JPH09317758A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a low cost of a bearing device provided with a pressure applying structure by a method wherein a pressure applying means for a roller bearing in place of expensive rare-earth metal stone. SOLUTION: A shaft member 1 and a bearing member 40 are assembled to be relatively rotatable through a roller bearing 3 and a dynamic pressure bearing 4 arranged axially in spaced-apart relation and at the same time a pressure chamber 14 is formed between an end surface 1a of the shaft member 1 facing against the dynamic pressure bearing 4 and the bearing member 40, thereby fluid is supplied from the dynamic pressure bearing 4 to the pressure chamber 14 when the bearing device is operated so as to apply a pressure against the roller bearing 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device used for video, audio, information equipment, and other precision rotating equipment such as a magnetic disk drive, an optical disk drive, a laser printer, and a VTR.

[0002]

2. Description of the Related Art As a conventional bearing device of this type, there is known a bearing device incorporated into a spindle motor of a magnetic disk device as shown in FIG. 6 (Japanese Patent Laid-Open No. 6-31).
No. 1702). In this bearing device, a shaft member b fixed to a base (not shown) and a sleeve member d on which a magnetic disk (not shown) is mounted and which is driven to rotate by a rotation drive unit c are separated from each other in the axial direction. Rolling bearing (ball bearing) e
And a dynamic pressure bearing f. The first permanent magnet g is fixed to the shaft member b in the vicinity of the dynamic pressure bearing f, and the first permanent magnet g is opposed to the first permanent magnet g with the same pole and repels. The second permanent magnet h is fixed to the sleeve member d, and the first permanent magnet g
By applying at least a part of the repulsive force of the second permanent magnet h in the direction of the rolling bearing e, a preload is applied to the rolling bearing e.

[0003]

However, in the above conventional bearing device, in order to apply a preload to the ball bearing e, the first permanent magnet g and the second permanent magnet h are provided in the vicinity of the upper portion of the dynamic pressure bearing f. A means for forming a repulsion type magnetic bearing or a suction type magnetic bearing by arranging and are opposed to each other is taken. Therefore, in order to apply a sufficient preload to the ball bearing e, it is necessary to use a magnet having a large repulsive force or attractive force, such as an expensive rare earth magnet, and it is difficult to reduce the cost. .

Therefore, the present invention has been made by paying attention to the problems of the conventional bearing device, and is provided with a preload applying structure by providing a preload applying means to the ball bearing instead of the expensive rare earth magnet. The purpose is to reduce the cost of the bearing device.

[0005]

In order to achieve the above object, a bearing device according to claim 1 of the present invention comprises a ball bearing in which a shaft member and a bearing member are axially spaced from each other, and a dynamic pressure bearing. It is assembled so as to be relatively rotatable via a bearing, and a pressure chamber is provided between an end surface of the shaft member on the dynamic pressure bearing side and the bearing member, and fluid is supplied from the dynamic pressure bearing to the pressure chamber during operation of the bearing device. It is characterized in that it is supplied to apply a preload to the ball bearing.

In the bearing device of the present invention configured as described above, the pressure generated in the lubricating fluid in the groove for generating the dynamic pressure of the dynamic pressure bearing by the rotation operation thereof is set in the pressure chamber facing the end surface of the shaft member. Supplied. The pressure causes the shaft member to be axially pressed and displaced to apply a preload to the ball bearing. Therefore, it is not necessary to separately provide preload applying means for the ball bearing outside the bearing device.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that members having equivalent functions are denoted by the same reference numerals in each drawing.

