JPH09119428A - Dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a desired lubrication fluid in a tapered surface side without enlarging a bearing and restrain the flow out and scattering of the lubrication fluid at the rotation time of a rotating member. SOLUTION: A radial bearing surface 8 formed on a shaft member 3 is faced to a radial bearing surface 9 formed on a sleeve 1 through a bearing clearance ΔR and tapered surfaces 10, 11 are connected to the axial direction both end parts of the radial bearing surface 9. In the slant for the axial center of both tapered surfaces 10, 11, one side tapered surface 10 is larger than the other. The so-called herring-bone shape grooves 12, 13 for dynamic pressure generation are formed on the radial bearing surface 9. The grooves 12, 13 are non-symmetry for an orthogonal plane to the axial center and the length L, of the axial direction of the spiral groove 12 of one tapered surface 10 side is longer than the length L6 of the axial direction of the spiral groove 13 of the other tapered surface 11 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing used for a video / information device such as a magnetic disk device, an optical disk device, a laser printer and a VTR.

[0002]

2. Description of the Related Art Conventional dynamic pressure bearings include those used in spindle motors of magnetic disk spindles, for example. In this spindle motor, for example, as shown in FIG. 6, an insertion hole 2 of a sleeve 1 in which a shaft member 3 fixed to a base plate 4 and having its axis oriented vertically is a bearing member.
The sleeve 1 side is configured to rotate.

That is, the outer peripheral surface of the shaft member 3 and the sleeve 1
The inner peripheral surface of the two radial bearings 40, 41 of the dynamic pressure bearing.
And the thrust receiving member 5 fixed to the upper end opening of the sleeve 1 and the upper end surface of the shaft member 3 form a thrust bearing, and the radial bearings 40 and 41 and the thrust bearing form the sleeve 1. The shaft member 3
Rotatably supported by.

In FIG. 6, reference numeral 19 denotes a hub integrally fixed to the sleeve 1, and includes a rotor 43 of the motor fixed to the hub 19 and a stator 44 of the motor fixed to the base plate 4. Thus, the sleeve 1 is rotationally driven at high speed. Moreover, 50 and 51 have shown the air vent hole. The radial bearings 40 and 41 include the radial receiving surface 46 provided on the outer peripheral surface of the shaft member 3 and the sleeve 1.
And the radial bearing surface 47 provided on the inner peripheral surface of the sleeve 1 and the radial bearing surface 47 face each other with a predetermined bearing gap therebetween, and are continuous with the inner peripheral surface of the sleeve 1 at both axial end portions of the radial bearing surface 47. A tapered surface 48 is provided so as to be farther from the outer peripheral surface of the shaft member 3 as it is farther from the bearing surface 47. Further, the radial bearing surface 47 and the tapered surface 48 of the sleeve 1 and the radial receiving surface 46 of the shaft member 3 are provided.
A lubricating fluid is interposed between the and. Here, the space formed between each of the tapered surfaces 48 and the outer peripheral surface of the shaft member 3 (hereinafter, referred to as a tapered space) holds a sufficient amount of lubricating fluid for the bearing.

The radial bearing surface 47 is provided with a so-called herringbone-shaped groove 49. This groove 4
The reference numeral 9 designates the lubricating fluid near the respective tapered surfaces 48 when the sleeve 1 rotates, and the radial receiving surface 46 and the radial bearing surface 4
It is for supplying to the axial center between 7 and 7. At this time, in the conventional dynamic pressure bearing, the inclination angle of the tapered surface 48 from the axis is generally set to 45 degrees.

[0006]

However, since the sleeve 1 (rotating member) supported by the dynamic pressure bearing as described above rotates at a high speed, when the sleeve 1 rotates, the lubricating fluid in the taper space is increased. A predetermined centrifugal force acts on the lubricant, and the centrifugal force may cause the lubricating fluid to flow out and scatter along the tapered surface 48 to the outside of the bearing.

When the lubricating fluid flows out and scatters as described above, the lubricating fluid required for the bearing decreases, which is one of the causes for shortening the life of the bearing, and a device provided with the bearing by the scattered lubricating fluid. There is a problem that the inside becomes dirty, and such a dynamic pressure bearing is not suitable for application to precision equipment such as a VTR. The present invention has been made in view of the above problems, and a desired lubricating fluid can be retained in the tapered space without increasing the size of the bearing, and the lubricating fluid flows out when the rotating member rotates. It is an object of the present invention to provide a dynamic pressure bearing capable of suppressing scattering.

