JP2013033116A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clean static removing means without separately setting a cleaning cycle in an image forming apparatus.SOLUTION: The image forming apparatus includes: a secondary transfer roller 35 that transfers a toner image carried on an intermediate transfer belt 31, to a sheet of paper S; a static removing member 40 that removes an electric charge of the sheet of paper S on which the toner image is transferred by the transfer roller 35; drive means (a support member 36 and a cam 37) that makes the transfer roller 35 come into pressure contact with/separate from the intermediate transfer belt 31 and makes the static removing member 40 come closer to/retreat from a conveying path of the sheet of paper S; and a cleaning member 45 that cleans the static removing member 40 when retreating from the conveying path of the static removing member 40. The approach/retreat operation of the static removing member 40 is synchronized with the pressure contact/separation operation of the transfer roller 35.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as an electrophotographic copying machine or printer.

  In general, in an electrophotographic color image forming apparatus, a toner image for each color formed on a photoreceptor is primarily transferred to an intermediate transfer belt and synthesized, and then the secondary transfer from the intermediate transfer belt to a transfer material is performed. doing. In the secondary transfer, an electric field having a reverse polarity is applied to the toner (usually negatively charged) on the intermediate transfer belt from the secondary transfer member and transferred to the transfer material. In such secondary transfer, an appropriate bias is considered in consideration of various colors of toner (variation in charge amount), various types and thicknesses (resistance values) of transfer materials, and environmental conditions such as temperature and humidity. The voltage is controlled.

  However, depending on the conditions, there may be a case where an electric charge more than necessary to attract the toner remains on the transfer material. In this case, due to the electric charge remaining on the transfer material, the transfer material does not peel off from the intermediate transfer belt and wraps around the belt (that is, the occurrence of a paper jam), or even when peeled, the image is discharged due to discharge at the time of peeling. There was a problem that noise was generated. Such a problem is likely to occur in a low humidity environment or when the transfer material is thin paper or recycled paper.

  For this reason, as shown in FIG. 12, the neutralization member 140 is disposed on the downstream side in the transport direction B of the sheet S in the vicinity of the secondary transfer roller 135 facing the intermediate transfer belt 131, and the secondary transfer is performed on the neutralization member 140. A voltage having a polarity opposite to that of the voltage and / or an AC voltage is applied to erase the excess charge applied to the paper S. However, the charge removal member 140 gradually deteriorates the charge removal performance due to paper dust, floating toner, and discharge products adhering to the tips (discharge locations), and image noise may occur due to paper jam or abnormal discharge. . In addition, since the bias voltage is set high for the certainty of static elimination, the degree of dirt adhesion is large and deterioration of the static elimination capability is inevitable.

  Therefore, conventionally, various means for cleaning dirt adhering to the tip of the static elimination member have been taken in order to prevent deterioration of the static elimination performance. For example, Patent Document 1 discloses a mechanism for manually operating a cleaning member. Patent Document 2 discloses a mechanism for automatically cleaning the cleaning member by moving it in the long side direction of the charge removal member. Patent Document 3 discloses a mechanism for cleaning a cleaning member by automatically or manually moving it in the short side direction of the static elimination member.

  However, in the conventional cleaning mechanism, it is necessary to execute a cleaning operation separately from the normal image forming operation for cleaning the static eliminator, regardless of whether it is automatic or manual. This reduces the productivity of image formation. . The cleaning operation needs to be performed periodically, and a method of shortening one cleaning time to increase the frequency or increasing one cleaning time to decrease the frequency is employed. In any case, since the image forming process is stopped / interrupted during cleaning, productivity is sacrificed.

  Furthermore, since the pointed end of the static elimination member is always exposed, it is easily contaminated and easily damaged. For example, when a paper jam occurs, unfixed toner on the transfer material is often scattered at the secondary transfer portion, and the charge removal member is accelerated. Also, when removing the jammed transfer material or replacing the transfer member, the transfer material or the user's hand may come into contact with the tip of the static elimination member, the tip may be bent or broken, or the user's hand may be damaged. To do.

JP 2004-45958 A Japanese Patent Laid-Open No. 9-190051 Japanese Patent Laid-Open No. 8-211751

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of cleaning a static eliminating unit without separately setting a cleaning cycle.

