JP2011025565A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve stability of liquid supply during a recording process without upsizing the apparatus and to solve the problem that it is impossible to enhance air bubble discharging performance by liquid circulation with a little waste liquid amount. <P>SOLUTION: The image forming apparatus includes: a first liquid path 11 from an ink cartridge 10 to a head 1, communicating with one of ports of a common flow path; a second liquid path 12 from the ink cartridge 10 to the head 1, communicating with the other port of the common flow path 4. The first liquid path 11 includes: a first flow path 21 communicating with the head; a second flow path 22 communicating with the cartridge 10, and having an opening/closing valve 24; a flow path resistance varying unit 25 allowing the communication between the first flow path 21 and the second flow path 22; a third flow path 23 allowing the second flow path 22 or the cartridge 10 to communicate with the flow path resistance varying unit 25; and an assist pump 26 disposed in the third flow path 23. In the case of ejecting droplets from nozzles 2, the liquid is fed by the assist pump 26 from the cartridge 10 to the head 1 in the state where the head 1 and the cartridge 10 communicate with each other through the flow path resistance varying unit 25. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a recording head for discharging 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, an “image forming apparatus” is an apparatus that forms an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics (simple liquid ejection apparatus) In addition, “image formation” not only gives an image having a meaning such as a character or a figure to a medium but also gives an image having no meaning such as a pattern to the medium. It also means (including what is simply referred to as a droplet discharge device or a liquid discharge device). In addition, the term “ink” is not limited to what is referred to as ink, but can be used for image formation such as recording liquid, fixing processing liquid, liquid, DNA sample, patterning material, resin, and the like. It is used as a general term for liquids. 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. Further, “image” means not only a two-dimensional image but also a three-dimensional image (stereoscopic image).

  As a liquid discharge head (droplet discharge head) used as a recording head, a piezoelectric head or the like is used to displace a diaphragm and change the volume in the liquid chamber to increase the pressure to discharge the liquid droplet. There is known a thermal type head in which a heating element that generates heat is provided, the pressure in the liquid chamber is increased by bubbles generated by the heat generation of the heating element, and droplets are discharged.

  As such a liquid discharge type image forming apparatus, an ink jet recording apparatus that discharges ink from nozzles of a head while circulating ink is known (Patent Document 1. Such an ink jet recording apparatus is, for example, an upstream side. The tank, the inkjet head, and the downstream tank are connected by a conduit, the liquid level of the upstream tank and the liquid level of the downstream tank are kept constant, and the ink in the upstream tank passes through the upstream flow path. It is circulated so as to flow into the ink jet head and further flow into the downstream tank from the ink jet head via the downstream flow path.

  In such an ink jet recording apparatus, it is required to maintain an appropriate circulation flow rate in order to prevent problems such as bubble mixing and ink leakage and to ensure good printing characteristics. In the apparatus described above, the circulation flow rate is determined by the flow resistance from the upstream tank to the downstream tank via the upstream flow path, the inkjet head, and the downstream flow path, and the heights of the upstream tank and the downstream tank. It is determined by the difference. Therefore, in order to adjust the flow rate, it is necessary to adjust according to the positions of the upstream tank, the downstream tank, the inkjet head, and the like. That is, for example, in order to increase the flow rate, it is necessary to increase the difference between the height of the upstream tank and the height of the downstream tank, so the height position of the upstream tank is raised and the height position of the downstream tank is increased. Must be lowered.

  However, in general, there are many physical restrictions on the arrangement of the tank, and it is difficult to adjust the height, and if the height difference is changed, the flow resistance changes accordingly. It is difficult to ensure a sufficient flow rate.

  Therefore, for example, an inkjet head having an upstream port and a downstream port communicating with the pressure chamber facing the nozzle, an upstream tank that communicates with the inkjet head via the upstream port, and can store ink, and a downstream port It has a circulation system that communicates with the inkjet head and communicates with a downstream tank that can store ink and a circulation pump that returns ink from the downstream tank to the upstream tank. Has a release valve that can be opened and closed, drives the circulation pump by closing the release valve, makes the downstream tank liquid level negative, and returns ink from the downstream tank to the upstream tank via the return flow path. Some have an ink supply mechanism that circulates water (Patent Document 2).

  In addition, there are provided a nozzle that ejects ink droplets, a pair of at least two ink supply ports, and an ink flow path that connects the pair of ink supply ports to each other and communicates each ink supply port with each nozzle. A head, an ink tank that stores ink, a first tube that communicates at least one of the pair of ink supply ports with the ink tank, and another ink supply port of the pair of ink supply ports A second tube that communicates with the ink tank, a pump that sends ink from the ink tank toward the head via the first tube, a valve that is provided on the second tube and that can be opened and closed, and a pump control unit that controls the pump And a valve control unit that controls opening and closing of the valve (Patent Document 3).

JP-T-2002-533247 JP 2008-162262 A JP 2008-246860 A

  However, in the configuration disclosed in Patent Document 2, an upstream tank and a downstream tank are necessary in addition to the replaceable ink tank, and there are restrictions on the arrangement thereof, which increases the size and cost of the apparatus. Inevitable. In addition, since the pressure is controlled by the air volume in the tank, the pressure change in the tank increases due to changes in the air temperature, and the desired conditions may not be obtained, and many tanks and tubes are included. Since a high degree of airtightness is required for the entire liquid delivery system, there is a problem that the realization is quite difficult.

  Further, in the configuration disclosed in Patent Document 3, circulation is possible with a simple and small mechanism. However, when the head is lengthened or applied to a line head in which a plurality of heads are arranged, ink is used. This increases the pressure loss when ink is fed. For this reason, it is necessary to increase the pressure of the pump for feeding the ink. However, if the pressure of the pump is increased, the ink is liable to dripping from the nozzles of the head, and the wasted ink is increased. There is a problem that pressure control to avoid this is extremely difficult.

  The present invention has been made in view of the above-described problems, and improves the stability of liquid supply during recording without increasing the size of the apparatus, and improves the bubble discharge performance by liquid circulation with a small amount of waste liquid. Objective.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The first liquid path is
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank and having flow path opening and closing means;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. It was set as the structure which liquefies.

An image forming apparatus according to the present invention includes:
A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The second liquid path has a liquid feeding means,
The first liquid path is
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. It was set as the structure which liquefies.

An image forming apparatus according to the present invention includes:
A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The second liquid path has a liquid feeding means,
The first liquid path is
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank and having flow path opening and closing means;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. It was set as the structure which liquefies.

An image forming apparatus according to the present invention includes:
A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The first liquid path and the second liquid path are both
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank and having flow path opening and closing means;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. It was set as the structure which liquefies.

  Here, the liquid tank can be configured to have a communication path communicating with the atmosphere through a valve that can be opened and closed.

  The second liquid path may be connected to the inside of the liquid tank via a foam-breaking member.

  According to the image forming apparatus of the present invention, the first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head and the other port side of the common flow path of the liquid discharge head are communicated. A first liquid path that communicates with the liquid discharge head, a second flow path that communicates with the liquid tank and that has a flow path opening / closing means, and a first flow path. A pressure regulating valve for communicating the channel with the second channel, a third channel for communicating the second channel or the liquid tank with the pressure regulating valve, and a liquid feeding means provided in the third channel; The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel, and when ejecting liquid droplets from the nozzle, Liquid is fed from the liquid tank to the head by the liquid feeding means while the liquid tank is in communication with the liquid tank. Therefore, the appropriate assist pressure is automatically adjusted according to the discharge amount of the head and applied to the head to increase the length of the liquid path, increase the discharge flow rate, and increase the viscosity of the discharge liquid. Inadequate refilling can be avoided, bubble exhaustion can be improved while suppressing wasteful liquid consumption by liquid circulation, and liquid supply during initial filling and maintenance is performed by the channel opening / closing means provided in the second channel. The liquid can be directly fed to the first flow path by means to shorten the filling time, and the maintenance effect is enhanced by being able to perform pressure discharge for discharging bubbles from the nozzle.

