JP3744235B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus applying a copying machine, a laser printer, or other electrophotographic method, and transferring an image by secondary transfer of the toner image onto a recording medium from an intermediate transfer body onto which the toner image has been transferred. The present invention relates to an image forming apparatus to be formed, and particularly to a cleaning technique for a transfer unit in a secondary transfer unit.
[0002]
[Prior art]
Conventionally, as an image forming apparatus applying the above-described copying machine, laser printer, or other electrophotographic method, toner images such as yellow, magenta, cyan, and black that are sequentially formed on a photosensitive drum are transferred onto an intermediate transfer belt. The toner images of each color transferred on the intermediate transfer belt in a superimposed manner are collectively transferred onto the recording medium by the pressure contact force and electrostatic attraction force between the backup roll and the secondary transfer roll. There is a configuration in which a color image is formed by fixing an unfixed toner image of each color on a recording medium by a fixing device after the transfer.
[0003]
Such an image forming apparatus presses a secondary transfer roll against an intermediate transfer belt onto which a toner image of each color has been transferred, and secondary-transfers the toner images transferred onto the intermediate transfer belt onto a recording medium. A color image is formed. Therefore, in the image forming apparatus, when the toner image transferred onto the intermediate transfer belt comes into contact with the secondary transfer roll, the toner is transferred to the secondary transfer roll by a pressure contact force, and the toner adhered to the secondary transfer roll. However, it adheres to the back surface of the recording medium that is next transported to the secondary transfer position and causes the back surface of the recording medium to become dirty.
[0004]
Therefore, in order to prevent such backside contamination of the recording medium due to toner adhesion to the secondary transfer roll, a technique for cleaning the secondary transfer roll or the like in the image forming apparatus using the transfer roll including the secondary transfer roll. For example, those disclosed in JP-A-8-63011, JP-A-8-272235, JP-A-8-328401, JP-A-9-6146 and the like have already been proposed.
[0005]
The image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 8-63011 includes a photoconductor, a developing unit that sequentially forms toner images of each color on the photoconductor, and an intermediate transfer member disposed in contact with the photoconductor. A first power supply device that applies a primary transfer voltage to the intermediate transfer member and sequentially transfers the toner image on the photosensitive member to the intermediate transfer member to form a color toner image; and a contact with the intermediate transfer member When a transfer material exists between the transfer member disposed between the photosensitive member and the transfer member, a secondary transfer voltage is applied to the transfer member, and the color toner of the intermediate transfer member A second transfer circuit configured to transfer an image to a transfer material and to apply a voltage having a polarity opposite to the secondary transfer voltage to the transfer member when no transfer material exists between the photosensitive member and the transfer member; And a power supply device.
[0006]
Further, an image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 8-272235 includes an image carrier that electrostatically carries a toner image, a transfer member that abuts on the surface of the image carrier and applies a transfer bias, a transfer member And a bias applying unit that sequentially applies bias currents having different polarities to the transfer member when no transfer material is present at the position. The bias applying unit has the same polarity as the toner constituting the toner image. After applying the same polarity current, a reverse polarity current having a current value opposite to that of the toner and having an absolute value equal to or larger than the absolute value of the same polarity current is applied.
[0007]
Further, an image forming apparatus according to the above-mentioned JP-A-8-328401 includes an image carrier that electrostatically carries a toner image, a transfer member that abuts on the surface of the image carrier and applies a transfer bias, When a transfer material is passed between the image carrier and the transfer member, a transfer bias is applied to the transfer member to transfer the toner image formed on the surface of the image carrier to the transfer material and to the transfer position. In an image forming apparatus comprising: a bias applying unit configured to flow a current having the same polarity as the charging polarity of the toner to the transfer member and then to flow a reverse polarity current to the transfer member at the time of cleaning without the presence of at least immediately after the cleaning From the start of the first image formation until the transfer bias is applied, a bias having the same polarity as the transfer bias is applied to the transfer member.
[0008]
Still further, the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 9-6146 transfers a photoreceptor on which a toner image corresponding to an image to be formed is formed, and a toner image on the photoreceptor onto an intermediate transfer member. A primary transfer member, a secondary transfer member that is provided so as to be capable of being pressed against and separated from the intermediate transfer member, and that transfers a toner image on the intermediate transfer member onto a recording sheet, and an intermediate that drives the intermediate transfer member to rotate. An image forming apparatus comprising: a transfer member driving unit; a cleaner blade which is provided so as to be capable of being pressed against and separated from the intermediate transfer member and removes a toner image on the intermediate transfer member; and the secondary transfer A secondary transfer member holding means for selectively switching and holding the member in a pressure contact state or a separated state with respect to the intermediate transfer member, and the cleaner blade in a pressure contact state with respect to the intermediate transfer member. A cleaner blade holding means for selectively switching and holding the separated state, a paper jam detecting means for detecting a paper jam in the recording paper conveyance path, and a paper jam release detecting means for detecting that the paper jam condition has been released. A voltage applying means for applying a voltage to the secondary transfer member; and a control means for controlling the operation of the holding means, the driving means, and the voltage applying means based on detection signals from the detecting means; And the control means holds the cleaner blade in pressure contact with the intermediate transfer body and detects the secondary transfer member after the intermediate transfer is detected after detecting that the paper jam state has been released. The intermediate transfer member is held in a separated state, the intermediate transfer member is rotated one or more times to clean the intermediate transfer member, and the secondary transfer is performed after the intermediate transfer member is cleaned. The transfer member is held in contact with the intermediate transfer member by switching the pressure state, a voltage is applied to the secondary transfer member, and the secondary transfer member is rotated one or more times to clean the secondary transfer member. It is configured to do.
[0009]
[Problems to be solved by the invention]
However, the above prior art has the following problems. That is, all of the techniques disclosed in the above-mentioned JP-A-8-63011, JP-A-8-272235, JP-A-8-328401, JP-A-9-6146, etc. When a recording medium (transfer material) is passed between the transfer member or the intermediate transfer member and the transfer unit, a transfer bias is applied to the transfer unit to record the toner image formed on the surface of the image carrier or intermediate transfer member. At the time of cleaning in which the recording medium is not present at the transfer position while being transferred to the medium, a voltage having the same polarity as the charging polarity of the toner is applied to the transfer means, so that when the recording medium is not present at the transfer position, It is configured to prevent the toner on the intermediate transfer member from being transferred to the transfer means. Further, the techniques disclosed in Japanese Patent Laid-Open No. 8-272235 and Japanese Patent Laid-Open No. 8-328401 apply a voltage having the same polarity as the charging polarity of the toner to the transfer means during cleaning when the recording medium is not present at the transfer position. At the same time, by applying a voltage having a polarity opposite to the charging polarity of the toner, the toner adhering to the transfer means is completely reverse transferred onto the image carrier to prevent the backside of the recording medium from being stained. is there. Further, the technique disclosed in the above Japanese Patent Application Laid-Open No. 9-6146 discloses a toner remaining on the intermediate transfer member and the secondary transfer member after the paper jam is released by controlling the contact and separation between the cleaner blade and the secondary transfer member. In the image forming operation that is performed after clearing the paper jam, a clean image can be formed without causing contamination such as fog and streaks due to residual toner. The image quality of the image to be improved is improved.
[0010]
However, in recent years, in an image forming apparatus such as a color copying machine, as image quality progresses, a toner image for process control (hereinafter referred to as “patch”) or a resist control is used in order to guarantee the image quality of a color image. Various toner images such as patches for transfer are transferred onto the intermediate transfer body before the start of image forming operation or at the timing between the recording medium passing, and these process control patches and resist control patches are detected. Thus, the image forming operation is controlled.
[0011]
Accordingly, as in the techniques disclosed in the above-mentioned JP-A-8-63011, JP-A-8-272235, JP-A-8-328401, JP-A-9-6146, etc. When the toner image is not transferred to the recording medium as described above, the reverse bias voltage having the same polarity as the toner charging polarity is transferred for a certain period of time when the transfer bias is turned off or when the recording medium is not present at the transfer position. It has been confirmed that the method of cleaning the secondary transfer member by applying to the means is insufficient as a countermeasure against the toner contamination of the secondary transfer member as described below.
[0012]
As disclosed in Japanese Patent Laid-Open No. 8-328401, when the bias voltage applied to the transfer member is turned off between the recording medium passing sheets, the recording medium on the intermediate transfer member A process control patch or a resist control patch transferred between sheets is transferred onto the transfer member due to the pressure contact force between the intermediate transfer member and the transfer member, and the process or resist transferred onto the transfer member is transferred. The control patch is transferred to the back surface of the next recording medium, and has a problem that it causes back surface contamination.
