JP6191295B2 - 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. .

  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. A method of supplying ink to a head tank (including sub tanks and buffer tanks) above the recording head (this is called an “off-carriage method”) is performed.

  By using such a tube to supply ink, the carriage section on which the recording head and the head tank are mounted can be reduced in weight and size, and the apparatus, including the structure system and drive system, can be significantly downsized. it can.

  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 print medium, the pressure loss becomes larger because the tube length becomes longer.

  For this reason, a method of supplying ink from the main tank to the recording head by a pump is adopted, but a sensor for detecting the pressure of the recording head and a control device for driving the pump are required, resulting in an increase in cost.

  Also, the ink cartridge is placed at a position lower than the recording head in the direction of gravity to create a negative pressure on the droplet discharge surface of the recording head, and ink is naturally supplied to the head tank as the recording head ejects ink. There is also a way to do it. However, in this case, since the height in the direction of gravity is directly connected to the formation of the negative pressure of the recording head, there arises a disadvantage that the height of the apparatus is increased due to layout restrictions.

  Therefore, conventionally, ink is supplied to the head tank in a positive pressure state, and the differential pressure valve (negative pressure interlocking valve) is opened to supply ink when the negative pressure in the head tank is larger than a predetermined pressure. Is known (Patent Document 1).

  In addition, the ink pack inside the ink cartridge is pressurized with pressurized air from a pressure pump to supply ink to the recording head, and the atmosphere that can communicate with the atmosphere through a gas supply path that passes between the pressure pump and the ink cartridge. It is known that an open valve is provided, and the atmospheric open valve is configured to be pressed and opened when the carriage moves in a direction from the liquid ejecting area toward the non-liquid ejecting area in the moving range of the carriage ( Patent Document 2).

  In addition, a pressurizing pump for positive pressure of ink is provided between the main tank and the recording head, a subtank for storing the liquid discharged from the pressurizing pump is provided, and a flow path connected to the recording head is smaller than a predetermined pressure in the subtank. Provided with a negative pressure maintenance mechanism that supplies liquid only when the pump reaches the outlet, a bypass is provided to connect the pump suction port to the pump suction port, and the valve opens only when the pressure at the pump discharge port exceeds a predetermined pressure. And what is provided with the relief valve which flows a liquid from a pump discharge port to a pump suction port is known (patent document 3).

Japanese Patent No. 3606282 JP 2007-261033 A JP 2008-296415 A

  However, in the configuration disclosed in Patent Document 1, the valve body of the negative pressure interlocking valve for preventing the positive pressure ink from flowing into the sub tank is sealed only by the spring. For this reason, if the positive pressure state is maintained without releasing the positive pressure state after the printing is completed or the machine is stopped, foreign matter may be caught in the seal part of the valve body, or the sealing surface may be depressed due to compression set, resulting in a sealing performance. If it is deteriorated, the ink will continue to flow into the sub tank. As a result, the pressure formed in the sub-tank is broken, and eventually ink drops from the nozzles of the recording head, increasing wasteful ink consumption. Further, when the apparatus is not used, the nozzle surface of the recording head is moisturized by the cap. However, if the ink continues to flow into the sub tank, there is a problem that the ink overflows from the cap and stains the inside of the apparatus. In addition to the valve body, the ink supply tube and the sub-tank joint, if the sealing state is incomplete, may cause positive pressure ink to leak from that portion, resulting in wasteful consumption of ink. There is a problem that the inside of the apparatus is soiled.

  Further, in the configuration disclosed in Patent Document 2, in order for the ink bag to change by pressurization, the ink bag must be formed of, for example, a flexible material. Lower. Further, since the ink cartridge exterior and the ink bag are pressurized with air, the ink cartridge exterior must be made into a completely sealed space, which increases the cost.

  Moreover, in the structure disclosed in Patent Document 3, the relief valve provided between the discharge port and the suction port of the pump operates only when a predetermined pressure is exceeded. However, a positive pressure less than a predetermined pressure remains for a long time. Therefore, when a leak path is formed in the system over time when the apparatus is not in use, such as a solvent crack, for example, liquid leaks from the leak path due to the remaining positive pressure, and as a result, the inside of the apparatus is soiled. There is a problem.

