JP6512165B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus provided with a plurality of photosensitive drums along a transfer belt.

  Some electrophotographic image forming apparatuses include a plurality of photosensitive drums along a transfer belt. The surface of each photosensitive drum is charged and exposed according to image data to form an electrostatic latent image, and further, a toner of each color is attached to the electrostatic latent image to develop a toner image of each color Form. A toner image of each color formed on each photosensitive drum is primarily transferred onto a transfer belt to form a full-color toner image, and a full-color toner image is secondarily transferred to a sheet.

  In the image forming apparatus, at the time of primary transfer, a difference occurs in the flow of the transfer current between the toner adhesion portion and the non-toner adhesion portion of the photosensitive drum, and the transfer memory image is affected by affecting the charging characteristics of the photosensitive drum. It may occur. By reducing the transfer current, it is possible to suppress the flow of the transfer current into the photosensitive drum, but there is a possibility of causing a transfer failure.

  Therefore, for example, in the image forming apparatus described in Patent Document 1, a photosensitive member is disposed by arranging a charge removal light source (charge removal unit) between primary transfer and cleaning on the photosensitive drum, and irradiating the photosensitive drum with the charge removal light. The drum is subjected to charge removal (so-called charge removal after transfer). The charge removal light source can apply charge removal light to the photosensitive drum adjacent to the downstream side in the rotational direction of the intermediate transfer belt to charge the photosensitive drum (so-called charge removal prior to transfer). As a result, the potential of the photosensitive drum before primary transfer is lowered, so that generation of a transfer memory image can be prevented without causing transfer failure even if the transfer current is lowered. Further, since one charge removal light source serves both after transfer transfer charge removal and before transfer transfer of two adjacent photosensitive drums, there is no need to newly provide a charge removal light source, and cost reduction is realized.

  However, in the above-described charge removal light source, since the LEDs as the light source are constituted by an LED array arranged along the axial direction of the photosensitive drum, in order to have both post-transfer charge removal and pre-transfer charge removal. There is a problem that a dedicated LED facing each direction is required, and the number of LEDs increases.

  On the other hand, for example, in the image forming apparatus described in Patent Document 2, the charge removal before transfer and the charge removal after transfer are performed using a charge removal unit (charge removal device) including one LED (light source) and a light guide. We have proposed a sidelight static elimination system that has both functions. The light guide includes a first reflecting portion and a second reflecting portion (two reflecting surfaces) along the axial direction of the photosensitive drum.

JP, 2011-221405, A JP, 2013-113901, A

  As described above, in the charge removal apparatus having one light source and the light guide, the charge removal light for achieving the charge removal before transfer output from the light guide and the charge removal light for the charge removal after transfer, of the photosensitive drum It is necessary to suppress the light amount unevenness in the axial direction. In order to suppress the light quantity unevenness of the static elimination light, the required accuracy of the shape of the reflecting surface of the light guide is very high. The reflection surface of the light guide is formed by arranging a plurality of prisms (grooves) in the axial direction, but the emission angle of light (light output from the emission surface side) reflected and output by the prism and the prism It is different from the emission angle of light transmitted without reflection and output from the rear surface of the prism (light output from the side of the reflective surface). Therefore, it is difficult to equalize in the axial direction the charge removal light before transfer, the charge removal light after transfer, and the light amount in the light guide provided with one reflection surface, and in the above-described charge removal device, the light reflection member has two reflection surfaces. Was equipped. However, since the mold cost for forming the two axially long reflecting surfaces becomes very high, the cost per product increases.

  With regard to the pre-transfer charge removal light quantity, if the light quantity is too small, the effect of preventing the transfer memory image can not be sufficiently obtained, and if the light quantity is too large, character blurring occurs to cause image deterioration. With regard to the amount of charge removal after transfer, if the amount of light is too small, the function as the charge removal will not be sufficient, and if the amount of light is too large, carriers generated by exposure will be generated excessively, leading to the generation of a transfer memory image. . Therefore, it is necessary to make both the pre-transfer charge removal light quantity and the post-transfer charge removal light quantity uniform in the desired range over the entire axial direction, but particularly in the light guide having one reflective surface, the desired pre-transfer charge removal It is very difficult to realize the light quantity and the post-transfer charge removal quantity over the entire axial direction.

  Therefore, in consideration of the above circumstances, the present invention has an object to realize a desired pre-transfer charge removal light amount and a post-transfer charge removal light amount with respect to a photosensitive drum with a simple configuration.

