JP5073596B2 - Image forming apparatus - Google Patents

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. (Simply causing the droplet to land on the medium). In addition, the term “ink” is not limited to what is called ink, but is any liquid that can form an image, such as a recording liquid, a fixing liquid, a liquid, a DNA sample, or a patterning material. Used as a general term. 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.

  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.

  In such a liquid ejection type image forming apparatus, it is particularly desired to improve the image forming throughput, that is, to increase the image forming speed. From the large-capacity ink cartridge (main tank) installed on the main body through the tube. There is a system in which ink is supplied to a sub tank (also referred to as a head tank) above the head. By adopting a method of supplying ink using such a tube, the carriage portion can be reduced in weight and size, and the apparatus including the structure system and the drive system can be significantly reduced in size.

  However, in order to further improve the printing throughput, tube fluid resistance increases as the number of nozzles in the head increases, the ink flow rate increases as the head drive frequency increases, and the ink viscosity increases for short-time drying. The problem of insufficient ink supply occurs due to the pressure loss. In particular, in an apparatus for recording on a large-sized printing medium, the tube length becomes longer, so the pressure loss becomes larger and the problem is serious.

To solve this problem, as described in Patent Document 1, a differential pressure valve is provided on the upstream side of ink supply of the head so that ink is supplied when the negative pressure in the sub tank is higher than a predetermined pressure. Is effective. Thereby, the above-mentioned problem of insufficient refill is solved. Further, Patent Document 1 discloses a technique for performing choke cleaning, which has a mechanical mechanism capable of forcibly opening a differential pressure valve in order to further improve the bubble discharge performance of the head portion.
Japanese Patent No. 4032953

Other documents related to the present invention include Patent Documents 2 and 3.
JP 2008-023789 A JP 2008-023790 A

  However, the technique described in Patent Document 1 described above has a problem that the ink supply system becomes complicated because a dedicated drive source is required to open the differential pressure valve. In addition, since air mixed in the ink supply path can be discharged only by chalk cleaning, there is also a problem that the bubble discharge performance is not sufficient.

  The present invention has been made in view of the above problems, and even when a large flow rate of ink supply is required, the negative pressure in the sub tank can be maintained within an appropriate range without causing a shortage of refill, and the bubble discharge property can be simplified. It is intended to be realized with a configuration.

In order to solve the above problem, an image forming apparatus according to claim 1 is provided:
A recording head for discharging droplets;
A sub tank for storing ink to be supplied to the recording head;
A main tank for supplying liquid to the sub tank;
Liquid feeding means for feeding the liquid from the main tank to the sub-tank,
The sub tank is provided with a supply valve that opens when the negative pressure in the sub tank is equal to or higher than a predetermined value, and enables supply of liquid into the sub tank.
Supply valve drive means for opening the supply valve regardless of the negative pressure in the sub-tank,
The supply valve driving means is driven and controlled by the liquid feeding means ,
The sub tank includes at least a part of a first flexible member, and a first spring member that urges the first flexible member in a direction in which the volume of the sub tank is increased.
The supply valve driving means is configured to contact with and separate from the first flexible member and open the supply valve by pressing the first flexible member .

According to the onset bright, while maintaining a proper negative pressure can have a large flow rate supplied to the record head stably, to ensure bubble discharge resistance of the head with a simple construction, reliable imaging A device can be obtained.

Embodiments of the present invention will be described below with reference to the accompanying drawings. 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. 1 is a schematic front view of the recording apparatus, FIG. 2 is a schematic plan view, and FIG. 3 is a schematic side view.
The ink jet recording apparatus includes a guide rod 2 that is a guide member horizontally mounted on the left and right side plates 1L and 1R provided upright on the main body frame 1, and a guide rail attached to a rear frame 1B that is horizontally mounted on the main body frame 1. 3, the carriage 4 is slidably held in the main scanning direction (guide rod longitudinal direction), and the carriage 4 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.

  The carriage 4 has, for example, yellow (Y), cyan (C), magenta (M), black (K) (hereinafter, Y, C, M, and K sub-signs are added to the codes when distinguishing colors). The recording heads 10 for ejecting ink droplets of each color are arranged in a direction in which a plurality of ink ejection ports (nozzles) cross the main scanning direction, and the ink droplet ejection direction is directed downward.

  Here, the recording head 10 is composed of a heating element substrate 12 and a liquid chamber forming member 13 as shown in FIG. 4, and the common flow path 17 and the liquid chamber (individual flow paths) are formed from the flow path formed in the head base member 19. ) The ink sequentially supplied to 16 is ejected as droplets. This recording head 10 is of a thermal type that obtains a discharge pressure by boiling the ink film by driving the heat generating element 14, and the direction of ink flow to the discharge energy acting part (heat generating part) in the liquid chamber 16 and the nozzles. This is a side shooter type configuration in which the opening center axis of 15 is a right angle.

  As the recording head, there are various methods such as a method in which the diaphragm is deformed by using a piezoelectric element, and the diaphragm is deformed by an electrostatic force to obtain a discharge pressure. Although the thermal head method is advantageous in that it is easy to increase the nozzle density, it is easy to generate bubbles in the head in principle, and the problem of bubble discharge is different from other methods. Since it is comparatively large, a big effect is acquired by applying this invention.

