Pressure adjustment device, droplet discharge device, pressure adjustment method, and program

Abstract

To provide a pressure adjustment device which enables downsizing of the device and precise pressure control, and to provide a droplet discharge device, a pressure adjustment method, and a program.SOLUTION: A pressure adjustment device 100 includes: a gas passage 44 which may form a sealed space CS; a pneumatic pump 441 which is provided at the gas passage 44 and sends a gas at the suction side to the discharge side; a plurality of atmosphere release valves 445 at least one of which is provided at a suction side gas passage 442 and a discharge side gas passage 444 of the pneumatic pump 441 and which release atmospheric air from or close the suction side gas passage 442 and the discharge side gas passage 444; and a control unit 50. When the pneumatic pump 441 is driven, the control unit 50 controls opening / closing operation of the atmosphere release valves 445 to adjust a pressure in the sealed space CS formed at one of the suction side gas passage 442 and the discharge side gas passage 444 and then adjust a pressure of the other gas passage.SELECTED DRAWING: Figure 7B

Description

Technical Field

[0001] The present invention relates to a pressure adjusting device, a droplet discharging device, a pressure adjusting method, and a program.

Background Art

[0002] Conventionally, a droplet discharging device that discharges droplets onto a recording surface of a recording medium to record an image is known. The droplet discharging device includes a tank containing ink, and the ink is sent to an inkjet head by a pump. Then, the ink sent to the inkjet head is discharged from nozzles at an appropriate timing, and an image is formed on the recording medium.

[0003] In the ink supply system of such a droplet discharging device, maintenance such as ink circulation and discharge is performed by adjusting the pressure in the tank. For example, Patent Document 1 describes an ink supply device that shortens the time for discharge maintenance by communicating a chamber on the pump side via a solenoid valve and selectively switching a pressurization target. Further, for example, Patent Document 2 describes a droplet discharging device that realizes miniaturization of the device by enabling both circulation and discharge maintenance by an air supply pump.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when attempting to perform maintenance on a plurality of large tanks all at once, the invention of Patent Document 1 requires a high-output air supply pump with a large flow rate. On the other hand, when attempting to perform both circulation and discharge maintenance as in the invention of Patent Document 2 using a high-output air supply pump, if the air capacity of the tank is not large, it is difficult to precisely control the pressure inside the tank during circulation maintenance, and the device cannot be miniaturized.

[0006] The present invention has been made in view of such circumstances. Its object is to provide a pressure adjustment device, a droplet discharge device, a pressure adjustment method, and a program capable of miniaturizing the device and enabling precise pressure control.

Means for Solving the Problems

[0007] In order to solve the above problems, the invention according to claim 1 is a pressure adjustment device, comprising: a gas flow path capable of forming a sealed space; a pneumatic pump provided in the gas flow path for sending the gas on the suction side to the discharge side; a plurality of atmosphere release valves provided at least one by one in the gas flow path on the suction side and the gas flow path on the discharge side of the pneumatic pump for opening or closing the gas flow path on the suction side and the gas flow path on the discharge side to the atmosphere; a control unit, when driving the pneumatic pump, the control unit controls the opening and closing operations of the plurality of atmosphere release valves to adjust the pressure of the sealed space formed in one of the gas flow paths on the suction side and the gas flow path on the discharge side, and then adjusts the pressure of the other gas flow path.

[0008] The invention according to claim 2 is the pressure adjustment device according to claim 1, wherein the control unit adjusts the pressure of the sealed space in the gas flow path on the suction side by closing the atmosphere release valve in the gas flow path on the suction side.

[0009] The invention according to claim 3 is the pressure adjustment device according to claim 2, wherein The control unit closes the atmosphere release valve of the gas flow path on the suction side after a predetermined time from the drive of the pneumatic pump.

[0010] The invention according to claim 4 is a pressure regulating device according to claim 2, comprising an air quantity detection unit that detects the air quantity of at least one of the gas flow path on the suction side and the gas flow path on the discharge side, and the control unit closes the atmosphere release valve of the gas flow path on the suction side according to the detection result of the air quantity detection unit.

[0011] The invention according to claim 5 is a pressure regulating device according to claim 2, comprising a pressure detection unit that detects the pressure of the sealed space, and the control unit closes the atmosphere release valve on the suction side according to the detection result of the pressure detection unit.

[0012] The invention according to claim 6 is a pressure regulating device according to claim 1, wherein the pneumatic pump is a diaphragm pump.

[0013] The invention according to claim 7 is a droplet discharge device, comprising the pressure regulating device according to any one of claims 1 to 6, a tank that communicates with the gas flow path on the suction side and stores a liquid, a liquid flow path that sends out the liquid in the tank, and a droplet discharge head that discharges the liquid sent from the tank as droplets. The control unit adjusts the pressure in the tank by adjusting the pressure of the gas flow path on the suction side.

