JP2014046644A - Head tank, head unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: a head unit cannot reduce useless liquid consumption caused by a bubble discharge operation without shortage of supplying.SOLUTION: A head unit includes: a first flow passage 621 communicating between a liquid reservoir 604 and a recording head 24; a second flow passage 622 communicating between the liquid reservoir 604 and the recording head 24; a first filter member 635 arranged in the first flow passage 621; and a second filter member 645 arranged in the second flow passage 622. Flow passages 641 and 642, provided at the upstream side of the second filter member 645 of the second flow passage 622, are arranged at an upper position relative to flow passages 631 and 632 provided at the upstream side of the first filter member 635 of the first flow passage 621. The area of the first filter member 635 is larger than that of the second filter member 645, and a wall surface of a flow passage (332) of the first flow passage 621 is formed of a deformable film 602 so that the fluid resistance can be changed.

Description

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

  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. .

  In such an image forming apparatus, when bubbles are mixed in a head tank (also referred to as a sub tank or a buffer tank) that temporarily stores a liquid to be supplied to the recording head, the bubbles may reach the nozzles during droplet discharge. If it enters, drop ejection failure or drop ejection failure occurs, so it is necessary to discharge bubbles.

  Conventionally, a bubble reservoir capable of trapping bubbles contained in a liquid is provided, and the flow path resistance is between the first flow path resistance value and the second flow path resistance value that is larger than the first flow path resistance value. The changeable bubble trap channel, the bubble can be transferred against the buoyancy of the bubble, and the flow rate resistance is between the first channel resistance value and the second channel resistance value. The bubble non-trapping channel having a determined cross-sectional area is provided in parallel with each other, and the bubble trap channel and the bubble non-trapping channel are changed by changing the channel resistance of the bubble trap channel. Distributing means for changing the distribution ratio of the flowing liquid is known, and the distributing means is configured so that when liquid droplets are ejected from the head, more liquid flows to the bubble trap channel side than the bubble non-trap channel. (Patent Document 1).

Japanese Patent No. 4407170

  By the way, when a filter member for filtering foreign matter in the liquid is arranged in the flow path from the head tank to the recording head, especially when a highly viscous liquid is used, a supply shortage to the recording head does not occur. Therefore, it is necessary to increase the filter area.

  However, increasing the filter area consumes a large amount of liquid in the head tank when discharging bubbles in the head tank from the nozzles of the recording head.

  Therefore, when the liquid is supplied to the head through the same filter member in both the bubble trap channel and the bubble non-trap channel as in the configuration disclosed in Patent Document 1 described above, the bubble is discharged. There is a problem that the amount of liquid that is wasted increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce wasteful liquid consumption accompanying the bubble discharging operation without causing insufficient supply.

In order to solve the above problems, the head tank according to the present invention is:
A head tank having a liquid storage chamber that is disposed between a recording head that discharges droplets and a main tank that stores liquid to be supplied to the recording head and temporarily stores liquid to be supplied to the recording head. And
A first flow path through the liquid storage chamber and the recording head;
A second flow path through the liquid storage chamber and the recording head;
A first filter member disposed in the first flow path;
A second filter member disposed in the second flow path,
At least a part of the flow path upstream of the second filter member of the second flow path is disposed at a position above the flow path upstream of the first filter member of the first flow path,
The area of the first filter member is larger than the area of the second filter member,
At least the first flow path can change the fluid resistance;
When droplets are ejected from the recording head, the fluid resistance of the first flow path is smaller than the fluid resistance of the second flow path,
When suction is performed from the recording head side in a state where the supply of the liquid to the liquid storage chamber is stopped, the fluid resistance of the first flow path becomes larger than the fluid resistance of the second flow path. The configuration.

  According to the present invention, it is possible to reduce wasteful liquid consumption accompanying the bubble discharging operation without causing supply shortage.