  In addition, among thermal heads, there is an edge shooter method in which the discharge direction is different. In this edge shooter method, the heating element 14 is gradually destroyed by an impact when bubbles disappear, so-called cavitation. There is a problem with the phenomenon. On the other hand, in the side shooter method described above, bubbles grow, and when the bubbles reach the nozzle 15, the bubbles communicate with the atmosphere, and the bubbles do not contract due to a temperature drop. Therefore, there is an advantage that the life of the recording head is long. Further, there is a structural advantage that the energy from the heating element 14 can be more efficiently converted into the formation of ink droplets and the kinetic energy of the flight, and the meniscus can be quickly returned by supplying ink. Therefore, the ink jet recording apparatus employs a side shooter type recording head.

  On the other hand, below the carriage 4, a sheet 20 on which an image is formed by the recording head 10 is conveyed in a direction perpendicular to the main scanning direction (sub-scanning direction). As shown in FIG. 3, the paper 20 is sandwiched between a transport roller 21 and a pressing roller 22, transported to an image forming area (printing unit) by the recording head 10, sent onto a printing guide member 23, and discharged. A pair of rollers 24 feeds in the paper discharge direction.

  At this time, the scanning of the carriage 4 in the main scanning direction and the ink ejection from the recording head 10 are synchronized at an appropriate timing based on the image data, and an image for one band is formed on the paper 20. After image formation for one band is completed, a predetermined amount of paper 20 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, a sub tank (head tank) 30 having an ink chamber for temporarily storing ink to be ejected is integrally connected to the upper portion of the recording head 10. Here, “integral” includes that the recording head 10 and the sub-tank 30 are connected by a tube, a pipe, and the like, both of which are mounted on the carriage 4 together.

  The sub tank 30 is provided with an ink supply tube 42 from an ink cartridge (main tank) 40 containing inks of various colors that are detachably attached to a cartridge holder 41 provided on one end side in the main scanning direction on the apparatus main body side. Through this, ink of each color is supplied.

  A maintenance / recovery mechanism 51 that performs maintenance / recovery of the recording head 10 is disposed on the other end side in the main scanning direction of the apparatus main body. The maintenance / recovery mechanism 51 includes a cap member 52 for capping the nozzle surface of the recording head 10, a suction pump 53 for sucking the inside of the cap member 52, a discharge path 54 for discharging waste liquid of ink sucked by the suction pump 53, and the like. The waste liquid discharged from the discharge path 54 is discharged to a waste liquid tank 55 disposed on the main body frame 1 side.

  Next, the configuration of the sub tank 30 will be described with reference to FIGS. 5 is a front explanatory view of the head tank, FIG. 6 is a cross-sectional explanatory view of the head tank along the line AA in FIG. 5, and FIG. 6 is a cross-sectional explanatory view for explaining the operation thereof. Here, in order to facilitate the understanding of each drawing, the description of components is omitted as appropriate, or a partial cross section is used. In addition, hatching indicating a cross section is omitted (the same applies hereinafter).

  As shown in FIG. 6, the sub tank 30 has two chambers, an ink chamber 101 and a pressurizing chamber 102. Inside the ink chamber 101, a filter 109 is provided in the vicinity of the connection portion with the recording head 10, and is configured to supply the recording head 10 with ink that has been filtered to remove foreign matters. A film member 107, which is a first flexible member, is provided on one wall surface of the sub tank 30 and is urged by a spring 108 in the direction of expanding the volume of the sub tank 30. Thereby, as shown in FIG. 6, the film member 107 has a shape that bulges toward the outside of the sub tank 30.

  In close proximity to the film member 107, a negative pressure interlocking valve 105 as a supply valve is provided. The negative pressure interlocking valve 105 is a valve that controls the communication and non-communication between the ink chamber 101 and the pressurizing chamber 102. Normally, as shown in FIG. However, as shown in FIG. 7, the ink inside the ink chamber 101 is consumed, and the film member 107 is displaced (deformed) inside the ink chamber 101 to be pushed by the film member 107 to open. ing. That is, the negative pressure interlocking valve 105 opens when the negative pressure inside the sub tank 30 is larger than a predetermined value, and receives the inflow of ink from the pressurizing chamber 102 to the ink chamber 101 as shown in FIG. It is a supply valve in the present invention that enables supply of liquid into a sub tank.

  In addition, an air amount detection sensor 103 including electrode pins 103a and 103b for detecting the air amount in the head tank is provided on the upper portion of the sub tank 30. The two electrode pins 103a and 103b of the air amount detection sensor 103 are provided so that their tips are at different height positions so that a plurality of liquid surface states can be detected.

  An ink supply port 110 is provided in the pressurizing chamber 102 of the sub tank 30. A connecting member 31 in FIG. 2 is connected to the ink supply port 110 and communicates with the ink supply tube 42.

  Next, the ink supply system according to the first embodiment of the present invention will be described with reference to FIGS. 8 is an explanatory diagram for explaining the ink supply system, FIG. 9 is an explanatory diagram for explaining different states of the system, FIG. 10 is an explanatory diagram of a cartridge holder part of the system, and FIG. 11 is an explanatory diagram of the system. It is explanatory drawing of a connection member part. Each figure is an explanatory diagram of the ink supply method, and the shape and arrangement of the members are shown deformed for easy understanding.

