JP2011148101A - Liquid storage tank, liquid ejection head unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a liquid stagnates, thereby hindering stable ejection of droplets due to difficulties in miniaturization of a sub tank while a filter member is arranged in the sub tank and in improvement of bubble dischargeability. <P>SOLUTION: An ink storage part 22 of the sub tank 4 is divided to an upstream chamber 35 and a downstream chamber 36 by the filter member 207 arranged in a direction along a droplet ejection direction. The sub tank has a supply route 203 which supplies the ink from the downstream chamber 36 of the ink storage part 22 to a supply port portion 14 of a head 2, and a discharge route 25 which discharges outside the ink discharged from an outlet portion 15 of the head 2. An exhaust route 40 is provided which makes the highest portion of the upstream chamber 36 communicate with a discharge route 39 led to the discharge route 25. A check valve 41 is set on the upstream side from a communicating part with the exhaust route 40 in the discharge route 39, which permits flow in a direction for the ink to flow from the discharge route 25 to the outside and blocks flow in a direction for the ink to flow from the outside to the discharge route 25. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 one 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 (Patent Document 1). In this case, the ink is supplied from the main tank to the recording head through the sub tank and discharged from the recording head. However, if the supply tube is long, the flow resistance becomes large, resulting in insufficient supply of ink to the recording head. Cause non-ejection. Therefore, in order to reduce the overall flow resistance, it is necessary to increase the area of the filter provided in the sub tank and reduce the filter resistance.

  In addition, as a filter, the filter unit etc. which formed in the column shape and provided the check valve which accommodated the float ball in this upper surface part are also known (patent document 2).

JP 2009-126044 A JP 2007-152848 A

  In recent years, image forming apparatuses have been required to be smaller. However, for high-speed printing, the number of nozzles of a liquid discharge head has been increasing, and ink supplied to one liquid discharge head having an increased number of nozzles. Since the amount also increases, the amount of ink that must be stored in the sub tank increases, and the volume of the sub tank tends to increase. On the other hand, in order to reduce the size of the liquid discharge head unit, it is necessary to install the sub tank as effectively as possible and to reduce the volume of the entire sub tank.

  However, in the configuration disclosed in Patent Document 1, the subtank is arranged in the horizontal direction, so that the subtank becomes large, and as described above, the flow resistance of the entire ink supply path is lowered. In addition, since the filter area is increased, there is a problem that the subtank becomes extremely large.

  On the other hand, bubbles invade and occur in the sub tank over time due to the dissolved gas in the supply tube and ink. If these bubbles are not reliably discharged, droplet ejection bending and droplet discharge defects will occur, and it is necessary to efficiently discharge the bubbles in the sub tank.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to reduce the size of a tank having a built-in filter and to improve bubble discharge performance.

Liquid tank In order to solve the above-mentioned problem, a liquid storage tank according to the present invention includes:
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 member disposed in a direction along the droplet discharge direction, and liquid from the downstream chamber of the storage portion. A supply path for supplying the liquid to the supply port of the head, and a discharge path for discharging the liquid discharged from the discharge port of the head to the outside,
An exhaust path that communicates the highest part of the upstream chamber of the housing portion with the discharge path;
In the discharge path, the liquid is allowed to flow in the direction in which the liquid tends to flow from the discharge path to the upstream side of the communication portion with the exhaust path, and flows from the outside to the discharge path. A check valve for blocking the flow of the liquid is provided in a direction to be attempted.

  Here, it can be set as the structure by which the bubble pool is provided in the highest site | part of the top | upper surface of the upstream chamber of the said tank main body.

  In addition, a communication path smaller than the flow path resistance of the filter that connects the highest position of the top surface of the downstream chamber of the tank main body and the portion of the discharge path that is higher than the highest portion of the top surface is provided. It can be configured.

The liquid discharge head unit according to the present invention is
A liquid discharge head unit comprising a head for discharging droplets and a liquid storage tank for storing liquid to be supplied to the head,
The head is provided with a common liquid chamber having a supply port portion and a discharge port portion,
In the liquid storage tank, a storage portion that is divided into an upstream chamber and a downstream chamber by a filter member that is disposed in a direction along a droplet discharge direction and stores liquid to be supplied to the head in the tank main body, and the storage A supply path for supplying liquid from the downstream chamber to the supply port of the head, and a discharge path for discharging liquid discharged from the discharge port of the head to the outside,
An exhaust path that communicates the highest part of the upstream chamber of the housing portion with the discharge path;
In the discharge path, the liquid is allowed to flow in the direction in which the liquid tends to flow from the discharge path to the upstream side of the communication portion with the exhaust path, and flows from the outside to the discharge path. A check valve for blocking the flow of the liquid is provided in a direction to be attempted.