  In the image forming apparatus according to the present invention, an annular transfer belt rotating in a predetermined direction, a plurality of photosensitive drums disposed along the rotational direction of the transfer belt, and an image formed on the plurality of photosensitive drums A plurality of primary transfer portions for transferring the toner to the transfer belt, a plurality of charge removal portions for removing potentials by irradiating the plurality of photosensitive drums with the charge removing light, and removing toner remaining on the plurality of photosensitive drums A plurality of cleaning units, the charge removing units being disposed between the respective primary transfer units and the respective cleaning units, the light guiding member being long in the axial direction of the And a light source disposed on one end side in the longitudinal direction of the light guide, and configured to be capable of irradiating the charge removing light on the upstream side and the downstream side of the light guide in the rotational direction of the transfer belt; Direction of rotation of the belt A first light shielding portion provided between the photosensitive drum on the downstream side of the light guide and the light guide, and adjusting the amount of charge before transfer from the light guide to the photosensitive drum on the downstream side And between the photosensitive drum on the upstream side of the light guide and the light guide in the rotational direction of the transfer belt, and after transfer from the light guide to the photosensitive drum on the upstream side At least one of the second light shielding portion for adjusting the amount of static elimination light is provided.

  By adopting such a configuration, a simple configuration in which the first light blocking portion and the second light blocking portion are provided between the photosensitive drum and the charge removing portion enables the charge removal light from the light guide to be desirably removed before transfer. The light amount and the charge removal amount after transfer can be used. Therefore, it is not necessary to finely control the light amount of light incident from the light source, and the light source may be set to receive light of a light amount exceeding the pre-transfer charge removal charge amount and the post-transfer charge removal charge amount. In addition, a light guide provided with only one reflective surface can be used, and it is not necessary to make the plurality of reflective portions formed on the reflective surface complicated. This can also reduce the cost of the light guide.

  The first light shielding portion may be provided separately from a drum frame for mounting the upstream photosensitive drum, and may be mounted on the drum frame.

  The second light shielding portion may be provided separately from the drum frame for mounting the upstream photosensitive drum, and may be mounted on the drum frame.

  By adopting such a configuration, a unit (for example, a photosensitive drum corresponding to yellow, etc.) unnecessary for the first light shielding portion and the second light shielding portion, and the first light shielding portion and the second light shielding portion are attached. The first light shielding portion and the second light shielding portion may be attached only to units other than the units that do not need to be (for example, the photosensitive drum corresponding to black). Further, since the first light shielding portion and the second light shielding portion are detachable members, the configuration for simultaneously shielding the post-transfer charge-removing light and the pre-transfer charge-removing light can be realized without complication. In addition, when it is desired to change the pre-transfer charge removal charge amount and the post-transfer charge removal charge amount by preparing a light blocking member provided with a first light blocking portion and a second light blocking portion that allow static elimination light of various light amounts, the light blocking member It is possible to respond immediately without changing the drum unit or the drum frame.

  Alternatively, the first light shielding portion may be integrally provided on a drum frame for mounting the upstream photosensitive drum.

  The second light shielding portion may be integrally provided on a drum frame for mounting the upstream photosensitive drum.

  By adopting such a configuration, it is possible to reduce the number of parts and to suppress the cost while maintaining the light shielding accuracy well for the static elimination light output from the light guide of the static elimination portion.

  Alternatively, the above-described image forming apparatus further includes a plurality of developing units corresponding to each of the plurality of photosensitive drums, and the first light shielding portion is provided to the developing unit corresponding to the downstream photosensitive drum. It may be done.

  By adopting such a configuration, by providing the first light shielding portion at a position where the charge removal light is diffused far from the light guide of the charge removal portion, even if the position fluctuation of the first light blocking portion occurs, the photosensitive drum It is possible to suppress the change in the light quantity of the static elimination light irradiated to the light.

  The first light shielding portion and / or the second light shielding portion may be arranged in the axial direction of the photosensitive drum such that the amount of light discharged from the discharging portion to the photosensitive drum is uniform in the axial direction of the photosensitive drum. It may be configured to have different amounts of light blocking depending on the position.

  By adopting such a configuration, the light blocking amount of the first light blocking portion and the second light blocking portion is increased as the light amount increases, when the light amount varies according to the axial position of the light guide of the charge removal portion. By reducing the light shielding amount of the first light shielding portion and the second light shielding portion as the light amount decreases, it is possible to make the static elimination light amount obtained through the first light shielding portion and the second light shielding portion uniform in the axial direction. For example, the static elimination light output on the side far from the light source may be weaker than the static elimination light output on the side closer to the light source in the light guide. In this case, the first light blocking portion and the second light blocking portion are set to maximize the light blocking amount near the light source and to decrease the light blocking amount as the distance from the light source increases.

  For example, the first light shielding portion and / or the second light shielding portion may be configured to have a light shielding region having different transmittance depending on the position of the photosensitive drum in the axial direction.

  By adopting such a configuration, the first light blocking portion and the second light blocking portion can set different amounts of light blocking in the axial direction with a simple configuration such as a light blocking filter that realizes a light blocking region. For example, the light blocking filter provided in the first light blocking portion and the second light blocking portion is configured by setting the transmittance to be lower as the position to be blocked increases and setting the transmittance to be higher as the position to be blocked smaller. .

