JP2009153263A - Polygon mirror motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polygon mirror motor that maintains high and stable rotation performance, even if the motor is applied with a strong impact from the outside. <P>SOLUTION: The polygon mirror motor includes: a plate-shaped motor base 11; a rotor 2 rotatably supported to the motor base 11 via a bearing unit 12; and a polygon mirror 3 concentrically fixed to the rotor 2. A stopper 4 which limits the axial movement of the rotor 2 is arranged at the motor base 11. The stopper 4 includes a support column 41 erecting on the motor base 11 in a position adjacent to the rotor 2, and an arm-shaped hanging part 42 extending to the rotor 2 side from the upper end of the support column 41. The hanging part 42 is adjacent to the rotor 2 at its tip, and covers the axial center of the rotor 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polygon mirror motor built in a laser beam printer (hereinafter abbreviated as LBP) and used to deflect and scan a laser beam, and in particular, even if an impact force acts on the polygon mirror, the high speed thereof. The present invention relates to a polygon mirror motor capable of maintaining stable performance during rotation.

  In recent years, in response to high-speed printing and high definition of LBP, it is required to scan a laser beam at higher speed and higher accuracy. The polygon mirror motor is responsible for the basic part of high-precision laser scanning, which has a regular polygonal polygonal mirror (polygon mirror) whose outer peripheral surface is a reflection surface, and which is reflected by each reflection surface. The beam is irradiated onto the photosensitive recording medium through the deflecting lens.

  Therefore, the polygon mirror motor is required to have a high speed and stable rotation performance. Further, in order to obtain a fine and high-quality printer output, it is necessary that the reflecting surface of the polygon mirror is free from fouling and scratches, and that the laser beam reflectivity is constant.

  Here, as the polygon mirror motor, in order to limit the movement of the rotor portion in the axial direction, a retaining plate is provided on the optical unit chassis housing the motor, and the retaining plate is disposed between the rotor magnet and the polygon mirror. It is known that it is positioned or the cover of the optical unit chassis is brought close to the tip of the rotating shaft (for example, Patent Document 1).

  In addition, in order to limit the flow of air accompanying the rotation of the polygon mirror and reduce the generation of wind noise, the polygon mirror and its driving unit are covered with a cover member, and the laser beam in the cover member passes through the part. The thing of the structure which opened only the window is known (for example, patent document 2).

Japanese Patent Application Laid-Open No. 07-123670

Japanese Patent Laid-Open No. 10-148784

  However, since the retaining plate disclosed in Patent Document 1 only covers a part of the outer periphery of the rotor magnet, the polygon mirror motor is impacted from the axial direction during transportation and installation of the polygon mirror and the LBP incorporating the same. When force is applied and the rotor magnet collides with the retaining plate, an eccentric load is applied to the rotor magnet due to the collision with the retaining plate, and the entire rotor portion is inclined to the retaining plate placement side by the eccentric load, and the rotor portion Stable rotation performance is impaired.

  In particular, in a motor that rotates at a high speed (about 30,000 rpm) such as a polygon mirror motor, rotation imbalance not only increases vibration and noise during rotation, but also greatly deteriorates the scanning performance of the polygon mirror. End up.

  Further, in Patent Document 1, in the case where the cover of the optical unit chassis is close to the tip of the rotating shaft, when an impact force is applied to the polygon mirror motor from the axial direction, the rotor portion is different from the above-described retaining plate. Although an eccentric load can be prevented from acting on the rotating shaft, a certain gap must be provided between the rotating shaft and the resin cover.

  This is because the axial position of the resin cover with respect to the rotation shaft is a position as a result of combining a plurality of members, so that it is necessary to take into account a variation in dimensional tolerance of each member. However, in this case, if the rotor part protrudes excessively in the direction in which the rotor part comes off, there is a high possibility that the peripheral edge of the lower end of the shaft hits the sliding surface of the radial bearing. Therefore, a structure in which a plurality of members are interposed between the rotating shaft and a member having a pressing function is not desirable.

