JPS60138508A - Rotary polygon mirror scanner - Google Patents

Abstract

PURPOSE:To obtain a rotary polygon mirror device with good performance by reducing the weight and variation because of the employment of a small-sized brushless motor, and forming a magnetic pole for frequency detection and a comb-shaped conductive pattern at desired positions. CONSTITUTION:The collar 10b made of a magnetic body provided with a stator yoke 4 fixed at the upper end opening part of a base 2, driving circuit storage part 5, armature coil 6, printed board 7, Hall element arranged at the outer circumferential part of the reverse surface of the board 7, etc., functions as the support member for a polygon mirror 12. The disk type brushless motor suitable for mass-production, so the prolongation of life is expected, variation is reduced, and constant rotation is realized. Further, the magnetic pole for frequency detection and comb-shaped conductive pattern 7 are formed at the most preferable positions, so the rotary polygon mirror scanner incorporating a frequency generation with good performance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating polygon mirror scanning device used in an image recording device such as a facsimile, for example, which irradiates a rotating polygon mirror with a laser beam and scans a screen with the reflected light.

Conventionally, information signals have been recorded by polarizing an information laser beam modulated by an information signal using a mirror or other polarizing means and scanning it over a scanned surface on which a photoreceptor is arranged.
It is well known to read information on a scanned surface. There are various types of such optical polarizers, one of which is a rotating polygon scanning device. This rotating polygon mirror scanning device has a high polarization speed and can perform continuous optical photometry, so it is possible to record or read out high-density information at high speed.

However, the conventional rotating polygon mirror scanning device uses a cylindrical motor with a salient pole rotor, so although it is a device that requires a small size, it is heavy and expensive due to its wooden shape. I couldn't find something cheap and high-performance. Particularly thin ones could not be obtained.

These are disclosed in JP-A-49-93027 and JP-A-57-62751. In addition, in the structure of the shaft rotating type shown at both ends, it is extremely difficult to center the bearing, so an air bearing is used to rotate the rotating polygon mirror at a constant rate without dynamic fluctuation. That was impossible.

Furthermore, conventional rotating polygon scanning devices have difficulty in scanning at a constant rotational speed, and must use large and expensive tachometer generators and encoders as means for detecting rotational conductivity. The scanning device itself was also large and expensive.

In order to eliminate the drawbacks of the conventional rotating polygon mirror scanning device, the present applicant previously developed a rotating polygon scanning device in which an incident light beam is polarized by a rotating polygon mirror, using a polygon mirror and a flat circular mirror. It has a 2P field magnet that is magnetized so as to have annular N and S magnetic poles alternately, and a comb-shaped conductive pattern for frequency detection is provided on the part facing the frequency detection magnetic pole. The present invention provides a rotating polygon mirror scanning device characterized in that a stator armature is provided with a stator armature.

Here, the frequency detection magnetic pole of the field magnet and the conductive pattern create a frequency generator! However, since the field magnet having the frequency detection magnetic pole is a rotor, the more the frequency detection magnetic pole is provided on the outer periphery of the field magnet, the more the field magnet has a relationship with the stator armature. Since the relative rotational speed is high, it is desirable to obtain a highly accurate rotational speed signal. For this reason,
As a matter of course, the position detecting element is generally a magneto-electric transducer such as a Hall element, a Hall IC, or a 1m resistance element. Conventionally, this position sensing element has been provided on the inner or outer periphery of the conductive pattern.In providing the position sensing element on the inner periphery of the conductive pattern, it is necessary to place the position sensing element on the inner periphery of the conductive pattern. It is necessary to install the position sensing element on the printed circuit board, but since the alignment accuracy of the position sensing element is very difficult, it is desirable to install it on the outer periphery of the printed circuit board as much as possible. If installed, the drawback is that the rotating polygon mirror scanning device becomes large in diameter.

The present invention has been made based on the above circumstances, and is light in weight, small in size, inexpensive, and equipped with a rotational speed detection means.
The purpose of this invention was to obtain a rotating polygon mirror scanning device that has high performance, is thin in the axial direction, and is capable of scanning at a constant rotational speed.

An embodiment of the present invention will be described below with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. 1 to 7.

Figure 1 is a vertical cross-sectional view of the rotating polygon mirror scanning device, and Figure 2 is a vertical cross-sectional view of the rotating polygon mirror scanning device.
FIG.

