JPH0560134A - Fluid bearing motor - Google Patents

Abstract

PURPOSE:To provide a fluid bearing motor capable of preventing the occurrence of the vibration of a shaft for pivotally supporting a rotor when the rotor is rotated at a high speed and capable of reducing the outer size of the whole motor. CONSTITUTION:A rotating force generating means formed with rotating magnetic field generation sections 8, 9 and a magnet 6 fixed to the first base 3 to be located in a rotor 5 and a bearing means in the radial direction R supported by the first and second bases 3, 4 and formed with a main spindle 1 having a fluid groove section 1a and a sleeve 2 are provided. A receiving member 7 having a fluid groove section 7b on the face and fixed to the main spindle 1 and a bearing means in the thrust direction T formed with the ceiling section of the rotor 5 are provided. The receiving member 7 is brought into contact with the outside face by the magnetic attraction component (direction A) of the rotating force generating means when the rotor 5 is stationary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid dynamic bearing motor,
For example, it is suitable for a brushless motor that is particularly small and requires high precision and high-speed rotation, such as a mirror driving unit of a laser scanner used in a document reading device, a spindle motor of a hard magnetic disk device, and a head driving motor of a video device. The present invention relates to a fluid dynamic bearing motor.

[0002]

2. Description of the Related Art A brushless motor having excellent performance can be realized by using a fluid bearing in a rotary bearing portion of a motor which is required to be small in size, high in precision and high in speed. The proposal is made for the fluid bearing of the publication. FIG. 4 is a cross-sectional view of a main part of the present proposal, and a schematic description will be given with reference to this figure. A main shaft 100 having a large number of fluid groove portions 100a formed on the outer peripheral surface is fixed to a base 30 in a single-supported state. .. Further, the base 30 is provided with a rotating magnetic field generating means, which is composed of a core 8 and a coil 9 laminated for generating a rotating magnetic field, in an annular shape.

On the other hand, the rotor 20 having the permanent magnet 60 fixed to the outer peripheral surface is formed in a cylindrical shape and has a porous body 21.
Is integrally provided in the ceiling portion, and is inserted into the main shaft 100 as shown in the figure to support the radial direction R and the thrust direction T. In the configuration described above, when a rotating magnetic field is generated in the rotating magnetic field generating means, high-speed rotation of the rotor 20 is started as the permanent magnet 60 is attracted. Before or after this, air or the like is drawn in the direction of arrow H in the figure. As a result of the fluid being introduced between the main shaft 100 and the inner diameter surface of the rotor 20, retention in the radial direction R is performed using the fluid as a medium. This fluid is further introduced between the end portion of the main shaft 100 and the porous body 21 to exhaust the excess fluid in the direction of arrow K to support the thrust direction T while maintaining an appropriate interval. This proposal is particularly easy to assemble and has been put to practical use for rotating a polygon mirror of a laser printer.

[0004]

However, according to the above proposal, since the main shaft is cantilevered with respect to the base, it is necessary to increase the shaft rigidity. In order to increase the shaft rigidity, the shaft diameter is increased. However, there is a problem in that the outer shape of the entire motor becomes large when is increased. Further, when the rotor is rotated at a high speed, there is a problem that shaft vibration occurs if there is a poor dynamic balance of the rotor. Therefore, the fluid dynamic bearing motor of the present invention has been made in view of the above problems, and an object thereof is to prevent generation of shaft vibration for rotor shaft support when rotating a rotor at a high speed, and It is an object of the present invention to provide a fluid dynamic bearing motor whose outer dimensions can be reduced.

[0005]

[Means for Solving the Problems] and

In order to solve the above problems and achieve the purpose,
The hydrodynamic bearing motor of the present invention is a hydrodynamic bearing motor in which the radial direction bearing means and the thrust direction bearing means of a hat-shaped rotor that rotates around a main shaft of a base are constituted by fluid bearings, and are located inside the rotor. As described above, the rotating force generating means formed by the rotating magnetic field generating portion fixed to the base and the magnet provided on the inner peripheral surface of the rotor, and the fluid supported on the outer peripheral surface both supported by the base. The radial direction bearing means formed by the main shaft having a groove portion and a sleeve fixed to a rotation center portion of the rotor and inserted and supported by the main shaft; and a fluid groove portion on the surface and fixed to the main shaft. The thrust direction bearing means formed by the receiving member and the outer surface portion of the ceiling portion of the rotor, and the magnetic attraction of the rotational force generating means when the rotor is stationary. As well as the outer surface and the receiving member in the contact state by the force, during rotation of the rotor and the radial bearing means, fluid to the thrust direction bearing means serve to function a fluid bearing is appropriately introduced.

