Circulation device

Abstract

To absorb pulsation.SOLUTION: A circulation device according to an aspect includes a storage unit for storing a liquid and a liquid droplet discharge unit for discharging the liquid, and controls circulation of the liquid flowing through channels allowing communication between the storage unit and the liquid droplet discharge unit. Such a circulation device includes a robotic unit, a first pressurizing unit, a second pressurizing unit, a first valve unit, and a second valve unit. The robotic unit is mounted with the liquid droplet discharge unit. The first pressurizing unit feeds the liquid stored in the storage unit to the liquid droplet discharge unit through a first channel allowing communication between the storage unit and the liquid droplet discharge unit. The second pressurizing unit feeds the liquid recovered in the liquid droplet discharge unit to the storage unit through a second channel allowing communication between the storage unit and the liquid droplet discharge unit. The first valve unit is interposed between the first pressurizing unit and the liquid droplet discharge unit. The second valve unit is interposed between the second pressurizing unit and the liquid droplet discharge unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The disclosed embodiments relate to a circulatory device. [Background technology]

[0002] 2. Description of the Related Art Known printing devices include inkjet printers and inkjet plotters that use an inkjet recording method. Such inkjet printing devices are equipped with a liquid ejection head for ejecting liquid.

[0003] Furthermore, for devices that eject liquid, such as inkjet printing devices, various technologies have been proposed, such as technologies for controlling the ejection of liquid, technologies for preventing waste of ejected liquid, and technologies for making liquid replacement more efficient. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-226313 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-167934 [Patent Document 3] Patent No. 4235631 Summary of the Invention

[0005] A circulation device according to one aspect of the embodiment comprises a storage section for storing liquid and a droplet discharge section for discharging the liquid, and controls the circulation of the liquid supplied from the storage section to the droplet discharge section. The circulation device comprises a robot section carrying the droplet discharge section, a first pressure application section for supplying the liquid stored in the storage section to the droplet discharge section through a first flow path connecting the storage section and the droplet discharge section, a second pressure application section for supplying the liquid recovered in the droplet discharge section to the storage section through a second flow path connecting the storage section and the droplet discharge section, a first valve section interposed between the first pressure application section and the droplet discharge section, and a second valve section interposed between the second pressure application section and the droplet discharge section. The robot section comprises an arm section that can move freely, and the first valve section is provided on the tip side of the arm section where the droplet discharge section is attached to the robot section. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of a circulation device according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating a configuration example of a circulation mechanism of the circulation device according to the embodiment. [Figure 3] FIG. 3 is a diagram schematically illustrating a configuration example of a circulation device according to a modified example. [Figure 4] FIG. 4 is a diagram schematically illustrating a configuration example of a circulation mechanism of a circulation device according to a modified example. [Figure 5] FIG. 5 is a diagram illustrating an example of a functional configuration of the circulation device according to the embodiment. [Figure 6] FIG. 6 is a diagram showing an outline of the flow rate control data according to the embodiment. [Figure 7] FIG. 7 is a diagram schematically illustrating an example of the relationship between the flow rate of the liquid and time according to the embodiment. [Figure 8] FIG. 8 is a diagram showing the measurement results of the circulation pressure of the liquid during printing according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the circulation device disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the invention according to the present application is not limited to the embodiments described below.

[0008] The circulation device disclosed in the present application can be applied to inkjet printers and inkjet plotters that use the inkjet recording method, as well as various other devices that eject droplets using the inkjet method.

[0009] <Circulation system configuration example> The configuration of a circulation device according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram schematically illustrating a configuration example of a circulation device according to an embodiment. Figure 2 is a diagram schematically illustrating a configuration example of a circulation mechanism of a circulation device according to an embodiment.

[0010] 1 or 2, the circulation device 200 includes a base 10, a tank 201, a discharge pump 202, a suction pump 203, a first proportional valve 204, a second proportional valve 205, and a heater 206. As shown in Fig. 1 or 2, the circulation device 200 also includes a first pressure sensor 208, a second pressure sensor 209, a third pressure sensor 210, a fourth pressure sensor 211, a flow meter 212, a droplet discharge head 213, and a robot unit 220. The circulation device 200 having such a configuration controls the circulation of the liquid supplied from the tank 201 to the droplet discharge head 213, as shown in Fig. 2.

