JP2001175094A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the failure of an image by improving a cleaning stage for a transfer roller. SOLUTION: This device is equipped with a photoreceptor 31 where a toner image is developed, the transfer roller 351 arranged to be opposed to the photoreceptor 31, a pre-transfer guide guiding a sheet member 13 to a transfer position between the photoreceptor 31 and the roller 351, and a transfer output applying means 100 applying transfer output to the roller 351. The applying means 100 applies the transfer output having a reverse polarity to the electrification polarity of toner to the roller 351 at the transfer time when the toner image on the photoreceptor 31 is transferred to the member 13, while it applies the transfer output having the same polarity as the electrification polarity of the toner to the roller 351 at the non-transfer time, whereby the roller 351 is cleaned and further the transfer output applied to the roller 351 is gradually reduced when such cleaning is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer using an electrophotographic process.

[0002]

2. Description of the Related Art As a transfer unit in an image forming apparatus of this type, a transfer unit provided with a transfer roller facing a photoreceptor has been put to practical use. In the transfer roller, the toner adheres to the roller surface with long-term use, and the adhered toner adheres to a sheet member during transfer, which adversely affects the image. For this reason, for the purpose of cleaning the transfer roller, for example, at the time of start-up of the image forming apparatus main body other than at the time of transfer during normal image formation,
Alternatively, the transfer roller is cleaned during standby (during standby). That is, by applying a charge having the same polarity as the charge polarity of the toner to the transfer roller, the toner on the transfer roller is returned (returned) to the photosensitive drum.

[0003]

However, when the transfer roller is cleaned, the potential of the transfer roller (potential of the same polarity as the polarity of the toner to be used, + several hundred volts to about 10
00V), the pre-transfer guide provided immediately upstream of the transfer roller for the purpose of guiding the leading end of the sheet member to the photosensitive drum and the transfer roller also bears substantially the same electric charge, and the transfer roller is cleaned. When the voltage applied to the transfer roller is stopped, the charges accumulated in the pre-transfer guide are released at once from the leading end of the pre-transfer guide, and the area of the surface of the photosensitive drum facing the leading end of the pre-transfer guide extends in the width direction. High potential (+ several hundred V-
(About 1000 V).

Thereafter, when the photosensitive drum rotates and passes through the cleaning unit, a part of the toner collected by the cleaning unit is caused by the edge portion of the photosensitive member being charged to a high potential. Therefore, when the next image formation is performed, the toner attached to the edge portion is transferred onto the sheet member, and the image is soiled.

[0005] As a countermeasure, (a) the pre-transfer guide is grounded (dropped to GND) so that no charge is accumulated in the pre-transfer guide. (A) The distance between the pre-transfer guide and the photosensitive drum is increased so that the pre-transfer guide does not release electric charges. (C) The guide before transfer is made nonconductive. And so on.

However, if the pre-transfer guide is grounded, in a high-temperature and high-humidity environment, a transfer roller to which a transfer output is applied may leak from a transfer-applied sheet member having a reduced resistance value, causing transfer failure. Would.

If the distance between the pre-transfer guide and the photosensitive drum is increased, the sheet member cannot be accurately guided to the transfer area of the photosensitive drum, and there is no point in providing the pre-transfer guide.

If the pre-transfer guide is made of a non-conductive material, the pre-transfer guide may be frictionally charged due to rubbing of the sheet member when passing through the pre-transfer guide, resulting in image defects.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an image forming apparatus capable of preventing an image defect by cleaning a charger.

[0010]

In order to achieve the above object, a first aspect of the present invention provides a photoconductor on which a toner image is developed, a transfer roller opposed to the photoconductor, and a photoconductor. A pre-transfer guide that guides the sheet member to a transfer position between the transfer rollers, and a transfer output applying unit that applies a transfer output to the transfer roller, wherein the transfer output applying unit includes:
At the time of transfer for transferring the toner image on the photoconductor onto the sheet member, a transfer output having a polarity opposite to the charge polarity of the toner is applied to the transfer roller. An image forming apparatus configured to clean the transfer roller by applying a transfer output to the transfer roller, and to gradually reduce the transfer output applied to the transfer roller when the cleaning is completed. Is configured as

