JP6287578B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a tandem type image forming apparatus.

  In general, a tandem type image forming apparatus including a plurality of image forming units arranged at positions along a rotating endless intermediate transfer belt is known. In the tandem-type image forming apparatus, each of the image forming units includes a drum-shaped image carrier (photoconductor) and a charging unit, a developing unit, a primary transfer unit, a charge eliminating unit, and a cleaning disposed around the image bearing unit. . Each of the image forming units sequentially forms images (toner images) of different colors on the surface of the intermediate transfer belt.

  Hereinafter, in the tandem type image forming apparatus, a direction in which the intermediate transfer belt rotates along the arrangement direction of the plurality of image forming units is referred to as a belt rotation direction.

  Further, in the tandem type image forming apparatus, it is known that the charge eliminating unit of each of the image forming units has both a function of irradiating post-transfer charge removal light and a function of irradiating pre-transfer charge removal light (for example, Patent Document 1).

  The post-transfer charge removal light is a charge removal light that is applied to a position after image transfer on the image carrier from between the transfer portion and the cleaning portion in each of the image forming portions. Further, the pre-transfer charge removal light is a charge removal light applied to an image carrier of an image forming unit adjacent to the downstream side in the belt rotation direction from between the transfer unit and the cleaning unit in a certain image forming unit.

JP 2011-221405 A

  By the way, in the image forming unit on the most downstream side in the belt rotation direction, the charge removal light output from the charge removal unit toward the downstream side in the belt rotation direction does not function as the pre-transfer charge removal light. For this reason, in the image forming unit on the most downstream side, the static eliminator consumes power wastefully.

  In addition, adopting the static elimination unit that does not output the pre-transfer static elimination light toward the downstream side in the belt rotation direction only in the image forming unit on the most downstream side is against the need to make the parts as common as possible.

  An object of the present invention is to rotate the direction of the intermediate transfer belt while sharing the parts of each of the plurality of static elimination units as much as possible when the neutralization unit of each of the plurality of image forming units also functions as post-transfer neutralization and pre-transfer neutralization. Another object of the present invention is to provide an image forming apparatus capable of preventing wasteful power consumption in an image forming unit located on the most downstream side of the image forming apparatus.

  An image forming apparatus according to an aspect of the present invention includes a plurality of image forming units and a reflecting unit. The plurality of image forming units are respectively arranged at positions along the rotating endless intermediate transfer belt. Each of the image forming units includes an image carrier, a developing unit that develops an electrostatic latent image on the surface of the image carrier, a primary transfer unit that transfers an image to the intermediate transfer belt, and a cleaning unit that cleans the surface of the image carrier. And a static elimination unit. Each of the image forming units forms images of different colors on the surface of the intermediate transfer belt. The neutralization unit provided in each of the image forming units includes a first neutralization light that travels between the primary transfer unit and the cleaning unit toward the upstream side in the rotational direction of the intermediate transfer belt and the rotational direction of the intermediate transfer belt. 2nd discharge light which goes to the downstream side. The reflection unit transmits the second charge removal light in the most downstream image forming unit located on the most downstream side in the rotation direction of the intermediate transfer belt to the upstream side in the rotation direction of the intermediate transfer belt among the plurality of image forming units. Reflects in the direction it heads.

  According to the present invention, when the neutralization unit of each of the plurality of image forming units also functions as post-transfer neutralization and pre-transfer neutralization, the rotation direction of the intermediate transfer belt while sharing the components of each of the plurality of neutralization units as much as possible It is possible to provide an image forming apparatus capable of preventing wasteful power consumption in the image forming unit located on the most downstream side.

FIG. 1 is a configuration diagram of an image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic plan view of the static elimination unit in the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of the charge removal unit and the reflection unit in the image forming unit other than the black image forming unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view of the charge removal unit and the reflection unit in the black image forming unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 5 is a schematic side view of the image forming unit and the light shielding switching unit in the color mode in the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is a schematic side view of the image forming unit and the light shielding switching unit in the monochrome mode in the image forming apparatus according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view of the charge removal unit and the reflection unit in the black image forming unit of the image forming apparatus according to the second embodiment of the present invention. FIG. 8 is a configuration diagram of the charge removal unit in the image forming apparatus according to the third embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, Comprising: It does not have the character which limits the technical scope of this invention.