  According to the image forming apparatus of the present invention, the first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head and the other port side of the common flow path of the liquid discharge head are communicated. A second liquid path, the second liquid path has a liquid feeding means, and the first liquid path has a first flow path communicating with the liquid discharge head, and a second flow path communicating with the liquid tank. A pressure regulating valve for communicating the first channel and the second channel, a third channel for communicating the second channel or the liquid tank and the pressure regulating valve, and a third channel. The pressure adjusting valve has an internal flow path resistance that changes according to the flow rate of the liquid flowing through the first flow path. The liquid is discharged from the liquid tank by the liquid feeding means in a state where the liquid discharge head and the liquid tank are in communication with each other. Since the liquid is fed to the nozzle, the appropriate assist pressure is automatically adjusted according to the discharge amount of the head and applied to the head to increase the length of the liquid path, increase the discharge flow rate, and increase the discharge liquid. Insufficient refill due to viscosity increase can be avoided, bubble discharge can be improved while suppressing wasteful liquid consumption by liquid circulation, and nozzles are also maintained during maintenance from the liquid supply amount of the liquid supply means in the second liquid path Since the liquid can be circulated without discharging the liquid, the amount of waste liquid can be reduced.

  According to the image forming apparatus of the present invention, the first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head and the other port side of the common flow path of the liquid discharge head are communicated. A second liquid path, the second liquid path has a liquid feeding means, the first liquid path communicates with a first flow path communicating with the liquid discharge head, a liquid tank, and a flow path opening / closing means. A second flow path having a pressure control valve that communicates the first flow path and the second flow path, a third flow path that communicates the second flow path or the liquid tank and the pressure control valve, And a liquid supply means provided in the third flow path, and the pressure regulating valve discharges the liquid droplets from the nozzle by changing the internal flow path resistance according to the flow rate of the liquid flowing through the first flow path. When the liquid discharge head and the liquid tank are in communication with each other via the pressure regulating valve, Is applied to the head while automatically adjusting the appropriate assist pressure according to the discharge amount of the head, increasing the length of the liquid path, increasing the discharge flow rate, Insufficient refill due to increased viscosity of the discharged liquid can be avoided, bubble discharge performance can be improved while suppressing wasteful liquid consumption in the liquid circulation, and the channel opening / closing means provided in the second channel During initial filling or maintenance, the solution can be directly fed to the first flow path to shorten the filling time, and the bubble can be discharged from the nozzle by pressurizing and improving the maintenance effect. The amount of waste liquid can be reduced because the liquid can be circulated without discharging the liquid from the nozzle even during maintenance from the amount of liquid fed by the liquid feeding means in the liquid path.

  According to the image forming apparatus of the present invention, the first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head and the other port side of the common flow path of the liquid discharge head are communicated. A second liquid path, and each of the first liquid path and the second liquid path is a first channel that communicates with the liquid ejection head, a second tank that communicates with the liquid tank, and has a channel opening / closing means. A flow path, a pressure adjustment valve that communicates the first flow path and the second flow path, a third flow path that communicates the second flow path or the liquid tank and the pressure regulation valve, and a third flow And a pressure adjusting valve has a pressure adjusting valve that changes its internal flow path resistance according to the flow rate of the liquid flowing through the first flow path, and discharges liquid droplets from the nozzle. With the liquid discharge head and the liquid tank communicating with each other via the adjustment valve, the liquid is supplied by the liquid feeding means. Since it is configured to send liquid from the body tank to the head, it is applied to the head while automatically adjusting the appropriate assist pressure according to the discharge amount of the head, making the liquid path longer, increasing the discharge flow rate, and discharging Insufficient refill due to high viscosity of the liquid can be avoided, the bubble circulation can be improved while suppressing wasteful liquid consumption by the liquid circulation, and the flow path opening / closing means provided in the second flow path can be used for the initial stage. The filling time can be shortened by feeding directly to the first flow path with the liquid feeding means during filling and maintenance, and the maintenance effect is enhanced by the ability to pressurize and discharge bubbles from the nozzle. Sometimes it is possible to always discharge bubbles by forming an ink tank-first liquid path-head-second liquid path-ink tank circulation path, and the liquid from both directions to the head during recording. Since the sheet is possible, it is possible to perform a more stable supply, in particular, it becomes possible to stable liquid supplying a plurality of heads in an elongated head with elongated connected in series.

It is typical explanatory drawing with which it uses for description of 1st Embodiment of this invention. It is explanatory drawing which shows an example of a flow-path resistance variable unit. It is a plane explanatory view of a valve body similarly. It is a flowchart with which it uses for description of an example of the initial stage filling operation | movement of the embodiment. It is a flowchart with which it uses for description of the other example of the initial stage filling operation | movement of the embodiment. FIG. 6 is a flowchart for explaining the printing operation in the same manner. It is a flowchart with which it uses for description of a clean operation | movement similarly. It is typical explanatory drawing with which it uses for description of 2nd Embodiment of this invention. It is a flowchart with which it uses for description of the initial stage filling operation | movement of the embodiment. FIG. 6 is a flowchart for explaining the printing operation in the same manner. It is a flowchart with which it uses for description of a clean operation | movement similarly. It is typical explanatory drawing with which it uses for description of 3rd Embodiment of this invention. It is a flowchart with which it uses for description of the initial stage filling operation | movement of the embodiment. FIG. 6 is a flowchart for explaining the printing operation in the same manner. It is a flowchart with which it uses for description of a clean operation | movement similarly. It is typical explanatory drawing with which it uses for description of 4th Embodiment of this invention. It is a flowchart with which it uses for description of the initial stage filling operation | movement of the embodiment. FIG. 6 is a flowchart for explaining the printing operation in the same manner. It is a flowchart with which it uses for description of a clean operation | movement similarly. It is typical explanatory drawing with which it uses for description of 5th Embodiment of this invention. It is typical explanatory drawing with which it uses for description of 6th Embodiment of this invention. It is typical explanatory drawing with which it uses for description of 7th Embodiment of this invention. It is side surface explanatory drawing of a sub tank similarly. It is typical explanatory drawing with which it uses for description of 8th Embodiment of this invention. 1 is a schematic front explanatory view showing an ink jet recording apparatus as an image forming apparatus according to the present invention. It is a schematic plane explanatory drawing similarly. It is a schematic side surface explanatory drawing similarly. FIG. 2 is a schematic explanatory diagram for explaining an ink supply circulation system (ink supply system) of the apparatus. It is block explanatory drawing which shows an example of the control part of the apparatus. It is explanatory drawing which similarly shows an example of the relationship between head discharge flow volume, head pressure loss, and assist flow volume.

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 FIG. FIG. 1 is a schematic explanatory diagram for explaining the embodiment.
The liquid ejection head 1 includes a plurality of nozzles 2 that eject droplets, a plurality of individual channels 3 that communicate with each nozzle 2, and a common channel 4 that communicates with each individual channel 3. 4 is provided with ports 5 and 6 on one end side and the other end side in the nozzle arrangement direction, respectively. An ink cartridge (main tank) 10 that is a liquid tank stores ink to be supplied to the liquid ejection head 1.

  Then, a first liquid path 11 that communicates from the ink cartridge 10 to one port 5 side of the common flow path 4 of the liquid ejection head 1 and a first liquid path 11 that communicates to the other port 6 side of the common flow path 4 of the liquid ejection head 1. 2 liquid paths 12.

