JP5038045B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that supports a plurality of toner images along the moving direction of the surface of an image carrier, and more particularly to processing of a toner image on the surface of an image carrier that cannot be transferred due to a jam of a recording material.

  Along with the increase in the speed of image forming apparatuses, large image forming apparatuses that carry a plurality of toner images on the surface of an intermediate transfer belt have been put into practical use. Here, a plurality of types of toner images differing in the type, size, front and back of the recording material to be transferred are carried and arranged continuously at intervals of several tens of mm in the moving direction of the intermediate transfer belt. Then, the arranged toner images are sequentially conveyed to the transfer unit, and transferred onto the surface to be transferred of the recording material to be transferred, which is fed in time.

  In an image forming apparatus using an intermediate transfer belt, an intermediate transfer belt cleaning device is usually disposed on the downstream side of the transfer unit to remove residual toner that has passed through the transfer unit. In addition, a transfer rotator cleaning device is disposed on a transfer rotator (transfer roller or transfer belt) that forms a transfer portion by pressure-contact rotation with an intermediate transfer belt via a recording material. Adhering toner is removed.

  These cleaning apparatuses can also employ a blade system, but in the case of an intermediate transfer belt or a transfer rotator imparted with elasticity on the surface, an electrostatic brush system (for example, Patent Documents 1 and 2) is preferred.

JP 2001-305878 A Japanese Patent No. 3236442 JP 2002-207403 A

  The intermediate transfer belt cleaning device is arranged assuming a small amount of untransferred toner that has passed through the transfer portion. Therefore, a toner image with a large amount of toner loaded such as a full-color solid image that passes through the transfer portion is cleaned. Insufficient performance.

  For this reason, when a toner image that cannot be transferred to the recording material is generated on the intermediate transfer belt due to a jamming of the recording material, supply stop, or the like, the image formation is completely interrupted and the cleaning mode is executed. In the cleaning mode, a voltage having a polarity opposite to that at the time of transfer is applied to the transfer portion to prevent transfer to the transfer rotator, and the intermediate transfer belt is idled to transfer all toner images on the intermediate transfer belt to the intermediate transfer belt. Pass multiple times through belt cleaning device. Thus, a large amount of toner carried on the intermediate transfer belt is collected by the intermediate transfer belt cleaning device without contaminating the transfer rotator, and the intermediate transfer belt is cleaned to a practical level.

  At this time, when the intermediate transfer belt cleaning device is of an electrostatic brush type, the amount of toner that can be removed in one pass is limited, so the number of times of passing through the intermediate transfer belt cleaning device increases, and the image forming apparatus Longer downtime.

  In the cleaning mode, all the toner images already formed on the intermediate transfer belt are uniformly removed, so that another recording material or a toner image that can be transferred to the other surface of the recording material is wasted. Since the amount of toner to be processed including a transferable toner image increases and a large cleaning load is applied, the life and performance of the intermediate transfer belt cleaning device may be reduced.

  By the way, if the intermediate transfer belt cleaning device is arranged in multiple stages along the intermediate transfer belt or the cleaning performance is increased in capacity, there is a possibility that a toner image with a large amount of applied toner can be removed in one pass. However, in a normal operation state, the cleaning performance is greatly surplus, and the driving load of the intermediate transfer belt and the intermediate transfer belt cleaning device is increased, which is contrary to the power saving of the image forming apparatus. The cost of parts increases without fail, making it difficult to reduce the size of the image forming apparatus.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing downtime when a jam or a supply stop of a recording material occurs without improving the cleaning performance of an intermediate transfer belt cleaning device.

  The image forming apparatus of the present invention includes an image carrier on which a first toner image and a second toner image transferred to different recording materials are carried along a moving direction, and the image carrier through a recording material. A transfer rotating member that forms a transfer portion by rotating in pressure contact; and a transfer voltage is applied to the transfer portion to transfer the first toner image from the image carrier to a first recording material, and then the second toner. Power supply means for transferring the image to the second recording material, image carrier cleaning means for removing toner from the image carrier on the downstream side of the transfer section along the image carrier, and attached to the transfer rotator And a transfer rotator cleaning means for removing toner. A first removal mode in which a voltage having a polarity opposite to the transfer voltage is applied to the transfer unit and the toner image of the image carrier passed through the transfer unit is removed by the image carrier cleaning unit; And a second removal mode in which a toner image transferred to the transfer rotator by applying a voltage having the same polarity as the voltage to the transfer unit is removed by the transfer rotator cleaning means. When the first recording material can no longer be supplied to the transfer section, the first removal mode is executed when the amount of applied toner per unit area of the first toner image exceeds a predetermined amount. However, when the amount of applied toner per unit area of the first toner image is equal to or less than a predetermined amount, the second removal mode is executed and the transfer of the second toner image to the second recording material is continued.

  In the image forming apparatus of the present invention, since the first toner image that can no longer be transferred to the first recording material is transferred to the transfer rotator and the transfer of the second toner image to the second recording material continues, the second toner image Don't waste it. Since the second toner image is carried away by the second recording material, it does not become a cleaning load of the image carrier cleaning means. When the first toner image exceeds the cleaning capability of the transfer rotator cleaning means, the first cleaning mode is applied to prevent contamination of the transfer rotator. Therefore, the first toner image attached to the transfer rotator does not stain the second recording material when the second toner image is transferred.

