JP2014065594A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simply configured image forming device capable of preventing contamination of a conveyance roller pair or staining of an image surface caused by undried ink for a long time and easy in maintenance.SOLUTION: An uneven layer 31 is formed in the outer peripheral surface of a driven side roller 19b brought into contact with the image forming surface of a sheet. A cleaning unit 20 for cleaning the driven side roller 19b includes a supply roller 21 and a liquid suction roller 23 arranged from an upstream side in the rotational direction of the driven side roller 19b. The supply roller 21 and the liquid suction roller 23 are contactable with or separable from the driven side roller 19b. A control unit 90 brings the supply roller 21 and the liquid suction roller 23 into contact with the driven side roller 19b to execute cleaning based on the number of accumulated printed sheets or a total ink discharge amount from the last cleaning execution time of the driven side roller 19b.

Description

  The present invention relates to an image forming apparatus that forms an image by ejecting liquid ink onto a recording medium, and more particularly to a cleaning method for a pair of conveying rollers that conveys a recording medium after an image is formed. .

  Image forming apparatuses such as facsimile machines, copiers, and printers are configured to form an image on a sheet (recording medium) such as paper, cloth, or OHP sheet, but the sheet on which the image is formed is discharged as a pair. In general, the roller is sandwiched between a pair of rollers and discharged onto a predetermined discharge tray.

  In such an image forming apparatus, when images are continuously formed on a large number of sheets, the ink on the sheet is discharged if the ink attached on the sheet is nipped by the discharge roller pair before completely drying. It may adhere to the roller outer peripheral surface on the image surface side of the roller pair. Then, when the next conveyed sheet is sandwiched between the discharge roller pair, the ink adhered to the outer peripheral surface of the discharge roller pair is retransferred onto the sheet, and the image surface is stained (offset). there were.

  The above-mentioned problems are likely to occur when water-based ink that requires time to dry is used in an inkjet recording apparatus that records an image by ejecting ink from ejection nozzles corresponding to printing positions in accordance with sheet conveyance. . In addition, pigment ink and dye ink have different penetrability tendencies to the sheet, and re-transfer of ink tends to occur when a pigment ink in which a coloring material is relatively likely to remain on the sheet is used.

  In order to solve the above problems, for example, in Patent Document 1, a recording sheet is sandwiched in a recording sheet discharge roller that discharges a recording sheet on which an image is recorded to a discharge unit on the downstream side of the image forming apparatus. A driving roller and a driven roller are provided as a pair, and a small area contact outer peripheral layer is formed on the outer peripheral surface of the driven roller arranged on the image surface side, which makes point contact or surface contact with the recording sheet at a number of locations. A recording sheet discharge roller device is disclosed. It also describes that the wear-resistant particles are 50 to 120 μm and the particle distribution density with respect to the outer peripheral surface of the roller is 20% to 80%.

  Further, Patent Document 2 includes an ink adhering unit for adhering ink to a recording medium, and a processing liquid adhering unit for adhering a processing liquid to a recording medium to which ink is adhered, and has a glass transition temperature of −5 ° C. An ink jet recording apparatus using a treatment liquid containing an emulsion of an acrylic resin having a temperature of 30 ° C. or lower and a urethane resin having a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower and / or an emulsion of a block copolymer is disclosed. Yes.

  Patent Document 3 discloses an ink jet recording apparatus including a cleaning liquid application roller that applies a cleaning liquid to a printing surface side roller of a conveyance roller, and a wiping roller that wipes the cleaning liquid from the printing surface side roller. Yes.

JP 2008-302513 A JP 2011-105900 A JP 2007-223739 A

  According to the configuration of Patent Document 1, the contact area of the driven roller with respect to the sheet is reduced by forming a small area contact outer peripheral layer on the outer peripheral surface of the driven roller, and ink or the like adheres to the outer peripheral surface of the driven roller. It becomes difficult. However, even if the particle size of the wear-resistant particles and the particle distribution density with respect to the outer peripheral surface of the roller are within the range described in Patent Document 1, the point contact effect is not sufficient, and the adhesion of the ink to the outer peripheral surface of the roller and the subsequent sheet There was a possibility that retransfer to the film could not be completely prevented.