  The present invention has been made in view of the above problems, and has an object to release a positive pressure state of a liquid with a simple configuration and reliably prevent liquid leakage from a head or a joint part. To do.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path through the liquid tank and the recording head;
Liquid feeding means for feeding the liquid provided in the first flow path;
A second flow path that bypasses the liquid feeding means and communicates with the first flow path;
A first on-off valve provided in the second flow path;
Valve opening means for opening the first on-off valve;
Among the first flow paths, a second opening / closing which is opened only when the pressure of the flow path on the recording head side is reduced between the recording head and the liquid feeding means, and is otherwise normally closed. A valve,
The first on-off valve is a normally closed valve;
When image formation is performed, by driving the liquid feeding means, a flow path between the liquid feeding means and the first on-off valve, and between the liquid feeding means and the second on-off valve. The liquid in the flow path is brought into a positive pressure state,
After the image formation is stopped, the first opening / closing valve is opened for a predetermined period by the valve opening means.

  According to the present invention, the positive pressure state of the liquid can be released with a simple configuration, and the leakage of the liquid from the head and the joint portion can be reliably prevented.

1 is a schematic plan view illustrating an example of an ink jet recording apparatus as an image forming apparatus according to the present invention. FIG. 2 is a schematic explanatory diagram for explaining an ink supply system according to the present invention. It is a typical explanatory view of an example of a head tank. It is typical explanatory drawing of the on-off valve in 1st Embodiment of this invention. It is a perspective explanatory view of the valve box of the on-off valve. It is typical explanatory drawing with which the opening-closing operation | movement of the on-off valve in 1st Embodiment and description of the means to decompress pressure ink are provided. It is a flowchart with which it uses for description of the whole flow of pressure reduction control in 1st Embodiment. It is typical explanatory drawing with which it uses for description of the on-off valve in 2nd Embodiment of this invention. It is typical explanatory drawing with which it uses for the valve opening operation | movement of the on-off valve in 2nd Embodiment, and description of the means to decompress pressure ink. It is typical explanatory drawing with which it uses for description of the on-off valve in 3rd Embodiment of this invention. It is typical explanatory drawing with which it uses for the valve opening operation | movement of the on-off valve in 3rd Embodiment, and the description of the means to decompress pressure ink. It is typical explanatory drawing with which it uses for description of the on-off valve 28 in 4th Embodiment of this invention.

  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 FIG. FIG. 1 is a schematic plan view of the recording apparatus.

  This ink jet recording apparatus is a serial type image forming apparatus, and a carriage 4 is held by two guide rails 40 and 41 so as to be movable in the main scanning direction. The carriage 4 is reciprocally scanned (moved) by a main scanning motor 13 via a timing belt 14 that is stretched between a driving pulley 16 and a driven pulley 17. In addition to the guide rails 40 and 41, the carriage may be movably held by a sheet metal.

  A recording head 1 having nozzles for ejecting ink droplets of a plurality of colors (for example, yellow (Y), cyan (C), magenta (M), and black (Bk)) is attached to the carriage 4. The nozzles of the recording head 1 are arranged in a direction that intersects the scanning direction of the carriage 4.

  The recording head 1 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes 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, and an electrostatic force. A device provided as an energy generating means for discharging ink, such as an electrostatic actuator using, can be used.

  The carriage 4 is mounted with a head tank (head tank) 5 for temporarily storing ink supplied from the ink cartridge 23 and stabilizing the pressure of the ink supplied to the recording head 1. The head tank 5 is integrally connected to the recording head 1.

  The ink cartridge 23 is detachably attached to the apparatus main body for each color. The ink cartridge 23 and the head tank 5 are connected by a supply tube 22, and ink of each color is supplied from the ink cartridge 23 to the head tank 5 of the recording head 1 through the supply tube 22.

  Here, although one supply tube 22 is illustrated, the ink cartridge 23 and the head tank 5 communicate with each color, and the head tank 5 is also provided for each color. Further, here, one head tank 5 is arranged for each color, but a configuration may be adopted in which two colors are stored separately in one head tank 5.

  In the middle of the supply tube 22, there is provided a pressurizing pump 25 including liquid feeding means for pressurizing the ink in the ink cartridge 23 and supplying it to the head tank 5. A detour 29 that directly connects the inlet and outlet of the pressurizing pump 25 is provided. An on-off valve 28 as a first on-off valve is provided on the flow path of the bypass circuit 29. The on-off valve 28 is a normally closed valve.

  Further, a maintenance / recovery mechanism 8 for maintaining and recovering the state of the nozzles of the recording head 1 is disposed in a non-printing area on one side of the carriage 4 in the scanning direction. The position of the maintenance / recovery mechanism 8 is defined as a home position (home position) of the carriage 4.

  The maintenance / recovery mechanism 8 includes caps 18 for capping each ink discharge surface (nozzle surface) of the recording head 1 to retain moisture. The maintenance / recovery mechanism 8 also includes a blade-like wiper member 12 that wipes the nozzle surface, and an empty discharge receiver that receives empty discharged droplets discharged in an empty discharge operation that discharges ink droplets (empty discharged droplets) that do not contribute to printing. Etc.

