JPS61143714A - Optical deflector - Google Patents

Abstract

PURPOSE:To improve the accuracy of speed control by providing respectively a light emitting element and photodetector in the position smaller than the radius of the circumscribed circle of a polygon mirror and larger than the radius of the inscribed circle thereof and on both sides of the non-mirror face of the polygon mirror. CONSTITUTION:The light emitting element 13 and photodetector 24 constituting a speed detecting means are respectively provided in the position of the radius r3 to make r2<r3<r1 when the radius of the circumscribed circle of the polygon mirror 35 is designated as r1 and the radius of the inscribed circle thereof as r2 and on both sides of the non-mirror face of the polygon mirror 35. The light emitting element 13 is fixed to the 2nd housing 12 and the photodetector 24 is fixed to a coil substrate 22. the polygon mirror 35 worked precisely is functioned as a shutter and the light from the photodetector 13 for speed detection is turned on and off in order to detecting the rotating speed of the polygon mirror 35 by such constitution. The exact speed detection signal is thereby obtd. from the photodetector 24. The size in the radial direction of the body is reduced and the packaging is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is suitable for use in laser printers, digital copying machines, facsimile machines, and other types of optical information processing devices equipped with laser deflectors.

This is a super-heavy optical deflector that uses a coreless flat brushless motor system.In particular, the radial dimension of the optical deflector body has been shortened by devising the arrangement position of the light-emitting element and light-receiving element that make up the speed detection means. The present invention relates to an optical deflector that is easy to implement, reduces speed detection errors due to surface deflection of a mirror, and enables accurate speed control.

Prior Art Conventionally, various optical devices such as laser deflectors for laser printers, laser deflectors for digital copying machines, laser deflectors for facsimile machines, and barcode readers for PO8 terminals use lasers for reading and writing. In order to deflect light, an optical deflector using a polygon mirror (polygon mirror) is used.

In general, the inner rotor type, outer rotor type, and coreless flat type are known as brushless motor types used in this type of optical deflector.

In terms of cost, these brushless motor systems are ranked in the following order: coreless flat type, outer rotor type, and inner rotor type.

Coreless flat brushless motor systems are the most advantageous.

Furthermore, since this coreless flat type has less cogging and large inertia, it is superior to other types in terms of rotational unevenness and jitter characteristics at low speed rotations of, for example, about 4.000 rpm. Furthermore, its weight is light and l! It has many advantages such as low noise.

Figures 10 (1) and (2) show the main parts of a conventional coreless flat brushless motor type optical deflector.
- Figure 1 (1) is a longitudinal sectional view, and Figure (2) is a plan view. In the drawing, 41 is a first casing, 41a
42 is a second casing; 43 is a window portion opened in a part thereof;
is a first magnetic iron plate, 44 is a coil board, 45 is a coreless flat coil, 46 is a circuit board, 47a and 47b are rotor speed detection elements, 51 is a rotating shaft, 52 is a flange, 53
54 is a ring-shaped rotor magnet, 55 is a polygon mirror, and 56a and 56b are bearing parts.

The configuration of the conventional optical deflector shown in FIGS. 1O (1) and (2) is as follows.

First, the fixed armature is inside the first housing 41.

A first magnetic iron plate 43 constituting a magnetic circuit and a coil substrate 44 on which coreless flat coils 45 are arranged are fixed.

The coil board 44 is a so-called printed board, and although not particularly shown, a wiring pattern for wiring these components is formed on the board.

A ring-shaped rotor magnet 54 which is axially opposed to the coreless flat coil 45 shown in FIG. 10 (1) constituting the stationary armature with an appropriate gap therebetween and is magnetized into multiple poles, and a magnetic circuit. A second magnetic iron plate 53 for configuring the flange 5, and a polygon mirror 55 for laser deflection
2, and furthermore, the flange 52 is fixed to the rotating shaft 5.
1 to form a rotor assembly.

