JP2012121147A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an adhesive residue of bubbles to an upstream side surface and a downstream side surface of a filter member arranged in a supply path from a head tank to a head.SOLUTION: In the head tank 29, a liquid storage part 211 is arranged in a tank case 210 for storing ink supplied from a main tank as a filter upstream chamber, a filter member 212 is disposed at a lower part of the liquid storage part 211 for removing foreign substances in the ink in the perpendicular direction, a supply path 215 communicating from a downstream side chamber of the filter member to a supply path 205 of a recording head 24, and the supply path 215 from the downstream chamber of the head tank 29 and the supply path 205 of the recording head 24 are formed in the oblique upward direction.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a recording head that discharges droplets.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously). Serial type image forming device that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  In the present application, “image forming apparatus” means an apparatus for forming an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. "Image formation" is not only the application of images with meanings such as characters and figures to the medium, but also the addition of images with no meaning such as patterns to the medium (simply applying droplets to the medium) Also means landing). The term “ink” is not limited to what is referred to as ink, but is used as a general term for all liquids that can perform image formation, such as recording liquid, fixing processing liquid, liquid, and resin. . The term “paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper, recording It is used as a general term for what includes what is called paper. In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  By the way, in a liquid ejection type image forming apparatus, if foreign matter or bubbles are mixed in the liquid ejection head, droplet ejection bends or droplet ejection defects occur. For example, a head tank that supplies liquid to the recording head ( Ink is supplied from the (sub tank) to the recording head via a filter member.

  For example, a cartridge provided with a plurality of channels, filters, and reflux channels to remove bubbles, thickened ink, and the like present in the pressurized liquid chamber of the recording head (Patent Document 1), and an ink cartridge via an ink supply tube Ink is supplied to the head tank unit containing the filter, ink is supplied from the head tank unit to the recording head for printing, and the head tank unit is rotated so that the filter can be set in the horizontal state and the vertical state. There is what can be provided (Patent Document 2).

  Further, as a conventional image forming apparatus, a configuration in which a nozzle surface of a recording head is arranged in a vertical direction and droplets are discharged in a horizontal direction is known (Patent Document 3).

JP 2006-68904 A JP-A-11-105300 Japanese Patent No. 3589238

  By the way, as described above, in the horizontal type image forming apparatus in which the nozzle surface of the recording head is arranged vertically and the liquid droplets are ejected in the horizontal direction, a filter is applied to the recording head from the vertical center of the head tank. Since the liquid is supplied via the member, if bubbles that have flowed into the head tank adhere to the filter member, the liquid cannot pass through the filter member, causing an initial filling failure, or the liquid to the recording head side. The supply cannot be made in time, resulting in a discharge failure.

  The present invention has been made in view of the above-described problems, and an object thereof is to reduce the residual adhesion of bubbles to the filter member.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head having a plurality of nozzles for discharging droplets;
A head tank for supplying liquid to the recording head;
A filter member provided between the recording head and the liquid stored in the head tank;
The recording head has a nozzle surface arranged in a vertical direction, and discharges droplets in a horizontal direction.
The filter member is disposed vertically in the lower part of the liquid storage portion of the head tank,
The flow path for supplying the liquid to the recording head from the downstream side of the filter member is configured to be inclined upward.

  According to the image forming apparatus of the present invention, the recording head has the nozzle surface disposed in the vertical direction, ejects liquid droplets in the horizontal direction, and the filter member is vertically disposed below the liquid storage portion of the head tank. The flow path for supplying the liquid to the recording head from the downstream side of the filter member is inclined upward, so that bubbles adhering to the filter member rise by buoyancy. Remaining on the filter member is reduced.