  Here, the first liquid path 11 is a flow having a first flow path 21 that communicates with the liquid ejection head 1 through the filter 7, and an open / close valve (valve) 24 that communicates with the ink tank 10 and is a flow path opening / closing means. A second flow path 22 composed of paths 22a and 22b, a flow path resistance variable unit 25 which is a pressure adjusting valve for communicating the first flow path 21 and the second flow path 22, and a second flow path. A third flow path 23 that communicates between the 22 flow paths 22a and 22b (this point is referred to as a branch portion 22c) and the pressure regulating valve 25; and a liquid feeding means provided in the third flow path 23. And a certain pump (assist pump) 26 (pump P1).

  The variable flow path resistance unit 25, which is a pressure adjustment valve, has an internal flow path resistance that changes according to the flow rate of the liquid (ink) flowing through the first flow path 21.

  The ink cartridge 10 is provided with an atmosphere communication portion 30 and a detection electrode 31 that detects the liquid level, and is arranged so that the liquid level in the ink cartridge 10 is lower than the nozzle surface of the head 1. Has been. Thus, in a state where ink is filled in the ink path, the head 1 is held at a negative pressure due to the water head difference h between the liquid levels of the head 10 and the ink cartridge 10. It can be performed.

  A maintenance / recovery mechanism 51 is disposed on the head 1 side. The maintenance / recovery mechanism 51 prevents moisture drying of the ink during non-ejection, and at the same time removes bubbles in the head 1 and sucks ink in the head 1 when the nozzle 2 is clogged. The cap 52 is provided. When sucking the ink in the head 1, the nozzle surface of the head 1 is capped by the cap 52, and the ink is discharged to the waste liquid tank 56 by the suction pump 53. Here, the cap 52 is used for both moisturizing and sucking, but a cap having independent roles may be formed. Further, the sucked ink may be returned to the ink cartridge 10 instead of the waste liquid tank 56. In addition, the waste liquid tank 56 may serve not only as a suction operation but also as an empty discharge receiver that receives empty discharge droplets that do not contribute to image formation from the head 1. The wiper member 57 is attached to the wiping unit 58, and the wiper member 57 wipes the nozzle surface 2a of the head 1 after maintenance, thereby adjusting the meniscus of the nozzle surface. The cap 52 and the wiper member 57 are moved back and forth with respect to the nozzle surface 2a of the head 1 by a moving mechanism (not shown) (in this example, the cap 52 and the wiper member 57 are moved up and down).

Next, an example of the variable flow path resistance unit 25 will be described with reference to FIGS. FIG. 2 is a schematic explanatory view of the variable flow path resistance unit, and FIG. 3 is an explanatory plan view of the valve body of the unit.
The variable flow resistance unit 25 includes a pipe member 41 that is a flow path forming member and a valve body 42 that is a movable member that is movably accommodated in the pipe member 41 in a free state.

  The pipe member 41 has a port 43 a that connects the first flow path 21, a port 43 b that connects the flow path 22 a of the second flow path 22, and a port 43 c that connects the third flow path 23. ing. The valve body 42 is a stepped shaft-shaped member having step portions having different diameters in the ink flow direction, and has at least three step portion elements of an upper portion 42t, a central portion 42m, and a lower portion 42b. The diameter is smaller than the lower part 42b. The valve body 42 is movable inside the pipe member 41, and takes the position shown in FIG. 2A, the position shown in FIG. 2B, or an intermediate position depending on the state of the internal flow. .

  Here, as shown in FIG. 3, the upper portion 42 t of the valve body 42 is a communication path that communicates the first flow path 41 and the third flow path 43 in a direction along the ink flow direction. A through hole 44 serving as a first throttle portion is provided. Further, the second throttle portion 48 is formed between the lower portion 42b of the valve body 42 and the flow path portion 47b of the pipe member 41, and the valve body 42 moves according to the state of the internal flow as described above. As a result, the aperture amount of the second aperture section 48 changes.

  Here, as shown in FIG. 3, the through holes 44 are equally divided into four equal parts around the central axis of the valve element 42, but the size of the holes can be reduced to increase the number of holes, Conversely, it is also possible to enlarge the holes and reduce the number of holes as appropriate. However, it is preferable that the through holes 42 be evenly arranged in the circumferential direction in the valve body upper portion 42t in that the valve body 42 is moved straight using the flow of ink discharge from the head 1.

  The pipe member 41 has a horizontal hole (a part of the third flow path 23 between the position of the central portion 42m of the valve body 42, that is, between the first throttle portion 44 and the second throttle portion 48). Port) 43c is formed.

Here, the assist principle by the flow path resistance variable unit 25 and the assist pump 26 will be described.
First, in a state where no droplet is discharged from the head 1 or a condition where the discharge flow rate is small, the flow path resistance variable unit 83 is in the state shown in FIG. In this state, the valve body 42 is on the port 43b side. As shown in FIG. 2A, the sum of the fluid resistance between the gap Gb between the pipe member 41 and the lower portion 42b of the valve body 42 and the through hole 84 serving as the first throttle portion is the pipe member 41 and the valve body. 42 is larger than the fluid resistance of the gap Gt of the upper part 42t, and further, there is a first flow path 21 having a large fluid resistance and a filter on the head side (not shown) at the tip of the port 43a. The sent ink flows to the port 43b side where it easily flows (arrow C). Therefore, the ink flow generated by the pump 26 only circulates in the loop path formed by the flow path 22b of the second flow path 22 from the third flow path 23 through the flow path resistance variable unit 25. The pressure of the head 1 is hardly affected.

  On the other hand, when the discharge flow rate of the head 1 is high, the flow path resistance variable unit 83 is in the state shown in FIG. The gap Gt between the pipe member 41 and the upper part 42t of the valve body 42 is narrow, and the valve body 42 is caused to flow by the ink flow caused by the droplet discharge from the head 1 indicated by the arrow Qh passing through the pipe passage hole 44 as the first throttle part. The valve body 42 is moved by being pulled toward the port 43a (moves upward in the figure). Thereby, the lower part 42b of the valve body 42 moves to the small diameter part (flow-path part 47b: 2nd narrowing part 48) of the pipe member 41, and the gap between the pipe member 41 and the lower part 42b of the valve body 42 is a small gap. Gb1. As shown by the arrow Qa, the ink sent by the pump 26 tends to flow through this narrow gap Gb1 (arrow D), and pressure is generated. This pressure can reduce the pressure loss that occurs when ink flows through the head 1, and can provide a large flow of ink.

  In the variable flow path resistance unit 25, the condition in which the discharge flow rate of the head 1 increases and the pressure loss increases, the ink flow direction between the peripheral surface of the lower part 42b of the valve body 42 and the flow path part 47b of the tube member 41 increases. The opposing length (the length of the second throttle portion 48) becomes longer, the length of the lower gap 42b of the valve body 42 and the narrow gap Gb1 between the pipe members 41 becomes longer, and the pressure is increased by the pump (assist pump) 26. Increase the effect. This eliminates the complexity of controlling the flow rate adjustment valve with another actuator or the like as in the prior art, and realizes a stable ink supply automatically with a simple configuration.

Next, a first example of the initial filling operation with respect to the head in the first embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by opening the valve 24 and driving the assist pump 26, the ink sent from the assist pump 26 passes through the flow path resistance variable unit 25 from the third flow path 23 and passes through the second flow path. 22 and circulates to the ink cartridge 10 or the third flow path 23 via the valve 24, and the third flow path 23 and the second flow path 22 are filled with ink.