  Moreover, in the structure of patent document 2, since the ink adhering to a recording medium is coat | covered with the resin film formed by drying of a process liquid, adhesion of the ink to the roller surface in the downstream of an ink adhesion means can be suppressed. . However, when the conveyance speed of the recording medium is high, the treatment liquid cannot be dried in time, and there is a possibility that ink adheres to the roller surface.

  In the configuration of Patent Document 3, since the cleaning liquid application roller and the wiping roller are always in contact with the printing surface side roller, the cleaning liquid is applied and wiped even when the printing surface side roller is not soiled. The liquid is wasted and the life of the cleaning liquid application roller and the wiping roller is shortened. Further, when the cleaning liquid is not sufficiently wiped off by the wiping roller, the cleaning liquid remaining on the printing surface side roller may cause bleeding of the recording surface of the paper.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an image forming apparatus having a simple configuration that can prevent contamination of a pair of conveyance rollers and image surface contamination due to undried ink over a long period of time and is easy to maintain. The purpose is to provide.

  In order to achieve the above object, a first configuration of the present invention includes an image forming unit that forms an image by ejecting liquid ink onto a recording medium, and a recording medium on which an image is formed by the image forming unit. A conveying member configured to include a conveying roller that contacts the image forming surface side and a nip forming member that is pressed against the conveying roller to form a nip portion, and the conveying roller in a state where a recording medium is sandwiched between the nip portions And a recording medium conveyance device that conveys a recording medium by rotating the nip forming member, a supply roller that supplies a cleaning liquid to the conveyance roller, and a cleaning that is supplied from the supply roller A liquid absorption roller that absorbs the liquid, and a first position where the supply roller and the liquid absorption roller are driven to rotate in contact with the transport roller; A cleaning unit that is selectively disposed at a second position separated from the transport roller, a cleaning liquid supply mechanism that supplies a cleaning liquid to the supply roller, and the supply roller and the liquid suction roller from the second position. Move to the first position, supply the cleaning liquid from the cleaning liquid supply mechanism to the supply roller to execute the cleaning of the transport roller, and after the cleaning of the transport roller is finished, the supply roller and the liquid suction roller And a control means for moving the lens to the second position.

  According to the first configuration of the present invention, it is possible to effectively prevent the occurrence of offset due to ink adhesion to the transport roller and to maintain the offset prevention effect for a long period of time. In addition, the supply roller and the liquid absorption roller are brought into contact with the conveyance roller only when the conveyance roller is cleaned, so that bleeding of the image by the cleaning liquid and unnecessary consumption of the cleaning liquid can be suppressed. The service life of the product becomes longer. As a result, maintenance work such as replacement of the supply roller and the liquid absorption roller is reduced, and the running cost of the image forming apparatus is also reduced.

1 is a side sectional view showing an internal configuration of an ink jet printer 100 that is an example of an image forming apparatus according to the present invention. 1 is a partially enlarged view of the discharge roller pair 15 and the cleaning unit 20 in FIG. A partially enlarged view of the conveying roller pair 13b and the cleaning unit 20 in FIG. A partially enlarged view of the conveying roller pair 13c and the cleaning unit 20 in FIG. Side sectional view of the driven roller 19b constituting the discharge roller pair 15 Side surface sectional view of the supply roller 21 provided in the cleaning unit 20 Side surface sectional view of the liquid absorption roller 23 provided in the cleaning unit 20 The figure which shows the other structural example of the cleaning unit 20. A block diagram showing an example of a control path used in the printer 100 A flowchart showing a control example for performing the cleaning operation of the discharge roller pair 15 based on the cumulative number of printed sheets since the previous cleaning execution. A flowchart showing a control example for performing the cleaning operation of the discharge roller pair 15 based on the total ink ejection amount from the previous cleaning execution.

  Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing an internal configuration of an ink jet printer 100 which is an example of an image forming apparatus of the present invention.

  As shown in FIG. 1, in the printer 100, a paper feed cassette 3 that is a paper storage unit is disposed below the inside of the printer main body 2. Inside the paper feed cassette 3, a predetermined number of sheets (for example, about 500 sheets) such as cut paper before printing, which is an example of a recording medium, is stacked and accommodated. A paper feeding device 4 is arranged on the downstream side of the paper feeding cassette 3 in the paper conveyance direction, that is, above the right side of the paper feeding cassette 3 in FIG. The sheet feeding device 4 separates and feeds the sheets P one by one toward the upper right of the sheet feeding cassette 3 in FIG. The paper feed cassette 3 can be pulled out horizontally from the front side of the printer body 2 to replenish paper P.

