JP2002311371A - Optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical deflector capable of realizing miniaturization, fast starting, a small loss and a low cost. SOLUTION: A driving coil 24 is mounted to a driving circuit substrate 26 through a driving circuit substrate 26 through a positioning member 28. Thus, a distance between the coil 24 and a driving magnet 30 is reduced. As the result of this, conventionally leaked magnetic flux B1 is used effectively. Consequently, without increasing magnetic fluxe density of magnetic fluxes B2 from the magnet 30 to the substrate 26, a rotator 20 can be started fast and driving efficiency can be improved. Since there is no need to increase the size of the magnet 30, a low cost is realized and the increase of the mass of the rotator 20 can be prevented with this, thereby the small loss is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in, for example, an image reading system such as a digital copying machine or a facsimile or an image writing system such as a laser beam printer. The invention relates to an optical deflector for scanning a body.

[0002]

2. Description of the Related Art FIG. 6 is a sectional view showing the structure of a conventional optical deflector.

The optical deflector 100 has a fixed shaft 104 press-fitted into a base member 102 on the stator side.
A rotor 106 (rotating body) is attached to the fixed shaft 104. The rotor 106 is axially supported by a dynamic pressure bearing in the radial direction, and is floated by a magnetic bearing 108 in the thrust direction.

The rotor 106 has a light source (not shown).
A polygon mirror 110 (polygon mirror) that deflects the light beam emitted from the light source is attached. The rotor 10
6 has a ring shape as a whole, and 8
A drive magnet 112 in which N poles and S poles are alternately magnetized such that adjacent sections have different polarities in each equally divided section.
Is glued.

On the other hand, an iron-based drive circuit board 114 is disposed on the base member 102. On the iron-based drive circuit board 114, a drive coil 116 which is a coreless coil is provided.
Are arranged at each predetermined position.

The excitation switching of the drive coil 116 is controlled by the iron-based drive circuit board 114, and the rotor 106 is driven to rotate by the magnetic force acting between the drive coil 112 and the drive magnet 112.

[0007] In response to demands for high-speed driving and low current,
In order to increase the magnetic force of the drive magnet 112,
The drive magnet 112 is increased in volume, or a small neodymium magnet (not shown) having a relatively strong magnetic force is used.

In recent years, downsizing, high-speed starting, low loss, and low cost have been demanded. As described above, increasing the volume of the driving magnet 112 requires, as shown in FIG. And iron drive board 114
Is effective to increase the magnetic flux density of the magnetic flux B2 between the rotation speed and the inertia force (inertia force) of the rotating body 106.
And the loss during driving increases. Further, increasing the volume of the drive magnet 112 causes a problem that the size of the optical deflector 100 is increased.

On the other hand, when a neodymium magnet is used, a relatively strong magnetic force can be obtained, and miniaturization and high-speed startup are possible. However, since it is very expensive, there is a problem that the cost is increased.

In particular, there are the following problems in increasing the magnetic flux density of the magnetic flux B2 between the driving magnet 112 and the iron-based driving board 114.

As a first problem, by increasing the magnetic flux density, the attraction force acting between the drive magnet 112 and the iron-based drive board 114 increases, and the rotating body 106 fixing the drive magnet 112 is increased. The force in the thrust direction (on the iron-based drive board 114 side) acting on the motor increases.

For this reason, the load on the magnetic bearing 108 that supports the rotating body 106 in the thrust direction is increased, and there is a problem that the magnetic bearing 108 needs to be enlarged and a strong magnet must be used.

As a second problem, there is a problem that an increase in the magnetic flux density causes an increase in an alternating magnetic field and an increase in iron loss.

Here, usually, the magnetic flux density of the magnetic flux B2 between the driving magnet 112 and the iron-based driving board 114 is designed to be uniform. However, as shown in FIG. Leakage magnetic flux B <b> 1 not contributing to driving of rotating body 106 is generated.

Therefore, in order to solve the above-mentioned problems, how to effectively use the leakage magnetic flux B1 for driving is a clue for solving the problem.

