Liquid circulation device, liquid discharge apparatus, and image forming apparatus

Abstract

To provide a circulation device which can reduce pulsation of a pressure occurring when a pump is driven to send a liquid from a recovery tank to a supply tank with a simple structure.SOLUTION: A liquid circulation device includes: a supply tank 210 and a recovery tank 220; a head 100 which discharges a liquid; a path on which the liquid circulates through the head 100; a liquid feeding pump 202 which is provided at a liquid path 203 to feed the liquid to the supply tank 210; a supply side air pump 81 which is provided at a supply side air path 83 communicating with a gas space 210a of the supply tank 210; a recovery side air pump 82 which is provided at a recovery side air path 84 communicating with a gas space 220a of the recovery tank 220; and a bypass path 90 which connects the gas space 210a of the supply tank with the gas space 220a of the recovery tank and serves as a passage of the gas flowing from the supply tank 210 to the recovery tank 220. A flow rate of the gas flowing in the bypass path 90 is smaller than a maximum flow rate of the liquid flowing in the liquid feeding pump 202.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a liquid circulation device, a liquid ejection device, and an image forming apparatus. [Background technology]

[0002] A liquid ejection device equipped with a circulation type head as a liquid ejection head is known. A liquid circulation device is known as a mechanism for circulating liquid, which generates a pressure difference between a recovery tank under negative pressure and a supply tank under positive pressure, transfers liquid from the supply tank to the recovery tank via the liquid ejection head, and returns the liquid from the recovery tank to the supply tank (see, for example, Patent Document 1).

[0003] In such a liquid circulation system, the liquid is sent from the recovery tank to the supply tank by a pump, but there is a problem in that large pressure fluctuations occur when the pump is driven, resulting in pulsation.

[0004] Patent Document 1 discloses a configuration in which, in order to improve response to pressure changes, a means for adjusting the pressure in the gas layer portions of the supply-side tank and the recovery-side tank is provided, and an opening / closing valve is provided in the path connecting the gas layer portions. Summary of the Invention [Problem to be solved by the invention]

[0005] However, a configuration in which an on-off valve is provided in a gas flow path has the problem that the device becomes larger and more expensive, and the pressure control system becomes more complicated.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid circulation device that can reduce, with a simple configuration, pressure pulsations that occur when a pump is driven to send liquid from a collection tank to a supply tank. [Means for solving the problem]

[0007] In order to solve the above problems, the liquid circulation device of the present invention comprises a supply tank and a recovery tank for storing liquid, a head for discharging the liquid, a path for circulating the liquid via the head, a liquid delivery pump provided in the liquid path that transfers liquid from the recovery tank to the supply tank and delivers the liquid to the supply tank, a supply-side air pump provided in a supply-side air path that communicates with the gas space of the supply tank, a recovery-side air pump provided in a recovery-side air path that communicates with the gas space of the recovery tank, and a bypass path that connects the gas space of the supply tank and the gas space of the recovery tank and serves as a flow path for gas flowing from the supply tank to the recovery tank, and is characterized in that the flow rate of gas flowing through the bypass path is smaller than the maximum flow rate of liquid flowing through the liquid delivery pump. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a liquid circulation device that can reduce, with a simple configuration, pressure pulsations that occur when a pump is driven to send liquid from a collection tank to a supply tank. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic explanatory diagram of a printing apparatus that is an example of a liquid ejection apparatus according to the present invention. [Figure 2] FIG. 2 is an explanatory plan view showing an example of a head unit. [Figure 3] FIG. 1 is an explanatory perspective view showing an external appearance of an example of a liquid ejection head. [Figure 4] 3 is a cross-sectional explanatory diagram of the liquid ejection head in a direction (longitudinal direction of the liquid chamber) perpendicular to the nozzle arrangement direction. FIG. [Figure 5] FIG. 2 is an explanatory piping diagram showing an example of the mechanism of a liquid circulation device. [Figure 6] FIG. 2 is a functional block diagram of a control unit of a liquid ejection device equipped with a liquid circulation device. [Figure 7] FIG. 10 is an explanatory diagram schematically illustrating the configuration of a main part of a conventional liquid circulation device. [Figure 8] 1 is an explanatory diagram schematically illustrating an example of a configuration of a main part of a liquid circulation device according to the present invention. [Figure 9] FIG. 10 is an explanatory diagram schematically illustrating another example of the configuration of the main part of the liquid circulation device. [Figure 10] FIG. 10 is an explanatory diagram schematically illustrating another example of the configuration of the main part of the liquid circulation device. [Figure 11] FIG. 10 is an explanatory diagram schematically illustrating another example of the configuration of the main part of the liquid circulation device. [Figure 12] FIG. 10 is an explanatory diagram schematically illustrating another example of the configuration of the main part of the liquid circulation device. DETAILED DESCRIPTION OF THE INVENTION

[0010] The liquid circulation device, liquid ejection device, and image forming device according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what one skilled in the art can conceive. Any embodiment that achieves the functions and effects of the present invention is within the scope of the present invention.

[0011] A printing apparatus, which is one embodiment of a liquid ejection apparatus according to the present invention, will be described with reference to Figures 1 and 2. The liquid ejection apparatus and printing apparatus of this embodiment include a liquid circulation apparatus according to the present invention, which will be described later. FIG. 1 is a schematic explanatory diagram of a printing apparatus, and FIG. 2 is a plan explanatory diagram of an example of a head unit of the printing apparatus.

[0012] This liquid ejection device, i.e., printing device 1000, includes a conveying means 1 for conveying a continuous body 10, which is the ejection target (ejected medium) onto which the ejected liquid is applied, a guiding and conveying means 3 for guiding and conveying the continuous body 10 conveyed from the conveying means 1 to a printing means 5, a printing means 5 for printing by ejecting liquid onto the continuous body 10 to form an image, a drying means 7 for drying the continuous body 10, and a discharge means 9 for discharging the continuous body 10.

[0013] The continuous body 10 is fed from the original winding roller 11 of the carrying-in means 1, guided and conveyed by the rollers of the carrying-in means 1, the guide and conveying means 3, the drying means 7 and the discharge means 9, and wound up by the winding roller 91 of the discharge means 9.

[0014] In the printing means 5, this continuous body 10 is transported on a transport guide member 59 opposite the head unit 50 and head unit 55, an image is formed by liquid ejected from the head unit 50, and post-processing is performed by processing liquid ejected from the head unit 55.

[0015] Here, in the head unit 50, for example, from the upstream side in the medium transport direction, full line type head arrays 51K, 51C, 51M, and 51Y for four colors (hereinafter referred to as "head array 51" when no distinction is made between colors) are arranged.

[0016] Each head array 51 is a liquid ejection means, and ejects liquid (for example, ink) of black K, cyan C, magenta M, or yellow Y onto the transported continuum 10. However, the types and number of colors are not limited to these.

