JPH0261007B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field of the Invention] The present invention is applicable to an image scanning device such as a facsimile, in which a rotating polygon mirror is irradiated with a laser beam and the reflected light is scanned on a screen. This is a rotating polygon mirror scanning device that can be used in many other fields such as laser printers, image scanners, and shape measuring machines.

[Technical background and conventional problems]

Conventionally, an information laser beam modulated by an information signal is polarized using a mirror or other polarizing means, and the information signal is recorded by scanning it over a scanned surface on which a photoreceptor or the like is arranged. It is well known to read out information signals on a scanning 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 fast polarization speed,
Since continuous light polarization is possible, high-speed, high-density information recording or reading is possible.

For example, in printing methods such as wire dot printers used in personal computers and word processors,
The printing speed is slow, and high-precision printing is impossible due to the limited number of dots. Also, since a loud printing sound is generated during printing, there is a problem of noise.

In particular, with the development of office automation equipment, it is common to have multiple office automation equipment in one room, and when multiple wire dot printers are running simultaneously,
The loud printing sound has a synergistic effect and becomes a type of noise, which is a nuisance that causes discomfort not only to the person operating the OA equipment but also to those in the surrounding area. Ta.

For these reasons, a rotating polygon mirror scanning device is desired not only for measuring instruments but also for laser printers.

However, the conventional rotating polygon mirror scanning device simply attaches the rotating polygon mirror to the rotating shaft of a core motor with a salient pole rotor and rotates the rotating polygon mirror, so it is very large. As a result, the structure was not suitable for use in today's high-density packaging electronic equipment.

In particular, radial gap type iron core motors with salient pole rotors do not have a coreless structure and are not suitable for high speed rotations of several to 100,000 rotations. This makes it unsuitable for the necessary rotating polygon mirror scanning device.

For example, these conventional ones include JP-A-49
Some of these are disclosed in Publications No.-93027 and No. 57-62751. In addition, with the structure of the both-end shaft rotating type disclosed in these documents, it is difficult to use a hydrodynamic air bearing in order to achieve constant rotation and high speed rotation without dynamic fluctuations, or it is difficult to use an air bearing. Even if air bearings were used, the greatest advantage of using air bearings could not be fully demonstrated.

In addition, as mentioned above, according to the conventional rotating polygon mirror scanning device using a radial gap type iron core motor with a salient pole rotor, the iron core is large, long in the axial direction, thick, and heavy. Since the rotary polygon mirror is simply attached to the rotating shaft of the motor, today's high-speed motors are required to be light, thin, and compact, and in particular, are required to be compact and lightweight so that they do not become a burden when attached to the housing. When used in densely packaged electronic equipment, it has the drawbacks of being heavy, large, and expensive, and not being able to produce highly accurate products, and especially not being able to produce thin products.

Furthermore, in the conventional rotating polygon mirror scanning device using a core type motor, since the core type motor is used, cogging inevitably occurs, and smooth rotation cannot be achieved, resulting in uneven rotation. When used in a laser printer or the like, there was a drawback that scanning unevenness occurred and accurate screen scanning could not be performed.

In particular, according to the conventional rotating polygon mirror scanning device, when a rotating polygon mirror with a small number of reflective surfaces is used in order to be constructed at low cost,
When rotated at high speeds, the windage loss was large, resulting in a very harsh and loud rotating sound. In addition, the large windage loss hinders high-speed rotation, making it impossible to rotate smoothly, causing uneven scanning as described above, and making it impossible to perform accurate screen scanning. Furthermore, due to the above drawbacks, it is impossible to use an inexpensive rotary polygon mirror having a fractional facet as the rotary polygon mirror, resulting in the drawback that an inexpensive rotary polygon scanning device cannot be formed.

[Problem of the present invention]

The present invention is a small, flat, lightweight, and inexpensive rotating polygon mirror scanning device that is useful for use in high-density packaging electronic equipment that is required to be light, thin, and compact. In order to reduce the burden on the casing of the
The object of the present invention is to provide a rotating polygon mirror scanning device that rotates smoothly and efficiently with little windage loss and low rotational noise even when using an inexpensive rotating polygon mirror with a small fractional shape.