An image forming apparatus according to the present invention includes:
In an image forming apparatus comprising: a head that discharges liquid droplets; a liquid storage tank that stores liquid to be supplied to the head; and a liquid storage unit that stores liquid to be supplied to the liquid storage tank.
The head is provided with a common liquid chamber having a supply port portion and a discharge port portion,
The liquid storage tank stores a liquid to be supplied to the head, a storage section divided into an upstream chamber and a downstream chamber by a filter member disposed in a direction along a droplet discharge direction, and a downstream chamber of the storage section A supply path for supplying the liquid from the supply port portion of the head and a discharge path for discharging the liquid discharged from the discharge port portion of the head to the outside,
An exhaust path that communicates the highest part of the upstream chamber of the storage section of the liquid storage tank, the discharge path of the liquid storage tank, and the path through the liquid storage tank;
In a path passing between the discharge path of the liquid storage tank and the liquid storage tank, the liquid tends to flow from the discharge path to the liquid storage tank upstream of the communication portion with the exhaust path. Is configured to be provided with a check valve that allows the flow of the liquid and blocks the flow of the liquid in a direction in which the liquid flows to the discharge path.

  According to the liquid storage tank of the present invention, the tank main body stores the liquid to be supplied to the head, and the storage portion is divided into the upstream chamber and the downstream chamber by the filter member disposed in the direction along the droplet discharge direction. And a supply path for supplying the liquid from the downstream chamber of the storage unit to the supply port of the head, and a discharge path for discharging the liquid discharged from the discharge port of the head to the outside. It has an exhaust path that communicates the highest part with the discharge path. The discharge path has an upstream side of the communication part with the exhaust path, and the liquid flows in the direction in which the liquid flows from the discharge path to the outside. And a check valve that blocks the flow of liquid in the direction of flowing from the outside to the discharge path is provided, so that the bubble discharge performance is improved while the liquid storage tank is reduced in size. be able to.

  According to the liquid discharge head unit of the present invention, the head is provided with the common liquid chamber having the supply port portion and the discharge port portion, and the liquid storage tank stores the liquid to be supplied to the head in the tank body. An accommodating portion that is divided into an upstream chamber and a downstream chamber by a filter member disposed in a direction along the droplet discharge direction, a supply path that supplies liquid from the downstream chamber of the accommodating portion to the supply port of the head, and the head A discharge path for discharging the liquid discharged from the discharge port portion to the outside, and has an exhaust path that communicates the highest portion of the upstream chamber of the storage section with the discharge path. The liquid flow is allowed in the direction in which the liquid is going to flow from the discharge path to the upstream side of the communication part, and the liquid flow is blocked in the direction from the outside to the discharge path. A configuration with a stop valve In, while reducing the size of the head unit according to miniaturization of the liquid storage tank can improve the bubble discharge resistance, it is possible to perform stable ejection.

  According to the image forming apparatus of the present invention, the head is provided with the common liquid chamber having the supply port portion and the discharge port portion, and the liquid storage tank stores the liquid to be supplied to the head. A storage section divided into an upstream chamber and a downstream chamber by a filter member disposed in a direction along the direction of the head, a supply path for supplying liquid from the downstream chamber of the storage section to the supply port section of the head, and a discharge port section of the head An exhaust path that discharges the discharged liquid to the outside and communicates the highest part of the upstream chamber of the storage section of the liquid storage tank with the path through the discharge path of the liquid storage tank and the liquid storage tank And the liquid passage between the discharge path of the liquid storage tank and the liquid storage tank has a liquid in the direction in which the liquid is about to flow from the discharge path to the liquid storage tank, upstream of the communication portion with the exhaust path. Allow the flow of Since the check valve for blocking the flow of liquid is provided in the direction to flow to the discharge path, it is possible to improve the bubble discharge property while reducing the size of the liquid storage tank, and stably. High-quality images can be formed by discharging droplets.