[0016]

SUMMARY OF THE INVENTION In view of the above fact, the present invention adjusts the distance between the driving magnet and the driving coil to effectively utilize the leakage magnetic flux for driving, thereby reducing the size. It is an object of the present invention to provide an optical deflector capable of realizing high-speed startup, low loss and low cost.

[0017]

According to a first aspect of the present invention, there is provided an optical deflector having a base member and a rotating member rotatably provided with respect to the base member, wherein the base member or the rotating member is rotated. A drive magnet in which N poles and S poles are alternately arranged along the circumferential direction on one side of the body, and a layer in which a conductive wire is wound and disposed on the other of the base member or the rotating body so as to face the drive magnet. In a light deflector in which the rotating body rotates with respect to the base member by a magnetic force generated between the drive magnet and the driving coil, the drive member having the base member or the rotating body, A separation distance adjusting means for reducing a separation distance between a driving coil and the driving magnet is provided.

Next, the operation and effect of the optical deflector according to the first aspect will be described.

A rotating member is provided on the base member so as to be rotatable with respect to the base member. The rotating body rotates with respect to the base member by a magnetic force generated between the driving magnet and the driving coil.

However, conventionally, there has been a problem that a part of the magnetic flux from the driving magnet toward the driving coil leaks from the space near the driving magnet to the outside, so that the driving efficiency cannot be improved.

Therefore, according to the present invention, the distance between the drive coil and the drive magnet can be adjusted by the distance adjusting means while the distance between the rotating body and the base member is kept constant. The magnetic flux leaked outside in the deflector can be effectively used, and the leakage of the magnetic flux can be reduced or prevented. Therefore, the rotating body can be started at a high speed, and the driving efficiency can be increased.

As a result, since it is not necessary to increase the magnetic flux density between the drive coil and the drive magnet, it is not necessary to increase the volume of the drive magnet, and the size of the optical deflector can be reduced.

Also, since it is not necessary to increase the volume of the driving magnet, it is not necessary to increase the size of the rotating body. As a result, an increase in the inertial force of the rotating body can be prevented, so that a loss during driving can be reduced (low loss).

Further, by effectively utilizing the leakage magnetic flux, it is not necessary to use an expensive neodymium magnet or the like for the drive magnet, and low cost can be realized.

[0025] In the optical deflector according to claim 2, it is preferable that a distance between an upper surface of the drive coil and a lower surface of the drive magnet is 0.5 mm or more and 1.0 mm or less.

According to a third aspect of the present invention, in the optical deflector, a drive circuit board made of a magnetic material and controlling the rotation of the rotating body is provided on the base member, and the drive coil is provided on the drive circuit board. Preferably, the drive magnet is provided on the rotating body side, and the separation distance adjusting means is provided between the drive coil and the drive circuit board.

According to a fourth aspect of the present invention, in the optical deflector, the thickness of the distance adjusting means is such that the distance between the upper surface of the drive coil and the lower surface of the drive magnet is 0.5 mm or more.
Preferably, the thickness is set to be 0 mm or less.

In the optical deflector according to the fifth aspect, it is preferable that the distance adjusting means is made of a non-magnetic material.

[0029] In the optical deflector according to claim 6, the separation distance adjusting means is preferably an elastic body.

[0030] In the optical deflector according to claim 7, the separation distance adjusting means is preferably formed of an adhesive layer having a vibration absorbing property.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical deflector according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the optical deflector 10 includes a base member 12 on the stator side. A circular opening 14 is formed in the base member 12, and a fixed shaft 16 is press-fitted into the opening 14.

A plurality of herringbone grooves 18 having a depth of several μm for forming a dynamic pressure bearing are formed on the outer peripheral surface of the fixed shaft 16.

A rotating body 20 described later is rotatably mounted on the fixed shaft 16.

At the outer peripheral edge of the opening 14, a thrust bearing magnet 22 (a stator magnet 22) functioning as a magnetic bearing for floating the rotating body 20 is arranged.

On a portion other than the stator-side magnet 22 on the base member 12, there is provided an iron-based drive circuit board 26 which controls the excitation switching of the drive coil 24, which will be described later, and controls the rotation drive of the rotating body 20. Are located.

