JP2005246727A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which stacking performance of discharge sheets is enhanced through a simple arrangement. <P>SOLUTION: Printing is performed in the mode of small feeding amount even if a mode of large feeding amount is specified in an image forming apparatus having a mode of relatively large feeding amount and a mode of relatively small feeding amount when a solid image is printed at least partially on a sheet, when a solid image is printed on the sheet during first or last scan, under a low humidity environment, under a low humidity low temperature environment, when the print rate for the sheet is not lower than a predetermined value, or when the sheet is carried in the direction intersecting the papermaking direction perpendicularly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of forming an image on a sheet with a recording liquid.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, etc., a recording head (image forming means) composed of a droplet discharge head for discharging recording liquid droplets is used. 2. Description of the Related Art Inkjet recording apparatuses that perform image formation (recording, printing, and printing are also used synonymously) by adhering recording liquid droplets (hereinafter also referred to as ink droplets) to a sheet while being conveyed are known. .

  As a droplet discharge head, a piezo type using an electromechanical conversion element such as a piezoelectric element, or an electrothermal conversion element such as a heating resistor arranged in the discharge is used to generate bubbles by boiling the ink film. A thermal type that discharges ink droplets, an electrostatic type that discharges ink droplets by deforming a diaphragm that forms the wall surface of the discharge chamber with an electrostatic force, and the like are used.

  By the way, in the ink jet recording method, in order to adhere ink to paper, when an image is formed, there is a phenomenon that the paper expands due to moisture contained in the ink, and paper fibers on the image forming surface expand to curl the paper. There is a problem that the paper stacking property deteriorates.

  That is, as shown in FIG. 18A, when the recording liquid droplet 502 is ejected from the recording head 501 to form an image on one side of the paper 503, the paper 503 is printed as shown in FIG. When the fibers on the surface expand to form a curl and are discharged onto the discharge tray 504 via the pair of conveying rollers 504 and the pair of discharge rollers 505 as shown in FIG. There is a tendency that jammed paper and the like are sequentially stacked and the paper discharge port 507 is blocked.

In order to solve the problems peculiar to the ink jet recording apparatus that performs image formation with such a recording liquid, for example, as disclosed in Patent Document 1, the time until the ink is dried is determined by temperature, humidity, and printing rate. It is known that the conveyance of the paper after the image formation is temporarily stopped until the drying time elapses, and the paper is discharged after the drying time elapses to prevent the paper from being discharged in a curled shape. Yes.
JP-A-8-267846

Further, as disclosed in Japanese Patent Application Laid-Open No. H10-228688, the hot air blowing means capable of adjusting the air volume for blowing hot air on the recording paper, and the air volume of the hot air blowing means are controlled according to the dot density of the image data to be printed. A device having an air flow control means is also known.
Japanese Patent Laid-Open No. 11-179889

  However, in the apparatus disclosed in Patent Document 1, since the paper is temporarily stopped, the user may misunderstand that a jam has occurred. In addition, the provision of a means for blowing hot air like the device disclosed in Patent Document 2 has a problem that the size of the device is increased.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus having a simple configuration and improved sheet discharge stackability.

  In order to solve the above-described problem, an image forming apparatus according to the present invention has a plurality of modes in which a single sheet feed amount is relatively different, and a mode with a small feed amount even when a mode with a large feed amount is designated. The configuration is such that printing can be performed.

  Here, when printing is performed in a mode with a small feed amount even when a mode with a large feed amount is designated, when printing a solid image on at least a part of the paper, a solid image is printed in the first scan or the last scan on the paper. When printing an image, in a low humidity environment, in a low humidity and low temperature environment, when the printing rate for the paper is greater than or equal to a predetermined value, or when transporting the paper in a direction perpendicular to the perforated direction It is preferable that The recording liquid is preferably a pigment-based ink. Furthermore, it is preferable that the mode with a large feed amount is a high-speed print mode, and the mode with a small feed amount is a high-quality print mode.

  The image forming apparatus according to the present invention is configured to be capable of intermittently transporting paper after image formation.

  Here, when the paper after image formation is transported intermittently, even when a mode with a large feed amount is specified, printing with a mode with a small feed amount prints a solid image on at least a part of the paper. When printing a solid image in the first scan or the last scan of the paper, in a low humidity environment, in a low humidity and low temperature environment, when the printing rate for the paper is a predetermined value or more, When transporting in a direction perpendicular to the perforated direction, it is preferably any one of them. The recording liquid is preferably a pigment-based ink.

  The image forming apparatus according to the present invention is configured to send the paper after image formation to the double-sided conveyance path for double-sided printing even during single-sided printing.

  Here, when the paper is fed into the double-sided conveyance path by single-sided printing, it is preferable to display that the paper is being dried.

  The image forming apparatus according to the present invention has a plurality of modes with relatively different sheet feed amounts at one time, and can perform printing in a mode with a small feed amount even when a mode with a large feed amount is designated. Therefore, when curling is likely to occur on the paper, the feeding mode can be reduced to increase the drying time, and the paper discharge stackability can be improved with a simple configuration.

  According to the image forming apparatus of the present invention, the paper after image formation can be transported intermittently. Therefore, when curling is likely to occur on the paper, the paper can be transported intermittently to increase the drying time, and the simple configuration Thus, the paper discharge stackability can be improved.