FIG. 3 is a side explanatory view of a mechanism unit of the image forming apparatus according to the present invention. It is explanatory drawing which looked at FIG. 1 from the arrow A direction. It is typical explanatory drawing with which it uses for description of an example of the liquid supply system in the apparatus. It is side surface explanatory drawing seen from the arrow B direction of FIG. 6 of the head unit which concerns on 1st Embodiment of this invention. It is side surface explanatory drawing seen from the arrow C direction of FIG. It is back explanatory drawing. FIG. 6 is an explanatory cross-sectional view taken along line X1-X in FIG. 5. FIG. 6 is a cross-sectional explanatory view taken along line X2-X in FIG. 5. It is principal part cross-sectional explanatory drawing of the filter member with which it uses for description of an effect | action of the embodiment. It is a typical explanatory view of a filter part of a head tank concerning a 2nd embodiment of the present invention. It is a typical explanatory view of a channel portion on the upstream side of a filter from a liquid storage chamber of a head tank according to a third embodiment of the present invention. It is a typical explanatory view of a head unit concerning a 4th embodiment of the present invention.

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

  This image forming apparatus is a serial type image forming apparatus, and has an image forming unit 2, a transport mechanism unit 5 and the like inside the apparatus main body, and can stack sheets 10 as recording media on the lower side of the apparatus main body. A paper feed tray (including a paper feed cassette and used as a paper feed unit) 4 is provided.

  Then, the paper 10 fed from the paper feed tray 4 is taken in, and the paper 10 is intermittently transported in the vertical direction (direction along the vertical direction) by the transport mechanism unit 5, while being horizontally moved by the image forming unit 2. After the droplets are ejected and a required image is recorded, the sheet 10 on which the image is formed is further conveyed upward through the sheet discharge conveyance unit 6 and is discharged onto a sheet discharge tray 7 provided on the upper side of the apparatus main body. The paper 10 is discharged.

  When performing double-sided printing, after the printing on one side (front surface) is completed, the paper 10 is taken into the reversing unit 8 from the paper discharge conveyance unit 6 and conveyed by the conveyance mechanism unit 5 in the reverse direction (downward). The other side (back side) is reversed and sent to the transport mechanism 5 again, and after the other side (back side) printing is completed, the paper 10 is discharged to the discharge tray 7.

  Here, the image forming unit 2 slidably holds a carriage 23 on which a recording head 24 is mounted with a main guide member 21 and a sub-guide member 22 that are horizontally mounted between the left and right side plates 101L and 101R. The main scanning motor of the moving mechanism moves and scans in the main scanning direction via a timing belt spanned between the driving pulley and the driven pulley.

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

  The recording head 24 has two nozzle rows each having a plurality of nozzles for ejecting a plurality of droplets. One nozzle row of the recording head 24a has yellow (Y) droplets, and the other nozzle row has A magenta (Y) droplet is ejected, one nozzle row of the recording head 24b ejects a black (K) droplet, and the other nozzle row ejects a cyan (C) droplet.

  In addition, a head tank 29 for supplying ink of each color corresponding to each nozzle row of the recording head 24 is mounted on the carriage 23, and each color that is detachably attached to the apparatus main body is mounted on the head tank 29. Ink is supplied from the ink cartridge (main tank).

  In addition, as the liquid discharge head, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses liquid film boiling using an electrothermal transducer such as a heating resistor, a shape memory alloy actuator that uses a metal phase change due to a temperature change, A device equipped with pressure generating means (actuator means) for generating a pressure for discharging liquid, such as an electrostatic actuator using electrostatic force, can be used.

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

  The conveyance mechanism unit 5 includes an endless conveyance belt 51 that is stretched between a conveyance roller 52 that is a driving roller and a driven roller 53, a charging roller 54 that charges the conveyance belt 51, and the image forming unit 2. And a platen member 55 that maintains the flatness of the conveyor belt 51 at a portion facing the plate. The conveyance belt 51 rotates in the sheet conveyance direction (sub-scanning direction) when the conveyance roller 52 is rotationally driven via a timing belt and a timing pulley by a sub-scanning motor (not shown).