  Further, the printer 100 includes a first paper transport path 7 therein. The first paper transport path 7 is located on the upper right, which is the paper feed direction of the paper feed cassette 3. The paper P sent out from the paper feed cassette 3 is transported vertically upward along the side surface of the printer body 2 by the first paper transport path 7.

  A registration roller pair 8 is provided at the downstream end of the first paper transport path 7 with respect to the paper transport direction. Further, a first belt conveyance unit 5 and a recording unit 9 are disposed in the immediate vicinity of the registration roller pair 8 on the downstream side. The recording unit 9 includes four recording heads (line heads) that form yellow (Y), magenta (M), cyan (C), and black (K) images. The paper P sent out from the paper feed cassette 3 reaches the registration roller pair 8 through the first paper transport path 7. The registration roller pair 8 feeds the paper P toward the first belt conveyance unit 5 by correcting the oblique feeding of the paper P and timings the ink ejection operation executed by the recording unit 9. The first paper transport path 7 is provided with transport roller pairs 13a for transporting the paper P at appropriate positions.

  In addition, the recording unit 9 prevents the ink discharge failure due to drying or clogging of the recording head, from the ink discharge nozzles of all the recording heads at the start of printing after stopping for a long time, and between printing operations. Prepares for the next printing operation by executing a purge for ejecting ink having a high viscosity in the nozzle from an ink ejection nozzle having an ink ejection amount equal to or less than a specified value.

  A second paper transport path 10 is provided on the downstream side (left side in FIG. 1) of the first belt transport unit 5 with respect to the paper transport direction. The paper P that has passed through the first belt conveyance unit 5 is discharged from the second paper conveyance path 10 to a paper discharge tray 17 provided on the upper surface of the printer 100 via a discharge roller pair 15 that is an example of a recording medium conveyance member. Is done. The second paper transport path 10 is provided with transport roller pairs 13b and 13c for transporting the paper P at appropriate positions as in the first paper transport path 7. The transport roller pairs 13b and 13c and the discharge roller pair 15 are rollers that make contact with the recording surface of the paper P among the rollers constituting each roller pair (the driven roller 19b in FIGS. 2 to 4). A cleaning unit 20 is provided for cleaning.

  In the upper part of the printer main body 2, a tank 40 that stores cleaning liquid to be supplied to each cleaning unit 20, a flow path 50 that connects each cleaning unit 20 and the tank 40, and a cleaning liquid in the tank 40 are flow paths 50. And a pump 60 for delivering to the pump. The tank 40, the flow path 50, and the pump 60 constitute a cleaning liquid supply mechanism that supplies the cleaning liquid to the supply roller 21 (see FIGS. 2 to 4) in the cleaning unit 20. When the ink ejected from the recording head of the recording unit 9 is water-based ink, water is used as the cleaning liquid. When the ink is an oil-based ink, paraffin oil, vegetol, soybean oil or the like is used as the cleaning liquid.

  2 to 4 show a part of the cleaning unit 20 that cleans the discharge roller pair 15, the transport roller pair 13 b and 13 c in FIG. 1, and the driven roller 19 b that contacts the recording surface of the paper P in each roller pair. It is an enlarged view. Hereinafter, the detailed configuration of the discharge roller pair 15 and the cleaning unit 20 attached to the discharge roller pair 15 will be described with reference to FIG. 2 in addition to FIG. 1, but the conveyance roller pair 13b shown in FIGS. The basic structure of 13c and the cleaning unit 20 attached thereto are also the same as those in FIG.

  As shown in FIG. 2, a discharge roller pair 15 including a driving roller 19a and a driven roller 19b is disposed in the vicinity of the paper discharge port 2a of the printer body 2 in the paper width direction (direction perpendicular to the paper surface of FIG. 2). A plurality of pairs are arranged along.

  The driving roller 19a is composed of rubber rollers such as ethylene propylene diene monomer (EPDM), chloroprene (CR), urethane, and is supported by a frame (not shown) above the paper discharge port 2a. (Not shown). The driven roller 19b is pressed against the driving roller 19a with a predetermined pressing force by an urging member (not shown) such as a coil spring. A cleaning unit 20 for cleaning the driven roller 19b is disposed on the side of the driven roller 19b opposite to the driving roller 19a.

