JP6138618B2 - Optical scanning device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an optical scanning apparatus that scans an object to be scanned with a light beam, and an image forming apparatus including the optical scanning apparatus.

  For example, in an electrophotographic image forming apparatus, the surface of a photoreceptor (scanned body) is uniformly charged, and then the surface of the photoreceptor is scanned with a light beam to form an electrostatic latent image on the surface of the photoreceptor. The electrostatic latent image on the surface of the photoconductor is developed with toner to form a toner image on the surface of the photoconductor, and the toner image is transferred from the photoconductor to the recording paper via the intermediate transfer body, or the toner image is transferred to the photoconductor. Directly onto the recording paper.

  The photoconductor is scanned with the light beam by an optical scanning device. In an optical scanning device, a light beam is emitted from a light emitting element, is incident on a photosensitive member while being deflected by a polygon mirror (deflecting unit), and the photosensitive member is scanned with the light beam. Further, a BD sensor for detecting the light beam deflected by the polygon mirror is provided, and the scanning timing of the photosensitive member by the light beam is set based on the detection timing of the light beam by the BD sensor.

  For example, in Patent Document 1, a light beam is directly incident on a BD sensor and the light beam is detected by the BD sensor immediately before the scanning of the photosensitive member is started. In Patent Documents 2 and 3, immediately before the scanning of the photosensitive member is started, the light beam is reflected by a mirror and incident on the BD sensor, and the light beam is detected by the BD sensor.

JP 61-261714 A Japanese Patent Laid-Open No. 08-190071 JP 2002-131664 A

  In Patent Documents 1 to 3, the orientation and position of the light receiving surface of the BD sensor and the reflecting surface of the mirror are set so that the light beam is perpendicularly incident on the light receiving surface of the BD sensor. This is because when the light beam is incident perpendicularly to the light receiving surface of the BD sensor, the reflected light is incident on the light receiving surface of the BD sensor even if the light beam is reflected by an element or wiring near the BD sensor. This is because no noise is generated in the detection output of the BD sensor.

  However, when the orientation and position of the mirror reflection surface and the light receiving surface of the BD sensor are set so that the light beam is perpendicularly incident on the light receiving surface of the BD sensor, the degree of freedom of the arrangement position of the BD sensor is low. Therefore, this may be an adverse effect of downsizing and thinning of the optical scanning device.

  Further, in Patent Documents 1 to 3, a mirror or a mirror is disposed at a position outside the deflection angle range of the light beam in the period from the start of scanning of the photosensitive member to the end of scanning, that is, the deflection angle range of the light beam corresponding to the scanning range of the photosensitive member. A BD sensor is arranged. Therefore, it is necessary to provide an arrangement space for the mirror and the BD sensor, which also has a negative effect on the downsizing and thinning of the optical scanning device.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and has a high degree of freedom in the arrangement position of the BD sensor and can be further miniaturized, and an image forming apparatus including the same. An object is to provide an apparatus.

In order to solve the above problems, an optical scanning device of the present invention includes a light emitting element that emits a light beam, a deflection unit that deflects the light beam, and an optical sensor that detects the light beam deflected by the deflection unit. And a housing attached to either side of the optical sensor, and based on the detection timing of the light beam by the optical sensor, the scanning of the object to be scanned by the light beam deflected by the deflection unit An optical scanning device for setting timing, wherein a light receiving surface of the optical sensor is disposed in parallel with an attachment side surface to which the optical sensor is attached, and the light beam is transmitted in a longitudinal direction and a short direction of the attachment side surface. The light is incident on the light receiving surface of the photosensor in an oblique direction with respect to each.

  In such an optical scanning device of the present invention, since the light beam is incident obliquely on the light receiving surface of the optical sensor, the degree of freedom of the optical sensor arrangement position is increased, and the optical sensor arrangement position is light. There is no adverse effect of downsizing and thinning of the scanning device.

  In addition, when the light beam is incident obliquely on the light receiving surface of the optical sensor, if the light beam is reflected by an element or wiring near the optical sensor, the reflected light enters the light receiving surface of the optical sensor. Although it becomes easy and the possibility that noise is generated in the detection output of the optical sensor is increased, this point can be solved by providing a separate means.

  In other words, in the present invention, the light beam is intentionally made incident on the light receiving surface of the optical sensor in an oblique direction to increase the degree of freedom of the arrangement position of the optical sensor. As a result, the optical scanning device can be significantly reduced in size.

  In the optical scanning device of the present invention, a slit through which the light beam immediately before entering the light receiving surface of the optical sensor passes, and an inner edge portion of the slit facing in a direction opposite to the deflection direction of the light beam. Has a cross-sectional shape inclined in an oblique direction in which the light beam is incident.

  When such a slit is provided, the light beam is mostly incident only on the optical sensor, and the light beam is hardly incident on the elements or wirings in the vicinity of the optical sensor. The light is not reflected and incident on the light receiving surface of the photosensor, and noise is not generated in the detection output of the photosensor.

  If the inner edge of the slit facing in the direction opposite to the deflection direction of the light beam has a cross-sectional shape inclined in the oblique direction where the light beam is incident, the light beam is reliably incident on the optical sensor through the slit. However, the opening width of the slit can be narrowed on the light beam incident side, and the influence of disturbance light on the optical sensor can be suppressed satisfactorily.

  Furthermore, in the optical scanning device of the present invention, the optical scanning device includes a slit through which the light beam immediately before entering the light receiving surface of the optical sensor, and the center of the slit is from a perpendicular passing through the center of the light receiving surface of the optical sensor. Is also shifted in the direction opposite to the deflection direction of the light beam.

  In this case as well, the width of the slit can be reduced while the light beam is reliably incident on the optical sensor through the slit, and the influence of disturbance light on the optical sensor can be suppressed satisfactorily.

The optical scanning device of the present invention further includes a detection mirror that reflects the light beam deflected by the deflecting unit and causes the light beam to enter the light receiving surface of the optical sensor. disposed deflection angle range of the light beam corresponding to the scanning range, the detecting mirror is arranged outside the deflection angle range of the light beam.