First, the structure will be described. FIG. 1 is a sectional view of a first embodiment of a bearing device 20 of the present invention. A cylindrical shaft member 1 and a sleeve member 2 are relatively rotatably assembled via a deep groove ball bearing (hereinafter, simply referred to as a ball bearing) 3 and a dynamic pressure bearing 4 which are spaced apart in the axial direction. There is. In the ball bearing 3, the inner peripheral surface of the inner ring 3n is fitted to the outer peripheral surface of the shaft member 1, and the outer peripheral surface of the outer ring 3g facing the inner ring 3n with a plurality of balls 3t interposed is provided in the lower portion of the sleeve member 2. It is fitted on the inner peripheral surface of the large-diameter cylindrical hole 5. Dynamic bearing 4
The outer peripheral surface of the shaft member near the one end (upper end) surface 1a of the shaft member 1 is a radial outer peripheral surface 7, and the inner peripheral surface of the upper cylindrical hole 9 of the sleeve member 2 facing the radial outer peripheral surface 7 with a radial bearing gap 8 therebetween. The surface is a radial bearing surface 10, and a groove 11 for generating, for example, a spiral dynamic pressure is formed on the radial bearing surface 10 by means of ball rolling or the like.

The upper cylindrical hole 9 of the sleeve member 2 is disposed opposite to the end surface 1a of the shaft member 1 on the side of the dynamic pressure bearing 4 via the axial clearance space S, and is attached to the sleeve member 2 by means of caulking or the like. It is closed by the fixed lid member 13, and the space S
Is configured as the pressure chamber 14. Therefore, the sleeve member 2 and the lid member 13 form a bearing member 40.

A magnetic fluid seal 15 is attached to the open end of the cylindrical hole 5 on the side of the ball bearing 3 on the lower side of the sleeve member 2 to prevent the dust generated from the ball bearing 3 from being discharged to the outside. Next, the operation of this embodiment will be described.

In the bearing device 20 configured as described above, when the bearing device is operated, that is, when the shaft member 1 and the bearing member 40 are relatively rotated, the bearing device 20 is previously supplied into the groove 11 for generating the dynamic pressure of the dynamic pressure bearing 4. A pressure is generated in the lubricating fluid being retained, the shaft member 1 and the sleeve member 2 are supported in a non-contact manner with each other through the radial bearing gap 8, and inclination and eccentricity of the sleeve member 2 with respect to the shaft member 1 are prevented. Not only that, the pressure of the lubricating fluid is also transmitted to the lubricating fluid in the pressure chamber 14 to press the end surface 1a of the shaft member 1 downward (the ball bearing 3 side) in the drawing. This pressing force is transmitted through the shaft member 1 and is applied to the inner ring 3n of the ball bearing 3 fitted to the shaft member 1 to load the ball 3
A preload is applied to t, and the ball bearing 3 supports the radial load and the thrust load applied to the shaft member 1 or the sleeve member 2.

Thus, according to this embodiment, it is possible to give the required rigidity to the ball bearing 3 without separately providing the ball bearing preload applying means by using an expensive rare earth magnet or the like. The cost of the entire device can be reduced. Moreover, of the two sets of bearings which are interposed between the shaft member 1 and the sleeve member 2 at a distance in the axial direction, only one is the ball bearing 3 and the other is the dynamic pressure bearing 4 having the radial bearing gap 8. Therefore, as compared with the case of a bearing device that uses the ball bearing 3 for both bearings, it is less susceptible to misalignment due to an assembly error of the bearings, and as a result, when the present bearing device 20 is incorporated in a spindle motor. Also, it is possible to reduce the swing of the non-rotational synchronous component of the motor as compared with the conventional bearing device. By the way,
According to the research results of the inventors of the present application, the main cause of the runout of the non-rotational synchronization component of the spindle motor is due to the assembly error of the two ball bearings rather than the runout of the non-rotational synchronization component of the ball bearing unit. It has been found that the effect of misalignment is large.

The types of lubricating fluid used for the ball bearing 3 and the dynamic pressure bearing 4 and their seals will be described below. The type of lubricating fluid for both bearings may be the same or different. For example, grease is used for the ball bearing 3 and lubricating oil is used for the dynamic pressure bearing 4. Grease is used for both the ball bearing 3 and the dynamic pressure bearing 4. Lubricating oil is used for both the ball bearing 3 and the dynamic pressure bearing 4. Magnetic fluid is used for both the ball bearing 3 and the dynamic pressure bearing 4. Various other measures are possible.

