JP2006162642A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of margin, to prevent the inside of the apparatus from being soiled with toner forced out of an edge, to reduce waste of prints disposed of, and to minimize the calibration time, by synchronizing the edge of a transfer material and the edge of a toner image when conducting a special printing mode, such as frameless printing. <P>SOLUTION: When a special print mode is set, a synchronization shift detecting operation by a detecting means and correction control by a correcting means are preformed, prior to a printing operation. This makes it possible to output a print in a regular mode, without extending time from the start of the printing operation to the output of the print, that is, a first printing time; whereas in another special printing mode, such as frameless printing, a print in which registrations are synchronized with high accuracy can be output. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In an image forming apparatus such as a copying machine, a printer, and a fax machine, an electrophotographic system using toner is often used. Conventionally, in these electrophotographic image forming apparatuses, an image is printed with a certain margin (edge) provided from the edge of the paper. However, with the diversification of printer demand in recent years, not only electrophotographic image forming apparatuses but also printed materials output by inkjet and other printing methods can be used as catalogs and pamphlets, or silver halide photography Opportunities to use as an alternative are increasing. For applications such as catalogs, pamphlets, and silver salt photo substitution, there is a growing demand for marginless printing. In particular, for electrophotographic image forming apparatuses, it is strongly desired to realize marginless printing for business use because of its high productivity.

However, when performing marginless printing in a conventionally known electrophotographic image forming apparatus, the edge portion of the toner image formed on the image carrier and the edge portion of the transferred material to be conveyed are accurately detected. It needs to be well synchronized. In other words, if the edge portion of the toner image and the edge portion of the transfer material cannot be synchronized, a margin is generated even though margin-less printing is specified, or the toner protruding from the edge portion of the transfer material It adheres to the electrostatic transfer belt that electrostatically conveys the transfer material and causes backside contamination, or adheres to the secondary transfer roller in the intermediate transfer system and causes backside contamination. Problems such as contamination with toner. Although it is possible to suppress the occurrence of margins by taking a large portion of the added portion, such a correspondence eventually increases the amount of toner that protrudes from the edge portion of the transfer material, and the above-mentioned backside dirt, etc. Cause problems. Further, the toner that protrudes from the edge portion of the transfer material is essentially unnecessary toner, and becomes one of the factors that increase the toner consumption more than necessary. However, it has been very difficult in the past to synchronize the edge portion of the transfer material and the edge portion of the toner image at a level required for borderless printing.
As a workaround for such a problem, for example, Patent Document 1 proposes a method of using a transfer material having a structure in which a half cut is inserted so that a blank portion can be cut off. Alternatively, Patent Document 2 proposes a method in which a backup member that is slightly larger than the transfer material is transported at the same time as the transfer material, and toner positioned outside the transfer material is transferred to the backup member. .
However, both of these methods are wasteful in that the margin is cut off and discarded every time borderless printing is performed once, or the backup member is ejected and discarded every time printing is performed once. Has occurred.

  In order to avoid such waste, it is necessary to strictly control the edge portion of the transfer material and the edge portion of the toner image. However, in order to synchronize the two, it is necessary to accurately control the moving speed of the image carrier and the conveyance speed and conveyance position of the transfer material. For these controls, for example, the image carrier and the transfer material are conveyed. The conveyance speed varies due to the thermal expansion of the conveyance roller due to the dimensional tolerance of the conveyance roller and the temperature rise in the apparatus. Such a variation in the conveyance speed is a level that hardly poses a problem in normal printing, but becomes a level that cannot be ignored in a situation where strict registration control is required such as borderless printing. .