  The operation of the maintenance / recovery mechanism 8 is as follows. If the ink attached to the nozzle surface of the recording head 1 loses moisture due to drying, the nozzle may be clogged. When a nozzle is clogged, ink cannot be ejected from the nozzle, which affects the image. In order to prevent this, when the power is turned off or when there is no print job, the carriage 4 is moved to the home position 100 shown in FIG. The maintenance / recovery mechanism 8 removes the thickened ink by sucking with a dedicated pump while the nozzle surface is capped when the ink adhering to the nozzle surface thickens and clogs the nozzle. There is also.

  Further, the wiper member 12 wipes off ink adhering to the nozzle surface and forms a meniscus on the nozzle surface. The wiper member 12 protrudes to the head side when wiping the nozzle surface. Then, the carriage 4 scans toward the projected wiper member 12 to wipe the nozzle surface. Here, the nozzle surface is wiped in the carriage scanning direction with respect to the nozzle surface, but may be wiped in the sub-scanning direction.

  Here, the lever member 105 is disposed on the end side of the home position 100, that is, near the side plate 34R. One end of the lever member 105 is connected (connected) to the on-off valve 28. When the carriage 4 moves to the end side from the home position 100, the carriage 4 and the lever member 105 come into contact with each other, so that the lever member 105 is operated and the on-off valve 28 is temporarily opened.

  Further, a transport belt 51 is provided for transporting the paper 19 set in a paper feed tray (not shown). The conveyor belt 51 is wound around the conveyor roller 52 and the driven roller 53 and moves around.

  The conveyance roller 52 is rotationally driven by the sub-scanning motor 151 via the timing belt 32 and the timing roller 33 fixed to the shaft 52 a of the conveyance roller 52.

  In this image forming apparatus, the sheets 19 are separated and fed one by one from the sheet feeding tray, and conveyed in the sub-scanning direction (conveying direction) by the conveying belt 51. Therefore, by driving the recording head 1 according to the image signal while moving the carriage 4, ink droplets are ejected onto the stopped sheet 19 to record one line, and after the sheet 19 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the rear end of the paper 19 has reached the recording area, the recording operation is finished, and the paper 19 is discharged to a paper discharge tray (not shown).

  For example, the present invention can be applied to a configuration in which the recording head 1 discharges droplets in the horizontal direction.

  Next, an ink supply system according to the present invention will be described with reference to FIG. FIG. 2 is a schematic explanatory diagram for explaining the same.

  As described above, the ink cartridge 23 and the head tank 5 communicate with each other through the liquid supply tube 22. Since the head tank 5 and the recording head 1 are attached integrally, the ink cartridge 23 and the recording head 1 are substantially communicated by the supply tube 22.

  A pressure pump 25 is provided between the ink cartridge 23 and the recording head 1. The pressurizing pump 25 is provided with a pump 61 serving as liquid feeding means, and a check valve 62a provided before and after (upstream and downstream) of the pump 61 to prevent liquid feeding from the recording head 1 side to the ink cartridge 23 side. 62b. Accordingly, ink is fed only in one direction by driving the pressure pump 25.

  Further, the flow path between the downstream check valve 62b and the head tank 5 and the flow path between the upstream check valve 62a and the ink cartridge 23 are directly connected, bypassing the pressure pump 25. A detour 29 is provided.

  A normally closed on-off valve 28 is provided in the flow path of the bypass 29. As the on-off valve 28, a diaphragm valve is preferable, and the present invention can be realized by other valves.

  On the other hand, an on-off valve 64 that is a second on-off valve is provided in the head tank 5.

  The on-off valve 64 is normally closed, and only when the ink is discharged and the pressure (negative pressure) of the ink following the recording head 1 from the head tank 5 decreases, that is, the pressure of the flow path on the recording head 1 side is stopped. The valve opens only when By opening the on-off valve 64, the ink pressurized by the pressurizing pump 25 is filled in the head tank 5. As a result, the predetermined pressure returns to the pressure of the ink that has decreased due to the droplet ejection of the recording head 1, and becomes constant.

  Further, in order to prevent the nozzle surface (droplet ejection surface) 77 of the recording head 1 from being dried, a cap 18 for capping the nozzle surface 77 is provided. For example, when the ink adhering to the nozzle surface 77 thickens and clogs the nozzle, the nozzle surface 77 is capped and sucked by the suction pump 65 to eliminate the nozzle clogging. The ink sucked by the suction pump 65 is stored in the waste liquid tank 80.

