JPS60214333A - Rotary polygon mirror scanning device - Google Patents

Abstract

PURPOSE:To obtain a small-sized, lightweight, thick, and inexpensive scanning device while prolonging its life by using a disk type brushless motor which suits to mass-production. CONSTITUTION:A 2P-pole annular field magnet 11 which has magnetic poles N and S alternately is fixed to the reverse surface of a collar 10b made of a magnetic body, and faces an armature coil group 6 having a printed board 7 on the top surface. A rotary polygon mirror 12 is axially flat and in a square shape while having reflecting surfaces 12a on the periphery at four positions, and fixed to the top surface of the collar 10b. A comb-shaped conductive pattern 15 for rotating speed detection is formed on the surface of the printed board 7, which faces the field magnet 11 across a fine gap. Driving magnetic poles 11a of the field magnet 11 are magnetized into eight N and S magnetic poles alternately at equal intervals, and about 180 magnetic poles 11b rotor rotating speed detection are formed at its peripheral part and magnetized so that N and S are intenser than N' and S'.

Description

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

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 is required to be small, it is heavy and has a large amount of phantom grains. It was not possible to obtain a large, low-cost, high-performance product. 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. Furthermore, it is difficult for conventional rotating polygon mirror scanning devices to scan at a constant rotational speed, and a large and expensive tacho generator or encoder must be used as rotational speed detection means. As a result, the rotating polygon mirror scanning device itself has become large and expensive.

Therefore, the applicant previously proposed a 2P (P is 1
A field magnet having a driving magnetic pole with a positive integer (a positive integer above) and a frequency detection magnetic pole magnetized so that the driving magnetic pole has strong magnetized parts and weakly magnetized parts alternately at a fine pitch. The above disadvantages are solved by providing a rotating polygon mirror scanning device characterized by a frequency structure in the part facing the magnetic pole for frequency detection, which is equipped with a rotational speed detection means, is light in superimposition, and is small in size. We have provided a rotating polygon mirror scan that is inexpensive, thin in the axial direction, and capable of scanning at a constant rotation speed.

Here, when forming the driving magnetic pole and the frequency detection magnetic pole, first magnetize the driving magnetic pole on the magnet, and then use another magnetizer to magnetize and form the frequency detection magnetic pole. If the frequency detection magnetic pole is not formed in the correct position, a high-performance frequency power generation voltage cannot be obtained. Furthermore, since magnetization must be performed twice as described above, it is time consuming and has the disadvantage of not being suitable for mass production.

The present invention aims to improve the rotating polygon mirror scanning device of the optical invention described above, and by forming the drive magnetic pole only once, the frequency detection magnetic pole is also correctly magnetized at the same time. This was done so that the process could be omitted and field magnets having the driving magnetic pole and the frequency detection magnetic pole could be mass-produced at low cost.

The object of the present invention is mainly to apply a bond for forming a driving magnetic pole to the entire surface facing the stator armature of a magnet, which has uneven portions alternately formed at a fine pitch on the frequency detection magnetic pole forming portion. By performing magnetization, a driving magnetic pole and a frequency detection magnetic pole are achieved on the same surface.

The present invention will be described in detail below with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. 1 to 8.

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 Approximately of the support 2 - a fixed shaft having a screw groove fixed vertically in the center, 4
is a flat annular stator yoke that is fixed to the upper opening of the support 2, and is formed by compression molding, for example, a mixed powder of iron powder and glass powder.