As a measure for solving such a problem, for example, a method proposed in Patent Document 3 may be used. According to this, since the registration control is executed by the calibration operation that directly reads the distance between the toner image formed on the transfer material and the edge portion of the transfer material, the control accuracy can be improved. However, in such a method, an output product on which a calibration pattern is printed is discharged every calibration operation, and waste is generated such as discarding the output product. In addition, it is possible to perform registration control with appropriate accuracy immediately after performing such calibration, but as the printing operation is repeated, the transfer speed of the transfer material varies as described above. In particular, the stability is insufficient for a case where strict registration control is required, such as borderless printing.
JP 2001-205936 A JP 2004-45457 A Japanese Patent Laid-Open No. 10-186752

  In view of the above problems, the present invention synchronizes the edge portion of the transfer material and the edge portion of the toner image even when performing borderless printing, for example, so that no toner is generated without causing a margin. Image formation that does not impair productivity during normal printing by minimizing calibration time and enabling stable registration control, such as preventing contamination of the machine and generating wasteful prints. An object is to provide an apparatus.

  The present invention is an image forming apparatus having the following configuration.

  That is, an image forming apparatus according to a first aspect of the present invention includes an image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, and a developing device that visualizes the electrostatic latent image as a toner image. A transfer bias applying means for transferring the toner image on the image carrier directly or directly to an intermediate transfer medium and then transferring it to a transfer material; and an unfixed toner image transferred on the transfer material as a permanent image. An image forming apparatus having a heat-fixing device for heat-fixing as a registration synchronization unit for synchronizing the toner image primarily transferred to the image carrier or the intermediate transfer medium and the conveyance of the transfer material , A detection unit that detects the synchronization shift, and a correction unit that performs correction control according to the amount of synchronization shift detected by the detection unit. When a specific print mode is set, the print operation is performed. Over it is characterized by performing the correction control by the synchronization deviation detecting operation and the correcting means by the detecting means.

  As a result, in the normal print mode, it is possible to output the printed material without increasing the time from the start of the printing operation until the printed material is output, that is, the first print time, while at the same time as in the case of borderless printing. In this print mode, it is possible to output a printed matter in which registration is synchronized with higher accuracy.

  An image forming apparatus according to a second aspect of the present invention includes an image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, and a developing device that visualizes the electrostatic latent image as a toner image. A transfer bias applying means for transferring the toner image on the image carrier directly or directly to an intermediate transfer medium and then transferring the toner image onto the transfer material; and an unfixed toner image transferred onto the transfer material permanently An image forming apparatus having a heat-fixing device for heat-fixing as an image, and a resist for synchronizing the transfer of a toner image on the image carrier or primary transfer onto an intermediate transfer medium and the transfer material A synchronization synchronization means, a detection means for detecting the synchronization deviation, and a correction means for performing correction control in accordance with the amount of synchronization deviation detected by the detection means, when a specific print mode is set. Executed The frequency of execution of the correction control by the synchronization deviation detecting operation and the correcting means by the detecting means, is characterized in the case is different that the normal print mode is set.

  As a result, during continuous printing in the normal print mode, it is possible to continuously output the printed matter without impairing productivity, that is, the print speed, while in continuous printing in a specific print mode such as during borderless printing. Makes it possible to continuously output printed materials with synchronized registration more accurately.

  Next, an image forming apparatus according to a third aspect of the present invention includes an image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, and a development that visualizes the electrostatic latent image as a toner image. An apparatus, transfer bias applying means for transferring the toner image on the image carrier directly or directly to an intermediate transfer medium, and then transferring the transferred image onto the transfer material; and an unfixed toner image transferred onto the transfer material. An image forming apparatus having a heat fixing device for heat fixing as a permanent image, and registration synchronization for synchronizing the toner image primarily transferred to the image carrier or the intermediate transfer medium and the transfer of the transfer material Means, a detecting means for detecting the synchronization deviation downstream of the transfer bias applying means, and a correcting means for performing correction control in accordance with the amount of synchronization deviation detected by the detecting means. In the image forming apparatus, when a specific print mode is set, prior to the printing operation is characterized by performing the correction control by the synchronization deviation detecting operation and the correcting means by the detecting means.

  As a result, it is possible to measure the amount of synchronization between the transfer material and the image with the actual product, and to perform registration correction control with higher accuracy.