  The ink cartridge (main tank) 40 in which the ink is stored includes an ink bag 40a in which ink is stored and a case member 40b in which the ink bag 40a is stored in a sealed state. The ink cartridge 40a is disposed between the ink bag 40a and the case member 40b. An air layer is formed in the sealed space 40c (hereinafter, the air layer in the sealed space 40 will be described as “air layer 40c”). The ink cartridge 40 is attached to the cartridge holder 41.

  As shown in FIG. 10, an ink port 45 and an air port 44 are provided on the ink cartridge mounting surface side of the cartridge holder 41. When the ink cartridge 40 is mounted, the ink holder 40 is shown in FIGS. As described above, the ink bag 40 a of the ink cartridge 40 and the liquid supply tube (ink supply tube) 42 communicate with each other, and the air layer 40 c communicates with the air supply tube 70.

  A pressure pump 78 is connected to the air supply tube 70 via a connection member 60, and the ink bag 40 a can be pressurized by taking air in and out of the air layer 40 c in the ink cartridge 40. Here, since the ink bag 40 a communicates with the pressurizing chamber 102 of the sub tank 30 via the ink supply tube 42 and the connecting member 31, the pressure of the ink in the pressurizing chamber 102 is driven by driving the pressurizing pump 78. Can be controlled.

  Thus, by driving the pressurizing pump 78, ink can be supplied from the ink cartridge 40 to the sub tank 30 side. Here, the pressurizing pump 78 constitutes a liquid supply means for feeding ink from the main tank (ink cartridge) 40 to the sub tank 30.

  On the other hand, a supply valve driving member 112 as supply valve driving means for opening the supply valve 105 regardless of the negative pressure in the sub tank 30 is disposed on the sub tank 30 side so as to face the film member 107 side of the sub tank 30.

  In the supply valve driving member 112, a pressure chamber 116 capable of containing ink is formed by a casing 114 and an elastic film 115 which is an elastic member, and the elastic film 115 is a film member of the sub tank 30 by expanding and contracting the pressure chamber 116. The elastic film 115 comes into contact with and separates from the film member 107, and the elastic film 115 expands and presses the film member 107 of the sub tank 30. Can be opened regardless of pressure.

  In order to drive and control the supply valve driving member 112 by the liquid feeding means, the connection member 31 on the sub tank 30 side communicates with the ink supply port 35 communicating with the pressurizing chamber 102 of the sub tank 30 and the supply valve driving member 112. A valve communication port 36 is provided. The ink supply port 35 and the valve communication port 36 are configured to communicate with the ink supply tube 42 through the connection member 31.

  A working fluid supply port 117 is provided in the upper part of the casing 114 of the supply valve driving member 112, and the working fluid supply port 117 communicates with the valve communication port 36 of the connection member 31 through the communication path 120.

  Therefore, when the pressure pump 78 as the liquid feeding means is driven and the ink is pressurized and supplied from the ink cartridge 40 to the pressure chamber 102 of the sub-tank 30, the supply pressure is greater than a predetermined value. As shown in FIG. 9, the pressure chamber 116 of the supply valve driving member 112 expands and the elastic film 115 expands and abuts against and presses the film member 107 of the sub tank 30, so that the negative pressure interlocking valve 105 is connected to the sub tank 30. The ink chamber 101 can be forcibly opened regardless of the negative pressure in the ink chamber 101.

  On the other hand, when the pressurizing pump 78 does not pressurize the ink or when the applied pressure is small (when the feeding pressure is a predetermined value or less), the pressure of the supply valve driving member 112 is shown in FIG. Since the volume of the chamber 116 is contracted and the elastic film 115 is retracted from the film member 107, the negative pressure interlocking valve 105 is closed.

  A choke valve 91 that can freely open and close the flow path is provided in the middle of the ink supply tube 42. Thereby, the supply of ink from the ink cartridge 40 to the sub tank 30 can be stopped as necessary.

Next, the initial ink filling into the recording head 10 will be described with reference to FIGS.
FIG. 12 shows a state before the initial ink filling. Since the ink chamber 101 of the sub-tank 30 is at atmospheric pressure, the file member 107 is pushed outward by the action of the spring 108, and the negative pressure interlocking valve 105 is closed by the spring 106, The space between the ink chambers 101 is closed.

  In this state, the choke valve 91 is first closed, and the suction pump 53 is driven by sealing the nozzle surface of the recording head 10 with the cap 52 as shown in FIG. Then, since a large negative pressure (for example, −100 kPa) is formed in the ink chamber 10, the negative pressure interlocking valve 105 is opened. Thereby, air is discharged from the pressurizing chamber 102 of the sub tank 30. Further, since the supply valve driving member 112 discharges air from the pressure chamber 116, the elastic film 115 contracts and deforms as shown in FIG.

  Next, the pressure pump 78 is driven to pressurize the 40 ink bags 40a of the ink cartridge (for example, 40 kPa). Then, the choke valve 91 is opened. As a result, the pressure chamber 102, the ink chamber 101, and the recording head 10 of the sub tank 30 are filled with ink, the ink is filled into the pressure chamber 116 of the supply valve driving member 112, and the elastic film 115 is the film member of the sub tank 30. Since the film member 107 bulges out and presses the film member 107, the supply valve 105 is maintained in a state where it is forcibly opened by the supply valve driving member 112 (forced open state).

