JP2006163128A - Deflection scanner and scanning optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deflection scanner and a scanning optical apparatus in which a rotating polygon mirror is accurately assembled into the deflection scanner, incoming and outgoing on a reflection face is reduced, and a high picture quality is realized. <P>SOLUTION: A typical structure of the deflection scanner and the scanning optical apparatus of the present invention is that the deflection scanner has the rotating polygon mirror 3 which deflects and scans a laser luminous flux and a flange member 2 composed of at least one or more members which support the rotating polygon mirror 3 being inserted into the central hole of the rotating polygon mirror 3. The linear thermal expansion coefficient of the flange member 2 is denoted by α1, the linear thermal expansion coefficient of the rotating polygon mirror 3 is denoted by α2, the outer diameter of the outer part 2a of the flange member 2 and the rotating polygon mirror 3 is denoted by D, normal environmental temperature is denoted by tJ, low temperature side operational environmental temperature is denoted by tL, high temperature side operational environmental temperature is denoted by tH, the fitting gap of the outer part 2a is denoted by Δd, then the deflection scanner is characterized by satisfying the conditions D×(α2-α1)×(tJ-tL)<Δd≤0.01 when α1≤α2 holds, and D×(α1-α2)×(tH-tJ)<Δd≤0.01 when α1>α2 holds. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a deflection scanning apparatus and a scanning optical apparatus that are used in an image forming apparatus such as a laser beam printer and deflect and scan a laser beam.

  A scanning optical device used in an image forming apparatus such as a laser beam printer or a laser facsimile includes a deflection scanning device. In the deflection scanning device, a dynamic pressure bearing that can obtain a stable and smooth rotation is widely used in a bearing portion that supports a rotating polygon mirror that rotates at high speed. FIG. 4 shows a conventional deflection scanning apparatus described in Patent Document 2 (Japanese Patent Laid-Open No. 2002-130282).

  As shown in FIG. 4, the deflection scanning apparatus includes a sleeve 102 that rotatably supports a shaft 101 in a bearing hole, a thrust cover 103 that is fixed to the lower end of the sleeve 102 and seals the bearing hole, and a thrust cover 103. And the oil filled between the inner surface of the bearing hole of the sleeve 102 and the outer surface of the shaft 101 and between the thrust plate 104 and the end surface of the shaft 101. The end surface of the shaft 101 is formed in a convex shape, and is held in a pivot shape by a thrust plate 104 to constitute a pivot thrust bearing.

  A flange member 110 is fixed to the upper part of the shaft 101, and the rotary polygon mirror 111 is placed on the flange member 110. The rotary polygon mirror 111 has a reflecting surface 111a, and is pressed against the flange member 110 by a presser spring, and is integrally coupled to the flange member 110 and the rotor 112. The inner diameter of the central hole 111b of the rotary polygon mirror 111 is about 0.05 mm larger than the outer diameter of the shaft 101, and the assembly of the rotary polygon mirror 111 to the rotor 112 is disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 8-338961). As shown, the shaft 101 is loosely fitted in the center hole 111b of the rotary polygon mirror.

  The rotor 112 includes a permanent magnet 112a and a yoke 112b that supports the permanent magnet 112a. A circuit board 114 is fixed to the sleeve 102, and a stator core 113 b of the stator 113 is supported upright on the circuit board 114. The stator coil 113a wound around the stator core 113b faces the permanent magnet 112a of the rotor 112, and a motor that rotationally drives the rotary polygon mirror 111 is configured by both of them.

JP-A-5-134102 JP 2002-130282 A JP-A-8-338961

  However, according to the above prior art, with respect to the assembly of the rotating polygon mirror, since the center hole 111b of the rotating polygon mirror 111 is loosely fitted to the shaft 101, the relative position of the rotating polygon mirror 111 and the shaft 101 is the same as that described above. There is a tendency to be fixed in an eccentric state within the range of the dimensional difference. That is, the reflecting surface 111a of the rotating polygon mirror 111 is moved in and out by an amount that the rotating polygon mirror 111 is eccentric.

  For example, Japanese Patent Application Laid-Open No. 61-28919 discloses a scanning optical system in which a laser beam is incident on a rotary polygon mirror at a predetermined angle with respect to the optical axis. In such a scanning optical system, if the surface of the reflecting surface of the rotary polygon mirror enters or exits, a deviation occurs in the sub-scanning direction at the laser beam irradiation position of the photosensitive drum, and periodic pitch unevenness occurs on the image. End up.

  In general, when the laser beam incident on the fθ lens is a laser beam converged in the main scanning direction, when the reflection surface of the rotary polygon mirror enters or exits, the laser beam irradiation position of the photosensitive drum in the main scanning direction. Deviation occurs, resulting in degradation of image quality.

  Accordingly, the present invention provides a deflection scanning device and a scanning optical device capable of realizing high-quality image quality by accurately assembling the rotary polygon mirror to the deflection scanning device and reducing the entrance and exit of the reflecting surface. The purpose is to do.

In order to solve the above problems, a typical configuration of a deflection scanning apparatus and a scanning optical apparatus according to the present invention includes a rotating polygon mirror that deflects and scans a laser beam, and a rotation of the rotating polygon mirror that is fitted into the center hole of the rotating polygon mirror. In a deflection scanning apparatus having a fitting member composed of at least one member for holding a polygon mirror, the linear expansion coefficient of the fitting member is α1, the linear expansion coefficient of the rotary polygon mirror is α2, The outer diameter of the fitting portion of the fitting member with the rotary polygon mirror is D, the normal temperature environment temperature is tJ, the low temperature side operating environment temperature is tL, the high temperature side operating environment temperature is tH, and the fitting gap of the fitting portion is Δd,
When α1 ≦ α2
D × (α2−α1) × (tJ−tL) <Δd ≦ 0.01,
When α1> α2
D × (α1-α2) × (tH−tJ) <Δd ≦ 0.01,
It is characterized by satisfying.

  As described above, according to the present invention, the eccentricity of the rotary polygon mirror can be reduced as much as possible, and the rotary polygon mirror and the flange member or the shaft can be tightly fitted even if the environmental temperature of the deflection scanning device fluctuates. Therefore, it is possible to avoid the problem of surface deformation. Therefore, in the oblique incident optical system and the converging optical system, the amount of laser beam irradiation position deviation at the position corresponding to the photosensitive drum can be reduced, and a high-quality image can be obtained.

[First embodiment]
A first embodiment of a deflection scanning device and a scanning optical device according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a deflection scanning apparatus according to this embodiment. FIG. 3 is a configuration diagram of the scanning optical device.

(Scanning optical device)
The scanning optical device is used in an image forming apparatus such as a laser beam printer or a laser facsimile. As shown in FIG. 3, the scanning optical device generates a laser beam L from a semiconductor laser unit 31 that is a light source means. On the optical path of the laser beam L, a cylindrical lens 32 constituting the incident optical system, the rotary polygon mirror 3, and a deflection scanning device 34 for rotating the rotary polygon mirror 3 are sequentially arranged. On the optical path in the reflection direction of the rotary polygon mirror 3, an Fθ lens 35 and a folding mirror 36 constituting a scanning optical system and a photosensitive drum 37 serving as a scanning surface are arranged.

  The scanning optical device includes a deflection scanning device, a semiconductor laser unit 31 that is a light source unit that emits a laser beam, and an incident optical system that guides the laser beam from the semiconductor laser unit 31 to the reflecting surface of the rotary polygon mirror 3. A cylindrical lens 32, and an Fθ lens 35 and a folding mirror 36 constituting a scanning optical system that guides the laser beam reflected by the reflecting surface 3b of the rotating polygon mirror 3 to the surface to be scanned. The laser beam from the cylindrical lens 32 is incident on the reflecting surface 3b of the rotary polygon mirror 3 as a convergent beam within the main scanning section.

  In addition, a signal detection mirror 38 that reflects a part of the laser beam L that is deflected and scanned outside the effective image area of the photosensitive drum 37 is disposed, and an imaging lens 39 and an optical path in the reflection direction of the signal detection mirror 38 are disposed. A signal detection sensor 310 is provided. The optical member is accommodated in a space sealed by an optical box 311 and a lid (not shown).

  The laser beam L generated from the semiconductor laser unit 31 forms a line image on the rotary polygon mirror 3 by the cylindrical lens 32. The laser beam L is deflected by rotating the rotary polygon mirror 3 by the deflection scanning device 34, reflected by the folding mirror 36 by the Fθ lens 35, and image-scanned on the photosensitive drum 37.

The Fθ lens 35 is designed such that the light beam reflected by the rotary polygon mirror 3 is condensed so as to form a spot on the photosensitive drum 37, and the scanning speed of the spot is kept constant. In order to obtain such characteristics of the Fθ lens 35, the Fθ lens 35 is composed of two lenses, a spherical lens or toric lenses 35a and 35b.

  Further, a part of the deflected laser beam L is reflected by the signal detection mirror 38 using a portion outside the image region, guided to the signal detection sensor 310 via the imaging lens 39, and detected, and the writing position Adjustments are made.

  By the rotation of the rotary polygon mirror 3, the main scanning by the light beam is performed on the photosensitive drum 37, and the sub scanning is performed by rotating the photosensitive drum 37 around the axis of the cylinder. In this way, an electrostatic latent image is formed on the surface of the photoreceptor.

(Deflection scanning device)
As shown in FIG. 1, the deflection scanning apparatus includes a shaft 1, a flange member 2 that is a fitting member, a rotary polygon mirror 3, a presser spring 4, and a G ring 5. Further, the deflection scanning device includes a sleeve 102 that rotatably supports the shaft 1 in the bearing hole, a thrust cover 103 that is fixed to the lower end of the sleeve 102 and seals the bearing hole, and a thrust supported by the thrust cover 103. The plate 104 has oil filled between the inner surface of the bearing hole of the sleeve 102 and the outer surface of the shaft 1 and between the thrust plate 104 and the end surface of the shaft 1. The end surface of the shaft 1 is formed in a convex shape and is held in a pivot shape by a thrust plate 104 to constitute a pivot thrust bearing.

  A flange member 2 is fixed to the upper portion of the shaft 1, and a rotary polygon mirror 3 is placed on the flange member 2. The rotary polygon mirror 3 has a reflecting surface 3 b and is pressed against the flange member 2 by the presser spring 4 and is integrally coupled to the flange member 2 and the rotor 112.

  The rotor 112 includes a permanent magnet 112a and a yoke 112b that supports the permanent magnet 112a. A circuit board 114 is fixed to the sleeve 102. The wound stator coil 113a faces the permanent magnet 112a of the rotor 112, and a motor that rotationally drives the rotary polygon mirror 3 is configured by both of them.

(Relationship between the outer shape portion 2a of the flange member 2 and the inner diameter portion 3a of the rotary polygon mirror 3)
In the above configuration, the relationship between the outer shape portion 2a of the flange member 2 and the inner diameter portion 3a that is the center hole of the rotary polygon mirror 3 will be described. The outer diameter of the outer portion 2a that is the fitting portion of the flange member 2 is D1 [mm], the linear expansion coefficient of the flange member 2 is α1, the inner diameter of the inner diameter portion 3a of the rotary polygon mirror 3 is D2 [mm], and the rotary polygon mirror When the linear expansion coefficient of 3 is α2, the ambient temperature environment temperature is tJ, the low temperature side operating environment temperature is tL, the high temperature side operating environment temperature is tH, and the difference between the outer diameter D1 and the inner diameter D2 is Δd [mm], Δd is The relationship satisfies the following formula.

When α1 ≦ α2 (D2 × α2−D1 × α1) × (tJ−tL) <Δd ≦ 0.01 (1) When α1> α2 (D1 × α1−D2 × α2) × (tH −tJ) <Δd ≦ 0.01 (2) Expression The left side of the above expression indicates the amount of change in the fitting gap Δd between the flange member 2 and the rotary polygon mirror 3 when the ambient temperature of the deflection scanning device fluctuates. Represents. When the linear expansion coefficient α2 of the rotary polygon mirror 3 is larger than the linear expansion coefficient α1 of the flange member 2, in the equation (1), when the operating environment temperature of the deflection scanning device decreases, the fitting gap Δd decreases.

  At this time, when the inner diameter D2 of the rotary polygon mirror is smaller than the outer diameter D1 of the flange member 2, and the rotary polygon mirror 3 is tightly fitted to the flange member 2, the reflecting surface 3b of the rotary polygon mirror 3 is obtained. May be deformed. When the surface deformation occurs, the spot shape of the laser beam is distorted, or the laser irradiation position on the photosensitive drum is shifted, leading to a decrease in image quality.

  Therefore, in the present embodiment, the fitting gap Δd is set so that the rotary polygon mirror 3 does not get stuck in the flange member 2 even if the operating environment temperature of the deflection scanning device changes. (TJ−tL) on the left side of the equation (1) is a difference between the normal temperature operating environment temperature tJ and the low temperature side operating environment temperature tL. For example, when the normal operating environment temperature tJ is 25 ° C. and the operating environment temperature tL on the low temperature side of the image forming apparatus is 10 ° C., (tJ−tL) is 15 ° C. That is, the fitting gap Δd in the normal temperature environment is regulated so that the rotary polygon mirror 3 does not become a tight fit with the flange member 2 even when the ambient temperature reaches 10 ° C.

  However, care must be taken when the linear expansion coefficient of the shaft 1 is smaller than the linear expansion coefficient α1 of the flange member 2. Since the flange member 2 is fixed to the shaft 1 by means such as shrink fitting, when the environmental temperature fluctuates to the low temperature side, the outer shape of the flange member 2 is affected by the shaft 1 and is smaller than the reduction amount of the flange member alone. Becomes smaller. Therefore, in the calculation of the expression (1), there is a possibility that the rotary polygon mirror 3 becomes a tight fit with respect to the flange member 2. Therefore, in such a case, the linear expansion coefficient α1 is defined as the linear expansion coefficient by the combination of the shaft 1 and the flange member 2. As a result, the rotary polygon mirror 3 does not become an interference fit with the flange member 2 even if the environmental temperature fluctuates to the low temperature side.

  0.01 on the right side represents the maximum value of the fitting gap Δd in a normal temperature environment. If the fitting gap Δd is too large, the rotary polygon mirror 3 may be assembled with the flange member 2 and the shaft 1 being largely decentered as described above. Therefore, a large amount is generated in the entrance and exit of the reflecting surface 3b, which is not preferable.

  For example, as in JP-A-61-28919, in the case of a scanning optical system (referred to as an oblique incidence optical system) in which a laser beam is incident on a rotary polygon mirror at a predetermined angle with respect to the optical axis (laser from the cylindrical lens 32) The light beam is incident on the reflecting surface 3b of the rotating polygon mirror 3 at an angle from other than the deflection scanning surface), the predetermined angle is α, the sub-scan magnification of the scanning system is β, the reflecting surface of the rotating polygon mirror is Assuming that the amount of entry / exit is δ1, the pitch unevenness amount P in the sub-scanning direction is represented by P = 2δ1αβ. That is, δ1 = P / (2αβ).

  Here, the allowable value of the pitch unevenness amount in the sub-scanning direction is preferably suppressed to 1/3 or less of the scanning line interval in the sub-scanning direction on the photosensitive drum surface. If it exceeds this, pitch unevenness becomes a problem in the image.

  Therefore, the allowable value of the amount of entry / exit δ1 of the reflecting surface 3b of the rotary polygon mirror is P = 0.014 [mm] (equivalent to 600 dpi), and the value of the oblique incidence optical system is, for example, α = 13 [°] (0. 227 [rad]), β = 0.87, δ1 = 0.035 [mm]. Further, the amount of entry / exit δ1 of the reflecting surface 3b is the amount of entry / exit of the reflecting surface 3b with respect to the center of rotation of the rotating polygon mirror 3, the degree of coaxiality of the flange member 2 with respect to the shaft 1, and the fitting of the flange member 2 and the rotating polygon mirror 3. It consists of a gap Δd. If the amount of the reflection surface 3b of the rotating polygon mirror 3 is about 0.02 [mm] and the coaxiality is about 0.005 [mm], the fitting gap Δd is about 0.01 [mm]. Become. That is, in order to suppress pitch unevenness in the sub-scanning direction in the oblique incidence optical system, it is preferable to suppress the fitting gap Δd to about 0.01 [mm] or less.

Further, in the case of an optical system (referred to as a converging optical system) in which the laser beam incident on the fθ lens is a laser beam converged in the main scanning direction (the laser beam from the cylindrical lens 32 is incident on the reflecting surface 3 b of the rotary polygon mirror 3. The same applies to the scanning optical apparatus that enters with a convergent light beam in the main scanning section. In this case, if the reflection surface 3b of the rotary polygon mirror 3 is large in and out, a deviation occurs in the main scanning direction at the irradiation position of the laser beam on the photosensitive drum. The deviation amount δY can be expressed by the following formula 1.

Here, δ2 is the amount of entry / exit of the reflecting surface 3b of the rotary polygon mirror 3, f is the focal length of the fθ lens, Sk is the convergent light beam incident on the fθ lens from the back main plane of the fθ lens, and converged by the fθ lens. A distance to the image forming position, A is an angle in the main scanning direction formed by the optical axis of the fθ lens and the laser beam incident on the rotary polygon mirror 3, and B is an arbitrary value by the optical axis of the fθ lens and the rotary polygon mirror 3. This is the angle in the main scanning direction formed by the laser beam deflected and reflected at an angle.

When this equation is converted into an equation for calculating δ2, the following equation 2 is obtained.

The allowable value of the shift amount δY in the main scanning direction is preferably set to 1/3 or less of the scanning line interval, similarly to the pitch unevenness in the sub-scanning direction. By applying an example of the optical system to this equation and calculating the entrance / exit δ2 of the surface of the rotary polygon mirror 3, δY = 0.014 [mm], f = 136 [mm], Sk = 102 [mm], A = 60 Assuming ° and B = 30 °, δ2 is approximately 0.035 [mm]. That is, as in the case of the oblique incidence optical system, the fitting gap Δd between the rotary polygon mirror 3 and the flange member 2 is preferably set to 0.01 [mm] or less.

  Here, since the fitting gap Δd is 0.01 [mm] or less, the expression on the left side of the expressions (1) and (2) is expressed by the following expression (3), where D is the outer diameter of the flange member. (4) It can approximate.

When α1 ≦ α2, D × (α2−α1) × (tJ−tL) <Δd ≦ 0.01 (3) When α1> α2, D × (α1−α2) × (tH−tJ) < Δd ≦ 0.01 (4) Formula Next, a specific example is shown using Formula (3). When the material of the flange member 2 is brass, the linear expansion coefficient α1 is 20 × 10 −6 [K−1], and when the material of the rotary polygon mirror 3 is aluminum, the linear expansion coefficient α2 is 23 × 10 −6 [K−1]. The outer diameter D of the flange member 2 is 4 [mm], the normal temperature environment temperature tJ is 25 ° C., and the low temperature side operation environment temperature tL is 10 ° C. When these values are applied to the equation (3), the fitting gap Δd is 0.00018 <Δd ≦ 0.01. Therefore, the inner diameter of the rotary polygon mirror 3 may be set in the range of 4.0018 [mm] to 4.01 [mm].

  Here, for example, when the material of the shaft 1 is stainless steel, the linear expansion coefficient is about 10 × 10 −6 [K−1], which is smaller than the linear expansion coefficient α 1 of the flange member 2. Therefore, a linear expansion coefficient combining the shaft 1 and the flange member 2 is used for α1. When the linear expansion coefficient α1 is 12 × 10 −6 [K−1], 0.00066 <Δd ≦ 0.01. In other words, if the inner diameter of the rotary polygon mirror 3 is larger than 4.00066 [mm], there is no interference fit with the flange member 2 even when the atmospheric temperature of the rotary polygon mirror 3 reaches 10 ° C.

  From the above specific example, for example, if the outer diameter of the flange member 2 is 4 [mm] and the inner diameter of the rotary polygon mirror 3 is 4.001 [mm], the difference in diameter is 0.001 [mm] It is usually difficult to insert the rotary polygon mirror 3 into the flange member 2. Therefore, as a method of assembling the rotary polygon mirror 3, it is preferable to assemble the rotary polygon mirror 3 to the flange member 2 in a state where the rotary polygon mirror 3 is heated and expanded to widen the inner diameter. If the amount to expand the inner diameter is 0.01 [mm], the rotary polygon mirror 3 is heated from room temperature to about 108 ° C. Alternatively, a method of assembling the rotary polygon mirror 3 by cooling and reducing the flange member 2 may be used. Thereafter, the presser spring 4 and the G ring 5 are inserted into the shaft 1 to urge the upper surface of the rotary polygon mirror 3, and the rotary polygon mirror 3 is fixed to the flange member 2 while being abutted against it.

  Equation (4) shows the range of the fitting gap Δd when the linear expansion coefficient α2 of the rotary polygon mirror 3 is smaller than the linear expansion coefficient α1 of the flange member 2. In this case, the rotary polygon mirror 3 is tightly fitted to the flange member 2 when the ambient temperature of the deflection scanning device changes to the high temperature side. (TH−tJ) on the left side is a difference between the high temperature side operating environment temperature tH and the normal temperature environment temperature tJ. For example, when the high temperature side operating environment temperature tH is 60 ° C. and the normal temperature environment temperature tJ is 25 ° C., it is 35 ° C. . That is, the fitting gap Δd in the normal temperature environment is defined so that the rotary polygon mirror 3 does not become a tight fit with the flange member 2 even when the operating environment temperature reaches the high temperature side. Also in this case, when the linear expansion coefficient of the shaft 1 is larger than the linear expansion coefficient α1 of the flange member 2, a linear expansion coefficient obtained by combining the shaft 1 and the flange member 2 with the linear expansion coefficient α1 is used.

  In this way, the fitting gap is defined in consideration of the linear expansion coefficient of the rotary polygon mirror 3 and the flange member 2 or the shaft 1 and the environmental temperature of the deflection scanning device. As a result, even if the environmental temperature of the deflection scanning device fluctuates, the rotary polygon mirror 3 and the flange member 2 do not have a tight fit, so that it is possible to avoid surface deformation problems, and the rotary polygon The eccentricity of the mirror 3 can be reduced as much as possible. Therefore, in the oblique incident optical system and the converging optical system, the amount of laser beam irradiation position deviation at the position corresponding to the photosensitive drum can be reduced, and a high-quality image can be obtained.

[Second Embodiment]
Next, a second embodiment of the deflection scanning apparatus and the scanning optical apparatus according to the present invention will be described with reference to the drawings. FIG. 2 is a sectional view of the deflection scanning apparatus according to this embodiment. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 2A, the deflection scanning apparatus according to this embodiment includes a shaft 6, a rotary polygon mirror 7, and a flange member 8. In the present embodiment, the shaft 6 functions as a fitting member, and the rotary polygon mirror 7 is fitted to the shaft 6. Thus, the rotary polygon mirror 7 may be configured to be fitted to the shaft 6 without the flange member 8 being interposed. The relationship of the fitting clearance between the outer diameter 6a of the shaft 6 and the inner diameter 7a of the rotary polygon mirror 7 is the same as in the first embodiment.

  The shaft 6 has a shaft outer portion 6 b having a diameter different from that of the fitting portion 6 a of the rotary polygon mirror 7. Thereby, when the rotary polygon mirror 7 is heated and assembled to the shaft 6, the inner diameter 7a of the rotary polygon mirror 7 contacts the shaft 6 in the middle of insertion, the temperature of the rotary polygon mirror 7 is lowered, and the inner diameter 7a is reduced. To avoid being difficult to assemble.

  If the length (fitting length) of the fitting portion 6a in the rotation axis direction is as short as possible, the concern that the rotating polygon mirror 7 contacts the shaft 6 when the rotating polygon mirror 7 is assembled can be reduced. In addition, if the shaft 6 and the rotary polygonal mirror 7 are tightly fitted due to variations in environmental temperature due to variations in parts during mass production, the shorter the fitting length is, the more the deformation of the reflecting surface of the rotary polygonal mirror 7 will be. There are few.

  In order to reduce the deformation of the reflecting surface of the rotary polygon mirror 7 as much as possible, the fitting length between the shaft 6 and the rotary polygon mirror 7 is at least half the length (thickness) of the rotary polygon mirror 7 in the rotation axis direction. Good to do. If the fitting length is less than half, even if the interference fit is about 0.001 [mm], the reflective surface of the rotary polygon mirror 7 hardly deforms.

  FIG. 2B is a partial cross-sectional view of another deflection scanning device. FIG. 2B is a partial cross-sectional view of the deflection scanning device. The shaft 9 is formed with an outer shape portion 9 a that fits with the inner diameter 10 a of the rotary polygon mirror 10, and the axial length of the outer shape portion 9 a is less than half of the axial thickness of the rotary polygon mirror 10. ing. In such a configuration, the rotary polygon mirror 10 may be fitted to the shaft 9.

  As described above, the fitting gap between the shaft 6 (the shaft 9) and the rotary polygon mirror 7 (the rotary polygon mirror 10) is defined as in the first embodiment. As a result, as in the first embodiment, the rotary polygon mirror 7 (10) and the shaft 6 (axis 9) do not become an interference fit even when the environmental temperature of the deflection scanning device fluctuates. Deformation defects can be avoided and the eccentricity of the rotary polygon mirror 7 (10) can be reduced as much as possible. Therefore, in the oblique incident optical system and the converging optical system, the amount of laser beam irradiation position deviation at the position corresponding to the photosensitive drum can be reduced, and a high-quality image can be obtained.

It is sectional drawing of the deflection | deviation scanning apparatus concerning 1st embodiment. It is sectional drawing of the deflection | deviation scanning apparatus concerning 2nd embodiment. (A) It is sectional drawing of a deflection | deviation scanning apparatus. (B) It is a fragmentary sectional view of another deflection scanning device. It is a block diagram of the conventional scanning optical apparatus. It is sectional drawing of the conventional deflection | deviation scanning apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 6, 9 ... Shaft (corresponding to fitting member) 2, 8 ... Flange member (corresponding to fitting member) 2a, 9a ... Outer part 3, 10, 7 ... Rotary polygon mirror 3a ... Inner diameter part 3b ... Reflecting surface 4 ... Presser spring 5 ... Ring 6a ... Fitting portion 6b ... Shaft outer portion 7a, 10a ... Inner diameter 31 ... Semiconductor laser unit 32 ... Cylindrical lens 34 ... Deflection scanning device 35 ... F.theta. 37 ... photosensitive drum 38 ... signal detection mirror 39 ... imaging lens 102 ... sleeve 103 ... thrust cover 104 ... thrust plate 112 ... rotor 112a ... permanent magnet 112b ... yoke 113a ... stator coil 114 ... circuit board

Claims (6)

A deflection scanning apparatus having a rotary polygon mirror that deflects and scans a laser beam, and a fitting member that is fitted in a central hole of the rotary polygon mirror and includes at least one member that holds the rotary polygon mirror In
The linear expansion coefficient of the fitting member is α1, the linear expansion coefficient of the rotary polygon mirror is α2, the outer diameter of the fitting portion of the fitting member with the rotary polygon mirror is D, the ambient temperature is tJ, and the low temperature side When the operating environment temperature is tL, the high temperature side operating environment temperature is tH, and the fitting gap of the fitting portion is Δd,
When α1 ≦ α2
D × (α2−α1) × (tJ−tL) <Δd ≦ 0.01,
When α1> α2
D × (α1-α2) × (tH−tJ) <Δd ≦ 0.01,
A deflection scanning device characterized by satisfying The deflection scanning device according to claim 1, wherein a length of the fitting portion in the rotation axis direction is not more than half of a length of the rotary polygon mirror in the rotation axis direction. A rotary shaft constituting a fitting member is fitted into the center hole of the rotary polygon mirror, and the length of the rotary shaft fitting portion in the rotation axis direction is half of the length of the rotary polygon mirror in the rotation axis direction. The deflection scanning apparatus according to claim 1, wherein a step having a different outer diameter is provided on the rotating shaft so as to satisfy the following conditions. The rotating polygon mirror is assembled to the fitting member in a state where the rotating polygon mirror is heated to a predetermined temperature, or the rotating polygon mirror is assembled in a state where the fitting member is cooled to a predetermined temperature. The deflection scanning device according to any one of claims 1 to 3. 5. A deflection scanning apparatus according to claim 1, light source means for emitting a laser beam, and incident optics for guiding the laser beam from the light source means to the reflecting surface of the rotary polygon mirror. A scanning optical device comprising: a system; and a scanning optical system that guides a laser beam reflected by the reflecting surface of the rotating polygon mirror to a surface to be scanned,
2. A scanning optical apparatus according to claim 1, wherein the laser beam from the incident optical system is incident on the reflecting surface of the rotary polygon mirror as a convergent beam within a main scanning section. 5. The deflection scanning device according to claim 1, a light source unit, an incident optical system that guides a laser beam from the light source unit to a reflection surface of the rotary polygon mirror, and the rotation A scanning optical system having a scanning optical system that guides a laser beam reflected by a reflecting surface of a polygon mirror to a scanned surface,
2. A scanning optical apparatus according to claim 1, wherein the laser beam from the incident optical system is incident on the reflecting surface of the rotary polygon mirror at an angle from other than the deflection scanning surface.

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