  An image forming apparatus according to a fourth aspect of the present invention includes an image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, and a developing device that visualizes the electrostatic latent image as a toner image. A transfer bias applying means for transferring the toner image on the image carrier directly or directly to an intermediate transfer medium and then transferring the toner image onto the transfer material; and an unfixed toner image transferred onto the transfer material permanently An image forming apparatus having a heat fixing device for heat fixing as an image and a transport path for double-sided printing for transporting the transfer material on which a toner image is heat fixed again to the transfer unit, and the image carrier or intermediate transfer medium And a registration synchronization means for synchronizing the transfer of the transfer material, and a detection means for detecting the synchronization deviation downstream of the transfer bias applying means in the process direction. And a correction unit that performs correction control according to the amount of synchronization shift detected by the detection unit, and a synchronization shift detection operation by the detection unit that is executed when a specific print mode is set And the execution frequency of the correction control by the correction means is different from that when the normal print mode is set.

  In the image forming apparatus according to the fifth aspect of the present invention, in the image forming apparatuses according to the third and fourth aspects of the present invention, the synchronous shift amount is detected in the transfer material in the synchronous shift detection operation by the detecting means. The detection pattern for printing is printed.

  Further, the image forming apparatus of the sixth invention of the present application is the image system apparatus of the fifth invention of the present application, wherein the image forming apparatus transports the transfer material, on which the toner image is heated and fixed, to the transfer section again. After the detection pattern is printed on the first surface of the transfer material, the detection unit detects the amount of synchronous deviation, and the transfer material is transported for the duplex printing. After passing through the path, correction control is executed based on the detected amount of synchronization deviation, and transfer in a specific print mode is performed on the second surface of the transfer material.

  The image forming apparatus of the seventh invention of the present application is the image forming apparatus of the fifth and sixth inventions of the present application, wherein the detection pattern is a toner image color having the lowest visibility among the toner image colors of the image forming apparatus. It is characterized by being formed by.

  An image forming apparatus according to an eighth aspect of the present invention is characterized in that the specific print mode in the image forming apparatuses according to the first to seventh aspects of the present invention is a borderless print mode having no print margin.

  According to the present invention, the detailed calibration operation is executed only in a specific print mode that requires particularly precise registration control such as borderless printing, so that productivity during normal printing is not impaired, and It is possible to provide an image forming apparatus capable of accurate registration control as required. In particular, the above-described accurate registration control enables borderless printing that minimizes the amount of application or produces no margins even without application, and prevents contamination of the printed material and contamination of the image forming apparatus. In addition, it is possible to prevent waste such as cutting off and discarding the blank portion.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows an in-line image forming apparatus using an intermediate transfer body system used in this embodiment. The image forming apparatus of this example is a laser beam printer using an electrophotographic process, and is a full-color image forming apparatus including a plurality of process stations and an intermediate transfer belt as an intermediate transfer member.

  The intermediate transfer belt 27 is wound around each of a drive 22 roller, a secondary transfer counter roller 26, and a tension roller 13.

  On the peripheral surface of the intermediate transfer belt 27, yellow, magenta, cyan, and black image forming portions, that is, process stations 31Y to 31Bk for the respective colors are arranged.

  Each process station is attachable to and detachable from the image forming apparatus main body as a process cartridge, and each process cartridge includes photosensitive drums 1Y to 1Bk, primary chargers 2Y to 2Bk, developing devices 8Y to 8Bk, and cleaning device 10Y. -10Bk are integrated together.

  The controller unit 45 arranged in the apparatus main body sends image signals corresponding to the image information to the scanner units 11Y to 11Bk at a predetermined timing, and the optical information 12Y to 12Bk corresponding to the image signals is sent from each scanner unit to each process. The photosensitive drums 1Y to 1Bk in the station are irradiated and latent images are formed on the photosensitive drums 1Y to 1Bk. When the photosensitive drums 1Y to 1Bk further advance in the direction of the arrow, the latent images are developed by the developing devices 8Y to 8Bk to become toner images.

  The photosensitive drums 1Y to 1Bk in each process station are in contact with primary transfer rollers 4Y to 4Bk, which are primary transfer charging means, via the intermediate transfer belt 27, and the primary transfer rollers 4Y to 4Bk are in contact with the primary transfer rollers 4Y to 4Bk. A primary transfer bias is applied from the transfer bias power sources 32Y to 32Bk.