  The ink cartridge 23 may be a sealed container containing ink in an ink bag, or may be an air release container having an air communication part and opening the inside to the atmosphere.

In FIG. 2, only one color is shown, but when a plurality of inks are supplied, the ink cartridge 23, the supply tube 22, and the head tank 5 are provided for each color as described above. . Moreover, although the pressurization pump 25 exists for every color, the actuator of the pressurization pump 25 does not need to be divided for every color.

  Next, an example of the head tank will be described with reference to FIG. FIG. 3 is a schematic explanatory view of the head tank.

  A bendable film member 200 is stretched at the opening of the head tank 5. A spring 82 is provided between the film member 200 and the wall surface 201 inside the tank, and the film member 200 is pressurized outward.

  An open / close valve 64 is movably provided on the wall surface 201 inside the tank. The on-off valve 64 is provided with a seal portion 83 that seals between the wall surface 201. The on-off valve 64 is pressurized by the spring 101 so as to be always closed.

  In the head tank 5, as the negative pressure in the head tank 5 decreases from the state shown in FIG. 3A, the film 200 is recessed inside as shown in FIG. Become.

  When the recessed film 200 presses the on-off valve 64 that has been normally closed under pressure applied by the spring 101, the seal portion 83 in the on-off valve 64 is temporarily separated from the wall surface 201 to open the ink. Is supplied.

  Thus, when the pressurized ink is supplied to the head tank 5 and the pressure in the head tank 5 increases, the film 200 expands and the on-off valve 64 returns to the closed state by the spring 101.

  In the present embodiment, the opening / closing valve 64 is described as being arranged in the head tank 5, but the position of the opening / closing valve 64 and the opening / closing mechanism are not limited to the above example.

  For example, an opening / closing valve 64 is provided between the junction J of the detour 29 and the supply tube 22 and the head tank 5, and pressure detection means is provided in the head tank 5, and the detected negative pressure in the head tank 5 is a predetermined value. It is also possible to perform control to open the on-off valve 64 when it is lowered.

  Next, the on-off valve 28 in the first embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a schematic explanatory view of the on-off valve, in which (a) shows a closed state, and (b) shows an open state. FIG. 5 is a perspective explanatory view of a valve box of the on-off valve.

  The on-off valve 28 has a mortar-shaped valve box 73. The valve box 73 is provided with a flow path 73 a that communicates with the bypass 29, and an opening at the inclined surface 73 b of the flow path 73 a serves as a seal portion 76. And in the valve box 73, it has the diaphragm 72 which opens and closes the seal part 76 in the direction orthogonal to the detour 29. The diaphragm 72 is pressurized in a direction to close the seal portion 76 by a spring 71. The outer periphery of the diaphragm 72 is fixed, and can be deformed to a mountain side or a valley side.

  A diaphragm 74 is provided in a hole 73 c provided in the center of the valve box 73. The outer periphery of the diaphragm 72 is fixed, and can be deformed to a mountain side or a valley side.

  A lever member 105 is connected to the diaphragm 74 on the outside. The lever member 105 is movably held by the holding portion 108 and receives a force on the arrow β side by a spring 107. That is, normally, the lever member 105 is not in the state of pushing the diaphragm 74 toward the inside of the valve box 73.

  As shown in FIG. 4A, the on-off valve 28 is in a closed state in which the seal portion 76 is closed by the diaphragm 72 when no force is applied to the lever member 107 in the direction of the arrow α.

  In this state, as shown in FIG. 4B, when the lever member 105 moves in the direction of the arrow α, the diaphragm 74 swells in the direction of the arrow α, pushing out the diaphragm 72 that is in close contact with the inclined surface 73b of the valve box 73. . As a result, the seal portion 76 is opened and the on-off valve 28 is opened.

  This valve open state is only while the lever member 105 receives a force in the direction of the arrow α and pushes the diaphragm 72 through the diaphragm 74.

  When the lever member 105 no longer receives the force in the direction of the arrow α, the lever 107 returns to the position shown in FIG. 4A by the spring 107, and the diaphragm 74 expands outward. The diaphragm 72 receives the force of the spring 71 and closes the seal portion 76 again, so that the on-off valve 28 is closed.

  Next, the valve opening operation of the on-off valve 28 and the means for depressurizing the pressurized ink in the first embodiment will be described with reference to FIG. FIG. 6 is a schematic explanatory diagram for explaining the same.

  Here, the carriage 4 is movable in the direction of the arrow γ beyond the cap position (home position 100) by the cap 18.