FIG. 3 is a side explanatory view of a mechanism unit of the image forming apparatus according to the present invention. It is explanatory drawing which looked at FIG. 1 from the arrow A direction. FIG. 6 is an explanatory diagram of a recording head. 2 is a schematic explanatory diagram of an ink supply / discharge system of the apparatus. FIG. It is a typical side surface explanatory view of the filter upstream side of the head unit. It is a typical side surface explanatory view of the filter upstream side of the head unit. It is a front section explanatory drawing of a head tank similarly. It is a flowchart with which it uses for description of initial filling operation | movement.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is an explanatory side view of the mechanism of the image forming apparatus, and FIG. 2 is an explanatory view of FIG.

  This image forming apparatus is a serial type image forming apparatus, and has an image forming unit 2, a transport mechanism unit 5 and the like inside the apparatus main body, and can stack sheets 10 as recording media on the lower side of the apparatus main body. A paper feed tray (including a paper feed cassette and used in the meaning of a paper feed unit) 4 is provided, the paper 10 fed from the paper feed tray 4 is taken in, and the paper 10 is moved vertically by the transport mechanism 5 (vertical). The image forming unit 2 discharges droplets in the horizontal direction and records a desired image while intermittently transporting the sheet 10 on the sheet 10 on the sheet discharge unit 6. The sheet 10 is discharged to a sheet discharge tray 7 provided on the upper side of the apparatus main body.

  Also, when performing double-sided printing, after the printing on one side (front side) is completed, the paper 10 is taken into the reversing unit 8 from the paper discharge unit 6 and reversed while being conveyed in the reverse direction (downward) by the transport mechanism unit 5. Then, the other side (back side) is sent to the transport mechanism 5 again as a printable side, and the paper 10 is discharged to the discharge tray 7 after the other side (back side) printing is completed.

  Here, the image forming unit 2 slidably holds a carriage 23 on which a recording head 24 is mounted with a main guide member 21 and a sub guide member 22 that are horizontally mounted between the left and right side plates 101L and 101R, and a main scanning motor. 25, the moving scanning is performed in the main scanning direction via the timing belt 28 passed between the driving pulley 26 and the driven pulley 27.

  The carriage 23 has recording heads 24a and 24b composed of liquid ejection heads for ejecting ink droplets of each color of yellow (Y), magenta (M), cyan (C), and black (K). As shown, the recording head 24 is arranged in a sub-scanning direction perpendicular to the main scanning direction, and the droplet discharge direction is mounted in the horizontal direction. That is, a horizontal driving method is employed in which a nozzle surface on which nozzles for discharging droplets are formed is arranged in the vertical direction and includes a recording head 24 that discharges droplets in the horizontal direction.

  As shown in FIG. 3, the recording head 24 has two nozzle arrays Na and Nb in which nozzles 201 for discharging a plurality of droplets are arranged, and one nozzle array Na of the recording head 24a is yellow ( Y), the other nozzle row Nb is a magenta (Y) droplet, one nozzle row Na of the recording head 24b is a black (K) droplet, and the other nozzle row Nb is cyan (C ) Droplets are discharged respectively.

  The liquid discharge head constituting the recording head 24 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change due to liquid film boiling using an electrothermal conversion element such as a heating resistor, and a metal due to a temperature change. A shape memory alloy actuator using a phase change, an electrostatic actuator using an electrostatic force, or the like provided as pressure generating means for generating a pressure for discharging a droplet can be used. The carriage 23 can also be mounted with a liquid discharge head that discharges a fixing liquid that reacts with the ink to enhance the fixability of the ink.

  The carriage 23 is equipped with a head tank 29 for supplying ink of each color corresponding to each nozzle row Na, Nb of the recording head 24. The head tank 29 is detachably attached to the apparatus main body. Ink is supplied from an ink cartridge (main tank) 30 of each color via a supply tube 31.

  Further, an encoder scale 121 having a predetermined pattern is stretched between the both side plates 101L and 101R along the main scanning direction of the carriage 23, and the carriage 23 is composed of a transmission type photosensor that reads the pattern of the encoder scale 121. An encoder sensor 122 is provided, and the encoder scale 121 and the encoder sensor 122 constitute a linear encoder (main scanning encoder) 123 that detects the movement of the carriage 23.