  Alternatively, the first light blocking portion and / or the second light blocking portion may be configured to have light blocking walls having different heights in accordance with the axial position of the photosensitive drum.

  By adopting such a configuration, the first light blocking portion and the second light blocking portion can set different amounts of light blocking in the axial direction with a simple configuration of the light blocking wall. For example, the light shielding walls provided in the first light shielding portion and the second light shielding portion are configured such that the height is set higher as the light shielding amount is to be increased and the height is decreased as the light shielding amount is reduced. .

  Alternatively, the first light shielding portion and / or the second light shielding portion is a light shielding area having a predetermined transmittance, and is configured to have a light shielding area having a different width depending on the axial position of the photosensitive drum. It may be done.

  By adopting such a configuration, the first light blocking portion and the second light blocking portion can set different amounts of light blocking in the axial direction with a simpler configuration of a light blocking filter having a predetermined transmittance. For example, the light shielding filters provided in the first light shielding portion and the second light shielding portion are configured such that the width is set narrower as the light shielding amount is to be increased and the width is set wider as the light shielding amount is reduced.

  According to the present invention, it is possible to realize the desired pre-transfer charge removal light amount and the post-transfer charge removal light amount with respect to the photosensitive drum with a simple configuration.

FIG. 1 is a cross-sectional view showing a color printer according to an embodiment of the present invention. FIG. 1 is a cross-sectional view showing an image forming unit in a color printer according to an embodiment of the present invention. It is a sectional view showing a drum unit in a color printer concerning one embodiment of the present invention. It is a perspective view showing a drum unit in a color printer concerning one embodiment of the present invention from the left. It is a perspective view showing the drum unit in the color printer concerning one embodiment of the present invention from the right side. It is a perspective view showing the front part of the drum frame of the drum unit in the color printer concerning one embodiment of the present invention. It is a perspective view showing the back of the drum frame of the drum unit in the color printer concerning one embodiment of the present invention. It is a perspective view which shows the light guide of the static elimination apparatus in the color printer which concerns on one Embodiment of this invention. It is a side view showing the light guide of the static elimination device in the color printer concerning one embodiment of the present invention from the left. It is a side view which shows the light guide of the static elimination apparatus in the color printer which concerns on one Embodiment of this invention from right side. It is sectional drawing which shows typically the state which outputs static elimination light from an output surface and a reflective surface in the static elimination apparatus of the color printer which concerns on one Embodiment of this invention. It is a perspective view which shows the front part of the light guide of the static elimination apparatus in the color printer which concerns on one Embodiment of this invention. It is a perspective view showing the back of the light guide of the static elimination device in the color printer concerning one embodiment of the present invention. FIG. 1 is a perspective view showing a light shielding member in a color printer according to an embodiment of the present invention. It is a perspective view showing the front of the shading member in the color printer concerning one embodiment of the present invention from the front. FIG. 3 is a perspective view showing the rear of the light shielding member in the color printer according to the embodiment of the present invention from the rear. In a color printer concerning one embodiment of the present invention, it is a perspective view showing a shading member to which a light guide of a static elimination device was attached. In a color printer concerning one embodiment of the present invention, it is a perspective view showing a drum frame of a drum unit to which a light shielding member and a light guide of a static elimination device were attached. It is a top view showing a drum unit in a color printer concerning one embodiment of the present invention. It is a top view showing the front part of the drum unit in the color printer concerning one embodiment of the present invention. It is a top view showing the back of the drum unit in the color printer concerning one embodiment of the present invention. It is a side view showing the front of a drum unit in a color printer concerning one embodiment of the present invention. It is a side view showing the back of the drum unit in the color printer concerning one embodiment of the present invention.

  First, the entire configuration of a color printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. Hereinafter, for convenience of description, the front side of the sheet of FIG. 1 is referred to as the front side of the color printer 1.

  The color printer 1 includes a substantially box-like printer main body 2, and a paper feed cassette 3 containing paper (recording medium) is provided at the lower part of the printer main body 2. Is provided.

  An annular intermediate transfer belt 5 (transfer belt) rotating in a predetermined direction is provided between a plurality of rollers at a central portion of the printer body 2, and a laser scanning unit (LSU) is provided below the intermediate transfer belt 5. An exposure unit 6 composed of Below the intermediate transfer belt 5, four image forming units 7 are provided for each toner color (for example, four colors of yellow, magenta, cyan, and black). The secondary transfer portion 8 is provided at the right end of the intermediate transfer belt 5, and the cleaning unit 10 for cleaning the intermediate transfer belt 5 is provided at the left end of the intermediate transfer belt 5. The secondary transfer portion 8 is configured of a part on the right end side of the intermediate transfer belt 5 and a secondary transfer roller 8 a.

