JP2504063B2 - Bearing device - Google Patents

Description

The present invention relates to a bearing device used in audio equipment, video equipment, office equipment and the like.

[Conventional technology]

As a bearing device for a rotary cylinder for a magnetic head of conventional audio equipment, video equipment, etc., for example, a sleeve fixed to an upper cylinder is rotatably fitted around a shaft fixed to a lower cylinder, and the outer circumference of the shaft is fixed. A dynamic pressure type radial bearing that supports the sleeve in the radial direction is provided on the surface, and a spherical body is press-fitted and fixed to the inner peripheral surface of the upper end of the sleeve to form a thrust receiver. There is known a structure in which a pivot type thrust bearing for supporting the sleeve in the axial direction is formed by making the upper surface of the shaft and the flat surface of the upper end face each other with or without a lubricant.

[Problems to be Solved by the Invention]

In this type of bearing device, it is necessary to reduce the height change of the magnetic head during use of the bearing as much as possible, and for example, it is required to suppress the height change within 5 μm.

Therefore, in the conventional pivot type thrust bearing, the thrust bearing is hardened by a bearing steel ball (SUJ2).
Use one that has been tempered (hardness H _R C60 ~ 66),
On the other hand, the shaft is made of stainless round steel (SUS420J2) that has been quenched and tempered (hardness H _R C45 to 60).

However, for the bearing device, for example, 2000
The result of the long-term wear test over time is as shown in FIG. 4, and the abutting surfaces of the spherical body 1 and the shaft body 2 which support the thrust bearing are greatly worn,
The total amount of wear reached 14 μm. (Both the sphere shown in FIG. 4 (a) and the shaft end surface shown in FIG. 4 (b) are shown by changing the magnification in the axial direction and the radial direction to 10: 1.) It is considered that the wear of the end face of the shaft is promoted by the powder being caught in the contact surface between the sphere and the shaft.

The present invention has been made by paying attention to such a conventional problem, and an object thereof is to reduce the wear of the entire thrust bearing by increasing the hardness of a spherical body that serves as a thrust receiver. It is an object of the present invention to provide a bearing device that can maintain axial accuracy within a predetermined range for a long period of time.

[Means for solving the problem]

In the bearing device of the present invention which achieves the above object, one of a shaft body and a sleeve fitted into the shaft body is rotatably supported by the other via a radial bearing, and one end portion of the sleeve is provided. In a bearing device in which a thrust bearing made of a spherical body is fixed to the shaft bearing, and a thrust bearing is configured between the thrust bearing and an end surface of the shaft body that axially opposes and contacts the thrust bearing, the thrust bearing is made of cemented carbide. It is made of an alloy, and the hardness of the thrust receiver is made higher than the hardness of the end face of the shaft body, and a concave spherical surface having a radius of curvature slightly larger than the radius of the thrust receiver is directly formed on the end face of the shaft body.

[Action]

The hardness of the spherical thrust bearing made of cemented carbide is higher than the hardness of the end face of the shaft, and the end face of the shaft contacting this thrust receiver is a concave spherical surface with a radius of curvature slightly larger than the radius of the thrust receiver. As a result, abrasion powder is unlikely to be generated, and therefore abrasion is not promoted by the abrasion powder, and the amount of abrasion on the thrust bearing surface of the shaft body remains extremely small. Further, since the concave spherical surface is directly formed on the shaft body, there is no possibility of eccentricity after the concave spherical surface is formed by aligning the center of the concave spherical surface with the shaft center of the shaft body.

〔Example〕

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

FIG. 1 is a vertical sectional side view showing an embodiment in which the bearing device of the present invention is applied to a rotary cylinder for a magnetic head.

In this bearing device, a lower end portion of a shaft body 10 which is a fixed shaft is fixed to a lower cylinder 11 by press fitting or the like. On the other hand, the sleeve 12 rotatably fitted around the shaft body 10 is fixed to the upper cylinder 13. Herringbone-shaped dynamic pressure generating grooves 14a and 14b are provided on the outer peripheral surface of the shaft body 10 to form a sleeve 1.
A dynamic pressure type radial bearing 14 that supports 2 in the radial direction is configured.