FIG. 3 is an explanatory diagram of an ink supply system of the image forming apparatus according to the first embodiment of the present invention. It is a cross-sectional explanatory drawing of the sub tank which follows the AA line of FIG. It is a flowchart with which it uses for description of the operation | movement which fills the head with the ink in the ink supply system. It is a flowchart with which it uses for description of the bubble discharge | emission operation | movement which discharges | emits the bubble mixed in the ink supply system. It is a section explanatory view equivalent to the section which meets the BB line of Drawing 2 of the liquid discharge head unit in a 2nd embodiment of the present invention. 1 is a schematic explanatory diagram for explaining an example of an overall configuration of an image forming apparatus according to the present invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram of an ink supply system of the image forming apparatus according to the embodiment, and FIG. 2 is an explanatory sectional view of a sub tank along the line AA in FIG.
The liquid discharge head unit 1 (hereinafter also simply referred to as “head unit”) includes a head 2 that discharges droplets and a sub tank 4 that is a liquid storage tank according to the present invention that stores ink to be supplied to the head 2. I have.

  Here, the head 2 includes a plurality of nozzles 11 that discharge droplets, a liquid chamber 12 that communicates with each nozzle 11, a common liquid chamber 13 that supplies ink to each liquid chamber 12, and ink in the common liquid chamber 13. Are provided with a supply port portion (ink supply port) 14 for supplying ink, a discharge port portion (ink discharge port) 15 for discharging ink from the common liquid chamber 13, and the like.

  In the tank (sub tank) 4, an ink storage portion 22 that stores ink to be supplied to the head 2 is formed in a tank case (tank main body) 21 by a recess formed on a side surface. A filter member 207 that filters ink in a direction along the droplet discharge direction (longitudinal direction: vertical direction) is disposed in the ink storage unit 22. The ink storage unit 22 includes a filter upstream chamber 35 and a filter downstream chamber 36. It is divided into and. Further, a supply port 24 that supplies ink from the filter downstream chamber 36 to the ink supply port 14 of the head 2 and a discharge path 25 that discharges ink discharged from the ink discharge port 15 of the head 2 to the outside are provided. .

  In the upper part of the filter upstream chamber 35, an ink supply flow path port portion 27 provided at the upper part of the tank case 21 faces, and a partition wall 202 extending from the bottom surface 35 c of the filter upstream chamber 35 to the top surface 35 a is provided. The ink from the ink supply port 27 does not flow directly into the supply path 203 leading to As a result, the ink supplied from the ink supply flow path port 27 flows into the filter upstream chamber 35, passes through the filter 207, passes through the filter downstream chamber 36, flows into the supply path 203, and is supplied from the supply port 24 to the head 2. Supplied to. A communication path (not shown) that connects the filter downstream chamber 36 and the supply flow path 203 is formed in the upper portion of the partition wall 202.

  In addition, the top surface 35a of the filter upstream chamber 35 of the ink storage unit 22 is an inclined surface that is inclined upward toward the center, and the upstream bubble reservoir that traps bubbles in the highest portion 35b of the center of the top surface 35a. 37 is provided. Further, the upstream bubble reservoir 37 connects the filter upstream chamber 35 to a discharge path 39 that is a part of the ink return flow path 53 that communicates the discharge path 25 of the sub tank 4 and the main tank (liquid storage means) 5. An exhaust path 40 is provided. The discharge path 39 allows ink to flow in the direction in which the ink flows from the discharge path 39 toward the ink return flow path 53, and in the direction in which the ink flows to the discharge path 25 of the sub tank 4. A check valve 41 that shuts off the flow is provided on the upstream side (sub tank 4 side) of the discharge path 29 with respect to the communication part (joining point) with the exhaust path 40.

  The tank case 21 of the sub-tank 4 is a member opened on one side, and a film member 23 (shown with shading in FIG. 1) as a flexible elastically deformable member is attached to the opening. It is attached to absorb pressure fluctuations. The tank case 21 can obtain a damper effect that absorbs the pressure due to the vibration of the ink at the respective portions in the ink storage portion 22 and the supply path 203 partitioned by the partition wall 202.

  On the other hand, a replaceable main tank (ink cartridge) 5 for supplying ink to the sub tank 4 is disposed on the apparatus main body side. Then, the ink is supplied from the main tank 5 to the sub tank 4 by the ink supply pump 52 through the ink supply path 51. The discharge path 25 of the sub tank 4 is connected to the main tank 5 via an ink return path 53, and an open / close valve (valve) 54 is interposed in the ink return path 53.

