JPH06118326A - Light deflector - Google Patents

Abstract

PURPOSE:To provide the light deflector which has long service life by reducing the contact friction between a shaft and a rotary body due to the magnetization of the magnet of a scanner motor. CONSTITUTION:This light deflector has a dynamic pressure air bearing which uses one of a sleeve 3 and a shaft 1 inserted into the sleeve 3 as a rotary member and the other as a fixed member, and the magnet 6 for rotary driving which is magnetized into two poles is fixed on the line connecting the border of the magnetization eccentrically with the center of the stator core 7. Consequently, the magnetic unbalance force by the bipolar magnetized magnet becomes minimum and the contact friction of the bearing is reducible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light for rotating a rotary polygonal mirror having a plurality of reflecting mirror surfaces on its outer periphery and reflecting a light beam incident on the reflecting mirror surfaces to deflect and scan the image carrier or a recording member. Regarding the deflector.

[0002]

2. Description of the Related Art Generally, an image reading device that scans an image carrier or the like with a light beam emitted from a light source such as a laser to read the image, or a recording medium with a light beam modulated by an image signal or a character signal. In the image recording apparatus for recording an image by using the rotary polygonal mirror having a plurality of reflecting mirror surfaces on its outer circumference, a means for scanning the light beam is used.

As an optical deflector of this type, a rotary bearing, which is preferably a dynamic pressure air bearing or the like, in which one of a sleeve and a shaft, which are inserted into each other, is a rotating member, and the other is a fixed member, is attached to the rotating member. A rotating torque generating function for generating a rotating torque by a magnetic circuit formed by winding an electromagnetic coil around a permanent magnet (magnet) and an annular iron core (stator core) installed on a fixed member, which constitutes a so-called scanner motor, and a rotating body in the axial direction. There is known an optical deflector having a magnetic circuit that also has the function of a magnetic bearing that holds the.

FIG. 5 is an explanatory view of a schematic structure of an image recording apparatus using this type of optical deflector, in which 30 is a laser and 31 is a laser.
Is a collimator lens, 32 is a condensing optical system, 33 is a photoconductor as a recording medium, 53 is a rotating polygon mirror, 53-1 is a plurality of reflecting mirror surfaces constituting a rotating polygon mirror, and 57 is a rotation driving mechanism (scanner motor). Reference numerals 58 and 58 denote dust-proof covers (hereinafter simply referred to as covers), and 58-1 denote openings (entrance / emission windows) through which light beams enter and exit.

In the figure, the rotary polygon mirror 53 is rotated in the direction of arrow A by a scanner motor 57. A light beam emitted from a laser 30 such as a semiconductor laser or a gas laser is modulated by an image signal or the like by a modulation means (not shown), and is incident on the reflecting mirror surface 53-1 of the rotary polygon mirror 53.
The light beam (reflected light beam) reflected by the reflecting mirror surface 53-1 of the rotating polygonal mirror 53 passes through the condensing optical system 32 and the photoconductor 3
3 is projected.

This reflected light beam is deflected in the direction of arrow B as the rotary polygon mirror 53 rotates in the direction of arrow A, and is reflected by the photosensitive member 3.
3. Main scanning is performed on the upper part. Along with this, sub-scanning is performed by rotation of the photoconductor 33 in the direction of arrow C, and a two-dimensional image is written on the photoconductor 33. A dustproof cover 58 having a light beam entrance / exit window 58-1 is attached to prevent dust from adhering to the reflecting mirror surface 53-1 of the rotary polygon mirror 53.

FIG. 6 is a cross-sectional view for explaining the structure of a conventional optical deflector, and FIG. 7 is a schematic view of an essential part of a magnet portion showing a magnetized state of a magnet constituting the scanner motor of FIG. A fixed shaft, 1-1 is a groove for dynamic pressure generation, 2 is a housing, 3 is a rotating sleeve, 3-1 is a flange, 4 is a cover, 4-1 is an entrance / exit window, 5 is a yoke, 6 is a magnet,
7 is a stator core, 8 is a stud, 9 is a circuit board, 10
Is a magnetic detection element, 11 is a rotary polygon mirror, 12 is a cap flange, 13, 17, 18, 20 are screws, 14 is a window glass, 15 is a gap, 16 is a shaft flange, 19 is a collar, 21 is a balance ring, 22 Is a reflecting mirror surface, 23 is an air pocket, 24 is an electromagnetic coil, and 25 is a fine hole.