[0013]
Further, as disclosed in the above-mentioned JP-A-8-63011, when a recording medium is present at the transfer position, a voltage having a polarity opposite to the charged polarity of the toner is mechanically applied to the transfer means. In this case, if the position of the image area on the intermediate transfer body and the recording medium is shifted due to poor conveyance of the recording medium or an error in the size of the recording medium, a toner image that is not transferred to the recording medium is transferred onto the transfer body. The process control patch or the resist control patch formed in the non-image area corresponding to the interval between the sheets of the intermediate transfer member is transferred onto the recording medium. Has a new problem.
[0014]
Further, as disclosed in the above-mentioned JP-A-8-272235 and JP-A-8-328401, when a recording medium is not present at the transfer position, a current of the same polarity as that of the toner is applied. In the case where the cleaning is performed by applying a reverse polarity current having a current value opposite to that of the toner and having an absolute value equal to or greater than the absolute value of the same polarity current, before the start of the image forming operation. A cleaning cycle in which a patch for process control or a patch for resist control is transferred onto the intermediate transfer member, and then a current having the same polarity as that of the toner is applied, and then a current having a polarity opposite to that of the toner is applied. Therefore, it takes a long time to actually start the image forming operation, and there is a new problem that the productivity is greatly reduced.
[0015]
Further, as disclosed in Japanese Patent Laid-Open No. 9-6146, when the secondary transfer member is configured to be selectively switchable between the press-contact state and the separated state with respect to the intermediate transfer member, the cleaning cycle is performed. After the process and resist control patches are formed correspondingly, the image forming operation cannot be executed for one rotation or more of the secondary transfer member, and the productivity is greatly reduced. Has new problems.
[0016]
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to provide a toner image for process control and a toner image for resist control in order to improve image quality. Even in the image forming apparatus configured to transfer onto the intermediate transfer body, it is possible to reliably prevent the backside contamination from occurring on the recording medium, and the productivity is greatly reduced. An object of the present invention is to provide an image forming apparatus capable of preventing the above.
[0017]
Another object of the present invention is an image forming apparatus configured to transfer a process control toner image and a resist control toner image onto an intermediate transfer member for high image quality. However, an object of the present invention is to provide an image forming apparatus capable of reliably preventing transfer of these process control toner image and resist control toner image onto a recording medium.
[0018]
[Means for Solving the Problems]
In order to solve the above problems, the invention described in claim 1 is an image forming unit capable of forming a plurality of toner images of different colors, and a toner image formed by the image forming unit is temporarily transferred and held. An intermediate transfer body for transfer, a first transfer means for transferring the toner image formed by the image forming means onto the intermediate transfer body, and a toner image transferred onto the intermediate transfer body. Second transfer means for transferring onto the medium and transfer bias for applying a transfer bias voltage for transferring the toner image transferred onto the intermediate transfer body onto the recording medium to the second transfer means Voltage applying means; When the toner image transferred to the image area on the intermediate transfer body is located over both the area corresponding to the recording medium on the intermediate transfer body and the other area, the second transfer means includes a recording medium. Control to apply a reverse transfer bias voltage having a polarity opposite to that of the transfer bias voltage over both the region and the other region. And a transfer bias voltage application control means.
[0019]
As the image forming means, for example, an image carrier on which an electrostatic latent image is formed and a plurality of toner images having different colors can be formed by developing the electrostatic latent image formed on the image carrier. A device provided with developing means is used. However, the present invention is not limited to this, and the image forming unit includes an image carrier on which an electrostatic latent image is formed and an electrostatic latent image formed on the image carrier with a predetermined color toner. It is also possible to use a plurality of image forming units each including a developing unit that develops the toner, and a plurality of image forming units that sequentially form a plurality of toner images having different colors.
[0020]
As the second transfer means, for example, a transfer roller composed of a backup roll that supports the intermediate transfer member from the back surface and a secondary transfer roll that is in pressure contact with the backup roller via the intermediate transfer member is used.
[0024]
or, Claim 2 According to the present invention, a detection unit that detects a recording medium is provided immediately before the second transfer unit, and a bias voltage applied to the second transfer unit is controlled based on a detection result of the detection unit. Is.
[0025]
further, Claim 3 The bias voltage applied to the second transfer means based on the detection result of the size of the recording medium is detected by the recording medium containing member containing the recording medium. It is comprised so that it may control.
[0026]
Also, Claim 4 The image forming means is configured such that the image forming means can form a plurality of toner images having different colors and a control toner image for controlling the image forming operation.
[0027]
[Action]
[0030]
Claim 1 In the invention described in the above, the transfer bias voltage application control means is configured such that the toner image transferred to the image area on the intermediate transfer body includes both the area corresponding to the recording medium on the intermediate transfer body and the other area. Since the reverse transfer bias voltage having the opposite polarity to the transfer bias voltage is applied to the second transfer means over both the recording medium area and the other area, the second transfer means is controlled to convey the recording medium. To prevent a partially missing image from being transferred onto a recording medium even when the image area on the intermediate transfer member and the recording medium are misaligned due to a defect or an error in the recording medium size. Therefore, it is possible to always form a good image.
[0031]
or, Claim 2 According to the present invention, a detection unit that detects the recording medium is provided immediately before the second transfer unit, and the bias voltage applied to the second transfer unit is controlled based on the detection result of the detection unit. Since the recording medium is actually detected by the detection means, the transfer bias voltage applied to the second transfer means can be controlled, and due to poor conveyance of the recording medium, an error in the recording medium size, etc. It is possible to reliably prevent the toner image for process control and the toner image for resist control from being transferred onto the recording medium, or the transfer of a partially missing image onto the recording medium.
[0032]
further, Claim 3 In the invention described in the above, the size of the recording medium is detected by the recording medium containing member containing the recording medium, and the bias voltage applied to the second transfer means is determined based on the detection result of the size of the recording medium. Since it is configured to control, even when a recording medium of a different size is erroneously accommodated in the recording medium accommodating member, a process control toner image or a resist control toner image is transferred onto the recording medium, It is possible to reliably prevent a partially missing image from being transferred onto the recording medium.
[0033]
Also, Claim 4 In the invention described in the above, the image forming unit is configured to be able to form a plurality of toner images having different colors and a control toner image for controlling the image forming operation. Image quality can be improved by transferring a toner image for process control and a toner image for resist control onto the intermediate transfer body and detecting these toner images before starting or between the recording media. However, the process control toner image or the resist control toner image transferred to the non-image area on the intermediate transfer member is erroneously transferred onto the recording medium. Can be prevented.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0035]
Embodiment 1
FIG. 2 shows a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
[0036]
In FIG. 2, reference numeral 1 denotes a main body of a color electrophotographic copying machine, and an automatic document transport for automatically transporting documents 2 one by one on the upper part of the color electrophotographic copying machine body 1. An apparatus 3 and a document reading device 4 that reads an image of the document 2 conveyed by the automatic document conveying device 3 are provided. The document reader 4 illuminates a document 2 placed on a platen glass 5 with a light source 6, and reflects a reflected light image from the document 2 from a full-rate mirror 7, half-rate mirrors 8 and 9, and an imaging lens 10. The image reading element 11 composed of a CCD or the like is scanned and exposed through a reduction optical system, and the color material reflected light image of the document 2 is formed at a predetermined dot density (for example, 16 dots / mm) by the image reading element 11. It is supposed to read.
[0037]
The color material reflected light image of the document 2 read by the document reading device 4 is subjected to image processing, for example, as document reflectance data of three colors of red (R), green (G), and blue (B) (8 bits each). The image processing apparatus 12 sends a predetermined correction such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame erasing, color / moving editing, etc., to the reflectance data of the document 2. Image processing is performed.
[0038]
The image data that has been subjected to the predetermined image processing by the image processing device 12 as described above is a four-color document of yellow (Y), magenta (M), cyan (C), and black (BK) (8 bits each). The color material gradation data is sent to a ROS 13 (Raster Output Scanner), and the ROS 13 performs image exposure with laser light in accordance with the original color material gradation data.
[0039]
An image forming unit A capable of forming a plurality of toner images having different colors is disposed inside the color electrophotographic copying machine main body 1. The image forming means A mainly includes a photosensitive drum 17 as an image carrier on which an electrostatic latent image is formed, and a plurality of different colors by developing the electrostatic latent image formed on the photosensitive drum 17. And a rotary developing device 19 as developing means capable of forming a toner image.
[0040]
As shown in FIG. 2, the ROS 13 modulates a semiconductor laser (not shown) according to the original color material gradation data, and emits a laser beam LB from the semiconductor laser according to the gradation data. The laser beam LB emitted from the semiconductor laser is deflected and scanned by the rotary polygon mirror 14 and scanned and exposed on the photosensitive drum 17 as an image carrier through the f · θ lens 15 and the reflection mirror 16.
