JP7199263B2 - Fluid dynamic bearing device - Google Patents

Description

The present invention relates to a fluid dynamic bearing device.

As is well known, fluid dynamic bearing devices have features such as high speed rotation, high rotational accuracy and low noise. Therefore, the fluid dynamic bearing device is used as a bearing device for motors mounted in various electrical equipment including information equipment, and more specifically, for spindle motors incorporated in disk drive devices such as HDDs. It is suitably used as a bearing device for a fan motor incorporated in a driving device, a PC, etc., or a polygon scanner motor incorporated in a laser beam printer (LBP).

An example of a fluid dynamic bearing device is described in Patent Document 1. This fluid dynamic bearing device comprises a housing with one or both axial ends open, a bearing sleeve disposed on the inner periphery of the housing, and a shaft member removably inserted into the inner periphery of the bearing sleeve. a radial bearing portion for supporting the shaft member in the radial direction with an oil film of lubricating oil formed in the radial bearing gap; a thrust bearing portion for supporting one or both ends of the shaft member in the axial direction; and a disk-shaped member (for example, a seal member having a hole in the center, a thrust member having no hole, etc.).

Efforts are being made to improve the processing accuracy and assembly accuracy of each component in the fluid dynamic pressure bearing device having the above-described configuration in order to ensure high bearing performance that is required as information equipment becomes more sophisticated. On the other hand, along with the trend toward lower prices of information equipment, demands for cost reduction of this type of fluid dynamic bearing device are becoming more and more severe.

An important point in reducing the cost of this type of fluid dynamic bearing device is to improve the efficiency of the assembly process. That is, the housing and the sealing member or the housing and the thrust member are usually fixed using an adhesive, but it takes a relatively long time from application of the adhesive to hardening, which reduces the efficiency of the assembly process. It is the cause. In addition, it is necessary to use an adhesive other than the members to be fixed to each other, which is one of the factors that presses the assembly cost.

On the other hand, it has been attempted to employ press-fitting as a fixing means, but there are concerns that the press-fitting force may reduce the dimensional accuracy of the parts and the generation of abrasion powder (particles) due to the sliding of the parts during press-fitting. Also, in order to obtain a high fixing force, it is necessary to secure a suitable interference, which requires a high pushing force, making it difficult to accurately position the disk-shaped member or the bearing sleeve in the axial direction. A new problem arises.

To solve this problem, for example, Patent Document 2 discloses a technique for fixing a disk-shaped member to the inner periphery of a housing by welding the outer peripheral surface of the disk-shaped member to the inner peripheral surface of the housing using ultrasonic waves or the like. Proposed. This method does not require the use of an adhesive, and can be fixed at low cost. In addition, since the time and effort of applying and drying the adhesive can be saved, it is also excellent in terms of work efficiency. In addition, since the press-fitting margin can be reduced compared to the case of fixing by press-fitting, the disk-shaped member can be positioned easily and with high accuracy, and as a result, the bearing performance can be improved. Of course, since the problem of particles is also eliminated or alleviated, there is also the advantage of reducing the labor of post-processing.

JP 2004-176815 A JP-A-2005-90653

By the way, when the disk-shaped member is fixed to the housing by welding as described in Patent Document 2, there is a problem that the portion of the disk-shaped member or the housing melted during welding flows into a region where it should not originally flow. can be. Taking the sealing member as an example, when the sealing member is fixed to the inner periphery of the housing by welding, it is necessary to melt the contact portion (which may be a press-fitting portion) between the sealing member and the housing. It is difficult to melt only the amount necessary for forming the welded portion, and surplus molten resin that is not necessary for forming the welded portion is inevitably produced. On the other hand, a circulation path may be formed between the lower end surface of the seal member and the upper end surface of the bearing sleeve for circulating lubricant such as lubricating oil filled in the bearing inner space within the bearing inner space. be. In this case, the surplus molten resin flows toward the bearing sleeve, which may cause the molten resin to flow into the circulation path and fill the circulation path with the molten portion. This may hinder the smooth circulation of lubricating oil, making it difficult to obtain stable bearing performance.

In view of the above circumstances, the disk-shaped member is firmly fixed to the housing by welding, and the surplus molten resin generated during welding is prevented from flowing into the bearing sleeve as much as possible, thereby achieving good bearing performance. A technical problem to be solved is to provide a fluid dynamic pressure bearing device that can stably perform at a low cost.

The above problems are solved by a fluid dynamic bearing device according to the present invention. That is, this bearing device includes a housing having at least one axial end open, a bearing sleeve arranged on the inner periphery of the housing, a shaft member having a shaft portion inserted into the inner periphery of the bearing sleeve, and a housing. The shaft is radially supported by a film of lubricating fluid formed in the radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft. In a fluid dynamic bearing device comprising a radial bearing portion, both the housing and the disc-shaped member are made of resin, and a welded portion is formed between the housing and the disc-shaped member, whereby the disc-shaped member is attached to the housing. It is fixed to the inner periphery, and a first annular space is provided in a region adjacent to the welded portion on one end side in the axial direction so as to be able to hold surplus molten resin generated when the welded portion is formed. characterized by

As described above, in the fluid dynamic bearing device according to the present invention, the welded portion is formed between the housing and the disk-shaped member, both of which are made of resin, and the welded portion and the region adjacent to the welded portion at one end in the axial direction are welded. A first annular space is provided to hold the surplus molten resin generated during the formation of the portion. In this manner, both the disk-shaped member and the housing are made of resin, and the welded portion is formed between the disk-shaped member and the housing. Sufficient fixing strength can be obtained between In addition, in the present invention, the first annular space is provided in the region adjacent to the welded portion on one axial end side thereof so as to be able to hold the surplus molten resin generated when the welded portion is formed. Even when a surplus amount of molten resin that is not necessary for forming the portion is generated, most of this surplus amount of molten resin can be made to flow toward the first annular space and be held. As a result, the excess molten resin flowing from between the housing and the disk-shaped member toward the bearing sleeve side is avoided or suppressed as much as possible, and problems caused by the inflow, such as the lubricating oil circulation path, are prevented. It is possible to prevent a situation such as blocking the Of course, if the disk-shaped member is fixed to the housing by providing a welded portion, the use of an adhesive can be omitted, and press-fitting can be omitted or reduced (reduced interference). Work can be performed efficiently and at low cost. As described above, according to the present invention, it is possible to fix the disk-shaped member to the housing with high accuracy by welding and to obtain high fixing strength. In addition, it is possible to avoid or suppress flow of surplus molten resin generated at the time of welding into undesirable regions, thereby avoiding deterioration in bearing performance caused by the flow of the molten resin. Therefore, it is possible to provide a fluid dynamic bearing device capable of stably exhibiting good bearing performance at low cost.

Further, in the fluid dynamic bearing device according to the present invention, the second annular space is provided in a region between the housing and the disk-shaped member and adjacent to the welded portion on the other axial end side thereof. The size of the radial gap of the annular space may be smaller than the size of the radial gap of the first annular space.

