JPS5913113A - Dynamic-pressure thrust bearing - Google Patents

Abstract

PURPOSE:To stabilize the axial displacement of a shaft and attain a prescribed thrust load carrying capacity, by using the gap between a thrust bearing member and a thrust load carrying member to control the pressure of a lubricant in the clearance of a thrust bearing so that the pressure is constant. CONSTITUTION:Cylindrical holes 11, 12 of small and large diameters are coaxially provided in a housing member 9. A sleeve 13 and a thrust bearing member 15 are secured in the holes 11, 12. The top of the thrust bearing member 15 serves as a thrust load carrying surface 16. An annular protrusion 18 is provided on the surface 16 along its inner circumferential edge. Spiral grooves 20 for causing dynamic pressure are provided between the outside of the protrusion 18 and the outer circumferential edge of the surface 16. A communication groove 21 is provided on the bottom of the bearing member 15 so that the groove extends in a radial direction and communicates with a fluid passage groove 22 extending in an axial direction on the peripheral surface of the bearing member 15. A housing 10 is thus constructed so that it rotatably supports a shaft 40 having a thrust member 30.

Description

Detailed Description of the Invention The present invention relates to a dynamic pressure type thrust bearing, and in particular, a shaft body having a thrust bearing member is disposed on the inner periphery of a housing having a thrust bearing member, and In a dynamic pressure type thrust bearing in which at least one of the thrust bearing member and the thrust receiving member is provided with a groove for generating dynamic pressure, at least one of the thrust bearing member and the thrust receiving member has an annular convex portion on the outflow end side only for generating dynamic pressure. By providing a circulation path for the lubricant that protrudes from the thrust bearing gap and flows out through the annular convex part, the floating amount (axial displacement amount) of the shaft body is stabilized and a large thrust load capacity can be obtained. This is what I did.

Conventionally, as this type of dynamic pressure type thrust bearing, those shown in FIGS. 1 and 2 are known. In both figures, reference numeral 1 indicates the shaft, 2 indicates the thrust bearing member, and 6 indicates the thrust bearing part of the housing 4. The thrust bearing surface 5 of the thrust bearing part B in FIG. A herringbone-shaped groove 6 is formed in the thrust bearing surface 5 of the thrust bearing part B shown in FIG.

When the above-mentioned shaft body 1 rotates, dynamic pressure is generated due to the pumping action of the groove 6, and the lubricant is applied to the thrust between the thrust bearing surface 5 of the thrust bearing part B and the thrust end surface 7 of the thrust bearing member 2. It flows into the bearing gap 8, causing the shaft body 1 to float and support the thrust load.

When the above bearing is used in a flat motor etc., the rotor fixed to the shaft body 1 and the stator fixed to the housing 4 face each other on a plane with a small gap in the axial direction. It is necessary to stabilize the relative displacement, that is, the flying height of the shaft body 1 by reducing it.

However, in a conventional bearing in which only the groove 6 for generating dynamic pressure is provided in the thrust bearing part 6, the axial position of the shaft body 1 changes greatly between when it is stopped and when it rotates, and the thrust load changes. If the viscosity of the lubricant, such as oil or grease, changes depending on the weather or ambient temperature, the flying height of the shaft body will fluctuate greatly, resulting in an unstable axial position.

In particular, in the bearing shown in FIG. 1, the lubricant leaks through the gap between the inner peripheral edge of the thrust bearing part 3 and the shaft body 1, which prevents the pressure of the lubricant from increasing and reduces the thrust load capacity. There are drawbacks. Furthermore, in both of the bearings shown in FIG. 1 and FIG. There are drawbacks.

This invention was made to eliminate the above-mentioned drawbacks, and an object of the invention is to provide a hydrodynamic thrust bearing in which the flying height of the shaft body is stable; The object of the present invention is to provide a dynamic pressure type thrust bearing that has a small starting torque and a large thrust load capacity.