Reference numeral 5 denotes a gap, which is a drive circuit housing portion. Reference numeral 6 denotes an armature coil wound into a frame shape, and an appropriate number of armature coils are arranged on the stator yoke 4. This is explained in FIG. Reference numeral 7 denotes a printed circuit board having a through hole in the center and a printed wiring conductor section (not shown), and is fixed on the upper surface of the armature coil 6. Reference numeral 8 denotes a magnetoelectric transducer such as a Hall element or a Hall IC used as a position detection element disposed on the lower surface of the printed circuit board 7 at a position facing the frame cavity 9 of the armature coil 6. The arrangement position of the magnetoelectric transducer 8 will be described later. Reference numeral 10 denotes a cylindrical rotating shaft having a cylindrical bearing part 10a rotatably mounted on the outer periphery of the fixed shaft 3, and a collar 10b integrally formed on the outer periphery of the bearing part 10a. The rotating shaft 1o is made of a magnetic material. Further, a collar 10b made of a magnetic material for closing the magnetic path of the field magnet 11, which will be described later, functions as a support member for a rotating polygon mirror 12, which will be described later. Reference numeral 11 denotes a 2P (P is a positive integer of 1 or more) pole annular field magnet (see Figure 4), which is fixed to the lower surface of the collar 10b, which is a magnetic material, and has N and S magnetic poles alternately. , an armature coil 6 fixed to the lower surface of the collar 10b and having a printed circuit board 7 on the upper surface.
The group is facing each other. The above-mentioned collar 10b is provided with a vertically extending bent portion tOC on its outer periphery, and this bent portion 10c
The field magnet 11 is held in place. 12
is a rotating polygon mirror, which has a rectangular shape that is flat in the axial direction and has four reflective surfaces 12a around it.
It is fixed on the top surface of.

Reference numeral 13 denotes a windshield disk 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 disc body 13 is unnecessary when the rotating polygon mirror 12 is a polyhedron, but when the rotating polygon mirror 12 is a small body such as a three-sided mirror or a four-sided mirror, it is unnecessary. It is necessary. That is, when the rotating polygon mirror 2 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 is no place for the wind to escape, and conversely, a loud rotation noise is generated due to the rotation of the rotating polygon mirror 12. On the other hand, the rotating polygon mirror 1
When 2 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 noise.
When the rotating polygon mirror 12 is an oligohedron, the windshield disc body 13
By providing this, the wind on the reflecting surface 12a has no escape route due to the disk body 13, so the rotating polygon mirror 12
The wind rotates together with the reflecting surface 12a as the rotating polygon mirror 12 rotates. Therefore, the wind pressure resistance becomes smaller compared to the case where the windshield disc body 13 is not provided.
This has the effect of significantly reducing the noise generated by the rotation of the

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

As is clear from this Fig. 3, six armature coils 6-
1. ......, 6-. 6 are wound into a fan frame shape, and six armature coils 6-1.・・・
..., 6-6 are arranged at equal intervals so as not to overlap each other. 3 armature coils 6-1°...
, 6-3, the magnetoelectric conversion element 8-1,
8-2 and 8-3 are provided. This will be explained in more detail in FIG.

A disk-shaped printed circuit board 7 is fixedly installed on 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 on the surface of the magnet (see FIG. 7). The printed circuit board 7 and the field magnet 11 face each other with a small gap in between. As shown in FIG. 4, the field magnet 11 is magnetized to have eight driving magnetic poles 11a having N and S magnetic poles alternately spaced at equal intervals. Approximately 180 frequency detection magnetic poles 11b for rotor rotational speed detection are formed. N and S are N'.

N′ is also strongly magnetized. The reason for this is that an annular magnet having concave and convex portions alternately formed at a fine pitch is formed at the position of the frequency detection magnetic pole forming portion 11b, and an 8-pole magnetizer for forming driving magnetic poles (not shown) is used. By magnetizing and forming driving magnetic poles on the magnet, a frequency detecting magnetic pole is formed in the frequency detecting magnetic pole forming part having the uneven portion, and eight driving magnetic poles are magnetized and formed in the other magnet parts. This is because the field magnet 11 shown in FIGS. 4 and 5 is formed. That is, when the drive magnetic pole is magnetized and formed on the concave and convex portions of the magnet, the concave portions are weakly magnetized and the convex portions are strongly magnetized. Therefore,
The frequency detection magnetic pole 11b has strong magnetized parts (N, S
pole) and weakly magnetized part (N').

N' poles) are formed alternately. The N' pole corresponds to the S pole, and the N' pole functions as the N pole.

Therefore, the magnetic flux density waveform in the gap formed by the field magnet 11 is as shown in FIG.

As shown in FIG. 8, 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 formed by the driving magnetic pole 11a A finely uneven waveform is formed at the peaks or valleys of the density waveform.

