JP4932217B2 - Polygon mirror scanner motor - Google Patents

Description

  The present invention relates to a polygon mirror scanner motor having high-speed rotation used for laser scanning in a laser beam printer, a copying machine, or the like.

  Conventionally, this type of polygon mirror scanner motor generally has a structure in which a polygonal polygon mirror is mounted on a rotor boss fixed to a rotor frame (see, for example, Patent Document 1).

  FIG. 8 shows a conventional polygon mirror scanner motor described in Patent Document 1. In FIG.

  In FIG. 8, the rotary shaft 1 is rotatably supported with respect to the inner diameter hole of the bearing 3 fixed to the substrate 2, and the rotor boss 6 on which the polygon mirror 4 is installed is fastened. A polygon mirror 4 is fixed to the upper portion of the rotor boss 6 by a grip ring 8 via a mirror pressing spring 7. A rotor frame 9 is fixed so as to face the polygon mirror 4 via the rotor boss 6, and a rotor magnet 10 is fixed to the inner periphery of the rotor frame 9. The above is the structure of the rotating body. A stator coil 11 is disposed on the substrate 2 at a position facing the rotor magnet 10, and a Hall element for detecting a phase during rotation is mounted on the outer periphery of the stator coil 11.

  A plurality of mirror-finished mirrors are formed on the side surface of the polygon mirror 4. The mirror surface has a high degree of flatness in order to accurately perform the polarization scanning of the light beam. The polygon mirror receiving surface of the rotor boss 6 is also required to have extremely high processing accuracy. This is because when the polygon mirror receiving surface is not formed flat, the polygon mirror is distorted, and the accuracy of polarization scanning of the light beam deteriorates.

The operation of the polygon mirror scanner motor configured as described above will be described below. First, a current flows through the stator coil 11 to generate a driving force by an attractive force and a repulsive force generated between the rotor magnet 10 and the Hall element mounted on the substrate 2 detects the phase of the rotor magnet 10. The rotating body supported by the bearing 3 can be continuously rotated, and a polarization beam is scanned by projecting a light beam onto the polygon mirror 4 mounted on the rotating body.
JP-A-11-14928

  However, in the conventional configuration, when the rotor frame mounting surface of the rotor boss is not formed flat, a gap is generated in the outer peripheral portion between the rotor frame top surface and the rotor frame mounting surface of the rotor boss, and the gap is a rotor accompanying high-speed rotation. It has been found that there is a problem that the amount of displacement in the thrust direction of the frame top surface is increased to cause vibration and noise.

  The present invention solves the above-described conventional problems, and suppresses vibrations that occur when there is a gap in the outer peripheral portion between the rotor frame top surface and the rotor frame mounting surface of the rotor boss, resulting in low vibration and low noise. An object is to provide a polygon mirror scanner motor.

  In order to solve the above-described conventional problems, the polygon mirror scanner motor of the present invention has a tapered shape in which the rotor frame mounting surface of the rotor boss that contacts the top surface of the rotor frame gradually approaches the polygon mirror side from the outer peripheral portion toward the inner peripheral portion. Alternatively, a step is provided so that the outer peripheral portion of the rotor frame mounting surface is thicker than the inner peripheral portion.

  According to the polygon mirror scanner motor of the present invention, it is possible to obtain an advantageous effect that it is possible to reduce vibration and noise that occur when a gap exists in the outer peripheral portion between the rotor frame top surface and the rotor frame mounting surface.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a rotor boss of a polygon mirror scanner motor according to Embodiment 1 of the present invention.

  In FIG. 1, the same components as those in FIG.

  In FIG. 1, the shape of the rotor frame mounting surface 6a is a tapered shape that gradually approaches the polygon mirror side from the outer peripheral portion toward the inner peripheral portion.

  FIG. 2 is a sectional view of the rotor assembly in which the rotor boss 6 is fixed to the rotor frame 9 of the polygon mirror scanner motor according to the first embodiment of the present invention.

  In FIG. 2, the same components as those in FIG.

  In FIG. 2, by fixing the rotor boss 6 to the rotor frame 9, the rotor frame top surface 9a and the rotor frame mounting surface 6a are in close contact with each other.

  FIG. 3 is a cross-sectional view of the rotor assembly when there is a gap in the outer periphery between the rotor frame top surface 9a and the rotor frame mounting surface 6a of the polygon mirror scanner motor.