Bearing portions 56a and 56b are lightly press-fitted into the rotating shaft 51 of the rotor assembly constructed in this way, respectively.

The bearing parts 56a and 56b of the rotor assembly are connected to the first housing 4.
1. They are each supported by the second casing 42.

Therefore, the rotor assembly has a bearing portion 56a.

It can rotate around 56b.

Further, in order to control the rotational speed of the rotor, a circuit board 46 on which rotor speed detection elements 47a and 47b are attached to the outer peripheral position of the polygon mirror 55 of this rotor assembly.
furthermore, this circuit board 46 is placed in the second casing 42.
Fixed to.

As shown in FIG. 10 (1) and (2), a conventional coreless flat brushless motor type optical deflector has a fixed armature having a plurality of coreless flat coils 45 and a multi-pole magnetized A rotor having a ring-shaped rotor magnet 54 and a polygon mirror 55 having a mirror surface parallel to the rotation axis 51, and a window portion 4 that accommodates each of these parts and forms an optical path to the mirror surface of the polygon mirror 55.
1a, and a housing 41.

In this optical deflector, the window portion 41 provided in the first housing 41
A forms a part of the optical path from the outside, and in order to deflect the laser light from the outside by the polygon mirror 55, the laser light is directed in the desired direction by the optical path from the laser light source to the mirror surface (reflection). It acts to deflect.

By the way, in order to rotate the rotor at a constant speed, it is necessary to detect the rotation speed of the rotor and perform constant speed control on the target rotation speed.

To this end, as described above, rotor speed detection elements 47a and 47b are arranged on one circuit board 46 as rotor speed detection means. The speed detection element 47a is a light emitting element such as an LED, and 47b is a light receiving element such as a phototransistor.

The detection signal from this speed detection means is used to perform constant speed control of the rotor to which the polygon mirror 55 is fixed.

As described above, in the conventional coreless flat brushless motor type optical deflector, the speed detection element 47a.

47b are arranged on the circuit board 46 provided at a radius position larger than the radius of the circumscribed circle of the polygon mirror 55, that is, at a position on the outer periphery of the mirror surface of the polygon mirror 55.

As a result, the radial dimension of the optical deflector body inevitably increases, and the mounting position is restricted.

In addition, since the reflection of the mirror surface of the polygon mirror 55 is used to detect the speed, it is greatly affected by the surface deflection of the polygon mirror 55 caused by eccentricity of the rotor, etc., and the speed detection error increases. There were some inconveniences.

Purpose Therefore, the optical deflector of the present invention solves these inconveniences in the conventional coreless flat brushless motor type optical deflector, and detects speed by using the polygonal part of a precisely machined polygon mirror. Therefore, by shortening the radial dimension of the optical deflector to reduce its size and removing mounting constraints, by using a precisely machined polygon mirror, the polygon mirror due to eccentricity of the rotor can be reduced. It is an object of the present invention to reduce speed detection errors caused by surface runout as much as possible, and to perform accurate speed control.

Structure To achieve this, the optical deflector of the present invention includes a fixed armature having a plurality of coreless flat coils, a ring-shaped rotor magnet magnetized into multiple poles, and a polygon formed with a mirror surface parallel to the rotation axis. In an optical deflector using a coreless flat brushless motor, which consists of a rotor having a mirror, and a casing that houses these parts and has a window that forms an optical path to the polygon mirror, the radius of the circumcircle of the polygon mirror is When rl is the radius of the inscribed circle, a light-emitting element and a light-receiving element constituting the speed detection means are installed at the position of the radius r3, where rl<r3<rl, and on both sides of the non-mirror surface of the polygon mirror. , are arranged respectively.

More specifically, regarding the principle of the optical deflector of this invention, in order to detect the rotational speed of the rotor, a precisely processed polygon mirror is used as a shutter.
By turning on and off the light from the light emitting element for speed detection, an accurate speed detection signal can be obtained from the light receiving element.