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

  The reversing unit 8 reverses the paper 10 partially discharged to the paper discharge tray 7 by the switchback method and feeds the paper 10 between the conveyance belt 51 and the presser roller 48. A claw 81, a reversing guide member 82, a reversing roller 83 and a spur 84 as a reversing roller, a conveyance auxiliary roller 85 facing the driven roller 53, and a reverse conveying portion of the conveying belt 51 (moving in a direction opposite to the paper feeding direction). And a detour guide member 86 that guides the sheet 10 separated from the reverse conveyance portion of the conveyance belt 51 between the conveyance belt 51 and the pressing roller 48 by detouring the charging roller 54.

  Further, a maintenance / recovery mechanism (maintenance unit) 9 for maintaining and recovering the state of the nozzles of the recording head 24 is disposed in a non-printing area on one side of the carriage 23 in the scanning direction.

  A suction cap 91 and a moisturizing cap 92 for capping each nozzle surface 124 (see FIG. 1) of the recording head 24 and a wiper member for wiping (wiping) the nozzle surface 124 are provided on the frame 90 of the maintenance and recovery mechanism 9. A wiper blade (first wiper member) 94 and the like are held. Further, as will be described later, a wiping member (second wiper member) 202 which is a cleaning member for wiping and cleaning the guide member of the recording head 24 is provided.

  The suction cap 91 is held by a cap holder 93, details of which will be described later. A suction discharge path 97 having a suction pump 96 as suction means is connected to the suction cap 91, and the suction discharge path 97 communicates with a waste liquid tank 98.

  The wiper member 94 is held by a wiper holder 194, and protrusions provided on both sides (main scanning direction) of the wiper holder 194 fit into guide grooves of a wiping guide 195 arranged in the sub-scanning direction, and move in the vertical direction (of the recording head 24). The nozzle surface of the recording head 24 is wiped from the upper direction to the lower direction (arrow direction in FIG. 2) (this is called “vertical wiping”).

  Further, an empty discharge receiver 95 is provided for receiving droplets when performing preliminary discharge (empty discharge) for discharging droplets that do not contribute to recording in order to discharge the thickened ink.

  Here, a capping mechanism stepping motor (not shown) is disposed inside the frame 90 of the maintenance / recovery mechanism 9, and when the capping mechanism stepping motor is rotated forward, the suction cap together with the cap holder 93 is passed through a gear and a cam (not shown). 91, a cap holder (not shown) and a moisturizing cap 92 perform capping and decapping operations, respectively. Further, the suction pump 96 is driven by rotating the capping mechanism stepping motor in the reverse direction.

  Further, a wiper driving stepping motor for driving a pinion that meshes with a rack provided in the wiper holder 194 is provided, and the wiper member 94 is moved in the vertical direction by driving the stepping motor forward and backward.

  In this image forming apparatus configured as described above, the paper 10 is separated and fed from the paper feed tray 4 one by one, and the paper 10 is electrostatically attracted to the charged transport belt 51, and the transport belt 51 is moved by the circular movement. The paper 10 is conveyed in the vertical direction. Therefore, by driving the recording head 24 according to the image signal while moving the carriage 23, ink droplets are ejected onto the stopped paper 10 to record one line, and after the paper 10 is conveyed by a predetermined amount, The next line is recorded, and the sheet 10 for which recording has been completed is discharged to the discharge tray 7.

  When the nozzle of the recording head 24 is maintained and recovered, the carriage 23 is moved to a position facing the maintenance and recovery mechanism 9 that is the home position, and the nozzle that performs suction and discharge from the nozzle by performing capping by the suction cap 91. By performing a maintenance and recovery operation such as suction and empty discharge for discharging droplets that do not contribute to image formation, image formation by stable droplet discharge can be performed.

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

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

  Next, an example of a liquid supply system in the image forming apparatus will be described with reference to FIG. FIG. 3 is a schematic explanatory view of the ink supply system.