Another challenge is to enable the adoption of hydrodynamic air bearings (hydrodynamic group bearings) and highly efficient coreless flat brushless motors, which prevent cogging and significant rotational unevenness, and ensure smooth rotation.
The object of the present invention is to mass-produce a rotating polygon mirror scanning device with good precision, efficiency, and long life that enables screen scanning at low cost.

[Means for achieving the problem of the invention]

The problem of the present invention is to provide a rotating polygon mirror scanning device that polarizes an incident light beam irradiated to the rotating polygon mirror by rotating a rotating polygon mirror whose outer periphery is a polygon mirror. A N pole is placed on one side of a rotary polygon mirror that is supported in a freely movable manner.
A flat field magnet having 2P (P is an integer of 1 or more) S poles alternately is provided, and a stator coreless armature is provided at a fixed side position facing the field magnet with an axial gap interposed therebetween. , in a rotating polygon mirror scanning device configured to rotate a rotating polygon mirror by exciting the stator coreless armature, the rotating polygon mirror is provided with a surface on a reflection side facing the coreless stator armature of the rotating polygon mirror. This can be achieved by providing a rotating polygon mirror scanning device characterized by being provided with a windshield plate having a longer radius than the reflecting surface.

[Embodiments of the invention]

A first embodiment of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 is a longitudinal cross-sectional view of the rotating polygon mirror scanning device 1, and FIG. 2 is an exploded perspective view of the main parts of FIG. 1. The following description will be made mainly with reference to FIGS. 1 and 2.

1 is a rotating polygon mirror scanning device; 2 is a flat cup-shaped stator yoke support having a concave portion 2a (however,
(not shown in FIG. 2), 3 is the support 2
Screw grooves (spiral grooves) forming hydrodynamic air bearings fixed vertically in the approximate center of This is a fixed shaft having a groove (which may be a groove, etc.) 3a formed on its outer periphery. Note that there is a screw groove 3 on the outer periphery of the fixed shaft 3.
a is formed, but it may be formed on the rotating shaft 10 (cylindrical bearing portion 10a), or may be formed on both.

Reference numeral 4 denotes a stator yoke made of a flat annular magnetic material fixed to the upper opening of the support 2, for example, a stator yoke made of a compression molded mixed powder of iron powder and plastic powder, or a magnetic material such as iron powder. A desired result can be obtained by using a resin containing powder.

Reference numeral 5 denotes a drive circuit housing cavity formed by the stator yoke 4 and the support body 2 having the recess 2a. As an example of effectively utilizing this drive circuit housing cavity 5, a cavity 5 is formed on the lower surface of the stator yoke 4. A printed circuit board is disposed, electrical components are disposed on the printed circuit board, a cutout such as a through hole is formed in a part of the stator yoke 4, and the printed circuit board on the lower surface of the stator yoke 4 is inserted using the cutout. and printed circuit board 7
This method is not limited to this method, but there are many other methods that can effectively utilize the void portion 5.

In this way, if the drive circuit is built in, the rotating polygon mirror scanning device 1 with an integrated drive circuit can be installed.
can be configured compactly and suitable for use in high-density packaging electronic equipment.

Reference numeral 6 denotes an air-core type coreless armature coil, which is placed on the stator yoke 4 (in this case, it is preferable that the stator yoke 4 is insulated and shielded).
An appropriate number of coreless armature coils 6-1, for example, six coreless armature coil groups 6-1, for configuring a three-phase brushless motor.
..., 6-6 are arranged at regular intervals so as not to overlap each other, thereby forming a coreless stator armature 15 for a three-phase brushless motor. This will be explained in detail later with reference to FIG. 3.

Reference numeral 7 denotes a printed circuit board having a through hole in the center and a printed wiring conductor (printed power distribution pattern) (not shown) formed by means such as etching, and includes an armature coil 6 (stator armature 15).
It is fixed on top.