[0014] The invention according to claim 8 is a gas flow path capable of forming a sealed space, A pneumatic pump provided in the gas flow path for sending the gas on the suction side to the discharge side, and a plurality of atmosphere release valves provided in at least one of the gas flow path on the suction side and the gas flow path on the discharge side of the pneumatic pump, for opening or closing the gas flow path on the suction side and the gas flow path on the discharge side to the atmosphere. A pressure adjustment method of a pressure adjustment device comprising: When the pneumatic pump is driven, the opening and closing operations of the plurality of atmosphere release valves are controlled to adjust the pressure of the sealed space formed in one of the gas flow path on the suction side and the gas flow path on the discharge side, and then the pressure of the other gas flow path is adjusted. A pressure adjustment step is provided.

[0015] The invention according to claim 9 is the pressure adjustment method according to claim 8, wherein: In the pressure adjustment step, the pressure of the sealed space in the gas flow path on the suction side is adjusted by closing the atmosphere release valve on the suction side.

[0016] The invention according to claim 10 is the pressure adjustment method according to claim 9, wherein: In the pressure adjustment step, the atmosphere release valve of the gas flow path on the suction side is closed after a predetermined time from the start of driving of the pneumatic pump.

[0017] The invention according to claim 11 is the pressure adjustment method according to claim 9, wherein: The pressure adjustment device includes an air amount detection unit for detecting the air amount in at least one of the gas flow path on the suction side and the gas flow path on the discharge side. In the pressure adjustment step, the atmosphere release valve of the gas flow path on the suction side is closed according to the detection result of the air amount detection unit.

[0018] The invention according to claim 12 is the pressure adjustment method according to claim 9, wherein: The pressure adjustment device includes a pressure detection unit for detecting the pressure of the sealed space. In the pressure adjustment step, the atmosphere release valve on the suction side is closed according to the detection result of the pressure detection unit.

[0019] The invention according to claim 13 is a program, wherein: A gas flow path capable of forming a sealed space, A pneumatic pump provided in the gas flow path for sending the gas on the suction side to the discharge side, A plurality of atmosphere release valves provided at least one each in the gas flow path on the suction side and the gas flow path on the discharge side of the pneumatic pump, for opening or closing the gas flow path on the suction side and the gas flow path on the discharge side to the atmosphere, and a computer of a pressure adjustment device including the same, When the pneumatic pump is driven, the opening and closing operations of the plurality of atmosphere release valves are controlled to adjust the pressure of the sealed space formed in one of the gas flow paths on the suction side and the gas flow path on the discharge side, and then function as a control unit for adjusting the pressure of the other gas flow path.

Effect of the Invention

[0020] According to the present invention, miniaturization of the device and precise pressure control become possible.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9A

Figure 9B

Figure 10A

Figure 10B

Figure 10C

Mode for Carrying Out the Invention

[0022] Hereinafter, the droplet discharge device according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, those having the same functions and configurations are denoted by the same reference numerals, and the description thereof is omitted.

[0023] [Overall Configuration of Inkjet Recording Apparatus] FIG. 1 is a side sectional view showing a main configuration of an inkjet recording 1 which is an embodiment of the droplet discharge device of the present invention. The inkjet recording apparatus 1 includes a paper feed unit 10, an image forming unit 20, a paper discharge unit 30, a liquid feed unit 40 (see FIG. 2), a control unit 50 (see FIG. 3), and the like.

[0024] In the following, the X direction, Y direction, and Z direction shall refer to the directions shown in FIG. 1. Further, in the following, the X direction, Y direction, and Z direction will be described as the width direction, conveyance direction, and height direction, respectively.

[0025] (Paper Feeding Unit) The paper feeding unit 10 stores the recording medium P before image formation. The paper feeding unit 10 conveys the recording medium P to the image forming unit 20 under the control of the control unit 50. The paper feeding unit 10 includes a paper feed tray 11, a conveyance unit 12, and the like.

[0026] {Paper Feed Tray} The paper feed tray 11 is a plate-like member that stores the recording medium P. The paper feed tray 11 is provided so that one or a plurality of recording media P can be placed thereon. The paper feed tray 11 moves up and down according to the amount of the recording medium P placed thereon. The paper feed tray 11 is held at a position where the uppermost recording medium P is conveyed by the conveyance unit 12 in the vertical movement direction.

[0027] {Conveyance Unit} The conveyance unit 12 conveys the recording medium P from the paper feed tray 11 to the image forming unit 20. The conveyance unit 12 includes a conveyance mechanism. The conveyance mechanism drives a belt 123 to convey the recording medium P on the belt 123. The belt 123 is annular, and the inside of the ring is supported by a plurality of rollers 121 and 122.

[0028] The conveyance unit 12 includes a supply unit. The supply unit delivers the uppermost recording medium P placed on the paper feed tray 11 onto the belt 123. The conveyance unit 12 conveys the recording medium P along the belt 123 by the supply unit.

[0029] (Image Forming Unit) The image forming unit 20 cooperates with the liquid feeding unit 40 to perform a recording operation on the recording medium P under the control of the control unit 50. The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a paper heating unit 23, a head unit 24, an irradiation unit 25, a delivery unit 26, and the like.

[0030] {Image Forming Drum} The image forming drum 21 carries the recording medium P along the cylindrical outer peripheral surface and conveys the recording medium P as it rotates. The conveyance surface of the image forming drum 21 faces the paper heating unit 23, the head unit 24, and the irradiation unit 25, and performs image forming processing on the conveyed recording medium P.