  Further, the main tank 5 is provided with an air release pipe 55 for preventing the ink in the tank 5 from being exposed to the outside air for a long time and drying or solidifying. The flow path of the atmosphere opening pipe 55 has an elongated tubular shape, and the humidity in the pipe changes along its length, so that it is possible to prevent the ink in the main tank 5 from coming into direct contact with the outside air. Therefore, the ink is prevented from being dried or thickened or solidified.

  In this ink supply system, the ink stored in the sub tank 4 is supplied from the ink supply port 14 at one end of the head 2 to one end of the common liquid chamber 13 through the supply port 24 and supplied to the common liquid chamber 13. A circulation path of ink not used for droplet ejection passes through the ink discharge port 15 at the other end of the head 2 and returns from the discharge path 26 of the sub tank 4 to the main tank 5 via the ink return path 53 including the discharge path 29. Configure. The ink flow path between the ink return path 53 of the circulation path and the main tank 5 can be stopped by an open / close valve 54 that can be opened and closed.

Next, in the ink supply system including such a circulation path, the operation of filling the ink of the head 2 will be described with reference to the flowchart shown in FIG.
First, the valve 54 is opened, and the ink supply pump 52 is driven (operated) from the main tank 5 through the ink supply path 51 to feed the liquid to the sub tank 4. This ink flows into the filter upstream chamber 35 from the ink supply flow path port 27 of the sub tank 4. At this time, since the air in the ink containing portion 22 is discharged through the exhaust path 40 that connects the filter upstream chamber 35 and the discharge path 39, ink filling in the filter upstream chamber 35 is started.

  The ink to the filter upstream chamber 35 is filled from the highest portion (position portion) 35 b of the top surface 35 a of the filter upstream chamber 35 to the upstream bubble reservoir 37, passes through the exhaust path 40, and reaches the discharge path 39. As a result, the ink that has flowed into the filter upstream chamber 35 is accumulated from below from the bottom surface 35 c of the filter upstream chamber 35 to the top surface 35 a by the partition wall 202, passes through the filter 207, and flows into the filter downstream chamber 36. Further, the ink that has flowed into the filter downstream chamber 36 is supplied to the supply path 203 and is sent to the head 2 through the supply port 24.

  It should be noted that the upstream bubble reservoir is located at the highest portion (position portion) 35b of the top surface 35a of the filter upstream chamber 35 so that the air (bubbles) in the filter upstream chamber 35 can be efficiently discharged to the discharge path 39. 37 is provided, it becomes easy for bubbles to gather at the upstream bubble reservoir 37, and the bubbles can be efficiently discharged to the discharge path 39 in a short time.

  Next, the ink sent to the head 2 is sent to the common liquid chamber 13 through the ink supply port 14. Part of the ink that has flowed into the common liquid chamber 13 is discharged from each nozzle 11. Further, the ink in the common liquid chamber 13 is discharged from the ink discharge path 25 to the discharge path 39 through the ink discharge port 15, merges with the ink flowing out from the exhaust path 40, and returned to the main tank 5 from the ink return path 53. .

  Here, after the ink is fed into the ink return path 53 and passes through the valve 54, the valve 54 is closed. Here, the time until the ink passes from the start of liquid feeding to the sub tank 4 by the pump 52 until it passes to the valve 54 is measured in advance, and the timing for closing the valve 54 is obtained by the passage of this time.

  Thereafter, the pressure of the ink supply pump 52 is adjusted, the ink is discharged from the nozzle 11 of the head 2 to the outside, and the bubbles in the nozzle 11 are discharged. At this time, the nozzle surface 11a of the recording head 2 is capped with a cap member (not shown), and the suction means connected to the cap member is driven to suck and discharge ink from the nozzle 11 to discharge bubbles in the nozzle 11. These pressure discharge and suction discharge can be used in combination.

  Then, the ink supply pump 52 is opened, the flow of ink is stopped, and a negative pressure necessary for ink discharge generated by the water head difference between the main tank 5 and the nozzle 11 of the head 2 is created.

  Thereafter, the surface of the nozzle is wiped by an unillustrated elastic body, preferably a wiper member such as silicon rubber, and the ink dripping on the nozzle surface 11a is wiped off to form the meniscus of the nozzle 11 to complete the ink filling.

  In this way, the head 2 can be filled with ink, and the ink can always be supplied from the main tank 5 to the head 2 through the sub tank 4 so that ink can be ejected.

