peripheral surface 9c of the seal member 9 is press-fit into the large diameter inner peripheral surface 7a1 of the housing 7, even if the small diameter outer peripheral surface 7a5 of the housing 7 bulges, the diameter becomes larger than the large diameter outer peripheral surface 7a4. Since it can prevent, the fluid dynamic pressure bearing device 1 can be attached to the inner periphery of the bracket 6 (refer FIG. 1), without trouble.

Although the case where the convex part of the sealing member 9 was provided in cyclic | annular form (cylindrical form) was shown in the above embodiment, it is not restricted to this. For example, convex portions protruding downward from the outer diameter end of the disk portion 9 a of the seal member 9 may be provided at a plurality of places separated in the circumferential direction.

In the above embodiment, the thrust bearing portion T supports the shaft member 2 in the thrust direction by causing the convex spherical surface 2b at the lower end of the shaft member 2 and the thrust bearing surface (thrust plate 10) to contact and slide. Although the case where it was comprised by what is called a pivot bearing was shown, you may comprise not only this but the thrust bearing part T by what is called dynamic pressure bearing. In this case, a flange portion may be provided at the lower end of the shaft member, and both end surfaces of the flange portion may be supported by the dynamic pressure bearing in both thrust directions.

Further, in the above embodiment, the fluid dynamic pressure bearing device 1 of the partial fill structure in which the internal space of the housing 7 is provided with the void portion not filled with the lubricating oil is shown. The present invention may be applied to a fluid dynamic pressure bearing device of a so-called full fill structure in which a space is filled with lubricating oil (not shown).

Moreover, in the above embodiment, the case where the shaft member 2 is the rotation side and the housing 7 and the bearing sleeve 8 are the fixed side is shown, but conversely, the shaft member 2 is the fixed side, the housing 7 and the bearing sleeve 8 may be the rotation side.

In the above embodiments, the fluid dynamic pressure bearing device 1 is applied to a fan motor. However, the present invention is not limited thereto. For example, a spindle motor of a disk drive device such as an HDD or a polygon scanner of a laser beam printer The present invention can also be applied to motors and the like.

Reference Signs List 1 fluid dynamic bearing 2 shaft member 7 housing 8 bearing sleeve 9 seal member 9 a disc portion 9 b cylindrical portion (convex portion)
10 Thrust Plate P1 Oil Reservoir (First Oil Reservoir)
P2 Second oil reservoir A1, A2 Radial bearing surface G1, G2 Dynamic pressure groove R1, R2 Radial bearing portion T Thrust bearing portion

Claims

A shaft member, a bearing sleeve in which the shaft member is inserted in the inner periphery, a bottomed cylindrical housing which holds the bearing sleeve in the inner periphery and has an opening at one end in the axial direction, the housing A seal member provided at the opening of the bearing, and a radial bearing portion for relatively rotatably supporting the shaft member by an oil film formed in a radial bearing gap between the outer circumferential surface of the shaft member and the inner circumferential surface of the bearing sleeve; A fluid dynamic bearing device comprising:
The seal member has a disk portion disposed on one side in the axial direction of the bearing sleeve, and a convex portion protruding to the other side in the axial direction from the outer diameter end of the disk portion, and the outer peripheral surface of the seal member is A fluid dynamic bearing device fixed to the inner circumferential surface of the housing.
The fluid dynamic bearing according to claim 1, wherein an end face of the disk portion of the seal member is in contact with an end face of the bearing sleeve.
The fluid dynamic pressure according to claim 1 or 2, wherein a first oil reservoir is formed between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve, and an oil surface is provided in the first oil reservoir. Bearing equipment.
The fluid dynamic bearing according to claim 3, wherein the first oil reservoir has a bowl-like cross-sectional shape whose radial width is gradually reduced toward the other axial side.
The fluid according to claim 3 or 4, wherein a recess is provided at the inner diameter end of the end face of the disk portion of the seal member, and a second oil reservoir is formed by the recess, the end face of the bearing sleeve and the outer peripheral surface of the shaft member. Dynamic pressure bearing device.
The fluid dynamic bearing according to any one of claims 1 to 5, wherein the bearing sleeve is sandwiched from both sides in the axial direction by the disk portion of the seal member and the housing.
The fluid dynamic bearing according to claim 6, wherein the outer peripheral surface of the convex portion of the seal member and the inner peripheral surface of the housing are fitted with an interference.
The fluid dynamic pressure bearing device according to claim 7, wherein the inner peripheral surface of the convex portion of the seal member and the outer peripheral surface of the bearing sleeve are fitted with an interference.
The fluid dynamic bearing according to claim 7 or 8, wherein a linear expansion coefficient of the seal member is larger than a linear expansion coefficient of the housing.
The housing and the seal member are formed of a resin material containing reinforcing fibers, and the compounding ratio of reinforcing fibers in the resin material of the housing is larger than the compounding ratio of reinforcing fibers in the resin material of the seal member 10. A fluid dynamic bearing device according to item 9.
The fluid dynamic bearing according to claim 9, wherein the housing is formed of brass and the seal member is formed of a resin material.
The fluid motion according to any one of claims 7 to 11, wherein the housing has a large diameter outer peripheral surface and a small diameter outer peripheral surface, and the seal member is fitted with an interference in an axial region of the small diameter outer peripheral surface. Pressure bearing device.