Reference numeral 8 denotes a magnetoelectric transducer such as a Hall element or a Hall IC used as a position detection element, which is disposed on the lower surface of the printed circuit board 7 at a position facing the frame cavity 9 of the armature coil 6. This magnetoelectric conversion element has 3
Three magnetoelectric transducers 8-1, ..., 8-3 are used to configure the phase brushless motor, and the magnetoelectric transducer 8-1 is located at position 9 in the cavity within the frame of the armature coil 6-2. The magnetoelectric conversion element 8-2
is arranged at position 9 in the hollow part of the armature coil 6-1, and the magnetoelectric conversion element 8-3 is arranged in the hollow part 9 of the armature coil 6-1.
-3 is arranged at the 9th position in the frame cavity.

Details of the arrangement position of the magnetoelectric transducer 8 will be described later.

Reference numeral 10 denotes a rotating shaft having a cylindrical bearing portion 10a rotatably mounted on the outer circumference of the fixed shaft 3, and a field magnet support collar 10b integrally formed on the outer circumference of the bearing portion 10a so as to extend in a radial outward direction. in,
It also functions as a bearing.

In addition, in the case of the rotating shaft 10 in this embodiment,
Cylindrical bearing portion 10a and field magnet support collar 10
a, but it does not necessarily have to be formed in this way, and a rotating shaft consisting only of the cylindrical bearing part 10a may be used, and such a rotating shaft may be provided with a separate appropriate means. The field magnet support flange 10a may be fixedly formed by.

However, in this embodiment, the cylindrical bearing portion 10c
A rotating shaft 10 having a field magnet support collar 10b integrally formed therein is adopted.

The rotating shaft 10 is currently made of a magnetic material. For this reason, the field magnet support collar 10
b also serves as a rotor yoke for closing the magnetic path of the field magnet 11, which will be described later.

Further, as will be clear from the description below, the field magnet support collar 10b functions as a support member for the rotating polygon mirror 12, which will be described later.

Reference numeral 11 denotes a flat annular field magnet (no. 4), the coreless stator armature 15 consisting of armature coils 6-1, . They are made to face each other with an axial gap 16 in between, so that they can rotate relative to each other.

The field magnet support collar 10b is provided with a bent portion 10c extending vertically downward on its outer periphery. The generation of leakage magnetic flux is prevented as much as possible. Furthermore, this bent portion 10c facilitates positioning of the field magnet 11 and facilitates dynamic balance.

Reference numeral 12 denotes a rotating polygon mirror whose outer circumferential surface is a fractional mirror, which is currently integrally formed of aluminum and has been polished to have a reflective surface 12a on its outer circumference. 4
It has a rectangular plate shape of a four-sided mirror which is a decimal mirror in an axially flat plane having a reflecting surface 12a at a location, and a field magnet supporting collar 10b.
is fixed to the upper surface of the board by appropriate means.

In addition, although the reflecting surface 12a and the rotating polygon mirror 12 in this embodiment are formed of an integral material,
It goes without saying that it is not always necessary to do this, and that the reflective surface 12a may be formed on the outer circumferential surface of the rotating polygon mirror 12 body made of plastic or the like by employing vapor deposition means such as plating or coating.

Reference numeral 13 denotes a windshield disc body for rotating and transporting the air layer located on the reflecting surface 12a with the rotation of the rotating polygon mirror 12, and is formed to have a longer radius than the rotating polygon mirror 12, and It is fixed on the upper surface of the polygon mirror 12 by appropriate means.

Regarding the reason why this windshield disc body 13 is necessary, when the windshield disc body 13 is a polyhedron in which a large number of reflective surfaces 12a of the rotating polygon mirror 12 are formed, the windshield disc body 13 does not need to be particularly provided. Although this is not a problem, it plays an important function when the rotating polygon mirror 12 is a fractional face, such as a three-sided mirror or a four-sided mirror, in order to be formed at low cost.