  Accordingly, it is possible to reduce the downtime when the recording material is jammed or the supply is stopped without improving the cleaning performance of the image carrier cleaning means.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. In the image forming apparatus of the present invention, as long as the toner image that can no longer be transferred is disposed and the transfer of the toner image that can be transferred is continued, a part or all of the configuration of each embodiment is replaced with the alternative configuration. Other embodiments can also be implemented.

  Therefore, the present invention is not limited to an image forming apparatus using an intermediate transfer member, and can also be implemented in an image forming apparatus including a photosensitive drum and a photosensitive belt capable of carrying a plurality of toner images.

  In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

  In addition, about the general matter of the image forming apparatus shown by patent documents 1-3, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

<First Embodiment>
1 is an explanatory diagram of the configuration of the image forming apparatus of the first embodiment, FIG. 2 is an explanatory diagram of the configuration of an image forming unit, FIG. 3 is an explanatory diagram of the configuration of an intermediate transfer belt, and FIG. 4 is a secondary transfer roller cleaning device. It is explanatory drawing of this structure.

  As shown in FIG. 1, the image forming apparatus 100 according to the first embodiment is a tandem type full-color copying machine in which four image forming units Pa, Pb, Pc, and Pd are arranged in a straight section of an intermediate transfer belt 11. The intermediate transfer belt 11 having a peripheral length of 2400 mm and formed endlessly carries a maximum of eight A4 laterally-fed toner images in the section from the image forming portion Pa to the secondary transfer portion T2.

In an image forming portion Pa, which is an example of a toner image forming portion, a yellow toner image is formed on the photosensitive drum 1 a and is primarily transferred to the intermediate transfer belt 11. In the image forming section Pb, which is an example of a toner image forming unit, a magenta toner image is primarily transferred superimposed is formed on the intermediate transfer belt 1 1 the yellow toner image on the photosensitive drum 1b. In the image forming portions Pc and Pd, which are examples of the toner image forming portion, a cyan toner image and a black toner image are formed on the photosensitive drums 1c and 1d, respectively, and similarly, are sequentially transferred onto the intermediate transfer belt 11 in order.

  The four-color toner images primarily transferred to the intermediate transfer belt 11 are transported to the secondary transfer portion T2 and collectively transferred to the recording material P. The recording material P is taken out from the paper feeding device 40 or the paper feeding device 45 one by one and fed to the secondary transfer portion T2 by the registration roller 43.

  The recording material P onto which the toner image has been secondarily transferred by the secondary transfer portion T2 is heated and pressed by the fixing device 17 to fix the toner image on the surface, and then is discharged from the discharge roller 18 to the downstream post-processing device. Discharged.

  The paper feeding device 40 can stack recording materials P of various sizes corresponding to the longitudinal feed of A3 size recording material and the lateral feed of A4 size recording material.

  The separating device 42 separates the recording material P drawn from the paper feeding device 40 by the pickup roller 41 one by one and sends it to the registration roller 43.

  The registration roller 43 receives and waits for the recording material P in the stopped state, nipping and conveying the recording material P in synchronization with the toner image on the intermediate transfer belt 11, and feeding the recording material P to the secondary transfer portion T2.

  The reversal conveyance path 50 refolds the recording material P, onto which the toner image is secondarily transferred on the surface and fixed by the fixing device 17, by the reversal roller 48, and then re-feeds the recording material P to the registration roller 43 in a reverse state.

  A number of conveyance rollers (not shown) for conveying the recording material P are arranged between the separation device 42 and the registration rollers 43 and in the reverse conveyance path 50.

  The image forming portions Pa, Pb, Pc, and Pd are configured in the same manner except that the color of toner used in the attached developing devices 4a, 4b, 4c, and 4d is different from yellow, magenta, cyan, and black. Hereinafter, the image forming unit Pa will be described, and the other image forming units Pb, Pc, and Pd will be described by replacing “a” at the end of the reference numerals with “b”, “c”, and “d”.

  As shown in FIG. 2, the image forming unit Pa includes a primary charging device 2a, an exposure device 3a, a developing device 4a, a primary transfer roller 5a, and a cleaning device 6a around the photosensitive drum 1a.

The photosensitive drum 1a is configured by applying an organic photoconductor layer (OPC) having a negative polarity on the outer peripheral surface of an aluminum cylinder having a diameter of 80 mm. Sensitive light drum 1a is rotatably supported at both ends by a flange, and transmits a driving force from a driving motor (not shown) at one end, a predetermined process speed: arrow (peripheral speed 300 mm / sec) Rotate in the direction.

  The primary charging device 2a presses the charging roller against the photosensitive drum 1a to be driven to rotate, and applies a voltage obtained by superimposing a DC voltage and an AC voltage to the charging roller from the power source D3, thereby uniformizing the surface of the photosensitive drum 1a. Charge to negative potential.

  The exposure device 3a scans, with a polyhedral mirror, a laser beam obtained by ON-OFF modulation of scanning line image data obtained by developing a yellow separation color image, and writes an electrostatic image of the image on the surface of the charged photosensitive drum 1a.

  The developing device 4a attaches negatively charged toner to the exposed portion of the electrostatic image on the photosensitive drum 1a to reversely develop the electrostatic image. The developing device 4a rotates the developing sleeve 4s carrying the toner, and applies a voltage obtained by superimposing an AC voltage on a negative DC voltage from the power source D4 to the developing sleeve 4s.

