JPH01154116A - Rotating body supporting device - Google Patents

Abstract

PURPOSE:To increase bearing rigidity in axial direction and to reduce rotational deflection by concentrically positioning a spiral groove which generates dynamic pressure by means of the rotation of a rotating body and a spiral groove which generates vacuum of atmospheric pressure or less and composing a dynamic pressure thrust. CONSTITUTION:The spiral groove 23a which generates the dynamic pressure by the rotation of the rotating body 21 and the spiral groove 23b which generates vacuum of atmospheric pressure or less are concentrically positioned on the upper surface of a base table 11 or the bottom surface of the rotating body 21, and the dynamic pressure thrust bearing is composed. When a rotating assembly body 16 is rotated at high speed, vacuum is created inside of the dynamic pressure thrust bearing by the spiral groove 23b which generates vacuum of atmospheric pressure of less, and the rotating assembly 16 is attracted downward so that flotation quantity is reduced. Thus, the bearing rigidity in the axial direction, which is reverse proportional to the square of the bearing space, is improved with the simple composition, and the rotational deflection is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotating body support device that rotatably supports a rotating body mounted on a fixed shaft.

Conventional technology In recent years, with the development of office equipment, printer-related equipment that records and prints information is required to be faster, smaller, and lower in cost. Printers with good print quality and high speed are emerging.

-JG This laser beam printer uses a rotating polyhedral mirror light deflector to scan laser light emitted from a semiconductor laser light source, forms an electrostatic latent image on a photoreceptor, and outputs a print using an electrophotographic process. It is configured.

Since the rotating polyhedral optical deflector mainly determines the printing quality and high speed of a laser beam printer, it is required to support the rotating body at high speed and with high precision. To date, rotor support devices using dynamic pressure air bearings have been developed to meet this requirement.

We have already proposed an example of a high-speed and thin rotating body supporting device in which a rotating body supporting device as shown in Japanese Patent Application No. 62-5301 is applied to a rotating polyhedral optical deflector. Hereinafter, an application example of this prior application will be explained with reference to the drawings. FIG. 3 shows a sectional view of a rotating polyhedral optical deflector using this rotating body support device.

In FIG. 3, reference numeral 51 is a rotating body having a flange-like shape and having a center of rotation in the vertical direction, and a rotating polyhedral mirror 52 is in contact with the upper surface 51a of the flange portion and fixed by means such as adhesive. Reference numeral 53 designates a ring-shaped rotor magnet, which is bonded to a bank yoke 54 made of a soft magnetic material and magnetized with multiple poles in the direction of the rotation axis.
is in contact with the upper surface of the rotating polyhedral mirror 52 and fixed by adhesive or other means. Further, the diameters of the flange portion of the rotating body 51 and the back yoke 54 are made larger than the outer diameter of the rotating polygon mirror 52. In other words, the rotating polygon mirror 52 is connected to the flange portion of the rotating body 51 having a larger diameter and the back yoke 54.
It's stuck in.

55 is a sub-rotor made of soft magnetic material;
It is arranged with a certain gap in the axial direction from the rotor magnet 53 so that the magnetic flux from the rotor magnet flows therethrough, and is fixed to the rotating member 52 by adhesive or other means. That is, the rotating body 51, the rotating polyhedral mirror 52, the rotor magnet 53, the back yoke 54, and the sub-rotor 55 are fixed to each other and constitute a rotating assembly 56.

A smooth bottom surface portion 51b is formed on the lower end surface of the flange portion of the rotating body 51, and a base 61 having a smooth surface 61a is arranged opposite to the bottom surface portion 51b. Further, a spiral groove 63 is formed in the flat surface 61a of the base 61 in a direction in which air is sucked from the outermost periphery to the inner periphery of the rotary assembly as the rotary assembly 56 rotates. Also, 61b
is a seal that prevents air from flowing out. As a result, the dynamic pressure thrust bearing is configured to face the bottom surface portion 51b of the rotating member 51. In addition, the portions of the bottom surface portion 51b that are not involved in the dynamic pressure air bearing are provided with a pad 51c. Also,
61C is a pressure regulating hole that communicates with the outside from this hollow hole 51c.