That is, when the rotating polygon mirror 12 is a polyhedron, even if the rotating polygon mirror 12 rotates, there is little wind pressure resistance of the air layer on the reflective surface 12a, so there is almost no air layer on the reflective surface 12a, so it is difficult to use as a windshield. Even if the disc body 13 is provided, the windage loss is small and it does not have any important meaning, but if the rotating polygon mirror body 12 is a decimal shape such as a tetrahedron as shown in FIG. , there are many air layers on the reflective surface 12a, which increases wind pressure resistance (windage loss), so if the rotating polygon mirror 12 rotates at high speed in this state, it not only produces a loud rotation sound, but also reduces efficiency due to windage loss. This has the disadvantage that the rotating polygon mirror scanning device 1 has poor performance.

Therefore, the rotating polygon mirror 12 is a decimal surface (mirror).
In this case, by providing the windshield disk 13 on the upper surface of the rotating polygon mirror 12 as described above, the air layer that has no escape route on the reflective surface 12a can be integrated with the rotation of the rotating polygon mirror 12. Since the windshield disc body 13 is not provided, the wind pressure resistance is reduced, and the rotation noise generated by the high speed rotation of the rotating polygon mirror 12 is extremely small. , rotating polygon mirror scanning device 1
can be constructed into a useful device that rotates with very small rotational noise (substantial rotational noise accompanying rotation, such rotational noise is almost never generated). Therefore, even if an inexpensive rotating polygon mirror 12 having a small fractional shape is used, a highly accurate rotating polygon scanning device 1 can be mass-produced at low cost.

FIG. 3 shows six coreless armature coils 6-1, . . . , forming the coreless stator armature 15.
FIG. 6 is a perspective view for explaining the conditions and arrangement method of the 6-6 group.

As is clear from FIG. 3, the six coreless armature coils 6-1, .
The armature coils 6-1, . The opening angle (based on the line) is formed to have an opening angle equal to the width of one magnetic pole of the field magnet 11, so that high efficiency can be obtained.

In addition, six armature coils 6-1, ..., 6-
6 are arranged on the above-described stator yoke 4 (not shown) at equal intervals so as not to overlap with each other. 3 armature coils 6-1, 6-2, 6-3
A magnetoelectric transducer 8 is placed in each of the frame cavities 9.
-2, 8-1, and 8-3 are arranged. Details of the arrangement positions of the magnetoelectric transducers 8-2, 8-1, and 8-3 will be described later in FIG.

FIG. 4 is a bottom view of the field magnet 11.
Pole, S pole magnetic poles are alternately equally spaced at equal intervals of 8
This example shows that an 8-pole structure is used in this embodiment.

FIG. 5 is a developed view of the field magnet 11 and six coreless armature coils 6-1, . , 8-3.

As is clear from FIG. 5 (see also FIG. 3), armature coils 6-1, . . . , which constitute the coreless stator armature 15 of the three-phase brushless motor
6-6 indicates that the opening angle between the effective conductor portions 6a and 6b that contributes to the generated torque in the radial direction is the field magnet 1.
Approximately 2n-1 times the width of one magnetic pole of 1, in this example,
n=1 is selected, and it is an air-core type formed with an opening angle width approximately equal to one magnetic pole width of the field magnet 11, that is, an opening angle width of 45 degrees, and each armature coil 6- As shown in FIGS. 3 and 5, the groups 1, . . . , 6-6 are arranged at regular intervals so as not to overlap each other.

The armature coils 6-1, ..., 6-6 groups are composed of two armature coils 6 groups that are electrically in the same phase and are out of phase by 180 degrees in the circumferential direction.
A coreless stator armature 15 is formed for assembling to configure a three-phase brushless motor.

That is, the U-phase armature coils 6-1 and 6-
4. The V-phase armature coils 6-2 and 6-4 and the W-phase armature coils 6-3 and 6-6 form a set for each phase. One magnetoelectric conversion element 8 is provided for each of the six armature coil groups of each phase group.

The magnetoelectric conversion elements 8-1, . The reason for doing this will be explained below.

The U-phase armature coils 6-1 and 6-4, the V-phase armature coils 6-2 and 6-4, and the W-phase armature coils 6-3 and 6-6 are arranged in order at the energizing angle. They are arranged so that they are offset by 60 degrees.

