JPS61255842A - Method for molding bearing surface of dynamic pressure type bearing - Google Patents

Abstract

PURPOSE:To provide a method for molding the bearing surface of a dynamic pressure type bearing capable of molding the bearing surface having good accuracy, by a method wherein the dynamic pressure type bearing comprising a thermoplastic resin is molded and the bearing surface thereof is subjected to machine while a mold heated to temp. lower than the m.p. of the thermoplastic resin is pressed to the bearing surface to mold grooves for generating dynamic pressure and machining is applied to the peripheral parts of the grooves. CONSTITUTION:A dynamic pressure type bearing 1 has a ring shaped metal element comprising a ferromagnetic material and the element 5 made of a thermoplastic resin integrally formed along with said element 3 by injection molding. A concave sink is generated to the central part of a part 7 coming to a bearing surface in an injection molding state. Then, the metal element 3 is held by a chuck and the part 7 is subjected to machining to obtain a flat bearing surface. Next, the dynamic pressure type bearing 1 is heated to temp. lower than the m.p. of the thermoplastic resin and a mold 11 having projections 9 are pressed to the part 7 coming to the bearing surface to mold spiral grooves 13 for generating dynamic pressure. The element 13 is chucked by a magnetic chuck and machining is applied to the built-up peripheral parts 15 of the grooves for generating dynamic force to obtain a flat bearing surface 17 having good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a bearing surface of a hydrodynamic bearing used in various fields such as office machines, video equipment, and audio equipment.

[Conventional technology]

Hydrodynamic bearings whose bearing surfaces are made of thermoplastic resin are molded by injection molding, but hydrodynamic bearings with spiral grooves on the flat bearing surface have protrusions corresponding to the spiral grooves. Molded thermoplastic resin is heated and melted into a flat mold by injection light.

[Problem that the invention seeks to solve]

Since the heated and molten thermoplastic resin is cooled in the mold and the bearing surface is formed, warpage and sink marks occur on the bearing surface, making it impossible to obtain a bearing surface with good precision. An object of the present invention is to provide a method for forming a bearing surface of a hydrodynamic bearing, which can form a bearing surface with good quality.

[Means for solving problems]

A hydrodynamic bearing in which the portion that will become the bearing surface is made of thermoplastic resin is molded by injection molding, the portion that will become the bearing surface is machined to a predetermined dimensional accuracy, and the portion that will become the bearing layer is made of thermoplastic resin. Pressing a mold that is heated to a temperature lower than the melting point and has protrusions corresponding to grooves for generating dynamic pressure.
Therefore, grooves for generating dynamic pressure are formed in the part that will become the bearing surface.
This is a method of forming a bearing surface of a hydrodynamic bearing, in which the bearing surface is formed by machining the portion around the groove for generating dynamic pressure in the portion that becomes the bearing surface.

〔Example〕

In FIG. 1, a hydrodynamic bearing 1 includes a ferromagnetic annular metal material 3 and a thermoplastic resin material 5 integrally injection molded with the metal material 3. As shown in FIG. The thermoplastic resin material 5 has polyphenylene sulfide resin as its main component, and contains 15 to 301111% carbon fiber, 5 to 20 weight percent polytetrafluoroethylene resin, and 1 to 100 ml of hydrangea oil.
15% heavy view is added. The metal material 3 is located at the lower part of the outer periphery, the thermoplastic resin material 5 is located at the center and upper part in the radial direction, and the portion 7 that becomes the bearing surface of the hydrodynamic bearing 1 is made of thermoplastic resin. It is located at the top of the material 5. At the time of injection molding, it was intended that the portion 7 that would become the bearing surface would be flat, but in the shape as injection molded, a concave bulge was formed in the center of the portion 7 that would be the bearing surface. The metal material 3 is chucked with a magnetic chuck, and the portion 7 that will become the bearing surface is machined to a predetermined dimensional accuracy by cutting or grinding, etc., to form a planar bearing with good accuracy as shown in Fig. 2. A surface portion 7 is obtained. Next, the dynamic pressure type bearing 1 is heated to a temperature lower than the melting point of the thermoplastic resin, for example, 150°C to 300°C.
Placed below 1. When the mold 11 is pressed against the portion 7 that will become the bearing surface, a highly accurate spiral groove for generating dynamic pressure 13 will be formed in the portion 7 that will become the bearing surface, as shown in FIG.
is formed. In this case, a slight bulge will occur in the peripheral portion 15 such as the same edge of the groove 13 for generating dynamic pressure, but the portion 7 that will become the bearing surface before being pressed by the gold Wll has good accuracy. After being pressed by the mold 11, there is little disturbance in the shape of the portion 15 around the groove for generating dynamic pressure. If the mold 11 is heated to a temperature higher than the melting point of the thermoplastic resin, the portion that will become the bearing surface will melt when it comes into contact with the mold 11, so that the portion 7 of the rod that will become the bearing surface will melt when it comes into contact with the mold 11. Warpage becomes larger after cooling. In addition, when the mold 11 is heated to a temperature higher than room temperature (and lower than the melting point of the thermoplastic resin), the portion 7 that is flush with the bearing surface is
1, the portion 7 that becomes the bearing surface is molded with good precision because it easily flows when pressed. Next, the metal material 3 is chucked with a magnetic chuck, and the protrusions around the grooves 15 for generating dynamic pressure are removed by cutting or grinding, etc., and machined to a predetermined dimensional accuracy.
As shown in the drawings and FIG. 5, a planar bearing surface 17 with good accuracy is obtained.

