JP2997499B2 - Bearing device and its manufacturing method - Google Patents

Description

The present invention relates to a hydrodynamic bearing device, and particularly to a hydrodynamic bearing device having a hydrodynamic groove suitable for a cylinder bearing of a magnetic recording / reproducing device (hereinafter referred to as a VTR). Bearing device and its manufacturing method.

[Conventional technology]

Bearing devices used as conventional dynamic pressure thrust bearings are disclosed in Journal of the Japan Society of Mechanical Engineers, Vol. 89, No. 812 (1986), No. 58
As described from page to page 63, a spiral dynamic pressure generating groove was provided on the slip surface.

On the other hand, the dynamic pressure generating groove was formed by a photo-etching method as described in JP-B-62-49352.

[Problems to be solved by the invention]

In the conventional bearing device, the dynamic pressure generating groove of the thrust bearing is formed by the photo-etching method, which is difficult to mass-produce and takes a long time for processing. Atsuta.

An object of the present invention is to provide a bearing device that can easily mass-produce a groove for generating a dynamic pressure, shortens processing time, and reduces manufacturing cost.

[Means for solving the problem]

In order to achieve the above object, the bearing device of the present invention is configured such that a rotating member and a stationary member face each other via a fluid film, and the facing slip surface has a curved shape which is radially extended from the center of the slip surface to the outer periphery. In a bearing device in which a plurality of grooves having a shape and a width gradually narrowing toward the center and a substantially uniform depth are formed, each groove has an outer shape obtained by inverting each groove and a predetermined height. It is configured such that a mold having a convex portion is formed by plastic working by pressing against one of the slip surfaces.

Then, the rotating member and the stationary member face each other via the fluid film, and the facing slip surface has a curved shape extending radially from the center of the slip surface to the outer periphery, and has a width gradually narrowing toward the center. A bearing device with a plurality of grooves having a uniform depth is formed by pressing a mold having a convex part consisting of an inverted shape of each groove and a predetermined height against one of the sliding surfaces. Are formed to form respective grooves.

Also, the height of the convex portion of the mold is such that the central portion is high and the outer peripheral portion is formed low. A configuration in which the ratio of the height of the convex portions is changed may be used.

Further, after the groove is transferred, a mold having a smooth pressing portion is pressed against the groove transfer surface to form a bearing device by plastic working.

In addition, the height of the pressing portion of the mold is such that the central portion is high and the outer peripheral portion is formed low, and the die is formed of a material having a different longitudinal elastic modulus, so that the pressing portions of the central portion and the outer peripheral portion are formed. The height ratio may be changed.

In a VTR that includes a rotating part having a magnetic head and a fixed part that supports the rotating part, and a magnetic tape is wound around the rotating part for recording and reproduction, the VTR is arranged to face the upper end surface of a shaft provided at the center of the fixed part. The thrust bearing which is provided, rotates with the rotating part, and floats and supports the rotating part via the fluid film has the same configuration as the bearing device according to the first aspect.

A laser beam printer that includes a rotating unit having a polygonal mirror and a fixed unit that supports the rotating unit, and is provided at the center of the rotating unit in a laser beam printer that records laser light on a photosensitive drum by reflecting laser light with the polygonal mirror of the rotating unit. A thrust bearing arranged opposite to a lower end surface of the shaft that rotates together with the rotating portion, and is fixed to the fixed portion and floats and supports the shaft via a fluid film, has the same configuration as the bearing device according to claim 1. And

[Action]

According to the present invention, the mold is pressed against the sliding surface of the bearing device, and the width of the spiram-shaped dynamic pressure generating groove provided on the sliding surface of the thrust bearing is continuously narrowed in the rotation direction and the center direction of the shaft. By doing so, the cross-sectional area of the groove decreases in the direction of rotation. Therefore, the lubricant such as oil disposed between the width and the thrust bearing promotes the pump action accompanying the rotation of the shaft, generates a large pressure, forms a fluid film, and obtains a large supporting load capacity. . Similarly, the floating amount of the support member in the bearing device in the axial direction increases.