  In FIG. 3, the same components as those in FIG.

  In FIG. 3, the rotor frame mounting surface 6a to be processed into a flat shape has a tapered shape that gradually approaches the polygon mirror side from the inner periphery toward the outer periphery. In this case, fixing the rotor boss 6 to the rotor frame 9 results in the presence of a gap in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a.

  FIG. 4 is a graph showing the vibration level during rotation of the polygon mirror scanner motor according to the first embodiment of the present invention for each gap amount existing on the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a.

  In FIG. 4, when the rotational speed is taken on the horizontal axis and the vibration level (large vibration from minus to plus) is taken on the vertical axis, the vibration level is in a flat state where there is no gap due to the presence of a gap (20 μm). By comparison, it can be seen that the number of revolutions is getting worse. As a result, the relationship between the amount of clearance existing in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a and the vibration level became clear.

  In this way, it has been found that when the rotating body rotates, the vibration level deteriorates as the amount of the clearance between the rotor frame top surface 9a and the rotor frame mounting surface 6a increases. As a result of various studies paying attention to the relationship between the clearance and the vibration level existing in the outer peripheral portion between the surface 9a and the rotor frame mounting surface 6a, the following has been found.

  FIG. 5 shows the outer peripheral portion of the rotor frame top surface 9a associated with the amount of clearance existing in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a during rotation of the polygon mirror scanner motor according to the first embodiment of the present invention. It is the graph which described the amount of thrust direction displacement.

  In FIG. 5, when the horizontal axis represents the rotational speed and the vertical axis represents the thrust direction displacement amount of the outer periphery of the rotor frame top surface 9a, the thrust direction displacement amount is calculated between the rotor frame top surface 9a and the rotor frame mounting surface 6a. When there is a gap (20 μm) at the outer periphery, the amount of displacement in the thrust direction is about four times that of a flat state where there is no gap (here, the outer diameter of the rotor frame 9 is φ24, the plate thickness is 0.2 mm). 5 mm). Here, although the outer peripheral portion of the rotor frame top surface 9a is displaced in the thrust direction, a force that displaces the outer periphery of the rotor frame top surface 9a in the thrust direction due to the centrifugal force accompanying high-speed rotation during rotation. At this time, when there is a gap in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a, the displacement in the thrust direction is larger than the flat state where there is no gap. Will be encouraged. In addition, this phenomenon becomes more prominent as the amount of displacement in the thrust direction increases as the rotational speed increases (the centrifugal force increases). As a result, the relationship of the amount of displacement in the thrust direction of the outer peripheral portion of the rotor frame top surface 9a with the amount of clearance existing in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a became clear.

  4 and 5, when there is a gap in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a, the outer peripheral portion of the rotor frame top surface 9a is caused by the centrifugal force accompanying high-speed rotation. It is presumed that the displacement in the thrust direction is repeated by the amount, and as a result, vibration is generated. Thus, vibration can be suppressed in a flat state where there is no gap in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a.

  FIG. 6 shows before and after fixing the axial dimension difference (hereinafter referred to as taper height) of the rotor frame mounting surface 6a of the polygon mirror scanner motor in Embodiment 1 of the present invention to the rotor frame 9. It is the graph which measured by comparison.

  In FIG. 6, when the taper height of the rotor frame mounting surface 6a measured before and after fixing the motor frame on the horizontal axis and the rotor frame 9 on the vertical axis is taken from the shape of the rotor frame mounting surface 6a in FIG. It can be seen that the taper height of the frame mounting surface 6a tends to shift to a substantially flat state after the rotor frame 9 is fixed. This is because when the rotor boss 6 is fixed to the rotor frame 9, the rotor frame mounting surface 6 a follows the planar shape of the rotor frame 9, whereby the rotor boss 6 is moved to the rotor frame 9 in FIG. 2. By fixing, the rotor frame top surface 9a and the rotor frame mounting surface 6a can be brought into a flat contact state.

(Embodiment 2)
FIG. 7 is a cross-sectional view of the rotor boss of the polygon mirror scanner motor according to Embodiment 2 of the present invention.

  In FIG. 7, the same components as those in FIG.

  In FIG. 7, the shape of the rotor frame attachment surface 6a is formed so as to provide a step so that the outer peripheral portion is thicker than the inner peripheral portion. By providing the step and having the structure in which the outer peripheral portion of the rotor frame mounting surface 6a is in close contact with the rotor frame top surface 9a, a gap is generated in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a. There is no.