,. When the same lubricating fluid is used for both bearings as in the case of No. 1, it is possible to prevent the risk that the lubricating fluids of the ball bearing 3 and the dynamic pressure bearing 4 are mixed with each other to change the lubricating characteristics. . Also, when different lubricating fluids are used for both bearings as in the case of (1), it is possible to select the optimal lubricating fluid for each bearing, and it is possible to design fine bearing performance.

Further, when the magnetic fluid seal 15 is attached to the lower end of the sleeve member 2 on the side of the ball bearing 3 as in the present embodiment, the ball bearing 3 and the dynamic pressure bearing 4 as in the above case. If both are lubricated using magnetic fluid,
This is preferable because there is no change in lubrication characteristics due to mixing of the lubricating fluid and leakage of the lubricating fluid to the outside of the bearing device.

Further, the bearing member 40 has a taper portion 16 for holding the lubricating fluid protruding from the bearing clearance 8 of the dynamic pressure bearing 4 toward the ball bearing 3 side by surface tension, and the taper portion 16 of the radial bearing surface 10 on the ball bearing 3 side. Is provided adjacent to the end of the lubricating oil, thereby preventing the lubricating fluid from leaking and splashing to the surroundings. The taper angle θ of the tapered portion 16 with respect to the axis is 2
The range of ° to 45 ° is preferred. If the taper angle θ is less than 2 °, the amount of lubricating fluid that can be retained in the taper portion 16 is small, whereas if the taper angle θ exceeds 45 °, the lubricating fluid may be easily scattered by the centrifugal force when the bearing device rotates. is there. When the rotation speed is higher than 3600 rpm,
When the taper angle θ of the tapered portion 16 with respect to the axis is set to 30 ° or less, the effect of preventing the lubricating fluid from scattering becomes more remarkable.

Incidentally, the radial bearing surface 10 and the taper portion 16
If an oil repellent having a property of repelling a lubricating fluid is applied to at least one of the radial bearing surface 10 and the outer peripheral surface of the shaft member 1 facing the taper portion 16 in advance, the lubrication repelled by the oil repellent is applied. There is an advantage that the fluid moves to the bearing gap 8 due to the capillary phenomenon and does not scatter to the outside, and the outflow / scattering of the lubricating fluid from the bearing gap 8 can be reliably prevented. Specifically, for example, when fluorine oil is used as the lubricating fluid, silicon oil is previously applied as the oil repellent, and when mineral oil or synthetic oil is used as the lubricating fluid,
It is advisable to deposit a modified fluorinated oil film as the oil repellent.

FIG. 2 is a sectional view of a second embodiment of the bearing device of the present invention. In the bearing device 20 of this embodiment, the inner ring 3n of the ball bearing 3 is removed, and the raceway surface 3k of the ball 3t is directly formed on the outer peripheral surface of the shaft member 1. There is an advantage that the outer diameter of the entire bearing device can be reduced by omitting the inner ring 3n. The sleeve member 2 is made of a soft metal such as free-cutting brass or phosphor bronze having good workability and slidability, and the radial bearing surface 1 on the inner peripheral surface of the sleeve member 2 is used.
The groove 11 for generating the dynamic pressure can be easily plastically machined to 0, and the wear caused by the contact between the radial bearing surface 10 and the radial outer peripheral surface 7 generated when the dynamic pressure bearing 4 is started is mitigated. The radial bearing surface 10 of the dynamic pressure bearing 4
The dynamic pressure generating groove 11 is an asymmetrical herringbone groove to enhance the radial load capacity. A cylindrical roller member 17 is press-fitted into the upper end portion of the inner peripheral surface of the sleeve member 2 to form a pressure chamber 14 between the end surface 1a of the shaft member 1 and the cylindrical roller member 17 in the axial direction. . Therefore, the sleeve member 2 and the cylindrical roller member 17 form a bearing member 40. In addition, the seal at the lower end of the ball bearing 3 in this case is
This is done with a general ball bearing shield or seal 3s attached to the outer ring 3g.

