JP2003057906A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an excessive cleaning load on a photoreceptor cleaning means caused due to a jam, in a color image forming device that forms an image in such a manner that toner images formed by corresponding photoreceptor units are superimposed onto an intermediate transfer body. SOLUTION: In case a jam detecting means detects a jam during image formation, the jam is processed according to a jam process program and the output of a primary transfer means is turned on for a fixed length of time and then turned off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used for color image formation such as a copying machine, a printer and a fax machine, and more particularly, a photoconductor unit for forming a toner image on an image forming body is provided along an intermediate transfer body. The present invention relates to a so-called tandem type image forming apparatus in which a plurality of sets are arranged and a toner image is superposed on the intermediate transfer member to form a color image.

[0002]

2. Description of the Related Art A photoconductor unit which is provided with a charging means, an exposing means and a developing means on the periphery of an image forming body, and which transfers a toner image formed on the image forming body onto an intermediate transfer body by a primary transfer means. A plurality of sets are provided along the intermediate transfer body, and a toner image is superimposed on the intermediate transfer body to form a color image,
In a tandem type image forming apparatus that transfers a color image formed by superimposing on a transfer material by a secondary transfer means, a toner image formed on an image forming body of each photoconductor unit is primarily transferred. In order to clean the transfer residual toner generated when the image is transferred to the intermediate transfer body by the means, a photoconductor cleaning means is provided at a position downstream of the primary transfer means along each image forming body. Further, an intermediate transfer member cleaning unit for cleaning transfer residual toner generated when the color image transferred on the intermediate transfer member is transferred onto the transfer material by the secondary transfer unit is provided along the intermediate transfer member as a secondary transfer unit. It is provided in the downstream position. (1) A blade made of an elastic resin is used as the photosensitive member cleaning unit and the intermediate transfer member cleaning unit,
The transfer residual toner in the adhered state is cleaned by rubbing the surface of the image forming body or the surface of the intermediate transfer body. However, the blade cleaning means has a limited cleaning ability. For example, when a jam occurs and the primary transfer is turned off and the toner image on the image forming body reaches the photoreceptor cleaning means without being transferred, A large amount of adhered toner reaches the photoconductor cleaning means, and it is difficult to clean all at once,
A part of the toner slips between the image forming body and the blade to cause cleaning failure, which causes toner filming. As means for improving the cleaning ability, a cleaning assisting means for contacting a rotating brush or a rotating sponge roller charged with a polarity opposite to that of the adhered toner with an image forming body to clean the image forming body is provided at an upstream position of the blade cleaning means, or cleaning charging is performed. It has been done. (2) Further, in the electrophotographic photosensitive member which is an image forming member, the characteristics of the photosensitive member particularly change the surface potential of the photosensitive member depending on the environment and use conditions. In order to obtain a uniform color image, it is necessary to keep the surface potential of the photoconductor constant, and a surface potential sensor that detects the surface potential of the photoconductor is installed, and the surface potential of the photoconductor is detected using the detection result of the sensor. The charging potential correction operation for correcting (3) Further, the toner image formed on the photoconductor unit is transferred onto the intermediate transfer body in an overlapping manner, and the color toner image on the intermediate transfer body is transferred onto the transfer material such as recording paper by the secondary transfer means. Is transcribed to. The secondary transfer means (secondary transfer roller) is normally in a released state separated from the intermediate transfer body during idling, and is controlled so as to be in a contact state before the recording sheet reaches the transfer position and a bias voltage is applied. Has been done.

[0003]

The present invention has been made to solve the following three problems.

(1) When a conveyance error such as a jam occurs during image formation, if an image having a high printing rate is being formed on the image forming body, many images are formed on the image forming body. Toner remains, and a large load is applied to the photoconductor cleaning means for cleaning the toner. Conventionally, in order to deal with such a situation, each photoconductor cleaning means of a plurality of photoconductor units has become complicated and large, and a pre-cleaning charger has been provided in order to improve the cleaning performance on the image forming body. .

It is a first object of the present invention to provide a color image forming apparatus in which an excessive cleaning load is not applied to each photoconductor cleaning means even when a conveyance error such as a jam occurs. In the color image forming apparatus in which the excessive load is not applied, the pre-cleaning charger is not required for the plurality of photoconductor units, and the cleaning mechanism is simplified, which is advantageous in space and cost. Further, it is expected that the mechanism for collecting the cleaned toner will be simplified and similarly advantageous.

