JP5440361B2 - Liquid storage tank, liquid discharge head unit, and image forming apparatus - Google Patents

Description

  The present invention relates to a liquid storage tank, a liquid discharge head unit, and an image forming apparatus.

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a complex machine of these, for example, a liquid discharge recording type image forming using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. As an apparatus, an ink jet recording apparatus or the like is known. This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Yes, it is also ejected onto a recording medium or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). And a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting liquid droplets without moving the recording head There are line type image forming apparatuses using

  In the present application, the “image forming apparatus” of the liquid discharge recording method is an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply It also means that a droplet is landed on a medium). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials, resins and the like are also included. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  As an ink supply method in such an ink jet recording apparatus used as an image forming apparatus, a sub tank (also synonymous with a buffer tank, a head tank, etc.) is disposed on the recording head side, and a main tank is disposed on the apparatus main body side. A system is known in which ink is replenished and supplied from the main tank to the sub tank, and ink is supplied from the sub tank to the recording head.

  In such an ink supply system, there is a type in which ink is supplied from a main tank to a sub tank via a supply tube, and a filter for filtering impurities in the ink is further provided in the sub tank.

  In addition, there exists a thing as described in patent document 1 thru | or 3 regarding the backflow prevention of the liquid with respect to a liquid storage tank, etc., for example.

JP 2005-199448 A JP 2003-53985 A Japanese Patent No. 3478116

  When the filter is disposed in the liquid storage tank as described above, if the filter structure is, for example, a mesh-like structure with non-uniform density, the head and tank are filled with ink (liquid) for the first time (initial filling). When the filter is wet with ink, a phenomenon occurs in which air does not permeate. For this reason, when ink is initially filled in the tank, there is a problem that air (bubbles) does not permeate due to the filter getting wet with ink, and bubbles remain on the upstream side of the filter of the storage portion for storing ink. The initial filling includes not only the case where the empty head or tank is filled with ink, but also the case where the cleaning liquid or filling liquid is filled in advance and this is replaced with ink.

  In view of this, an exhaust path for removing air bubbles staying upstream in the storage section partitioned by the filter is provided, and this exhaust path is communicated with an ink discharge path from the head so that air (bubbles) is passed through the exhaust path during initial filling. It is conceivable to remove the ink, but at this time, the ink that has not passed through the filter may flow backward to the head side.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to enable air bubbles to be discharged from the head tank while suppressing the backflow of liquid that has not passed through the filter of the head tank to the head.

In order to solve the above problems, the liquid storage tank according to the present invention is:
A liquid storage tank for storing liquid to be supplied to a head for discharging droplets,
The tank main body contains liquid to be supplied to the head, and is divided into an upstream chamber and a downstream chamber by a filter, and a supply path for supplying liquid from the downstream chamber to the supply port of the head And a discharge path for discharging the liquid discharged from the discharge port portion of the head to the outside,
A communication path that communicates the upstream chamber of the housing portion and the discharge path;
The communication path is a path in which an inlet portion is provided in the upstream chamber and discharges air in the upstream chamber to the discharge path when the liquid is initially filled.
The fluid resistance of at least a portion of the communication path is greater than the fluid resistance of the filter;
The discharge path is provided with a backflow prevention means for blocking the flow of liquid in the direction toward the discharge port portion of the head, on the upstream side in the liquid discharge direction from the portion where the communication path opens. .

  The liquid discharge head unit according to the present invention is a unit in which a head for discharging liquid droplets and a liquid storage tank according to the present invention for storing liquid supplied to the head are integrated.

  The image forming apparatus according to the present invention includes the liquid storage tank according to the present invention or the liquid discharge head unit according to the present invention.

According to the liquid container tank according to the present invention, can be discharged bubbles from the head tank while suppressing the backflow of the liquid head does not pass through the filter F Ddotanku.

  Since the liquid discharge head unit according to the present invention integrates the head and the liquid storage tank according to the present invention, air bubbles are discharged from the head tank while suppressing the backflow of liquid that has not passed through the filter of the head tank to the head. And stable droplet discharge can be performed.

  According to the image forming apparatus of the present invention, since the liquid storage tank according to the present invention or the liquid discharge head unit according to the present invention is provided, a high quality image can be formed by performing stable droplet discharge.