An image forming apparatus according to an aspect of the present invention is
Transfer means for transferring the toner image carried on the image carrier to a transfer material;
Neutralizing means for neutralizing the charge of the transfer material onto which the toner image has been transferred by the transfer means;
A drive unit that presses / separates the transfer unit with respect to the image carrier, and drives the discharger to approach / withdraw from the transfer path of the transfer material;
A cleaning means for cleaning the static elimination means when the static elimination means is retracted from the conveyance path;
With
The approach / retraction operation of the static elimination means is synchronized with the pressure contact / separation operation of the transfer means;
It is characterized by.

  In the image forming apparatus, the charge eliminating unit approaches / retreats with respect to the conveyance path in synchronization with the pressing / separating operation of the transfer unit with respect to the image carrier, and is cleaned by the cleaning unit at the time of retraction. In normal control of the image forming apparatus, when the image forming process for one job is completed, or when the well-known image stabilization control is started, the transfer member (secondary transfer member) is an image carrier (intermediate transfer belt). Spaced apart. Since the static eliminator is cleaned at this timing, there is no need to set a separate cleaning cycle.

  By the way, in this specification, the operation of the discharging means is synchronized with the operation of the transferring means that the pressing / separating operation of the transferring means and the approaching / retracting operation of the discharging means are performed at the same time, or the proximity of the discharging means This means that the retracting operation is performed with a slight time lag in the pressing / separating operation of the transfer means.

  According to the present invention, the static eliminator can be cleaned without separately setting a cleaning cycle.

1 is a schematic configuration diagram of an image forming apparatus. FIG. 2A is a front view showing a time when the secondary transfer roller is pressed, and FIG. 4B is a front view showing the time when the secondary transfer roller is separated. FIG. 5A is a perspective view showing a charge removal member and a cleaning member, FIG. 5A is a perspective view showing a state close to a conveyance path, and FIG. It is a front view which shows 2nd Example. (A) is a front view showing when the secondary transfer roller is pressed, (B) is a front view showing a state in which the secondary transfer roller is separated and the charge eliminating member is in close proximity, (C) FIG. 6 is a front view showing a state in which the secondary transfer roller is separated and the charge removal member is retracted. It is a block diagram of a control circuit showing a fourth embodiment. It is a flowchart figure of the control procedure which shows 4th Example. The modification 1 of a cleaning member is shown, (A) is explanatory drawing which shows the state before an assembly, (B) is explanatory drawing which shows the assembled state. It is explanatory drawing which shows the modification 2 of a cleaning member. It is explanatory drawing which shows the modification 3 of a cleaning member. FIG. 5A is a front view showing a time when the secondary transfer roller is pressed, and FIG. 5B is a front view showing the time when the secondary transfer roller is separated. It is a front view which shows the attachment structure of the conventional static elimination member.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings. In each figure, the same code | symbol is attached | subjected about the same member and part, and the overlapping description is abbreviate | omitted.

(Schematic configuration of color image forming apparatus, see FIG. 1)
As shown in FIG. 1, a color image forming apparatus as an example to which the present invention is applied is a tandem type electrophotographic printer, which is roughly Y (yellow), M (magenta), C (cyan), K ( The process unit 10 (10y, 10m, 10c, 10k) for forming toner images of each color (black) and the intermediate transfer unit 30 are configured.

  The process unit 10 includes a photosensitive drum 11, a charging charger 12, a developing device 13, an image exposure device 14 using an LED, and the like. The light emitted from the image exposure device 14 is used on the respective photosensitive drums 11. The electrostatic latent image drawn on the image is developed by the developing device 13 to form toner images of respective colors. The intermediate transfer unit 30 includes an intermediate transfer belt 31 that is rotationally driven endlessly in the direction of arrow A, and each photoconductor drum 11 is subjected to an electric field applied from a primary transfer roller 32 facing each photoconductor drum 11. The toner image formed above is primarily transferred onto the intermediate transfer belt 31 and synthesized. Note that such an electrophotographic image forming process is well known, and a detailed description thereof will be omitted.

  An automatic paper feeding unit 50 for feeding materials to be transferred (hereinafter referred to as paper) one by one is disposed at the lower part of the apparatus main body, and the paper passes from the paper feeding roller 51 through the timing roller 52 to the intermediate transfer belt. The toner image (composite color image) is secondarily transferred by the electric field applied from the secondary transfer roller 35 by being conveyed to the nip portion between the roller 31 and the secondary transfer roller 35. Thereafter, the sheet is conveyed to the fixing unit 55 where the toner is heated and fixed, and is discharged to a tray portion 56 disposed on the upper surface of the apparatus main body.