According to the above configuration, when cleaning of the transfer roller is completed, the voltage applied from the transfer roller to the photosensitive member is gradually reduced, so that the electric charge charged in the pre-transfer guide is instantaneously discharged. Therefore, application of a high-potential electric charge in an edge shape to a region of the photosensitive drum facing the leading end of the pre-transfer guide is prevented. Therefore, even if the toner passes through the cleaning area immediately after the completion of the cleaning, extra toner is prevented from adhering to the surface of the photosensitive drum, and
It is possible to execute clear image formation. Here, the transfer output is stopped after the transfer output applied to the transfer roller is gradually reduced (claim 2).
This is a specific embodiment. Although it may be reduced continuously, it is easier to control if it is reduced stepwise. In order to achieve the above object, the present invention is directed to a photoconductor that circulates around a toner image forming area, a transfer area, and a cleaning area including a charging area, an exposure area, and a developing area; A toner image forming means for forming a predetermined toner image in a developing area on a photoreceptor on which an electrostatic latent image has been formed by passing through an exposure area, and transferring the toner image on the photoreceptor to a sheet member in the transfer area Transfer roller, transfer output applying means for applying a transfer output to the transfer roller, a pre-transfer guide for guiding a sheet member to the transfer area, and removing residual toner after transfer from the photoreceptor surface in the cleaning area. And a transfer device for transferring the toner image on the photoconductor onto a sheet member during the transfer of the toner image onto the sheet member. The transfer roller is configured to apply a transfer output having the same polarity as the charged polarity of the toner to the transfer roller during non-transfer, while applying the transfer output to the transfer roller, thereby cleaning the transfer roller; The forming means is configured such that when the cleaning of the transfer roller is completed, a portion of the photoconductor facing the transfer guide passes through the cleaning region at least once and further passes through the charging region once, and then a new toner is formed on the photoconductor. The image forming apparatus is configured to form an image.

According to the above arrangement, at the end of the cleaning of the transfer roller, the portion of the photosensitive member facing the transfer guide has passed through the cleaning region at least once and further has passed through the charging region once, and then a new image is formed on the photosensitive member. A toner image is formed.

The toner image forming means includes a charger for charging a photoreceptor in a charging area, an exposing means for exposing an image on the photoreceptor in an exposure area, and a toner for forming an electrostatic latent image on the photoreceptor in a developing area. (Claim 4), which is one specific embodiment. The photoreceptor is charged by a charger in a charging area, and an image is exposed by an exposure unit in an exposure area,
A toner image is formed by supplying toner to the electrostatic latent image by the developing means in the developing area.

Further, since the cleaning of the transfer roller is performed during warm-up of the image forming apparatus or during standby, it is possible to avoid adversely affecting image formation.

Further, since the cleaning of the transfer roller is performed during toner replenishment to the developing device (Claim 6), adverse effects on image formation can be avoided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, first, an overall configuration of an embodiment in which an image forming apparatus according to the present invention is applied to a copying machine will be described, and then a configuration relating to a characteristic portion of the present invention, that is, transfer will be described. The control mainly by the device will be described.

FIG. 1 is an overall sectional view of an embodiment in which an image forming apparatus according to the present invention is applied to a copying machine.
FIG. 1 is an enlarged view illustrating a main part of the image forming apparatus, and will be described below with reference to FIGS.

The copying machine 1 has an apparatus main body 2 and an original presser 3 mounted on the upper part of the apparatus main body 2 so as to be openable and closable. The apparatus main body 2 includes a paper feeding unit 10 provided at a lower portion.
A sheet member transport section 20 disposed above the sheet feeding section 10; an image forming section 30 disposed above the sheet member transport section 20; The image forming unit 30 includes a fixing unit 40 disposed downstream in the direction, and an image reading unit 50 including an optical system member disposed above the image forming unit 30 and the fixing unit 40.