This optical deflector has its axis 1 fixed, and this axis 1
The sleeve inserted into the shaft is of a fixed shaft type that rotates. Here, the shaft 1 will be described as a fixed shaft, and the sleeve 3 will be described as a rotating sleeve. In FIG. 6 and FIG. 7, one end of the fixed shaft 1 is fixed to the shaft flange 16, and they are fixed by screws 17
It is fixed to the housing 2 by.

On the peripheral surface of the fixed shaft 1, a dynamic pressure generating groove 1-1 which functions as a radial bearing is provided. This radial bearing is a bearing for preventing the center of rotation from deviating from a predetermined position even when a force acts in a direction perpendicular to the axial direction. The rotor portion constituting the scanner motor is a portion inserted into the fixed shaft 1 with a gap 15 therebetween, and the rotary sleeve 3, the yoke 5 fixed to the rotary sleeve 3 by press fitting or adhesion, and the magnet fixed to the yoke 5. 6 and a balance ring 21.

A rotary polygon mirror 11 is attached to this rotor portion. The rotary polygon mirror 11 is attached by the polygon mirror 11
The center hole is inserted into the rotary sleeve 3, the cap flange 12 is applied from above and the screw is fixed to the rotary sleeve 3. Between the upper end of the fixed shaft 1 and the cap flange 12, the thrust direction (axial direction)
An air pocket 23 that suppresses the damping of the air is formed.
The fine holes 25 communicate the air pocket 23 with the outside air to stabilize the damping effect of the air pocket 23.

On the other hand, the stator portion constituting the scanner motor is a housing 2 and a screw 17 attached to the housing 2.
A fixed shaft 1 whose one end is fixed to the shaft flange 16 fixed by means of press fitting or the like, a stator core 7 fixed to the housing 2 by a screw 20 via a collar 19, and a toroidal type wound around the stator core 7 The coil 24, a circuit board 9 supported by the studs 8 attached to the stator core 7, a magnetic detection element (sensor) 10 that is preferably a hall element and is installed upright on the circuit board 9, and the like.

A magnet 6 which constitutes a so-called scanner motor section for driving the rotary polygon mirror to rotate is a permanent magnet and is magnetized in two poles as shown in FIG. Attractive force is working. This attractive force acts so that the opposing positions of the magnet 6 and the stator core 7 are not displaced in the axial direction (thrust direction) of the motor. That is, when the magnet 6 moves to the right, a component that pulls back to the left appears in the attraction force and is pulled back, and when it moves to the left, a component that pulls back to the right appears and pulls back. Thus, the magnet 6 and the stator core 7 are made to face each other at a predetermined axial position by the magnetic attraction force. That is, the magnet 6 and the stator core 7 form a magnetic thrust bearing.

As the magnetic detection element 10, for example, a Hall element is used. This detects the leakage magnetic flux of the magnet 6 and detects whether the N pole or the S pole has passed when the magnet 6 rotates. The detection signal of the magnetic detection element 10 is sent to a control circuit unit (not shown) through the wiring printed on the circuit board 9. The control circuit section determines the direction of the current flowing through the electromagnetic coil wound around each part of the stator core 7 based on this detection signal. As a result, the interaction with the magnet 6 generates a force in the direction of continuing the rotation.

When the rotary sleeve 3 rotates, the dynamic pressure generating groove 1-1 creates a high-pressure air layer around the shaft 1 (the gap 15). This pressure forms a dynamic air bearing in which the rotary sleeve 3 is supported in a state of floating above the shaft 1. In the figure, the dynamic pressure generating groove 1-
Although 1 is provided on the outer periphery of the fixed shaft 1, a dynamic pressure generating groove 1-1 may be provided on the inner wall of the rotating sleeve 3 instead of this.

The air layer in the gap 15 functions to keep the center of rotation of the rotor part constant. For example, if the rotary sleeve 3 is displaced to the left in the figure, the gap of the gap 15 on the right becomes large, and the pressure in the gap in this portion becomes smaller than that before the displacement. On the other hand, since the gap on the left side is small, the pressure in the gap in this part is larger than that before the gap. When the magnitude relation of the pressure is as described above, the rotary sleeve 3 is pushed rightward and finally returned to the original position.