[0017] The head array 51 is, for example, as shown in FIG. 2, in which liquid ejection heads (hereinafter also simply referred to as heads) 100 are arranged in a staggered pattern on a base member 52, but is not limited to this.

[0018] Next, an example of a liquid ejection head will be described with reference to FIGS. The liquid ejection head of this embodiment is a circulation type liquid ejection head. FIG. 3 is an explanatory perspective view of the appearance of the liquid ejection head, and FIG. 4 is an explanatory cross-sectional view of the head in a direction perpendicular to the nozzle arrangement direction (longitudinal direction of the liquid chamber).

[0019] This liquid ejection head is made by laminating and joining a nozzle plate 101, a flow path plate 102, and a diaphragm member 103 as a wall member. It is also equipped with a piezoelectric actuator 111 that displaces a vibration region (diaphragm) 130 of the diaphragm member 103, a common liquid chamber member 120 that also serves as a frame member for the head, and a cover 129. The portion consisting of the flow path plate 102 and the diaphragm member 103 is called a flow path member 140.

[0020] The nozzle plate 101 has a plurality of nozzles 104 that eject liquid.

[0021] The flow path plate 102 has formed therein through holes and grooves that serve as individual liquid chambers 106 that communicate with the nozzles 104 via nozzle communication paths 105, supply-side fluid resistance portions 107 that communicate with the individual liquid chambers 106, and liquid introduction portions 108 that communicate with the supply-side fluid resistance portions 107. The nozzle communication paths 105 are flow paths that communicate with the nozzles 104 and the individual liquid chambers 106. The liquid introduction portions 108 communicate with a supply-side common liquid chamber 110 via openings 109 in the vibration plate member 103.

[0022] The diaphragm member 103 has a deformable vibration area 130 that forms the wall surface of the individual liquid chamber 106 of the flow path plate 102. Here, the diaphragm member 103 has a two-layer structure (not limited to this) and is formed from a first layer that forms a thin portion from the flow path plate 102 side and a second layer that forms a thick portion, and the deformable vibration area 130 is formed in the first layer in a portion that corresponds to the individual liquid chamber 106.

[0023] On the opposite side of the vibration plate member 103 from the individual liquid chamber 106, a piezoelectric actuator 111 including an electromechanical conversion element is arranged as a driving means (actuator means, pressure generating means) for deforming the vibration region 130 of the vibration plate member 103.

[0024] This piezoelectric actuator 111 is formed by forming grooves in a piezoelectric member bonded onto a base member 113 by half-cut dicing, and forming a required number of columnar piezoelectric elements 112 in a comb-like shape at predetermined intervals.

[0025] The piezoelectric element 112 is bonded to a protrusion 130a, which is an island-shaped thick portion formed in the vibration region 130 of the vibration plate member 103. A flexible wiring member 115 is also connected to the piezoelectric element 112.

[0026] The common liquid chamber member 120 forms a supply-side common liquid chamber 110 and a discharge-side common liquid chamber 150. The supply-side common liquid chamber 110 communicates with a supply port 171, and the discharge-side common liquid chamber 150 communicates with a discharge port 181.

[0027] Here, the common liquid chamber member 120 is composed of a first common liquid chamber member 121 and a second common liquid chamber member 122, and the first common liquid chamber member 121 is joined to the vibration plate member 103 side of the flow path member 140, and the second common liquid chamber member 122 is stacked and joined to the first common liquid chamber member 121.

[0028] The first common liquid chamber member 121 forms a downstream common liquid chamber 110A, which is a part of the supply side common liquid chamber 110 that communicates with the liquid introduction portion 108, and a discharge side common liquid chamber 150 that communicates with the discharge flow path 151. The second common liquid chamber member 122 forms an upstream common liquid chamber 110B, which is the remaining part of the supply side common liquid chamber 110.

[0029] Furthermore, the flow path plate 102 is formed with discharge flow paths 151 that extend along the surface of the flow path plate 102 and communicate with each individual liquid chamber 106 via a nozzle communication path 105. The discharge flow paths 151 communicate with a discharge-side common liquid chamber 150.

[0030] In this liquid ejection head, for example, by lowering the voltage applied to the piezoelectric element 112 from a reference potential (intermediate potential), the piezoelectric element 112 contracts, the vibration area 130 of the vibration plate member 103 is pulled, and the volume of the individual liquid chamber 106 expands, causing liquid to flow into the individual liquid chamber 106.

[0031] Thereafter, the voltage applied to the piezoelectric element 112 is increased to expand the piezoelectric element 112 in the stacking direction, and the vibration region 130 of the vibration plate member 103 is deformed in the direction toward the nozzle 104, thereby contracting the volume of the individual liquid chamber 106, thereby pressurizing the liquid in the individual liquid chamber 106 and ejecting the liquid from the nozzle 104.

[0032] Furthermore, liquid that is not ejected from the nozzle 104 passes through the nozzle 104 and is discharged from the discharge flow path 151 to the discharge-side common liquid chamber 150, and is then supplied again from the discharge-side common liquid chamber 150 to the supply-side common liquid chamber 110 through an external circulation path.

[0033] The method of driving the head is not limited to the above example (pull-push hitting), and pull hitting or push hitting can also be performed depending on the driving waveform applied.

[0034] The circulation type liquid ejection head provided in the liquid circulation device of this embodiment may be a head of an individual liquid chamber type in which liquid circulates near the nozzle, or a head in which liquid circulates only through a common liquid chamber.

[0035] Next, the mechanism of the liquid circulation device provided in the liquid ejection device and printing device according to this embodiment will be described with reference to FIG. Figure 5 is an explanatory diagram of the piping of the liquid supply device. The arrows in the figure indicate the direction of liquid movement.

[0036] The liquid circulation device of this embodiment includes a plurality of circulating heads 100 arranged in a line. Only the heads 100 at both ends are shown in Fig. 5 . The arrangement direction of the plurality of heads 100 is preferably the width direction of the discharge target (continuum 10 in the example of FIG. 1) onto which the discharged liquid is applied.

[0037] The liquid circulation device 200 includes a main tank (liquid tank) 201, which is a liquid storage means for storing the liquid discharged from the head 100, a supply tank 210, a recovery tank 220, and a sub-tank 290. The liquid circulation device 200 also includes a first liquid feed pump 202A, a second liquid feed pump 202B, and a third liquid feed pump 209, which are arranged in the liquid path.

[0038] It also includes a first manifold 230 and a second manifold 240 to which multiple heads 100 communicate, a first head tank (pressurized head tank) 300a and a second head tank (depressurized head tank) 300b for each head 100 (hereinafter referred to as head tanks 300 when no distinction is made), and a degassing device 260 which is a degassing means for removing dissolved gas from the liquid.