  In this case, ink may not be filled at a time depending on the capacity of each exhausted part (pressure chamber 116, pressurizing chamber 102, ink chamber 101, recording head 10), suction pressure, and the like. At that time, a desired initial filling state can be formed by repeating the above-described series of operations for closing the choke valve 91 again and driving the suction pump 53 to increase the pressure and then opening the choke valve 91 a plurality of times. .

  In this embodiment, since the air amount detection sensor 103 is provided in the upper part of the ink chamber 101, it is possible to easily detect whether the filling state is good or bad. Here, “good filling state” does not necessarily mean a state where all the air in the ink supply path is replaced with ink. It is sufficient if the air can be discharged to a level that does not hinder ink supply to the recording head 10.

  Thereafter, the suction pump 53 and the pressure pump 78 are stopped from the state shown in FIG. By stopping the pressurizing pump 78, the supply valve driving member 112 that has been expanded contracts and returns to a natural state as shown in FIG. As a result, the elastic film 107 of the supply valve driving member 112 that has forcibly opened the negative pressure interlocking valve 105 of the sub tank 30 is separated, and the forced opening state of the negative pressure interlocking valve 105 is released.

  At this time, while a large negative pressure remains in the ink chamber 101, the negative pressure interlocking valve 105 is open, so that ink is continuously supplied from the ink cartridge 40, and the ink chamber 101 is gradually moved by the action of the spring 108. Inflate. When the negative pressure in the ink chamber 101 becomes smaller than a certain value, the negative pressure interlocking valve 105 is naturally closed. At this time, the spring 108 and the spring 106 of the negative pressure interlocking valve 105 are set so that the negative pressure of the ink chamber 101 is, for example, about −500 Pa.

  In printing, the pressure pump 78 is driven to keep the pressure in the pressure chamber 102 of the sub tank 30 at a high level (for example, about 15 kPa). The pressure at this time is set to a pressure value (for example, about 15 kPa) at which the negative pressure interlocking valve 105 is not forcibly opened.

  As a result, when ink is consumed by printing and the ink chamber 101 reaches a certain negative pressure or higher, the negative pressure interlocking valve 105 is pushed by the film member 107 and automatically opens, and the pressurized ink is applied at a high speed. The ink chamber 101 is replenished from the pressure chamber 102. When the negative pressure in the ink chamber 101 is reduced by ink replenishment, the film member 107 is separated from the negative pressure interlocking valve 105 and the negative pressure interlocking valve 105 is automatically closed by the restoring force of the spring 106. The negative pressure in the chamber 101 does not deviate from the appropriate range.

  Thus, in this ink supply system, since the ink cartridge 40 is pressurized by the pressure pump 78, for example, the ink supply tube 42 becomes long like a recording device that prints on a wide medium, and the fluid resistance of the tube is increased. However, the ink refill shortage to the recording head 10 does not occur.

  In addition, since the negative pressure interlocking valve 105 is provided, the ink is automatically replenished by the amount consumed from the ink chamber 101 without being excessively supplied by the pump 78. Further, since the sub-tank 30 (pressure adjusting tank) that maintains an appropriate negative pressure is connected to the common flow path 17 of the recording head 10, stable ink discharge can be performed under an appropriate negative pressure. .

  In addition, the ink supply pressure from the ink cartridge 40 can be controlled in at least two stages, and the negative pressure interlocking valve 105 is forced when the ink is pressurized with a supply pressure larger than the supply pressure at the time of printing. Therefore, when the recording head 10 has an ejection failure, recovery by pressurization can be performed.

  That is, in an ink jet recording apparatus, it sometimes happens that ink is not normally ejected from a nozzle due to, for example, bubbles being mixed from the nozzle during printing. In the conventional small-sized ink jet recording apparatuses, so-called suction recovery in which ink is sucked from the recording head side and bubbles are discharged together with ink from the nozzle is common for recovery from the abnormal state. However, when the head becomes large due to high-speed printing, it becomes difficult to perform capping that can completely seal the nozzle. Even in such a case, the ink supply system realizes refilling at high speed by pressurization assistance, and maintains an appropriate negative pressure while replenishing ink on demand by the action of the negative pressure interlocking valve. In addition, pressure recovery can be performed. Therefore, for example, even if the ink supply tube 42 becomes long as in a recording apparatus that prints on a wide-width medium and the fluid resistance of the tube increases, it is possible to prevent insufficient refilling of ink on the recording head 10. Therefore, it is particularly suitable for a wide and high speed ink jet recording apparatus.

  As described above, the sub tank is provided with a supply valve that opens when the negative pressure in the sub tank is equal to or higher than a predetermined value, and enables the supply of liquid into the sub tank. The supply valve is independent of the negative pressure in the sub tank. Since the supply valve driving means is configured to be driven and controlled by the liquid supply means, a large flow rate can be supplied to the recording head and an appropriate negative pressure can be stably maintained. At the same time, it is possible to obtain a highly reliable image forming apparatus by ensuring the bubble discharge performance of the head with a simple configuration.

  Further, as in the above embodiment, the supply valve driving means 112 is driven when the supply pressure of the liquid supply means (pressure pump 78) is larger than a predetermined value to open the supply valve 105, thereby simplifying. The pressure recovery can be performed with a simple system, and the discharge reliability is improved.