[0008]

In order to achieve the above object, the dynamic pressure bearing of the present invention has a radial bearing provided on the outer peripheral surface of the shaft member by inserting the shaft member into an insertion hole provided in the bearing member. The surface and the radial bearing surface provided in the insertion hole are opposed to each other with a predetermined bearing gap, and the insertion hole is continuous with both axial end portions of the radial bearing surface, and is further away from the radial bearing surface. In a dynamic pressure bearing that is provided with two tapered surfaces that are separated from the outer peripheral surface of the shaft member, the inclination angle from the axial center of one of the two tapered surfaces to the axial center of the other tapered surface. Is set to be larger than the inclination angle of the one of the radial receiving surface and the radial bearing surface, and the lubricating fluid near the one tapered surface is provided on the one tapered surface side of at least one of the radial receiving surface and the radial bearing surface. A first groove capable of generating a dynamic pressure that is pumped toward the other side, and a lubricating fluid near the other tapered surface provided on the other tapered surface side of at least one of the radial receiving surface and the radial bearing surface. A second groove capable of generating a dynamic pressure that is pumped toward one taper surface side, and further, the dynamic pressure by the first groove is higher than the dynamic pressure by the second groove. It is characterized by being set.

In the above-described dynamic pressure bearing, when the bearing member or the shaft member rotates, the dynamic pressure of the first groove and the second groove causes the lubricating fluid to flow between the radial receiving surface and the radial bearing surface. Although the pressure is fed, the dynamic pressure generated by the first groove is higher than the dynamic pressure generated by the second groove, so that the position where the two dynamic pressures are balanced is biased toward the other tapered surface and The lubricating fluid between the shaft member and the shaft member is shifted and distributed toward the other tapered surface.

As a result, the lubricating fluid located in the space between the one tapered surface and the shaft member outer peripheral surface is eliminated or reduced, and at the same time, the lubricating fluid is located in the space between the other tapered surface and the shaft member outer peripheral surface. Lubricating fluid increases. As a result, when the bearing member or the shaft member is rotating, the lubricating fluid is retained mainly on the one tapered surface side having a large inclination angle and on the other tapered surface side having a small inclination angle.

Further, when the bearing member and the shaft member are in the non-rotating state, the lubricating fluid is not pumped by the first groove and the second groove, so that the lubricating fluid is supplied to the two tapered surfaces and the outer circumference of the shaft member. It is also held separately in the two spaces formed by the surface and.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. The dynamic pressure bearing of this embodiment is applied to a spindle motor. The basic configuration of the spindle motor according to the present embodiment is substantially the same as that of the above-mentioned conventional example, and as shown in FIG. 1, from the lower side with respect to the insertion hole 2 of the sleeve 1 constituting the bearing member. By inserting the shaft member 3 and further fixing the lower end portion of the shaft member 3 to the base plate 4, the sleeve 1 side is rotatable. In this embodiment, unlike the conventional example, the sleeve 1 and the hub 19 are integrally formed.

The thrust load between the shaft member 3 and the sleeve 1 is supported by the thrust bearing formed by the thrust receiving member 5 attached to the upper end opening of the sleeve 1 and the upper end surface of the shaft member 3. Further, the radial load between the shaft member 3 and the sleeve 1 is supported by the two radial bearings 6 and 7 which are dynamic pressure bearings. The two radial bearings 6 and 7 are the outer peripheral surface of the shaft member 3 and the sleeve 1.
And an inner peripheral surface of the same, and are arranged at predetermined intervals in the axial direction (vertical direction). As shown in FIG. 2, the two radial bearings 6 and 7 respectively have a cylindrical radial receiving surface 8 formed on the outer peripheral surface of the shaft member 3 and a cylindrical radial receiving surface formed on the inner peripheral surface of the sleeve 1. The bearing surface 9 is opposed to the bearing surface 9 in the radial direction with a predetermined bearing gap ΔR, and tapered surfaces 10 and 11 are continuous with both ends of the radial bearing surface 9 in the axial direction. The two tapered surfaces 10 and 11 are formed so as to be inclined so as to move away from the cylindrical outer peripheral surface of the shaft member 3 as the distance from the radial bearing surface 9 increases. Then, the both tapered surfaces 1
Regarding the inclinations of 0 and 11, the inclination angle θ ₁ which is the inclination angle from the axis of the one tapered surface 10 (the upper tapered surface) is the one of the other tapered surface 11 (the lower tapered surface). It is set to be larger than the inclination angle θ ₂ which is the inclination angle from.

