JP2006215588A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus preventing occurrence of the fogging of an image caused by a contact type cleaning member for cleaning an intermediate transfer body, and providing a high-quality image. <P>SOLUTION: A cleaning blade 30 is controlled to abut on an intermediate transfer belt 11 after the trailing end of a toner image obtained by superposing a plurality of toner images formed on the intermediate transfer belt 11 passes and before the leading end of a residual toner image left after transfer remaining after secondarily transferring the toner image reaches, and separate therefrom so that the separate position of the cleaning blade may not reach a primary transfer area where primary transfer is performed before the leading end of the toner image primarily transferred first in a next image forming process reaches. At this time, the separation timing of the cleaning blade is controlled by setting the write-in timing of a latent image corresponding to the toner image primarily transferred first in the next image forming process as reference. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly to an image forming apparatus having a contact-type cleaning member that removes toner remaining on an intermediate transfer member.

  Conventionally, in this type of image forming apparatus, a toner image primarily transferred from a latent image carrier such as a photosensitive member to an intermediate transfer member such as an intermediate transfer belt is secondarily transferred to a recording medium such as transfer paper. To do. Then, the transfer residual toner remaining on the intermediate transfer member after the secondary transfer is brought into contact with the surface of the intermediate transfer member and scraped off the transfer residual toner on the intermediate transfer member by a contact type cleaning member such as a cleaning blade. Remove from.

  In the contact cleaning member, the contact / separation operation with respect to the intermediate transfer member is controlled by a control unit that performs sequence control of the image forming apparatus. Thereby, the contact-type cleaning member can be brought into contact with and separated from the intermediate transfer member at a predetermined timing. Then, the contact-type cleaning member comes into contact with the surface of the rotating intermediate transfer member, whereby the transfer residual toner remaining on the surface of the intermediate transfer member is removed.

  However, in an image forming apparatus to which such a contact-type cleaning member is applied, when the contact-type cleaning member is separated from the surface of the intermediate transfer member, a streaky cleaning release trace, toner drop, or the like occurs. This is because, for example, when the contact-type cleaning member is a cleaning blade, transfer residual toner scraped off by the cleaning blade is spilled or scattered when the cleaning blade is separated from the surface of the intermediate transfer member. Occur. As a result, when the dirt due to the cleaning cancellation mark or the toner drop overlaps with the toner image primarily transferred to the intermediate transfer member in the next image forming process, the image is fogged and abnormal on the recording medium. An image may be formed.

  In order to solve such a problem, Japanese Patent Laid-Open No. 5-6128 discloses that a color toner image sequentially formed on a belt-like recording medium by yellow, magenta and cyan color developers is transferred onto an intermediate transfer member. In the intermediate transfer body cleaning device of a full color image forming apparatus that forms a full color image by superimposing them, the circumference of the intermediate transfer body is formed to be longer than the length of the full-size maximum transfer paper to be used, and the intermediate transfer body Cleaning blade means for removing residual toner on the intermediate transfer body between the image transfer position from the transfer body to the transfer paper and the toner image transfer position from the belt-shaped recording medium to the intermediate transfer body. The belt-shaped recording medium provided at the time of the first copy cycle in the case of full-color copying on a full-size transfer paper provided so as to be able to contact with and separate from the transfer body After the trailing edge of the cyan toner image transferred onto the intermediate transfer member has passed through the cleaning blade means, the leading edge position of the intermediate transfer member after transferring the image onto the transfer paper is the cleaning blade. Before reaching the means, the cleaning blade means is brought into contact with the surface of the intermediate transfer body, and the yellow toner image transferred onto the intermediate transfer body from the belt-like recording medium during the second copy cycle Before the tip of the cleaning blade means reaches the cleaning blade means and before the cleaning blade means contact position on the intermediate transfer body reaches the toner image transfer position from the belt-like recording medium to the intermediate transfer body, A full-color image type comprising control means for controlling the cleaning blade means to be separated from the intermediate transfer member An intermediate transfer member cleaning device of the apparatus is disclosed.

  The image forming apparatus described in this publication does not necessarily have a clear configuration, but the cleaning blade does not have a scratch on the image area of the intermediate transfer member that transfers the toner image from the belt-like recording medium. Therefore, it is described that toner filming does not occur and image fogging due to toner filming on transfer paper can be prevented.

  By the way, in the conventional image forming apparatus, when the toner image formed on the latent image carrier is primarily transferred onto the intermediate transfer member, the toner image is always transferred to a fixed position on the intermediate transfer member. Was. For this reason, for example, if the rotational position detection mark or the like provided on the back surface of the intermediate transfer member is detected by the rotational position detection means, and the control unit of the image forming apparatus recognizes the rotational position of the intermediate transfer member, The toner image position on the intermediate transfer member can be easily recognized. Therefore, the contact / separation timing of the contact-type cleaning member for cleaning the intermediate transfer member can be controlled with respect to the toner image as a result by controlling the rotation position of the intermediate transfer member. It was.

