JPH07332353A - Dynamic pressurizing bearing - Google Patents

Abstract

PURPOSE:To provide a dynamic pressurizing bearing which has an excellent slidability of a bearing surface and an excellent productivity at a low cost. CONSTITUTION:On the outer surface of the shaft 30 of a dynamic pressure bearing having a sleeve 2 which cooperates with the shaft 30, a thrust bearing flange 35 is formed through the insertion molding of synthetic resin, and the thrust receiving surfaces 36 and 37 as the bearing surfaces having the grooves 36a and 37a for generating dynamic pressure are formed. Accordingly, the use of the thermoplastic resin having the large contraction performance is enabled, and the excellent dimension precision and the small change through the lapse of time are enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-cost dynamic pressure bearing having good slidability.

[0002]

2. Description of the Related Art As a conventional dynamic pressure bearing, there is, for example, one shown in FIG. This is used for a spindle motor of a magnetic disk device, and includes a shaft 1 and
It has a sleeve 2 which cooperates with the shaft 1 (that is, produces a dynamic pressure by a relative rotational movement). In this case, the shaft 1 is fixed, and the sleeve 2 rotates around the shaft 1 to generate a dynamic pressure and is supported in a non-contact manner.

The sleeve 2 is made of a soft metal such as a copper alloy or an aluminum alloy, has a shaft hole 3 in the shaft center portion, and has two radial bearing surfaces 4 and 5 as one bearing surface on the inner peripheral surface thereof. is doing. Herringbone-shaped grooves 4a and 5a for generating dynamic pressure are formed on the radial bearing surfaces 4 and 5, respectively. Also, one end of the sleeve 2 (upper end in FIG. 4)
In the recess 10 having a diameter larger than that of the shaft hole 3, two thrust bearing surfaces 7 and 8 are provided. One thrust bearing surface 7
Is formed on the lower surface of a doughnut-shaped thrust plate 9 attached so as to cover the upper end of the recess 10. The other thrust bearing surface 8 is formed on the bottom surface of the recess 10 facing the thrust plate 9.

The shaft 1 is made of stainless steel and has a housing 11
Has a thrust bearing flange 13 made of a soft metal such as a copper alloy or an aluminum alloy and press-fitted into the outer diameter surface 1a of the upper end portion. The thrust bearing flange 13 is located in the recess 10 of the sleeve 2, and the upper and lower surfaces are the thrust receiving surface 1 as one bearing surface.
5,16. A groove 15a for generating a dynamic pressure is formed on the thrust receiving surface 15 on the upper surface and faces the thrust bearing surface 7 which is the other bearing surface via a thrust bearing clearance 17 (however, the sleeve 2 does not rotate). Sometimes both sides 7,
No. 15 is in contact with each other and no thrust bearing clearance 17 is produced.
Further, the thrust receiving surface 16 on the lower surface has a groove for generating dynamic pressure.
6a is formed and is opposed to the other bearing surface, that is, the thrust bearing surface 8 via the thrust bearing clearance 18.

On the outer peripheral surface of the shaft 1, two radial receiving surfaces 21 and 22 are formed as the other bearing surface with a lubricant reservoir 24 interposed therebetween, and one bearing surface is provided through a bearing clearance 23. It faces the radial bearing surfaces 4, 5. A hub 25 is integrally rotatably attached to the outer peripheral surface of the sleeve 2, and an annular recess 26 is formed between the lower outer periphery of the sleeve 2 and the lower inner periphery of the hub 25. A rotor (magnet) 27 is fixed to the inner diameter surface of the hub of the recess 26, and a stator 28, which is circumferentially opposed to the rotor 27 with a radial air gap G, is fixed to the housing 11 and has a radial gap shape. A brushless DC motor M is configured. A magnetic disk (not shown) is mounted on the outer surface of the hub 25, and the motor M rotates the sleeve 2 to drive the magnetic disk.