  First Embodiment First, the image forming apparatus 10 according to a first embodiment of the present invention will be described with reference to FIGS. The image forming apparatus 10 according to the first embodiment of the present invention is an electrophotographic tandem type image forming apparatus. In the example shown in FIG. 1, the image forming apparatus 10 is a color printer. Other examples of the image forming apparatus 10 are a color copier, a color facsimile, or a multifunction machine having a color image forming function.

  [Schematic Configuration of Image Forming Apparatus 10] As shown in FIG. 1, the image forming apparatus 10 includes a sheet supply unit 2, a sheet conveying unit 3, a plurality of developer containers 40, and a plurality of image forming units in a housing 100. 4, an optical scanning unit 5, a fixing unit 6, an intermediate transfer belt 71, a secondary transfer unit 72, an operation display unit 80, a control unit 8, and the like. 5 and 6, the image forming apparatus 10 also includes a displacement mechanism 75 and a light shielding switching unit 77. 5 and 6 are schematic side views of all the image forming units 4 and the intermediate transfer belt 71 in the image forming apparatus 10.

  The sheet supply unit 2 includes a sheet cassette 21 that can be attached to and detached from the housing 100, and a sheet delivery unit 22 that sends out the recording sheet 9 accommodated in the sheet cassette 21 to the image forming unit 4. The recording sheet 9 is a sheet-like image forming medium such as paper, coated paper, postcard, envelope, and OHP sheet.

  The sheet delivery unit 22 includes a pickup roller 221 and a delivery roller 222. The sheet feeding unit 22 picks up the recording sheets 9 one by one from the sheet cassette 21 and further sends the recording sheets 9 to the sheet conveying path 300 of the sheet conveying unit 3.

  The sheet conveyance unit 3 includes a registration roller 31, a conveyance roller 32, a discharge roller 33, and the like. The registration roller 31 and the conveyance roller 32 convey the recording sheet 9 along the sheet conveyance path 300. Further, the discharge roller 33 discharges the recording sheet 9 on which an image has been formed in the middle of the sheet conveyance path 300 from the discharge port of the sheet conveyance path 300 onto the discharge tray 101.

  The developer container 40 and the image forming unit 4 are provided for each color of the developer (toner). The symbols Y, C, M, and K in the figure represent the corresponding developer colors (yellow, cyan, magenta, and black), respectively. The developer of each color is supplied to each of the image forming units 4 from each of the developer containers 40 that can be attached to and detached from the casing 100.

  Each of the image forming portions 4 provided for each color of the developer is disposed at a position along the rotating endless intermediate transfer belt 71. Each of the image forming units 4 forms images (toner images) of different colors on the surface of the rotating intermediate transfer belt 71 so as to overlap each other.

  Each of the image forming units 4 includes a drum-shaped photoconductor 41, a charging unit 42, a developing unit 43, a primary transfer unit 45, a charge eliminating unit 46, a primary cleaning unit 47, and the like. The photoreceptor 41 is an example of an image carrier.

  The intermediate transfer belt 71 is an endless belt-like member formed in an annular shape. The intermediate transfer belt 71 rotates in a state of being spanned between the driving roller 73 and the driven roller 74. In the following description, a direction in which the intermediate transfer belt 71 rotates (moves) along the arrangement direction of the plurality of image forming units 4 is referred to as a belt rotation direction R1.

  In each of the image forming units 4, the photoreceptor 41 rotates at a peripheral speed corresponding to the peripheral speed (moving speed) of the intermediate transfer belt 71, and the charging unit 42 uniformly charges the surface of the photoreceptor 41. Let

  Further, an electrostatic latent image is written on the surface of the photosensitive member 41 charged by the optical scanning unit 5 having a laser light source (not shown), the polygon mirror 51, and the deflecting optical device 52 by scanning the laser beam. Further, the developing unit 43 supplies the toner (developer) to the photoconductor 41 to develop the electrostatic latent image into a toner image. The optical scanning unit 5 is generally called a laser scanning unit (LSU).

  Further, the primary transfer unit 45 transfers the toner image on the photoreceptor 41 onto the surface of the intermediate transfer belt 71. Further, the primary cleaning unit 47 cleans the surface of the photoreceptor 41 by removing the toner remaining on the surface of the photoreceptor 41.