  In the cleaning unit 20, a supply roller 21 and a liquid absorption roller 23 are arranged in order from the upstream side with respect to the rotation direction of the driven side roller 19b. The rotation shafts of the supply roller 21 and the liquid absorption roller 23 are supported by a Y-shaped bearing member 24 having a bifurcated tip. The bearing member 24 is fixed to the unit main body 20a, and the unit main body 20a is urged by the compression spring 25 in the direction of the driven roller 19b. An iron core of a solenoid 27 is fixed to the bearing member 24.

  When cleaning the driven roller 19b, when the solenoid 27 is turned off and the iron core is protruded, the unit body 20a moves together with the bearing member 24 in a direction approaching the driven roller 19b by the urging force of the compression spring 25. Then, the supply roller 21 and the liquid absorption roller 23 are pressed against the driven roller 19b. After the cleaning is completed, the solenoid 27 is energized and the iron core is drawn, so that the unit body 20a moves together with the bearing member 24 in a direction away from the driven roller 19b against the urging force of the compression spring 25, and is supplied. The roller 21 and the liquid absorption roller 23 are separated from the driven side roller 19b.

  A supply liquid receiving portion 29 is disposed so as to surround the lower side of the supply roller 21, and one end of a flow path 50 is connected to the supply roller 21. The other end of the flow path 50 is connected to a tank 40 (both see FIG. 1) via a pump 60. The supply of the cleaning liquid to the supply roller 21 is controlled by the feed amount of the pump 60, and the supply amount of the cleaning liquid is lightly impregnated in the holding layer 35 (see FIG. 6) (liquid leakage from the supply roller 21 occurs). However, the supply liquid receiving portion 29 is arranged in case the supply amount of the cleaning liquid becomes excessive due to some trouble.

  FIG. 5 is a side sectional view of the driven roller 19b. On the outer peripheral surface of the driven roller 60b, there are formed concavo-convex layers 31 that make point contact or surface contact with the paper at a number of locations. The uneven layer 31 is composed of an adhesive layer 32 laminated on the outer peripheral surface of the roller body 30 and a large number of particles 33 (average particle diameter; 50 to 150 μm) fixed to the adhesive layer 32. Examples of the method for forming the uneven layer 31 on the driven roller 19b include a method of spraying particles after applying a binder (adhesive) to the roller surface, or spraying a mixture of the binder and particles onto the roller surface. It is done. Examples of the type of particles include ceramic (alumina, silicon carbide, etc.), glass beads, and the like. Examples of the binder include acrylic adhesives and epoxy adhesives.

  By forming the uneven layer 31 on the outer peripheral surface of the driven roller 19b, the outer peripheral surface of the driven roller 19b makes point contact or surface contact with the image surface of the paper. As a result, the contact area between the driven roller 19b and the paper can be made as small as possible, and the effect of preventing ink transfer from the image surface of the paper to the driven roller 19b is enhanced.

  FIG. 6 is a side sectional view of the supply roller 21. As shown in FIG. 6, the supply roller 21 includes a pipe-shaped central shaft 34 and a holding layer 35 laminated on the outer peripheral surface of the central shaft 34, and the central shaft 34 has a plurality of through holes 34 a. Is provided. The cleaning liquid supplied to the inside of the central shaft 34 through the flow path 50 (see FIGS. 2 to 4) exudes to the outside of the central shaft 34 from the through hole 34a and is supplied to the holding layer 35. The holding layer 35 is made of continuous pore foam, for example, PVA sponge (manufactured by Aion Co., Ltd.), felt material made of polyethylene terephthalate or polyimide, and the like.

  FIG. 7 is a side sectional view of the liquid absorption roller 23. As shown in FIG. 7, the liquid absorption roller 23 includes a central shaft 36 and a liquid absorption layer 37 that is laminated on the outer peripheral surface of the central shaft 36. As the liquid absorption layer 37, a continuous pore foam similar to the holding layer 35 of the supply roller 21, for example, a PVA sponge (manufactured by Aion Co., Ltd.) or a nonwoven fabric water supply roll (manufactured by Amvic Inc.) is used. The supply roller 21 and the liquid absorption roller 23 are detachable from the cleaning unit 20, and are replaced with a new supply roller 21 or liquid absorption roller 23 when the holding layer 35 or the liquid absorption layer 37 becomes dirty.