  In the color printer having the above configuration, the charge eliminating member 40 is disposed on the downstream side in the sheet conveying direction of the secondary transfer roller 35 that secondarily transfers the toner image from the intermediate transfer belt 31 to the sheet. It relates to the cleaning means. Examples thereof will be described below.

(Refer to the first embodiment, FIG. 2 and FIG. 3)
In the first embodiment, as shown in FIG. 2A, the secondary transfer roller 35 and the charge eliminating member 40 arranged on the downstream side in the transport direction B of the paper S are held by the support member 36. Is elastically urged in the direction of arrow C by a coil spring (not shown) and the position of the cam 37 is restricted. The cam 37 can be driven to rotate about a support shaft 38. The support member 36 is in contact with the shaft portion 35a of the secondary transfer roller 35, and holds the charge eliminating member 40 with the arm portion 36a.

  The support member 36 is made of an insulating material. A transfer voltage having a polarity opposite to the charging polarity of the toner (usually, the toner is negatively charged and a positive voltage is applied to the roller 35) is applied to the secondary transfer roller 35. As shown in FIG. 3A, the static elimination member 40 is a static elimination needle having a plurality of serrated tips arranged in a direction orthogonal to the conveyance direction B, and is formed on the downstream side of the secondary transfer unit. A voltage having a polarity opposite to the transfer voltage (or negative if the secondary transfer voltage is positive as described above) and / or an AC voltage is applied to S. By applying such a voltage, it is possible to erase excess charges on the sheet S, to ensure that the sheet S is peeled off from the intermediate transfer belt 31, and to prevent image noise from being caused by abnormal discharge.

  On the other hand, discharge products, paper powder, floating toner, and the like adhere to the charge removal member 40 (particularly, the tip), and the charge removal performance gradually deteriorates. Therefore, a cleaning member 45 for the static elimination member 40 is disposed. The cleaning member 45 is installed in a state where the position is fixed to a paper passing guide plate, a main body frame, etc. (not shown) so as to sandwich the static elimination member 40 from above and below. The cleaning member 45 takes in the dirt wiped from the static elimination member 40 into the inside, and a brush or a foam material can be used suitably. Urethane rubber, fine cloth, non-woven fabric, wrapping paper and the like may be used.

  Here, the pressure contact / separation operation of the secondary transfer roller 35 with respect to the belt 31 and the cleaning operation (proximity / retraction operation of the charge removal member 40 with respect to the conveyance path) will be described.

  During the printing operation, the secondary transfer roller 35 is positioned to the left as shown in FIG. 2A by the large diameter portion 37a of the cam 37 coming into contact with the support member 36, and is pressed against the belt 31 with a predetermined pressure. doing. At the same time, the static elimination member 40 also has a pointed tip protruding from the cleaning member 45 and close to the conveyance path. In this state, the secondary transfer roller 35 secondarily transfers the toner image onto the paper S, and the charge removal member 40 discharges the paper S immediately after the transfer.

  When one print job is completed, in the standby period until the next print operation, the cam 37 rotates 180 °, and the support member 36 moves in the direction of the arrow C and contacts the small diameter portion 37b. ), The secondary transfer roller 35 is kept away from the belt 31. At the same time, the charge removal member 40 is also retracted in the direction of arrow C, and the tip is accommodated in the cleaning member 45, so that the dirt is wiped off by the cleaning member 45 (see FIG. 3B). When the next print job is instructed, the cam 37 is further rotated 180 ° in the same direction (may be reversed), and the secondary transfer roller 35 is pressed against the belt 31 with the reverse operation to the above, and the charge is eliminated. The member 40 is close to the conveyance path. That is, the state returns to the state shown in FIG.

  In a color printer, image stabilization control that automatically performs registration of each color image and adjustment of toner density of each color is executed in a predetermined cycle. Also in such image stabilization control, the secondary transfer roller 35 is separated from the intermediate transfer belt 31 and, at the same time, the charge removal member 40 is cleaned.

  In the above operation, the static elimination member 40 moves close to / withdraws from the conveyance path simultaneously with the pressing / separating operation of the secondary transfer roller 35 to the intermediate transfer belt 31 and is cleaned by the cleaning member 40 at the time of withdrawal. In the normal control of the color printer, the secondary transfer roller 35 is separated from the intermediate transfer belt 31 when the print processing for one job is completed or the image stabilization control is started. Since the static elimination member 40 is cleaned at this timing, it is not necessary to set a separate cleaning cycle.