[0031] {Delivery Unit} The delivery unit 22 is provided at a position intervening between the conveyance unit 12 and the image forming drum 21. The delivery unit 22 includes a claw portion 221, a delivery drum 222, and the like.

[0032] The claw portion 221 is a cylindrical member that holds one end of the recording medium P conveyed by the conveyance unit 12. The delivery drum 222 is a member that guides the recording medium P held by the claw portion 221.

[0033] The delivery unit 22 picks up the recording medium P on the conveyance unit 12 with the claw portion 221 and places it along the outer peripheral surface of the delivery drum 222. By this operation, the delivery unit 22 delivers the recording medium P to the image forming drum 21.

[0034] {Paper Heating Unit} The paper heating unit 23 includes, for example, a heating wire and the like, and generates heat in response to energization. The paper heating unit 23 is controlled by the control unit 50 and generates heat so that the recording medium P passing near it reaches a predetermined temperature. The paper heating unit 23 is provided near the outer peripheral surface of the image forming drum 21 and is positioned upstream of the head unit 24 in the conveyance direction of the recording medium P.

[0035] A temperature sensor (not shown) is provided near the paper heating unit 23. The control unit 50 detects the temperature near the paper heating unit 23 with the temperature sensor. The control unit 50 controls the heat generation of the paper heating unit 23 based on the detected temperature.

[0036] {Head Unit} The head unit 24 ejects ink onto the recording medium P to form an image. The head unit 24 is provided with those corresponding to each of the colors C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, in the conveyance direction, the head units 24 corresponding to the respective colors of Y, M, C, and K are provided in order from upstream.

[0037] The head unit 24 of the present embodiment is provided such that a plurality of them are arranged with a length (width) covering the entire recording medium P in the width direction. That is, the inkjet recording apparatus 1 according to the present embodiment is of a line head type. The head unit 24 is configured by arranging a plurality of inkjet heads 24a (see FIG. 2), which are droplet ejection heads, in the width direction.

[0038] Note that the number of the head units 24 provided in the image forming unit 20 may be three or less or five or more. Also, a configuration in which a single inkjet head 24a constitutes the head unit 24 may be employed. Further, the inkjet recording apparatus 1 may be of a serial head type in which an image is formed by scanning a head unit 24 having a length in the width direction shorter than that of the recording medium P in the width direction.

[0039] The ink ejected by the head unit 24 is, for example, an ultraviolet curable ink. The ultraviolet curable ink is a gel ink that undergoes a phase change between a gel state and a liquid (sol) state according to temperature in a state where ultraviolet rays are not irradiated from the irradiation unit 25. The ultraviolet curable ink has a phase change temperature of, for example, about 40 to 100°C, and uniformly liquefies (solates) when heated to a temperature equal to or higher than the phase change temperature. On the other hand, the ultraviolet curable ink gels at about normal room temperature, that is, about 0 to 30°C.

[0040] {Irradiation unit} The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp. The irradiation unit 25 irradiates energy rays such as ultraviolet rays by the light emission of the fluorescent tube. The irradiation unit 25 is provided in the vicinity of the outer peripheral surface of the image forming drum 21. Also, the irradiation unit 25 is provided so as to be located on the downstream side of the head unit 24 in the conveyance direction of the recording medium P. The irradiation unit 25 irradiates energy rays on the recording medium P on which ink has been ejected. The ink on the recording medium P is cured by the action of the energy rays.

[0041] Note that the fluorescent tube that emits ultraviolet rays is not limited to a low-pressure mercury lamp. The fluorescent tube may be, for example, a mercury lamp having an operating pressure of about several hundred Pa to 1 MPa. Also, the fluorescent tube may be a light source that can be used as a germicidal lamp, for example, a cold cathode tube, an ultraviolet laser light source, a metal halide lamp, or a light emitting diode. Among these, it is desirable that the fluorescent tube is a light source that can irradiate ultraviolet rays with higher illuminance and is power-saving. The fluorescent tube is, for example, a light emitting diode or the like. Note that the energy rays are not limited to ultraviolet rays, and any energy rays having the property of curing the ink according to the properties of the ink may be used. And the light source is also replaced according to the energy rays.

[0042] In the above, the case where the head unit 24 ejects ultraviolet curable ink has been exemplified, but it is not limited thereto. The ink ejected by the head unit 24 may be aqueous ink or ink having other physical properties.

[0043] {Delivery Unit} The delivery unit 26 includes a conveyance mechanism. The conveyance mechanism drives a ring-shaped belt 263 whose inner side is supported by a plurality of rollers 261 and 262 to convey the recording medium P. The delivery unit 26 includes a cylindrical delivery roller 264. The delivery roller 264 delivers the recording medium P from the image forming drum 21 to the conveyance mechanism. The delivery unit 26 conveys the recording medium P delivered onto the belt 263 by the delivery roller 264 and sends it out to the paper discharge unit 30.

[0044] (Paper Discharge Unit) The paper discharge unit 30 discharges the recording medium P on which an image has been formed by the image forming unit 20. The paper discharge unit 30 includes a plate-shaped paper discharge tray 31 and the like. The recording medium P sent out from the image forming unit 20 by the delivery unit 26 is placed on the paper discharge tray 31. The paper discharge unit 30 stores the recording medium P until the user takes it out.