  When the polygon mirror rotates at a high speed, a vortex flow is generated on the rotational direction side of each reflecting surface r of the polygon mirror M as shown in FIG. 8, and the portion is gradually soiled by dust contained in the air. Although the reflectance of the reflective surface r is deteriorated, Patent Document 1 does not take measures against the contamination of the reflective surface caused by the vortex airflow.

  In this respect, if only the optical path portion through which the laser beam passes is opened as in Patent Document 2 and the entire apparatus is covered with a small cover member, dust can enter the cover member when the polygon mirror rotates. Although it is possible to reduce the generation of wind noise while preventing this, the cover member covers the entire polygon mirror, which complicates the structure and assembly procedure, and makes it difficult to inspect and repair the motor. There's a problem.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a polygon mirror motor having a simple structure capable of maintaining high stable rotation performance even when subjected to a strong impact from the outside. .

In order to achieve the above object, the present invention
A plate-shaped motor base 11, a rotor portion 2 that is rotatably supported by the motor base 11 via a bearing unit 12, and a polygon mirror 3 that is fixed concentrically to the rotor portion 2. In a polygon mirror motor having
The motor base 11 is provided with a stopper 4 for limiting the movement of the rotor portion 2 in the axial direction,
The stopper 4 has a height exceeding the position of the polygon mirror 3, and a column portion 41 that stands on the motor base 11 at a position adjacent to the rotor portion 2, and extends from the upper end of the column portion 41 to the rotor portion 2 side. An arm-shaped overhanging portion 42,
The overhang portion 42 is characterized in that the tip thereof is close to the rotor portion 2 and covers the axial center of the rotor portion 2.

Further, a plate-shaped motor base 11, a rotor portion 2 that is rotatably supported by the motor base 11 via a bearing unit 12, and a polygon mirror 3 that is fixed concentrically to the rotor portion 2 In a polygon mirror motor having
The motor base 11 is provided with a stopper 4 for limiting the movement of the rotor portion 2 in the axial direction,
The stopper 4 has a height exceeding the position of the polygon mirror 3, and a column portion 41 that stands on the motor base 11 at a position adjacent to the rotor portion 2, and extends from the upper end of the column portion 41 to the rotor portion 2 side. An arm-shaped overhanging portion 42,
The overhanging portion 42 is close to the rotor portion 2 or the polygon mirror 3 and covers at least two upper portions of the rotor portion 2 or the polygon mirror 3 with the axis of the rotor portion 2 as the axis of symmetry. To do.

  In addition, the support column 41 of the stopper 4 has a flat plate shape close to the circumscribed circle of the polygon mirror 3, and when its one end edge in the width direction is positioned on the perpendicular n to the axis of the polygon mirror 3, An angle θ formed by the plate surface of the support column 41 and the perpendicular n is set to 0 to 90 degrees with respect to the rotation direction of the polygon mirror 3 with respect to the perpendicular n.

Furthermore, a plate-shaped motor base 11, a rotor portion 2 that is rotatably supported by the motor base 11 via a bearing unit 12, and a polygon mirror 3 that is fixed concentrically to the rotor portion 2 In a polygon mirror motor having
The rotor unit 2 includes a rotor hub 22 having a flange portion 22A that supports the polygon mirror 3, and a rotor yoke 23 made of a magnetic material. Having a portion 23A and being concentrically fixed to the rotor hub 22,
The motor base 11 is provided with a stopper 4 that restricts the movement of the rotor part 2 in the axial direction. The stopper 4 is provided with a support part 41 that stands on the motor base 11 adjacent to the rotor part 2 and the support part 4. An arm-like overhanging portion 42 extending between the polygon mirror 3 and the rotor yoke 23 from the upper end of 41,
The protruding portion 42 is characterized in that the tip thereof is close to the upper surface portion 23A of the rotor yoke 23 and covers at least two portions of the upper surface portion 23A of the rotor yoke 23 with the axis of the rotor portion 2 as the axis of symmetry.

  According to the present invention, since the motor base is provided with the stopper that restricts the axial movement of the rotor portion, the stopper and the motor base can be easily formed separately.