Next, a bubble discharging operation for discharging bubbles mixed in the ink supply system will be described with reference to a flowchart shown in FIG.
When the main tank 5 is replaced to replenish the ink used for printing or the nozzle 11 or the like, air bubbles are mixed into each ink flow path and the ink containing portion 22 for some reason, and droplets are discharged from the nozzle 11. When trouble occurs, bubble discharge operation is performed to eliminate this.

  First, the supply pump 52 is operated to supply liquid to the sub tank 4, and the valve 54 is immediately opened. As a result, the ink flows into the filter upstream chamber 35 from the ink supply flow path port 27, and when bubbles are mixed in the ink supply path 51, the bubbles flow into the filter upstream chamber 35, and the filter It accumulates in the upper part of the upstream chamber 35. Further, the inside of the ink containing portion 22 is pressurized by the ink feeding, and the bubbles accumulated in the upper portion of the filter upstream chamber 35 are discharged from the exhaust path 40 to the discharge path 39. At the same time, ink is sent from the filter downstream chamber 36 to the head 2, and when bubbles are mixed in the common liquid chamber 13, the bubbles are discharged to the ink discharge path 25. The ink merged in the discharge path 39 via the ink discharge path 25 is further sent to the ink return path 53 and returned to the main tank 5.

  Thus, after all the bubbles mixed in the downstream of the valve 54 are discharged by liquid feeding, the valve 54 is closed. By using the time from the start of liquid feeding by the pump 52 to the sub-tank 4 until the valve 54 is closed as shown in the ink filling sequence, the timing of closing the valve 54 is used to surely discharge bubbles in the flow path. Can do.

  Thereafter, the pressure of the ink supply pump 52 is adjusted, the ink is discharged from the nozzle 11 to the outside, and the bubbles in the nozzle 11 are discharged. Also at this time, the nozzle surface 11a of the recording head 2 is capped with a cap member (not shown), and the suction means connected to the cap member is driven to suck and discharge ink from the nozzle 11 so that bubbles in the nozzle 11 are discharged. It can also discharge | emit, and these pressurization discharge | emission and suction discharge | emission can also be used together.

  Then, the ink supply pump 52 is opened, the flow of ink is stopped, and a negative pressure necessary for ink discharge generated by the water head difference between the main tank 5 and the nozzle 11 of the head 2 is created.

  Thereafter, here, the nozzle surface is wiped by an unillustrated elastic body, preferably a wiper member such as silicon rubber, and the ink dripping on the nozzle surface 11a is formed, the meniscus of the nozzle 11 is formed, and the bubble discharging operation is completed. .

  In this way, the air bubbles mixed in each ink flow path and the ink containing portion 22 can be discharged, and ink droplet ejection can be recovered.

  In addition, two detection electrodes 29 a and 29 b for detecting that the amount of ink in the ink containing portion 22 has become a predetermined amount or less are mounted on the upper part of the sub tank 4. At the tips of the detection electrodes 29a and 29b, a control unit for inputting a detection signal (not shown) is provided to constitute a liquid amount detection sensor. When the detection electrodes 29a and 29b are immersed in ink and at least one of the detection electrodes 29a and 29b is not immersed in ink, the conduction state between the detection electrodes 29a and 29b changes, so that the ink becomes a predetermined amount or less. Can be detected.

  By using this liquid amount detection sensor, it is possible to detect a state in which bubbles are accumulated in the ink containing portion 22, and when ink is filled, the ink containing portion 22 is filled with ink from an empty state, It is possible to reliably recognize that the bubbles are discharged from the state where the bubbles are accumulated in the portion 22.

  In the sequence of the filling operation and the bubble discharging operation described in FIG. 3 or FIG. 4 described above, the control is performed based on a predetermined time between the opening of the valve 54 and the passage of ink to the valve 54. By using the liquid amount detection sensor, it is only necessary to perform control in a short time from when the ink in the ink containing portion 22 is filled to when the bubbles pass through the valve 54. The reliability of recoverability can be increased.

  As described above, in this embodiment, the sub tank 4 is reduced in size by providing the filter member 207 in the ink container 22 in the sub tank 4 in the direction (vertical direction) along the droplet discharge direction.

  An exhaust path 40 is provided in order to discharge bubbles in the filter upstream chamber 35 of the sub tank 4, and the exhaust path 39 from the sub tank 4 is communicated. That is, if a discharge path for the discharge path 40 for discharging bubbles in the ink storage portion 22 of the sub tank 4 is newly provided, the piping of the liquid discharge unit and the image forming apparatus becomes complicated, resulting in an increase in cost. Therefore, the exhaust path 40 and the discharge path 39 are connected so that only one pipe to the ink return path 53 is required.