Here, the grooves 4a and 5a for generating dynamic pressure of the radial bearing surfaces 4 and 5 as one bearing surface constituting the radial bearing are formed on the inner diameter surface of the sleeve 2 by plastic rolling by ball rolling. Has been done. Further, the thrust bearing surfaces 15 and 16 as one bearing surface constituting the thrust bearing
The grooves 15a and 16a for generating the dynamic pressure are formed on the outer diameter surface 1 of the shaft 1.
The thrust bearing flange 13 press-fitted into a is formed on both end faces by plastic working by pressing.

[0007]

In the dynamic pressure bearing, the shaft 1 and the sleeve 2 rotate in contact with each other when starting and stopping. Therefore, in order to improve the durability of the bearing, it is desirable to use a material having good slidability on the bearing surface. However, in conventional hydrodynamic bearings, copper alloy or aluminum alloy, which does not necessarily have good slidability, is used as the material of the sleeve, so there may be problems in start / stop durability depending on the properties of the lubricant used. there were. In particular, thrust bearings have a problem in that the start / stop durability is often shorter than that of radial bearings, since the peripheral speed of the thrust bearing is high and the peripheral speed is high at the outer peripheral portion.

Further, since the thrust bearing flange is press-fitted into the outer diameter surface of the shaft, the number of parts is increased, and the inner diameter surface of the flange needs to be machined with high precision, which causes a problem of high cost. Therefore, the present invention has been made in view of the problems of the conventional dynamic pressure bearings described above, and provides a low cost dynamic pressure bearing excellent in sliding property of a bearing surface and excellent in mass productivity. It is an object.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a dynamic pressure bearing having a sleeve that cooperates with a shaft, and a synthetic resin insert-molded on the outer surface of the shaft has a bearing surface having a groove for generating dynamic pressure. It is characterized by being provided.

[0010]

The dynamic pressure bearing of the present invention has good slidability because the bearing surface having the groove for generating the dynamic pressure is made of synthetic resin. Moreover, the bearing surface is injection-molded by insert molding, and mass production is possible at low cost. The bearing surface having a groove for dynamic pressure generation, which is insert-molded, is closely attached and fixed to the shaft by utilizing shrinkage of the synthetic resin in the cooling process after molding. Therefore, it is possible to use a thermoplastic resin having a relatively large molding shrinkage, and there are few restrictions on the resin used.

In the bearing surface formed by insert molding of synthetic resin on the outer surface of the shaft, it is easy to ensure the accuracy of the dimension of the groove for dynamic pressure generation formed by simultaneous molding. In addition, the synthetic resin layer and the shaft are in close contact with each other, and the dimensional accuracy does not change with time. Further, in the case of the dynamic pressure bearing of the present invention, the squareness of the radial bearing surface and the thrust bearing surface is determined by the precision of the mold, and the quality is stable.

Incidentally, if an attempt is made to mold a synthetic resin layer on the inner diameter of a metal sleeve, the synthetic resin will peel off from the sleeve surface during the cooling process after molding. In order to prevent this, a thermosetting resin with less molding shrinkage is used, and an adhesive is applied to the inner surface of the metal sleeve in advance for molding. In that case, since a thermosetting resin is used, it is necessary to hold the resin in the mold until it is cured, which lengthens the molding cycle and reduces the mass productivity.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the same or corresponding portions as those of the conventional one are denoted by the same reference numerals, and duplicate description will be omitted. FIG. 1 is a cross-sectional view of a dynamic pressure bearing according to an embodiment of the present invention, which is composed of a shaft 30 and a sleeve 2 which makes a relative rotational movement around the shaft 30.

The shaft 30 is provided, for example, at two locations above and below the outer peripheral surface of a shaft body made of stainless steel hardened by heat treatment.
With the lubricant reservoir 24 in between, it has cylindrical radial receiving surfaces 33, 34 as bearing surfaces, and a thrust bearing flange 35 made of synthetic resin formed by insert molding on the outer diameter surface 31a of the upper end portion. Have Examples of the synthetic resin include PPS (polyphenylene sulfide)
A resin, epoxy resin, polyamide resin, or polyacetal resin filled with a wear resistance improving substance such as carbon fiber, econol, graphite, molybdenum disulfide, or polyimide is preferable.