That is, in the present invention, as in the illustrated embodiment, the shaft body 40 having the thrust bearing member 60 is disposed on the inner periphery of the housing 10 having the thrust bearing member 15, and the thrust bearing surface provided on the thrust bearing member 15 is 16 and a thrust end surface 62 provided on the thrust receiving member 60 are opposed to each other, and a dynamic pressure generating groove 20 is provided in at least one of the thrust receiving surface 16 and the thrust end surface 32,
At least one of the thrust receiving surface 16 and the thrust end surface 62 is provided with an annular protrusion 18 concentrically protruding along the outflow end side of the groove 20 for generating dynamic pressure. A circulation system in which the thrust bearing member 15 and the thrust bearing member 60 are brought into contact via the portion 18 and the lubricant flowing out from the thrust bearing gap 64 through the annular convex portion 18 when the shaft body 40 rotates is returned to the thrust bearing gap 64. The present invention relates to a dynamic pressure type thrust bearing characterized by providing a passage.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a first embodiment of the invention. The housing portion 9 is provided with a small-diameter cylindrical hole 11 and a large-diameter cylindrical hole 12 having the same central axis and opening in the vertical direction, respectively. A cylindrical sleeve 16 is fitted and fixed in the small diameter cylindrical hole 11, and a thrust bearing member 15 is fitted in the large diameter cylindrical hole 12 and brought into close contact with the bottom surface of the cylindrical hole 12. It is fixed. The housing 10 is composed of a housing member 9, a sleeve 16, and a thrust bearing member 15, and the sleeve 16 has a radial inner surface 1 on its inner peripheral surface.
4 is a cylindrical bearing member.

The thrust bearing section 4'' 15 is a disc-shaped body having the same inner diameter as the sleeve 16, and the thrust bearing surface 16 has a
An annular convex portion 18 is provided concentrically along the inner circumferential edge, and a groove 20 for generating dynamic pressure in a snot ξ spiral shape is provided between the outer edge of the annular convex portion 18 and the outer circumferential edge of the thrust receiving surface 16. (See figure (b)). The height of this annular convex portion 18 from the thrust receiving surface 16 is appropriately selected with a limit of several tens of micrometers. Furthermore, a communication groove 21 is provided in the bottom surface of the thrust bearing member 15 in the radial direction, and the communication groove 21 is communicated with a communication groove 22 provided in the axial direction on the outer peripheral surface. The communication groove 21 and the circulation groove 22 are not limited to one set as in the illustrated embodiment, but may be provided as a plurality of sets.

The sleeve 16 and the thrust bearing member 15 of the housing 10 have a shaft body 40 integrally molded with the thrust bearing member 60 disposed inside the large diameter cylindrical hole 12 and passed through the shaft body 40. , the thrust receiving member 60 includes:
A planar thrust end face 62 is formed opposite to the thrust receiving surface 16 of the thrust bearing member 15, and when the shaft body 40 is stopped, the thrust end face 32 is formed on the upper end face of the annular convex portion 18 of the thrust bearing member 15. A thrust bearing gap 34 is formed between the thrust bearing surface 16 of the thrust bearing member 15 and the thrust bearing surface 16 of the thrust bearing member 15 . Further, the shaft body 40 is formed with a radial outer surface 44 that faces the radial inner surface 14 of the sleeve 16, and a radial bearing gap 46 is formed between the radial inner surface 14 of the sleeve 16 and the radial inner surface 14 of the sleeve 16. The radial outer surface 44 of the shaft body 40 is provided with an asymmetric herringbone-shaped groove 50 whose top portion is deviated toward the thrust bearing member 15 side.
is the provision.