  A light sensor is arranged in the deflection angle range of the light beam in the scanning period from the start of scanning of the scanning object to the end of scanning, that is, the deflection angle range of the light beam corresponding to the scanning range of the scanning object, and the deflection angle range of the light beam If the detection mirror is arranged outside the light beam and the light beam is reflected by the detection mirror to the light sensor, the light beam is incident on the light receiving surface of the light sensor in an oblique direction. There is no need to provide a special arrangement space, and the optical scanning device can be reduced in size and thickness.

On the other hand, the optical scanning device of the present invention includes a plurality of light emitting elements that emit respective light beams, a deflecting unit that includes a plurality of deflecting surfaces that deflect each incident light beam, and each deflecting surface. Two imaging optical systems that guide the deflected light beams to the respective scanning objects, and an optical sensor that detects at least one of the light beams deflected by the deflection surfaces, Each imaging optical system is disposed on both sides of a straight line passing through the rotation axis of the deflection unit, and each light beam deflected by each deflection surface and guided to each scanning object through each imaging optical system. The optical scanning device that scans each scanned object by the optical sensor and sets the scanning timing of each scanned object by each light beam based on the detection timing of the light beam by the optical sensor, Reflect the deflected light beam Comprises a detecting mirror to be incident on the light receiving surface of the light sensor, and the substrate on which the light sensor is mounted, and a housing in which the light sensor is attached to either side, the light sensor, the object to be scanned The light beam is disposed in a deflection angle range corresponding to a scanning range of the body, the detection mirror is disposed outside the deflection angle range of the light beam, and the substrate is more than the imaging optical system. The light sensor is disposed at a position away from the deflection unit and parallel to the scanning direction of the scanned object by the light beam, and the light receiving surface of the light sensor is disposed in parallel with the mounting side surface to which the light sensor is mounted, The light beam is incident on the light receiving surface of the photosensor in an oblique direction with respect to each of the longitudinal direction and the short direction of the mounting side surface.

  In such an optical scanning device of the present invention, the optical sensor is arranged in the deflection angle range of the light beam corresponding to the scanning range of the scanning object, and the detection mirror is arranged outside the deflection angle range of the light beam, If the light beam is reflected by the detection mirror to the light sensor, the light beam is incident on the light receiving surface of the light sensor in an oblique direction. The scanning device can be reduced in size and thickness.

  In addition, since the substrate of the optical sensor is disposed at a position farther from the deflecting unit than the imaging optical system and parallel to the scanning direction of the scanned object by the light beam, the substrate does not interfere with the light beam, The arrangement space of the substrate can be minimized, and the optical scanning device can be reduced in size and thickness.

  An image forming apparatus according to the present invention includes the optical scanning device according to the present invention, and forms a latent image on a scanned object by the optical scanning device, and develops the latent image on the scanned object into a visible image. Then, the visible image is transferred and formed from the scanned body onto a sheet.

  Even in such an image forming apparatus, the same effects as those of the optical scanning apparatus of the present invention can be obtained.

  In the optical scanning device of the present invention, since the light beam is incident on the light receiving surface of the optical sensor in an oblique direction, the degree of freedom of the optical sensor arrangement position is increased, and the optical sensor arrangement position is the same as that of the optical scanning device. There is no negative effect of downsizing and thinning.

  In addition, when the light beam is incident obliquely on the light receiving surface of the optical sensor, if the light beam is reflected by an element or wiring near the optical sensor, the reflected light enters the light receiving surface of the optical sensor. Although it becomes easy and the possibility that noise is generated in the detection output of the optical sensor is increased, this point can be solved by providing a separate means.

  In other words, in the present invention, the light beam is intentionally made incident on the light receiving surface of the optical sensor in an oblique direction to increase the degree of freedom of the arrangement position of the optical sensor. As a result, the optical scanning device can be significantly reduced in size.

1 is a cross-sectional view illustrating an image forming apparatus including an embodiment of an optical scanning device of the present invention. It is a perspective view which shows the inside of the housing | casing of an optical scanning device from diagonally upward, Comprising: The state which removed the upper cover is shown. It is the perspective view which extracts and shows the some optical member of an optical scanning device, and has shown the state seen from the back side of FIG. It is a top view which extracts and shows a plurality of optical members of an optical scanning device. It is a side view which extracts and shows a plurality of optical members of an optical scanning device. It is a perspective view which expands and shows a BD mirror and a BD board | substrate seeing from the diagonally upward direction inside a housing | casing. It is a perspective view which expands and shows a BD mirror and a BD board | substrate seeing from the diagonally upward direction of the outer side of a housing | casing. It is a perspective view which expands and shows the attachment structure of the BD mirror in the lower surface of the baseplate of a housing | casing. It is a perspective view which shows the attachment structure of a BD mirror seeing from the direction 90 degrees different from FIG. (A) is a top view which shows typically the attachment aspect of a BD board | substrate, (b) is a top view which shows the comparative example of the attachment aspect of a BD board | substrate. It is sectional drawing which shows the slit which the light beam just before entering into the light-receiving surface of a BD sensor passes, formed in the side plate of a housing | casing. (A) is a graph showing a detection output of a BD sensor in which a light beam passes through a slit and is incident in an oblique direction, and (b) is a detection of a BD sensor in which the light beam is incident in an oblique direction with the slit omitted. It is a graph which shows an output.

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

  FIG. 1 is a sectional view showing an image forming apparatus provided with an embodiment of an optical scanning device of the present invention. In this image forming apparatus 1, a color image using each color of black (K), cyan (C), magenta (M), yellow (Y) or a monochrome image using a single color (for example, black) is used as a recording sheet. Print. For this reason, the developing device 12, the photosensitive drum 13, the drum cleaning device 14, the charging device 15 and the like are provided in each of the four in order to form four types of toner images corresponding to the respective colors. , Magenta, and yellow are associated with four image stations Pa, Pb, Pc, and Pd.