Figure 6 is a developed view of the field magnet and armature coil.
Furthermore, the arrangement positions of the magnetoelectric conversion elements are shown.

As is clear from FIG. 6, in the armature coil 6, the opening angle between the conductor portions 6a and 6b, which contributes to the generated torque in the radial direction, is approximately 2n-1 of the magnetic pole width of the field magnet 11 (however, n -1) In other words, the armature coils are wound with an opening angle width that is approximately equal to the magnetic pole width of the field magnet 11. Each of the six armature coil groups is shown in FIGS. 3 and 6. They are arranged at equal intervals so as not to 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 of the six groups of armature coils. The magnetoelectric conversion element 8 is the armature coil 6
It is stored and arranged in the frame cavity 9 of.

With reference to FIG. 6, armature coil 6-4.6-5.6-
Positions U, V, on the conductor portion 6a that contribute to the generated torque of 6.
The magnetoelectric transducer 8 disposed on the W is placed in the frame cavity 9 of the armature coil 6-1.6-2.6-3 located at the same position as the magneto-electric transducer 8.
The symbols V', U', and W' are placed at the positions of .

FIG. 7 is a plan view of the printed circuit board 7 of FIG. 1. A comb-shaped conductive pattern 15 as shown in FIG. 7 is formed on the surface of the printed circuit board 70 at a portion facing the frequency detection magnetic pole 11b of the field magnet 11. The pitch of this conductive pattern 15 is the same as the pitch of the frequency detection magnetic poles 11b shown in FIG. Conductive pattern 1
When every other line segment group in the radial direction of 5 faces, for example, N or S of the frequency detecting magnetic pole 11b, 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 the output terminal (not shown) of the conductive pattern 150.

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. 7, the detection output is obtained as a continuous wave. Further, when the number of rotations of the frequency detection magnetic pole 11 is constant, a detection output of a constant frequency can be obtained. The variation in the rotor rotational speed is extracted as a frequency modulation component of the detection output.

FIG. 9 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 being able to store multiple units in parallel, the above device 1'
The aim is to stabilize the In this rotating polygon mirror scanning device 1', a field magnet 11 and a rotating shaft 10 are integrally formed using a plastic magnet. After this formation, the driving magnetic pole 11a is magnetized to form the field magnet 11 in which the frequency detection magnetic pole 11b is also formed at the same time. In addition, when formed in this way, the surface of the rotating shaft 10 that comes into sliding contact with the fixed shaft 3 needs to be formed of an appropriate material as a bearing. It goes without saying that a ferrite magnet other than a plastic magnet, for example, may be used as described above.

FIG. 10 shows a rotating polygon mirror showing a third embodiment of the present invention.

In the scanning device 1', the air gap 5 shown in FIGS. 1 and 9 is completely eliminated, and the armature coil 6, field magnet 11, rotating polygon mirror 12, etc. are provided at the bottom, thereby stabilizing the device 1,'. In addition to this, the device 1' is formed to be thin. 14 is a thrust cap.

In this embodiment, a rotating shaft 10, a field magnet 1
1. The rotating polygon mirror 12, the windshield 13 and the thrust cap 14 are integrally formed with plastic magnets, and the rotating shaft 1
The rotating polygon mirror 12 is formed by coating the sliding surfaces of the fixed shaft 3 of the thrust cap 14 with fluororesin, and forming a reflective surface on the outer periphery of the rotating polygon mirror forming part. , magnetized as described above.

Since the present invention has the above 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, and thereby the left-hand rule of Schifleming is applied. This causes the field magnet 11 to rotate in an appropriate direction.

