JPH01316717A - Rotating polygon mirror drive motor - Google Patents

Abstract

PURPOSE:To enable stable rotation without any eccentricity by arranging a rotor magnet and a stator coil on the outer peripheral, side of the opposite surface of the thrust part of a dynamic fluid bearing, providing a support surface for supporting a rotary polygonal mirror in a fitting surface parallel to the opposite surface of the thrust part, and providing the opposite surface closer the outer periphery than the external peripheral surface of a shaft. CONSTITUTION:A thrust surface 22a which is the opposite surface of the thrust reception part 22 is a plane, a spiral groove (groove for dynamic pressure generation) is cut in a thrust surface 23a which is the opposite surface of a support part 23, and both thrust surfaces are provided closer to the outer periphery than the outer peripheral surface of the rotary shaft 20. Further, a rotor magnet 29 is positioned closer to the outer periphery than the thrust surfaces and the stator coil 32 is provided opposite the rotor magnet 29, fixed to a coil substrate 33, and positioned closer to the outer periphery than the thrust surfaces. Consequently, the wear of the thrust member is reduced and the high-accuracy rotary polygonal mirror driving motor is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drive motor for a rotating polygon mirror for deflecting and scanning a light beam, in particular a laser beam.

(Prior Art) Conventionally, in scanning optical devices, a method in which a rotating polygon mirror is rotated by a motor to deflect the mirror has been widely used due to its stability and high speed of scanning.

In recent years, hydrodynamic bearings with excellent high-speed stability, rotational accuracy, and long life have been put into practical use, and motors using these bearings have also been developed.

Conventional hydrodynamic bearings are composed of a shaft and a cylindrical member called a sleeve (shaft-sleeve type), and the shaft has herringbone-shaped grooves for generating dynamic pressure.

Thrust sections generally utilized magnetic repulsion or were lifted by the pressure of airflow sucked up from the shaft.

As a conventional example, a shaft-sleeve type dynamic pressure fluid shaft and receiver will be explained in FIG. 4 using a rotary polygon mirror drive motor as an example.

In FIG. 4, a rotating sleeve 2 is engaged with a fixed shaft 1 having a herringbone groove 1a and a spiral groove IC while maintaining a gap of 3 to 5 IL. Also,
A thrust member 7 that contacts and supports the shaft end ib during low speed and receives pressure in the thrust direction (axial direction) when floating is press-fitted into the upper part of the rotating sleeve 2 and positioned by a C ring 8. This thrust member 7 normally has a flat shaft end tb, and a spherical thrust bearing has a surface 7a, and if the fluid is gas, has a throttle hole 7b in the center.

Further, a rotating polygon mirror 5, a rotor magnet 3, and a balance ring 4.6 are fixed to the rotating sleeve 2. A stator coil 9 and a plurality of Hall elements 10 for coil control and tack signal detection are provided opposite the rotor magnet 3, forming a PLL control di(7) DC brushless Hall motor.

O-rings 12 and 14 are inserted between the case 11 and the cap 13, and between the case 11 and the flange portion 21 of the fixed shaft 1, and the laser beam entrance and exit windows 15, drive lead wires, and signal wires are connected to each other. Adhesion and hermetic sealing are used to ensure that the inside of the case is sufficiently sealed during delivery to the outside.

This prevents problems with dynamic pressure bearings caused by dust, moisture, etc.

Here, when the rotary sleeve 2 is directly driven by the motor, the fluid (gas such as air or liquid such as oil) sucked in as shown by arrow A by the belling pawn groove 1a carved in the shaft 1 is directed in the radial direction. By generating pressure and squeezing the fluid by the throttle hole 7b of the thrust member 7, a supporting force in the thrust direction (axial direction) is created, and furthermore, when the rotation speed exceeds a certain number, the fluid is supported by a film of fluid in both the radial and thrust directions. You'll end up getting beaten up.

A particular problem with hydrodynamic bearings is solid contact during low-speed rotation, and the life of the bearing is determined by how well each part can withstand such contact rotation.

In a vertical motor like this, the outer diameter of the shaft and the inner diameter of the sleeve are almost equal, so in the radial direction it is sufficient to increase the hardness of each material and apply a lubricating coating (Teflon-impregnated). The member 7 receives all the thrust loads such as the weight of the rotating body and the attraction force of the magnet 3 and the stator, which has a great effect not only on durability but also on the increase/decrease in starting torque.

Therefore, a plastic material (polyacetal, PPS type) with good self-lubricity and wear resistance is selected.