[0011] The base 10 is placed on a horizontal floor surface, for example, indoors or outdoors. A tank 201 for storing liquid is installed on the base 10. This makes it possible to prevent the surface of the liquid stored in the tank 201 from swaying.

[0012] The robot unit 220 attached to the base 10 has an arm unit 221. The arm unit 221 is made up of a plurality of parts attached so as to be able to bend, stretch, and rotate freely. The arm unit 221 can move the droplet ejection head 213 attached to the tip of the arm unit 221 and change the position, posture, and angle of the droplet ejection head 213 in accordance with a predetermined command. The arm unit 221 illustrated in FIG. 1 is not particularly limited to the configuration shown in FIG. 1 as long as it has the degree of freedom to move the droplet ejection head 213 and change the position, posture, and angle required for the droplet ejection head 213.

[0013] The discharge pump 202 and the suction pump 203 are provided at the base side of the arm part 221 where the robot part 220 is attached to the base 10. In the circulation device 200, a considerable amount of pulsation is generated by the discharge pump 202 and the suction pump 203. The circulation device 200 according to the embodiment is provided with a first proportional valve 204 and a second proportional valve 205, which will be described below, thereby absorbing the pulsation caused by the discharge pump 202 and the suction pump 203.

[0014] As shown in Fig. 2, the first proportional valve 204 is interposed in a first flow path RT1 between the discharge pump 202 and the droplet discharge head 213, and is provided on the tip side of the arm unit 221 to which the droplet discharge head 213 is attached to the robot unit 220, as shown in Fig. 1. Furthermore, as shown in Fig. 2, the second proportional valve 205 is interposed in a second flow path RT2 between the suction pump 203 and the droplet discharge head 213, and is provided on the tip side of the arm unit 221 to which the droplet discharge head 213 is attached to the robot unit 220, as shown in Fig. 1. The first proportional valve 204 and the second proportional valve 205 can be mounted on the arm unit 221 by being installed on a frame member (not shown) attached to the tip of the arm unit 221. This allows the first proportional valve 204 and the second proportional valve 205 to be firmly fixed.

[0015] Furthermore, by mounting the first proportional valve 204 and the second proportional valve 205 on the tip side of the arm portion 221 to which the droplet discharge head 213 is attached, a certain distance is provided between the discharge pump 202 and the suction pump 203 and the droplet discharge head 213. This allows the circulation device 200 to prevent pulsation caused by the discharge pump 202 and the suction pump 203 from being transmitted to the droplet discharge head 213. Furthermore, the circulation device 200 can suppress pulsation reaching the droplet discharge head 213 as much as possible by the first proportional valve 204 and the second proportional valve 205.

[0016] The heater 206 is provided, for example, inside the tank 201 and inside the droplet discharge head 213. The heater 206 may be provided adjacent to the tank 201, rather than inside the tank 201, as long as the heater 206 is provided at a position where the heat of the heater 206 can be transmitted. Similarly, the heater 206 may be provided adjacent to the droplet discharge head 213, rather than inside the droplet discharge head 213, as long as the heater 206 is provided at a position where the heat of the heater 206 can be transmitted. The heater 206 may also be provided in either the tank 201 or the droplet discharge head 213.

[0017] <Modification> 1 shows an example in which the discharge pump 202 and the suction pump 203 are mounted on the base side of the arm unit 221 where the robot unit 220 is assembled to the base 10, but this example is not particularly limiting. A modified example of the mounting positions of the discharge pump 202 and the suction pump 203 will be described using FIG. 3. FIG. 3 is a diagram schematically showing an example of the configuration of a circulation device according to this modified example.

[0018] For example, as shown in Fig. 3, the circulation device 200 may have the discharge pump 202 and the suction pump 203 disposed at an intermediate position near the midpoint between the tip and base of the arm portion 221. By disposing the discharge pump 202 and the suction pump 203 at the intermediate position of the arm portion 221 as shown in Fig. 3, the output efficiency of each pump can be increased compared to disposing them at the base side of the arm portion 221 as shown in Fig. 1. Note that at least one of the discharge pump 202 and the suction pump 203 may be disposed at an intermediate position near the midpoint between the tip and base of the arm portion 221.

