Image forming apparatus

Abstract

The present disclosure relates to an image forming apparatus. The image forming apparatus includes a plurality of photosensitive members, a scanner unit including a light source, a rotatable polygon mirror, and a reflection member, and a fixing portion. A part of a laser beam emitted from the light source is reflected by the rotatable polygon mirror toward a fixing device side, and a remaining part of the laser beam is reflected by the rotatable polygon mirror toward a side opposite to the fixing device side. Among the part of the laser beam reflected by the rotatable polygon mirror toward the fixing device side, a laser beam reflected toward the reflection member provided at a position farthest from the rotatable polygon mirror travels downward with respect to a horizontal direction. A rotation axis of the rotatable polygon mirror is inclined with respect to a vertical direction.

Description

[0001] This application is a divisional application of the patent application with application number 201910920493.3, titled "Image forming apparatus", filed on September 27, 2019. TECHNICAL FIELD

[0002] The present application relates to an image forming apparatus using electrophotography, such as a copier or a laser beam printer. BACKGROUND

[0003] As an image forming apparatus using electrophotography, an image forming apparatus in which photosensitive members and developing devices corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K) are arranged substantially in a line is known. The image forming apparatus disclosed in Japanese Patent Application Publication No. JP 2011-112705 A is provided with cartridges 151Y, 151M, 151C, and 151K for the associated colors of Y, M, C, and K, respectively, each of which assembles the photosensitive member and the developing device integrally as a unit as shown in Figure 5 . Above these cartridges 151Y, 151M, 151C, and 151K, a single optical scanning device 152 for irradiating the respective photosensitive members with a light beam is provided. The recording material by the fixing device 155 as an image heating portion is discharged onto a stack tray 156.

[0004] Further, in the image forming apparatus shown in Figure 8 , the optical scanning device 152 is configured in the following manner. The optical scanning device 152 deflects the light beam from a light source by a single deflector 153 so that the photosensitive members of the cartridges 151Y, 151M, 151C, and 151K are scanned with the light beam by a plurality of deflection (reflection) mirrors 154Y, 154M, 154C, and 154K. Further, in the image forming apparatus, a stack tray 156 for stacking the recording material discharged thereon by the fixing device 155 as an image heating portion is provided above the optical scanning device 152.

[0005] The image forming apparatus disclosed in JP 2005-91966 A is provided with a single optical scanning device 162 for irradiating a plurality of photosensitive members 161Y, 161M, 161C, and 161K juxtaposed, in which the light beam is provided below the photosensitive members as shown in Figure 6The optical scanning device 162 deflects a light beam from a light source by a single reflector 163 so that the light beam scans the photosensitive members 161Y, 161M, 161C, and 161K by a plurality of deflection mirrors 164Y, 164M, 164C, and 164K. In addition, in the image forming apparatus, a stack tray 166 for stacking recording materials passed through a fixing device 165 as an image heating portion and discharged thereon is provided at an upper portion of the image forming apparatus.

[0006] The image forming apparatus disclosed in JP 2006-30912A is provided with a single optical scanning device 172 for irradiating a plurality of photosensitive members 171Y, 171M, 171C, and 171K juxtaposed, the light beam being provided above the photosensitive members, as shown in Figure 7 The optical scanning device 172 deflects a light beam from a light source by a single reflector 173 so that the light beam scans the photosensitive members 171Y, 171M, 171C, and 171K by a plurality of deflection mirrors 174Y, 174M, 174C, and 174K. In addition, in the image forming apparatus, a stack tray 176 for stacking recording materials passed through a fixing device 175 as an image heating portion and discharged thereon is provided above the optical scanning device 172.

[0007] However, in the above-described image forming apparatuses disclosed in JP 2011-112705A, JP 2005-91966A, and JP 2006-30912A, in order to facilitate the optical scanning device, there arises a problem of making the height of the main assembly of the image forming apparatus large.

[0008] In particular, the optical scanning device of the JP 2011-112705A and JP 2006-30912A type is required to be provided with a deflection (reflection) mirror above the photosensitive member closest to the color (yellow in JP 2011-112705A) of the fixing device as the image heating portion. In that case, when a stack tray having an inclined surface so as to be low at the image heating portion side is provided to avoid the deflection mirror, it is necessary to increase the height of the main assembly of the image forming apparatus.

[0009] Therefore, it is a main object of the present application to provide an image forming apparatus in which an internal space thereof is effectively utilized. SUMMARY

[0010] According to an aspect of the present application, there is provided an image forming apparatus including: a plurality of photosensitive members; a scanner unit configured to scan the photosensitive members with laser beams according to image information, wherein the scanner unit includes light sources corresponding to the photosensitive members, respectively, a rotatable polygon mirror configured to reflect and deflect the laser beams emitted from the light sources, and a plurality of reflecting members configured to reflect the laser beams reflected by the rotatable polygon mirror, respectively; and a fixing part configured to fix toner images formed on the photosensitive members and then superimposed on a recording material on the recording material, wherein a portion of the laser beams emitted from the light sources is reflected by the rotatable polygon mirror toward a side on which a fixing device is provided, and a remaining portion of the laser beams is reflected by the rotatable polygon mirror toward a side opposite to the side on which the fixing device is provided, wherein, among the portion of the laser beams reflected by the rotatable polygon mirror toward the side on which the fixing device is provided, the laser beams reflected toward a reflecting member provided at a position farthest from the rotatable polygon mirror travel downward with respect to a horizontal direction, and wherein a rotation axis of the rotatable polygon mirror is inclined with respect to a vertical direction.