  The primary transfer roller 5a is pressed against the photosensitive drum 1a via the intermediate transfer belt 11 to form a primary transfer portion T1 between the photosensitive drum 1a and the intermediate transfer belt 11, and the intermediate transfer belt 11 is converted into a toner image. Hold it again. By applying a positive DC voltage from the power source D1 to the primary transfer roller 5a, the negatively charged toner image is primarily transferred from the photosensitive drum 1a to the intermediate transfer belt 11.

  The cleaning device 6a removes the transfer residual toner that passes through the primary transfer portion T1 and remains on the surface of the photosensitive drum 1a, and prepares for the next toner image formation.

  An intermediate transfer belt 11, which is an example of an intermediate transfer member, which is an example of an image carrier, carries a toner image that has been primarily transferred by the primary transfer portion T <b> 1 and is subjected to secondary transfer to the recording material P. Transport to part T2.

  The intermediate transfer belt 11 is supported by the tension roller 12, the driving roller 13, and the backup roller 14, and rotates in the direction of the arrow at a predetermined process speed (peripheral speed: 300 mm / second).

  The secondary transfer roller 15, which is an example of a transfer rotator, is pressed against the backup roller 14 via the intermediate transfer belt 11 and rotates between the intermediate transfer belt 11 and the secondary transfer roller 15. Form.

  In the secondary transfer portion T2, the recording material P is nipped and conveyed over the toner image on the intermediate transfer belt 11. The negatively charged toner image of the intermediate transfer belt 11 is secondarily transferred to the recording material P by applying a positive voltage to the secondary transfer roller 15 from a power source D2 which is an example of a power supply unit.

  The backup roller 14 bends the circulation path of the intermediate transfer belt 11 on the downstream side of the secondary transfer portion T2, and separates the recording material P attached to the intermediate transfer belt 11 by curvature.

  The fixing device 17 forms a fixing portion T3 by pressing the pressure roller 17b against a heating roller 17a having a lamp heater disposed at the center by a spring bias. The fixing unit T3 sandwiches and conveys the recording material P that has been secondarily transferred with the toner image received from the secondary transfer unit T2, heats and presses the toner image, and fixes the toner image on the surface of the recording material P.

  A cleaning device 20, which is an example of an image carrier cleaning unit, removes transfer residual toner that has passed through the secondary transfer portion T <b> 2 and remained on the intermediate transfer belt 11. The cleaning device 20, which is an example of an electrostatic cleaning device, is configured using the same functional members as the cleaning device 30 for the secondary transfer roller 15 described later.

  The conductive fur brushes 21a and 21b, which are examples of brush members, are rotationally driven in the counter direction with respect to the intermediate transfer belt 11 supported by the tension roller 12, and rub against the surface of the intermediate transfer belt 11.

  The metal rollers 22a and 22b are driven to rotate with the conductive fur brushes 21a and 21b on the opposite side of the intermediate transfer belt 11 to charge the conductive fur brushes 21a and 21b.

  The metal roller 22a is charged with a negative voltage from the power supply 24a, and charges the conductive fur brush 21a located near the secondary transfer portion T2 to a negative polarity.

  The metal roller 22b is applied with a positive voltage from the power source 24b, and charges the conductive fur brush 21b located on the side close to the image forming portion Pa to the positive polarity.

  The conductive fur brush 21 a electrically adsorbs toner charged to a polarity (positive polarity) opposite to the normal charging polarity from the intermediate transfer belt 11. According to the potential difference formed on the metal roller 22a, the conductive fur brush 21a, and the intermediate transfer belt 11 connected in series to the power supply 24a, the positively charged toner passes through the conductive fur brush 21a from the intermediate transfer belt 11 to the metal. Adsorbed to the roller 22a.

  The conductive fur brush 21 b electrically adsorbs toner charged to the same polarity (negative polarity) as the normal charging polarity from the intermediate transfer belt 11. In accordance with the potential difference formed on the metal roller 22b, the conductive fur brush 21b, and the intermediate transfer belt 11 connected in series to the power supply 24b, the negatively charged toner is transferred from the intermediate transfer belt 11 to the metal via the conductive fur brush 21b. Adsorbed to the roller 22b.

  The toner collected on the metal rollers 22a and 22b is scraped off from the metal rollers 22a and 22b to the apparatus housing 25 by the cleaning blades 23a and 23b.

By the way, even if the conductive fur brush 21a removes the transfer residual toner whose charging polarity is reversed on the intermediate transfer belt 11, the toner on the intermediate transfer belt 11 is not charged or is normally charged with negative polarity. Remains. Among these, uncharged toner is charged negatively due to charge injection or discharge caused by the negative voltage applied to the conductive fur brush 21a.

  Since the conductive fur brush 21b disposed on the downstream side in the moving direction of the intermediate transfer belt 11 is charged with a positive voltage, the negatively charged toner on the intermediate transfer belt 11 is removed. it can.

  However, when a large amount of toner is conveyed at a time, a large amount of charge is supplied to the tips of the conductive fur brushes 21a and 21b and the charge is lost. Therefore, a substantial part of the toner is contained in the conductive fur brushes 21a and 21b. And is taken around by the intermediate transfer belt 11.