[0014] Here, the inclination angle theta ₁ and theta ₂ of the tapered surfaces 10 and 11, the theta ₁ is in the range of 3 to 30 °, a range of theta ₂ of 2~29 °, θ _1> θ ₂ and It is better to select as appropriate under the following conditions. If the inclination angle θ ₁ exceeds 30 ° or the inclination angle θ ₂ exceeds 29 °, the direction of the reaction received from the tapered surfaces 10 and 11 against the centrifugal force acting on the lubricating fluid 15 when the sleeve 1 rotates. As the lubricating fluid 15 approaches the direction parallel to the axis, the lubricating fluid 15 is likely to be scattered outside the bearing. In addition, if the inclination angle θ ₁ is less than 3 °, the inclination angle θ ₂
Is less than 2 °, in order to secure the required amount of the lubricating fluid 15, the axial length L of the tapered surfaces 19 and 11 is required.
₁ and L ₂ become longer.

The axial lengths of the two tapered surfaces 10 and 11 are the axial length L ₂ of the other tapered surface 11 rather than the axial length L _{1 of the one} tapered surface 10. Is set to be long. This is because, as will be described later, when the sleeve 1 is rotated, the distribution of the lubricating fluid is the other tapered surface 11
This is to get closer to the side. Further, in the radial bearing surface 9, as in the conventional case, a plurality of spiral grooves 12 and 13 for forming dynamic pressure, which form so-called herringbone-shaped grooves, are formed. However, in the present embodiment, the spiral grooves 12 and 13 are asymmetric with respect to a plane perpendicular to the axis, and the spiral groove 12 on the side of one tapered surface 10 from the bent portion of the herringbone groove is. The axial length L ₅ is the spiral groove 1 on the side of the other tapered surface 11 from the bent portion of the herringbone-shaped groove.
3 is set to be longer than the axial length L ₆ . As a result, when the sleeve 1 rotates, the dynamic pressure by the groove 12 on the one tapered surface 10 side of the bent portion becomes higher, and the groove 12 on the one tapered surface 10 side of the bent portion constitutes the first groove. Further, the groove 13 on the other tapered surface 11 side of the bent portion constitutes a second groove.

A lubricating fluid 15 composed of oil, grease, magnetic fluid or the like is interposed between the radial bearing surface 9 and the tapered surfaces 10 and 11 and the radial receiving surface 8. Next, the operation and effects of the dynamic pressure bearing having the above configuration will be described. The space formed between the tapered surfaces 10 and 11 and the outer peripheral surface of the shaft member 3 will be described as taper spaces 16 and 17 in the following description.

In the non-rotating state in which the sleeve 1 is not rotationally driven, the lubricating fluid 15 has a bearing gap ΔR between the radial bearing surface 9 and the radial receiving surface 8 and two tapered spaces 1.
6 and 17 exist. That is, at the time of non-rotation, the amount of lubricating fluid 15 required for the bearing is held separately in the two tapered spaces 16 and 17, as in the conventional case. Here, the lubricating fluid 15 in the two tapered spaces 16 and 17 is held in the tapered spaces 16 and 17 by its surface tension, but the lubricating fluid 15 held in the tapered spaces 16 and 17 is
The axial lengths L ₃ and L _{4 of the above} are calculated from the static balance between the surface tension of the lubricating fluid 15 on the one tapered surface 10 side and the surface tension of the lubricating fluid 15 on the other tapered surface 11 side. The side of the other tapered surface 11 where the inclination angle of the tapered surface is small is slightly longer.

When the sleeve 1 rotates from this state, the dynamic fluid generated by the first groove 12 causes the lubricating fluid 15 near the one taper surface 10 to be pumped toward the other taper surface 11 side, and also the second fluid. Due to the dynamic pressure generated by the groove 13, the lubricating fluid 15 near the other tapered surface 11 is pumped toward the one tapered surface 10 side, and the required amount of lubricating fluid 15 is supplied to the bearing gap ΔR.