  In particular, the stopper has a height exceeding the position of the polygon mirror and stands on the motor base at a position adjacent to the rotor portion, and an arm-like protrusion extending from the upper end of the column portion to the rotor portion side. Therefore, the entire stopper portion is not covered with the stopper, and the stopper does not get in the way during inspection and repair inside the motor.

  In addition, since the tip of the overhanging part covers the rotor part or the upper part of the polygon mirror with the axis of the rotor part as the axis or the axis of symmetry, the rotor part receives axial impact force. Even in this case, the eccentric load due to the collision with the protruding portion does not act on the rotor portion or the polygon mirror fixed to the rotor portion. For this reason, the stable rotation performance of a rotor part or a polygon mirror can be maintained.

  In addition, the stopper column is a flat plate that is close to the circumscribed circle of the polygon mirror, and when the edge in the width direction is positioned on a perpendicular line to the axis of the polygon mirror, Since the angle formed with the perpendicular line is set to 0 to 90 degrees with respect to the rotation direction of the polygon mirror with reference to the perpendicular line, the column portion is large with respect to the airflow generated in the rotation direction of the polygon mirror. It does not become air resistance, but it can prevent the wind noise during rotation of the polygon mirror from being increased by the support column. In addition, when the ridge angle of the polygon mirror passes the position of the support column, the support column covers the upstream portion in the rotational direction of the reflecting surface that continues to the back of the ridge angle, so that the inflow of air to the location is blocked. Occurrence of vortex airflow in the upstream portion of the reflecting surface in the rotation direction is suppressed, and as a result, contamination of the reflecting surface due to dust in the air can be suppressed.

  Further, as another aspect, even in a configuration in which the tip of the overhanging portion is close to the upper surface portion of the rotor yoke and covers at least two portions of the upper surface portion of the rotor yoke with the axis of the rotor portion as the axis of symmetry, When an impact force is received, it is possible to prevent the eccentric load due to the collision with the projecting portion from acting on the rotor portion, and to maintain its stable rotation performance.

  Hereinafter, the configuration of a polygon mirror motor (scanning motor) according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a first embodiment of a polygon mirror motor according to the present invention. The motor constitutes a scanning device used in LBP or the like, and the form thereof may be an outer rotor type (inner rotor type) in which a rotor portion 2 (rotor) is provided outside a stator portion 1 (stator). Yes).

  In this example, the stator unit 1 includes a plate-like motor base 11 fixed in an apparatus such as an LBP, a bearing unit 12 fixed to the motor base 11, and the like. The bearing unit 12 includes a bearing casing 12A that is fixed to the motor base 11 in a penetrating state, and a cylindrical bearing 12B that is fitted into the bearing casing 12A.

  A stator core 13 is fitted and fixed to the outer peripheral portion of the bearing casing 12 </ b> A, and a stator coil 14 through which a drive current (armature current) flows is wound around the stator core 13.

  The bearing 12B is a fluid bearing (radial bearing) made of an oil-free metal, and a rotary shaft 21 is passed through the bearing 12B, and between the inner peripheral surface of the bearing 12B and the outer peripheral surface of the rotary shaft 21. Filled with lubricating oil that generates dynamic pressure.

  The bearing 12B receives a radial load acting on the rotating shaft 21, and the thrust load acting on the rotating shaft 21 is supported by a seat 12C disposed on the bottom surface of the bearing casing 12A. The bearing 12B can be replaced with other sliding bearings or rolling bearings.

  On the other hand, the rotor unit 2 includes a rotating shaft 21 that is rotatably supported by the bearing unit 12, a rotor hub 22 that is fixed to the tip of the rotating shaft 21, a rotor yoke 23 that is integrally fixed to the rotor hub 22, and the like. Is done. Among these, the rotating shaft 21 is inserted into the bearing 12B so as to be movable in the axial direction. Further, the rotor yoke 23 is made of a magnetic material, and its form is a concave shape in cross section having an upper surface portion 23A fixed to the rotor hub 22 and an annular body portion 23B hanging from the periphery of the upper surface portion. A field magnet 24 that generates a magnetic flux (field magnetic flux) necessary for generating a rotational force is fixed to the inner surface of the annular body 23B at a position facing the stator core 13.

