JP2007002856A - Polygon mirror scanner motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize an eccentric rate inside a bearing by solving the precession of a sleeve by a bearing load generated at the iron core part of a coil and increase accuracy and life in a polygon mirror scanner motor used for laser scanning of a laser beam printer and a laser beam copying machine. <P>SOLUTION: The folded part 104a of one of two sets of dynamic pressure generating grooves is disposed at a position facing a polygon mirror 106, and the folded part 105a of the other dynamic pressure generating groove is disposed at a position facing the core part 108 of the coil generating a magnetic rotating force so that a bearing load by the polygon mirror 106 and the bearing load generated at the core part 108 of the coil are pivotally supported at positions where these dynamic pressure generating grooves face each other to minimize the eccentric rate inside the bearing. As a result, the polygon mirror scanner motor increased in accuracy and life can be provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polygon mirror scanner motor that is used for laser scanning of a laser beam printer, a laser copying machine, and the like, and particularly suitable for high-speed rotation, low power consumption, miniaturization, and long life.

  Conventionally, as a polygon mirror scanner motor suitable for this high speed rotation, high accuracy, and long life, there has been the following (for example, see Patent Document 1).

  FIG. 7 shows the structure of a conventional polygon mirror scanner motor. In FIG. 7, the fixed shaft 101 is directly fixed to the base plate 102, and the sleeve 103 is rotatably inserted into the fixed shaft 101, and at least one of the fixed shaft 101 and the sleeve 103 is rotated by rotation. A groove 115 for generating dynamic pressure (hereinafter referred to as a dynamic pressure generating groove) is arranged to form a dynamic pressure bearing portion.

The gravity center position 106a in the thickness direction of the polygon mirror 106 is arranged so as to be positioned at the center 114 of the dynamic pressure bearing portion.
Japanese Patent No. 3312695 (page 5, FIG. 1)

However, in the conventional configuration described above, the center of the polygon mirror 106 in the thrust direction, that is, the center of gravity position 106a of the polygon mirror 106 is arranged at the center 114 of the hydrodynamic bearing, thereby suppressing eccentricity during rotation of the polygon mirror 106. In reality, however, the coil core 108 is energized with respect to the load applied to the hydrodynamic bearing by the polygon mirror 106, and rotates between the rotor magnet 110 disposed at the opposite position. The magnetic rotational force generated to drive the body is often larger as the load applied to the dynamic pressure bearing portion, and the gravity center position 106a of the polygon mirror 106 is arranged at the center of the dynamic pressure bearing portion. Even when the eccentricity of the polygon mirror 106 is to be suppressed, the anti-polygon mirror side is rubbed due to the influence of the magnetic rotational force. By the to, polygon mirror 106, will be the precession, a problem arises in that the eccentric. In particular, when high-speed rotation of 30000 to 50000 min ⁻¹ is required, when the dynamic pressure bearing portion is arranged at a position away from the coil core portion 108 where the magnetic rotational force is generated, it occurs in the coil core portion 108. The impact of the pulsating motion due to the magnetic rotational force exerted on the hydrodynamic bearing is large, and for polygon mirror scanner motors that are generally used by repeatedly starting and stopping, there is a problem of significantly reducing the bearing life. In order to solve this problem, the diameter of the fixed shaft 101 is increased to increase the bearing rigidity. In this case, however, an increase in power loss due to an increase in bearing loss and a reduction in the size of the motor. It had the problem of becoming difficult.

  The present invention solves such a conventional problem, reduces the load applied to the bearing portion resulting from rotation without reducing the bearing life, and is suitable for low power consumption and miniaturization. An object is to provide a polygon mirror scanner motor.

In order to solve the above-mentioned problems, the present invention is to generate one of the two sets of dynamic pressure generating grooves, with the folded portion of one of the dynamic pressure generating grooves facing the center of gravity of the polygon mirror. By disposing the groove turn-up part at a position approximately opposite to the central part in the thrust direction of the coil core that generates the drive torque, the bearing load load caused by the polygon mirror and the bearing load load generated in the coil core part can be reduced by rotation. Avoid the end of the dynamic pressure generating groove where the axial support force generated in the dynamic pressure generating groove (hereinafter referred to as dynamic pressure) is extremely small, and support the shaft at a position that is roughly opposite to the folded part of each dynamic pressure generating groove. Therefore, the polygon mirror scanner motor is characterized in that the eccentric amount of the hydrodynamic bearing portion can be suppressed to a minimum, and the accuracy and the life are increased.