The upper and lower surfaces of the thrust bearing flange 35 are thrust bearing surfaces 36 and 37, respectively, which serve as bearing surfaces. The thrust bearing surface 36 on the upper surface has a groove 3 for generating dynamic pressure.
6a is formed, and a thrust receiving surface 37 on the lower surface is formed with a groove 37a for generating dynamic pressure. These dynamic pressure generating grooves 36a and 37a are formed by transferring from the mold during insert molding of the thrust bearing flange 35.

The thrust bearing flange 35, which is insert-molded on the shaft 30, comes into close contact with the outer diameter surface 31a of the shaft due to the contraction of the synthetic resin. In the example shown in the figure, a circumferential groove 31b for preventing slipping out is provided in advance on the shaft outer diameter surface 31a. However, the circumferential groove 31b for preventing slippage may be provided if necessary, and may not be provided when the axial load is small. Instead of the circumferential groove 31b, a knurled pattern such as an iris pattern may be used, and the shape and the number of circumferential grooves are not particularly limited.

The sleeve 2 of this embodiment is made of a soft metal, has two radial bearing surfaces 4 and 5 on the inner diameter surface of the shaft hole 3, and has grooves 4a and 5a for dynamic pressure generation by ball rolling, respectively. It is formed and faces the radial receiving surfaces 33, 34 of the shaft 30, which is the other bearing surface. Further, the two thrust bearing surfaces 7 and 8 provided facing the recess 10 at the upper end of the sleeve 2 are the thrust receiving surface 3 which is the bearing surface of the shaft 30.
It faces 6,37.

Next, the operation will be described. In the stationary state before rotation, the thrust bearing surface 7 is in contact with the thrust bearing surface 36 that is the other bearing surface facing the thrust bearing surface 7, and the thrust bearing clearance 17 is not present between both bearing surfaces. When the sleeve 2 rotates around the shaft 30 of the dynamic pressure bearing, the fluid pressure in the thrust bearing clearances 17, 18 increases due to the pumping action of the dynamic pressure generating grooves 15a, 16a for the thrust bearing, and the thrust receiving surface 36 , 37 rotate in non-contact with the thrust bearing surfaces 7, 8. At the same time, the pumping action of the dynamic pressure generating grooves 4a, 5a for the radial bearing increases the pressure of the fluid in the radial bearing clearance 23, so that the radial receiving surface 33,
34 rotates without contacting the radial bearing surfaces 4a and 5a.

However, in the initial stage of rotation, the thrust bearing clearance 17 is generated by the pumping action of the groove 36a for generating dynamic pressure.
The pressure of the fluid inside is insufficient to float the sleeve 2, and the thrust bearing surface 7 and the thrust receiving surface 36 rotate in contact with each other. Even when the sleeve 2 stops rotating from the shaft 1 without contacting the shaft 1, when the rotation speed decreases, the fluid pressure in the thrust bearing clearance 17 decreases and the thrust bearing surface 7 and the thrust bearing surface 7 are reduced. Similarly, the surface 36 starts rotating in contact with the surface 36.

At this time, the thrust bearing surface 36 of the thrust bearing flange 35 rotating in contact with each other is made of a synthetic resin having a good slidability, and the contact resistance of the sleeve made of a soft metal with the thrust bearing surface 7 is small, so that the wear of both is carried out. Is significantly reduced compared to the conventional one. The dynamic pressure bearing of this embodiment, which uses a synthetic resin only for the thrust bearing, is particularly applicable to a bearing having a smaller radial load than the axial load,
The durability of the hydrodynamic bearing at start and stop is greatly improved, and the bearing life is extended.

