JP2002250888A - Polygon scanner motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and make light in weight in a structure, with which the position of a rotor is detected by mounting a Hall element on a ferrous substrate, by making use of a thin plate driving magnet, to cut the time of start up, and to reduce power consumption. SOLUTION: The polygon scanner motor is provided with a stator part 23 which is composed of a stator 21, on which a bearing part 21a is formed, and a motor core 22, a rotor part 25 which is loosely inserted into the bearing part of the stator part 23 in a way that a driving magnet 28 is arranged opposite to the outer periphery of the motor core 22, a Hall element 40 which is arranged at a prescribed position on a printed wiring board 4 on the ferrous base surface of which the wiring is printed and detects the magnetic force of the driving magnet 28. The Hall element 40 is arranged at a detected position on which the magnetic force of the driving magnet 28 is maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a laser scanning device for scanning a laser beam, such as a laser beam printer and a digital copier, and more specifically, a Hall element for detecting a magnetic force from a thin driving magnet. For a polygon scanner motor arranged at a magnetic force detection peak position.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus equipped with a laser scanning system such as a laser printer, a digital copier, and a laser facsimile machine of monochrome or full color has excellent features such as high image quality, high-speed printing, and quietness. It is rapidly spreading due to cost reduction. A polygon scanner motor mounted on this laser scanning system is required to have a rotation speed according to a printing speed and a pixel density.
In recent years, with the increase in print speed and resolution of image quality, polygon scanner motors have a
Realization of a high-speed rotation speed of 50,000 rpm and improvement of its reliability are required. Therefore, conventional ball bearing type bearings cannot meet the required quality in terms of bearing life, bearing noise, etc.Therefore, those using pneumatic bearings have been commercialized as polygon scanner motors for high-speed rotation. ing.

As a polygon scanner motor having a dynamic pressure bearing structure used in such a laser scanning system, for example, one having a radial structure is disclosed in Japanese Patent Application Laid-Open No. Hei 8-1960056.
And Japanese Patent Application Laid-Open No. 9-182357. In particular, a conventional polygon scanner motor in which a back yoke made of iron is fixed to the inside of a rotor made of an aluminum alloy or the like by bonding or the like, and a driving magnet having a thickness of 2 mm is inserted inside the back yoke.

[0004]

However, in the conventional polygon scanner motor as described above, in order to reduce the size and weight of the polygon scanner motor itself, when the printed wiring board is made of iron, When the magnetic field is disturbed between the iron substrate and the driving magnet, when the rotor position by the magnetic pole is detected by the Hall element, the sensing is not performed normally. This can be solved by increasing the magnetic force, but increasing the magnetic force requires a thicker magnet, so it is necessary to provide an outer thickness to avoid interference with the core. There is.

That is, the driving magnet is required to be thicker in the outer diameter direction, and a stronger and wider magnetic force is required. As described above, since the driving magnet cannot be actually made thin, it has been difficult to realize a reduction in size and weight. Also, when the driving magnet is made thicker, especially in a polygon scanner motor rotating at a high speed, the inertia and the windage of the rotor increase, so that there is a problem that the starting time cannot be shortened and the current consumption cannot be reduced. Was.

The present invention has been made in view of the above, and in a structure in which a Hall element is mounted on an iron substrate to detect a rotor position, a thin and thin driving magnet realizes a reduction in size and weight and a start-up operation. An object of the present invention is to reduce time and power consumption.

[0007]

According to a first aspect of the present invention, there is provided a polygon scanner motor according to the first aspect, wherein the stator includes a stator having a bearing portion, a motor core, and a bearing for the stator. The rotor is disposed at a predetermined position on a rotor which is loosely inserted into a portion and a driving magnet is arranged so as to face the outer periphery of the motor core, and is disposed at a predetermined position on a printed wiring board printed and wired on an iron base surface, and detects a magnetic force of the driving magnet. And a magnetic sensor, wherein the magnetic sensor is disposed at a detection position where the magnetic force from the driving magnet is maximized.