[0039] The liquid stored in the main tank 201 is sent (supplied) to the sub-tank 290 by a third liquid sending pump 209 via a liquid sending path 289 including a filter 205. The sub-tank 290 is provided with a liquid level detection means 291 and an electromagnetic valve 292 that constitutes an atmosphere opening mechanism that opens the inside of the sub-tank to the atmosphere.

[0040] The sub-tank 290 and the supply tank 210 are connected via a first liquid path 203A, and a first liquid feed pump 202A is provided in the first liquid path 203A. The sub-tank 290 and the supply tank 210 are also connected via a backflow liquid path 285, and a solenoid valve 287 is provided in the backflow liquid path 285.

[0041] The supply tank 210 has a gas space 210a above the liquid surface, and is configured so that liquid and gas coexist. The supply tank 210 is provided with a liquid level detection means 211 that detects the liquid surface, and an electromagnetic valve 212 that serves as an atmosphere opening mechanism that opens the inside of the tank to the atmosphere.

[0042] The sub-tank 290 and the recovery tank 220 are connected via a second liquid path 203B, and a second liquid feed pump 202B is provided in the second liquid path 203B. The sub-tank 290 and the recovery tank 220 are also connected via a backflow liquid path 286, and a solenoid valve 288 is provided in the backflow liquid path 286.

[0043] The recovery tank 220 has a gas space 220a above the liquid surface, and is configured so that liquid and gas coexist. The recovery tank 220 is provided with a liquid level detection means 221 that detects the liquid surface, and an electromagnetic valve 222 that serves as an atmosphere opening mechanism that opens the interior to the atmosphere.

[0044] The supply tank 210 is connected to the first manifold 230 through a liquid path 281 that includes a degasser 260 and a filter 261 .

[0045] The first manifold 230 is connected to the supply port (supply port 171 in FIG. 3) side of the head 100 via a supply path 231. The supply path 231 is connected to the supply port 171 of the head 100 via a first head tank 300a. A solenoid valve 232 that opens and closes the path is provided upstream of the first head tank 300a in the supply path 231. The solenoid valves 232 are provided according to the number of heads 100, and can be individually controlled to open and close. In addition, a pressure sensor 233 is provided in the first manifold 230.

[0046] The recovery tank 220 is connected to the second manifold 240 via a liquid path 282 .

[0047] The second manifold 240 is connected to the exhaust port (exhaust port 181 in FIG. 3) side of the head 100 via an exhaust path 241. The exhaust path 241 is connected to the exhaust port 181 of the head 100 via a second head tank 300b. A solenoid valve 242 that opens and closes the path is provided on the exhaust path 241 downstream of the second head tank 300b. The solenoid valves 242 are provided according to the number of heads 100, and can be individually controlled to open and close. In addition, a pressure sensor 243 is provided in the second manifold 240.

[0048] Furthermore, a manifold connection path 270 is provided to connect the first manifold 230 and the second manifold 240. The manifold connection path 270 is provided with a solenoid valve 271 on the first manifold 230 side and a solenoid valve 272 on the second manifold 240 side.

[0049] In this way, a circulation path is formed from the sub-tank 290 via the first liquid path 203A, the supply tank 210, the liquid path 281, the degassing device 260, the first manifold 230, the head 100, the second manifold 240, the liquid path 282, the recovery tank 220, and the second liquid path 203B before returning to the sub-tank 290.

[0050] The supply tank 210 and the recovery tank 220 are in communication with each other via a sub-tank 290 and a liquid path 203 (a first liquid path 203A and a second liquid path 203B). In the following description of the transfer of liquid between the supply tank 210 and the recovery tank 220, the sub-tank 290 may be omitted.

[0051] Furthermore, the head 100 is blocked from the circulation path by solenoid valves (232, 242, 271, 272). The solenoid valves (232, 242, 271, 272) constitute a means for switching between a first path in which the manifold connection path 270 constitutes a part of the circulation path and a second path in which the manifold connection path 270 is blocked from the circulation path and the head 100 constitutes a part of the circulation path.

[0052] By closing the solenoid valves 232 and 242 and opening the solenoid valves 271 and 272, a first path is formed in which the manifold connection path 270 becomes part of the circulation path and the head 100 does not become part of the circulation path. On the other hand, by opening the solenoid valves 232 and 242 and closing the solenoid valves 271 and 272, a second path is formed in which the head 100 becomes part of the circulation path and the manifold connection path 270 does not become part of the circulation path.

[0053] The supply tank 210, the recovery tank 220, the first liquid feed pump 202A, and the second liquid feed pump 202B constitute a means for generating pressure that circulates the liquid through the circulation path.

[0054] Next, the supply and circulation of the liquid will be described. (1) Transfer of liquid from the main tank 201 to the sub-tank 290: When the liquid level detection means 291 detects a shortage of liquid, the third liquid supply pump 209 is used to supply liquid from the main tank 201 to the sub-tank 290 via the liquid supply path 289 until the liquid level detection means 291 indicates that the liquid level is full.

[0055] (2) Transfer of liquid from the sub-tank 290 to the supply tank 210: The first liquid feed pump 202A is used to supply liquid from the sub-tank 290 to the supply tank 210 via the liquid path 203A.

[0056] (3) Transfer of liquid from the recovery tank 220 to the sub-tank 290: The second liquid supply pump 202B is used to supply liquid from the recovery tank 220 to the sub-tank 290 via the liquid path 203B.

[0057] (4) Transfer of liquid from the supply tank 210 to the head 100 and from the head 100 to the recovery tank 220: A pressure difference is generated between the supply tank 210 and the recovery tank 220 by using the first liquid feed pump 202A to supply ink to the supply tank 210 until the pressure sensor 233 reaches a target pressure (e.g., a pressure that results in pressurization) and the second liquid feed pump 202B to supply liquid to the sub-tank 290 until the pressure sensor 243 reaches a target pressure (e.g., a pressure that results in negative pressure). In response to this pressure difference, liquid can be circulated from the supply tank 210 through the liquid path 281, the filter 261, the degassing device 260, the first manifold 230, the multiple supply paths 231, the multiple first head tanks 300a, the multiple heads 100, the multiple discharge paths 241, the multiple second head tanks 300b, the second manifold 240, and the liquid path 282 to the recovery tank 220. At this time, the solenoid valves 232 and 242 are open, and the solenoid valves 271 and 272 are closed.

[0058] On the other hand, when the solenoid valves 232, 242 are closed and the solenoid valves 271, 272 are open, and the first liquid supply pump 202A and the second liquid supply pump 202B are driven to generate a pressure difference, the liquid can be circulated from the supply tank 210 via the liquid path 281, the filter 261, the degassing device 260, the first manifold 230, the manifold connection path 270, the second manifold 240, and the liquid path 282 to the recovery tank 220 in accordance with this pressure difference.