  In particular, the rotor hub 22 constituting the rotor part 2 has a collar part 22A to support the polygon mirror 3, and the polygon mirror 3 is pressed against the collar part 22A by a clamp plate 25 attached to the rotary shaft 21. Yes. Thus, the polygon mirror 3 is fixed concentrically to the rotor portion 2, and the bottom surface of the polygon mirror 3 and the upper surface portion 23A of the rotor yoke 23 are opposed to each other with the flange portion 22A interposed therebetween.

  The polygon mirror 3 deflects and reflects a laser beam emitted from a light source such as a semiconductor laser (not shown) while rotating at high speed, and forms an image on a photosensitive member on a rotating drum (not shown) to form an electrostatic latent image. The outer peripheral end surface of the polygon mirror 3 is a reflecting surface 31 for deflecting and reflecting the laser beam toward the rotating drum.

  Here, the motor base 11 is provided with a stopper 4 that restricts movement of the rotor portion 2 in the axial direction. The stopper 4 is formed by bending a metal plate or the like, and is fixed to the motor base 11 so as to be detachable from the motor base 11 with screws or the like. The stopper 4 is fixed to the motor base 11 so as not to block the optical path of the laser beam.

  In particular, the stopper 4 of this example has a height exceeding the position of the polygon mirror 3 and stands on the motor base 11 at a position adjacent to the rotor portion 2, and the rotor from the upper end of the column portion 41. And an arm-like overhanging portion 42 extending to the side of the portion 2 so that the tip of the overhanging portion 42 is close to the rotor portion 2 (the upper end of the rotating shaft 21) and covers the axial center thereof. It is. In this example, since the rotary shaft 21 penetrates the rotor hub 22, the tip of the overhanging portion 42 covers the upper end of the rotary shaft 21 in a close state. In a mode in which the protrusion does not protrude onto the rotor hub 22, the tip of the overhanging portion 42 is close to the upper surface of the rotor hub 22 and covers the axial center (on the extended line of the rotating shaft 21).

  According to the polygon mirror motor having such a stopper 4, even if the rotor unit 2 receives an impact force and tries to move in the axial direction, the movement in the same direction is limited by the overhanging unit 42, and the shaft of the rotor unit 2 is An eccentric load does not act on the rotor portion 2 because the core (the upper end of the rotating shaft 21) collides with the overhang portion 42. For this reason, the stable rotation performance of the rotor part 2 and the polygon mirror 3 fixed to the rotor part can be maintained. Further, the stopper 4 does not become an obstacle to inspection and repair.

  In particular, as is apparent from FIG. 2, the support column 41 of the stopper 4 has a plate shape close to the circumscribed circle C of the polygon mirror 3. When the support column 41 is positioned on one vertical line n with respect to the axis line of the polygon mirror 3 (the same center line of the rotation shaft 21 as the axis of the rotor unit 2), the support column 41 has one end edge 41A in the width direction. The angle θ formed by the plate surface 41B and the perpendicular n is set to be 90 degrees with respect to the rotation direction of the polygon mirror 3 with respect to the perpendicular n.

  According to this, since the column portion does not have a large air resistance against the air flow generated in the rotation direction of the polygon mirror 3 around the polygon mirror 3, the wind noise during the rotation of the polygon mirror 3 is increased by the column portion 41. In addition, when the ridge angle 32 of the polygon mirror 3 passes the position of the column portion 41 as shown in FIG. 3, the column portion 41 is connected to the rear side of the ridge angle 32 in the rotation direction upstream portion (FIG. 3). In this case, the inflow of air to the relevant part is blocked and the generation of the vortex air current in the upstream part 31A in the rotational direction of the reflecting surface 31 is suppressed, and as a result, the dust is caused by dust in the air. The contamination of the reflecting surface 31 can be suppressed.

  Such a vortex airflow suppression action becomes more prominent as the support column 41 is closer to the circumscribed circle C of the polygon mirror 3, but the distance G between the one end edge 41A of the support column 41 and the circumscribed circle C of the polygon mirror 3 is increased. When the thickness t (see FIG. 1) of the polygon mirror 3 is not more than twice, a favorable suppression effect on the generation of vortex air current can be obtained. In this example, the gap G is set to 1 mm, which is half the thickness t (2 mm) of the polygon mirror 3. Here, in FIG. 2 and FIG. 3, the dotted arrow represents the movement of the airflow generated by the rotation of the polygon mirror 3.