In addition, the light emitting element and light receiving element constituting such a speed detecting means may be one or more depending on the accuracy of speed control.
It is not limited to just one piece, but a plurality of pieces may be arranged.

Next, an embodiment of the optical deflector of the present invention will be described in detail with reference to one drawing.

FIG. 1 is a longitudinal sectional view showing the configuration of essential parts of an embodiment of the optical deflector of the present invention. In the drawings, 11
is the first casing, lla is a mechanical part constituting a labyrinth mechanism for preventing the bearing oil from scattering, llb is a window portion opened in a part thereof, 12 is the second casing, and 12a is the bearing oil. 13 is a light emitting element constituting a speed detection means;
4 is a preload spring, 21 is a first magnetic iron plate, 22 is a coil substrate, 23 is a coreless flat coil, 24 is a light receiving element constituting the speed detection means, 31 is a rotating shaft, 32 is a flange,
32a is a mechanical part forming a part of the labyrinth mechanism for preventing scattering of bearing oil; 33 is a second magnetic iron plate; 34
is a ring-shaped rotor magnet, 35 is a polygon mirror, 36a
and 36b indicate the bearing portion.

As shown in FIG. 1, a first casing 11 made of a lightweight non-magnetic material has a polygon mirror 3 provided therein.
A window portion 11b forming a part of the optical path to the polygon mirror 35 is provided to allow the laser beam to enter the polygon mirror 35.

In addition, to prevent bearing oil, grease, etc. from scattering,
The part of the housing 11 where the bearing part 36a is attached is
A mechanical portion 11a constituting a labyrinth mechanism for preventing scattering of bearing oil is provided to prevent scattering of bearing oil and grease. Similarly, a mechanism portion 12a that constitutes a part of a labyrinth mechanism for preventing scattering of bearing oil is provided in a portion of the second housing 12 where the bearing portion 36b is attached.
The mechanical part 32a of the flange 32 is also filled with bearing oil.
Constructs a labyrinth mechanism to prevent grease from scattering.

First, the configuration of the fixed armature will be explained. Note that the members constituting the fixed armature are numbered in the 20s from 21 to 24.

A first magnetic iron Fi21 for configuring a magnetic circuit and a coil board 22 are fixed inside the first casing If, and the coil board 22 includes a coreless flat coil 23 and a light-receiving light-receiving coil for speed detection. The element 24 and a group of necessary circuit components are arranged and fixed. In this way, the fixed armature is constructed.

The following Figures 2 (1) and (2) are structural diagrams showing the detailed structure of the coil base @22 of the optical deflector of the present invention shown in Figure 1, and Figure 1 (1) is a plan view and a diagram. (2) is a longitudinal cross-sectional view. Reference numerals in the drawings are the same as in FIG. 1, and 22a to 22a-
22f is a hole for mounting the coil board 22, 24a is a slit plate arranged close to the light receiving element 24, 25a to 25c
indicates a rotor position detection element, IC1 and IC2 are integrated parts, R1-R3 are resistors, and C is a capacitor.

The coil board 22 is a so-called printed circuit board, and a wiring pattern for wiring these components is formed on the board.

Further, the light receiving element 24 for speed detection and the slit plate 24a are arranged on the coil substrate 22 at a position with a diameter r3.

FIG. 3 is a schematic plan view showing another example of a slit plate provided near the light-receiving element 24 for speed detection. Reference numerals in the drawing are the same as in FIG. 2, and 24b indicates a slit plate. .

In this FIG. 3, the slit direction of the slit plate 24b is
It is provided in a direction perpendicular to the slit direction of the slit plate 24a in FIG. That is, while the slit direction in FIG. 2 is the circumferential direction, the slit direction in FIG. 31 is the radial direction.

In this way, the slit directions of the slit plates 24a and 24b provided near the light receiving element 24 for speed detection are
It may be in the circumferential direction as shown in FIGS. (1) and (2), or it may be in the radial direction as shown in FIG.