  By using the cleaning unit 20 configured as described above, the cleaning liquid is applied to the outer peripheral surface of the driven roller 19b on which the uneven layer 31 is formed by the supply roller 21, and the applied cleaning liquid is sucked together with the ink by the liquid absorption roller 23. As a result, the ink stain on the driven roller 19b that contacts the image surface of the paper can be reduced. Thereby, the occurrence of offset due to ink can be effectively prevented, and the offset prevention effect can be maintained over a long period of time.

  FIG. 8 is a diagram illustrating another configuration example of the cleaning unit 20. In FIG. 8, the bearing member 24 that supports the supply roller 21 and the liquid absorption roller 23 is U-shaped, and the configuration is the same as that of FIG. 2 except that the solenoid 27 is disposed upside down.

  In the configuration of FIG. 8, when cleaning the driven roller 19 b, when the solenoid 27 is energized and the iron core is drawn, the unit body 20 a together with the bearing member 24 is driven by the urging force of the compression spring 25. The supply roller 21 and the liquid suction roller 23 are pressed against the driven roller 19b. After the cleaning is completed, the solenoid 27 is turned off and the iron core is protruded so that the unit body 20a moves together with the bearing member 24 in a direction away from the driven roller 19b against the urging force of the compression spring 25. The supply roller 21 and the liquid absorption roller 23 are separated from the driven roller 19b.

  Here, the time for cleaning the driven roller 19b is much shorter than the time for not cleaning. With the configuration shown in FIG. 8, the energization of the solenoid 27 is turned on when the driven roller 19b is cleaned and the energization of the solenoid 27 is turned off when the driven roller 19b is not cleaned. The power consumption can be reduced by shortening the configuration.

  FIG. 9 is a block diagram illustrating an example of a control path used in the printer 100. In addition, since various controls of each part of the apparatus are performed when using the printer 100, the control path of the entire printer 100 becomes complicated. Therefore, here, a portion of the control path that is necessary for the implementation of the present invention will be mainly described.

  The image input unit 70 is a receiving unit that receives image data transmitted to the printer 100 from a personal computer or the like. The image signal input from the image input unit 70 is converted into a digital signal and then sent to the temporary storage unit 94.

  The operation unit 80 is provided with a liquid crystal display unit 81 and an LED 82. The liquid crystal display unit 81 and the LED 82 indicate the state of the printer 100, and display the image forming status and the number of copies to be printed. . Various settings of the printer 100 are performed from a printer driver of a personal computer.

  In addition, the operation unit 80 is provided with a stop / clear button used when image formation is stopped, a reset button used when various settings of the printer 100 are set to a default state, and the like.

  The control unit 90 includes a central processing unit (CPU) 91 as a central processing unit, a read only memory (ROM) 92 that is a read-only storage unit, a random access memory (RAM) 93 that is a read / write storage unit, A plurality of (two in this case) I's for transmitting control signals to the temporary storage unit 94 for storing image data and the like, the counter 95, and the devices in the printer 100 and receiving input signals from the operation unit 50. / F (interface) 96, and at least an arithmetic unit 97 that performs arithmetic processing of numerical values necessary for control. Further, the control unit 90 can be arranged at an arbitrary location inside the apparatus main body.

  In addition, the control unit 90 transmits a control signal from the CPU 91 to the respective units and devices in the printer 100 through the I / F 96. In addition, a signal indicating the state and an input signal are transmitted from each part or device to the CPU 91 through the I / F 96. Examples of each part and device controlled by the control unit 90 include the recording unit 9, the belt conveyance unit 5, the registration roller pair 8, the cleaning unit 20, the pump 60, and the operation unit 80.

  The ROM 92 stores data that does not change during use of the printer 100, such as a control program for the printer 100 and numerical values necessary for control. The RAM 93 stores necessary data generated during the control of the printer 100, data temporarily required for the control of the printer 100, and the like. The RAM 93 (or ROM 92) also stores the number of printed sheets and the cumulative ejection amount (cumulative printing rate) of ink that triggers the cleaning operation of the driven roller 19b by the cleaning unit 20. The counter 95 adds up the number of printed sheets and counts it.