[0041]
The photosensitive drum 17 on which the laser beam LB is scanned and exposed by the ROS 13 is driven to rotate at a predetermined speed in the direction of the arrow by a driving unit (not shown). The surface of the photosensitive drum 17 is charged in advance with a predetermined polarity (for example, negative polarity) and a potential by a scorotron 18 for primary charging, and then laser light LB is scanned and exposed in accordance with the original color material gradation data. As a result, an electrostatic latent image is formed. The electrostatic latent image formed on the photosensitive drum 17 includes four color developing devices 19Y, 19M, 19C, and 19BK of yellow (Y), magenta (M), cyan (C), and black (BK). The rotary developing device 19 is reversely developed with, for example, a negatively charged toner having the same polarity as the charged polarity of the photosensitive drum 17 to form a toner image of a predetermined color. The toner image formed on the photosensitive drum 17 is negatively charged by the pre-transfer charger 20 as necessary, and the charge amount is adjusted.
[0042]
The toner images of the respective colors formed on the photosensitive drum 17 are transferred onto a primary transfer roll as a first transfer unit on an intermediate transfer belt 21 as an intermediate transfer member disposed below the photosensitive drum 17. 22 is transferred in multiples. The intermediate transfer belt 21 is moved at the same moving speed as the peripheral speed of the photosensitive drum 17 by a driving roll 23, a driven roll 24a, a tension roll 24b, and a backup roll 25 as a counter roll constituting a part of the secondary transfer means. It is supported so as to be rotatable along the arrow direction.
[0043]
On the intermediate transfer belt 21, four colors of yellow (Y), magenta (M), cyan (C), and black (BK) are formed on the photosensitive drum 17 according to the color of the image to be formed. All or part of the toner image is transferred in a state of being sequentially superimposed by the primary transfer roll 22. The toner image transferred onto the intermediate transfer belt 21 is recorded on a recording sheet 26 as a recording medium conveyed to the secondary transfer position at a predetermined timing, and a backup roll 25 that supports the intermediate transfer belt 21, Transfer is performed by the pressure contact force and electrostatic attraction force of the secondary transfer roll 27 that constitutes a part of the second transfer unit that is in pressure contact with the backup roll 25. As shown in FIG. 2, the recording paper 26 is supplied from any one of a plurality of paper feeding cassettes 28, 29, 30, 31 as recording medium accommodation members disposed in the lower part of the color electrophotographic copying machine main body 1. Paper of a predetermined size is fed by feed rolls 28a, 29a, 30a, 31a. The fed recording paper 26 is conveyed to a secondary transfer position of the intermediate transfer belt 21 by a plurality of conveyance rolls 32 and registration rolls 33 at a predetermined timing. Then, as described above, a toner image of a predetermined color is collectively transferred from the intermediate transfer belt 21 to the recording paper 26 by the backup roll 25 and the secondary transfer roll 27 as secondary transfer means. It has become so.
[0044]
The recording paper 26 onto which the toner image of a predetermined color has been transferred from the intermediate transfer belt 21 is separated from the intermediate transfer belt 21 and then conveyed to the fixing device 35 by the conveying belt 34. Thus, the toner image is fixed on the recording paper 26 by heat and pressure, and in the case of single-sided copying, the toner image is directly discharged onto the paper discharge tray 36 and the color image copying process is completed.
[0045]
On the other hand, in the case of double-sided copying, the recording paper 26 on which the color image is formed on the first surface (front surface) is not discharged onto the paper discharge tray 36 as it is, but the conveyance direction is changed downward by a reversing gate (not shown). The three rolls are temporarily conveyed to the reverse passage 39 by the tri-roll 37 and the reverse roll 38 in pressure contact. Then, the recording paper 26 is conveyed to the double-sided passage 40 by the reversing roll 38 which is reversed this time, and is temporarily conveyed to the registration roll 33 by the conveying roll 41 provided in the double-sided passage 40 and stopped. The recording paper 26 is transported again by the registration roll 33 in synchronization with the toner image on the intermediate transfer belt 21, and the toner image transfer / fixing process is performed on the second surface (back surface) of the recording paper 26. After being performed, it is discharged onto the discharge tray 36.
[0046]
In FIG. 2, 42 is a cleaning device for removing residual toner, paper dust and the like from the surface of the photosensitive drum 17 after the transfer process is completed, and 43 is an intermediate transfer for cleaning the intermediate transfer belt 21. The belt cleaner 44 and the manual feed tray 44 are shown.
[0047]
FIG. 1 is a block diagram showing image forming means A of the color electrophotographic copying machine.
[0048]
In this color electrophotographic copying machine, as described above, after the surface of the photosensitive drum 17 is uniformly charged to a predetermined potential by the scorotron 18 for primary charging, the surface of the photosensitive drum 17 has ROS 13. Thus, an image corresponding to a predetermined color is exposed to form an electrostatic latent image. The electrostatic latent images formed on the surface of the photosensitive drum 17 corresponding to the respective colors are developed by the corresponding color developing devices 19Y, 19M, 19C, and 19BK. The toner image T of the color is formed.
[0049]
For example, if the electrostatic latent image formed on the photosensitive drum 17 corresponds to a yellow color, the electrostatic latent image is developed by the yellow developing device 19Y and is applied to the photosensitive drum 17. In this case, a yellow toner image T is formed. For other magenta, cyan, and black colors, corresponding toner images T are sequentially formed on the photosensitive drum 17 by the same process.
[0050]
The toner images T of the respective colors sequentially formed on the photosensitive drum 17 are transferred from the photosensitive drum 17 to the surface of the intermediate transfer belt 21 at the primary transfer position where the photosensitive drum 17 and the intermediate transfer belt 21 are in contact with each other. Transcribed. At this primary transfer position, a semiconductive primary transfer bias roll 22 is disposed on the back side of the intermediate transfer belt 21, and the intermediate transfer belt 21 is moved by the primary transfer bias roll 22. The surface of the photosensitive drum 17 is brought into contact. A voltage having a polarity opposite to the toner charging polarity is applied to the bias roller 22 for primary transfer, and the toner image T formed on the photosensitive drum 17 is pressed against the intermediate transfer belt 21 and electrostatically attracted. Transcribed by force.
[0051]
In the case of forming a single color image, the toner image T of a predetermined color that is primarily transferred onto the intermediate transfer belt 21 is immediately secondary transferred onto the recording paper 26, but the toner images T of a plurality of colors are overlaid. In the case of forming a combined color image, the steps of forming a toner image T of a predetermined color on the photosensitive drum 17 and performing primary transfer of the toner image T onto the intermediate transfer belt 21 are performed in a predetermined number of colors. Repeated for minutes.
[0052]
For example, when a full color image is formed by superposing four color toner images T of yellow (Y), magenta (M), cyan (C), and black (BK), one of them is formed on the photosensitive drum 17. At each rotation, yellow (Y), magenta (M), cyan (C), and black (BK) toner images T are sequentially formed, and these four color toner images are sequentially superimposed on the intermediate transfer belt 21. Primary transfer is performed in the combined state.
[0053]
At this time, the intermediate transfer belt 21 rotates at a period synchronized with the photosensitive drum 17 while holding the yellow unfixed toner image T that is primarily transferred first, and the intermediate transfer belt 21 is placed on the intermediate transfer belt 21. Is a state in which unfixed toner images T of magenta, cyan and black are sequentially superimposed on the unfixed toner image T of yellow at each predetermined position determined by the position detection sensor 45. It is transcribed with.
[0054]
The unfixed toner image T primarily transferred to the intermediate transfer belt 21 in this way is conveyed to a secondary transfer position facing the conveyance path of the recording paper 26 as the intermediate transfer belt 21 rotates.
[0055]
As described above, the recording paper 26 is fed from the predetermined paper feed cassettes 28, 29, 30, 31 by the feed rolls 28 a, 29 a, 30 a, 31 a, and is transported to the registration roll 33 by the transport roll 32. Then, the sheet is fed by the registration roll 33 between the nip portion between the secondary transfer roll 27 and the intermediate transfer belt 21 at a predetermined timing.
[0056]
Further, a backup roll 25 that is a counter electrode of the secondary transfer roll 27 is disposed on the back side of the intermediate transfer belt 21 at the secondary transfer position. At the secondary transfer position, the semiconductive secondary transfer roll 27 is brought into pressure contact with the intermediate transfer belt 21 at a predetermined timing, and a voltage having a polarity opposite to the toner charging polarity is applied to the backup roll 25, whereby the intermediate transfer is performed. The unfixed toner image T transferred onto the belt 21 is electrostatically secondary transferred onto the recording paper 26 at the secondary transfer position.