  Further, the ink supply pressure can be controlled at a high speed by using the pressurizing pump 78 as the liquid feeding means and pressurizing the ink bag with air pressure to feed the ink. Further, if air pressure is directly used as an open / close drive source of the supply valve, control with good responsiveness can be performed.

  In addition, the sub tank 30 includes at least a first flexible member (film member 107) and a first spring member (spring) that urges the first flexible member in the direction of expanding the volume of the sub tank. 108), and the supply valve driving means 112 contacts and separates from the first flexible member and presses the flexible member to open the supply valve (negative pressure release valve 105). Thus, a stable negative pressure can be formed, and the supply valve can be easily opened and closed by pressurization.

  In this case, the supply valve driving means 112 has a sealed space (pressure chamber 116) having a wall surface made of an elastic member (elastic film 115) at least partially, and the sealed space serves as a liquid feeding means (pressure pump 78). By adopting the communication structure, the supply valve can be easily opened and closed by putting ink in and out of the sealed space.

Next, an ink supply system according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 15 is an explanatory diagram for explaining the supply system, and FIG. 16 is an explanatory diagram for explaining the operation thereof.
This ink supply system is different from the above-described first embodiment in the ink feeding pressure control method. In other words, in the system of the first embodiment, the ink bag 40a of the ink cartridge 40 is pressurized by air pressure. A pressure pump (liquid feed pump) 178 is provided, and the pressure pump 178 is driven to feed ink to the sub tank 30 and pressurize the ink in the ink supply tube 42.

  The supply valve driving member 112 is provided with a pressure sensor 113. Based on the detection result of the pressure sensor 113, the pressure in the pressure chamber 116 is set to about 15 kPa during normal printing, and the negative pressure interlocking valve 105 is formed by the elastic film 115. The pressurizing pump 78 is controlled so as to pressurize the pressurizing chamber 102 in a state where the pressure does not open.

  When the recording head 10 is initially filled or when pressure is restored, the pressure is supplied to the supply valve driving member 112 by the pressure pump 178 so that the pressure in the pressure chamber 116 becomes 40 kPa. Accordingly, as shown in FIG. 16, the pressure chamber 116 expands, the elastic film 115 expands, and the negative pressure interlocking valve 105 is pushed through the film member 107, thereby forcibly opening the negative pressure interlocking valve 105. be able to. In addition, as the pressurization pump 178 in this embodiment, the thing of the system which can send liquids bidirectionally, such as a tubing pump, is suitable.

  Also in this embodiment, functions such as initial filling using a choke valve, automatic negative pressure control, refill assist by pressurization, and pressure recovery can be achieved as in the first embodiment.

Next, an ink supply system according to a third embodiment of the present invention will be described with reference to FIG. FIG. 17 is an explanatory diagram for explaining the supply system.
The sub tank 30 of the ink supply system in this embodiment is the film member 107, the spring 108, the negative pressure interlocking valve 105, and the pressurizing chamber 102, which are the main components for generating negative pressure, as described in the first embodiment. The description is omitted because it is the same as.

  Here, the sub-tank 30 is provided with an exhaust portion 130 at an upper portion thereof, and is provided with an atmosphere release valve 131 that opens and closes a communication path between the ink chamber 101 and the exhaust portion 130, and the atmosphere release valve 131 is a spring 132. It is biased in the closing direction. The exhaust unit 130 may be provided with a porous body such as a highly foamed resin, a porous resin film, a foamed metal, a metal mesh, or porous ceramics as necessary. The air release valve 131 is a normally closed valve, and the ink chamber 101 is normally kept sealed. By providing the sub tank 30 with an atmospheric valve (atmospheric release valve 131) that can be freely opened and closed, the air in the liquid supply path can be easily discharged.

  Further, outside the sub tank 30, a supply valve driving member 112 for forcibly opening the negative pressure interlocking valve 105 at a position facing the film member 107 and an atmosphere capable of forcibly opening the atmosphere release valve 131 are provided. A valve drive member 119 is provided.

  The supply valve driving member 112 has the same configuration as that of the supply valve driving member 112 of the first embodiment, and a pressure chamber 116a capable of containing ink is formed by a casing 114a and an elastic film 115a which is an elastic member. As the chamber 116a expands and contracts, the elastic film 115a expands and retracts with respect to the film member 107 of the sub tank 30, the elastic film 115a contacts and separates from the film member 107, and the elastic film 115a expands and the sub tank 30 By pressing the film member 107, the supply valve 105 can be opened regardless of the negative pressure in the sub tank 30.

  The atmospheric valve drive member 119 has the same configuration as the supply valve drive member 112 of the first embodiment, and a pressure chamber 116b capable of containing ink is formed by the casing 114b and an elastic film 115b which is an elastic member. When the elastic film 115b expands and contracts, the elastic film 115b expands and retracts with respect to the film member 107 of the sub tank 30, the elastic film 115b contacts and separates from the film member 107, the elastic film 115b expands, and the film of the sub tank 30 The air release valve 131 can be opened by pressing the member 107.

  The pressure chambers 116 a and 116 b of the supply valve driving member 112 and the atmospheric valve driving member 119 communicate with the air layer 40 c of the ink cartridge 40 through the air tube 121 and the cartridge holder 41.