A fixed shaft 60 is fixed to the center of the base 61 by press-fitting or the like, and the rotary assembly 56 is rotatably mounted on the fixed shaft 60 with a certain gap between the outer circumference of the fixed shaft and the fixed shaft 60. A herringbone groove 62 is formed at one location on the circumferential surface of the fixed shaft with an arrow-shaped tip facing in the direction of rotation of the rotating assembly 56, thereby forming a hydrodynamic radial bearing.

In addition, on the lower surface of the flat portion 51b of the rotating member 51 on the outside and inside the outermost diameter, and on the upper surface of the sub-rotor 55 inside the outermost diameter, there are grooves 57 for attaching weights for adjusting the dynamic balance Y. 58 is formed, and the dynamic balance can be adjusted with the rotating assembly 56 assembled.

Further, 65 is a fixed coil board fixed to the morph frame 64 with screws 71.

In the rotating polyhedral optical deflector configured as described above, by energizing the fixed coil substrate 65, rotation torque is generated in the magnetic flux in the air gap between the rotor magnet 53 and the sub-rotor 55, and the rotation assembly 56 is rotationally driven. The bottom surface portion 51b of the zero-rotating body 51 and the opposing portion of the flat surface portion 61a of the base 61 are in contact with each other, but immediately, due to the action of the spiral groove 63, air flows in and air pressure is generated, and the rotating assembly 56 It is supported without contacting the base 61 and rotates at high speed with low loss. Similarly, the rotating body 51 and the fixed shaft 6
Due to the function of the herringbone groove 62, air flows into the gap at 0, generating air pressure, and the fixed shaft 60 and rotating assembly 56
When the six-rotation assembly is stopped, which is supported in a non-contact state in the radial direction, air pressure decreases as the rotational speed decreases, and the opposing portions of the bottom surface 51b of the rotor 51 and the flat surface 61a of the base 61 come into contact with each other. state and stops.

Problems to be Solved by the Invention It is generally known that the bearing stiffness of a hydrodynamic bearing is inversely proportional to the square of the bearing gap. Therefore, it is desirable that the bearing gap, ie, the flying height, be small to some extent. However, in the above configuration, when the rotating assembly 56 rotates at a high speed, the air flowing in through the spiral groove 63 causes the rotating assembly 56 to float significantly, increasing the gap in the bearing and reducing the bearing rigidity in the axial direction. Therefore, unless the dynamic balance of the rotating assembly is adjusted very strictly, there is a problem in that the rotational runout becomes large.

In order to solve this problem, there are ways to reduce the flying height and improve bearing rigidity by increasing the tN of the rotating assembly or reducing the area of the hydrodynamic thrust bearing. However, when the rotating assembly is started or stopped, damage to the bearing due to friction is large and the life of the bearing is shortened, which is a new problem.

Means for Solving the Problems In order to solve the above problems, the rotation support device of the present invention includes:
On the top surface of the base or the bottom surface of the rotating body, a spiral groove that generates dynamic pressure by the rotation of the rotating body and a spiral groove that generates a vacuum below atmospheric pressure are arranged concentrically, forming a dynamic pressure thrust bearing. are doing.

Operation The present invention provides that, when the rotating assembly rotates at high speed, the spiral groove that generates a vacuum below atmospheric pressure creates a vacuum inside the hydrodynamic thrust bearing and sucks the rotating assembly downward, by the above means. Reduce the floating height. Therefore, with a very simple configuration, it is possible to increase the bearing rigidity in the axial direction, which is inversely proportional to the square of the bearing gap, and to reduce rotational runout.

EXAMPLE Hereinafter, an example of a rotating polyhedral mirror light deflector using a rotating body support device according to the present invention will be described with reference to the drawings. FIG. 1 shows a sectional view of a rotating polyhedral mirror light deflector in an embodiment of the present invention, and FIG. 2 shows an exploded perspective view.