  When the valve 24 is closed after a predetermined time has elapsed (after the counter is up), the ink sent from the assist pump 26 passes through the first flow path 21 of the first liquid path 11 and the common flow path 4 of the head 1. And circulates in the ink cartridge 10 via the second liquid path 12. Note that a counter is used as the time measuring means, and it is determined that a predetermined time has elapsed since the counter was increased.

  Next, a time until the ink cartridge 10 is circulated after the valve 24 is closed is set in advance, and the valve 24 is opened after the time has elapsed (after the counter is increased). As a result, a head pressure h is applied to the head 1.

  Then, the suction pump 53 is driven to bring the inside of the cap 52 into a negative pressure state to eliminate bubbles remaining in the nozzle 2 of the head 1 (cap suction is performed), and the cap 52 is separated from the nozzle surface 2 a of the head 1. (Release head capping) The wiper member 57 is moved to the wiping position and moved relative to the head 1 to wipe the nozzle surface 2a of the head 1 (head wiping), and the head 1 is driven to drive a predetermined droplet. A desired meniscus is formed on the nozzle 2 by ejecting a number of ink droplets from the nozzle (empty ejection).

  Thereafter, the assist pump 26 is stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the initial filling of the ink into the head 1 is completed.

Next, a second example of the initial filling operation for the head in the first embodiment will be described with reference to the flowchart of FIG.
This example is an example in the case of using a pump of a system that requires priming water as the assist pump 26.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, the valve 24 is closed, the assist pump 26 is driven, the nozzle surface 2a of the head 1 is capped with the cap 52, the suction pump 53 is driven to start the nozzle suction, and the nozzle suction is stopped after a predetermined time has elapsed. . Accordingly, when the assist pump 26 is a pump that requires priming water, the nozzle 24 is sucked with the valve 24 closed, and air is sucked from the nozzle 2 of the head 1, whereby the assist pump 26 is discharged from the ink cartridge 10. Can assist priming up to.

  As a result, the ink fed from the assist pump 26 passes through the flow path resistance variable unit 25 from the third flow path 23, passes through the second flow path 22 and the valve 24, and the ink cartridge 10 or the third flow. Circulating to the path 23, the third flow path 23 and the second flow path 22 are filled with ink.

  When the valve 24 is closed after a lapse of a predetermined time from the nozzle suction stop (after counting up), the ink fed from the assist pump 26 passes through the first flow path 21 of the first liquid path 11 to the head 1. The common flow path 4 is filled and further circulated to the ink cartridge 10 via the second liquid path 12.

  Next, a time until the ink cartridge 10 is circulated after the valve 24 is closed is set in advance, and the valve 24 is opened after the time has elapsed (after the counter is increased). As a result, a head pressure h is applied to the head 1.

  Then, the suction pump 53 is driven to bring the inside of the cap 52 into a negative pressure state to eliminate bubbles remaining in the nozzle 2 of the head 1 (cap suction is performed), and the cap 52 is separated from the nozzle surface 2 a of the head 1. (Release head capping) The wiper member 57 is moved to the wiping position and moved relative to the head 1 to wipe the nozzle surface 2a of the head 1 (head wiping), and the head 1 is driven to drive a predetermined droplet. A desired meniscus is formed on the nozzle 2 by ejecting a number of ink droplets from the nozzle (empty ejection).

  Thereafter, the assist pump 26 is stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the initial filling of the ink into the head 1 is completed.

Next, the printing operation in the first embodiment will be described with reference to the flowchart of FIG.
After receiving the print job signal, the temperature inside the apparatus is first detected by a temperature sensor to estimate the ink temperature. Based on the temperature of the ink, the flow rate of liquid fed by the assist pump 26 is determined (assist pump drive condition setting), and the assist pump 26 is driven. After that, the cap 52 covering the nozzle surface 2a of the head 1 is separated from the nozzle surface 2a (head capping is released), and after a predetermined number of drops are ejected, the printing operation is started.

  At this time, since the assist pump 26 is driven, the ink supply tube or the like forming the first flow path 21 of the first liquid flow path 11 is a long system, and even when high viscosity ink is used, ink supply is performed. Since the accompanying pressure loss can be reduced appropriately, good printing can be performed without causing insufficient ink supply.

  After printing, the nozzle surface 2a of the head 1 is capped with a cap 52. Thereafter, the assist pump 26 is stopped. Here, the assist pump 26 may be stopped immediately after printing. Further, here, the liquid feeding amount of the assist pump 26 is controlled based on the ink temperature. However, depending on the conditions such as the ink supply specifications, the liquid feeding amount that does not cause shortage of supply under the lowest temperature environment condition Liquid can also be fed under temperature conditions.

Next, the cleaning operation in the first embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by closing the valve 24 and driving the assist pump 26, the ink sent from the assist pump 26 passes from the third flow path 23 through the flow path resistance variable unit 25 and passes through the first liquid path 11. Are sent to the common liquid chamber 4 of the head 1 through the first flow path 21, and bubbles are discharged from the nozzle 2 together with the ink.

  Then, after a predetermined time has elapsed (after the counter is up), the valve 24 is opened, the cap 52 is separated from the nozzle surface 2a of the head 1 (head capping is released), and the wiper member 57 is set to the wiping position and is relative to the head 1 , The nozzle surface 2a of the head 1 is wiped (head wiping), and the head 1 is driven to eject a predetermined number of ink droplets from the nozzle (empty ejection). Form a meniscus.

  Thereafter, the assist pump 26 is stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the cleaning operation of the head 1 is completed.

  As described above, the first liquid path includes a first liquid path that communicates from the liquid tank to one port side of the common flow path of the head, and a second liquid path that communicates to the other port side of the common flow path of the head. The radial path includes a first flow path communicating with the liquid discharge head, a second flow path communicating with the liquid tank and having a flow path opening / closing means, and a pressure communicating the first flow path and the second flow path. An adjustment valve, a third flow path that communicates the second flow path or liquid tank and the pressure adjustment valve, and a liquid feeding means provided in the third flow path. The internal flow path resistance changes in accordance with the flow rate of the liquid flowing through one flow path, and when the liquid droplets are ejected from the nozzle, the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. By configuring the liquid to be sent from the liquid tank to the head by liquid feeding means, the discharge amount of the head can be reduced. Applying to the head while automatically adjusting the appropriate assist pressure, the liquid path can be lengthened, the discharge flow rate can be increased, the refill shortage due to increased viscosity of the discharged liquid can be avoided, etc. Bubbles can be improved while suppressing wasteful liquid consumption by circulation, and liquid is supplied directly to the first flow path by the liquid supply means at the time of initial filling or maintenance by the flow path opening / closing means provided in the second flow path. Thus, the filling time can be shortened, and the maintenance effect is enhanced by being able to pressurize and discharge bubbles from the nozzle.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic explanatory diagram for explaining the embodiment.
In this embodiment, the on / off valve 24 interposed in the flow path 22b of the second flow path 22 of the first liquid path 11 in the first embodiment is not provided, and the liquid feed pump 27 (pump) is provided in the second liquid path 12. P2) is interposed. Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

Next, the initial filling operation for the head in the second embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by driving the assist pump 26, the ink sent from the assist pump 26 passes through the variable flow resistance unit 25 from the third flow path 23 and passes through the second flow path 22 and the valve 24. Then, it circulates to the ink cartridge 10 or the third flow path 23, and the third flow path 23 and the second flow path 22 are filled with ink.

  Then, after a predetermined time has elapsed (after the counter is increased), the liquid feeding pump 27 is driven (liquid feeding pump P2 driving), and liquid feeding from the head 1 side to the ink cartridge 10 side is performed. Thereby, the ink sent from the assist pump 26 fills the common flow path 4 of the head 1 via the first flow path 21 of the first liquid path 11 and further passes through the second liquid path 12 to the liquid feed pump 27. Circulates to the ink cartridge 10 via

  Next, a time from the start of driving of the liquid feeding pump 27 to the circulation to the ink cartridge 10 is set in advance, and the liquid feeding pump 27 is stopped after the time has elapsed (after the counter is increased). As a result, a head pressure h is applied to the head 1.