  A pressure pump 78 is connected to the air layer 40 c of the ink cartridge 40 via an air supply tube 70, and the pressure chambers 116 a and 116 b can be expanded and contracted by driving the pressure pump 78. .

  In this embodiment, both the elastic film 115a and the elastic film 115b are made of silicone rubber that is rich in elasticity, but the thickness of the elastic film 115b that constitutes the atmospheric valve driving member 119 is set to the thickness of the supply valve driving member 112. The elastic film 115a is thicker than the elastic film 115a.

Next, the initial ink filling into the recording head 10 in this embodiment will be described with reference to FIGS.
First, in the state before the initial ink filling, as shown in FIG. 18, the ink chamber 101 of the sub tank 30 is at atmospheric pressure, so the negative pressure interlocking valve 105 is closed by the action of the spring 106.

  Here, when the pressurizing pump 78 is driven to pressurize the ink bag 40a of the ink cartridge 40 (for example, 50 kPa), air is sent to the atmospheric valve driving member 119 and the supply valve driving member 112, which member 119, As shown in FIG. 19, 112 also expands the pressure chambers 116b and 116b, and the elastic films 115b and 115a bulge out.

  As a result, the atmospheric valve driving member 119 opens the atmospheric release valve 131 and the supply valve driving member 112 opens the negative pressure interlocking valve 105, so that the pressurized ink in the ink bag 40 a converts the air in the ink chamber 101 into the sub tank. It is sent into the sub tank 30 while being exhausted from the exhaust part 130 at the upper part of 30. There is a filter 109 at the bottom of the ink chamber 101, and the ink does not pass through the filter 109 due to the meniscus holding force of the fine mesh of the filter 109, so the ink level in the ink chamber 101 rises.

  Then, as shown in FIG. 20, when the air amount detection sensor 103 above the ink chamber 101 detects the ink liquid level, the pressure applied by the pressure pump 78 is decreased. By appropriately setting the pressure (for example, 40 kPa), as shown in FIG. 21, only the atmospheric valve driving member 119 having a relatively thick elastic film 115b and a large self-shrinking force is separated from the atmospheric release valve 131. The supply valve driving member 112 having a relatively thin elastic film 115a and a small self-shrinkage force can maintain the negative pressure interlocking valve 105 in the open state.

  In this state, the inside of the ink chamber 101 is pressurized by the pressurizing pump 78, so that the meniscus of the filter 109 is broken and the recording head 10 is filled with ink. After the recording head 10 is filled with ink, the pressure pump 78 is stopped. Then, since the pressures in the pressure chambers 116a and 116b are reduced, the elastic film 115a and the elastic film 115b are returned to the natural state by the respective restoring forces, and the pressure of the negative pressure interlocking valve 105 by the supply valve driving member 112 is released. .

  As a result, as shown in FIG. 22, the negative pressure interlocking valve 105 is closed, and the inflow of ink into the ink chamber 101 is stopped. At the same time, since the spring 108 pushes the film member 107 in the direction of expanding the volume of the ink chamber 101, a negative pressure is formed in the ink chamber 101, and a printing operation is possible.

  In the present embodiment, the negative pressure interlocking valve 105 and the pressurizing pump 78 are provided in the same manner as the ink supply system described above. Therefore, the pressurizing pump 78 is driven during printing so that the pressurizing chamber 102 of the sub tank 30 is appropriately pressurized. By maintaining the pressure at (for example, 15 kPa), it is possible to stably form an image without causing refill shortage even when a large flow rate of ink supply is required, such as printing a solid black image at high speed.

  In addition, the pressure chambers 116b and 116a of the atmospheric valve driving member 119 and the supply valve driving member 112 expand due to pressurization during printing, but as shown in FIG. 23, the atmospheric valve driving member 119, the supply valve driving member 112 and By appropriately setting the interval between the sub tanks 30, the valves 105 and 131 are held closed at the pressure during printing.

  In the present embodiment, the pressurizing pump 78 that pressurizes the ink in the ink cartridge 40 is controlled to pressurize at least the ink pressure in three stages. The lowest pressure (for example, 15 kPa) is a refill assist pressure for printing. At this pressure, the atmospheric valve driving member 119 and the supply valve driving member 112 are not forcibly opened. At the next highest pressure (for example, 40 kPa), as shown in FIG. 21, only the negative pressure interlocking valve 105 is forcibly opened by the supply valve driving member 112 to achieve the pressure recovery of the recording head 10. At the highest pressure (for example, 50 kPa), the air release valve 131 is forcibly opened by the air valve driving member 119, so that the air in the ink chamber 101 can be easily discharged from the exhaust unit 130.

  In the present embodiment, the pressure recovery of the recording head 10 is possible, but suction recovery may be used in the same manner as in the second embodiment. Further, in the present embodiment, since the atmospheric valve driving member 119 and the supply valve driving member 112 are controlled by directly using the air pressure, a system with better responsiveness can be obtained as compared with the case where liquid is used.

  Further, as in the present embodiment, the sub tank 30 includes at least a first flexible member (film member 107) and a first flexible member that urges the first flexible member in the direction of expanding the volume of the sub tank. And the atmospheric valve driving means 119 is in contact with and away from the first flexible member and presses the first flexible member to press the atmospheric valve (atmosphere). With the configuration in which the release valve 131) is opened, the interior of the ink chamber 101 can be temporarily communicated with the atmosphere and reset to a stable negative pressure. Air can be easily discharged.