On the other hand, the mold is elastically deformed by pressing the mold with the shape where the periphery of the convex part is low and the height continuously increases with respect to the center direction against the sliding surface of the thrust bearing. Thereby, the height becomes uniform over the entire area of the convex portion. As a result, the bottom of the groove becomes substantially flat, but the land portion of the groove has a low center portion and a high peripheral portion, resulting in an uneven groove depth.

Furthermore, by pressing a mold having a shape in which the peripheral portion of the smooth pressing portion is low and continuously high with respect to the center direction against the groove transfer surface, the mold is elastically deformed, so that the mold has a uniform height over the entire area of the pressing portion. It will be. As a result, the land portion is compression-molded to a predetermined uniform height, and the depth of the groove is substantially uniform both in the central portion and in the peripheral portion.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS.

As shown in FIGS. 1 to 3, a shaft (rotating member)
Bearing device 30 including 3 and thrust bearing (stationary member) 1
Curved surface (spiral shape) extending radially from the center of the sliding surface 1a to the outer periphery on the sliding surface 1a of one of the thrust bearings 1
Dynamic pressure generating grooves 2 are provided. In the dynamic pressure generating groove 2, a number of grooves having the same shape are regularly arranged, and the width b of each groove is set.
Is continuously narrowed in the rotation direction A of the shaft facing the sliding surface 1a. Further, as shown in FIG. 1, the cross section of the groove is rectangular, and the groove depth d is substantially uniform over the entire area.

The thickness of the base (disk) of the thrust bearing 1 in this embodiment is 1.8 mm and its diameter is 15 mm, and this embodiment is particularly effective for application to such an ultrathin thrust bearing. The maximum width c of each dynamic pressure generating groove 2 is 0.5 mm, and the width e of the portion of the groove 2 opening to the central recess 2a is 0.05 to 0.1 mm. The diameter of the recess 2a is 0.5 mm. on the other hand,
The depth d of the groove 2 in this embodiment is 3 μm.

 Next, the operation of the present embodiment will be described.

As shown in FIG. 3, the thrust bearing 1 having a spiral dynamic pressure generating groove 2 formed thereon is interposed via a fluid film 4 of oil or the like such that the end surface 3a of the shaft 3 faces the sliding surface 1a. Deploy. In this embodiment, oil having a viscosity of about 40 centistokes is used. By rotating the shaft 3 in the direction A in such a state, the fluid filled in the dynamic pressure generating groove 2 becomes smaller as the groove 2 has a spiral shape and the width gradually decreases in the rotational direction. Therefore, pressure is generated by the pump action of the groove. For this reason, as shown in FIG. 3, a large fluid pressure is generated near the center of the shaft. As a result, a large supporting load is obtained for the thrust bearing 1, and the axial floating amount of the shaft 3 and the like also increases.

The dynamic pressure generating groove can be easily formed by the method shown in FIGS. In FIG.
Has a convex portion 5a having a shape obtained by inverting the dynamic pressure generating groove 2 formed in the thrust bearing and having a predetermined height. Therefore,
The convex portion 5a of the mold 5 is pressed against the sliding surface 1a of the thrust bearing 1 to transfer the dynamic pressure generating groove 2 to the sliding surface 1a. In addition,
As shown in FIG. 5, the protrusion 5a of the mold 5 as the first mold is provided.
Is processed such that the inner peripheral portion is high and the outer peripheral portion is low.

When the dynamic pressure generating groove 2 of the thrust bearing is coined in such a state, the surface pressure distribution of the die is small because the width of the convex portion 5a of the inner peripheral portion is small and the cross-sectional area is small as shown in FIG. , The inner circumference is higher than the outer circumference. Along with this, the elastic deformation in the height direction of the convex portion 5a of the mold becomes larger at the inner peripheral portion than at the outer peripheral portion, as shown in FIG. Therefore, the height of the convex portion 5a of the mold becomes substantially uniform over the entire area,
As shown in FIG. 8, the bottom of the groove becomes substantially flat. However, as shown in the figure, the height f of the land portion 1b of the groove is not uniform because the width g of the outer peripheral portion is wider than the inner peripheral portion, and the outer peripheral portion is higher than the inner peripheral portion.