According to the present invention, in a structure for detecting a rotor position by mounting a Hall element on an iron substrate, a magnetic sensor for detecting a magnetic force is disposed at a position where magnetic flux lines gather most, and an output value thereof is provided. , A normal rotor position detection can be realized even if the magnetic force of the driving magnet is disturbed by the influence of the iron substrate.

Further, in the polygon scanner motor according to the second aspect, the driving magnet has a thickness of about one.
mm or less.

According to the present invention, since the magnetic sensor is provided at the position where the lines of magnetic force gather most in claim 1,
A thin magnet of about 1 mm, which could not be used conventionally due to the problem of sensing of the magnetic sensor, can be used.

Further, in the polygon scanner motor according to the present invention, the magnetic sensor is disposed near a center between adjacent slots of the motor core.

According to the present invention, the magnetic sensor is disposed at the center position of the slot groove of the motor core in the first or second aspect, so that a stable magnetic force can be detected.

According to a fourth aspect of the present invention, in the polygon scanner motor, the driving magnet is a ferrite magnet, and the magnetic sensor is located at a predetermined distance inward from an outer peripheral surface of the driving magnet. It is what is arranged.

According to the present invention, claim 1, 2 or 3
In the case of using a ferrite-based magnet as the material of the driving magnet, the magnetic force characteristics of the ferrite-based magnet are determined, and the outer peripheral surface of the driving magnet is arranged at a predetermined distance inside the region where the lines of magnetic force converge to be stable. Magnetic detection becomes possible.

Further, in the polygon scanner motor according to the present invention, the driving magnet is a rare earth magnet, and the magnetic sensor is spaced a predetermined distance inward from an outer peripheral surface of the driving magnet. Is to be placed.

According to the present invention, claim 1, 2 or 3
In the case where the material of the driving magnet is a rare earth magnet such as neodybond, the magnetic characteristics of the magnet are to be determined, and the magnet is disposed at a predetermined distance from the outer peripheral surface of the driving magnet, where the magnetic field lines are most concentrated. Thereby, stable magnetic detection becomes possible.

In the polygon scanner motor according to the present invention, the magnetic sensor detects a magnetic force from the driving magnet on a horizontal plane or an inclined plane.

According to the present invention, in any one of the first to fifth aspects, when detecting the magnetic force of the driving magnet,
By arranging the detection surface in accordance with the detection characteristics of the horizontal type that detects the magnetic force vertically and the tilt type that detects the magnetic force with an inclination angle, the magnetic force can be detected without being affected by the disturbance of the magnetic field.

Further, in the polygon scanner motor according to the present invention, the magnetic sensor is a Hall element for detecting by a Hall effect.

According to the present invention, by arranging the Hall element for detecting by the Hall effect at the position where the lines of magnetic force gather most in any one of the first to sixth aspects, accurate magnetic pole detection becomes possible.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a polygon scanner motor according to the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to this embodiment. In addition, this polygon scanner motor is described as an example mounted on an image forming apparatus such as a laser printer. However, in addition to the polygon mirror, the polygon scanner motor can be similarly developed to a device that rotates a disk-shaped thin body at a high speed. It is. In addition to the polygon scanner motor, the rotor and the drive magnet portion are thin and a magnetic sensor is arranged on an iron substrate, and the present invention can be similarly applied to a motor having a purpose as described later.

The polygon scanner motor according to the present invention is mounted on a laser scanning system (laser writing unit) such as a laser printer or a digital copier, rotates a polygon mirror at a predetermined speed, and deflects and scans the light by a reflection surface on its side.
Further, it is used for an apparatus that optically scans the surface of a photoreceptor with a laser beam via each lens and mirror.
Therefore, the quality (jitter characteristics, tilting, etc.) of the polygon scanner motor affects the image quality, so that it is positioned as an important unit.

FIG. 1 is a sectional view showing a configuration of a polygon scanner motor according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a polygon scanner motor, reference numeral 2 denotes a DC motor having a brushless motor structure, and reference numeral 3 denotes a polygon mirror serving as a rotating polygon mirror.