In this way, by providing the second annular space in the region between the housing and the disk-shaped member and adjacent to the welded portion on the opposite side of the first annular space in the axial direction, the disk-shaped member Even if the surplus molten resin flows forward in the pushing direction due to heating for welding while the pushing is performed, the welded portion and the other axial end side thereof, that is, the front side in the pushing direction of the disk-shaped member. Excess molten resin can be captured by the two annular spaces. Also, at this time, by making the size of the radial gap of the second annular space smaller than the size of the radial gap of the first annular space, the excess molten resin generated during the welding can flow into the second annular space. It is possible to minimize the inflow and guide most of the remainder to the first annular space. As a result, it is possible to reliably prevent the molten resin from flowing into undesirable areas such as lubricating oil circulation paths.

Further, in the fluid dynamic bearing device according to the present invention, the third annular space is provided in a region between the housing and the disk-shaped member and adjacent to the first annular space on the outer side in the axial direction. The size of the radial gap of the annular space may be smaller than the size of the radial gap of the first annular space.

As described above, an excess amount of molten resin that is not necessary for forming the welded portion is generated during welding, and this excess amount of molten resin may remain as flash after solidification. If this burr protrudes outside the bearing from between the housing and the disk-shaped member, it is necessary to provide a post-process for removing the burr, which increases the number of man-hours and, in turn, increases the processing cost. Here, as described above, in a region adjacent to the first annular space on the opposite side of the weld in the axial direction, in other words, further away from the bearing sleeve than the first annular space when viewed from the weld. By providing the third annular space on the side, even if the surplus molten resin that flows into the first annular space is larger than the volume of the first annular space, the surplus molten resin that becomes the excess volume can be captured by the third annular space located on the outside of the bearing to reliably prevent the burr from popping out of the bearing.

Further, in the fluid dynamic bearing device according to the present invention, the disk-shaped member and the housing are fixed by press-fitting, and a welded portion may be formed in a region to be an interference.

In this way, by providing the welding portion in the area that will be the interference at the time of press-fitting, welding can be effectively achieved. In addition, since the press-fitting portion and the welding portion need not be provided separately, even if the first annular space is provided, an increase in the axial dimension of the disk-shaped member can be suppressed, and the fluid dynamic bearing device can be made as required. It is possible to fit within the dimensions. Furthermore, if sufficient fixing strength is ensured by the welded portion, a high press-in force is not required, so that the tightening margin suitable for positioning will suffice. In addition, if the interference can be reduced, the surplus molten resin generated during welding can be reduced accordingly. It is possible to trap in the annular space and prevent entry or exit into unwanted areas.

Further, in the fluid dynamic bearing device according to the present invention, both the housing and the disk-shaped member are made of one or more thermoplastic resins selected from the group consisting of LCP, PPS, PBT, and PA. may be

A housing that is excellent in strength, dimensional stability, cleanliness, oil resistance, and heat resistance by forming the housing and the disc-shaped member from one or more types of thermoplastic resins selected from the above group. And it becomes possible to obtain a disk-shaped member. Of course, by forming the housing and the disk-shaped member from the same composition of thermoplastic resin, it is possible to obtain good weldability, thereby making it possible to impart high fixing strength between the two members.

Further, in the fluid dynamic bearing device according to the present invention, the disk-shaped member may be a seal member that forms a seal space with the shaft portion.

Alternatively, the disk-shaped member may be a thrust bush that forms a thrust bearing portion with the shaft member.

Since the sealing member is usually fixed to the inner circumference of the opening of the housing with its axial end surface pushed toward the axial end surface of the bearing sleeve, the configuration according to the present invention can be easily and preferably applied. be able to. Similarly, the thrust bushing is also fixed to the inner periphery of the opening of the housing with its axial end surface pushed toward the axial end surface of the bearing sleeve, so that the configuration according to the present invention can be easily and preferably applied. can do.

In the fluid dynamic bearing device according to the above description, as described above, the disk-shaped member is firmly fixed to the housing by welding, and at the same time, the surplus molten resin generated during welding is prevented from flowing into the bearing sleeve as much as possible. By preventing this, it is possible to stably exhibit good bearing performance. Therefore, it is possible to suitably provide a motor equipped with this fluid dynamic bearing device, for example.

As described above, according to the present invention, the disk-shaped member is firmly fixed to the housing by welding, and the surplus molten resin generated during welding is prevented from flowing into the bearing sleeve as much as possible. It is possible to provide a fluid dynamic bearing device that can stably exhibit bearing performance at low cost.

1 is a cross-sectional view of a fan motor according to a first embodiment of the invention; FIG. FIG. 2 is a cross-sectional view of the fluid dynamic bearing device shown in FIG. 1; 3 is a cross-sectional view of the bearing sleeve shown in FIG. 2; FIG. 3 is an enlarged cross-sectional view of a main part of the fluid dynamic bearing device shown in FIG. 2; FIG. 3A is a view for explaining a procedure of a process of fixing the disk-shaped member shown in FIG. 2 to a housing, FIG. 4A being a view showing a state before welding of the sealing member is started, and FIG. FIG. 8C shows a state immediately after the sealing member is pressed into the housing, and FIG. 4D shows a state after the press-fitting. FIG. 6 is an enlarged cross-sectional view of a main portion of a fluid dynamic bearing device according to a second embodiment of the present invention; FIG. 5 is a cross-sectional view of a fluid dynamic bearing device according to a third embodiment of the present invention; FIG. 4 is a cross-sectional view of a fluid dynamic bearing device according to a fourth embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below based on the drawings.

FIG. 1 conceptually shows one configuration example of a fan motor according to the present embodiment. This fan motor includes a fluid dynamic bearing device 1, a shaft member 2 serving as a rotating portion of the fluid dynamic bearing device 1, a rotor 3 to which the shaft member 2 is attached and has blades (not shown), and a blade attached to the rotor 3. a stator coil 5 facing the rotor magnet 4 with a radial gap therebetween; and a motor base 6 on which the stator coil 5 is mounted and serving as a holding member constituting the stationary side of the fan motor. The housing 7 of the fluid dynamic bearing device 1 is fixed to the inner circumference of the motor base 6 , and the rotor 3 is fixed to one end of the shaft member 2 of the fluid dynamic bearing device 1 . In the fan motor configured as described above, when the stator coil 5 is energized, the rotor magnet 4 rotates due to the electromagnetic force between the stator coil 5 and the rotor magnet 4 . The rotor 3 fixed to rotates integrally.

When the rotor 3 rotates, air is sent upward or downward in FIG. Therefore, while the rotor 3 is rotating, a downward or upward thrust in FIG. A magnetic force (repulsive force) is applied between the stator coil 5 and the rotor magnet 4 in a direction to cancel this thrust force. acts on the thrust bearing portion T of . The magnetic force in the direction of canceling the thrust can be generated, for example, by arranging the stator coil 5 and the rotor magnet 4 so as to be offset in the axial direction (detailed illustration is omitted). Further, when the rotor 3 rotates, a radial load acts on the shaft member 2 of the fluid dynamic bearing device 1 . This radial load acts on the radial bearing portions R<b>1 and R<b>2 of the fluid dynamic bearing device 1 .

