JP4789591B2 - Polygon mirror scanner motor - Google Patents

Description

  The present invention relates to a polygon mirror scanner motor used for laser scanning of a laser printer, a laser copying machine, etc., and particularly improves the fastening structure between a rotating shaft and a rotor boss serving as a reference surface for supporting the polygon mirror.

  In recent years, laser printers and laser copying machines are required to have high-speed printing and high image quality. As a result, polygon mirror scanner motors are also required to be rotated at a high speed and reduced in rotation unevenness (referred to as jitter).

  Among them, the influence of the surface accuracy and assembly accuracy of the polygon mirror on the jitter is significant. In recent years, the mirror surface processing technology of the polygon mirror has progressed, and the flatness of the mirror can be finished with very high accuracy, so that it is a problem to improve the assembly accuracy for attaching the polygon mirror to the motor.

  If a non-uniform load is applied to the polygon mirror when the polygon mirror is attached, the polygon mirror is deformed, and variation (so-called surface collapse) occurs between the reflection surfaces of the laser beam with respect to the reference surface (see, for example, Patent Document 1). .

  Conventionally, a configuration is known in which a polygon mirror is pressed by a leaf spring and attached to a plane perpendicular to the rotation axis of a rotor boss fastened and fixed to a rotation shaft in order to make the load when attaching the polygon mirror to a motor uniform. (For example, refer to Patent Document 2).

  FIG. 2 is a sectional view of the conventional polygon mirror scanner motor. Reference numeral 1 denotes a rotating shaft, and 2 a rotor boss, which is press-fitted and fixed to the rotating shaft 1. Reference numeral 3 denotes a polygon mirror, which is inserted along the polygon mirror fitting portion 2b of the rotor boss 2 and is inserted in a compressed state between a retaining ring (grip ring) 5 fixed to the rotating shaft 1 and a mirror presser spring. The polygon mirror 3 is fixed by the pressing force of the (leaf spring) 4.

  When the rotor boss is fastened to the rotating shaft by press-fitting or the like, the rotor boss is deformed in the outer peripheral direction due to stress strain due to the tightening allowance. Due to this stress strain, the diameter of the fitting portion with the polygon mirror, that is, the polygon mirror fitting portion changes, interferes with the polygon mirror, and deteriorates the flatness of the mirror surface (laser light reflecting surface). If the gap between the polygon mirror and the polygon mirror fitting portion is increased in order to eliminate the influence of the above, the variation in the deviation (referred to as the eccentricity) between the rotation axis and the center axis of the polygon mirror also increases during assembly. Therefore, when the amount of eccentricity increases, the distance between the polygon mirror and the laser differs for each surface, which causes a problem of adversely affecting jitter.

  In order to solve this problem, a configuration has been proposed in which an annular groove is formed between the rotary shaft press-fitting portion of the rotor boss and the polygon mirror insertion portion to eliminate the influence of stress strain (for example, see Patent Document 3).

FIG. 3 shows a cross-sectional view of a conventional polygon mirror scanner motor disclosed in Patent Document 3. In FIG. 3, an annular groove 2c is formed between the rotary shaft 1 press-fitting portion 2d of the rotor boss 2 and the polygon mirror fitting portion 2b.
Japanese Utility Model Publication No. 3-2887 (page 1-2, Fig. 1) Japanese Utility Model Publication No. 3-45073 (microfilm of Japanese Utility Model Application No. 1-103627 (page 3, FIG. 1)) Japanese Patent No. 3675125 (page 4, FIG. 1)

  However, in the conventional configuration disclosed in Patent Document 3 described above, when the inner diameter of the polygon mirror is relatively large with respect to the rotation axis, an annular groove is formed in the rotor boss so that the stress strain at the time of fastening is reduced to the polygon. Although it is possible to prevent the mirror fitting part from being affected, the polygon mirror is reduced in size and the inner diameter of the polygon mirror is reduced, so that the polygon mirror fitting part of the rotor boss becomes thinner in the conventional configuration. Since an annular groove cannot be formed, the amount of deformation and variation due to press fitting and the like increase.

  The present invention solves such a conventional problem, suppresses the deformation amount of the polygon mirror fitting portion of the rotor boss that occurs after being press-fitted into the rotating shaft, and reduces the fitting tolerance between the polygon mirror and the rotor boss. An object of the present invention is to provide a highly accurate polygon mirror scanner motor.

In order to solve the above-mentioned problems, the present invention provides a space on the rotor boss side in the axial direction intermediate between the rotation shaft and the rotor boss fastening portion so as not to contact the rotation shaft even after fastening, and a polygon on the radial extension line of the space Forming a mirror fitting portion, where t is the height of each of the two upper and lower fastening portions of the rotating shaft and the rotor boss, and the height from the lower end of the upper fastening portion to the upper end of the fitting portion with the polygon mirror And a polygon mirror scanner motor configured such that the relationship between t and s is s> t, where s is the height from the upper end of the lower fastening portion to the lower end of the fitting portion with the polygon mirror. is there.