With the above configuration, when the shaft body 40 supported in the radial direction and the axial direction via the sleeve 16 and the thrust bearing member 15 of the housing 10 rotates, the grooves provided on the thrust bearing surface 16 of the thrust bearing member 15 rotate. Dynamic pressure is generated by the pumping action of the radially shaped groove 20, and the lubricant (in this embodiment, a gas such as oil, grease or air) flows radially inward into the thrust bearing gap 34. At the beginning of rotation of the shaft body 40, the thrust bearing member 30 contacts the upper end surface of the annular convex portion 18 of the thrust bearing member 15 and blocks the outflow of the lubricant that has flowed into the thrust bearing gap 64. As the rotation of the body 40 progresses, the pressure of the lubricant increases and the pressure at the annular convex portion 18 becomes the highest. In this way, when the lubricant pressure rises to a certain level, the thrust receiving member 6
An upward force acts on the shaft 40, causing the shaft body 40 to float. Shaft body 4
0, the thrust receiving member 60 and the annular convex portion 18
If a gap (11) is created between the two, the lubricant will flow out over the annular convex portion 18 into the gap 48 between the thrust bearing member 15 and the shaft body 40, so the pressure of the lubricant will increase. descend. Even if the lubricant flows out beyond the annular convex portion 18, the radial outer surface 44 of the shaft body 40 is provided with an asymmetric herringbone-shaped groove 50, and the dynamic pressure due to this groove 50 is applied to the radial bearing clearance 46. Therefore, it does not leak out of the housing 10, but flows into the thrust bearing gap 64 again through the communication groove 21 and the circulation groove 22 of the thrust bearing member 15. In this way, the gap 48 between the thrust bearing member 15 and the shaft body 40, the communication groove 21 of the thrust bearing member 15, and the circulation groove 22 are made to communicate with each other, thereby forming a lubricant circulation path. and annular convex portion 18
By circulating the lubricant that has flowed out around the thrust bearing member 15, the pressure of the lubricant can be kept constant. A constant gap (h) is always maintained between the shaft body 4 and the annular convex portion 18 of the shaft body 4.
The flying height of 0 is stabilized, a constant thrust load capacity is obtained, and the flying height of the shaft body 40 is also reduced.

Note that the inner diameter dimension of the thrust bearing member 15 is the same as that of the sleeve 13.
It may be larger than the inner diameter dimension of.

FIG. 4 shows a modification of the first embodiment explained in FIG. In this modification, a herringbone-shaped groove 20 for generating dynamic pressure is provided on the thrust bearing surface 16 of the thrust bearing member 15, and two annular protrusions 1 are provided at the top (outflow end side) of the groove 20.
8 are provided adjacent to each other at appropriate intervals. An axial circulation hole 26 is provided in the recess between the annular protrusions 180, and the circulation hole 26 is communicated with a communication groove 21 provided in the radial direction on the bottom. Groove 22
It is communicated with. The small-diameter cylindrical hole 11 of the cow-using 10 has its inner circumferential surface as the radial inner surface of the shaft body 40.
The radial outer surface 44 of the shaft body 40 is provided with a groove 50 in a serpentine shape.

In the bearing configured as described above, when the shaft body 40 rotates, the lubricant flowing into the thrust bearing gap 64 due to the dynamic pressure in the herringbone-shaped groove 20 increases to the highest pressure at the top of the groove 20.

As a result, when the shaft body 40 floats and a gap (!1) is created between the thrust receiving member 60 and the annular protrusion 18, the lubricant flows out over the annular protrusion 18 and into the circulation hole 26.
After that, the pressure does not increase and there is a constant gap (h
) is maintained in an equilibrium state, and the flying height of the shaft body 40 becomes stable. The lubricant flowing into the circulation hole 23 branches from the communication groove 21 of the thrust bearing member 15 and flows into the thrust bearing member 1.
5 and the shaft body 40 and the flow groove 22, the flow returns to the thrust bearing gap 34. The lubricant leaking into the gap 48 between the thrust bearing member 15 and the shaft body 40 is prevented from leaking to the outside by the dynamic pressure of the serpentine groove 50 provided on the radial outer surface 44 of the shaft body 40. Ru.

Note that the circulation passage from the circulation hole 26 to the communication groove 22 through the communication groove 21 and the circulation passage from the circulation hole 23 to the gap 48 between the thrust bearing member and the shaft body through the communication groove 21 are separated. may be provided.

FIG. 5 shows a second embodiment of the invention. In this embodiment, the lower end of the cylindrical hole 11 of the housing member 9 is closed with a radial bearing member 16 having a groove-shaped cross section, the end on the radial outer surface 44 side of the shaft body 40 is sealed, and the radial outer surface 44 of the shaft body 40 is sealed.
4 is provided with a vertically symmetrical herringbone-shaped groove 50. The configuration of the thrust bearing member 15 is the same as that shown in FIG. 3, so the same parts are designated by the same reference numerals.