  For example, when a cleaning time of 3 seconds is provided, in an apparatus capable of printing x sheets per minute, the number of prints lost by the cleaning operation is x− (x / 60) × 3 seconds = 0.95x sheets. That is, the productivity is reduced by 5%. Such a decrease in productivity does not occur in the first embodiment.

  In the first embodiment, the secondary transfer roller 35 and the charge removal member 40 are fixed to the same support member 36, so that the pressure contact / separation operation of the secondary transfer roller 35 and the approach / retraction operation of the charge removal member 40 are performed. Are performed at the same time. Therefore, it has a simple configuration, does not reduce productivity, and can increase the number of cleanings, so that the static elimination member 40 can be kept clean at all times. For example, when the cleaning operation is performed once for every 500 prints, if the life of the static elimination member 40 is 500,000, the cleaning operation is performed 1,000 times. In the first embodiment, cleaning is performed at the end of one job. For example, when 10 sheets are printed in one job, the cleaning is performed 50,000 times, and the cleaning operation is actually performed 50 times. It will be.

  Further, the discharging member 40 is covered and hidden by the cleaning member 45 during the retraction (see FIGS. 2B and 3B). Thus, for example, contamination of the static elimination member 40 due to scattered toner generated when a paper jam occurs can be avoided, and the user's hand does not come into contact with the tip of the static elimination member 40 when handling the paper jam.

  In addition, as the static elimination member 40, although the static elimination needle which has the several saw-tooth-shaped tip arrange | positioned in the direction orthogonal to the conveyance direction B was shown, it is not limited to this, A several needle shape (wire) May be a static elimination needle protruding toward the conveyance path.

(Refer to the second embodiment, FIG. 4)
A second embodiment is shown in FIG. In the first embodiment, the neutralization member 40 is sandwiched from above and below by the cleaning member 45 composed of two members. However, as shown in FIG. 4, the neutralization member 40 is an arm portion of the support member 36 composed of an insulating material. The cleaning member 45 may be mounted on 36a and pressed against the charge removal member 40 from above. The cleaning member 45 is also fixed in position in this case.

  In the second embodiment, the cleaning member 45 is composed of one member, and its operation and effect are the same as those of the first embodiment.

(Refer to the third embodiment, FIG. 5)
In the third embodiment, as shown in FIG. 5A, the support member 36 is composed of three segments 36b, 36c, and 36d, and each is connected by a pin 36e. The segment 36b contacts the support shaft 35a of the secondary transfer roller 35, the segment 36c connects the segments 36b and 36d and contacts the cam 37, and the segment 36d holds the charge eliminating member 40.

  In the third embodiment, the secondary transfer roller 35 and the charge removal member 40 operate independently while being linked. That is, when the printing operation is performed, the large-diameter portion 37a of the cam 37 contacts the segment 36c, so that the positions of the segments 36b and 36d are restricted to the left as shown in FIG. As a result, the secondary transfer roller 35 is brought into pressure contact with the belt 31 with a predetermined pressure, and the static elimination member 40 has a pointed end protruding from the cleaning member 45 and is close to the conveyance path. In this state, the secondary transfer roller 35 secondarily transfers the toner image onto the paper S, and the charge removal member 40 discharges the paper S immediately after the transfer.

  When one print job is completed, first, the cam 37 rotates approximately 30 ° clockwise (see FIG. 5B). As a result, the segment 36c comes into contact with the middle step portion 37c of the cam 37 and is inclined at substantially 45 °. As a result, the segment 36b moves in the direction of arrow C, and the secondary transfer roller 35 maintains a state of being separated from the belt 31. The segment 36d does not move, and the charge eliminating member 40 maintains a close position to the transport path. Further, when the cam 37 rotates in the clockwise direction (180 ° from the state of FIG. 5A), the segment 36c contacts the large diameter portion 37b of the cam 37. At this time, the position of the segment 36b does not change, and the secondary transfer roller 35 maintains the separated state. On the other hand, the static eliminating member 40 moves (retracts) in the direction of the arrow C integrally with the segment 36c, and the tip is accommodated in the cleaning member 45, so that the dirt is wiped off by the cleaning member 45 (FIG. 5C )reference).

  When the next print job is commanded, the cam 37 is rotated by 180 °, and when the secondary transfer roller 35 is in the separated position, the neutralization member 40 moves in the proximity with the reverse operation. The secondary transfer roller 35 performs a pressure contact operation. As a result, the secondary transfer roller 35 and the charge removal member 40 are restored to the state shown in FIG.