  However, in the image forming apparatus configured such that the position of the toner image formed on the intermediate transfer body by sequentially transferring the toner images sequentially from the latent image carrier is shifted for each image forming process. When the contact / separation timing of the cleaning member is controlled by the above-described conventional control method, there is a problem in that it cannot be controlled in accordance with the toner image position. In this case, dirt such as a cleaning release mark or toner drop by the contact type cleaning member overlaps with the toner image, and the image is fogged, so that a high quality image cannot be obtained.

  Conventionally, toner images sequentially formed on a latent image carrier with two or more color developers are primarily transferred onto an intermediate transfer member and superimposed, and a plurality of toner images are formed on the intermediate transfer member at a time. An image forming apparatus for forming is known. In this image forming apparatus as well, image fogging may occur due to the influence of contamination such as cleaning removal traces caused by the contact-type cleaning member and toner dropping. However, in this image forming apparatus, no consideration has been given to such cleaning traces and dirt such as toner dropping. For this reason, in such an image forming apparatus, image fogging occurs, and a high-quality image cannot be obtained.

The present invention has been made in view of the above problems, and a first object is to determine the position of a toner image formed on an intermediate transfer member by primary transfer of a toner image from a latent image carrier. Even in an image forming apparatus configured to be shifted for each image forming process, an image forming apparatus capable of obtaining a high-quality image without causing image fogging by a contact-type cleaning member that cleans the intermediate transfer member. Is to provide.
A second object is to primarily transfer and superimpose toner images sequentially formed on the latent image carrier with two or more color developers onto the intermediate transfer member, and onto the intermediate transfer member at once. In an image forming apparatus that forms a plurality of toner images, by providing an image forming apparatus capable of obtaining a high-quality image without causing image fogging by a contact-type cleaning member that cleans the intermediate transfer member. is there.

  In order to achieve the first object, the inventions of claims 1 and 2 develop a latent image sequentially formed on a latent image carrier with a developer of two or more colors to form a toner image, and The toner image is primarily transferred onto the intermediate transfer member and superimposed to form a toner image on the intermediate transfer member. After the toner image is secondarily transferred, the toner image comes into contact with the surface of the intermediate transfer member. A contact-type cleaning member that removes transfer residual toner remaining on the intermediate transfer member, and the contact-type cleaning member performs secondary transfer of the toner image after the trailing edge of the toner image has passed. After that, the front end portion of the toner image remaining on the intermediate transfer body comes into contact before reaching the front end portion of the toner image, and is first transferred first onto the intermediate transfer body in the next image forming step. Before reaching the intermediate transfer member surface. In the image forming apparatus in which the position where the contact type cleaning member is separated does not reach the primary transfer area where the primary transfer is performed, in the next image forming step, first, the contact type cleaning member is placed on the intermediate transfer member. Control means is provided for controlling the timing at which the contact-type cleaning member is separated from the intermediate transfer body with reference to the toner image to be primarily transferred.

  Here, the “toner image that is first primarily transferred onto the intermediate transfer member in the next image forming step” means that the contact-type cleaning member abuts on the surface of the intermediate transfer member and removes the transfer residual toner image. Means a toner image which is first primarily transferred onto the intermediate transfer member. Further, “on the basis of the toner image” means the control means such as the writing timing of the writing means for writing the latent image corresponding to the toner image on the latent image carrier, the primary transfer timing of the toner image, etc. Means that the position on the intermediate transfer member in the toner image to be primarily transferred first can be recognized as a reference.

  The image forming apparatus according to claim 1 controls the separation timing of the contact-type cleaning member on the basis of the toner image first primarily transferred onto the intermediate transfer member in the next image forming process. There is no influence on the positional relationship between the rotational position of the intermediate transfer member to be carried and the position of the toner image. For this reason, even in an image forming apparatus configured to shift the position of the toner image formed on the intermediate transfer member for each image forming process, the separation position of the contact-type cleaning member performs primary transfer. The separation timing of the contact-type cleaning member can be controlled so as not to reach the primary transfer region. Accordingly, even in this case, it is possible to prevent image fogging caused by dirt such as a cleaning release trace or toner dropping by the contact-type cleaning member.

In particular, according to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit is configured to generate a latent image corresponding to a toner image that is first primarily transferred onto the intermediate transfer member in the next image forming step. The timing at which the contact-type cleaning member is separated from the intermediate transfer member is controlled on the basis of the writing timing.
The image forming apparatus is configured to control the separation timing of the contact cleaning member with reference to the writing timing of the latent image corresponding to the toner image. With this configuration, the control unit is also used as a control unit that controls the writing timing of the latent image provided in the image forming apparatus, so that the control unit can perform intermediate transfer in the next image forming step. It becomes possible to easily recognize the position of the toner image that is first primarily transferred onto the body. Therefore, in order to recognize the position of the toner image, it is not necessary to provide a new member or device separately, and the cost can be reduced.