  In each of the image stations Pa, Pb, Pc, and Pd, after the residual toner on the surface of the photosensitive drum 13 is removed and collected by the drum cleaning device 14, the surface of the photosensitive drum 13 is set to a predetermined potential by the charging device 15. It is charged uniformly, the surface of the photosensitive drum 13 is exposed by the optical scanning device 11, an electrostatic latent image is formed on the surface, and the electrostatic latent image on the surface of the photosensitive drum 13 is developed by the developing device 12, A toner image is formed on the surface of the photosensitive drum 13. As a result, a toner image of each color is formed on the surface of each photosensitive drum 13.

  Subsequently, while the intermediate transfer belt 21 is moved in the direction of the arrow C, the residual toner on the intermediate transfer belt 21 is removed and collected by the belt cleaning device 22, and then each color toner image on the surface of each photoconductive drum 13 is intermediate transferred. The toner images are sequentially transferred onto the belt 21 and overlapped to form a color toner image on the intermediate transfer belt 21.

  A nip area is formed between the intermediate transfer belt 21 and the transfer roller 23a of the secondary transfer device 23, and the recording sheet conveyed through the S-shaped sheet conveyance path R1 is sandwiched in the nip area. While being conveyed, the color toner image on the surface of the intermediate transfer belt 21 is transferred onto the recording paper. Then, the recording paper is sandwiched between the heating roller 24 and the pressure roller 25 of the fixing device 17 and heated and pressed to fix the color toner image on the recording paper.

  On the other hand, the recording paper is pulled out from the paper feeding cassette 18 by the pickup roller 33 and is transported through the paper transporting path R 1, via the secondary transfer device 23 and the fixing device 17, and through the paper discharge roller 36. To 39. In this paper transport path R1, after the recording paper is temporarily stopped and the leading edges of the recording paper are aligned, the recording paper is fed in accordance with the transfer timing of the toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 23a. A registration roller 34 that starts conveyance, a conveyance roller 35 that facilitates conveyance of the recording paper, and the like are arranged.

  Next, the configuration of the optical scanning device 11 of this embodiment will be described in detail with reference to FIGS. FIG. 2 is a perspective view showing the inside of the housing 41 of the optical scanning device 11 of FIG. 1 as viewed obliquely from above, and shows a state where the upper lid is removed. FIG. 3 is a perspective view showing a plurality of optical members extracted from the optical scanning device 11, and shows a state viewed from the back side of FIG. 4 and 5 are a plan view and a side view showing a plurality of optical members extracted from the optical scanning device 11. FIG. FIG. 5 also shows the photosensitive drums 13 arranged outside the optical scanning device 11.

  The housing 41 has a rectangular bottom plate 41a and four side plates 41b and 41c surrounding the bottom plate 41a. A square polygon mirror 42 in a plan view is arranged at the approximate center of the bottom plate 41a. In addition, a polygon motor 43 is fixed substantially at the center of the bottom plate 41 a, the rotation center of the polygon mirror 42 is connected and fixed to the rotation axis of the polygon motor 43, and the polygon mirror 42 is rotated by the polygon motor 43.

  In addition, on the outer side of one side plate 41b of the housing 41, a driving substrate 46 on which two first semiconductor lasers 44a and 44b and two second semiconductor lasers 45a and 45b (four semiconductor lasers in total) are mounted. Is fixed. The first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b face the inside of the housing 41 through the respective holes formed in the side plate 41b.

  The first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are symmetrical about the virtual straight line M, assuming a virtual straight line M extending in the main scanning direction X through the rotation center of the polygon mirror 42. Is arranged. A direction perpendicular to the main scanning direction X is defined as a sub-scanning direction Y, and a direction perpendicular to the main scanning direction X and the sub-scanning direction Y (longitudinal direction of the rotation axis of the polygon motor 43) is defined as a height direction Z.

  The drive board 46 is a flat printed board and has circuits for driving the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b. Each of the first semiconductor lasers 44a and 44b and each of the second semiconductor lasers 45a and 45b are arranged on a substantially same plane (YZ plane) by being mounted on a flat printed board, and with respect to the plane, The respective light beams L1 to L4 are emitted in the vertical direction (main scanning direction X) and inward of the housing 41.

  On the drive substrate 46 (YZ plane), the first semiconductor lasers 44a and 44b are arranged at different positions in the sub-scanning direction Y and the height direction Z, and similarly, the second semiconductor lasers 45a and 45b are also in the sub-scanning direction. They are arranged at different positions in the Y and height directions Z.

  Further, the first incident optical system 51 that guides the light beams L1 and L2 of the first semiconductor lasers 44a and 44b to the polygon mirror 42, and the light beams L3 and L4 of the second semiconductor lasers 45a and 45b to the polygon mirror 42. A second incident optical system 52 is provided. The first incident optical system 51 includes two collimator lenses 53a and 53b, two apertures 54, two mirrors 55a and 55b arranged at the same height as the first semiconductor laser 44a, and a cylindrical lens 56. Become. Similarly, the second incident optical system 52 includes two collimator lenses 57a and 57b, two apertures 58, two mirrors 59a and 59b arranged at the same height as the second semiconductor laser 45b, and a cylindrical lens. 56 etc. Each collimator lens 53a, 53b, each aperture 54, and each mirror 55a, 55b of the first incident optical system 51, each collimator lens 57a, 57b, each aperture 58, and each mirror 59a, 59b of the second incident optical system 52. Are arranged symmetrically about the virtual straight line M. The virtual straight line M passes through the center of the cylindrical lens 56, one half of the cylindrical lens 56 divided by the virtual straight line M is disposed in the first incident optical system 51, and the other half of the cylindrical lens 56 is half-sided. Arranged in the second incident optical system 52.