The paper supply unit 10 includes a paper supply cassette 11 or 1
The sheet members 13 stacked and mounted on the sheet feed roller 2 are sent out to the outlet side (the left side in FIG. 1) of the sheet feed cassette 11 or 12 by the rotation of the sheet feed roller 14 having an arc outer peripheral portion (substantially semicircular shape). By separating the sheet members 13 at the uppermost position by one pair of separating claws (not shown) provided at both ends in the width direction of the sheet cassettes 11 and 12, respectively.
Sheets are fed to the sheet conveying section 20 side by sheet.

The paper transport section 20 transports the sheet member 13 fed from the paper feed section 10 to a transport roller pair 21, a registration roller pair 22, a pre-transfer guide 261 and an upper pre-transfer guide 26.
2 transports the paper toward the image forming unit 30. Further, the sheet member transporting section 20 includes the image forming section 3.
0, the sheet member 13 on which an image has been formed is guided from the fixing unit 40 to the discharge roller pair 24 side.
3 is discharged onto a discharge tray 25 by a discharge roller pair 24.

The image forming section 30 forms a predetermined toner image on the photosensitive drum 31 by an electrophotographic process, and transfers the formed toner image onto the sheet member 13. The image forming unit 30 includes a photoconductive drum 31 rotatably supported on a photoconductive drum, and a charger 32, an exposure unit 33, and a developing device around the photoconductive drum 31 along the rotation direction. Means 34, transfer roller 351, cleaning means 36
And a static elimination lamp 37.

The charger 32 charges the photosensitive drum 31 to a fixed polarity (positive in this embodiment) in the charging area T4.

The exposure means 33 includes an image reading section 50 described later.
The laser light R to which the intensity is applied in accordance with the image data of the document read by the laser beam is output from the laser light emitter 331, and is charged via the polygon mirror 332 and the reflection mirror 333 to the positively charged photosensitive drum 31. Upper exposure area T5
Is to be irradiated. The irradiated laser light R reduces the surface potential of the photosensitive drum 31 in accordance with an image, and forms an electrostatic latent image on the surface of the photosensitive drum 31 in accordance with original image data. . This light irradiation is repeatedly scanned in the width direction of the rotating photosensitive drum 31 to the exposure area T5 between the charger 32 and the developing means 34 by the rotation of the polygon mirror 332.

The developing means 34 attaches the same polarity, that is, positively charged toner in the developing area to the portion of the electrostatic latent image on the photosensitive drum 31 where the positive charge has been reduced (the potential has been reduced) by the laser beam R. It is made to let. Thus, the electrostatic latent image formed on the photosensitive drum 31 is developed by the toner, and a toner image is formed on the surface of the photosensitive drum 31 as a visible image. This developing method is generally called a reversal developing method.

The transfer unit 35 has a back surface of the sheet member 13 by a transfer roller 351 opposed to the transfer area T2 of the photosensitive drum 31 in a non-contact state (having a gap of about 0.25 mm). , A negative corona discharge (−1000 V in this embodiment) is performed to electrostatically transfer the toner image formed on the photosensitive drum 31 onto the sheet member 13. The transfer roller 351 is connected to a transfer output applying unit 100 that applies a transfer output to the transfer roller 351.

The cleaning means 36 covers the entire area of the cleaning blade 361 in the width direction (longitudinal direction).
2, the distal end of the cleaning blade 361 is urged toward the surface of the photosensitive drum 31 by the urging force of an urging means (not shown) around the support shaft 363. And
The residual toner adhering to the surface of the photosensitive drum 31 after the transfer is scraped off by the tip of the cleaning blade 361 in the cleaning area T3.

The static elimination lamp 37 is formed in an array in which a plurality of LED lamps are arranged in one or more rows over the entire area of the photosensitive drum 31 in the width direction. The static elimination lamp 37 irradiates the surface of the photosensitive drum 31 with LED lamp light to remove residual charges on the surface of the photosensitive drum 31.

In the separating device 23, three separating claws 231 are provided at equal intervals in the width direction of the toner receiving portion side surface 364 of the cleaning portion 36 (only one is shown in FIG. 2). Note that the separation claw 231 is configured such that the coil spring 232 is
1b and a required portion 233 of the side surface 364, and urges the separation claw 23 in a counterclockwise direction.
Therefore, the tip of the separation claw 231 is in contact with the peripheral surface of the photosensitive drum 31. The sheet member 13 is separated from the photosensitive drum 312 by the separation claw 231 and is conveyed.