  For this reason, when the toner image carried on the intermediate transfer belt 11 cannot be transferred due to a jam or the like of the recording material P, the control unit 110 stops the formation of a new toner image and causes the intermediate transfer belt 11 to move. Idle multiple times. Thus, the toner image carried on the intermediate transfer belt 11 is electrically adsorbed in a plurality of times to clean the intermediate transfer belt 11 to a practical level.

  As shown in FIG. 3, the intermediate transfer belt 11 is an elastic belt having a three-layer structure in which an elastic layer 11b is integrated on a resin layer 11a and a surface layer 11c is formed on the surface.

The resin layer 11a bears tension and rigidity, and is formed to a thickness of 50 μm using a resin material in which carbon black is dispersed in a polyimide resin and the volume resistivity is adjusted to 10 ⁷ Ωcm.

The elastic layer 11b is made of an electrolyte dispersed rubber (EDPM) having a volume resistivity of medium resistance (volume resistivity 10 ⁴ to 10 ¹⁰ Ωcm) by imparting elasticity to the surface to alleviate pressure concentration during pressure welding. The thickness is 50 μm.

The surface layer 11c increases the secondary transferability by reducing the adhesive force of the toner to the surface of the intermediate transfer belt 11, and is formed to a thickness of 20 μm using a fluorine resin material having a volume resistivity of 10 ¹³ Ωcm. .

As shown in FIG. 4, the secondary transfer roller 15 is composed of an elastic layer 15b of an electrolyte dispersed rubber (EDPM) foam material having a volume resistivity of medium resistance (volume resistivity 10 ⁴ to 10 ¹⁰ Ωcm), and a metal core 15a. It is constituted by covering.

  A cleaning device 30 as an example of a transfer rotator cleaning means is an electrostatic brush cleaning device that performs electrical adsorption and mechanical scraping of toner particles by conductive fur brushes 31a and 31b that rotate at high speed in a charged state. It is. The cleaning device 30 removes the toner attached to the secondary transfer roller 15 at the secondary transfer portion T2, and does not attach the toner from the secondary transfer roller 15 to the back surface of the recording material P.

  Conductive fur brushes 31a and 31b, which are examples of brush members, are formed by flocking carbon dispersed nylon fibers having a resistance value of 10 MΩ and a fiber thickness of 6 denier on the metal roller surface at a flocking density of 500,000 / inch2.

  The conductive fur brushes 31 a and 31 b are rotationally driven in the counter direction with respect to the secondary transfer roller 15 and rub against the surface of the secondary transfer roller 15.

  The conductive fur brushes 31a and 31b rotate in the direction of the arrow at a peripheral speed of 50 mm / sec while maintaining an intrusion amount of about 1.0 mm with respect to the secondary transfer roller 15.

  The metal rollers 32a and 32b are formed of an anodized aluminum pipe and are driven to rotate in the width direction with the conductive fur brushes 31a and 31b. On the opposite side of the secondary transfer roller 15, the conductive fur brush 31a, 31b is contacted. The metal rollers 32a and 32b rotate in the direction of the arrow at a peripheral speed of 50 mm / second while maintaining an intrusion amount of about 1.0 mm with respect to the conductive fur brushes 31a and 31b.

  The metal roller 32a is charged with a negative DC voltage of −500 V (with respect to ground) from the power source 34a to charge the conductive fur brush 31a to a negative polarity.

  The metal roller 32b is applied with a positive DC voltage + 500V (with respect to ground) from the power supply 34b, and charges the conductive fur brush 31b to a positive polarity.

  As a result, the conductive fur brush 31 a electrically adsorbs the toner charged to a polarity (positive polarity) opposite to the normal charging polarity from the secondary transfer roller 15. According to the potential difference formed on the metal roller 32a, the conductive fur brush 31a, and the secondary transfer roller 15 connected in series to the power supply 34a, the positively charged toner is transferred from the secondary transfer roller 15 to the conductive fur brush 31a. After that, it is attracted to the metal roller 32a.

  Further, the conductive fur brush 31 b electrically adsorbs the toner charged to the normal charging polarity (negative polarity) from the secondary transfer roller 15. In accordance with the potential difference formed on the metal roller 32b, the conductive fur brush 31b, and the secondary transfer roller 15 connected in series to the power supply 34b, the negatively charged toner passes from the secondary transfer roller 15 to the conductive fur brush 31b. Then, it is attracted to the metal roller 32b.

  The toner collected on the metal rollers 32a and 32b is scraped off from the metal rollers 32a and 32b to the apparatus housing 35 by the cleaning blades 33a and 33b.

  The cleaning blades 33a and 33b are made of urethane rubber, and are arranged with an intrusion amount of 1.0 mm with respect to the metal rollers 32a and 32b.

  As with the cleaning device 20, the cleaning device 30 has an electrical limit on the cleaning ability of the conductive fur brushes 31a and 31b. When a full-color solid image is transferred to the secondary transfer roller 15 at the secondary transfer portion T2 and a large amount of toner is conveyed to the cleaning device 30 at a time, a large amount of toner is transferred to the tips of the conductive fur brushes 31a and 31b. Charge is supplied and the charge is lost. For this reason, a substantial part of the toner passes through the conductive fur brushes 31 a and 31 b and is rotated around the secondary transfer roller 15.

  A table showing the result of evaluating whether or not the recording material P that has passed through the secondary transfer portion T2 immediately after the toner transfer amount of the toner image that is secondarily transferred to the secondary transfer roller 15 is contaminated. It is shown in 1.