Mainly referring to FIGS. 1 and 2, 1 is a rotating polygon mirror scanning device showing a first embodiment of the present invention, 2 is a flat cup-shaped support (not shown in FIG. 2), and 3 is the above-mentioned A spiral group fixing shaft is fixed perpendicularly to the approximate center of the support 2, and 4 is a flat annular stator yoke fixed to the upper opening of the support 2. It is made by compressing and molding a mixed powder. 5
7 is an air gap, a driving circuit housing portion, and 6 is an armature coil wound into a frame shape, which is disposed in an appropriate number on the stator yoke 4. This will be explained in FIG. 3. 8 is a printed circuit board having a through hole in the center and a printed wiring conductor (not shown), and is fixed on the upper surface of the stator armature consisting of 6 groups of armature coils.8 is the outer periphery of the lower surface of the printed circuit board 7. This is a magnetoelectric transducer such as a Hall element or a Hall IC used as a position detection element disposed at the position of the magnetoelectric transducer 8.The arrangement position of the magnetoelectric transducer 8 will be described later.10
is a cylindrical bearing (rotating shaft) having a cylindrical bearing part 10a rotatably mounted on the outer periphery of the fixed shaft 3 and a flange 10b integrally formed on the outer periphery of the bearing part 10a. Bearing 1
0 is formed of a magnetic material. Further, a flange 10b formed on a magnetic body for closing the magnetic path of a field magnet (to be described later) 11 functions as a support member for a rotating polygon mirror 12 to be described later. Reference numeral 11 denotes a 2P (P is a positive integer of 1 or more) pole annular field magnet having N and S magnetic poles alternately fixed on the lower surface of the collar 10b, which is a magnetic yoke (see Fig. 4). The stator armature is fixed to the lower surface of the flange 10b and faces a stator armature consisting of 6 groups of armature coils having a printed circuit board 7 on the upper surface. Tsuba 10 above
b is provided with a bent portion 10c extending vertically on its outer periphery,
The field magnet 11 is held at this bent portion 10e. Reference numeral 12 denotes a rotating polygon mirror, which has a rectangular shape that is flat in the axial direction and has four reflective surfaces 12a around its periphery, and is fixed on the upper surface of the collar 10b. Reference numeral 13 denotes a windshield disc having a radius longer than the radius of the rotating polygon mirror 12, and is fixed on the upper surface of the rotating polygon mirror 12. This windshield disk body 13 is unnecessary when the rotating polygon mirror 12 is a polyhedron, but when the rotating polygon mirror 12 is an oligohedron such as a three-sided mirror or a four-sided mirror, it is unnecessary. It is necessary. That is, when the rotating polygon mirror 12 is a polyhedron, there is little wind pressure resistance even if the rotating polygon mirror 12 rotates, so if the windshield disc body 13 is provided, there will be no place for the wind to escape, and conversely, the rotating polygon mirror 12 will rotate. The rotation of the polygon mirror 12 produces a loud rotation sound.

On the other hand, when the rotating polygon mirror 12 is an oligohedron such as a tetrahedron, its reflecting surface 12a has a large wind pressure resistance, so if the rotating polygon mirror 12 rotates at high speed as it is, it will generate a loud rotation sound. Therefore, when the rotating polygon mirror 12 is an oligohedron, if the windshield disc body 13 is provided, the reflective surface 1
2a has no escape route due to the disk body 13, so as the rotating polygon mirror 12 rotates, the wind blows away from the reflecting surface 1.
The above wind direction rotates together with 2a. For this reason, the wind pressure resistance is reduced compared to the case where the windshield disc body 13 is not provided, so that the sound generated by the rotation of the rotating polygon mirror 12 is effectively reduced.

FIG. 3 is a perspective view for explaining the conditions and arrangement method of the armature fill 6 group.

As is clear from FIG. 3, the stator armature consists of six groups of six armature coils.
-1. . . . , 6-6 is formed into a fan frame shape with six armature coils 6-1.・
..., 0 armature coils 6-1 and 6-2, between armature coils 6-2 and 6-3, and armature coils arranged at equal intervals so as not to overlap each other. 6-3 and 6-4
A magnetoelectric conversion element 8-1.8-2.8-3 is arranged between them.

A disk-shaped printed circuit board 7 is fixed to the upper surface of the stator armature consisting of 6 groups of armature coils.
A comb-shaped conductive pattern 15 for detecting the rotational speed of the rotor is formed in a ring shape on the outer periphery of the 0 surface (see Fig. 6).The printed circuit board 7 and the field magnet 11 face each other with a small gap in between. are doing. As shown in FIG. 4, the field magnet 11 has a driving magnetic pole 11a of the field magnet 11.
is magnetized into an 8-pole structure having N and S magnetic poles alternately spaced at equal intervals, and around 180 frequency detection magnetic poles 11b for detecting the rotor rotational speed are formed around the 8-pole structure.