As shown in FIG. 2, on the iron-based drive circuit board 26, an annular positioning member 28 (separation distance adjusting means) is arranged concentrically with the opening 14. The positioning member 28 is formed of a non-magnetic elastic member.

The thickness T of the positioning member 28 in the axial direction (the direction of arrow A in FIG. 1) of the optical deflector 10 is
4 is set so that the shortest distance between the upper surface of the drive magnet 4 and the lower surface of the drive magnet 30 described later is 0.5 mm or more and 1.0 mm or less.

Further, as shown in FIG.
On the 8, six drive coils 24 are arranged at substantially equal intervals.

The drive coil 24 is formed by laminating a plurality of conductor layers wound on the same plane a plurality of times in the axial direction of the optical deflector 10. It has a trapezoidal shape.

On the other hand, in the rotating body 20, a rotating shaft 32 made of ceramic and formed in a hollow cylindrical shape is inserted through the fixed shaft 16 with a gap of about 3 to 8 μm.

For this reason, when the rotating shaft 32 rotates around the fixed shaft 16 at high speed, a dynamic pressure is generated between the fixed shaft 16 and the rotating shaft 32, and the dynamic pressure causes the dynamic shaft to move along the radial direction of the fixed shaft 16. And the opposing dynamic pressure bearings are configured.

A rotating polygon mirror 34 (polygon mirror) made of aluminum is attached to a predetermined position on the outer periphery of the rotating shaft 32 by a fixing spring (not shown). The rotary polygon mirror 34 is formed in a polygonal column shape, and each side surface is processed into a mirror surface.

An aluminum flange 36 is fixed to the lower part of the rotary polygon mirror 34 by shrink fitting or press fitting.

A ring-shaped drive magnet 30 is mounted on the lower surface of the flange 36 at a position corresponding to the drive coil 24.

In the drive magnet 30, N poles and S poles are alternately magnetized so that adjacent sections have different polarities in each section divided into eight equal parts at a central angle of 45 degrees.

A comb-shaped frequency power generation pattern 38 (FG pattern 38) is formed on the upper surface of the iron-based drive circuit board 26 at a position facing the drive magnet 30 by etching or the like. The rotation speed of the rotating body 20 is detected based on the induced voltage generated in the pattern 38.

On the bottom surface of the rotating shaft 32, a magnet 40 for the thrust bearing (rotor-side magnet 40) constituting a magnetic bearing with the stator-side magnet 22 is attached. The rotor-side magnet 40 and the stator-side magnet 22 are magnetized to have the same polarity so that a repulsive force acts.

In this magnetic bearing, the repulsive force acting between the rotor-side magnet 40 and the stator-side magnet 22 is set to be larger than the load of the rotating body 20. The body 20 rises.

As described above, the rotating body 20 is supported in the thrust direction (the direction of arrow A in FIG. 1) by the magnetic bearing, and is supported in the radial direction (the direction of arrow B in FIG. 1) by the dynamic pressure bearing. I have.

Thus, by controlling the iron-based drive circuit board 26 to apply a voltage to each drive coil 24, a current flows through each drive coil 24 and each drive coil 24
The electromagnetic field acts on the magnetic field of the driving magnet 30 and the above-described current, and a rotational driving force is generated on the driving magnet 30. By this rotation driving force, the rotating body 20 rotates at a high speed in a state of floating in the air.

Next, the operation and effects of the optical deflector 10 of the present embodiment will be described.

As shown in FIG. 3, the iron-based drive circuit board 26
The drive coil 24 is mounted on the iron-based drive circuit board 26 via the positioning member 28 with the separation distance between the drive coil 2 and the drive magnet 30 kept constant.
The distance between the drive magnet 30 and the drive magnet 30 can be reduced.

As a result, the leakage magnetic flux B1 which has conventionally leaked is passed through the inside of the drive coil 24, whereby the leakage magnetic flux B1 can be effectively used. Thus, the magnetic flux density of the magnetic flux B1 passing through the inside of the drive coil 24 increases, so that high-speed startup and low current of the rotating body 20 can be realized.

For this reason, it is not necessary to increase the magnetic flux density of the magnetic flux B2 from the drive magnet 30 to the iron-based drive circuit board 26, so that it is not necessary to increase the size of the drive magnet 30. As a result, the size of the rotating body 20 and thus the size of the optical deflector 10 can be reduced.