  In each of the image forming units 7, the photosensitive drum 11 is rotatably provided. The photosensitive drum 11 is formed in, for example, a cylindrical shape elongated in the front-rear direction, and the front-rear direction is the axial direction of the photosensitive drum 11. Around the photosensitive drum 11, a charging device 12, a developing device 13 (developing unit), a primary transfer portion 14, a charge removing device 15 (a charge removing portion), and a cleaning device 16 (cleaning portion) The processes are arranged in order. The photosensitive drum 11 is attached to the drum unit 17, and the charging device 12, the static elimination device 15 and the cleaning device 16 are also attached to the drum unit 17. A toner container 18 corresponding to each image forming unit 7 is provided above the developing device 13 for each toner color (for example, four colors of yellow, magenta, cyan, and black). The primary transfer portion 14 is configured by a part of the intermediate transfer belt 5 and the primary transfer roller 14 a, and the primary transfer roller 14 a is disposed to face the upper surface of the photosensitive drum 11 with the intermediate transfer belt 5 interposed therebetween. . The static eliminator 15 includes a light guide 25 and a light source 26, and the light guide 25 is covered by a light shielding member 27.

  At one side of the printer body 2 (right side in the drawing), a sheet conveyance path 20 is provided in the vertical direction. A paper feed unit 21 is provided at the upstream end of the conveyance path 20, the above-mentioned secondary transfer unit 8 is provided in the middle stream part of the conveyance path 20, and a fixing device 22 is provided downstream of the conveyance path 20. A sheet discharge outlet 23 is provided at the downstream end of the conveyance path 20.

  Next, an image forming operation of the color printer 1 having such a configuration will be described. When the color printer 1 is powered on, various parameters are initialized, and initialization such as temperature setting of the fixing device 22 is performed. Then, when image data is input from a computer or the like connected to the color printer 1 and an instruction to start printing is issued, an image forming operation is performed as follows.

  First, after the surface of the photosensitive drum 11 is charged by the charging device 12, an electrostatic latent image is formed on the surface of the photosensitive drum 11 by the laser light (see arrow L) from the exposure unit 6. Next, the electrostatic latent image is developed into a toner image of a corresponding color by the developing device 13 with the toner supplied from the toner container 18. The toner image is primarily transferred onto the surface of the intermediate transfer belt 5 by the primary transfer portion 14. A full-color toner image is formed on the intermediate transfer belt 5 as each image forming unit 7 sequentially repeats the above operation. The charge and toner remaining on the photosensitive drum 11 are removed by the charge removing device 15 and the cleaning device 16.

  On the other hand, the sheet taken out of the sheet feeding cassette 3 or the manual feeding tray (not shown) by the sheet feeding portion 21 is conveyed to the secondary transfer portion 8 at the same timing as the image forming operation described above. In the section 8, the full color toner image on the intermediate transfer belt 5 is secondarily transferred onto the sheet. The sheet on which the toner image has been secondarily transferred is conveyed to the downstream side of the conveyance path 20 and enters the fixing device 22, where the toner image is fixed on the sheet. The sheet on which the toner image is fixed is discharged onto the discharge tray 4 from the discharge port 23.

  Next, the configuration of the drum unit 17 according to the present embodiment will be described with reference to FIGS.

  The drum unit 17 includes a drum frame 30 having at least a front plate portion 31 and a rear plate portion 32. The drum frame 30 rotatably supports the photosensitive drum 11 between the front plate portion 31 and the rear plate portion 32. Do. A charging device 12 is fixed on the lower side of the drum frame 30 to charge the lower surface of the photosensitive drum 11 in the front-rear direction, and the right side of the photosensitive drum 11 is on the right side of the drum frame 30 in the front-rear direction A cleaning device 16 is fixed which charges across. Further, the light guide 25 and the light shielding member 27 of the static elimination device 15 are attached to the drum frame 30 on the upper right side of the attachment position of the cleaning device 16. For example, as shown in FIG. 6, in the front plate portion 31 of the drum frame 30, a first front positioning hole 33 for positioning the front of the light guide 25 and a second front positioning for positioning the front end of the light shielding member 27 A hole 34 is provided. As shown in FIG. 7, the rear plate portion 32 of the drum frame 30 includes a first rear positioning hole 35 for positioning the rear of the light guide 25 and a second rear positioning for positioning the rear end of the light shielding member 27. Holes 36, 37 are provided.

  Next, the structure of the static elimination apparatus 15 of this embodiment is demonstrated, referring FIGS. 2-5, FIGS. 8-13, and FIGS. 17-23. Since the static elimination devices 15 of the four image forming units 7 have the same configuration, one static elimination device 15 will be described below.

  After the primary transfer by the primary transfer unit 14 in the image forming unit 7 including the charge removal device 15, the charge removal device 15 removes the potential of the surface of the photosensitive drum 11 (post-transfer charge removal). Furthermore, in the image forming unit 7 downstream of the image forming unit 7 including the charge removing device 15 in the rotational direction of the intermediate transfer belt 5, the charge removing device 15 performs the photosensitive drum 11 before the primary transfer by the primary transfer unit 14. The potential on the surface of the photosensitive drum 11 on the downstream side is removed (pre-transfer removal).