The rotation speed can be determined by feeding back a signal from a frequency generator formed by the frequency detection magnetic pole 11b and the conductive pattern 15 to the rotation speed control circuit.
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.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-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 the armature coil group, and FIG. FIG. 5 is a bottom view of a field magnet having frequency detection magnetic poles shown as an example; FIG. 5 is a bottom perspective view of the field magnet and magnet; FIG. 6 is a developed view of the field magnet and armature coil group; 8 is a diagram of the magnetic flux density waveform formed by the field magnet of FIG. 6, FIG. 9 is a longitudinal sectional view showing the second embodiment of the present invention, and FIG. The figure is a longitudinal sectional view showing a third embodiment of the present invention. 1, 1', 1'--Rotating polygon mirror scanning device, 2...
・Flat cup-shaped support, 3... Fixed shaft, 4... Magnetic yoke, 5... Gap (drive circuit storage part), 6...
Armature coil, 7... Printed circuit board, 8... Position detection element (magnetoelectric conversion element), 9... Cavity within frame of armature coil, 10... Rotating shaft, 10 a... Bearing part, 1
0b... Tsuba, 11... Field magnet, 12...
Rotating polygon mirror, 13... Disc for windshield, 14... Thrust cap, 15... Conductive pattern. Patent applicant Yoshi Takahashi Terushi Figure 3 Figure 4 d-ko Z%

Claims (1)

[Claims] (1) A rotating polygon scanning device in which an incident light beam is polarized by a rotating polygon mirror, which has a polygon mirror and flat annular N and S magnetic poles alternately on the rotation axis. 2P (P is a positive integer greater than or equal to 1) pole driving magnetic pole and the driving magnetic pole are provided with concavities and convexities alternately at a fine pitch to form magnetization so that strong magnetized parts and weakly magnetized parts are alternately provided. A field magnet having a frequency detection magnetic pole is attached, and a stator armature having a comb-shaped conductive pattern for frequency detection on a portion facing the frequency detection magnetic pole is arranged on the fixed side facing the field magnet. A rotating polygon mirror scanning device characterized by: (2) For this purpose, the above-mentioned field magnet is formed by applying a magnetic pole to the frequency detection magnetic pole forming part of the magnet beforehand with a pitcher. - The frequency detection magnetic pole having the uneven portion is simultaneously formed by magnetizing the driving magnetic pole over the entire magnet having the frequency detection magnetic pole forming portion and the driving magnetic pole forming portion having the uneven portion. A rotating polygon mirror scanning device according to claim (1). (3) The field magnet is formed integrally with the rotating shaft using a plastic magnet, and then the driving magnetic pole and the frequency detection magnetic pole are formed. 2) The rotating polygon mirror scanning device described in section 2). (4) The rotating polygon mirror scanning device according to claim (3), wherein the field magnet and the rotating shaft are integrally formed. (5) A rotating polygon mirror is formed by integrally forming the field magnet, the rotating shaft, and the rotating polygon mirror forming portion, and forming a reflective surface on the rotating polygon mirror forming portion. 4) The rotating polygon mirror scanning device described in section 4). (6) The rotating polygon mirror scanning device according to claim (5), wherein the rotating polygon mirror has a windshield disk on its upper part. (7) The rotating polygon scanning bearing as set forth in claim (6) is characterized in that the field magnet, rotating shaft 1, rotating polygon mirror, and windshield disc body are integrally formed. A rotating polygon mirror scanning device according to any one of claims (1) to (7). (9) The member for closing the magnetic path of the field magnet and the supporting member of the rotating polygon mirror are integrally formed.
3) The rotating polygon mirror scanning device according to any one of items 3). (10 The armature coil forming the stator armature above is
Claims (1) to (9) characterized in that the conductor portion contributing to the generated torque is wound so that the opening angle width is approximately equal to the magnetic pole width of the field magnet. )
The rotating polygon mirror scanning device according to any one of the items. (b) The armature coil group is arranged at equal intervals so as not to overlap each other.
1) The rotating polygon mirror scanning device according to any one of items 1 to 00. (6) Claims (1) to (b) characterized in that the rotational position detection means is a magnetoelectric conversion element.
Rotary polygon mirror scanning device 0 (b) according to any one of the claims, characterized in that only one magnetoelectric transducer is provided for each group of several armature coils that are electrically in phase. Rotating polygon mirror scanning device O a4 described in range @ section The above magnetoelectric transducer is disposed at a position in the hollow part within the frame of the armature coil, which is located at the same position as the conductor part that contributes to the generated torque of the armature coil. A rotating polygon mirror scanning device according to claim α4.