Here, three magnetoelectric conversion elements 8-1, ..., 8
-3 is provided for each armature coil 6-1, . . . in order to configure a three-phase brushless motor.
..., 6-6 would be expensive if provided with a magnetoelectric transducer 8 for each, so a common magnetoelectric transducer 8 could be used for the armature coils 6 located in the same phase position to reduce the cost. This is because it can be configured.

Magnetoelectric conversion elements 8-1, which are position detection elements,...
. . , 8-3 is preferably arranged at a position facing the effective conductor portion 6a or 6b.

However, if the armature coils 6-4, 6-5, 6
If positions U, V, and W on -6 are selected, if arranged in such a position, the arrangement of the magnetoelectric transducer 8 will be difficult due to the presence of the printed circuit board 7, and if When the magnetoelectric conversion element 8 is arranged on the surface of the printed circuit board 7, the length of the gap 16 between the field magnet 11 and the stator yoke 4 increases by the thickness of the element 8, making it impossible to obtain a large torque. It becomes impossible to obtain an efficient three-phase brushless motor.

Therefore, the effective conductor portion 6 of the armature coil 6-4
b, effective conductor portion 6a of armature coil 6-5, position U on effective conductor portion 6a of armature coil 6-6,
Magnetoelectric conversion elements 8-1, 8-2 arranged in V, W,
8-3 and the armature coil 6- located at the same position as this
2, 6-1, 6-3 symbol U' in the frame cavity 9,
By arranging them at the V' and W' positions, the length of the air gap 16 is not increased, and an efficient three-phase brushless motor is obtained.

FIG. 6 is a longitudinal sectional view of a rotating polygon mirror scanning device 1' showing a second embodiment of the present invention, and this rotating polygon mirror scanning device 1' is almost the same as that shown in the first embodiment. The axial thickness of the drive circuit storage cavity 5' is increased, and a plurality of printed circuit boards equipped with control circuits, drive circuits, etc. can be arranged in parallel in this cavity 5'. This is aimed at stabilizing and increasing the accuracy of the rotating polygon mirror scanning device 1'.

FIG. 7 shows a longitudinal sectional view of a rotating polygon mirror scanning device 1'' showing a third embodiment of the present invention, in which the voids 5 and 5' shown in FIGS. 1 and 6 are completely eliminated,
By providing components such as the stator armature 15, field magnet 11, and rotating polygon mirror 12 in the lower position, the rotating polygon mirror scanning device 1'' is stabilized, and the scanning device 1'' is thin and flat in the axial direction. This made it possible to obtain.

In this rotating polygon mirror scanning device 1'', a rotating shaft 10 and a fixed shaft 3 are formed protruding from the upper part of the rotating polygon mirror 12. 1', and if it is desired to configure the rotating polygon mirror scanning device 1'' to be even more flat, the rotating polygon mirror 12 can be This is possible by making sure that it does not protrude too much from the top. Note that the reference numeral 14 indicates a thrust cap.

[Action of the invention]

Rotating polygon mirror scanning device 1, 1' shown in the present invention,
1'', when the magnetoelectric conversion element 8 detects the N pole and the S pole of the field magnet 11, the signal is transmitted to a drive circuit (not shown), which causes a current in an appropriate direction to flow through the armature coil 6. As a result, the field magnet 11 rotates in a predetermined direction according to Fleming's left-hand rule.

Therefore, the rotating polygon mirror 12 fixed to the field magnet support collar 10a also rotates, and the polygon mirror 12
The information laser beam irradiated onto the reflective surface 12a of
The reflected light becomes polarized and scans the screen.

〔Effect of the invention〕

According to the present invention, even if a rotating polygon mirror made of an inexpensive dot-shaped mirror is used, there is almost no windage loss, so the rotation noise is small, and the efficiency is good. A small, flat, and lightweight rotating polygon mirror scanning device useful for electronic equipment can be mass-produced at an extremely low cost. Moreover, since it is lightweight, the load placed on the casing when it is attached to the casing can be reduced, so it can be used in various high-density packaging electronic devices.