[0011] According to another aspect of the present application, there is provided an image forming apparatus including: a plurality of photosensitive members; a scanner unit configured to scan the photosensitive members with laser beams according to image information, wherein the scanner unit includes light sources corresponding to the photosensitive members, respectively, a rotatable polygon mirror configured to reflect and deflect the laser beams emitted from the light sources, and a plurality of reflecting members configured to reflect the laser beams reflected by the rotatable polygon mirror, respectively; and a fixing part configured to fix toner images formed on the photosensitive members and then superimposed on a recording material on the recording material, wherein a portion of the laser beams emitted from the light sources is reflected by the rotatable polygon mirror toward a side on which a fixing device is provided, and a remaining portion of the laser beams is reflected by the rotatable polygon mirror toward a side opposite to the side on which the fixing device is provided, wherein, among the portion of the laser beams reflected by the rotatable polygon mirror toward the side on which the fixing device is provided, the laser beams reflected toward a reflecting member provided at a position farthest from the rotatable polygon mirror travel downward with respect to an arrangement direction of the photosensitive members, and wherein a rotation axis of the rotatable polygon mirror is inclined with respect to a direction perpendicular to the arrangement direction of the photosensitive members.

[0012] Other features of the present application will become apparent from the following description of example embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a sectional view showing an image forming apparatus according to Embodiment 1.

[0014] Figure 2 is a sectional view of an optical scanning apparatus according to Embodiment 1.

[0015] Figure 3is a cross-sectional view of an optical system according to Embodiment 1 toward a polygon mirror of an optical scanning device.

[0016] Figure 4 is a schematic cross-sectional view of an optical scanning device according to Embodiment 1.

[0017] Figure 5 is a cross-sectional view for illustrating a conventional image forming apparatus.

[0018] Figure 6 is a cross-sectional view for illustrating a conventional image forming apparatus.

[0019] Figure 7 is a cross-sectional view for illustrating a conventional image forming apparatus.

[0020] Figure 8 is a cross-sectional view for illustrating a conventional image forming apparatus. DETAILED DESCRIPTION

[0021] Embodiments of the present application will be specifically described with reference to the accompanying drawings. The size, material, shape, and relative arrangement of the constituent elements described in the following embodiments should be appropriately changed depending on the structure and various conditions of the device to which the present application is applied. Thus, the scope of the present application is not intended to be limited to the following embodiments unless otherwise specified.

[0022] [Embodiment 1]

[0023] (image forming apparatus)

[0024] Reference Figure 1 An image forming apparatus according to Embodiment 1 will be described. Figure 1 is a cross-sectional view showing a laser beam printer as the image forming apparatus 100 of this embodiment. Hereinafter, the general structure and functions of the laser beam printer will be described. In the following description, with respect to the image forming apparatus 100, the front side is the side on which the process cartridge PK is provided. The rear side is the side on which the process cartridge PY is provided. The front-rear direction includes a direction from the rear side of the image forming apparatus toward the front side (forward direction) and a direction opposite to the forward direction (rearward direction).

[0025] Inside the image forming apparatus 100, the first to fourth (four) portions PY, PM, PC, and PK are arranged and disposed in a horizontal direction (in-line configuration, tandem type) from the front side toward the rear side. The four process cartridges in this embodiment have a configuration in which process cartridges corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors are arranged in this order from the rear side toward the front side. Each process cartridge in this embodiment is prepared by integrally assembling a photosensitive drum 11 as a photosensitive member (image bearing member) and a developing roller 12 as a process member that can act on the drum as a unit. In addition, each process cartridge also functions as a cartridge that accommodates toner. Among the four process cartridges, the color of the toner accommodated in the process cartridge PK disposed at a position farthest from the fixing device 30 as an image heating portion is black. Among the four process cartridges, the toner volume of the process cartridge PK corresponding to black disposed at the most front side is greater than the toner volumes of the process cartridges PY, PM, and PC corresponding to the other three colors.

[0026] Incidentally, here, as the cartridges, process cartridges integrally including a photosensitive member, a process member that can act on the photosensitive member, and a cartridge that accommodates toner are described as examples, but the present application is not limited to this. For example, a configuration in which a cartridge that accommodates toner is provided separately from a process cartridge that integrally includes a photosensitive member and a process member that can act on the photosensitive member can also be employed.

[0027] Above these process cartridges PY, PM, PC, and PK, an optical scanning device 2 as an optical scanning portion is provided. The optical scanning device 2 scans the surface (surface to be scanned) of the photosensitive drum of each process cartridge with a light beam, thereby forming an electrostatic latent image. In each process cartridge, the electrostatic latent image formed on the photosensitive drum is developed by the developing roller 12, thereby forming a toner image on the photosensitive drum.

