JPH0635650Y2 - Dynamic air bearing motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a motor that supports a rotor portion by a dynamic pressure air bearing. More specifically, the present invention relates to a dynamic pressure air bearing motor suitable for use in a motor that rotates at high speed, particularly a motor of an optical scanning device that rotates a polygon mirror or the like.

(Prior Art) A motor that rotates at a high speed, such as a laser scanning motor, a magnetic drum motor, a gyro motor, or a high-speed spindle motor, has a dynamic pressure air that supports a rotor portion with a dynamic pressure due to a relative motion based on the rotation. Bearings are used. For example,
In an optical scanning device using a polygon mirror used in a laser beam printer, a facsimile, etc., when the polygon mirror vibrates when a disturbance such as vibration is received, the optical scanning line is disturbed and the image quality is deteriorated. A dynamic pressure air bearing motor as shown in FIG. 7 is used.

In this dynamic pressure air bearing motor, a dynamic pressure bearing 107 is formed between an outer peripheral surface 103 of a rotating body 101 to which a magnet 105 is attached and an inner peripheral surface 106 of a cylindrical bearing member 104 having a coil 102 arranged at the center. While supporting the radial direction, the rotating body
A thrust magnetic bearing 110 utilizing the attraction / repulsion force of the magnets 108, 109 is formed between the 101 and the bearing member 104 to achieve axial (axial) support. Furthermore,
In this dynamic pressure air bearing motor, axial vibration is applied to the magnetic bearing 11
Since it is difficult to suppress it by only 0, an air damper 113 is provided by providing a ventilation hole 113 that communicates the internal closed space 111 formed between the rotating body 101 and the bearing member 104 with the motor outside 112. I try to get the effect. That is, the vibration of the rotating body 101 causes the internal closed space 111 to pass through the ventilation hole 113.
Air flows in and out. Since the small vent holes 111 act as a resistance against the entry and exit of air, they act as a damper against the vibration of the rotating body 101, and suppress the axial vibration of the rotating body 101. The ventilation holes 113, which are small holes, are effective for high-frequency vibrations, and in the case of low-frequency vibrations, air easily passes through the ventilation holes 113 according to the vibrations, so it is not effective as a damper. Low frequency vibrations are suppressed by the thrust magnetic bearing 110.

(Problems to be solved by the invention) The damping characteristics of this dynamic pressure air bearing motor are as follows:
It depends on the diameter and length of the ventilation hole 113 perforated in 1, and it is necessary to control the diameter and length of the ventilation hole 113 according to the mass of the rotating body 101 and the air volume in the motor. However, the size of φ 0.4 × 5 mm is the limit in the current processing technology,
It is difficult to machine a hole that is thinner and longer than this, and when the rotation target 114 mounted on the rotating body 101, for example, the polygon mirror becomes large, there is a problem that it is difficult to control the damping characteristic accordingly.

An object of the present invention is to provide a dynamic pressure air bearing motor structure that can be easily formed even with a thin and long ventilation hole, and to make it possible to change the damping characteristics according to the mass on the rotating body side.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides a rotating body and a cylindrical bearing member for accommodating the rotating body, and the outer peripheral surface of the rotating body and the bearing member. And a stator-side coil fixed to the bearing member by forming a dynamic pressure air bearing between the magnet and the magnet mounted on the inner peripheral surface of the rotating body and concentrically arranged in the center of the bearing member. In a dynamic pressure air bearing motor that constitutes a motor between the shaft and the motor, the internal space formed by the rotating body and the bearing member is a substantially closed space, and the shaft that communicates the internal space with the outside of the motor. The groove forming members for suppressing the directional vibration are formed by groove processing on any of the surfaces where the groove forming members abut each other.

Further, the dynamic pressure air bearing of the present invention makes the internal space formed by the rotating body and the bearing member a substantially closed space, while depending on the mass of the rotating body communicating the internal space with the outside of the motor. A damping plate having a radial slit of a size is interposed between the surfaces where the constituent members abut each other.

(Operation) Therefore, before assembling the components of the dynamic pressure air bearing motor, if a groove that connects the internal closed space and the outside of the motor is machined on any of the abutting surfaces of the components, or a slit corresponding to the groove is formed. By interposing the damping plate, the ventilation hole having a desired diameter and length can be formed only by assembling the dynamic pressure air bearing motor. In addition, the groove processing on the surface in the open state can be performed by a known groove processing technology or slit processing technology, and can be formed in a required width with a width depth of the order of μm or less.

(Embodiment) Hereinafter, the configuration of the present invention will be described in detail based on an embodiment shown in the drawings. The present embodiment is applied to a rotary driving device for a polygon mirror used in an optical scanning device such as a laser printer or a facsimile.