  The same operation is performed at the start of image stabilization control.

  The cleaning operation and its effects in the third embodiment are basically the same as those in the first embodiment. Particularly in the third embodiment, it is possible to prevent the secondary transfer roller 35 from being soiled by dirt spilled from the cleaning member 45. That is, since the cleaning member 45 is located immediately above the secondary transfer roller 35, the dirt that has moved from the static elimination member 40 to the cleaning member 45 spills downward from the cleaning member 45 and the secondary transfer roller 35 may be soiled. It is preferable to prevent such fouling.

  In the third embodiment, the neutralizing member 40 is retracted and cleaned after the secondary transfer roller 35 is separated. That is, even if dirt spills downward from the tip of the cleaning member 45 in the state shown in FIG. 5C, it only falls by the side of the secondary transfer roller 35, and the secondary transfer roller 35 is not damaged. Absent.

  Similarly, the static elimination member 40 performs a proximity operation before the secondary transfer roller 35 performs a pressure contact operation. Even during the proximity operation, dirt may spill downward from the tip of the cleaning member 45. Also in this case, since the secondary transfer roller 35 is in the retracted position, it is not soiled.

(Refer to the fourth embodiment, FIGS. 6 and 7)
In the fourth embodiment, the apparatus shown in FIG. 5 is used, and each time the cumulative number of sheets S (that is, the number of printed sheets) reaches a predetermined number, the proximity / retraction operation (cleaning operation) of the static elimination member 40 is performed. ).

  In the fourth embodiment, as shown in FIG. 6, a CPU 60 for controlling the entire color printer is provided with a storage means 61 for counting the number of prints and storing the cumulative number of prints. The motor M which drives 37 is controlled. At the end of each job or in image stabilization control, only the secondary transfer roller 35 is pressed / separated. The predetermined cumulative number of prints for operating the static elimination member 40 is, for example, 1000 sheets.

  As shown in FIG. 7, the print processing for one job is continued (NO in step S1, step S2). When the print processing for one job is completed (YES in step S1), the cumulative number of prints is checked (step S3). . If the cumulative number of prints does not exceed 1000, the cam 37 is rotated about 30 ° (step S4). As a result, only the secondary transfer roller 35 is separated from the intermediate transfer belt 31. If the cumulative number of prints is 1000 or more (YES in step S3), the cam 37 is rotated 180 ° (step S5). As a result, the secondary transfer roller 35 is separated from the belt 31, and the charge removal member 40 is retracted to perform cleaning. After the processing of steps S4 and S5, the cam 37 is reversed when the next print job is instructed.

  As in the fourth embodiment, the static eliminator 40 is cleaned at a predetermined cycle by controlling the static eliminator 40 so that the proximity / retraction operation (cleaning operation) is performed every time the cumulative number of printed sheets reaches a predetermined number. In addition, it is possible to avoid deformation and damage such as sag, fold, and bend of the static elimination member 40 due to excessive cleaning operation.

(Modification of cleaning member, see FIGS. 8 to 10)
The cleaning member 45 is a member that is in pressure contact with the charge removal member 40, and it is preferable that the pressure contact member is in pressure contact with the opposite side of the charge removal member 40 more strongly than the pointed end side. In other words, by setting the cleaning force on the rear end side opposite to the tip end side higher, it becomes easier to take in the dirt wiped from the static elimination member 40 into the cleaning member 45, and the dirt spills out of the cleaning member 45. Contamination of the secondary transfer roller 35 and the machine is avoided as much as possible. In addition, when the static elimination member 40 is composed of a plurality of serrated or needle-like static elimination needles arranged in a direction orthogonal to the conveyance direction B, and the static elimination needle has a sharp tip facing the conveyance path, the sharp tip is The cleaning member 45 may be stuck. However, by setting the pressure of the cleaning member 45 low in the direction in which the static elimination member 40 is close to the transport path, the risk of tip deformation and damage can be avoided.

  As shown in FIG. 8 (A), the first modification of the cleaning member in which the opposite side of the static elimination member 40 is pressed more strongly than the pointed end side has the rectangular parallelepiped-shaped cleaning members 45a and 45b in the vertical direction. The holding plate 46 having the rigidity of the cleaning member 45b is inclined so that the rear end portion is strongly pressed against the cleaning member 45a (see FIG. 8B).

  As shown in FIG. 9, Modification 2 of the cleaning member 40 has a higher rigidity of the cleaning member 45 c placed on the rear end side than the cleaning member 45 b placed on the pointed end side with respect to the rectangular parallelepiped cleaning member 45 a. It is a thing.