N and S are more strongly magnetized than N' and S'. The frequency detection magnetic pole 11b is formed on the surface of the field magnet 11 facing the conductive pattern 15. This frequency detection magnetic pole 11b has strong magnetized parts (N, E! poles) and weakly magnetized parts (N', S' poles) alternately at fine pitches along the circumferential direction on the outer periphery of the driving magnetic pole 11a. It is formed by double magnetization means as shown in FIG. The N' pole corresponds to the S pole, and the N' pole functions as the N pole. Drive magnetic pole 1
The north pole of the driving magnetic pole 11a has a strong magnetized N pole and a weakly magnetized N' pole alternately magnetized at a fine pitch, and the S pole of the driving magnetic pole 11a has a strong magnetized S pole and a weakly magnetized S pole. Frequency detection magnetic pole 1 is formed by alternately magnetizing the N' poles of the magnetized part at a fine pitch.
The magnetic flux density waveform forming 1b is as shown in FIG.

As shown in FIG. 7, since the magnetic flux density waveform formed by the frequency detection magnetic pole 11b is superimposed on the magnetic flux density waveform formed by the driving magnetic pole 11a, the magnetic flux density formed by the driving magnetic pole 11a is A waveform with fine irregularities is formed at the peaks or valleys of the waveform.

As is clear from FIG. 5, in the armature coil 6, the opening angle between the conductor portions 6& and 6b, which contribute to the generated torque in the radial direction, is approximately 2n-1 of the magnetic pole width of the field ignet 11 (however, n = 1) times, that is, the opening angle width is approximately equal to the magnetic pole width of field magnet 11. Each armature coil group of 6 is shown in Figs. As shown in the figure, they are spaced apart so that they do not overlap each other. The 6 groups of armature coils are 3 groups, each consisting of 2 groups of 6 armature coils that are electrically in phase but 180 degrees out of phase in the circumferential direction.
We have set up a group. That is, armature coils 6-1 and 6-4.6
-2 and 6-5.6-3 and 6-6 form each set. One magnetoelectric conversion element 8 is provided in each group of 6 armature coils.

FIG. 6 is a plan view of the printed circuit board 7 of FIG. 1. A comb-like conductive pattern 15 is formed in a ring shape on the surface of the printed circuit board 70 at a portion facing the frequency detection magnetic pole 11b of the field magnet 11, as shown in FIG. The pitch of this conductive pattern 15 is the same as the pitch of the frequency detection magnetic poles 11b shown in FIG. When every other line segment group in the radial direction of the conductive pattern 15 faces, for example, N or S of the frequency detection magnetic pole, the line segment group between these faces N' or N'. As a result, an electromotive force is generated in each line segment in the same direction according to the rotational speed of the frequency detection magnetic pole 11b, and a detection output of a frequency corresponding to the rotational speed of the rotor is obtained from an output terminal (not shown) of the conductive pattern 15.

Although the pulsed magnetic flux generated by the frequency detection magnetic pole 11b appears intermittently, since the conductive pattern 15 is formed all around the circumference as shown in FIG. 6, the detection output is obtained as a continuous wave. Further, when the rotation speed of the frequency detection magnetic pole is constant, a detection output of a constant frequency can be obtained. The variation in the rotational speed is extracted as a frequency modulation component of the detection output. The magnetoelectric conversion element 8 is disposed on the surface of the printed circuit board 7 facing the locus on which the upper C conductive pattern 15 is formed, as shown in FIGS. i to 3 and 6. In FIG. 6, a radial conductor portion 15a of the conductive pattern 15 is shown.
is a conductor portion that contributes to power generation, and the magnetoelectric conversion element 8-1 is disposed between conductor portions 15a-1 and 15a-2 that contribute to power generation. Here, the conductive pattern 15 is a conductor portion in the radial direction. The pitch between 15a and 15a is narrow, and the magnetoelectric transducer 8-1 is thick.
1 terminal to the printed circuit board 7, for example, if the magnetoelectric transducer 8-1 cannot be disposed between the conductor parts 15a-1 and 15a-2, the conductor part 15a-
It is also possible to form a ring-shaped conductive pattern 15 in which an appropriate number of radial conductor parts 15&, such as 1 and 15a-2, are omitted. In this case, if it is inconvenient that a uniform power generation waveform signal cannot be obtained due to the omission of several conductor parts 15aVr in the predetermined radial direction, 180 degrees in electrical angle from the place where the conductor parts 15a are omitted is Approximately the same number of conductor portions 15a of the conductive pattern 15 whose phase is shifted in the circumferential direction may also be omitted. It goes without saying that similar measures may be taken for the other two magnetoelectric conversion elements 8.

By doing as described above, the magnetoelectric conversion element 8 can be arranged at a reasonable position, and it is convenient to make a hole in the printed circuit board 7 and store the magnetoelectric conversion element 8 in the hole. Soldering the terminals of the element 8 becomes easier.