The fixing section 40 is disposed downstream of the image forming section 30 in the sheet member conveying direction, and fixes the sheet member 13 on which the toner image has been transferred in the image forming section 30 to a heating roller 41 having a heater 411 therein. And a pressing roller 42 pressed against the heating roller 41 to apply heat and heat to fuse and fix the toner image on the sheet member 13.

The image reading unit 50 includes a contact glass 51
By irradiating light from the exposure lamp 52 to the original placed on the upper side, the reflected light is guided to a photoelectric conversion unit 57 including a CCD line sensor and the like via reflection mirrors 53, 54, and 55, and a lens 56. , For reading image information of a document. Note that the exposure lamp 52 and the reflecting mirror 53 constitute a scanning operation unit, and the scanning operation unit is placed on the contact glass 51 by reciprocating in a horizontal direction in FIG. 1 at a predetermined speed. The entire surface of the document can be scanned, and image information on the entire surface of the document can be read.

FIG. 3 is a timing chart relating to the operation of the transfer roller, the charging device, and the exposure means. Hereinafter, portions relating to the present invention will be described with reference to FIG.

The period from time t0 to time t1 is the period of toner image transfer, and the transfer potential -100 is applied to the transfer roller 351 by the transfer output applying means 100 in the transfer area T2.
By applying 0 V, a toner image is transferred from the photosensitive drum 31 to the sheet member 13.

During the period from time t1 to time t2, no potential is applied to the transfer roller 351 and the standby state is maintained.

Then, during the period from time t2 to time t3, the transfer roller 351 is cleaned. That is, a potential of +760 V is applied to the transfer roller 351 from the transfer output applying unit 100, and the transfer roller 351 and the photosensitive drum 31
Is rotated, the toner adhering to the entire surface of the transfer roller 351 is returned (returned) to the photosensitive drum 31 side. Therefore, the toner is removed from the surface of the transfer roller 351 and is cleaned. The toner returned from the surface of the transfer roller 351 to the photosensitive drum 31 is removed by the cleaning device 36 by the rotation of the photosensitive drum 31.

When the cleaning of the transfer roller 351 is completed at time t3, the potential 760V at that time is set to 0V in five steps.
Has dropped. That is, 670 V at time t3 and time t4
480V at time t5, 290V at time t5, 100 at time t6
V and drop to 0V at time t7. In addition. At this time,
The period from time t3 to t4, the period from time t4 to t5, the period from time t5 to t6, and the period from time t6 to t7 are each set to 20 msec.

As described above, the potential of the transfer output applying means 100 is not instantaneously lowered to 0 V at the end of the cleaning of the transfer roller 351 but is gradually lowered in five steps, and takes 80 msec. Potential 670
Since the voltage is reduced from V to 0 V, the discharge from the front end of the pre-transfer guide 261 to the opposing portion of the photosensitive drum 31 is prevented instantaneously. In the case of the present embodiment, the diameter of the photosensitive drum is 30 mm, and the number of rotations is 1
rps (60 rpm), the photosensitive drum 3
1 moves about 7.5 mm in a time of 80 msec, so that even if the front end of the pre-transfer guide 261 is discharged to the opposing part of the photosensitive drum 31, the above-mentioned about 7.5 m is required.
m, the surface of the photosensitive drum 31 is prevented from being charged in an edge shape. For this reason, even if the opposing portion of the photosensitive drum 31 passes through the cleaning area T3, it is possible to prevent toner adhesion by the cleaning device 36.

Thereafter, when an image formation start signal is generated next, the charging device 37 is turned on at time t8, and the photosensitive drum 3
One surface is charged by the charger 32, and from time t8 (c / 3
At time t9 after 60) sec, image exposure is performed by the exposure unit 32, and at time t10 after (d / 360) sec from time t8, the transfer potential (-1000) is transferred by the transfer roller 351.
V) is applied to the photosensitive drum 31 to transfer an image onto the sheet member 13.