  Then, when the carriage 4 moves in the direction of the arrow γ beyond the home position 100, the carriage 4 can come into contact with the end of the scanning path of the carriage 4 so that the carriage 4 can move in the direction of the arrow γ. The lever member 105 of the on-off valve 28 is disposed at the pushed position.

  With this configuration, when the droplet discharge by the recording head 1 is completed, the carriage 4 moves to the home position 100 where the cap 18 is disposed, as shown in FIG. At this time, the opening / closing valve 28 is in a closed state because the spring 71 pressurizes the diaphragm 72.

  Here, as shown in FIG. 6B, when the carriage 4 moves in the direction of the arrow γ beyond the home position 100, one side surface of the carriage 4 contacts the lever member 105 and comes into contact therewith.

  Thereafter, when the carriage 4 pushes the lever member 105, the lever member 105 bends the diaphragm 74 in the direction of arrow α. Thereby, as described above, the diaphragm 72 overcomes the pressure applied by the spring 71 and bends, and the on-off valve 28 is opened.

  When the on-off valve 28 is opened, the ink pressurized by the pressurizing pump 25 (ink in the supply tube 22 from the check valve 62b to the on-off valve 64, ink from the junction J to the on-off valve 28) However, the pressure is reduced as the volume of the diaphragm 72 is increased by the valve opening operation.

  Further, since the ink in the ink cartridge 23 from the opening / closing valve 28 is at atmospheric pressure, the pressurized ink passes through the opening / closing valve 28 due to the pressure difference when the opening / closing valve 28 is opened. Move to the 23 side. As a result, the pressurized ink is reduced to atmospheric pressure.

  After the pressurized ink is depressurized to atmospheric pressure, the carriage 4 returns to the home position shown in FIG. 6A, the cap 18 capping the nozzle surface 77, and the apparatus stops operating.

  On the other hand, when the carriage 4 is separated from the lever member 105, the diaphragm 74 is deflected to the outside of the valve box 73 by the pressure of the spring 107, and accordingly, the diaphragm 72 closes the seal portion 76 and blocks the flow path of the bypass 29. Therefore, the on-off valve 28 is closed again.

  As described above, the ink pressure in the positive pressure state can be reliably returned to the atmospheric pressure immediately after the end of printing by only moving (moving) the carriage 4 to the end in the main scanning direction. In addition, it is possible to obtain a configuration capable of releasing pressure at low cost without requiring any complicated parts or control equipment for performing this pressure reduction.

  Further, since the pressure can be reliably released, positive ink can be reliably prevented from leaking from the joint with the recording head 1 and the supply tube 22 when the apparatus is not used, and the reliability is improved.

  It should be noted that the time for pressing the lever member 105 with the carriage 4 to reduce the pressure of the pressurized ink to atmospheric pressure is short, but it is preferable to experimentally determine the time. While the carriage 4 is pressing the lever member 105, the nozzle surface 77 may be dried and the nozzle may be clogged. Therefore, it is preferable to set the decompression time as short as possible.

  If it takes time to reduce the pressure, it is preferable to actively control the maintenance and recovery operation such as discharging the dry ink on the nozzle surface 77 with the cap 18 after the carriage 4 returns to the home position.

  In this case, whether or not the pressure has been reduced can be detected by mounting a pressure sensor, for example, but if the on-off valve 28 is opened, it is obvious that the pressure is reduced through the ink cartridge 23 that is at atmospheric pressure. It is. Therefore, by measuring the time required from valve opening to pressure reduction without mounting a pressure sensor, and controlling the valve opening time based on the measurement result, the sensor becomes unnecessary and the cost increase is suppressed. Can do.

  Next, the overall flow of the pressure reduction control in the first embodiment will be described with reference to the flowchart of FIG.

  First, when printing is started, the cap 18 is separated from the nozzle surface 77 of the recording head 1. Thereafter, driving of the pressure pump 25 is started to pressurize the ink in the pressure pump 25 and the on-off valve 64. At this time, since the on-off valve 28 is closed, the ink up to the on-off valve 28 in the bypass 29 is also pressurized.

  When the printing operation is started, the pressurized ink is sent to the head tank 5 in a timely manner.

  Then, when printing is completed, the driving of the pressure pump 25 is stopped. At this time, the ink in the pressurizing pump 25 and the on-off valve 64 and the ink up to the on-off valve 28 in the bypass circuit 29 are kept in the pressurized state.