[0059] The liquid level detection means 211, 221, 291 provided in each tank are not particularly limited, and may be, for example, a float type that detects the presence or absence of liquid, a method that detects the presence or absence of liquid based on the output of a voltage detected using at least two or more electrode pins, or a laser liquid level detection method.

[0060] Furthermore, solenoid valves 212, 222, 292 serving as atmosphere opening mechanisms are provided in the supply tank 210, the recovery tank 220, and the sub-tank 290, respectively. By controlling the solenoid valves, it is possible to communicate the inside of the tank with the atmosphere.

[0061] Furthermore, the liquid circulation device 200 according to this embodiment is provided with an air supply / discharge system that adjusts the internal pressure of the supply tank 210 and the recovery tank 220. The air supply / discharge system includes a gas storage means (supply-side air tank) (not shown) connected to the supply tank 210, and a gas storage means (recovery-side air tank) (not shown) connected to the recovery tank 220.

[0062] The air supply and exhaust system includes a supply-side air path 83 that connects the supply tank 210 and the supply-side air tank, a supply-side air pump 81 that is provided in the supply-side air path 83 and pressurizes (and in some cases depressurizes) the supply tank 210, a recovery-side air path 84 that connects the recovery tank 220 and the recovery-side air tank, and a recovery-side air pump 82 that is provided in the recovery-side air path 84 and depressurizes the recovery tank 220. The supply-side air pump 81 may also reduce the pressure in the supply tank 210 so that the negative pressure therein is smaller than that in the recovery tank 220 .

[0063] Next, we will explain the roles of the gas space 210a of the supply tank 210 and the gas space 220a of the recovery tank 220. In the gas space 210a and the gas space 220a, the liquid surface is in contact with gas (air, inert gas, etc.).

[0064] Here, if a pressurized state of gas (positive pressure) is generated in the supply tank 210 and a reduced air state (negative pressure) is generated in the recovery tank 220, the gas is compressible and can store pressure. In this case, the air can be considered to be similar to a capacitor component when expressed in an equivalent electric circuit, and can also be expressed as compliance (elastic component).

[0065] When the liquid feed pumps 202 (first liquid feed pump 202A and second liquid feed pump 202B) provided in the liquid path 203 (203A and 203B) communicating with the supply tank 210 and the recovery tank 220 are driven, a pressure change (pulsation) occurs. This pressure change is transmitted through the liquid path, and when it is transmitted to the nozzle meniscus, it can lead to liquid overflow and the entrainment of air bubbles, so compliance (elastic component) is required to suppress this.

[0066] Generally, gas has compressible properties and can become a compliance component, so by providing gas space 210a and gas space 220a, large pressure changes can be suppressed. Furthermore, the liquid circulation device of this embodiment is provided with a bypass path 90 that communicates with the gas space 210a and the gas space 220a, thereby reducing pressure pulsations that occur when liquid is transferred from the recovery tank 220 to the supply tank 210.

[0067] Next, an overview of the control unit of the liquid ejection device (printing device) of this embodiment will be described with reference to FIG. FIG. 6 is a functional block diagram of the control unit.

[0068] The control unit 500 includes a main control unit 500A that is made up of a CPU 501 that controls the entire device, a ROM 502 that stores fixed data such as various programs including programs executed by the CPU 501, and a RAM 503 that temporarily stores image data and the like.

[0069] The control unit 500 is equipped with a rewritable nonvolatile memory 504 (NVRAM) for retaining data even when the power to the device is cut off. The control unit 500 is equipped with an ASIC 505 that processes various signal processes for image data, image processing such as sorting, and other input / output signals for control, and transmits and receives data to and from a printer driver 590 via a host I / F 506.

[0070] The control unit 500 includes a print control unit 508 including a data transfer means, a drive signal generating means, and a bias voltage output means for driving and controlling each head 100 of the head unit 50, and a drive IC (herein referred to as a "head driver") 509 for driving each head 100.

[0071] The control unit 500 includes a solenoid valve control unit 510 that controls the driving of the solenoid valves 232, 242, 271, 272 and the solenoid valves 212, 222, 292, 287, 288 of the solenoid valve group 550.

[0072] The control unit 500 includes a supply system control unit 511 that controls the driving of the third liquid feed pump 209 .

[0073] The control unit 500 is equipped with a first liquid supply pump 202A and a second liquid supply pump 202B (hereinafter referred to as liquid supply pumps 202 when not distinguished), as well as a pressure system control unit 512 that drives and controls the supply side air pump 81 and the recovery side air pump 82.

[0074] The control unit 500 has an I / O unit 513. The I / O unit 513 can process various sensor information, and acquires the detection results of the pressure sensors 233 and 243 and information from a group of various sensors 515. The I / O unit 513 then extracts information necessary for controlling the device and uses it for control by the print control unit 508, solenoid valve control unit 510, supply system control unit 511, and pressure system control unit 512.

[0075] The control unit 500 is connected to an operation panel 514 for inputting and displaying information required for this device.

[0076] <Main components of the liquid circulation device> FIG. 7 is an explanatory diagram that schematically shows an example of the configuration of the main parts of a conventional liquid circulation device. 7, the supply tank 210, the recovery tank 220, and the head 100 form a liquid circulation system that circulates the liquid and ejects the liquid from the head 100. The liquid circulation system transfers the liquid to the head 100 based on the pressure difference between the supply tank 210 and the recovery tank 220. In addition, the liquid path 203 is provided with a liquid sending pump 202 that sends the liquid from the recovery tank 220 to the supply tank 210 .

[0077] When liquid is supplied toward the head 100 and the liquid in the supply tank 210 decreases, the volume of the gas space 210a of the supply tank 210 increases and the internal pressure of the supply tank 210 decreases. In response to this, the supply-side air pump 81 is operated to supply gas to the supply tank 210, thereby adjusting the internal pressure of the supply tank 210.

[0078] On the other hand, when liquid is recovered in the recovery tank 220 and the amount of liquid increases, the volume of the gas space 220a of the recovery tank 220 decreases, and the internal pressure of the recovery tank 220 increases. In response to this, the recovery-side air pump 82 is operated to suck out the gas in the recovery tank 220, thereby adjusting the internal pressure of the recovery tank 220.

[0079] When the liquid in the supply tank 210 decreases and the liquid in the recovery tank 220 increases, the liquid is sent from the recovery tank 220 to the supply tank 210 by the liquid sending pump 202 . When liquid is supplied and the amount of liquid in the supply tank 210 increases, the volume of the gas space 210a in the supply tank 210 decreases, and the internal pressure of the supply tank 210 increases. On the other hand, when the amount of liquid in the recovery tank 220 decreases, the volume of the gas space 220a in the recovery tank 220 increases, and the internal pressure of the recovery tank 220 decreases.