[0019] 2 illustrates an example in which the first proportional valve 204 is inserted in the first flow path RT1 between the discharge pump 202 and the droplet discharge head 213, and the second proportional valve 205 is inserted in the second flow path RT2 between the suction pump 203 and the droplet discharge head 213. However, this example is not particularly limiting. A modified example of the mounting positions of the first proportional valve 204 and the second proportional valve 205 will be described using FIG. 4. FIG. 4 is a diagram schematically illustrating an example of the configuration of a circulation mechanism of a circulation device according to this modified example.

[0020] As shown in Fig. 4, the first proportional valve 204 and the second proportional valve 205 may be built into the droplet discharge head 213. As shown in Fig. 4, by placing the first proportional valve 204 and the second proportional valve 205 closer to the droplet discharge head 213 than in the example shown in Fig. 2, it is possible to improve the response performance to pulsation caused by each pump. At least one of the first proportional valve 204 and the second proportional valve 205 may be built into the droplet discharge head 213.

[0021] 1, it is desirable that the first proportional valve 204 and the second proportional valve 205 are each provided on the tip side of the arm portion 221, but if the first proportional valve 204 and the second proportional valve 205 are interposed at least in the first flow path RT1 and the second flow path RT2, respectively, it is possible to expect some effect of making it difficult for pulsation to be transmitted to the droplet discharge head 213. Note that at least one of the first proportional valve 204 and the second proportional valve 205 may be provided on the tip side of the arm portion 221.

[0022] Furthermore, the circulation device 200 may be provided with a single pump that integrates the discharge pump 202 and the suction pump 203 as a mechanism for circulating the liquid. A proportional valve that controls the flow rate of the liquid is installed on the liquid discharge side between the discharge pump 202 and the droplet discharge head 213. Alternatively, a proportional valve that controls the flow rate of the liquid is installed on the liquid recovery side between the discharge pump 202 and the droplet discharge head 213. This makes it difficult for pulsation caused by the pump to be transmitted to the droplet discharge head 213, even when a pump that integrates the discharge pump 202 and the suction pump 203 is used.

[0023] The tank 201 and the droplet discharge head 213 may be configured to be heat-insulating, which makes them less susceptible to fluctuations in outside air temperature and is expected to improve the thermal efficiency of the heater 206.

[0024] <Example of functional configuration> An example of the functional configuration of the circulation device 200 according to the embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of the functional configuration of the circulation device according to the embodiment.

[0025] Note that FIG. 5 shows an example of the functional configuration of the circulation device 200 according to the embodiment, and the configuration does not need to be particularly limited to the example shown in FIG. 5 as long as it can realize the various functions of the circulation device 200 according to the embodiment. Also, FIG. 5 shows the components of the circulation device 200 according to the embodiment as functional blocks, and descriptions of other general components are omitted. Also, the components of the circulation device 200 shown in FIG. 5 are functionally conceptual, are not limited to the example shown in FIG. 5, and do not necessarily need to be physically configured as shown. For example, the specific form of distribution and integration of the functional blocks is not limited to that shown, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0026] 5, the circulation device 200 includes a tank 201, a discharge pump 202, a suction pump 203, a first proportional valve 204, a second proportional valve 205, and a heater 206. The circulation device 200 also includes an input / output interface 207, a first pressure sensor 208, a second pressure sensor 209, a third pressure sensor 210, a fourth pressure sensor 211, a flow meter 212, and a droplet discharge head 213. The circulation device 200 also includes a storage 214, a processor 215, and a robot unit 220.

[0027] The circulation device 200 shown in FIG. 5 includes a first flow path RT1 and a second flow path RT2 (see FIG. 2). The first flow path RT1 is a flow path for allowing the liquid stored in the tank 201 to flow into the droplet discharge head 213. The second flow path RT2 connects the tank 201 and the droplet discharge head 300 and is a flow path for returning the liquid that has flowed into the droplet discharge head 213 to the tank 201. Liquid that is not discharged from the droplet discharge head 213 to the outside and is collected within the droplet discharge head 300 is returned to the tank 201 via the second flow path RT2. The first flow path RT1 and the second flow path RT2 can be implemented, for example, by piping made of a predetermined material that does not interact with components of the liquid. The circulation device 200 having these components controls, for example, the circulation of the liquid supplied from the tank 201 to the droplet discharge head 213.