(2) When the surface potential is corrected by using the surface potential sensor to correct the surface potential of the photosensitive member, the photosensitive member is charged to each photosensitive member unit and a predetermined exposure is performed by the exposing means, and then the surface is exposed. Although the surface potential is detected by the potential sensor, since toner adheres to the exposed photoconductor and the primary transfer means is in the inoperative state, each photoconductor is exposed in the same manner as in (1). An excessive cleaning load is applied to the body cleaning means.

It is a second object of the present invention to provide a color image forming apparatus in which an excessive cleaning load is not applied to each photoconductor cleaning means even when the surface potential is corrected by using the surface potential sensor.

(3) At the start of color image formation, charging is performed by the charging means substantially at the same time in each photoconductor unit.
Image exposure is performed by the exposure unit on the surface of each photoconductor in the charged state, and the developing bias is turned on at the timing when the tip of the charged region reaches the developing position.
However, there is development in which strip-shaped development (toner adhesion) is performed on the tip portion of the charging area due to a difference in the rise of the power source of the charging unit.
On the other hand, since the secondary transfer means is in the contact state before the recording paper reaches the transfer position, the belt-shaped toner is transferred to the intermediate transfer body and further transferred to the secondary transfer roller. There is a problem that the toner transferred to the secondary transfer roller contaminates the back surface of the recording paper during image formation.

A third object of the present invention is to provide a color image forming apparatus capable of preventing the back surface of the transfer material from being contaminated due to the toner adhesion to the secondary transfer roller which occurs at the start of color image formation. Especially.

[0010]

The first object of the present invention is to:
An image forming body and a charging means, an exposing means, provided on the periphery thereof,
A plurality of sets of photoconductor units having a developing unit and a photoconductor cleaning unit for cleaning the image forming body after transfer, an intermediate transfer body to which the toner image formed on the image forming body is transferred by the primary transfer unit, An image forming apparatus provided with a secondary transfer means for transferring a toner image formed by superimposing on the intermediate transfer body to a transfer material, an intermediate transfer body cleaning means for cleaning the intermediate transfer body after transfer, and a control section. In the above, an error detection unit for determining whether or not there is an abnormality in the image forming apparatus is provided, and the control unit detects the error by the error detection unit, and the error is an error that needs to immediately stop the image forming operation. If it is determined that the image forming operation is immediately stopped, the image forming state at the time of the error occurrence is stored, and when the image forming is returned,
The control unit controls, based on the memory, the primary transfer output for each of the plurality of sets of photoconductor units to be turned on for a certain period of time and then returned to off to clean the intermediate transfer body. A plurality of image forming apparatuses (invention of claim 1), and an image forming body and a charging means, an exposing means, a developing means, and a photoconductor cleaning means for cleaning the image forming body after transfer, which are provided on the periphery of the image forming body. A pair of photoconductor units, an intermediate transfer member on which a toner image formed on the image forming member is transferred by a primary transfer unit, and a toner image formed by overlapping on the intermediate transfer member is transferred to a transfer material 2 In an image forming apparatus provided with a next transfer unit, an intermediate transfer member cleaning unit for cleaning an intermediate transfer member that has finished transfer, and a control unit, a transfer error detecting unit is provided in a transfer path of the transfer material. When the transfer error detection unit detects a transfer material transfer error and the transfer error is determined to be a transfer error that occurs before the transfer material reaches the secondary transfer position. The secondary transfer means is separated from each other, and one is set for each of the plurality of photoconductor units.
This is accomplished by an image forming apparatus (invention of claim 2) characterized in that the next transfer output is turned on for a certain period of time and then returned to off to control the cleaning of the intermediate transfer member.

