JP3858557B2 - Optical deflector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflector mounted on a laser copying machine, a laser printer, or the like.
[0002]
[Prior art]
In recent years, a proportion of the use of a dynamic pressure air bearing type optical deflector mounted on a laser copying machine, a laser printer or the like is increasing. The reason for this is that the number of rotations of the optical deflector is steadily increasing as the speed and resolution of laser copying machines and laser printers increase.
[0003]
That is, in conventional bearings using dynamic pressure fluid such as ball bearings and oil, oil is used for the medium on the fixed shaft side and the rotating body side. This is because there is a problem such as rapid deterioration of the optical deflector and shortening the life of the optical deflector.
[0004]
There are roughly two types of structures of such a dynamic pressure air bearing type optical deflector. One is a type in which the drive magnet provided on the rotating body and the coil provided on the fixed side face each other in the radial direction, which is called a radial gap type, and the other is the drive magnet provided on the rotating body and the fixed side. Is a type facing the rotating shaft direction, and is called an axial gap type or a surface facing type.
[0005]
Here, as a configuration example of the radial gap type optical deflector, as represented by Japanese Patent Laid-Open No. 9-311287 in FIG. 8, a rotating sleeve 102 is provided around a fixed shaft 100 while maintaining a predetermined gap. It is inserted.
[0006]
A polygon mirror 104 and a drive magnet 106 are fixed to the rotating sleeve 102, and a drive coil 108 is disposed opposite the drive magnet 106 in the radial direction of the drive magnet 106.
[0007]
On the other hand, as an example of the configuration of the axial gap type optical deflector, as represented by Japanese Patent Laid-Open No. 9-312962 in FIG. 9, a rotating sleeve 112 fitted around a fixed shaft 110 while holding a predetermined gap. The polygon mirror 114 and the drive magnet 116 are fixed to each other, and a drive coil 118 is disposed on the drive magnet 116 so as to face the axial direction of the fixed shaft 110.
[0008]
[Problems to be solved by the invention]
Here, FIGS. 10A and 10B show the coil 120 disposed in the drive coil 118, but the coil 120 actually contributes to the drive of the drive magnet 116 shown in FIG. The portion is an area 122. On the other hand, the area 124 on the inner edge side and the area 126 on the outer edge side of the drive coil 118 of the coil 120 hardly contribute to the drive of the drive magnet 116.
[0009]
However, as shown in FIG. 9, since the drive coil 118 is disposed outside the outer periphery of the rotating sleeve 112, in order to make the area 122 (see FIG. 10) face the drive magnet 116, the drive magnet is correspondingly increased. The length of 116 in the radial direction must be increased. Therefore, the inertia of the rotating body 128 increases, the startup time of the laser printer is long, and the steady current also increases.
[0010]
In consideration of the above-described facts, an object of the present invention is to obtain an optical deflector that minimizes inertia of a rotating body, shortens the startup time of a laser printer, and has a small steady current.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a fixed shaft, a cylindrical sleeve that is inserted through the fixed shaft with a gap and rotates by generating dynamic pressure between the fixed shaft, and a rotation attached to the sleeve. A polygon mirror, an annular drive magnet directly fitted on the sleeve, a drive coil in which a plurality of coils are arranged annularly facing the drive magnet, and a circuit board on which the drive coil is mounted. In the optical deflector, all the winding portions that are located on the inner edge side of the driving coil and do not contribute to driving are arranged between the lower surface of the sleeve and the circuit board.
In the invention described in claim 1, is inserted through the circular cylindrical sleeve with a gap to the fixed shaft, rotates by generating dynamic pressure between the fixed shaft. A rotating polygon mirror and a drive magnet are attached to the sleeve.
[0012]
This drive magnet is faced with a drive coil in which a plurality of coils are arranged in an annular shape, and a winding portion of a coil located on the inner edge side of the drive coil is arranged inside the inner edge of the drive magnet.
[0013]
On the other hand, when a current is passed through the coil, a magnetic field is generated in the coil, and a rotating body constituted by a rotating polygon mirror or the like can be rotated around a fixed axis by the magnetic force received by the magnetic field. The portion hardly contributes to the rotation of the rotating body.