  Further, a first imaging optical system 61 for guiding the light beams L1 and L2 of the first semiconductor lasers 44a and 44b reflected by the polygon mirror 42 to the two photosensitive drums 13 corresponding to black and cyan, and a polygon mirror There is provided a second imaging optical system 62 that guides the light beams L3 and L4 of the second semiconductor lasers 45a and 45b reflected by 42 to the two photosensitive drums 13 corresponding to magenta and yellow. The first imaging optical system 61 includes an fθ lens 63 and four mirrors 64a, 64b, 64c, 64d, and the like. Similarly, the second imaging optical system 62 includes an fθ lens 65 and four mirrors 66a, 66b, 66c, 66d, and the like. The fθ lens 63 and the mirrors 64a, 64b, 64c, and 64d of the first imaging optical system 61 and the fθ lens 65 and the mirrors 66a, 66b, 66c, and 66d of the second imaging optical system 62 are the virtual straight line M. Are arranged symmetrically around the center.

  Further, a BD substrate 73 on which the BD mirror 71 and the BD sensor 72 are mounted is provided on the first imaging optical system 61 side, and a BD on which the BD mirror 74 and the BD sensor 75 are mounted on the second imaging optical system 62 side. A substrate 76 is provided. The BD mirror 71 and the BD sensor 72 on the first imaging optical system 61 side and the BD mirror 74 and the BD sensor 75 on the second imaging optical system 62 side are arranged symmetrically about the virtual straight line M. .

  Next, the optical paths until the light beams L1 and L2 of the first semiconductor lasers 44a and 44b enter the respective photosensitive drums 13 and the light beams L3 and L4 of the second semiconductor lasers 45a and 45b are respectively Each optical path until it enters the photosensitive drum 13 will be described.

  First, in the first incident optical system 51, the light beam L1 of the first semiconductor laser 44a is transmitted through the collimator lens 53a to be collimated, is narrowed by the aperture 54, is incident on the mirrors 55a and 55b, and is reflected. Then, the light passes through the cylindrical lens 56 and enters the reflection surface 42 a of the polygon mirror 42. Further, the light beam L2 of the first semiconductor laser 44b is transmitted through the collimator lens 53b to be collimated, and is narrowed down by the aperture 54, and passes through the empty space E below the mirror 55b (downward in the height direction Z). Then, the light passes through the cylindrical lens 56 and enters the reflection surface 42 a of the polygon mirror 42. The cylindrical lens 56 condenses and emits the light beams L1 and L2 only in the height direction Z so as to be substantially converged by the reflection surface 42a of the polygon mirror 42.

  Here, although the first semiconductor lasers 44a and 44b are arranged at different positions in the height direction Z on the drive substrate 46 (YZ plane), the light beams L1 and L2 of the first semiconductor lasers 44a and 44b are arranged. The incident spots of the light beams L1 and L2 are substantially overlapped on the reflection surface 42a of the polygon mirror 42 by setting the emission direction of the light beam or the direction of the mirrors 55a and 55b. For this reason, the light beams L1 and L2 of the first semiconductor lasers 44a and 44b are incident on the reflecting surface 42a of the polygon mirror 42 from obliquely upward and obliquely downward directions. Further, when viewed in the Z direction, the light beams L1 and L2 are incident on the reflecting surface 42a in a state of overlapping on the same straight line.

  In the first imaging optical system 61, the light beams L1 and L2 reflected by the reflecting surface 42a of the polygon mirror 42 move away from each other in the diagonally downward direction and the diagonally upward direction. One light beam L1 is reflected obliquely downward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 63 and is reflected by one mirror 64a, and is applied to the photosensitive drum 13 on which a black toner image is formed. Incident. The other light beam L2 is reflected obliquely upward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 63, and is sequentially reflected by the three mirrors 64b, 64c, and 64d to form a cyan toner image. Is incident on the photosensitive drum 13.

  Further, the polygon mirror 42 is rotated at a constant angular velocity by a polygon motor 43, sequentially reflects each light beam L1, L2 on each reflecting surface 42a, and repeats each light beam L1, L2 in the main scanning direction X at a constant angular velocity. To deflect. The fθ lens 63 condenses and emits the light beams L1 and L2 so as to have a predetermined beam diameter on the surface of each photosensitive drum 13 in both the main scanning direction X and the sub-scanning direction Y, and The light beams L1 and L2 deflected at a constant angular velocity in the main scanning direction X by the polygon mirror 42 are converted so as to move at a constant linear velocity along the main scanning lines on the respective photosensitive drums 13. Thus, the light beams L1 and L2 repeatedly scan the surface of the photosensitive drum 13 in the main scanning direction X.

  One light beam L1 is reflected by the BD mirror 71 and enters the BD sensor 72 immediately before the main scanning of each photosensitive drum 13 by the light beams L1 and L2 is started. The BD sensor 72 receives the light beam L1 at a timing immediately before the main scanning of each photosensitive drum 13 is started, and outputs a BD signal indicating the timing immediately before the start of the main scanning. Based on this BD signal, the main scanning start time of each photosensitive drum 13 by each light beam L1, L2 is set, and modulation of each light beam L1, L2 according to each image data of black and cyan is started.

  On the other hand, the photosensitive drums 13 on which the black and cyan toner images are formed are driven to rotate, and the two-dimensional surface (circumferential surface) of each photosensitive drum 13 is scanned by the light beams L1 and L2. Each electrostatic latent image is formed on the surface of each photosensitive drum 13.

  Next, in the second incident optical system 52, the light beam L3 of the second semiconductor laser 45a is transmitted through the collimator lens 57a to be collimated, and is narrowed by the aperture 58, and below the mirror 59a (in the height direction Z). Passes through the empty space E (downward), passes through the cylindrical lens 56, and enters the reflecting surface 42 a of the polygon mirror 42. In addition, the light beam L4 of the second semiconductor laser 45b is transmitted through the collimator lens 57b to be collimated, is focused by the aperture 58, is incident on the respective mirrors 59a and 59b, is reflected, and is transmitted through the cylindrical lens 56. Then, the light enters the reflecting surface 42a of the polygon mirror 42.