When the shaft body 40 rotates, the lubricant flows back through the same circulation path as in the embodiment shown in FIG.

FIG. 6 shows a modification of the embodiment shown in FIG. 5, in which the radial outer surface 44 portion of the shaft body 40 is formed to have a small diameter, and a separate thrust receiving member 60 is fixed to the shaft 67. body 40
The radial outer surface 44 of the housing 10 is directly inserted into the cylindrical hole 11 of the housing 10 without providing any pressure generating material on the radial outer surface 44 of the housing 10.

In the embodiments shown in FIGS. 3 to 5 above, the shaft body 40
A groove 50 for generating dynamic pressure is provided on the radial outer surface 44 of the housing 10, but the groove 50 may also be provided on the housing 10 side.

The inner diameter of the thrust bearing member 15 is made smaller than the inner diameter of the cylindrical hole 11, and at least one of the radial inner surface of the thrust bearing member 15 and the radial outer surface of the shaft body 40 facing the radial inner surface of the thrust bearing member 15 is made smaller than the inner diameter of the cylindrical hole 11. A herringbone-shaped groove or a sno-iral groove may be formed.

FIG. 7 shows a third embodiment in which the present invention is applied to a spindle unit. This spindle unit includes a dynamic pressure bearing member 60 and a radial bearing member 62, which are integrally molded with a radial bearing part 60a and a thrust bearing part 60b.
and are fitted on both the upper and lower sides of the housing member 9, respectively,
The upper radial outer surface 44a of the shaft body 40 is connected to the hydrodynamic bearing member 6.
The lower radial outer surface 44b is supported in the radial direction by the radial bearing member 62, respectively, by the radial bearing portion 60a. Upper radial outer surface 44a of shaft body 40
The lower radial outer surface 44b is provided with a herringbone-shaped groove 50b which is vertically symmetrical. Magnetic fluid seals 65 are provided at both ends of the housing 10 to prevent leakage of lubricants such as oil and grease sealed within the housing 10.

The thrust receiving surface of the thrust bearing portion 60b of the above-mentioned hydrodynamic bearing member 60 is provided with a groove 20 for generating dynamic pressure in the shape of a serpentine ξ and an annular convex portion 18, as in the embodiment shown in FIG. be.

The thrust bearing part 30 facing the thrust bearing part 60b of the dynamic pressure bearing member 60 is molded integrally with the shaft 67. A hole 65 is provided.

In the bearing configured as described above, as the shaft body 40 rotates, the pressure of the lubricant flowing into the thrust bearing gap 34 increases, and the annular convex portion 1 of the thrust bearing portion 60 and the thrust bearing portion 601) increases.
When a gap is created between the shaft member 8 and the shaft body 40, the lubricant flowing out beyond the annular convex portion 18 is transferred to the thrust receiving member 3.
0 flows out into the circulation hole 35 of No. 0, passes from the circulation hole 65 through the gap between the anti-thrust end surface of the thrust receiving member 30 and the housing 10, and then flows between the outer peripheral surface of the thrust receiving member 60 and the housing 10. Thrust bearing clearance 6
Reflux to 4 to maintain constant pressure.

Note that when air is used as the lubricant and the upper magnetic fluid seal 65 is omitted, the lubricant flowing out from the thrust bearing gap 64 through the annular convex portion 18 when the shaft body 40 rotates is discharged to the outside from the circulation hole 35. Ru.

FIG. 8 shows a modification of the embodiment shown in FIG. 7, in which the shaft 67 consists of a large diameter part 41 and a small diameter part 42,
This figure shows a lubricant circulation path when the shaft 67 is fitted and fixed to the small diameter portion 42 of the shaft 67. A circulation hole 65 is provided in the axial direction of the inner peripheral surface of the thrust receiving member 60, and the circulation hole 6
A radial communication hole 36 is provided between the intermediate position of 5 and the outer peripheral surface of the thrust receiving member 30. In this way,
Since the lubricant that has flowed into the circulation hole 65 flows out to the outer circumferential surface of the thrust receiving member 60 through the communication hole 66, the direction of the lubricant flow can be restricted to the radial direction rather than the axial direction as shown in FIG. can. Therefore, both ends of the housing 10, especially the end on the thrust receiving member 30 side, can be easily sealed. Seal bodies 65 are identified at both ends of the housing 10, and the outer circumferential surface of the shaft body 40 facing the seal bodies 65 is provided with snot-shaped grooves 51a and 51b.