  The light guide 25 of the static eliminator 15 has a long shape in the front-rear direction, and the length is determined by the length of the photosensitive drum 11 or the distance between the front plate portion 31 and the rear plate portion 32 of the drum frame 30. Too long. The light guide 25 is disposed to face the photosensitive drum 11 as shown in FIG. 2 and FIG. 3, and in the following, the surface of the light guide 25 facing the photosensitive drum 11 is referred to as an emitting surface 40. The surface of the light guide 25 opposite to the emission surface 40 is referred to as a reflection surface 41. In the present embodiment, the light guide 25 is disposed to face the light emission surface 40 on the left side and slightly upward so as to face the upper right side surface of the photosensitive drum 11 while avoiding the cleaning device 16. The light guide 25 has, for example, a convex cross-sectional shape in which the emission surface 40 side is curved, and the reflection surface 41 is formed in a planar shape.

  On the side of the reflection surface 41 of the light guide 25, as shown in FIG. 8 and the like, a plurality of reflection parts 42 are arranged in parallel at equal intervals in the front-rear direction of the light guide 25. Each of the reflecting portions 42 is, for example, a groove having a V-shaped cross section, which is long in the cross direction with the front-rear direction as shown in FIG. 11, and the light incident from the front end of the light guide 25 It acts as a prism which reflects on the side and the reflecting surface 41 side. The light reflected toward the reflecting surface 41 by the reflecting portion 42 of the light guide 25 is used as the charge-removing light before transfer in the photosensitive drum 11 (the charge removal downstream of the light guide 25 in the rotational direction of the intermediate transfer belt 5) The photosensitive drum 11) on the downstream side of the photosensitive drum 11 corresponding to the device 15 is irradiated. The light reflected by the reflecting portion 42 of the light guide 25 toward the emitting surface 40 is transferred to the photosensitive drum 11 on the upstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5 as the post-transfer discharge light. The photosensitive drum 11) corresponding to the device 15 is irradiated.

  Further, as shown in FIG. 12 and the like, a first front positioning portion 43 for positioning the light guide 25 in the front-rear direction is formed at the front of the light guide 25, and the rear end of the light guide 25 is formed. As shown in FIG. 13 etc., the 1st rear positioning part 44 for positioning the light guide 25 in directions other than the front-back direction is formed. The first front positioning portion 43 is formed of, for example, two protrusions, and the light guide 25 is positioned in the front-rear direction by sandwiching the edge of the first front positioning hole 33 of the front plate portion 31 of the drum frame 30. Ru. The first rear positioning portion 44 is formed, for example, in a rectangular shape in cross section, and by fitting the first rear positioning hole 35 of the rear plate portion 32 of the drum frame 30, the light guide 25 is not in the front-rear direction. It is positioned in the direction.

  The light source 26 of the static eliminator 15 is provided on the front side of the light guide 25, and is configured of an LED or the like that causes static elimination light to enter the front end of the light guide 25.

  As shown in FIGS. 2 to 5 and FIGS. 14 to 23, the light shielding member 27 has a long shape in the front-rear direction, the length thereof is shorter than the length of the light guide 25, and the front plate of the drum frame 30 The distance between the portion 31 and the rear plate portion 32 is substantially equal. Further, as shown in FIGS. 14 to 16 and the like, the light shielding member 27 covers the first light shielding portion 50 covering the reflecting surface 41 of the light guide 25 from the right side in the front-rear direction and the second covering the light emitting surface 40 from the left side. For example, it may have a substantially U-shaped cross-sectional shape that covers the light guide 25 from below, or may be formed so that the light guide 25 can be fitted. The light blocking member 27 may include one of the first light blocking portion 50 and the second light blocking portion 51.

  The first light shielding portion 50 is provided between the photosensitive drum 11 on the downstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5 and the light guide 25, and the photosensitive on the downstream side from the light guide 25. The amount of charge before transfer to the body drum 11 is adjusted. The second light shielding portion 51 is provided between the photosensitive drum 11 on the upstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5 and the light guide 25, and the photosensitive on the upstream side of the light guide 25. The amount of charge removal after transfer to the body drum 11 is adjusted. The first light shielding unit 50 and the second light shielding unit 51 include, for example, a light shielding filter (light shielding region) having a predetermined transmittance, and the discharge light from the light guide 25 is passed through the light shielding filter to adjust the amount of discharge light. Alternatively, a light shielding wall having a predetermined height may be provided, and the charge removal light from the light guide 25 to the photosensitive drum 11 may be blocked by the light shielding wall to adjust the amount of charge removal light.