  In addition, although the second semiconductor lasers 45a and 45b are arranged at different positions in the height direction Z on the drive substrate 46 (YZ plane), the light beams L3 and L4 of the second semiconductor lasers 45a and 45b Depending on the setting of the emission direction or the orientation of the mirrors 59a and 59b, the incident spots of the light beams L3 and L4 are substantially overlapped on the reflection surface 42a of the polygon mirror 42. Therefore, the light beams L3 and L4 of the second semiconductor lasers 45a and 45b are incident on the reflecting surface 42a of the polygon mirror 42 from the obliquely downward direction and the obliquely upward direction. Further, when viewed in the Z direction, the light beams L3 and L4 enter the reflecting surface 42a in a state where they overlap each other on the same straight line.

  In the second imaging optical system 62, the light beams L3 and L4 reflected by the reflecting surface 42a of the polygon mirror 42 move away from each other in an obliquely upward direction and an obliquely downward direction. One light beam L3 is reflected obliquely upward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 65, and is sequentially reflected by the three mirrors 66b, 66c, and 66d to form a magenta toner image. Is incident on the photosensitive drum 13. The other light beam L4 is reflected obliquely downward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 65 and is reflected by one mirror 66a, and forms a yellow toner image. Incident on the drum 13.

  The other light beam L4 is reflected by the BD mirror 74 and incident on the BD sensor 75 immediately before the main scanning of each photosensitive drum 13 by the light beams L3 and L4 is started. A BD signal indicating the timing immediately before the start of main scanning of each photosensitive drum 13 by each of the light beams L3 and L4 is output, and a cyan and black toner image is formed according to the BD signal. The start timing of scanning is determined, and modulation of the light beams L3 and L4 corresponding to the cyan and black image data is started.

  On the other hand, the respective photosensitive drums 13 on which magenta and yellow toner images are formed are driven to rotate, and the two-dimensional surfaces (peripheral surfaces) of the respective photosensitive drums 13 are scanned by the respective light beams L3 and L4. Each electrostatic latent image is formed on the surface of each photosensitive drum 13.

  In the optical scanning device 11 having such a configuration, the polygon mirror 42 is disposed substantially at the center of the bottom plate 41 a of the housing 41, and each first semiconductor laser is centered on the virtual straight line M passing through the rotation center of the polygon mirror 42. 44a, 44b and the second semiconductor lasers 45a, 45b are arranged symmetrically, the first incident optical system 51 and the second incident optical system 52 are arranged symmetrically, and the first imaging optical system 61 and the second connection are arranged. Since the image optical system 62 is arranged symmetrically, when viewed from the side, the polygon mirror 42, the first semiconductor lasers 44a and 44b, the second semiconductor lasers 45a and 45b, the first incident optical system 51, In addition, the optical scanner 11 can be reduced in size by concentrating the second incident optical system 52 and the like in a small space.

  By the way, although the size of the optical scanning device 11 is reduced by appropriately setting the arrangement positions of a plurality of optical members such as mirrors and lenses, the BD mirrors 71 and 74, the BD sensors 72 and 75, and the It is necessary to reduce the size of the optical scanning device 11 by appropriately setting the arrangement positions of the BD substrates 73 and 76 as well. In particular, since the BD substrates 73 and 76 are large in size, depending on their arrangement positions, the BD substrates 73 and 76 may prevent the optical scanning device 11 from being downsized, or may block the light beams L1 to L4.

  Therefore, in the optical scanning device 11 of the present embodiment, the arrangement positions of the BD mirrors 71 and 74, the BD sensors 72 and 75, and the BD substrates 73 and 76 are set as shown in FIGS. .

  In FIG. 4, the light beams L <b> 1 to L <b> 4 are repeatedly deflected in a generally fan-shaped range (not shown) by being reflected by the polygon mirror 42. This generally fan-shaped range includes the deflection angle range α of each of the light beams L1 to L4 in the scanning period from the start of scanning of the effective scanning region H of each photosensitive drum 13 to the end of scanning. The effective scanning area H is an area on each photosensitive drum 13 scanned by each light beam L1 to L4, and includes an area where an electrostatic latent image is formed. Actually, the effective scanning area H of each photosensitive drum 13 is located above each mirror 64a, 64d, 66a, 66d, but the effective scanning area H is shown in a two-dimensional plane.

  As shown in FIGS. 4 and 5, the BD sensors 72 and 75 and the BD substrates 73 and 76 are arranged inside the deflection angle range α, and the BD mirrors 71 and 74 are arranged inside the housing 41 and the deflection angle range α. It is arranged outside. The BD substrates 73 and 76 are provided so as to overlap the outside of the side plates 41c of the casing 41, and the light receiving surfaces of the BD sensors 72 and 75 are provided through the slits 41e (shown in FIG. 2) of the side plates 41c. It faces inward.

  The BD mirrors 71 and 74 reflect the respective light beams L1 and L4 immediately before entering the deflection angle range α and make them incident on the BD sensors 72 and 75, respectively. Each BD sensor 72, 75 detects each light beam L1, L4 and outputs a respective BD signal. Then, based on each BD signal, each light beam L1 to L4 enters the deflection angle range α, and at the same time, modulation of each light beam L1 to L4 corresponding to each image data is started, and the surface of each photosensitive drum 13 is started. Each electrostatic latent image is formed.

  In the optical scanning device 1 having such a configuration, the light beams L1 and L4 are reflected diagonally downward (YZ direction) and diagonally outward (XY direction) by the polygon mirror 42, and are outside the deflection angle range α. The light is reflected by the BD mirrors 71 and 74 obliquely upward (YZ direction) and obliquely inward (XY direction), and enters the BD sensors 72 and 75 inside the deflection angle range α. The light receiving surfaces of the BD sensors 72 and 75 are arranged to be parallel to the XZ plane. Therefore, the light beams L1 and L4 are incident on the light receiving surfaces of the BD sensors 72 and 75 in an oblique direction (non-vertical direction).