  The charge removal unit 46 provided in each of the image forming units 4 is provided between the primary transfer unit 45 and the primary cleaning unit 47. For example, the charge removal unit 46 is fixed to a surface of the primary cleaning unit 47 on the primary transfer unit 45 side.

  The charge removal unit 46 is a device that outputs light (charge removal light) for discharging the photoreceptor 41. The static elimination unit 46 outputs a first static elimination light L1 and a second static elimination light L2.

  The first charge removal light L1 is charge removal light that travels between the primary transfer portion 45 and the primary cleaning portion 47 toward the upstream side in the belt rotation direction R1. On the other hand, the second charge removal light L2 is charge removal light that travels between the primary transfer portion 45 and the primary cleaning portion 47 toward the downstream side in the belt rotation direction R1.

  In the example shown in FIG. 2, the static elimination unit 46 includes a light source 461 and an optical branching device 462 mounted on a substrate 460, and the optical branching unit 462 removes the emitted light (static elimination light) from the light source 461. The electric light L1 and the second charge eliminating light L2 are branched.

  That is, in the charge removal unit 46, the light source 461 is a light source shared by the outputs of the first charge removal light L1 and the second charge removal light L2. The light source 461 is, for example, a light emitting diode.

  In each of the image forming units 4, the first charge removal light L 1 is a post-transfer removal that is irradiated between a portion of the photoconductor 41 facing the primary transfer unit 45 and a portion corresponding to the primary cleaning unit 47. It is lightning.

  On the other hand, in each of the image forming units 4, the second charge-removing light L <b> 2 has a location corresponding to the developing unit 43 in the image forming unit 4 adjacent to the image forming unit 4 on the downstream side in the belt rotation direction R <b> 1. This is a pre-transfer charge eliminating light that is irradiated between a portion corresponding to the primary transfer portion 45.

  In this embodiment, the black image forming unit 4K, the magenta image forming unit 4M, the cyan image forming unit 4C, and the yellow image forming unit 4Y are arranged in order from the downstream side to the upstream side in the belt rotation direction R1. Has been placed.

  Accordingly, the second charge removal light L2 (the charge removal light before transfer) is transferred from the charge removal section 46 of the yellow image formation section 4Y to the photoreceptor 41 of the cyan image formation section 4C, one downstream side. The image forming section 4C for cyan is one downstream from the charge eliminating section 46 to the photoconductor 41 of the magenta image forming section 4M, and the one downstream from the charge eliminating section 46 of the magenta image forming section 4M. The photosensitive member 41 of the black image forming unit 4K is irradiated with the light.

  When the three photosensitive members 41 corresponding to three colors (black, magenta, and cyan) that are relatively conspicuous are irradiated with the second charge removal light L2 in addition to the first charge removal light L1, the primary transfer portion 45 is used. The transfer voltage can be kept relatively low. As a result, image memory problems are less likely to occur.

  In the yellow image forming unit 4Y disposed on the most upstream side in the belt rotation direction R1, the photoreceptor 41 does not receive the pre-transfer charge removal light. However, since the yellow image is not conspicuous, the problem of the image memory is not easily revealed even if the second charge eliminating light L2 (pre-transfer charge eliminating light) is not applied to the photoconductor 41 of the yellow image forming unit 4Y.

  The roller-shaped secondary transfer unit 72 transfers the image (toner image) transferred to the surface of the intermediate transfer belt 71 to the recording sheet 9 moving on the sheet conveyance path 300.

  The fixing unit 6 sandwiches the recording sheet 9 on which the toner image is formed between a fixing roller 61 including a heater 610 such as a halogen heater and a pressure roller 62, and sends the recording sheet 9 to a subsequent process. Thus, the fixing unit 6 heats the toner image (image) on the recording sheet 9 and fixes the image on the recording sheet 9.

  The control unit 8 displays an operation menu or the like on the operation display unit 80, and based on input information input through the operation display unit 80 and detection information of various sensors (not shown), Control electrical equipment.

  For example, the control unit 8 includes a microprocessor unit (MPU) and a storage unit. The MPU executes various arithmetic processes by executing a control program recorded in advance in the storage unit. Thereby, the control unit 8 controls the image forming apparatus 10 in an integrated manner.