[0045] (Liquid feeding unit) FIG. 2 is a schematic configuration diagram of the liquid feeding unit 40. In FIG. 2, a plurality of inkjet heads 24a are omitted and only one inkjet head 24a is shown. The liquid feeding unit 40 includes a liquid storage unit 41, a plurality of tanks 42, a liquid flow path 43, a gas flow path 44, and the like.

[0046] {Liquid storage unit} The liquid storage unit 41 stores inks of various colors supplied to each part of the liquid feeding unit 40. Although omitted in FIG. 2, the liquid storage unit 41 is provided individually for each ink color. When the supply valve 4312 described later is opened, the ink is supplied to the first tank 421 by the supply pump 4311 via the first liquid flow path 431. The entire liquid storage unit 41 is replaceable and is detachably formed with the first liquid flow path 431 regardless of the operating status of the supply pump 4311.

[0047] {Tank} The tank 42 includes, for example, a first tank 421, a second tank 422, and the like. Each tank 42 includes a liquid storage portion IS and a gas storage portion GS. The tank 42 stores the ink supplied from the liquid storage unit 41 in the liquid storage portion IS and supplies the ink to the inkjet head 24a. The gas storage portion GS is above the ink liquid level and stores gases such as air. Note that the capacity of the tank 42 is less than or approximately the same as that of the liquid storage unit 41.

[0048] Also, each tank 42 is provided with a pressure measurement unit PM which is a pressure gauge capable of measuring the internal pressure. The pressure measurement unit PM acquires the pressure value in each tank 42 and sequentially outputs it to the control unit 50.

[0049] In addition, a liquid level measurement unit LM is provided for each of the tanks 42. The liquid level measurement unit LM is, for example, a float sensor, which acquires measurement data related to the liquid level position of the ink in each tank 42 and outputs it to the control unit 50. The control unit 50 acquires the remaining ink amount in each tank 42 from the measurement data, and appropriately feeds the ink from the liquid storage unit 41 on the upstream side in the liquid feeding direction or the first tank 421. Note that the remaining amount of ink in the liquid storage unit IS is adjusted so that the gas storage units GS of the first tank 421 and the second tank 422 are in the range of 150 ml or more and 250 ml or less, for example.

[0050] In addition, an ink heating unit (not shown) for maintaining the internal ink at an appropriate temperature is provided in the tank 42. The ink heating unit is composed of a heater, a heat transfer member for transferring heat from the heater, and the like. As the heater constituting the ink heating unit, for example, a heating wire that generates Joule heat when energized is used. As the heat transfer member constituting the ink heating unit, a member having a high thermal conductivity, for example, a heat conduction plate formed of various metals (alloys), is used.

[0051] 〔First Tank〕 The first tank 421 temporarily stores the ink supplied from the liquid storage unit 41. By providing the liquid feeding unit 40 with the first tank 421, the pressure change due to the pulsation when the supply pump 4311 supplies the ink in the liquid storage unit 41 is alleviated.

[0052] 〔Second Tank〕 The second tank 422 temporarily stores the ink fed from the first tank 421. By applying an appropriate negative pressure to the second tank 422 by a back pressure pump 4431 described later, leakage of ink from the inkjet head 24a during normal times is suppressed. With this configuration, it is not necessary to arrange the second tank 422 below the inkjet head 24a and control the back pressure of the nozzles of the inkjet head 24a by the head difference. As a result, the second tank 422 can be arranged at an arbitrary position with respect to the inkjet head 24a, and the liquid feeding unit 40 and the inkjet recording apparatus 1 can be miniaturized.

[0053] {Liquid Flow Path} The liquid flow path 43 is an ink flow path that communicates from the liquid storage section 41 to the inkjet head 24a. The liquid flow path 43 includes a first liquid flow path 431, a second liquid flow path 432, a third liquid flow path 433, and a fourth liquid flow path 434. The liquid flow path 43 preferably has ink resistance and has a hollow annular tube structure.

[0054] 〔First Liquid Flow Path〕 The first liquid flow path 431 communicates the liquid storage section 41 with the first tank 421. A supply pump 4311 and a supply valve 4312 are provided in the first liquid flow path 431. The control unit 50 opens the supply valve 4312, which is an electromagnetic valve, and drives the supply pump 4311 according to the measurement result of the liquid level measurement section LM of the first tank 421. The control unit 50 feeds the ink in the liquid storage section 41 into the first tank 421 by this control.

[0055] 〔Second Liquid Flow Path〕 The second liquid flow path 432 communicates the first tank 421 with the second tank 422. A liquid feed pump 4321 is provided in the second liquid flow path 432. The liquid feed pump 4321 is, for example, a diaphragm pump, and feeds the ink in the first tank 421 into the second tank 422 according to the measurement result of the liquid level measurement section LM of the second tank 422 under the control of the control unit 50.