  In order to achieve the second object, the inventions of claims 3 and 4 primarily transfer the toner images sequentially formed on the latent image carrier with the developer of two or more colors onto the intermediate transfer member. After a plurality of toner images are formed on the intermediate transfer member at the same time, and each toner image is secondarily transferred, the transfer residue remaining on the intermediate transfer member is in contact with the surface of the intermediate transfer member. In the image forming apparatus having the contact-type cleaning member for removing the toner, the contact-type cleaning member passes all the toner images after the rear end of the last toner image of the toner images has passed. Among the transfer residual toner images remaining on the intermediate transfer body after the transfer, the first transfer residual toner image comes into contact before reaching the leading end, and in the next image forming process, the first 1 is formed on the intermediate transfer body. Next transfer -Before the leading edge of the image reaches, the position where the contact-type cleaning member is separated on the surface of the intermediate transfer member is separated so as not to reach the primary transfer region where the primary transfer is performed. As described above, a control means for controlling the timing at which the contact-type cleaning member is separated from the intermediate transfer member is provided.

  In this image forming apparatus, a toner image for a plurality of surfaces can be formed on the intermediate transfer member at a time, and two or more images can be formed in one image forming process. Therefore, the image forming speed when forming the same image can be improved. In addition, after the cleaning by the contact-type cleaning member and dirt such as toner dropping do not overlap with the toner image in the next image forming apparatus, image fogging does not occur.

In particular, the invention according to claim 4 is the image forming apparatus according to claim 3, wherein the control means uses the toner image first transferred onto the intermediate transfer member in the next image forming step as a reference. It is characterized in that the timing at which the contact-type cleaning member is separated from the intermediate transfer member is controlled.
This image forming apparatus is configured to form a plurality of toner images on the intermediate transfer member at a time, and the position of the toner image formed on the intermediate transfer member is determined for each image forming step. Even in the image forming apparatus configured to be shifted, the separation timing of the contact cleaning member is controlled so that the separation position of the contact cleaning member does not reach the primary transfer region where the primary transfer is performed. be able to. Accordingly, even in this case, it is possible to prevent image fogging caused by dirt such as a cleaning release trace or toner dropping by the contact-type cleaning member.

  According to the first and second aspects of the present invention, the position of the toner image formed on the intermediate transfer member by the primary transfer of the toner image from the latent image carrier is shifted for each image forming step. Also in the image forming apparatus, there is an excellent effect that it is possible to provide an image forming apparatus capable of obtaining a high-quality image without causing image fogging by the contact-type cleaning member for cleaning the intermediate transfer member. is there.

  In particular, according to the second aspect of the present invention, it is not necessary to separately provide a new member or device for recognizing the position of the toner image on the intermediate transfer member, so that it is possible to reduce the cost. There is.

  According to the invention of claim 3, the toner images sequentially formed on the latent image carrier by the developer of two or more colors are primarily transferred and superimposed on the intermediate transfer member, and the toner image is formed on the intermediate transfer member at a time. An image forming apparatus capable of obtaining a high-quality image without causing image fogging by a contact-type cleaning member that cleans the intermediate transfer member even in an image forming apparatus that forms a plurality of toner images. There is an excellent effect of being able to.

  In particular, according to the fourth aspect of the present invention, a plurality of toner images are formed on the intermediate transfer member at the same time, and the positions of the toner images formed on the intermediate transfer member are determined by the image. Even in the image forming apparatus configured to be shifted for each forming process, there is an excellent effect that a high-quality image can be obtained without image fogging by the contact-type cleaning member.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described.
First, the configuration and operation of the entire copying machine according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. This copying machine is composed of a color image reading device (hereinafter referred to as a scanner unit) and a color image recording device (hereinafter referred to as a printer unit) which are not shown.

  In the scanner unit of the present embodiment, an image of a document placed on a contact glass is formed on a color sensor via an illumination / mirror optical system such as an illumination lamp, a mirror group, and a lens, and color image information of the document is recorded. Are read for each color separation light of, for example, Blue (hereinafter referred to as B), Green (same as G), and Red (same as R), and converted into an electrical image signal. The color sensor includes B, G, and R color separation means and a photoelectric conversion element such as a CCD, and can perform simultaneous reading of three colors.

  The B, G, and R image signals obtained by the scanner unit are subjected to color conversion processing by an image processing unit (not shown) based on the intensity level. By this color conversion processing, color image data of Black (hereinafter referred to as Bk), Yellow (same as Y), Cyan (same as C), and Magenta (same as M) are obtained. Specifically, the illumination / mirror optical system scans a document in response to a start signal linked to the printer unit to obtain color image data. In the present embodiment, since one color image data is obtained for each original scan in the illumination / mirror optical system, four color image data of Bk, Y, C, and M are obtained. In order to obtain this, the above document scanning is repeated four times in total.