  According to the first aspect of the invention, the center of gravity position of the polygon mirror to which the bearing load load by the polygon mirror acts and the center of the coil core portion to which the bearing load load generated in the coil core portion acts in the thrust direction are respectively different. The eccentricity of the rotating body (sleeve) with respect to the bearing gap is supported by a pivotal support at a position approximately opposite to the folded portion of the dynamic pressure generating groove where the dynamic pressure generated by the pressure generating groove, so-called bearing load force is stably obtained. The amount (hereinafter referred to as the eccentricity in the bearing) can be minimized, and an advantageous effect of high accuracy and long life can be obtained.

  Further, according to the invention described in claim 3, it is possible to obtain an effect that the bearing loss can be reduced without reducing the eccentricity in the bearing.

  According to the first aspect of the present invention, two sets of dynamic pressure generating grooves are provided on the inner surface of the sleeve rotatably inserted in a fixed shaft fixed to the base plate directly or via the housing, Each of the dynamic pressure generating grooves forms a V-groove having a folded portion, and the folded portion of one dynamic pressure generating groove is positioned substantially opposite to the center of gravity of the polygon mirror, and the other dynamic pressure generating groove is The folded portion has an effect that the eccentricity in the bearing can be suppressed to a minimum by disposing the folded portion at a position approximately opposite to the central portion in the thrust direction of the coil core that generates the drive torque.

  The invention according to claim 2 is the polygon mirror scanner motor according to claim 1, wherein the length of the dynamic pressure generating groove on the coil core portion side is set longer than the dynamic pressure generating groove on the polygon mirror side, In contrast to the polygon mirror that always generates a constant load load, the coil core has the maximum magnetic rotational force that the polygon mirror scanner motor has at the time of start-up when it starts up rapidly from the stopped state to the rated rotation speed. Bearings generated by the dynamic pressure bearing part on the coil core side and the eccentricity ratio in the dynamic pressure bearing part on the polygon mirror side are suppressed by suppressing the variable load generated by the magnetic rotational force having a certain period during steady rotation. By making the eccentricity ratio approximately the same or smaller, the pestle movement is suppressed, and the life during intermittent operation is prolonged.

  The invention according to claim 3 is the polygon mirror scanner motor according to claim 1 or 2, wherein the outer diameter of the fixed shaft or the inner diameter of the sleeve is ΦD, and Φ2 ≦ ΦD ≦ Φ3 is set. It has the effect of avoiding an increase in bearing loss due to an increase in the diameter of the fixed shaft, without deteriorating the eccentricity in the bearing, and allowing the shaft deflection to be set within an optimum range. .

  Hereinafter, more specific embodiments of the present invention will be described with reference to the drawings.

Example 1
FIG. 1 is a structural sectional view of a polygon mirror scanner motor in Embodiment 1 of the present invention.
In FIG. 1, the same components as those in FIG.

The fixed shaft 101 is fixed to the base plate 102 directly or via a housing 107, and two sets of dynamic pressure generating grooves 104 and 105 are formed on the inner surface of the sleeve 103 that is rotatably inserted into the fixed shaft 101. Is provided. A coil core 108 is disposed on the base plate 102, and a rotor magnet 110 is fastened and fixed to the sleeve 103 via a rotor frame 109 so as to face the coil core 108, and the polygon mirror 106. Is provided. The folded portion 104a of the dynamic pressure generating groove 104 formed on the inner surface of the sleeve 103 is the center in the thrust direction of the polygon mirror 106, the so-called polygon mirror center of gravity position 106a, and the folded portion 105a of the other dynamic pressure generating groove 105. The coil iron core portion 108 is configured to be substantially opposite to the thrust direction center portion 108a.

  2A is a bearing cross-sectional view showing details of the dynamic pressure generating grooves 104 and 105 in the polygon mirror scanner motor according to the present invention, and FIG. 2B is a folded portion 104a of the dynamic pressure generating groove 104 and the folded back of the dynamic pressure generating groove 105. FIG. 6 is a schematic diagram showing a distribution of dynamic pressure generated by rotation at a portion 105a and end portions 104b and 105b of the dynamic pressure generating grooves 104 and 105.