1 is a schematic front view illustrating the overall configuration of an example of an image forming apparatus according to the present invention. Similarly it is principal part plane explanatory drawing. It is explanatory drawing with which it uses for description of the ink supply system of the apparatus. It is a side explanatory view similarly. (A) is typical sectional explanatory drawing used for description of the head unit which concerns on 1st Embodiment of this invention, (b) is a partial sectional explanatory view of the head unit. It is explanatory drawing similar to FIG. 5 with which it uses for description of the effect | action at the time of the ink initial filling with respect to the head unit. It is explanatory drawing of the state similarly following FIG. It is explanatory drawing of the state similarly following FIG. It is explanatory drawing of the state similarly following FIG. It is explanatory drawing of the state similarly following FIG. It is explanatory drawing of the state similarly following FIG. It is explanatory drawing of the normal use condition of the head unit. It is typical sectional explanatory drawing with which it uses for description of the head tank which is a liquid storage tank which concerns on 2nd Embodiment of this invention. It is typical sectional explanatory drawing with which it uses for description of the head tank which is a liquid storage tank which concerns on 3rd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus including a liquid discharge head unit integrated with a liquid storage tank according to the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram for explaining the overall configuration of the image forming apparatus, and FIG. 2 is a schematic plan explanatory diagram of the apparatus.

  This image forming apparatus is a line type image forming apparatus, and includes an apparatus main body 1, a paper feed tray 2 on which paper P is stacked and fed, a paper discharge tray 3 on which printed paper P is discharged and stacked, and paper P An image forming unit 5 that includes a head module 51 that constitutes a recording head that discharges and prints droplets on a sheet P that is transported by the transport unit 4. The head cleaning device 6 that is a maintenance / recovery mechanism that performs maintenance / recovery of each recording head of the image forming unit 5 after printing is completed or at a required timing, a conveyance guide portion 7 that opens and closes the head cleaning device 6, and the image forming unit 5 An ink tank unit 8 composed of sub-tanks that supply ink to the head module 51, and a main tank that supplies ink to the ink tank unit 8. And a tank unit 9.

  The apparatus main body 1 includes front and rear side plates and stays (not shown), and the sheets P stacked on the sheet feed tray 2 are fed one by one to the transport unit 4 by the separation roller 21 and the sheet feed roller 22. Is done.

  The transport unit 4 includes a transport driving roller 41A, a transport driven roller 41B, and an endless transport belt 43 wound around these rollers 41A and 41B. A plurality of suction holes (not shown) are formed on the surface of the transport belt 43, and a suction fan 44 that sucks the paper P is disposed below the transport belt 43. Further, conveyance guide rollers 42A and 42B are respectively held on guides (not shown) on the conveyance driving roller 41A and conveyance driven roller 41B and are in contact with the belt 43 by their own weight.

  The conveyance belt 43 rotates around when the conveyance driving roller 41A is rotated by a motor (not shown), and the paper P is sucked onto the conveyance belt 43 by the suction fan 44 and is conveyed by the rotation movement of the conveyance belt 43. The transport driven roller 41 </ b> B and the transport guide rollers 42 </ b> A and 42 </ b> B rotate following the transport belt 43. Further, an empty discharge cleaning device 45 that removes empty discharge droplets attached to the conveyor belt 43 by empty discharge is disposed below the transfer belt 43.

  An image forming unit 5 composed of a plurality of head modules 51 for discharging droplets to be printed on the paper P is disposed above the transport unit 4 so as to be movable in the arrow A direction (and the reverse direction). The image forming unit 5 is moved to above the cleaning device 6 during the maintenance and recovery operation (during cleaning), and is returned to the position shown in FIG. 1 during image formation.

  The image forming unit 5 is a head module in which liquid discharge head units (hereinafter referred to as “head units”) 101 according to the present invention in which a head for discharging droplets and a head tank which is a liquid storage tank are integrated are arranged in a line. Recording head units) 51A, 51B, 51C, and 51D are arranged along the sheet conveyance direction and attached to the line base member 52.

  Here, one of the two nozzle rows of the head modules 51A and 51B ejects yellow (Y) droplets and the other of the magenta (M) droplets, and the two nozzle rows of the head modules 51C and 51D. On the other hand, cyan (C) droplets are discharged, and on the other hand, black (K) droplets are discharged. That is, in the image forming unit 5, two head modules 51 that discharge droplets of the same color are arranged side by side in the paper transport direction, and the two head modules 51 form a nozzle row corresponding to the paper width. It has a configuration.

