JPH07310733A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE:To provide an easy fabrication method and prevent the occurrence of seizure by forming a dynamic pressure generation groove on the external surface of a bearing member or a rotor via a printing process. CONSTITUTION:The outer surface of a rotor 2 is roughly machined to a rough outer diameter at a lacing process and, then, the outer surface of a rotor 2 is satin finished chemically, in order to increase material adhesion strength. A paste material made of polyamide imide resin as a base and containing PTFE particulates dispersed is printed on the outer surface of the rotor 2 by use of a screen printing machine. In this case, an arbitrary groove pattern is preliminarily formed on a screen plate, thereby forming a desired dynamic pressure generation groove 15 out of the paste material on the outer surface of the rotor 2. The groove 15 is formed between the layers of the paste material on the surface of the rotor 2, and the paste material is cured after printing. In addition, the surface of the cured paste material is finished at a racing process, thereby providing the groove 15 of the specified depth as well as the rotor 2 having the specified outer diameter. According to this construction, easy machining can be ensured and high slidability can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device which bears a bearing load by a dynamic pressure of a fluid occupying a bearing gap such as air, oil or magnetic fluid. More specifically, the present invention is for dynamic pressure generation of a dynamic pressure bearing device suitable for supporting a shaft of a rotor of a motor that rotates at high speed such as a laser scanning motor or a high speed spindle motor. Regarding the structure of the groove.

[0002]

2. Description of the Related Art A laser scanning motor, a magnetic drum motor, a gyro motor, or a motor that rotates at high speed such as a high-speed spindle motor is capable of rotating at high speed. A hydrodynamic bearing that supports the rotor (rotating shaft) is used. Since this hydrodynamic bearing generates dynamic pressure during rotation to levitate and support the rotating shaft, a very narrow fixed bearing gap (exaggerated in the drawing is shown between the rotating shaft and the bearing member. However, usually, several μm to several tens of μm) are formed. For this reason, the rotary shaft and the bearing member will come into contact during rotation unless they are precisely finished so that unnecessary protrusions do not occur on the outer peripheral surface (bearing surface) of the rotary shaft and the inner peripheral surface (bearing surface) of the bearing member. As a result, frictional heat is generated, and there is a risk of causing a so-called seizure phenomenon in which the shaft and the bearing adhere to each other due to melting of the contact portion. This seizure phenomenon generally causes the seizure caused by contact in the state where the bearing load capacity is low at the time of starting and stopping, but also occurs when contact occurs at high speed rotation due to vibration when an external force is applied.

On the other hand, in a high-speed rotary motor such as a laser scanning motor in which dynamic pressure bearings are frequently used, the weight is reduced to shorten the rise time, and the dynamic pressure bearings are driven inside the rotary shaft. It is required to arrange a magnet, a coil, and an iron core to make the motor compact and minimize the runout and tilt of the rotating shaft. In the case of a hydrodynamic bearing having such a structure, since the shape and structure of the rotating shaft becomes complicated, it is much more advantageous to machine an aluminum alloy in terms of processing cost. Is desired to be made of aluminum or the like. Then, in order to improve the wear resistance of aluminum and the like, the bearing member is conventionally subjected to hard alumite treatment, and the rotor is subjected to Ni—P electroless plating containing SiC fine particles.

Further, the dynamic pressure bearing is provided with a groove called a groove having a depth of several μm for generating a dynamic pressure. For example, when providing a dynamic pressure generation groove on the rotor side, conventionally, after finishing the outer diameter of the aluminum rotor to a predetermined value by lace processing, an etching resist is formed corresponding to the shape of the dynamic pressure generation groove. Then, etching is performed to form a dynamic pressure generating groove. Then, the Ni-P-SiC plating film is formed on the surface of the rotor.

On the other hand, in Japanese Unexamined Patent Publication No. 4-78313, in order to shorten the start-up time of the motor, the thrust bearing surface and the radial bearing surface of the rotary member are made of synthetic resin having good slidability and wear resistance. Formed dynamic bearing devices have been proposed. Then, in this dynamic pressure bearing device, a part of the resin layer covering the entire circumferential surface of the rotor or the bearing member is recessed by using an injection molding die or ball rolling technique to form a bearing surface made of synthetic resin. It has been proposed to integrally form the dynamic pressure generating groove.