  In this example, the polygon mirror 3 is a regular hexagon having six reflecting surfaces as shown in FIGS. 2 and 3, but it may be a square or a regular pentagon.

  Further, the angle θ is not limited to 90 degrees with respect to the rotation direction of the polygon mirror 3, and may be changed within a range of 0 to 90 degrees. FIG. 4 shows an example in which the angle θ is 0 degree, that is, the column part 41 is arranged so that its width direction coincides with the perpendicular line n. In this case, the column part 41 is against the air flow generated in the rotation direction of the polygon mirror 3. Since the air resistance is not large, wind noise during rotation of the polygon mirror 3 is not increased by the support column 41, and when the ridge angle 32 of the polygon mirror 3 passes the position of the support column 31, the support column 41 Covers the upstream portion in the rotational direction of the reflective surface 31 connected to the rear of the ridge angle 32 and blocks the inflow of air to the location, so that the generation of vortex airflow in the upstream portion in the rotational direction of the reflective surface 31 is suppressed, As a result, the contamination of the reflecting surface 31 due to dust in the air can be suppressed.

  Next, FIG. 5 shows a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the part which is common in 1st Example, and detailed description is abbreviate | omitted. Here, FIG. 5 is an example in which the upper two portions of the rotor portion 2 with the axis of the rotor portion 2 (rotating shaft 21) as the axis of symmetry are covered with the tip of the overhang portion 42. The tip of this is not in contact with the rotor part 2 and is close to the upper surface of the clamp plate 25 constituting the rotor part 2.

  As is apparent from FIG. 6, in this example, the tip of the overhanging portion 42 is bifurcated, and the two branching pieces 42A and 42A are in close proximity to each other at two opposite positions of the clamp plate 25 with the rotating shaft 21 therebetween. Covering. It should be noted that the tip of the overhanging portion 42 is not bifurcated, but a hole through which the rotating shaft 21 is passed is formed at the tip so that the periphery of the rotating shaft 21 is covered with the tip of the overhanging portion 42 over the entire circumference. In other words, the point is that the tip of the overhanging portion 42 is close to the rotor portion 2 and the polygon mirror 3 and is symmetrical with respect to the rotation axis 21 at least at two locations on the rotor portion 2 or the upper portion 2 of the polygon mirror 3. What is necessary is just to be set as the structure which covers a location.

  Even in such a configuration, as in the first embodiment, even if the rotor part 2 receives an impact force and tries to move in the axial direction, the movement in the same direction is limited by the overhanging part 42, and Since it is possible to prevent the eccentric load from acting, it is possible to maintain the stable rotation performance of the rotor unit 2 and the polygon mirror 3 fixed to the rotor unit 2.

  Further, by making the form and angle of the support part 41 the same as in the first embodiment, the wind noise during rotation of the polygon mirror 3 is not increased by the support part 41 and the contamination of the reflecting surface 31 is suppressed. can do.

  Next, FIG. 7 shows an embodiment in which the tip of the overhanging portion 42 is brought close to the upper surface portion 23A of the rotor yoke 23 as a third embodiment of the present invention. As is clear from FIG. 7, in this example, the height of the column portion 41 is set lower than the position of the polygon mirror 3, and the overhang portion 42 is located between the polygon mirror 3 and the rotor yoke 23 from the upper end of the column portion 41. It is extended. The tip of the overhanging portion 42 is close to the upper surface portion 23A of the rotor yoke 23 and covers two portions of the upper surface portion 23A of the rotor yoke 23 with the axis of the rotor portion 2 (rotating shaft 21) as the axis of symmetry.

  In this example as well, the tip of the overhanging portion 42 is bifurcated in the same way as in the second embodiment. 23A may be covered with the tip of the overhanging portion 42 over the entire circumference. In short, the tip of the overhanging portion 42 is symmetrical with respect to the rotating shaft 21 while being close to the upper surface portion 23A of the rotor yoke 23. What is necessary is just to be set as the structure which covers at least two places of 23 A of upper surface parts which become.