Further, a spherical body 15 as a thrust receiver is press-fitted and fixed to the inner peripheral surface of the upper end portion of the sleeve 12 in the axial direction, and the thrust receiver 15 and the upper end surface 10A of the shaft body 10 are intervened with or without a lubricant. To form a pivot type thrust bearing S for supporting the sleeve 12 in the axial direction. Shaft
A concave spherical surface 30 is formed on the upper end surface 10A of 10 as shown enlarged in FIG. That is, as shown in FIG. 3, the upper end surface 10A of the shaft body 10 facing the convex spherical surface 15A of the thrust receiver 15 made of cemented carbide has a concave spherical surface 30 at the center in the radial direction instead of a flat surface. . Radius of curvature of the concave spherical surface 30
Rs is configured to be larger than the radius of curvature Rx of the convex spherical surface 15A of the thrust receiver 15.

And Thus, the shaft 10 is hardened, whereas consisting tempering or precipitation hardening treatment hardness was subjected to heat treatment such as H _R C45~60 stainless round bars (SUS420J2.SUS630.SUS631 etc.), the thrust bearing 15 is made of cemented carbide of Hv1300 or higher, for example
It consists of WC-Co alloy and other tungsten carbide based alloys.

The inner peripheral surface of the upper end portion of the sleeve 12 is provided with an air vent groove 16 axially communicating the air between the upper end portion of the shaft body 10 and the thrust receiver 15 to the outside air, and the middle portion of the sleeve 12 is provided. Is also provided with an air vent hole 17 that penetrates in the radial direction,
Air between the outer peripheral surface of the sleeve 10 and the sleeve 12 is communicated with the outside air to reduce air resistance at the time of assembling the bearing and to escape bubbles contained in a lubricant such as oil to the outside.

In the rotary drive motor of the bearing device, a cylindrical rotor magnet 18 is attached to a disk 19 fixed to the outer peripheral surface of a sleeve 12, and a stator coil 20 facing the outer peripheral surface of the rotor magnet 18 with a cylindrical surface is attached to a side wall of the lower cylinder 11. Is formed by being attached to.

Further, a cylindrical fixed-side rotary transformer 21 arranged on the outer circumference of the sleeve 12 is attached to the lower cylinder 11, and the rotary-side rotary transformer 22 opposed to the outer peripheral surface of the fixed-side rotary transformer 21 by a cylindrical surface is provided. A signal attached to the disk 19 and taken out from the magnetic head 23 attached to the upper cylinder 13 is transmitted to the fixed rotary transformer 21 via the rotary rotary transformer 22.

 Next, the operation will be described.

The above-mentioned bearing device is driven by filling the clearance of the radial bearing 14 between the sleeve 12 and the shaft body 10 with a lubricant such as oil (synthetic hydrocarbon oil, fluorine oil, etc.), grease, or by air. When the stator coil 20 of the rotary drive motor fixed to the lower cylinder 11 is energized, the rotor magnet is driven.
Rotational force is generated in 18 and the sleeve 12 and the accessories directly or indirectly fixed thereto rotate together. When the sleeve 12 rotates, dynamic pressure is generated by the dynamic pressure generation grooves 14a and 14b of the shaft body 10 to generate a fluid film in the clearance of the radial bearing 14, and the pressure of this fluid film causes the sleeve 12 to move against the shaft body 10. While being supported in the radial direction while maintaining a non-contact state, the thrust receiver 15 makes point contact with the upper end surface of the shaft body 10, so that the sleeve 12 is supported in the axial direction by the upper end surface 10A of the shaft body 10 and rotates. .

In order to confirm the wear resistance performance of the bearing device using the above-mentioned cemented carbide sphere for the thrust bearing 15, the bearing end face 10A is a plane perpendicular to the axis of the shaft body 10 The results of the wear test over time are shown in FIG. SUS420J2 was used for the shaft, and synthetic hydrocarbon oil was used for the lubricant (the thrust receiver shown in Fig. 2 (a) and the shaft end face shown in Fig. 2 (b) both have a magnification of 10 in the axial direction and in the radial direction. It has been changed to 1).