In the embodiments shown in FIGS. 7 and 8, since the hydrodynamic bearing member is constructed as an integral piece, it is not only possible to assemble the bearing easily, but also when the hydrodynamic bearing member is made of synthetic resin. In this case, a groove for generating dynamic pressure can be provided on both the thrust bearing part and the radial bearing part by simultaneous processing, and the molding process becomes extremely easy.

In each of the embodiments shown in FIGS. 3 to 8, the housing is not limited to being rotated; the housing may also be rotated.

Further, the housing 10 may not be composed of the housing ↑y (+ material 9, the sleeve 16, and the thrust bearing member 15), but may be composed of one member or a plurality of members.

Furthermore, the dynamic pressure type thrust bearing can be used not only vertically but also horizontally or upside down.

FIGS. 9 to 13 show usage examples in which the present invention is applied to a bearing for a floppy disk drive motor (flat motor).

FIG. 9 shows a first example of use, in which reference numeral 40
70 is a rotating disk fixed to the shaft 40; 72 is the head of the rotating disk; 74 is a fixed plate; 75 is a housing member fixed to the fixed plate 74; a sleeve for supporting in the radial direction, 15 a thrust bearing part for supporting the rotary disk 70 in the axial direction, 76 a seal body, 78 a rotor, 8
0 indicates a stator, respectively.

FIG. 1θ shows the housing member 75 and sleeve 1 of FIG.
6 and the thrust bearing member 15 are shown enlarged. The inner peripheral surface of the sleeve 16 is provided with a herringbone-shaped groove 50 for generating dynamic pressure. The thrust bearing surface 16 of the thrust bearing member 15 has an annular convex portion 1 on the inner peripheral edge.
8, and a spiral groove 20 for generating dynamic pressure is provided on the outer peripheral edge. This groove 20 is provided with a narrow width not on the entire surface of the thrust receiving surface 16 but only on a portion close to the outer peripheral edge in order to reduce the torque. Further, a circulation groove 24 is provided in the axial direction on the inner peripheral surface of the thrust bearing member 15, and the circulation groove 24 is connected to the circulation groove 22 provided in the axial direction on the outer peripheral surface via the communication groove 21 provided in the radial direction on the bottom surface. Let's communicate.

11 and 12 are a first modification and a second modification of FIG. 10, respectively.

FIG. 11 shows the thrust bearing surface 16 of the thrust bearing member 15.
An annular convex portion 18 is provided along the inner edge of a spiral groove 20 provided on a part of the outer peripheral edge of the annular convex portion 18 , a circulation hole 23 is provided inside the annular convex portion 18 , and the circulation hole 26 is connected to the communication groove 21 . FIG. 12 shows a case in which a herringbone-shaped groove 20 is provided in a part of the outer peripheral edge of the thrust bearing surface 16 of the thrust bearing member 15, and a groove 20 is provided at the top of the groove 20. An annular protrusion 18 of a strip is provided, and the annular protrusion 1
8, the circulation hole 23b provided inside the groove 20, and the circulation groove 22 are respectively communicated with the communication groove 21.

FIG. 13 shows a second usage example in which the radial outer surface side of the shaft body 40 is penetrated into the fixed platen 74 and the thrust bearing member 15 is
This is the case when it is inverted. Reference numeral 13 is a sleeve, 30
70 is a rotating disk fixed to the thrust receiving member 30; 72 is a head fixed to the upper end of the shaft 40; 75 is a fixed plate 74 fixed to the rotating disk; 78 is a rotor, and 80 is a stator. The configuration of the thrust bearing member 15 is the same as that shown in FIG. 3, and an asymmetric herringbone-shaped groove 50 is provided on the radial outer surface 19- of the shaft body 40.