  The printer unit in this embodiment is provided with a writing optical unit (not shown) as exposure means and a photosensitive drum 1 as a latent image carrier. The writing optical unit converts the color image data from the above-described scanner unit into an optical signal, and forms a negative latent image corresponding to the original image on the photosensitive drum 1 that is uniformly charged to a negative polarity. Examples of the writing optical unit include a semiconductor laser, a light emission drive control unit that controls light emission and drive thereof, a polygon mirror, a rotation drive motor that rotationally drives the semiconductor mirror, an f / θ lens, and a reflection mirror. Can be used. The photosensitive drum 1 is driven to rotate in the direction of arrow A in FIG. 1, that is, counterclockwise.

  Around the photosensitive drum 1, there are a photosensitive member cleaning device 2 as a photosensitive member cleaning unit, a neutralizing lamp as a neutralizing unit (not shown), a charging charger 3 as a charging unit as a charging unit, and a developing unit. A revolver developing unit 4 that is a rotary developing device and an intermediate transfer unit 10 are disposed.

  The photoconductor cleaning device 2 includes a fur brush 2a and a photoconductor cleaning blade 2b, and cleans the surface of the photoconductor drum 1 after the primary transfer.

  The revolver developing unit 4 includes a Bk developing unit 4a, a Y developing unit 4b, a C developing unit 4c, and an M developing unit 4d, and the revolver developing unit rotates so that the photosensitive unit in each color developing unit is rotated. The development position facing the body drum 1 can be positioned. Each of these developing devices includes a developing paddle as a stirring means (not shown) that pumps up and stirs the developer, a toner density detection sensor (not shown) that detects a toner density of the developer, and the developer And a developing sleeve (not shown) as a developer carrying member (not shown) that contacts the surface of the photosensitive drum 1. When the copying machine is in a standby state, these four developing units are inoperative by cutting off the developer on the developing sleeves. Note that the internal structures of these four developing units are exactly the same.

  The intermediate transfer unit 10 includes an intermediate transfer belt 11 as an intermediate transfer member, a primary transfer bias roller 12 as a charge applying unit, a primary transfer power source 18 as a power source connected thereto, and a primary transfer. The configuration is such that the grounding roller 13 as the pre-charger, the driving roller 14 as the belt driving unit, the tension roller 15, the secondary transfer counter roller 16, and the cleaning counter roller 17 are stretched. All the rollers that stretch the intermediate transfer belt 11 are made of a conductive material, and the rollers other than the primary transfer bias roller 12 are grounded. The drive roller 14 is connected to a drive motor 19, and the drive of the intermediate transfer belt 21 is controlled by a control unit 100 as a control means for controlling the drive motor.

  The primary transfer bias roller 12 that stretches the intermediate transfer belt 11 is connected to the primary transfer region formed by a nip formed by the contact between the intermediate transfer belt and the photosensitive drum 1. It is arranged on the downstream side of the belt surface movement direction, that is, the belt rotation direction. The primary transfer bias roller 12 is applied with a DC or AC bias, or a DC and AC primary transfer bias that is constant current or constant voltage controlled by the primary transfer power source 18. A grounded earth roller 13 is disposed upstream of the primary transfer area in the belt rotation direction. The intermediate transfer belt 11 is pressed against the photosensitive drum 1 by the primary transfer bias roller 12 and the earth roller 13 to form the nip portion.

  Around the intermediate transfer belt 11, a cleaning blade 30 as a contact type cleaning member and a transfer unit 40 as a transfer means are arranged. The transfer unit 40 includes a paper transfer belt 41 as a transfer material carrier, a transfer cleaning blade 42 for cleaning the surface of the paper transfer belt, and a secondary transfer facing the secondary transfer counter roller 16 of the intermediate transfer unit 10. A bias roller 43, a secondary transfer power source 47 connected thereto, a first support roller 44a located at an end portion on the paper feed unit side (not shown), and a second support located at an end portion on the fixing unit 60 side. It has a roller 44b, a third support roller 44c facing the transfer cleaning blade 42, a transfer paper discharger 45, and a paper transfer belt discharger 46. Further, the transfer unit 40 can be brought into and out of contact with the intermediate transfer belt 11 by a contact and separation mechanism (not shown). The transfer unit 40 is not limited to this configuration, and for example, a configuration in which a member having another shape such as a drum is used instead of the paper transfer belt 41 may be used.

  The cleaning blade 30 can be brought into and out of contact with the intermediate transfer belt 11 by a contact and separation mechanism 31. As this contact / separation mechanism, a known contact / separation mechanism using a solenoid or a cam mechanism can be applied. The contact / separation mechanism 31 is controlled by a control unit 100 that performs sequence control of the copying machine. Accordingly, the cleaning blade 30 can be brought into contact with or separated from the intermediate transfer belt 11 at a timing controlled by the control unit 100.