  The cleaning member 45 may have a brush shape. When using a brush as a cleaning member, in order to press the opposite side of the static elimination member 40 more strongly than the tip side, the brush density on the opposite side is made higher than the tip side or the brush on the opposite side than the tip side is used. What is necessary is just to raise the fineness. Alternatively, as in Modification 3 shown in FIG. 10, the bristle of the brush 45 d may be shorter on the opposite side than the pointed side.

(Refer to the fifth embodiment, FIG. 11)
In the fifth embodiment, as shown in FIG. 11A, a wire 41 that performs corona discharge arranged in a direction orthogonal to the conveyance direction B of the paper S is used as the static elimination means. Although not shown, the shield plate 42 to which the static elimination wire 41 is attached is held by a support member (for example, the support member 36 shown in FIG. 2) that holds the secondary transfer roller 35. Therefore, the static elimination wire 41 approaches / withdraws to / from the conveyance path in synchronization with the pressure contact / separation operation of the secondary transfer roller 35 with respect to the belt 31. On the other hand, the cleaning member 45 is arranged in a fixed position, sandwiches the retracted static elimination wire 41, and wipes off the dirt (see FIG. 11B). The operations of the secondary transfer roller 35 and the static elimination wire 41 may be either the first embodiment or the third embodiment.

  Note that the image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  Particularly, in the various embodiments, the form in which the sheet is conveyed in the vertical direction through the secondary transfer unit is shown, but the form in which the sheet is conveyed in the horizontal direction through the secondary transfer unit may be used.

  As described above, the present invention is useful for an image forming apparatus using an electrophotographic method, and is particularly excellent in that the static eliminator can be cleaned without separately setting a cleaning cycle.

DESCRIPTION OF SYMBOLS 10 ... Process unit 31 ... Intermediate transfer belt 35 ... Secondary transfer roller 36 ... Supporting member 37 ... Cam 40 ... Static elimination member 41 ... Static elimination wire 45 ... Cleaning member 60 ... CPU
61 ... Storage means S ... Paper

Claims (12)

Transfer means for transferring the toner image carried on the image carrier to a transfer material;
Neutralizing means for neutralizing the charge of the transfer material onto which the toner image has been transferred by the transfer means;
A drive unit that presses / separates the transfer unit with respect to the image carrier, and drives the discharger to approach / withdraw from the transfer path of the transfer material;
A cleaning means for cleaning the static elimination means when the static elimination means is retracted from the conveyance path;
With
The approach / retraction operation of the static elimination means is synchronized with the pressure contact / separation operation of the transfer means;
An image forming apparatus.   The transfer means and the charge removal means are fixed to the same support member, and the pressure contact / separation operation of the transfer means and the approach / retraction operation of the charge removal means are performed simultaneously. The image forming apparatus according to 1.   The image forming apparatus according to claim 1, wherein the cleaning unit is positioned immediately above the transfer unit, and the charge removal unit performs a retreat operation after the transfer unit is separated.   4. The image forming apparatus according to claim 1, wherein the cleaning unit is positioned immediately above the transfer unit, and the neutralization unit performs a proximity operation before the transfer unit is pressed. 5. A storage means for storing the cumulative number of sheets to be transferred;
The static elimination means performs a proximity / retraction operation every time the cumulative transport number reaches a predetermined number.
The image forming apparatus according to claim 1, 3 or 4.   6. The image forming apparatus according to claim 1, wherein the discharging unit is covered by the cleaning unit when retracted.   7. The image forming apparatus according to claim 1, wherein the charge eliminating unit includes a wire that performs corona discharge and is disposed in a direction orthogonal to the transport direction. 8.   The neutralization unit includes a plurality of serrated or needle-shaped neutralization needles arranged in a direction orthogonal to the conveyance direction, and the neutralization needle has a pointed tip facing the conveyance path. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 8, wherein the cleaning unit includes a member that presses against the static elimination needle, and the pressing member presses the opposite side relatively strongly than the pointed end side.   The image forming apparatus according to claim 8, wherein the cleaning unit has a brush shape and has a higher brush density on the opposite side than the tip side.   9. The image forming apparatus according to claim 8, wherein the cleaning unit has a brush shape and has a bristle on the opposite side of the tip side shorter than the pointed end side.   The image forming apparatus according to claim 8, wherein the cleaning unit has a brush shape and has a higher brush fineness on the opposite side than the tip side.

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