[0028] The tank 201 stores the liquid to be supplied to the droplet discharge head 213. The tank 201 functions as a storage unit that stores the liquid to be supplied to the droplet discharge head 213.

[0029] The discharge pump 202 functions as a first pressure application unit that supplies the liquid stored in the tank 201 to the droplet discharge head 213 through the first flow path RT1. The discharge pump 202 generates a positive pressure for sending the liquid stored in the tank 201 to the droplet discharge head 213. The discharge pump 202 discharges the liquid from the tank 201 to the droplet discharge head 213 at a preset constant pressure.

[0030] The suction pump 203 functions as a second pressure application unit that supplies the liquid collected in the droplet discharge head 213 to the tank 201 through the second flow path RT2. The suction pump 203 generates negative pressure to suck the liquid from the droplet discharge head 213 and return it to the tank 201. The suction pump 203 returns the liquid from the droplet discharge head 213 to the tank 201 at a preset constant pressure.

[0031] The discharge pump 202 and the suction pump 203 can be implemented by a rotary pump such as a gear pump or a positive displacement pump such as a diaphragm pump.

[0032] The first proportional valve 204 functions as a first valve unit interposed in the first flow path RT1 between the tank 201 and the droplet discharge head 213. The first proportional valve 204 proportionally controls the flow rate of the liquid supplied from the tank 201 to the droplet discharge head 213. The first proportional valve 204 can continuously change the cross-sectional area of ​​the liquid flow path between 0 and 100%, and controls the flow rate of the liquid to a desired flow rate. For example, the first proportional valve 204 can suppress pulsation generated in the liquid by the discharge pump 202 by reducing the cross-sectional area of ​​the liquid flow path.

[0033] The second proportional valve 205 functions as a second valve unit interposed in the second flow path RT2 between the tank 201 and the droplet discharging head 213. The second proportional valve 205 proportionally controls the flow rate of the liquid delivered from the droplet discharging head 213 to the tank 201. The second proportional valve 205 can continuously change the cross-sectional area of ​​the liquid flow path between 0 and 100%, and controls the flow rate of the liquid to a desired flow rate. For example, the second proportional valve 205 can reduce the pulsation generated in the liquid by the suction pump 203 by reducing the cross-sectional area of ​​the liquid flow path.

[0034] The first proportional valve 204 and the second proportional valve 205 can be implemented by an electromagnetic proportional switching valve or a pneumatic proportional switching valve.

[0035] The heater 206 heats the liquid stored in the tank 201 and the liquid circulating through the droplet ejection head 213 .

[0036] The input / output interface 207 exchanges various types of information with the robot section 220. The input / output interface 207 can send control signals to the robot section 220 to cause it to perform predetermined operations.

[0037] The first pressure sensor 208 measures the fluid pressure of the liquid fed from the tank 201 to the droplet ejection head 213 by the ejection pump 202. The first pressure sensor 208 measures the pressure downstream of the ejection pump 202 in the circulation direction of the liquid in the circulation device 200. The first pressure sensor 208 sends the measurement result to the processor 215.

[0038] The second pressure sensor 209 measures the fluid pressure of the liquid sucked from the droplet ejection head 213 by the suction pump 203 and delivered to the tank 201. The second pressure sensor 209 measures the pressure upstream of the suction pump 203 in the circulation direction of the liquid in the circulation device 200. The second pressure sensor 209 sends the measurement result to the processor 215.

[0039] The third pressure sensor 210 measures the fluid pressure of the liquid flowing through the first flow path RT1 between the first proportional valve 204 and the droplet discharging head 300. The third pressure sensor 210 measures the fluid pressure of the liquid that has passed through the first proportional valve 204 and is about to flow into the droplet discharging head 213. In other words, the third pressure sensor 210 measures the fluid pressure downstream of the first proportional valve 204 in the circulation direction of the liquid in the circulation device 200. The third pressure sensor 210 sends the measurement result to the processor 215.

[0040] The fourth pressure sensor 211 measures the fluid pressure of the liquid flowing through the second flow path RT2 between the second proportional valve 205 and the droplet discharging head 300. The fourth pressure sensor 211 measures the fluid pressure of the liquid immediately after it is sent from the droplet discharging head 213 to the tank 201 and before it passes through the second proportional valve 205. In other words, the fourth pressure sensor 211 measures the pressure upstream of the second proportional valve 205 in the circulation direction of the liquid in the circulation device 200. The fourth pressure sensor 211 sends the measurement result to the processor 215.