  A distribution tank (supply member) 54 that supplies ink to each head unit 101 is arranged for each head module 51 above the head module 51, and the distribution tank 54 and the head unit 101 are connected by a tube 55. ing. A sub tank 81 is disposed upstream of the distribution tank 54 and connected via a supply tube 82. A main tank 91 for storing ink is disposed on the upstream side of the sub tank 81, and the main tank 91 and the sub tank 81 are connected by a supply path by a supply tube 92.

  On the downstream side of the transport unit 4, a transport guide portion 7 that discharges the paper P to the paper discharge tray 3 is provided. The paper P guided and conveyed by the conveyance guide unit 7 is discharged to the paper discharge tray 3. The paper discharge tray 3 includes a pair of side fences 31 that regulate the width direction of the paper P and an end fence 32 that regulates the front end of the paper P.

  The maintenance / recovery mechanism (head cleaning device) 6 includes four rows of cleaning units 61 </ b> A to 61 </ b> D corresponding to each head module 51 of the image forming unit 5, and one cleaning unit 61 corresponds to each head module 51. A cap member 62 for capping the nozzle surface corresponding to the head 101 and a wiping member (wiper member) 64 for wiping the nozzle surface are formed. The cap member 62 of each cleaning means 61 can be moved up and down independently for each row. Further, below the cleaning unit 61, suction pumps 63 </ b> A to 63 </ b> D that are suction units for sucking ink from the nozzles with the cap member 62 capping the nozzle surface of the head unit 101 are arranged.

  In this image forming apparatus, after the printing is finished, the ink is sucked from the nozzles while the nozzle surface of each head unit 101 of the head module 51 that discharges droplets is capped by the cleaning unit 61, or the head module When the ink adhering to the nozzle surface of each head unit 101 of 51 is cleaned with a wiping member, as shown in FIG. By rotating and making the space between the image forming unit 5 larger than that at the time of image formation, a space for moving the image forming unit 5 is secured. At this time, the conveyance guide plate 71 of the conveyance guide portion 7 disposed on the upper portion of the head cleaning device 6 is also rotated upward in the direction of arrow C at the fulcrum 72, and the upper portion of the head cleaning device 6 is opened.

  Then, after the transport unit 4 and the transport guide portion 7 are released (released), the image forming unit 5 moves in the paper passing direction (arrow A direction), is stopped above the head cleaning device 6, and is cleaned. 61 rises and shifts to the cleaning operation (maintenance recovery operation) of each head module 51.

Next, details of the ink supply system including the head module of the image forming apparatus will be described with reference to FIGS.
The sub tank 81 and the distribution tank 54 of the head module 51 are connected via a supply tube 82, and are suitable for holding the meniscus of the nozzle of the head unit 101 due to the water head difference between the sub tank 81 and the nozzle surface of the head unit 101. Negative pressure is generated. As will be described later, the head unit 101 includes a head 201 that ejects droplets and a head tank 202 that supplies ink to the head 201.

  The sub tank 81 is a pack-type sub tank. That is, the sub tank 81 is configured by storing a flexible pack 83 for storing ink in a sealed case 84. The pack-type sub-tank prevents ink from directly contacting the atmosphere to prevent the ink from increasing in viscosity due to water evaporation, and also maintains a constant amount of dissolved oxygen in the ink to prevent bubbles from accumulating in the head unit 101. be able to.

  A pressurizing pump 85 that pressurizes between the pack 83 and the case 84, an electromagnetic valve 88 (V) for releasing air, and a pressure sensor 89 (S) are connected to the sub tank 81 via a tube or the like. . At the time of the maintenance operation performed before printing after being left, the inside of the case 84 of the sub tank 81 is pressurized by the pressure pump 85, the ink is sent to the head tank 201 of the head unit 101, and the ink is ejected from the nozzles of the head 201. Maintenance will be performed. This maintenance operation is performed after the image forming unit 5 moves to the upper part of the cleaning device 6.

  A main tank 91 for storing ink is disposed on the upstream side of the sub tank 81. The main tank 91 and the sub tank 81 are connected by a supply path by a supply tube 92, and an electromagnetic valve 93 is provided in the supply path. The ink supply from the main tank 91 to the sub tank 81 is controlled by opening / closing the electromagnetic valve 93.