  According to the image forming apparatus of the present invention, since the paper after image formation is sent to the double-sided conveyance path for double-sided printing even when single-sided printing is performed, if the paper tends to be curled, the double-sided conveyance path is used to dry time. The paper discharge stacking property can be improved with a simple configuration.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. A first embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram illustrating the overall configuration of the image forming apparatus, FIG. 2 is a plan explanatory diagram of an image forming unit and a sub-scanning conveyance unit of the apparatus, and FIG. 3 is a perspective explanatory diagram of a carriage portion of the apparatus. 4 is a perspective explanatory view of an ink supply system for the head of the apparatus, FIG. 5 is an explanatory view of a part of the sub-scanning conveyance section and the discharge conveyance section of the apparatus, and FIG. It is explanatory drawing of a set direction.

  This image forming apparatus has an image forming part (means) 2 for forming an image, a sub-scanning conveying part (means) 3, etc. in the inside (enclosure) of the apparatus main body 1. The paper 5 is fed one by one from the paper feed unit (means) 4 provided, and the paper 5 is conveyed by the image forming unit 2 while the sub-scanning conveying unit 3 conveys the paper 5 at a position facing the image forming unit 2. After forming (recording) a desired image by ejecting liquid droplets on the sheet, normally, in the case of single-sided printing, on the sheet discharge tray 8 formed on the upper surface of the apparatus main body 1 through the sheet discharge conveyance unit (means) 7. In the case of double-sided printing, the paper 5 is discharged and sent from the middle of the paper discharge conveyance unit 7 to the double-side unit 10 provided at the bottom of the apparatus main body 1 to perform switchback conveyance and again to the sub-scanning conveyance unit 3. The paper is fed to form images on both sides, and then discharged onto the paper discharge tray 8.

  The image forming apparatus also has an image reading unit (scanner) for reading an image above the discharge tray 8 above the apparatus main body 1 as an input system for image data (print data) formed by the image forming unit 2. Part) 11. The image reading unit 11 includes a scanning optical system 15 including an illumination light source 13 and a mirror 14 and a scanning optical system 18 including mirrors 16 and 17. The scanned document image is read as an image signal by the image reading element 20 disposed behind the lens 19, and the read image signal is digitized and subjected to image processing, and the image-processed print data is printed. be able to.

  Further, this image forming apparatus uses an information processing apparatus such as an external personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera as an input system for image data (print data) formed by the image forming unit 2. For example, print data including image data from the host side can be received via a cable or a network, and the received print data can be processed and printed.

  Here, as shown in FIG. 2, the image forming unit 2 of the image forming apparatus is guided by a carriage guide 21 and moved on a carriage 23 that can move in a main scanning direction (a direction perpendicular to the sheet conveying direction). A recording head 24 that discharges droplets of each color is mounted, the carriage 23 is moved in the main scanning direction, and the paper 5 is fed from the recording head 24 in the paper transporting direction (sub-scanning direction) by the sub-scanning transport unit 3. It is a shuttle type in which droplets are ejected to form an image. A configuration using a line-type head can also be used.

  The recording head 24 has two droplet discharge heads that discharge black (Bk) ink, and one droplet discharge that discharges cyan (C) ink, magenta (M) ink, and yellow (Y) ink. The head is composed of a total of five droplet discharge heads (hereinafter simply referred to as “heads”), and each color ink is supplied from a sub tank 25 mounted on the carriage 23 as shown in FIG.

  Ink is replenished and supplied to the sub tank 25 from a color ink cartridge 26 (FIG. 1) which is a main tank detachably mounted in the apparatus main body 1 via a tube 28 as shown in FIG. . In addition to the recording head 24 that discharges ink droplets, a recording head that discharges a fixing treatment liquid (fixing ink) that reacts with the recording liquid (ink) to improve the fixing property of the ink can be provided.

  The recording head 24 uses a piezoelectric element as a pressure generating means (actuator means) for pressurizing the ink in the ink flow path (pressure generation chamber) to deform the vibration plate that forms the wall surface of the ink flow path. A so-called piezo type that discharges ink droplets by changing the volume in the flow channel, or discharges ink droplets with a pressure generated by heating the ink in the ink flow channel using a heating resistor to generate bubbles. The so-called thermal type, the diaphragm that forms the wall surface of the ink flow path and the electrode are placed opposite to each other, and the diaphragm is deformed by the electrostatic force generated between the vibration plate and the electrode, thereby the ink flow path inner volume It is possible to use an electrostatic type or the like that discharges ink droplets by changing the above.

  Further, a maintenance / recovery mechanism (hereinafter referred to as “sub-system”) 127 including a head cleaning device for maintaining and recovering the state of the nozzles of the recording head 24 is provided in a non-printing area on one side in the scanning direction of the carriage 23. It is arranged. The subsystem 127 includes cap members 128a, 128b, 128c, 128d, and 128d for capping the nozzle surfaces of the heads of the recording head 24, a wiper blade 129 for wiping the nozzle surfaces, and the like. 128b are held in the same cap holder 128A, cap members 128c and 128d are held in the same cap holder 128B, and cap member 128e is held in the cap holder 128C.

  As shown in FIG. 5, the sub-scanning conveyance unit 3 is a belt conveyance unit that performs conveyance in the lateral direction in which the sheet 5 is electrostatically attracted and conveyed in a direction perpendicular to the separation direction. Endlessly spanned between a transport roller 32 that is a driving roller and a driven roller (tension roller) 33 for transporting the fed paper 5 by changing the transport direction by approximately 90 degrees and facing the image forming unit 2. And a charging roller 34 to which a high voltage is applied from a high voltage power source (not shown) for charging the surface of the conveyor belt 31.