Next, the heights of the lands can be easily made uniform by the method shown in FIGS. 9 to 11, and grooves having a uniform depth can be formed. In FIG. 9, a pressing portion of a mold 7 as a second mold
7? A has a convex smooth surface in the center. Accordingly, the pressing portion 7a of the mold 7 is pressed against the sliding surface 1a of the thrust bearing 1, and the height f of the land portion 1b is compression-molded to a predetermined uniform height to form the groove depth uniformly. I do. As shown in the figure, the height i of the pressing portion 7a of the mold 7 is high at the inner peripheral portion,
The outer periphery is machined low.

When the thrust bearing is pressed in such a state,
As shown in FIG. 10, the surface pressure distribution of the mold is higher at the inner periphery than at the outer periphery. Along with this, the elastic deformation in the height direction of the pressing portion 7a of the mold 7 becomes larger at the inner periphery than at the outer periphery, as shown in FIG. Therefore, the pressing portion of the mold 7 becomes substantially flat over the entire area, and a thrust bearing having a substantially uniform groove depth can be formed as shown in FIG.

As described above, when the mold 7 whose pressing surface continuously changes is used, a thrust bearing having a substantially uniform groove depth can be easily formed by elastic deformation in the height direction of the mold. it can.

According to the present embodiment, the width of the dynamic pressure generating groove is narrowed in the rotation direction of the shaft, so that the pumping action of the groove is promoted, and a large supporting load capacity and a large floating amount in the axial direction can be obtained. . In addition, the above-described dynamic pressure generating groove presses a mold having a convex portion having an outer shape obtained by transferring the groove shape and a predetermined height against either the sliding surface of the thrust bearing or the sliding surface of the shaft. By doing so, it can be easily formed, so that the processing time can be greatly reduced as compared with photo-etching. Furthermore, when the thrust bearing of the present embodiment is used for a cylinder portion of a VTR or a polygon mirror bearing portion of a laser beam printer, a large supporting load capacity and a floating amount in the axial direction can be obtained, so that the rotational load torque can be reduced. it can.

In the above embodiment, the thrust bearing having the groove formed therein is a stationary member. However, since the thrust bearing has the same operation relative to the corresponding member, it may be applied to a rotating member.

FIG. 12 is a perspective view of a VTR 8 according to another embodiment of the present invention, in which the cylinder 9 is shown with the outer box partially transparent. FIG. 13 illustrates this cylinder 9.

In the embodiment of FIG. 13, a grooved thrust bearing is applied to a rotating member. In this figure, the thrust bearing 1 in which the dynamic pressure generating groove is formed on the sliding surface has the sliding surface of the shaft 3.
And is fixed to the upper cylinder 10 so as to face. By rotating the upper cylinder 10 with the driving force of the motor 11 in such a state, the thrust bearing 1 also rotates, so that the groove surface also rotates, and the fluid pressure is generated by the pump action of the dynamic pressure generating groove. Then, the upper cylinder 10 is levitated and supported in the axial direction.

FIG. 14 is a perspective view of a laser beam printer according to another embodiment of the present invention, and includes a correction lens 13, a cylindrical lens 14, a collimator lens 15, a semiconductor laser 16,
The photosensitive drum 17 and the laser scanner 18 are illustrated. FIG. 15 illustrates this laser scanner 18.

In the embodiment shown in FIG. 15, a grooved thrust bearing is applied to the fixing member. In this figure, a motor 11, a radial bearing 19, a polysilicon mirror 20, and a housing 21 are illustrated. The thrust bearing 1 having the dynamic pressure generating groove formed on the sliding surface is fixed to the housing such that the sliding surface faces the shaft 3. When the polygon mirror 20 is rotated by the driving force of the motor 11 in such a state, the shaft 3 fitted to the polygon mirror 20 also rotates, so that the relative sliding between the shaft 3 and the grooved thrust bearing 1 occurs. And the fluid pressure is generated by the pumping action of the dynamic pressure generating groove, and the polygon mirror 20 is floated and supported in the axial direction.

As described above, since the thrust bearing to which the present invention is applied can obtain a large floating amount, a VTR cylinder unit having a small rotational load torque and a polygon mirror unit of a laser beam printer can be realized.