  In addition, an atmospheric valve driving unit 119 for opening and closing the atmospheric valve (atmospheric release valve 131) is provided, and the atmospheric valve driving unit 119 is driven and controlled by the liquid feeding unit (pressurizing pump 78), so that the recording head can be controlled. Since the atmospheric valve can be opened and closed only by the liquid supply pressure, the air in the liquid supply path can be easily discharged with a simple system.

  The atmospheric valve driving means 119 has a sealed space (pressure chamber 116b) having a wall surface made of an elastic member (elastic film 115b) at least partially, and the sealed space communicates with the liquid feeding means. Thus, the atmospheric valve can be easily opened and closed by putting ink into and out of the sealed space.

Next, an ink supply system according to a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 24 is an explanatory diagram for explaining the supply system, and FIG. 25 is an explanatory diagram for explaining the operation thereof.
The system of the present embodiment differs from the system of the third embodiment only in the configuration of the atmospheric valve drive member 119 and the supply valve drive member 112. In the system of the third embodiment, the pressure chambers 116a and 116b that can be expanded and contracted are formed using the elastic film 115a and the elastic film 115b having different thicknesses, and the amount of deformation at the same pressure is made different, so that the low pressure condition In the case where the feed pressure is not more than a predetermined value, only the negative pressure interlocking valve 105 is forcibly opened.

  On the other hand, in the supply valve driving member 112 of the present embodiment, the side facing the sub tank 30 is formed by the film member 155 that is the second flexible member, and the volume of the pressure chamber 116a is reduced by using the film member 155. A tension spring 118a, which is a second spring member that is urged in the direction to be moved, is provided. Similarly, in the atmospheric valve driving member 119, the side facing the sub tank 30 is formed by a film member 155 which is a third flexible member, and the film member 155 is urged in a direction to reduce the volume of the pressure chamber 116b. A tension spring 118b, which is a third spring member, is provided.

  The spring constant of the tension spring 118a of the atmospheric valve driving member 119 is made larger than the spring constant of the tension spring 118b of the supply valve driving member 112.

  Accordingly, by appropriately applying pressure to the pressure chamber 116a of the supply valve driving member 112 and the pressure chamber 116b of the atmospheric valve driving member 119, the supply valve driving is performed more than the atmospheric valve driving member 119, as shown in FIG. The member 112 is greatly deformed, and the negative pressure interlocking valve 105 can be forcibly opened while the air release valve 131 is closed. In this system, since the tension spring is used, the operating pressures of the atmospheric valve driving member 119 and the supply valve driving member 112 can be set more freely.

  As described above, the supply valve driving means 112 includes at least a part of the sealed space (pressure chamber 116a) having a wall surface made of the second flexible member (film member 155) and the second flexible member as the sealed space. The second spring member (spring 118a) for urging in the direction of reducing the volume of the liquid is provided, and the sealed space communicates with the liquid feeding means (pressurizing pump 78), so that a desired operation is achieved. The pressure can be easily obtained.

  Further, the atmospheric valve driving member 119 urges at least a part of the third flexible member (film member 155) and the third flexible member in a direction to reduce the volume of the sealed space (pressure chamber 116b). By having a configuration including the third spring member (spring 118b), a desired operating pressure can be easily obtained.

Next, an ink supply system according to a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 26 is an explanatory diagram for explaining the supply system, and FIG. 27 is an explanatory diagram for explaining the operation thereof.
The system of this embodiment is different from the system of the third embodiment in the configuration and arrangement of the atmospheric valve driving member 119 and the supply valve driving member 112. In the system of the third embodiment, the elastic film 115a and the elastic film 115b having different thicknesses are used to vary the expansion and contraction characteristics, and only the negative pressure interlocking valve 105 can be forcibly opened under low pressure conditions.

  In contrast, in the system of the present embodiment, the elastic film 115 is the same, and the deformation characteristics of the pressure chambers 116 a and 116 b are the same, but the atmospheric valve driving member 119, the supply valve driving member 112 and the sub tank 30 are the same. The intervals are different. Specifically, the atmospheric valve driving member 119 is arranged farther from the sub tank 30 than the supply valve driving member 112.

  Thereby, the expansion amount when the pressurizing pump 78 is driven is not different between the atmospheric valve driving member 119 and the supply valve driving member 112, but only the negative pressure interlocking valve 105 can be forcibly opened as shown in FIG. . In this system, since the atmospheric valve driving member 119 and the supply valve driving member 112 can be used as common parts, a low-cost system can be obtained.

  As described above, in the ink supply system according to the present invention, negative pressure interlocking is achieved with a simple configuration using the same pump while realizing a large flow of ink using a negative pressure interlocking valve and a pressurizing pump. The valve can be forcibly opened to allow pressure recovery of the recording head. If the atmosphere release valve is further provided in the head tank, the air in the head tank can be easily discharged by further diverting the same pump.