FIG. 3 is a graph showing the eccentricity of the sleeve 103 with respect to the fixed shaft 101 during 30000 min ⁻¹ in the polygon mirror scanner motor according to the present invention and the conventional configuration as the eccentricity in the bearing.

  With the above configuration, when a magnetic rotational force is generated between the coil core portion 108 and the rotor magnet 110 and the polygon mirror 106 is rotated, a bearing load due to centrifugal force acts on the gravity center position 106a of the polygon mirror 106. A bearing load due to a magnetic rotational force acts on the central portion 108a in the thrust direction of the coil core portion 108, and dynamic pressure is generated in the dynamic pressure generating grooves 104 and 105 by rotation as shown in FIG. 2b.

  Depending on the relationship between the bearing load and the dynamic pressure resulting from the rotation, the fixed shaft 101 and the sleeve 103 start a plowing motion. The dynamic pressure generating grooves 104 and 105 are the most affected by the plowing motion. Are the end portions 104b and 105b of the dynamic pressure generating grooves 104 and 105, in which the generation of the dynamic pressure is the least, the center of gravity position 106a of the polygon mirror 106 and the thrust direction of the coil core portion 108 where the respective bearing load is generated. By placing the central portion 108a and the folded portions 104a and 105a of the dynamic pressure generating grooves 104 and 105 where the dynamic pressure is generated at the highest position, approximately in a position facing each other, the load load is stably supported. As shown in Fig. 2, the eccentricity in the bearing can be suppressed to 10% or less in an environment of 0 ° C to 80 ° C, and the revolving motion of the rotating body can be suppressed. It is, and long life polygon mirror scanner motor with high accuracy can be obtained.

(Example 2)
FIG. 4 is a structural cross-sectional view of a sleeve according to the second embodiment of the present invention.

4, the inner surface of the sleeve 103 is provided with dynamic pressure generating grooves 104 and 105.
Position facing the coil core from the dynamic pressure generating groove 104 located facing the polygon mirror

The length of the dynamic pressure generating groove 105 in the installation is set to be long.

  FIG. 5 is a structural sectional view showing the bearing load at the start of rotation.

In FIG. 5, as a feature of the hydrodynamic bearing, when the rotating body is in a stopped state, the shaft 101 and the sleeve 103 are in contact with each other at any position of the dynamic pressure generating grooves 104 and 105, but the rotating body rotates. Is started, dynamic pressure proportional to the number of rotations is generated in the dynamic pressure generating grooves 104 and 105.

  In the case of a polygon scanner motor equipped with a hydrodynamic bearing, it is generally used in a so-called intermittent operation where the start and stop are repeated, and the dynamic pressure generation grooves 104 and 105 that greatly affect the intermittent operation life are generally used. The applied load is different between the dynamic pressure generating groove 105 at a position facing the coil core portion 108 that generates a magnetic rotational force in the radial direction and the dynamic pressure generating groove 104 at a position facing the polygon mirror 106.

  In the case of a hydrodynamic bearing composed of a sleeve rotatably inserted into a fixed shaft, the fulcrum of the rotating body is a thrust fulcrum 113 which is the tip of the shaft 101, but at the initial stage of starting the rotating body, the polygon mirror 106 The bearing load 111 acting on the dynamic pressure generating groove 104 at a position opposite to the position of the rotor is only at a position facing the coil core 108 that generates a magnetic rotational force, whereas the mass of the rotating body only acts in the direction of gravity. It can be seen that the magnetic rotational force acts on the dynamic pressure generating groove 105 at the position apart from the thrust direction fulcrum 113 so as to face the dynamic pressure bearing 105 regardless of the motor posture. At the start of startup, the relationship between the bearing load loads is significant, and the bearing load load 112 acting on the dynamic pressure generating groove 105 generates the maximum magnetic rotational force that the polygon mirror scanner motor has.

  According to this embodiment, the bearing load load 112 acting in the radial direction at a position away from the thrust direction fulcrum 113 with respect to the length of the dynamic pressure generating groove 104 that pivotally supports the bearing load 111 acting in the thrust direction at the start of rotation. By setting the length of the dynamic pressure generating groove 105 that supports the shaft to be long, the plowing motion at the start of the rotation of the polygon mirror scanner motor is suppressed, and in particular, the lifetime during intermittent operation is prolonged, and two sets of By optimizing the length of the dynamic pressure generating grooves 104 and 105, it is possible to reduce the size and thickness.