  The arithmetic unit 97 calculates the image printing rate and the average printing rate of a predetermined number of images based on the image data stored in the temporary storage unit 94. Further, the ink discharge amount from the recording head of the recording unit 9 is calculated based on the calculated printing rate.

  FIG. 10 is a flowchart illustrating a control example of the cleaning operation of the discharge roller pair 15 in the printer 100. The cleaning procedure of the discharge roller pair 15 will be described along the steps of FIG. 10 while referring to FIGS. 1 to 9 as necessary. Here, water-based ink is used as the ink of the printer 100. The cleaning procedure for the transport roller pairs 13b and 13c shown in FIGS. 3 and 4 is exactly the same.

  When image data is transmitted from a host device such as a personal computer and printing by the printer 100 is started (step S1), the number of prints is counted by the counter 95 in the control unit 90 (step S2). Then, it is determined whether or not printing is completed (step S3). If printing is continued, the process returns to step S2 to continue counting the number of printed sheets.

  When printing is completed (YES in step S3), the control unit 90 calculates the cumulative number of printed sheets N since the end of the previous cleaning operation from the number of printed sheets counted by the counter 95, and the cumulative number of printed sheets N is predetermined. It is determined whether or not the number of printed sheets A is greater than or equal to A (step S4).

  When the cumulative number of printed sheets N is equal to or larger than the number of printed sheets A, the unit body 20a is moved by the urging force of the compression spring 25 by operating the solenoid 27 (the iron core protrudes in FIG. 2 and the iron core is pulled in FIG. 8). It moves in the direction approaching the driven side roller 19b, and the supply roller 21 and the liquid suction roller 23 are pressed against the driven side roller 19b (step S5).

  Cleaning liquid (here, water) in the tank 40 is supplied to the pressed supply roller 21 by the pump 60 (step S6). The supplied water oozes out from the holding layer 39 of the supply roller 21 and wets the surface of the driven roller 15a. The water overflowing from the supply roller 21 accumulates in the supply liquid receiving unit 29, but if it is a small amount of water, it naturally evaporates, so the supply timing is set so that the supply liquid receiving unit 29 does not become full.

  The ink adhering to the surface of the driven roller 15a is absorbed together with the cleaning liquid (water) by the liquid absorbing roller 23 that is pressed downstream of the pressure contact position of the supply roller 21 with respect to the rotation direction of the driven roller 15a. Is done.

  Next, it is determined whether or not the cleaning operation is completed (step S7). If the cleaning operation is continued (YES in step S7), the process returns to step S6 and the cleaning liquid is supplied to the supply roller 21. Continue supplying. When the cleaning operation has been completed (NO in step S7), the solenoid 27 is actuated (the iron core is retracted in FIG. 2 and the iron core is protruded in FIG. 8) to resist the urging force of the compression spring 25. Then, the unit main body 20a moves away from the driven roller 19b, and the supply roller 21 and the liquid absorption roller 23 are separated from the driven roller 19b (step S8). Then, the cumulative number of printed sheets N is reset (step S9), and the process ends.

  According to the above procedure, the driven roller 19b is automatically cleaned when the cumulative number of printed sheets N after the previous cleaning operation exceeds a predetermined number of printed sheets A. The driven roller 19b can be cleaned at a proper timing. Moreover, since unnecessary cleaning operation can be avoided, waste of the cleaning liquid (water) is suppressed, and the service life of the supply roller 21 and the liquid suction roller 23 is extended. As a result, maintenance work such as replacement of the supply roller 21 and the liquid absorption roller 23 and replenishment of water to the tank 40 is reduced, and the running cost of the printer 100 is also reduced.

  Here, the necessity of executing the cleaning operation is determined based on the cumulative number N of prints from the previous cleaning operation, but the necessity of executing the cleaning operation is determined based on the total ink discharge amount from the previous cleaning operation. You may judge no. Specifically, as shown in FIG. 11, the ink discharge amount is calculated for each print image from the print rate calculated based on the image data (step S2), and calculated after the end of printing (YES in step S3). It is determined whether or not the total ink discharge amount obtained by accumulating the added ink discharge amount from the previous cleaning execution is equal to or greater than a predetermined discharge amount B (step S41), and the total ink discharge amount is equal to or greater than the discharge amount B. (YES in step S4), the supply roller 21 and the liquid suction roller 23 are pressed against the driven roller 19b (step S5), and the cleaning operation is started.