[0014]
For this reason, the inner diameter dimension of a drive coil becomes small by arrange | positioning all the winding parts which do not contribute to the drive located in the inner edge side of a drive coil between the lower surface of a sleeve, and a circuit board.
[0015]
On the other hand, since the winding portion of the coil does not contribute to driving the rotating body, the outer diameter of the drive coil is reduced without reducing the inner diameter of the drive coil without affecting the magnetic force. can do.
[0016]
Thus, by reducing the outer diameter of the drive coil, the outer diameter of the drive magnet can also be reduced, and the inertia for rotating the rotating body can be prevented from becoming unnecessarily large. This can contribute to shortening the startup time of the printer and reducing the steady current.
[0017]
According to a second aspect of the present invention, in the optical deflector according to the first aspect, the circuit board is iron-based, and an end of the circuit board is located at an inner edge of the winding portion. And
[0019]
In the second aspect of the invention, the circuit board is made of iron and the end of the circuit board is arranged at the inner edge of the winding portion so that the end face of the iron board is located on the inner edge of the drive coil. Compared with the case where the coil extends to the winding portion, the force for attracting the drive magnet to the drive coil side is weakened, and the magnetism of the magnet that floats a rotating body such as a rotary polygon mirror can be reduced.
[0020]
In addition, since the end face of the iron-based substrate does not extend to the coil winding part, the magnetic flux flowing from the drive magnet to the coil winding part is reduced as much as possible (leakage of magnetic flux leakage), and the efficiency of the optical deflector is reduced. Can be prevented.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an optical deflector 10 according to the first embodiment.
[0022]
Here, an outline of the configuration of the optical deflector 10 will be described. The optical deflector 10 is provided with a fixed shaft 12, and the fixed shaft 12 is fixed to the housing 18 with screws 14 and nuts 16.
[0023]
A plurality of dynamic pressure generating grooves 20 of several μm are formed on the outer peripheral surface of the fixed shaft 12, and a cylindrical rotating sleeve 22 is provided on the fixed shaft 12 with a gap of several μm between the fixed shaft 12. And is rotatably inserted.
[0024]
An annular drive magnet 24 is fitted on the outer periphery of the rotary sleeve 22. A pedestal 26 is projected on the top surface of the drive magnet 24, and a rotary polygon mirror 28 is placed on the pedestal 26 and fixed to the rotary sleeve 22 by an annular fixing member 30.
[0025]
On the other hand, a holder 34 is erected in a ring shape on the resin substrate 32 attached to the housing 18, and a thrust magnet 36 is attached to the tip of the holder 34.
[0026]
An annular thrust magnet 38 is provided at a radially outer end position of the drive magnet 24 so as to face the thrust magnet 36, and is positioned at a predetermined interval from the thrust magnet 36. The thrust magnet 36 and the thrust magnet 38 are magnetized so as to have different polarities from each other, and an attractive force acts on each other.
[0027]
This attraction force is set to be larger than the load in the thrust direction of the rotating body 40 composed of the rotating sleeve 22, the drive magnet 24, the rotating polygon mirror 28, and the fixed member 30. 40 floats and is held at a predetermined height.
[0028]
On the other hand, as shown in FIG. 2A, the drive magnet 24 is magnetized with N and S poles so that adjacent sections have different polarities. A drive coil 42 is disposed at a position facing the drive magnet 24 in the axial direction.
[0029]
A plurality of coils 48 are arranged in the drive coil 42, and the rotating body 40 shown in FIG. A weight 31 is added to each of the drive magnet 24 and the fixed member 30 to correct the rotational imbalance of the rotating body 40.
[0030]
With the above configuration, when the rotating body 40 rotates, dynamic pressure is generated in the gap between the fixed shaft 12 and the rotating sleeve 22, and the rotating sleeve 22 is supported in a non-contact manner in the radial direction of the fixed shaft 12. .