  Further, the above-described printer unit further includes a recording medium in a secondary transfer area formed between the secondary transfer bias roller 43 of the transfer unit 40 and the secondary transfer counter roller 16 of the intermediate transfer belt 11. A paper feeding unit (not shown) that feeds the transfer paper 70, a paper transport unit 50 that transports the transfer paper 70 on which the toner image is secondarily transferred by the transfer unit 40, and a toner on the transfer paper 70 that is transported by the paper transport unit. A fixing unit 60 is also provided as fixing means for fixing the image.

  Next, an example of the image forming operation of the copying machine when the order of development is Bk, Y, C, M will be described. The order of image formation is not limited to this.

  Before starting the image forming cycle, the photosensitive drum 1 is rotated in the direction of arrow A in FIG. 1, and the charging charger 3 starts corona discharge. Thereby, the surface of the photosensitive drum 1 is uniformly charged to a predetermined potential with a negative charge. The intermediate transfer belt 11 of the intermediate transfer unit 10 is driven at the same speed as the photosensitive drum 1, and rotates in the direction of arrow B in FIG.

  When the copy key is input and the copy operation is started, the Bk process is started first, and the color image information of the original is read by the above-described scanner unit, and the above-described Bk image data obtained from this image information is used to perform the above-described operation. A Bk latent image is formed on the photosensitive drum 1 by the laser beam of the writing optical unit in the printer unit. The writing timing by the writing optical unit is controlled by the control unit 100. The Bk toner negatively charged by the Bk developing device 4a adheres to the Bk latent image and develops it to form a Bk toner image. At this time, in order to surely develop the Bk latent image, the developing sleeve of the Bk developing unit 4a is rotated in advance before the tip of the Bk latent image reaches the developing position of the Bk developing unit. As a result, when the leading edge of the Bk latent image reaches the development position, the developer is in a spiked state, so that the entire Bk latent image can be reliably developed.

  In the Bk developing device 4a, the developer formed on the developing sleeve is quickly cut off when the rear end of the Bk latent image passes the developing position. As a result, the Bk developing unit 4a becomes inoperative. At this time, at least the leading end of the Y latent image to be developed next is completely inactivated before reaching the developing position of the Bk developing unit 4a. The developer can be cut off by switching the developing sleeve of the Bk developing device 4a in the direction opposite to the rotating direction during the developing operation. The Bk toner image formed on the photosensitive drum 1 by the Bk developing device 4a in this way is primary on the surface of the intermediate transfer belt 11 that is driven at a constant speed with the photosensitive drum by the primary transfer electric field in the primary transfer region. Transcribed. The surface of the photosensitive drum 1 after the primary transfer is cleaned by the photosensitive member cleaning device 2 and is uniformly discharged by the discharging lamp. This completes the Bk process.

  In parallel with the primary transfer of the Bk toner image, the next Y process is started on the photosensitive drum 1 side. That is, the color image information of the original is read again at a predetermined timing, and the Y latent image is formed on the photosensitive drum 1 by laser light under the control of the control unit 100 based on the Y image data obtained from the image information. And a Y toner image is formed by the Y developing device 4b. The rotation of the developing sleeve in the Y developing device 4b is started after the rear end portion of the Bk latent image has passed through the developing position of the Y developing device and before the leading end portion of the Y latent image has reached. The When the rear end portion of the Y latent image passes, the developer formed on the developing sleeve is cut off as in the case of the Bk developing device 4a described above, and the Y developing device 4b is disabled. Activated. Also at this time, it is made to be completely inactivated before the leading edge of the next C latent image arrives. The Y toner image thus developed and formed on the photosensitive drum 1 is aligned with the image surface onto which the Bk toner image on the intermediate transfer belt 11 has been transferred and is primarily transferred.

  Thereafter, in the C process and the M process, as in the Y process described above, latent image formation, development, and primary transfer are performed based on the respective image data. In this way, the Bk, Y, C, and M toner images sequentially formed on the photosensitive drum 1 are primarily transferred onto the same image surface on the intermediate transfer belt 11 to thereby perform the intermediate transfer. A toner image in which these four colors overlap is formed on the belt.

  The toner image formed by superimposing the toner images primarily transferred onto the intermediate transfer belt 11 as described above is secondarily transferred onto the transfer paper 70. Sent to the secondary transfer area. The transfer paper 70 is fed to the secondary transfer area by a registration roller (not shown) at the timing when the leading end of the toner image on the intermediate transfer belt 11 reaches the secondary transfer area. The secondary transfer bias roller 43 of the transfer unit 40 is pressed against the intermediate transfer belt 21 by a transfer contact / separation mechanism (not shown), and the secondary transfer bias roller 43 is pressed against the secondary transfer bias roller 43 by the secondary transfer power source 47. By applying a secondary transfer bias, the toner image on the intermediate transfer belt 11 is secondarily transferred onto the transfer paper 70.