FIG. 8 is an explanatory view of the rotary polygon mirror and its deflection operation, and is a top view with the cover 4 of FIG. 6 removed. As shown in the figure, the rotary polygon mirror 11 has a regular polygonal shape when viewed from above in the axial direction, and has a large number of reflecting mirror surfaces 22 on its outer periphery (side surface). In the figure, a light beam such as a laser beam that has entered through the window glass 14 of the entrance window 4-1 is reflected by the reflecting mirror surface 22 of the rotary polygon mirror 11, and passes through the window glass 14 of the entrance window 4-1 again. Is emitted.

When the light beam is incident on the reflecting mirror surface at the position of the entrance window 4-1 and the rotary polygon mirror 11 rotates, the reflected light beam of the light beam is gradually changed in direction and deflected. As the rotation advances and the next reflecting mirror surface rotates, the light beam in turn enters it. With this reflecting mirror surface, deflection is performed in the same manner as the previous reflecting mirror surface. Therefore, the reflected light beam scans a certain angular range, and its scanning speed depends on the rotation speed of the rotary polygon mirror 11.

The above-mentioned optical deflector is a fixed shaft type in which the shaft 1 is fixed, but there is also known a rotary shaft type in which a sleeve is fixed to a housing and a rotary shaft is inserted therein. A conventional technique relating to this type of optical deflector is disclosed in, for example, JP-A-62-23.
It is disclosed in Japanese Patent No. 1922.

[0019]

In the above prior art, since there is a gap for adhesion between the rotary sleeve 3 and the magnet 6, the center of the outer diameter of the magnet 6 is eccentrically fixed with respect to the center of the rotary sleeve. Has been done. Due to this eccentricity, a magnetic imbalance occurs between the stator core 7 and the magnet 6. This magnetic imbalance gives a force to a specific direction of the bearing sliding surface. This is called magnetic imbalance force.

Due to this magnetic unbalanced force, and by having the dynamic pressure air bearing structure, the shaft 1 of the rotating body and the rotating sleeve 3 are brought into concentrated contact with each other at a specific position at the time of starting and stopping the rotation, and the bearing is abraded. However, there is a problem that the life is shortened. That is, in the dynamic pressure air bearing, the pressure in the bearing clearance 15 is small at the time of starting and stopping the rotation, and the shaft 1 and the sleeve 3 rotate while making contact with each other. Then, the pressure increases as the rotation speed increases, and the two are not in contact with each other.

However, since the pressure in the bearing gap 15 is uniform in the radial direction, when an external force in a specific direction is applied to the radial direction at the time of starting and stopping the rotation, the contact time and the contact force increase, and the bearing Further promotes wear and shortens life. As described above, in the dynamic pressure air bearing structure, if there is an eccentricity between the magnet 6 and the stator core 7, the magnetic unbalanced force caused by the two-pole magnetized magnet greatly affects the life of the optical deflector.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a long-life optical deflector having a rotary drive mechanism having a scanner motor having a two-pole magnetized magnet and a bearing having a dynamic pressure air bearing. To provide.

[0023]

In order to achieve the above object, the present invention relates to an optical deflector having a scanner motor structure for rotating a rotary polygon mirror by providing a bearing with a dynamic pressure air bearing. The magnet is eccentrically fixed to the rotating sleeve on the line connecting the magnetizing boundaries.

That is, according to the present invention, as illustrated in FIG. 1, a dynamic pressure air bearing in which one of the sleeves 3 and the shaft 1 into which the sleeve 3 is inserted is a rotating member and the other is a fixed member. A rotary polygon mirror 11 fixed to the rotating member and having a plurality of reflecting mirror surfaces 22 formed on the outer periphery thereof, a rotary driving magnet 6 fixed to the rotating member, and an electromagnetic coil 24 provided on the fixing member. Wound stator core 7
And a magnetic circuit having a magnetic bearing function for holding the rotary member in the axial direction of the shaft 1, and the rotary polygon mirror 11 is rotated to make the light incident. In an optical deflector for deflecting a light beam by reflecting it on the reflecting mirror surface 22 of the rotary polygon mirror 11,
The magnet 6 is magnetized into two poles, and the eccentric direction of the outer diameter center of the magnet 6 with respect to the shaft center of the bearing is eccentric on a line connecting the two-pole magnetization boundary 6-1 of the magnet 6. It is characterized in that it is allowed to stick.