[0006]

However, when the hard alumite treatment and the Ni-P electroless plating containing SiC fine particles are applied, both materials have very high hardness and excellent wear resistance, but impurities in the plating reaction. It can be said that since it is a plating solution in which a large amount of SiC is dispersed, reaction unevenness is likely to occur and projections are generated on the film, so there is a problem that the contact between the rotor and the bearing may cause seizure due to impact or posture change during high rotation of the rotor. Have Further, the number of steps for forming the groove for generating the dynamic pressure is very large, and since the rotor or the bearing member, which is race-finished with high accuracy, is etched and plated, its accuracy and process control are difficult and defective. easy.

Further, in the case of Japanese Patent Laid-Open No. 4-78313, there is a drawback that it is difficult to obtain the dimensional accuracy of the groove for generating dynamic pressure because it is formed by using an injection molding die or ball rolling.

The present invention is relatively easy to manufacture,
Moreover, it is an object of the present invention to provide a dynamic pressure bearing that does not cause seizure.

[0009]

To achieve the above object, the present invention provides a spiral dynamic pressure on either or both of the opposing bearing surfaces of a rotor and a bearing member that rotatably supports the rotor. In a dynamic pressure bearing device that is provided with a groove for generating pressure to increase the fluid pressure in the bearing gap to support the bearing load by the action of the groove for generating dynamic pressure during rotation, provide a groove for generating dynamic pressure on the circumferential surface of the bearing member or rotating body. It is formed by printing.

Further, in the dynamic pressure bearing device of the present invention, the dynamic pressure generating grooves are printed by using a paste material in which PTFE fine particles are dispersed in a polyamide-imide resin.

Further, according to the method of processing a dynamic pressure bearing device of the present invention, a resin material is printed on the peripheral surface of the bearing member or the rotating body to cover it with a resin layer, and a groove for dynamic pressure generation is formed between the resin layers. The resin layer is formed, and the resin layer is cured and then turned to obtain a predetermined outer diameter dimension.

[0012]

Therefore, the dynamic pressure generating groove is formed by the resin layer printed on the peripheral surface of the rotor or the bearing member. For example, a resin layer is printed on a portion other than a portion corresponding to the dynamic pressure generating groove, and a portion between the resin layers where the resin layer does not exist is formed as the dynamic pressure generating groove. After the resin layer is cured, the machining allowance is removed by turning to obtain a predetermined outer diameter. At the same time, a dynamic pressure generating groove having a predetermined depth is obtained.

Further, since the portion of the rotor or the bearing member that comes into contact with the other side is covered with the resin layer, the slidability is improved and seizure is eliminated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings. The present embodiment is applied to a motor for rotating a polygon mirror used in an optical scanning device such as a laser printer or a facsimile at high speed.

FIG. 2 shows an embodiment of a polygon mirror driving motor incorporating the dynamic pressure bearing of the present invention. This polygon mirror driving motor has a cylindrical rotating body (rotor) 2 that supports the polygon mirror 1, and a cylindrical body that fits the rotating body 2 to form a hydrodynamic bearing between the rotating body 2. -Shaped bearing member 5, a driving core (coil) 9 that is installed in the center of the bearing member 5 and that constitutes a stator set, and a driving magnet 10 that is fixed to the inner peripheral surface of the rotating body 2 and that constitutes a rotor set. It is mainly composed of Coil 9 and magnet 10
The motor 3 is constituted by and. Between the rotor set and the stator set, for example, the upper ends of the iron cores 8 and the rotor 2 are respectively provided with magnets 11 and 12 which constitute magnetic crust bearings for levitating the rotor 2 in the axial direction. The magnets 11 and 12 levitate the rotating body 2 by its attractive force,
The rotor set and the stator set are supported so as not to come into contact with each other in the thrust direction. A rotating object such as the polygon mirror 1 is attached to the rotating body 2. The polygon mirror 1 attached to the upper part of the rotating body 2 is pressed by the balancer 13 via the disc spring 14 and fixed to the rotating body 2. Further, the polygon mirror 1 is covered with a cover 6 composed of a flange 6a of the bearing member 5 and an upper lid 6b fixed to the flange 6a.

On the outer peripheral surface of the rotating body 2, as shown in FIG. 4, a spiral dynamic pressure generating groove 15 for generating dynamic pressure is provided.
Is printed to 5 μm to 20 μm by lace processing
Is formed with a depth of. The dynamic pressure generating groove 15 is formed by a resin layer, for example, a polyamide-imide resin layer 7 in which PTFE fine particles are dispersed.