  Even in such a configuration, as in the first embodiment, even if the rotor part 2 receives an impact force and tries to move in the axial direction, the movement in the same direction is limited by the overhanging part 42, and Since it is possible to prevent the eccentric load from acting, the stable rotation performance of the rotor unit 2 and the polygon mirror 3 fixed to the rotor unit 2 can be maintained. In the third embodiment, since the support column 41 is not adjacent to the polygon mirror 3, the form and the arrangement angle are not limited.

1 is a longitudinal sectional view showing a polygon mirror motor according to the present invention. Explanatory drawing showing the relative positional relationship between the polygon mirror and the stopper Explanatory drawing showing the movement of the airflow generated by the rotation of the polygon mirror Explanatory drawing showing an example of changing the stopper The side view which shows the other embodiment of the polygon mirror motor based on this invention Schematic plan view of the motor shown in FIG. The side view which shows the other embodiment of the polygon mirror motor based on this invention Explanatory drawing which shows the generation | occurrence | production state of the eddy current in the conventional motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator part 11 Motor base 12 Bearing unit 2 Rotor part 21 Rotating shaft 22 Rotor hub 22A collar part 23 Rotor yoke 23A Top surface part 3 Polygon mirror 31 Reflecting surface 4 Stopper 41 Strut part 41A One end edge of the strut part in the width direction 41B Plate surface of the strut part 42 Overhang

Claims (4)

In a polygon mirror motor having a plate-like motor base, a rotor portion that is rotatably supported with respect to the motor base via a bearing unit, and a polygon mirror fixed concentrically to the rotor portion,
The motor base is provided with a stopper for restricting the movement of the rotor portion in the axial direction,
The stopper has a height exceeding the position of the polygon mirror, and a column portion standing on the motor base at a position adjacent to the rotor portion, and an arm shape extending from the upper end of the column portion to the rotor portion side. And a protruding portion of
The overhanging portion is a polygon mirror motor characterized in that the tip of the overhanging portion is close to the rotor portion and covers the axial center of the rotor portion. In a polygon mirror motor having a plate-like motor base, a rotor portion that is rotatably supported with respect to the motor base via a bearing unit, and a polygon mirror fixed concentrically to the rotor portion,
The motor base is provided with a stopper for restricting the movement of the rotor portion in the axial direction,
The stopper has a height exceeding the position of the polygon mirror, and a column portion standing on the motor base at a position adjacent to the rotor portion, and an arm shape extending from the upper end of the column portion to the rotor portion side. And a protruding portion of
The overhanging portion has a tip that is close to the rotor portion or the polygon mirror and covers at least two upper portions of the rotor portion or the polygon mirror with the axis of the rotor portion as an axis of symmetry. Polygon mirror motor.   The stopper column is a flat plate close to the circumscribed circle of the polygon mirror, and when the one end in the width direction is located on a perpendicular line to the axis of the polygon mirror, the column of the column 3. The polygon mirror according to claim 1, wherein an angle formed by a surface and the perpendicular is set to 0 to 90 degrees with respect to a rotation direction of the polygon mirror with respect to the perpendicular. motor. In a polygon mirror motor having a plate-like motor base, a rotor portion that is rotatably supported with respect to the motor base via a bearing unit, and a polygon mirror fixed concentrically to the rotor portion,
The rotor portion has a rotor hub having a flange portion that supports the polygon mirror and a rotor yoke made of a magnetic material, and the rotor yoke has an upper surface portion that faces the bottom surface of the polygon mirror across the flange portion. Fixed concentrically to the rotor hub,
The motor base is provided with a stopper for restricting the movement of the rotor portion in the axial direction. The stopper is provided on the motor base adjacent to the rotor portion and from the upper end of the column portion. An arm-like protruding portion extending between the polygon mirror and the rotor yoke;
2. The polygon mirror motor according to claim 1, wherein the projecting portion has at least two top surface portions of the rotor yoke having a symmetric axis about the axis of the rotor portion, with the tip thereof being close to the top surface portion of the rotor yoke.

Images