  Here, the belt conveying means by the conveying belt 31 and the charging roller 34 is a static conveying device in which the sheet 5 to which the recording liquid adheres is surely adsorbed to the conveying belt 31 without floating from the belt surface even when the sheet 5 is conveyed in the horizontal direction. The power can be obtained. This is different from the configuration in which only the conveyance in the longitudinal direction of the sheet is allowed while using the conveyance belt and the charging roller as before.

  The sub-scanning conveyance unit 3 also includes a guide member (platen) 35 that guides the conveyance belt 31 in a region opposite to the image forming unit 2 and a pressing member that presses the paper 5 against the conveyance belt 31 at a position facing the conveyance roller 32. A roller 36 and a pressure roller 37 that presses the sheet 5 against the conveying belt 31 at a position facing the platen 35 on the upstream side of the carriage 23 are provided.

  The conveyance belt 31 of the sub-scan conveyance unit 3 is rotated in the belt conveyance direction (sub-scanning direction) in FIG. 2 by rotating the conveyance roller 32 from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133. It is configured to do.

  The transport belt 31 includes, for example, a surface layer that is a sheet adsorption surface formed of a pure resin material that is not subjected to resistance control, such as ETFE pure material, and a back layer that is subjected to resistance control using carbon with the same material as the surface layer. It has a two-layer structure (medium resistance layer, earth layer).

  Further, on the downstream side of the sub-scanning conveyance unit 3, as a part of the paper discharge unit 7, separation is a separation unit for separating the paper 5 on which the image is formed and conveyed by the conveyance belt 31 from the conveyance belt 31. The claw 71, the paper discharge roller 72 for contacting and discharging the lower side of the separated paper 5, the spur 73 facing the paper discharge roller 72, and the paper 5 fed from the transport belt 31 are A spur 78 having a diameter smaller than that of the spur 73 facing the paper discharge roller 72 is disposed above and on the upstream side of the separation claw 71 as a lift suppression means for suppressing the lift.

  As shown in FIG. 6, the paper feed unit 4 can be inserted and removed from the front side of the apparatus main body 1, and a paper feed cassette 41 that stacks and stores a large number of papers 5, and the paper 5 in the paper feed cassette 41. A sheet feeding roller 42 and a friction pad 43 for separating and feeding the sheets one by one are provided.

  In the paper feed cassette 41, it is possible to set the paper 5A in the direction to be conveyed in the horizontal direction. For example, A4 size paper can be set in a direction in which the cassette insertion direction is vertically long, and the setting of the paper in the direction of the horizontal eye direction conveyance is not prohibited in this image forming apparatus.

  As described above, the paper feed cassette 41 is provided in the paper feed cassette 41 by including the paper feed cassette 41 as a paper feed unit that can be set in a direction perpendicular to the direction of the paper separation and the direction of conveyance by the conveyance belt 31 constituting the belt conveyance unit. It is also possible to set paper in the horizontal direction, and it is possible to set paper of the same size in the same cassette with both vertical and horizontal eyes, improving usability.

  Then, by making the insertion direction of the paper feed cassette 41, which is the paper feed means, into the apparatus main body 1 and the direction of paper separation, the paper replenishment operation on the front surface of the apparatus main body 1 becomes possible, which is convenient. Will improve.

  In addition, the paper feed unit 4 includes a manual feed tray 46 for loading and storing the paper 5, a manual feed roller 47 for feeding the paper 5 one by one from the manual feed tray 46, and a lower side of the apparatus main body 1. A transport roller 48 for transporting paper 5 fed from an optional paper feed cassette or duplex unit 10 and a transport roller 49 for feeding the fed paper 5 to the sub-scanning transport unit 3 are provided. ing. In addition, it is possible to perform the setting in the direction in which the conveyance is in the horizontal direction even with manual paper feeding.

  As shown in FIGS. 5 and 7, the paper discharge conveyance unit 7 includes a separation claw 71 that is a separation unit for separating the paper 5 on which the image is formed and conveyed by the conveyance belt 31 from the conveyance belt 31. A paper discharge roller 72 that contacts and conveys the lower side of the separated paper 5, a spur 73 that opposes the paper discharge roller 72, and is sent out between the paper discharge roller 72 and the spur 73 as shown in FIG. 1. A pair of discharge conveyance rollers 74, 75, and 76 that convey the sheet 5 and a pair of discharge rollers 77 that send the sheet 5 to the discharge tray 8 are provided. A conveyance path for discharging the paper 5 to the paper discharge tray 8 is a discharge conveyance path 70.

  The duplex unit 10 receives a sheet 5 conveyed by being guided by the branch plate 60 from the side surface of the apparatus main body 1 and conveys the sheet 5 downward, and includes a vertical conveyance unit 101a that constitutes a vertical duplex conveyance path 90c, and a vertical duplex conveyance path 90c. Subsequently, a horizontal feeding conveyance path 90a that conveys in the horizontal direction and a horizontal conveyance section 101b that constitutes a switchback conveyance path 90b are integrally provided.

  The vertical double-sided conveyance path 90c is provided with a double-sided entrance roller pair 91 for conveying the fed paper 5 downward and a conveyance roller pair 92 for sending it out to the horizontal taking-in conveyance path 90a. 93, and the switchback conveyance path 90b includes a double-sided exit roller 94 composed of a reverse roller for reversing and refeeding the sheet 5 fed from the take-in conveyance path 90a and three double-sided conveyance roller pairs 95. Yes.

