JPH11218714A - Optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical deflector capable of suppressing the oscillation of a coil substrate on which a rotor and a driving coil are fixed. SOLUTION: An oscillation suppressing magnet 30 of which outer periphery is magnetized by alternately arraying S and N poles so that a magnetic pole having the same polarity as that of a driving magnet 20 is arranged in the radius direction of the magnet 20 is fixed on a position which is the same axis as the magnet 20 and opposed to the side face of a driving coil 28 on the side of a rotor 40. Since rotary shaft direction (vertical direction) force applied from the coil 28 fixed on a coil substrate 26 to the magnet 30 fixed on the rotor 40 side and rotary shaft direction (vertical direction) force applied from the coil 28 to the magnet 20 fixed on the rotor 40 side are mutually canceled, the oscillation of the rotor 40 and the coil substrate 26 can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading system such as a digital copying machine or a facsimile or an image writing system such as a laser beam printer for scanning a document image or a photosensitive member with a light beam emitted from a laser light source. It relates to an optical deflector.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration of a conventional optical deflector. In FIG. 1, a sleeve 1 externally fitted via a dynamic pressure bearing to a fixed shaft 10 erected on a base member 18 on the stator 50 side.
A pedestal 16 is fixed to 4, and a rotating polygon mirror 100 (polygon mirror) for deflecting the light beam in a predetermined direction is fixed on the pedestal 16. The fixed shaft 10 is provided with a groove 10A for generating dynamic pressure.
Air is supplied to a gap 12 provided between the fixed shaft 10 and the sleeve 14 to generate a dynamic pressure between the fixed shaft 10 and the sleeve 14, thereby forming a dynamic pressure bearing.
And a rotor (rotating body) 40 having the same.

In the lower portion of the pedestal 16 constituting the rotor 40, N-poles and S-poles are alternately arranged so that adjacent sections have different polarities in each of eight sections each having a central angle of 45 degrees in a ring shape. The drive magnet 20 magnetized is adhered.

A coil substrate 26 is fixed to the base member 18 on the stator 50 side.
On the upper side, six drive coils 28 are arranged at predetermined intervals so as to oppose each other in the circumferential direction of the drive magnet 20, and a control circuit (not shown) for controlling the excitation of the drive coils 28 is provided. A magnetic pole detecting element (for example, a Hall element) 34 for detecting the coil magnetic pole (U-phase, V-phase, W-phase) of each drive coil 28 is provided below the coil substrate 26 so as to correspond to each drive coil 28. . 32 is a yoke, 22,
Reference numeral 24 denotes a thrust bearing magnet.

A drive circuit 28, which is a coreless coil provided on a coil substrate 26, is subjected to excitation switching control by a control circuit, and the rotor 40 is rotated by a magnetic force acting between the drive coil 28 and the drive magnet 20 on the rotor 40 side. It is configured to be driven.

FIG. 8 schematically shows the relationship between the force acting between the drive coil 28 on the stator 50 and the drive magnet 20 on the rotor 40. The cross section of the drive coil 28 and only the drive magnet 20 are taken out. Is shown. At the timing shown in FIG. 8, a current flows in a direction from the back of the paper toward the front at a portion 28A of the cross section of the drive coil 28,
A current flows through the portion 28B in a direction from the front to the back of the page. At this time, a magnetic field is generated in the drive coil 28 in the direction of the arrow X. In the figure, the upper side (the magnet side) of the drive coil 28 is the N pole and the lower side is the S pole.

On the other hand, the direction of the magnetic field at the N pole of the drive magnet 20 is in the direction of arrow P, and the direction of the magnetic field at the S pole is in the direction of arrow Q. At this time, according to Fleming's left-hand rule, a magnetic force F4 is directed to the right in the drawing at the portion 28A of the cross section of the drive coil 28, and a magnetic force F5 is applied to the portion 28B of the cross section of the drive coil 28 in the same direction as the magnetic force F4. Works. Since the drive coil 28 is fixed to the stator 50 side, a magnetic force F4 is applied to the N pole and the S pole of the drive magnet 20.
Due to the reaction caused by F5, the rotational force F4 'in the left direction on the drawing,
F5 'acts, and as a result, the rotor 40 on which the drive magnet 20 is fixed is rotated in the arrow Y direction.

When the optical deflector is driven, a force acts on the rotor 40 in the direction of the rotation axis (vertical direction) in addition to the force acting on the rotor in the rotation direction. This is the drive coil 28
An S-pole or an N-pole is formed on the upper surface of the drive coil 28 depending on the direction of the current flowing through the rotor, and this acts on the magnetic pole of the drive magnet 20 fixed to the rotor 14 side. A directional force is generated. Due to the vertical force, the rotor 40 and the coil substrate 26 fixed to the stator 50 side vibrate due to the action and reaction thereof. This vibration occurs not only during steady rotation of the rotor 40 but also particularly at the time of startup, and the rotor 40 may collide with the stator 50 in some cases.