In this case, the thrust bearing flange 35 provided with the thrust receiving surface 36 which is the bearing surface having the groove 36a for generating the dynamic pressure is formed by insert molding, and like a conventional metal flange. Since there is no need to perform cutting work, assembly by press-fitting into the shaft is unnecessary, and since the grooves 36a and 37a for generating dynamic pressure can be processed during molding, mass productivity is excellent and the cost is low. Further, the air vent hole for communicating the air pocket in the dynamic pressure bearing to the outside can be machined at the time of insert molding as required, whereas it was machined conventionally, but in that respect as well. Cost is reduced.

FIG. 2 shows another embodiment. In this second embodiment, both the radial bearing and the thrust bearing of the shaft 30A are
This is different from the first embodiment in that the shaft body is integrally formed by insert molding of synthetic resin. That is, the thrust bearing flange 35A made of synthetic resin is insert-molded on the upper end of the shaft 30A made of stainless steel, and at the same time, the radial receiving surfaces 33A, 34A of the shaft outer diameter surface are also insert-molded with the same synthetic resin layer 40. . At the same time when the insert molding is performed, the thrust receiving surfaces 36A and 37A of the thrust bearing flange 35A have grooves 36a and 37 for generating dynamic pressure.
a is formed, and the radial receiving surface 33A of the shaft outer diameter surface,
Grooves 33a and 34a for generating dynamic pressure are formed in 34A. If the thickness of the synthetic resin layer 40 of the radial receiving surfaces 33A, 34A, which is the bearing surface, is too thin, the resin flow is poor, and if it is too thick, it becomes difficult to secure the molding accuracy.
A degree is preferable.

In this embodiment, since both the radial bearing and the thrust bearing are formed by insert molding of synthetic resin, the mass productivity is further excellent and the cost is low. In addition, insert molding on the outer diameter surface of the shaft has the advantages that the dimensional accuracy of the bearing surface at the time of molding is improved and that the synthetic resin is in close contact with the shaft, so there is little risk of aging. In this embodiment, even if the radial load is large, the start / stop durability of the radial bearing surface can be improved.

FIG. 3 shows still another embodiment. This embodiment is an example of a shaft penetrating type in which the shaft 30B penetrates the sleeve 2A. That is, the shaft 30B has a thrust bearing flange 35B made of synthetic resin near the center of the stainless steel shaft, and radial receiving surfaces 33B, 34B as synthetic resin bearing surfaces integrally formed on the shaft outer diameter surfaces on both sides thereof. In addition to the insert molding, the thrust bearing surfaces 36B and 37B of the thrust bearing flange 35B have grooves 36a for generating dynamic pressure,
37a and the radial receiving surface 33 of the shaft outer diameter surface
Grooves 33a and 34a for generating dynamic pressure are formed in B and 34B.

The sleeve 2A has a large-diameter recess 10A in the middle of the shaft hole 3A penetrating the shaft core.
The thrust bearing flange 35B of the shaft 30B is arranged at 0A. Then, on the inner diameter surface of the shaft hole 3A on both sides of the recess 10A, radial bearing surfaces 4A, which face the radial receiving surfaces 33B, 34B of the shaft through the radial bearing clearance 23,
5A is formed. On the other hand, on the opposing flat surfaces of the recess 10A, the thrust bearing surface 7A, which opposes the thrust receiving surfaces 36B, 37B of the thrust bearing flange 35B insert-molded on the shaft (in the rotating state) via the thrust bearing clearances 17, 18, 8A is formed.

Also in this embodiment, it is possible to obtain substantially the same actions and effects as those of the second embodiment. In each of the above-described embodiments, the structure in which the bearing surfaces on both sides of the thrust bearing flange receive the axial load has been described, but if the axial load is applied in one direction, the end surface of the shaft is directly attached. The thrust bearing surface may be used and the thrust bearing flange may be omitted.