A second object of the present invention is to provide a plurality of sets each having an image forming body and a charging means, an exposing means, a developing means provided on the periphery of the image forming body, and a photoreceptor cleaning means for cleaning the image forming body after transfer. Of the photoconductor unit, an intermediate transfer member on which the toner image formed on the image forming member is transferred by a primary transfer unit, and a secondary toner image formed by superimposing the toner image on the intermediate transfer member onto a transfer material. In an image forming apparatus provided with a transfer unit, an intermediate transfer member cleaning unit for cleaning an intermediate transfer member after transfer, and a control unit, each of the plurality of sets of photosensitive member units is exposed between an exposing unit and a developing unit. A potential detecting means for detecting the potential of the body is provided respectively, and after the charging by the charging means and the exposure of a predetermined light amount by the exposing means are performed, the surface potential is detected and detected by the potential detecting means. A charging potential control program for changing the charging potential of the charging means until the surface potential reaches a preset reference value, and the control unit executes the primary transfer in executing the charging potential control program. This is achieved by an image forming apparatus (invention of claim 5) characterized in that the primary transfer by means is controlled to be turned on.

A third object of the present invention is to provide a plurality of sets each having an image forming body and a charging means, an exposing means, a developing means provided on the periphery of the image forming body, and a photoconductor cleaning means for cleaning the image forming body after transfer. Of the photoconductor unit, an intermediate transfer member on which the toner image formed on the image forming member is transferred by a primary transfer unit, and a secondary toner image formed by superimposing the toner image on the intermediate transfer member onto a transfer material. In an image forming apparatus provided with a transfer unit, an intermediate transfer member cleaning unit that cleans an intermediate transfer member that has been transferred, and a control unit, in the image formation, the control unit turns on a plurality of charging units at substantially the same time. The contact timing of the secondary transfer means is such that the secondary transfer means comes into contact with the secondary transfer means after a lapse of time from the charging position of the photoconductor unit farthest to the secondary transfer means to the secondary transfer position. It is achieved by an image forming apparatus and performs control (invention of claim 7).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a color image forming apparatus to which the present invention is applied will be described with reference to the configuration diagram shown in FIG.

A plurality of sets of photoconductor units 10Y, 10M,
10C and 10K are provided along the intermediate transfer belt 7 which is a belt-shaped intermediate transfer member. Photoconductor unit 1
0Y, 10M, 10C, and 10K are process units that form yellow (Y), magenta (M), cyan (C), and black (K) toner images. The photoconductor unit 10Y that forms the image Y) will be described.

The photoconductor unit 10Y has a cylindrical photoconductor surface from the upstream side around an image forming body (photoconductor drum) 1Y in which a photosensitive layer is provided on the outer periphery of a conductive substrate which is cylindrical and rotates in the direction of the arrow. The charging means 2Y of the scorotron type for charging, the exposure means 3Y for scanning in parallel with the rotation axis of the photoconductor drum 1Y to perform Y image exposure, and the photoconductor drum 1Y are rotated at a predetermined interval to have the same polarity as the toner. A developing sleeve 4Y for performing reversal development with respect to the image exposure portion is provided by a developing sleeve to which a developing bias voltage in which a DC voltage or a DC voltage and an AC voltage are superimposed is applied, and a toner image of Y is formed on the photoconductor. Is formed.

The photosensitive drum 1Y is provided with roller-shaped primary transfer means (primary transfer roller) 5Y facing each other with a belt-shaped intermediate transfer member (intermediate transfer belt) 7 interposed therebetween. 1
The secondary transfer roller 5Y is in a separated state except during image formation, is in a pressure contact state during image formation, applies a DC voltage having a polarity opposite to that of the toner, and forms a transfer electric field at the primary transfer position, thereby forming a photosensitive drum. The Y toner image on 1Y is transferred onto the intermediate transfer belt 7. The transfer residual toner remaining on the photoconductor drum 1Y after the transfer is cleaned by the photoconductor cleaning means 6Y having a cleaning blade.

The intermediate transfer belt 7 is a semi-conductive endless belt and is stretched around a plurality of rollers 71 and 72, and is rotated in the direction of the arrow by a drive motor during image formation. In this embodiment, the photoconductor units 10Y, 10M, 10 are arranged from the upstream side of the rotating intermediate transfer belt 7.
C, 10K are arranged side by side, and each photosensitive drum 1Y, 1M, 1C, 1K is instructed by an image recording start instruction.
Is rotated in the direction of the arrow, and the charging means 2Y, 2M, 2
By the charging action of C and 2K, the photosensitive drums 1Y and 1Y
Application of a uniform potential is started on M, 1C, and 1K, respectively.