Reference numeral 4 denotes a printed wiring board for wiring and mounting each circuit such as a driver and IC components on an iron plate, reference numeral 5 denotes an air dynamic pressure bearing in radial and thrust directions, and reference numeral 6 denotes a protrusion. , Reference numeral 21 denotes a stator, reference numeral 22 denotes a motor core, and reference numeral 23 denotes a stator.
r: stator part, reference numeral 24 denotes a shaft part, reference numeral 25 denotes a rotor part, reference numeral 26 denotes a rotor, reference numeral 2
Reference numeral 7 denotes an annular yoke (which is a yoke) made of iron (which is a magnetic material), and reference numeral 28 denotes an annular driving magnet provided inside the yoke 27.

Reference numeral 29 denotes a thrust plate having a function of a stopper in the thrust direction and a thrust dynamic pressure groove. Reference numeral 31 denotes a mounting hole provided on the center axis of the polygon mirror 3; 40 is a Hall effect device (Hall effect device,
Hereinafter, it is called a Hall element). Reference numeral 45 denotes a dynamic pressure bearing surface formed in the radial and thrust directions.
Hereinafter, the configuration relationship of these parts will be described.

The polygon scanner motor 1 has a shaft 2
The brushless DC motor 2 rotates the polygon mirror 3 pivotally supported at 4 at a high speed.
In addition, the lower part is insulated on a steel plate about 1 mm thick,
A printed wiring board 4 on which printed wiring is provided is provided thereon, and a lower portion of the rotor 21 is positioned and fitted in the hole.

The DC motor (DC brush motor) 2
A stator 21 fixed to the printed wiring board 4 by appropriate means such as caulking is provided with a stator portion 23 in which a motor core 22 is fixed at a predetermined position by light press-fitting. The rotor part 25 is rotatably supported via the bearing 5.

The rotor portion 25 is provided inside a yoke 27 made of a magnetic material fixed to the outer periphery of the rotor 26, for example, a neodybond magnet (neodymium (Nd) which is a ferrite rubber magnet or a rare earth magnet.
d)), samarium-cobalt (samarium (Sm)
A ring-shaped driving magnet 28 made of a system is fixed, and a rotor 26 is rotated by a force acting between a magnetic field generated by a driving current flowing through the motor core 22 and a magnetic field generated by the driving magnet 28.

The polygon mirror 3 is made of an aluminum material, has a regular hexagonal thin plate shape for performing a conformal scan with a laser beam, and has a circular mounting hole 31 formed at the center thereof. On the side surface of the polygon mirror 3, a reflection surface 32 having a mirror finish of a submicron order is formed to reflect a laser beam. The polygon mirror 3
Is not limited to a regular hexagon, and may be any regular polygon.

In order to fix the polygon mirror 3 to the rotor 26 by using the mounting hole 31, the rotor 26 has an annular protrusion 6 fitted in the mounting hole 31 and formed concentrically with the rotor 26. ing. That is, the mounting hole 3 of the polygon mirror 3
1 is inserted into the protrusion 6 and a predetermined pressure is applied to the upper edge of the protrusion 6 (a pressure that does not deform the surface mirror surface of the polygon mirror 3).
And the protrusion 6 is plastically deformed toward the polygon mirror 3 so that the mounting hole 31 is provided with a radial pulling force to secure the projection 6 from falling off.

In order to rotatably provide the rotor portion 25 on the stator portion 23, a small-diameter portion 21
a is formed coaxially, and the rotor 26 is
The rotor 26 is rotatably supported by the stator 21 by being loosely inserted into the a. Further, a thrust plate 29 as a dynamic pressure generating member is fixed to the shaft portion 24 at the distal end of the small diameter portion 21a by caulking. This limits the movement of the rotor 26 in the thrust direction.