  In an electrophotographic image forming apparatus, for example, when a negative organic semiconductor electrophotographic photosensitive member (OPC photosensitive member) is used as a photosensitive drum and an exposed portion in which negative charges are attenuated by exposure is developed, the negative electrode A developer containing a neutral toner is used. Therefore, a positive transfer bias is applied to the transfer roller from the transfer bias power source.

  Each color toner image is primary-transferred sequentially onto the intermediate transfer belt 27 at each primary transfer portion facing the primary transfer rollers 4Y to 4Bk as transfer means, and toner images of four colors of yellow, magenta, cyan, and black are obtained. The superimposed full color image is once formed on the intermediate transfer belt 27.

As the intermediate transfer belt 27, PVDF (vinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), polyimide, PET (polyethylene) having a thickness of 50 to 200 μm and a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ωcm. A resin film such as terephthalate) or polycarbonate, or a rubber base layer having a thickness of about 0.5 to 2 mm, for example, EPDM, which is coated with, for example, urethane rubber dispersed with a fluorine resin such as PTFE. Use.

  In a normal printing operation, when a transfer material is fed into the image forming apparatus from the paper feed cassette 15 or the like by the pickup roller 16 and the paper feed rollers 17 and 18, first, four color toners formed on the intermediate transfer belt are used. In order to synchronize the transfer of the image and the transfer material, for example, a roller-shaped synchronous rotating body, that is, a registration roller 19A and a registration counter roller 19B (hereinafter referred to as a registration roller pair 19A and B) are temporarily sandwiched. After that, the sheet is conveyed to the secondary transfer unit at a predetermined timing set in advance. In the secondary transfer portion, the four-color toner images formed on the intermediate transfer belt 27 are secondarily transferred collectively by the action of the secondary transfer roller 28 applied with a bias from the secondary transfer bias power source 33.

  After the transfer process, the transfer material P is transported to the fixing device 21 where it is heated and pressurized to fix the toner image on the transfer material surface as a permanent image.

  The material P to be transferred that has passed through the fixing device is discharged to the discharge tray 20 by the action of the discharge roller pairs 13A and B and 14A and B.

  On the other hand, residual toner remaining on the intermediate transfer belt 27, contamination toner caused by jam of the transfer material or ground fog in the non-image portion of the photosensitive drum 1, or registration mark and density detection on the intermediate transfer belt 27 The toner formed as a pattern is collected by the belt cleaner 24.

  Next, a case where borderless printing is executed using the image forming apparatus will be described with reference to FIG.

  In a normal printing operation, the material to be transferred is conveyed to the secondary transfer portion at a predetermined timing set in advance as described above when performing the secondary transfer. There is a need to synchronize the image on the intermediate transfer belt 27 and the material to be transferred by conveying the material to be transferred with timing. For this reason, in this embodiment, when borderless printing is designated, the intermediate transfer belt circumferential length detection is performed as a synchronization shift detection operation prior to the printing operation.

  A detection mark 29 for detecting the belt circumference is written at the end of the intermediate transfer belt 27, and is configured to be read by the circumference detection sensor 30. To detect the circumference of the intermediate transfer belt, first, the intermediate transfer belt 27 is rotated at a constant speed by the action of the driving roller 22, and the circumference detection sensor 30 detects the detection mark 29 to the arithmetic control device 40 serving as a correction means. Send detection signal. The arithmetic and control unit 40 calculates the circumferential length of the intermediate transfer belt 27 from the time interval at which the detection signal is sent and the rotational speed of the drive roller 22. Next, the arithmetic and control unit 40 calculates the distance from each station to the secondary transfer portion based on the circumference of the intermediate transfer belt 27 and ends the circumference detection operation.

  Next, an image is formed on the intermediate transfer belt 27 by the above-described latent image formation, development, and primary transfer.

  On the other hand, simultaneously with the above-described operation, the material to be transferred is conveyed to the registration roller pair 19A / B by the action of the paper supply rollers 17 and 18 in the paper supply unit.