FIG. 2 is a cross-sectional view of the fluid dynamic bearing device 1 according to this embodiment. This fluid dynamic bearing device 1 includes a housing 7 , a bearing sleeve 8 arranged on the inner circumference of the housing 7 , a shaft member 2 inserted in the inner circumference of the bearing sleeve 8 , and a housing 7 rather than the bearing sleeve 8 . and a seal member 9 disposed on the inner circumference of the housing 7 on the opening side of the housing. Here, the seal member 9 corresponds to the disc-shaped member (a disc-shaped member having a hole in the center) according to the present invention. The internal space of the housing 7 is filled with a predetermined amount of lubricating oil 11 (indicated by relatively dense dotted hatching in FIG. 2), and at least a radial bearing R1 that supports the shaft member 2 in the radial direction. , R2 and the space around the thrust bearing portion T supporting the lower end of the shaft member 2 in the thrust direction are filled with lubricating oil 11. As shown in FIG. In the following, for convenience of explanation, the side on which the seal member 9 is arranged is referred to as the upper side and the axially opposite side is referred to as the lower side, but the posture of the fluid dynamic bearing device 1 during use is not limited.

The housing 7 has a shape (a so-called bottomed cylindrical shape) having a cylindrical portion 7a and a bottom portion 7b that closes the lower end side of the cylindrical portion 7a. 7a and bottom portion 7b are integrally formed of resin. Any resin can be used as the resin material for forming the housing 7. From the viewpoint of obtaining the housing 7 excellent in strength, dimensional stability, cleanliness, oil resistance, and heat resistance, for example, The housing 7 is preferably made of one or more thermoplastic resins selected from the group consisting of LCP, PPS, PBT, and PA. As for the sealing member 9, the above-described resin materials can be suitably used. It is preferable to form it with resin.

A stepped portion 7c is formed integrally with the tubular portion 7a and the bottom portion 7b on the inner circumference of the boundary portion between the tubular portion 7a and the bottom portion 7b, and the upper end surface 7c1 of the stepped portion 7c is formed on the lower end surface 8b of the bearing sleeve 8 (on the outer peripheral side thereof). area) are in contact. A thrust plate 10 made of resin, for example, is arranged on the upper end surface 7b1 of the bottom portion 7b of the housing 7. As shown in FIG. In this case, the upper end surface 10a of the thrust plate 10 functions as a thrust bearing surface. However, the thrust plate 10 is not necessarily provided and may be omitted. In that case, the upper end surface 7b1 of the bottom portion 7b serves as a thrust bearing surface.

The shaft member 2 has a shaft portion 2a inserted into the inner circumference of the bearing sleeve 8, and a convex spherical tip portion 2b provided at one longitudinal end of the shaft portion 2a. In this case, at least the shaft portion 2a of the shaft member 2 is made of a highly rigid metal material such as steel such as stainless steel. The outer peripheral surface 2a1 of the shaft portion 2a is formed into a smooth cylindrical surface, and is formed so that the outer diameter dimension is constant over the entire length of the shaft portion 2a. The outer diameter dimension of the shaft portion 2 a is smaller than the inner diameter dimension of the bearing sleeve 8 and the seal member 9 , so the shaft member 2 can be inserted into and removed from the bearing sleeve 8 and the seal member 9 . A tip portion 2 b of the shaft portion 2 a is in contact with an upper end surface 10 a of a thrust plate 10 provided on the bottom portion of the housing 7 .

The bearing sleeve 8 is made of metal. In this embodiment, the bearing sleeve 8 is mainly composed of one or both of copper-based powder (including not only pure copper powder but also copper alloy powder) and iron-based powder (including not only pure iron powder but also iron alloy powder). It is formed in a cylindrical shape with a porous body of sintered metal containing. In this case, the internal cavity of the bearing sleeve 8 is impregnated with lubricating oil 11 . The bearing sleeve 8 is fixed to the housing 7 via a seal member 9 with its lower end surface 8b in contact with the upper end surface 7c1 of the stepped portion 7c of the housing 7 (details will be described later). Thereby, relative positioning of the housing 7 and the bearing sleeve 8 in the axial direction is achieved.

The inner peripheral surface 8a of the bearing sleeve 8 is provided with two cylindrical radial bearing surfaces in the axial direction that form a radial bearing gap between the inner peripheral surface 8a and the outer peripheral surface 2a1 of the opposing shaft portion 2a. As shown in FIG. 3, each radial bearing surface is formed with dynamic pressure generating portions (radial dynamic pressure generating portions) A1 and A2 for generating a dynamic pressure action on the lubricating oil 11 in the radial bearing gap. there is The radial dynamic pressure generating portions A1 and A2 of the present embodiment each include a plurality of upper dynamic pressure grooves Aa1 and lower dynamic pressure grooves Aa2 which are inclined in opposite directions and spaced apart in the axial direction. It has a convex hill portion that partitions the dynamic pressure grooves Aa1 and Aa2, and exhibits a herringbone shape as a whole. The hill portions of the present embodiment include the inclined hill portion Ab provided between the dynamic pressure grooves adjacent in the circumferential direction, and the annular groove portion provided between the upper and lower dynamic pressure grooves Aa1 and Aa2 and having substantially the same diameter as the inclined hill portion Ab. Hill Ac.

In the upper radial dynamic pressure generating portion A1, the axial dimension of the upper dynamic pressure groove Aa1 is larger than the axial dimension of the lower dynamic pressure groove Aa2. On the other hand, in the lower radial dynamic pressure generating portion A2, the axial dimension of the lower dynamic pressure groove Aa2 is larger than the axial dimension of the upper dynamic pressure groove Aa1. Furthermore, the axial dimension of the upper dynamic pressure groove Aa1 that constitutes the radial dynamic pressure generating portion A1 is equal to the axial dimension of the lower dynamic pressure groove Aa2 that constitutes the radial dynamic pressure generating portion A2. The axial dimension of the lower dynamic pressure generating groove Aa2 constituting the pressure generating portion A1 is equal to the axial dimension of the upper dynamic pressure generating groove Aa1 constituting the radial dynamic pressure generating portion A2. Therefore, when the shaft member 2 rotates, the lubricating oil 11 in the upper (radial bearing portion R1) and lower (radial bearing portion R2) radial bearing clearances is pushed toward the lower and upper radial bearing clearances, respectively. be

The radial dynamic pressure generating portions A1 and A2 are formed, for example, at the same time as the bearing sleeve 8 is molded (more specifically, after metal powder is compacted and then sintered, a sintered body is subjected to sizing processing. It may be formed by molding at the same time as the bearing sleeve 8 having the finished dimensions is formed by molding, or, considering the good workability of sintered metal, it may be transferred to a bearing material having a smooth inner peripheral surface. It may be formed by applying plastic working such as molding. Also, one or both of the radial dynamic pressure generating portions A1 and A2 may be formed on the outer peripheral surface 2a1 of the opposing shaft portion 2a.

As shown in FIG. 3, an annular groove 8c1 is formed in the upper end surface 8c of the bearing sleeve 8 over the entire circumference of the upper end surface 8c. The annular groove 8c1 is open upward without being closed by the seal member 9 in the assembled state of the fluid dynamic bearing device 1 (see FIG. 2). A first radial groove 8c2 that opens to the annular groove 8c1 and extends to the outer peripheral surface 8d of the bearing sleeve 8 is formed in the upper end surface 8c, and the outer peripheral surface 8d extends axially. An axial groove 8d1 penetrating through is formed. A second radial groove 8b1 extending in the radial direction is formed in the lower end surface 8b of the bearing sleeve 8 (see FIG. 3 for both). Therefore, as will be described later, when the lubricating oil 11 flows upward from the upper radial bearing gap, the lubricating oil 11 flows into the axial groove 8d1 via the annular groove 8c1 and the first radial groove 8c2. Then, it can again flow into the lower radial bearing gap via the second radial groove 8b1. That is, the circular groove 8c1, the first and second radial grooves 8c2 and 8b1, the axial groove 8d1, and the like described above constitute a circulation path through which the lubricating oil 11 can circulate. In this embodiment, the series of grooves 8b1, 8c1, 8c2 and 8d1 described above are all formed on the bearing sleeve 8 side. All or part of them may be provided on the side of the facing member (sealing member 9, housing 7). For example, the first radial groove 8c2 may be formed in the lower end surface 9c of the seal member 9, or the axial groove 8d1 may be formed in the cylindrical portion 7a of the housing 7 side.