Reference numeral 45 in the drawing denotes a hydrodynamic bearing surface, and each component surface (the stator portion 23, the rotor 26,
On the contact surface of the thrust plate 29), a dynamic pressure groove (groove) of about 5 μm is formed by, for example, turning. The surface is treated with a metal in which fine particles of a fluorine compound such as PTFE having a coefficient of friction and having water repellency are dispersed. Thus, a small gap is formed so that the rotor 26 can rotate smoothly and stably at a high speed around the small-diameter portion 21a by the dynamic pressure action.

A cylindrical yoke 27 made of a magnetic material (such as iron) is fitted around the outer periphery of the rotor portion 25, and a ring-shaped driving magnet 28 having a thickness of about 1 mm is fixed inside the yoke 27. ing. In other words, the polygon scanner motor 1 according to the present embodiment is provided with an iron Of the yoke 27 is press-fitted. That is, since the magnetic force is weak only with the driving magnet 28, a magnetic body (yoke 27) is provided outside the driving magnet 28. In this case, iron is provided in an amount to be magnetically saturated.

In consideration of the optimum position in the magnetic force distribution of the driving magnet 28, the driving magnet 28
Hall Effect (Hall Effect)
t) a kind of galvanomagnetic effect (electromagnetic conversion type)
The Hall element 40 for detecting the magnetic pole position is applied to a predetermined position (relation with the motor core 22) at a predetermined interval (angle).
Are provided on the printed wiring board 4.

The Hall effect is provided by providing a pair of terminals through which a current flows and a pair of detection terminals in a direction perpendicular to the terminal along the surface of the semiconductor element, and flowing the current in a direction perpendicular to the element (or When a magnetic field is applied in the direction of a predetermined inclination angle), a voltage is generated between the detection terminals in a voltage substantially proportional to the magnetic field.

The Hall element is used for detecting a magnetic field (magnetic field), and is formed of GaAs (gallium arsenide) or InS.
b (indium antimony) is a kind of semiconductor element manufactured using Si (silicon) or the like as a material. Among them, as the Hall element 40 in this embodiment, an InSb Hall element which is generally considered to have high sensitivity is used.

As a detection mode of the Hall element, a type in which the sensor surface made of InSb is oriented horizontally in the resin package as shown in FIG. 2 (hereinafter, referred to as a horizontal Hall element 40a), As shown in FIG. 3, there is a type inclined at 45 degrees (hereinafter referred to as an inclined Hall element 40b). This horizontal Hall element 40
Since the magnetic detection sensitivity characteristics of the a and the inclined Hall element 40b are different from each other, it is necessary to arrange them at positions optimal for the characteristics.

Here, these two types of Hall elements 4
0, the optimum position is evaluated, that is, in which position the Hall element 40 is arranged and the output voltage of the Hall element 40 indicating the magnetic force is highest by an experiment, and the Hall element 40 is determined according to the result. Deploy.

First, experimental conditions and methods relating to this evaluation experiment (magnetic field analysis) will be described. FIG. 4 is an explanatory diagram showing a moving direction of the Hall element 40 with respect to the driving magnet 28. The position where the Hall element 40 contacts the outer peripheral surface of the driving magnet 28 is set to 0 (reference position), the outside direction is set to minus (-), and the inside direction is set to plus (+).

FIG. 5 is an explanatory diagram showing an arrangement relationship of the Hall element 40 with respect to the motor core 22. In this case, the shape of the core 22a is shown, but the coil is actually wound. Here, the motor core 22
, A slot gap A of the core 22a,
The output characteristics of the Hall element 40 are evaluated at two positions of the slot center B. Further, as a material of the driving magnet 28, a 1 mm thick neodybond magnet,
Two types of magnets are provided. Also,
It is assumed that the hall element 40 is mounted on the printed wiring board 4 made of iron.

FIGS. 5 and 6 show the evaluation results under such experimental conditions. FIG. 6 is a graph showing Hall element characteristics when a neodybond magnet is used. FIG. 7 is a graph showing Hall element characteristics when a ferrite magnet is used. This 2
The two graphs show the characteristic results of the Hall element when a load resistance of 400Ω is connected to the Hall element and a voltage of 4 V is applied under the above-described conditions as shown on the left. In FIG. 6, the neodybond magnet is abbreviated as neody in the column of driving magnet.