FIG. 8 shows a rotating polygon mirror scanning device 1' showing a second embodiment of the present invention. By increasing the thickness width of the gap 5 shown in FIG. 1, a printed circuit board equipped with a control circuit, a drive circuit, etc. In addition to making it possible to store a plurality of mirrors in parallel, the apparatus 1' is stabilized.0 Figure 9 shows a rotating polygon mirror scanning apparatus 1' showing a third embodiment of the present invention; There is no void 5 shown in FIG. 8,
Armature coil 6, field magnet 11, rotating polygon mirror 12
By providing the device 1' at the bottom, the device 1' is stabilized and the device 1' is formed to be thin. 14 is a thrust cap.

Since the present invention has the above-mentioned configuration, when the magnetoelectric conversion element 8 detects the N or S magnetic pole of the field magnet 11, a current in an appropriate direction is caused to flow through the armature coil 6, thereby converting the field according to Fleming's left-hand rule. The magnetic magnet 11 rotates in an appropriate direction.

Furthermore, by controlling the frequency detection magnetic pole 11b, the rotating polygon mirror 12 can be scanned at a constant rotation speed.

Therefore, the rotating polygon mirror 12 fixed to the rotating shaft 10 rotates, and the information laser beam irradiated onto the reflective surface 12a of the polygon mirror 12 scans the screen at a constant speed with polarized reflected light.

As is clear from the above description, the rotating polygon mirror scanning device of the present invention uses a disk-type brushless motor that is suitable for mass production, so it can be expected to have a long life, and is small, thin, and inexpensive with light overlap. can get. Also, it is easy to obtain a device that rotates at a constant rate with little fluctuation. In addition, since the magnetic pole for frequency detection and the comb-shaped conductive pattern for frequency detection can be formed in the most desirable position, a rotating polygon mirror scanning device with a built-in frequency generator of high performance can be rationally built in, and positioning is extremely easy. Since the position detection element can be disposed at a suitable position, there is an advantage that the rotary polygon mirror device can be mass-produced extremely easily.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a first embodiment of the present invention, FIG. 2 is an assembled view of the same, FIG. 3 is a perspective view showing an example of the arrangement method of an armature coil group, and FIG. 4 is an example. FIG. 5 is a developed view of the field magnet and armature coil group; FIG. 6 is a plan view of a printed circuit board on which a conductive pattern is formed; FIG. 7 is a diagram of the magnetic flux density waveform formed by the field magnet shown in FIG. 5, FIG. 8 is a vertical sectional view showing the second embodiment of the present invention, and FIG. 9 is a vertical sectional view showing the third embodiment of the present invention. It is. 1.1', 1'... Rotating polygon mirror scanning device, 6... Armature coil, 7... Printed circuit board, 8... Position detection element (magnetoelectric conversion element), 11... Field magnet, 1
2... Rotating polygon mirror, 13... Windshield disc body 1.14
... Thrust cap, 15...4 [pattern. Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1. In a rotating polygon mirror scanning device in which an incident light beam is polarized by a rotating polygon mirror, a polygon mirror and a 2P (P
is a positive integer of 1 or more) as a rotor, it has a field magnet as a rotor having frequency detection magnetic poles magnetized to form poles, and has an armature coil group at a fixed side position facing the field magnet. The stator armature is fixedly installed, and a printed circuit board with a ring-shaped comb-like conductive pattern for frequency detection is placed on the stator and armature surfaces facing the field magnet. Fixed installation, above,
A rotating polygon mirror scanning device characterized in that a position detection element is disposed on a printed circuit board surface facing a locus on which a conductive pattern is formed. 2. The rotating polygon mirror scanning device according to claim 1, wherein the position detection element is disposed between radial conductor parts that contribute to power generation of the conductive pattern. . 3. The rotation according to claim 1 or 2, wherein the member for closing the magnetic path of the field magnet and the supporting member of the rotating polygon mirror are integrally formed. Polygon mirror scanning device. 4. The rotating polygon mirror scanning device according to any one of claims 1 to 3, wherein the rotating polygon mirror has a windshield disk on its upper part. 5. The armature coil forming the stator armature is characterized in that the conductor portion that contributes to the generated torque is wound so that the opening angle width is approximately equal to the magnetic pole width of the field magnet. A rotating polygon mirror scanning device according to any one of claims 1 to 4. 6. The armature coil group is arranged at equal intervals so as not to overlap with each other.Claims 1 to 5, characterized in that the armature coils rotate. A rotating polygon mirror scanning device according to any one of the ranges 1 to 6. 8. The rotating polygon mirror scanning device according to claim 7, wherein only one magnetoelectric conversion element is provided for each of several armature coil groups that are electrically in phase.