  In addition, the first light shielding portion 50 and / or the second light shielding portion 51 is a shaft of the photosensitive drum 11 so that the amount of light removed from the discharging device 15 to the photosensitive drum 11 is uniform in the axial direction of the photosensitive drum 11. It is preferable to have different amounts of light blocking depending on the position of the direction. Then, the first light shielding portion 50 and / or the second light shielding portion 51 can change the amount of static elimination light according to the change of the amount of light shielding. For example, the first light shielding unit 50 and / or the second light shielding unit 51 is configured to have a light shielding filter (light shielding region) having different transmittances according to the axial position of the photosensitive drum 11, and changes in transmittance Can change the light shielding amount. Alternatively, the first light shielding portion 50 and / or the second light shielding portion 51 are configured to have light shielding walls having different heights in the axial direction of the photosensitive drum 11, and the light shielding amount is changed by the change of the height of the light shielding wall It can be done. Alternatively, the first light shielding portion 50 and / or the second light shielding portion 51 is a light shielding filter (light shielding area) having a predetermined transmittance, and the light shielding areas having different widths according to the position of the photosensitive drum 11 in the axial direction. The light shielding amount can be changed by changing the width of the light shielding area.

  As shown in FIG. 15, a second front positioning portion 52 for positioning the light shielding member 27 is formed at the front end of the light shielding member 27, and at the rear end of the light shielding member 27 as shown in FIG. Second rear positioning portions 53, 54 for positioning the member 27 are formed. The second front positioning portion 52 has, for example, a shape projecting forward, and by being fitted into the second front positioning hole 34 of the front plate portion 31 of the drum frame 30, the front portion of the light shielding member 27 is positioned. Ru. The second rear positioning portions 53 and 54 have, for example, a shape that protrudes rearward, and are fitted to the second rear positioning holes 36 and 37 of the rear plate portion 32 of the drum frame 30 to make the light shielding member 27 The back of the is positioned.

  According to the present embodiment, as described above, the color printer 1 (image forming apparatus) is disposed along the annular intermediate transfer belt 5 (transfer belt) rotating in a predetermined direction and the rotation direction of the intermediate transfer belt 5 The photosensitive drums 11, the plurality of primary transfer portions 14 for transferring the image formed on the plurality of photosensitive drums 11 to the intermediate transfer belt 5, and the plurality of photosensitive drums 11 A plurality of charge removal devices 15 (charge removal portions) that remove potentials, and a plurality of cleaning devices 16 (cleaning portions) that remove toner remaining on the plurality of photosensitive drums 11 are provided. Each static elimination device 15 is disposed between each primary transfer portion 14 and each cleaning device 16, and the light guide 25 long in the axial direction of each photosensitive drum 11 and the front end side of the light guide 25 (longitudinal direction And the light source 26 disposed at the one end side, and configured to be capable of irradiating the charge removing light on the upstream side and the downstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5. The color printer 1 is further provided between the photosensitive drum 11 on the downstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5 and the light guide 25, and the photosensitive on the downstream side from the light guide 25. Between the first light-shielding portion 50 for adjusting the amount of charge before transfer to the body drum 11 and the photosensitive drum 11 on the upstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5 And at least one of a second light shielding portion 51 which is provided and adjusts the amount of charge removal after transfer from the light guide 25 to the photosensitive drum 11 on the upstream side.

  With such a configuration, it is desirable to use a simple configuration in which the first light shielding portion 50 and the second light shielding portion 51 are provided between the photosensitive drum 11 and the charge removing device 15 so that the charge removal light from the light guide 25 is desired. It is possible to use the pre-transfer charge removal light amount or the post-transfer charge removal light amount. Therefore, it is not necessary to finely control the light amount of light incident from the light source 26, and the light source 26 may be set to receive light of a light amount exceeding the pre-transfer charge removal charge amount and the post-transfer charge removal charge amount. Moreover, the light guide 25 provided with only one reflective surface 41 can be used, and it is not necessary to make the several reflection part 44 formed in the reflective surface 41 into a complicated structure. Thereby, the cost of the light guide 25 can also be held down.

  Further, according to the present embodiment, the first light shield 50 separates light from the drum frame 30 for mounting the photosensitive drum 11 on the upstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5. It is provided on the member 27 and attached to the drum frame 30. The second light shielding portion 51 is provided on the light shielding member 27 separately from the drum frame 30 for mounting the photosensitive drum 11 on the upstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5. Attached to 30.

  As a result, the first light shielding portion 50 and the second light shielding portion 51 may not be attached to a unit (for example, the photosensitive drum 11 corresponding to yellow, etc.) unnecessary for the first light shielding portion 50 and the second light shielding portion 51. The first light shielding portion 50 and the second light shielding portion 51 (light shielding member 27) may be attached only to units other than the necessary units (for example, the photosensitive drum 11 corresponding to black and the like). Further, since the first light shielding portion 50 and the second light shielding portion 51 (light shielding member 27) are detachable members, a configuration for simultaneously shielding the post-transfer charge-removing light and the pre-transfer charge-removing light is realized without complication. can do. Also, when it is desired to change the pre-transfer charge removal charge amount and the post-transfer charge removal charge amount by preparing the light shielding member 27 provided with the first light shielding unit 50 and the second light shielding unit 51 that allow discharge light of various light amounts. It is only necessary to change the light shielding member 27 and it is possible to respond immediately without changing the drum unit 17 or the drum frame 30.