  Here, the incidence of the light beams L1 and L4 on the light receiving surfaces of the BD sensors 72 and 75 in the oblique direction (non-vertical direction) increases the degree of freedom of the arrangement positions of the BD sensors 72 and 75. This is intentionally set to reduce the arrangement space of the BD substrates 73 and 76. In other words, the BD substrates 73 and 76 are arranged inside the deflection angle range α, and the BD substrates 73 and 76 are arranged on the XZ plane so as to overlap the side plates 41c of the housing 41. The arrangement space of 73 and 76 is minimized, but for this purpose, the light beams L1 and L4 are reflected by the BD mirrors 71 and 74 outside the deflection angle range α to be inside the deflection angle range α. It is necessary to enter the BD sensors 72 and 75 in an oblique direction.

  The reduction in the arrangement space of the BD substrates 73 and 76 will be described in more detail. Since the BD sensors 72 and 75 and the BD substrates 73 and 76 are arranged inside the deflection angle range α, the depth of the optical scanning device 11 is increased. In the direction (main scanning direction X), it is not necessary to provide a special arrangement space for the BD sensors 72 and 75 and the BD substrates 73 and 76, and the deflection angle range α is between the mirrors 64a and 66a. The depth of the optical scanning device 11 need not be increased significantly.

  In addition, since the BD substrates 73 and 76 are arranged on the XZ plane so as to overlap the outside of the side plates 41c of the casing 41, the BD sensors 72 are arranged in the horizontal width direction (sub-scanning direction Y) of the optical scanning device 11. , 75 and the BD substrates 73 and 76 need not be provided with a particularly wide space, the width of the housing 41 can be set in accordance with the positions of the mirrors 64a and 66a, and the width of the optical scanning device 11 can be increased. Can be set to a minimum.

  Furthermore, since the height of each BD substrate 73 and 76 is set to be equal to or less than the height of each side plate 41c of the housing 41, each BD substrate 73 and 76 causes the height of the optical scanning device 11 to be increased. There is nothing.

  The BD mirrors 71 and 74, the BD sensors 72 and 75, and the BD substrates 73 and 76 are arranged such that the light beams L 1 and L 4 are incident on the light receiving surfaces of the BD sensors 72 and 75 in an oblique direction. By adopting the arrangement configuration, the arrangement space of each of the BD substrates 73 and 76 is greatly reduced. Therefore, it can be said that the optical scanning device 11 can be remarkably reduced in size by intentionally setting the oblique incidence of the light beams L1 and L4.

  Next, the mounting structure of the BD mirrors 71 and 74 and the BD substrates 73 and 76 will be described in detail. FIG. 6 is an enlarged perspective view showing the BD mirrors 71 and 74 and the BD substrates 73 and 76 when viewed from the diagonally upper side of the housing 41. FIG. 7 is a perspective view showing the BD mirrors 71 and 74 and the BD substrates 73 and 76 in an enlarged manner when viewed from the obliquely upward direction outside the housing 41.

  As shown in FIGS. 6 and 7, a recess 41d is formed outside the side plate 41c of the housing 41, and a BD substrate 73 (or 76) is fixed to the recess 41d. A slit 41e is formed inside the recess 41d, and the light receiving surface of the BD sensor 72 (or 75) faces the inside of the housing 41 through the slit 41e.

  Here, as shown in FIGS. 4 and 5, the mirrors 64 a and 66 a reflect the light beams L 1 and L 4 immediately before entering the respective photosensitive drums 13, and the first and second imaging optical systems 61. 62 are mirrors that are furthest away from the polygon mirror 42, and further reflect the light beams L1 and L4 detected by the BD sensors 72 and 75, respectively. For this reason, the mirrors 64a and 66a in the last stage are referred to.

  Since each BD board 73 and 76 is provided so as to overlap the outside of each side plate 41c of the housing 41, each of the last stages disposed on the inside of each side plate 41c (both ends inside the housing 41). The mirrors 64a and 66a are arranged outside the mirrors 64a and 66a, and therefore at a position away from the mirrors 64a and 66a at the last stage, and the BD sensors 72 and 75 are also arranged at the same position. ing. Therefore, the BD sensors 72 and 75 and the BD substrates 73 and 76 do not interfere with the light beams L1 to L4. Therefore, not only the arrangement space of the BD sensors 72 and 75 and the BD substrates 73 and 76 is greatly reduced, but they do not interfere with the light beams L1 to L4.

  FIG. 8 is an enlarged perspective view showing the mounting structure of the BD mirrors 71 and 74 on the lower surface of the bottom plate 41a of the housing 41. FIG. FIG. 9 is a perspective view showing the mounting structure of the BD mirrors 71 and 74 as viewed from a direction 90 ° different from FIG. As shown in FIGS. 8 and 9, a recess 41f is formed on the lower surface of the bottom plate 41a, and a BD mirror 71 (or 74) is disposed in the recess 41f. A support piece 41g projects from the inside of the recess 41f, and a BD mirror 71 (or 74) is superimposed on the support piece 41g. A spring member 81 having a substantially U-shaped cross section is connected to the support piece 41g. The BD mirror 71 (or 74) is held together, and the BD mirror 71 (or 74) is held.

  In addition, the light beam L1 (or L4) reflected by the polygon mirror 42 passes through the BD mirror 71 (or 74) and is incident on the concave portion 41f and reflected by the BD mirror 71 (or 74). An emission hole 41i is formed for emitting the light beam L1 (or L4) to the BD sensor 72 (or 75).

  As is apparent from FIG. 4, when each BD mirror 71, 74 is viewed in plan, each BD mirror 71, 74 is disposed below each mirror 64b, 64c, 66b, 66c, but each BD mirror 71, 74 is Since each recess 41f is provided on the bottom surface of the bottom plate 41a, each BD mirror 71, 74 can be attached to or detached from the bottom surface of the bottom plate 41a regardless of the presence or absence of the mirrors 64b, 64c, 66b, 66c. Can do.