Here, c: from charging region T4 by charging device 32 to exposure region T5
D: The angle (°) from the charged area T4 to the transfer area T2.

Next, a method for solving the problems of the present invention without using the above method will be described in detail. FIG. 4 is a timing chart, which will be described below with reference to FIG.

A period from time t20 to time t21 is a transfer period, and the transfer output applying means 1
00, a transfer potential of −1000 V is applied to transfer the toner image from the photosensitive drum 31 to the sheet member 13.

During the period from time t21 to time t22, no potential is applied to the transfer roller 351 and the standby state is maintained.

Then, the transfer roller 351 is cleaned during a period from time t22 to time t23. That is, while applying a potential of +760 V to the transfer roller 351 from the transfer output applying unit 100 and rotating the transfer roller 351 and the photosensitive drum 31, the toner adhering to the surface of the transfer roller 351 is transferred to the photosensitive drum 31 side. Let me return. Accordingly, the surface of the transfer roller 351 is cleaned by removing the toner. Then, the toner returned from the surface of the transfer roller 351 to the photosensitive drum 31 side is removed by the cleaning unit by passing through the cleaning area next by the rotation of the photosensitive drum 31. Immediately after the cleaning step at time t23, the transfer output applying unit 100
The potential applied to the transfer roller 351 is reduced to zero.

Thereafter, even if the image formation start signal is immediately generated, at least the portion of the photosensitive drum 31 facing the leading end of the pre-transfer guide 261 is at least two.
The image formation is set to start after passing through the cleaning area T3. That is, when the facing portion (the portion of the photosensitive drum 31 facing the leading end of the pre-transfer guide 261) passes through the cleaning area T3 for the first time, the toner adheres to the facing portion of the photosensitive drum 31. When the toner passes through the cleaning area T3 for the second time, the toner adhering to the opposing portion is removed from the photosensitive drum 31 and cleaned. Then, by setting the start point (region) of the image forming start after the opposite portion where the toner is removed from the photosensitive drum 31, the toner adhered to the edge portion of the photosensitive drum 31 is reliably removed, and then the image is formed. Since the formation is started, a defective image is not formed.

Therefore, when the cleaning process is completed at time t23, at least (1+ (a + b) / 360) sec.
The exposure by the exposure means 33 is started at a later time t25.

From time t25, (c / 360) se
The charging of the photosensitive drum 31 by the charger 32 is performed before the time t24 before c.

Then, from time t24 (d / 360) s
At time t26 after ec, the transfer from the photosensitive drum 31 to the sheet member 13 is performed by the transfer roller 351.

Here, a: the angle (°) from the position T1 of the photosensitive drum 31 facing the tip of the pre-transfer guide 261 to the cleaning area T3 by the cleaning blade 361 b: the angle from the cleaning area T3 to the exposure area T5 (°) c: from charging area T4 to exposure area T5 by charging device 32
D: The angle (°) from the charged area T4 to the transfer area T2.

In the cleaning process, when toner is supplied to the developing device 34, aging during startup by turning on the main switch of the image forming device 1 (warm-up by driving various devices in the image forming device main body for a predetermined time). That is, it is efficient to execute it during the period, but it may also be executed during a standby period in which image formation is not performed for a long time. Further, during the continuous image formation, the first embodiment can be executed between the sheet members 13, that is, between sheets.
However, in order to perform the cleaning process between sheets, a high potential surface potential (+
(Approximately 800 V), it is necessary to apply a potential of approximately +1560 V obtained by adding +760 V to the surface potential from the transfer roller 351 to the photosensitive drum 31.

In the above-described embodiment, the reversal developing system is used as the developing device. However, a so-called regular developing system using a photosensitive member and a toner charged to a polarity opposite to the charging polarity can be applied. is there.

In the above-described embodiment, the so-called vertical transport path for transporting the sheet member from below to above has been described as the transport path of the sheet member. However, the sheet member is transported in a substantially horizontal direction. You may.

In the above-described embodiment, the description has been made by applying the photosensitive drum as the photosensitive member. However, the photosensitive member may be a photosensitive belt.