[0028] Below the process cartridges PY, PM, PC, and PK, an intermediate transfer belt unit 20 is provided. The intermediate transfer belt unit 20 includes an intermediate transfer belt 21, which is a loop-shaped belt, and a plurality of stretching rollers, which are composed of a driving roller 22, a tension roller 23, and a driven roller 24. The intermediate transfer belt 21 is stretched by the driving roller 22, the tension roller 23, and the driven roller 24, and is rotated in a direction indicated by an arrow in FIG. 1. Figure 1Rotate in the direction of the arrow in the image. The photosensitive drum 11 of the processing cartridge contacts the upper surface of the intermediate transfer belt 21. Inside the intermediate transfer belt 21, four primary transfer rollers 25 are provided opposite to the photosensitive drum 11 of the processing cartridge. The primary transfer rollers 25 (25a, 25b, 25c, 25d) successively transfer the toner image from the opposite photosensitive drums 11 (11a, 11b, 11c, 11d) onto the intermediate transfer belt 21 in a superimposed manner. Towards the drive roller 22, the secondary transfer roller 26 contacts the intermediate transfer rollers 21. The secondary transfer roller 26 transfers the toner image from the intermediate transfer belt 21 onto the recording material.

[0029] Inside the rear image forming apparatus, at its upper part, there is a fixing device 30, which serves as an image heating section for heating an image formed on the recording material, and an ejection device 40, which serves as an ejection section. On the upper surface of the image forming apparatus, there is a stacking tray 50 for stacking the recording material on which the image is formed. The fixing device 30 uses a fixing device including a fixing film 31 and a pressing roller 32. The ejection device 40 includes ejection rollers 41 and 42, and ejects the recording material passing through the fixing device 30 toward the stacking tray 50. The stacking tray 50 is positioned above the optical scanning device 2.

[0030] The sheet S of recording material, which is stacked in the feed tray 61 of the feed device 60, is made of... Figure 1 Feeding is performed by a feed roller 62 rotating in the direction of the arrow, and the multi-feed sheet is separated and fed by a separating roller 63. The sheet S is then fed into the gap between the drive roller 22 and the secondary transfer roller 26, and the toner image formed on the intermediate transfer belt 21 is transferred onto the sheet S fed into the gap between the drive roller 22 and the secondary transfer roller 26. Additionally, the sheet S with the toner image transferred onto it is fed into the gap between the fixing film 31 and the pressing roller 32, where it is heated and pressed, fixing the toner image onto the sheet S. The sheet S with the toner image fixed onto it is discharged onto the discharge tray 50 via discharge rollers 41 and 42.

[0031] Here, in the image forming apparatus, the processing cartridges PY, PM, PC, and PK are basically arranged in a row. However, because the processing cartridge PK, which is used for black among the four colors, is also used for monochrome printing, the amount of black toner used is greater than the amount of the other three colors used. Therefore, in order to reduce the frequency of processing cartridge replacement while miniaturizing the image forming apparatus, it is effective to make the volume of black toner larger than the volume of the toners for the other colors.

[0032] The replacement of the process cartridge is performed by opening the front cover 90 by a rotational movement thereof as indicated by arrow Rl, and then pulling out the process cartridge toward the front side of the main assembly of the image forming apparatus (in the direction of arrow U). Therefore, the volume and height of the process cartridge PK, which are larger than those of the other process cartridges, can be effectively utilized for the internal space, and the size of the image forming apparatus can be reduced when the process cartridge PK is at the front-most side of the main assembly (when pulled out).

[0033] Further, as described above, the stacking tray 50 is provided at the upper portion of the optical scanning device 2. The stacking tray 50 is inclined downward with respect to the horizontal surface toward the fixing device 30 so as to improve the positioning and orientation characteristics of the discharged sheet. The optical scanning device 2 is inclinedly provided in the direction in which the inclined surface 51 of the stacking tray 50 extends on the rear side upper portion 13 of the optical scanning device 2. By providing the stacking tray 50 in this way, the internal space of the image forming apparatus on the side below the stacking tray 50 is effectively utilized, so that the height of the image forming apparatus can be suppressed to a low level.

[0034] Further, the stacking tray 50 provided above the optical scanning device 2 is formed in the following shape.

[0035] The stacking tray 50 has an inclined surface 51 inclined downward between the mirror 10c as the first reflecting member and the polygon mirror 4 as the rotatable polygon mirror, which are included in the optical scanning device 2, as shown in Figure 2 The stacking tray 50 has a flat surface 52 extending in the horizontal direction from between the mirror 10c (first reflecting member) and the polygon mirror 4 (rotatable polygon mirror) toward the side away from the fixing device 30. The inclined surface 51 has a configuration in which the recording material slides (moves) toward the discharge roller side so as to establish the positioning and orientation among the discharged recording material and stack the recording material on the stacking tray 50, and in which the end portion of the recording material is thus positioned and oriented by the wall of the image forming apparatus. Incidentally, in this embodiment, the flat surface 52 of the stacking tray 50 is provided on the front side of the image forming apparatus, but the present application is not limited to this, and the surface of the stacking tray 50 on the front side can also be a moderately curved surface.

[0036] Further, the stacking tray 50 has the inclined surface 51 directly above the rotation center of the photosensitive drum 11a closest to the fixing device 30. The stacking tray 50 has the flat surface 52 directly above the rotation center of the photosensitive drum 11d farthest from the fixing device 30. As Figure 4As shown, the intersection 53 of the inclined surface 51 and the flat surface 52 of the stacking tray 50, where they intersect each other, is positioned relative to the horizontal direction between the rotation centers of the two photosensitive drums 11b and 11c near the polygon mirror 4 (rotatable polygon mirror). Figure 4 In the diagram, the vertical line from the rotation center of one photosensitive drum 11b near the polygon mirror 4 is represented by X2, and the vertical line from the rotation center of the other photosensitive drum 11c near the polygon mirror 4 is represented by X3. The intersection 53 of the inclined surface 51 and the flat surface 52 of the stacking tray 50, where they intersect each other, is located between the vertical lines X2 and X3.