  As described above, when the ink is initially filled in the sub tank 4, the ink also enters the exhaust path 40. Although a valve 54 is provided between the discharge path 39 and the ink return flow path 53, the valve 54 is located on the downstream side of the connecting portion between the discharge path 39 and the exhaust path 40, so that the ink that has entered from the exhaust path 40 is present. May flow backward to the discharge path 25 of the sub tank 4 and flow into the head 2 side. The ink flowing from the exhaust path 40 is the ink before passing through the filter 207, and may contain impurities that clog the nozzle 11 and the flow path, and this ink is supplied to the head 2. As a result, clogging of the nozzle 11 and the flow path is generated, resulting in an ejection failure of ink ejected from the nozzle 11.

  Therefore, the ink flow is allowed in the discharge path 39 in the direction in which the ink flows from the discharge path 25 to the ink return path 53, and in the direction in which the ink flows from the ink return path 53 to the discharge path 25. A check valve 41 for blocking the ink flow is provided on the upstream side (sub tank 4 side) of the connection point (communication part) between the discharge path 39 communicating with the discharge path 25 and the exhaust path 40.

  As this check valve 41, for example, a small diaphragm type check valve having a simple structure and a resistance cost that is generally commercially available, or a ball type check valve that operates by an internal ball can be used. As a result, the ink discharged from the exhaust path 40 does not flow backward in the direction of the discharge path 25, so that the ink that does not pass through the filter 207 is not supplied to the head 2, and ejection due to clogging of the nozzles 11 or the like. Defects can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional explanatory view corresponding to a cross section taken along line BB of FIG. 2 of the liquid ejection head unit in the same embodiment.
In the first embodiment, when the ink filling sequence shown in FIG. 3 and the bubble discharge sequence shown in FIG. 4 are performed, the ink flows from the ink supply flow path port 27 of the sub tank 4 into the filter upstream chamber 35 and the upstream of the filter. The bubbles in the chamber 35 are discharged to the discharge path 39 through the exhaust path 40, but the bubbles in the filter downstream chamber 36 become a gap between particles and fibers constituting the filter member 207 when the filter member 207 is wet with ink. Thus, a liquid meniscus is generated, and bubbles remain in the filter downstream chamber 36 without passing through the filter. In the state where air bubbles are accumulated in the ink storage unit 22, the air bubbles cover the filter member 207 arranged in the vertical direction, the effective area of the filter member 207 is reduced, the filter resistance is increased, and the ink supply to the head 2 is hindered Insufficient supply of ink ejected from the nozzles 11 may result in non-ejection. Further, even if ink with reduced air dissolved in the ink is supplied from the main tank in order to improve the stable ejection performance, bubbles remaining in the filter downstream chamber 36 are dissolved in the ink, resulting in poor droplet ejection from the nozzle 11. May occur.

  In this case, in order to discharge the bubbles in the filter downstream chamber 36, the liquid supply amount of the ink supply pump 52 is increased, the ink flow rate and the ink pressure are increased, and the bubbles are discharged from the filter downstream chamber 36. The liquid can be discharged from the supply port 14 of the head 2 to the common liquid chamber 13 and from the discharge port 15 to the discharge route 25 through the supply route 203. However, when bubbles enter the common liquid chamber 13, some of the bubbles may flow into the liquid chamber 12 and cause a drop ejection failure from the nozzle 11.

  Therefore, in the present embodiment, the top surface 36a of the filter downstream chamber 36 of the ink containing portion 22 is also an inclined surface that inclines upward toward the center portion, and a downstream bubble pool is formed at the highest portion 36b of the center portion of the top surface 36a. A communication path 26 is provided to connect the filter downstream chamber 36 and the discharge path 25 from the downstream bubble reservoir 38. Thus, the downstream bubble reservoir 38 is provided at the highest portion (position portion) 36b of the top surface 36a of the filter downstream chamber so that the bubbles in the filter downstream chamber 36 can be efficiently discharged to the discharge path 25. Thus, the bubbles can be efficiently discharged to the discharge path 25 in a short time.

  In this case, the flow path resistance of the communication path 26 is larger than the flow path resistance from the supply port 14 to the discharge port 15 of the head 2. This is because if the flow path resistance of the communication path 26 is smaller, most of the ink flows into the ink discharge path 25 as it is through the communication path 26 and is discharged to the discharge path 39 to the common liquid chamber 13. This is because the amount of flowing ink is reduced and the bubbles of the head 2 cannot be discharged.