The polygon mirror rotation driving device includes a rotating body (rotor) 1 that supports and rotates a polygon mirror 14, and a cylindrical shape that houses the rotating body 1 and forms a dynamic pressure air bearing 7 between the rotating body 1 and the rotating body 1. Bearing member 4, a center pole 15 disposed in the center of the bearing member 4 for supporting the coil 5, and a base member for supporting the center pole 15 and closing the bottom portion of the bearing member 4.
16 and a small control motor 17 composed of a drive coil 5 fixed to the bearing member 4 side and a rotor magnet 2 fixed to the rotating body 1 side.

The center of gravity of the entire rotating system including the polygon mirror 14 deviates from the axis of rotation on the rotating body 1 due to a processing error of the rotating body 1 or an installation error when the polygon mirror 14 is attached to the rotating body 1, etc. A balance plate 18 for balance adjustment is attached in order to prevent collapse and vibration. The balance plate 18 is made of aluminum, synthetic resin, or the like in a disk shape, and is provided with holes for balance adjustment if necessary.

A shallow and narrow groove 13 is formed by laser beam machining or the like in a portion of the lower surface of the balance plate 18 that abuts the upper end surface of the bearing member 4. It is preferable that the groove 13 is normally formed in a straight line as shown in FIGS. 2A and 2B because it facilitates the processing, but the groove 13 is not particularly limited to this, and for example, as shown in FIG. It is also possible to form grooves 13 on both the balance plate 18 side and the bearing member 4 side to which stepped portions 26 and 27 are fitted and which are fitted together as shown in FIG. It is possible. In this case, it is possible to prevent dust and the like from entering through the groove 13. Further, the length of the groove 13 can be adjusted by inclining the direction of the groove 13, that is, between the radial direction and the tangential direction. The balance plate 18 fixed to the upper end surface of the rotating body 1 simultaneously makes the internal space 11 formed by fitting the bearing member 4 and the rotating body 1 into a substantially closed space. However, this internal space
11 communicates with the outside air through a gap between the groove 13 and the dynamic pressure air bearing 7.

Further, as shown in FIG. 4 and FIG. 5, a damping plate provided with slits 28 communicating with the motor internal space 11 and the motor external 12 without groove processing being performed on the members themselves constituting the dynamic pressure air bearing motor. The ventilation holes may be formed by interposing 29 between components, for example, between the balance plate 18 and the rotating body 1 or between the bearing member 4 and the base member 16. In this case, the damping plate
It is preferable to provide circular holes 30 at both ends of the slit 28 of 29 so as to surely communicate with the internal space 11 and the outside 12 of the motor, or to form a slit that completely traverses the damping plate 29. The size of the ventilation hole can be adjusted by the width of the slit 28 and the thickness of the damping plate 29, and the length can be adjusted by changing the inclination θ of the slit 28.

The bearing member 4 has a bottomed cylindrical shape by fixing a base member 16 to the bottom surface with screws or the like. The inner peripheral surface 6 of the bearing member 4 forms a bearing surface and is surface-treated to improve wear resistance. For example, JP-A-63-235
It is provided to provide an abrasion resistant coating or a lubricious coating as disclosed in No. 719. In addition, an annular peripheral groove 33 for supplying air to the dynamic pressure air bearing 7 formed between the inner peripheral surface 6 of the bearing member 4 and the rotating body 1 is formed.
Is provided so that air is introduced into the motor from the upper end surface of the bearing member 4 through the air holes 34. It is preferable to introduce the air from the periphery of the polygon mirror 14 housed in the housing 31 of the attachment device in order to prevent the entry of dust, but it is not particularly limited to this.
The air holes 34 may be opened directly on the peripheral surface of the bearing member 4. At the position near the upper end of the bearing member 4, the motor is attached to the housing 31 of an optical scanning device such as a laser printer.
A flange 32 is formed for mounting on the same.

The rotating body 1 has a small cylindrical portion 1a for mounting the polygon mirror 14 on an upper end portion protruding outside the bearing member 4, and a large cylindrical portion 1b forming a dynamic pressure air bearing 7 between the rotating member 1 and the bearing member 4.
It is provided so that the polygonal mirror 14 is supported by the shoulder portion 1c at the boundary between and. Large cylindrical portion housed in bearing member 4
Grooves (not shown) for generating dynamic pressure are formed in the outer peripheral surface 3 of 1b by etching or the like to a depth of about 5 μm to 20 μm. The shape and arrangement of the groove are not particularly limited, and the outer peripheral surface 3 where the groove is formed similarly to the inner peripheral surface 6 of the bearing member 4 is surface-treated to improve wear resistance. (JP-A-63-235719).
A cylindrical yoke 35 is provided on the inner peripheral surface side of the large cylindrical portion 1b of the rotating body 1.
Is fixed, and the cylindrical drive magnet 2 is fixed inside the yoke 35.