[0037] The height relationship relative to the vertical direction between the recording material stacking surface of the stacking tray 50 and the discharge opening 43 through which the recording material is discharged onto the stacking tray 50 is as follows. The stacking tray 50 includes an inclined surface 51 and a flat surface 52 as the recording material stacking surface. Figure 4 As shown, the first intersection point between the vertical line X2 passing through the rotation center of the photosensitive drum 11a closest to the fixing device 30 and the stacking tray 50 (inclined surface 51) is the first position 51a. The second intersection point between the vertical line X3 passing through the rotation center of the photosensitive drum 11d furthest from the fixing device 30 and the stacking tray 50 (flat surface 52) is the second position 52a. The shape of the stacking tray 50 is such that the height relationship between the discharge opening 43, the first position 51a of the stacking tray 50, and the second position 52a of the stacking tray 50 satisfies: (first position 51a of the stacking tray 50) < (discharge opening 43) < (second position 52a of the stacking tray 50).

[0038] Furthermore, light beams L1, L2, L3, and L4 emitted from the optical scanning device 2 and incident on the photosensitive drums 11a, 11b, 11c, and 11d are incident obliquely on the respective photosensitive drums from the side opposite to the fixing device 30, relative to the vertical direction of the image forming apparatus. Therefore, compared to the case where the light beams are incident on the photosensitive drums in a vertical direction, the optical scanning device 2 can be positioned in front of the image forming apparatus, thus avoiding interference between the upper rear part 13 of the optical scanning device 2 and the inclined surface 51 of the stacking tray 50, thereby suppressing the height of the image forming apparatus to a low level. In this embodiment, the light beams are incident on the photosensitive drums at an angle of 10° relative to the vertical lines X1, X2, X3, and X4.

[0039] Next, we will refer to Figure 2 and Figure 3 Describe optical scanning device 2. Figure 2 This is a cross-sectional view of the optical scanning device 2 in this embodiment, and a cross-sectional view of the optical scanning system in which a beam deflected by a polygonal mirror is guided to a photosensitive drum. Figure 3is a sectional view of an incident optical system on a polygon mirror of an optical scanning device.

[0040] As Figure 2 shown in FIG. 1, the optical scanning device 2 according to this embodiment is an optical scanning section for scanning a plurality of photosensitive drums with light beams emitted from a plurality of light sources via optical members by a polygon mirror 4 as a rotatable polygon mirror included in a deflector. In Figure 2 the optical scanning device 2 shown in FIG. 1, the optical members shown are a first imaging lens 8 as a first imaging member, a second imaging lens 9 as a second imaging member, and mirrors 10a, 10b, 10c, 10d, 10e, and 10f as reflecting members. The deflector includes the polygon mirror 4 as a rotatable polygon mirror. The optical scanning device 2 includes the deflector including the polygon mirror 4, the imaging lenses 8 and 9, the mirrors 10a-10f, and a frame 2a to which these members are mounted. The deflector including the polygon mirror 4 is mounted on the frame 2a on the upper surface side. In the optical scanning device 2, these optical members are disposed in a bidirectional asymmetric manner between a scan area Al and a scan area A2 with respect to the polygon mirror 4. Here, the scan area Al is a first area on the fixing device 30 side (image heating section side) and is an area through which the light beams LI and L2 incident on the photosensitive drums 11a and 11b pass. The scan area A2 is a second area on the side opposite to the fixing device 30 side (opposite to the image heating section side) and is an area through which the light beams L3 and L4 incident on the photosensitive drums 11c and 11d pass. The optical scanning device 2 deflects the light beams LI, L2, L3, and L4 emitted from the plurality of light sources into the scan area Al on the fixing device 30 side and the scan area A2 on the side opposite to the fixing device 30 in a separated manner by the polygon mirror 4. Among the reflecting members of the optical scanning device 2, the mirror 10c is a first reflecting member disposed at a position farthest from the polygon mirror 4 in the scan area Al as a first area and reflects the light beam LI reflected toward the scan area Al toward the photosensitive drum 11a. In addition, the mirror 10f is a second reflecting member disposed at a position farthest from the polygon mirror 4 in the scan area A2 as a second area and reflects the light beam L4 reflected toward the scan area A2 toward the photosensitive drum 11d.

[0041] The optical scanning device 2 is configured such that the axis of the facet mirror 4 is tilted relative to the vertical direction, such that the image heating portion side is lower than the opposite side of the image heating portion relative to the horizontal line (straight line Y). Here, in the image forming apparatus 100 of this embodiment, the horizontal direction refers to the direction of the straight line Y connecting the rotation centers of the two furthest photosensitive drums 11a and 11d of the four photosensitive drums. Furthermore, the deflector including the facet mirror 4 is positioned near the photosensitive drum 11c relative to the midpoint CH between the two photosensitive drums 11b and 11c. That is, the deflector is positioned relative to the horizontal direction closer to the photosensitive drum 11c on the opposite side of the image heating portion than the photosensitive drum 11b on the image heating portion side, wherein the two photosensitive drums 11b and 11c are also configured to simultaneously sandwich the deflector and be closest to it. Therefore, the facet mirror 4 is tilted relative to the horizontal direction, allowing the optical scanning device 2 to be tilted relative to the horizontal direction in the image forming apparatus. Furthermore, in the horizontal direction, the position of the facet mirror 4 is made closer to the photosensitive drum 11c rather than the photosensitive drum 11b, so that even when the facet mirror 4 is tilted from the horizontal direction, the lengths of the light beams L1, L2, L3, and L4 can remain the same. Incidentally, the midpoint CH is also the midpoint between the rotation centers of the photosensitive drums 11a and 11d. Therefore, passing through... Figure 2 The vertical line XC of the midpoint CH shown is a vertical line equidistant from the vertical line X1 passing through the rotation center of the photosensitive drum 11a and the vertical line X4 passing through the rotation center of the photosensitive drum 11b. Regarding this vertical line XC, the side of vertical line X1 is the image heating portion side, while the side of vertical line X4 is the image heating portion opposite to the side opposite to the image heating portion side.