[0056] Although not shown in FIG. 2, a known degassing module for degassing the ink that has passed through may be provided in the second liquid flow path 432. Further, when a degassing module is provided in the second liquid flow path 432, the first tank 421 and the second tank 422 may be communicated with each other by another liquid flow path so that the ink can circulate between the first tank 421 and the second tank 422.

[0057] 〔Third Liquid Flow Path and Fourth Liquid Flow Path〕 The third liquid flow path 433 communicates the second tank 422 with the inlet of the inkjet head 24a. The fourth liquid flow path 434 communicates the outlet of the inkjet head 24a with the first liquid flow path 431 (or the first tank 421). A circulation valve 4341, which is a solenoid valve, is provided in the fourth liquid flow path 434 and is opened in an ink circulation maintenance process described later under the control of the control unit 50.

[0058] {Gas flow path} The gas flow path 44 has a hollow annular tube structure and is provided to communicate the gas storage portions GS of the respective tanks 42. The gas flow path 44 includes a pneumatic pump 441, a first gas flow path 442, a second gas flow path 443, a third gas flow path 444, an atmosphere release valve 445, and the like.

[0059] {Pneumatic pump} The pneumatic pump 441 is under the control of the control unit 50. During image formation, it is not normally driven. During maintenance, it is driven to suck the gas on the first gas flow path 442 side and discharge it to the third gas flow path 444 side. By this drive of the pneumatic pump 441, a discharge maintenance process is executed in which the inside of the second tank 422 is pressurized to discharge ink from the inkjet head 24a. Also, by this drive of the pneumatic pump 441, a circulation maintenance process is executed in which the inside of the first tank 421 is depressurized to send ink from the outlet of the inkjet head 24a to the first tank 421. Detailed descriptions of the discharge maintenance process and the circulation maintenance process will be given later.

[0060] In this embodiment, the pneumatic pump 441 is a high-output pump with a large flow rate that can pressurize the inside of the second tank 422 to enable discharge of ink from the inkjet head 24a in the discharge maintenance process. Specifically, for example, the flow rate of the pneumatic pump 441 is 2 L / min or more. Also, from the viewpoints of durability, cost, size, and variety, the pneumatic pump 441 is preferably a diaphragm pump.

[0061] 〔First gas flow path〕 The first gas flow path 442 is a gas flow path on the suction side of the pneumatic pump 441 and communicates with the gas storage part GS of the first tank 421.

[0062] 〔Second gas flow path〕 The second gas flow path 443 is a gas flow path that communicates with the gas storage part GS of the second tank 422. The control unit 50 adjusts the pressure in the second tank 422 by means of a back pressure pump 4431 provided in the second gas flow path 443. By this control, the control unit 50 applies an appropriate negative pressure to the nozzles of the inkjet head 24a to generate a head meniscus, and prevents ink from leaking out of the nozzles at timing other than during image formation and various maintenance operations.

[0063] 〔Third gas flow path〕 The third gas flow path 444 is a gas flow path on the discharge side of the pneumatic pump 441 and communicates the first gas flow path 442 and the second gas flow path 443. A buffer tank 4441 is provided in the third gas flow path 444.

[0064] <Buffer tank> The buffer tank 4441 is a tank that stores air pressurized by the pneumatic pump 441. The capacity of the buffer tank 4441 is, for example, about 40 ml.

[0065] 〔Atmospheric release valve〕 The atmospheric release valve 445 is an electromagnetic valve that opens and closes under the control of the control unit 50 and is provided in the gas flow path 44. The atmospheric release valve 445 selectively opens and closes the provided gas flow path 44 and the tank 42 communicating with the gas flow path 44 to the atmosphere. The atmospheric release valve 445 includes a first atmospheric release valve 4451, a second atmospheric release valve 4452, a common atmospheric release valve 4453, and a third atmospheric release valve 4454.

[0066] <First atmospheric release valve> The first atmospheric release valve 4451 is provided in the first gas flow path 442. Normally, the first atmospheric release valve 4451 is open, and the gas storage part GS of the first tank 421 and the first gas flow path 442 are open to the atmosphere.

[0067] <Second Atmosphere Release Valve> The second atmosphere release valve 4452 is provided in the second gas flow path 443 on the suction side of the back pressure pump 4431. The second atmosphere release valve 4452 is opened when the back pressure pump 4431 is driven.

[0068] <Common Atmosphere Release Valve> The common atmosphere release valve 4453 is provided between the pneumatic pump 441 and the buffer tank 4441 in the third gas flow path 444. The common atmosphere release valve 4453 is in a closed state during the operation of the inkjet head 24a, and is in an open state during the maintenance of the inkjet recording apparatus 1.

[0069] <Third Atmosphere Release Valve> The third atmosphere release valve 4454 is provided between the buffer tank 4441 and the second gas flow path 443 in the third gas flow path 444. The third atmosphere release valve 4454 is closed except during discharge maintenance.

[0070] (Control Unit) FIG. 3 is a block diagram showing the internal configuration of the inkjet recording apparatus 1. The control unit 50 controls each part constituting the inkjet recording apparatus 1. As shown in FIG. 3, the control unit 50 is connected to each part constituting the inkjet recording apparatus 1. The control unit 50 includes a CPU (Central Processing Unit) 51, a RAM (Random Access Memory) 52, a ROM (Read Only Memory) 53, and the like.