  As described above, the transfer paper 70 onto which the toner image formed by overlapping four colors on the intermediate transfer belt 11 is secondarily transferred is then placed on the transfer unit 40 at a portion facing the transfer paper neutralization charger 45. Be transported. When passing through the facing portion, the transfer paper 70 is neutralized by the transfer paper neutralization charger 45 in the operating state, and peeled off from the paper transfer belt 41. The peeled transfer paper 70 is sent by the paper transport unit 50 between the fixing roller pair 61 of the fixing unit 60. In the fixing roller pair 61, the toner image on the transfer paper 70 is melted and fixed in a fixing region including a nip portion formed between the rollers. Then, the transfer paper 70 is carried out and stacked on a copy tray (not shown).

  Further, after the transfer paper 70 is peeled off, the charge remaining on the surface of the paper transfer belt 41 is neutralized by the paper transfer belt neutralization charger 46. The surface of the paper transfer belt 41 is further cleaned by the transfer cleaning blade 42.

  When performing repeat copy in the copying machine, the scanner unit proceeds to the Bk process for the first color on the second sheet at a predetermined timing following the M process for the fourth color on the first sheet, and the photosensitive drum in the printer unit. 1 to form a latent image.

  The copy mode for obtaining four full colors has been described above. However, in the other three-color copy mode and the two-color copy mode, the same operation as that of the above-described four-color copy mode is performed except that the colors used are different. Will do.

Next, the contact / separation timing of the cleaning blade 30, which is a characteristic part of the present invention, will be described with reference to FIGS. Here, a case will be described in which 40 A4 plates are copied in the vertical direction from the same document.
FIG. 2 is a timing chart of the contact / separation operation of the cleaning blade 30 in the present embodiment. FIG. 2 shows the writing optical unit based on the timing at which a rotation position detection mark (not shown) provided on the back surface of the edge of the intermediate transfer belt 11 is detected and the F gate signal sent from the control unit 100. Shows the writing timing for forming a latent image on the photosensitive drum 1 and the timing at which the cleaning blade 30 contacts and separates from the intermediate transfer belt 11 on the same time axis. The timing chart shown in FIG. 2 is obtained when the belt peripheral length of the intermediate transfer belt 11 is 565 mm and the surface moving speed of the intermediate transfer belt is 200 mm / s.

  When a print key is input (time point a in FIG. 2), in the intermediate transfer unit 10, when the drive motor 19 operates and the intermediate transfer belt 11 starts to rotate, the rotation provided in the intermediate transfer unit. The belt mark detection sensor 32 as a position detection means detects the rotational position detection mark. Then, the rotational position information of the intermediate transfer belt 11 detected by the belt mark detection sensor 32 is input to the control unit 100, and the control unit recognizes the rotational position of the intermediate transfer belt (time b in FIG. 2).

  Thus, the control unit 100 that has recognized the rotational position of the intermediate transfer belt 11 outputs an F gate signal to the writing optical unit. As a result, the writing optical unit starts forming a latent image based on the image information of the original read by the scanner unit (at time c in FIG. 2). In the control unit 100 in the present embodiment, the writing optical unit writes the Bk latent image after a time corresponding to 60 mm in terms of the belt circumference has elapsed with respect to the detection timing by the belt mark detection sensor. Control to start.

  The control unit 100 that has output the F gate signal to the writing optical unit controls the contact / separation mechanism 31 of the cleaning blade in order to separate the cleaning blade 30 from the intermediate transfer belt 11. As a result, the cleaning blade 30 is separated from the intermediate transfer belt 11 (d point in FIG. 2). In the present embodiment, the cleaning blade 30 is controlled to be separated from the intermediate transfer belt after a time corresponding to 618.1 mm when converted to the belt circumference with respect to the writing timing of the writing optical unit. is doing.

  With the above settings, when the separation timing of the cleaning blade 30 is controlled in accordance with the writing timing, as shown in FIG. 3, the Bk latent formed on the photosensitive drum 1 at this writing timing is as shown in FIG. When the tip of the Bk toner image on the intermediate transfer belt 11 corresponding to the image is about 25 mm before the contact position of the cleaning blade with the intermediate transfer belt, the cleaning blade is separated. As a result, not only the cleaning release trace that occurs when the cleaning blade 30 is separated, but also the contamination of the toner drop scattered at this time does not affect the Bk toner image.