[0031]
On the other hand, an annular silicon steel plate 44 is disposed on the back surface of the substrate 32 so as to face the drive magnet 24. This silicon steel plate 44 faces a portion contributing to driving of the drive magnet 24, that is, an area 46 located in the winding portion of the coil 48 shown in FIG. The magnetic force between them is strengthened.
[0032]
Here, the coil 48 arranged in the drive coil 42 includes an area 46 that contributes to driving of the drive magnet 24 and areas 50 (inner edges of the drive coil 24) and 52 (drive) that hardly contribute to driving of the drive magnet 24. The outer edge side of the coil 24).
[0033]
On the other hand, as shown in FIG. 1, the area 50 of the coil 48 is opposed to the bottom surface 22 </ b> A of the rotating sleeve 22. For this reason, as shown by the phantom line, the inner diameter dimension of the drive coil 42 is smaller than when the area 50 faces the drive magnet 24.
[0034]
However, since the area 50 of the coil 48 does not contribute to the rotation of the rotating body 40 by the drive magnet 24, the outer diameter of the drive coil 42 is reduced by the amount that the inner diameter of the drive coil 42 is reduced without affecting the magnetic force. Can be reduced in diameter.
[0035]
Thus, by reducing the outer diameter of the drive coil 42, the outer diameter of the drive magnet 24 can also be reduced, and the inertia for rotating the rotating body 40 is prevented from becoming unnecessarily large. This can contribute to shortening the startup time of the laser printer and reducing the steady current.
[0036]
On the other hand, FIG. 3 shows a modification of the first embodiment. Note that the description of the same contents as in the first embodiment is omitted.
[0037]
Here, the area 50 that is the winding portion of the coil 48 and a part of the area 46 in the winding portion are opposed to the bottom surface 22 </ b> A of the rotating sleeve 22. Thus, by arranging the drive coil 42 further inside, the substrate 32 on which the drive coil 42 is mounted can be made smaller.
[0038]
In this case, the silicon steel plate 44 is opposed to the area 46 of the coil 48 in accordance with the position of the drive coil 42 so that magnetic flux is not generated as much as possible in the area 50 that does not contribute to the drive of the drive magnet 24. It is desirable.
[0039]
Next, an optical deflector according to the second embodiment will be described. Note that the description of the same contents as in the first embodiment is omitted.
[0040]
As shown in FIG. 4, a substrate 56 is attached to the housing 18, and the substrate 56 is formed of an iron system such as a silicon steel plate. The end face of the substrate 56 is located at the inner edge of the area 50 of the drive coil 42.
[0041]
Therefore, as compared with the case where the end surface of the substrate 56 extends to the area 50 of the drive coil 42, the force for attracting the drive magnet 24 toward the drive coil 42 is weakened, and the thrust magnet 36 that floats the rotating body 40. , 38 can be reduced in magnetism.
[0042]
Further, since the end face of the substrate 56 does not extend to the area 50 of the drive coil 42, the magnetic flux flowing from the drive magnet 24 to the area 50 can be reduced as much as possible, and the efficiency of the optical deflector 58 can be prevented from lowering.
[0043]
In the present embodiment, the magnetic attractive force of the thrust magnets 36 and 38 is used as the floating method of the rotating body 40, but the present invention is not limited to this.
[0044]
For example, a repulsive magnet may be used to face the drive magnet to float the rotating body, and the same effect is exhibited in that the magnetic force of the repulsive magnet can be weakened.
[0045]
Further, an area 50 that is a winding portion of the coil 48 of the drive coil 42 is opposed to the bottom surface 22A of the rotary sleeve 22, but the drive coil 42 is opposed to the bottom surface 22A of the rotary sleeve 22 as shown in FIG. The area 50 and a part of the area 46 in the winding portion may be opposed to each other.
[0046]
As a result, the outer diameter of the drive magnet 24 can be reduced, so that the inertia of the rotating body 40 can be reduced, and as a result, the startup time of the laser printer can be shortened and the steady current can be reduced. Moreover, since the mass of the rotary body 40 also becomes small, the rotary body 40 can be levitated with a small magnetic attraction force.