[0057]
In this embodiment, as shown in FIG. 1, a voltage having the same polarity as the toner charging polarity is not directly applied to the secondary transfer roll 27, but the secondary transfer roll 27 is interposed via the intermediate transfer belt 21. A voltage having the same polarity as the charging polarity of the toner is applied to the backup roll 25 in pressure contact from a high voltage power supply 47 for transfer bias as a transfer bias voltage application means by a bias roll 46. However, it may of course be configured such that a voltage having the same polarity as the charging polarity of the toner is directly applied to the secondary transfer roll 27.
[0058]
Then, the recording paper 26 onto which the unfixed toner image is transferred is peeled off from the intermediate transfer belt 21 and sent to the fixing device 35 by the electrode member 48, the guide plate 49 and the transport belt 34 disposed downstream of the secondary transfer portion. Then, the fixing process of the unfixed toner image T is performed.
[0059]
On the other hand, after the secondary transfer of the unfixed toner image T is completed, residual toner is removed by the intermediate transfer belt cleaner 44.
[0060]
The intermediate transfer belt 21 has a volume resistivity of 10 by dispersing an appropriate amount of a conductive agent such as carbon black in a synthetic resin such as polyimide, polycarbonate, polyester, or polypropylene, or various rubbers. ⁶ -10 ¹⁴ It is formed by a film-like belt adjusted so as to be Ω · cm. The thickness of the intermediate transfer belt 21 is set to 0.1 mm, for example. The circumferential length of the intermediate transfer belt 21 is set to an integral multiple (for example, 3 times) of the circumferential length of the photosensitive drum 17.
[0061]
The secondary transfer roll 27 and the intermediate transfer belt cleaner 44 are disposed so as to be in contact with and away from the intermediate transfer belt 21. When a color image is formed, the unfixed toner image T of the final color is formed. Until the toner is primarily transferred onto the intermediate transfer belt 21, at least the intermediate transfer belt cleaner 44 is separated from the intermediate transfer belt 21.
[0062]
Further, the secondary transfer roll 27 includes a surface layer made of a urethane rubber tube in which carbon is dispersed and an inner layer made of foamed urethane rubber in which carbon is dispersed. Is provided with a fluorine coat. The secondary transfer roll 27 has a volume resistivity of 10 ^Three -10 ^Ten The roll diameter is set to 28 mm, and the hardness is set to, for example, 30 ° (Asuka C).
[0063]
On the other hand, the backup roll 25 includes a surface layer made of a tube of EPDM and NBR blend rubber in which carbon is dispersed, and an inner layer made of EPDM rubber, and has a surface resistivity of 10 ⁷ -10 ^Ten The roll diameter is Ω / □ and the roll diameter is φ28 mm, and the hardness is set to 70 ° (Asuka C), for example.
[0064]
The electrode member 48 disposed downstream of the nip portion at the secondary transfer position is preferably a sheet metal as a conductive plate-like member, and in this embodiment, a stainless steel plate having a thickness of 0.5 mm is used. A sheet having a needle shape on the side of the sheet 26 is used. Further, the tip of the electrode member 48 on the secondary transfer region side is 1 mm from the line formed by the nip portion between the backup roll 25 and the secondary transfer roll 27, and is 7 mm from the exit of the nip portion. Are located apart.
[0065]
By the way, in the color electrophotographic copying machine according to the first embodiment, the intermediate transfer body in which at least part of the toner image transferred to the non-image area and the image area on the intermediate transfer body is other than the area corresponding to the recording medium. When located above, the second transfer means includes transfer bias voltage application control means for controlling to apply a reverse transfer bias voltage having a reverse polarity to the transfer bias voltage to at least an area other than the recording medium. It is configured.
[0066]
That is, in the color electrophotographic copying machine according to the first embodiment, as shown in FIG. 3, the surface of the intermediate transfer belt 21 is divided into an image area 50 and a non-image area 51 in advance. Is set corresponding to the maximum size (for example, A3 size) recording paper 26 that can be copied by the color electrophotographic copying machine. On the surface of the intermediate transfer belt 21, for example, two image areas 50 corresponding to the recording paper 26 of A3 size are set, and a space between these image areas 50 is a non-image area 51. The intermediate transfer belt 21 detects the mark 52 provided at the reference position by the position detection sensor 45, thereby recognizing the positions of the image area 50 and the non-image area 51. The toner image T corresponding to the above is transferred. In addition, when the color electrophotographic copying machine forms an image on the recording paper 26 of A4 size or less which is half or less of the A3 size, the image area 50 is divided into two areas 50a and 50b (for example, areas corresponding to the A4 size). ), And the toner image of the document 2 can be transferred to each of the areas 50a and 50b in the image area 50.
[0067]
Further, in the color electrophotographic copying machine, as the image quality is improved, the process control patch and the resist control patch are applied before the start of the image forming operation or on the recording medium in order to guarantee the image quality of the color image. It is configured to transfer onto the intermediate transfer member at the timing between sheet passing, detect the process control patch and the resist control patch, and control the image forming operation based on the detection result. .
[0068]
That is, in the color electrophotographic copying machine, when the power switch of the copying machine is turned on, when a predetermined number of copies are taken, or after a copy button for starting a copying operation is pressed, As shown in FIG. 4, during the setup operation before actually starting the copying operation, the image area 50 of the intermediate transfer belt 21 is yellow (Y), magenta (M), cyan (C), black (BK). ) Process control patches 53Y, 53M, 53C, and 53BK of different colors are formed at different densities, and each color of yellow (Y), magenta (M), cyan (C), and black (BK) is formed. Lateral V-shaped patches 54Y, 54M, 54C, and 54BK for resist control are formed at a predetermined pitch.
[0069]
In the color electrophotographic copying machine, as shown in FIG. 5, yellow (Y), magenta (M), and cyan are formed in the non-image area 50 corresponding to the interval between the recording sheets 26 on the intermediate transfer belt 21. (C) and black (BK) process control patches 55Y, 55M, 55C, and 55BK are formed at two types of density of 60% and 20%, and yellow (Y) and magenta (M). , Cyan (C), black (BK) laterally V-shaped patches 56Y, 56M, 56C, and 56BK for resist control of each color are formed at a predetermined pitch.
[0070]
Process control patches 53Y, 53M, 53C, 53BK and 54Y, 54M, 54C, 54BK formed on the intermediate transfer belt 21 and resist control patches 55Y, 55M, 55C, 55BK and 56Y, 56M, 56C, 56BK is detected by an optical sensor 57 disposed above the driven roll 24a as shown in FIG.
[0071]
Further, in the color electrophotographic copying machine, at least a part of the toner image transferred to the non-image area 51 and the image area 50 of the intermediate transfer belt 21 is on the intermediate transfer belt 21 other than the area corresponding to the recording paper 26. When positioned, the secondary transfer means is provided with a CPU 60 as a transfer bias voltage application control means for controlling to apply a reverse transfer bias voltage having a reverse polarity to the transfer bias voltage to at least an area other than the recording paper 26. It is configured.
[0072]
Further, in the color electrophotographic copying machine, as shown in FIG. 1, a paper detection sensor 58 for detecting the recording paper 26 is arranged on the upstream side of the secondary transfer position. The leading edge and trailing edge of the recording paper 26 conveyed to the secondary transfer position in contact with the intermediate transfer belt 21 are detected.
[0073]
The color electrophotographic copying machine is provided with a humidity sensor 59 for detecting humidity inside the intermediate transfer belt 21.
[0074]
FIG. 6 is a block diagram showing a control circuit of the color electrophotographic copying machine.
[0075]
In FIG. 6, 60 is a CPU that controls the image forming operation of the color electrophotographic copying machine, and also functions as a transfer bias voltage application control means, and 61 is a user that designates the number of copies, the copy magnification, the size of the recording paper 26, and the like. An interface 45 is a position detection sensor for detecting a mark 52 provided on the intermediate transfer belt 21, and 57 is a process control patch 53Y, 53M, 53C, 53BK and 54Y, 54M transferred onto the intermediate transfer belt 21. , 54C, 54BK and registration control patches 55Y, 55M, 55C, 55BK and 56Y, 56M, 56C, 56BK, an optical sensor 58, a sheet detection sensor 62 disposed in front of the secondary transfer position, 62 Are provided in the paper cassettes 28, 29, 30, 31. A cassette sensor 59 detects the size of the recording paper 26 accommodated in the paper feed cassettes 28, 29, 30, 31 by a size detection unit, and 59 is a humidity for detecting humidity inside the color electrophotographic copying machine main body 1. A sensor 47 is a high voltage power supply for transfer bias voltage as transfer bias voltage application means for applying a transfer bias voltage to the backup roll 27 as secondary transfer means, and 13 is an image corresponding to the image of the document 2 on the photosensitive drum 17. Image exposure for forming patches 53Y, 53M, 53C, 53BK and 54Y, 54M, 54C, 54BK for exposure and process control and patches 55Y, 55M, 55C, 55BK and 56Y, 56M, 56C, 56BK for resist control ROS 63 for rotating the intermediate transfer belt 21 Belt driving motor 64, ROM storing a program for CPU 60 to perform image forming operation and transfer bias voltage application control operation of color electrophotographic copying machine, 65 storing data for CPU 60 to perform control operation, etc. Each RAM to be used is shown.