FIG. 16 schematically shows how to form the groove in the present invention in relation to the stationary member and the rotating member. FIG. 16 shows the relationship of the groove width depending on the rotation direction in the case of a thrust bearing. As shown in the figure, rotation and stationary are relative relationships. In the present invention, the relationship of narrowing (widening) in the rotation direction is defined by FIG.

〔The invention's effect〕

According to the present invention, since a plurality of grooves (dynamic pressure generating grooves) are formed by pressing the mold on the sliding surface of the bearing device, a bearing device having a large bearing support load and capable of stable support can be realized. .

Further, according to the present invention, it is possible to provide a thrust bearing in which the pumping action of the dynamic pressure generating groove is promoted and a large supporting load capacity and an axial floating amount are obtained. Therefore, the torque loss on the sliding surface of the thrust bearing is small,
The amount of wear is also greatly reduced.

Further, since the thrust bearing can be easily formed by the plastic working method, the working time is shortened, the manufacturing cost is reduced, and the mass productivity is remarkably improved.

[Brief description of the drawings]

1 is a sectional view of a thrust bearing according to one embodiment of the present invention, FIG. 2 is a front view of the thrust bearing of FIG. 1, FIG. 3 is a pressure distribution diagram of the thrust bearing surface of FIG. Is a sectional view showing a method of forming the groove of the thrust bearing of FIG. 1, FIG. 5 is a sectional view of a mold, FIG. 6 is a sectional view showing a surface pressure when the mold is pressed, and FIG.
FIG. 8 is a sectional view showing the elastic deformation of the mold, FIG. 8 is a sectional view of the thrust bearing formed in FIG. 4, and FIG. 9 shows a forming method for pressing the mold to make the groove depth uniform. FIG. 10 is a cross-sectional view showing the surface pressure when pressing the mold, FIG. 11 is a cross-sectional view showing the elastic deformation of the mold, FIG. 12 is a perspective view of another embodiment of the present invention, FIG. FIG. 13 is a sectional view of the VTR cylinder unit of FIG. 12,
FIG. 14 is a perspective view of another embodiment of the present invention, FIG. 15 is a sectional view of the polygon mirror unit of FIG. 10, and FIG. 16 defines the width direction of the groove when the present invention is applied to a thrust bearing. FIG. 1 ... thrust bearing, 2 ... dynamic pressure generating groove, 3 ... shaft, 4
…… Fluid film, 5,7 …… Mold, 30 …… Bearing device.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Terayama 502 Kandamachi, Tsuchiura-shi, Ibaraki Pref.Hitachi, Ltd.Mechanical Research Laboratory Co., Ltd. In-house (72) Inventor Juichi Morikawa 1410 Inada, Kata-shi, Ibaraki Pref.Hitachi, Ltd.Tokai Plant, Hitachi, Ltd. References JP-A-3-37413 (JP, A) JP-A-1-170527 (JP, A) JP-B-50-37635 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) F16C 17/00-33/28 B21D 22/00-22/30

Claims (2)

(57) [Claims] A rotating member and a stationary member oppose each other via a fluid film, and have a curved surface extending radially from the center of the sliding surface to the outer periphery of the sliding surface and gradually narrowing toward the center. In a bearing device having a plurality of grooves having a width and a substantially uniform depth, the grooves press a second mold after being pressed against one of the slip surfaces by a first mold. The first mold has an outer shape obtained by inverting the groove, and a convex portion having a predetermined height in which a central portion is high and an outer peripheral portion is low,
The said 2nd metal mold | die has a smooth shape which becomes convex toward a center part, The bearing apparatus characterized by the above-mentioned. 2. A rotating member and a stationary member opposing each other via a fluid film, and a curved surface extending radially from the center of the sliding surface to the outer periphery of the opposing sliding surface and gradually narrowing toward the center. In a method of manufacturing a bearing device having a plurality of grooves having a width and a substantially uniform depth, a convex portion having a predetermined height in which a center portion of a pressing portion is higher and an outer peripheral portion is lower in an outer shape in which the grooves are inverted. After pressing the mold with one of the slip surfaces and transferring the same, the mold having a smooth shape convex toward the center is pressed against the transfer surface of the transfer groove to a uniform depth. A method of manufacturing a bearing device, characterized in that a groove is formed by plastic working.