  A liquid is supplied from the liquid cartridge (main tank) 200 to the head tank 29 by a supply pump 501 through a supply path 506, and a pressure buffer chamber 502 and a choke valve chamber 503 are provided between the supply pump 501 and the head tank 29. Yes.

  Here, the supply pump 501 is a diaphragm pump, and a part of the wall surface of the pump chamber 511 is formed by a deformable diaphragm 512, and a spring 513 that pushes the diaphragm 512 outward is provided in the pump chamber 511.

  Further, a diaphragm pressing member 515 that presses the diaphragm 512 is disposed outside the pump chamber 511, and the diaphragm pressing member 515 is pressed against the diaphragm 512 side by the restoring force of the spring 517. On the other hand, an eccentric cam 516 is arranged on the opposite side of the diaphragm pushing member 515 from the spring 517.

  The supply pump 501 sucks ink from the liquid cartridge 200 when the pump chamber 511 expands, and supplies the liquid to the head tank 29 when the pump chamber 513 contracts.

  That is, by rotating the eccentric cam 516, the diaphragm pushing member 515 is pushed toward the pump chamber 511 by the restoring force of the spring 517 to push the diaphragm 512, the pump chamber 511 contracts, and ink is supplied to the pressure buffer chamber 502. Supply.

  Further, when the eccentric cam 516 rotates, the diaphragm pushing member 515 moves backward in the direction away from the diaphragm 512 of the pump chamber 511, and the diaphragm 512 is pushed outward by the restoring force of the spring 513 in the pump chamber 511. The pump chamber 511 expands and sucks liquid from the liquid cartridge 200 into the pump chamber 511.

  In this supply pump 501, the pressure in the pump chamber 511 is generated by the restoring force of the springs 517 and 513. When the pump chamber 511 is expanded, the pressure is reduced by the restoring force of the spring 513, and the pump chamber When 511 contracts, the pressure increases due to the restoring force of the spring 517.

  Here, when the drive of the eccentric cam 516 continues during printing, the inside of the head tank 29 becomes an overnegative pressure due to the pressure drop due to the drive of the supply pump 501 and the pressure drop due to printing, and the print quality is maintained normally. There is a risk that it will not be possible.

  Therefore, here, a pressure buffer chamber 502 is provided between the pump chamber 511 and the head tank 29 to relieve pressure.

  The pressure buffer chamber 502 is formed of, for example, an elastic member 522 that is a member in which a part of the wall surface of the buffer chamber 521 can be deformed, and its volume can be changed. A pressing member 523 such as a spring that pressurizes the elastic member 522 from the outside toward the inside is provided.

  When liquid is supplied to the pressure buffer chamber 502 from the pump chamber 511, the buffer chamber 521 is also filled with the liquid and is in a pressurized state. The liquid discharged from the recording head 24 is filled in the head tank 29, and the liquid reduced from the pressure buffer chamber 502 is supplied from the pump chamber 511.

  Thus, even if the pressure in the pump chamber 511 increases or decreases due to the expansion and contraction of the pump chamber 511, the pressure buffer chamber 502 increases or decreases so as to relieve the pressure increase or decrease. Even if there is a pressure drop due to printing, the inside of the head tank 29 does not become overnegative. In order to obtain the pressure value to be maintained, the pressure is adjusted by the pressing force of the pressure member 523.

  The pressure buffer chamber 502 may be incorporated in the pump chamber 511 or the head tank 29 as long as it is between the pump chamber 511 and the head tank 29.

  Further, the volume change amount of the pressure buffer chamber 502 is set to be equal to or more than the product of the driving cycle of pressing the pump chamber 511 and the maximum discharge amount per unit time from the recording head 24. If the driving cycle is shortened, the volume of the pressure buffer chamber 502 can be reduced. If the driving cycle is long, the volume of the pressure buffer chamber 502 is also increased. When the drive cycle is shortened, the number of times of pressing the supply pump 501 including a diaphragm pump is increased, and a highly durable one is required.

  Further, a choke valve chamber 503 is provided between the downstream side of the pressure buffer chamber 502 and the head tank 29.