Next, the rotor assembly will be described. The members constituting the rotor assembly are numbered in the 30s from 31 to 35.

Figures 4 (1) and (2) are structural diagrams showing the detailed structure of the rotor assembly of the optical deflector of the present invention shown in Figure 1, where Figure (1) is a plan view and Figure (2) is a vertical sectional view.

Reference numerals in the drawings are the same as in FIG. 1, and 32b
32e indicates a hole in which the flange 32 is attached.

As shown in FIGS. 4(1) and 4(2), the rotor assembly of the optical deflector of the present invention includes a rotating shaft 31, a flange 32,
Second magnetic iron plate 33, ring-shaped rotor magnet 34. and a polygon mirror 35.

That is, while maintaining an appropriate gap with the coreless flat coil 23 that constitutes a part of the fixed armature shown in FIG.

A ring-shaped rotor magnet 34 facing in the axial direction and magnetized into multiple poles, a second magnetic iron plate 33 for forming a magnetic circuit, and a polygon mirror 35 for laser deflection are integrated into the flange 32. and then flange 3
2 is integrally fixed to the rotating shaft 31 to constitute a rotor assembly.

As shown in FIGS. 4(1) and (2), if the polygon mirror 35 for laser deflection is integrally fixed to the ring-shaped rotor magnet 34 and the flange 32, the optical deflector can be The dimensions are also reduced. Therefore, even if the light emitting element 13 and the light receiving element 24 constituting the speed detecting means are arranged on both sides of the polygon mirror 35, the optical deflector can be made smaller than the conventional optical deflector.

The bearing portions 36a and 36b are lightly press-fitted into the rotating shaft 31 of the rotor assembly constructed in this way, respectively.

These bearing parts 36a, 36b are supported by the first housing 11 and the second housing 12, respectively, so that the rotor assembly rotates around the bearing parts 36a, 36b.

In the optical deflector shown as an example in FIG. 1, the excitation phase is detected in the 8-pole, 3-phase, 6-coil motor section by the output signal of the rotor position detector composed of rotor position detection elements 25a to 25c. When the six coils are switched and energized in sequence, the rotor is rotated at a rotation speed proportional to the voltage supplied to the motor according to Fleming's left-hand rule (so-called 814 rule).

In addition, when explaining using the 814 rule, the force of F=Bli (here, F is the generated force, B is the magnetic flux density, and i is the exciting current) is
This is the force acting on the coil. However, since the optical deflector of the present invention uses a brushless motor in which the coil is fixed and the rotor magnet rotates, the rotation direction of the rotor magnet is opposite to Bit's law.

FIG. 5 is a layout diagram showing the relationship between the coils of the 8-pole, 3-phase, 6-coil motor shown in FIG. 2 and the arrangement positions of the rotor position detection elements 25a to 25c.

The reference numerals in the drawings are the same as those in FIGS. 1 and 2, and U, V, and W represent each of the three-phase coils, Cp represents the inter-coil pitch, and CP represents the coil pitch.

FIG. 6 is a circuit diagram showing an example of the coil connections and drive circuit of the 8-pole, 3-phase, 6-coil motor shown in FIG. In the drawings, U, V, and W indicate three-phase coils, and Q1 to Q6 indicate transistors.

FIG. 7 is a time chart showing an example of rotor magnets, rotating magnetic fields, and coil positions in the 8-pole, 3-phase, 6-coil motor section shown in FIG.

In the time chart in the drawing, the vertical axis is magnetic flux density.

The horizontal axis shows the rotation angle.

As already explained, in order to rotate the rotor at a constant speed, it is necessary to detect the speed of the rotor and perform constant speed control with respect to the target rotation speed.

In the optical deflector of this invention, when the polygon mirror 35 rotates, the mirror 35 functions as a shutter.
The light from the light emitting element 13 is turned on and off, and the light from the light receiving element 2
given to 4.