As shown in Table 1, the cleaning device 30 sufficiently cleans the secondary transfer roller 15 at a process speed of 300 mm / sec if the toner adhering to the secondary transfer roller 15 is 0.40 mg / cm ² or less. it can.

<Double-sided printing mode>
FIG. 5 is an explanatory diagram of the arrangement of the front surface toner image and the back surface toner image in the duplex printing mode.

  As shown in FIG. 5, in the section from the image forming portion Pa to the secondary transfer portion T2 of the intermediate transfer belt 11, a maximum of eight A4 lateral feed toner images are carried. When image formation is performed in the duplex printing mode, the control unit 110 transfers the front toner image Za transferred to the front surface of the recording material and the rear toner image Zb transferred to the rear surface of the recording material to the intermediate transfer belt 11. It is carried alternately in the moving direction. A plurality of front toner images Za, which are examples of first toner images, and back toner images Zb, which are examples of second toner images, are carried along the movement direction.

  The controller 110 transfers the surface toner image Za onto the recording material P fed from the sheet feeding device 40 by using a waiting time for fixing and reversing after the surface toner image Za is transferred to the recording material P. The image is transferred and fixed, reversed, and placed on the reverse conveyance path 50.

  Accordingly, it is possible to continuously perform image formation with a small distance between paper sheets of 50 mm to 100 mm, and to realize productivity (number of output sheets per minute) substantially equal to the single-sided printing mode.

  The control unit 110 includes a recording material (an example of the first recording material) fed from the paper feeding device 40 and a recording material (an example of the second recording material) fed from the reverse conveyance path 50. Are alternately fed to the secondary transfer portion T2. The reverse conveyance path 50, which is an example of a refeed path, supplies the first recording material, to which the surface toner image Za, which is an example of a first toner image, is fixed, to the transfer unit again as a second recording material.

  The control unit 110 causes the reversal conveyance path 50 to wait for a plurality of recording materials P, and from the reversal conveyance path 50 one after another at the timing at which the corresponding backside toner image Zb is conveyed to the secondary transfer unit T2. The recording material P is fed to the secondary transfer portion T2.

<Cleaning control when recording stops during recording>
FIG. 6 is a flowchart of cleaning control in duplex printing.

  As shown in FIG. 2, when the recording material P is jammed in the image forming apparatus 100, the image formation is stopped and the rotation of the intermediate transfer belt 11 is stopped in order to avoid the collision of the recording material P. At this time, the stopped intermediate transfer belt 11 is left with a toner image whose transfer destination has been lost due to a jam.

  Thereafter, when the jammed sheet is removed by the operator, the control unit 110 executes the first cleaning mode and disposes of all the toner images carried on the intermediate transfer belt 11.

  In the first cleaning mode, which is an example of the first removal mode, the control unit 110 applies a negative DC voltage from the power source D2 to the secondary transfer roller 15 to transfer the intermediate transfer belt 11 to the secondary transfer roller 15. Blocks toner image transfer. That is, a voltage having a polarity opposite to the transfer voltage is applied from the power source D2 to the secondary transfer roller 15. Further, in order to preferentially attract the negatively charged toner image passing through the secondary transfer portion T2, the control unit 110 reverses the voltage polarity of the power sources 24a and 24b from that during normal image formation. Further, the control unit 110 reverses the polarity of the voltage applied from the power source D1 to the primary transfer roller 5a and the like, reversely transfers the toner image from the intermediate transfer belt 11 to the photosensitive drum 1a, and collects it by the cleaning device 6a.

  In this state, the intermediate transfer belt 11 is idled a plurality of times, and the toner image carried on the intermediate transfer belt 11 is cleaned a plurality of times in stages, and finally the intermediate transfer belt 11 is put into a practical level. Clean up to When the first cleaning mode is executed from the beginning in the image forming apparatus to process all the toner images, a downtime of 30 seconds occurs until the cleaning is completed.

  However, in the double-sided printing mode shown in FIG. 5, the control unit 110 does not apply toner to the recording material P waiting on the reverse conveyance path 50 unless the cleaning load of the surface toner image exceeds the cleaning capability of the cleaning device 30. Continue image transfer.

The video counter 107 processes the image data of the surface toner image and calculates the total density of each color for each 1-inch square block in the recording material P. Each time a surface toner image is formed on the intermediate transfer belt 11, it is determined whether or not there is a block in which the amount of applied toner per unit area exceeds a predetermined amount, and the determination result is held. When the secondary transfer is completed, the determination result is discarded. In this embodiment, this predetermined amount is 0.4 mg / cm ² . As a result, the video counter 107 holds which surface toner image currently carried on the intermediate transfer belt 11 has a block whose toner amount exceeds 0.4 mg / cm ² .

  When the new supply of the recording material P is stopped and the secondary transfer of the surface toner image becomes impossible, the control unit 110 determines the evaluation result of the video counter 107 as the evaluation reference of the data table stored in the storage device 109 in advance. Compare. If the evaluation criteria are met, the second cleaning mode is executed. If the evaluation criteria are not met, the first cleaning mode is executed.