  In order to reduce the vibration level of the polygon mirror scanner motor in the embodiment of the present invention to, for example, 20 dB or less from the result of FIG. 4, the shape of the rotor frame mounting surface 6a is changed from the outer peripheral portion toward the inner peripheral portion. A taper shape asymptotic to the mirror side, or a step where the outer peripheral portion of the rotor boss receiving surface is thicker than the inner peripheral portion, and the height of the taper or step is based on the result of FIG. By fixing the rotor boss 6 to the rotor frame 9, the rotor frame top surface 9 a and the rotor frame mounting surface 6 a are brought into a flat contact state and do not affect the basic characteristics of the polygon mirror scanner motor. To do.

  Here, when the rotor frame 9 and the rotor boss 6 are fixed, if the rotor frame 9 needs to be thicker than the rotor boss 6, depending on the surface state of the rotor frame 9, the rotor frame mounting surface 6a may be fixed at the time of fixing. Since it follows the shape of the rotor frame top surface 9a, the rotor frame top surface 9a and the rotor frame mounting surface 6a cannot be brought into close contact with each other. Therefore, when the thickness of the rotor boss 6 is T and the thickness of the rotor frame 9 is t, the rotor boss 6 must be formed such that T ≧ t.

  From the above-described embodiment, the shape of the rotor frame mounting surface 6a provided on the rotor boss 6 that contacts the rotor frame top surface 9a is tapered from the outer peripheral portion toward the inner peripheral portion toward the polygon mirror, or the rotor boss receiving portion. Vibration and noise generated when there is a gap in the outer peripheral portion between the rotor frame top surface 9a and the rotor frame mounting surface 6a by forming a step so that the outer peripheral portion of the surface 6a is thicker than the inner peripheral portion. Can be reduced.

  The polygon mirror scanner motor according to the present invention can reduce vibration and noise that occur when there is a gap in the outer periphery between the top surface of the rotor frame and the mounting surface of the rotor frame. Useful for machine applications.

Sectional view of rotor boss of polygon mirror scanner motor in Embodiment 1 of the present invention Sectional view of rotor assembly in which rotor boss is fixed to rotor frame of polygon mirror scanner motor according to Embodiment 1 Cross-sectional view of a rotor assembly in which there is a gap in the outer periphery between the top surface of the rotor frame and the mounting surface of the rotor frame of the comparative polygon mirror scanner motor of the present invention The graph which expressed the vibration level at the time of rotation of the polygon mirror scanner motor in Embodiment 1 of this invention according to the clearance amount which exists in the outer peripheral part between a rotor frame top surface and a rotor frame attachment surface. The thrust direction displacement amount of the outer peripheral portion of the rotor frame top surface according to the gap amount existing in the outer peripheral portion between the rotor frame top surface and the rotor frame mounting surface at the time of rotation of the polygon mirror scanner motor in Embodiment 1 of the present invention is expressed. Chart The graph which measured comparatively before and after fixing the taper height of the rotor boss receiving surface of the polygon mirror scanner motor in Embodiment 1 of this invention to a rotor frame. Sectional view of rotor boss of polygon mirror scanner motor in Embodiment 2 of the present invention Sectional view of a conventional polygon mirror scanner motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Board | substrate 3 Bearing 4 Polygon mirror 6 Rotor boss 6a Rotor frame attachment surface 7 Mirror holding spring 8 Grip ring 9 Rotor frame 9a Rotor frame top surface 10 Rotor magnet 11 Stator coil

Claims (3)

A rotor having a polygonal polygon mirror mounted on a rotor boss fixed to the rotor frame;
The rotor boss includes a surface on which the polygon mirror is mounted on one side and a rotor frame mounting surface that is in close contact with the rotor frame top surface of the rotor frame on the other side,
A polygon mirror scanner motor characterized in that the rotor frame mounting surface is formed in a tapered shape asymptotically approaching a surface on which the polygon mirror is mounted from the outer peripheral portion toward the inner peripheral portion. 2. The polygon mirror scanner motor according to claim 1, wherein a difference in height between the outermost peripheral portion and the innermost peripheral portion of the taper on the rotor frame mounting surface is set to about 1 to 20 [mu] m. . The thickness of the rotor boss is T, if the thickness of the rotor frame was t, polygon mirror scanner motor according to claim 1 or 2, characterized in that formed as a T ≧ t.