The present invention is not limited to the fixed shaft type in which the shaft of the bearing is fixed, but is a rotary shaft type dynamic pressure air in which the sleeve side is used as a fixed member and the rotary polygon mirror is fixed to the rotary shaft inserted into this. It goes without saying that the same can be applied to an optical deflector having a bearing. Further, the present invention is not limited to a so-called inner rotor type scanner motor in which a rotating magnet is arranged on the inner circumference of a stator core, but an optical deflection having a so-called outer rotor type scanner motor in which a rotating magnet is arranged on the outer circumference of a stator core. Can also be applied to vessels,
Further, it can be similarly applied to a driving motor other than the optical deflector.

[0026]

The magnetic imbalance force is proportional to the difference in magnetic force. When the sleeve 3 is eccentric in the NS pole direction of magnetizing the magnet, the difference in magnetic force becomes maximum. Since the magnetic force is almost zero at the polarization position (the boundary of magnetization) perpendicular to this direction, the magnetic imbalance force can be brought close to zero even if the magnet is eccentric.

In the above-mentioned structure of the present invention, the eccentric direction of the outer diameter center of the magnet 6 with respect to the shaft center of the bearing of the scanner motor having the dynamic pressure air bearing is defined by the boundary 6-of the two poles of the magnet 6. The contact force of the bearing is not reduced and the wear of the bearing is reduced by eccentrically and fixing on the line connecting the No. 1 and No. 1. Therefore, the life of the optical deflector can be extended.

[0028]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a part of the optical deflector according to an embodiment of the present invention (a),
(B) is a plan view showing the main part thereof. In the figure,
1 is a fixed shaft, 1-1 is a groove for dynamic pressure generation, 2 is a housing,
3 is a rotary sleeve, 3-1 is a flange, 4 is a cover, 4
-1 is an entrance / exit window, 5 is a yoke, 6 is a magnet, 7 is a stator core, 8 is a stud, 9 is a circuit board, 10 is a magnetic detection element, 11 is a rotating polygon mirror, 12 is a cap flange, 13, 17, 18 , 20 is a screw, 14 is a window glass, 15 is a gap, 16 is a shaft flange, 19 is a collar, 21 is a balance ring, 22 is a reflecting mirror surface, 24 is an electromagnetic coil, 25 is a fine hole, and 26 is an adhesive gap.

The optical deflector shown in the figure is substantially the same in structure as that described in the section of the prior art,
In the following, description may be duplicated for convenience of understanding the structure.
This optical deflector is of a fixed shaft type in which a shaft 1 is fixed and a sleeve inserted and attached to the shaft 1 rotates. Here, the shaft 1 will be described as a fixed shaft and the sleeve 3 will be described as a rotating sleeve.

As shown in FIG. 1 (a), one end of the fixed shaft 1 is fixed to the shaft flange 16, which is the screw 1
It is fixed to the housing 2 by 7. On the peripheral surface of the fixed shaft 1, a dynamic pressure generating groove 1-1 that functions as a radial bearing is provided.
Is provided. This radial bearing is a bearing for preventing the center of rotation from deviating from a predetermined position even when a force acts in a direction perpendicular to the axial direction.

The rotor portion which constitutes the scanner motor is a portion which is inserted into the fixed shaft 1 with a gap 15 therebetween, and the rotary sleeve 3 and the yoke 5 and the yoke 5 which are fixed to the rotary sleeve 3 by press fitting or adhesion. It is composed of a fixed magnet 6 and a balance ring 21. On the other hand, the stator portion that constitutes the scanner motor includes a housing 2, a fixed shaft 1 whose one end is fixed to the shaft flange 16 fixed to the housing 2 with a screw 17 by press fitting, and a screw 20 via a collar 19 to the housing 2. The stator core 7 fixed by, the electromagnetic coil 24 preferably wound in the stator core 7 in the toroidal form, the circuit board 9 supported by the studs 8 attached to the stator core 7, and installed on the circuit board 9 in a standing manner. It is composed of a magnetic detection element 10 or the like, which is preferably a Hall element.