In the bearings shown in FIGS. 9 to 13 above, the floating of the shaft 40 and the circulation of lubricant when the shaft 40 rotates are the same as in the case of FIGS. 3 to 6 described above. In particular, by applying the present invention to such a flat motor, the rotary disk 70 forms an oil film or a gas film in a minute gap between the annular convex portion 18 of the thrust bearing member 15, and the thrust bearing member 15 is heated. Since it rotates while maintaining a state parallel to the thrust bearing surface 16, if the thrust bearing surface 16 of the thrust bearing member 15 is made to be exactly perpendicular to the radial inner surface 14 of the sleeve 16,
The axial runout of the rotary disk 70 is reduced, thereby making it possible to reduce the radial deflection on the side surface of the head 72 of the rotary disk 70, making it possible to stably obtain extremely high rotation accuracy.

FIG. 14 shows an application example of the present invention, but there is no circulation path for the lubricant to flow out from the thrust bearing gap 64 through the annular convex portion 18, and there is no groove for generating dynamic pressure on the radial outer surface 44. . The other parts of the illustrated embodiment are constructed almost the same as the embodiment shown in FIG.

Therefore, when air is used as a lubricant, when the shaft body 40 rotates, the lubricant flows out from the thrust bearing gap 64 through the annular convex portion 18.
It is discharged to the outside from the gap between 4 and 4.

As is clear from the above description, the present invention provides a groove for generating dynamic pressure formed on at least one of the thrust receiving surface of the thrust bearing member and the thrust end surface provided on the thrust receiving member. An annular projection is provided to bring the thrust bearing member into contact with the thrust receiving member through the annular projection, and the pressure of the lubricant flowing into the thrust bearing gap when the shaft rotates is increased by the annular projection. The shaft body is displaced in the axial direction, and the lubricant flowing out through the annular convex portion is circulated through the circulation passage. Therefore, according to the present invention, the pressure of the lubricant in the thrust bearing gap is constant because it is adjusted by the gap between the thrust bearing member and the thrust bearing member, and the axial displacement of the shaft body is stable and constant. thrust load capacity is obtained.

However, according to this invention, the reflux of the lubricant starts from the time when the shaft body is displaced in the axial direction after one rotation, and the pressure of the lubricant is adjusted, so that the axial displacement of the shaft body can be reduced. Furthermore, even if the viscosity of the lubricant changes depending on the ambient temperature, the axial displacement of the shaft does not change. In addition, the thrust load capacity is high and there is no leakage of lubricant.

Further, according to the present invention, when the shaft body is stopped, the thrust receiving member and the thrust bearing member are in contact with each other via the annular convex portion, and since the contact area is small, the starting torque can be reduced.

Further, since the dynamic pressure generating portion and the annular convex portion of the thrust bearing member can be integrally formed by pressing or molding, it is possible to produce the thrust bearing member at a low cost with a simple process.

[Brief explanation of drawings]

7g Figures 1 and 2 respectively show conventional hydrodynamic thrust bearings, Figures 1 (a) and 2 (a) are cross-sectional views, and Figure 1 (1)) and Figure 2 ( b) is a plan view of the thrust receiving surface, FIG. 3 shows the first embodiment of the invention, FIG. 5 shows a modification of the first embodiment of the invention, FIG. 5(a) is a sectional view thereof, FIG. 5(b) is a plan view of the thrust receiving surface, and FIG. 6 is a cross-sectional view showing a modification of the second embodiment of the present invention, FIG. 7 is a cross-sectional view showing a third embodiment of the invention, and FIG. 8 is a cross-sectional view showing a modification of the second embodiment of the invention. FIG. 9 is a sectional view showing a modification of the third embodiment; FIG. 9 is a sectional view showing a first usage example of the invention;
Figure (,) is an enlarged sectional view of the main part of Figure 9, Figure 10 (b) ζ
・The plan view of FIG. 11 and FIG. 12 respectively show a first modification and a second modification of the first usage example of this invention, and FIG. 11(a) and FIG. 11(1)) and FIG. 12(b) are plan views thereof, and FIG. 13 is a sectional view showing a second usage example of the present invention.
FIG. 4 is a sectional view showing an example of application of the present invention. 23- In the figure, 10 is a housing, 14 is a radial inner surface, 15 is a thrust bearing member, 16 is a thrust bearing surface, 18 is an annular convex portion, 20 is a groove for generating dynamic pressure, 21 is a communication groove, and 22 is a distribution groove. , 23 is a circulation hole, 60 is a thrust receiving member, 32 is a thrust end face, 34 is a thrust bearing gap, 65 is a circulation hole, 66 is a communication hole, 40 is a shaft body, 44 is a radial outer surface, 4
8 is a gap between the thrust bearing member and the shaft body. Patent applicant NSK Ltd. representative Patent attorney Tetsuya Mori Patent attorney Yoshiaki Naito Patent attorney Shimizu Masaru Kajiyama Kore24-