[0042] In this embodiment, a so-called oblique incident optical system is employed. For example... Figure 3 As shown, the oblique incident optical system is an optical system in which beams L1 and L2 are incident obliquely on a plane D perpendicular to the rotation axis C of the polygon mirror 4. The incident optical system, consisting of the light source portion 3, the collimating lens 5, and the cylindrical lens 6, is arranged perpendicularly to the plane D perpendicular to the rotation axis C, and the beams are incident on the reflecting surface 7 of the polygon mirror 4 at a desired angle θ relative to the plane D perpendicular to the reflecting surface 7, such that these incident optical systems are symmetrical with respect to the plane D. Figure 2 Of the multiple light sources shown, the light source portion 3 on the side above plane D is the first light source, which is tilted at a desired angle θ relative to plane D. A light beam L1 emitted from the upper light source portion 3 is incident on the reflective surface 7 of the polygon mirror 4 from the tilted upper side at an angle θ. The light beam L1 emitted from the upper light source portion 3 from the upper side tilted relative to plane D towards the reflective surface 7 of the polygon mirror 4 is reflected by the reflective surface 7 of the polygon mirror 4... Figure 2the scanning region Al shown in FIG. 1 and reflected toward the upper side tilted with respect to the plane D. Thus, the light beams LI and L2 from the (two) light source portions 3 of the upper and lower sides are made to be incident on the reflecting surface 7 from the tilted upper and lower sides, respectively, whereby the light beams LI and L2 are separable in the upper and lower light paths after being reflected by the mirror 4. Figure 2 the scanning region Al shown in FIG. 1 and reflected toward the upper side tilted with respect to the plane D. Thus, the light beams LI and L2 from the (two) light source portions 3 of the upper and lower sides are made to be incident on the reflecting surface 7 from the tilted upper and lower sides, respectively, whereby the light beams LI and L2 are separable in the upper and lower light paths after being reflected by the mirror 4.

[0043] Incidentally, although Figure 3 the scanning region Al shown in FIG. 1 and reflected toward the upper side tilted with respect to the plane D. Thus, the light beams LI and L2 from the (two) light source portions 3 of the upper and lower sides are made to be incident on the reflecting surface 7 from the tilted upper and lower sides, respectively, whereby the light beams LI and L2 are separable in the upper and lower light paths after being reflected by the mirror 4. Figure 2 the scanning region Al shown in FIG. 1 and reflected toward the upper side tilted with respect to the plane D. Thus, the light beams LI and L2 from the (two) light source portions 3 of the upper and lower sides are made to be incident on the reflecting surface 7 from the tilted upper and lower sides, respectively, whereby the light beams LI and L2 are separable in the upper and lower light paths after being reflected by the mirror 4. Figure 2 the scanning region Al shown in FIG. 1 and reflected toward the upper side tilted with respect to the plane D. Thus, the light beams LI and L2 from the (two) light source portions 3 of the upper and lower sides are made to be incident on the reflecting surface 7 from the tilted upper and lower sides, respectively, whereby the light beams LI and L2 are separable in the upper and lower light paths after being reflected by the mirror 4.

[0044] Next, referring again to Figure 2 The optical scanning device 2 in this embodiment will be described. The light beams LI and L2 assigned to the scanning region Al as the first region and the light beams L3 and L4 assigned to the scanning region A2 as the second region will be described sequentially.

[0045] The light beams incident on the reflecting surface 7 of the mirror 4 are reflected at an angle θ with respect to the plane D perpendicular to the rotation axis C of the mirror 4.

[0046] First, on the scanning region Al side, the two light beams LI and L2 reflected by the reflecting surface 7 are incident on the first imaging lens 8, which is the first imaging member common to the light beams LI and L2.

[0047] Among the light beams from the first imaging lens 8, the outgoing light beam L2 toward the upper side inclined with respect to the plane D perpendicular to the rotation axis C is reflected by the first mirror 10a. Thereafter, the light beam L2 is reflected again by the second mirror 10b and passes through the second imaging lens 9, and then reaches the photosensitive drum lib.

[0048] Among the light beams from the first imaging lens 8, the outgoing light beam Ll toward the lower side inclined with respect to the plane D perpendicular to the rotation axis C passes below the first mirror 10a and is reflected by the third mirror 10c, and then passes through the second imaging lens 9, and then reaches the photosensitive drum 11a. Here, the third mirror 10c of the reflecting members of the optical scanning device 2 is the first reflecting member, which is provided at a position farthest from the polygon mirror 4 in the scanning area Al that is the first area and reflects the light beam Ll toward the photosensitive drum 11a. As described above, the light beam Ll reflected by the reflecting surface 7 of the polygon mirror 4 toward the scanning area Al and the lower side inclined with respect to the plane D is then reflected only by the above-described first reflecting member, the mirror 10c, until the light beam Ll reaches the photosensitive drum 11a.