In the photoconductor unit 10Y, the exposure means 3Y
The image writing by the electric signal output from the control section is started by the electrostatic latent image corresponding to the Y output image is formed on the photosensitive drum 1Y, and the Y toner image reversely developed by the developing unit 4Y is Primary transfer roller 5Y to which a bias having the opposite polarity to the toner is applied at the primary transfer position of Y
Thus, the transfer is performed on the intermediate transfer belt 7.

Slightly after the operation of the photoconductor unit 10Y, the photoconductor unit 10M starts image writing by an electric signal corresponding to the image data of M in synchronization with the toner image of Y, and the image is written on the photoconductor drum 1M. Is an electrostatic latent image corresponding to the output image of M, and the toner image of M reverse-developed by the developing unit 4M is the toner of Y on the intermediate transfer belt 7 by the primary transfer roller 5M at the primary transfer position of M. Transferred over the image.

Then, the intermediate transfer belt 7 is synchronized with the Y and M toner images, and the C toner image corresponding to the C image data formed on the photoconductor drum 1C by the photoconductor unit 10C becomes C. The toner image of C is superposed on the toner images of Y and M by the primary transfer roller 5C at the transfer position.

By a similar process, the Y, M, and C superimposed toner images are synchronized with each other, and the photoconductor unit 10K
The K toner image using K toner corresponding to the K image data formed on the photoconductor drum 1K by the above-mentioned Y, M, C is transferred by the primary transfer roller 5K at the K transfer position.
The toner image of K is superposed on the toner image of No. 1 and the color toner image of Y, M, C and K is superposed on the intermediate transfer belt 7.

Photosensitive drums 1Y, 1M, 1 after primary transfer
Transfer residual toner remaining on the peripheral surfaces of C and 1K is cleaned by the photoconductor cleaning means 6Y, 6M, 6C and 6K.

In synchronism with the formation of the color toner images formed on the intermediate transfer belt 7 in a superimposed manner, the transfer material P stored in the paper supply cassette 20 which is the transfer material storage means is supplied by the paper supply means 21. A plurality of intermediate rollers 22A, 2
It is conveyed to the secondary transfer position through the 2B, 22C and the registration roller 23.

Reference numeral 9 denotes a roller-shaped secondary transfer means (secondary transfer roller), which is transferred onto the intermediate transfer belt 7 only before and after the transfer material P passes therethrough and secondary transfer of a color image is performed on the transfer material P. A DC voltage having a polarity opposite to that of the toner is pressed and applied, and the superimposed color toner images on the intermediate transfer belt 7 are collectively transferred onto the transfer material P, and Y, M, C and K are transferred onto the transfer material P.
Will be present.

The transfer material P on which the color toner image is transferred is
The toner image on the transfer material P is fixed by being conveyed to the fixing device 24 and subjected to heat and pressure between the fixing roller and the pressure bonding roller, and then discharged to the outside of the apparatus main body by the discharging roller. It

The transfer residual toner remaining on the peripheral surface of the intermediate transfer belt 7 after the transfer is charged with a polarity opposite to that of the adhered toner provided facing the driven rollers 73 and 74 with the intermediate transfer belt 7 interposed therebetween. Cleaning is performed by the intermediate transfer member cleaning unit 8 having a strong cleaning ability, which is composed of a cleaning assisting unit 81 using a rotating brush or a rotating sponge roller in contact with the cleaning blade 82.

FIG. 2 shows a time chart of the above-described color image formation. (Embodiment 1) In the color image forming apparatus described in Embodiment 1, a color image formation is made so that an excessive cleaning load is not applied to each photoconductor cleaning means 6 even when a conveyance error such as a jam occurs. It is a device.

In the color image forming apparatus shown in FIG. 1, paper detecting sensors SP1, SP2 and SP3 are provided as error detecting means C02 in the conveying path of the transfer material P and are used for sequential image forming control. It also serves as an error detection unit that is also used to detect a conveyance error such as a jam. FIG. 3 shows a control block diagram of this embodiment.
When the paper detection sensors SP1, SP2, and SP3 do not detect the passage of the paper at a predetermined timing after the image formation is started, the control unit C01 detects that a jam causing a conveyance error has occurred. Further, this conveyance error is a so-called no-foot jam conveyance error detected by the paper detection sensors SP1 and SP2 on the upstream side of the secondary transfer position, or near the fixing device 24 on the downstream side of the secondary transfer area. It is determined whether there is a so-called fixing jam conveyance error detected by the SP3 provided.