[0071] The CPU 51 reads out various programs, data, etc. corresponding to the processing content from a storage device such as the ROM 53 and executes them. The CPU 51 controls the operations of each part of the inkjet recording apparatus 1 according to the executed processing content. The RAM 52 temporarily stores various programs, data, etc. processed by the CPU 51. The ROM 53 stores various programs, data, etc. read by the CPU 51 and the like.

[0072] Further, as shown in FIG. 3, a pressure adjusting device 100 for adjusting the pressure in the gas flow path 44 in the discharge maintenance process and the circulation maintenance process described later is configured by the gas flow path 44 and the control unit 50.

[0073] [Discharge Maintenance Process] Regarding the ink discharge maintenance process in the inkjet recording apparatus 1 configured as described above, it will be described with reference to FIGS. 4 to 5B. FIG. 4 is a flowchart showing an example of the discharge maintenance process.

[0074] First, the control unit 50 forms a sealed space in the third gas flow path 444 by closing the common atmosphere release valve 4453 and the third atmosphere release valve 4454 (step S101). Hereinafter, as shown in FIG. 5A, the sealed space in the third gas flow path 444 when the common atmosphere release valve 4453 is closed is referred to as the sealed space CS.

[0075] The control unit 50 drives the pneumatic pump 441 (step S102). At this time, as shown in FIG. 5A, the first atmosphere release valve 4451 is in an open state. Therefore, even when the pneumatic pump 441 is driven, the atmosphere is sucked from the first atmosphere release valve 4451, and the first tank 421 remains at atmospheric pressure. On the other hand, since the sealed space CS is formed in the third gas flow path 444 on the discharge side of the pneumatic pump 441, a pressure is applied to the sealed space CS.

[0076] The control unit 50 waits for a predetermined time from the start of driving of the pneumatic pump 441 (step S103). After the predetermined time has elapsed (step S103; Yes), the control unit 50 stops the pneumatic pump 441 (step S104). Then, the third atmosphere release valve 4454 is opened. Then, as shown in FIG. 5B, the pressurized air in the sealed space CS flows into the second tank 422 and the inside of the second tank 422 is pressurized. As a result, ink is discharged from the inkjet head 24a communicating with the second tank 422 (step S105).

[0077] The control unit 50 waits for a predetermined time after the opening of the third atmosphere release valve 4454 (step S106). After the elapse of the predetermined time (step S106; Yes), the control unit 50 opens the common atmosphere release valve 4453 (step S107). Thereby, the pressure in the second tank 422 is released. Then, the control unit 50 opens the back pressure valve 4452 and drives the back pressure pump 4431 to reapply a predetermined negative pressure to the second tank 422.

[0078] By such discharge maintenance processing, foreign matters, air bubbles, ink solidified in the nozzles, etc. in the inkjet head 24a can be discharged outside the inkjet head 24a.

[0079] [Circulation Maintenance Processing] Next, the ink circulation maintenance processing in the inkjet recording apparatus 1 configured as described above will be described with reference to FIGS. 6 to 9B. FIG. 6 is a flowchart showing an example of the circulation maintenance processing.

[0080] First, the control unit 50 forms a sealed space CS by closing the common atmosphere release valve 4453 and the third atmosphere release valve 4454 (step S201). Also, the control unit 50 drives the pneumatic pump 441. At this time, as shown in FIG. 7A, the first atmosphere release valve 4451 is in an open state. Therefore, similar to the discharge maintenance processing, the inside of the first tank 421 remains at atmospheric pressure, and a pressure is applied to the sealed space CS (step S202).

[0081] The control unit 50 waits for a predetermined time from the start of driving of the pneumatic pump 441 until the sealed space CS reaches the limit applied pressure (step S203). After the elapse of the predetermined time (step S203; Yes), the control unit 50 closes the first atmosphere release valve 4451 (step S204). Then, by continuing the driving of the pneumatic pump 441, the measured value of the pressure measurement unit PM of the first tank 421, that is, the pressure value in the first tank 421 is reduced to a predetermined value (step S205).

[0082] When the first atmosphere release valve 4451 is closed in step S204, the pneumatic pump 441 starts to suck the gas in the first tank 421. Therefore, the pressure value in the first tank 421 decreases. However, as shown in FIG. 7B, in step S102, due to the pressure resistance formed in the sealed space CS, the suction force of the pneumatic pump 441 decreases compared to when the common atmosphere release valve 4453 is open (i.e., when no pressure is applied). Therefore, as shown in FIG. 8, the negative pressure generation rate in the first tank 421 decreases compared to when no pressure is applied. As a result, even if the pneumatic pump 441 is a high-output pump, precise pressure control in the first tank 421 becomes possible.

[0083] Returning to FIG. 6, when the pressure value in the first tank 421 has decreased to a predetermined value (step S205; Yes), the control unit 50 stops the pneumatic pump 441 (step S206). Then, with the back pressure valve 4452 closed, the control unit 50 drives the liquid feed pump 4321 and opens the circulation valve 4341. As a result, the ink circulates in the liquid feed unit 40 (step S207).