  Thereafter, the arithmetic and control unit 40 operates the electromagnetic clutch 41 in synchronization with the timing of image formation on the intermediate transfer belt 27 based on the result calculated by the circumference detection operation, and registers the power of the feeding motor 42. By transmitting to the roller 19A, rotation of the registration roller pair 19A / B is started and the transfer material P is conveyed to the secondary transfer portion. In this way, the secondary transfer portion performs the secondary transfer of the borderless image in a state in which the leading end portion of the image and the leading end portion of the transfer material are synchronized with higher accuracy than when normal printing is designated.

  The amount of correction by the arithmetic and control unit 40 based on the above-described detection operation is not at a level that poses a problem in performing a normal print operation. For this reason, in normal printing, the above-described detection operation is not performed, and the printing operation is performed only under conditions where it is required to precisely control and synchronize the timing of writing the latent image as in borderless printing. The detection operation is performed in advance. Further, it is preferable that such a detection operation be performed more frequently than other correction control execution timings during normal printing, whereby the leading edge registration caused by the peripheral length change caused by the thermal expansion of the intermediate transfer belt 27 due to the temperature rise in the apparatus. It is possible to sequentially correct the change of. In this embodiment, the correction operation is performed once every 10 sheets during borderless continuous printing.

  As a result, the leading edge of the toner image and the leading edge of the material to be transferred P are transferred in synchronization with very high accuracy without extending the first printout time during normal printing and during borderless printing. There was no protrusion of toner on the image, and the obtained image could be printed without causing any margin. Further, no margin was generated and no toner contamination of the secondary transfer roller 28 was observed even after 100 sheets were printed continuously.

  In this embodiment, in the intermediate transfer system using the intermediate transfer belt, the intermediate transfer belt circumference detection is used as the synchronization shift detection operation. However, the present invention is not limited to this, and for example, an intermediate transfer drum is used. It is also possible to correspond to an image forming apparatus using a method or an electrostatic conveyance belt. In addition to the circumference detection described above, a conventionally known method can be implemented as the synchronization shift detection operation.

(Second embodiment)
FIG. 3 shows the configuration of the image forming apparatus used in this embodiment.

  In the full-color image forming apparatus using the in-line method shown in FIG. 3, an electrostatic adsorption conveyance belt (hereinafter simply referred to as “conveyance belt”) 14 as a transfer unit is provided with a drive 22 roller, an adsorption counter roller 25, and a tension roller 13a. , 13b.

  Process stations 31Y, 31M, 31C, and 31Bk, which are image forming portions for yellow, magenta, cyan, and black, are arranged along the circumferential surface of the conveyance belt, and the conveyance belt 14 is arranged in the direction of the arrow in the figure. By rotating, the transfer material is sequentially conveyed to each process station. Here again, each process station can be attached to and detached from the image forming apparatus main body as a process cartridge. Each process cartridge includes photosensitive drums 1Y to 1Bk, primary chargers 2Y to 2Bk, developing devices 8Y to 8Bk, and cleaning. The devices 10Y to 10Bk are integrated together.

  Then, in the same manner as described with reference to FIG. 1, each of the process stations 31Y to 31Bk performs an image forming operation at a predetermined timing, thereby forming a toner image of each color on the photosensitive drums 1Y to 1Bk. .

  The photosensitive drums 1Y to 1Bk in each process station are in contact with transfer rollers 4Y to 4Bk, which are transfer charging means, via a conveyor belt 14, and transfer biases from transfer bias power sources 32Y to 32Bk are applied to the transfer rollers 4Y to 4Bk. Is applied.

  When the transfer material P is fed from the paper feed cassette 15 or the like into the image forming apparatus by the feed rollers 17 and 18, first, in order to synchronize the image forming operation and the transfer of the transfer material P, a pair of registration rollers 19A. After being once sandwiched by B, it is guided to a suction portion where the transfer material P and the transport belt 14 are sucked.

  In the suction portion, for example, a suction roller 28 as a suction member is opposed to the suction facing roller 25 via the transport belt 14 and sandwiches the transport belt 14 and the transfer material P. When a voltage is applied to the suction roller 28 from the suction bias power source 32A, which is a high voltage source, a charge is applied to the transfer material, and the transfer material to which the charge is applied is transported by polarizing the transport belt 14. The belt 14 is electrostatically adsorbed.