The function and effect of the bearing device of this embodiment other than those described above are the same as those of the first embodiment. Next, a third embodiment of the bearing device of the present invention will be described with reference to FIG. 3, which is a sectional view of a spindle motor.

This embodiment is a bearing device 2 according to the present invention.
0 is installed in the actual HDD spindle motor 21 by fixing the shaft member and rotating the bearing member.
The shaft member 1 of 0 is fixed to the base 22, and the sleeve member 2 disposed above the shaft member 1 is integrally fitted to the inner periphery of the hub (rotating body) 23 on which a magnetic disk (not shown) is mounted. ing. Further, the ball bearing 3 is fitted to the lower portion of the shaft member 1 by fitting the inner ring 3n thereof to the shaft member 1 and the outer ring 3g thereof to the inner peripheral surface of the hub (rotating body) 23, thereby rotating the inner ring fixed outer ring. It is installed in.

The radial bearing surface 10 on the inner peripheral surface of the sleeve member 2 is formed with a spiral dynamic pressure generating groove 11 by means of ball rolling or the like, and the inner peripheral surface of the sleeve member 2 is formed. A taper portion 16 is provided adjacent to the end of the radial bearing surface 10 on the ball bearing 3 side. A cylindrical roller member 17 is press-fitted into the upper end of the inner peripheral surface of the sleeve member 2, and a pressure chamber 14 is provided between the upper end surface 1a of the shaft member 1 and the axial gap. Therefore, the hub 23, the sleeve member 2, and the cylindrical roller member 17 form a bearing member 40.

An annular recess 24 is provided on the lower surface of the hub 23. The recess 24 has an innermost hub surface 23n and an outermost hub surface 23g on which the outer ring 3g of the sleeve member 2 and the ball bearing 3 are fitted. And the annular recess 2 located between
The rotor (magnet) 25 is fixed to the inner peripheral surface 24n of the rotor 4, while the rotor 25 is attached to the outer peripheral surface 27g of the annular projecting portion 27 of the base 22 formed so as to project into the annular concave portion 24. A motor M is configured by fixing stators 28, which are arranged to face each other in the radial direction across an air gap.

The operation of the spindle motor 21 constructed as described above is as follows. When the coil of the stator 28 of the motor M is energized, the hub 23 is driven. The hub 23 is rotatably supported by the shaft member 1 through the fluid film in the ball 3t of the ball bearing 3 and the radial bearing gap 8 of the dynamic pressure bearing 4, and therefore is driven to rotate around the shaft member 1. During such driving, a dynamic pressure is generated in the lubricating fluid in the bearing clearance 8 by the pumping action of the dynamic pressure generating groove 11 of the dynamic pressure bearing 4, and the sleeve member 2 of the bearing device 20 causes the shaft member 1 to move.
Rotate without contact. The transmission of the dynamic pressure generated by the lubricating fluid in the bearing clearance 8 increases the pressure of the lubricating fluid in the pressure chamber 14 and pushes the hub 23 upward. As a result, the hub 23 is fitted on the innermost peripheral surface 23n. The upward force acts on the outer ring 3g of the ball bearing thus set, and a preload is applied to the ball 3t.

With this preload, the rigidity of the ball bearing 3 is increased, and the ball bearing 3 supports the radial load and the thrust load applied to the shaft member 1 or the bearing member 40. Thus, also in the third embodiment, the ball bearing 3 can be provided with a required rigidity without separately providing the ball bearing preloading means, and the cost of the spindle motor 21 can be reduced. Moreover, since the two sets of bearings interposed between the shaft member 1 and the bearing member 40 are the dynamic bearing 4 having the ball bearing 3 and the radial bearing gap 8 on the other side, the bearing assembly error results. The effects of misalignment are less likely to occur, and the shake of the non-rotational synchronization component of the spindle motor 21 is suppressed, so that stable rotation of the hub 23 and thus of the magnetic disk is ensured.