  The displacement mechanism 75 shown in FIGS. 5 and 6 is a mechanism for changing the positional relationship between the intermediate transfer belt 71 and the photosensitive member 41 (image carrier). The displacement mechanism 75 can selectively switch the operation states of the plurality of image forming units 4 to a plurality of operation modes including a first color mode and a second color mode by changing the positional relationship. The displacement mechanism 75 is an example of the color mode switching unit.

  In the present embodiment, the displacement mechanism 75 can selectively switch the operation state between a color mode corresponding to the first color mode and a monochrome mode which is an example of the second color mode. The color mode is a mode in which the photoconductors 41 of all the image forming units 4 operate in contact with the intermediate transfer belt 71. On the other hand, the monochrome mode is a mode in which only the photosensitive member 41 of the black image forming unit 4K located on the most downstream side in the belt rotation direction R1 is in contact with the intermediate transfer belt 71.

  For example, the displacement mechanism 75 rotates a support frame 76 that supports the primary transfer unit 45 of the remaining image forming units 4 (4Y, 4C, 4M) excluding the driven roller 74 and the black image forming unit 4K. It is a mechanism to move. In this case, the displacement mechanism 75 rotates the support frame 76 around the primary transfer portion 45 of the black image forming portion 4K, for example. The displacement mechanism 75 is, for example, a solenoid actuator.

  When the color mode is selected, the control unit 8 turns on the charge removal unit 46 of the image forming unit 4 for all four colors. On the other hand, when the monochrome mode is selected, the control unit 8 controls the neutralization unit 46 of the black image forming unit 4K operating in the monochrome mode and the magenta adjacent to the upstream side of the belt rotation direction R1. The charge removing unit 46 of the image forming unit 4M is turned on, and the other charge removing units 46 are turned off.

  As described above, in the image forming apparatus 10, the static elimination unit 46 of each of the image forming units 4 also functions as post-transfer static elimination and pre-transfer static elimination. In addition, each of the static eliminating units 46 is the same component. Here, consider a case where the image forming apparatus 10 does not include the reflection unit 48. In this case, in the black image forming unit 4K located on the most downstream side in the belt rotation direction R1, the second charge removal light L2 output from the charge removal unit 46 toward the downstream side in the belt rotation direction R1 is: It does not function as the pre-transfer charge eliminating light. For this reason, in the black image forming unit 4K, the charge eliminating unit 46 consumes power wastefully.

  In addition, in the black image forming unit 4K located on the most downstream side, the use of the charge eliminating unit 46 that does not output the second charge eliminating light L2 (the charge eliminating light before transfer) is desired to make the parts as common as possible. It is against the need.

  On the other hand, when the image forming apparatus 10 including the reflection unit 48 is employed, the reflection unit 48 effectively uses the second charge removal light L2 of the black image formation unit 4K as described below. Therefore, in the case where the charge removal unit 46 functions as both post-transfer charge removal and pre-transfer charge removal, the black parts located on the most downstream side in the belt rotation direction R1 while sharing the parts of the plurality of charge removal units 46 as much as possible. It is possible to prevent wasteful power consumption in the charge removal section 46 of the image forming section 4K.

  Hereinafter, the reflection part 48 will be described. The reflection unit 48 transmits the second charge elimination light L2 in the black image forming unit 4K located on the most downstream side in the belt rotation direction R1 among the plurality of image forming units 4 to the upstream side in the belt rotation direction R1. Reflects in the direction toward. The reflection part 48 is, for example, a mirror, a silver metal stay, or a silver paint. The black image forming unit 4K is an example of the most downstream image forming unit.

  As shown in FIGS. 3 and 4, each of the static elimination units 46 in the present embodiment includes a transparent cover that covers the light source 461 and the optical branching device 462 that output the first static elimination light L1 and the second static elimination light L2. Part 4600 is provided. The cover unit 4600 is a dust-proof cover that prevents dust such as the developer from entering the optical system portion of the charge removal unit 46.

  3 and 4, a part of the photoconductor 41 and a part of the primary cleaning unit 47 are drawn with imaginary lines (two-dot chain lines). In addition to the cover portion 4600 being colorless and transparent, the cover portion 4600 may be colored and transparent.