Upon detection of the transport error, the control section C01 immediately determines the state when the transport error occurs in the RAMC03.
To record. When the conveyance error is determined to be a fixing jam by the paper detection sensor SP3, for example, the control unit C
01 calls the jam processing program (1) C04 corresponding to the fixing jam conveyance error to perform the jam processing operation. That is, the image forming operation performed by the apparatus is immediately turned off. When the operator removes the jammed paper and performs a recovery operation, the control unit C01 changes the developing unit 4 and the primary developing unit 4 for each of the photoconductor units 10Y, 10M, 10C, and 10K from the state at the time of the conveyance error stored in the RAMC03. It is checked whether or not there is a toner image on the photosensitive drum 1 between the transfer roller 5 and when it is determined that there is a toner image, the primary transfer roller 5
Is turned on, and the toner at the position of the developing unit 4 becomes 1
After a lapse of a time obtained by adding a slight margin time (α) to the time (t ₀ ) required to reach the next transfer roller 5,
The next transfer roller 5 is turned off. When it is determined that there is no toner image on the photosensitive drum 1 between the developing unit 4 and the primary transfer roller 5, the primary transfer roller 5 remains in the OFF state. For example, when the control unit C01 recognizes that the state is as shown in the time chart of FIG. 4 when detecting the occurrence of a fixing jam, the primary transfer rollers 5Y, 5M, and 5C are in the ON state only during (t ₀ + α) when returning. After that, it is turned off and the primary transfer roller 5K is kept off.

When it is determined that a fixing jam conveyance error has occurred, the control unit causes the jam processing program (1) C to be executed.
The image forming operation is turned off by 04, and the above-mentioned processing is performed at the time of return, and the toner on each photoconductor drum 10 at the time of the conveyance error is transferred onto the intermediate transfer belt 7 by the primary transfer roller. To be done. At the time of restoration, the secondary transfer roller 9 is in an inoperative state, and the residual toner in the middle of image formation, which is generated at the time of jamming, which has been transferred onto the intermediate transfer belt 7, is cleaned by the intermediate transfer member cleaning means 8 and the state before the jam occurs. Return to.

Next, a case where a no-foot jam is detected as a transport error will be described.

Upon detection of the transport error, the control section C01 immediately records the state at the time of the transport error in the RAM C03. When it is determined that a no-feed jam due to a transport error has occurred, the control unit C01 responds to a no-foot jam transport error with a jam processing program (2).
Jam is called by calling C05. That is,
Since the transfer material P having the image that has passed the secondary transfer position may be present in the transport path, the secondary transfer roller 9 is not operated and the carry-out operation is continued without turning off the operation. In addition, the image formation on the transfer material that causes the conveyance error jam occurs on each of the photoconductor units 10Y, 10M, 10C,
Since the process has already been performed for 10K, the control unit C01 changes the state of each of the photoconductor units 10Y, 10M, 10C, 10K from the state at the time of the conveyance error stored in the RAMC03.
For each of the above, whether or not there is a toner image on the photosensitive drum 1 between the developing means 4 and the primary transfer roller 5 is checked.
The secondary transfer roller 5 continues to be in the ON state as it is, and the time required for the toner at the position of the developing unit 4 to reach the primary transfer roller 5 (t ₀ ) is added with a slight margin time (α). After that, it is turned off. Also, the developing means 4
If it is determined that there is no toner image on the photosensitive drum 1 between the primary transfer roller 5 and the primary transfer roller, the primary transfer roller 5
Switches to the OFF state. For example, when the control unit C01 determines that the state shown in the time chart of FIG.
Y, 5M, and 5C continue to be in the ON state for (t ₀ + α), and the primary transfer roller 5K is in the OFF state. In the present embodiment, the toner on each photoconductor drum 10 at the time of the jam is transferred onto the intermediate transfer belt 7 by the primary transfer roller 5, and the residual toner at the time of the jam transferred to the intermediate transfer belt 7 is The intermediate transfer member cleaning unit 8 cleans and stops.