If the gap between the shaft end 1b and the thrust member 7 is large, the stability of the bearing will be greatly affected.
(above) It has a spherical shape.

(Issue 8 to be solved by the invention) As understood here, it is desirable that this thrust member 7 hits at the center of rotation (center of the sleeve) as much as possible, but the diameter of the thrust member 7 (for example, ΦlO ~
Since the radius of curvature of the spherical surface 7a is larger than that of Φ15),
In addition to errors during machining, even a slight inclination during press-fitting of the thrust member 7 causes the contact point to deviate significantly from the center (for example, by 2 to 3 degrees).

As a result, the initial starting torque is larger (for example, about 2 to 3 times) compared to the case where the contact point is near the throttle hole 7b, and the starting torque is increased due to faster wear and generation of wear particles. This increases the possibility of troubles caused by abrasion particles that prevent the motor from starting.

In order to prevent such defects, conventionally, the accuracy of the press-fitting jig for the thrust member has been increased. Paying close attention to the press-fitting process.After each assembly, a lot of time and effort was spent checking the contact points.

The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and
The purpose is to reduce wear on thrust members,
Another object of the present invention is to provide a highly accurate rotating polygon mirror drive motor.

(Means for Solving the Problems) A motor of the present invention for achieving the above object employs the following configuration.

First, one of the shaft and the sleeve provided around the shaft is fixed, and the other rotates.

Radial support during rotation of the rotating shaft or sleeve (abbreviated to the rotating side) is provided by grooves for generating dynamic pressure carved in at least one of the outer circumferential surface of the shaft and the inner circumferential surface of the sleeve. The axial support during zero rotation provided by the shaft is provided by opposing thrust sections formed in the shaft and sleeve. This thrust portion is provided perpendicularly to the axial direction, and grooves are carved on the opposing surfaces for generating dynamic pressure. This opposing surface is provided on the 0-rotation side, and a rotor magnet is provided on the outer periphery of the opposing surface. A fixed sleeve or shaft facing this rotor magnet (abbreviated as the fixed side)
On the 0 rotation side where the stator coil is provided, a mounting surface is provided parallel to the opposing surface of the thrust portion, and a rotating polygon mirror is provided on this mounting surface.

(Function) As in the past, the 6-turn polygon mirror, whose rotating side rotates due to the force of attraction between the rotor magnet and the stator coil, is mounted on a mounting surface provided parallel to the opposing surface of the thrust section, so that the mirror surface is The rotation will be performed at right angles to the child.

In the present invention, the facing surface of the thrust portion is provided on the outer circumference of the shaft rather than the outer circumference of the shaft, and support in the thrust direction (axial direction) can be performed more stably than in the past. Therefore, the friction of the thrust portion can be reduced compared to the conventional case. Furthermore, since stable rotation can be performed, a hydrodynamic bearing motor that can rotate with high precision can be obtained.

(Embodiment) FIG. 1 is a sectional view showing a hydrodynamic bearing motor to which a first embodiment of the present invention is applied.

A rotating shaft 20 having herringbone grooves 20a and 20b is fitted around the outer periphery of a rotating shaft 20 with four fixing sleeves 21 supporting the rotary shaft 20 with a gap of several inches. At the upper part of this rotating shaft 20, there is a thrust receiving part (one thrust part) 22 extending perpendicularly to the rotating shaft 20, and at the upper part of the fixed sleeve 21 there is a thrust supporting part (the other thrust part) which is perpendicular to the fixed sleeve 21. There are 23 parts. These thrust receiving portions 22 and thrust supporting portions 23 are opposed to each other. The thrust surface 22a, which is the opposing surface of the thrust receiving part 22, is a flat surface.
The thrust surface 23a, which is the opposing surface of the rotation tdI 20, has a spiral groove (dynamic pressure generating groove) carved therein. Incidentally, the relationship between the spiral groove of the thrust surface and the plane may be reversed as described above.
The 0-rotation polygon mirror 25, which has a surface 24 and is parallel to the thrust surface 22a, is centered by a mounting sleeve 27 via an elastic member 26, and the mounting sleeve 27 is attached to the rotating shaft 20 by a screw 28. A rotor yoke 30 that covers the rotor magnet 29 is provided on the opposite surface of the thrust surface of the thrust receiving portion 22 of the zero-rotation shaft 20 to be attached.

An FG magnet 31 is attached to this outer peripheral portion. The rotor magnet 29 is located on the outer periphery of the thrust surface.