  If the apparatus is left in this state, the pressure of the ink continues to act on the joint part and the on-off valve 28 over time, and if a slight leak path occurs, the ink leaks into the apparatus body at once. The body will be soiled. Further, when pressurized ink leaks from the on-off valve 64 into the head tank 5, the pressure in the head tank 5 shifts from a predetermined negative pressure value to the positive pressure side, and as a result, the recording head 1 normally moves from the recording head 1 at the next image formation. It becomes impossible to discharge droplets.

  Therefore, in the present embodiment, the carriage 4 is moved to the home position 100 after the drive of the pressurizing pump 25 is stopped. Then, the carriage 4 is moved from the home position 100 to a position where it comes into contact with one end of the lever member 105, and the lever member 105 is pushed. When pushing the lever member 105, the carriage 4 is moved slowly with respect to the lever member 105 so that the lever member 105 is not damaged.

  When the lever member 105 is pressed, the on-off valve 28 is temporarily opened only during that time, and is passed through the bypass 29. Thereby, the pressurized ink is decompressed to atmospheric pressure.

  After the pressure is reduced to atmospheric pressure (after a predetermined time has elapsed), the carriage 4 is moved to the home position 100. Then, a maintenance and recovery operation is performed to remain on the nozzle surface 77 and remove the dried ink. Thereafter, the nozzle surface 77 is capped with the cap 18 to keep the moisture. The maintenance / recovery operation for the nozzle surface 77 is not necessarily performed, and may be performed according to the characteristics of the ink.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic explanatory view for explaining the on-off valve 28 in the same embodiment.

  The on-off valve 28 provided in the detour 29 is provided with a diaphragm 72 and a spring 71 in the valve box 73 as in the case of the on-off valve 28 of the first embodiment, and the diaphragm 71 pressurizes the diaphragm 72. Thus, the flow path of the detour 29 is always blocked.

  The diaphragm 72 is a flexible film such as rubber, for example, and a lever member 105 is connected to the inside thereof.

  With this configuration, the on-off valve 28 in the closed state as shown in FIG. 8A is connected as shown in FIG. 8B when the position of the lever member 105 moves in the arrow α direction. The formed diaphragm 72 is bent to be in a valve open state. When the lever member 105 returns to the position shown in FIG. 8A, the diaphragm 72 is closed by closing the flow path 73a by the pressure of the spring 71, and the detour 29 is closed.

  Next, the valve opening operation of the on-off valve 28 and the means for depressurizing the pressurized ink in the second embodiment will be described with reference to FIG. FIG. 9 is a schematic explanatory view for explaining the same.

  Here, the lever member 105 has a crank shape as a whole and is supported by a shaft 106 so as to be rotatable.

  The lever member 105 of the on-off valve 28 is disposed at a position where the carriage 4 is pushed by the carriage 4 when the carriage 4 moves in the arrow γ direction beyond the home position 100.

  With this configuration, when the droplet discharge by the recording head 1 is completed, the carriage 4 moves to the home position 100 where the cap 18 is disposed, as shown in FIG. At this time, the opening / closing valve 28 is in a closed state because the spring 71 pressurizes the diaphragm 72.

  Here, as shown in FIG. 9B, when the carriage 4 moves in the direction of the arrow γ beyond the home position 100, one side surface of the carriage 4 contacts the lever member 105 and comes into contact therewith. Since the lever member 105 can rotate around the shaft 106 as described above, the lever member 105 rotates when the carriage 4 pushes the lever member 105.

  Due to the rotation of the lever member 105, the pressure force of the spring 71 is overcome and the diaphragm 72 is pulled outward.

  Therefore, the diaphragm 72 is separated from the seal portion of the bypass 29, and the on-off valve 28 is opened.

  In this case, since the diaphragm 72 is pulled while being rotated by the lever member 105, the diaphragm 72 is preferably a low-hardness elastic body that hardly affects the rotation. Further, the lever member 105 sets the lever ratio so as to overcome the pressure applied by the spring 71 by being pushed by the carriage 4.

  When the on-off valve 28 is opened, the ink pressurized by the pressurizing pump 25 (ink in the supply tube 22 from the check valve 62b to the on-off valve 64, ink from the junction J to the on-off valve 28). The pressure is reduced to atmospheric pressure.

  This is because the volume is increased due to the valve opening operation of the diaphragm 72, and because the pressurized ink flows to the ink cartridge 23 through the bypass 29, and the pressure becomes atmospheric pressure.

  After the pressurized ink is depressurized to atmospheric pressure, the carriage 4 returns to the home position 100 as shown in FIG. 9A, the cap 18 caps the nozzle surface 77, and the apparatus stops.