[0076]
In the above configuration, in the color electrophotographic copying machine according to the first embodiment, the process control toner image and the resist control toner image are transferred onto the intermediate transfer member to improve the image quality as follows. Even if the image forming apparatus is configured to transfer to the recording medium, it is possible to reliably prevent the backside contamination of the recording medium from occurring, and it is possible to prevent the productivity from being significantly reduced. It has become. In the color electrophotographic copying machine, it is possible to reliably prevent the process control toner image and the resist control toner image from being transferred to the secondary transfer means or transferred onto the recording medium. Yes.
[0077]
First, the rotation of the intermediate transfer belt during a normal image copying operation, the toner image transferred onto the intermediate transfer belt, the conveyance state of the recording paper, and the transfer bias voltage applied to the secondary transfer means The control operation will be described.
[0078]
That is, in the color electrophotographic copying machine according to the first embodiment, as shown in FIG. 2, the document 2 is set at a predetermined position, and the number of copies, the copy magnification, the size of the recording paper 26, etc. are set by the user interface 61. When designated and the copy button is pressed, the photosensitive drum 17 is rotationally driven by the control of the CPU 60, and the belt driving motor 63 for rotationally driving the intermediate transfer belt 21 is turned on as shown in FIG. The intermediate transfer belt 21 is driven to rotate. Further, the intermediate transfer belt 21 is rotated on the backup roll 25 of the secondary transfer unit by the CPU 60 serving as a transfer bias voltage application control unit, and at the same time, a reverse transfer bias of, for example, +550 V is supplied via the transfer bias voltage high-voltage power supply 47. A voltage is applied. The reverse transfer bias voltage applied to the backup roll 25 of the secondary transfer unit is not limited to +550 V, and the toner image transferred onto the intermediate transfer belt 21 is transferred to the secondary transfer position as will be described later. When passing the toner, the toner does not adhere to the secondary transfer roll 27 provided at the secondary transfer position, and is set to an optimum value for cleaning the secondary transfer roll 27. In the first embodiment, the secondary transfer roll 27 is configured to remain in pressure contact with the intermediate transfer belt 21 while the belt drive motor 63 is rotating.
[0079]
4 and 7, the image area 50 of the intermediate transfer belt 21 is set up after the copy button for starting the copying operation is pressed and before the copying operation is actually started. During operation, patches 53Y, 53M, 53C, and 53BK for process control of each color of yellow (Y), magenta (M), cyan (C), and black (BK) formed on the photosensitive drum 17 are different. A plurality of density-transferred patches and horizontal V-shaped patches 54Y, 54M, 54C, and 54BK for resist control of each color of yellow (Y), magenta (M), cyan (C), and black (BK) are predetermined. It is transcribed at a pitch of. Patches 53Y, 53M, 53C, 53BK for process control of each color transferred to the image area 50 of the intermediate transfer belt 21 and laterally V-shaped patches 54Y, 54M, 54C, 54BK for resist control of each color are as follows: As shown in FIG. 1, the density and position data of these process control patches and resist control patches detected by the optical sensor 57 are sent to the CPU 60 as shown in FIG. The CPU 60 determines whether the density and position data of the process control patch and the resist control patch are within a predetermined range, and the density and position data of the patch falls within the predetermined range. Thus, various parameters for image formation are controlled.
[0080]
Further, the process control patches 53Y, 53M, 53C, 53BK transferred to the image area 50 of the intermediate transfer belt 21 and the resist control patches 54Y, 54M, 54C, 54BK for each color are secondary transfer positions. Even when passing through, the CPU 60 maintains a state where a reverse transfer bias voltage of, for example, +550 V is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47, as shown in FIG. Therefore, the process control patches 53Y, 53M, 53C, and 53BK transferred to the image area 50 of the intermediate transfer belt 21 and the resist control patches 54Y, 54M, 54C, and 54BK for each color are subjected to secondary transfer. When passing through the position, the reverse transfer bias voltage applied to the backup roll 25 causes the image to be transferred onto the intermediate transfer belt 21 and transferred onto the secondary transfer roll 27 that is in pressure contact with the intermediate transfer belt 21. There is nothing. The process control patches 53Y, 53M, 53C, and 53BK transferred to the image area 50 of the intermediate transfer belt 21 and the resist control patches 54Y, 54M, 54C, and 54BK for each color are subsequently transferred to the intermediate areas. The toner is removed from the intermediate transfer belt 21 by the transfer belt cleaner 43.
[0081]
Next, as shown in FIGS. 5 and 7, the image area 50 of the intermediate transfer belt 21 and the area corresponding to the interval between the recording paper 26 are the areas of the original 2 formed on the photosensitive drum 17. The toner image 70 corresponding to the image and yellow (Y), magenta (M), cyan (C), and black (BK) process control patches 55Y, 55M, 55C, and 55BK have two types of density. At the same time, the horizontal V-shaped patches 56Y, 56M, 56C, and 56BK for resist control of each color of yellow (Y), magenta (M), cyan (C), and black (BK) are transferred at a predetermined pitch. Transcribed.
[0082]
At that time, when a full-color image is formed, yellow (Y), magenta (M), cyan (C), and black each time the photosensitive drum 17 rotates in the image area 50 of the intermediate transfer belt 21. The toner images of the respective colors (BK) are transferred, and in the area corresponding to the interval between the recording sheets 26, as shown in FIG. , Magenta (M), cyan (C), and black (BK) process control patches 55Y, 55M, 55C, and 55BK are transferred at two densities, and yellow (Y) and magenta (M ), Cyan (C), and black (BK) laterally V-shaped patches 56Y, 56M, 56C, and 56BK for resist control of the respective colors are transferred at a predetermined pitch.
[0083]
Further, when the final toner image 70, that is, a full-color image is formed in the image area 50 of the intermediate transfer belt 21, yellow (Y), magenta (M), cyan (C), and black (BK). When forming a toner image 70 in which toner images of four colors are transferred in multiple, or images of one to three colors of yellow (Y), magenta (M), cyan (C), and black (BK). If there is, a reverse transfer bias voltage of, for example, +550 V is still applied to the backup roll 25 until the toner images 70 of one to three colors are transferred.
[0084]
When the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 as described above passes the secondary transfer position, the CPU 60, as shown in FIG. For example, a transfer bias voltage of −2.2 KV is applied to the backup roll 25 via 47. Therefore, the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 is transferred from above the intermediate transfer belt 21 by the transfer bias voltage applied to the backup roll 25 when passing the secondary transfer position. In synchronization with the toner image, the toner image is transferred onto the recording paper 26 conveyed to the secondary transfer position.
[0085]
At this time, the transfer bias voltage applied to the backup roll 25 of the secondary transfer unit is not limited to -2.2 KV, and the final toner image 70 transferred onto the intermediate transfer belt 21 is subjected to the secondary transfer. When passing through the transfer position, it is set to an optimum value for transferring onto the recording paper 26. Therefore, in the color electrophotographic copying machine according to this embodiment, as shown in FIG. 1, the humidity in the copying machine main body 1 is detected by the humidity sensor 59, and the CPU 60 is based on the detection result of the humidity sensor 59. The transfer bias voltage applied to the backup roll 25 is controlled in the range of −1.5 KV to −3.0 KV so that optimum transferability of the toner image 70 can be obtained.
[0086]
On the other hand, the process control patches 55Y, 55M, 55C, 55BK transferred to the area corresponding to the interval between the recording sheets 26 of the intermediate transfer belt 21 as described above, and the horizontal direction for resist control of each color. When the V-shaped patches 56Y, 56M, 56C, and 56BK pass through the secondary transfer position, the CPU 60, as shown in FIG. 7, supplies the selected recording paper 26 via the transfer bias voltage high-voltage power supply 47. For example, a reverse transfer bias voltage of +550 V is applied to the backup roll 25 over the entire non-image area 51 corresponding to the size. Therefore, the process control patches 55Y, 55M, 55C, 55BK transferred to the non-image area 51 corresponding to the interval between the recording sheets 26 of the intermediate transfer belt 21 and the resist control patches 56Y for the respective colors. , 56M, 56C and 56BK are transferred onto the intermediate transfer belt 21 by the reverse transfer bias voltage applied to the backup roll 25 when passing through the secondary transfer position, and are transferred to the intermediate transfer belt 21. There is no transfer onto the secondary transfer roll 27 in pressure contact.