[0080] In this case, the internal pressure of the supply tank 210 cannot be reduced even if the supply-side air pump 81 is operated, and pressure pulsation occurs until the internal pressure is reduced due to a decrease in liquid. Similarly, the internal pressure of the recovery tank 220 cannot be increased even if the recovery-side air pump 82 is operated, and pressure pulsation occurs until the internal pressure is increased due to an increase in liquid.

[0081] To address this problem, the liquid circulation device according to the present invention suppresses the occurrence of the pressure pulsation by providing a bypass path 90. Hereinafter, an embodiment of the liquid circulation device according to the present invention will be described.

[0082] [First embodiment] 8(A) and 8(B) are explanatory diagrams schematically illustrating the configuration of the main parts of the liquid circulation device according to the first embodiment. Note that the arrows in the drawings indicate the movement directions of the liquid and gas.

[0083] The liquid circulation device of this embodiment includes a supply tank 210 and a recovery tank 220 for storing liquid, a head 100 for ejecting the liquid, a path for circulating the liquid through the head 100, a liquid delivery pump 202 provided in a liquid path 203 for transporting liquid from the recovery tank 220 to the supply tank 210 and delivering the liquid toward the supply tank 210, a supply-side air pump 81 provided in a supply-side air path 83 communicating with the gas space 210a of the supply tank 210, a recovery-side air pump 82 provided in a recovery-side air path 84 communicating with the gas space 220a of the recovery tank 220, and a bypass path 90 that connects the gas space 210a of the supply tank and the gas space 220a of the recovery tank and serves as a flow path for gas flowing from the supply tank 210 to the recovery tank 220, and the flow rate of gas flowing through the bypass path 90 is smaller than the maximum flow rate of liquid flowing through the liquid delivery pump 202.

[0084] As shown in FIG. 8(B), when the flow rate of the gas flowing through the bypass path 90 is F2 and the flow rate of the liquid flowing through the liquid feed pump 202 is F1, the liquid circulation device of this embodiment is F1 MAX >F2 Satisfy the relationship. Here, the "flow rate" is the amount of liquid or gas moved per unit time, and the "maximum flow rate" is the maximum flow rate of liquid or gas that can be supplied by the pump.

[0085] By providing the bypass path 90, gas can be constantly circulated from the supply tank 210 to the recovery tank 220. As a result, even if the liquid supply pump 202 operates and the amount of liquid in the supply tank 210 increases, the gas in the gas space 210a is discharged through the bypass path 90, thereby suppressing an increase in the internal pressure of the supply tank 210 and suppressing pressure pulsations. Furthermore, even if the liquid in the recovery tank 220 decreases due to operation of the liquid feed pump 202, gas is supplied to the gas space 220a through the bypass path 90, so that a decrease in the internal pressure of the recovery tank 220 is suppressed, and pressure pulsation is suppressed.

[0086] On the other hand, when the liquid feed pump 202 is not operating, the transfer of liquid stops and the internal pressure of the supply tank 210 drops, but the internal pressure of the supply tank 210 is adjusted by operating the supply-side air pump 81 to supply gas to the supply tank 210. Also, the internal pressure of the recovery tank 220 rises, but the internal pressure of the recovery tank 220 is adjusted by operating the recovery-side air pump 82 to suck out the gas in the recovery tank 220.

[0087] Since the flow rate F2 of the gas flowing through the bypass path 90 is smaller than the maximum value of the flow rate F1 of the liquid flowing through the liquid supply pump 202, the fluctuations in the internal pressure of the supply tank 210 and the recovery tank 220 do not exceed the range of internal pressure fluctuations associated with the operation of the liquid supply pump 202. With the configuration of this embodiment, the internal pressure of the supply tank 210 and the recovery tank 220 can be easily adjusted within a certain range, and pressure pulsation can be reduced with a simple configuration.

[0088] <Flow rate of supply air pump> In the liquid circulation system of the present embodiment, it is preferable that the maximum flow rate of the gas flowing through the supply air pump 81 is greater than the flow rate of the gas flowing through the bypass path 90 .

[0089] As shown in FIG. 8(B), when the flow rate of the gas flowing through the bypass path 90 is F2 and the flow rate of the gas flowing through the supply-side air pump 81 is F3, the liquid circulation device of this embodiment is as follows: F3 MAX >F2 It is preferable that the following relationship is satisfied.

[0090] With this configuration, fluctuations in the internal pressure of the supply tank 210 caused by gas flowing out through the bypass path 90 do not exceed the range of internal pressure fluctuations associated with the operation of the supply-side air pump 81, making it easy to adjust the pressure within the supply tank 210 within a certain range.

[0091] Furthermore, the flow rate of the gas flowing through the supply-side air pump 81 is preferably greater than the sum of the flow rate of the gas flowing through the bypass path 90 and the flow rate of the liquid supplied from the supply tank 210 to the head 100 .

[0092] As shown in FIG. 8(B), when the flow rate of the gas flowing through the supply-side air pump 81 is F3, the flow rate of the gas flowing through the bypass path 90 is F2, and the flow rate of the liquid supplied from the supply tank 210 to the head 100 is F4, the liquid circulation device of this embodiment is as follows: F3>(F2+F4) It is preferable that the following relationship is satisfied.

[0093] With this configuration, fluctuations in the internal pressure of the supply tank 210 (decrease in internal pressure) due to circulation of the liquid can be taken into consideration, and the pressure inside the supply tank 210 can be adjusted within a certain range.

[0094] Furthermore, it is preferable that the flow rate of gas flowing through the supply side air pump 81 is greater than the sum of the flow rate of gas flowing through the bypass path 90 and the flow rate of liquid supplied from the supply tank 210 to the head 100, which is the flow rate increased due to the liquid being ejected from the head 100.

[0095] As shown in FIG. 8(B), when the flow rate of the liquid flowing through the supply-side air pump 81 is F3, the flow rate of the gas flowing through the bypass path 90 is F2, the flow rate of the liquid supplied from the supply tank 210 toward the head 100 is F4, and the flow rate of the liquid discharged from the head 100 is F7, the liquid circulation device of this embodiment is as follows: F3>(F2+F4+F7) It is preferable that the following relationship is satisfied.

[0096] By adopting such a configuration, fluctuations in the internal pressure of the supply tank 210 (decrease in internal pressure) caused by the ejection of liquid from the head 100 can be taken into consideration, and the pressure inside the supply tank 210 can be more reliably adjusted within a certain range.

[0097] <Flow rate of the recovery air pump> In the liquid circulation system of the present embodiment, it is preferable that the maximum flow rate of the gas flowing through the recovery air pump 82 is greater than the flow rate of the gas flowing through the bypass path 90 .

[0098] As shown in FIG. 8(B), when the flow rate of the gas flowing through the bypass path 90 is F2 and the flow rate of the gas flowing through the recovery side air pump 82 is F5, the liquid circulation device of this embodiment is as follows: F5 MAX >F2 It is preferable that the following relationship is satisfied.