  Further, the branch plate 96 for switching between the conveyance path of the sheet 5 from the take-in conveyance path 90a to the switchback conveyance path 90b and the conveyance path for refeeding from the switchback conveyance path 90b to the conveyance roller pair 48 can be swung. Provided. The branch plate 96 can swing between a switchback side position shown by a solid line in FIG. 1 and a refeeding side position shown by a broken line.

  Note that the branch plate 60 is disposed at the discharge side position indicated by the solid line in FIG. 1 in order to switch the conveyance direction of the sheet 5 to the discharge tray 8 direction and the duplex conveyance unit 10 side on the downstream side of the discharge conveyance roller pair 75. The paper 5 can be swung between the double-sided position shown in the broken line, and when the paper 5 is in the paper discharge side position, the paper 5 is guided to the paper discharge roller pair 76 side. Guide to pair 91 side.

  Although not shown, an image start sensor for detecting the leading edge of the paper 5 on the upstream side in the paper conveyance direction of the image forming unit 2 and an image end for detecting the trailing edge of the paper 5 on the downstream side in the paper conveyance direction are also shown. A sensor is provided.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. The figure is a schematic block diagram of the control unit.
The control unit 200 includes a CPU 201 that controls the entire image forming apparatus, a ROM 202 that stores programs executed by the CPU 201 and other fixed data, a RAM 203 that temporarily stores image data (print data), and the like. Non-volatile memory (NVRAM) 204 for holding data even while the power is cut off, image processing for performing various signal processing and rearrangement on image data, and other input / output signals for controlling the entire apparatus An ASIC 205 for processing and a scanner control unit 206 for performing image reading by the image reading unit 11 and data processing of the read image are provided.

  The control unit 200 also has an I / F 207 for transmitting and receiving data and signals used when receiving data from an external device, and a head drive control for driving and controlling the recording head 21 of the image forming unit 2. Unit 208 and head driver 209, main scanning motor 121 for main scanning of carriage 23, sub-scanning motor 131 for rotating conveying roller 32 by rotating conveying roller 32, paper feeding motor 141, paper discharging motor 151, double-sided conveying Motor driving units 211 to 215 including motor drivers for independently driving various motors (drive sources) such as the motor 161 are provided.

  Also, a sheet feeding electromagnetic clutch for rotationally driving the sheet feeding roller 43, a branching plate solenoid for swinging and displacing the branching plate 60 between the paper discharge position and the double-sided position, and the branching plate 96 with a switchback position and a refeeding position. A clutch drive unit 216 for driving a branch plate solenoid or the like (which is referred to as a “clutch 171”), a high voltage circuit 217 for applying a high voltage to the charging roller 34, and the like. Yes.

  The control unit 200 further includes an environmental sensor 218 for detecting environmental conditions (humidity and temperature), an I / O 221 for capturing detection signals of various sensors such as the image start sensor and the image end sensor described above, An operation panel 222 for inputting and displaying information necessary for this apparatus is connected.

  When the original image is read by the image reading unit 2, the control unit 200 processes the read image and stores it in a buffer in the scanner control unit 206. In addition, when print data or the like is received from an external host such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, or an imaging apparatus such as a digital camera via the external I / F 207, the I / F 207 Store in the included receive buffer.

  Then, the CPU 201 reads and analyzes the image data from the scanner control unit 206 and the I / F 207, performs necessary image processing, data rearrangement processing, and the like in the ASIC 205, and transfers the print image data to the head drive control unit 208. To do. The generation of dot pattern data for outputting an image based on data from the outside may be performed by storing font data in the ROM 202, for example, or the image data is converted into bitmap data by a printer driver on the external host side. The image may be developed and transferred to the image forming apparatus.

  Upon receiving image data (dot pattern data) corresponding to one line of each recording head 24, the head drive control unit 208 transfers the dot pattern data for one line to the head driver 209, and the head driver 288 performs dot printing. Based on the pattern data, a required drive waveform is selectively applied to the actuator means of the recording head 24 and driven, and droplets are ejected from the required nozzles of each recording head 24.

  In the image forming apparatus configured as described above, the sheets 5 are fed one by one from the sheet feeding unit 4 or the duplex unit 10 and are pressed against the transport belt 31 by the pressing roller 36 to change the transport direction by approximately 90 °. .

  On the other hand, the high-pressure conveying belt 31 is charged with a predetermined charging pattern by contacting the charging roller 34 to which a high applied voltage is applied while being driven in a circular manner. In other words, the polarity of the output of the high-voltage circuit 217 applied to the charging roller 34 is switched at a predetermined time interval to charge the conveying belt 31 at a predetermined charging pitch at which the polarity changes alternately.

  When the paper 5 is fed onto the conveyance belt 31 charged to this high potential, the inside of the paper 5 is in a polarized state, and the charge having the opposite polarity to the charge on the conveyance belt 31 comes into contact with the conveyance belt 31 of the paper 5. The charge on the transporting belt 31 and the charge on the transported paper 5 are electrostatically attracted to each other, and the paper 5 is electrostatically attracted to the transport belt 31. In this way, the sheet 5 strongly adsorbed to the transport belt 31 is calibrated for warpage and unevenness, and a highly flat surface is formed.