[0087]
Thereafter, when the belt drive motor 63 that rotationally drives the intermediate transfer belt 21 is stopped, the application of the bias voltage to the backup roll 25 is turned off.
[0088]
As described above, in the color electrophotographic copying machine according to the first embodiment, the process control patches 55Y, 55M for each color are formed in the non-image area 51 corresponding to the interval between the recording sheets 26 of the intermediate transfer belt 21. Even when 55C and 55BK and patches 56Y, 56M, 56C and 56BK for resist control for each color are transferred to improve the quality of the color image, the process control patches for these colors and the resist control for each color are used. Therefore, the backside of the recording paper 26 can be reliably prevented from being transferred onto the secondary transfer roll 27 in pressure contact with the intermediate transfer belt 21.
[0089]
Second, when a size mismatch occurs between the toner image transferred onto the intermediate transfer belt and the recording paper during a normal image copying operation, a control operation of the transfer bias voltage applied to the secondary transfer unit explain.
[0090]
In the color electrophotographic copying machine according to the first embodiment, as shown in FIG. 8, after the copy button for starting the copying operation is pressed in the image area 50 of the intermediate transfer belt 21, as described above. A patch for process control of each color of yellow (Y), magenta (M), cyan (C), and black (BK) formed on the photosensitive drum 17 during the setup operation before actually starting the copying operation. A plurality of 53Y, 53M, 53C, and 53BK are transferred at different densities, and a horizontal V-shaped shape is used for resist control of each color of yellow (Y), magenta (M), cyan (C), and black (BK). The patches 54Y, 54M, 54C, and 54BK are transferred at a predetermined pitch.
[0091]
Thereafter, the final toner image 70 is transferred to the image area 50 of the intermediate transfer belt 21 as shown in FIG. Then, when the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 passes the secondary transfer position as described above, the CPU 60, as shown in FIG. For example, a transfer bias voltage of −2.2 KV is applied to the backup roll 25. Therefore, the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 is transferred from above the intermediate transfer belt 21 by the transfer bias voltage applied to the backup roll 25 when passing the secondary transfer position. In synchronization with the toner image, the toner image is transferred onto the recording paper 26 conveyed to the secondary transfer position.
[0092]
At that time, as shown in FIG. 6, the CPU 60 detects the size along the conveyance direction of the recording paper 26 based on a signal from the paper detection sensor 58 or the cassette sensor 62. As shown in FIG. 8, for example, a transfer bias voltage of −2.2 KV is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47 only in an area corresponding to the size along the conveyance direction of the recording paper 26. Then, a reverse transfer bias voltage of, for example, +550 V is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47 to the portion where the mismatch between the recording paper 26 and the toner image 70 occurs. The protruding toner image 70 is prevented from being transferred onto the secondary transfer roll 27. The cassette sensor 62 does not directly detect the size along the transport direction of the recording paper 26, but can detect the size along the transport direction of the recording paper 26 to be stored in the paper feed cassette. it can. Therefore, when the size of the recording paper 26 to be accommodated in the paper feed cassette is, for example, the A4 size along the longitudinal direction of the recording paper 26, the cassette sensor 62 determines the size of the recording paper 26 in the longitudinal direction. It is detected that it is A4 size along the transport direction. When the toner image 70 formed on the intermediate transfer belt 21 is A3 size, the CPU 60 determines that a mismatch between the recording paper 26 and the toner image 70 has occurred, and protrudes from the recording paper 26. A reverse transfer bias voltage is applied to the toner image 70.
[0093]
Thereafter, the CPU 60 transfers the process control patches 55Y, 55M, 55C, and 55BK for each color transferred to the area corresponding to the interval between the recording sheets 26 of the intermediate transfer belt 21 and the horizontal V-shape for resist control for each color. When the shaped patches 56Y, 56M, 56C, and 56BK pass through the secondary transfer position, as shown in FIG. 8, the non-in accordance with the size of the selected recording paper 26 is supplied via the high voltage power supply 47 for transfer bias voltage. By applying a reverse transfer bias voltage of, for example, +550 V to the backup roll 25 over the entire image area 51, the process control patch for each color and the resist control patch for each color are transferred onto the secondary transfer roll 27. Is prevented.
[0094]
As described above, in the color electrophotographic copying machine according to the first embodiment, the toner image 70 transferred to the image region 50 of the intermediate transfer belt 21 and the toner image 70 and the recording paper 26 to be transferred are interposed. Even when a mismatch occurs, it is possible to reliably prevent the toner image 70 protruding from the recording paper 26 from being transferred to the secondary transfer roll 72 and causing the back-contaminated recording paper 26 to be transported next. ing.
[0095]
Third, it is not necessary to transfer the toner image on the intermediate transfer belt onto the recording paper, such as when the recording paper jammed after the jamming of the recording paper occurs in the paper conveyance system, and A control operation of the transfer bias voltage applied to the secondary transfer unit when the recording paper and the toner image pass through the secondary transfer position will be described.
[0096]
In the color electrophotographic copying machine according to the first embodiment, as shown in FIG. 9, the setup is performed after the copy button for starting the copying operation is first pressed and before the copying operation is actually started. During operation, transfer and detection operations of the process control patches 53Y, 53M, 53C, and 53BK for each color and the laterally V-shaped patches 54Y, 54M, 54C, and 54BK for registration control of each color are performed.
[0097]
Thereafter, as shown in FIG. 9, the final toner image 70 is transferred to the image area 50 of the intermediate transfer belt 21, but the jam occurs after the recording paper 26 is jammed in the paper conveyance system. For example, when the generated recording paper 26 is removed, it is not necessary to transfer the toner image on the intermediate transfer belt onto the recording paper 26 that is conveyed while remaining in the paper conveyance system. Therefore, when the CPU 60 detects that the recording paper 26 has jammed, the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 passes through the secondary transfer position as shown in FIG. In addition, the reverse transfer bias voltage of, for example, +550 V is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47. Therefore, the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 is transferred onto the intermediate transfer belt 21 by the reverse transfer bias voltage applied to the backup roll 25 when passing the secondary transfer position. Then, the toner image is transferred onto the recording paper 26 conveyed to the secondary transfer position in synchronization with the toner image.
[0098]
At that time, as shown in FIG. 6, the CPU 60 detects the size along the conveyance direction of the recording paper 26 based on a signal from the paper detection sensor 58 or the cassette sensor 62. As shown in FIG. 8, for example, a transfer bias voltage of −2.2 KV is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47 only in an area corresponding to the size along the conveyance direction of the recording paper 26. Then, a reverse transfer bias voltage of, for example, +550 V is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47 to the portion where the mismatch between the recording paper 26 and the toner image 70 occurs. The protruding toner image 70 is prevented from being transferred onto the secondary transfer roll 27. The cassette sensor 62 does not directly detect the size along the transport direction of the recording paper 26, but can detect the size along the transport direction of the recording paper 26 to be stored in the paper feed cassette. it can. Therefore, when the size of the recording paper 26 to be accommodated in the paper feed cassette is, for example, the A4 size along the longitudinal direction of the recording paper 26, the cassette sensor 62 determines the size of the recording paper 26 in the longitudinal direction. It is detected that it is A4 size along the transport direction. When the toner image 70 formed on the intermediate transfer belt 21 is A3 size, the CPU 60 determines that a mismatch between the recording paper 26 and the toner image 70 has occurred, and protrudes from the recording paper 26. A reverse transfer bias voltage is applied to the toner image 70.
[0099]
Thereafter, the CPU 60 transfers the process control patches 55Y, 55M, 55C, and 55BK for each color transferred to the area corresponding to the interval between the recording sheets 26 of the intermediate transfer belt 21 and the horizontal V-shape for resist control for each color. When the shaped patches 56Y, 56M, 56C, and 56BK pass through the secondary transfer position, as shown in FIG. 8, the non-in accordance with the size of the selected recording paper 26 is supplied via the high voltage power supply 47 for transfer bias voltage. By applying a reverse transfer bias voltage of, for example, +550 V to the backup roll 25 over the entire image area 51, the process control patch for each color and the resist control patch for each color are transferred onto the secondary transfer roll 27. Is prevented.