[0047]
Further, in the present invention, the outer peripheral surface of the rotating sleeve is constant, but as shown in FIG. 6, a stepped portion 62 having a reduced diameter may be provided on the outer peripheral surface on the bottom surface side of the rotating sleeve 60. By externally fitting the drive magnet 64 to the stepped portion 62, the outer diameter of the drive magnet 64 can be reduced, and the inertia and size reduction of the optical deflector 66 can be expected.
[0048]
Further, in this embodiment, the winding portion located on the inner edge side of the drive coil is opposed to the bottom surface of the rotating sleeve, but the winding portion only needs to be arranged on the inner side of the inner edge portion of the drive magnet. It is not limited, and varies depending on the shape of the rotating sleeve.
[0049]
For example, as shown in FIG. 7, in a rotating sleeve 70 provided with a stepped portion 68 that is reduced in diameter on the outer peripheral surface, an area 74 that is a winding portion of the drive coil 72 is disposed opposite the stepped portion 68. .
[0050]
【The invention's effect】
Since the present invention is configured as described above, in the first aspect of the invention, the outer diameter of the drive magnet can be reduced by reducing the outer diameter of the drive coil, and the rotating body can be rotated. It is possible to prevent an unnecessary increase in inertia, thereby contributing to shortening the startup time of the laser printer and reducing the steady current. According to the second aspect of the present invention, compared with the case where the end face of the iron-based substrate extends to the winding portion of the coil located on the inner edge side of the drive coil, the force for attracting the drive magnet to the drive coil side Becomes weak, and the magnetism of a magnet that floats a rotating body such as a rotating polygon mirror can be reduced. In addition, since the end face of the iron-based substrate does not extend to the winding portion of the coil, the magnetic flux flowing from the driving magnet to the winding portion of the coil can be reduced as much as possible to prevent the efficiency of the optical deflector from being lowered.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an optical deflector according to a first embodiment.
2A is a conceptual diagram showing a positional relationship between a drive magnet and a drive coil, and FIG. 2B is an enlarged view showing a coil disposed in the drive coil.
FIG. 3 is a schematic sectional view showing a modification of the optical deflector according to the first embodiment.
FIG. 4 is a schematic cross-sectional view of an optical deflector according to a second embodiment.
FIG. 5 is a schematic sectional view showing a modification of the optical deflector according to the second embodiment.
FIG. 6 is a schematic sectional view showing a modification of the optical deflector according to the present invention.
FIG. 7 is a schematic cross-sectional view showing another modification of the optical deflector according to the present invention.
FIG. 8 is a schematic sectional view of an optical deflector according to a conventional example.
FIG. 9 is a schematic sectional view of an optical deflector according to a conventional example.
FIG. 10A is a conceptual diagram showing a positional relationship of drive coils, and FIG. 10B is an enlarged view showing coils arranged in the drive coils.
[Explanation of symbols]
10 Optical deflector 22 Rotating sleeve (sleeve)
22A Bottom 24 Drive magnet 42 Drive coil 46 Area 48 Coil 50 Area (winding part)
56 Substrate 58 Optical deflector 60 Rotating sleeve (sleeve)
64 Driving magnet 66 Optical deflector 70 Rotating sleeve (sleeve)
72 Drive coil 74 area (winding part)

Claims (2)

A fixed shaft, a circular cylindrical sleeve which rotates to generate a dynamic pressure between the inserted with a gap to the fixed shaft fixed shaft, a rotary polygon mirror attached to the sleeve, directly to the sleeve In an optical deflector comprising an externally mounted annular drive magnet, a drive coil in which a plurality of coils are arranged annularly facing the drive magnet, and a circuit board on which the drive coil is mounted ,
An optical deflector characterized in that all winding portions located on the inner edge side of the drive coil and not contributing to driving are arranged between the lower surface of the sleeve and the circuit board. The optical deflector according to claim 1, wherein the circuit board is iron-based, and an end portion of the circuit board is located at an inner edge of the winding portion.

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