[0049] The first imaging lens 8 is shared between the light beams Ll and L2, and provides the second imaging lens 9 for each of the light beams Ll and L2.

[0050] On the other hand, on the scanning area A2 side, the two light beams L3 and L4 reflected by the reflecting surface 7 are incident on the first imaging lens 8, which is the first imaging member common to the light beams L3 and L4.

[0051] Among the light beams from the first imaging lens 8, the outgoing light beam L3 toward the lower side inclined with respect to the plane D perpendicular to the rotation axis C is reflected by the fourth mirror 10d. Thereafter, the light beam L3 is reflected again by the fifth mirror 10e and passes through the second imaging lens 9, and then reaches the photosensitive drum lie.

[0052] Among the light beams from the first imaging lens 8, the outgoing light beam L4 toward the upper side inclined with respect to the plane D perpendicular to the rotation axis C passes above the fourth mirror 10d and is reflected by the sixth mirror 10f, and then passes through the second imaging lens 9, and then reaches the photosensitive drum lid. Here, the sixth mirror 10f of the reflecting members of the optical scanning device 2 is the second reflecting member, which is provided at a position farthest from the polygon mirror 4 in the scanning area A2 that is the second area and reflects the light beam L4 toward the photosensitive drum lid. As described above, the light beam L4 reflected by the reflecting surface 7 of the polygon mirror 4 toward the scanning area A2 and the upper side inclined with respect to the plane D is then reflected only by the above-described second reflecting member, the mirror 10f, until the light beam L4 reaches the photosensitive drum lid.

[0053] Similarly to the scanning area Al, on the scanning area A2 side, the first imaging lens 8 is also shared between the light beams L3 and L4, and the second imaging lens 9 is provided for each of the light beams L3 and L4.

[0054] On the scanning area Al side, as described above, the upper light beam L2 with respect to the plane D perpendicular to the rotation axis C is separated from the lower light beam LI by the mirror 10a and is guided to the photosensitive drum lib on the multi-mirror 4 side. In addition, the lower light beam LI with respect to the plane D perpendicular to the rotation axis C is guided to the photosensitive drum 11a on the image heating portion side by the mirror 10c as the first reflecting member. As described above, the mirror 10c as the first reflecting member is provided at a position farthest from the multi-mirror 4 (on the image heating portion side in this embodiment). Therefore, on the scanning area Al side as the image heating portion side, the upper light beam L2 is separated using a mirror at a position close to the multi-mirror 4. Therefore, it is possible to effectively utilize a narrow space between the process cartridge PY and a lower portion of the image heating portion including the stack tray 50 of the inclined surface 51 on the opposite side of the image heating portion, so that the image heating portion side is lower than the opposite side of the image heating portion. Incidentally, the range of a portion below the stack tray 50 on the image heating portion side is an overlapping range between the scanning area Al of the optical scanning device 2 on the image heating portion side with respect to the vertical direction and a region on the vertical line XI side (the image heating portion side) with respect to the vertical line XC.

[0055] On the other hand, on the scanning area A2 side, in contrast to the above case, the lower light beam L3 with respect to the plane D perpendicular to the rotation axis C is separated from the upper light beam L3 by the mirror 10d and is guided to the photosensitive drum lib on the multi-mirror 4 side. In addition, the upper light beam L4 with respect to the plane D perpendicular to the rotation axis C is guided to the photosensitive drum lid on the opposite side of the image heating portion by the mirror 10f as the second reflecting member. The mirror 10f as the second reflecting member is provided at a position farthest from the multi-mirror 4 (on the opposite side of the image heating portion in this embodiment) as described above. Therefore, on the scanning area A2 side as the opposite side of the image heating portion, the lower light beam L3 is separated by the mirror 10d at a position close to the multi-mirror 4. Therefore, it is possible to widely secure a space above the process cartridge Pk on the frontmost side (the opposite side of the image heating portion).

[0056] In addition, as described above, the optical scanning device 2 is provided so that the axis of the multi-mirror 4 is inclined with respect to the vertical direction so that the image heating portion side is lower than the opposite side of the image heating portion. In addition, in the optical scanning device 2, the light beam LI reflected by the reflecting surface 7 of the multi-mirror 4 toward the scanning area Al shown in Fig. 6 and toward the lower side inclined with respect to the plane D is reflected by the mirror 10c toward the photosensitive drum 11a. In addition, in the optical scanning device 2, the light beam L4 reflected by the reflecting surface 7 of the multi-mirror 4 toward the scanning area A2 shown in Fig. 6 and toward the upper side inclined with respect to the plane D is reflected by the mirror 10f toward the photosensitive drum lid on the opposite side of the image heating portion. Figure 2 In addition, as described above, the optical scanning device 2 is provided so that the axis of the multi-mirror 4 is inclined with respect to the vertical direction so that the image heating portion side is lower than the opposite side of the image heating portion. In addition, in the optical scanning device 2, the light beam LI reflected by the reflecting surface 7 of the multi-mirror 4 toward the scanning area Al shown in Fig. 6 and toward the lower side inclined with respect to the plane D is reflected by the mirror 10c toward the photosensitive drum 11a. In addition, in the optical scanning device 2, the light beam L4 reflected by the reflecting surface 7 of the multi-mirror 4 toward the scanning area A2 shown in Fig. 6 and toward the upper side inclined with respect to the plane D is reflected by the mirror 10f toward the photosensitive drum lid on the opposite side of the image heating portion.Figure 2 The light beam L4 that is reflected by the scanning area A2 shown in Figure 2 and is reflected toward the upper side inclined with respect to the plane D is reflected by the mirror 10d toward the photosensitive drum 11d. With this configuration, the optical scanning device 2 can be changed into various shapes that do not have bilateral symmetry with respect to the axis of the polygon mirror 4, so that the shape of the optical scanning device 2 can be formed depending on the housing of the image forming apparatus. Therefore, the space inside the image forming apparatus can be effectively utilized.