  Thereafter, a Y toner image or the like is sequentially superimposed on the Bk toner image, whereby a toner image is formed on the intermediate transfer belt 11, and the toner image is fed onto the transfer paper 70 fed at a predetermined timing. Next transfer completes the first image forming process. At the time of this image forming process, the control unit 100 lastly writes the leading edge of the M latent image corresponding to the M toner image that is primarily transferred onto the photosensitive drum 1 (time point e in FIG. 2). The cleaning blade 30 is controlled to contact the intermediate transfer belt 11 after a time corresponding to 637.6 mm in terms of the belt circumferential length has elapsed (time point f in FIG. 2).

  Subsequently, when starting the next second image forming process, the control unit 100 first detects the rotational position detection mark after starting the formation of the M latent image in the first image forming process. With respect to (time point g in FIG. 2), when the time corresponding to the belt circumference is 60 mm (time point h in FIG. 2), the writing optical unit starts writing the Bk latent image. Is controlling. As a result, the toner image on the intermediate transfer belt 11 in the second image forming process is formed at the same position as the toner image position in the first image forming process.

  With this setting, when the contact timing of the cleaning blade 30 is controlled in accordance with the writing timing, the cleaning blade performs the rear of the toner image in the first image forming process as shown in FIG. After the end portion has passed, the toner image can be brought into contact before the leading end portion of the residual toner image remaining on the intermediate transfer belt 11 after the toner image is secondarily transferred. Thus, the cleaning blade 30 does not disturb the toner image existing on the intermediate transfer belt 11.

Also in the second image forming process, similarly to the first image forming process described above, the writing optical unit writes the Bk latent image at the second image forming process. On the other hand, the cleaning blade 30 is controlled to be separated from the intermediate transfer belt after a time corresponding to 618.1 mm in terms of the belt circumferential length has elapsed.
By repeating the above operations, 40 high-quality copy images free from abnormal images due to image fogging can be obtained.

  Next, a modified example of the above embodiment will be described with reference to FIGS. In this modification, two toner images are formed on the intermediate transfer belt at a time, and two images are formed in one image forming process to perform copying. Since the configuration in this modification is almost the same as that of the above embodiment, only the contact / separation timing of the cleaning blade 30 which is a feature of the present invention will be described. In this case, 40 A4 plates are copied in the horizontal direction.

FIG. 5 is a timing chart similar to FIG. 2 showing the contact / separation operation of the cleaning blade 30 in this modification.
When the print key is input (time point a in FIG. 5), the rotation mark detection sensor 32 detects the rotation position detection mark, and the rotation position information detected by the belt mark detection sensor is input to the control unit 100. The As a result, the controller 100 recognizes the rotational position of the intermediate transfer belt 11 (time b in FIG. 5).

  In this way, the control unit 100 that has recognized the rotational position of the intermediate transfer belt 11 outputs an F gate signal to the writing optical unit, and causes the writing optical unit to start latent image formation (at time c in FIG. 5). ). In the control unit 100 in the present modification, the writing optical unit moves to the first Bk latent time after a time corresponding to 60 mm in terms of belt circumference has elapsed with respect to the detection timing by the belt mark detection sensor 32. Control is performed to start writing the image. Further, the control unit 100 that has output the F gate signal to the writing optical unit causes the cleaning blade 30 to move after a time corresponding to 618.1 mm when converted to the belt circumference with respect to the writing timing. Control is performed so as to be separated from the intermediate transfer belt.

  With the above settings, when the separation timing of the cleaning blade 30 is controlled according to the writing timing, one sheet formed on the photosensitive drum 1 at this writing timing as shown in FIG. When the tip of the Bk toner image on the intermediate transfer belt 11 corresponding to the Bk latent image of the eye is approximately 25 mm before the contact position of the cleaning blade with the intermediate transfer belt, the cleaning blade is separated. Become. As a result, not only the cleaning release trace that occurs when the cleaning blade 30 is separated, but also the contamination of the toner drop scattered at this time does not affect the Bk toner image.

  Thereafter, a Y toner image or the like is sequentially superimposed on the first Bk toner image and the second Bk toner image, thereby forming two toner images on the intermediate transfer belt 11. These toner images are secondarily transferred to the transfer paper 70 fed at a predetermined timing, thereby completing one image forming process. In the image forming process, the control unit 100 writes the M latent image corresponding to the M toner image primarily transferred at the end of the first sheet onto the photosensitive drum 1 (at time e in FIG. 5). On the other hand, the cleaning blade 30 is controlled to come into contact with the intermediate transfer belt 11 after a time corresponding to 637.6 mm in terms of the belt circumferential length has elapsed (time point f in FIG. 5).

  Subsequently, when starting the second image forming process for forming the next third and fourth images, the control unit 100 starts forming the second M latent image in the first image forming process. After a time corresponding to 87 (60 + 27) mm when converted to the belt circumference with respect to the detection timing at which the rotational position detection mark is first detected (at time g in FIG. 5) later (time h in FIG. 5). The writing optical unit controls to start writing the third Bk latent image. As a result, the toner images on the intermediate transfer belt 11 in the second image forming process are formed by being shifted by 27 mm from the respective toner image positions in the first image forming process.