  When the cumulative number of printed sheets N reaches a predetermined number of printed sheets A during continuous printing or when the total ink discharge amount reaches a predetermined discharge amount B, the printing is interrupted and the driven roller 19b is cleaned. May be performed. However, if continuous cleaning is interrupted and the cleaning operation is executed, the image forming efficiency is lowered. Therefore, it is preferable to execute the cleaning operation after the continuous printing is completed, as shown in FIGS.

  In addition, when the average printing rate in the printing operation immediately before executing the cleaning operation exceeds a predetermined printing rate, or when printing is continuously performed for a predetermined number of printed sheets or more, at least the suction with the supply roller 21 is performed. The surface of the driven roller 19b can be more effectively cleaned by increasing the contact pressure of any of the liquid rollers 23 to the driven roller 19b or by increasing the rotational speed. In this way, it is possible to suppress and prevent the adhering component remaining on the surface of the driven roller 19b from being completely cleaned and dried and stuck to the surface of the driven roller 19b within the printing stop time. This is preferable because it is possible.

  Further, when there is no printing operation for a predetermined time or more, the cleaning operation may be executed by pressing the supply roller 21 and the liquid absorption roller 23 against the driven roller 19b. Further, when there is no printing operation for a predetermined time or more, the cleaning operation may be performed by pressing the supply roller 21 and the liquid absorption roller 23 against the driven roller 19b in advance at the start of the next printing operation. In this way, when the printing operation is not performed for a long time, it is possible to remove the ink fixed to the driven roller 19b in advance in preparation for the next printing operation.

  In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example in which the uneven layer 31 is formed on the driven roller 19b in the discharge roller pair 15 in which the nip portion is formed by press-contacting the two rollers, the driving roller 19a and the driven roller 19b, has been described. However, when the image forming surface of the paper comes into contact with the driving side roller 19a, the uneven layer 31 may be formed on the driving side roller 19a, and the cleaning unit 20 may be disposed on the driving side roller 19a.

  Moreover, in the said embodiment, although the supply roller 21 and the liquid absorption roller 23 are made to contact or evacuate with respect to the driven side roller 19b using the solenoid 27, it replaces with the solenoid 27 and uses a cam mechanism or a gear mechanism. The supply roller 21 and the liquid absorption roller 23 may be moved.

  In the above embodiment, the line head type ink jet printer 100 using four color inks of yellow, magenta, cyan and black to obtain a full color image has been described. The present invention can also be used for an inkjet recording apparatus provided with the above, an inkjet recording apparatus having a different number of colors, or a serial type inkjet recording apparatus that performs recording while a recording head scans a recording medium.

  The present invention is not limited to a recording medium conveying apparatus having a pair of roller-like conveying members. For example, a belt in which a nip portion is formed by press-contacting a conveying roller and an endless belt wound around a plurality of rollers. The present invention can be applied in exactly the same manner to an image forming apparatus provided with a roller type recording medium conveyance device.

  Further, the present invention is not limited to the ink jet recording apparatus, and can be used for other image forming apparatuses including an image forming unit that forms an image by discharging liquid ink onto a recording medium.

  The present invention can be used in an image forming apparatus that forms an image by ejecting liquid ink onto a recording medium such as a sheet like an ink jet recording apparatus. By using the present invention, an image that can prevent image defects due to adhesion of undried ink to a conveying member such as a pair of conveying rollers disposed on the downstream side of the image forming unit and ink transfer from the conveying member to a subsequent recording medium can be prevented. The forming apparatus can be provided with a simple configuration.

9 Recording unit (image forming unit)
13b, 13c Transport roller pair (recording medium transport device)
15 Discharge roller pair (recording medium transport device)
19a Driving side roller (nip forming member)
19b Follower roller (conveyance roller)
20 Cleaning unit 21 Supply roller 23 Absorption roller 24 Bearing member 27 Solenoid 31 Concavity and convexity layer 34 Central axis (supply roller)
34a Through hole 35 Retaining layer (Liquid absorption roller)
36 Central axis 37 Liquid absorbing layer 40 Tank (cleaning liquid supply mechanism)
50 flow path (cleaning liquid supply mechanism)
60 Pump (cleaning liquid supply mechanism)
90 Control unit (control means)
95 counter (counting means)
97 Calculation unit 100 Printer (image forming apparatus)
P paper (recording medium)