In the evaluation result of FIG.
In the case of the inclined Hall element 40b, the inverted slot gap (or the center of the inverted slot), and in the case of a neodybond magnet, the maximum output of the inclined Hall element 40b is +
The position is about 1 to 1.2. In addition, in the evaluation result of FIG. 7, for example, a 45-degree tilt type Hall element 40b
In the case of the inverted slot gap (or the inverted slot center) and a ferrite magnet, the output maximum value of the inclined Hall element 40b is also at a position of about +1 to 1.2. Therefore, it can be understood that the inclination type Hall element has a characteristic in which the peak value becomes remarkable, and the sensing of the magnetic pole becomes easier.

Also, from the evaluation results, first, no matter which type of the Hall element is used, the output waveform becomes higher when the Hall element is disposed inside (+ direction) with respect to the driving magnet 28. It can be confirmed that the characteristic in which the difference in height is remarkable is obtained particularly in the case of the Hall element inclined at 45 degrees. Second
In addition, when the core a is arranged at the slot position (slot gap A), a characteristic result in which the height of the output waveform is more remarkable than that at the slot center B is obtained.
The peak value of the output voltage becomes significant. Third, a 45-degree inclined Hall element 40b with respect to the horizontal Hall element 40a.
In this case, an output voltage having a remarkable peak value is obtained.

By this magnetic field analysis, the point of the Hall element 40 where the magnetic field lines (the output of the Hall element) are collected most is determined. By arranging the Hall element 40 at that position, the output voltage value is subjected to signal processing (predetermined processing). A / D conversion is performed using the threshold value, and the rotor position can be detected from the value after the A / D conversion. In addition, if the Hall element is arranged at the position where the change of the output waveform is the largest regardless of whether the output voltage is + or-, the detection processing can be performed by appropriately setting the threshold level of the A / D conversion. Become.

Therefore, if the thickness of the driving magnet 28 is 1
Even if the Hall element 40 is mounted on the printed wiring board 4 made of iron, normal sensing can be performed. Therefore, the rotor can be realized by the driving magnet 28 having a thickness of 1 mm, which cannot be realized conventionally due to the disturbance of the sensing characteristics. Therefore, the size and weight of the rotating body can be reduced, and the inertia of the rotor and the increase in air volume can be suppressed. Furthermore, since the startup time and the rated current value at the time of startup are reduced, power consumption can be reduced.

[0046]

As described above, according to the polygon scanner motor of the present invention (claim 1), in the structure in which the Hall element is mounted on the iron substrate and the rotor position is detected, the position where the lines of magnetic force gather most is determined. By arranging a magnetic sensor that detects the magnetic force at that position and processing the output value, it is possible to perform normal rotor position detection even if the magnetic force of the driving magnet is disturbed by the influence of the iron substrate. Accordingly, the thin driving magnet can be reduced in size and weight, and the inertial force due to the thinner rotor can be reduced, so that the starting time can be reduced and the power consumption can be reduced.

According to the polygon scanner motor of the present invention (claim 2), since the magnetic sensor is provided at the position where the lines of magnetic force gather most in claim 1, it cannot be used conventionally due to the problem of sensing of the magnetic sensor. Since a magnet as thin as about 1 mm can be used, the cost can be reduced, and inertia and windage loss of the rotor due to the thinner rotor can be reduced.

According to the polygon scanner motor of the present invention (claim 3), the magnetic sensor is arranged near the center of the slot gap of the motor core in claim 1 or 2, so that more stable magnetic force detection is realized. I do.

According to the polygon scanner motor of the present invention (claim 4), when the driving magnet is made of a ferrite magnet, the magnetic force characteristics of the ferrite magnet can be reduced. And the magnetic field is arranged at a predetermined distance from the outer peripheral surface of the drive magnet where the lines of magnetic force gather most, so that a stable magnetic force can be detected regardless of the magnet material.