In FIG. 1, 1) is a rotating body having a flange-like shape and having a center of rotation in the vertical direction, and a rotating polygon mirror 12 is in contact with the upper surface 1)a of the flange portion and fixed by means such as adhesive. There is. Reference numeral 13 denotes a ring-shaped rotor magnet, which is bonded to a back yoke 14 made of a soft magnetic material and magnetized with multiple poles in the direction of the rotation axis.
is in contact with the upper surface of the rotating polyhedral mirror 12 and fixed by adhesive or other means. Further, the diameters of the flange portion of the rotating body 1) and the back yoke 14 are made larger than the outer diameter of the rotating polygon mirror 12. In other words, the rotating polygon mirror 12 is a flange portion of the rotating body 1) having a larger diameter and a back yoke 14.
It's stuck in.

15 is a sub-rotor made of soft magnetic material;
It is arranged with a certain gap in the axial direction from the rotor magnet 13 so that the magnetic flux from the rotor magnet flows therethrough, and is fixed to the rotating body 12 by adhesive or other means. That is, the rotating body 1), the rotating polygon mirror 12, the rotor magnet 13, the back yoke 14, and the sub-rotor 15 are fixed to each other and constitute a rotating assembly 16.

A smooth bottom surface portion 1)b is formed on the lower end surface of the flange portion of the rotating body 1), and a base 21 having a smooth surface 21a is arranged opposite to the bottom surface portion 1)b. Further, a spiral groove 23a is formed in the flat surface 21a of the base 21 in a direction that draws air from the outermost periphery to the inner periphery of the rotary assembly as the rotary assembly 16 rotates. Also, 21
b is a seal portion that prevents air from flowing out. As a result, the bottom part 1) b of the rotating body 1) and the smooth plane 21 of the base 21
The bearings a are opposed to each other and constitute a dynamic pressure thrust bearing. Further, on the inner circumference of the spiral groove 23a, there is a spiral groove 23b formed in a direction in which air is sucked out from the innermost circumference of the rotating body to the outer circumference by the rotation of the rotating assembly 16, and is opposed to the bottom surface part 1) b of the rotating body. This creates a vacuum below atmospheric pressure.

Further, 21c is a seal portion that prevents air from flowing in. The directions of zero or more two sets of spiral grooves are shown in the exploded perspective view of FIG. 2. In this embodiment, the rotating assembly 16 is clockwise when viewed from above.

Further, 23c is a deep groove, and 21d is a pressure regulating hole connecting the inside of the bearing to the atmosphere, where the air sucked out by the spiral groove 23b has the same pressure as the atmospheric pressure.

A fixed shaft 20 is fixed to the center of the base 21 by press-fitting or the like, and the rotary assembly 16 is rotatably mounted on the fixed shaft 20 with a certain gap between the outer circumference of the fixed shaft and the fixed shaft 20. A herringbone groove 22 is formed at one location on the circumferential surface of the fixed shaft with an arrow-shaped tip facing in the direction of rotation of the rotating assembly 16, thereby forming a hydrodynamic radial bearing.

In addition, near the joint between the base 21 and the fixed shaft 20, there is a pressure regulating hole 21e that connects the inside of the bearing and the atmosphere.
The lower end of the cylindrical part is at the same pressure as atmospheric pressure.

Also, on the lower surface of the flat part 1) b of the rotating body 1) on the outside and inside the outermost diameter, and on the upper surface of the sub-rotor 15 inside the outermost diameter, there are grooves for attaching weights for adjusting the dynamic balance. 17 and 18 are formed, and the dynamic balance can be adjusted with the rotating assembly 16 assembled.

In the exploded perspective view of the embodiment shown in FIG. 2, reference numeral 25 denotes a fixed coil board 25a125b which is fixed to the motor frame 24 with a mounting screw 31 and can be divided into two parts, and includes a plurality of flat coils 26 and a rotor magnet. It is composed of a position detection sensor 27 and a printed circuit board 28. In this example, a flexible printed circuit board is used as the printed circuit board 28. A plurality of flat coils 26 and a rotor magnet position detection sensor 27 are wired on a printed circuit board 28 and further molded with resin 30.