Further, preferably, a first labyrinth portion formed between the receiving member and the outer surface of the ceiling portion and a second labyrinth portion formed between the base and the cylindrical edge portion of the rotor are provided. Further, it is provided and acts to prevent the lubricating fluid from scattering outside the rotor. Further, preferably, a holding means for the magnetic fluid is provided in the outer peripheral edge portion of the receiving member, and an annular convex portion is further formed at the edge portion of the outer surface of the ceiling portion to form a magnetic seal.
It works to prevent the lubricating fluid from splashing outside.
Further, preferably, the outer surface portion of the rotor is integrally formed with the sleeve to reduce the number of parts and the number of assembling steps. Then, the outer side surface portion is formed by a member different from the sleeve, and a fluid groove portion is formed in the different member to be integrated with each other to reduce the cost.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a central cross section of the fluid dynamic bearing motor of the first embodiment, which includes a polygon mirror, a magnetic head,
The spindle and other parts for performing a predetermined operation are omitted and shown, and only the basic components are shown.

In the figure, the end of the main shaft 1 has a mounting hole 3
It is press-fitted or the like to the first base 3 having a formed therein and is vertically provided integrally. A large number of helibone-shaped fluid grooves 1a are specially processed on the outer peripheral surface of the main shaft 1, while a threaded portion 1b is formed on the other end of the main shaft 1, and a mounting hole 4a is formed as shown in the drawing. The main shaft 1 is fixed to both the first and second bases by being inserted into the perforated second base 4 and then fixed with the screw 12. Therefore, the first and second bases are integrally configured via the connecting member 10 and the like.

Next, FIG. 2 is a view taken in the direction of arrow XX in FIG. 1, showing a state on the surface of the receiving member 7 fixed to the main shaft 1. As shown in FIG. Has a circular ring shape, and a large number of helibone-shaped fluid groove portions 7b are formed concentrically with respect to the mounting hole portion 7d of the main shaft 1, while a convex portion 7a forming a labyrinth portion described later is formed concentrically. ing.

Again, in FIG. 1, the receiving member 7 is fixed to a predetermined position in the axial direction of the main shaft 1 by using a screw or the like (not shown), and a hub portion 7c is integrally formed. next,
The first base 3 is provided with a core mounting portion 3h that is concentric with the spindle 1, and a labyrinth recess 3b that forms a labyrinth portion, which will be described later, concentrically. A coil 9 is wound around the core 8 made of laminated magnetic plates,
While forming a rotating magnetic field generating part, it is positioned and fixed to the core mounting part 3h.

Next, the hat-shaped rotor 5 rotatably supported by the above-mentioned main shaft 1 has a shape in which the above-mentioned rotating magnetic field generating portion is incorporated. On the other hand, at the center of rotation of the rotor 5, a through hole 2a and a flange 2b having an inner diameter larger than the outer dimension of the main shaft 1 by a predetermined clearance.
The sleeve 2 integrally formed with is fixed to form a bearing portion in the radial direction R, and the flange portion 2b is integrally formed so as to face the fluid groove portion 7b of the receiving member 7 described above. It forms the bearing.

Further, the permanent magnet 6 positioned on the outer circumference of the rotating magnetic field generating portion and attracted by the rotating magnetic field is multi-polarized to a predetermined number of poles, and the inner peripheral surface of the rotor 5 is as shown in the figure. It is fixed. Here, the permanent magnet 6 is located slightly displaced from the core 8 on the first base 3 side, and the rotor 5 is supported by the component 7 of the magnetic attraction force generated between the permanent magnet 6 and the core 8. As a result of moving the rotor 5 to the side, the flange portion 2b of the sleeve 2 and the fluid groove portion 7b of the receiving member 7 are brought into contact with each other when the rotor 5 is stationary.

On the other hand, a labyrinth groove portion b is formed on the outer side of the ceiling portion of the rotor 5 concentrically with the sleeve 2 so as to enter the convex portion 7a of the receiving member 5.
While forming the labyrinth, the labyrinth convex portion 5a is formed at the edge portion of the cylindrical portion of the rotor 5, and the second labyrinth is formed so as to enter the labyrinth concave portion 3b of the first base 3. The first and second labyrinths prevent the fluid lubricant and the like contained in the rerotator 5 from scattering to the outside, while preventing foreign matter such as dust from entering.

In the structure described above, when the rotating magnetic field acts on the rotating magnetic field generating portion, the rotor 5 is rotated. With this rotation, the internal pressure of the thrust bearing portion rises due to the action of the fluid groove portion. The fluid bearing in the thrust direction T is formed by balancing the contact state and the receiving member 7 from the contact state. Further, the internal pressure between the outer peripheral surface of the main shaft 1 and the through hole 2a of the sleeve 2 also rises due to the action of the fluid groove portion 1a. As a result, the sleeve 2 and the main shaft 1 are balanced in a separated state to form a fluid bearing in the radial direction R. .. As a result of the above configuration, it is possible to prevent the vibration of the spindle 1 from occurring due to the high speed rotation of the rotor 5. Further, even if the diameter of the main shaft 1 is reduced, the rigidity of the shaft can be secured, so that the degree of freedom in design can be increased and the outer shape of the entire motor can be reduced.