Further, the tapered portion 16 on the inner peripheral surface of the sleeve member 2 holds the lubricating fluid protruding from the bearing gap 8 of the dynamic pressure bearing 4 by the action of surface tension, so that the lubricating fluid leaks from the dynamic pressure bearing 4. It is possible to avoid the situation where the ball head 3 and the annular recess 24 pass through and scatter to the outside of the hub 23, thereby damaging the rotating magnetic head.

FIG. 4 shows a fourth embodiment of the bearing device of the present invention. This embodiment is also an example in which the bearing device 20 according to the present invention is incorporated in an actual HDD spindle motor 21 as in the case of the third embodiment. However, this case is different in that the sleeve member is fixed and the shaft member is rotated, and the bearing device 20 shown in the second embodiment is installed upside down. That is, the sleeve member 2 is fixed to the base 22 by means such as screwing, and the shaft member 1 is integrally fitted to the hub 23 through the shaft center of the hub 23 having a cup-down shape. . The outer ring 3g of the ball bearing 3 is fitted into the upper inner peripheral surface of the fixed sleeve member 2, the inner ring 3n of the ball bearing 3 is removed, and the raceway surface 3k of the ball 3t is formed directly on the outer peripheral surface of the shaft member 1. I am doing it. The inner peripheral surface of the lower portion of the sleeve member 2 is the radial bearing surface 10 of the dynamic pressure bearing 4, and for example, an asymmetric herringbone-shaped groove 11 for generating dynamic pressure is formed on the surface, and the shaft member 1
The radial outer peripheral surface 7 of the lower part of the bearing. The pressure chamber 14 is formed by fixing a flat plate 31 to the lower end of the inner circumference of the sleeve member 2 with screws or the like to close the opening. Therefore, the sleeve member 2 and the flat plate 31 form the bearing member 4
0. Further, a magnetic fluid seal 15 is provided at the upper open end of the sleeve member 2 to seal the gap between the outer peripheral surface of the shaft member 1 with the magnetic fluid, and a sleeve such as a lubricant in the ball bearing 3 is provided. The member 2 is prevented from scattering to the outside.

In the motor M for integrally rotating the hub 23 with the shaft member 1, the stator 28 is fixed to the outer peripheral surface of the sleeve member 2 of the bearing device, and the stator 28 is arranged radially opposite to each other with an air gap. The rotor 25 is fixed to the inner peripheral surface 23n of the cup-shaped hub 23.

According to this embodiment, the inner ring 3 of the ball bearing 3 is
Since n is omitted, there is an advantage that the outer diameter of the sleeve member 2 is reduced and the device can be downsized. Other functions and effects are similar to those of the third embodiment.

Further, FIG. 5 shows a fifth embodiment of the bearing device of the present invention. In this embodiment, the bearing device 20 according to the present invention is incorporated in the HDD spindle motor 21 by fixing the sleeve member and rotating the shaft member.
3, the ball bearing 3 is disposed outside the hub 23, and both ends of the long shaft member 1 are supported by bearings, which is different from the above-described embodiments. That is, the through hole 32 is formed in the axial center portion of the base 22 of the spindle motor, and the sleeve member 2 is inserted and fixed to the inner peripheral surface of the through hole 32. The sleeve member 2 is made of a soft metal such as free-cutting brass or phosphor bronze having excellent workability and slidability, and a groove 11 for generating dynamic pressure is formed on the inner radial bearing surface 10 thereof by ball rolling or the like. The dynamic pressure bearing 4 is formed by being formed by plastic working. The base 22 is fixed to a mounting plate 33 by bolts, and the lower opening of the sleeve member 2 is closed by fitting a ball 34. The lower end side of the shaft member 1 is inserted into the sleeve member 2, and the upper end side is HD.
A lid 21f fixed to a mounting plate 33, which is a fixing member of the D spindle motor 21, is penetrated. A bearing case 35 containing the ball bearing 3 is attached to the lid 21f,
The upper end of the shaft member 1 is rotatably supported by the ball bearing 3. Therefore, the ball 34, the sleeve member 2, the base 22, the mounting plate 33, the bearing case 35, and the lid 21f constitute a bearing member 40. The lower radial outer peripheral surface 7 of the shaft member 1 is disposed so as to face the radial bearing surface 10 of the sleeve member 2 with a bearing clearance 8 interposed between the flat lower end surface 1b of the shaft member 1 and the ball 34. The pressure chamber 14 is provided with a slight gap in the axial direction. The arrangement of the motor M in this embodiment is the same as that in the case of the fourth embodiment.