  The choke valve chamber 503 is formed of an elastic member 532 in which a part of the wall surface of the valve chamber 531 can be deformed. A liquid outlet 530 that communicates with the head tank 29 is provided at a position where the elastic member 532 is closed by the elastic member 532 when the elastic member 532 is deformed to the inner side, in this case, on the lower surface of the valve chamber 531.

  When the supply pump 501 is stopped and the liquid is sucked from the recording head 24 side, the elastic member 532 is deformed as shown by the broken line, and the outflow port 530 is closed. Thereby, the negative pressure is increased on the downstream side of the choke valve chamber 503, and the pressure of the fluid is increased from the upstream side by the supply pump 501, so that the speed of the fluid can be increased at a stretch and the bubbles can be discharged efficiently.

  Next, a first embodiment of the present invention will be described with reference to FIGS. 4 is an explanatory side view of the head unit according to the embodiment as viewed from the direction of arrow B in FIG. 6, FIG. 5 is an explanatory side view from the direction of arrow C in FIG. 6, FIG. FIG. 8 is an explanatory sectional view taken along line X1-X in FIG. 5, and FIG. 8 is an explanatory sectional view taken along line X2-X in FIG.

  The head tank 29 is connected to the recording head 24 via the relay flow path member 600. Here, the head tank 29 and the recording head 24 are integrally configured as a head unit including the relay flow path member 600, but the present invention is not limited to this.

  Here, the head tank 29 is welded with films 602 and 603 which are deformable members on both surfaces of the tank case member 601.

  A liquid storage chamber 604 that temporarily stores the liquid supplied from the liquid cartridge 200 is provided in the tank case member 601. A part of the wall surface of the liquid storage chamber 604 is formed of a film 602.

  The liquid storage chamber 604 is supplied with a liquid via a supply path 611 connected to the liquid cartridge 200 side and supplied with a liquid, and a flow path 612 and a flow path 613. A filter member 610 is provided between the channel 612 and the channel 613 for filtering foreign matter in the liquid.

  Further, in the liquid storage chamber 604, a valve body 618 pressurized by a valve 617 is provided at an outlet portion of the flow path 613 toward the liquid storage chamber 604 side. A sheet member 615 is bonded to the film 603 that forms one wall surface of the liquid storage chamber 604, and a negative pressure spring 614 is provided between the sheet member 615 and the opposite wall surface of the liquid storage chamber 604. . A lever member 616 is disposed between the seat member 615 and the valve body 618 described above.

  With this configuration, when the negative pressure in the liquid storage chamber 604 increases, the film 603 is pulled inward, so that the sheet member 615 contacts the lever member 616 and is pressurized by the valve spring 617. Is released.

  By opening the valve body 618, the liquid is supplied into the liquid storage chamber 604 from the supply path 611 on the positive pressure side through the flow path 613. When the liquid is supplied into the liquid storage chamber 604, the pressure in the liquid storage chamber 604 increases, so that the sheet member 615 of the film 603 is separated from the lever member 616, and the valve body 618 closes the flow path 613.

  Accordingly, when the liquid droplets are ejected from the recording head 24 and the negative pressure in the liquid storage chamber 604 of the head tank 29 increases, the valve body 618 is opened and the liquid is replenished from the supply side. When the negative pressure decreases, the valve body 618 is closed and the supply is stopped.

  In the head tank 29, the first flow path 621 and the second flow path 622 are provided in parallel between the liquid storage chamber 604 and the relay flow path member 600 communicating with the recording head 24.

  Here, the first channel 621 includes a channel 631 that communicates with the liquid storage chamber 604, a channel 632 that communicates with the channel 631, a channel 633 that communicates with the channel 632, one that communicates with the channel 633, and the other. Is constituted by a flow path 634 communicating with the relay flow path member 600.

  The second channel 622 includes a channel 641 that communicates with the liquid storage chamber 604, a channel 642 that communicates with the channel 641, a channel 643 that communicates with the channel 642, one that communicates with the channel 643, and the other that It is constituted by a flow path 644 that communicates with the relay flow path member 600.