  According to the first aspect of the present invention, since the stress strain of the fastening portion of the rotor boss fastened to the rotary shaft and fastened by the swivel is not transmitted to the polygon mirror fitting portion, the deformation amount before and after fastening can be greatly suppressed. It is possible to reduce the variation in the diameter of the polygon mirror fitting portion.

Moreover, this invention has the effect of suppressing the diameter change of a polygon mirror fitting part appropriately by comprising a polygon mirror fitting part away from the part to which a rotating shaft and a rotor boss | hub are fastened.

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

(Embodiment 1)
FIG. 1 shows only a sectional view of a rotating portion of a polygon scanner motor, a fastening portion of a rotor boss, and a fixing portion of a polygon mirror according to Embodiment 1 of the present invention, and the other components are the same as those of the prior art shown in FIG. Therefore, it is omitted.

  In FIG. 1, 1 is a rotary shaft having a diameter of 3 mm, 2 is a rotor boss, and a rotary shaft 1 is fastened by a tightening swivel with a fastening margin of 5 μm, and 3 is a polygon mirror through a polygon mirror fitting portion 2b of the rotor boss 2 , Fitted and fixed. A groove 2 a having a depth of 10 μm, which is deeper than the tightening margin of 5 μm between the rotary shaft 1 and the rotor boss 2, is formed at an intermediate portion of the rotor boss 2 fastened to the rotary shaft 1 by the tightening fit. The polygon mirror fitting portion 2b into which the rotor boss and the polygon mirror 3 are fitted is formed on the radial extension of the groove 2a.

With the above configuration, the stress change in the radial direction of the rotor boss 2 due to the fastening of the rotating shaft 1 and the rotor boss 2 is not transmitted to the polygon mirror fitting portion 2b, and the diameter change of the polygon mirror fitting portion 2b is minimized before and after the fastening. In addition, the rotating shaft 1 and the rotor boss 2 maintain an appropriate fastening force.

  In the present embodiment, the fastening portions of the rotating shaft 1 and the rotor boss 2 are formed at two axially upper and lower portions, each having a length t of 0.5 mm, from the lower end of the upper fastening portion to the upper end of the polygon mirror fitting portion. The distance s is set to 0.7 mm. Similarly, the distance s from the upper end of the lower fastening portion to the lower end of the polygon mirror fitting portion is also set to 0.7 mm. As described above, by making the relationship of s> t, the diameter change amount of the polygon mirror fitting portion 2b can be effectively suppressed.

  Table 1 shows data on the diameter change amount of the polygon mirror fitting portion under three conditions when there is no groove 2a, when s <t, and when s> t. In the case of s> t, the diameter change amount remains at 0 to 2 μm, and it can be confirmed that there is an effect that the stress strain does not affect the polygon mirror fitting portion. Note that the same effect can be obtained by any method as long as the rotary shaft and the rotor boss are fastened by press fitting or shrink fitting.

The polygon mirror scanner motor of the present invention suppresses the amount of change in the diameter of the polygon mirror fitting portion that fits the polygon mirror of the rotor boss in the fastening method between the rotating shaft and the rotor boss that supports the polygon mirror. It is useful as a polygon mirror scanner motor that can be designed to have a small fitting tolerance between the mirror and the rotor boss, effectively suppress the amount of eccentricity between the polygon mirror and the rotating shaft, and require stable laser scanning accuracy.

Sectional drawing of the fastening part of the rotating shaft, rotor boss | hub, and polygon mirror in Embodiment 1 of this invention Sectional view of a conventional polygon mirror scanner motor Cross section of another conventional polygon mirror scanner motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Rotor boss 2a Groove of rotor boss inner diameter 2b Polygon mirror fitting part 2c Ring groove 2d Rotating shaft press-fitting part 3 Polygon mirror 4 Leaf spring 5 Grip ring s Distance of polygon mirror fitting part of fastening part t Fastening part length

Claims (1)

A rotating shaft, a rotor boss that is fastened to the outer periphery of the rotating shaft by a swivel, a polygon mirror that is fixed to the rotor boss, a rotor magnet that forms a magnetic circuit, a rotor magnet that holds the rotor magnet, and is fixed to the rotor boss A cup-shaped rotor frame, and a space portion where the rotation shaft and the rotor boss are not in contact with each other is provided in the middle in the axial direction between the rotation shaft and the fastening portion of the rotor boss, and an outer periphery corresponding to the space portion of the fastening portion It has a fitting portion between the polygon mirror on the respective height of the fastening portion of the upper portion and the lower portion of the said rotary shaft rotor boss and t, fitting between the polygon mirror from the lower end of the upper fastening portion When the height from the upper end of the part to the upper end of the lower fastening part to the lower end of the fitting part with the polygon mirror is s, the relationship between t and s is A polygon mirror scanner motor, characterized in that> is t.

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