The seal member 9 is made of resin and has an annular shape, and is fixed to the inner periphery of the housing 7 (a specific fixing mode will be described later). The inner periphery of the seal member 9 is provided with a relatively small-diameter inner peripheral surface 9a and a relatively large-diameter large inner peripheral surface 9b. In this case, as shown in FIG. 2, the small-diameter inner peripheral surface 9a forms a seal space S with a constant radial dimension between the opposing outer peripheral surface 2a1 of the shaft portion 2a. The seal space S prevents the lubricating oil 11 from leaking out of the fluid dynamic bearing device 1 within the expected range of temperature change. Also, the annular space between the large-diameter inner peripheral surface 9b and the outer peripheral surface 2a1 of the shaft portion 2a can function as a buffer for the lubricating oil 11 depending on its size, for example.

A lower end surface 9c of the seal member 9 contacts the upper end surface 8c of the bearing sleeve 8, and an outer peripheral surface (large-diameter outer peripheral surface 9d) of the seal member 9 is fixed to the cylindrical portion 7a of the housing 7. As shown in FIG. More specifically, a welded portion 12 is formed between the outer peripheral surface of the seal member 9 and the inner peripheral surface of the cylindrical portion 7a of the housing 7, and the seal member 9 is attached to the housing 7 via the welded portion 12. It is fixed on the inner circumference. In this embodiment, the welded portion 12 is formed over the entire circumference of the seal member 9 . The seal member 9 is welded and fixed to the tubular portion 7a of the housing 7 by press fitting, and the press fitting portion 15 overlaps the weld portion 12 over its entire area. A process of forming the welded portion 12 will be described later.

4, the seal member 9 has a relatively large diameter outer peripheral surface 9d and a relatively small diameter outer peripheral surface 9e. The shaped portion 7a has a relatively large diameter inner peripheral surface 7d and a relatively small diameter inner peripheral surface 7e. Here, the small-diameter outer peripheral surface 9e of the seal member 9 is provided on the side closer to the lower end surface 9c, and the large-diameter outer peripheral surface 9d is provided on the side farther from the lower end surface 9c. The large-diameter inner peripheral surface 7d of the housing 7 is provided on the far side from the bearing sleeve 8, that is, on the axial upper end side of the housing 7, and the small-diameter inner peripheral surface 7e is provided on the side closer to the bearing sleeve 8, that is, on the large-diameter inner peripheral side. It is provided closer to the center in the axial direction of the housing 7 than the surface 7d. Here, the large-diameter inner peripheral surface 7d and the small-diameter inner peripheral surface 7e may be continuous via an inclined surface 7f as shown in FIG. It may be continuous through In this case, a weld portion 12 and a press-fit portion 15 are formed in a region where the small-diameter inner peripheral surface 7e of the housing 7 and the large-diameter outer peripheral surface 9d of the seal member 9 overlap in the radial direction (see FIG. 5 described later). .

A first annular space 13 is formed in a region adjacent to the welded portion 12 on the upper end side in the axial direction, and a second annular space 14 is formed in a region adjacent to the welded portion 12 on the lower end side in the axial direction. is formed. In this embodiment, the first annular space 13 is formed between the large-diameter inner peripheral surface 7d of the housing 7 and the large-diameter outer peripheral surface 9d of the seal member 9 , and the second annular space 14 is formed in the small-diameter inner surface of the housing 7 . It is formed between the peripheral surface 7 e and the small-diameter outer peripheral surface 9 e of the seal member 9 . Here, the radial clearance W1 of the first annular space 13 is preferably set larger than the radial clearance W2 of the second annular space 14 . Further, when compared with the welded portion 12, the radial gap W1 of the first annular space 13 is larger than the radial dimension W0 of the welded portion 12, and the radial gap W2 of the second annular space 14 is larger than the welded portion 12. It is preferably set smaller than the radial dimension W0.

In a state where the fluid dynamic bearing device 1 having the above configuration is arranged in the posture shown in FIG. , simply referred to as the internal space of the housing 7), at least the space around the radial bearing gaps between the radial bearing portions R1 and R2 and the thrust bearing portion T (specifically, the lower end surface 8b of the bearing sleeve 8 and the shaft member). 2 and the upper end surface 10a of the thrust plate 10) is filled with lubricating oil 11. As shown in FIG. In the present embodiment, an annular space formed between the chamfered portion on the inner peripheral side of the upper end of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a and the chamfered portion on the inner peripheral side of the lower end of the bearing sleeve 8 are further provided in this embodiment. An annular space formed between the shaft portion 2a and the outer peripheral surface 2a1 is also filled with the lubricating oil 11 (see FIG. 2).

2, in addition to the space described above, an annular space formed between the chamfered portion on the outer peripheral side of the upper end of the bearing sleeve 8 and the small-diameter inner peripheral surface 7e of the housing 7, and the outer periphery of the lower end of the bearing sleeve 8 are shown in FIG. An annular space formed between the side chamfered portion and the small-diameter inner peripheral surface 7e of the housing 7; A case where the axial groove 8d1 formed in and the second radial groove 8b1 formed in the lower end surface 8b are also filled with the lubricating oil 11 is illustrated, but depending on the case, these outer annular spaces, The series of grooves 8b1, 8c1, 8c2, 8d1 may not be filled with lubricating oil 11 (in other words, they may be filled with outside air). Of course, in this case, the annular space formed between the large-diameter inner peripheral surface 9b of the seal member 9 and the outer peripheral surface 2a1 of the shaft portion 2a and the seal space S may not be filled with the lubricating oil 11. . Also, in this case, part or all of the series of grooves 8b1, 8c1, 8c2, 8d1 described above may be omitted.

Here, as the lubricating oil 11, a known lubricating oil can be used. For example, when temperature changes during use or transportation of the fluid dynamic bearing device 1 are considered, an ester-based or PAO-based lubricating oil is suitable. used.

The fluid dynamic bearing device 1 having the above configuration is assembled, for example, in the following procedure. Mainly referring to FIG. 5, details will be described centering on the process of fixing the seal member 9 to the housing 7 by welding.

First, the bearing sleeve 8 is prepared, the internal cavity of which is impregnated with the lubricating oil 11 . Then, the bearing sleeve 8 is introduced into the inner circumference of the housing 7, and the lower end surface 8b is brought into contact with the upper end surface 7c1 of the stepped portion 7c of the housing 7. As shown in FIG. FIG. 5(a) shows the state at this time, in which the bearing sleeve 8 is arranged on the inner periphery of the housing 7 while being axially positioned with respect to the housing 7. As shown in FIG. At this time, the seal member 9 has not yet been introduced into the inner periphery of the housing 7 (waiting above the housing 7). The introduction of the bearing sleeve 8 into the inner periphery of the housing 7 may or may not be accompanied by press fitting. In the former case, the interference is set to be relatively small (so-called light press-fit state). is formed.