  And between the flow path 632 and the flow path 633 of the 1st flow path 621, the 1st filter member 635 which filters the foreign material in a liquid is arrange | positioned. A second filter member 645 that filters foreign matter in the liquid is disposed between the flow path 642 and the flow path 643 of the second flow path 622.

  Here, the area of the first filter member 635 is larger than the area of the second filter member 645.

  In addition, the flow paths 641 and 642 that are upstream of the second filter member 645 in the second flow path 622 are upstream of the first filter member 635 in the first flow path 621. It is provided at a position (high position) above the flow paths 631 and 632 that are paths.

  As a result, the bubbles mixed in the liquid storage chamber 604 rise by buoyancy, so that the flow path on the upstream side of the second filter member 645 from the flow path 642 opened to the liquid storage chamber 604 of the second flow path 622. 642.

  In addition, a part of the wall surface of the flow path 632 that is a flow path upstream of the first filter member 635 in the first flow path 621 is formed of the deformable film 602 as described above.

  Thus, the film 602 is maintained in the state of FIG. 7 in a state where the liquid supply to the liquid storage chamber 604 is possible, but suction is performed from the recording head 24 side in a state where the liquid supply to the liquid storage chamber 604 is stopped. Then, the film 602 is deformed inward and changes in the direction in which the fluid resistance of the flow path 632 increases, so that the fluid resistance in the first flow path 621 also increases.

  In addition, a part of the wall surface of the flow path 642 that is the flow path upstream of the second filter member 645 in the second flow path 622 is formed of the deformable film 602 as described above.

  Thus, the film 602 is maintained in the state shown in FIG. 8 in a state where the liquid supply to the liquid storage chamber 604 is possible, but suction is performed from the recording head 24 side in a state where the liquid supply to the liquid storage chamber 604 is stopped. Then, the film 602 is deformed inward and changes in the direction in which the fluid resistance of the flow path 642 increases, so that the fluid resistance in the second flow path 622 also increases.

  Here, the flow path shape (flow path diameter, flow path length) and the characteristics of the film 602 are such that the fluid resistance of the first flow path 621 changes from the fluid resistance value R1 to the fluid resistance value R2 (R1 <R2). Is set.

  In addition, the fluid resistance of the second channel 622 is set with the channel shape (channel diameter, channel length) and the characteristics of the film 602 so that the fluid resistance value R3 changes from the fluid resistance value R3 to the fluid resistance value R4 (R3 <R4). Has been.

  The fluid resistance values R3 and R4 of the fluid resistance of the second channel 622 are set between the fluid resistance value R1 and the fluid resistance value R2 of the first channel 621 (R1 <R3, R4 <R2). Yes.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 9 is a cross-sectional explanatory view of a main part of a filter member provided for the description.

  First, when liquid droplets are being ejected from the recording head 24, liquid is supplied from the liquid cartridge 200, which is the main tank, to the liquid storage chamber 604 in accordance with liquid consumption.

  At this time, since the film 602 of the head tank 29 is not deformed (finely moves according to pressure fluctuation), the fluid resistance of the first channel 621 becomes the resistance value R1, and the fluid resistance of the second channel 622 is the resistance value. R3, and R1 <R3.

  Therefore, the first flow path 621 is easier to flow the liquid than the second flow path 622, and the liquid in the liquid storage chamber 604 is mainly supplied to the recording head 24 through the first flow path 621. Since the first filter member 635 disposed in the first flow path 621 has a large area, the flow is not hindered and supply to the recording head 24 is not insufficient.

  On the other hand, as described above, the bubbles mixed in the liquid storage chamber 604 enter the flow path 642 from the flow path 641 of the second flow path 622 at a higher position, and are stopped by the second filter member 645 to flow. Gather in the road 642.