In the first embodiment, when the cleaning is completed, the voltage applied to the transfer roller is reduced stepwise, and then the voltage application is stopped. The voltage application may be stopped after the voltage is reduced in a linear function or other functions.

In the second embodiment, after the cleaning of the transfer roller is completed, the image formation is started after the portion of the photosensitive drum facing the leading end of the pre-transfer guide has passed the cleaning area at least twice. However, after the opposing portion has passed the cleaning area at least once, image formation may be started from the photoreceptor area subsequent to the opposing part. This is because, after the cleaning of the transfer roller, the portion of the photosensitive drum facing the leading end of the pre-transfer guide passes through the cleaning area at least once, so that toner adheres to the facing portion and is contaminated. If the image forming start point is located on the upstream side in the rotation direction of the photoconductor from the contaminated area, before the image is formed on the contaminated area, the contaminated area passes through the cleaning area and the toner is removed and collected. There is no problem even if the image formation is performed after reaching the image formation area. In this case, the timing of starting image formation can be earlier than in the second embodiment.

[0054]

As described above, according to the first aspect of the present invention, there is provided a photoconductor on which a toner image is developed, a transfer roller opposed to the photoconductor, and a transfer position between the photoconductor and the transfer roller. A pre-transfer guide that guides the sheet member; and a transfer output applying unit that applies a transfer output to the transfer roller, wherein the transfer output applying unit is configured to transfer a toner image on the photoconductor onto a sheet member. In the meantime, while applying a transfer output of a polarity opposite to the charge polarity of the toner to the transfer roller,
During non-transfer, the transfer roller is cleaned by applying a transfer output having the same polarity as the charged polarity of the toner to the transfer roller. Further, at the end of the cleaning, the transfer output applied to the transfer roller is gradually reduced. The image forming apparatus is configured as described above.

According to the above configuration, by performing the cleaning of the transfer device, it is possible to prevent a decrease in the transfer efficiency, and it is possible to stably perform high-quality image formation over a long period of time, and to finish the cleaning. In this case, since the voltage applied to the transfer roller is gradually reduced, the charge charged on the pre-transfer guide can be prevented from being instantaneously released. The application of a high-potential electric charge in the form of an edge to the facing portion is prevented. Accordingly, extra toner is prevented from adhering to the surface of the photoconductor, and a clear image can be formed.

The transfer output applied to the transfer roller is reduced stepwise, and then the transfer output application is stopped (Claim 2). The control can be made easier.

According to a third aspect of the present invention, there is provided a photoconductor which circulates through a toner image forming area including a charging area, an exposure area and a developing area, a transfer area and a cleaning area;
A toner image forming means for forming a predetermined toner image in a developing area on a photoconductor on which an electrostatic latent image is formed by passing through the charging area and the exposure area; and a sheet member for transferring the toner image on the photoconductor in the transfer area. A transfer roller for transferring the image onto the transfer roller, a transfer output applying unit for applying a transfer output to the transfer roller, a pre-transfer guide for guiding a sheet member to the transfer area, and a residual after transfer from the photoconductor surface in the cleaning area. A transfer device for removing a toner, wherein the transfer output applying unit transfers a transfer output having a polarity opposite to a charged polarity of the toner to the transfer roller during transfer of transferring the toner image on the photoconductor onto a sheet member. On the other hand, during non-transfer, the transfer roller having the same polarity as the charge polarity of the toner is applied to the transfer roller to clean the transfer roller. Made, the toner image forming means,
At the end of the cleaning of the transfer roller, the photosensitive member portion facing the transfer guide moves the cleaning area by at least one.
The image forming apparatus is configured to form a new toner image on the photoreceptor after passing through the charging area once and further once through the charging area.

According to the above arrangement, at the end of the cleaning of the transfer roller, the photosensitive member portion facing the leading end of the transfer guide passes through the cleaning region at least once and further passes through the charging region once, and then is placed on the photosensitive member. It is possible to start new toner image formation, without performing special operations,
In addition, image formation can be started after a very short time after the completion of cleaning without any configuration.