  In this way, the transfer material P adsorbed on the conveyance belt 14 sequentially passes through each process station, and the respective color toner images developed on the photosensitive drums 1Y to 1Bk in the above-described process are successively transferred. Thereafter, the unfixed toner color image is heated and pressed by the fixing device 21 to become a permanent image.

As the conveyor belt 14, PVDF (vinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), polyimide, PET (polyethylene terephthalate) having a thickness of 50 to 200 μm and a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ωcm. ), A resin film such as polycarbonate, or a rubber base layer having a thickness of about 0.5 to 2 mm, such as EPDM, is coated with, for example, urethane rubber dispersed with a fluorine resin such as PTFE. Use.

  The conveyor belt 14 does not normally carry a toner image directly on its surface, but contaminated toner adheres to the conveyor belt 14 due to jamming or ground fog on a non-image area, or an operation such as density detection. Sometimes, a detection patch is carried directly on the conveyor belt 14. In order to clean such toner on the conveyor belt 14, a cleaning bias having a polarity opposite to that at the time of transfer is applied to the transfer rollers 4Y to 4Bk at each process station 31, and the contaminated toner on the conveyor belt 14 is exposed. The cleaning process of transferring to the drums 1Y to 1Bk and recovering to the drum cleaners 10Y to 10Bk is performed at a predetermined timing.

  The material P to be transferred that has passed through the fixing device 21 is discharged to the paper discharge tray 20 by the action of the discharge roller pairs 13A and B and 14A and B, or when performing double-sided printing, When the rear end passes through the S portion, the pair of paper discharge rollers 14A and B rotate reversely, and the transfer material P is switched back, passes through the double-sided conveyance path D, and is again guided to the registration roller portion.

  A sensor 43 is installed between the pair of paper discharge rollers 13A · B and 13A · B so that the toner image formed on the edge portion of the transfer material P and the transfer material can be detected.

  As the sensor 43, a conventionally known sensor can be used. For example, a combination of an infrared light emitting element such as an LED and a light receiving element such as a photodiode can be used. In this embodiment, a color sensor composed of a white LED and a charge storage sensor with an RGB on-chip filter is used.

  Next, a case where borderless printing is executed using the image forming apparatus will be described.

  In the normal printing operation, the image forming operation is started at the predetermined timing set in advance as described above when performing the transfer. However, when performing the borderless printing, the transfer of the material P to be transferred at a more detailed timing. It is necessary to synchronize the conveyance and the image forming operation. For this reason, in the present embodiment, when borderless printing is designated, a synchronization shift detection pattern shown in FIG. 4 is printed on the transfer material P as a synchronization shift detection operation prior to the print operation.

When printing the synchronization shift detection pattern, a detection pattern print start signal is sent to the controller unit 45 from the arithmetic and control unit 40 as the correction means after t ₀ sec from the start of rotation of the registration roller pair 19A and 19B. . When the controller unit 45 receives the print start signal, the controller unit 45 sends an image signal corresponding to the detection pattern to the scanner unit of the first station having yellow toner, which is the least visible color among the toner colors of the image forming apparatus. Then, the latent image writing operation to the photosensitive drum 1Y is started. This latent image is developed by the developing device 8Y and transferred to the transfer material P by the action of the transfer roller 4Y. The transfer material P to which the developer has been transferred passes through the fixing device 21 and then passes the discharge roller pair 13A / B. pass. Distance x ₂ between the trailing edge and the toner image B of the distances x ₁ and the transfer material P between the leading edge portion and the toner image A portion of the transfer material P is measured by the detector 43, where . Thus, if the process speed is v mm / s, the latent image writing timing in the first station when performing borderless printing is t ₀ −x ₁ / v sec after the rotation start timing of the registration roller pair 19A / B. The latent image writing end timing is after t ₀ + (d + x ₂ ) / v sec.