Claims (12)

An image forming unit that forms an image by ejecting liquid ink on a recording medium;
A recording medium including a conveying roller that is in contact with the image forming surface side of the recording medium on which an image is formed in the image forming unit, and a nip forming member that is pressed against the conveying roller to form a nip portion; A recording medium conveying apparatus that conveys a recording medium by rotating the conveying roller and the nip forming member in a state where the medium is sandwiched between the nip portions;
In an image forming apparatus comprising:
A supply roller that supplies the cleaning liquid to the transport roller, and a liquid absorption roller that absorbs the cleaning liquid supplied from the supply roller, and the supply roller and the liquid absorption roller are in contact with the transport roller. A cleaning unit that is selectively disposed at a first position that is driven to rotate and a second position that is spaced apart from the transport roller;
A cleaning liquid supply mechanism for supplying a cleaning liquid to the supply roller;
The supply roller and the liquid absorption roller are moved from the second position to the first position, the cleaning liquid is supplied from the cleaning liquid supply mechanism to the supply roller, and the transport roller is cleaned, Control means for moving the supply roller and the liquid absorption roller to the second position after completion of cleaning of the transport roller;
An image forming apparatus comprising: Having a counting means for accumulating and counting the number of printed sheets;
The control unit moves the supply roller and the liquid absorption roller to the second position when the cumulative number of printed sheets counted since the previous cleaning of the transport roller counted by the counting unit reaches a predetermined number of printed sheets. The image forming apparatus according to claim 1, wherein the image forming apparatus moves to the first position to perform cleaning of the transport roller.   When the printing operation immediately before the cleaning of the transport roller is continuous printing, and the number of continuous prints counted by the counting unit exceeds a predetermined number of prints, the control means The image forming apparatus according to claim 2, wherein a contact pressure with respect to at least one of the liquid rollers is increased. A calculation unit that calculates a printing rate of an image formed by the image forming unit based on image data, and calculates an ink discharge amount from the calculated printing rate;
The control unit moves the supply roller and the liquid absorption roller to the second when the total ink discharge amount calculated by the calculating unit from the previous cleaning of the transport roller has reached a predetermined discharge amount. The image forming apparatus according to claim 1, wherein the transport roller is moved from a position to the first position to perform cleaning of the transport roller.   When the average printing rate of the predetermined number of sheets immediately before executing the cleaning of the transport roller calculated by the arithmetic unit is equal to or greater than a predetermined value, the control unit transports at least one of the supply roller and the liquid absorption roller. The image forming apparatus according to claim 4, wherein a contact pressure with respect to the roller is increased.   The control unit moves the supply roller and the liquid absorption roller from the second position to the first position to perform cleaning of the transport roller when a printing operation is not performed for a predetermined time or longer. The image forming apparatus according to claim 1.   The control means moves the supply roller and the liquid absorption roller from the second position to the first position immediately before the next printing operation when the printing operation is not executed for a predetermined time or longer, and moves the feeding roller. The image forming apparatus according to claim 6, wherein cleaning is performed.   The unevenness layer comprised by the adhesion layer laminated | stacked on the outer peripheral surface of the said conveyance roller and the many particle | grains adhering to this adhesion layer is formed in the said conveyance roller, The thru | or 1 thru | or characterized by the above-mentioned. The image forming apparatus according to claim 7.   The supply roller is composed of a pipe-shaped central axis provided with a plurality of through holes on the outer peripheral surface, and a holding layer that is stacked on the outer peripheral surface of the central axis and holds the cleaning liquid. 9. The image forming apparatus according to claim 1, wherein the cleaning liquid supplied to the inner side of the shaft exudes outward from the through hole and is supplied to the holding layer.   The image forming apparatus according to claim 9, wherein the holding layer is formed of a continuous pore foam or a nonwoven fabric.   The said liquid absorption roller is formed with the center axis | shaft and the liquid absorption layer which consists of a continuous pore foam or a nonwoven fabric laminated | stacked on the outer peripheral surface of this center axis | shaft, The any one of Claim 1 thru | or 10 characterized by the above-mentioned. An image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the supply roller and the liquid absorption roller are detachable.

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