The rotating body 2 and the cylindrical bearing member 1 are made of aluminum (including aluminum alloy). An alumite layer is formed on the inner peripheral surface of the bearing member 1, that is, the bearing surface 1a. The outer peripheral surface of the rotating body 2 is covered with the resin layer 7 to form a dynamic pressure generating groove 15. The dynamic pressure generating groove 15 is formed as follows.

First, the outer peripheral surface of the rotating body 2 is subjected to a rough finish by lacing (turning) to a roughly outer diameter. Then, in order to improve the adhesion strength of the material, the rotating body 2
The outer peripheral surface is chemically treated with plain material. After that, a paste material in which the PTFE particles are dispersed based on the polyamide-imide resin is printed on the outer peripheral surface of the rotating body 2 using a screen printing machine. At this time, by forming an arbitrary groove pattern on the screen plate, the dynamic pressure generating groove 15 having a desired pattern shape is formed by the paste material in the rotating body 2.
Is formed on the outer peripheral surface of the. The dynamic pressure generating groove 15 is formed between layers of the paste material on the surface of the rotating body 2 as shown in FIG. After printing is completed, as shown in FIG. 1 (B), the paste material is cured, and then the surface thereof is finished by lace processing, and the dynamic pressure generating groove 15 having a predetermined depth and the rotating body having a predetermined outer diameter dimension are formed. Form 2.

It should be noted that the above-mentioned embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the resin layer 7 is applied to the surface of the rotating body 2 by screen printing, but the present invention is not limited to this and may be applied by another printing method such as offset printing. , Bearing member 5
You may make it print on the inner peripheral surface side. Furthermore, the resin to be printed is not particularly limited to the above-mentioned polyamide-imide resin, and other resins having a low friction coefficient and good slidability may be adopted.

[0020]

As is clear from the above description, the dynamic pressure bearing device of the present invention has the dynamic pressure generating groove formed by printing on the peripheral surface of the bearing member or the rotary member, so that the dynamic pressure generating device can be used. Grooves can be easily processed. In addition, since the surface of the rotor or the bearing member is covered with the resin layer functioning as a lubricant, the slidability is improved, and seizure is eliminated even if a shock or a change in posture occurs during rotation.

Further, in the case of the second aspect of the present invention, the PTFE fine particles dispersed in the polyamide-imide resin provide better slidability.

Further, in the case of the third aspect of the invention, since the final finishing process is performed after the resin layer is formed by printing, the allowable range of the dimensional accuracy in the preceding step, that is, the turning step of the rotating member or the bearing member is widened. , You can get stable quality. Therefore, according to the present invention, the seizure load can be improved in a range where the control of the bearing clearance is relatively easy, and seizure becomes difficult.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a structure of a groove for dynamic pressure generation, which is a main part of a dynamic pressure bearing device of the present invention, and an example of a manufacturing method thereof. FIG. 1A shows a state in which a resin layer is formed by printing, and FIG. Shows a state in which the groove for dynamic pressure generation is finished by turning the resin layer.

FIG. 2 is a central vertical cross-sectional view showing an embodiment of a polygon mirror motor to which a dynamic pressure bearing device of the present invention is applied, showing a right half of a rotating body in section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bearing member 1a Bearing surface of bearing member 2 Rotating shaft 2a Bearing surface of rotating shaft 7 Resin layer 15 Dynamic pressure generating groove

Claims (3)

[Claims] 1. A spiral dynamic pressure generating groove is provided on one or both of opposing bearing surfaces of a rotating body and a bearing member that rotatably supports the rotating body, and the dynamic pressure generating groove is used during rotation. In the dynamic pressure bearing device for increasing the fluid pressure in the bearing gap to support the bearing load, the dynamic pressure generating groove is formed by printing on the peripheral surface of the bearing member or the rotating body. Dynamic bearing device. 2. The dynamic pressure bearing device according to claim 1, wherein the dynamic pressure generating groove is formed by printing using a paste material in which PTFE fine particles are dispersed in a polyamideimide resin. 3. A bearing member or a rotating member is printed with a resin material on the peripheral surface thereof to be covered with a resin layer, and dynamic pressure generating grooves are formed between the resin layers, and the resin layer is hardened and then turned. A method of processing a dynamic pressure bearing device, which comprises processing to obtain a predetermined outer diameter dimension.