  In the second cleaning mode, which is an example of the second removal mode, the transfer of the back surface toner image to the recording material P waiting in the reverse conveyance path 50 is continued ignoring the supply stop of the recording material P. A normal transfer voltage is applied from the power source D2 to the secondary transfer roller 15 to transfer the surface toner image of the intermediate transfer belt 11 to the secondary transfer roller 15, and is removed from the secondary transfer roller 15 and collected by the cleaning device 30. To do. That is, a voltage having the same polarity as the transfer voltage is applied from the power source D2 to the secondary transfer roller 15 to transfer it to the secondary transfer roller 15 and the toner is removed by the cleaning means of the secondary transfer roller 15.

The controller 110 stops the formation of a new toner image on the front surface toner image, but the formation of the back surface toner image corresponding to the number of the recording materials P waiting on the reversal conveyance path 50 ensures a necessary inter-paper distance. (Expand several times) and continue. Cleaning of the intermediate transfer belt 11 by the cleaning device 20 is continued as usual, and the voltage applied from the power source D1 to the primary transfer roller 5a and the like is continued as usual.

The control unit 110 continues the second cleaning mode as long as the amount of applied toner per unit area continues to be a predetermined amount or less (in this embodiment, 0.4 mg / cm ² or less). Then, when the surface toner image having a block with a toner application amount exceeding 0.4 mg / cm ² reaches the secondary transfer portion T2, the second cleaning mode is switched to the first cleaning mode, and the entire image formation is stopped. To do.

  That is, when the first recording material cannot be supplied to the transfer unit, the second removal mode is set so that the first removal mode is executed for the first toner image exceeding the cleaning capability of the transfer rotating member cleaning unit. This is executed to continue the transfer of the second toner image to the second recording material.

  In addition, when the first recording material cannot be supplied to the transfer unit and the first toner image matches the evaluation criterion that the predetermined cleaning load is light, the second removal mode is executed, and the evaluation criterion If the first toner image does not match, the first removal mode is executed.

  As a result, after the supply of the recording material P is stopped, the back surface toner image already formed on the intermediate transfer belt 11 is not wasted as long as the transfer to the recording material P waiting on the reverse conveyance path 50 is possible.

Further, the front toner image and the back toner image until the front toner image having a block with a toner loading amount exceeding 0.4 mg / cm ² reaches the secondary transfer portion T2 does not reach the cleaning device 20. For this reason, the cleaning load of the cleaning device 20 in the first cleaning mode is reduced, and the downtime until the cleaning is completed is greatly shortened.

  Further, if the supply of a new recording material P is resumed while the transfer of the back surface toner image is continued, the formation and transfer of the front surface toner image is immediately resumed, and the first cleaning mode or an emergency stop is performed. No time is required.

  Further, when the front toner image exceeds the cleaning capability of the cleaning device 30, the transfer of the back toner image is stopped, so that the back surface of the recording material P to which the back toner image is transferred can be prevented.

  Therefore, in a high-speed machine that requires high productivity, it is possible to reduce the decrease in productivity (the number of sheets processed per minute) when there is no paper.

  As shown in FIG. 6 with reference to FIG. 2, when a duplex printing job is received, the control unit 110 determines the order in which the front toner image and the rear toner image are formed (S11).

  The controller 110 alternately forms a front toner image and a back toner image, and alternately arranges them on the intermediate transfer belt 11 as shown in FIG. 5 (S12).

  When the duplex printing job is completed (YES in S13), the intermediate transfer belt 11 is stopped and the image forming apparatus 100 is put on standby for the next job input.

  If the supply of the recording material P is stopped by the end of the double-sided printing job (NO in S13) due to out of paper in the paper feeding device 40, double feeding of the separating device 42, or the like (YES in S14), the control unit 110 Reads data from the video counter 107 (S15).

If the toner image is a surface toner image having no block where the applied toner amount exceeds 0.4 mg / cm ² (NO in S16), the image forming sequence is readjusted (S11) and the image formation is continued (S11). S12). The readjustment is to stop the new formation of the front surface toner image and continue the formation of the necessary back surface toner image at an enlarged distance between sheets.

Control unit 110, if the surface toner image block is present the amount of applied toner exceeds 0.4mg / cm ² (YES in S16), by executing the first cleaning mode, carried on the intermediate transfer belt 1 1 The toner image is disposed (S17).

  The control unit 110 allows image formation to start retroactively by the number of disposed front and back toner images (S18), stops the intermediate transfer belt 11, and causes the image forming apparatus 100 to wait (S19).

  When the supply of a new recording material P is resumed (S20), the control unit 110 readjusts the image formation order (S11) and resumes image formation (S12).

  In the first cleaning mode, the transfer of the toner image from the intermediate transfer belt 11 to the secondary transfer roller 15 may be prevented by separating the secondary transfer roller 15 from the intermediate transfer belt 11.

<Modification of First Embodiment>
In the first embodiment, in order to determine the cleaning load of the surface toner image already carried on the intermediate transfer belt 11, the amount of applied toner is estimated by processing the image data of the surface toner image with a video counter.

  However, the method for determining the cleaning load of the surface toner image, which is an example of the first toner image, is not limited to the processing result of the image data. The density of the surface toner image on the intermediate transfer belt 11 and the amount of applied toner may be determined based on actually measured values. It is also possible to determine an image forming condition that has a correlation with the amount of toner applied to the surface toner image on the intermediate transfer belt 11, and to make an estimation.

For example, in the first embodiment, the applied toner amount of 0.40 mg / cm ² shown in Table 1 roughly matches the maximum density of each color toner. Therefore, in S15 and S16 in FIG. The second cleaning mode may be selected.