(Second Embodiment) In the color image forming apparatus described in the second embodiment, an excessive cleaning load may be applied to each photoconductor cleaning means 6 even when the surface potential is corrected by using the surface potential sensor. It is a color image forming apparatus that is not provided.

In the color image forming apparatus shown in FIG. 1, in each of the photoconductor units 10Y, 10M, 10C and 10K, a surface potential sensor SS for measuring the surface potential of the photoconductor is provided between the exposing means 3 and the developing means 4. It is provided and the surface potential of the photoconductor is adjusted. (Of course, the surface potential may be adjusted at any other time.) FIG.
Shows a control block diagram of the present embodiment. The adjustment for keeping the surface potential of the photoconductor constant is performed at the time of warming up when the power source SWC12 is turned on. Control unit C
When detecting that the power source SWC12 is turned on, the reference numeral 11 calls the stored surface potential adjusting program C13, and the photoconductor units 10Y, 10M, 10C, and 10K.
With respect to, the correction operation of the surface potential of the photoconductor is performed. FIG. 6 shows a time chart of the surface potential correction of the photoconductor. Now, for example, the surface potential correction of the photoconductor unit 10Y will be described. In the present embodiment, the charging output by the charging unit 2Y is adjusted and changed so that the surface potential of the photoconductor drum 1Y becomes a predetermined reference potential, and the exposure when performing the patch exposure by the exposure unit 3Y. The amount is made constant, the developing bias applied by the developing means 4Y is made constant, and the primary transfer roller 5Y is continuously turned on during the surface potential correction, so that the primary transfer is continuously performed.

In correcting the surface potential, the rotating photoconductor drum 1Y is first charged by a charging means 2Y with a preset initial value, and a predetermined exposure amount is applied to the charged photoconductor surface. Then, the exposure unit 3Y performs the patch-shaped exposure, and then the surface potential sensor S
The surface potential of the patch-shaped exposure area is detected by SY. When a measured value in which the detected surface potential of the photoconductor is different from the preset reference potential (for example, -600 V) is obtained, the calculation formula prepared in the calculation program is used to shift the shift direction with respect to the reference potential. By substituting the amount, the correction value of the charging output by the charging means 2Y can be obtained. After the charging unit 2Y outputs the charging output by the correction value again, the exposing unit 3Y performs the patch-like exposure with a predetermined exposure amount, and the surface potential sensor SSY detects the surface potential of the exposure area. The correction operation of the surface potential is repeatedly performed until the surface potential falls within a preset allowable range (for example, −600 V ± 10 V). In image formation, by setting the charge output by the charging unit 2Y to the final adjustment value, a stable and good color image can be obtained.

When correcting the surface potential described above,
Although a considerable amount of toner adheres to the patch-shaped exposure area by passing through the developing unit 4Y, in the present embodiment, the toner adhered to the exposure area on the photoconductor drum 1Y is in the operating state. By the primary transfer roller 5Y in
The toner transferred on the intermediate transfer belt 7 and transferred to the intermediate transfer belt 7 at the time of surface potential correction is cleaned by the intermediate transfer member cleaning unit 8.

The above-described operation of correcting the surface potential is carried out by the control section C11 independently for each color and simultaneously. At the start of this surface potential correction operation, the primary transfer roller is in the ON operation state, and when the surface potential correction operation is completed, the primary transfer roller 5 is in the OFF operation state.
(See FIG. 6) Also in the second embodiment, an excessive cleaning load is not applied to the photoconductor cleaning means 6Y, 6M, 6C, 6K of each photoconductor unit 10Y, 10M, 10C, 10K.

(Third Embodiment) The color image forming apparatus described in the third embodiment is a color image in which the back surface of the transfer material is prevented from being contaminated due to the adhesion of toner to the secondary transfer roller at the start of color image formation. It is a forming device.