  Next, each slit 41e formed in each side plate 41c of the housing 41 will be described in detail. Since not only the BD sensors 72 and 75 but also other elements and wirings are mounted on the BD substrates 73 and 76, the light receiving surfaces of the BD sensors 72 and 75 as shown in FIG. When the light beams L1 and L4 are incident in an oblique direction, the light beams L1 and L4 are reflected by other elements and wirings in the vicinity of the BD sensors 72 and 75, so that the BD sensors 72 and 75 The light may enter the light receiving surface, noise is generated in the detection outputs of the BD sensors 72 and 75, and errors occur in the scanning start timing of the photosensitive drums 13 by the light beams L1 to L4.

  If the orientation of the BD substrates 73 and 76 is set so that the light beams L1 and L4 are perpendicularly incident on the light receiving surfaces of the BD sensors 72 and 75 as shown in FIG. Even if each of the light beams L1 and L4 is reflected by other elements or wirings near the BD sensors 72 and 75, the reflected light hardly enters the light receiving surfaces of the BD sensors 72 and 75. , 75 does not cause noise. However, the lateral width of the housing 41 becomes wider, and the optical scanning device 11 becomes larger.

  For this reason, in the optical scanning device 11 of the present embodiment, each slit 41e (shown in FIGS. 2 and 6) is formed in each side plate 41c of the housing 41, and each light beam L1, L4 is sent to each slit 41e. The light beams are incident on the light receiving surfaces of the BD sensors 72 and 75, and the incident ranges of the light beams L1 and L4 in the vicinity of the light receiving surfaces of the BD sensors 72 and 75 are defined in a narrow range. The light is reflected by other elements or wirings in the vicinity of the BD sensors 72 and 75 so as not to enter the light receiving surfaces of the BD sensors 72 and 75.

  As shown in FIGS. 2 and 6, the shape of the light receiving surface of the BD sensor 72 (or 75) is a long rectangle, the shape of the slit 41e is also a long rectangle, and the light receiving surface of the BD sensor 72 (or 75) and the slit 41e. Are separated from each other, and the BD sensor 72 (or 75) and the slit 41e are arranged so that the respective long rectangles are parallel to each other. When such a slit 41e is provided, the light beam L1 (or L4) is substantially incident only on the light receiving surface of the BD sensor 72 (or 75), and the light beam L1 (or L4) is incident on the BD sensor 72 (or 75). ) Almost no incident on nearby elements, wirings, etc. Therefore, the light beam L1 (or L4) is not reflected by those elements, wirings, etc. and incident on the light receiving surface of the BD sensor 72 (or 75). , No noise is generated in the detection output of the BD sensor 72 (or 75).

  As shown in FIG. 6, the light beam L1 (or L4) reflected by the BD mirror 71 (or 74) is scanned along the scanning locus Q, and the light receiving surface of the BD sensor 72 (or 75) and the slit 41e. Across the direction perpendicular to their longitudinal direction. Thereby, the time when the light beam L1 (or L4) crosses the light receiving surface of the BD sensor 72 (or 75) is made the shortest time, the output time of the BD signal of the BD sensor 72 (or 75) is also made the shortest time, The main scanning start time of each photosensitive drum 13 is set accurately.

  FIG. 11 is a cross-sectional view showing the slit 41e, the BD sensor 72 (or 75), and the BD substrate 73 (or 76) formed in the side plate 41c. As shown in FIG. 11, the light beam L1 (or L4) is incident on the light receiving surface of the BD sensor 72 (or 75) in an oblique direction and is scanned (deflected) in the arrow direction F.

  The inner edge portion 41j of the slit 41e facing in the direction opposite to the arrow direction F has a cross-sectional shape inclined in an oblique direction where the light beam L1 (or L4) is incident. In this case, while the light beam L1 (or L4) is reliably incident on the light receiving surface of the BD sensor 72 (or 75) through the slit 41e, the opening of the slit 41e on the side on which the light beam L1 (or L4) is incident. The width S can be narrowed, and the light beam L1 (or L4) directed to incident light or an element or wiring near the BD sensor 72 (or 75) can be effectively blocked by the slit 41e. The disturbance light or the light beam L1 (or L4) hardly enters the elements or wirings, and the disturbance light or the light beam L1 (or L4) is reflected by the elements or the wirings to cause the BD sensor 72 (or 75). ) And the detection output of the BD sensor 72 (or 75) does not cause noise.

  Further, the center G of the slit 41e is shifted in the direction opposite to the arrow direction F from the perpendicular H passing through the center of the light receiving surface of the BD sensor 72 (or 75). Also in this case, the light beam L1 (or L4) is reliably incident on the light receiving surface of the BD sensor 72 (or 75) through the slit 41e, but the opening of the slit 41e on the side on which the light beam L1 (or L4) is incident. The width S can be narrowed, and the light beam L1 (or L4) incident on the ambient light or an element or wiring near the BD sensor 72 (or 75) can be effectively blocked by the slit 41e.

  Note that the inner edge 41k of the slit 41e facing the arrow direction F may also have a cross-sectional shape inclined in an oblique direction where the light beam L1 (or L4) is incident.

  FIG. 12A is a graph showing the detection output of the BD sensor 72 (or 75) in which the light beam L1 (or L4) has passed through the slit 41e and entered in an oblique direction, and FIG. It is a graph which shows the detection output of the BD sensor 72 (or 75) which the light beam L1 (or L4) entered in the diagonal direction in the abbreviated state.

  When the slit 41e is provided as in the present embodiment, the light beam L1 (or L4) enters only the light receiving surface of the BD sensor 72 (or 75) through the slit 41e, and the ambient light or the light beam L1 (or L4). Is reflected by an element or wiring in the vicinity of the BD sensor 72 (or 75) and does not enter the light receiving surface of the BD sensor 72 (or 75), so that only the BD signal bd as shown in FIG. Is output from the BD sensor 72 (or 75).