  Here, even when the paper 5 is transported in the lateral direction in which the direction of the separation is perpendicular to the transport direction, the transport belt 31 and the corresponding belt 5 are attracted to the transport belt 31 with a strong suction force. The charge amount of the charging roller 34 is set. As a result, it is possible to form an image while transporting the paper 5 in the horizontal direction in which the separation direction is orthogonal to the transport direction, and the printing speed can be improved and the paper 5 can be It can be set in either the eye or the side direction, improving usability.

  That is, the ink jet recording method has a particular problem of paper cockling. For this reason, as shown in FIG. 19A, when the paper 5B is transported in the longitudinal direction in which the direction of the paper 5B coincides with the transport direction, even if cockling occurs, as shown in FIG. Since the undulation is only performed in the direction (main scanning direction) orthogonal to the conveyance direction, the overall undulation amount is relatively small, and contact between the nozzle surface of the head and the paper 5B can be avoided.

  On the other hand, as shown in FIG. 20 (a), when the paper 5A is transported in the horizontal direction in which the direction of the perforation and the transport direction are orthogonal to each other, as shown in FIG. Because of the cockling, the sheet 5A is largely curled in the conveying direction, and the possibility that the nozzle surface of the head and the sheet come into contact with each other becomes extremely high.

  For this reason, in the conventional ink jet recording apparatus, it has not been possible to form an image while conveying the paper 5 in the horizontal direction in which the direction of the separation is perpendicular to the conveyance direction. Image formation by conveyance is also possible.

  In this way, the sheet 5 is electrostatically attracted to the conveyance belt 31, and the sheet 5 is conveyed (sent) in the sub-scanning direction by the circumferential movement of the conveyance belt 31.

  Therefore, by driving the recording head 24 according to the image signal while moving the carriage 23, ink droplets are ejected onto the stopped paper 5 to record one line, and when the recording for one line is completed. Then, the paper 5 is intermittently conveyed so that the paper 5 is fed by one line and the next line is recorded, and an image is formed on the paper 5. Upon receiving a recording end signal or a signal that the trailing edge of the paper 5 has reached the recording area, the recording operation is finished, and the paper 5 is sent to the paper discharge tray 8 or the duplex unit 10.

  Here, as described above, when the paper 5 is electrostatically attracted and transported in the horizontal direction by the transport belt 31, the paper 5 on which image formation has been completed tends to be curled in the transport direction. Since there is a possibility that the sheet is fed to the charging roller 34 while being adsorbed to the conveyance belt 31 without being separated from the curvature, the separation claw 71 for separating the paper 5 from the conveyance belt 31 is provided and the conveyance belt 31 is forced. The paper 5 is separated. As a result, it is possible to prevent the sheet 5 after the image formation from being sucked and conveyed by the conveyance belt 31 without being discharged.

  In addition, image formation can be performed by the horizontal direction conveyance in which the paper 5 is conveyed in a direction orthogonal to the separation direction by the conveyance belt 31, but when the paper 5 is separated from the conveyance belt 31, the recording is performed because the conveyance is in the horizontal direction. There is a high possibility that the sheet 5 to which the liquid adheres swells (lifts) so as to protrude upward. It has been experimentally confirmed that such a phenomenon does not occur in the vertical direction conveyance but appears in the horizontal direction conveyance. Therefore, a spur 78 is provided to prevent such lifting of the paper 5 so that the image forming surface of the paper 5 does not come into contact with the carriage 23 and is rubbed to cause an image defect.

In this image forming apparatus, pigment-based ink is used as a recording liquid. Specifically, for example, it is as follows.
<Black ink>
KM-9036 (manufactured by Toyo Ink) (self-dispersing pigment) 50% by weight
Glycerin 10% by weight
1,3 butanegio 15% by weight
2-ethyl-1,3-hexanediol 2% by weight
2-pyrrolidone 2% by weight
Surfactant (Specific Example 1-8) 1% by weight
Silicone antifoaming agent KS508 (self-emulsifying type) (manufactured by Shin-Etsu Chemical Co., Ltd.)
0.1% by weight
Residual amount of ion-exchanged water An ink composition having the above formulation was prepared and sufficiently stirred at room temperature, and then filtered through a membrane filter having an average pore size of 1.2 μm to obtain a black ink. This ink had a viscosity in a 22 ° C. environment of about 7 cp.

For the color ink, the polymer solution A is prepared as follows, and the pigment-containing polymer fine particle aqueous dispersion is prepared using the polymer solution A.
(Preparation of polymer solution A)
After sufficiently replacing nitrogen gas in the 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas introduction tube, reflux tube and dropping funnel, 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, Polyethylene glycol methacrylate 4.0 g, styrene macromer 4.0 g and mercaptoethanol 0.4 g were mixed and heated to 65 ° C. Next, 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxylethyl methacrylate, 36.0 g of styrene macromer, 3.6 g of mercaptoethanol, azobismethylvalero A mixed solution of 2.4 g of nitrile and 18 g of methyl ethyl ketone was dropped into the flask over 2.5 hours. After dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 g of azobismethylvaleronitrile was added and further aging was performed for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution having a concentration of 50%.

(Preparation of pigment-containing polymer fine particle aqueous dispersion)
28 g of polymer solution A, C.I. I. 26 g of Pigment Yellow 97, 13.6 g of a 1 mol / L aqueous potassium hydroxide solution, 20 g of methyl ethyl ketone and 13.6 g of ion-exchanged water were sufficiently stirred, and then kneaded using a roll mill. The obtained paste was put into 200 g of ion-exchanged water and sufficiently stirred, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain an aqueous dispersion of yellow polymer fine particles. The average particle size of the polymer fine particles of the dispersion obtained after the centrifugal separation treatment was 80 nm, and the solid content was 20% by weight.