In the color image forming apparatus shown in FIG. 1, the secondary transfer roller 9 capable of pressing and releasing pressure is in a released state during normal idling, and the image forming operation is started.
The charging means 2 of each of the photoconductor units 10Y, 10M, 10C and 10K is turned on, and the developing bias is turned on at the timing when the charging potential on the photoconductor drum 1 reaches the developing position of the developing means 4. There is. At this time, due to the difference in the rise of the power source of the charging unit 2, the photosensitive drum 1
Band-shaped toner adhesion occurs on the surface of the. The toner attached to the charging rising position is partially transferred to the intermediate transfer belt 7 in the primary transfer area located downstream.

In the color image forming apparatus of this embodiment, the belt-shaped toner transferred onto the intermediate transfer belt 7 is controlled so that the secondary transfer roller 9 contacts the intermediate transfer belt 7 after passing the secondary transfer position. The timing of pressing the secondary transfer roller 9 to the intermediate transfer belt 7 is the furthest from the secondary transfer position to the upstream side, and in the arrangement of the photoconductor units shown in FIG. It is assumed that the time when the toner reaches the secondary transfer position from the Y charging position elapses, starting from the time when the charging potential is generated on the photosensitive drum 1Y by the charging unit 2Y. FIG. 7 is a time chart at the start of image formation in the present embodiment. By performing such control, the belt-shaped toner generated at the start of charging passes through the secondary transfer position and is cleaned by the intermediate transfer member cleaning unit 8. After cleaning, the secondary transfer roller 9 comes into contact with the belt-shaped toner after passing, so that
It is possible to provide the color image forming apparatus in which the toner does not adhere to the secondary transfer roller 9 and the back surface is not contaminated.

[0041]

According to the first and second aspects of the present invention, since the toner remaining on the photoconductor when a jam occurs is transferred to the intermediate transfer body side, the photoconductor cleaning means in each photoconductor unit. It will not be a burden to me. Therefore, the pre-cleaning charging, which is provided to improve the cleaning performance of a plurality of photoconductors, becomes unnecessary, the cleaning mechanism is simplified compared to the conventional one, and the color image is advantageous in terms of space and cost. Forming equipment has been provided.

According to the fifth aspect of the present invention, since the toner adheres to the photoconductors exposed at the time of surface potential correction for each photoconductor unit, which is a burden on the photoconductor cleaning means, it is solved. In addition, the pre-cleaning charging, which was provided to improve the cleaning performance of a plurality of photoconductors, is not required, and the cleaning mechanism is simplified compared to the conventional one, which is advantageous in terms of space and cost. The device will be provided.

According to the seventh aspect of the invention, the back surface stain caused by the toner adhesion at the start of image formation is eliminated, and a good quality stain-free image can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a color image forming apparatus.

FIG. 2 is a time chart of color image formation.

FIG. 3 is a control block diagram according to the first embodiment.

FIG. 4 is a time chart showing a state when a jam occurs.

FIG. 5 is a control block diagram according to the second embodiment.

FIG. 6 is a time chart of surface potential correction.

FIG. 7 is a time chart at the start of image formation.

[Explanation of symbols]

1, 1Y (M, C, K) image forming body, photoconductor drums 2, 2Y (M, C, K) charging means, charger 3, 3Y (M, C, K) exposure means 4, 4Y (M, C, K) developing means 5, 5Y (M, C, K) primary transfer means, primary transfer rollers 6, 6Y (M, C, K) photoconductor cleaning means 7 intermediate transfer body, intermediate transfer belt 9 secondary Transfer unit, secondary transfer roller 10, 10Y (M, C, K) Photoreceptor unit SP1, SP2, SP3 Paper detection sensor SS, SSY (M, C, K) Surface potential sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/10 G03G 21/00 372 21/14 310 F term (reference) 2H027 DA02 DA38 EA01 EA18 EB04 EC20 ED03 ED16 ED24 EE02 EE07 EF06 EK01 EK09 2H030 AB02 AD02 AD05 AD17 BB42 BB53 2H134 GA06 GB02 KB07 KG01 KG04 KG08 KH01 KH14 KJ02 2H200 GA12 GB41 HA12 HA29 JC04 JC12 JC19 LA24 LB02 LB39 PA03 PA10 PA28 P21 PA21

Claims (7)