At this time, the axial length L of the first groove 12 is L.
_FiveIs the axial length L of the second groove 13 ₆Because it is longer than
In addition, the dynamic pressure due to the first groove 12 is due to the second groove 13.
The dynamic pressure becomes higher than the dynamic pressure by the first groove 12 and the second groove.
Distribution of the lubricating fluid 15 until the dynamic pressure due to 13 is balanced
Moves to the other tapered surface 11 side. The first groove 12
Lubrication that balances the dynamic pressure of the second groove 13 with the dynamic pressure of the second groove 13.
The position of the fluid is the same as the bending part of the herringbone groove.
Axial length L with the surface of lubricating fluid on the tapered surface 10 side₅₁But
Axial length L of the second groove 13₆Immediately in the same position as
L in FIG. 2 (b)₆= L₅₁To the position where
When the surface of the lubricating fluid 15 on the supersurface 10 side is positioned
You.

As described above, when the sleeve 1 rotates, the lubricating fluid 15 on one taper surface 10 side during non-rotation is sent toward the other taper surface 11, and during rotation of the sleeve 1, The lubricating fluid 15 does not exist in the tapered space 16 on the one tapered surface 10 side. As a result, the lubricating fluid 15 is prevented from flowing out and scattering from the side of the one tapered surface 10 having a large inclination angle.

On the other hand, the taper space 1 of the other tapered surface 11
Although the axial length L ₄₁ of the lubricating fluid 15 in 7 is longer than that during non-rotation, the inclination angle of the other tapered surface 11 is set to be small, so that the lubricating fluid 15 has a surface tension and the other tapered surface It is held in the taper space 17 on the 11 side. Further, since the other tapered surface 11 has a small inclination angle, the direction of the reaction force received from the tapered surface 11 against the centrifugal force acting on the lubricating fluid 15 during rotation is the plane side (radial direction) perpendicular to the axis. It is possible to prevent the lubricating fluid 15 from scattering near the outside of the bearing.

Here, during the rotation of the sleeve 1, as described above, the lubricating fluid 15 in the taper space 16 on the one taper surface 10 side when not rotating is in the taper space 17 on the other taper surface 11 side. In the taper space 17 on the side of the other tapered surface 11 having the smaller inclination angle, a larger amount of the lubricating fluid 15 is retained, and the axial length L _{41 of the} lubricating fluid 15 retained in the tapered space 17 is increased. However, the amount of the lubricating fluid 15 that can be retained in the taper space 17 per unit length along the axial direction increases at a square rate as the distance from the radial bearing surface 9 increases. Further, since the tapered space 16 on the side of the one tapered surface 10 retains a large amount of the lubricating fluid 15 during rotation and rest, the axial length L ₁ of the _one tapered surface 10 can be shortened, and the tapered surfaces 10 and 11 of both tapered surfaces 10 and 11 can be shortened. Compared to the case where both the inclination angles are made small and the axial length L ₁ of _one tapered surface 10 is made long, the axial length L of the tapered surfaces 10 and 11 is increased.
The sum of ₁ and L2 can be shortened.

As described above, in the dynamic pressure bearing of the present embodiment, it is possible to prevent the lubricating fluid 15 from flowing out and scattering during rotation, and to avoid increasing the axial length of the sleeve 1.
Further, the lubricating fluid 15 in the taper spaces 16 and 17 repeats the axial movement as described above each time the sleeve 1 starts and stops rotating, so that the lubricating fluid 15 in the bearing gap ΔR is replaced each time and shearing occurs. The deterioration of the lubricating fluid 15 due to the force is reduced. Therefore, deterioration of the bearing performance can be suppressed for a longer period of time than in the past, and excellent durability can be obtained.

In the above embodiment, the first groove 12
Although the example in which both the first groove 12 and the second groove 13 are provided on the radial bearing surface 9 has been described, both the first groove 12 and the second groove 13 may be provided on the radial receiving surface 8. Alternatively, the first groove 12 is provided on the radial bearing surface 9 or the radial receiving surface 8, and the second groove 12 is provided.
The groove 13 may be provided on the radial bearing surface 9 or the radial receiving surface 8. Alternatively, the first groove 12 and the second groove 13 may be provided on both the radial bearing surface 9 and the radial receiving surface 8.

Further, in the above embodiment, the first groove 12
By making the axial length L ₅ of the first groove 12 longer than the axial length L ₆ of the second groove 13, the dynamic pressure by the first groove 12 becomes larger than the dynamic pressure by the second groove 13. However, the setting means for increasing the dynamic pressure by the first groove 12 is not limited to this. For example, the depths, angles, groove width ratios, etc. of the grooves 12, 13 are set asymmetrically, or the width of the bearing gap ΔR is set so as to change in the axial direction. The dynamic pressure may be set to be larger than the dynamic pressure generated in the second groove 13.