In the case of this embodiment, the shaft member 1 is thus
Is extended to the outside of the hub 23 and its end is rotatably held by the bearing member 40 via the ball bearing 3, so the ball bearing 3 and the dynamic pressure bearing 4 are largely separated in the axial direction, and the shaft member is There is an advantage that the whirling of 1 can be suppressed. Other functions and effects are similar to those of the above-described fourth embodiment.

In each of the above-described embodiments, the case where the groove 11 for generating the dynamic pressure of the dynamic pressure bearing 4 is formed on the radial bearing surface 10 of the inner surface of the sleeve member 2 is shown, but the invention is not limited to this. The groove 11 for pressure generation may be provided on the radial outer peripheral surface 7 of the shaft member 1, or may be provided on both the radial outer peripheral surface 7 and the radial bearing surface 10. When the groove 11 for generating dynamic pressure is provided on the radial outer circumferential surface 7, martensitic stainless steel is used as the material of the shaft member 1 and the hardness is maintained at about HRC 40 to 50 which can be plastically worked by heat treatment, whereby the radial Groove 1 for generating dynamic pressure on outer peripheral surface 7
1 can be easily plastically worked by ball rolling. Further, the shaft member 1 is made of a hardenable material such as stainless steel and hardened by heat treatment or the like.
The dynamic pressure generating groove 11 may be formed by etching. The groove pattern of the dynamic pressure generating groove 11 is not limited to that of the embodiment, and various other groove patterns can be adopted.

Further, in the above embodiment, the deep groove ball bearing is adopted as the ball bearing, but the present invention is not limited to this, and another ball bearing such as a four-point contact ball bearing can be appropriately selected.
Further, the type, structure, material, heat treatment and the like of the ball bearing do not have to be limited to the above embodiment, and may be changed as appropriate.

[0033]

As described above, in the bearing device of the present invention, the pressure of the dynamic pressure bearing is used to apply the preload to the ball bearing. This eliminates the need for an expensive preload applying means that uses force or suction force, which can reduce the cost of the bearing device and facilitate the downsizing of the bearing device.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of a bearing device of the present invention.

FIG. 2 is a sectional view of a second embodiment of the bearing device of the present invention.

FIG. 3 is a sectional view of a third embodiment in which the bearing device of the present invention is applied to a spindle motor.

FIG. 4 is a sectional view of a fourth embodiment in which the bearing device of the present invention is applied to a spindle motor.

FIG. 5 is a sectional view of a fifth embodiment in which the bearing device of the present invention is applied to a spindle motor.

FIG. 6 is a sectional view of a spindle motor using a conventional bearing device.

[Explanation of symbols]

 1 Shaft member 2 Sleeve member 3 Ball bearing 4 Dynamic pressure bearing 14 Pressure chamber 20 Bearing device 40 Bearing member

Claims (1)

[Claims] 1. A shaft member and a bearing member are rotatably assembled relative to each other via a ball bearing and a dynamic pressure bearing which are arranged at intervals in the axial direction, and an end face of the shaft member on the dynamic pressure bearing side. A bearing device, wherein a pressure chamber is provided between the bearing member and the pressure chamber, and a fluid is supplied from the dynamic pressure bearing to the pressure chamber when the bearing device is activated to apply a preload to the ball bearing.