[Claims] 1. A plurality of sets of photoconductor units having an image forming body and a charging means, an exposing means, a developing means provided on the periphery of the image forming body, and a photoconductor cleaning means for cleaning the image forming body after transfer, and the image. An intermediate transfer member for transferring the toner image formed on the forming member by the primary transfer unit, a secondary transfer unit for transferring the toner image formed on the intermediate transfer member to the transfer material, and the transfer is completed. An image forming apparatus having an intermediate transfer member cleaning unit for cleaning the intermediate transfer member and a control unit is provided with an error detecting unit for determining whether or not there is an abnormality in the image forming apparatus, and the control unit causes an error in the error detecting unit. When the error is detected and it is determined that the error is an error that needs to immediately stop the image forming operation, the image forming operation is immediately stopped, and The image forming state is stored in the memory, and when the image forming is restored, the control unit turns on the primary transfer output for a certain period of time to each of the plurality of photoconductor units based on the memory, and then returns to the OFF state, and the intermediate transfer body is returned. An image forming apparatus, which is controlled so as to perform cleaning. 2. A plurality of photoconductor units having an image forming body and a charging means, an exposing means, a developing means provided on the periphery of the image forming body, and a photoconductor cleaning means for cleaning the image forming body after transfer, and the image. An intermediate transfer member for transferring the toner image formed on the forming member by the primary transfer unit, a secondary transfer unit for transferring the toner image formed on the intermediate transfer member to the transfer material, and the transfer is completed. In an image forming apparatus provided with an intermediate transfer member cleaning unit for cleaning an intermediate transfer member and a control unit, a transfer error detection unit is provided in a transfer path of the transfer material, and the control unit transfers the transfer error by the transfer error detection unit. When a material transport error is detected and it is determined that the transport error is a transport error that occurs before the transfer material reaches the secondary transfer position, the secondary transfer unit is separated and 1 for each set of photoconductor units
An image forming apparatus characterized in that the next transfer output is turned on for a certain period of time and then turned off to control the intermediate transfer member to be cleaned. 3. The image forming apparatus according to claim 1, wherein the fixed time is longer than a time required for each photoconductor unit to reach a primary transfer position from a developing position. . 4. The operation of turning on the primary transfer output for a certain period of time is performed only for a photoconductor unit that is determined to have a toner image between a developing position and a primary transfer position. The image forming apparatus according to Item 1 or 2. 5. A plurality of sets of photoconductor units having an image forming body and a charging means, an exposing means, a developing means provided on the periphery of the image forming body, and a photoconductor cleaning means for cleaning the image forming body after transfer, and the image. An intermediate transfer member for transferring the toner image formed on the forming member by the primary transfer unit, a secondary transfer unit for transferring the toner image formed on the intermediate transfer member to the transfer material, and the transfer is completed. In an image forming apparatus provided with an intermediate transfer member cleaning unit for cleaning an intermediate transfer member and a control unit, the potential of the photosensitive member is detected between the exposure unit and the developing unit in each of the plurality of photosensitive unit units. Each potential detecting means is provided, and the surface potential is detected by the potential detecting means after the charging by the charging means and the exposure of a predetermined amount of light by the exposing means are performed, and the detected surface potential is preset. Has a charging potential control program for changing the charging potential of the charging unit until the reference value is reached, and the control unit executes the primary transfer by the primary transfer unit when executing the charging potential control program. O
An image forming apparatus, wherein the image forming apparatus is controlled so as to perform N. 6. The image forming apparatus according to claim 5, wherein the charging potential control program is executed during warm-up. 7. A plurality of sets of photoconductor units having an image forming body and a charging means, an exposing means, a developing means provided on the periphery of the image forming body, and a photoconductor cleaning means for cleaning the image forming body after transfer, and the image. An intermediate transfer member for transferring the toner image formed on the forming member by the primary transfer unit, a secondary transfer unit for transferring the toner image formed on the intermediate transfer member to the transfer material, and the transfer is completed. In the image forming apparatus provided with the intermediate transfer member cleaning unit for cleaning the intermediate transfer member and the control unit, in image formation,
The control section turns on the plurality of charging means almost at the same time, and the pressure of the secondary transfer means is determined by the time required to reach the secondary transfer position from the charging position of the photoconductor unit farthest from the secondary transfer means. An image forming apparatus characterized in that control is performed so that the contact is made after a lapse of time.