  Further, according to the present embodiment, the first light shielding unit 50 and / or the second light shielding unit 51 is configured such that the amount of charge removal light from the charge removal unit 15 to the photosensitive drum 11 becomes uniform in the axial direction of the photosensitive drum 11. The light shielding amount is different depending on the position of the photosensitive drum 11 in the axial direction.

  Thereby, when the light quantity is different according to the position of the light guide 25 of the static elimination device 15 in the axial direction, the light shielding quantity of the first light shielding part 50 and the second light shielding part 51 is increased as the light quantity increases, and the light quantity is small. By making the amount of light shielding of the first light shielding portion 50 and the second light shielding portion 51 so small, it is possible to make the amount of static elimination light obtained through the first light shielding portion 50 and the second light shielding portion 51 uniform in the axial direction. For example, the static elimination light output on the side (rear side) far from the light source 26 may be weaker than the static elimination light output on the side (front side) closer to the light source 26 in the light guide 25. In this case, the first light blocking portion 50 and the second light blocking portion 51 are set to maximize the light blocking amount near the light source 26 and to decrease the light blocking amount as the distance from the light source 26 increases.

  Note that according to the present embodiment, the first light shielding unit 50 and / or the second light shielding unit 51 have, for example, light shielding filters (light shielding areas) having different transmittances according to the position of the photosensitive drum 11 in the axial direction. And be configured.

  Thus, the first light blocking portion 50 and the second light blocking portion 51 can set different amounts of light blocking in the axial direction with a simple configuration of a light blocking filter. For example, the light shielding filters provided in the first light shielding unit 50 and the second light shielding unit 51 are configured such that the transmittance is set lower as the light shielding amount is to be increased, and the transmittance is set higher as the light shielding amount is decreased. Be done.

  Alternatively, according to the present embodiment, the first light shielding portion 50 and / or the second light shielding portion 51 is configured to have the light shielding walls having different heights in accordance with the position of the photosensitive drum 11 in the axial direction.

  Thus, the first light blocking portion 50 and the second light blocking portion 51 can set different amounts of light blocking in the axial direction with a simple configuration of the light blocking wall. For example, the light shielding walls provided in the first light shielding portion 50 and the second light shielding portion 51 are configured such that the height is set to be higher as the light shielding amount is to be larger and the height is set to be smaller as the light shielding amount is to be smaller. Be done.

  Alternatively, according to the present embodiment, the first light shielding portion 50 and / or the second light shielding portion 51 is a light shielding filter (light shielding region) having a predetermined transmittance, and corresponds to the position of the photosensitive drum 11 in the axial direction. It is configured to have light shielding filters of different widths.

  As a result, the first light blocking portion 50 and the second light blocking portion 51 can set different amounts of light blocking in the axial direction with a simpler configuration of a light blocking filter having a predetermined transmittance. For example, the light shielding filters provided in the first light shielding unit 50 and the second light shielding unit 51 are configured such that the width is set narrower as the light shielding amount is to be increased and the width is set wider as the light shielding amount is reduced. .

  In the above-described embodiment, the first light shielding portion 50 and the second light shielding portion 51 are provided separately from the drum frame 30 on the light shielding member 27 and are attached to the drum frame 30. It is not limited. For example, in another embodiment, the first light shielding unit 50 and the second light shielding unit 51 are attached to the drum frame 30 for attaching the photosensitive drum 11 on the upstream side of the light guide 25 in the rotation direction of the intermediate transfer belt 5. It may be provided integrally. In this case, the first light shielding portion 50 and the second light shielding portion 51 are integrally formed on the drum frame 30 without providing the light shielding member 27 separate from the drum frame 30. As a result, it is possible to reduce the number of parts and to reduce the cost while maintaining the light shielding accuracy well for the static elimination light output from the light guide 25 of the static elimination device 15.

  Alternatively, in another embodiment, in the configuration provided with a plurality of developing devices 13 (developing units) corresponding to each of the plurality of photosensitive drums 11, the first light shielding portion 50 for adjusting the amount of charge before discharging is a light shielding member 27 and the drum frame 30 may be provided in the developing device 13 corresponding to the photosensitive drum 11 on the downstream side of the light guide 25 in the rotational direction of the intermediate transfer belt 5. In this case, the first light shielding portion 50 is integrally formed on a developing frame or the like that constitutes the developing device 13. The charge removing light output from the light guide 25 of the charge removing device 15 is diffused as the distance from the light guide 25 increases, so that the first light shielding portion 50 removes the charge removing light to the photosensitive drum 11 at a position far from the light guide 25. When the first light shielding portion 50 is provided on the side close to the light guide 25 and the position fluctuation of the first light shielding portion 50 occurs, the light amount change of the static elimination light irradiated to the photosensitive drum 11 Becomes larger. However, as described above, according to the configuration in which the first light shielding portion 50 is provided at a position where the charge removal light is diffused far from the light guide 25 of the charge removal device 15, even if the position variation of the first light shield portion 50 occurs. The change in the light amount of the static elimination light irradiated to the photosensitive drum 11 can be suppressed small.