Next, the seal member 9 is introduced into the inner circumference of the housing 7 from its one open end side. Here, the outer diameter dimension of the large-diameter outer peripheral surface 9 d of the seal member 9 is set larger than the inner diameter dimension of the small-diameter inner peripheral surface 7 e of the housing 7 . Therefore, when starting the introduction from the one end opening side of the housing 7, the sealing member 9 first comes into contact with the inclined surface 7f of the tubular portion 7a of the housing 7 (the state shown in FIG. 5B).

After the initial placement of the bearing sleeve 8 and the seal member 9 with respect to the housing 7 is completed as described above, the seal member 9 is pressed downward. As a result, the press-fitting of the sealing member 9 into the cylindrical portion 7a of the housing 7 is started. At this time, by heating the contact portion (press-fit portion 15) between the seal member 9 and the housing 7, welding of the contact portion (press-fit portion 15) is started (see FIG. 5(c)). . The above-described welding by heating is performed, for example, by applying ultrasonic vibration to the contact portion (press-fitting portion 15), though not shown. The interference I at this time is determined by the radial dimension difference between the small-diameter inner peripheral surface 7 e of the housing 7 and the large-diameter outer peripheral surface 9 d of the seal member 9 .

In this manner, while pressing the seal member 9 downward, the abutting portion (here, the press-fit portion 15) between the seal member 9 and the housing 7 is heated, so that the seal member 9 is moved to a predetermined position in the axial direction of the housing 7. Here, the lower end face 9c of the seal member 9 is introduced with press fitting to a position where it contacts the upper end face 8c of the bearing sleeve 8 (see FIG. 5(d)). Also, the welded portion 12 is formed in the press-fitting portion 15 or in a region around the press-fitting portion 15 (see FIG. 4). As a result, the seal member 9 is welded and fixed to the inner periphery of the housing 7 by press-fitting, and the bearing sleeve 8 is axially sandwiched between the housing 7 and the seal member 9, and the bearing sleeve 8 is pushed into the housing. Fixed to 7. Welding (in other words, heating of the contact portion) may start when the lower end surface 9c of the seal member 9 and the inner peripheral surface (here, the inclined surface 7f) of the housing 7 come into contact with each other. It may start earlier. Alternatively, it may be started after the sealing member 9 is started to be press-fitted into the housing 7 .

Further, as described above, when the contact portion (here, the press-fit portion 15) between the seal member 9 and the housing 7 is welded by heating, the surplus portion not required for forming the weld portion 12 (see FIG. 4) is melted. Resin inevitably forms. This surplus molten resin tends to flow toward the bearing sleeve 8 as the sealing member 9 is pushed downward, for example. Here, as described above, by providing the first annular space 13 in the area adjacent to the press-fitting portion 15 which will be the welding portion 12 on one end side in the axial direction (see FIG. 5(d)), The excess molten resin can be prevented or suppressed from flowing into the bearing sleeve 8 as much as possible, and the excess molten resin can be retained (captured) in the first annular space 13 .

With the housing 7, the bearing sleeve 8, and the seal member 9 fixed to each other and subassembled in this way, a predetermined amount of lubricating oil 11 is poured into the inner space of the housing 7 (for example, the inner circumference of the bearing sleeve 8). to fill. After that, the shaft portion 2a is inserted into the inner periphery of the seal member 9 and the bearing sleeve 8, and the tip portion 2b provided at the lower end thereof is brought into contact with the upper end surface 10a of the thrust plate 10. As shown in FIG. As a result, the fluid dynamic bearing device 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 provided on the upper and lower sides of the inner peripheral surface 8a of the bearing sleeve 8 and the shaft portion facing the radial bearing surfaces are separated from each other. The pressure of the oil film formed in the radial bearing gap between the outer peripheral surface 2a1 of 2a is increased by the dynamic pressure action of the radial dynamic pressure generating portions A1 and A2, and the radial bearing portion supports the shaft member 2 in the radial direction in a non-contact manner. R1 and R2 are formed at two locations in the axial direction. At the same time, a thrust bearing portion T is formed on the inner bottom surface of the housing 7 (the upper end surface 10a of the thrust plate 10 in this embodiment) to contact and support the shaft member 2 in one thrust direction. As described with reference to FIG. 1, a magnetic force acts on the shaft member 2 as an external force to press the shaft member 2 downward (toward the bottom portion 7b of the housing 7). Therefore, it is possible to prevent the shaft member 2 from being excessively floated as the shaft member 2 rotates, and thus from falling off from the inner periphery of the bearing sleeve 8 as much as possible.

As described above, in the fluid dynamic bearing device 1 according to the present invention, the welded portion 12 is formed between the housing 7 and the seal member 9, both of which are made of resin, so that the seal member 9 is pushed down with a large force. Sufficient fixing strength can be obtained between the seal member 9 and the housing 7 without pressing. In addition, in the fluid dynamic bearing device 1 according to the present embodiment, the region adjacent to the welded portion 12 on the upper end side in the axial direction can hold the surplus molten resin generated when the welded portion 12 is formed. An annular space 13 is provided. By providing the first annular space 13 in this way, an excess amount of molten resin unnecessary for forming the welded portion 12 is generated around the press-fit portion 15 (FIGS. 5C and 5D) during welding. Even in this case, most of this surplus molten resin can be made to flow toward the first annular space 13 and be held. As a result, the excess molten resin flowing from between the housing 7 and the seal member 9 toward the bearing sleeve 8 can be avoided or suppressed as much as possible, and problems caused by the inflow, such as lubricating oil, can be prevented. It is possible to prevent a situation in which the first radial groove 8c2 and the axial groove 8d1, which serve as circulation paths, are blocked.

Of course, if the sealing member 9 is fixed to the housing 7 by providing the welded portion 12, the use of an adhesive can be omitted, and press-fitting can be omitted or reduced (reduced interference). The assembly work (fixing work) for 7 can be performed efficiently and at low cost. As described above, according to the present invention, the sealing member 9 can be accurately fixed to the housing 7 by welding, and high fixing strength can be obtained. In addition, it is possible to avoid or suppress the flow of surplus molten resin generated at the time of welding into an undesirable area (bearing sleeve 8 side), thereby avoiding deterioration of bearing performance caused by the flow of the molten resin. . Therefore, it is possible to provide the fluid dynamic bearing device 1 capable of stably exhibiting good bearing performance at low cost.

Further, when the seal member 9 is welded to the cylindrical portion 7a of the housing 7 by press-fitting so that the press-fitting portion 15 overlaps the welding portion 12 in its entirety as in the present embodiment, the welding portion 12 It is preferable to set the volume of the first annular space 13 larger than the volume of (the press-fit portion 15). By setting the volume of the first annular space 13 in this way, even if all the surplus molten resin flows into the first annular space 13 as described above, all the molten resin is It can be held within the annular space 13 . Therefore, it is possible to prevent the molten resin from popping out as burrs due to solidification from the one end opening side of the housing 7 .