Claims (6)

[Claims] (1) A shaft body having a thrust bearing member is disposed on the inner periphery of a nozzle having a thrust bearing member, and a thrust bearing surface provided on the thrust bearing member and a thrust end face provided on the thrust bearing member are opposed to each other, In a dynamic pressure type thrust bearing in which at least one of the thrust receiving surface and the thrust end surface is provided with a groove for generating dynamic pressure, at least one of the thrust receiving surface and the thrust end surface is provided with a groove for generating dynamic pressure on the outflow end side thereof. An annular convex portion is concentrically protruded along the shaft, and when the shaft body is stopped, the thrust bearing member and the thrust bearing member are brought into contact through the annular convex portion, and when the shaft body is rotated, the annular convex portion is formed from the thrust bearing umbrella gap. A dynamic pressure type thrust bearing characterized in that a circulation passage is provided through which all of the lubricant flowing out flows back into the bearing gap. (2) A cylindrical shape is formed on the thrust bearing surface, and an annular convex portion is provided on the inner peripheral edge of the thrust bearing surface, and the gap between the thrust bearing member and the shaft body and the radius of the bottom surface of the thrust bearing member are 2. The dynamic pressure type thrust bearing according to claim 1, wherein a lubricant circulation passage is formed by a communication groove provided in the axial direction and a circulation groove provided in the axial direction on the outer circumferential surface. (3) A herringbone-shaped groove is formed on the thrust bearing surface, and two annular protrusions are provided adjacent to each other at the top of the aperture, so that the gap between the thrust bearing member and the shaft body and the mutual relationship between the annular protrusions are A patent in which a lubricant circulation passage is formed by circulation holes provided in the axial direction in the four parts between them, communication grooves provided in the radial direction on the bottom surface of the thrust bearing member, and circulation grooves provided in the axial direction on the outer peripheral surface. A dynamic pressure type thrust bearing according to claim 1. (4) Forming a groove in the shape of a cylindrical shape on the thrust receiving surface,
An annular convex portion is provided on the inner peripheral edge of the thrust receiving surface, and a circulation hole is provided in the axial direction at the joint with the shaft of the thrust receiving member, and a gap between the anti-thrust end surface and outer peripheral surface of the thrust receiving member and the housing. 2. A dynamic pressure type thrust bearing according to claim 1, wherein a lubricant circulation passage is formed by a lubricant circulation passage. (5) Forming a spiral groove on the thrust receiving surface,
An annular convex portion is provided on the inner peripheral edge of the thrust receiving surface, a circulation hole is provided in the axial direction of the joint with the shaft of the thrust receiving member, and a communication hole is provided between the circulation hole and the outer peripheral surface of the thrust receiving member. 2. The dynamic pressure type thrust bearing according to claim 1, wherein a lubricant circulation passage is formed by the lubricant circulation passage. (6) The radial outer surface side of the shaft body passes through the housing, and the asymmetrical Hering whose top part is deviated toward the thrust bearing member side at least to one side between the radial inner surface of the housing and the radial outer surface of the shaft body. A hydrodynamic thrust bearing according to any one of claims 1 to 5, wherein a bone-shaped groove is formed.