  In the above embodiments, the negative pressure interlocking valve and the atmosphere release valve are described as being provided in the sub tank. However, these valves are not limited to the sub tank, and may be located anywhere in the ink supply path. Can also be provided. The present invention is not limited to an image forming apparatus that ejects ink, but can be applied to a droplet ejecting apparatus that ejects various liquids.

1 is a schematic front explanatory view showing an example of 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 an enlarged explanatory view of a main part for explaining a recording head of the same apparatus. It is front explanatory drawing which shows an example of the sub tank of the apparatus. FIG. 6 is a cross-sectional explanatory view of the head tank taken along line AA in FIG. 5. It is sectional explanatory drawing similarly provided for the effect | action description. It is explanatory drawing with which it uses for description of the ink supply system in 1st Embodiment of this invention. It is explanatory drawing explaining the different state of the system similarly. It is explanatory drawing of the cartridge holder part of the same system. It is explanatory drawing of the connection member part of the system. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing with which it uses for description of the ink supply system in 2nd Embodiment of this invention. It is explanatory drawing similarly provided for the effect | action description. It is explanatory drawing with which it uses for description of the ink supply system in 3rd Embodiment of this invention. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing similarly provided for the effect | action description at the time of the initial filling. It is explanatory drawing with which it uses for description of the ink supply system in 4th Embodiment of this invention. It is explanatory drawing similarly provided for the effect | action description. It is explanatory drawing with which it uses for description of the ink supply system in 5th Embodiment of this invention. It is explanatory drawing similarly provided for the effect | action description.

Explanation of symbols

4 ... carriage 10 ... recording head 30 ... sub tank 40 ... ink cartridge (main tank)
42 ... Ink supply tube 78 ... Pressurizing pump 101 ... Ink chamber 102 ... Pressurizing chamber 105 ... Negative pressure release valve (supply valve)
107: Film member (first flexible member)
108... Spring (first spring member)
112 ... Supply valve driving member (means)
115, 115a, 115b ... elastic membrane (elastic member)
116, 116a, 116b ... pressure chamber 155 ... film member (second and third flexible members)

Claims (7)

A recording head for discharging droplets;
A sub tank for storing ink to be supplied to the recording head;
A main tank for supplying liquid to the sub tank;
Liquid feeding means for feeding the liquid from the main tank to the sub-tank,
The sub tank is provided with a supply valve that opens when the negative pressure in the sub tank is equal to or higher than a predetermined value, and enables supply of liquid into the sub tank.
Supply valve drive means for opening the supply valve regardless of the negative pressure in the sub-tank,
The supply valve driving means is driven and controlled by the liquid feeding means ,
The sub tank includes at least a part of a first flexible member, and a first spring member that urges the first flexible member in a direction in which the volume of the sub tank is increased.
The supply valve driving means opens and closes the supply valve by making contact with and separating from the first flexible member and pressing the first flexible member. Image forming apparatus. 2. The image forming apparatus according to claim 1 , wherein the supply valve driving means has a sealed space having a wall surface made of an elastic member at least partially, and the sealed space communicates with the liquid feeding means. An image forming apparatus. 2. The image forming apparatus according to claim 1 , wherein the supply valve driving unit includes at least a part of a sealed space having a wall surface made of a second flexible member, and the second flexible member is disposed in the sealed space. An image forming apparatus, comprising: a second spring member that urges the volume in a direction to reduce the volume, wherein the sealed space communicates with the liquid feeding unit. A recording head for discharging droplets;
A sub tank for storing ink to be supplied to the recording head;
A main tank for supplying liquid to the sub tank;
Liquid feeding means for feeding the liquid from the main tank to the sub-tank,
The sub tank is provided with a supply valve that opens when the negative pressure in the sub tank is equal to or higher than a predetermined value, and enables supply of liquid into the sub tank.
Supply valve drive means for opening the supply valve regardless of the negative pressure in the sub-tank,
The supply valve driving means is driven and controlled by the liquid feeding means,
The sub tank has an air valve that can be opened and closed freely.
The sub tank includes at least a part of a first flexible member, and a first spring member that urges the first flexible member in a direction in which the volume of the sub tank is increased.
The image forming apparatus, wherein the atmospheric valve is opened by being pressed by the first flexible member. A recording head for discharging droplets;
A sub tank for storing ink to be supplied to the recording head;
A main tank for supplying liquid to the sub tank;
Liquid feeding means for feeding the liquid from the main tank to the sub-tank,
The sub tank is provided with a supply valve that opens when the negative pressure in the sub tank is equal to or higher than a predetermined value, and enables supply of liquid into the sub tank.
Supply valve drive means for opening the supply valve regardless of the negative pressure in the sub-tank,
The supply valve driving means is driven and controlled by the liquid feeding means,
The sub tank has an air valve that can be opened and closed freely.
An atmospheric valve driving means for opening and closing the atmospheric valve;
The image forming apparatus, wherein the atmospheric valve driving means is driven and controlled by the liquid feeding means. 6. The image forming apparatus according to claim 5 , wherein the atmospheric valve driving means has a sealed space having a wall surface made of an elastic member at least partially, and the sealed space communicates with the liquid feeding means. An image forming apparatus. 6. The image forming apparatus according to claim 5 , wherein the atmospheric valve driving member is attached at least partially to a third flexible member and the third flexible member in a direction to reduce the volume of the sealed space. An image forming apparatus comprising: a third spring member for biasing.

Images