The magnet 6 which constitutes a so-called scanner motor unit for driving the rotary polygon mirror to rotate is a permanent magnet and is magnetized in two poles as shown in FIG. Has a magnetic attraction.
This attractive force acts so that the opposing positions of the magnet 6 and the stator core 7 are not displaced in the axial direction (thrust direction) of the motor. That is, when the magnet 6 moves to the right, a component that pulls back to the left appears in the attraction force and is pulled back, and when it moves to the left, a component that pulls back to the right appears and pulls back. Thus, the magnet 6 and the stator core 7 are
It is made to oppose at a predetermined position in the axial direction.
That is, the magnet 6 and the stator core 7 form a magnetic thrust bearing.

As the magnetic detection element 10, for example, a Hall element is used. This detects the leakage magnetic flux of the magnet 6 and detects whether the N pole or the S pole has passed when the magnet 6 rotates. The detection signal of the magnetic detection element 10 is sent to a control circuit unit (not shown) through the wiring printed on the circuit board 9. The control circuit section determines the direction of the current flowing through the electromagnetic coil wound around each part of the stator core 7 based on this detection signal. As a result, the interaction with the magnet 6 generates a force in the direction of continuing the rotation.

When the rotary sleeve 3 rotates, the dynamic pressure generating groove 1-1 produces an air layer of high pressure around the shaft 1 (the gap 15). This pressure forms a dynamic air bearing in which the rotary sleeve 3 is supported in a state of floating above the shaft 1. In the figure, the dynamic pressure generating groove 1-
Although 1 is provided on the outer circumference of the fixed shaft 1, a dynamic pressure generating groove 1-1 may be provided on the inner wall of the rotary sleeve 3 instead of this.

The air layer in the gap 15 acts to keep the center of rotation of the rotor part constant. For example, if the rotary sleeve 3 is displaced to the left in the figure, the gap of the gap 15 on the right becomes large, and the pressure in the gap in this portion becomes smaller than that before the displacement. On the other hand, since the gap on the left side is small, the pressure in the gap in this part is larger than that before the gap. When the magnitude relation of the pressure is as described above, the rotary sleeve 3 is pushed rightward and finally returned to the original position.

FIG. 2 is a plan view showing an essential part of the positional relationship between the sleeve and the magnet for explaining the detailed construction of the first embodiment of the present invention. In the present embodiment, the shaft (fixed shaft) is shown. That is, the magnet 6 is eccentrically fixed to the rotary sleeve 3 with respect to the center of 1 in the polarization position direction, that is, on the line connecting the magnetization boundaries 6-1. That is,
The magnet 6 and the rotary sleeve 3 are fixed by filling an adhesive gap 26 with an adhesive material.

Although the eccentricity varies depending on the bearing material, it is an amount that produces a force that does not cause wear of the bearing. Figure 3 shows two magnets that make up the scanner motor.
It is an explanatory view of magnetizing in the case of polar magnetization,
(A) is a magnetization waveform diagram, the horizontal axis shows the amount of rotation (rotation angle) of the magnet, the vertical axis shows the magnetic flux density Bg, and (b) is a plan view of a two-pole magnetized magnet.

As shown in the figure, the magnetic flux of the magnet 6 is distributed at 0 to 360 degrees of its rotation as shown in FIG. At the boundary 6-1 of magnetization, the magnetic flux is 0. Figure 4
6 is an explanatory view of a magnetic unbalanced force of the magnet when the magnet constituting the scanner motor is magnetized in two poles.
1 is the outer circumference of the magnet 6, 71 is the inner circumference of the stator core 7, 10 is the magnetic sensor, 0c is the center of the stator core 7, 0m is the center of the magnet 6, and e is the amount of eccentricity between the magnet 6 and the stator core 7. Here, the center of the stator core is the same as the center of the bearing.

The magnetic imbalance force F is represented by the function F (θ, e, β) of θ, β, e in FIG. Therefore, when the magnetic sensor 10 in FIG. 4 is eccentric in the direction of the magnet polarization position (boundary of magnetization) (β = 0), the magnetic unbalanced force is F1, and when the magnet is eccentric in the NS pole direction ( When the magnetic imbalance force of β = π / 2) is F2, F1
And F2, as is clear from the magnetization waveform of FIG.
It can be seen that> F1.