  In the color printer 1, the cleaning unit 10 is provided on the most upstream side of the plurality of photosensitive drums 11 in the rotational direction of the intermediate transfer belt 5. Therefore, among the plurality of photosensitive drums 11, the cleaned intermediate transfer belt 5 reaches the most upstream photosensitive drum 11, and there is no residual toner on the intermediate transfer belt 5. Therefore, since the primary transfer efficiency of the most upstream side photosensitive drum 11 is high and the pre-transfer static elimination light source is not required, the static elimination device 15 or the light shielding member 27 may not be provided.

  In the present embodiment, the case where the configuration of the present invention is applied to the color printer 1 has been described, but in another different embodiment, other image formation including a plurality of photosensitive drums such as a copying machine, a facsimile machine, and a multifunction machine It is also possible to apply the configuration of the present invention to the device.

1 Color printer (image forming device)
5 Intermediate transfer belt (transfer belt)
7 image forming unit 11 photosensitive drum 12 charging device 13 developing device (developing unit)
14 Primary Transfer Unit 15 Electric Discharger (Electrostatic Discharge Unit)
16 Cleaning device (cleaning unit)
Reference Signs List 17 drum unit 25 light guide 26 light source 27 light shielding member 30 drum frame 31 front plate portion 32 rear plate portion 40 light emitting surface 41 reflecting surface 42 reflection portion 50 first light shielding portion 51 second light shielding portion

Claims (10)

An annular transfer belt rotating in a predetermined direction;
A plurality of photosensitive drums disposed along the rotational direction of the transfer belt;
A plurality of primary transfer portions for transferring the images formed on the plurality of photosensitive drums to the transfer belt;
A plurality of charge removal units that remove potentials by irradiating the plurality of photosensitive drums with charge removal light;
And a plurality of cleaning units for removing toner remaining on the plurality of photosensitive drums,
The charge removal units are disposed between the respective primary transfer units and the respective cleaning units, and disposed at one end side of the light guide which is long in the axial direction of the respective photosensitive drums and the light guide. A light source, and configured to be capable of irradiating the charge removing light upstream and downstream of the light guide in the rotational direction of the transfer belt;
And a light shielding member having a U-shaped cross section and covering the light guide from below,
The light shielding member is
It is provided between the photosensitive drum on the downstream side of the light guide and the light guide in the rotational direction of the transfer belt, and the amount of charge before transfer from the light guide to the photosensitive drum on the downstream side A first light shield to adjust the
It is provided between the photosensitive drum on the upstream side of the light guide and the light guide in the rotational direction of the transfer belt, and the amount of charge after the transfer from the light guide to the photosensitive drum on the upstream side An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the first light shielding portion is provided separately from a drum frame for mounting the photosensitive drum on the upstream side, and is attached to the drum frame.   2. The image forming apparatus according to claim 1, wherein the second light shielding portion is provided separately from a drum frame for mounting the upstream photosensitive drum, and is mounted on the drum frame.   The image forming apparatus according to claim 1, wherein the first light shielding portion is integrally provided on a drum frame for mounting the photosensitive drum on the upstream side.   The image forming apparatus according to claim 1, wherein the second light shielding portion is integrally provided on a drum frame for mounting the upstream photosensitive drum. And a plurality of developing units respectively corresponding to the plurality of photosensitive drums,
The image forming apparatus according to claim 1, wherein the first light shielding portion is provided in the developing unit corresponding to the downstream photosensitive drum.   The first light shielding portion and / or the second light shielding portion may be arranged in the axial direction of the photosensitive drum such that the amount of light discharged from the discharging portion to the photosensitive drum is uniform in the axial direction of the photosensitive drum. The image forming apparatus according to any one of claims 1 to 6, wherein the image forming apparatus has different amounts of light blocking depending on positions.   8. The image forming apparatus according to claim 7, wherein the first light shielding portion and / or the second light shielding portion includes a light shielding region having different transmittance depending on the position of the photosensitive drum in the axial direction. Image forming device.   The first light shielding portion and / or the second light shielding portion according to claim 7, characterized in that the first light shielding portion and / or the second light shielding portion have light shielding walls having different heights according to the axial position of the photosensitive drum. Image forming device.   The first light shielding portion and / or the second light shielding portion is a light shielding area having a predetermined transmittance, and is configured to have a light shielding area having a different width depending on the position of the photosensitive drum in the axial direction. The image forming apparatus according to claim 7, wherein

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