[0100]
As described above, in the color electrophotographic copying machine according to the first embodiment, the toner image 70 transferred to the image region 50 of the intermediate transfer belt 21 and the toner image 70 and the recording paper 26 to be transferred are interposed. Even when a mismatch occurs, it is possible to reliably prevent the toner image 70 protruding from the recording paper 26 from being transferred to the secondary transfer roll 72 and causing the back-contaminated recording paper 26 to be transported next. ing.
[0101]
Fourthly, when the recording paper is fed from the paper feed cassette or when it is transported by the paper transport system, a recording paper transport failure occurs and the image corresponding to the recording paper on the intermediate transfer belt. A control operation of the transfer bias voltage applied to the secondary transfer unit when a positional deviation occurs between the area and the recording sheet will be described.
[0102]
In the color electrophotographic copying machine according to the first embodiment, the final toner image 70 is transferred to the image area 50 of the intermediate transfer belt 21 as shown in FIG. The conveyance state of the recording paper 26 to the secondary transfer position may deviate from the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21.
[0103]
At that time, as shown in FIG. 10, the CPU 60 detects the leading and trailing ends of the recording paper 26 conveyed to the secondary transfer position and the intermediate transfer belt 21 by the paper detection sensor 58 disposed at the secondary transfer position. It is detected that a positional deviation has occurred with respect to the final toner image 70 transferred to the image area 50. Then, as shown in FIG. 10, the CPU 60 performs at least the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 with respect to the area outside the recording paper 26 or the image area of the intermediate transfer belt 21. For example, a reverse transfer bias voltage of +550 V, for example, is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47 for all regions of the final toner image 70 transferred to 50. Therefore, the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 is transferred onto the intermediate transfer belt 21 by the reverse transfer bias voltage applied to the backup roll 25 when passing the secondary transfer position. In other words, the toner image is not transferred onto the recording paper 26 that is conveyed to the secondary transfer position with the conveyance position shifted.
[0104]
By the way, in the fourth case, when the recording paper 26 is fed from the paper feed cassettes 28 to 31 or when the recording paper 26 is transported by the paper transporting system, the transport failure of the recording paper 26 occurs. It is assumed that a positional shift occurs between the image area 50 corresponding to the recording paper 26 on the intermediate transfer belt 21 and the recording paper 26. The intermediate transfer belt 21 is rotationally driven in synchronization with the photosensitive drum 17, and the entire image forming means A such as the ROS 13 is controlled by the CPU 60 on the photosensitive drum 17 so that a toner image is formed. Since the toner image is formed and transferred onto the intermediate transfer belt 21, it is almost possible that the position of the toner image 70 transferred onto the intermediate transfer belt 21 is displaced. It is difficult.
[0105]
Note that, as shown in FIG. 11, the CPU 60 has patches 53Y, 53M, 53C, 53BK or 55Y, 55M, 55C, 55BK for process control of each color even when a conveyance failure of the recording paper 26 occurs. In addition, the laterally V-shaped patches 54Y, 54M, 54C, 54BK or 56Y, 56M, 56C, and 56BK for resist control for each color can be transferred onto the recording paper 26, and the toner is removed from the recording paper 26. If it is determined that there is no image, a transfer bias voltage is applied to the backup roll 25, and process control patches 53Y, 53M, 53C, 53BK or 55Y, 55M, 55C, 55BK for each color, and resist control for each color are applied. Horizontal V-shaped patches 54Y, 54M, 54C, 54 for All of K or 56Y, 56M, 56C, and 56BK may be transferred onto the recording paper 26, or the transfer bias voltage applied to the backup roll 25 is turned off or the reverse transfer bias voltage is applied. As a result, patches 53Y, 53M, 53C, 53BK or 55Y, 55M, 55C, and 55BK for process control of each color, and laterally oriented V-shaped patches 54Y, 54M, 54C, 54BK, and 56Y for resist control of each color, All of 56M, 56C, and 56BK may be configured not to be transferred onto the recording paper 26.
[0106]
Fifth, the control operation of the transfer bias voltage applied to the secondary transfer means when a size mismatch occurs between the toner image transferred onto the intermediate transfer belt and the recording paper during the normal image copying operation. explain.
[0107]
In the color electrophotographic copying machine according to the first embodiment, as shown in FIG. 12, as described above, after the copy button for starting the copying operation is pressed in the image area 50 of the intermediate transfer belt 21. A patch for process control of each color of yellow (Y), magenta (M), cyan (C), and black (BK) formed on the photosensitive drum 17 during the setup operation before actually starting the copying operation. A plurality of 53Y, 53M, 53C, and 53BK are transferred at different densities, and a horizontal V-shaped shape is used for resist control of each color of yellow (Y), magenta (M), cyan (C), and black (BK). The patches 54Y, 54M, 54C, and 54BK are transferred at a predetermined pitch.
[0108]
Thereafter, the final toner image 70 is transferred to the image area 50 of the intermediate transfer belt 21 as shown in FIG. Then, when the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 passes the secondary transfer position as described above, the CPU 60, as shown in FIG. For example, a transfer bias voltage of −2.2 KV is applied to the backup roll 25. Therefore, the final toner image 70 transferred to the image area 50 of the intermediate transfer belt 21 is transferred from above the intermediate transfer belt 21 by the transfer bias voltage applied to the backup roll 25 when passing the secondary transfer position. In synchronization with the toner image, the toner image is transferred onto the recording paper 26 conveyed to the secondary transfer position.
[0109]
At this time, as shown in FIG. 12, the CPU 60 detects that the recording paper 26 has passed the secondary transfer position based on a signal from the paper detection sensor 58 or the cassette sensor 62, and the CPU 60 For example, a transfer bias voltage of −2.2 KV is applied to the backup roll 25 via the transfer bias voltage high-voltage power supply 47 only in an area corresponding to the size along the conveyance direction of the recording paper 26, so After passing through the next transfer position, the transfer bias voltage high-voltage power supply 47 is always turned on for a fixed time (for example, the time corresponding to the maximum size recording paper 26) regardless of whether or not a size mismatch of the recording paper 26 occurs. Then, a reverse transfer bias voltage of, for example, +550 V is applied to the backup roll 25, and the toner image 70 protruding from the recording paper 26 It has become a surely be prevented from being transferred onto the secondary transfer roll 27.
[0110]
Embodiment 2
FIG. 13 shows Embodiment 2 of the present invention. In Embodiment 2, the configuration of the image forming means is different from that of Embodiment 1, and an electrostatic latent image is formed as the image forming means. A plurality of image forming units, and a plurality of developing units that develop the electrostatic latent image formed on the image bearing member with toner of a predetermined color. One that sequentially forms a plurality of different toner images is used.
[0111]
FIG. 13 shows a tandem type color electrophotographic copying machine as an image forming apparatus according to Embodiment 2 of the present invention.
[0112]
In FIG. 13, reference numeral 101 denotes a main body of a tandem type digital color copying machine. A platen cover 103 that presses a document 102 onto a platen glass 105 is placed on an upper portion of one end side of the digital color copying machine main body 101. A document reading device 104 that reads an image of the document 102 placed on the platen glass 105 is provided. The document reader 104 illuminates a document 102 placed on a platen glass 105 with a light source 106, and reflects a reflected light image from the document 102 from a full-rate mirror 107, half-rate mirrors 108 and 109, and an imaging lens 110. The image reading element 111 composed of a CCD or the like is scanned and exposed through the reduction optical system, and the color material reflected light image of the original 2 is scanned at a predetermined dot density (for example, 16 dots / mm) by the image reading element 111. It is supposed to read.
[0113]
The color material reflected light image of the original 102 read by the original reading device 104 is, for example, IPS 112 (three-color original reflectance data of red (R), green (G), blue (B) (each 8 bits)). In this IPS 112, the reflectance data of the document 2 is subjected to predetermined corrections such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, frame erasing, color / moving editing, etc. Image processing is performed.
[0114]
The image data that has been subjected to the predetermined image processing by the IPS 112 as described above is the original color material floor of four colors of yellow (Y), magenta (M), cyan (C), and black (K) (8 bits each). ROS 114Y, 114M, 114C of image forming units 113Y, 113M, 113C, 113BK for each color of yellow (Y), magenta (M), cyan (C), and black (K) as described below. , 114BK (Raster Output Scanner). In these ROSs 114Y, 114M, 114C, and 114BK, image exposure using laser light is performed in accordance with original color material gradation data of a predetermined color.
[0115]
Incidentally, in the tandem type digital color copying machine main body 101, four image forming units 113Y, 113M, 113C, and 113BK of yellow (Y), magenta (M), cyan (C), and black (K) are provided. These are arranged in parallel at regular intervals in the horizontal direction.