  Then, the suction pump 53 is driven to bring the inside of the cap 52 into a negative pressure state to eliminate bubbles remaining in the nozzle 2 of the head 1 (cap suction is performed), and the cap 52 is separated from the nozzle surface 2 a of the head 1. (Release head capping) The wiper member 57 is moved to the wiping position and moved relative to the head 1 to wipe the nozzle surface 2a of the head 1 (head wiping), and the head 1 is driven to drive a predetermined droplet. A desired meniscus is formed on the nozzle 2 by ejecting a number of ink droplets from the nozzle (empty ejection).

  Thereafter, the assist pump 26 is stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the initial filling of the ink into the head 1 is completed.

Next, the printing operation in the second embodiment will be described with reference to the flowchart of FIG.
After receiving the print job signal, the temperature inside the apparatus is first detected by a temperature sensor to estimate the ink temperature. Based on the temperature of the ink, the flow rate of liquid fed by the assist pump 26 is determined, and the assist pump 26 is driven. Then, the liquid feed pump 27 is driven. After that, the cap 52 covering the nozzle surface 2a of the head 1 is separated from the nozzle surface 2a (head capping is released), and after a predetermined number of drops are ejected, the printing operation is started.

  At this time, since the assist pump 26 is driven, the ink supply tube or the like forming the first flow path 21 of the first liquid flow path 11 is a long system, and even when high viscosity ink is used, ink supply is performed. Since the accompanying pressure loss can be reduced appropriately, good printing can be performed without causing insufficient ink supply.

  After printing, the nozzle surface 2a of the head 1 is capped with a cap 52. Thereafter, the liquid feed pump 27 is stopped and the assist pump 26 is stopped.

  In this way, by driving the liquid feeding pump 27 during printing, even when bubbles are generated during printing, the bubbles can be removed as they are.

Next, the cleaning operation of the second embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, the assist pump 26 is driven, and the suction pump 53 is driven to perform cap suction, whereby bubbles are discharged from the nozzle 2 of the head 1 together with ink. Then, the cap 52 is moved away from the nozzle surface 2a of the head 1 (head capping is released), and the wiper member 57 is moved to the wiping position to move relative to the head 1, thereby wiping the nozzle surface 2a of the head 1. (Head wiping) A desired meniscus is formed on the nozzle 2 by driving the head 1 to eject a predetermined number of ink droplets from the nozzle (empty ejection).

  Thereafter, the assist pump 26 is stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the cleaning operation of the head 1 is completed.

  As described above, the first liquid path communicating from the liquid tank to one port side of the common flow path of the head and the second liquid path communicating to the other port side of the common flow path of the liquid discharge head are provided. The two liquid paths have liquid feeding means, and the first liquid path has a first flow path communicating with the head, a second flow path communicating with the liquid tank, a first flow path and a second flow path. A pressure regulating valve for communicating the channel, a third channel communicating the second channel or liquid tank and the pressure regulating valve, and a liquid feeding means provided in the third channel, The adjustment valve has an internal flow path resistance that changes according to the flow rate of the liquid flowing through the first flow path, and the head and the liquid tank communicate with each other via the pressure adjustment valve when ejecting droplets from the nozzle. In this state, the liquid is discharged from the liquid tank to the head by the liquid feeding means, so that the discharge amount of the head Appropriate assist pressure is automatically adjusted accordingly and applied to the head to avoid the shortage of refill caused by lengthening the liquid path, increasing the discharge flow rate, increasing the viscosity of the discharge liquid, etc. It is possible to improve the bubble discharge performance while suppressing wasteful liquid consumption by circulation, and also to circulate without discharging the liquid from the nozzle during maintenance from the liquid supply amount of the liquid supply means of the second liquid path. The amount can be reduced.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 12 is a schematic explanatory diagram for explaining the embodiment.
In this embodiment, in addition to the first embodiment, a liquid feed pump 27 (pump P2) is interposed in the second liquid path 12 as in the second embodiment. Since other configurations are the same as those of the first and second embodiments, description thereof is omitted.

Next, the initial filling operation with respect to the head in the third embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by opening the valve 24 and driving the assist pump 26, the ink sent from the assist pump 26 passes through the flow path resistance variable unit 25 from the third flow path 23 and passes through the second flow path. 22 and circulates to the ink cartridge 10 or the third flow path 23 via the valve 24, and the third flow path 23 and the second flow path 22 are filled with ink.

  Next, when the valve 236 is closed after a predetermined time has elapsed since the assist pump 26 is driven (after the counter is increased), the ink fed from the assist pump 26 passes through the first flow path 21 of the first liquid path 11. It is sent to the inside of the head 1. When a preset time until the inside of the head 1 is filled with ink has elapsed (after the counter is up), the valve 24 is opened. A head pressure h is applied to the head 1, and in this state, bubbles remaining in the nozzle 2 of the head 1 are eliminated by sucking the cap, and the nozzle surface 2a of the head 1 is wiped by the wiper member 57 to drive the head 1. A desired meniscus can be formed on the nozzle 2 by ejecting a predetermined number of ink droplets from the nozzle.

  Next, the ink is circulated to the ink cartridge 10 side by the liquid feed pump 27 while the second liquid path 12 is filled with ink. At this time, the valve body 42 of the fluid resistance control unit 25 is controlled as described above by suppressing the amount of liquid fed by the liquid feed pump 27 to the amount of ink discharged from the head 1 (for example, about 0.1 cc / sec). The fluid resistance of the first liquid passage 11 can be reduced and the pressure can be controlled to a pressure lower than the meniscus holding pressure at which ink does not leak from the nozzles 2 of the head 1, and wasteful ink is consumed. Initial filling is possible. In the prior art, since the pressure is controlled by the pressure, it is extremely difficult to control the minute pressure below the meniscus holding force. However, according to the configuration of the present invention, the pressure can be controlled by the flow rate of the pump 27. The main feature is that it can be easily obtained.

Next, the printing operation in the third embodiment will be described with reference to the flowchart of FIG.
After receiving the print job signal, the temperature inside the apparatus is first detected by a temperature sensor to estimate the ink temperature. Based on the temperature of the ink, the flow rate of liquid fed by the assist pump 26 is determined, the valve 24 is opened, the assist pump 26 is driven, and the liquid feed pump 27 is driven. After that, the cap 52 covering the nozzle surface 2a of the head 1 is separated from the nozzle surface 2a (head capping is released), and after a predetermined number of drops are ejected, the printing operation is started.

  After printing, the nozzle surface 2a of the head 1 is capped with a cap 52. Thereafter, the liquid feed pump 27 is stopped and the assist pump 26 is stopped.

Next, the cleaning operation of the third embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by closing the valve 24 and driving the assist pump 26, the ink sent from the assist pump 26 passes from the third flow path 23 through the flow path resistance variable unit 25 and passes through the first liquid path 11. Are sent to the common liquid chamber 4 of the head 1 through the first flow path 21, and bubbles are discharged from the nozzle 2 together with the ink.

  Then, after a predetermined time has elapsed (after the counter is up), the valve 24 is opened, the cap 52 is separated from the nozzle surface 2a of the head 1 (head capping is released), and the wiper member 57 is set to the wiping position and is relative to the head 1 , The nozzle surface 2a of the head 1 is wiped (head wiping), and the head 1 is driven to eject a predetermined number of ink droplets from the nozzle (empty ejection). Form a meniscus.