The polygon mirror 14 is fitted into the small cylindrical portion 1a of the rotating body 1,
The corrugated spring 36 is placed on it, and the balance plate 18 is fixed to the rotating body 1 by fixing it. Further, as shown in FIG. 3 (B), a mirror retainer 37, a leaf spring 38, and a balance plate 18 are sequentially stacked on the polygon mirror 14.
It is fixed to the small cylindrical portion 1a of the rotating body 1 by a mounting screw 39 penetrating the balance plate 18, the leaf spring 38, and the mirror retainer 37. As a result, the bottom surface of the balance plate 18 presses the polygon mirror 18 against the shoulder 1c of the rotating body 1 via the corrugated spring 36 or the leaf spring 38, and fixes the same at the same time as positioning.

The rotation balance adjustment of the entire rotation system including the polygon mirror 18 is not particularly limited to the one using the balance plate 18, and a hole for balance adjustment is provided in the rotating body 1 itself without using the balance plate 18. Alternatively, or in combination with the balance plate 18, the balance of the rotating body 1 can be adjusted.

A center pole 15 arranged at the center of the bearing member 4 is fixed to the base 5 member 16 by integral molding or screwing. A stator core 21 is fitted on the outer peripheral surface of the center pole 15, and the coil 5 is wound between a non-magnetic coil plate 19 fitted in the stator core 21. A claw portion 20 for preventing the coil 5 from coming off is provided on the coil plate 19 so as to project outside the core 21 and in a substantially axial direction, and the claw portion 20 is used to wind the coil 5. Then, it is fixed with synthetic resin. Also,
If necessary, a circuit board 24 for a frequency generator is installed at a position near the upper end of the center pole 15, and a magnet 23 for frequency power generation is provided on the rotor 1 side so as to face the circuit board 24.
Is stuck. A coil pattern is formed on the circuit board 24, and the rotation speed signal is generated when the magnet 23 rotates together with the rotating body 1. Furthermore, the base member
A circuit board 22 for driving is screwed under 16
Together with the base member 16, the air flow between the inside 11 of the motor and the outside 12 of the bearing member 4 is blocked. On the circuit board 22, a circuit pattern for energizing the coil 5 to drive the rotating body 1 to rotate is formed. The base member 16
A lead-out hole for pulling out a lead wire connected to the drive coil 5 and the circuit board 22 to the outside is appropriately formed as necessary. Further, a protective cover 25 is fixed as necessary.

The center pole 15 on the stator side and the pair of ring-shaped magnets 8 constituting the thrust magnetic bearing 10 on the rotary body 1 side,
9 are fixed so as to face each other. These magnets 8 and 9 are magnetized in the axial direction so that the opposing surfaces become poles that repel each other. The magnets 8 and 9 are arranged such that the center positions in the axial direction are displaced from each other, whereby an attractive force in the axial direction is generated, whereby the entire rotating body 1 having the polygon mirror 14 and the like floats. ing.

The polygon mirror rotation driving device configured as described above operates as follows.

When the drive coil 5 is energized, the drive magnet 2 is rotationally biased and the rotating body 1 is rotationally driven together with the polygon mirror 14. As the rotor 1 rotates, air is introduced into the dynamic pressure generating groove through the air holes 34 and the circumferential groove 33, and the dynamic pressure air bearing 7 formed by this group and the inner peripheral surface 6 of the bearing member 4 is formed.
A dynamic pressure is generated in the radial direction, and the radial load of the rotating body 1 is supported. By forming the air holes 34 and the circumferential groove 33, the dynamic pressure effect between the bearing member 4 and the rotating body 1 is increased, and the rigidity of the dynamic pressure bearing is increased. On the other hand, the load in the thrust direction of the rotating body 1 is the thrust magnetic bearing 1 composed of the thrust magnets 8 and 9.
Supported by 0.

Here, when a disturbance is applied to the rotating body 1 that is rotating, the rotating body 1
Tries to vibrate in the thrust direction. Then, air flows in and out of the internal space 11 formed between the bearing member 4 and the rotating body 1 through the ventilation hole formed by the groove 13 and the counterpart component. That is, when the entire rotating body 1 floats from the bearing member 4, air enters through the groove 13, and when it sinks with respect to the bearing member 4, air exits through the groove 13. Since the groove 13 serves as a resistance against the entry and exit of air, it acts as a damper against the vibration of the rotating body 1 and suppresses the vibration of the rotating body 2.