The grooves 12 and 13 for generating dynamic pressure are shown in FIG.
As shown in FIG. 3, a groove 19 parallel to the axis is provided in the bent portion 18 of the first groove 12 and the second groove 13 (FIG. 3A), or the provision of the groove in the bent portion 19 is stopped. (Fig. 3
(B)), a so-called modified herringbone groove shape may be formed. Further, in the above-described embodiment, the thrust bearing side, that is, the upper tapered surface is configured to be one tapered surface 10 and the lower tapered surface is the other tapered surface 11, but the upper tapered surface is It may be configured such that the other tapered surface and the lower tapered surface become one tapered surface.

Further, although the case where the sleeve 1 side rotates has been described in the above embodiment, the shaft member 3 side may rotate. Further, the rotation driving mechanism of the sleeve 1 is not limited to the above-mentioned configuration, and may be a plane opposed motor or the like. Next, a second embodiment will be described based on the drawings. The same members as those in the first embodiment are denoted by the same reference numerals and described.

In the second embodiment, as shown in FIG. 4, a rolling bearing 20 is used in place of the lower radial bearing 7 in the first embodiment, and the radial load is applied by the rolling bearing 20. And the axial load is supported, and the thrust bearing formed at the upper end of the shaft member 3 is omitted. The rolling bearing 20 has a raceway groove 21 on the inner ring side formed directly on the outer peripheral surface of the shaft member 3 to reduce the thickness of the bearing by the thickness of the inner ring member. Further, the outer ring 22 has a cylindrical shape extending in the axial direction (vertical direction), and balls 23 as rolling elements are arranged on the lower side. The sleeve 1 made of a soft metal is coaxially fixed to the upper inner peripheral surface of the outer ring 22, and the radial bearing surface 9 of the radial bearing 6 is attached to the inner peripheral surface of the sleeve 1 as in the first embodiment. And tapered surfaces 10 and 11 following the radial bearing surface 9.

The outer ring 22 is a shoulder pad outer ring 22, and one of the grooves (lower shoulder) is dropped to form the groove into an arc shape, so that the balls 23 as rolling elements can be assembled. Making it easy. In this case, since only the thrust load in one direction can be supported, in the present embodiment, the non-contact seal 24 is attached to the opening at the lower end of the outer ring 22 to prevent slipping out and prevent grease from scattering. If the shaft member 3 can be removed from the sleeve 1 or the outer ring 22, the seal 24 as described above is not necessary. Further, if shoulders are provided on both sides of the raceway groove of the outer ring 22 and a so-called ball-introducing groove is provided on one shoulder, the shaft member 3 can be prevented from coming off without the seal 24.

An annular steel plate 25 centered on the shaft member 3 is fixed to the lower surface of the outer peripheral portion of the hub 19, and a magnet 26 is provided on the upper surface of the base plate 4 facing the steel plate 25 in the vertical direction. It is fixed. Then, by the attraction between the steel plate 25 and the magnet 26, the lower surface of the outer peripheral portion of the hub 19 is attracted toward the upper surface of the base plate 4 with a predetermined attraction force, so that the rolling bearing 20 is preloaded. Has been done.
Since the outer peripheral portion of the hub 19 may be attracted to the base plate 4 side, the hub 19 side may be a magnet or both may be magnets. Further, the magnet may be a permanent magnet or an electromagnet.

The upper radial bearing 6 has the same structure as the radial bearing 6 of the first embodiment. A non-contact seal 28 is arranged above the radial bearing 6 and fixed to the outer ring 22. This non-contact seal 2
The reason why 8 is provided is to prevent foreign matter from entering and to prevent the initial scattering of the lubricating fluid 15 adhering to the surfaces other than the bearing surface during assembly. The non-contact seal 28 may be a labyrinth seal.

Even with the above-described structure, when the sleeve 1, the hub 19, and the outer ring 22 rotate, the radial load between the shaft member 3 and the sleeve 1 is supported by the radial bearing 6 and the rolling bearing 20. . Other configurations, operations, effects, etc. are similar to those of the first embodiment. Next, a third embodiment will be described. The same members as those in the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

The basic configuration of the third embodiment is similar to that of the first and second embodiments, and as shown in FIG. 5, a deep groove is used as a bearing for supporting the lower portion of the shaft member 3. The ball bearing 30 is used. Further, the sleeve 1 of the upper radial bearing 6 is composed of two layers, an inner layer 1a and an outer layer 1b. The outer layer 1b is made of a ferrous material such as SUJ2 or SUS440C, and the inner layer 1a is made of sintered metal. , Soft metals such as copper alloys and aluminum alloys are used. The inner layer 1a and the outer layer 1b may both be made of a ferrous metal such as SUJ2, and only the outer layer 1b may be quenched.