The to-be-transferred material P whose position is detected is sent to the paper discharge roller pair 14A / B as it is. When the rear end portion of the transfer material P passes through the S portion, the paper discharge roller pair 14A / B rotates in reverse, the transfer material P is switched back and sent to the double-sided conveyance portion, and the transfer material P is again turned on. It is conveyed to the registration roller pair 19A and 19B and is once clamped. Then, after t ₀ −x ₁ / v sec from the start of rotation of the registration roller pair 19A / B, the arithmetic and control unit 40 transmits a print start signal to the controller unit 45, and the latent image writing of the edgeless image in the first station is performed. Start and end after t ₀ + (d + x ₂ ) / v sec. In addition, latent image writing from the second station to the fourth station is started and ended in synchronization with the first station latent image writing. The leading end portion and the trailing end portion of the toner image developed by the developing units 8Y to 8Bk are transferred to the transfer material P in synchronization with the leading edge and the trailing end of the transfer material P with very high accuracy.

  The amount of correction by the above-described detection operation is not at a level that poses a problem when performing a normal printing operation. For this reason, the above-described detection operation is not performed in normal printing, and only under conditions where it is required to strictly control and synchronize the latent image writing timing as in borderless printing, prior to the printing operation. Thus, the above detection operation is performed. Further, it is preferable that such a detection operation be performed more frequently than other correction control execution timings at the time of normal printing, so that a change in the conveyance speed caused by the expansion of the registration rollers 19A and B due to the temperature rise in the apparatus is sequentially performed. It becomes possible to correct. In this embodiment, the correction operation is performed once every 10 sheets during borderless continuous printing.

  As a result, the leading edge of the toner image and the leading edge of the transfer material P are transferred in synchronization with very high accuracy without extending the first printout time during normal printing, and during borderless printing. There was no protrusion of toner, and the resulting image could be printed without causing any margins. Further, no margin was generated and no toner contamination of the conveyor belt 14 was observed even after 100 continuous printings.

  Further, on the transfer material P used for the detection operation such as the first and eleventh sheets, the detection mark of FIG. 4 is printed on the back surface of the borderless image print surface. Because of this, the visibility could be kept low.

  In the present embodiment, in the electrostatic adsorption conveyance belt method, a method of detecting printing of a synchronization shift detection pattern using a color sensor as a synchronization shift detection operation is used, but the present invention is not limited to this, for example, It is also possible to correspond to an image forming apparatus using an intermediate transfer method. In addition to the above-described method, the synchronization shift detection operation can be performed by a conventionally known method.

  The detection mark is printed on the back side of the borderless image printing surface at a rate of 1 out of 10 sheets, but the detection mark is printed on the transfer material without discharging the image. Is also possible. Further, in each of the first and second embodiments, the end of the transfer material and the end of the toner image are aimed to be completely coincident with each other. For example, in the case where an additional area is provided for the purpose of suppressing the occurrence of margins more reliably without providing other cleaning means and having the risk of stains on the back, according to the present invention, the additional area is minimized. It is possible to suppress the toner consumption.

1 is a sectional view of a configuration of an image forming apparatus according to a first embodiment of the present invention. The block diagram which shows the 1st Example of this invention Sectional view of the configuration of an image forming apparatus showing a second embodiment of the present invention Configuration diagram of a synchronization shift detection pattern used in the second embodiment of the present invention

Explanation of symbols

14 Electrostatic Adsorption Transport Belt 19A Registration Roller 19B Registration Counter Roller 27 Intermediate Transfer Belt 29 Perimeter Detection Mark 30 Perimeter Detection Sensor 40 Arithmetic Control Device P Transfer Material X ₁ Distance D from Transfer Material Lead Edge to Lead Detection Mark D Detection the distance from the trailing edge of the distance X ₂ transfer material between the marks to the rear end detection mark

Claims (8)