As is clear from the figure, no abrasion was observed in the thrust receiver 15 made of cemented carbide of Hv1300 or higher, and the contact surface with the shaft body 10 remained smooth. On the other hand, shaft 10
A slight dent due to wear was recognized on the upper end surface 10A of the bearing at the contact portion with the thrust receiver 15, but the wear amount was 4 μm.
It was nothing more than Thus, if this bearing device is used for a long time, the change in axial height of the magnetic head is 5 μm.
It is possible to keep it within. Furthermore, in the present embodiment, since the end surface 10A of the shaft body 10 is the concave spherical surface 30 as described above, the contact area between the convex spherical surface 15A of the thrust receiver 15 and the end surface 10A of the shaft body 10 is larger than that of the end surface 10A being flat. Become. As a result, the contact surface pressure per unit area decreases, and there is an advantage that the wear of the end surface 10A of the shaft body 10 can be further reduced.

Next, a method of forming the concave spherical surface 30 on the end surface of the shaft body 10 will be described. First, a cylindrical body having an inner diameter that can be fitted into the outer peripheral surface of the shaft body 10 used as a fixed shaft is prepared, and one end of the inner peripheral surface of this cylindrical body in the axial direction is harder than the shaft body 10. A shaft (10) is inserted into this jig by using a jig (not shown) in which a pressing member having a high height is fixed by press fitting or the like. The pressing body has a surface facing the shaft body 10 having a convex spherical surface at the center in the radial direction, and the shaft body 10
Has a hardness of H _R C45-60. A spherical body may be used as the pressing body. The shaft 10 is fixed and the pressing body of the jig is pressed against the end face 10A of the shaft to give a predetermined pressing load, or the shaft 10 is pressed against the pressing body of the fixed jig, or By pressing both the jig and the shaft body 10 in the axial direction, a pressing load by the pressing body of the jig is applied to the end surface 10A of the shaft body. In addition,
An air vent groove for communicating air between the shaft body 10 and the pressing body to the outside air is provided on the inner peripheral surface of one end of the cylindrical body. As a result, the end surface 10A of the shaft body is plastically deformed and springs back by the pressing body having a hardness higher than that of the shaft body 10, and the end surface 10A of the shaft body has a curvature radius Rs larger than that of the convex spherical surface of the pressing body. A concave spherical surface 30 is formed.

The radial clearance between the cylindrical body of the jig and the shaft body 10 can be made smaller than the radial clearance between the sleeve 12 and the shaft body 10 used as a product, and the end surface 10A of the shaft body has a shaft. It is possible to form the concave spherical surface 30 with less eccentricity from the axis of the body 10.

Further, by using a different radius of curvature of the convex spherical surface of the pressing body of the jig from the radius of curvature Rx of the spherical surface 15A of the thrust receiver 15 used as a product, according to the radius of curvature of the convex spherical surface of each pressing body. A concave spherical surface 30 having a radius of curvature Rs can be formed on the end surface 10A of the shaft body.

It should be noted that, instead of the above jig, the thrust receiver 15 used as a product is fixed to the sleeve 12 used as a product by means such as press fitting, and the one with or without other accessories attached to it is used. May be, in this case the shaft
The concave spherical surface 30 can also be formed on the end surface 10A of the shaft body by performing the same operation as above with or without fixing 10 to the lower cylinder 11 in advance by means such as press fitting.

In this case, the thrust bearing 15
A bearing device is obtained in which the sleeve 12 to which is fixed is inserted and a predetermined pressing load is applied to form the concave spherical surface 30, and at the same time, the assembly is completed.

Incidentally, when the concave spherical surface 30 is formed on the end surface 10A of the shaft body having a low hardness before heat treatment such as quenching tempering or precipitation hardening treatment by plastic deformation, the hardness of the shaft body 10 is passed through a heat treatment step such as quenching tempering or precipitation hardening treatment. In the intermediate process until the temperature becomes high, the concave spherical surface 30 and the outer diameter surface of the shaft body 10 are easily scratched by the handling of the shaft body 10, and the concave spherical surface 30 is deformed by heat treatment. However, after heat treatment, the end face 10
When the concave spherical surface 30 is formed on A by plastic deformation, the shaft body 10 has high hardness, so that the concave spherical surface 30 and the outer diameter surface are not easily scratched. Further, since the plastically deformed concave spherical surface 30 does not need to be heat-treated, the concave spherical surface 30 is not deformed by heat treatment.