Further, in the present embodiment, between the small-diameter inner peripheral surface 7e of the housing 7 and the small-diameter outer peripheral surface 9e of the seal member 9, the first annular space 13 is adjacent to the welded portion 12 on the opposite side in the axial direction from the first annular space 13. A second annular space 14 is provided in the region where the By providing the annular space (second annular space 14) on the side closer to the bearing sleeve 8 than the welding portion 12 in this way, when the seal member 9 is pushed in, the surplus molten resin generated by heating for welding is Even if it flows forward in the pushing direction, the excess molten resin can be captured by the second annular space 14 provided on the other axial end side of the welding portion 12, that is, on the front side of the sealing member 9 in the pushing direction. At this time, by making the size of the radial gap W2 of the second annular space 14 smaller than the size of the radial gap W1 of the first annular space 13, the surplus molten resin generated during welding can be It is possible to minimize the amount that flows into the second annular space 14 and guide the remaining most to the first annular space 13 . This makes it possible to reliably prevent the molten resin from flowing into undesirable areas such as the first radial groove 8c2 that constitutes the circulation path.

Further, in the fluid dynamic bearing device 1 according to the present embodiment, part of the internal space of the housing 7 (here, the radial bearing gap, the space around the thrust bearing portion T, etc.) is filled with the lubricating oil 11 (see FIG. 2 ), and the rest of the interior space of the housing 7 is filled with air. This means that the amount of lubricating oil 11 filled in the internal space is less than the total volume of the internal space, so to speak, a partially filled oil-retaining structure. In the fluid dynamic bearing device 1 according to the present invention, the shaft member 2 can be freely inserted into and removed from the bearing sleeve 8 (and the seal member 9). 8 and the seal member 9 are fixed, and before the shaft member 2 is inserted into the inner circumference of the bearing sleeve 8, the inner space of the housing 7 is simply filled with lubricating oil 11 using a suitable lubricator. A necessary amount of lubricating oil 11 can be supplied to the inner space of the housing 7 . Therefore, large-scale equipment for lubricating such as vacuum impregnation and high-precision adjustment or management of the oil level are not required, and the manufacturing cost of the fluid dynamic bearing device 1 can be reduced.

Further, since an external force is applied to the shaft member 2 to press the shaft member 2 against the bottom portion 7b side of the housing 7 (to support the shaft member 2 in the other thrust direction), it is possible to support the shaft member 2 in both thrust directions. Become. As a result, the support accuracy (rotational accuracy) in the thrust direction can be enhanced. In this embodiment, the external force is applied by magnetic force, and this magnetic force is applied to the stator coil 5 provided on the motor base 6 that holds the housing 7 on the inner circumference, and the rotor magnet 4 provided on the rotor 3 as an axis. I tried to give it by shifting it in the direction and arranging it. Various motors in which this type of fluid dynamic bearing device 1 is incorporated include a rotor magnet 4 and a stator coil 5 as essential constituent members. Therefore, by adopting the above configuration, the external force can be applied at low cost without causing a particular increase in cost.

Although the first embodiment of the present invention has been described above, the fluid dynamic bearing device 1 according to the present invention is not limited to the above-exemplified forms, and can take any form within the scope of the present invention.

FIG. 6 shows an enlarged cross-sectional view of a main part of a fluid dynamic pressure bearing device 20 according to a second embodiment of the invention. As shown in FIG. 6, this fluid dynamic bearing device 20 differs from that of the fluid dynamic bearing device 1 according to the first embodiment in the manner in which the housing 7 and the seal member 9 are fixed. Specifically, as shown in FIG. 6, in the fluid dynamic bearing device 20 according to this embodiment, the outer circumference of the seal member 9 is a large-diameter outer peripheral surface 9d (in this embodiment, a first large-diameter outer peripheral surface 9d). A second large-diameter outer peripheral surface 9g having a larger diameter than the first large-diameter outer peripheral surface 9d is formed on one axial end side (the side far from the bearing sleeve 8) of the first large-diameter outer peripheral surface 9d. In this case, a third annular space 16 is formed between the second large-diameter outer peripheral surface 9g and the large-diameter outer peripheral surface 7d of the housing 7, which face each other in the radial direction. The radial clearance W3 of this third annular space 16 is larger than the radial clearance W1 of the axially adjacent first annular space 13 . In addition, since the configuration other than the above is the same as that of the first embodiment, detailed description thereof will be omitted.

In this way, by providing the third annular space 16 in the region located further away from the bearing sleeve 8 in the axial direction than the first annular space 13 when viewed from the welding portion 12, the first annular space 13 can be temporarily Even if the surplus molten resin that has flowed in is larger than the volume of the first annular space 13, the surplus molten resin that is excessive in volume is further removed in the third annular space 16 located on the outside of the bearing without leaking. can be captured. Therefore, it is possible to reliably prevent the surplus molten resin from solidifying and projecting out of the bearing as burrs, omitting the post-process for burr removal, and eventually reducing the processing cost.

FIG. 7 shows a cross-sectional view of a fluid dynamic bearing device 21 according to a third embodiment of the invention. As shown in FIG. 7, in this fluid dynamic bearing device 21, the form of the housing and disk-shaped member to be welded is that of the fluid dynamic bearing device 1 according to the first embodiment (bottomed cylindrical housing 7). and the hollow disk-shaped sealing member 9). Specifically, in the fluid dynamic pressure bearing device 21 according to the present embodiment, the housing 22 is provided with a tubular portion 22a and an upper end of the tubular portion 22a, and has an inner peripheral surface 22b1 and an outer peripheral surface 2a1 of the shaft portion 2a. and a sealing portion 22b forming a sealing space S therebetween. In this case, the lower end side of the tubular portion 22a is open, and the thrust member 23 closes the lower end open side. Here, the thrust member 23 is made of resin and integrally has a disk-shaped bottom portion 23a and a tubular portion 23b extending in the axial direction (thickness direction) from the peripheral portion of the bottom portion 23a. In this embodiment, the thrust member 23 corresponds to a disk-shaped member (a solid disk-shaped member without a hole in the center) according to the present invention. In this case, the bearing sleeve 8 is housed in the inner periphery of the housing 22 with its upper end surface 8c in contact with the lower end surface 22b2 of the seal portion 22b. The upper end surface 23c of the tubular portion 23b of the thrust member 23 is brought into contact with the lower end surface 8b of the bearing sleeve 8, and the thrust member 23 in the abutted state is fixed to the inner periphery of the tubular portion 22a of the housing 22 by welding. It is More specifically, a welded portion 24 is formed between the large-diameter outer peripheral surface 23d of the thrust member 23 and the small-diameter inner peripheral surface 22d of the cylindrical portion 22a of the housing 22. A thrust member 23 is fixed to the inner circumference of the housing 22 . In this embodiment, the thrust member 23 is press-fitted and fixed to the inner periphery of the housing 22 by welding.

A first annular space 25 is formed in a region adjacent to the welded portion 24 on its axial lower end side, and a second annular space 26 is formed in a region adjacent to the welded portion 12 on its axial upper end side. is formed. In this embodiment, the first annular space 25 is formed between the large diameter inner peripheral surface 22 c of the housing 22 and the large diameter outer peripheral surface 23 d of the thrust member 23 , and the second annular space 26 is formed within the small diameter inside of the housing 22 . It is formed between the peripheral surface 22 d and the small-diameter outer peripheral surface 23 e of the thrust member 23 . Also in this embodiment, the radial clearance of the first annular space 25 is preferably set larger than the radial clearance of the second annular space 26 .