  Thereafter, the assist pump 26 is stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the cleaning operation of the head 1 is completed.

As described above, the first liquid path communicating from the liquid tank to one port side of the common flow path of the head and the second liquid path communicating to the other port side of the common flow path of the liquid discharge head are provided. The two liquid paths have liquid feeding means, the first liquid path has a first flow path communicating with the liquid discharge head, a second flow path communicating with the liquid tank and having flow path opening / closing means, A pressure adjusting valve that communicates the first channel with the second channel, a third channel that communicates the second channel or liquid tank with the pressure regulating valve, and a feed provided in the third channel. The pressure adjusting valve has an internal flow path resistance that changes in accordance with the flow rate of the liquid flowing through the first flow path. A configuration in which liquid is fed from the liquid tank to the head by the liquid feeding means while the head and the liquid tank are in communication. By adjusting the appropriate assist pressure according to the discharge amount of the head, it is applied to the head to refill the liquid path, lengthening the discharge flow rate, increasing the viscosity of the discharge liquid, etc. Insufficiency can be avoided, bubble discharge performance can be improved while suppressing wasteful liquid consumption by liquid circulation, and liquid supply means can be used during initial filling or maintenance by means of a channel opening / closing means provided in the second channel. The liquid can be fed directly to the first flow path to shorten the filling time, and the bubble discharge from the nozzle can be pressurized and discharged to increase the maintenance effect. Furthermore, the liquid feed amount of the liquid feed means in the second liquid path Even during maintenance, the liquid can be circulated without discharging from the nozzle, and the amount of waste liquid can be reduced.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 16 is a schematic explanatory diagram for explaining the embodiment.
In this embodiment, in addition to the first embodiment, the second liquid path 12 also communicates with the liquid discharge head 1 through the filter 17 through the filter 17 and the ink tank 10 to open and close the flow path. A second flow path 62 composed of flow paths 62 a and 62 b having an on-off valve (valve) 64 as a means, and a flow that is a pressure adjusting valve for communicating the first flow path 61 and the second flow path 62. A third flow path 63 communicating between the variable resistance unit 65 and the flow paths 62a and 62b of the second flow path 62 (this point is referred to as a branching section 62c) and the pressure regulating valve 65; And a pump (reversible pump) 66 (pump P3) which is a liquid feeding means provided in the third flow path 63. The variable flow path resistance unit 65, which is a pressure adjustment valve, has an internal flow path resistance that changes according to the flow rate of the liquid (ink) flowing through the first flow path 61.

Next, the initial filling operation of the fourth embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by opening the valve 24 and driving the assist pump 26, the ink sent from the assist pump 26 passes through the flow path resistance variable unit 25 from the third flow path 23 and passes through the second flow path. 22 and circulates to the ink cartridge 10 or the third flow path 23 via the valve 24, and the third flow path 23 and the second flow path 22 are filled with ink.

  When the valve 24 is closed after a predetermined time has elapsed (after the counter is up), the ink fed from the assist pump 26 passes through the first flow path 21 of the first liquid path 11 and passes through the common flow path 4 of the head 1. Fulfill. When the head 1 is filled with ink (counter up for a predetermined time), the valve 24 is opened. As a result, a head pressure h is applied to the head 1. In this state, bubbles remaining in the nozzle 2 of the head 1 are eliminated by sucking the cap, and the nozzle surface 2 a of the head 1 is wiped by the wiper member 57. And a desired meniscus is formed on the nozzle 2 by ejecting a predetermined number of ink droplets from the nozzle.

  Next, the first flow path 61 and the third flow path of the second liquid path 12 are driven by driving the liquid feed pump 66 with the valve 64 closed so that the liquid feed direction is the arrow A direction. Ink is circulated to the cartridge 10 side while filling 63 with ink. At this time, the amount of liquid fed by the liquid feed pump 66 is suppressed to the amount of ink discharged from the head 1 (for example, about 0.1 cc / sec), so that the valve element 42 of the flow path resistance variable unit 26 as described above. As a result, the fluid resistance of the first liquid path can be reduced, and the pressure can be controlled to a pressure lower than the meniscus holding pressure at which the ink does not leak from the nozzle 2 of the head 1, and wasteful ink is consumed. Initial filling is possible.

  When the ink from the second liquid path 12 reaches the ink cartridge 10, the liquid feed pump 66 is stopped, the valve 64 is opened, and then the liquid feed pump 66 is set so that the liquid feed direction is the arrow B direction. Driven, the air bubbles remaining in the second flow path 62 are discharged to the ink cartridge 10, and the initial filling is completed.

Next, the printing operation of the fourth embodiment will be described with reference to the flowchart of FIG.
After receiving the print job signal, the temperature inside the apparatus is first detected by a temperature sensor to estimate the ink temperature. Based on the temperature of the ink, the flow rate of liquid fed by the assist pump 26 is determined (assist driving condition setting). Then, the valves 24 and 64 are opened, and the assist pump 26 and the liquid feed pump 66 are driven. After that, the cap 52 covering the nozzle surface 2a of the head 1 is separated from the nozzle surface 2a (head capping is released), and after a predetermined number of drops are ejected, the printing operation is started.

  At this time, during printing, ink can be supplied from both directions of the first liquid path 11 and the second liquid path 12 by feeding the liquid to the head 1 side by the pumps 26 and 66 with the valves 24 and 64 opened. Thus, the pressure adjusting valve (flow path resistance variable unit 25, 65) is operated according to the amount of ink discharged from the nozzle 2 of the head 1, so that the supply can be performed with a small pressure fluctuation.

  After printing, the nozzle surface 2a of the head 1 is capped with a cap 52. Thereafter, the liquid feed pump 27 is stopped and the assist pump 26 is stopped.

Next, the cleaning operation of the fourth embodiment will be described with reference to the flowchart of FIG.
First, it is determined whether or not the ink cartridge 10 has been installed. If the ink cartridge 10 has not been installed, a cartridge installation request is displayed. When it is confirmed that the ink cartridge 10 has been installed, the maintenance is performed. The nozzle surface 2 a of the head 1 is capped with the cap 52 of the recovery mechanism 51.

  Next, by closing the valves 24 and 64 and driving the assist pump 26 and the liquid feed pump 66, the ink fed from the assist pump 26 and the liquid feed pump 66 flows from the third flow paths 23 and 63. The fluid passes through the variable path resistance units 25 and 65, passes through the first flow paths 21 and 61 of the first and second liquid paths 11 and 12, and is sent to the common liquid chamber 4 of the head 1. Discharge.

  Then, after a predetermined time has elapsed (after the counter is increased), the valves 24 and 64 are opened, the cap 52 is separated from the nozzle surface 2a of the head 1 (head capping is released), and the wiper member 57 is set to the wiping position with respect to the head 1 By relatively moving, the nozzle surface 2a of the head 1 is wiped (head wiping), and the head 1 is driven to eject a predetermined number of ink droplets from the nozzle (empty ejection). A desired meniscus is formed.

  Thereafter, the assist pump 26 and the liquid feed pump 66 are stopped, and the nozzle surface 2 a of the head 1 is capped with the cap 52.

  Thereby, the cleaning operation of the head 1 is completed.