FIG. 6 shows a hydrodynamic bearing device using a hydrodynamic bearing 1, in which the hydrodynamic bearing 1 is fitted and attached to the bottom of the inner peripheral surface of the sleeve n. A shaft 5 having a planar end surface is fitted into the inner circumferential surface of the tube, and a herringbone-shaped groove is provided on the outer diameter surface of the shaft 5. When the shaft δ rotates, the end surface of the shaft comes out of contact with the bearing surface 17 due to the pumping action of the groove 13 for pressure generation.
Further, the shaft 5 is brought out of contact with the sleeve n due to the pumping action of the herringbone groove n.

Note that the groove for generating dynamic pressure] 3 may be a herringbone-shaped groove.

In addition, when the hydrodynamic bearing l has a metal material 3 and a thermoplastic resin material 5 integrally injection molded with the metal material 3, the deformation of the thermoplastic resin material 5 is caused by the metal material 3. element 13
Therefore, deformation of the portion 7 that becomes the bearing surface during injection molding and deterioration of the bearing surface 17 over time are small.

Furthermore, the thermoplastic resin material 5 may be located on the outer periphery and upper part of the solid metal material 3. Furthermore, the bearing surface 17 may be flat, spherical, or conical.

Furthermore, the hydrodynamic bearing l may be used in a vertical, horizontal, or inverted form.

Alternatively, a bearing device may be used in which the hydrodynamic bearing 1 rotates and the shaft 5 does not rotate.

〔Effect of the invention〕

The deformation caused by the injection molding of the portion 7 that will become the bearing surface is removed by machining, and the mold 11 is pressed against the portion 7 that will become the bearing surface with good accuracy to form the groove 13 for generating dynamic pressure. A good groove 13 for generating dynamic pressure is obtained, and there is little disturbance in the shape of the portion 15 around the groove 13 for generating dynamic pressure. In addition, the grooves 13 for generating dynamic pressure are formed by pressing the mold 11 heated to a temperature lower than the melting point of the thermoplastic resin on the portion 7 that will become the bearing surface. It flows easily when pressed by
Furthermore, since the thermoplastic resin material 5 does not melt, the shape is less likely to be disturbed after cooling. Therefore, the groove 13 for generating dynamic pressure with good precision can be obtained, and the portion 15 around the groove for generating dynamic pressure is less deformed. Furthermore, since the slight deformation of the portion 15 around the groove for generating dynamic pressure is finished into a good bearing surface 7 by machining, the bearing surface 17 with good precision can be formed (').

[Brief explanation of drawings]

1 to 4 are manufacturing process diagrams showing an embodiment of the present invention, in which FIG. 1 is a sectional view of a hydrodynamic bearing after injection molding, and FIG. 2 is a sectional view of a hydrodynamic bearing after injection molding. Figure 3 is a cross-sectional view of the hydrodynamic bearing after it has been pressed by the mold, and Figure 4 is the hydrodynamic bearing after machining the area around the groove for generating dynamic pressure. FIG. 5 is a plan view of the hydrodynamic bearing shown in FIG. 4, and FIG. 6 is a sectional view of a hydrodynamic bearing device using the hydrodynamic bearing. In the figure, 1 is a dynamic pressure type bearing, 7 is a portion that becomes a bearing surface, 9 is a protrusion, 11 is a mold, 13 is a mold for generating dynamic pressure, 15 is a peripheral portion, and 17 is a bearing surface. Patent applicant NSK Ltd. Figure 2 ◇

Claims (5)

[Claims] (1) A hydrodynamic bearing in which the portion that will become the bearing surface is made of thermoplastic resin is molded by injection molding, the portion that will become the bearing surface is machined to a predetermined dimensional accuracy, and the portion that will become the bearing surface is heated. By pressing a mold that is heated to a temperature lower than the melting point of the plastic resin and has protrusions corresponding to the grooves for generating dynamic pressure, grooves for generating dynamic pressure are formed in the portion that will become the bearing surface, and the grooves for generating dynamic pressure are formed in the portion that will become the bearing surface. A method for forming the bearing surface of a hydrodynamic bearing, in which the bearing surface is formed by machining the area around the groove for generating hydrodynamic pressure. (2) The bearing surface of the hydrodynamic bearing according to claim 1, wherein the hydrodynamic bearing has a metal material and a thermoplastic resin material integrally injection molded with the metal material. Molding method. (3) A method for forming a bearing surface of a hydrodynamic bearing according to claim 1, wherein the bearing surface is planar. (4) A method for forming a bearing surface of a hydrodynamic bearing according to claim 1, wherein the bearing surface is spherical. (5) A method for forming a bearing surface of a hydrodynamic bearing according to claim 1, wherein the bearing surface has a conical shape.