  Further, the flow path resistance of the communication path 26 is such that the time during which ink flows out from the filter downstream chamber 36 to the discharge path 25 during ink filling, and the head through the supply flow path 203 from the filter downstream chamber 36 through the communication path 204. It is preferable to set the resistance value so that the time required to reach the portion (communication portion) connecting the discharge path 25 and the communication path 26 after being supplied to 2 is approximately the same.

  In the ink filling sequence described with reference to FIG. 3, the timing at which the valve 54 is closed is when ink is sent into the ink return path 53, but is sent from the discharge path 25 into the ink return path 53. Since there are two paths of ink that flows from the discharge path 39 via the head 2 and ink that flows via the filter upstream chamber 35, one of them flows out from the discharge path 25 to the discharge path 39 first. This is because if the liquid is fed into the ink return path 53 and the valve 54 is closed, bubbles remain in the other path.

  In addition, since the time for the ink to flow out to the discharge path 25 varies depending on the flow paths of the head 2 and the tank 4 and the flow path resistance of the filter member 207, the flow path resistance value of the communication path 26 is the above-described discharge path. It may be set from the time when ink flows out to 25.

  With this configuration, air bubbles remaining in the filter downstream chamber 36 are discharged from the highest portion (position portion) 36 b of the top surface 36 a of the filter downstream chamber 36 through the communication path 26 to the discharge path 25. Then, the ink is further discharged from the discharge path 39 to the ink return channel 53. Since the ink flowing through the communication path 26 is the ink that has passed through the filter member 207, there is no possibility that the nozzle 11 or the flow path is clogged with impurities even if the ink flows backward through the discharge path 25.

  In this way, the air bubbles in the filter upstream chamber 35 and the filter downstream chamber 36 are discharged from the respective flow paths by the exhaust path 40 and the communication flow path 26, and stable without causing droplet discharge defects. Droplet discharge can be performed.

Next, an example of the overall configuration of the image forming apparatus including the ink supply system described in the above embodiments will be described with reference to FIG.
In this image forming apparatus, a recording head 101 composed of the liquid discharge head unit 1 is mounted on a carriage 103, and is slid by a main guide rod 104 and a sub guide member (not shown) that are horizontally mounted between the left and right side plates 100A and 100B. Supports freely. The recording head 101 is moved and scanned in the main scanning direction by the main scanning motor 106 via the timing belt 105. On the other hand, the recording medium 107 is opposed to the nozzle surface 11a of the recording head 101, and is conveyed by the conveying roller 109 in a direction orthogonal to the moving direction of the recording head 101, and ink droplets ejected from the recording head 101 according to the image. An image is formed by adhesion.

  Ink is supplied to the recording head 101 from the main tank unit 102 in which the main tank 5 and the atmosphere release pipe 55 are accommodated via the ink supply pump 52 through the flexible ink supply path 51. Ink that has not been ejected or discharged from the nozzles is returned to the main tank unit 102 through the ink return path 53.

  The cap member 111 provided outside the recording area is made of an elastic body, preferably silicon rubber, for capping the nozzle surface 108 having the plurality of nozzles 11. At the time of non-recording, the recording head 101 moves to above the cap member 111, and the cap member 111 moves by a cap moving mechanism (not shown) to cap the nozzle surface 108. In the cap member 111, an ink absorbing sheet 112 is provided for facilitating suction during ink suction, moistening the atmosphere in the cap, and the like.

  Two tubes 113, 114 are connected to the cap member 111 on the bottom surface, and the tube 113 communicates with the atmosphere via the atmosphere release valve 115. The tube 114 is connected to the suction pump 116, and the nozzle surface 108 is capped by the cap member 111, and the suction pump 116 is driven to generate a negative pressure in the cap member 111 with the atmosphere release valve 115 closed. Then, ink is sucked from the nozzles of the recording head 101 and the air release valve 115 is opened to discharge the ink accumulated in the space 117 in the cap member 111 to the waste liquid tank 118. Further, the cap member 111 prevents the nozzles of the recording head 101 from drying by contacting and holding the nozzle surface 108 with the atmosphere release valve 115 closed.

  Further, a wiper blade (wiper member) 119 is moved to a height at which it contacts the nozzle surface 108 of the recording head 101 by a wiper moving mechanism (not shown), and the recording head 101 is moved in the main scanning direction. The ink and dust adhering to 108 can be wiped off, and the meniscus on the nozzle surface 108 can be generated and cleaned.