[0084] Such circulation maintenance processing can suppress problems such as changes in the viscosity of the ink that is not ejected from the inkjet head 24a and separation of components.

[0085] [Effects of the present embodiment] In the conventional circulation maintenance processing, the common atmosphere release valve 4453 was not closed, and the pneumatic pump 441 was driven with the first atmosphere release valve 4451 closed from the beginning. Then, when the pressure value in the first tank 421 reached a predetermined value, the liquid feed pump 4321 was driven to circulate the ink.

[0086] However, when the inside of the first tank 421 is depressurized by a large-sized pneumatic pump 441 with a large air flow rate, the speed from the start of driving of the pneumatic pump 441 until the pressure inside the first tank 421 becomes negative pressure becomes too fast. As a result, as shown in FIG. 9A, an overshoot may occur between when the pressure measurement unit PM of the first tank 421 measures that the pressure inside the first tank 421 has reached a predetermined value and when the driving of the pneumatic pump 441 is stopped. Then, as a result of opening the circulation valve 4341 while the negative pressure is excessive, ink may be rapidly sucked into the first tank 421, destroying the meniscus of the inkjet head 24a.

[0087] On the other hand, in the ink circulation process according to the present embodiment, as shown in FIG. 9B, the control unit 50 controls the opening and closing operation of the atmosphere release valve 445 when the pneumatic pump 441 is driven to form a sealed space CS in the third gas flow path 444 which is the discharge-side gas flow path 44. Then, after adjusting the pressure of the sealed space CS, the control unit 50 adjusts the pressure of the first gas flow path 442 which is the suction-side gas flow path 44 on the other hand. According to this configuration, even if the pneumatic pump 441 is enlarged for ink discharge maintenance of the inkjet head 24a, the pressure inside the first tank 421 can be precisely controlled due to the pressure resistance of the sealed space CS. Further, according to this configuration, since the pressure inside the first tank 421 can be precisely controlled regardless of the air capacity of the first tank 421, the pressure adjustment device 100 and the inkjet recording device 1 can be designed to be miniaturized.

[0088] [Other configurations] As described above, specific explanations have been made based on the embodiments according to the present invention, but the present invention is not limited to the above-described embodiments. Of course, various modifications including the scope of the invention described in the claims and its equivalent scope are possible.

[0089] For example, in the above description, in step S203, the first atmosphere release valve 4451 is closed after a predetermined time from the start of driving of the pneumatic pump 441, but it is not limited to this. For example, the control unit 50 may close the first atmosphere release valve 4451 at the timing when the common atmosphere release valve 4453 in step S201 is closed. Also in this configuration, by closing the common atmosphere release valve 4453, the sealed space CS is formed, and pressure is applied to the sealed space CS. Therefore, similar to the above, the suction pressure of the pneumatic pump 441 can be controlled.

[0090] However, as the time from the start of driving of the pneumatic pump 441 to the closing of the first atmosphere release valve 4451 becomes longer, the pressure value in the sealed space CS increases, and the pressure value in the first tank 421 gradually decreases. Specific examples are shown in FIGS. 10A to 10C. FIG. 10A is a graph showing the change in the pressure value in the first tank 421 when the first atmosphere release valve 4451 is closed before the start of driving of the pneumatic pump 441. FIG. 10B is a graph showing the change in the pressure value in the first tank 421 when the first atmosphere release valve 4451 is closed after a predetermined time from the start of driving of the pneumatic pump 441. FIG. 10C is a graph showing the change in the pressure value in the first tank 421 when the first atmosphere release valve 4451 is closed after a predetermined time longer than that in FIG. 10B from the start of driving of the pneumatic pump 441.

[0091] Also, in the above description, in step S204, the first atmosphere release valve 4451 is closed after a predetermined time from the start of driving of the pneumatic pump 441, but it is not limited to this. That is, a pressure measurement unit PM may be provided in the third gas flow path 444 as a pressure detection unit, and the control unit 50 may be configured to close the first atmosphere release valve 4451 when the measured value of the pressure measurement unit PM reaches a predetermined value.

[0092] Similarly, a liquid level measurement unit LM may be used as an air amount detection unit, and the control unit 50 may be configured to close the first atmosphere release valve 4451 when the measured value thereof reaches a predetermined value. Specifically, the control unit 50 can calculate the air amount in the first tank 421 from (the capacity of the first tank 421 - the measurement result of the liquid level measurement unit LM).

[0093] In the above description, in step S205, the measured value of the pressure measurement unit PM of the first tank 421 is used, but it is not limited to this. That is, by adjusting the applied pressure to the sealed space CS, the lower limit value of the pressure in the first tank 421 may be set to a predetermined value preferable for ink circulation maintenance. In this configuration, the pressure measurement unit PM may not be provided in the first tank 421.

[0094] In the above description, the case where the droplet discharge device is the inkjet recording device 1 is exemplified, but it is not limited to this. That is, the present invention may be various droplet discharge devices that discharge droplets of a liquid other than ink from a nozzle.

[0095] In addition, an example of using a hard disk, a semiconductor non-volatile memory, etc. as a computer-readable medium of the program according to the present invention is disclosed, but it is not limited thereto. As other computer-readable media, portable recording media such as CD-ROM can be applied. Also, a carrier wave is applied as a medium for providing the data of the program according to the present invention via a communication line.