The fluid dynamic bearing device 21 configured as described above is assembled, for example, in the following procedure. First, although illustration is omitted, the bearing sleeve 8 is introduced into the inner circumference of the housing 22 from the lower end opening side, and the upper end surface 8c is brought into contact with the lower end surface 22b2 of the seal portion 22b. Next, the thrust member 23 is introduced into the inner periphery of the housing 22 from the lower end opening side, like the bearing sleeve 8 . Here, the outer diameter dimension of the large-diameter outer peripheral surface 23 d of the thrust member 23 is set larger than the inner diameter dimension of the small-diameter inner peripheral surface 22 d of the cylindrical portion 22 a of the housing 22 . As a result, when starting the introduction from the opening side of the lower end of the housing 22, the thrust member 23 first comes into contact with the stepped portion between the large-diameter inner peripheral surface 22c and the small-diameter inner peripheral surface 22d of the cylindrical portion 22a of the housing 22.

After the initial placement of the bearing sleeve 8 and the thrust member 23 with respect to the housing 22 is completed as described above, the thrust member 23 is pressed upward. As a result, the thrust member 23 starts to be press-fitted into the cylindrical portion 22a of the housing 22. As shown in FIG. At this time, although not shown, the contact portion (press-fitting portion 27) between the thrust member 23 and the housing 22 is heated to start welding of the contact portion (press-fitting portion 27). The above-described welding by heating is performed by, for example, applying ultrasonic vibration to the contact portion (press-fitting portion 27), although this is also omitted from the drawing.

In this way, while pressing the thrust member 23 upward, the abutment portion (here, the press-fitting portion 27) between the thrust member 23 and the housing 22 is heated. is introduced to a predetermined position in the axial direction of the housing 22, here a position where the upper end surface 23c of the thrust member 23 contacts the lower end surface 8b of the bearing sleeve 8 with press fitting. Also, the welded portion 24 is formed in the press-fitting portion 27 or in a region around the press-fitting portion 27 (see FIG. 7). As a result, the thrust member 23 is welded and fixed to the inner circumference of the housing 22 by press-fitting, and the bearing sleeve 8 is axially sandwiched between the housing 22 and the thrust member 23, and the bearing sleeve 8 is pushed into the housing. 22.

Further, as described above, when the contact portion (press-fitting portion 27) between the thrust member 23 and the housing 22 is welded by heating, excess molten resin that is not necessary for forming the welded portion 24 is inevitably produced. This surplus molten resin tends to flow toward the bearing sleeve 8 as the thrust member 23 is pushed upward, for example. Here, as described above, by providing the first annular space 25 (see FIG. 7) in the area adjacent to the press-fitting portion 27 which will be the welding portion 24 on the lower end side in the axial direction, the surplus generated during welding heating can be Inflow of the molten resin to the bearing sleeve 8 side can be prevented or suppressed as much as possible, and the excess molten resin can be held (captured) in the first annular space 25 .

With the housing 22, the bearing sleeve 8, and the thrust member 23 fixed to each other and subassembled in this way, a predetermined amount of lubricating oil 11 is poured into the inner space of the housing 22 (for example, the inner circumference of the bearing sleeve 8). to fill. After that, the shaft portion 2a is inserted into the inner circumferences of the thrust member 23 and the bearing sleeve 8, and the tip portion 2b provided at the lower end thereof is brought into contact with the upper end surface 10a of the thrust plate 10. As shown in FIG. As a result, the fluid dynamic bearing device 1 shown in FIG. 7 is completed. In addition, in the assembly process according to the present embodiment, the work may be performed upside down. That is, the bearing sleeve 8 and the thrust member 23 may be introduced downward while the one end opening side of the housing 22 is directed upward.

As described above, in the fluid dynamic bearing device 21 according to the present embodiment, the welded portion 24 is formed between the housing 22 made of resin and the thrust member 23 as a disc-shaped member. Sufficient fixing strength can be obtained between the thrust member 23 and the housing 22 without pushing the thrust member 23 in. Further, in the present invention, a first annular space 25 is provided in a region adjacent to the welded portion 24 on the lower end side in the axial direction so as to be able to hold surplus molten resin generated when the welded portion 24 is formed. By providing the first annular space 25 in this way, even if an excess amount of molten resin unnecessary for forming the welded portion 24 is generated around the press-fitting portion 27 (FIG. 7) during welding, the excess amount Most of the molten resin can be flowed toward the first annular space 25 and held. As a result, the excess molten resin flowing from between the housing 22 and the thrust member 23 toward the bearing sleeve 8 is avoided or suppressed as much as possible, and problems caused by the inflow, such as lubricating oil, are prevented. It is possible to prevent a situation in which the second radial groove 8b1 and the axial groove 8d1, which serve as circulation paths, are blocked.

In the above embodiments, the case where the present invention is applied to the fluid dynamic pressure bearing devices 1, 20, and 21 having a so-called partial-fill oil-retaining structure was exemplified. It is also possible to apply the present invention to a bearing device. FIG. 8 shows a cross-sectional view of a fluid dynamic bearing device 31 according to one example (fourth embodiment of the present invention). This fluid dynamic bearing device 31 differs from the fluid dynamic bearing devices 1, 20, 21 according to the first to third embodiments in the oil-impregnated structure. Specifically, the entire internal space of the fluid dynamic bearing device 1 (housing 7), which is separated from the external space via the seal space S, is filled with lubricating oil. In this case, the inner peripheral surface 32a of the seal member 32 disposed on the one end opening side of the housing 7 is tapered so that the diameter decreases toward the center in the axial direction. A seal space S is formed between 2a1. 8, the oil surface of the lubricating oil is maintained within the seal space S. In FIG.

The seal member 32 is fixed to the inner periphery of the housing 7 with its lower end surface 32b in contact with the upper end surface 8c of the bearing sleeve 8. As shown in FIG. Specifically, a welded portion 33 is formed between the large-diameter outer peripheral surface 32c of the seal member 32 and the small-diameter inner peripheral surface 7e of the tubular portion 7a of the housing 7, and the welded portion 33 is used for sealing. A member 32 is secured to the inner periphery of housing 7 . In this embodiment, the seal member 32 is press-fitted and fixed to the inner periphery of the housing 7 by welding, and the press-fitting portion 36 overlaps the welding portion 33 over its entire area.

A first annular space 34 is formed in a region adjacent to the welded portion 33 on the upper end side in the axial direction, and a second annular space 35 is formed in a region adjacent to the welded portion 33 on the lower end side in the axial direction. is formed. In this embodiment, the first annular space 34 is formed between the large-diameter inner peripheral surface 7d of the housing 7 and the large-diameter outer peripheral surface 32c of the seal member 32 , and the second annular space 35 is formed in the small-diameter inner surface of the housing 7 . It is formed between the peripheral surface 7 e and the small-diameter outer peripheral surface 32 d of the seal member 9 .