  A maintenance / recovery mechanism 9 for maintaining and recovering the state of the nozzles 124b of the recording head 24 is disposed in the non-printing area on one side in the scanning direction of the carriage 23. The maintenance and recovery mechanism 9 includes a suction cap 92A and a moisturizing cap 92B for capping each nozzle surface 202 (see FIG. 3) of the recording head 24 (referred to as “cap 92” when not distinguished), and a nozzle surface 202. A wiper member (wiper blade) 93 for wiping (wiping) is held, and droplets are received when preliminary discharge (empty discharge) is performed to discharge droplets that do not contribute to recording in order to discharge thickened ink. An empty discharge receiver 94 is provided. A suction pump 96 as suction means is connected to the suction cap 92 </ b> A, and the suction pump 96 communicates with a waste liquid tank 97.

  The paper 10 in the paper feed tray 4 is separated one by one by a paper feed roller (half-moon roller) 43 and a separation pad 44 and fed into the apparatus main body, and conveyed along the conveyance guide member 45 by the conveyance mechanism unit 5. It is fed between the belt 51 and the presser roller 48 and is attracted to the transport belt 51 and transported.

  The conveyance mechanism unit 5 includes an endless conveyance belt 51 that is stretched between a conveyance roller 52 that is a driving roller and a driven roller 53, a charging roller 54 that charges the conveyance belt 51, and the image forming unit 2. And a platen member 55 that maintains the flatness of the conveyor belt 51 at a portion facing the plate.

  The conveyance belt 51 rotates in the belt conveyance direction (sub-scanning direction, paper conveyance direction) when the conveyance roller 52 is rotationally driven by the sub-scanning motor 151 via the timing belt 152 and the timing pulley 153. In this conveyance belt 51, the area from the conveyance roller 52 that adsorbs the paper 10 facing the image forming unit 2 to the driven roller 53 is a normal conveyance portion 51a, and the area from the driven roller 53 to the conveyance roller 52 is reversely conveyed. This is referred to as a portion 51b.

  In addition, a code wheel 154 is attached to the shaft 52 a of the transport roller 52, and an encoder sensor 155 including a transmission type photo sensor for detecting a pattern formed on the code wheel 154 is provided. The code wheel 154 and the encoder sensor 155 A rotary encoder (sub-scanning encoder) 156 that detects the amount and position of movement of the conveyor belt 51 is configured.

  The paper discharge unit 6 includes a paper discharge guide member 61, a paper discharge conveyance roller 62 and a spur 63, a paper discharge roller 64 and a spur 65, and the paper 10 on which an image is formed is discharged to the paper discharge roller 64 and the spur 65. The paper is discharged face-down onto the paper discharge tray 7 from the middle.

  The reversing unit 8 reverses the paper 10 partially discharged to the paper discharge tray 7 by the switchback method and feeds the paper 10 between the conveyance belt 51 and the presser roller 48. A claw 81, a reverse guide member 82, a reverse roller 83 and a spur 84 as a reverse roller, a driven auxiliary roller 85 facing the driven roller 53, a reverse feed portion 51b of the transport belt 51, and a reverse feed of the transport belt 51 A detour guide member 86 for guiding the sheet 10 separated from the portion 51 b between the conveyance belt 51 and the pressing roller 48 by detouring the charging roller 54 is provided.

  In this image forming apparatus configured as described above, the paper 10 is separated and fed from the paper feed tray 4 one by one, and the paper 10 is electrostatically attracted to the charged transport belt 51, and the transport belt 51 is moved by the circular movement. The paper 10 is conveyed in the vertical direction. 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 10 to record one line, and after the paper 10 is conveyed by a predetermined amount, The next line is recorded, and the sheet 10 for which recording has been completed is discharged to the discharge tray 7.