[0116]
These four image forming units 113Y, 113M, 113C, and 113BK are all configured in the same manner, and are roughly divided into a photosensitive drum 115 that rotates at a predetermined rotational speed in the direction of the arrow, and the photosensitive drum 115. Formed on the photosensitive drum 115, a scorotron 116 for primary charging that uniformly charges the surface of the photosensitive drum 115, an ROS 114 that exposes an image corresponding to each color on the surface of the photosensitive drum 115 to form an electrostatic latent image, and the like. The developing unit 117 and the cleaning device 118 for developing the electrostatic latent image.
[0117]
As shown in FIG. 2, the ROS 114 modulates the semiconductor laser 119 according to the original color material gradation data, and emits a laser beam LB from the semiconductor laser 119 according to the gradation data. The laser beam LB emitted from the semiconductor laser 119 is deflected and scanned by the rotary polygon mirror 122 via the reflection mirrors 120 and 121, and again carries an image via the reflection mirrors 120 and 121 and the plurality of reflection mirrors 123 and 124. Scanning exposure is performed on the photosensitive drum 115 as a body.
[0118]
From the IPS 12, image data of each color is provided to the image forming units 113Y, 113M, 113C, and 113BK of the colors of yellow (Y), magenta (M), cyan (C), and black (BK). Are sequentially output, and laser beams LB emitted according to image data from these ROSs 114Y, 114M, 114C, and 114BK are scanned and exposed on the surfaces of the respective photosensitive drums 115Y, 115M, 115C, and 115BK, and electrostatic latent An image is formed. The electrostatic latent images formed on the photosensitive drums 115Y, 115M, 115C, and 115BK are respectively yellow (Y), magenta (M), cyan (C), and black by the developing units 117Y, 117M, 117C, and 117BK. It is developed as a toner image of each color of (BK).
[0119]
Yellow (Y), magenta (M), cyan (C), and black (BK) sequentially formed on the photosensitive drums 115Y, 115M, 115C, and 115BK of the image forming units 113Y, 113M, 113C, and 113K, respectively. The toner images of the respective colors are transferred in multiple by the primary transfer rolls 126Y, 126M, 126C, and 126BK onto the intermediate transfer belt 125 disposed below the image forming units 113Y, 113M, 113C, and 113BK. The transfer belt 125 is wound around the drive roll 127, the stripping roll 128, the steering roll 129, the idle roll 130, the backup roll 131, and the idle roll 132 with a constant tension. By a drive roll 127 that is rotationally driven by a dedicated drive motor with excellent constant speed, it is circulated at a predetermined speed in the direction of the arrow. As the transfer belt 125, for example, a flexible synthetic resin film such as PET is formed in a belt shape, and both ends of the synthetic resin film formed in a belt shape are connected by means such as welding, thereby providing an endless belt. What was formed in the shape is used.
[0120]
The yellow (Y), magenta (M), cyan (C), and black (BK) toner images transferred onto the transfer belt 125 in a multiple manner are transferred to the backup roll 131 by a secondary transfer roll 133. The recording paper 134 that has been secondarily transferred onto the recording paper 134 by the pressure contact force and electrostatic force and onto which the toner images of the respective colors have been transferred is transported to the fixing device 137 by the two transport belts 135 and 136. The recording paper 134 on which the toner images of the respective colors are transferred undergoes a fixing process with heat and pressure by the fixing device 137 and is discharged onto a discharge tray 138 provided outside the copying machine main body 101.
[0121]
As shown in FIG. 13, the recording paper 134 has a predetermined size from any of a plurality of paper feed cassettes 139, 140, 141, and includes a paper feed roller 142 and a pair of paper transport rollers 143, 144. Then, the paper is once transported to the registration roll 147 through a paper transport path 146 consisting of 145. The transfer paper 134 supplied from any one of the paper feed cassettes 139, 140, 141 is delivered onto the intermediate transfer belt 125 by a registration roll 147 that is rotationally driven at a predetermined timing.
[0122]
In the four image forming units 113Y, 113M, 113C, and 113BK of the yellow, magenta, cyan, and black colors, as described above, the yellow, magenta, cyan, and black toner images are respectively obtained. They are sequentially formed at a predetermined timing.
[0123]
The photosensitive drums 115Y, 115M, 115C, and 115BK are subjected to subsequent image formation after the toner image transfer process is completed and residual toner and paper dust are removed by the cleaning devices 118Y, 118M, 118C, and 118BK. Prepare for the process. Further, residual toner is removed from the intermediate transfer belt 125 by a belt cleaner 148.
[0124]
Incidentally, in the tandem color electrophotographic copying machine, as in the first embodiment, at least a part of the toner image transferred to the non-image area 51 and the image area 50 on the intermediate transfer belt 125 is recorded. When positioned on the intermediate transfer belt 125 other than the area corresponding to the medium 134, the backup roll 131 and the secondary transfer roll 133 as the second transfer means have at least a transfer bias voltage in an area other than the recording medium 134. It is configured to include a CPU as a transfer bias voltage application control means for controlling to apply a reverse transfer bias voltage of reverse polarity.
[0125]
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.
[0126]
【The invention's effect】
As described above, according to the present invention, there is provided an image forming apparatus configured to transfer a process control toner image and a resist control toner image onto an intermediate transfer member in order to improve image quality. In addition, it is possible to provide an image forming apparatus capable of preventing the occurrence of contamination on the back surface of the recording medium with certainty, as well as preventing a significant reduction in productivity.
[0127]
Further, according to the present invention, even in an image forming apparatus configured to transfer a process control toner image and a resist control toner image onto an intermediate transfer body for high image quality, It is possible to provide an image forming apparatus capable of reliably preventing a process control toner image and a resist control toner image from being transferred onto a recording medium.
[Brief description of the drawings]
FIG. 1 is a block diagram showing image forming means of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 3 is an explanatory diagram showing an image area and a non-image area of the intermediate transfer belt.
FIG. 4 is an explanatory diagram showing a process control patch and a resist control patch transferred onto the intermediate transfer belt.
FIG. 5 is an explanatory diagram showing a process control patch and a resist control patch transferred onto the intermediate transfer belt.
FIG. 6 is a block diagram showing a control circuit of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 7 is a timing chart showing an image forming operation of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 8 is a timing chart showing an image forming operation of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 9 is a timing chart showing an image forming operation of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 10 is a timing chart showing an image forming operation of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 11 is a timing chart showing an image forming operation of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 12 is a timing chart showing an image forming operation of a color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 13 is a block diagram showing a tandem type color electrophotographic copying machine as an image forming apparatus according to Embodiment 2 of the present invention.
[Explanation of symbols]
17: photosensitive drum (image carrier), 21: intermediate transfer belt (intermediate transfer body), 22: primary transfer roll (primary transfer means), 25: backup roll (secondary transfer means), 26: recording paper (Recording medium), 27: secondary transfer roll (secondary transfer means), 47: high voltage power supply for transfer bias (transfer bias voltage applying means), 53Y, 53M, 53C, 53BK, 54Y, 54M, 54C: for process control Patch 55Y, 55M, 55C, 55BK, 56Y, 56M, 56C, 56BK: patch for resist control, 58: paper detection sensor, 60: CPU (transfer bias voltage application control means), 62: cassette sensor.

Claims (4)

An image forming unit capable of forming a plurality of toner images of different colors, an intermediate transfer member for temporarily transferring and holding the toner image formed by the image forming unit, and a toner image formed by the image forming unit A first transfer unit for transferring the toner image onto the intermediate transfer member, a second transfer unit for transferring the toner image transferred onto the intermediate transfer member onto a recording medium, and the intermediate transfer member. Transfer bias voltage applying means for applying a transfer bias voltage for transferring the toner image transferred thereon onto the recording medium to the second transfer means, and toner transferred to the image area on the intermediate transfer member When the image is located over both the area corresponding to the recording medium on the intermediate transfer member and the other area, the second transfer means includes a transfer bias over both the area of the recording medium and the other area. An image forming apparatus characterized by comprising a transfer bias voltage application control means for applying a reverse transfer bias voltage of pressure and opposite polarity, the. A detection unit for detecting a recording medium is provided immediately before the second transfer unit, and a bias voltage applied to the second transfer unit is controlled based on a detection result of the detection unit. The image forming apparatus according to item 1 . The recording medium containing member containing the recording medium detects the size of the recording medium, and controls the bias voltage applied to the second transfer means based on the detection result of the size of the recording medium. The image forming apparatus according to claim 1 or 2 . Said image forming means, claim paragraphs 1 through the third term, which is a possible form the toner image for control for controlling a plurality of toner images and an image forming operation of different colors The image forming apparatus described in 1.

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