<Yellow ink>
Yellow polymer fine particle dispersion 40% by weight
Glycerin 5% by weight
Diethylene glycol 15% by weight
2,2,4-Trimethyl-1,3-pentanediol 2% by weight
1% by weight of Na salt of surfactant (specific example 2-8)
Silicone defoamer KS531 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1% by weight
Residual amount of ion-exchanged water An ink composition having the above formulation was prepared and sufficiently stirred at room temperature, and then filtered through a membrane filter having an average pore size of 1.2 μm to obtain a yellow ink. This yellow ink had a 22 ° C. ring viscosity of about 5.5 cp.

(Preparation of pigment-containing polymer fine particle aqueous dispersion)
The pigment type is C.I. I. An aqueous dispersion of magenta polymer fine particles was obtained in the same manner except that the pigment red 122 was used. The average particle size of the polymer fine particles of the dispersion obtained after the centrifugal separation treatment was 150 nm, and the solid content was 20% by weight.

<Magenta ink>
Dispersion of magenta polymer fine particles 50% by weight
Glycerin 5% by weight
Diethylene glycol 15% by weight
2,2,4-Trimethyl-1,3-pentanediol 2% by weight
1% by weight of Na salt of surfactant (specific example 2-8)
Silicone defoamer KS531 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1% by weight
Residual amount of ion-exchanged water An ink composition having the above formulation was prepared and sufficiently stirred at room temperature, and then filtered through a membrane filter having an average pore diameter of 1.2 μm to obtain an ink. This magenta ink had a viscosity of about 5.5 cp in a 22 ° C. environment.

(Preparation of pigment-containing polymer fine particle aqueous dispersion)
The pigment type is C.I. I. An aqueous dispersion of cyan polymer fine particles was obtained in the same manner except that Pigment Blue 15: 3 was used. The average particle size of the polymer fine particles of the dispersion obtained after the centrifugal separation treatment was 115 nm, and the solid content was 20% by weight.

<Cyan ink>
Cyan polymer fine particle dispersion 40% by weight
Glycerin 5% by weight
Diethylene glycol 15% by weight
2,2,4-Trimethyl-1,3-pentanediol 2% by weight
1% by weight of Na salt of surfactant (specific example 2-7)
Silicone defoamer KS531 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1% by weight
Residual amount of ion-exchanged water An ink composition having the above formulation was prepared and sufficiently stirred at room temperature, and then filtered through a membrane filter having an average pore size of 1.2 μm to obtain an ink. This cyan ink had a viscosity of about 5.5 cp in a 22 ° C. environment.

  Such a pigment-based ink quickly penetrates into the paper, whereas drying takes time. Therefore, the present invention is more effective when applied to an image forming apparatus using the pigment-based ink. It is.

Next, sub-scanning (paper feed) control in this image forming apparatus will be described with reference to FIG.
First, in this image forming apparatus, as shown in FIG. 8A, a standard (high-speed printing) mode in which the recording head 24 is main-scanned and printed while feeding the paper 5 at a feed amount A, and FIG. As shown in FIG. 3, the print head 24 is main-scanned and printed while the paper 5 is fed at a feed amount B (B <A). Here, the high-speed print mode with the feed amount A is used as it is as a mode with a relatively large feed amount, and the high-quality print mode with the feed amount B is used as it is as a mode with a relatively small feed amount.

  As shown in FIG. 9, the current mode specified when printing is performed (meaning including default specification) is a mode with a relatively large feed amount (high-speed print mode with a feed amount A). In this case, the mode change condition establishment flag is checked to determine whether or not the mode change condition is established. If the mode change condition is established, the paper feed amount is set to a mode with a relatively small feed amount. Change and set to (High-quality printing mode for feed amount B).

  Here, although only the feed amount of the paper 5 is changed from the feed amount A in the high-speed print mode to the feed amount B, the print mode itself is not changed, but the print mode can also be changed.

Next, different examples of determining whether the mode change condition is satisfied will be described with reference to FIGS.
First, the first example will be described with reference to FIG. 10. It is determined whether or not a solid image such as a photographic image is included in the image printed on the paper 5, and when the solid image is included, the solid image is the first one. Whether it is 1 line (area printed in the first main scan) or the last line (area printed in the last main scan), and if the solid image is included in the first line or the last line, change condition Set the establishment flag.

  That is, when a solid image is printed, the amount of recording liquid adhering to the paper increases. Therefore, if the paper 5 is fed with a large feed amount A, the recording liquid is likely to be discharged and curled while it is not drying. Therefore, even when a large feed amount A is specified, the time is changed to a small feed amount B to increase the drying time, and the paper 5 is prevented from being discharged while being curled.

  In this case, the mode can be changed to a mode in which the feed amount is reduced if a solid image is included even partially. Here, the feed amount is reduced when the first line or the last line contains a solid image, but when the first line or the last line contains a solid image, it becomes curled. It is based on easy things. In this way, curling can be reduced while reducing the case where the feed amount is changed as small as possible.

  Here, a case where a solid image is partly included (including the case where the entire surface is a solid image) is taken as an example, but the mode can be changed only when the entire surface is a solid image.