  As shown in FIG. 3, in all the remaining image forming units 4 (4M, 4C, 4Y) except the black image forming unit 4K, the first charge removal light L1 passes through the cover unit 4600. The portion of the image forming unit 4 after the image transfer on the photoconductor 41 is irradiated. Further, the second charge elimination light L2 passes through the cover portion 4600 and is irradiated to a location before image transfer on the adjacent photoreceptor 41 (not shown) on the downstream side.

  Further, as shown in FIG. 4, in the black image forming unit 4K, the first charge removal light L1 passes through the cover unit 4600 and after image transfer on the photoconductor 41 of the black image forming unit 4K. It is irradiated to the place. On the other hand, in the black image forming unit 4K, the second charge eliminating light L2 is reflected by the reflecting unit 48, travels upstream in the belt rotation direction R1, passes through the cover unit 4600, and passes through the black image. The portion of the photoconductor 41 of the forming unit 4K is irradiated with the image transferred portion.

  In the example shown in FIG. 4, the reflection part 48 is formed along the surface of the cover part 4600. In this case, the reflection portion 48 is formed along at least a downstream surface of the cover portion 4600 in the belt rotation direction R1. If the reflection part 48 is also formed on the other surface of the cover part 4600, the second charge removal light L2 is more efficiently reflected toward the upstream side in the belt rotation direction R1.

  In addition, since the reflection portion 48 is formed along the surface of the cover portion 4600, the reflection portion 48 can be integrated with the charge removal portion 46 of the black image forming portion 4K, and the parts can be compact. Can be realized. For example, it is conceivable that the reflection part 48 is bonded to the surface of the cover part 4600.

  In FIG. 4, the reflection portion 48 is formed along the inner surface of the cover portion 4600. However, it is conceivable that the reflection part 48 is formed along the outer surface of the cover part 4600.

  In the black image forming unit 4K, both the first charge removal light L1 and the second charge removal light L2 act as the post-transfer charge removal light. As a result, it is possible to prevent wasteful power consumption in the black image forming unit 4K located on the most downstream side in the belt rotation direction R1, while sharing the components of each of the plurality of static eliminating units 46.

  In the image forming apparatus 10, the relative permittivity of the photoreceptor 41 of the black image forming unit 4 </ b> K (the most downstream image forming unit) is higher than the relative permittivity of the photoreceptor 41 of the other image forming units 4. Is also considered large. For example, the photoconductor 41 of the black image forming unit 4K (the most downstream image forming unit) is an amorphous silicon (a-Si) photoconductor, and the photoconductors 41 of all the remaining image forming units 4 are used. It may be an organic photoreceptor (OPC).

  In general, the amorphous silicon photoconductor has a relative dielectric constant larger than that of the organic photoconductor, and is more excellent in durability (abrasion resistance) than the organic photoconductor. However, since the amorphous silicon photoconductor has a large relative dielectric constant, it is necessary to irradiate a stronger (large light amount) static elimination light than the organic photoconductor.

  In the image forming apparatus 10 including the reflection unit 48, the post-transfer neutralization light that is stronger than the other photoconductors 41 is irradiated on the photoconductor 41 of the black image forming unit 4 </ b> K. For this reason, even if the light sources 461 of the four static elimination units 46 and the power supplied to the light sources 461 are the same, the photoconductor 41 (the amorphous silicon photoconductor) of the black image forming unit 4K is sufficient. It is possible to remove static electricity.

  In other words, even if only the photoconductor 41 of the black image forming unit 4K is of a different type, the four static elimination units 46 and the power supplied to them can be shared, and the apparatus It can be simplified.

  On the other hand, it is conceivable that all the photoconductors 41 are of the same type. In this case, the power supplied to the neutralization unit 46 of the black image forming unit 4K can be made smaller than that to the other neutralization units 46. As a result, it is possible to reduce the power consumption of the charge removal unit 46 by the amount that wasteful charge removal light output is eliminated.

  Next, a case where the image forming apparatus 10 does not include the light shielding switching unit 77 will be considered before the description of the light shielding switching unit 77. In this case, when the monochrome mode (single color mode) is selected, when the neutralization unit 46 of the second magenta image forming unit 4M from the most downstream side in the belt rotation direction R1 emits light, There is a possibility that the 1 static elimination light L1 may adversely affect the stopped photoconductor 41 in the magenta image forming unit 4M.