Further, a stator coil 32 is provided opposite to the rotor magnet 29, and this stator coil 32 is connected to a coil substrate 3.
It is fixed at 3. The stator coil 32 is also located on the outer periphery of the thrust surface. 34 is a motor case that is fitted and fixed to the fixed sleeve 21. rotor yoke 30
By narrowing the gap between the opposing circumferential surfaces of the motor case 34 and the motor case 34, it is possible to prevent dust from entering the bearing section.

35 is a driver circuit board for controlling and driving the rotation of the motor, and is connected to the motor case 3 by screws 36.
It is fixed at 4.

Further, the driver circuit board 35 and the coil board 33 are electrically connected by a connector 37.

The diameter of the circumscribed circle of the rotating polygon mirror 25 is less than or equal to the outer diameter of the rotor yoke 30. This is the mirror surface of the rotating polygon mirror 25.

In particular, this is to prevent contamination that tends to occur at the boundary between adjacent surfaces. That is, the rotating polygon mirror 25 is the rotor yoke 30.
If the outer diameter is larger than the outer diameter of the rotor yoke 30, the wind will be cut directly at the corner of the rotating polygon mirror 25.If the circumscribed circle diameter of the rotating polygon mirror 25 is set to be less than or equal to the outer diameter of the rotor yoke 30, the wind will be cut by the rotor yoke. This reduces the amount of dust adhering to the rotating polygon mirror.

In addition, in this embodiment, the rotor yoke 30 is provided as a cover for the rotor magnet, but it is possible to configure the motor with just the rotor magnet, but considering ease of assembly and machining accuracy, a rotor yoke is recommended. This embodiment is an example applied to a surface facing flat motor.

(Other Embodiments) FIG. 2 shows a second embodiment of the present invention, which has almost the same configuration as the dynamic pressure fluid bearing motor shown in FIG. 1, but the motor type is a circumferentially opposed inner rotor motor. It has become. In FIG. 2, a rotor magnet 4 is attached to the outer periphery of the rotating shaft 20.
Fix 0.

41 is an FG magnet attached to rotor magnet 40. 42 is a stator coil provided on the outer periphery of the rotor magnet 40, and the third embodiment of the 0-order outer rotor motor is connected to the coil board 43, and the rotor yoke 50 is fixed to the 0-rotation shaft 20 shown in FIG. , attach the rotor magnet 51 there. An FG magnet 52 is attached to the rotor magnet 51. 53 is a stator coil connected to a coil board 54. In this way, the rotor magnet is placed outside the stator coil 53.
51, and by narrowing the gap between the opposing circumferential surfaces of the motor case 55 and the rotor yoke 50, as shown in the previous embodiment, it is possible to prevent dust from entering.

(Effects of the Invention) According to the present invention, the rotor magnet and the stator coil are arranged on the outer peripheral side of the opposing surface of the thrust section of a hydrodynamic bearing, and the rotating polygon mirror is arranged on the mounting surface parallel to the opposing surface of the thrust section. A supporting surface is provided to support the shaft, and this opposing surface is located on the outer circumferential part of the shaft rather than the outer circumferential surface of the shaft (by doing so, stable rotation can be obtained without eccentricity in the support in the thrust direction (axial direction), and therefore, the center of the thrust part can be A hydrodynamic bearing motor with low wear and high precision can be constructed, and is particularly effective as a scanning motor for laser beam printers and the like.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hydrodynamic bearing motor to which a first embodiment of the present invention is applied, and FIG. 2 is a sectional view of a second embodiment of the present invention.
FIG. 3 is a sectional view of a third embodiment of the present invention, and FIG. 4 is a sectional view of a conventional hydrodynamic bearing motor. Explanation of symbols 20... Rotating shaft 21... Fixed sleeve 22
... Thrust receiving part 23... Thrust support part 24.
... Mounting is on a surface 25 ... Rotating polygon mirror 29 ... Rotor magnet 32 ... Stator coil 34 ... Motor case

Claims (1)

[Claims] A shaft on which one is fixed and the other rotates, a sleeve provided on the outer circumference of this shaft, and a sleeve provided on at least one of the outer circumferential surface of the shaft and the inner circumferential surface of the sleeve for radial support during rotation. a groove for generating dynamic pressure; a thrust part perpendicular to the opposing axial direction formed on the shaft and sleeve for axial support during rotation; a groove for generating dynamic pressure carved in the facing surface provided, a rotor magnet provided on the outer periphery of the facing surface on the rotating side, and a stator coil provided on the stationary side facing the rotor magnet. and a mounting surface provided on the rotation side parallel to the opposing surface of the thrust section for mounting the rotating polygon mirror.