  When performing maintenance and recovery of the nozzles of the recording head 24, the carriage 23 is moved to a position facing the maintenance and recovery mechanism 9 that is the home position, and the suction cap 92a is capped to perform suction and discharge from the nozzles 124b. By performing a maintenance and recovery operation such as nozzle suction and idle ejection for ejecting droplets that do not contribute to image formation, image formation by stable droplet ejection can be performed.

  In the case of performing duplex printing, the first surface printing performs the operation as described above, and when the rear end of the paper 10 passes through the reversing part branch (switching claw 81), the paper discharge roller 64 is driven in reverse. The sheet 10 is switched back, guided to the reversing guide member 82 side, conveyed between the reversing roller 83 and the spur 84, and the sheet 10 is sent between the reverse conveying portion 51 b of the conveying belt 51 and the conveying auxiliary roller 85. It is.

  As a result, the sheet 10 is attracted to the transport belt 51, transported by the circular movement of the transport belt 51, separated from the transport belt 51 on the transport roller 52 side, and guided by the detour guide member 86 (via the detour path). Then, the second side printing is performed by feeding again between the normal conveyance portion 51a of the conveyance belt 51 and the pressing roller 48 and being adsorbed by the conveyance belt 51, and again adsorbed and conveyed to the image forming area by the recording head 24. After that, the paper is discharged to the paper discharge tray 7.

  Here, since the charging roller 54 is disposed inside the detour path at the time of reversal (inside the detour guide member 86), the sheet 10 is always attracted onto the transport belt 51 in a newly charged state. become.

Next, the ink supply / discharge system of the image forming apparatus will be described with reference to the schematic explanatory view of FIG.
The main tank (ink cartridge) 11 stores ink ejected from the recording head 24 and is detachably attached to the apparatus main body. The main tank 11 and the head tank 29 are connected via a supply tube (supply path) 12, and a supply pump 13 including a reversible pump is provided in the supply path 12. For example, the supply pump 13 supplies ink from the main tank 11 toward the head tank 29 during forward rotation, and returns ink from the head tank 29 toward the main tank 11 during reverse rotation.

  The recording head 24 and the head tank 29 are integrated as a head unit 100. Ink is supplied from the head tank 29 to the common liquid chamber 214 to the recording head 24, ink is supplied from the common liquid chamber 214 to the individual liquid chamber 213, and the ink in the individual liquid chamber 213 is pressurized and liquid is supplied from the nozzle 201. Drops are ejected. By reversing the supply pump 13 described above to return ink from the head tank 29 side to the main tank 11 side, a negative pressure is formed in the head tank 29.

  On the other hand, the suction cap 92a for capping the nozzle surface 124 of the recording head 24 is arranged in the vertical direction in accordance with the recording head 24, and is advanced and retracted with respect to the recording head 24 by a cap moving mechanism (not shown).

  The suction cap 92a is provided with a discharge port (suction port) 190 on the bottom surface 192a in the height direction, a discharge path 191 leading to the waste liquid tank 97 is connected to the suction port 190, and a suction pump 96 is provided in the discharge path 191. It has been. In addition, an air release port 192 is provided in the upper portion of the suction cap 92a in the height direction, and an air release path 193 that connects to the atmosphere in the cap inner space 194 formed at the time of capping is connected to the air release port 192. An air release valve 98 that opens and closes the path 193 is provided. An absorption member 99 that absorbs liquid is disposed in the suction cap 92a.

Next, a head unit in which a recording head and a head tank according to an embodiment of the present invention are integrated will be described with reference to FIGS. 5 is an explanatory side view of the upstream side of the filter member, FIG. 6 is an explanatory side view of the downstream side of the filter member, and FIG. 7 is an explanatory front sectional view of the head tank. Here, a description will be given of a portion related to one color ink.
As described above, the head unit 100 is a unit in which the recording head 24 that discharges droplets and the head tank 29 as a liquid storage tank that stores ink to be supplied to the head 24 are integrated.

  As described above, the recording head 24 includes a plurality of nozzles 201 that discharge droplets, an individual liquid chamber 203 that communicates with each nozzle 201, and a common liquid chamber 204 that supplies ink to each liquid chamber 203. A supply path 205 from the head tank 29 is provided in the common liquid chamber 204.