  In addition, when the monochrome mode is selected and the neutralization unit 46 of the second magenta image forming unit 4M from the most downstream side in the belt rotation direction R1 is turned off, the most downstream side for black The image forming unit 4K does not perform static elimination before transfer. In this case, there is a risk of image quality failure due to the transfer memory during image formation in the monochrome mode.

  On the other hand, if the image forming apparatus 10 including the light shielding switching unit 77 is employed, the first charge removal light L1 from the charge removal unit 46 adversely affects the photoconductor 41, as will be described below. In addition, it is possible to prevent the occurrence of image quality defects caused by turning off the charge removal unit 46

  The light shielding switching unit 77 outputs the first charge removal light L1 in the magenta image forming unit 4M located adjacent to the upstream side of the belt rotation direction R1 with respect to the black image forming unit 4K operating in the monochrome mode. It is possible to block.

  More specifically, when the color mode is selected, the light shielding switching unit 77 does not block the first static elimination light L1 toward the photoconductor 41 in the magenta image forming unit 4M. On the other hand, when the monochrome mode is selected, the light shielding switching unit 77 shields the first charge removal light L1 toward the photoconductor 41 in the magenta image forming unit 4M.

  The light shielding switching unit 77 is displaced in conjunction with the movement of the displacement mechanism 75 by being supported by the support frame 76. More specifically, the light shielding switching unit 77 is interlocked with the movement of the displacement mechanism 75 to block the optical path of the first static elimination light L1 in the magenta image forming unit 4M and the first static elimination light. It is displaced between the positions where the optical path of L1 is not blocked.

  When the color mode is selected, the light-shielding part that forms part of the light-shielding switching part 77 exists at a retracted position that does not block the optical path of the first charge removal light L1 (FIG. 5). On the other hand, when the monochrome mode is selected, the light shielding unit that forms part of the light shielding switching unit 77 is present at a blocking position that blocks the optical path of the first charge removal light L1.

  Therefore, when the color mode is selected in the second image forming unit 4 (4M) from the most downstream side in the belt rotation direction R1, the light shielding switching unit 77 receives the first charge removal light L1. The photosensitive member 41 is irradiated and the second charge eliminating light L2 is irradiated to the photosensitive member 41 of the image forming unit 4 (4K) on the most downstream side.

  Further, the light shielding switching unit 77 is configured to output the first charge removal light L1 when the monochrome mode is selected in the second image forming unit 4 (4M) from the most downstream side in the belt rotation direction R1. The photosensitive member 41 is not irradiated and the second charge eliminating light L2 is irradiated to the photosensitive member 41 of the image forming unit 4 (4K) on the most downstream side.

  As described above, when the image forming apparatus 10 is employed, the neutralization unit 46 of the magenta image forming unit 4M is lit in a state where the monochrome mode is selected. The black image forming unit 4K performs static elimination before transfer. For this reason, it is possible to prevent image quality defects due to the transfer memory during image formation in the monochrome mode.

  Further, in the magenta image forming unit 4M when the monochrome mode is selected, the first charge removal light L1 from the charge removal unit 46 is interrupted on the way to the photoconductor 41. For this reason, it is possible to prevent the first charge eliminating light L1 from adversely affecting the stopped photoconductor 41 in the magenta image forming unit 4M.

  Second Embodiment Next, an image forming apparatus 10A according to a second embodiment of the present invention will be described with reference to FIG. The image forming apparatus 10 </ b> A has a configuration in which the arrangement position of the reflection portion 48 is different from that of the image forming apparatus 10.

  FIG. 7 is a cross-sectional view of the charge removal unit 46 and the reflection unit 48 in the black image forming unit 4K of the image forming apparatus 10A. 7, the same components as those shown in FIGS. 1 to 6 are given the same reference numerals.

  The reflecting portion 48 of the image forming apparatus 10 is formed integrally with the cover portion 4600 of the charge eliminating portion 46 in the black image forming portion 4K. On the other hand, the reflection portion 48 of the image forming apparatus 10 </ b> A is fixed at a position spaced from the charge removal portion 46.

  Even when the image forming apparatus 10 </ b> A including the reflection unit 48 as shown in FIG. 7 is employed, the same effects as those obtained when the image forming apparatus 10 is employed can be obtained.