  On the other hand, when the slit 41e is omitted, ambient light or the light beam L1 (or L4) is incident not only on the light receiving surface of the BD sensor 72 (or 75) but also in the nearby elements and wirings in an oblique direction. Therefore, the disturbance light and the light beam L1 (or L4) may be reflected by those elements or wirings and enter the light receiving surface of the BD sensor 72 (or 75), as shown in FIG. The signal bs and noise ns are output from the BD sensor 72 (or 75). For this reason, an error may occur in the scanning start timing of each photosensitive drum 13 by each of the light beams L1 to L4.

  As described above, in the optical scanning device 11 of the present embodiment, the light beams L1 and L4 are incident on the light receiving surfaces of the BD sensors 72 and 75 in an oblique direction, whereby the BD sensors 72 and 75 can be freely arranged. By increasing the degree, the arrangement space of the BD substrates 73 and 76 is reduced, and the optical scanning device 11 is remarkably miniaturized. Further, since the BD substrates 73 and 76 are arranged at positions farther from the polygon mirror 42 than the last mirrors 64a and 66a, the BD sensors 72 and 75 and the BD substrates 73, 76 does not interfere with each of the light beams L1 to L4.

  The optical scanning device 11 of the above embodiment includes the first semiconductor lasers 44a and 44b, the second semiconductor lasers 45a and 45b, the first incident optical system 51, the second incident optical system 52, and the first imaging optical system. 61, the second imaging optical system 62, and the like are arranged symmetrically about a virtual straight line M extending in the main scanning direction X through the rotation center of the polygon mirror 42. The present invention can also be applied to a scanning device.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Optical scanning apparatus 12 Developing apparatus 13 Photosensitive drum (to-be-scanned body)
14 Drum cleaning device 15 Charging device 17 Fixing device 21 Intermediate transfer belt 22 Belt cleaning device 23 Secondary transfer device 33 Pickup roller 34 Registration roller 35 Transport roller 36 Paper discharge roller 41 Housing 42 Polygon mirror (deflection unit)
43 Polygon motors 44a, 44b First semiconductor laser (light emitting element)
45a, 45b Second semiconductor laser (light emitting element)
46 Driving substrate 51 First incident optical system 52 Second incident optical system 53a, 53b, 57a, 57b Collimator lens 55a, 55b, 59a, 59b Mirror 56 Cylindrical lens 61 First imaging optical system 62 Second imaging optical system 63 , 65 fθ lenses 63a, 65a
64a to 64d, 66a to 66d Mirrors 71 and 74 BD mirror (detection mirror)
72, 75 BD sensor (optical sensor)
73, 76 BD substrate

Claims (6)

A light emitting element that emits a light beam, a deflecting unit that deflects the light beam, a light sensor that detects the light beam deflected by the deflecting unit, and a housing in which the light sensor is attached to any side surface with the door, on the basis of the detection timing of the light beam by the optical sensor, wherein an optical scanning device for setting the scanning timing of the scanning subjects by the light beam deflected by the deflection unit,
The light receiving surface of the optical sensor is disposed in parallel with the mounting side surface to which the optical sensor is attached,
The optical scanning device according to claim 1, wherein the light beam is incident on a light receiving surface of the optical sensor in an oblique direction with respect to a longitudinal direction and a short direction of the mounting side surface . The optical scanning device according to claim 1,
A slit through which the light beam immediately before entering the light receiving surface of the optical sensor passes,
2. An optical scanning device according to claim 1, wherein an inner edge of the slit facing in a direction opposite to a deflection direction of the light beam has a cross-sectional shape inclined in an oblique direction in which the light beam is incident. The optical scanning device according to claim 1 or 2,
A slit through which the light beam immediately before entering the light receiving surface of the optical sensor passes,
The center of the slit is shifted in the direction opposite to the deflection direction of the light beam from the perpendicular passing through the center of the light receiving surface of the optical sensor. The optical scanning device according to any one of claims 1 to 3,
A detection mirror that reflects the light beam deflected by the deflecting unit to be incident on a light receiving surface of the optical sensor;
The optical sensor is disposed in a deflection angle range of the light beam corresponding to a scanning range of the scanned object,
The detection mirror, the optical scanning apparatus characterized by being arranged outside the deflection angle range of the light beam. A plurality of light emitting elements for emitting the respective light beams, a deflecting unit having a plurality of deflecting surfaces for deflecting the incident light beams, and the light beams deflected by the deflecting surfaces respectively. Two imaging optical systems that lead to the scanning object; and an optical sensor that detects at least one of the light beams deflected by the deflection surfaces, and the imaging optical systems are connected to the deflection unit. It is arranged on both sides of a straight line passing through the rotation axis, and scans each scanned object with each light beam deflected by each deflecting surface and guided to each scanned object through each imaging optical system, An optical scanning device that sets a scanning timing of each of the scanned objects by each light beam based on the detection timing of the light beam by the optical sensor,
A detection mirror that reflects the light beam deflected by the deflecting unit to be incident on a light receiving surface of the optical sensor;
A substrate on which the optical sensor is mounted ;
A housing attached to either side of the optical sensor ;
The optical sensor is disposed in a deflection angle range of the light beam corresponding to a scanning range of the scanned object,
The detection mirror is disposed outside a deflection angle range of the light beam ;
The substrate is disposed at a position farther from the deflection unit than the imaging optical system and in parallel with the scanning direction of the scanned object by the light beam ,
The light receiving surface of the optical sensor is disposed in parallel with the mounting side surface to which the optical sensor is attached,
The optical scanning device according to claim 1, wherein the light beam is incident on a light receiving surface of the optical sensor in an oblique direction with respect to a longitudinal direction and a short direction of the mounting side surface .   6. An optical scanning device according to claim 1, comprising: forming a latent image on a scanned object by the optical scanning device, and developing the latent image on the scanned object into a visible image. An image forming apparatus that transfers and forms the visible image from the scanned body onto a sheet.

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