  As described above, the first liquid path includes a first liquid path that communicates from the liquid tank to one port side of the common flow path of the head, and a second liquid path that communicates to the other port side of the common flow path of the head. Each of the path and the second liquid path includes a first flow path communicating with the liquid discharge head, a second flow path communicating with the liquid tank and having flow path opening / closing means, a first flow path, and a first flow path. A pressure adjusting valve for communicating the two flow paths, a third flow path for communicating the second flow path or the liquid tank and the pressure regulating valve, and a liquid feeding means provided in the third flow path. In the pressure adjustment valve, the internal flow path resistance changes according to the flow rate of the liquid flowing in the first flow path, and when the liquid droplets are ejected from the nozzle, the head and the liquid tank communicate with each other via the pressure adjustment valve. In such a state, the liquid is fed from the liquid tank to the head by the liquid feeding means. Appropriate assist pressure is automatically adjusted according to the discharge amount of the head and applied to the head to avoid the shortage of refill due to the increase in the length of the liquid path, increase in the discharge flow rate, and increase in the viscosity of the discharge liquid. It is possible to improve the bubble discharge performance while suppressing wasteful liquid consumption by the liquid circulation, and further, the first flow directly by the liquid feeding means at the time of initial filling or maintenance by the flow path opening / closing means provided in the second flow path. The filling time can be shortened by supplying the liquid to the passage, and the maintenance effect is enhanced by being able to pressurize and discharge the bubbles from the nozzle. Further, at the time of initial filling and maintenance, the ink tank-first liquid path-head-second By forming the circulation path of the liquid path-ink tank, it is possible to discharge the bubbles at all times, and moreover, since the liquid can be supplied from both directions to the head during recording, more stable supply is performed. Bets can be, in particular, it becomes possible to stable liquid supplying a plurality of heads in an elongated head with elongated connected in series.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 20 is a schematic explanatory diagram for explaining the embodiment.
In this embodiment, an atmosphere release valve 32 is provided in the atmosphere release passage 30 of the ink cartridge 10 in the third embodiment. Since other configurations are the same as those of the third embodiment, the description thereof is omitted.

  Here, when the ink is returned to the ink cartridge 10 by the liquid feeding pump 27 to form a circulation flow, the liquid feeding pressure of the liquid feeding pump 27 is reduced by closing the air release valve 32. To form a stable circulating flow.

Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 21 is a schematic explanatory diagram for explaining the embodiment.
In this embodiment, in the third embodiment, the ink cartridge 10 side of the second liquid path 21 is provided with a member (bubble-breaking member) 33 that bursts bubbles to return ink to the ink cartridge 10. . Further, the inside of the foam-breaking member 33 is communicated with the atmosphere opening passage 30 through the communication passage 34.

  The foam-breaking member 33 has a dome-shaped space, and when a liquid containing bubbles is introduced into the space, the bubbles are destroyed, the liquid is discharged to the lower part, and the air is discharged from the upper part. . As the foam-breaking member 33, an ultrafine fiber such as SUS or a fibrous member having protrusions and a large surface area is preferable.

  In this embodiment, air bubbles are mixed in the ink returned to the ink cartridge 10 through the second liquid path 12, but if there are many air bubbles, the air bubbles accumulate on the liquid surface of the ink cartridge 10 and are released from the hole opened to the atmosphere. Since there is a risk of leakage, the bubbles are ruptured by the foam-breaking member 33 to perform gas-liquid separation, the liquid is returned into the ink cartridge 10, and the gas is discharged into the atmosphere opening passage 30, thereby preventing such a problem. It is preventing.

Next, a seventh embodiment of the present invention will be described with reference to FIGS. FIG. 22 is a schematic explanatory view for explaining the embodiment, and FIG. 23 is a side explanatory view of the sub tank.
Here, a sub tank 71 for temporarily storing ink to be supplied to the head 1 is provided. The sub-tank 71 is provided with an ink containing portion 72 therein, and part of the wall surface of the ink containing portion 72 is formed by a flexible member 74 so as to be able to absorb pressure fluctuations. The flow path 76 is connected to the port 5 of the head 1 and the port 6 of the head 1. In addition, the first flow path 21 of the first liquid path 11 is connected to the ink container 72, and the flow path 76 is connected to the second liquid path 12. As shown in FIG. 23, the sub tank 71 is flat and has a sufficiently narrow shape so that air does not stay when ink is fed.

Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 24 is a schematic explanatory diagram for explaining the embodiment.
Here, instead of the ink cartridge 10 of the seventh embodiment, a liquid tank 80 having the same configuration as that of the ink cartridge 10 of the sixth embodiment is provided, and a large-capacity ink cartridge 81 that can be attached to and detached from the liquid tank 80 is used. Liquid is fed by a pump 82. When the detection electrode 31 of the liquid tank 80 detects that the remaining amount of ink is equal to or less than a predetermined amount, the pump 82 is driven by a drive control unit (not shown) to send liquid.

Next, an example of an ink jet recording apparatus as an image forming apparatus according to the present invention will be described with reference to FIGS. 25 is a schematic front view of the recording apparatus, FIG. 26 is a schematic plan view, and FIG. 27 is a schematic side view.
The ink jet recording apparatus includes a guide rod 102 that is a guide member horizontally mounted on the left and right side plates 101L and 101R provided upright on the main body frame 101, and a guide rail attached to a rear frame 101B that is horizontally mounted on the main body frame 101. 103, the carriage 104 is slidably held in the main scanning direction (guide rod longitudinal direction), and the carriage 104 is moved and scanned in the longitudinal direction (main scanning direction) of the guide rod 2 by a main scanning motor and a timing belt (not shown). To do.

  For example, one or a plurality of recording heads 110 that eject ink droplets of black (K), cyan (C), magenta (M), and yellow (Y) are mounted on the carriage 104. The ink discharge ports (nozzles) are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet discharge direction facing downward. The recording head 110 is composed of the liquid ejection head 1 described in the above embodiment.

  As the recording head 110, there are various types such as a thermal type using a heating resistor, a type using a piezoelectric element to deform the diaphragm, and a type using an electrostatic force to deform the diaphragm to obtain discharge pressure. Any of these methods can be applied to the image forming apparatus according to the present invention.

  On the other hand, below the carriage 104, a sheet 120 on which an image is formed by the recording head 110 is conveyed in a direction perpendicular to the main scanning direction (sub-scanning direction). As shown in FIG. 27, the paper 120 is sandwiched between a transport roller 121 and a presser roller 122, transported to an image forming area (printing unit) by the recording head 110, sent onto a printing guide member 123, and discharged. A pair of rollers 124 feeds in the paper discharge direction.

  At this time, scanning of the carriage 104 in the main scanning direction and ink ejection from the recording head 110 are synchronized at an appropriate timing based on the image data, and an image for one band is formed on the paper 120. After image formation for one band is completed, a predetermined amount of paper 120 is fed in the sub-scanning direction, and the same recording operation as described above is performed. These operations are repeated to form an image for one page.

  On the other hand, the sub-tank (buffer tank, head tank) 130 described in the seventh embodiment is integrally connected to the upper portion of the recording head 110 and has an ink storage portion for temporarily storing ink to be ejected. The

  The sub-tank 130 includes an ink cartridge (main tank) 176 that contains ink of each color that is detachably attached to a cartridge holder 177 provided on one end side in the main scanning direction on the apparatus main body side, and a tube member. They are connected via a liquid tube 171 that forms the first flow path of the first liquid path and a liquid tube 172 that forms the second liquid path.

  Further, a maintenance / recovery mechanism 151 that performs maintenance / recovery of the recording head 110 is arranged on the other end side in the main scanning direction of the apparatus main body. The maintenance / recovery mechanism 151 includes a cap 152 for capping the nozzle surface of the recording head 110, a suction pump 153 for sucking the inside of the cap 152, a discharge path 154 for discharging waste liquid of ink sucked by the suction pump 153, and the like. The waste liquid discharged from the discharge path 154 is discharged to a waste liquid tank 156 disposed on the main body frame 101 side.