  Next, a second example will be described with reference to FIG. 11. Based on the detection result of the environmental sensor 218, it is determined whether the environmental humidity is a predetermined value (for example, 15%) or less, and the environmental humidity is a predetermined value. When the environmental temperature is equal to or lower than the predetermined value (for example, 10 ° C.), it is determined whether or not the environmental temperature is equal to or lower than the predetermined value.

  That is, since the paper 5 is dry in a low humidity environment, the landed recording liquid is likely to penetrate rapidly and become curled. Therefore, even when a large feed amount A is specified, the small feed amount B is changed. Thus, the drying time is increased, and the sheet 5 is prevented from being discharged while being curled. In addition, since the recording liquid that has landed on the paper 5 is difficult to dry and curls in a low temperature environment, similarly, even when a large feed amount A is specified, it is changed to a small feed amount B to increase the drying time. 5 is reduced from being discharged while curled. Note that the mode can be changed only in a low humidity and low temperature environment.

  Next, a third example will be described with reference to FIG. 12. It is determined whether or not the conveyance direction of the sheet 5 is the transverse direction conveyance (conveyance in the direction in which the sheet separation direction is orthogonal to the conveyance direction). At the time of conveyance, a change condition satisfaction flag is set.

  That is, as described above, when the conveyance direction of the sheet 5 is the horizontal direction conveyance, the sheet 5 is easily curled. Therefore, when the conveyance amount by the electrostatic attraction force is being performed and the large feed amount A is specified. However, by changing the feed amount B to a small amount to save time, the paper 5 is reduced from being curled and discharged. In this case, by reducing the feed amount, the increase in the recording speed obtained by enabling the conveyance in the lateral direction is reduced. Therefore, the first example, the second example described above, or the first described below. Combination with 4 examples is preferred.

  Next, the fourth example will be described with reference to FIG. 13. It is determined whether or not the printing rate for the paper 5 is equal to or greater than a predetermined value (50%). Set the flag.

  That is, even when the image formed on the paper 5 is not a solid image, if the printing rate (image area / image formable area) increases, the amount of recording liquid adhering to the paper increases. When the paper 5 is fed, there is a high possibility that the recording liquid is discharged and curled while it is not drying. Therefore, even when a large feed amount A is specified, the feed time is changed to a small feed amount B. Earn and reduce the curling of the paper 5.

  In this way, even when a large feed amount is specified based on the type of image to be formed on the paper, environmental conditions, the relationship between the paper perforation direction and the conveyance direction, the printing rate for the paper, etc. By changing and feeding the paper, it is possible to reduce the curling of the paper and improve the paper discharge stackability.

Next, a second embodiment of the present invention will be described with reference to the timing charts of FIGS. 14 shows an example of a standard mode in which paper feeding for paper discharge is continuously performed, and FIG. 15 shows an example of a mode in which paper feeding for paper discharge is intermittently performed.
In the above embodiment, the time is increased by changing the paper feed amount during image formation. However, in this embodiment, the time until the paper after image formation is discharged to the paper discharge tray. The paper stacking property is improved by reducing the curling by earning.

  That is, in the normal case, as shown in FIGS. 14A and 14B, the sub-scanning driving is performed before the main scanning driving, and the droplet discharge from the recording head 24 and the paper by the conveying belt 31 as described above. 5 (sub-scanning), after printing (end of image formation) is started, skip conveyance of the paper 5 is started, and the conveyance belt 31 is continuously driven, as shown in FIG. The paper discharge roller 72 of the paper discharge unit 7, the paper discharge conveyance roller pairs 74 to 76, and the paper discharge roller pair 77 are continuously driven to discharge the paper 5. The sub-scanning motor 131 stops at an earlier stage than the paper discharge motor 161 if there is no next sheet.

  On the other hand, when the mode change condition (same as in the first embodiment) is satisfied, as shown in FIG. 15, after the end of printing (end of image formation), as shown in FIG. In addition, the conveying belt 31 is intermittently driven, and as shown in FIG. 5C, the paper discharge roller 72 of the paper discharge unit 7 and the roller pairs 74 to 77 are intermittently driven to form an image. The paper 5 that has been completed is transported intermittently for paper discharge.

  As a result, the time T2 from the end of image formation to the end of paper discharge becomes longer than the time T1 when the paper 5 is continuously conveyed (T2> T1), so the time of (T2-T1) is earned as the drying time. Therefore, the curling of the paper is reduced, and the paper discharge stackability is improved.

Next, a third embodiment of the present invention will be described with reference to FIG.
In this embodiment, even in the case of single-sided printing, when the mode change condition is satisfied, the paper 5 after completion of single-sided printing is sent to the double-sided unit 10 and the paper 5 is fed again using the same transport path as in double-sided printing. (Image formation is not performed on the other side.) The paper is then discharged onto the paper discharge tray 8.

  In this case, since the time until the paper 5 after single-sided printing is discharged to the paper discharge tray 8 is the same as that for double-sided printing, the display provided on the operation panel 222 or the like is turned on or blinked for the user. For example, the user is not misunderstood that a jam has occurred by performing a display indicating that it is drying.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
In this embodiment, the discharge start timing after the end of printing (after the end of image formation) is delayed, that is, the discharge is started after the drying time T3 has elapsed, and the mark ends when the mode change condition is satisfied. In this example, the conveyance of the rear sheet 5 is temporarily stopped. At this time, the user may misunderstand the jam. Therefore, as in the third embodiment, a display indicating that the sheet is being dried is displayed. By doing so, the user is not misunderstood as jamming.