[0099] With this configuration, fluctuations in the internal pressure of the recovery tank 220 due to the inflow of gas through the bypass path 90 do not exceed the range of internal pressure fluctuations associated with the operation of the recovery side air pump 82, making it easy to adjust the pressure within the recovery tank 220 within a certain range.

[0100] Furthermore, the flow rate of the gas flowing through the recovery air pump 82 is preferably greater than the sum of the flow rate of the gas flowing through the bypass path 90 and the flow rate of the liquid recovered in the recovery tank 220 via the head 100 .

[0101] As shown in FIG. 8(B), when the flow rate of the liquid flowing through the recovery side air pump 82 is F5, the flow rate of the gas flowing through the bypass path 90 is F2, and the flow rate of the liquid recovered in the recovery tank 220 is F6, the liquid circulation device of this embodiment is as follows: F5>(F2+F6) It is preferable that the following relationship is satisfied.

[0102] With this configuration, fluctuations in the internal pressure of the recovery tank 220 (increase in internal pressure) due to circulation of the liquid can be taken into consideration, and the pressure inside the recovery tank 220 can be adjusted within a certain range.

[0103] Furthermore, it is preferable that the flow rate of gas flowing through the recovery side air pump 82 is greater than the sum of the flow rate of gas flowing through the bypass path 90 and the flow rate of liquid recovered in the recovery tank 220 via the head 100, which is the flow rate that has decreased due to the liquid being ejected from the head 100.

[0104] As shown in FIG. 8(B), when the flow rate of the liquid flowing through the recovery side air pump 82 is F5, the flow rate of the gas flowing through the bypass path 90 is F2, the flow rate of the liquid recovered in the recovery tank 220 is F6, and the flow rate of the liquid discharged from the head 100 is F7, the liquid circulation device of this embodiment is as follows: F5>(F2+F6-F7) It is preferable that the following relationship is satisfied.

[0105] By adopting such a configuration, fluctuations in the internal pressure of the recovery tank 220 due to the ejection of liquid from the head 100 can also be taken into consideration, and the pressure within the recovery tank 220 can be adjusted within a certain range depending on whether or not liquid is being ejected from the head 100.

[0106] Second Embodiment 9 is an explanatory diagram schematically illustrating the configuration of the main parts of a liquid circulation device according to the second embodiment, in which the arrows indicate the movement directions of the liquid and gas. The liquid circulation device of this embodiment includes a variable resistor 90 a that can change the flow rate of the gas flowing through the bypass path 90 . The variable resistor 90a is not particularly limited as long as it is a means that can apply resistance to the gas flowing through the bypass path 90 and change the flow rate, but it is preferable that the resistance be changed according to the environmental temperature.

[0107] In the liquid circulation device of this embodiment, the flow rate of the gas flowing through the bypass path 90 changes depending on the environmental temperature. The liquid ejected from the head 100 may be one whose viscosity changes depending on the temperature of the ink, etc. In a high-temperature environment, the viscosity of such a liquid decreases, and the circulation flow rate increases, while in a low-temperature environment, the viscosity increases, and the circulation flow rate decreases. Therefore, it is preferable to be able to adjust the flow rate of the gas flowing through the bypass path 90 in accordance with changes in the flow rate of the liquid due to environmental temperature.

[0108] An example of a manner in which the flow rate of the gas flowing through the bypass path 90 changes is when the cross-sectional area of ​​at least a part of the flow path changes.

[0109] Moreover, the bypass path 90 may be provided with an environmental temperature detection means and a means for controlling the flow rate of the gas in accordance with the detection result of the environmental temperature detection means.

[0110] Third Embodiment 10 is an explanatory diagram schematically illustrating the configuration of the main parts of a liquid circulation device according to the third embodiment, in which the arrows indicate the movement directions of the liquid and gas. The liquid circulation device of this embodiment includes a buffer tank 92 that stores inert gas. The buffer tank 92 communicates with a supply-side air path 83, and the inert gas is supplied to the gas space 210a of the supply tank 210 via a supply-side air pump 81.

[0111] The inert gas stored in the buffer tank 92 may be, for example, nitrogen, but is not particularly limited as long as it is a gas that can prevent the circulating liquid from changing in quality (deteriorating).

[0112] According to the configuration of this embodiment, it is possible to prevent the liquid stored in the supply tank 210 from changing (deteriorating) due to oxygen and carbon dioxide in the air. Furthermore, since the inert gas is also sent to the recovery tank 220 through the bypass path 90, it is possible to prevent the circulating liquid from changing and also to prevent an increase in the amount of dissolved oxygen. This enables the head 100 to eject the liquid stably.

[0113] [Fourth embodiment] 11 is an explanatory view schematically illustrating the configuration of the main parts of a liquid circulation device according to the fourth embodiment, in which the arrows indicate the movement directions of the liquid and gas. The liquid circulation device of this embodiment includes a buffer tank 92 that stores an inert gas, and the buffer tank 92 communicates with a supply-side air path 83 and a recovery-side air path 84 . The inert gas supplied to the gas space 210a of the supply tank 210 via the supply side air pump 81 is supplied to the recovery tank 220 via the bypass path 90, and the inert gas supplied to the recovery tank 220 is recovered in the buffer tank 92 via the recovery side air pump 82.

[0114] As with the third embodiment, the configuration of this embodiment can prevent the circulating liquid from deteriorating and the amount of dissolved oxygen from increasing, enabling stable ejection of liquid from the head 100. Furthermore, since the inert gas is circulated via the buffer tank 92, the amount of inert gas used (consumption) can be reduced.

[0115] Fifth Embodiment FIG. 12 is an explanatory view schematically showing the configuration of a main part of a liquid circulation device according to a fifth embodiment. In the liquid circulation device of this embodiment, the supply-side air pump 81 applies a negative pressure to the supply tank 210 , and the internal pressure of the supply tank 210 is set to a negative pressure that is lower than that of the recovery tank 220 .

[0116] The circulation of liquid through the head 100 is achieved by transferring the liquid based on the pressure difference between the supply tank 210 and the recovery tank 220. However, if the pressure difference applied to the head 100 can be small, the internal pressure of the supply tank 210 can be made negative, just like the recovery tank 220, as in this embodiment.

[0117] The head 100 is a circulation type liquid ejection head. Examples of circulation-type liquid ejection heads include individual liquid chamber type heads in which liquid circulates near the nozzles, and heads in which liquid circulates only through a common liquid chamber. However, when the pressure difference between the supply tank 210 and the recovery tank 220 is small, as in this embodiment, a circulation-type liquid ejection head in which liquid circulates only through a common liquid chamber is preferable.