In the fluid dynamic pressure bearing device 31 having such a full-filled oil-impregnated structure, the welded portion 33 is formed between the housing 7 made of resin and the seal member 32 as a disc-shaped member, and the welded portion 33 and its By providing a first annular space 34 in a region adjacent to the lower end in the axial direction for holding the surplus molten resin generated when forming the welded portion 33, the surplus that is not necessary for forming the welded portion 33 is formed during welding. For example, even if the excess molten resin is generated around the press-fit portion 36, most of the excess molten resin can be made to flow toward the first annular space 34 and be held. As a result, the excess molten resin flowing from between the housing 7 and the seal member 32 toward the bearing sleeve 8 is avoided or suppressed as much as possible, and problems caused by the inflow, such as lubricating oil, are eliminated. It is possible to prevent a situation in which the first radial groove 8c2 and the axial groove 8d1, which serve as circulation paths, are blocked.

Further, in the above embodiment, the case where the pivot bearing portion is adopted as the thrust bearing portion T has been exemplified, but of course, it is also possible to adopt a form other than this. For example, the thrust bearing portion T can be composed of a so-called dynamic pressure bearing. In this case, although not shown, the tip (lower end) of the shaft member 2 is provided with a flat surface extending in a direction perpendicular to the center line of the shaft portion 2a instead of the spherical tip portion 2b. A dynamic pressure generating portion (thrust dynamic pressure generating portion) such as a dynamic pressure groove is formed on either one of the flat surface of the shaft member 2 and the upper end surface 10a of the thrust plate 10 facing the flat surface. In this case, as the thrust dynamic pressure generating part, in addition to a herringbone-shaped arrangement of a plurality of dynamic pressure grooves, a plurality of spiral dynamic pressure grooves may be arranged, or a stepped or wavy dynamic pressure groove may be arranged. It is possible to adopt a known thrust dynamic pressure generating part such as an arrayed one.

Of course, one or both of the radial dynamic pressure generating portions A1 and A2, which are formed between the radial bearing portions R1 and R2 and the outer peripheral surface 2a1 of the shaft portion 2a, may also have a so-called multi-arc shape, step shape, and wave shape. It is possible to adopt a known radial dynamic pressure generating part such as a shape.

Further, in the above embodiment, the housing 7 provided separately from the motor base 6 is fixed to the inner periphery of the motor base 6, but a portion corresponding to the motor base 6 may be provided integrally with the housing 7. can also

Further, in the above embodiment, the rotor magnet 4 and the stator coil 5 are displaced from each other in the axial direction, so that an external force is applied to the shaft member 2 to press the shaft member 2 against the bottom portion 7b side of the housing 7. However, means for applying such an external force to the shaft member 2 are not limited to those described above. Although illustration is omitted, for example, by arranging a magnetic member capable of attracting the rotor magnet 4 so as to face the rotor magnet 4 in the axial direction, the magnetic force can be applied to the rotor 3 . Further, when the thrust as the reaction force of the blowing action is sufficiently large and the shaft member 2 can be pushed downward only by this thrust, the magnetic force (magnetic attraction force) as the external force for pushing the shaft member 2 downward is You can omit it.

Further, in the above embodiment, the case where the present invention is applied to the fluid dynamic pressure bearing device 1 in which the rotor 3 having blades as the rotating member is fixed to the shaft member 2 has been described. As a member, it can be preferably applied to a disk hub having a disk mounting surface or a fluid dynamic pressure bearing device 1 in which a polygon mirror is fixed to the shaft member 2 . That is, the present invention is applicable not only to fan motors as shown in FIG. Apparatus 1 can also be preferably applied.

1, 20, 21, 31 Fluid dynamic pressure bearing device 2 Shaft member 3 Rotor 4 Rotor magnet 5 Stator coil 6 Motor bases 7, 22 Housings 7a, 22a Cylindrical part 7b Bottom part 7d, 22c Large diameter inner peripheral surface 7e, 22d Small diameter Inner peripheral surface 8 Bearing sleeve 8a Inner peripheral surface 8b Lower end surface 8b1 Second radial groove 8c Upper end surface 8c1 Annular groove 8c2 First radial groove 8d Outer peripheral surface 8d1 Axial grooves 9, 32 Seal member 9a Small diameter inner peripheral surface 9b Large Diameter inner peripheral surfaces 9c, 32b Lower end surfaces 9d, 32c Large diameter outer peripheral surfaces 9e, 32d Smaller diameter outer peripheral surface 9g Maximum diameter outer peripheral surface 10 Thrust plate 10a Upper end surface 11 Lubricating oil 12, 24, 33 Welding parts 13, 25, 34 First Annular spaces 14, 26, 35 Second annular spaces 15, 27, 36 Press-fit portion 16 Third annular space 22b Seal portion 23 Thrust member 23a Bottom portion 23b Cylindrical portion 23c Upper end surface 23d Large diameter outer peripheral surface 23e Small diameter outer peripheral surfaces A1, A2 Radial dynamic pressure generating portions Aa1, Aa2 Dynamic pressure groove I Interference R1, R2 Radial bearing portion S Seal space T Thrust bearing portion W0 Radial dimension (welding portion)
W1 radial clearance (first annular space)
W2 radial clearance (second annular space)
W3 radial clearance (third annular space)

Claims (7)

a housing having at least one axial end open; a bearing sleeve arranged on the inner periphery of the housing; a shaft member having a shaft portion inserted into the inner periphery of the bearing sleeve; and a film of lubricating fluid formed in a radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft, which supports the shaft in the radial direction. In a fluid dynamic bearing device comprising a bearing portion,
both the housing and the disk-shaped member are made of resin,
A welded portion is formed between the housing and the disk-shaped member, thereby fixing the disk-shaped member to the inner circumference of the housing,
A first annular space is provided in a region adjacent to the welded portion on one axial end side thereof so as to be able to hold surplus molten resin generated when the welded portion is formed, and
A second annular space is provided between the housing and the disk-shaped member and in a region adjacent to the welding portion on the other axial end side thereof,
A fluid dynamic pressure bearing device , wherein the size of the radial gap of the second annular space is smaller than the size of the radial gap of the first annular space . a housing having at least one axial end open; a bearing sleeve arranged on the inner periphery of the housing; a shaft member having a shaft portion inserted into the inner periphery of the bearing sleeve; and a film of lubricating fluid formed in a radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft, which supports the shaft in the radial direction. In a fluid dynamic bearing device comprising a bearing portion,
both the housing and the disk-shaped member are made of resin,
A welded portion is formed between the housing and the disk-shaped member, thereby fixing the disk-shaped member to the inner circumference of the housing,
A first annular space is provided in a region adjacent to the welded portion on one axial end side thereof so as to be able to hold surplus molten resin generated when the welded portion is formed, and
A third annular space is provided between the housing and the disk-shaped member and in a region adjacent to the first annular space on the outside in the axial direction,
A fluid dynamic pressure bearing device, wherein the size of the radial gap of the third annular space is smaller than the size of the radial gap of the first annular space. 3. A fluid dynamic pressure bearing device according to claim 1, wherein said disk-shaped member and said housing are fixed by press-fitting, and said welded portion is formed in a region serving as an interference margin. 4. The housing and the disk-shaped member are both made of one or more thermoplastic resins selected from the group consisting of LCP, PPS, PBT, and PA. The fluid dynamic bearing device according to . The fluid dynamic bearing device according to any one of claims 1 to 4 , wherein the disk-shaped member is a seal member that forms a seal space with the shaft portion. The fluid dynamic bearing device according to any one of claims 1 to 4 , wherein the disk-shaped member is a thrust bush forming a thrust bearing portion between itself and the shaft member. A motor comprising the fluid dynamic bearing device according to any one of claims 1 to 6 .

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