Therefore, the radius r1 of the circumscribed circle of the mirror. With respect to the radius r2 of the inscribed circle, a position 1 having a radius r3 satisfying the relationship rz<r3<rl, for example, a position on the second casing 12,
A light emitting element 13 such as an LED.

One or more light-receiving elements 2 such as phototransistors are fixed on opposite coil substrates 22 with mutually different phases.
Similarly, one or more 4 are arranged with their phases shifted from each other.

When one speed detection means is disposed, the light from the light emitting element 13 is turned off at the corner of the polygon mirror 35, and the level of the speed detection signal generated from the light receiving element 24 is changed. .

FIG. 8 is a layout diagram for explaining the arrangement of a polygon mirror and two speed detecting means in the case of an eight-pole, three-phase, six-coil motor. In the drawing, Ply P2
indicates a light receiving element.

In this FIG. 8, the number of mirror surfaces of the polygon mirror is N=8 (
), and the number of light-receiving elements P=2 (pieces).

FIG. 9 is a time chart showing an example of speed detection signals generated from the two speed detection means shown in FIG. In the drawing, T indicates one period of the speed detection signal generated from one speed detection means, and to indicates the time width of the speed detection signal.

As shown in FIG. 9, when two speed detection means are used, the outputs of the light receiving elements P1 and p2 are combined to generate a frequency signal corresponding to the speed of the rotor.

In addition, when it is necessary to change the on/off duty ratio of the frequency signal for reasons related to the control system, or for the purpose of preventing noise due to diffraction of light from the light emitting element, there may be a As shown in FIG. 2(1), a slit plate 24a is provided.

The direction of the slits in this slit plate 24a may be either the circumferential direction or the radial direction, as already explained with reference to FIGS. 2 and 3.

In this way, by appropriately selecting the width and direction of the slits in the slit plates 24a and 24b, as well as the mounting position, the required time width t can be determined. A pulse signal of 1 is obtained.

Here, the number of mirror surfaces or the number of angles of a polygonal rotor magnet (in the case of the embodiment shown in FIG. 1, the number of mirror surfaces as a polygon mirror) is N, and the number of light receiving elements 24 is p.
Then, the −Pnth light receiving element is arranged in a positional relationship expressed by the following formula with respect to the first light receiving element.

Here, Pn is 1, 2, 3.・・・・・・PHere,
If N=8 (corners) and p=4 (pieces), an example of the arrangement is shown in a table as follows.

In the speed detection means, the basic arrangement method is to arrange the same number of light emitting elements 14 on the circuit board 13 at a position opposite to the light receiving element 24 or on the second casing 12. In the case of arrangement according to (1), since the arrangement angle is small, the number of light receiving elements 24 can be smaller than that of the light receiving elements. The rotor can be controlled at a constant speed more accurately than in the case where only one light emitting element 14 and one light receiving element 24 are included. Regarding these constant speed controls,
Since this is the same as the conventional control method, a detailed explanation will not be provided.

Further, in the embodiments shown in FIG. 1 and subsequent figures, a case has been described in which a rotor assembly in which a polygon mirror 35 is integrally fixed around a rotor magnet 34 is used. However, it goes without saying that the conventional optical deflector shown in FIG. 1O, in which the rotor magnet 34 and the polygon mirror 35 are arranged at different positions in the axial direction, can be implemented in the same manner. Nor.

As explained in detail above, the optical deflector of the present invention includes a fixed armature having a plurality of coreless flat coils,
A rotor that has a ring-shaped rotor magnet magnetized into multiple poles and a polygon mirror with a mirror surface parallel to the rotation axis, and a window that houses each of these parts and forms an optical path to the polygon mirror. In a coreless flat brushless motor type optical deflector comprising a casing having:

When the radius of the circumscribed circle of the polygon mirror is r1 and the radius of the inscribed circle is rl, rl (radius r3 where r3 < rt)
and on both sides of the non-mirror surface of the polygon mirror,
A light emitting element and a light receiving element constituting the speed detecting means are arranged respectively.