In addition, it enables the adoption of hydrodynamic air bearings (hydrodynamic group bearings) and highly efficient coreless flat brushless motors, reducing the occurrence of cogging.
A rotating polygon mirror scanning device that prevents significant rotational unevenness, enables smooth high-speed rotation, enables highly accurate and high-speed screen scanning, has good efficiency, and has a long life can be mass-produced at low cost.

The coreless stator armature in the above embodiment is formed by a group of air-core coreless armature coils, but such a coreless stator armature may be formed by sheet coils or printed coils formed by means such as etching. You may do so.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a rotating polygon mirror scanning device showing a first embodiment of the present invention, FIG. 2 is an exploded perspective view of the main parts, and FIG. 3 is a coreless stator electric machine consisting of a group of coreless armature coils. 4 is a bottom view of the field magnet, FIG. 5 is a developed view of the field magnet and the coreless stator armature consisting of a group of coreless armature coils, and FIG. 6 is the second embodiment of the present invention.
FIG. 7 is a vertical cross-sectional view of a rotating polygon mirror scanning device showing a third embodiment of the present invention. [Explanation of symbols] 1, 1', 1''... Rotating polygon mirror scanning device, 2... Flat cup type stator yoke support, 2a... Recess, 3... Fixed shaft, 3a... Screw groove (spiral groove), 4... Stator York, 5,
5'...Driving circuit storage cavity, 6-1,...,6
-6... Coreless armature coil, 6a, 6b... Effective conductor portion contributing to generated torque, 7... Printed circuit board, 8... Magnetoelectric conversion element, 9... Hollow portion in frame, 10...
Rotating shaft, 10a...Cylindrical bearing part, 10b...Field magnet support collar, 10c...Bending part, 11...Field magnet, 12...Rotating polygon mirror, 12a...Reflecting surface,
13... Windshield disk body, 14... Thrust cap,
15... Coreless stator armature, 16... Air gap.

Claims (1)

[Scope of Claims] 1. A rotating polygon mirror scanning device that polarizes an incident light beam irradiated to the rotating polygon mirror by rotating a rotating polygon mirror whose outer periphery is a polygon mirror. N-pole and S-pole magnetic poles are alternately placed on one side of a rotary polygon mirror that is supported in a freely movable manner.
A flat field magnet having 2P (P is an integer of 1 or more) is provided, a stator coreless armature is provided at a fixed side position facing the field magnet through an axial gap, and the stator coreless armature is In a rotating polygon scanning device configured to rotate a rotating polygon mirror by excitation, a surface of the rotating polygon mirror on the opposite side facing the coreless stator armature has a radius longer than that of the reflecting surface of the rotating polygon mirror. A rotating polygon mirror scanning device characterized by being provided with a windshield plate. 2. The rotating polygon mirror according to claim 1, wherein the rotating polygon mirror is interposed between the upper surface of the rotor yoke that rotates together with the rotation shaft and the lower surface of the windshield plate. Device. 3. The rotating polygon mirror scanning device according to claim 2, wherein the rotor yoke is formed to be longer than the radius of the rotating polygon mirror. 4 The mechanism for rotatably supporting the rotating polygon mirror consists of a fixed shaft installed at a fixed side position and a rotating shaft that rotates around this fixed shaft, and the fixed shaft or the rotating shaft are opposed to each other. A dynamic pressure groove bearing is formed by forming a groove for forming a dynamic pressure groove bearing on at least one of the surfaces, and the rotating polygon mirror is configured to rotate integrally with a rotating shaft. A rotating polygon mirror scanning device according to claim 1. 5. The coreless armature coil constituting the stator coreless armature is an air-core coil in which the opening angle of the effective conductor portion contributing to the generated torque is approximately equal to the width of one magnetic pole of the field magnet. A rotating polygon mirror scanning device according to claim 1, characterized in that: 6. The rotating polygon mirror scanning device according to claim 5, wherein the coreless armature coils are arranged at regular intervals so as not to overlap each other.