According to the polygon scanner motor of the present invention (claim 5), when the material of the drive magnet is a rare-earth magnet such as neodybond, for example, Since the magnetic force characteristics of the magnet are determined and the magnet is arranged at a predetermined distance from the outer peripheral surface of the drive magnet where the lines of magnetic force gather most, a stable magnetic force can be detected regardless of the magnet material.

According to the polygon scanner motor of the present invention (claim 6), in any one of claims 1 to 5, when detecting the magnetic force of the driving magnet, the detection surface is configured to apply the magnetic force vertically. Since it is arranged in accordance with the respective detection characteristics of the horizontal type for receiving and detecting and the tilt type for detecting with a tilt angle, it is possible to perform magnetic force detection that is not affected by disturbance of the magnetic field due to the iron substrate facing the driving magnet.

According to the present invention, in any one of the first to sixth aspects, the Hall element for detecting by the Hall effect is arranged at the position where the lines of magnetic force gather most, so that the accurate detection of the magnetic pole at the position where the magnetic field is not disturbed. Can do it.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a polygon scanner motor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement state of a horizontal Hall element according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an arrangement state of a tilted Hall element according to the embodiment of the present invention;

FIG. 4 is an explanatory diagram showing a moving direction of the Hall element with respect to the driving magnet according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an arrangement relationship of a Hall element with respect to the motor core according to the embodiment of the present invention.

FIG. 6 is a graph showing Hall element characteristics when a neodybond magnet according to an embodiment of the present invention is used.

FIG. 7 is a graph showing Hall element characteristics when a ferrite magnet according to an embodiment of the present invention is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polygon scanner motor 2 DC motor 3 Polygon mirror 4 Printed wiring board 5 Air dynamic pressure bearing 22 Motor core 23 Stator part 25 Rotor part 27 Yoke 28 Driving magnet 40 Hall element 40a Horizontal hall element 40b Inclined hall element

Continued on the front page (72) Inventor Kaoru Kaneko 1-8 Nakase, Mihama-ku, Chiba-shi, Chiba F-term (reference) in Seiko Instruments Inc. 2C362 BA08 DA08 2H045 AA14 AA53 5H019 AA08 BB05 BB15 BB20 BB22 CC04 CC07 CC09 DD01 EE14 FF03 5H621 BB07 GA01 HH05 HH08 JK04 JK08 JK15 JK18 JK19 5H622 CA01 CA05 CA10 CB05 DD02 PP05 PP19 QB02 QB05

Claims (7)

[Claims] A stator comprising a stator having a bearing formed thereon and a motor core; a rotor loosely inserted into a bearing of the stator and having a driving magnet arranged to face an outer periphery of the motor core; and an iron base. A magnetic sensor that is disposed at a predetermined position on a printed wiring board having a printed wiring on the surface and detects a magnetic force of the driving magnet, comprising: a magnetic sensor configured to detect a magnetic force from the driving magnet. A polygon scanner motor, wherein the polygon scanner motor is arranged at a detection position where the maximum value is obtained. 2. The driving magnet according to claim 1, wherein the driving magnet has a thickness of about 1 mm.
The polygon scanner motor according to claim 1, wherein: 3. The polygon scanner motor according to claim 1, wherein the magnetic sensor is disposed near a center between adjacent slots of the motor core. 4. The driving magnet according to claim 1, wherein the driving magnet is a ferrite magnet, and the magnetic sensor is disposed inside the outer peripheral surface of the driving magnet at a predetermined distance. 3. The polygon scanner motor according to any one of 3. 5. The driving magnet is a rare-earth magnet, and the magnetic sensor is disposed at a predetermined distance inside the outer peripheral surface of the driving magnet. The polygon scanner motor according to any one of the above. 6. The polygon scanner motor according to claim 1, wherein the magnetic sensor detects a magnetic force from the driving magnet on a horizontal plane or an inclined plane. 7. The magnetic sensor according to claim 1, wherein the magnetic sensor is a Hall element that detects by a Hall effect.
The polygon scanner motor according to any one of the above.