Further, the vibration during the steady rotation is generated by the coil substrate 26.
The noise caused by chattering (vibration) and the image quality are adversely affected when used in a laser printer.

A technique for forming an air reservoir 70 above the dynamic pressure bearing as shown in FIG. 9 to suppress the vibration is disclosed in Japanese Patent Laid-Open No. 6-43381, and as shown in FIG. The cover 8 covers the rotary polygon mirror 100.
A technique of providing 0 is disclosed in Japanese Patent Application Laid-Open No. Hei 3-9318.

Further, as shown in FIG. 10, the drive coil 28 is connected to the base member 1 for the purpose of suppressing the chatter of the coil substrate 26.
For example, the adhesive 8 is bonded to the substrate 8 with an adhesive 90. These techniques are common, for example.

[0012]

In the above-mentioned conventional example, when the technique of forming an air pocket above the dynamic pressure bearing is adopted, the effect of suppressing the vibration of the rotor is because the air pocket functions as an air damper. However, vibration of the coil substrate cannot be suppressed. Further, there is a problem that processing is complicated and cost is increased.

When a technique of providing a cover so as to cover the rotary polygon mirror is employed, it is effective for noise reduction, but the cover needs to cover the entire rotor, so that the cover becomes large. There is a problem that the number of parts also increases.

Further, the method of bonding the drive coil to the base member is very effective against chattering of the coil substrate. However, since the coil substrate is completely fixed, the vibration of the rotor increases. Problem.

The present invention has been made in view of such circumstances, and has as its object to provide an optical deflector that suppresses vibration of a coil substrate on which a rotor and a drive coil are fixed.

[0016]

According to one aspect of the present invention, there is provided a drive magnet fixed to a rotor side and having a plurality of magnetic poles having different polarities alternately arranged in a circumferential direction. A drive coil fixed to the stator side facing the drive magnet so as to generate a rotational torque, and externally fitted via a dynamic pressure bearing to a fixed shaft provided on the stator side. A rotating polygon mirror that deflects the light beam in a predetermined direction is fixedly provided, and in an optical deflector that rotationally drives the rotating polygon mirror by excitingly controlling the drive coil, the same number of poles as the drive magnet is provided. And a vibration suppressing magnet in which a plurality of magnetic poles having different polarities are alternately arranged in the circumferential direction so that magnetic poles having the same polarity as the magnetic poles of the driving magnet are located in the radial direction of the driving magnet. On the magnet coaxially, and it is characterized in that fixedly provided at a position facing the side surface of the driving coil on the rotor side.

According to the optical deflector of the first aspect, the vibration suppressing magnet fixed on the rotor side receives the drive coil fixed on the coil substrate on the stator side in the rotation axis direction (vertical direction). The direction of the axis of rotation (vertical direction) that the force and the drive magnet fixed to the rotor side receive from the drive coil
Therefore, the vibrations of the rotor and the coil substrate can be suppressed.

According to the optical deflector of the first aspect,
There is no need to provide a cover to cover the rotating polygon mirror to reduce noise as in the prior art, and furthermore, an adhesive work is required to adhere the drive coil to the base member to suppress chattering of the coil substrate. Therefore, miniaturization of the optical deflector and simplification of assembly can be achieved.

According to a second aspect of the present invention, in the optical deflector of the first aspect, 1/2 of the sum of the outer diameter and the inner diameter of the drive magnet is L1, and the outer diameter of the vibration suppressing magnet is L1. Is L2, and 1/2 of the sum of the distance from the outer peripheral portion of the drive coil to the shaft center and the distance from the inner peripheral portion to the shaft center is M
1. When the distance from the inner periphery to the axis center is M2, L
The size of each part is set so that 2 / L1 ≒ M2 / M1.

According to the optical deflector of the second aspect, by setting the dimensions of each part as described above, the time required for each magnetic pole of the drive magnet to pass above the drive coil and each magnetic pole of the vibration suppressing magnet are set. Since the time required for passing through the side surface of the drive coil can be matched, the force acting on the vibration suppressing magnet and the force acting on the drive magnet can be most effectively canceled in addition to the effect described in claim 1. Can be.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a structure of an optical deflector according to an embodiment of the present invention. The same elements as those of the conventional optical deflector shown in FIG.
Duplicate description will be omitted. The configuration of the optical deflector according to the embodiment of the present invention is different from that of the conventional optical deflector shown in FIG. The vibration suppressing magnet 30 magnetized on the outer peripheral surface so that the S pole and the N pole are alternately arranged in the circumferential direction so that the magnetic poles having the same polarity as the magnetic poles are located, is combined with the driving magnet 20. It is provided on the lower part of the sleeve 14 on the rotor 40 side so as to be coaxial and opposed to the side surface of the drive coil 28, and the other configuration is completely the same.