The toner image forming means includes a charger for charging a photoreceptor in a charging area, an exposing means for exposing an image on the photoreceptor in an exposure area, and a toner on the electrostatic latent image of the photoreceptor in a developing area. (Claim 4), which is one specific embodiment. The photoreceptor is charged by a charger in a charging area, and an image is exposed by an exposure unit in an exposure area,
A toner image is formed by supplying toner to the electrostatic latent image by the developing means in the developing area.

Further, the cleaning of the transfer roller is performed during warm-up of the image forming apparatus or during standby (claim 5), so that adverse effects on image formation can be avoided. In addition, the waiting time can be effectively used.

Further, the cleaning of the transfer roller is performed during toner supply to the developing device (Claim 6), so that adverse effects on image formation can be avoided. In addition, the waiting time can be effectively used.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of an embodiment in which an image forming apparatus according to the present invention is applied to a copying machine.

FIG. 2 is an overall sectional view of a main part of the present invention.

FIG. 3 is a timing chart of the present invention.

FIG. 4 is a timing chart of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus) 2 ... Device body 13 ... Sheet member 30 ... Image forming part 31 ... Photoconductor drum (photoconductor) 32 ... Charger 33 ... Exposure means 34 ... Developing means 35 ... Transfer device 36 ... Cleaning Means 100: Transfer output applying means 261: Guide before transfer 351: Transfer roller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masatake Hayashi 1-2-28 Tamatsukuri, Chuo-ku, Osaka-shi Inside Mita Kogyo Co., Ltd. (72) Inventor Takaki Kamei 1-2-28 Tamazo, Chuo-ku, Osaka Mita Kogyo Co., Ltd. F-term (reference) 2H032 AA05 BA19 BA27 BA30 CA02 CA04 CA13

Claims (6)

[Claims] 1. A photoreceptor on which a toner image is developed, a transfer roller facing the photoreceptor, a pre-transfer guide for guiding a sheet member to a transfer position between the photoreceptor and the transfer roller, and the transfer A transfer output applying unit for applying a transfer output to a roller, wherein the transfer output applying unit is configured to transfer the toner image on the photoreceptor onto a sheet member at the time of transfer, the transfer output having a polarity opposite to the charge polarity of the toner. Is applied to the transfer roller, and at the time of non-transfer, the transfer roller is cleaned by applying a transfer output having the same polarity as the charged polarity of the toner to the transfer roller. An image forming apparatus configured to gradually reduce a transfer output applied to a roller. 2. The image forming apparatus according to claim 1, wherein the transfer output applied to the transfer roller is gradually reduced, and then the transfer output application is stopped. 3. A photoconductor circulating through a toner image forming area, a transfer area, and a cleaning area including a charged area, an exposed area, and a developing area, and an electrostatic latent image passing through the charged area and the exposed area. A toner image forming means for forming a predetermined toner image on the photoreceptor formed in the development area, a transfer roller for transferring the toner image on the photoreceptor on the sheet member in the transfer area, and a transfer roller A transfer output applying unit for applying an output; a pre-transfer guide for guiding a sheet member to the transfer area; and a cleaning device for removing residual toner after transfer from the photoconductor surface in the cleaning area. The application unit applies a transfer output having a polarity opposite to a charged polarity of the toner to the transfer roller at the time of transfer of transferring the toner image on the photoconductor onto a sheet member. On the other hand, at the time of non-transfer, the transfer roller is cleaned by applying a transfer output having the same polarity as the charged polarity of the toner to the transfer roller, and the toner image forming unit is configured to At the end of cleaning, the photoconductor portion facing the transfer guide passes through the cleaning region at least once, and further passes through the charging region once, and then forms a new toner image on the photoconductor. An image forming apparatus characterized in that: 4. The toner image forming means includes: a charger for charging a photoreceptor in a charging area; an exposing means for exposing an image on the photoreceptor in an exposure area; 4. The image forming apparatus according to claim 3, further comprising: a developing unit that supplies the toner. 5. The image forming apparatus according to claim 1, wherein the cleaning of the transfer roller is performed during warm-up of the image forming apparatus or during standby. 6. The image forming apparatus according to claim 1, wherein the cleaning of the transfer roller is performed while toner is supplied to the developing device.