1 is a schematic configuration diagram illustrating an overall configuration of a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is an explanatory plan view of an image forming unit and a sub-scanning conveyance unit of the apparatus. It is a perspective explanatory view of a carriage portion of the same device. It is a perspective explanatory view of an ink supply system for the head of the same device. It is explanatory drawing of a part of sub-scanning conveyance part and paper discharge conveyance part of the same apparatus. It is explanatory drawing of the paper feed cassette and paper set direction of the same apparatus. It is a schematic block diagram explaining the structure of the control part of the apparatus. FIG. 6 is an explanatory diagram for explaining modes of different sheet feeding amounts in the apparatus. FIG. 6 is a flowchart for explaining sub-scanning (paper feed) control in the apparatus. FIG. 6 is a flowchart for explaining a first example of a mode change condition establishment confirmation process. It is a flowchart with which it uses for description of the 2nd example of a mode change condition establishment confirmation process. It is a flowchart with which it uses for description of the 3rd example of a mode change condition establishment confirmation process. It is a flowchart with which it uses for description of the 4th example of mode change condition establishment confirmation processing. It is explanatory drawing with which it uses for description of the sheet | seat feed and discharge delivery in the standard mode with which it uses for description of 2nd Embodiment of this invention. FIG. 6 is an explanatory diagram for explaining sheet feeding and sheet discharging when a mode change condition is satisfied. It is a flowchart with which it uses for description of 3rd Embodiment of this invention. It is explanatory drawing with which it uses for description of the sheet | seat feed and discharge delivery in case the mode change conditions with which it uses for description of 4th Embodiment of this invention are satisfied. FIG. 10 is an explanatory diagram for explaining that a sheet is curled and closes a sheet discharge port. It is explanatory drawing with which it uses for description in the case of conveying a sheet | seat in a longitudinal direction. It is explanatory drawing with which it uses for description in the case of conveying a sheet | seat in a horizontal direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Apparatus main body 2 ... Image formation part 3 ... Sub-scanning conveyance part 4 ... Paper feed part 5 ... Paper 7 ... Paper discharge conveyance part 8 ... Paper discharge tray 10 ... Duplex unit 11 ... Image reading part 23 ... Carriage 24 ... Recording head DESCRIPTION OF SYMBOLS 31 ... Conveyance belt 32 ... Conveyance roller 34 ... Charging roller 71 ... Separation claw 72 ... Discharge roller 74-76 ... Discharge conveyance roller pair 77 ... Discharge roller pair

Claims (19)

  In an image forming apparatus that includes a recording head that discharges droplets of a recording liquid and forms an image by discharging droplets from the recording head while intermittently transporting the sheet, the sheet feed amount is relatively different. An image forming apparatus having a plurality of modes and capable of printing in a mode with a small feed amount even when a mode with a large feed amount is designated.   2. The image forming apparatus according to claim 1, wherein when a solid image is printed on at least a part of the sheet, printing is performed in a mode in which the feed amount is small.   3. The image forming apparatus according to claim 2, wherein printing is performed in a mode in which the feeding amount is small when a solid image is printed in the first scan or the last scan of the paper.   4. The image forming apparatus according to claim 1, wherein printing is performed in a mode in which the feed amount is small in a low humidity environment.   5. The image forming apparatus according to claim 4, wherein printing is performed in a mode in which the feed amount is small in a low temperature environment.   6. The image forming apparatus according to claim 1, wherein printing is performed in a mode in which the feed amount is small when a printing rate on a sheet is a predetermined value or more.   7. The image forming apparatus according to claim 1, wherein printing is performed in a mode in which the feeding amount is small when the sheet is conveyed in a direction perpendicular to the perforated direction.   8. The image forming apparatus according to claim 1, wherein the recording liquid is a pigment-based ink.   9. The image forming apparatus according to claim 1, wherein the mode with a large feed amount is a high-speed print mode, and the mode with a small feed amount is a high-quality print mode.   In an image forming apparatus that includes a recording head for discharging recording liquid droplets and forms an image by discharging droplets from the recording head while intermittently transporting the paper, the paper after image formation is transported intermittently. An image forming apparatus.   11. The image forming apparatus according to claim 10, wherein when the solid image is printed on at least a part of the sheet, the sheet after the image formation is intermittently conveyed.   12. The image forming apparatus according to claim 11, wherein the sheet after the image formation is intermittently conveyed when a solid image is printed in the first scan or the last scan on the sheet.   13. The image forming apparatus according to claim 10, wherein the sheet after image formation is intermittently conveyed in a low humidity environment.   14. The image forming apparatus according to claim 13, wherein the image-formed sheet is intermittently conveyed in a low temperature environment.   15. The image forming apparatus according to claim 10, wherein the image-formed sheet is intermittently conveyed when a printing rate on the sheet is a predetermined value or more.   17. The image forming apparatus according to claim 10, wherein the sheet after the image formation is intermittently conveyed when the sheet is conveyed in a direction perpendicular to the perforated direction. apparatus.   17. The image forming apparatus according to claim 10, wherein the recording liquid is a pigment-based ink.   In an image forming apparatus that includes a recording head that discharges droplets of recording liquid and forms an image by discharging droplets from the recording head while intermittently transporting a sheet of paper. An image forming apparatus characterized by feeding the paper after the image formation to a double-sided conveyance path for double-sided printing.   19. The image forming apparatus according to claim 18, wherein when the sheet is fed to a duplex conveying path by the single-sided printing, a display indicating that the sheet is being dried is displayed.

Images