Next, when the vibration suppressing magnet 30 is provided below the sleeve 14, that is, below the rotor 40 in FIG. 2, the driving magnet 20 and the vibration suppressing magnet 30
Fig. 4 schematically shows the relationship between the forces applied to the components. 2, the driving magnet 20 and the vibration suppressing magnet 30 are rotating in the direction of arrow A. At the timing shown in FIG. 2, the S pole magnetic pole 60 is located above the driving coil 28,
The magnetic pole 61 of the S pole of the vibration suppressing magnet 30 is opposed to the side surface 28A of the drive coil 28. At this time, since a current flows in the direction of the arrow B on the side surface 28A of the drive coil 28, a magnetic field is generated in the direction of the arrow C by the right-hand rule of ampere, and the upper surface of the drive coil 28 becomes the N pole and the lower surface becomes the S pole. Become a pole. As a result, the attractive force F1 acts on the magnetic pole 60 (S-pole) of the drive magnet 20 fixedly provided on the rotor 40 side, and a downward force is applied in the figure.

On the other hand, the magnetic flux of the magnetic pole 61 (S-pole) magnetized on the side surface of the vibration suppressing magnet 30 facing the side surface 28A of the drive coil 28 flows in the direction of arrow D and flows on the side surface 28A of the drive coil 28. It intersects at right angles with the current (direction of arrow B). As a result, the magnetic force F2 acts on the side surface 28A of the drive coil 28 downward in the figure according to Fleming's left-hand rule. Due to the reaction of the magnetic force F2, a force F3 acts on the vibration-suppressing magnet 30 fixedly provided on the rotor 40 side, that is, below the sleeve 14, in the upward direction in the drawing.

As a result, the two forces acting on the driving magnet 20 and the vibration suppressing magnet 30 in opposite directions are made equal to each other, so that these two forces cancel each other out, so that a driving coil is generated. Vibration generated when the driving magnet receives a force in the axial direction (vertical direction) by the generated magnetic field can be suppressed.

FIG. 5 shows a state in which the optical deflector is driven.
The direction and timing of the coil current flowing through each of the U-phase, V-phase, and W-phase drive coils 28, the magnetic poles generated on the upper surface of the drive coil 28 at that time, and the drive magnet 20
It shows the direction and magnitude of the force that is received.

FIG. 6 shows the directions and timings of the currents flowing through the U-phase, V-phase, and W-phase drive coils 28 when the optical deflector is being driven, and the side surfaces of each drive coil 28 are magnetized for vibration suppression. The timing at which the N pole and the S pole of the driving coil 30 pass, and the vibration suppressing magnet 30
8 shows the direction and magnitude of the force received from the current flowing through the side surface of No. 8.

As can be seen from FIGS. 5 and 6, the driving magnet 20 and the vibration suppressing magnet 30 receive a force from the driving coil at the same cycle in the rotation axis direction (vertical direction).
Moreover, the forces applied to the two magnets 20, 30 are opposite. By arranging the driving magnet 20 and the vibration suppressing magnet 30 in this manner, these magnets 20, 3
It is possible for the forces acting on zero to cancel each other out. That is, vibration can be suppressed.

FIG. 3 shows an example of the positional relationship between the vibration suppressing magnet 30 and the driving magnet 20 and the arrangement and size of the magnetic poles, and FIG. 4 shows an example of the positional relationship and the size of the driving coil. In FIG. 3, the vibration suppressing magnet 30 has the same number of poles as the driving magnet 20, and the S pole and the N pole are circular so that a magnetic pole having the same polarity as the magnetic pole of the driving magnet 20 is located in the radial direction of the driving magnet 20. The outer peripheral surface is magnetized so that eight magnetic poles are alternately arranged in the circumferential direction. This is because the forces applied to the two magnets 20 and 30 act in opposite directions as described above with reference to FIG.