  When the carriage 4 is separated from the lever member 105, the diaphragm 72 is bent so as to close the detour 29 by the pressure applied by the spring 71, and the flow path of the detour 29 is blocked. Therefore, the on-off valve 28 is closed again.

  When the diaphragm 72 bends in the valve closing direction, the lever member 105 also rotates as shown in FIG. 9A and returns to the initial position.

  As described above, the ink pressure in the positive pressure state can be surely returned to the atmospheric pressure immediately after the printing is completed only by moving the carriage 4 toward the end in the main scanning direction. At this time, since no complicated parts or control equipment for performing this pressure reduction is required, the pressure can be released at low cost.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is a schematic explanatory view for explaining the on-off valve 28 in the same embodiment.

  Here, in place of the lever member 105 in the first embodiment, a pipe line 85 having a terminal wall surface formed by a diaphragm 74 is provided.

  10A, when the diaphragm 74 is pressurized with air in the direction of the arrow B through the conduit 85 as shown in FIG. 10A, the diaphragm 74 is moved to the valve box as shown in FIG. 73 bends inside. As a result, the diaphragm 74 which has been pressed and bent inwardly deflects the diaphragm 72, and the flow path of the detour 29 is opened. That is, the on-off valve 28 is opened by pressurizing the diaphragm 74.

  In order to lift and open the diaphragm 72, it is necessary to overcome the pressure applied by the spring 71. In order to reliably open the valve, it is preferable to calculate the pressure of the pressurized air and the area of the diaphragm. .

  When the on-off valve 28 is opened, a bypass 29 is opened as shown in FIG.

  Then, after the valve is opened, when the pressure on the diaphragm 74 is released and returned to atmospheric pressure, the diaphragm 72 is again deflected to the inside of the valve box 73 by the pressure of the spring 71, and the flow path 73a following the detour 29 is closed. As a result, the on-off valve 28 is closed again.

  Next, the valve opening operation of the on-off valve 28 and the means for depressurizing the pressurized ink in the third embodiment will be described with reference to FIG. FIG. 11 is a schematic explanatory diagram for explaining the same.

  Here, the waste liquid tank 80 to which the suction pump 65 is connected communicates with the pipe line 85 of the on-off valve 28 via the flow path 88.

  Therefore, when the suction pump 65 is driven in a state where the cap 18 is separated from the nozzle surface 77 of the recording head 1, the suctioned air is transmitted to the conduit 85 along the arrow C direction by driving the suction pump 65. Since the end of the pipe 85 is sealed by the diaphragm 74, the diaphragm 74 is pressurized by the suction operation of the suction pump 65, and the on-off valve 28 is opened.

  With this configuration, when the droplet ejection by the recording head 1 is completed, the carriage 4 moves to the home position 100 where the cap 18 is provided. At this time, the opening / closing valve 28 is in a closed state because the spring 71 pressurizes the diaphragm 72.

  Therefore, as shown in FIG. 11A, by driving the suction pump 65, air is sent in the direction of arrow C through the flow path 88, and the diaphragm 74 is pressurized through the pipe 85. As a result, as shown in FIG. 11B, the diaphragm 72 is pushed, and the on-off valve 28 is opened.

  By opening the on-off valve 28, the ink pressurized by the pressurizing pump 25 (the ink in the supply tube 22 from the check valve 62b to the on-off valve 64, the junction J to the on-off valve 28). Some ink) is depressurized to atmospheric pressure.

  After the pressurized ink is depressurized to the atmospheric pressure, the suction pump 65 is driven in reverse, and the air in the pipe 85 is sucked in the direction of arrow D through the flow path 88, so that the pressure state on the diaphragm 74 is released. The on-off valve 28 is closed and the detour 29 is shut off. After the on-off valve 28 is closed, the cap 18 caps the nozzle surface 77 and stops the apparatus.

  As described above, the ink pressure in the positive pressure state can be reliably returned to the atmospheric pressure immediately after the end of printing only by the operation of the suction pump 65. In addition, since no complicated parts or control equipment is required to perform this decompression, the pressure can be released at low cost.

  Note that ink is stored in the waste liquid tank 80. Therefore, it is preferable to provide the flow path 88 connecting the pipe 85 and the waste liquid tank 80 on the ceiling surface so that the waste liquid does not flow into the pipe 85.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a schematic explanatory view for explaining the on-off valve 28 in the same embodiment.

  Here, a conduit 85 is provided on the back side of the diaphragm 72.