  The head tank 29 is provided with a liquid storage portion 211 as a filter upstream chamber that stores ink supplied from the main tank 11 in the tank case 210, and a filter member 212 that removes foreign matter in the ink below the liquid storage portion 211. Is provided in a vertical direction, and a supply path 215 that communicates from the upper part of the downstream chamber 213 of the filter member 212 to the supply path 205 of the recording head 24 is provided.

  Here, the supply path composed of the supply path 215 from the downstream chamber 213 of the head tank 29 and the supply path 205 of the recording head 24 is formed so as to be inclined upward (in a diagonally upward direction) as a whole. Has been.

  Since it comprised in this way, the bubble which flowed into the liquid storage part 212 of the head tank 29 or generate | occur | produced raises by buoyancy, and adhesion of the bubble to the upstream side surface of the filter member 212 reduces. Further, since the supply path 215 and the supply path 205 are formed obliquely upward, the bubbles that have passed through the filter member 214 are similarly lifted by buoyancy and moved to the common liquid chamber 204 side of the recording head 29. In addition, the adhesion of bubbles to the downstream side surface of the filter member 212 is reduced. The bubbles that have moved to the recording head 24 side are discharged from the nozzle 201 by a bubble discharge operation (such as a maintenance recovery operation).

  As described above, the recording head has the nozzle surface arranged in the vertical direction, ejects liquid droplets in the horizontal direction, and the filter member is arranged in the vertical direction below the liquid storage portion of the head tank. The flow path for supplying the liquid from the downstream side of the recording head to the recording head is inclined upward so that bubbles attached to the filter member may rise by buoyancy and remain on the filter member. It is possible to reduce discharge defects and supply shortages, and stable droplet discharge can be performed.

Next, the initial ink filling operation for the head unit 100 will be described with reference to the flowchart of FIG.
First, the air release valve (not shown) of the head tank 29 is opened to start filling the ink from the main tank 11 to the head tank 29. When the near full tank is detected by the liquid level detecting means (not shown) of the head tank 29, the ink is filled. To stop.

  Thereafter, the nozzle surface 201 of the recording head 24 is capped with the suction cap 92A, and the suction pump 96 is driven to perform suction at a predetermined suction pressure for a predetermined suction time. Accordingly, ink is sucked and supplied from the head tank 29 to the recording head 24 and filled in the recording head 24.

  After the predetermined number of times of suction is completed, the air release valve of the head tank 29 is closed, the suction cap 92A is separated from the nozzle surface of the recording head 24 (decapted), the nozzle surface 202 is wiped, and idle discharge is performed. The operation is performed to finish the initial filling.

  In the above embodiment, the serial type image forming apparatus is described in the above embodiment, but the present invention can be similarly applied to a line type image forming apparatus.

2 Image forming unit 4 Paper feeding unit 5 Conveying mechanism 6 Paper discharging unit 7 Paper discharging tray 8 Reversing unit 9 Maintenance / recovery mechanism 10 Paper (recording medium)
DESCRIPTION OF SYMBOLS 11 Main tank 12 Supply path 13 Supply pump 23 Carriage 24 Recording head 29 Head tank 51 Conveying belt 92a Suction cap 93 Wiper member 96 Suction pump 204 Common liquid chamber 205 Supply path 211 Liquid storage part 212 Filter member 215 Supply path

Claims (1)

A recording head having a plurality of nozzles for discharging droplets;
A head tank for supplying liquid to the recording head;
A filter member provided between the liquid storage portion for storing the liquid of the head tank and the recording head,
The recording head has a nozzle surface arranged in a vertical direction, and discharges droplets in a horizontal direction.
The head tank is disposed below the liquid container, and the filter member is disposed vertically.
An image forming apparatus, wherein a flow path for supplying the liquid to the recording head from a downstream side of the filter member is provided to be inclined upward.

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