Further, since it is not necessary to increase the size of the drive magnet 30, an increase in the weight of the rotating body 20 can be prevented, and an increase in the inertial force of the rotating body 20 can be prevented. As a result, it is possible to reduce the loss during the rotation driving of the rotating body 20.

Further, since it is not necessary to increase the magnetic flux density of the magnetic flux B2 from the drive magnet 30 to the iron-based drive circuit board 26, it is possible to prevent the increase in the alternating magnetic field and the iron loss.

Further, by preventing the magnetic flux density of the magnetic flux B2 from the drive magnet 30 to the iron-based drive circuit board 26 from increasing, the drive magnet 30 and the iron-based drive circuit board 2 are prevented from increasing.
6 can be prevented from increasing. Therefore, an increase in the load on the magnetic bearing can be prevented, and the problem of insufficient supporting force of the rotating body 20 does not occur.

Furthermore, it is not necessary to use a strong magnet, and the cost can be reduced.

Here, the positional relationship (separation distance) between the drive magnet 30 and the drive coil 24, the relationship between the magnetic flux density of the magnetic flux B1 passing through the drive coil 24, and the vibration (amplitude) of the drive coil 24 will be described.

FIG. 4 shows the magnetic flux density (T) of the magnetic flux passing through the inside of the drive coil 24 on the vertical axis, and the distance (m) between the lower surface of the drive magnet 30 and the upper surface of the drive coil 24 on the horizontal axis.
m) is a graph showing the relationship between the two.

The distance between the lower surface of the drive magnet 30 and the iron drive circuit board 26 is set to 4 mm.

As shown in FIG. 4, the magnetic flux density B1 passing through the drive coil 24 increases as the distance between them decreases. This magnetic flux density B1 has a separation distance of 0.5
When the distance becomes mm, the inclination is substantially constant.

As shown in FIG. 4, the separation distance is 2.0 mm
Then, the magnetic flux density of the magnetic flux B1 passing through the inside of the drive coil 24 is 0.060 (T), and the vibration of the drive coil 24 is 0.18 (μm). Also, the separation distance is 1.5mm
Then, the magnetic flux density of the magnetic flux B1 passing through the inside of the drive coil 24 is 0.069 (T), and the vibration of the drive coil 24 is 0.25 (μm). Furthermore, the separation distance is 1.0m
At m, the magnetic flux density of the magnetic flux B1 passing through the inside of the drive coil 24 is 0.074 (T), and the vibration of the drive coil 24 is 0.279 (μm).

On the other hand, as shown in FIG.
Move toward the drive magnet 30 as the drive coil 24
Vibration (amplitude) is large.

This is because an upward or downward magnetic field generated in the drive coil 24 when current is supplied acts on the drive magnet 30 to repeatedly attract and repel the drive coil 24. It increases as it gets closer. These vibrations cause electromagnetic noise.

Therefore, the optical deflector 10 of the positioning member 28
Is set so that the shortest distance between the upper surface of the drive coil 24 and the lower surface of the drive magnet 30 is 1.0 mm or less, so that the leakage magnetic flux B1 can be effectively used. Thus, the magnetic flux density of the magnetic flux B1 passing through the drive coil 24 can be effectively increased.

On the other hand, the thickness T of the positioning member 28 is set to such a value that the shortest distance between the upper surface of the drive coil 24 and the lower surface of the drive magnet 30 is 0.5 mm or more in FIG. As shown in the figure, even closer to 0.5 mm, there is not much change in the magnitude of the air gap magnetic flux density,
On the contrary, it is not preferable because the precision of the parts is increased.

That is, by setting the thickness T of the positioning member 28 as described above, it is possible to increase the magnetic flux density of the magnetic flux B1 passing through the drive coil 24, and at the same time, to prevent an increase in component accuracy. A synergistic effect can be obtained.

Further, since the positioning member 28 is made of a non-magnetic material, the iron loss is reduced as much as possible in comparison with the case where the drive coil 24 is directly disposed on the drive circuit board 26 without the intervention of the positioning member 28. be able to.