  Third Embodiment Next, an image forming apparatus 10B according to a third embodiment of the present invention will be described with reference to FIG. Compared with the image forming apparatus 10, the image forming apparatus 10 </ b> B has a configuration in which the light shielding switching unit 77 is removed and the charge removing unit 46 is replaced with a charge removing unit 46 </ b> B.

  FIG. 8 is a configuration diagram of the charge removal unit 46B in the image forming apparatus 10B. In FIG. 8, the same components as those shown in FIGS. 1 to 7 are given the same reference numerals. Hereinafter, differences between the charge removal unit 46B of the image forming apparatus 10B and the charge removal unit 46 of the image forming apparatus 10 will be described.

  As shown in FIG. 8, the charge removal unit 46B includes a first charge removal light source 4611 for the first charge removal light L1 and a second charge removal light source 4612 for the second charge removal light L2 mounted on the substrate 460. The first static elimination light source 4611 outputs light toward the upstream side in the belt rotation direction R1, and the second static elimination light source 4612 outputs light toward the downstream side in the belt rotation direction R1.

  Each of the charge removal units 46B has a circuit capable of independently turning on and off the first charge removal light source 4611 and the second charge removal light source 4612. The first static elimination light source 4611 and the second static elimination light source 4612 are, for example, a plurality of light emitting diodes arranged along the rotation axis direction of the photoreceptor 41.

  A first power supply line 463, a second power supply line 464, and a ground line 465 are formed on the substrate 460 of each of the charge removal units 46B.

  The first power supply line 463 is a power supply line for the first static elimination light source 4611, and the second power supply line 464 is a power supply line for the second static elimination light source 4612. In the substrate 460, a first terminal 4630 that is a connection end of the first power supply line 463 and a second terminal 4640 that is a connection end of the second power supply line 464 are provided independently. The ground line 465 is a line that connects the first power supply line 463 and the second power supply line 464 to a ground reference potential portion.

  The first power supply line 463 and the second power supply line 464 of the static eliminating unit 46 in the black image forming unit 4K, and the second power supply line 464 of the static eliminating unit 46 in the adjacent magenta image forming unit 4M. Is electrically connected to the first static elimination drive line 4601. Further, in the magenta image forming unit 4M, all of the remaining image forming units 4 except for the first power supply line 463 of the static eliminating unit 46, the black image forming unit 4K, and the magenta image forming unit 4M. The first static elimination light source 4611 and the second static elimination light source 4612 are electrically connected to a second static elimination drive line 4602.

  That is, the light source drive lines for the four static elimination units 46 are integrated into two lines, the first static elimination drive line 4601 and the second static elimination drive line 4602.

  When the color mode is selected, the control unit 8 outputs a light source drive signal to both the first charge removal drive line 4601 and the second charge removal drive line 4602. Thereby, both the post-transfer charge removal and the pre-transfer charge removal are performed in the image forming units 4 of all four colors.

  On the other hand, when the monochrome mode is selected, the control unit 8 outputs the light source drive signal to the first static elimination drive line 4601 and does not output the light source drive signal to the second static elimination drive line 4602. . Thereby, the post-transfer charge removal and the pre-transfer charge removal are performed only in the black image forming unit 4K.

  When the monochrome mode is selected, the first static elimination light source 4611 is turned off in the magenta image forming unit 4M. Therefore, it is possible to prevent the photosensitive member 41 of the stopped magenta image forming unit 4M from being adversely affected by the first charge eliminating light L1.

  [Other Application Examples] In the image forming apparatuses 10, 10A, and 10B described above, the positional relationship between the magenta image forming unit 4M and the cyan image forming unit 4C in the belt rotation direction R1 is reversed. It is also possible.

  In the image forming apparatuses 10 and 10A, the light shielding switching unit 77 may be an optical shutter fixed in the optical path of the first charge removal light L1 in the magenta image forming unit 4M. In this case, the optical shutter selectively selects the aperture portion located in the optical path of the first charge removal light L1 between a transparent state that allows the first charge removal light L1 to pass and an opaque state that blocks the first charge removal light L1. It is possible to switch to. The optical shutter is, for example, a liquid crystal shutter.

  The image forming apparatus according to the present invention can be freely combined with the above-described embodiments and application examples, or can be appropriately modified within the scope of the invention described in each claim. Alternatively, it may be configured by omitting a part.