Next, FIG. 3 (a) is a central sectional view of the second embodiment, and since it has substantially the same structure as the above-mentioned structure, the same portions as those in FIG. Will be omitted and only the differences will be described. First, the labyrinth grooves 3b of the first base 3 are provided in two rows as shown in the drawing, and the two rows of the labyrinth convex portions 5a of the rotor 5 are infiltrated into the grooves as shown in the drawing to improve airtightness. Form a high labyrinth. Further, while the labyrinth concave portion 7f is formed in the receiving member 7, the labyrinth convex portion 5f is formed on the rotor 5 side, and the labyrinth convex portion 5f on the rotor 5 side infiltrates into the labyrinth concave portion 7f to prevent the labyrinth. Is forming.

On the other hand, on the outer peripheral edge of the receiving member 7, a magnetic fluid holding portion 1 composed of an iron plate for adsorbing and holding a magnetic fluid and a magnet.
1 is provided, and an annular convex portion 5e is integrally formed from the outer peripheral edge portion of the ceiling portion of the rotor 5. By flowing the magnetic fluid between the magnetic fluid holding portion 11 and the convex portion 5e, the inside can be kept more airtight. Also, FIG.
As shown in (b), the surface of the sleeve 2 facing the receiving member 7 side is formed by another member 22, and the above-mentioned fluid groove portion is formed in this other member 22, and the receiving member 7 side is formed into a smooth surface. Alternatively, the thrust bearing portion may be formed by processing. Second of the above
Also in the embodiment, the same function as the operation of the first embodiment is performed, and the consumption of the liquid lubricant stored inside can be greatly reduced.

[0017]

As described above, according to the fluid dynamic bearing motor of the present invention, it is possible to prevent the shaft vibration for the rotor shaft support from occurring when the rotor is rotated at a high speed and to reduce the outer dimensions of the entire motor. There is.

[Brief description of drawings]

FIG. 1 is a central cross section of a fluid dynamic bearing motor according to a first embodiment.

FIG. 2 is a view on arrow XX in FIG.

3A is a center sectional view of the second embodiment, and FIG. 3B is a center sectional view of a sleeve 2. FIG.

FIG. 4 is a hydrodynamic bearing disclosed in Japanese Patent Laid-Open No. 63-214518 of the applicant of the present application.

[Explanation of symbols]

 1 main shaft, 2 sleeves, 3 1st base, 4 2nd base, 5 rotors, 6 permanent magnets, 7 receiving members, 8 cores, 9 coils, 11 magnetic fluid holding | maintenance parts, 12 screws.

Claims (5)

[Claims] 1. A hydrodynamic bearing motor comprising a radial bearing means and a thrust bearing means of a hat-shaped rotor that rotates around a main shaft of a base, which are fluid bearings. The hydrodynamic bearing motor is located inside the rotor. As described above, the rotating force generating means is formed by the rotating magnetic field generating portion fixed to the base and the magnet provided on the inner peripheral surface of the rotor, and both are supported by the base and the fluid is formed on the outer peripheral surface. The radial direction bearing means formed by the main shaft having a groove portion and a sleeve fixed to the rotation center portion of the rotor and inserted and supported by the main shaft; and a fluid groove portion on the surface and fixed to the main shaft. A thrust direction bearing means formed by a receiving member and an outer surface portion of the ceiling portion of the rotor, wherein the magnetic attraction component force of the rotational force generating means when the rotor is stationary. Fluid dynamic bearing motor, characterized by more the receiving contact state of the outer surface with a member. 2. A first labyrinth portion formed between the receiving member and the outer surface of the ceiling portion, and a second labyrinth portion formed between the base and the cylindrical edge portion of the rotor.
The hydrodynamic bearing motor according to claim 1, further comprising a labyrinth portion. 3. A magnetic seal is formed by providing magnetic fluid holding means at the outer peripheral edge of the receiving member, and further forming an annular convex portion at the edge of the outer surface of the ceiling portion. The fluid dynamic bearing motor according to claim 1 or 2. 4. The fluid dynamic bearing motor according to claim 1, wherein the outer surface portion of the rotor is integrally formed with the sleeve. 5. The fluid according to claim 1, wherein the outer side surface portion is formed of a member different from the sleeve, and a fluid groove portion is formed in the different member to be integrated. Bearing motor.