Therefore, according to the optical deflector of the present invention, since the speed detection means are disposed on both sides of the polygon mirror, the radial dimension of the optical deflector main body is shortened and the mounting becomes easy.

Further, as a speed detection means for controlling the rotor at a constant speed, a polygon mirror is used as a shutter to turn on and off light from one light emitting element. Therefore, the radii of the inner and circumscribed circles of the polygon mirror are larger than the length of its rotation axis, and since the polygon mirror is precisely machined, the speed detection signal extracted from the light receiving element is The influence of surface runout is reduced, and more accurate speed control can be performed.

In particular, if the speed detection means is composed of a plurality of light emitting elements and a plurality of light receiving elements, more accurate speed control becomes possible than when it is composed of a single light emitting element and a light receiving element. Excellent effects can be obtained.

[Brief explanation of drawings]

Sakuamizato is a vertical cross-sectional view showing the configuration of essential parts of an embodiment of the optical deflector of the present invention, and Figure 2 (1) and σ are the coils of the optical deflector of the present invention shown in Figure 1. These are structural diagrams showing the detailed configuration of the substrate 22, in which Figure (1) is a plan view, Figure (2) is a vertical cross-sectional view, and Figure 11 is another example of a slit plate provided near the light receiving element 24 for speed detection. Figure (1) is a plan view showing the detailed configuration of the rotor assembly of the optical deflector of the present invention shown in Figure 1. Figure (1) is a plan view. Figure (2) is a longitudinal cross-sectional view, and m is the coil of the 8-pole, 3-phase, 6-coil motor shown in Figure 2, and the rotor position detection elements 25a to 25.
10 is a circuit diagram showing an example of the coil connection and drive circuit of the 8-pole 3-phase 6-coil motor shown in FIG. The rotor magnet in the 8-pole 3-phase 6-coil motor part shown in the figure, and a time chart showing an example of the rotating magnetic field and coil position. JLIL is a time chart showing an example of the speed detection signal generated from the two speed detection means shown in FIG. 8, Illolm(1)k( υ- is a diagram showing an example of the configuration of essential parts of a conventional coreless flat brushless motor type optical deflector, where Figure (1) is a longitudinal sectional view and Figure (2) is a plan view. In the drawing, 11 is a first casing, lla is a mechanical part of the labyrinth mechanism, llb is a window opened in a part thereof, 12 is a second casing, and 12a is a mechanical part forming a part of the labyrinth mechanism. 13 is a light emitting element constituting the speed detecting means, 21 is a first magnetic iron plate, 22 is a coil substrate, 23 is a coreless flat coil, 24 is a light receiving element constituting the speed detecting means, 31 is a rotating shaft, and 32 is a flange. 32a is a mechanism part forming part of the labyrinth mechanism, 33 is a second magnetic iron plate, 3
4 is a ring-shaped rotor magnet, 35 is a polygon mirror, 36
a and 36b indicate bearing parts. Shin 1 Figure God 2 Figure O 4 Figure Zhong 6 Figure Ritsu 9 Figure

Claims (1)

[Scope of Claims] 1. A rotor having a fixed armature having a plurality of coreless flat coils, a multi-pole magnetized ring-shaped rotor magnet, and a polygon mirror having a mirror surface parallel to the rotation axis. In the coreless flat brushless motor type optical deflector, which includes a casing that houses these parts and has a window part that forms an optical path to the polygon mirror, the radius of the circumscribed circle of the polygon mirror is r_1,
When the radius of the inscribed circle is r_2, r_2<r_3<r
An optical deflector characterized in that a light emitting element and a light receiving element constituting a speed detecting means are respectively arranged at a position of 3 on a radius of _1 and on both sides of the non-mirror surface of the polygon mirror. 2. An optical deflector according to claim 1, characterized in that one or more light emitting elements and light receiving elements constituting the speed detection means are arranged.