As shown in FIG. 27, the ink supply / circulation system in this recording apparatus is configured to include a sub tank 130 similar to the sub tank 71 of the seventh embodiment in the first embodiment.
Here, an ink cartridge 176, a pump unit 180 that is a liquid feeding means, and a pressure control unit 181 are connected to the cartridge holder 177. A flow path communicating with the pump unit 180 and the pressure control unit 181 is provided inside the cartridge holder 177.

  The pump unit 180 includes an assist pump 26 and a third flow path 23. As the pump 78, various pumps such as a tubing pump, a diaphragm pump, and a gear pump can be applied. Further, the pressure control unit 181 includes a flow path variable unit 25, an on-off valve 24, and a second flow path 22.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. FIG. 28 is an overall block diagram of the control unit.
The control unit 500 temporarily stores a CPU 501 also serving as a means for controlling the assist operation and the maintenance / recovery operation for controlling the entire apparatus, a ROM 502 for storing programs executed by the CPU 501 and other fixed data, and image data. RAM 503 for storing, rewritable nonvolatile memory 504 for holding data even while the power of the apparatus is shut off, image processing for performing various signal processing and rearrangement on image data, and other control of the entire apparatus And an ASIC 505 for processing input / output signals.

  In addition, a print control unit 508 for driving and controlling the recording head 110 according to print data, a head driver (driver IC) 509 for driving the recording head 110 provided on the carriage 104 side, and moving and scanning the carriage 104. A main scanning motor 551 for rotating, a sub-scanning motor 552 for rotating and driving the conveyance roller 121 for conveying the paper 120, and a maintenance / recovery motor 512 for operating a cap lifting / lowering mechanism 513 for moving the cap 152 and wiper member of the maintenance / recovery mechanism 151 up and down. And a pump / valve drive unit 511 for driving the opening / closing valve 24, and the like.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 has an I / F 506 for transmitting and receiving data and signals to and from the host side, an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, and the like. From the host 600 side via the cable or network via the I / F 506.

  The CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the ASIC 505, and prints the image data. The data is transferred from the unit 508 to the head driver 509. Note that generation of dot pattern data for image output is performed by the printer driver 601 on the host 600 side.

  The print control unit 508 transfers the print data described above as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transfer of the print data and confirmation of the transfer to the head driver 509. The head driver 509 drives the actuator means based on print data corresponding to one line of the recording head 110 input serially.

  The I / O unit 515 acquires information from various sensor groups 516 mounted on the apparatus, extracts information necessary for controlling the printer, and uses it to control the print control unit 508 and the motor drive unit 510. . The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature in the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like. The I / O unit 515 can process various sensor information. Further, a detection signal from a temperature sensor 127 that detects environmental conditions (temperature and humidity) and a detection signal from a full tank detection sensor that detects whether the waste liquid tank 156 is full are also input.

  Control in the initial filling operation, printing operation, and cleaning operation in each of the embodiments is performed by the control unit 500.

A specific example of the assist operation of the printing operation in this recording apparatus will be described with reference to FIG.
For example, when the liquid tube 171 is provided with a long tube having a diameter of 2.8 mm and a length of 2500 mm, and a high viscosity ink of 16 cP is ejected, the fluid resistance of the liquid tube 171 is 2.7 e10 [Pa · s / m ³ ]. Further, in this embodiment, the fluid resistance of the joint with the filter 74 and the following 76 is 1e10 [Pa · s / m ³ ] and 2e9 [Pa · s / m ³ ], respectively.

  Here, when the limit value of the pressure loss that enables stable ejection from the recording head 10 is 2.5 kPa, and ink is ejected continuously from all the nozzles, the ejection flow rate is 0.1 cc / s. The pressure loss at that time is 6.9 kPa. Even in the absence of the pressure control unit 181, the pressure is 3.94 kPa, so that it cannot be naturally supplied by a simple water head difference ink supply system.

  Thus, when the pressure loss increases due to the resistance of the ink supply system and the refill is insufficient, the pump 26 is driven to draw ink from the third flow path 23 by the arrow Qa (Qa is the assist flow rate or the flow of the assisting liquid). However, it is also used as an arrow sign for convenience.) The liquid supply of the pump 26 can compensate for an insufficient supply amount of ink (refill assist).

  FIG. 30 shows an example of the relationship between the discharge flow rate of the recording head 110, the liquid feeding amount (assist flow rate) of the pump 26, and the pressure of the recording head 110. FIG. 30 shows a change in pressure loss of the ink supply system with respect to the head discharge flow rate when the assist flow rate is 0 to 2 cc / s. As described above, when the assist flow rate is “0”, the pressure loss of the head is about 7 kPa, and ink cannot be continuously ejected, resulting in ejection failure. However, by assisting with the pump 26, the pressure loss is 1 kPa. It becomes the following grade and can be continuously discharged.

  The present invention can be similarly applied to the case where inks of the same color are supplied to a plurality of heads, or the case where inks having different prescriptions are supplied to a plurality of heads instead of colors. Further, the present invention can also be applied to an ink supply system in a case where a liquid discharge head having a plurality of nozzle rows in one head discharges different types of liquid from one head. Further, the present invention is not limited to an image forming apparatus that discharges ink in a narrow sense, and can also be applied to a liquid discharging apparatus that discharges various liquids (included in the “image forming apparatus” in the present invention). .

DESCRIPTION OF SYMBOLS 1 Liquid discharge head 2 Nozzle 4 Common liquid chamber 10 Ink cartridge (liquid tank)
DESCRIPTION OF SYMBOLS 11 1st liquid path 12 2nd liquid path 21, 61 1st flow path 22, 62 2nd flow path 23, 63 3rd flow path 24, 64 On-off valve (flow path opening / closing means)
25, 65 Pressure regulating valve (variable flow resistance unit)
26 Assist pump 27, 66 Liquid feed pump 33 Foam-breaking member 71 Sub tank 104 Carriage 110 Recording head 130 Sub tank 141 Liquid tube (first flow path of the first liquid path)
142 Liquid tube (second liquid path)
176 Ink cartridge (Main tank: Liquid tank)
177 Cartridge holder 180 Pump unit 181 Pressure control unit

Claims (6)

A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The first liquid path is
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank and having flow path opening and closing means;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. An image forming apparatus characterized by being liquidated. A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The second liquid path has a liquid feeding means,
The first liquid path is
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. An image forming apparatus characterized by being liquidated. A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The second liquid path has a liquid feeding means,
The first liquid path is
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank and having flow path opening and closing means;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. An image forming apparatus characterized by being liquidated. A plurality of individual flow paths that communicate with a plurality of nozzles that discharge droplets, and a common flow path that communicates with each individual flow path, the common flow paths at one end side and the other end side in the nozzle arrangement direction A liquid ejection head provided with a port,
A liquid tank for storing liquid to be supplied to the liquid discharge head;
A first liquid path communicating from the liquid tank to one port side of the common flow path of the liquid discharge head;
A second liquid path communicating with the other port side of the common flow path of the liquid discharge head,
The first liquid path and the second liquid path are both
A first flow path communicating with the liquid ejection head;
A second flow path communicating with the liquid tank and having flow path opening and closing means;
A pressure regulating valve for communicating the first flow path and the second flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
The pressure regulating valve has an internal channel resistance that changes according to the flow rate of the liquid flowing through the first channel,
When liquid droplets are ejected from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means while the liquid ejection head and the liquid tank are in communication with each other via the pressure adjustment valve. An image forming apparatus characterized by being liquidated.   The image forming apparatus according to claim 1, wherein the liquid tank is provided with a communication path communicating with the atmosphere through a valve that can be opened and closed.   The image forming apparatus according to claim 1, wherein the second liquid path is connected to the inside of the liquid tank via a foam-breaking member.

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