In the rotary spindle described in the above embodiment, the sleeve 12 around the shaft body 10 and its accessory parts rotate, but on the contrary, the sleeve 12 is fixed to the lower cylinder 11, The present invention can also be applied to the structure in which the shaft body 10 fixed to the cylinder 13 is supported by the sleeve 12 and rotates.

In addition, since fluorine oil or a lubricant based on fluorine oil is inferior in rust prevention property to synthetic hydrocarbon oil, the use of fluorine oil or a lubricant based on fluorine makes the bearing more likely to rust.
In this case, the thrust bearing 15 is cemented carbide, the shaft body 10 is precipitation hardening stainless steel (SUS630.SUS631 etc.), the sleeve 12
It is preferable to use free-cutting yellow steel to prevent rust.

Further, an upper drum may be arranged above the upper cylinder 13 and the upper drum and the lower cylinder 11 may be integrated.

Further, the air vent hole 17 provided in the sleeve 12 may be omitted depending on the usage conditions.

Further, the radial bearing configured between the sleeve 12 and the shaft body 10 is not limited to the dynamic pressure type hydrodynamic bearing described in the above embodiment, and may be a hydrostatic type hydrodynamic bearing. Other sliding bearings or rolling bearings can also be used.

A flat motor in which the rotor magnet and the stator coil face each other in a plane may be used. Whether the rotor magnet 18 and the stator coil 20 are cylindrically opposed to each other in a circumferentially opposed motor or a planarly opposed motor, the shaft body of the sleeve 12 is
In order to prevent the thrust bearing 15 from coming off, it is preferable that the thrust bearing 15 be attracted toward the shaft body 10 by the axial attraction force generated by the rotor magnet and the stator coil.

〔The invention's effect〕

As described above, according to the present invention, the thrust receiver is a spherical body, and the surface of the shaft end face in contact with the thrust receiver is a concave spherical surface having a radius of curvature slightly larger than the radius of the thrust receiver. Since the hardness of the thrust receiver made of is higher than the hardness of the end surface of the shaft body, the wear of the end surface of the shaft body can be remarkably reduced, and a high-performance bearing device that maintains a predetermined axial accuracy for a long period of time can be provided. Further, since the concave spherical surface is directly formed on the shaft end surface, the plate having the concave spherical surface is arranged on the shaft end surface to place the plate between the thrust receiver and the shaft body. In addition, there is no possibility of eccentricity between the thrust receiver and the concave spherical surface, the axial and circumferential accuracy can be maintained, and higher performance can be achieved.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment in which the present invention is applied to a rotary cylinder for a magnetic head, and FIG. 2 shows a case where a thrust receiver made of a cemented carbide sphere is used so as to face a flat shaft end face. It is a principal part enlarged view which shows the result of a wear test (however, the enlargement ratio of an axial direction and a radial direction differs), and the same figure (a).
Is a thrust receiver, and FIG. 3B is a diagram showing a shaft end face. FIG. 3 is an enlarged side view of an essential part of FIG. 1. FIG. 4 is an enlarged view of an essential part showing the results of a wear test in a conventional bearing device. (However, the magnifying power in the axial direction is different from that in the radial direction).
Represents a thrust receiver, and FIG. 3B is a view showing a shaft end face. 10 is a shaft, 10A is an end face of the shaft, 12 is a sleeve, 14 is a radial bearing, 15 is a thrust bearing, S is a thrust bearing, and 30 is a concave spherical surface.

Claims (1)

(57) [Claims] 1. A shaft body and a sleeve fitted into the shaft body are rotatably supported by the other through a radial bearing, and a thrust receiver made of a spherical body is fixed to one end portion of the sleeve. In the bearing device in which the thrust bearing is formed between the thrust bearing and the end surface of the shaft body that is in contact with the thrust bearing so as to face the thrust bearing in the axial direction, the thrust bearing is made of cemented carbide. A bearing device having a hardness higher than that of an end surface of a shaft body, and a concave spherical surface having a radius of curvature slightly larger than a radius of the thrust receiver is directly formed on the end surface of the shaft body.