  Therefore, as described in the liquid supply system described above, the supply pump 501 is stopped, the nozzle surface 124 of the recording head 24 is capped with the cap 91, and the suction pump 96 is driven to perform suction, thereby the choke valve chamber. The outflow port 530 of 531 is closed, and the liquid supply to the liquid storage chamber 604 of the head tank 29 is stopped.

  As a result, the negative pressure increases in the first flow path 621 and the second flow path 622, and the film 602 is deformed (displaced) inward of the flow paths 632 and 642, respectively, as shown in FIG. 9B. Thus, fluid resistance increases in the first flow path 621 and the second flow path 622.

At this time, the fluid resistance of the first flow path 621 becomes the resistance value R2, which is higher than the resistance value R4 of the fluid resistance of the second flow path 622 (R2> R4), so that the second flow is higher than the first flow path 621. The channel 622 makes it easier for the liquid to flow. As a result, the bubbles collected in the flow path 642 of the second flow path 622 pass through the second filter member 645 and are sucked and discharged from the nozzles of the recording head 24.
Flow path

  The second filter member 645 of the second flow path 622 has a smaller area than the first filter member 635 and has a larger suction force and less liquid than when bubbles are discharged via the first filter member 635. Bubbles can be sucked with the discharged amount.

  As described above, useless liquid consumption associated with bubble discharge can be reduced without causing insufficient supply during droplet ejection.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 10 is a schematic explanatory view of a filter portion of the head tank according to the embodiment.

  In the present embodiment, the wall surface of the upstream flow path 642 of the second filter member 645 constituting the second flow path 622 is a wall surface 605 that does not deform. The fluid resistance of the second flow path 622 is set to a fluid resistance value R3 (R1 <R3 <R2).

  Even with this configuration, when droplets are ejected from the recording head 24, the liquid is mainly supplied through the first flow path 621, and the area of the first filter member 635 in the first flow path 621 is equal to the second flow path. Since it is larger than the area of the second filter member 645 of 622, supply shortage does not occur.

  When discharging bubbles, the fluid resistance of the first flow path 621 is greater than the fluid resistance of the second flow path 622, so the second flow path 622 in which the second filter member 645 having a relatively small area is disposed. The liquid can be sucked through, and bubbles can be reliably discharged while reducing wasteful liquid consumption.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 11 is a schematic explanatory view of the flow path portion on the upstream side of the filter from the liquid storage chamber of the head tank according to the embodiment.

  In this embodiment, the fluid resistance of the flow path 631 passing through the liquid storage chamber 604 and the flow path 632 on the upstream side of the filter member of the first flow path 621 is the upstream side of the filter member of the liquid storage chamber 604 and the second flow path 622. The fluid resistance of the flow path 641 through the flow path 642 is smaller.

  In addition, the position of the opening 631a of the flow path 631 of the first flow path 621 to the liquid storage chamber 604 is set on the film 603 more than the position of the opening 641a of the flow path 641 of the second flow path 622 to the liquid storage chamber 604. By setting the film 603 to a close position, the film 603 is deformed inward by a certain amount or more to the position shown by the broken line, so that the opening to the liquid storage chamber 604 of the flow path 631 of the first flow path 621 is almost blocked. .

  As a result, the fluid resistance of the first flow path 621 changes from a resistance value R1 when the opening 631a of the flow path 631 is open to a resistance value R2 (R1 <R2) when the film 603 is almost closed. Then, the flow path 641 is formed so that the resistance value R3 of the fluid resistance of the second flow path 622 has a relationship of R1 <R3 <R2.

  In addition, although the wall surface of the flow paths 632 and 642 is formed with the member 607 which does not deform | transform instead of the said film 602, it can also be formed with the film 602.

  Even if comprised in this way, the effect similar to each said embodiment can be acquired.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a schematic explanatory diagram of the head unit according to the embodiment.

  In the present embodiment, heating means 608 for heating the liquid is disposed in the flow path on the upstream side of the second filter member 645 constituting the second flow path. The fluid resistance of the first channel and the second channel is not particularly changed (may be changed), and the fluid resistance of the first channel is set to be smaller than the fluid resistance of the second channel. ing.