  The image data is evaluated, and the second cleaning mode may be selected in the case of a yellow monochrome image, a magenta monochrome image, a cyan monochrome image, or a black monochrome image.

  In the case of an image forming apparatus that executes the full color mode and the black monochrome mode, the second cleaning mode may be selected unconditionally as long as it is a black monochrome mode.

  A density sensor that detects the density of the toner image carried on the intermediate transfer belt 11 may be provided to measure the amount of applied toner, and the second cleaning mode may be selected based on the actual measurement result.

  A plurality of these methods may be combined to improve the estimation accuracy of the cleaning load.

  At least one of these may be detected and a match with the evaluation criteria of the data table stored in advance in the storage device 109 may be determined.

Second Embodiment
In the second embodiment, another control using the image forming apparatus 100, which is different from the first embodiment in inconvenience in supplying the recording material, which is a premise of the control, will be described with reference to FIGS. .

  As illustrated in FIG. 1, the image forming apparatus 100 includes an auto cassette change mechanism that switches the paper feeding from the paper feeding device 40 to the paper feeding device 45 when the paper feeding device 40 runs out of paper.

  The paper feeding device 40 separates the recording material P taken out by the pickup roller 46 by the separation device 47 and feeds it to the registration roller 43.

  However, when switching the paper feeding from the paper feeding device 40 to the paper feeding device 45, the feeding to the registration roller 43 may not be in time due to troublesome separation in the separation device 47. In such a case, the toner image carried on the intermediate transfer belt 11 in anticipation of paper feed cannot be transferred to the recording material P.

  As shown in FIG. 2, the control unit 110 can feed the recording material P in time based on the output of a recording material sensor (not shown) arranged upstream of the point where the conveyance paths of the paper feeding devices 40 and 45 join. If it is determined that there is no such control, the same control as in the first embodiment is performed.

  That is, when the first recording material cannot be supplied to the transfer unit, the second removal mode is set so that the first removal mode is executed for the first toner image exceeding the cleaning capability of the transfer rotating member cleaning unit. This is executed to continue the transfer of the second toner image to the second recording material.

  In addition, when the first recording material cannot be supplied to the transfer unit and the first toner image matches the evaluation criterion that the predetermined cleaning load is light, the second removal mode is executed, and the evaluation criterion If the first toner image does not match, the first removal mode is executed.

As shown in FIG. 6 with reference to FIG. 2, the control unit 110 refers to the video counter 107 (S15), and evaluates the toner loading amount of the toner image that has not been fed in time (S16). If the applied toner amount is 0.40 mg / cm ² or more (YES in S16), the first cleaning mode is executed (S17), and all the toner images already carried on the intermediate transfer belt 11 are disposed.

However, if the applied toner amount is less than 0.40 mg / cm ² (NO in S16), the second cleaning mode is executed (S12), and the toner image on the intermediate transfer belt 11 in time for the recording material P is recorded. Secondary transfer to material P.

<Third Embodiment>
In the third embodiment, another control using the image forming apparatus 100, which is different from the first embodiment in terms of supply of the recording material, which is a premise of the control, will be described with reference to FIGS. .

  As shown in FIG. 1, the image forming apparatus 100 feeds the A4 size recording material P from the paper feeding device 40 and feeds the A3 size recording material P from the paper feeding device 45. On the intermediate transfer belt 11, an A4 toner image that is secondarily transferred to the A4 size recording material P and an A3 toner image that is secondarily transferred to the A3 size recording material P are alternately formed in advance in anticipation of paper feeding. Supported. The A4 size recording material P and the A3 size recording material P are alternately fed to the registration roller 43 from the paper feeding device 40 and the paper feeding device 45.

  Thereby, it is possible to continuously perform image formation with a small distance between paper sheets of 50 mm to 100 mm, and to realize productivity substantially equal to the single-sided printing mode.

  In such a case, when feeding from the sheet feeding device 40 to the registration roller 43 is delayed or when the sheet feeding device 40 runs out of paper, an A4 toner image carried on the intermediate transfer belt 11 in anticipation of feeding. Cannot be transferred to the A4 recording material P.

  As shown in FIG. 2, the controller 110 feeds the A4 recording material P based on the output of a recording material sensor (not shown) arranged upstream of the point where the conveyance paths of the paper feeding devices 40 and 45 merge. If it is determined that it is not in time, the same control as in the first embodiment is performed.

  That is, when the first recording material cannot be supplied to the transfer unit, the second removal mode is set so that the first removal mode is executed for the first toner image exceeding the cleaning capability of the transfer rotating member cleaning unit. This is executed to continue the transfer of the second toner image to the second recording material.

  In addition, when the first recording material cannot be supplied to the transfer unit and the first toner image matches the evaluation criterion that the predetermined cleaning load is light, the second removal mode is executed, and the evaluation criterion If the first toner image does not match, the first removal mode is executed.

As shown in FIG. 6 with reference to FIG. 2, the control unit 110 refers to the video counter 107 (S15), and evaluates the toner application amount of the A4 toner image that has not been fed in time (S16). If the applied toner amount is 0.40 mg / cm ² or more (YES in S16), the first cleaning mode is executed (S17), and all the toner images already carried on the intermediate transfer belt 11 are disposed.