Further, in the embodiment, the material of the shaft to be used is stainless steel which is hardened by heat treatment, but it is not limited to this and may be a raw material which is not heat treated. Alternatively,
A good-cut copper alloy or aluminum alloy may be used. Further, the material of the bearing surface of the sleeve, which is a mating member that cooperates with the thrust bearing surface and the radial bearing surface, which are bearing surfaces made of synthetic resin, is not particularly limited, and may be any of the copper alloy and aluminum alloy shown in the examples. Besides, for example, stainless steel, synthetic resin or the like can be used.

In the embodiment, the shaft is fixed and the sleeve is rotated. However, the sleeve may be fixed and the shaft is rotated, or both the shaft and the sleeve may be rotated. Further, the dynamic pressure bearing can be used in any posture, and the thrust bearing flange side of the shaft end shown in the embodiment may be upside down, and the shaft may be vertical, horizontal, or diagonal. Absent.

Further, a groove 3 for generating a dynamic pressure for the radial bearing.
Although 3a and 34a are provided only on the radial receiving surfaces 33 and 34, they may be provided on both of the opposing radial bearing surfaces. Similarly, the dynamic pressure generating groove 36a for the thrust bearing,
37a may be provided not only on the thrust receiving surfaces 36, 37 but also on the opposing thrust bearing surfaces. Further, the grooves 33a, 34a, 3 for generating each dynamic pressure in the above embodiment
6a and 37a are not limited to the herringbone-shaped grooves, but may be a groove for dynamic pressure generation having a known shape such as a spiral shape.

The lubricant reservoir 24 shown in the first and second embodiments can be omitted in design. Further, the lubrication system of the dynamic pressure bearing of the present invention is not particularly limited,
In addition to oil lubrication and grease lubrication, various lubrication methods such as magnetic fluid lubrication, water lubrication and air lubrication can be applied. In the case of water lubrication, rusting of the shaft can be prevented by providing a synthetic resin layer not only on the bearing surface but also on the entire surface of the shaft.

The dynamic pressure bearing of the present invention as described above includes various spindles such as spindle motors for magnetic disks and optical disk devices, cylinder motors for audio equipment and video equipment, scanner motors for digital copying machines, fan motors and the like. Best suited as a unit bearing.

[0032]

As described above, according to the dynamic pressure bearing of the present invention, the bearing surface having the groove for dynamic pressure generation is provided in the synthetic resin insert-molded on the outer surface of the shaft. It is possible to provide a low-cost dynamic pressure bearing that has excellent slidability on the bearing surface and mass productivity.

Further, since the molding shrinkage of the synthetic resin is utilized, a thermoplastic resin having a relatively large shrinkage can be used, and since the synthetic resin layer and the shaft are in close contact with each other, the dimensional accuracy is excellent and the dimensional change with time. There is also an effect that a dynamic pressure bearing having a small amount can be obtained. Furthermore, the squareness of the radial bearing surface and the thrust bearing surface is determined by the precision of the mold, and it is possible to obtain a product of stable quality.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of another embodiment of the present invention.

FIG. 3 is a sectional view of still another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional dynamic pressure bearing.

[Explanation of symbols]

 2 sleeve 2A sleeve 30 shaft 30A shaft 30B shaft 33 radial receiving surface (bearing surface) 34 radial receiving surface (bearing surface) 33A radial receiving surface (bearing surface) 34A radial receiving surface (bearing surface) 33B radial receiving surface (bearing surface) 34B Radial receiving surface (bearing surface) 36 Thrust receiving surface (bearing surface) 37 Thrust receiving surface (bearing surface) 36A Thrust receiving surface (bearing surface) 37A Thrust receiving surface (bearing surface) 36B Thrust receiving surface (bearing surface) 37B Thrust Bearing surface (bearing surface) 33a Dynamic pressure generating groove 34a Dynamic pressure generating groove 36a Dynamic pressure generating groove 37a Dynamic pressure generating groove

Claims (1)

[Claims] 1. A dynamic pressure bearing having a sleeve that cooperates with a shaft, wherein a synthetic resin insert-molded on the outer surface of the shaft is provided with a bearing surface having a groove for generating dynamic pressure. Dynamic bearing.