An image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, a developing device that visualizes the electrostatic latent image as a toner image, and a toner image on the image carrier directly or directly An image forming apparatus having a transfer bias applying means for primary transfer to an intermediate transfer medium and then transferring to a transfer material, and a heat fixing device for heating and fixing an unfixed toner image transferred onto the transfer material as a permanent image And
Registration synchronization means for synchronizing the movement timing of the toner image on the image carrier or the toner image primarily transferred to the intermediate transfer medium and the conveyance timing of the transfer material; and the synchronization deviation. Detection means for detecting, and correction means for performing correction control according to the amount of synchronization shift detected by the detection means,
An image forming apparatus, wherein when a specific print mode is set, a synchronization shift detection operation by the detection unit and a correction control by the correction unit are executed prior to a print operation. An image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, a developing device that visualizes the electrostatic latent image as a toner image, and a toner image on the image carrier directly or directly An image forming apparatus having a transfer bias applying means for primary transfer to an intermediate transfer medium and then transferring to a transfer material, and a heat fixing device for heating and fixing an unfixed toner image transferred onto the transfer material as a permanent image And
A toner image primarily transferred onto the image carrier or an intermediate transfer medium, a registration synchronization means for synchronizing the conveyance of the transfer material, and a detection means for detecting the synchronization deviation; Correction means for performing correction control according to the amount of synchronization deviation detected by the detection means,
An image characterized in that the synchronization shift detection operation by the detection unit and the execution frequency of the correction control by the correction unit executed when a specific print mode is set are different from those in the case where the normal print mode is set. Forming equipment. An image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, a developing device that visualizes the electrostatic latent image as a toner image, and a toner image on the image carrier directly or directly An image forming apparatus having a transfer bias applying means for primary transfer to an intermediate transfer medium and then transferring to a transfer material, and a heat fixing device for heating and fixing an unfixed toner image transferred onto the transfer material as a permanent image And
The toner image primarily transferred to the image carrier or the intermediate transfer medium, registration synchronization means for synchronizing the transfer of the transfer material, and the transfer bias application means on the downstream side in the process direction. In an image forming apparatus, comprising: a detection unit that detects a synchronization shift; and a correction unit that performs correction control according to a synchronization shift amount detected by the detection unit.
An image forming apparatus, wherein when a specific print mode is set, a synchronization shift detection operation by the detection unit and a correction control by the correction unit are executed prior to a print operation. An image carrier, an exposure device that creates an electrostatic latent image on the image carrier in accordance with an image signal, a developing device that visualizes the electrostatic latent image as a toner image, and a toner image on the image carrier directly or directly A transfer bias applying unit that performs primary transfer onto an intermediate transfer medium and then transfer onto a transfer material, a heating fixing device that heats and fixes an unfixed toner image transferred onto the transfer material as a permanent image, and the toner image is heated An image forming apparatus having a conveyance path for double-sided printing for conveying the fixed material to be transferred to the transfer unit again;
The toner image primarily transferred to the image carrier or the intermediate transfer medium, registration synchronization means for synchronizing the transfer of the transfer material, and the transfer bias application means on the downstream side in the process direction. In an image forming apparatus, comprising: a detection unit that detects a synchronization shift; and a correction unit that performs correction control according to a synchronization shift amount detected by the detection unit.
An image characterized in that the synchronization shift detection operation by the detection unit and the execution frequency of correction control by the correction unit executed when a specific print mode is set are different from those in the case where the normal print mode is set. Forming equipment.   5. The image forming apparatus according to claim 3, wherein a detection pattern for detecting a synchronous shift amount is printed on the transfer material in the synchronous shift detection operation by the detection unit. The image forming apparatus has a conveyance path for double-sided printing that conveys the transfer material, on which the toner image is heated and fixed, to the transfer unit again.
After the detection pattern is printed on the first surface of the transfer material, the detection unit detects the amount of synchronous shift, and the detection is performed after the transfer material passes through the double-sided printing conveyance path. 6. The image forming apparatus according to claim 5, wherein correction control is executed based on the amount of synchronization shift, and transfer in a specific print mode is performed on the second surface of the transfer material.   The image forming apparatus according to claim 5, wherein the detection pattern is formed with a toner image color having the lowest visibility among toner image colors of the image forming apparatus.   8. The image forming apparatus according to claim 1, wherein the specific print mode is a borderless print mode having no print margin.

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