[0118] [Liquid circulation method] The liquid circulation method of this embodiment is a method for a liquid circulation device 200 including a supply tank 210 and a recovery tank 220 for storing liquid, a head 100 for ejecting the liquid, a path for circulating the liquid through the head 100, a liquid delivery pump 202 provided in a liquid path 203 for transferring the liquid from the recovery tank 220 to the supply tank 210 and delivering the liquid toward the supply tank 210, a supply-side air pump 81 provided in a supply-side air path 83 communicating with the gas space 210a of the supply tank 210, a recovery-side air pump 82 provided in a recovery-side air path 84 communicating with the gas space 220a of the recovery tank 220, and a bypass path 90 connecting the gas space 210a of the supply tank and the gas space 220a of the recovery tank, and providing a flow path for gas flowing from the supply tank 210 to the recovery tank 220, the method including reducing the flow rate of gas flowing through the bypass path 90 to be smaller than the maximum flow rate of liquid flowing through the liquid delivery pump 202.

[0119] The liquid circulation method of this embodiment includes controlling the maximum flow rate of gas flowing through the supply air pump 81 so that it is greater than the flow rate of gas flowing through the bypass path 90. It is preferable that the flow rate of the gas flowing through the supply-side air pump 81 is greater than the sum of the flow rate of the gas flowing through the bypass path 90 and the flow rate of the liquid supplied from the supply tank 210 to the head 100. It is also preferable that the flow rate of gas flowing through the supply side air pump 81 is greater than the sum of the flow rate of gas flowing through the bypass path 90 and the flow rate of liquid supplied from the supply tank 210 to the head 100, where the supply amount has increased due to the liquid being ejected from the head 100.

[0120] The liquid circulation method of this embodiment includes controlling the maximum flow rate of gas flowing through the recovery air pump 82 so that it is greater than the flow rate of gas flowing through the bypass path 90. It is preferable that the flow rate of the gas flowing through the recovery side air pump 82 is greater than the sum of the flow rate of the gas flowing through the bypass path 90 and the flow rate of the liquid recovered in the recovery tank 220 via the head 100. It is also preferable that the flow rate of gas flowing through the recovery side air pump 82 is greater than the sum of the flow rate of gas flowing through the bypass path 90 and the flow rate of liquid recovered in the recovery tank 220 via the head 100, where the amount of recovery has decreased due to the liquid being ejected from the head 100.

[0121] In the liquid circulation method of this embodiment, the flow rate of the gas flowing through the bypass passage is preferably controlled in accordance with the environmental temperature.

[0122] In addition, in a mode in which the liquid circulation device includes a buffer tank for storing inert gas, it is preferable to supply the inert gas to the gas space 210 a of the supply tank 210 via the supply-side air pump 81 .

[0123] In this specification, the term "liquid ejection device" refers to a device that includes a liquid ejection head and ejects liquid by driving the liquid ejection head, and is not limited to the example of the printing device shown in FIG.

[0124] In the present application, the term "liquid" is not particularly limited as long as it has a viscosity and surface tension that allows it to be ejected from a head, but it is preferably one whose viscosity becomes 30 mPa·s or less at room temperature and normal pressure, or upon heating or cooling. More specifically, it refers to solutions, suspensions, emulsions, etc. containing solvents such as water or organic solvents, colorants such as dyes or pigments, functionalizing materials such as polymerizable compounds, resins, and surfactants, biocompatible materials such as DNA, amino acids, proteins, and calcium, edible materials such as natural dyes, etc., and these can be used for applications such as inkjet inks, surface treatment liquids, liquids for forming components of electronic devices or light-emitting elements, liquids for forming electronic circuit resist patterns, and material liquids for 3D modeling.

[0125] "Liquid ejection heads" include those that use piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electrothermal conversion elements such as heating resistors, and electrostatic actuators consisting of a vibration plate and an opposing electrode as energy sources for ejecting liquid.

[0126] The term "liquid ejection device" includes devices that eject liquid by driving a liquid ejection head. Liquid ejection devices include not only devices that can eject liquid onto objects to which the liquid can adhere, but also devices that eject liquid into air or liquid.

[0127] This "liquid ejection device" can also include means for feeding, transporting, and discharging items onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

[0128] For example, examples of "liquid ejection devices" include image forming devices, which are devices that eject ink to form images on paper, and three-dimensional modeling devices (three-dimensional modeling devices), which eject modeling liquid onto a powder layer formed from layers of powder in order to create a three-dimensional object (a three-dimensional model).

[0129] Furthermore, the term "liquid ejection device" is not limited to devices that visualize meaningful images such as letters and figures using ejected liquid. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

[0130] The above-mentioned "object onto which a liquid can adhere" means an object onto which a liquid can adhere at least temporarily, an object onto which the liquid can adhere and stick, an object onto which the liquid can penetrate, etc. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects onto which a liquid can adhere.

[0131] The material of the "substance to which a liquid can adhere" may be any material to which a liquid can adhere, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics.

[0132] Furthermore, the term "liquid ejection device" includes, but is not limited to, a device in which a liquid ejection head and an object onto which liquid can be attached move relatively. Specific examples include a serial type device in which the liquid ejection head moves, and a line type device in which the liquid ejection head does not move.

[0133] Other examples of "liquid ejection devices" include a treatment liquid application device that ejects a treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and an injection granulation device that sprays a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0134] In the present application, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous.