  Since it comprised in this way, as shown to Fig.12 (a), if it attracts | sucks in the arrow A direction through the pipe line 85, the inside of the valve box 73 will be in a negative pressure state. Since the pressure inside the valve box 73 is negative and the ink in the bypass 29 is pressurized, a pressure difference is generated, and the diaphragm 72 is lifted from the bypass 29 side by this pressure difference. As a result, as shown in FIG. 12B, the on-off valve 28 is opened.

  In order to lift and open the diaphragm 72, it is necessary to overcome the pressure applied by the spring 71. In order to reliably open the valve, the negative pressure value generated inside the valve box 73 and the area of the diaphragm on which the pressure acts are applied. Is preferably calculated in advance.

  When the on-off valve 28 is opened, the bypass 29 is opened.

  Thereafter, when the inside of the valve box 73 is returned to the atmospheric pressure, the diaphragm 72 is again bent inside the valve box 73 by the pressure of the spring 71 and closes the flow path 73 a following the detour 29. Thereby, the on-off valve 28 is closed again.

  When the on-off valve 28 is used, the diaphragm 72 can be bent to the inside of the valve box 73 by the suction pump 65 sucking the conduit 85 after the printing is completed. As a result, the on-off valve 28 is opened, the bypass 29 is connected, and the pressurized ink is decompressed.

  Thereafter, when the suction pump 65 is rotated in the reverse direction and the deflection of the diaphragm 72 is returned to the state shown in FIG. 12A, the open / close valve 28 is closed by the pressure applied by the spring 71, and the bypass 29 is shut off. .

  The pressure reducing operation by the on-off valve 28 in this embodiment can also reduce the pressure of the pressurized ink to atmospheric pressure only by driving the suction pump. In addition, since no complicated parts or control equipment for reducing pressure is required, the pressure can be released at low cost and the reliability can be improved.

  In the present application, “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, and the like, and can be attached to ink droplets and other liquids. This includes recording media, 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 a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics or the like. In addition, “image formation” not only applies an image having a meaning such as a character or a figure to a medium but also applies an image having no meaning such as a pattern to the medium (simply applying a droplet to the medium). It also means to land on.

  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, DNA samples, resists, pattern materials, resins and the like are also included.

  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 image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

1 Recording head (liquid ejection head)
4 Carriage 5 Head tank 18 Cap 22 Supply tube (first flow path)
23 Ink cartridge (liquid tank)
25 Pressurizing pump 28 On-off valve (first on-off valve)
29 Detour 64 On-off valve (second on-off valve)
65 Suction pump (suction means)
100 Home position 105 Lever member

Claims (7)

A recording head for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path through the liquid tank and the recording head;
Liquid feeding means for feeding the liquid provided in the first flow path;
A second flow path that bypasses the liquid feeding means and communicates with the first flow path;
A first on-off valve provided in the second flow path;
Valve opening means for opening the first on-off valve;
Among the first flow paths, a second opening / closing which is opened only when the pressure of the flow path on the recording head side is reduced between the recording head and the liquid feeding means, and is otherwise normally closed. A valve,
The first on-off valve is a normally closed valve;
When image formation is performed, by driving the liquid feeding means, a flow path between the liquid feeding means and the first on-off valve, and between the liquid feeding means and the second on-off valve. The liquid in the flow path is brought into a positive pressure state,
An image forming apparatus, wherein after the image formation is stopped, the first opening / closing valve is opened for a predetermined period by the valve opening means. The recording head is mounted on a carriage that is reciprocally scanned;
A lever member is provided at a position where the carriage can come into contact with the end of the scanning path of the carriage,
One end of the lever member is connected to the first on-off valve,
2. The first on-off valve is opened when the carriage moves to the lever member side after image formation is stopped and the carriage pushes the lever member. Image forming apparatus. The image forming apparatus according to claim 2, wherein the lever member rotates when the lever member is pressed by the carriage to open the first on-off valve. The carriage moves to a position where a cap covering the nozzle surface of the recording head is disposed after pressing the lever member;
The image forming apparatus according to claim 2, wherein a nozzle surface of the recording head is covered with the cap. Suction means is connected to a cap covering the nozzle surface of the recording head,
The suction means communicates with the first on-off valve by a predetermined pipe line ,
After stopping the image formation, the image forming apparatus according to claim 1, characterized in that the open state of the first on-off valve by the pressure generated in the conduit by driving the suction means. A check valve is provided on the upstream side and the downstream side of the liquid feeding means to feed liquid from the liquid tank in the direction of the recording head and prevent liquid feeding from the recording head in the direction of the liquid tank. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The first on-off valve is a diaphragm valve;
The image forming apparatus according to claim 1, wherein the image forming apparatus opens and closes in a direction orthogonal to the second flow path.

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