2: Sheet feeding unit 3: Sheet conveying unit 4: Image forming unit 4C: Cyan image forming unit 4K: Black image forming unit 4M: Magenta image forming unit 4Y: Yellow image forming unit 5: Optical scanning unit 6: Fixing unit 8: Control unit 9: Recording sheet 10, 10A, 10B: Image forming apparatus 21: Sheet cassette 22: Sheet feeding unit 31: Registration roller 32: Conveying roller 33: Discharge roller 40: Developer container 41: Photoconductor 42 : Charging unit 43: Developing unit 45: Primary transfer unit 46, 46: Static eliminating unit 47: Primary cleaning unit 48: Reflecting unit 51: Polygon mirror 52: Deflection optical device 61: Fixing roller 62: Pressure roller 71: Intermediate transfer Belt 72: Secondary transfer unit 73: Drive roller 74: Driven roller 75: Displacement mechanism (color mode switching unit)
76: support frame 77: light shielding switching unit 80: operation display unit 100: casing 101: discharge tray 221: pickup roller 222: delivery roller 300: sheet conveyance path 460: substrate 461: light source 462: light splitter 463: first Feed line 464: Second feed line 465: Ground line 610: Heater 4600: Cover portion 4611: First static elimination light source 4612: Second static elimination light source 4630: First terminal 4640: Second terminal L1: First static elimination light L2: First 2 Static elimination light R1: Belt rotation direction

Claims (5)

An image carrier, a developing unit for developing an electrostatic latent image on the surface of the image carrier, a primary transfer unit for transferring an image to the intermediate transfer belt, and the image, which are respectively arranged at positions along the rotating endless intermediate transfer belt An image forming apparatus including a plurality of image forming units each including a cleaning unit for cleaning the surface of the carrier, and forming images of different colors on the surface of the intermediate transfer belt,
Provided in each of the image forming units, the first charge removal light traveling between the primary transfer unit and the cleaning unit toward the upstream side in the rotational direction of the intermediate transfer belt and the downstream side in the rotational direction of the intermediate transfer belt. A static elimination unit that outputs a second static elimination light;
Of the plurality of image forming units, the second static elimination light in the most downstream image forming unit located on the most downstream side in the rotation direction of the intermediate transfer belt is reflected in a direction toward the upstream side in the rotation direction of the intermediate transfer belt. A reflection part;
The state of the image forming unit is selectively switched between a first color mode in which all the image forming units operate and a second color mode in which only the most downstream image forming unit among the plurality of image forming units operates. A possible color mode switching unit ,
The static eliminator is
A first static elimination light source for the first static elimination light and a second static elimination light source for the second static elimination light;
A first power supply line for supplying power to the first static elimination light source;
A second power supply line for supplying power to the second static elimination light source;
A ground line connecting the first power feed line and the second power feed line to a ground reference potential unit,
The second of the charge removal unit in the one adjacent to the most downstream image forming unit among the first and second power supply lines and the plurality of image forming units in the charge eliminating unit of the most downstream image forming unit. The power supply line is electrically connected to a first charge removal drive line to which a light source drive signal is supplied in the first color mode and the second color mode,
Of the plurality of image forming units, the first power feeding line of the static eliminating unit and the first power feeding line of the static eliminating unit of all the remaining image forming units in one adjacent to the most downstream image forming unit, and the The second power supply line is an image forming apparatus that is electrically connected to a second charge removal drive line to which the light source drive signal is supplied only in the first color mode .   The image forming apparatus according to claim 1, wherein a relative dielectric constant of the image carrier of the most downstream image forming unit is larger than a dielectric constant of the image carrier of the other image forming unit.   2. The image forming apparatus according to claim 1, wherein the image carrier of the most downstream image forming unit is an amorphous silicon photoconductor, and the image carriers of the other image forming units are organic photoconductors. Each of the static elimination units includes a transparent cover that covers the light sources of the first static elimination light and the second static elimination light,
The reflective portion is formed along the surface of the cover portion, the image forming apparatus according to any one of claims 1 to 3. Yellow the image forming unit of the image is arranged on the most upstream side in the rotational direction of the intermediate transfer belt, an image forming apparatus according to any one of claims 1 to 4.

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