  When the bubble discharging operation is performed, the liquid on the second flow path side is heated by the heating unit 608 to reduce the viscosity, so that the liquid flows more easily on the second flow path side than the first flow path.

  Thereby, the same effect as each said embodiment can be acquired.

  In the present application, the “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, etc., and means a material to which ink droplets or other liquids can be attached. , Recording media, recording paper, recording paper, and the like. In addition, image formation, recording, printing, printing, and printing are all synonymous.

  The “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. “Formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply causing a droplet to land on the medium). ) Also means.

  The “ink” is not limited to an ink unless otherwise specified, but includes any liquid that can form an image, such as a recording liquid, a fixing processing liquid, or a liquid. Used generically, for example, includes DNA samples, resists, pattern materials, resins, and the like.

  In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  Further, the present invention can be applied to both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

  In the above-described embodiment, an example is described in which the paper is transported in the direction along the vertical direction (vertical direction) and the liquid droplets are discharged in the horizontal direction. However, the paper is transported in the horizontal direction and the liquid droplets are vertical. The present invention can be similarly applied to a configuration in which the ink is discharged downward.

2 Image forming unit 4 Paper feeding unit 5 Transport mechanism 6 Paper discharge transport unit 7 Paper discharge tray 8 Reversing unit 9 Maintenance recovery mechanism 10 Paper (recording medium)
23 Carriage 24 Recording head 29 Head tank 51 Conveying belt 91 Suction cap 97 Suction pump 124 Nozzle surface 200 Liquid cartridge (main tank)
601 Tank case member 602, 603 Film (deformable member)
604 Liquid storage chamber 621 1st flow path 622 2nd flow path 631-634 Flow path 635 1st filter member 641-644 Flow path 645 2nd filter member

Claims (7)

A head tank having a liquid storage chamber that is disposed between a recording head that discharges droplets and a main tank that stores liquid to be supplied to the recording head and temporarily stores liquid to be supplied to the recording head. And
A first flow path through the liquid storage chamber and the recording head;
A second flow path through the liquid storage chamber and the recording head;
A first filter member disposed in the first flow path;
A second filter member disposed in the second flow path,
At least a part of the flow path upstream of the second filter member of the second flow path is disposed at a position above the flow path upstream of the first filter member of the first flow path,
The area of the first filter member is larger than the area of the second filter member,
At least the first flow path can change the fluid resistance;
When droplets are ejected from the recording head, the fluid resistance of the first flow path is smaller than the fluid resistance of the second flow path,
When suction is performed from the recording head side in a state where the supply of the liquid to the liquid storage chamber is stopped, the fluid resistance of the first flow path becomes larger than the fluid resistance of the second flow path. A head tank characterized by that.   The head tank according to claim 1, wherein at least a part of the wall surface of the first flow path is formed of a deformable member.   The head tank according to claim 2, wherein at least a part of the wall surface of the second flow path is formed of a deformable member.   2. The head tank according to claim 1, wherein a wall surface of the liquid storage chamber facing the inlet to the first flow path and the second flow path is formed of a deformable member. A head tank that has a liquid storage chamber for storing a liquid to be supplied to a recording head that discharges droplets, and the liquid is supplied to the liquid storage chamber from the outside;
A first flow path through the liquid storage chamber and the recording head;
A second flow path through the liquid storage chamber and the recording head;
A first filter member disposed in the first flow path;
A second filter member disposed in the second flow path,
The second flow path is disposed above the first flow path,
The area of the first filter member is larger than the area of the second filter member,
At least in the second flow path, heating means for heating the liquid is disposed,
When droplets are ejected from the recording head, heating by the heating means is stopped,
The head tank, wherein when the suction from the recording head side is performed in a state where the supply of the liquid to the liquid storage chamber is stopped, heating by the heating unit is performed.   6. A head unit comprising the head tank according to claim 1 and the recording head integrated with each other.   An image forming apparatus comprising the head tank according to claim 1 or the head unit according to claim 6.

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