  A tube 155 that forms an air discharge path leading to a waste liquid tank (not shown) and an electromagnetic valve 156 that opens and closes the air discharge path 55 are provided above the distribution tank 54. When the air is discharged when the distribution tank 54 is initially filled and when the air is accumulated in the distribution tank 54, the electromagnetic valve 156 is opened to discharge the air. In addition, in order to make it easy to remove air, the top surface of the common flow path inside the distribution tank 54 is provided with an inclination.

  Further, a supply tube 55 for supplying ink is connected between the head tank 201 of each head unit 101 and the distribution tank 54. Further, a discharge tube 56 for discharging ink is connected to the head tank 201 of each head unit 101, and each discharge tube 56 is integrated into one by a circulation path 57 and connected to the distribution tank 54 via a circulation pump 58. Has been.

  The supply tube 55 and the discharge tube 56 that connect the distribution tank 54 and the head tank 202 of the head unit 101 are configured to be connected and separated by the joint member 110, respectively. Thus, when the head unit 101 is replaced, the supply channel and the discharge channel are separated from the joint member 110, and the head unit 101 is replaced with a new head unit 101. By interposing the joint member 110, the head unit 101 can be replaced even in a state where ink is contained in the flow path.

  Next, details of the head unit according to the first embodiment of the present invention will be described with reference to FIG. 5A is a schematic cross-sectional explanatory view of the head unit, and FIG. 5B is a partial cross-sectional explanatory view of the head unit.

  The head unit 101 is integrally provided with a head 201 that discharges droplets and a head tank 202 that stores ink to be supplied to the head 201.

  Here, the head 201 is common to a plurality of nozzles 211 that discharge droplets, a liquid chamber 212 that communicates with each nozzle 211, and a common liquid chamber (common flow path) 213 that supplies ink to each liquid chamber 212. A supply port (ink supply port) 214 that supplies (introduces) ink to the liquid chamber 213 and a discharge port (ink discharge port) 215 that discharges ink from the common liquid chamber 213 are provided.

  The head tank 202 is provided with an ink storage portion 223 for storing ink inside a tank case (tank body) 221, and a filter 224 for removing impurities and the like in the ink is provided in the storage portion 223 for storage. The part 223 is divided into a filter upstream chamber 223A and a filter downstream chamber 223B. The tank case (tank main body) 221 is formed of, for example, a member whose one surface (upstream chamber side or the like) is opened, and the opening 223 is sealed with a flexible film as a flexible member so that the accommodating portion 223 is formed. Is formed.

  The upstream chamber 223A of the storage unit 223 communicates with the ink supply port 225 connected to the ink supply tube 55, and the downstream chamber 223B communicates with the ink supply channel 226 that communicates with the supply port 214 of the head 201.

  Further, in the tank case 221, there is provided a discharge path 228 that communicates with the discharge port portion 215 of the head 201 and discharges ink discharged from the discharge port portion 215, and the ink discharge tube 56 is connected to the discharge path 228. The ink discharge port 229 communicates.

  In the tank case 221, a communication path 232 serving as a communication path that connects the upstream chamber 223A and the discharge path 228 is provided. Here, the filter 224 is arranged in a direction (vertically placed) along the ink supply direction, and the accommodating portion 223 is formed so that the upstream chamber 223A and the downstream chamber 223B are aligned in the horizontal direction, and the communication path is formed on the top surface side of the upstream chamber 223A. An inlet portion (upstream chamber side opening portion) 232a of 232 is provided.

  Further, the communication path 232 makes the fluid resistance of the portion (exit portion) 232 b that opens to the discharge path 228 larger than the fluid resistance of the filter 224.

  Further, in the discharge path 228, the flow of liquid (ink) in the direction toward the discharge port 215 side of the head 201, upstream of the discharge path 228 side opening (exit part) 232 b of the communication path 232 in the discharge direction. A check valve 262 is provided as a backflow prevention means for preventing the above. The check valve 262 includes a valve body 263 and a pressing member 264.

The operation at the time of initial ink filling for the liquid discharge head unit configured as described above will be described with reference to FIGS. In the figure, solid arrows indicate ink flow, and broken arrows indicate air flow.
First, as shown in FIG. 6, when the initial filling of the ink 300 into the head tank 202 is started, the upstream chamber 223A is gradually filled with ink. At this time, as the ink 300 is filled, the air in the upstream chamber 223A is discharged from the ink discharge port 229 from the communication path 232 through the discharge path 228, and the air in the upstream chamber 223A is gradually replaced with the ink 300.