(Example 3)
FIG. 6A is a graph showing the outer diameter and bearing loss of the fixed shaft 101 in Example 3 of the present invention, and FIG. 6B is a graph showing the relationship between the outer diameter of the fixed shaft 101 and the amount of deflection.

  Generally, it is known that when the outer diameter of the fixed shaft 101 is increased, the bearing loss increases and the power consumption increases.

Conversely, by reducing the outer diameter of the fixed shaft 101, it is possible to reduce bearing loss.

  On the other hand, the deflection amount of the fixed shaft 101 is inversely proportional to the outer diameter of the fixed shaft 101, and the deflection amount increases as the outer diameter of the fixed shaft 101 is reduced.

  In a polygon mirror scanner motor that requires high-speed rotation, low power consumption, and rotation accuracy, setting the outer diameter of the fixed shaft 101 in the range of Φ2 ≦ ΦD ≦ Φ3 reduces the bearing loss and the deflection of the fixed shaft 101. The amount is not significantly deteriorated, and low power consumption and miniaturization are possible.

  In the polygon mirror scanner motor of the present invention, the bearing load by the polygon mirror and the bearing load generated in the coil core are approximately opposite to the respective folded portions of the dynamic pressure generating grooves formed on the inner surface of the sleeve. By supporting the shaft, it has the advantageous effect of minimizing the eccentricity in the bearing, and laser scanning such as laser beam printers that require high speed rotation, high accuracy, low power consumption, downsizing and long life. It is useful as a polygon mirror scanner motor suitable for use.

1 is a structural sectional view showing a polygon mirror scanner motor in Embodiment 1 of the present invention. (A) Detailed view showing the dynamic pressure bearing portion of the polygon mirror scanner motor in the first embodiment of the present invention, (b) Schematic diagram showing the dynamic pressure generation state of the dynamic pressure bearing portion in the first embodiment of the present invention. The graph which showed the eccentricity in a bearing for operation | movement description of the polygon mirror scanner motor in Example 1 of this invention Sectional view of a sleeve structure showing a polygon motor in Embodiment 2 of the present invention Structural sectional drawing which shows the bearing load weight at the time of the rotation for the operation | movement description of the polygon motor in Example 2 of this invention (A) A graph showing the relationship between the shaft outer diameter and the bearing loss in Example 3 of the present invention, (b) a graph showing the relationship between the shaft outer diameter and the deflection amount in Example 3 of the present invention. Cross-sectional view of a conventional polygon mirror scanner motor

Explanation of symbols

101 Shaft 102 Base plate 103 Sleeve 104, 105, 115 Dynamic pressure generating grooves 104a, 105a Folded portions 104b, 105b of dynamic pressure generating grooves 104 and 105 Ends of dynamic pressure generating grooves 104 and 105 106 Polygon mirror 106a Polygon mirror 106 Center of gravity position 107 Housing 108 Coil core portion 108a Thrust direction center portion of coil core portion 109 Rotor frame 110 Rotor magnet 111 Bearing load load acting on dynamic pressure generating groove 104 112 Bearing load load acting on dynamic pressure generating groove 105 113 Thrust direction Support point 114 Center position of hydrodynamic bearing

Claims (3)

Two sets of dynamic pressure generating grooves are provided on the inner surface of the sleeve rotatably inserted in a fixed shaft fixed to the base plate directly or via the housing, and each of the dynamic pressure generating grooves has a folded portion. A folded portion of one dynamic pressure generating groove is positioned substantially opposite to the center of gravity of the polygon mirror, and the folded portion of the other dynamic pressure generating groove is a coil core portion that generates driving torque. A polygon mirror scanner motor characterized by being disposed at a position substantially opposite the central portion in the thrust direction. 2. The polygon mirror scanner motor according to claim 1, wherein the dynamic pressure generating groove on the coil core side is set to be longer than the dynamic pressure generating groove on the polygon mirror side. 2. The polygon mirror scanner motor according to claim 1, wherein when the outer diameter of the shaft or the inner diameter of the sleeve is ΦD, Φ2 ≦ ΦD ≦ Φ3 is set.

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