[0057] In addition, by adopting the above-described arrangement configuration of the reflecting members of the optical scanning device 2, the distance between the exit opening that is farthest from the fixing device 30 and the photosensitive drum corresponding to that exit opening is longer than the respective distances between the other exit opening and the associated photosensitive drum. The relationship of these distances is shown in Figure 4 shown. Figure 4 is a schematic cross-sectional view of the optical scanning device 2 in this embodiment. As shown in Figure 4 shown, the distance between the exit opening 14d that is farthest from the fixing device 30 and the photosensitive drum 11d corresponding to that exit opening 14d is longer than the distances between the other exit openings 14a, 14b, and 14c and the photosensitive drums 11a, 11b, and 11c, respectively. Specifically, the distance Ld between the exit opening 14d that is farthest from the fixing device 30 and the photosensitive drum 11d corresponding to that farthest exit opening 14d is longer than the distance La between the exit opening 14a that is closest to the fixing device 30 and the photosensitive drum 11a corresponding to the closest exit opening 14a. Incidentally, the relationship between the distances La, Lb, Lc, and Ld between the exit openings 14a, 14b, 14c, and 14d and the corresponding photosensitive drums 11a, 11b, 11c, and 11d is La = Lb = Lc < Ld. In addition, the distance ha from the rotation center of the photosensitive drum 11a that is closest to the fixing device 30 to the stacking tray 50 (inclined surface 51) with respect to the vertical direction is shorter than the distance hd from the rotation center of the photosensitive drum 11d that is farthest from the fixing device 30 to the stacking tray 50 (inclined surface 52) with respect to the vertical direction. Therefore, the space between the lower part of the stacking tray 50 on the image heating part side and the processing cartridge PY that is closest to the fixing device 30 provided on the image heating part side can be effectively utilized. At the same time, the space above the processing cartridge PK on the frontmost side (opposite side of the image heating part) can be widely ensured.

[0058] According to this embodiment, the space between the lower part of the stacking tray on the image heating part side and the processing cartridge that is closest to the fixing device provided on the image heating part side can be effectively utilized. At the same time, the space above the processing cartridge that is farthest from the fixing device provided on the opposite side of the image heating part (in this embodiment, the volume of the black processing cartridge is increased) can also be effectively utilized. Therefore, an image forming apparatus that effectively utilizes the internal space can be realized.

[0059] [Other Embodiments]

[0060] In the above-described embodiments, as an example of a configuration in which the light beam deflected by the deflector scans the photosensitive member with the optical member, a configuration in which the light beam scans the photosensitive member with two imaging lenses is described as an example, but the present application is not limited to this, and a single imaging lens or three or more imaging lenses can also be used. In addition, a configuration of a single mirror or two mirrors is also described as an example, but the present application is not limited to this, and can only need to be appropriately set.

[0061] In the above-described embodiments, as an example, a case in which the distances La, Lb, Lc, and Ld between the exit openings 14a, 14b, 14c, and 14d of the optical scanning device 2 and the corresponding photosensitive drums 11a, 11b, 11c, and 11d are La = Lb = Lc < Ld is described. However, the relationship of the distances La, Lb, Lc, and Ld is not limited to this. Among the distances La, Lb, Lc, and Ld, the distances Lc and Ld can be longer than the distances La and Lb, and the distances Lc and Ld can also be equal to each other. Also with this configuration, as in the above-described embodiments, the space between the lower part of the stack tray on the image heating portion side and the process cartridge provided on the image heating portion side can be effectively utilized. At the same time, the space above the process cartridge on the opposite side of the image heating portion can be widely ensured.

[0062] In the above-described embodiments, four process cartridges are used, but the number of process cartridges used is not limited to this, and can only need to be appropriately set as necessary.

[0063] In addition, in the above-described embodiments, as an example, a configuration in which the process cartridge is supported so as to be installable in and detachable from the support member pulled out from the rear side toward the front side of the image forming apparatus is described, but the present application is not limited to this. A configuration in which the process cartridge is directly installed in and directly detached from the image forming apparatus can also be employed.

[0064] In addition, in the above-described embodiments, as an example, a configuration in which the process cartridge including the photosensitive member, the processing member, and the cartridge containing the toner is installable in and detachable from the image forming apparatus is described, but the present application is not limited to this. For example, an image forming apparatus in which the respective configuration elements such as the photosensitive member, the processing member, and the toner cartridge configuring the cartridge are installable in and detachable from the image forming apparatus can also be employed.