[0135] For example, aspects of the present invention are as follows. <1> a supply tank and a recovery tank for storing the liquid; a head that ejects liquid; a path for circulating liquid through the head; a liquid transfer pump provided in a liquid path that transfers liquid from the recovery tank to the supply tank, the liquid transfer pump sending the liquid toward the supply tank; a supply-side air pump provided in a supply-side air path communicating with the gas space of the supply tank; a recovery-side air pump provided in a recovery-side air path communicating with the gas space of the recovery tank; a bypass path that connects the gas space of the supply tank and the gas space of the recovery tank and serves as a flow path for gas flowing from the supply tank to the recovery tank, The liquid circulation device is characterized in that the flow rate of the gas flowing through the bypass path is smaller than the maximum flow rate of the liquid flowing through the liquid feed pump. <2> The maximum flow rate of the gas flowing through the supply-side air pump is greater than the flow rate of the gas flowing through the bypass path. <1> 1 is a liquid circulation device according to the present invention. <3> The flow rate of the gas flowing through the supply side air pump is the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the liquid supplied from the supply tank to the head; <1> or <2> 1 is a liquid circulation device according to the present invention. <4> The flow rate of the gas flowing through the supply side air pump is the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the liquid supplied from the supply tank to the head, the flow rate being an increase in the supply amount due to the liquid being ejected from the head; <1> from <3> The liquid circulation device according to any one of the above items. <5> The maximum flow rate of the gas flowing through the recovery side air pump is greater than the flow rate of the gas flowing through the bypass path. <1> from <4> The liquid circulation device according to any one of the preceding claims . <6> The flow rate of the gas flowing through the recovery side air pump is the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the liquid recovered in the recovery tank via the head. <1> from <5> The liquid circulation device according to any one of the above items. <7> The flow rate of the gas flowing through the recovery side air pump is the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the liquid recovered in the recovery tank via the head, the flow rate being a decrease in the amount of recovery due to the liquid being discharged from the head; <1> from <6> The liquid circulation device according to any one of the above items. <8> The flow rate of the gas flowing through the bypass path varies depending on the ambient temperature. <1> from <7> The liquid circulation device according to any one of the above items. <9> The bypass path is characterized in that the cross-sectional area of ​​the flow path changes depending on the environmental temperature. <8> 1 is a liquid circulation device according to the present invention. <10> The bypass path is characterized by comprising an environmental temperature detection means and a means for controlling the flow rate of gas in accordance with the detection result of the environmental temperature detection means. <8> 1 is a liquid circulation device according to the present invention. <11> Equipped with a buffer tank for storing inert gas, the buffer tank is in communication with the supply-side air path; The inert gas is supplied to the gas space of the supply tank via the supply-side air pump. <1> from <10> The liquid circulation device according to any one of the above items. <12> the buffer tank is in communication with the supply-side air path and the recovery-side air path; the inert gas supplied to the supply tank is supplied to the recovery tank via the bypass path; The inert gas supplied to the recovery tank is recovered into the buffer tank via the recovery-side air pump. <11> 1 is a liquid circulation device according to the present invention. <13> The head is a circulation type liquid ejection head. <1> from <12> The liquid circulation device according to any one of the above items. <14> The aforementioned <1> from <13> 10. A liquid discharge apparatus comprising the liquid circulation device according to claim 9. <15> The aforementioned <1> from <13> 10. An image forming apparatus comprising the liquid circulation device according to claim 9. <16> a supply tank and a recovery tank for storing the liquid; a head that ejects liquid; a path for circulating liquid through the head; a liquid transfer pump provided in a liquid path that transfers liquid from the recovery tank to the supply tank, the liquid transfer pump sending the liquid toward the supply tank; a supply-side air pump provided in a supply-side air path communicating with the gas space of the supply tank; a recovery-side air pump provided in a recovery-side air path communicating with the gas space of the recovery tank; a bypass path that connects the gas space of the supply tank and the gas space of the recovery tank and serves as a flow path for gas flowing from the supply tank to the recovery tank, The liquid circulation method is characterized in that the flow rate of the gas flowing through the bypass path is set to be smaller than the maximum flow rate of the liquid flowing through the liquid feed pump. [Explanation of symbols]

[0136] 10 Continuum 81 Supply air pump 82 Recovery air pump 83 Supply air path 84 Recovery air path 90 Bypass Route 90a variable resistor 92 Buffer Tank 100 Liquid ejection head 171 Supply port (supply inlet) 181 Discharge port (discharge outlet) 200 Liquid circulation equipment 201 Main Tank 202 Liquid transfer pump 202A First liquid delivery pump 202B Second liquid delivery pump 209 Third liquid delivery pump 203 Liquid Path 203A First Liquid Path 203B Second liquid path 210 Supply Tank 220 Recovery Tank 289 Fluid Delivery Path 290 Subtank 300 head tank 1000 Liquid ejection device (printing device) [Prior art documents] [Patent documents]

[0137] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-68327

Claims

1. a supply tank and a recovery tank for storing the liquid; a head that ejects liquid; a path for circulating liquid through the head; a liquid transfer pump provided in a liquid path that transfers liquid from the recovery tank to the supply tank, the liquid transfer pump sending the liquid toward the supply tank; a supply-side air pump provided in a supply-side air path communicating with the gas space of the supply tank; a recovery-side air pump provided in a recovery-side air path communicating with the gas space of the recovery tank; a bypass path that connects the gas space of the supply tank and the gas space of the recovery tank and serves as a flow path for gas flowing from the supply tank to the recovery tank, A liquid circulation device, characterized in that the flow rate of the gas flowing through the bypass path is smaller than the maximum flow rate of the liquid flowing through the liquid feed pump.

2. 2. The liquid circulation system according to claim 1, wherein a maximum flow rate of the gas flowing through the supply-side air pump is greater than a flow rate of the gas flowing through the bypass passage.

3. The flow rate of the gas flowing through the supply side air pump is 3. The liquid circulation device according to claim 1, wherein the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the liquid supplied from the supply tank toward the head.

4. The flow rate of the gas flowing through the supply side air pump is 3. The liquid circulation device according to claim 1, wherein the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the liquid supplied from the supply tank to the head, the flow rate being an increase in the supply amount due to the liquid being ejected from the head.

5. 2. The liquid circulation system according to claim 1, wherein a maximum flow rate of the gas flowing through the recovery air pump is greater than a flow rate of the gas flowing through the bypass passage.

6. The flow rate of the gas flowing through the recovery side air pump is 6. The liquid circulation system according to claim 1, wherein the flow rate of the gas flowing through the bypass passage is greater than the sum of the flow rate of the gas flowing through the bypass passage and the flow rate of the liquid recovered in the recovery tank via the head.

7. The flow rate of the gas flowing through the recovery side air pump is 6. The liquid circulation device according to claim 1, wherein the flow rate of the gas flowing through the bypass path is greater than the sum of the flow rate of the gas flowing through the bypass path and the flow rate of the liquid recovered in the recovery tank via the head, the flow rate being reduced by the amount of liquid recovered due to the liquid being discharged from the head.

8. 2. The liquid circulation system according to claim 1, wherein the flow rate of the gas flowing through the bypass passage varies depending on the ambient temperature.

9. 9. The liquid circulation device according to claim 8, wherein the bypass path has a cross-sectional area that changes depending on the ambient temperature.

10. 9. The liquid circulation system according to claim 8, wherein the bypass path comprises an environmental temperature detection means, and a means for controlling the flow rate of the gas in accordance with the detection result of the environmental temperature detection means.

11. Equipped with a buffer tank for storing inert gas, the buffer tank is in communication with the supply-side air path; 2. The liquid circulation system according to claim 1, wherein an inert gas is supplied to the gas space of the supply tank via the supply-side air pump.

12. the buffer tank is in communication with the supply-side air path and the recovery-side air path; the inert gas supplied to the supply tank is supplied to the recovery tank via the bypass path; 12. The liquid circulation system according to claim 11, wherein the inert gas supplied to the recovery tank is recovered into the buffer tank via the recovery-side air pump.

13. 2. The liquid circulation device according to claim 1, wherein the head is a circulation type liquid ejection head.

14. A liquid ejection device comprising the liquid circulation device according to claim 1 or 13.

15. An image forming apparatus comprising the liquid circulating device according to claim 1 or 13.

Images