  Then, as shown in FIG. 7, the upstream chamber 223A is filled with the ink 300, the air in the upstream chamber 223A is replaced with the ink 300, and the ink 300 is further supplied, as shown in FIG. Although the ink 300 enters the communication path 232, the fluid resistance of the outlet portion 232b of the communication path 232 is larger than the fluid resistance of the filter 224, so that the ink 300 passes through the filter 224 and is downstream as shown in FIG. It flows into the chamber 223B side.

  When further ink is supplied from this state to the head tank 202, as shown in FIG. 10, the ink is filled into the common liquid chamber 213 of the head 201 through the supply path 226, and reaches the discharge path 228 of the head tank 202. As shown in FIG. 11, the ink is discharged from the ink discharge port 229, and the initial ink filling is completed.

  In the use state after the ink filling to the head unit 101 is completed, as shown in FIG. 12, the check valve 262 prevents the back flow of ink to the head 201 side, so that the upstream chamber 223A side not passing through the filter 224 Ink is prevented from entering the head 201.

  In this way, the liquid storage tank has a communication path that connects the upstream chamber of the storage section and the discharge path, and the fluid resistance of at least a part of the communication path is larger than the fluid resistance of the filter, and the communication path is communicated with the discharge path. Passing through the head tank filter by providing a backflow prevention means that prevents the flow of liquid in the direction toward the head discharge port side upstream of the portion where the path opens The liquid can be filled by discharging bubbles from the head tank while suppressing the backflow of the liquid that has not been performed to the head.

  In the liquid discharge head unit in which the liquid storage tank is integrated with the head, bubbles in the head tank are discharged, so that stable droplet discharge can be performed.

Next, a head tank which is a liquid storage tank according to a second embodiment of the present invention will be described with reference to FIG.
Here, an umbrella valve 272 is used as a backflow prevention means. Even if it does in this way, the effect similar to the said 1st Embodiment can be acquired, and reduction of a number of parts can be aimed at.

Next, a head tank that is a liquid storage tank according to a third embodiment of the present invention will be described with reference to FIG.
Here, a gas-liquid separation membrane 282 is used as a backflow prevention means. Even if it does in this way, the effect similar to the said 1st Embodiment can be acquired, space saving and reduction of a number of parts can be aimed at.

  In the above-described embodiment, an example in which the present invention is applied to a line type image forming apparatus has been described. However, the present invention can be similarly applied to a serial type image forming apparatus.

1 Device body 4 Transport unit (transport section)
5 Image forming unit 6 Cleaning device (maintenance and recovery mechanism)
7 Transport guide 8 Ink tank unit (sub tank unit)
9 Main tank unit 51 Head module (recording head unit)
54 Distribution tank (distribution member)
81 Sub tank 91 Main tank (ink cartridge)
101 Head Unit 201 Head 202 Head Tank 211 Nozzle 213 Common Liquid Chamber 214 Supply Port Portion 215 Discharge Port Portion 221 Tank Case 223 Storage Portion 223A Upstream Chamber 223B Downstream Chamber 224 Filter 226 Supply Channel 228 Discharge Channel 232 Communication Channel (Communication Channel)
262 Check valve 272 Umbrella valve 282 Gas-liquid separation membrane

Claims (3)

A liquid storage tank for storing liquid to be supplied to a head for discharging droplets,
The tank main body contains liquid to be supplied to the head, and is divided into an upstream chamber and a downstream chamber by a filter, and a supply path for supplying liquid from the downstream chamber to the supply port of the head And a discharge path for discharging the liquid discharged from the discharge port portion of the head to the outside,
A communication path that communicates the upstream chamber of the housing portion and the discharge path;
The communication path is a path in which an inlet portion is provided in the upstream chamber and discharges air in the upstream chamber to the discharge path when the liquid is initially filled.
The fluid resistance of at least a portion of the communication path is greater than the fluid resistance of the filter;
The discharge path is provided with backflow prevention means for blocking the flow of liquid in the direction toward the discharge port of the head, upstream of the liquid discharge direction with respect to the opening of the communication path. Liquid storage tank.   2. A liquid discharge head unit comprising a head for discharging droplets and a liquid storage tank according to claim 1 for storing a liquid to be supplied to the head.   An image forming apparatus comprising the liquid storage tank according to claim 1 or the liquid discharge head unit according to claim 2.

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