Explanation of Reference Numerals

[0096] 1 Inkjet recording device (droplet discharge device) 100 Pressure adjustment device 24a Inkjet head (droplet discharge head) 42 Tank 44 Gas flow path 441 Air pump 442 First gas flow path (suction side gas flow path) 444 Third gas flow path (discharge side gas flow path) 445 Atmosphere release valve 4451 First atmosphere release valve (suction side atmosphere release valve) 4453 Common atmosphere release valve (discharge side atmosphere release valve) 50 Control unit CS Sealed space GS Gas storage unit LM Liquid level measurement unit (air amount detection unit) PM pressure measurement unit (pressure detection unit)

Claims

1. A gas flow path capable of forming a sealed space, A pneumatic pump provided in the gas flow path for sending the gas on the suction side to the discharge side, A plurality of atmosphere release valves provided at least one each in the gas flow path on the suction side and the gas flow path on the discharge side of the pneumatic pump, for opening or closing the gas flow path on the suction side and the gas flow path on the discharge side to the atmosphere, And a control unit, When driving the pneumatic pump, the control unit controls the opening and closing operations of the plurality of atmosphere release valves to adjust the pressure of the sealed space formed in one of the gas flow path on the suction side and the gas flow path on the discharge side, and then adjusts the pressure of the other gas flow path. A pressure adjustment device.

2. The pressure adjustment device according to claim 1, wherein the control unit adjusts the pressure of the sealed space in the gas flow path on the suction side by closing the atmosphere release valve in the gas flow path on the suction side.

3. The pressure adjustment device according to claim 2, wherein the control unit closes the atmosphere release valve in the gas flow path on the suction side after a predetermined time from the start of driving the pneumatic pump.

4. Comprising an air volume detection unit for detecting the air volume of at least one of the gas flow path on the suction side and the gas flow path on the discharge side, The pressure adjustment device according to claim 2, wherein the control unit closes the atmosphere release valve in the gas flow path on the suction side according to the detection result of the air volume detection unit.

5. Comprising a pressure detection unit for detecting the pressure of the sealed space, The pressure adjustment device according to claim 2, wherein the control unit closes the atmosphere release valve on the suction side according to the detection result of the pressure detection unit.

6. The pressure adjustment device according to claim 1, wherein the pneumatic pump is a diaphragm pump.

7. The pressure adjustment device according to any one of claims 1 to 6, A tank communicating with the gas flow path on the suction side for storing liquid, A liquid flow path for sending out the liquid in the tank, A droplet discharge head for discharging the liquid sent from the tank as droplets, and The control unit is a droplet discharge device that adjusts the pressure in the tank by adjusting the pressure in the gas flow path on the suction side.

8. A gas flow path capable of forming a sealed space, An air pressure pump provided in the gas flow path for sending the gas on the suction side to the discharge side, and a plurality of atmosphere release valves provided one by one in at least the gas flow path on the suction side and the gas flow path on the discharge side of the air pressure pump, for opening or closing the gas flow path on the suction side and the gas flow path on the discharge side to the atmosphere. A pressure adjustment method for a pressure adjustment device, comprising: When driving the air pressure pump, controlling the opening and closing operations of the plurality of atmosphere release valves to adjust the pressure in the sealed space formed in one of the gas flow paths on the suction side and the gas flow path on the discharge side, and then adjusting the pressure in the other gas flow path. A pressure adjustment step.

9. The pressure adjustment step is the pressure adjustment method according to claim 8, wherein the pressure in the sealed space of the gas flow path on the suction side is adjusted by closing the atmosphere release valve on the suction side.

10. The pressure adjustment step is the pressure adjustment method according to claim 9, wherein the atmosphere release valve of the gas flow path on the suction side is closed after a predetermined time from the start of driving the air pressure pump.

11. The pressure adjustment device includes an air amount detection unit for detecting the air amount in at least one of the gas flow path on the suction side and the gas flow path on the discharge side, The pressure adjustment step is the pressure adjustment method according to claim 9, wherein the atmosphere release valve of the gas flow path on the suction side is closed according to the detection result of the air amount detection unit.

12. The pressure adjustment device includes a pressure detection unit for detecting the pressure in the sealed space, The pressure adjustment step is the pressure adjustment method according to claim 9, which closes the atmospheric release valve on the suction side according to the detection result of the pressure detection unit.

13. A gas flow path capable of forming a sealed space, A pneumatic pump provided in the gas flow path for sending the gas on the suction side to the discharge side, A plurality of atmospheric release valves provided in at least one of the gas flow path on the suction side and the gas flow path on the discharge side of the pneumatic pump, for opening or closing the gas flow path on the suction side and the gas flow path on the discharge side to the atmosphere, a computer of a pressure adjustment device comprising: A program that functions as a control unit for controlling the opening and closing operations of the plurality of atmospheric release valves during the driving of the pneumatic pump, adjusting the pressure of the sealed space formed in one of the gas flow path on the suction side and the gas flow path on the discharge side, and then adjusting the pressure of the other gas flow path.

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