  With this setting, when the contact timing of the cleaning blade 30 is controlled according to the timing of writing the M latent image corresponding to the first M toner image on the photosensitive drum 1, the cleaning blade As shown in FIG. 7, after the rear end portion of the second toner image in the first image forming process has passed, the toner image remains on the intermediate transfer belt 11 after secondary transfer of the two toner images. The first transfer residual toner image can come into contact with the front end before reaching. Thus, the cleaning blade 30 does not disturb the toner image existing on the intermediate transfer belt 11.

  Also in the second image forming step, the writing optical unit writes the first Bk latent image in the second image forming step as in the first image forming step. With respect to the timing, the cleaning blade 30 is controlled to be separated from the intermediate transfer belt 11 after a time corresponding to 618.1 mm in terms of the belt circumferential length has elapsed.

  By repeating the above operations, 40 high-quality copy images free from abnormal images due to image fogging can be formed faster than in the above embodiment. Even in the setting in this modification, the toner image position on the intermediate transfer belt 11 returns to the same position as the first toner image position in the 37th image forming process.

1 is a schematic configuration diagram of a main part in a printer unit of a copier according to an embodiment. 5 is a timing chart showing contact / separation timing of the cleaning blade in the embodiment. FIG. 5 is an explanatory diagram showing a toner image position at the timing of contact of the cleaning blade in the embodiment. FIG. 6 is an explanatory diagram illustrating a toner image position at the time of cleaning blade separation timing in the embodiment. The timing chart which shows the contact / separation timing of the cleaning blade in a modification. FIG. 9 is an explanatory diagram showing a toner image position at the timing of contact of a cleaning blade in a modification. FIG. 9 is an explanatory diagram showing a toner image position at the time of cleaning blade separation timing in a modified example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Photoconductor cleaning apparatus 3 Charging charger 4 Revolver developing unit 10 Intermediate transfer unit 11 Intermediate transfer belt 14 Drive roller 19 Drive motor 30 Cleaning blade 31 Contact / separation mechanism 32 Belt mark detection sensor 40 Transfer unit 50 Paper transport unit 60 Fixing unit 70 Transfer paper 100 Control unit

Claims (4)

The latent images sequentially formed on the latent image carrier are developed with a developer of two or more colors to form a toner image, and the toner image is primarily transferred and superimposed on the intermediate transfer member, whereby the intermediate image A contact-type cleaning member that forms a toner image on a transfer body, performs secondary transfer of the toner image, and then contacts the surface of the intermediate transfer body to remove residual toner remaining on the intermediate transfer body; ,
After the rear end portion of the toner image has passed through the contact-type cleaning member and before the front end portion of the transfer residual toner image remaining on the intermediate transfer body after the toner image is secondarily transferred. Abut,
In the next image forming step, the position where the contact-type cleaning member is separated on the surface of the intermediate transfer body is 1 before the leading edge of the toner image to be primarily transferred onto the intermediate transfer body first arrives. In an image forming apparatus that is separated so as not to reach the primary transfer area where the next transfer is performed,
Control means for controlling the timing at which the contact-type cleaning member is separated from the intermediate transfer body with reference to the toner image first transferred onto the intermediate transfer body in the next image forming step as a reference. An image forming apparatus having features. The image forming apparatus according to claim 1.
The contact type cleaning member serves as the intermediate transfer member based on the writing timing of the latent image corresponding to the toner image that is first primarily transferred onto the intermediate transfer member in the next image forming step. An image forming apparatus characterized by controlling the timing of separation from the image forming apparatus. Toner images sequentially formed on the latent image carrier by two or more color developers are primarily transferred and superimposed on the intermediate transfer member to form a plurality of toner images on the intermediate transfer member at once, In the image forming apparatus having a contact-type cleaning member that removes transfer residual toner remaining on the intermediate transfer member by contacting the surface of the intermediate transfer member after secondary transfer of the toner images.
After the rear end portion of the last toner image among the toner images has passed through the contact-type cleaning member, the transfer residual toner image remaining on the intermediate transfer body after secondary transfer of all the toner images Before the leading end of the first transfer residual toner image reaches,
In the next image forming step, the position where the contact-type cleaning member is separated on the surface of the intermediate transfer body is 1 before the leading edge of the toner image to be primarily transferred onto the intermediate transfer body first arrives. Control means for controlling the timing at which the contact-type cleaning member is separated from the intermediate transfer member is provided so as to be separated so as not to reach the primary transfer area where the next transfer is performed. Image forming apparatus. The image forming apparatus according to claim 3.
The control means controls the timing at which the contact-type cleaning member is separated from the intermediate transfer body on the basis of the toner image that is first primarily transferred onto the intermediate transfer body in the next image forming step. An image forming apparatus having features.

Images