[0065] Further, in the above-described embodiments, as the image forming apparatus, a printer is described as an example, but the present application is not limited thereto. For example, other image forming apparatuses, such as a copier, a facsimile apparatus, or other image forming apparatuses such as a multifunction machine having functions of these machines in combination, can be used. Further, the present application is not limited to the following image forming apparatus in which an intermediate transfer belt is used as an intermediate transfer member and toner images of respective colors are sequentially superimposed and transferred onto the intermediate transfer member and then transferred together onto a recording material. For example, the following image forming apparatus in which a recording material carrying member is used and toner images of respective colors are sequentially superimposed and transferred onto a recording material carried by the recording material carrying member can be used. By applying the present application to these image forming apparatuses, similar effects can be obtained.

[0066] Further, in the above-described embodiments, the horizontal direction is a direction of a straight line Y connecting rotation centers of the photosensitive drums 11a and 11d that are farthest apart from each other among the four photosensitive drums, but the present application can also be applied to an image forming apparatus in which the horizontal direction and the straight line Y are not parallel to each other.

[0067] While the present application has been described with reference to exemplary embodiments, it is to be understood that the application is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all the modifications and equivalent structures and functions.

Claims

1. An image forming apparatus characterized by comprising: The image forming apparatus includes: a plurality of photosensitive members; a scanner unit configured to scan the photosensitive members with laser beams according to image information, wherein the scanner unit includes light sources corresponding to the photosensitive members, respectively, a rotatable polygon mirror configured to reflect and deflect the laser beams emitted from the light sources, a frame configured to support the rotatable polygon mirror, and a plurality of reflection members configured to reflect the laser beams reflected by the rotatable polygon mirror, respectively; a fixing portion configured to fix toner images formed on the photosensitive members and then superimposed on recording materials on recording materials, and a discharge tray for receiving recording materials on which images are formed and discharged from inside the image forming apparatus, wherein the scanner unit is provided between the plurality of photosensitive members and the discharge tray with respect to a vertical direction, wherein the plurality of reflection members include a first reflection member provided at a position farthest from the rotatable polygon mirror toward a side on which the fixing portion is provided, and a second reflection member provided at a position farthest from the rotatable polygon mirror in a direction opposite to a side on which the fixing portion is provided, wherein a part of the laser beams emitted from the light sources is reflected by the rotatable polygon mirror toward the side on which the fixing portion is provided, and a remaining part of the laser beams is reflected by the rotatable polygon mirror toward the side opposite to the side on which the fixing portion is provided, wherein, among the part of the laser beams reflected by the rotatable polygon mirror toward the side on which the fixing portion is provided, the laser beams reflected toward the first reflection member travel downward with respect to a horizontal direction, wherein, among the remaining part of the laser beams, the laser beams reflected toward the second reflection member travel upward with respect to the horizontal direction, wherein a rotation axis of the rotatable polygon mirror is inclined with respect to the vertical direction, wherein, with respect to the vertical direction, the rotatable polygon mirror is located between a region of the frame supporting the rotatable polygon mirror and the plurality of photosensitive members, and wherein an optical path length from the rotatable polygon mirror to the first reflection member is longer than an optical path length from the rotatable polygon mirror to the second reflection member.

2. The image forming apparatus according to claim 1, wherein Optical path lengths from the rotatable polygon mirror to the respective photosensitive members are equal to each other.

3. An image forming apparatus characterized by comprising: The image forming apparatus includes: a plurality of photosensitive members; a scanner unit configured to scan the photosensitive members with laser beams according to image information, wherein the scanner unit includes light sources corresponding to the photosensitive members, respectively, a rotatable polygon mirror configured to reflect and deflect the laser beams emitted from the light sources, a frame configured to support the rotatable polygon mirror, and a plurality of reflection members configured to reflect the laser beams reflected by the rotatable polygon mirror, respectively; a fixing portion configured to fix toner images formed on the photosensitive members and then superimposed on recording materials on recording materials, and a discharge tray for receiving recording materials on which images are formed and discharged from inside the image forming apparatus, wherein the scanner unit is provided between the plurality of photosensitive members and the discharge tray with respect to a vertical direction, wherein the plurality of reflecting members include a first reflecting member provided at a position farthest from the rotatable polygon mirror toward a side on which the fixing portion is provided, and a second reflecting member provided at a position farthest from the rotatable polygon mirror in a direction opposite to the side on which the fixing portion is provided, wherein a part of the laser beam emitted from the light source is reflected by the rotatable polygon mirror toward the side on which the fixing device is provided, and the remaining part of the laser beam is reflected by the rotatable polygon mirror toward the side opposite to the side on which the fixing device is provided, wherein, among the part of the laser beam reflected by the rotatable polygon mirror toward the side on which the fixing device is provided, the laser beam reflected toward the first reflecting member travels downward with respect to an arrangement direction of the photosensitive members, wherein, among the remaining part of the laser beam, the light beam reflected toward the second reflecting member travels upward with respect to the arrangement direction of the photosensitive members, wherein a rotation axis of the rotatable polygon mirror is inclined with respect to a direction perpendicular to the arrangement direction of the photosensitive members, wherein, with respect to the vertical direction, the rotatable polygon mirror is located between a region of the frame supporting the rotatable polygon mirror and the plurality of photosensitive members, and wherein an optical path length from the rotatable polygon mirror to the first reflecting member is longer than an optical path length from the rotatable polygon mirror to the second reflecting member.

4. The image forming apparatus according to claim 3, wherein Optical path lengths from the rotatable polygon mirror to the respective photosensitive members are equal to each other.

Images