  In the above embodiment, an example in which the present invention is applied to an image forming apparatus is described. However, the exhaust path 40, the discharge path 39, and the check valve 41 in the above embodiment are integrated with a tank case of the sub tank 4. By providing, the liquid storage tank according to the present invention can be configured, and the liquid discharge head unit according to the present invention can be configured by integrating the liquid storage tank according to the present invention with the head.

  In the above-described embodiment, the present invention has been described with reference to an example in which the present invention is applied to an image forming apparatus having a printer configuration. However, the present invention is not limited to this. In addition, the present invention can also be applied to an image forming apparatus using a liquid other than the narrowly defined ink or a fixing processing liquid.

DESCRIPTION OF SYMBOLS 1 Liquid discharge head unit 2 Head 4 Sub tank 5 Main tank 11 Nozzle 13 Common liquid chamber 14 Supply port 15 Discharge port 21 Tank case 22 Ink accommodating part 23 Damper member (film member)
24 supply port 25 ink discharge path 26 communication path 39 discharge path 40 exhaust path 41 check valve 53 ink return path 101 recording head (liquid discharge head unit)
202 Partition part 203 Supply flow path 207 Filter member

Claims (5)

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 member disposed in a direction along the droplet discharge direction, and liquid from the downstream chamber of the storage portion. A supply path for supplying the liquid to the supply port of the head, and a discharge path for discharging the liquid discharged from the discharge port of the head to the outside,
An exhaust path that communicates the highest part of the upstream chamber of the housing portion with the discharge path;
In the discharge path, the liquid is allowed to flow in the direction in which the liquid tends to flow from the discharge path to the upstream side of the communication portion with the exhaust path, and flows from the outside to the discharge path. A liquid storage tank, characterized in that a check valve for blocking the flow of the liquid is provided in a direction to be attempted.   The liquid discharge head unit according to claim 1, wherein a bubble reservoir is provided at a highest portion of the top surface of the upstream chamber of the tank body.   A communication path smaller than the flow path resistance of the filter that communicates the highest position of the top surface of the downstream chamber of the tank body with the portion of the discharge path that is higher than the highest portion of the top surface is provided. The liquid discharge head unit according to claim 1, wherein the liquid discharge head unit is a liquid discharge head unit. A liquid discharge head unit comprising a head for discharging droplets and a liquid storage tank for storing liquid to be supplied to the head,
The head is provided with a common liquid chamber having a supply port portion and a discharge port portion,
In the liquid storage tank, a storage portion that is divided into an upstream chamber and a downstream chamber by a filter member that is disposed in a direction along a droplet discharge direction and stores liquid to be supplied to the head in the tank main body, and the storage A supply path for supplying liquid from the downstream chamber to the supply port of the head, and a discharge path for discharging liquid discharged from the discharge port of the head to the outside,
An exhaust path that communicates the highest part of the upstream chamber of the housing portion with the discharge path;
In the discharge path, the liquid is allowed to flow in the direction in which the liquid tends to flow from the discharge path to the upstream side of the communication portion with the exhaust path, and flows from the outside to the discharge path. A liquid discharge head unit characterized in that a check valve for blocking the flow of the liquid is provided in a direction to be tried. In an image forming apparatus comprising: a head that discharges liquid droplets; a liquid storage tank that stores liquid to be supplied to the head; and a liquid storage unit that stores liquid to be supplied to the liquid storage tank.
The head is provided with a common liquid chamber having a supply port portion and a discharge port portion,
The liquid storage tank stores a liquid to be supplied to the head, a storage section divided into an upstream chamber and a downstream chamber by a filter member disposed in a direction along a droplet discharge direction, and a downstream chamber of the storage section A supply path for supplying the liquid from the supply port portion of the head and a discharge path for discharging the liquid discharged from the discharge port portion of the head to the outside,
An exhaust path that communicates the highest part of the upstream chamber of the storage section of the liquid storage tank, the discharge path of the liquid storage tank, and the path through the liquid storage tank;
In a path passing between the discharge path of the liquid storage tank and the liquid storage tank, the liquid tends to flow from the discharge path to the liquid storage tank upstream of the communication portion with the exhaust path. The image forming apparatus is characterized in that a check valve that allows the flow of the liquid and blocks the flow of the liquid in a direction to flow to the discharge path is provided.

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