In the rotating polyhedral mirror light deflector configured as described above, by energizing the fixed coil substrate 25, rotation torque is generated in the magnetic flux in the air gap between the rotor magnet 13 and the sub-rotor 15, and the rotation assembly 16 is rotationally driven. . Said rotating body 1)
The bottom surface 1)b of the base 21 and the facing portion of the flat surface 21a of the base 21 are in contact with each other, but immediately, due to the action of the spiral groove 23a, air flows in and air pressure is generated, and the rotating assembly 1
6 is supported in a non-contact state with the base 1).

In addition, air flows into the gap between the opposing part of the rotating body 1) and the fixed shaft 20 due to the action of the herringbone groove 22, and air pressure is generated, and the rotating assembly 16 is non-uniform with respect to the fixed shaft 20 in the radial direction. It is supported in contact and rotates at high speed with low loss. Further, in the inner peripheral part of the spiral groove 23a, at the opposing part between the bottom surface 1)b of the rotating body 1) and the flat surface 21a of the base 21, the pressure regulating hole 2
Since the air flows out from 1d and creates a vacuum below atmospheric pressure, the rotating assembly 16 is sucked downward, reducing the flying height. Therefore, the bearing stiffness in the axial direction is inversely proportional to the square of the bearing gap. becomes larger and rotational runout becomes smaller.

Effects of the Invention As described above, the rotation support device of the present invention has a spiral groove on the top surface of the base or the bottom surface of the rotating body that generates dynamic pressure by the rotation of the rotating body, and a vacuum that is below atmospheric pressure. Since the spiral grooves are arranged concentrically to form a hydrodynamic thrust bearing, the flying height of the rotating body is reduced, and the bearing stiffness in the axial direction, which is inversely proportional to the square of the bearing gap, is increased, reducing rotational runout. becomes smaller. As a result, the dynamic balance does not need to be adjusted with high accuracy, and the adjustment becomes easy. Furthermore, even if vibration or impact force is applied to the rotating polyhedral mirror optical deflector, the bearing rigidity is large, so
The rotating body is kept stable and rotates with high precision.

Further, since there is no need to increase the mass of the rotating assembly or reduce the area of the hydrodynamic thrust bearing, even if the bearing rigidity is increased, the lifespan will not be reduced due to friction.

In addition, spiral grooves that generate a vacuum below atmospheric pressure can be made by etching or other methods at the same time as spiral grooves that generate dynamic pressure, so it is easy to create a means to increase rigidity, and it is extremely cost-effective. Excellent.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a rotating polygon mirror light deflector using the rotating body support device of the present invention, FIG. 2 is an exploded perspective view of the rotating polygon mirror light deflector in an embodiment of the present invention, and FIG. FIG. 2 is a cross-sectional view of a rotating polyhedral mirror light deflector using the rotating body support device of the prior application. 1)...Base, 21...Rotating body, 20
...Fixed shaft, 23a...Spiral groove that generates dynamic pressure, 23b...Spiral groove that generates vacuum below atmospheric pressure, 22...Hering Bone groove. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 2

Claims (3)

[Claims] (1) Consisting of a base, a fixed shaft with one end fixed to the base, a cylindrical part covered with the fixed shaft, and a rotating body having a bottom face facing the base, and the top face of the base or Means for generating dynamic pressure by the rotation of the rotating body and means for generating a vacuum below atmospheric pressure are arranged concentrically on the bottom surface of the rotating body, forming a dynamic pressure thrust bearing. Characteristic rotating body support device. (2) The means for generating dynamic pressure is a spiral groove formed in the direction of sucking air from the outermost circumference to the inner circumference of the rotating body as the rotating body rotates, and the means for generating a vacuum below atmospheric pressure, the dynamic pressure Claim (1) is characterized in that the spiral groove is located further inner than the spiral groove that generates the air and is formed in a direction to suck out air from the innermost circumference to the outer circumference of the rotating body. rotating body support device. (3) A herringbone groove that generates dynamic pressure due to the rotation of the rotating body is formed on the outer peripheral surface of the fixed shaft or the inner peripheral surface of the rotating body opposite to the outer peripheral surface, thereby forming a dynamic pressure radial bearing. A rotating body support device according to claim (1), characterized in that: