Scanning optical device and image forming apparatus

Abstract

The present disclosure relates to a scanning optical apparatus including an optical box accommodating a light source, a deflector, and a scanning lens. The deflector includes a coaxial portion positioned coaxially with a center of rotation of the polygon mirror. The optical box includes a plurality of fitting portions fitted to the coaxial portion at different positions. In the assembly parts, one of the assembly parts is taken as a reference, and the other of the assembly parts is arranged in the area. The region is a bisector between an incident laser beam emitted by a light source towards a polygon mirror and a laser beam reflected by the polygon mirror and reaching a write start position of a surface to be scanned in a rotational direction to an incident laser beam and reflected by the polygon mirror and reaching a write end position before incidence onto a scanning lens and arranging a region surrounded by a bisector between the lasers. The present disclosure also relates to an electrophotographic-type image forming apparatus.

Description

Technical Field

[0001] This invention relates to scanning optical devices and image forming apparatuses. Specifically, it relates to scanning optical devices and image forming apparatuses including such scanning optical devices, for example, in devices such as laser printers, copiers, or fax machines that have the function of forming images on transfer materials (recording materials) such as sheets. Background Technology

[0002] In image forming equipment such as conventional laser printers, scanning optics optically modulate a laser beam emitted from a light source according to an image signal. The optically modulated laser beam is deflected and scanned, for example, by a deflector comprising a rotatable polygonal mirror. The deflected and scanned laser beam is formed into an image on a photosensitive drum by a scanning lens (e.g., an fθ lens), creating an electrostatic latent image on the drum. Next, a developing unit develops the electrostatic latent image on the drum into a toner image, which is then transferred to a recording material such as recording paper. The recording material is fed to a fixing unit, and printing is performed by heating and fixing the toner on the recording material. Regarding image forming equipment, various products with different printing speeds, durability, etc., have been introduced to address various user needs. For example, more compact image forming equipment is required for personal use, while large-scale offices require both high printing speeds and high durability.

[0003] To address these diverse user demands, various image forming devices have been developed to accommodate different printing speeds and specifications. Simultaneously, scanning optical devices have also been developed and optimized for use with these image forming devices. For example, Japanese Patent No. 6700746 discloses a structure for an optical box capable of assembling multiple deflectors.

[0004] However, the traditional approach has the following problems. Specifically, the axes of the individual holes in the optical box, which assembles different deflectors, are common, and the rotatable facets have the same number of surfaces in each deflector. Therefore, it is difficult to handle rotatable facets with increased surface numbers to accelerate the printing speed of image forming equipment. Typically, once the number of surfaces of a rotatable facet is increased, the corresponding optical system and scanning optics become newer. This may lead to investments in new facilities such as manufacturing equipment and molds, potentially significantly increasing costs. Consequently, the cost of scanning optics and image forming equipment may rise. Summary of the Invention

[0005] The present invention was conceived in this context, and the object of the present invention is to realize a scanning optical device corresponding to various printing speeds at low cost by minimizing equipment investment as much as possible.

[0006] According to one aspect of the invention, (1) a scanning optical device is provided, comprising: a light source; a deflector configured to deflect a laser beam emitted from the light source, the deflector including a rotatable multifaceted mirror configured to reflect the laser beam; a scanning lens configured to focus the laser beam deflected by the rotatable multifaceted mirror onto a surface to be scanned; and an optical housing configured to house the light source, the deflector, and the scanning lens, wherein the deflector includes a coaxial portion coaxially positioned with respect to the rotation center of the rotatable multifaceted mirror, wherein the optical housing includes a plurality of mounting portions located at different positions in a plane perpendicular to the axial direction of the coaxial portion. The assembly is attached to the coaxial portion, and wherein, among the plurality of assembly portions, with one of the assembly portions as a reference, another of the assembly portions is disposed in a region that is a region enclosed in the rotational direction of the rotatable multifaceted mirror by the bisector between the incident laser beam, which is a laser beam emitted from the light source toward the rotatable multifaceted mirror, and the laser beam reflected by the rotatable multifaceted mirror and reaching the write start position of the scanned surface before being incident on the scanning lens, and the bisector between the incident laser beam and the laser beam reflected by the rotatable multifaceted mirror and reaching the write end position of the scanned surface before being incident on the scanning lens.

[0007] According to one aspect of the invention, (2) a scanning optical device is provided, comprising: a light source; a deflector configured to deflect a laser beam emitted from the light source, the deflector including a rotatable multifaceted mirror configured to reflect the laser beam; a scanning lens configured to focus the laser beam deflected by the rotatable multifaceted mirror onto a surface to be scanned; and an optical box configured to house the light source, the deflector, and the scanning lens, wherein the deflector includes a coaxial portion coaxially positioned with respect to the rotation center of the rotatable multifaceted mirror, wherein the optical box includes a point-symmetric aperture-shaped portion configured to restrict at least one direction in a plane perpendicular to the axial direction of the coaxial portion and not restrict the plane. The longitudinal direction of the aperture-shaped portion is the direction of an imaginary line connecting the intersection of the incident laser beam emitted from the light source toward the rotatable mirror and the laser beam reflected by the rotatable mirror and reaching the write start position of the scanned surface before being incident on the scanning lens, and the intersection of the incident laser beam and the laser beam reflected by the rotatable mirror and reaching the write end position of the scanned surface before being incident on the scanning lens, when the intersection of the incident laser beam and the laser beam reflected by the rotatable mirror and reaching the write end position of the scanned surface before being incident on the scanning lens is defined as a reference.

[0008] According to one aspect of the present invention, (3) an electrophotographic image forming apparatus is provided, comprising: an image carrier member including a scanned surface; a scanning optical device according to (1), the scanning optical device being configured to scan the image carrier member with a laser beam according to image information; and an image forming apparatus configured to transfer to a recording material and form an image on the recording material after developing an electrostatic latent image formed on the image carrier member according to the image information.

[0009] Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 These are schematic cross-sectional views of the image forming apparatus in Examples 1 and 2.

[0011] Figure 2 This is a schematic perspective view of the scanning optical device in Embodiments 1 and 2.

[0012] Figure 3 This is a top view of the laser beam being scanned at the start of the writing position in Examples 1 and 2.

[0013] Figure 4 This is a top view of scanning the laser beam at the center position in Examples 1 and 2.

[0014] Figure 5 This is a top view of the laser beam being scanned at the end of the writing position in Examples 1 and 2.

[0015] Figure 6 Parts (a) and (b) include schematic diagrams showing the shape of the rotatable multifaceted mirror in Embodiments 1 and 2.

[0016] Figure 7 Parts (a), (b), and (c) include enlarged diagrams showing the relationship between the phase of the rotatable polyhedron and the laser beam in Examples 1 and 2.

[0017] Figure 8 This is a schematic cross-sectional view showing the construction of the motor of the scanning optical device in Embodiments 1 and 2.

[0018] Figure 9 This is a schematic perspective view showing the construction of the optical box and motor of the scanning optical device in Embodiments 1 and 2.

[0019] Figure 10 Parts (a) and (b) include enlarged views showing the positional relationship between the hole in the scanning optics of Embodiment 1 and the shaft of the motor.

[0020] Figure 11 This is a schematic enlarged view showing the structure of the aperture of the scanning optical device in Embodiment 1.

[0021] Figure 12 This is a schematic diagram of the structure of the aperture of the scanning optical device in Embodiment 2.

[0022] Figure 13 Parts (a), (b), (c), (d1), (d2), and (e) include views showing variations of the holes in Embodiments 1 and 2. Detailed Implementation

[0023] [Example 1]

[0024] An image forming apparatus equipped with a scanning optical device according to an embodiment of the present invention will be described. Incidentally, in the following description, an image forming apparatus equipped with a scanning optical device according to an embodiment of the present invention will first be illustrated by example, and then the scanning optical device in the image forming apparatus will be described. Incidentally, unless specifically stated otherwise, the dimensions, materials, shapes, relative arrangements, etc., of the constituent components described in the following embodiments should not be construed as limiting the scope of the invention thereto.

[0025] Image forming equipment

[0026] Figure 1 This is a schematic cross-sectional view showing the electrophotographic image forming apparatus of Embodiment 1. The image forming apparatus 110 of Embodiment 1 is an image forming apparatus comprising a scanning optical device 101 as an exposure device, a photosensitive drum 103 as an image carrying member, and a processing cartridge 102 as an image forming device. A laser beam emitted from the scanning optical device 101 scans the photosensitive drum 103. The processing cartridge 102 performs imaging on a recording material P, such as recording paper, based on the scanned image. Here, a printer will be used as an example to describe the image forming apparatus 110.

[0027] like Figure 1 As shown, the image forming apparatus (printer) 110 emits a laser beam L based on image information acquired using the scanning optical device 101, and irradiates the photosensitive drum 103 built into the processing cartridge 102. A latent image is then formed on the photosensitive drum 103, and the latent image is developed into a toner image using a toner as a developer. Incidentally, the processing cartridge 102 is a cartridge that includes the photosensitive drum 103 and a charging device, a developing device, etc. (not shown), which are integrated into the processing apparatus acting on the photosensitive drum 103.

[0028] On the other hand, the recording material P stacked on the stacking plate 104 is fed while being separated one by one by the feed roller 105, and then further conveyed downstream by the intermediate roller 106. The toner image formed on the photosensitive drum 103 is transferred onto the conveyed recording material P by the transfer roller 107. The recording material P with the unfixed toner image is further conveyed downstream, and the toner image is fixed onto the recording material P by the fixing unit 108, which includes a heating element inside. Thereafter, the recording material P is discharged outside the equipment by the discharge roller 109.

[0029] Incidentally, in Embodiment 1, the charging device and developing device, which are processing devices acting on the photosensitive drum 103, are configured to be integrally disposed in the processing cartridge 102 together with the photosensitive drum 103. However, each processing device can be configured separately from the photosensitive drum 103. Furthermore, the image forming apparatus equipped with the scanning optical device 101 to which the present invention is applied is not limited to... Figure 1 Image forming devices in [the context of the image].

[0030] [Scanning Optical Device]

[0031] Next, we will use Figure 2 The scanning optical device 101 in the image forming apparatus 110 is described. Figure 2This is an explanatory diagram of the scanning optical device 101 in Embodiment 1. The scanning optical device 101 includes a semiconductor laser unit 1, an aperture stop 2a in the sub-scanning direction, an incident lens 3, an aperture stop 2b in the main scanning direction, a rotatable facet mirror 4, a motor 5, a rotation shaft 4c, a BD (beam detector) 6, a scanning lens 7, an optical box 9, and a cover 10. The semiconductor laser unit 1, as a light source, emits a laser beam. The motor 5, acting as a deflector, rotates and drives the rotatable facet mirror 4 integrally with it. The rotation shaft 4c is the rotation axis of the rotatable facet mirror 4. The BD 6 outputs a synchronization signal in response to the laser beam incident on it. The scanning lens 7 is a collective term for the scanning lenses 7a and 7b, and is a lens used to scan the laser beam deflected by the rotatable facet mirror 4 onto the scanned surface. In addition, the incident lens 3 is a composite deformable collimating lens that integrates a collimating lens and a cylindrical lens, and is integrally formed with the BD lens. The optical box 9 houses the semiconductor laser unit 1, the incident lens 3, the rotatable polygonal mirror 4, the motor 5, and the scanning lens 7. Additionally, as... Figure 2 As shown, the scanning direction of the laser beam L (or the rotation axis direction of the photosensitive drum 103) is defined as the main scanning direction (Dm), and the rotation direction of the photosensitive drum 103 is defined as the sub-scanning direction (Ds).

[0032] In this configuration, the laser beam L emitted from the semiconductor laser unit 1 has its beam width limited in the sub-scanning direction by the aperture stop 2a, and is formed as approximately collimated or converged light in the main scanning direction and converged light in the sub-scanning direction by the incident lens 3. Next, the laser beam L passes through the aperture stop 2b, limiting its beam width in the main scanning direction, and forms an image with a focal line shape elongated in the main scanning direction on the reflective surface of the rotatable polygon mirror 4. Furthermore, by rotating the rotatable polygon mirror 4, the laser beam L is deflected and scanned, and incident on the BD lens of the incident lens 3. The laser beam L, having passed through the BD lens, is then incident on the BD 6. At this time, the BD 6 detects the laser beam L and outputs a synchronization signal. This timing is defined as the synchronization detection timing at the write start position in the main scanning direction.

[0033] Next, the laser beam L is incident on scanning lenses 7a and 7b. Scanning lenses 7a and 7b are designed to focus the laser beam L to form a light spot on the photosensitive drum 103, and to maintain the scanning speed of the light spot at a constant speed. To obtain the characteristics of scanning lenses 7a and 7b in this manner, scanning lenses 7a and 7b are formed of aspherical lenses. The laser beam L, having passed through scanning lenses 7a and 7b, is emitted from the exit aperture of the optical box 9, and an image is formed and scanned on the photosensitive drum 103.

[0034] By rotating the rotatable polygonal mirror 4, the laser beam L is deflected and scanned, and the main scan is performed on the photosensitive drum 103 by the laser beam L. In addition, a secondary scan is performed by rotating the photosensitive drum 103 around its cylindrical axis. In this way, an electrostatic latent image is formed on the surface of the photosensitive drum 103.

[0035] [Optical system of scanning optical device]

[0036] Figure 2 The scanning optical device 101 shown illustrates an example of using a rotatable polyhedron with four surfaces (having a regular square shape) as the rotatable polyhedron 4. However, as... Figures 3 to 7 As shown, the scanning optical device 101 is configured as a common scanning optical device. Not only can a rotatable faceted mirror 4 with four surfaces be assembled into this common scanning optical device as a first rotatable faceted mirror, but a rotatable faceted mirror 14 with five surfaces (which has a regular pentagonal shape) can also be assembled into this common scanning optical device as a second rotatable faceted mirror with a different number of reflective surfaces. With this configuration, when using the rotatable faceted mirror 14 with five surfaces, even if the rotational speed of the motor 5 is the same as when using the rotatable faceted mirror 4 with four surfaces, the scanning speed can be increased by 1.25 times. Therefore, by changing the rotatable faceted mirror 4 with four surfaces in the scanning optical device 101 to the rotatable faceted mirror 14 with five surfaces, an image forming apparatus 110 with a printing speed increased by approximately 1.25 times can be achieved. Incidentally, for ease of understanding, in the accompanying drawings, the outline of the rotatable faceted mirror 4 with four surfaces is shown in dashed lines, and the outline of the rotatable faceted mirror 14 with five surfaces is shown in solid lines.

[0037] exist Figures 3 to 5 In the scanning optical device 101 shown, as described above, common components are used both when using the rotatable polymirror 4 with four surfaces and when using the rotatable polymirror 14 with five surfaces, except for the rotatable polymirror. In other words, the semiconductor laser unit 1, the incident lens 3, the BD 6, the scanning lenses 7a and 7b, the optical box 9, and the cover 10 are all identical and assembled in the same position.

[0038] In the rotatable polyfacet 4 with four surfaces and the rotatable polyfacet 14 with five surfaces in Embodiment 1, the distances from the rotation axis 4c to the reflecting surface and from the rotation axis 14c to the reflecting surface are different. Therefore, in order to use both with a common component, they are configured such that the rotatable polyfacet 4 with four surfaces and the rotatable polyfacet 14 with five surfaces can be assembled at the shifted positions of the rotation axis 4c and the rotation axis 14c, respectively.

[0039] (Write the start position)

[0040] exist Figure 3 The image shows the write start position 113 on one end portion of the image retention area 113 of the photosensitive drum 103. L The state of rotatable multifaceted mirrors 4 and 14 when the laser beam L is scanned. Reflection point 41 L Let 42 represent the reflection point of the laser beam L in a rotatable polyhedron 4 with four surfaces. L This represents the reflection point of the laser beam L in the rotatable polyhedron 14 with five surfaces. For example... Figure 3 As shown, reflection point 41 L Location and reflection point 42 L The positions are roughly the same or roughly overlapping. This arrangement allows rotatable polymirrors with four surfaces and rotatable polymirrors with five surfaces to use a common optical system.

[0041] (Central location)

[0042] exist Figure 4 The image shows the center position 113 of the image retention area 113 when the image is reached from the photosensitive drum 103. C The state of the rotatable multifaceted mirrors 4 and 14 during scanning by the laser beam L. At this time, the laser beam L is positioned at the center of the image-protecting region 113. C The light beam used for scanning, and also the beam that scans the optical axis in the design of scanning lenses 7a and 7b. For example... Figure 4 As shown, the reflection point 41 of the laser beam L in the rotatable polyhedron 4 with four surfaces C The position and the reflection point 42 of the laser beam L in the rotatable polyhedron 14 with five surfaces C Their positions are roughly the same.

[0043] (Write to the end position)

[0044] In addition, Figure 5 The image shows the write end position 113 on the other end portion of the image guarantee area 113 of the photosensitive drum 103 located in the main scanning direction Dm. R The states of the rotatable polymirrors 4 and 14 when the laser beam L is scanned. Similarly, in this case, the reflection point 41 in the rotatable polymirror 4, which has four surfaces. R The position and reflection point 42 in the rotatable polyhedron 14 with five surfaces R The positions are roughly the same. In the following description, the various reflection points 41 of the rotatable polyhedron 4 with four surfaces are... L 41 C and 41R Collectively referred to as reflection point 41, and each reflection point 42 of the rotatable polyhedron 14 having five surfaces. L 42 C and 42 R Collectively referred to as reflection point 42.

[0045] [A structure that makes the two reflection points coincide]

[0046] Will use Figure 6 and Figure 7 The specific construction is described in detail, ensuring that the reflection point 41 of the rotatable polyhedron 4 with four surfaces and the reflection point 42 of the rotatable polyhedron 14 with five surfaces coincide with each other. Figure 6 The diameter of the circumcircle (double-dotted line) of the rotatable polyhedron 4 with four surfaces shown in part (a) is set to φ20mm. That is, the radius R1 of the circumcircle of the rotatable polyhedron 4 with four surfaces is 10mm (R1=10mm). Therefore, geometrically, the distance L1 from the rotation axis 4c located at the center of the rotatable polyhedron 4 to the reflecting surface S1 is 7.07mm (L1=7.07mm).

[0047] On the other hand, similarly, for the rotatable polyhedron 14 with five surfaces, the diameter of the circumscribed circle (double-dotted line) is also similarly set to φ20mm. That is, the radius R2 of the circumscribed circle of the rotatable polyhedron 14 with five surfaces is also 10mm (R2 = 10mm). Therefore, geometrically, the distance L2 from the rotation axis 14c located at the center of the rotatable polyhedron 14 to the reflecting surface S2 is 8.09mm (L2 = 8.09mm). Therefore, in the rotatable polyhedron 4 with four surfaces and the rotatable polyhedron 14 with five surfaces, the distance L1 (7.07mm) from the center of the rotatable polyhedron 4 (rotation axis 4c) to the reflecting surface S1 and the distance L2 (8.09mm) from the center of the rotatable polyhedron 14 (rotation axis 14c) to the reflecting surface S2 are different. In other words, in order to make reflection points 41 and 42 be in approximately the same position, the positions of rotation axis 4c and rotation axis 14c are different when attempting to align reflection surfaces S1 and S2.

[0048] like Figure 7 As shown, the main scanning direction Dm is defined as the y-direction (the arrow side of the coordinate axis is +), and the direction perpendicular to the main scanning direction Dm is defined as the x-direction. In this case, when the rotation axis 4c of the rotatable polyfacet 4 with four surfaces is set to the origin (x, y) = (0, 0), the rotation axis 14c of the rotatable polyfacet 14 with five surfaces is set to (x, y) = (-0.838, -0.630).

[0049] The laser beam L emitted from semiconductor laser unit 1 toward rotatable multifaceted mirrors 4 and 14 is emitted from a direction tilted 75° counterclockwise relative to the x-axis.

[0050] Figure 7 Part (a) shows the write start position 113 on one end portion of the image assurance region 113 when the laser beam L is emitted. L The view of the state of each of the polyhedra 4 and 14 can be rotated. Figure 7 In part (a), the normals to the reflecting surfaces S1 and S2 of the rotatable polymirrors 4 and 14 are tilted counterclockwise by 52.6° from the x-axis. Therefore, the laser beam L reflected by the reflecting surfaces S1 and S2 of the rotatable polymirrors 4 and 14 is reflected in a direction tilted counterclockwise by 30.2° from the x-axis. At this time, the reflection point 41 of the rotatable polymirror 4 with four surfaces... L The coordinates are (7.119, 3.460), and the reflection point 42 of the rotatable polyhedron 14 with five surfaces is... L The coordinates are (7.121, 3.469). That is, the reflection point is 41. L and reflection point 42 L The positional offset between them is 0.009mm even on the larger side, and makes the reflection point 41 L Location and reflection point 42 L Their positions roughly overlap.

[0051] in addition, Figure 7 Part (b) shows the center position 113 of the image-guaranteed region 113 when the laser beam L is aligned with the image. C During scanning, the view of the state of each of the polyhedra 4 and 14 can be rotated. Figure 7 In part (b), the normals to the reflecting surfaces S1 and S2 of the rotatable polymirrors 4 and 14 are tilted counterclockwise by 37.5° from the x-axis. Therefore, the laser beam L reflected by the reflecting surfaces S1 and S2 of the rotatable polymirrors 4 and 14 is reflected in the x-direction. At this time, the reflection point 41 of the rotatable polymirror 4, which has four surfaces... C The coordinates are (6.283, 3.430), and the reflection point 42 of the rotatable polyhedron 14 with five surfaces is... C The coordinates are (6.273, 3.393). That is, the reflection point is 41. C and reflection point 42 C The positional offset between them, even on the larger side, is 0.038 mm, and makes the reflection point 41 C Location and reflection point 42 C Their positions roughly overlap.

[0052] Similarly, Figure 7Part (c) shows the write end position 113 on the other end portion of the image assurance region 113 when the laser beam L is emitted. R The view of the state of each of the polyhedra 4 and 14 can be rotated. Figure 7 In part (c), the normals to the reflecting surfaces S1 and S2 of the rotatable polymirrors 4 and 14 are tilted counterclockwise by 22.4° from the x-axis. Therefore, the laser beam L reflected by the reflecting surfaces S1 and S2 of the rotatable polymirrors 4 and 14 is reflected in a direction tilted clockwise by 30.2° from the x-axis. At this time, the reflection point 41 of the rotatable polymirror 4 with four surfaces... R The coordinates are (6.264, 3.361), and the reflection point 42 of the rotatable polyhedron 14 with five surfaces is... R The coordinates are (6.266, 3.367). That is, the reflection point is 41. R and reflection point 42 R The positional offset between them is 0.006 mm even on the larger side, and makes the reflection point 41 R Location and reflection point 42 R Their positions roughly overlap.

[0053] As described above, the reflection points 41 and 42 of the rotatable polyhedrons 4 and 14 are approximately aligned by shifting the rotation axis 4c of the rotatable polyhedron 4 with four surfaces and the rotation axis 14c of the rotatable polyhedron 14 with five surfaces. However, strictly speaking, in Embodiment 1, a maximum offset of 0.038 mm exists. However, in the optical system of Embodiment 1, since the positional offset between the reflection points 41 and 42 is allowed to be up to about 0.1 mm in the design, an offset of 0.038 mm is permissible.

[0054] Furthermore, in the optical system configuration of aperture stops 2a and 2b, incident lens 3, rotatable polygon mirrors 4 and 14, scanning lenses 7a and 7b, etc., in Embodiment 1, the permissible positional offset of reflection points 41 and 42 is set to approximately 0.1 mm. However, depending on the design of the optical system, a larger positional offset of reflection points 41 and 42 may be permissible. Therefore, the scope of the present invention is not limited to the arrangement or dimensions in Embodiment 1.

[0055] [The structure of the optical box and rotatable multifaceted mirror of the scanning optical device]

[0056] Next, we will use Figures 8 to 11 The description relates to the configuration of the optical box 9 of the scanning optical device 101 and the rotatable polyhedrons 4 and 14, and the connection between them. Figure 8 This is a schematic cross-sectional view of the motor 5 of the scanning optical device 101, and Figure 9This is a schematic exploded view showing the attachment state between the optical housing 9 and the motor 5 of the scanning optical device 101.

[0057] exist Figure 8 and Figure 9 The diagram shows rotating shafts 4c and 14c, which serve as the rotation centers of the rotatable polyhedrons 4 and 14, respectively. The motor 5 includes a shaft 40 as a coaxial portion, which is coaxially positioned with the rotating shafts 4c and 14c of the rotatable polyhedrons 4 and 14. More precisely, the shaft 40 is fixed to the base plate 51, and a sleeve 52, into which the shaft 40 is fitted, rotates together with the rotor 53, the rotatable polyhedrons 4 and 14, and the mirror pressing spring 55 via lubricating oil. That is, the rotating shafts 4c and 14c of the rotatable polyhedrons 4 and 14 and the central axis of the shaft 40 are on the same straight line. Furthermore, the shaft 40 protrudes towards the optical housing 9, and the optical housing 9 has a hole 91 as a mounting portion into which the shaft 40 is fitted. The base plate 51 of the motor 5 has fastening holes 54a and 54b for attaching the motor 5 to the optical housing 9.

[0058] Will use Figure 10 Describe the relationship between the hole 91 and the shaft 40 of the optical box 9. Figure 10 In part (a), the positional relationship between the shaft 40 and the hole 91 of the rotatable polyhedron 14 with five surfaces is shown, and... Figure 10 In section (b), the positional relationship between the shaft 40 and the hole 91 of the rotatable multifaceted mirror 14 with four surfaces is shown. Enlarged views of the vicinity of the hole 91 are shown on its right side. The optical box 9 includes multiple (two in embodiment 1) mounting parts (circular holes 91a and 91b) assembled to the shaft 40 at different locations in a plane perpendicular to the axial direction of the shaft 40.

[0059] Hole 91 has a double-circular shape formed by two connected circular holes, specifically hole 91a as another assembly part (second assembly part) and hole 91b as an assembly part (first assembly part). That is, holes 91a and 91b have arcuate shapes, and the arcuate shapes of holes 91a and 91b connect to form a single hole portion. Incidentally, the plane perpendicular to the axial direction of shaft 40 corresponds to the bottom surface of the optical box 9. When assembling a motor 5 equipped with a rotatable polyhedron 14 having five surfaces, the motor 5 is positioned by assembling hole 91a and shaft 40, and then fastened with screws. On the other hand, when assembling a motor 5 equipped with a rotatable polyhedron 4 having four surfaces, the motor 5 is positioned by assembling hole 91b and shaft 40, and then fastened with screws.

[0060] exist Figure 11The arrangement of circular holes 91a and 91b is shown in enlarged view. Circular hole 91a includes an arcuate portion 91c, and circular hole 91b includes an arcuate portion 91d. One end of the arcuate portion 91c of circular hole 91a and one end of the arcuate portion 91d of circular hole 91b are connected at a connecting portion 91e, and the other end of the arcuate portion 91c of circular hole 91a and the other end of the arcuate portion 91d of circular hole 91b are connected at a connecting portion 91f.

[0061] The imaginary line L3 (dashed line) connecting the center Ca of circular hole 91a and the center Cb of circular hole 91b is set at an angle of approximately 37.5° relative to the x-axis. That is, the angle of inclination of the imaginary line L3 is... Figure 7 The tilt of the normal direction (vertical direction) of the reflecting surfaces S1 and S2 in part (b). Incidentally, as Figure 7 As shown, the center Cb of the circular hole 91b is the origin (0, 0) of the xy coordinate system. The distance L4 between the center Ca of the circular hole 91a and the center Cb of the circular hole 91b is approximately 1.02 mm.

[0062] The laser beam emitted from the semiconductor laser unit 1 to the rotatable multifaceted mirrors 4 and 14 is defined as the incident beam (incident laser beam), and the laser beam that is scanned toward the photosensitive drum 103 after being reflected by the rotatable multifaceted mirrors 4 and 14 is defined as the reflected beam. Then, the angle of the imaginary line L3 connecting the center Ca of the circular aperture 91a and the center Cb of the circular aperture 91b is approximately the same as the angle bisector between the incident beam and the reflected beam that is scanned toward the center position 113c of the image assurance region 113 (see...). Figure 7 Part (b)).

[0063] Furthermore, the difference (=L2-L1) between the distance L4 between the circular holes 91a and 91b and the distance L1 from the rotation axis 4c of the rotatable polyhedron 4 with four surfaces to the reflecting surface S1 and the distance L2 from the rotation axis 14c of the rotatable polyhedron 14 with five surfaces to the reflecting surface S2 is approximately the same (see [reference]). Figure 6 In Example 1, the difference between distance L2 and distance L1 is 8.09mm - 7.07mm = 1.02mm.

[0064] Imaginary line 92 (double-dotted line) represents the incident beam and the direction towards the start position 113. L The bisecting line between the reflected beams during scanning, and imaginary line 93 represents the incident beam and the line bisector towards the end of the write position 113. R The bisector of the reflected beams during scanning. Specifically, for the imaginary line 92, its angle with respect to the x-axis is 52.6°, which is consistent with... Figure 7The angles (52.6°) of the normal directions of the reflecting surfaces S1 and S2 described in part (a) are approximately the same. For the imaginary line 93, its angle relative to the x-axis is 22.4°, which is consistent with... Figure 7 The angles (22.4°) of the normal directions of the reflecting surfaces S1 and S2 described in part (c) are approximately the same.

[0065] In Embodiment 1, between the rotatable multifaceted mirror 4 with four surfaces and the rotatable multifaceted mirror 14 with five surfaces, the reflection points 41 and 42 when scanning the image protection area 113 of the photosensitive drum 103 are approximately coincident. Therefore, with the center Cb of the circular aperture 91b as a reference, the position of the center Ca of the circular aperture 91a is preferably located in the region 94 between the imaginary line 92 and the imaginary line 93. Figure 11 (in the double-headed arrow). Region 94 is the region separated by imaginary lines 92 and 93, which rotates from imaginary line 92 to imaginary line 93 along the rotation direction of the rotatable multifaceted mirror 4, that is, the region on the acute angle side in Embodiment 1.

[0066] [Variation Example]

[0067] In Embodiment 1, it is constructed as a double circular shape with two circular holes 91a and 91b connected. However, as long as the distance L1 between the rotation axes 4c and 14c of the rotatable multifaceted mirrors 4 and 14 at the two positions is large enough relative to the diameter of the axis 40, it can be constructed as a shape in which two circular holes are set independently at the two positions.

[0068] Figure 13 Part (a) is a view showing a circular hole 120a provided on the optical box 9 and a circular hole 120b independent of the circular hole 120a. The circular hole 120b, as a first assembly part, and the circular hole 120a, as a second assembly part, each have an independent circular shape. The diameter of the circular shape of the circular holes 120a and 120b is smaller than the distance between the center of the circular shape of the circular hole 120a and the center of the circular shape of the circular hole 120b. Incidentally, in Figure 13 Above part (a), a rotatable polyhedron 4 with four surfaces, a rotatable polyhedron 14 with five surfaces, rotation axes 4c and 14c, and distance L1 are shown.

[0069] Circular hole 120a is a hole in which a shaft 40 having five surfaces is fitted, and circular hole 120b is a hole in which a shaft 40 having four surfaces is fitted. (As in...) Figure 13 As shown in part (a), when the distance L1 is greater than the diameter of the shaft 40 (in other words, the diameters of the circular holes 120a and 120b), it is possible to construct two independent circular holes 120a and 120b. Incidentally, Figure 13Part (b) shows the circular holes 91a and 91b in the above embodiment 1.

[0070] In Embodiment 1, it is assumed that the motor 5 is fastened to the optical box 9 using screws or the like. To allow the motor 5 equipped with rotatable facets 4 and 14 to be assembled at multiple locations, the fastening holes 54a and 54b provided on the substrate 51 are sized to be sufficiently large relative to the screw diameter. In Embodiment 1, examples of rotatable facets 4 with four surfaces and rotatable facets 14 with five surfaces are described; however, the scope of the invention is not limited to this in terms of the number of surfaces of the rotatable facets.

[0071] Furthermore, the rotational speed of each rotatable polyhedron can differ. In this case, the motor circuit design can be optimized by adjusting the windings, control resistors, etc., to achieve the best rotational characteristics. Alternatively, as long as the rotational characteristics meet the specifications of each rotatable polyhedron, the configuration can differ only in the rotational speed.

[0072] Furthermore, in this invention, an example is described where the diameters of the circumscribed circles of each of the rotatable polyhedrons are the same; however, the diameters of the circumscribed circles may be different.

[0073] As described above, by providing multiple attachment positions for each motor equipped with a rotatable facet with a different number of surfaces to be attached to the optical housing, multiple rotatable facets with different numbers of surfaces can be assembled into a common scanning optical device. That is, in Embodiment 1, the configuration is such that the deflector includes a coaxial portion positioned coaxially with the rotation axis of the rotatable facet, and the optical housing includes multiple assembly portions assembled to the coaxial portion of the deflector at different positions in a plane perpendicular to the axial direction of the coaxial portion of the deflector. Furthermore, among the circular holes 91a and 91b that are the multiple assembly portions, with reference to circular hole 91b, the position of circular hole 91a is set in a region 94 surrounded by imaginary lines 92 and 93. Thus, equipment investment can be minimized as much as possible, various types of scanning optical devices can be realized at low cost, and an inexpensive image forming device can be provided.

[0074] As described above, according to Embodiment 1, scanning optical devices corresponding to various printing speeds can be realized at low cost by minimizing equipment investment as much as possible.

[0075] [Example 2]

[0076] Next, we will use Figure 12The construction of the scanning optical device 101 according to Embodiment 2 of the present invention is described. Incidentally, the same reference numerals are used for the construction as described in Embodiment 1, and their description will be omitted. Since the overall construction and optical system of the scanning optical device 101 in Embodiment 2 are the same as those in Embodiment 1, repeated descriptions will be omitted.

[0077] The difference between Embodiment 2 and Embodiment 1 is that the hole 95 provided on the optical box 9 is constructed into an elongated hole shape, wherein the two semicircular shapes of the arcuate portions 95a and 95b are connected by straight portions 95c and 95d that are tangent to them. The optical box 9 includes the hole 95 as a point-symmetric hole-shaped portion, which restricts at least one direction in a plane (the bottom surface of the optical box 9) perpendicular to the axial direction of the axis 40, but does not restrict another direction in the plane perpendicular to said one direction. In Embodiment 2, the restricted direction is defined as the width direction 97, and the unrestricted direction is defined as the longitudinal direction 96.

[0078] More specifically, the arc portion 95a, as the second arc portion, is an arc portion on the other end side in the longitudinal direction 96, and is a semi-circular arc centered at point Cc (also called center Cc). The arc portion 95b, as the first arc portion, is an arc portion on one end side in the longitudinal direction 96, and is a semi-circular arc centered at point Cd (also called center Cd). The straight portion 95c, as the first straight portion, connects one end of the arc portion 95a and one end of the arc portion 95b. The straight portion 95d, as the second straight portion, connects the other end of the arc portion 95a and the other end of the arc portion 95b. Thus, the hole 95 is formed into an elongated hole shape.

[0079] The hole 95 has a point-symmetric shape with respect to point Ce. In the longitudinal direction 96 of the hole 95, the shaft 40 of the motor 5 can be assembled at any position between the semi-circular arc portions 95a and 95b at two locations. On the other hand, in the width direction 97 of the hole 95, the shaft 40 of the motor 5 is configured to be fitted into the hole 95 for positioning.

[0080] When assembling the rotatable polyfacet 14 with five surfaces into the optical box 9, the shaft 40 can be pushed towards and abut against the semi-circular arc portion 95a, and the motor 5 can be fastened to the optical box 9 by screws or the like. Conversely, when assembling the rotatable polyfacet 4 with four surfaces into the optical box 9, the shaft 40 can be pushed towards and abut against the semi-circular arc portion 95b, and the motor 5 can be fastened to the optical box 9 by screws or the like. In this way, the shaft 40 abuts against either side of the hole portion 95.

[0081] The distance L5 between the center Cc of the semicircular arc portion 95a and the center Cd of the arc portion 95b at the two locations is also set to the same length as in Embodiment 1. That is, it is set to the same length as the difference (1.02 mm) between the distance L1 from the rotation axis 4c of the rotatable polyfacet 4 with four surfaces to the reflecting surface S1 and the distance L2 from the rotation axis 14c of the rotatable polyfacet 14 with five surfaces to the reflecting surface S2.

[0082] As in Embodiment 1, the longitudinal direction 96 of the aperture 95 is set to the same angle (e.g., 52.6°) as the bisector of the angle between the incident beam and the reflected beam when scanning at the center position 113c of the image assurance region 113. That is, the longitudinal direction 96 is the direction of the imaginary line L3.

[0083] Similarly, in Embodiment 2, when scanning the image protection area 113 of the photosensitive drum 103 between the rotatable facet 4 with four surfaces and the rotatable facet 14 with five surfaces, the reflection points 41 and 42 are preferably made to approximately coincide. Therefore, with the center Cd of the arc portion 95b as a reference, the longitudinal direction 96 of the hole 95 is preferably located between the angle 98 formed by the imaginary line 92 (first bisector) and the imaginary line 93 (second bisector). In Embodiment 2, with the center Cd as the intersection of the imaginary lines 92 and 93 as a reference, its construction is as follows. That is, the longitudinal direction 96 of the hole 95 is the direction of the imaginary line L3 connecting the center Cd and the center Cc, and the center Cc is a point located in the region (angle 98) between the imaginary lines 92 and 93 in the rotation direction of the rotatable facet. The angle 98 between imaginary lines 92 and 93 refers to the angle from imaginary line 92 to imaginary line 93 in the rotation direction of the rotatable multifaceted mirror 4, and is also present in embodiment 2. Figure 12 The acute angle side in the middle.

[0084] Furthermore, since the rotatable facet can be assembled at any position between the longitudinal directions 96 of the aperture 95, it can be assembled not only at the contact position between the longitudinal directions 96, but also at a third or fourth position. Specifically, the rotatable facet can be assembled when the predetermined axis 40 and the arc portion 95a of the rotatable facet are not in contact. Additionally, the rotatable facet can be assembled when the predetermined axis 40 and the arc portion 95b of the rotatable facet are not in contact. Therefore, not only can rotatable facets with four surfaces or five surfaces be assembled into a common scanning optical device, but rotatable facets with different numbers of surfaces or circumscribed circles can also be assembled into a common scanning optical device.

[0085] In addition, in embodiment 2, the hole 95 is constructed as an elongated hole; however, the shape of the hole can be any shape, as long as the hole is elongated in the other direction (longitudinal direction 96) relative to one direction (i.e., the width direction 97) and has a point-symmetric shape such as a rectangle.

[0086] [Variation Example 1]

[0087] Figure 13 Part (d1) is a view showing a variant example. Component 122 includes a hole 122a into which the shaft 40 of a predetermined rotatable polyhedron is fitted. Component 122 is configured to be attached to an optical housing 9. For example, when attaching a rotatable polyhedron 4 having four surfaces, component 122 is attached to the optical housing 9, as... Figure 13 The upper part (d1) is shown in the figure above. Additionally, for example, when attaching a rotatable multifaceted mirror 14 with five surfaces, component 122 is flipped in its longitudinal direction (flipped left and right in the figure) and attached to the optical box 9, as shown. Figure 13 The following diagram shows part (d1). As a result, the positioning of axis 40 becomes more reliable.

[0088] Incidentally, for the optical box 9, it is sufficient that it has a hole and that the shaft 40 can pass through the hole 122a in both cases when the component 122 is flipped left and right. Furthermore, in Figure 13 In part (d1), a component 122 is used in a manner that flips left and right; however, it can be constructed as a separate component with holes respectively corresponding to the positions of the axes 40 of the respective rotatable polyhedrons.

[0089] [Variation Example 2]

[0090] Figure 13 Part (d2) is a view showing a variant example. Component 123 includes an arcuate portion 123a extending along the predetermined axis 40 of the rotatable multifaceted mirror. Component 123 is configured to be attached to the optical housing 9. Here, in Figure 13 Part (c) shows the hole 95 in Embodiment 2 described above. When the shaft 40 of a rotatable polyhedron 4, 14 abuts against the arcuate portions 95b, 95a of the hole 95 for fixation, component 123 can be used. For example, when a rotatable polyhedron 4 having four surfaces abuts against the hole 95, component 123 is attached to the optical housing 9, such as... Figure 13 The upper part (d2) is shown in the figure above. Additionally, for example, when the rotatable multifaceted mirror 14 with five surfaces is brought into contact with the hole 95, the component 123 is flipped in its longitudinal direction (flipped left and right in the figure) and attached to the optical box 9, as shown. Figure 13The figure below shows part (d2). Therefore, the positioning of hole 95 in the longitudinal direction 96 becomes more reliable. Furthermore, in Figure 13 In part (d2), a component 123 is used in a manner that flips left and right; however, it can be constructed as a separate component with the depth of the arc portion corresponding to the position of the axis 40 of each rotatable polyhedron.

[0091] [Variation Example 3]

[0092] Figure 13 Part (e) is a view showing a variant example. The nest 124 includes a hole 124a into which the predetermined shaft 40 of the rotatable multifaceted mirror is fitted. The nest 124 is configured to be fitted into an optical housing 9. For example, when attaching a rotatable multifaceted mirror 4 having four surfaces, the nest 124 is fitted into the optical housing 9 as follows: Figure 13 The figure above shows part (e). Additionally, for example, when attaching a rotatable multifaceted mirror 14 with five surfaces, the nest 124 is flipped in its longitudinal direction (flipped left and right in the figure) and assembled into the optical box 9, as shown. Figure 13 The figure below shows part (e). As a result, the positioning of axis 40 becomes more reliable.

[0093] Incidentally, it is assumed that the optical box 9 has holes for assembling the nest 124 therein. Furthermore, in Figure 13 In part (e), a nest 124 is used in a manner that flips left and right; however, it can be constructed as a separate nest with holes set to correspond to the positions of the axes 40 of the respective rotatable polyhedrons.

[0094] As described above, by changing the attachment positions of the individual motors equipped with rotatable facets having different numbers of surfaces, multiple rotatable facets with different numbers of surfaces can be assembled into a common scanning optical device. That is, in Embodiment 2, the deflector is also configured to include a coaxial portion coaxially positioned with the rotation axis of the rotatable facet, and the optical housing includes multiple assembly portions assembled to the coaxial portion of the deflector at different positions in a plane perpendicular to the axial direction of the coaxial portion of the deflector. Furthermore, by constructing the holes for attaching the individual motors in a point-symmetric shape, rotatable facets with various numbers of surfaces and diameters can be assembled, and the equipment investment for the scanning optical device can be further reduced.

[0095] As described above, according to Embodiment 2, scanning optical devices corresponding to various printing speeds can be implemented cheaply by minimizing equipment investment as much as possible.

[0096] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be accorded the broadest interpretation so as to cover all such variations and equivalent structures and functions.

Claims

1. A scanning optical device, comprising: light source; A deflector configured to deflect a laser beam emitted from the light source, the deflector including a rotatable multifaceted mirror configured to reflect the laser beam; A scanning lens, configured to focus a laser beam deflected by the rotatable multifaceted mirror onto the surface to be scanned; and An optical box configured to house the light source, the deflector, and the scanning lens. The deflector includes a coaxial portion that is coaxially positioned with respect to the rotation center of the rotatable multifaceted mirror. The optical box includes multiple assembly parts, which are assembled to the coaxial portion at different positions in a plane perpendicular to the axial direction of the coaxial portion. Among the plurality of assembly parts, taking one of the assembly parts as a reference, another of the assembly parts is provided in a region that is a region enclosed in the rotational direction of the rotatable faceted mirror by the bisector between the incident laser beam (which is a laser beam emitted from the light source toward the rotatable faceted mirror) and the laser beam reflected by the rotatable faceted mirror and reaching the write start position of the scanned surface before being incident on the scanning lens, and by the bisector between the incident laser beam and the laser beam reflected by the rotatable faceted mirror and reaching the write end position of the scanned surface before being incident on the scanning lens.

2. The scanning optical device according to claim 1, wherein the plurality of assembly parts are two, and When one of the assembly parts is a first assembly part and the other of the assembly parts is a second assembly part, the optical box can be assembled with either a first rotatable polyhedron or a second rotatable polyhedron that has a different number of reflective surfaces than the first rotatable polyhedron. The coaxial portion is assembled into the first assembly portion when it is coaxially positioned with the first rotatable multifaceted mirror, and the coaxial portion is assembled into the second assembly portion when it is coaxially positioned with the second rotatable multifaceted mirror.

3. The scanning optical device according to claim 2, wherein the first assembly portion and the second assembly portion have an arc shape, and A hole is formed by connecting the arc shape of the first assembly part and the arc shape of the second assembly part.

4. The scanning optical device according to claim 2, wherein the first assembly portion and the second assembly portion have a circular shape, and The diameter of the circular shape of the first assembly part and the second assembly part is smaller than the distance between the center of the circular shape of the first assembly part and the center of the circular shape of the second assembly part.

5. A scanning optical device, comprising: light source; A deflector configured to deflect a laser beam emitted from the light source, the deflector including a rotatable multifaceted mirror configured to reflect the laser beam; A scanning lens, configured to focus a laser beam deflected by the rotatable multifaceted mirror onto the surface to be scanned; and An optical box configured to house the light source, the deflector, and the scanning lens. The deflector includes a coaxial portion that is coaxially positioned with respect to the rotation center of the rotatable multifaceted mirror. The optical box includes a point-symmetric aperture-shaped portion configured to restrict at least one direction in a plane perpendicular to the axial direction of the coaxial portion, but not restricting another direction in the plane perpendicular to said one direction. Wherein, when the intersection of the first bisector between the incident laser beam emitted from the light source toward the rotatable mirror and the laser beam reflected by the rotatable mirror and reaching the write start position of the scanned surface before being incident on the scanning lens, and the second bisector between the incident laser beam and the laser beam reflected by the rotatable mirror and reaching the write end position of the scanned surface before being incident on the scanning lens, is defined as a reference, the longitudinal direction of the aperture-shaped portion is the direction of an imaginary line connecting the intersection point and the point located in the region from the first bisector to the second bisector in the rotation direction of the rotatable mirror.

6. The scanning optical device according to claim 5, wherein the coaxial portion is assembled by abutting against one side of the aperture-shaped portion in the longitudinal direction.

7. The scanning optical device according to claim 6, wherein when the other direction is the longitudinal direction, the aperture shape portion includes a first arcuate portion at one end in the longitudinal direction, a second arcuate portion at the other end in the longitudinal direction, a first straight portion connecting the first arcuate portion and the second arcuate portion at one end in one direction, and a second straight portion connecting the first arcuate portion and the second arcuate portion at the other end in one direction, and The optical box can be assembled with either a first rotatable polyhedron or a second rotatable polyhedron that has a different number of reflective surfaces than the first rotatable polyhedron. The coaxial portion is assembled into the first arc portion when it is coaxially positioned with the first rotatable multifaceted mirror, and the coaxial portion is assembled into the second arc portion when it is coaxially positioned with the second rotatable multifaceted mirror.

8. An electrophotographic image forming apparatus, comprising: An image carrier component, the image carrier component including a scanned surface; According to claim 1, the scanning optical device is configured to scan the image-carrying component with a laser beam based on image information; and An image forming apparatus configured to transfer an image onto a recording material and form an image on the recording material after developing an electrostatic latent image formed on an image carrier member based on image information.

Images