In the third embodiment, the inner layer 1a of the sleeve 1 is made of a soft metal as described above, whereby the first dynamic pressure generating member provided on the radial bearing surface 9 on the inner peripheral surface of the sleeve 1 is formed. The groove 12 and the second groove 13 can be easily worked by plastic working by means such as ball rolling. Further, by making the outer layer 1b of the sleeve 1 a hard material, it becomes easy to press fit the sleeve 1 into the hub 19 and the like.

Other configurations, operations, effects, etc. are the same as those of the first and second embodiments.

[0036]

As described above, in the dynamic pressure bearing of the present invention, when the shaft member and the bearing member are not rotating, the radial bearing surface and the two tapered surfaces and the outer peripheral surface of the shaft member are provided. Since the lubricating fluid is retained, the required amount of lubricating fluid is retained in the small gap. Also, during rotation, the first
Due to the asymmetry of the dynamic pressure between the groove and the second groove, the lubricating fluid gathers on the other tapered surface side with a small inclination angle from the shaft center, so that the lubricating fluid can be prevented from flowing out and scattering to the outside of the bearing. The effect is that the life of the bearing can be extended.

Further, as compared with the conventional case where the inclination angles of both tapered surfaces are set small in order to suppress the scattering of the lubricating fluid, the total length of the tapered surfaces in the axial direction can be shortened, so that the bearing It does not grow in size. Further, the lubricating fluid held between the two tapered surfaces and the radial bearing surface and the outer peripheral surface of the shaft member repeats axial movement every time the rotation is started / stopped. Each time it is replaced, deterioration of the lubricating fluid due to shearing force is reduced. As a result, there is also an effect that deterioration of bearing performance with time is suppressed as compared with the conventional case, and durability is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a spindle motor including a dynamic pressure bearing according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a dynamic pressure bearing according to a first embodiment of the present invention, (a) showing a non-rotating state and (b) showing a rotating state.

FIG. 3 is a diagram showing another example of the groove of the dynamic pressure bearing according to the first embodiment of the present invention, FIG. 3A is a view in which a groove that does not generate dynamic pressure is provided in the bent portion of the groove. FIG. 6B is a diagram showing a case where no groove is provided in the bent portion of the groove.

FIG. 4 is a sectional view showing a spindle motor provided with a dynamic pressure bearing according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing a spindle motor including a dynamic pressure bearing according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a spindle motor provided with a conventional dynamic pressure bearing.

[Explanation of symbols]

 1 sleeve (bearing member) 2 insertion hole 3 shaft member 4 base plate 6,7 radial bearing (dynamic pressure bearing) 8 radial bearing surface 9 radial bearing surface 10 one tapered surface 11 the other tapered surface 12 the first groove 13 the Groove 2 15 Lubricating fluid 16, 17 Taper space 19 Hub

Claims (1)

[Claims] 1. A shaft member is inserted into an insertion hole provided in a bearing member, and a radial bearing surface provided in the outer peripheral surface of the shaft member and a radial bearing surface provided in the insertion hole are provided with a predetermined bearing gap. The dynamic pressure bearing is formed so as to be opposed to each other, and the insertion hole is provided with two taper surfaces that are respectively continuous with both axial end portions of the radial bearing surface and that are further away from the shaft member outer peripheral surface as the distance from the radial bearing surface increases. In the two taper surfaces, the inclination angle from the axis of one taper surface is set to be larger than the inclination angle from the axis of the other taper surface, and at least one of the radial receiving surface and the radial bearing surface. A first groove provided on the side of the one tapered surface in which the dynamic fluid can be generated to pump the lubricating fluid near the one tapered surface toward the side of the other tapered surface; and the radial receiver. And a second groove that is provided on at least one of the radial bearing surfaces on the other tapered surface side and that can generate a dynamic pressure for pumping the lubricating fluid near the other tapered surface toward the one tapered surface side. Equipped with
Further, the dynamic pressure bearing is set such that the dynamic pressure generated by the first groove is higher than the dynamic pressure generated by the second groove.