FIG. 6 shows the vibration characteristics of the motor in the axial direction. In this characteristic diagram, the broken line shows the case of only the axial magnetic bearing, and the solid line shows the case of using the air damper together. As is clear from the figure, it can be understood that the peak of the amplitude becomes smaller and the resonance frequency becomes higher when the air damper is used together. Therefore, by optimally adjusting the size of the vent holes / grooves 13 according to the air capacity inside the motor, the mass of the entire rotating system, and the operating conditions, the amplitude is suppressed and the resonance frequency is in a relatively high frequency range that does not affect the control motor. , For example, it becomes possible to move from 70 Hz to 100 Hz. Then, this optimum vent hole can be easily secured by processing the groove 13 on the surface of the motor component or processing the slit 28 on the damping plate 29.

The above-described embodiment is an example of a 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 scope of the present invention. For example, in the present embodiment, the groove 13 forming a vent hole for communicating the internal space 11 and the motor exterior 12 is formed on the bottom surface of the balance plate 18, but the invention is not particularly limited to this, and the rotating body 1 Upper end surface, the leaf spring 38 for pressing the polygon mirror 14, the mirror pressing member 37, the base end surface of the bearing member 4, the base member 16
It may be formed on any butting surface of the motor component, such as the surface of the above. The same applies to the damping plate 29.

(Effect of the Invention) As is apparent from the above description, the dynamic pressure air bearing motor of the present invention has the vent holes formed by grooving the abutting surfaces of the components, so the vent holes can be easily processed. . Therefore, the ventilation hole having a diameter and a length corresponding to the mass of the rotating body can be provided to obtain optimum damping characteristics.
Further, in the present invention, when a damping plate having a slit penetrating the inside and outside of the bearing is interposed between the components, a large number of damping plates having different groove sizes are prepared in advance, so that other components can be It is possible to follow the sprung mass simply by determining the damping plate according to the size of the polygon mirror without changing it. That is,
When the damping plate is interposed, even if the mirror is changed, it is sufficient to change the damping plate having different groove sizes without changing other components.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view showing an example in which the present invention is implemented as a rotary driving device for a polygon mirror. 2A and 2B show an embodiment in which a groove constituting a balance plate ventilation hole is provided, and FIG. 2A is a bottom view and FIG. 2B is a side view. FIG. 3 (A) is an enlarged cross-sectional view of an essential part showing another embodiment of groove processing, and FIG. 3 (B) is an enlarged view of an essential part showing another embodiment of the mirror retainer. FIG. 4 is an enlarged cross-sectional view of an essential part of an embodiment using a damping plate according to another embodiment of the present invention. 5 (A) and 5 (B) are a plan view showing an example of the damping plate used in the embodiment of FIG. 4 and an explanatory view showing only a main part. FIG. 6 is a vibration characteristic diagram showing the relationship that the damper gives to the vibration of the rotating body. FIG. 7 is a central longitudinal sectional view showing an example of a conventional dynamic pressure air bearing motor. 1 ... Rotating body, 4 ... Bearing member, 7 ... Dynamic pressure air bearing, 3 ... Rotating body outer peripheral surface, 6 ... Bearing member inner peripheral surface, 11 ... Internal space, 12 ... Motor outside , 17 …… motor, 2 …… magnet, 5 …… coil, 13 …… groove, 28 …… slit, 29 …… damping plate.

Claims (2)

[Scope of utility model registration request] 1. A dynamic pressure air bearing is formed between an outer peripheral surface of the rotating body and an inner peripheral surface of the bearing member by fitting a rotating body and a cylindrical bearing member accommodating the rotating body. A dynamic pressure air bearing motor that constitutes a motor between a magnet attached to the inner peripheral surface of the rotating body and a stator-side coil that is concentrically arranged in the center of the bearing member and fixed to the bearing member, The internal space formed by the rotating body and the bearing member is a substantially closed space, while the constituent members abut against each other with a groove for connecting the internal space and the outside of the motor for suppressing axial vibration. A dynamic pressure air bearing motor characterized by being formed by grooving on one of the surfaces to be formed. 2. A dynamic air bearing is formed between an outer peripheral surface of the rotating body and an inner peripheral surface of the bearing member by fitting a rotating body and a cylindrical bearing member that houses the rotating body. A dynamic pressure air bearing motor that constitutes a motor between a magnet attached to the inner peripheral surface of the rotating body and a stator-side coil that is concentrically arranged in the center of the bearing member and fixed to the bearing member, While making the internal space formed by the rotating body and the bearing member a substantially closed space, a radial slit having a size corresponding to the mass of the rotating body that makes the internal space and the outside of the motor communicate with each other. A dynamic pressure air bearing motor, characterized in that a damping plate is provided between the surfaces where the constituent members abut each other.