Therefore, the magnet 6 and the stator core 7 are eccentric in the direction of the polarization position (magnetization boundary) of the magnet 6, that is, eccentric on the line connecting the magnetization boundaries, so that the two poles are attached. The magnetic unbalanced force due to the magnetic magnet can be minimized. by this,
It is possible to reduce the wear of the bearing of the rotary drive mechanism including the two-pole magnetized magnet in the scanner motor having the dynamic pressure air bearing, and to extend the life of the optical deflector.

[0041]

As described above, according to the present invention, it is possible to eliminate the influence of the magnetic unbalanced force which has been conventionally generated by fixing the magnets to the stator core in random directions, and to reduce the dynamic pressure. The contact force and contact time of the air bearing are reduced, the wear of the bearing can be reduced, and a long-life optical deflector can be provided.

[Brief description of drawings]

FIG. 1A is a partially cutaway sectional view illustrating a configuration of an embodiment of an optical deflector according to the present invention, and FIG. 1B is a plan view showing a main part thereof.

FIG. 2 is a plan view showing a main part of an arrangement relationship between a sleeve and a magnet for explaining a detailed configuration of an embodiment of the present invention.

[Fig. 3] Two magnets that compose the scanner motor
It is an explanatory view of magnetizing in the case of polar magnetization,
(A) is a magnetization waveform diagram, the horizontal axis shows the amount of rotation (rotation angle) of the magnet, the vertical axis shows the magnetic flux density Bg, and (b) is a plan view of a two-pole magnetized magnet.

[Fig. 4] Two magnets that compose the scanner motor
It is explanatory drawing of the magnetic unbalanced force of the magnet in the case of polar magnetization.

FIG. 5 is an explanatory diagram of a schematic configuration of an image recording apparatus using a conventional type of optical deflector.

FIG. 6 is a sectional view illustrating a structure of a conventional optical deflector.

FIG. 7 is a schematic diagram of a main part of a magnet portion showing a magnetized state of a magnet included in a scanner motor of a conventional optical deflector.

FIG. 8 is an explanatory diagram of a rotary polygon mirror and its deflection operation.

[Explanation of symbols]

1 ... Fixed shaft, 1-1 ... Groove for dynamic pressure generation, 2 ...
... Housing, 3 ... Rotating sleeve, 3-1
... Flange, 4 ... Cover, 4-1, ... Inlet / outgo window, 5 ... Yoke, 6 ... Magnet, 7
.... Stator core, 8 ... Stud, 9 ...
・ Circuit board, 10 ・ ・ ・ ・ Magnetic detection element, 11 ・ ・ ・
Rotating polygon mirror, 12 ... Cap flange, 13, 1
7, 18, 20 ... ・ Screw, 14 ・ ・ ・ ・ Window glass, 15 ・ ・ ・ ・ Gap, 16 ・ ・ ・ ・ Shaft flange,
19 ・ ・ ・ ・ Color, 21 ・ ・ ・ ・ ・ ・ Balance ring, 2
2 ... Reflective mirror surface, 24 ... Electromagnetic coil, 25 ...
... Micro holes, 26 ... Adhesive gaps.

Claims (1)

[Claims] 1. A mutually inserted sleeve, a dynamic pressure air bearing having one of a shaft for inserting the sleeve as a rotating member and the other as a fixed member, and a plurality of reflecting mirror surfaces fixed to the rotating member on the outer periphery. A rotary polygon mirror having the above-mentioned structure, a rotary drive magnet fixed to the rotary member, and a stator core around which an electromagnetic coil provided on the fixed member is wound. And a magnetic circuit having a function of holding a magnetic bearing in the axial direction of the shaft. By rotating the rotary polygon mirror, an incident light beam is reflected by the reflecting mirror surface of the rotary polygon mirror to perform deflection. In the optical deflector, the magnet is magnetized to have two poles, and a line connecting an eccentric direction of an outer diameter center of the magnet with respect to an axial center of the bearing to a magnetizing boundary of the two poles of the magnet. Optical deflector according to claim in that secured by decentering