Further, since the positioning member 28 is made of an elastic material, even if the magnetic flux B1 passes through the drive coil 24, the vibration of the drive coil 24 can be absorbed, and an increase in electromagnetic noise can be prevented.

Even when the positioning member 28 is formed of an adhesive layer having a vibration absorbing property, the vibration of the drive coil 24 can be absorbed, and an increase in electromagnetic noise can be prevented.

Next, an optical deflector according to a second embodiment of the present invention will be described.

The same components as those of the optical deflector 10 according to the first embodiment are denoted by the same reference numerals, and the description will not be repeated.

As shown in FIG. 5, the optical deflector of the present embodiment is different from the optical deflector 10 of the first embodiment in the shape of the positioning member 50.

That is, the positioning member 50 used in the optical deflector of this embodiment is set in a substantially trapezoidal shape along the outer periphery of the drive coil 24.

In the optical deflector of this embodiment, the same operation and effect as those of the optical deflector 10 of the first embodiment can be obtained.

In particular, the positioning member 50 of the present embodiment can reduce the mass of the positioning member 50 as compared with the positioning member 28 of the first embodiment. For this reason, the rotating body 2
0 inertia force can be reduced, and loss during rotational driving can be reduced. Further, the load on the magnetic bearing that supports the rotating body 20 can be reduced.

The shape of the positioning member is not limited to the donut shape as in the first embodiment and the trapezoidal shape along the drive coil 24 as in the second embodiment, but may be other shapes.

[0080]

According to the optical deflector of the present invention, downsizing, high-speed starting, low loss and low cost can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical deflector according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a drive coil, a separation distance adjusting unit, and a drive circuit board that constitute the optical deflector according to the first embodiment of the present invention.

FIG. 3 is a state diagram of a magnetic flux near a drive coil of the optical deflector according to the first embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a separation distance between a drive magnet and a lower surface of a drive coil and a magnetic flux density passing through the drive coil.

FIG. 5 is a configuration diagram of a drive coil, a separation distance adjusting unit, and a drive circuit board that constitute an optical deflector according to a second embodiment of the present invention.

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

FIG. 7 is a state diagram of a magnetic flux near a drive coil of a conventional optical deflector.

[Description of Signs] 10 Optical deflector 12 Base member 20 Rotating body 24 Drive coil 26 Drive circuit board 28 Positioning member (separation distance adjusting means) 30 Drive magnet

Claims (7)

[Claims] 1. A base member, and a rotating body rotatably provided with respect to the base member, wherein one of the base member and the rotating body has an N pole and an S pole along a circumferential direction. Are provided alternately, and a drive coil is provided on the other of the base member or the rotating body, the drive coil having a layer in which a conductive wire is wound and disposed opposite to the drive magnet, and the drive magnet and the drive coil are provided. In the optical deflector in which the rotating body rotates with respect to the base member by a magnetic force generated between the base member and the rotating body, a separation distance adjustment for reducing a separation distance between the driving coil and the driving magnet is provided on the base member or the rotating body. An optical deflector comprising means. 2. The optical deflector according to claim 1, wherein a distance between an upper surface of the drive coil and a lower surface of the drive magnet is 0.5 mm or more and 1.0 mm or less. 3. A drive circuit board, which is made of a magnetic material and controls the rotation of the rotating body, is provided on the base member, the drive coil is provided on the drive circuit board side, and the drive magnet is provided on the base member. The said separation distance adjustment means provided in the said rotating body side, was provided between the said drive coil and the said drive circuit board, The Claim 1 or 2 characterized by the above-mentioned.
An optical deflector according to item 1. 4. A thickness of the separation distance adjusting means is set to a thickness such that a separation distance between an upper surface of the drive coil and a lower surface of the drive magnet is 0.5 mm or more and 1.0 mm or less. The optical deflector according to claim 3, wherein 5. The optical deflector according to claim 1, wherein said separation distance adjusting means is made of a non-magnetic material. 6. The optical deflector according to claim 5, wherein said separation distance adjusting means is an elastic body. 7. The optical deflector according to claim 5, wherein said separation distance adjusting means is formed of an adhesive layer having a vibration absorbing property.