In FIG. 3, the half of the sum of the outer diameter and the inner diameter of the drive magnet 20 is L1, and the outer diameter of the vibration suppressing magnet 30 is L2. Assuming that the half of the sum of the distance to the shaft center 66 and the distance from the inner periphery to the rotation shaft center 66 is M1, and the distance from the inner periphery to the rotation shaft center 66 is M2, L2
The outer diameter L2 of the vibration suppressing magnet 30 that satisfies / L1 ≒ M2 / MI is set, the time required for each magnetic pole of the driving magnet 20 to pass above the driving coil 28, and the time when each magnetic pole of the vibration suppressing magnet 30 Most effectively by matching the times of passage through the two magnets 20,
It is possible to negate the force acting on 30.

In the present embodiment, the drive magnet 20 and the vibration suppressing magnet 30 are provided separately, but may be integrated.

[0031]

As described above, according to the first aspect of the present invention, according to the optical deflector of the first aspect, the vibration suppressing magnet fixed to the rotor is provided on the stator side. The force in the rotational axis direction (vertical direction) received from the drive coil fixed to the coil substrate and the force in the rotational axis direction (vertical direction) received from the drive coil by the drive magnet fixed to the rotor side mutually cancel each other. Therefore, vibration of the rotor and the coil substrate can be suppressed.

According to the optical deflector of the first aspect,
There is no need to provide a cover to cover the rotating polygon mirror to reduce noise as in the prior art, and furthermore, an adhesive work is required to adhere the drive coil to the base member to suppress chattering of the coil substrate. Therefore, miniaturization of the optical deflector and simplification of assembly can be achieved.

According to the optical deflector of the second aspect, by setting the dimensions of each part as described above, the time required for each magnetic pole of the drive magnet to pass above the drive coil and each magnetic pole of the vibration suppressing magnet are set. Since the time required for passing through the side surface of the drive coil can be matched, the force acting on the vibration suppressing magnet and the force acting on the drive magnet can be most effectively canceled in addition to the effect described in claim 1. Can be.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram schematically showing a relationship between forces applied to a driving magnet and a vibration suppressing magnet from a driving coil in FIG. 1;

FIG. 3 shows a vibration suppressing magnet 30 and a driving magnet 2;
Explanatory drawing which shows an example of the positional relationship with 0, the arrangement | positioning state of a magnetic pole, and a magnitude | size.

FIG. 4 is an explanatory diagram showing an example of a positional relationship and a size of a drive coil.

FIG. 5 is an explanatory diagram showing directions and timings of coil currents flowing through each drive coil, magnetic poles generated on the upper surface of the drive coil at that time, and directions and magnitudes of forces applied to the drive magnet from the magnetic poles.

FIG. 6 shows the direction and timing of a current flowing through each drive coil, and the side of each drive coil is indicated by N of a vibration suppressing magnet.
FIG. 4 is an explanatory diagram showing the timing at which the poles and S poles pass, and the direction and magnitude of the force that the vibration suppressing magnet receives from the current flowing through the side surface of each drive coil.

FIG. 7 is a sectional view showing the structure of a conventional optical deflector.

FIG. 8 is an explanatory diagram schematically showing a relationship between forces acting between a drive coil and a rotor in the optical deflector shown in FIG. 7;

FIG. 9 is a sectional view showing another example of the structure of a conventional optical deflector.

FIG. 10 is a sectional view showing another example of the structure of the conventional optical deflector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixed shaft 14 Sleeve 16 Pedestal 18 Base member 20 Drive magnet 28 Drive coil 30 Vibration suppression magnet 40 Rotor 50 Stator

Claims (2)

[Claims] 1. A drive magnet fixed to a rotor side and having a plurality of magnetic poles of different polarities alternately arranged in a circumferential direction, and fixed to a stator side facing the drive magnet so as to generate a rotational torque. Provided with a driving coil provided, and a rotating polygon mirror that deflects the light beam in a predetermined direction is fixed to a sleeve externally fitted to a fixed shaft provided on the stator side via a dynamic pressure bearing, In the optical deflector that rotationally drives the rotary polygon mirror by excitingly controlling the drive coil, a magnetic pole having the same number of poles as the drive magnet and having the same polarity as the magnetic pole of the drive magnet is positioned in the radial direction of the drive magnet. As described above, a vibration suppressing magnet in which a plurality of magnetic poles having different polarities are alternately arranged in the circumferential direction is coaxial with the driving magnet, and is opposed to a side surface of the driving coil on the rotor side. Optical deflector, characterized in that fixedly provided at a position. 2. The half of the sum of the outer diameter and the inner diameter of the driving magnet is L1, and the outer diameter of the vibration suppressing magnet is L1.
2. When the sum of the distance from the outer periphery to the shaft center of the drive coil and the distance from the inner periphery to the shaft center is M1, the distance from the inner periphery to the shaft center is M2 / L2 / L2. L1 ≒
The optical deflector according to claim 1, wherein the dimensions of each part are set so as to be M2 / M1.