However, if the applied toner amount of the A4 toner image is less than 0.40 mg / cm ² (NO in S16), the second cleaning mode is executed (S12), and the A3 toner image on the intermediate transfer belt 11 is A3. Secondary transfer is continuously performed on the recording material P.

  In this case, the paper feeding device 40 is a plain paper feeding device, the paper feeding device 45 is a thick paper feeding device, and a plain paper toner image that is secondarily transferred to the plain paper on the intermediate transfer belt 11 and a thick paper that is secondarily transferred to the thick paper. The same control is performed when toner images are alternately carried.

That is, when the feeding of the plain paper is delayed or stopped, the first cleaning mode is executed if the toner loading amount of the plain paper toner image is 0.40 mg / cm ² or more. However, if it is less than 0.40 mg / cm ² , the second cleaning mode is executed.

  In image formation using a plurality of paper feeding devices, when the amount of toner on the image when paper is not present is low, the amount of dirt on the secondary transfer roller is low, so that the electrostatic cleaning device can be used for cleaning.

  For this reason, priority is given to the continuation of the subsequent secondary transfer of the toner image, and unnecessary toner is processed by the secondary transfer roller cleaning device without performing separation of the secondary transfer portion or voltage reversal.

  As a result, the area where the toner image to be cleaned is present on the intermediate transfer belt is narrowed, and the time required for cleaning can be shortened.

  Further, since the secondary transfer of the usable toner image is continued while disposing of the toner image that is no longer needed, the downtime due to the inconvenience of the supply of the recording material is shortened.

  In particular, in a high-speed machine requiring high productivity, it is possible to reduce a decrease in throughput when there is no paper.

It is explanatory drawing of a structure of the image forming apparatus of 1st Embodiment. It is explanatory drawing of a structure of an image formation part. FIG. 6 is an explanatory diagram of a configuration of an intermediate transfer belt. It is explanatory drawing of a structure of a secondary transfer roller cleaning apparatus. It is explanatory drawing of arrangement | positioning of the front surface toner image and back surface toner image in double-sided printing mode. It is a flowchart of the cleaning control in double-sided printing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Photosensitive drum 2a Primary charging device 3a Exposure device 4a Developing device 5a Primary transfer roller 6a Cleaning device 11 Image carrier, intermediate transfer member (intermediate transfer belt)
12, 13, 14 Rotating body (tension roller, drive roller, backup roller)
15 Transfer rotator (secondary transfer roller)
20 Image carrier cleaning means, electrostatic cleaning device (cleaning device)
21a, 21b, 31a, 31b Brush member (conductive fur brush)
30 Transfer rotator cleaning means, electrostatic cleaning device (cleaning device)
50 Refeed path (reversed transport path)
108 Operation panel 109 Evaluation criteria for light cleaning load (storage device)
110 Control means (control unit)
D2 Power supply means (power supply)
P recording material S17 first removal mode (first cleaning mode)
S12 Second removal mode (second cleaning mode)
Pa, Pb, Pc, Pd Toner image forming unit (image forming unit)
T2 transfer section (secondary transfer section)

Claims (5)

An image carrier on which a first toner image and a second toner image transferred to different recording materials are carried along a moving direction;
A transfer rotating body that forms a transfer portion by press-contact rotation to the image carrier via a recording material;
Power supply means for applying a transfer voltage to the transfer section to transfer the second toner image to the second recording material after transferring the first toner image from the image carrier to the first recording material;
Image carrier cleaning means for removing toner from the image carrier on the downstream side of the transfer section along the image carrier;
An image forming apparatus comprising: a transfer rotator cleaning unit that removes toner attached to the transfer rotator;
A first removal mode in which a voltage having a polarity opposite to the transfer voltage is applied to the transfer unit and the toner image of the image carrier passed through the transfer unit is removed by the image carrier cleaning unit;
A second removal mode in which a toner image transferred to the transfer rotator by applying a voltage having the same polarity as the transfer voltage to the transfer unit is removed by the transfer rotator cleaning means;
When the first recording material cannot be supplied to the transfer unit, and the amount of applied toner per unit area of the first toner image exceeds a predetermined amount, the first removal mode is executed, and the first toner is executed. When the amount of applied toner per unit area of the image is a predetermined amount or less, the second removal mode is executed to continue the transfer of the second toner image to the second recording material. apparatus.   When the first recording material cannot be supplied to the transfer section, and the first toner image matches a predetermined evaluation criterion that the cleaning load is light, the second removal mode is executed. 2. The image forming apparatus according to claim 1, wherein if the first toner image does not match the evaluation criterion, the first removal mode is executed.   At least one of a measured value of the toner application amount of the first toner image, an image data processing result of the first toner image, and an image forming condition option correlated with the toner application amount of the first toner image. The image forming apparatus according to claim 2, wherein the image forming apparatus determines whether the evaluation criterion is met. The first toner image and the second toner image are alternately carried along the moving direction of the image carrier,
4. The image forming apparatus according to claim 3, further comprising a re-feeding path for supplying the first recording material on which the first toner image is fixed as the second recording material to the transfer unit again. The image carrier is an intermediate transfer body on which toner images are sequentially superimposed and primarily transferred by a plurality of toner image forming portions arranged along the moving direction,
2. The electrostatic cleaning device according to claim 1, wherein the image carrier cleaning means and the transfer rotator cleaning device are electrostatic cleaning devices that electrically remove toner by sliding a charged brush member against the image carrier. The image forming apparatus according to claim 1.

Images