[0041] The flow meter 212 measures the flow rate of the liquid supplied to the droplet ejection head 213. The flow meter 212 sends the measurement results to the processor 215.

[0042] The droplet discharge head 213 discharges the liquid supplied from the tank 201 toward the target object 50 shown in Fig. 1. The droplet discharge head 213 recovers the liquid that was not discharged and sends the recovered liquid to the tank 201.

[0043] The storage 214 stores programs and data necessary for various processes of the circulation device 200. The storage 214 includes, for example, a robot control data storage unit 241, a pump control data storage unit 242, and a flow rate control data storage unit 243.

[0044] The robot control data storage unit 241 stores control programs and data for controlling the operation of the arm unit 221 included in the robot unit 220. The data stored in the robot control data storage unit 241 includes, for example, data such as the procedure for work performed by the droplet ejection head 213, the direction of movement, position, posture, and angle during work (when ejecting liquid), and the like.

[0045] The pump control data storage unit 242 stores preset data for pump control. The pump control data includes, for example, a set value of the pressure (positive pressure) applied to the liquid when the discharge pump 202 discharges the liquid, and a set value of the pressure (negative pressure) applied to the liquid when the suction pump 203 sucks the liquid. When considering the discharge of liquid from the droplet discharge head 213, the positive pressure of the discharge pump 202 is preset to a value that is, for example, about 1.2 to 3 times higher than the pressure when the liquid is supplied to the droplet discharge head 213. On the other hand, the negative pressure of the suction pump 203 is preset to a value that is about 1.2 to 3 times lower than the pressure when the liquid is supplied to the droplet discharge head 213.

[0046] The flow rate control data storage unit 243 stores flow rate control data for controlling the flow rate of the liquid circulating between the tank 201 and the droplet ejection head 213. Fig. 6 is a diagram showing an outline of the flow rate control data according to this embodiment.

[0047] As shown in FIG. 6 , the flow control data stored in the flow control data storage unit 243 has a control object item and a target value item, and these items correspond to each other. Either the first proportional valve 204 or the second proportional valve 205 to be controlled is registered in the control object item. A target value for controlling the flow rate of the liquid is registered in the target value item. The target values ​​corresponding to the first proportional valve 204 and the second proportional valve 205 may be the same or different. For example, a target value in the form of an average flow rate over a certain period of time may be set for each of the first proportional valve 204 and the second proportional valve 205. Alternatively, for example, a target value of 50% of the maximum flow rate may be set for the first proportional valve 204, and a target value in the form of an average flow rate over a certain period of time may be set for the second proportional valve 205.

[0048] The processor 215 executes various processes in the circulation device 200 based on the programs, data, etc. stored in the storage 214. The processor 215 reads and executes the computer programs stored in the storage 214, thereby realizing various functions for controlling each part of the circulation device 200.

[0049] (Robot control) The processor 215 controls the operation of the arm unit 221 included in the robot unit 220 based on the control program, data, etc. stored in the robot control data storage unit 241. The processor 215 causes the arm unit 221 to perform a desired operation, for example, by outputting a command to control the operation of the arm unit 221 to an actuator or the like that drives the arm unit 110.

[0050] (Pump control) The processor 215 adjusts the positive pressure applied to the liquid when the discharge pump 202 pumps out the liquid so as to maintain a constant pressure based on the measurement results of the first pressure sensor 208 and the measurement results of the third pressure sensor 210. For example, the processor 215 adjusts the positive pressure of the discharge pump 202 so as to maintain the pressure of the liquid obtained from the measurement results of the first pressure sensor 208 at a pressure that is approximately 1.2 to 3 times greater than the pressure of the liquid obtained from the measurement results of the third pressure sensor 210.

[0051] Furthermore, processor 215 adjusts the negative pressure applied to the liquid when suction pump 203 suctions the liquid so as to maintain a constant pressure based on the measurement results of second pressure sensor 209 and third pressure sensor 210. For example, processor 215 adjusts the negative pressure of suction pump 203 so that the liquid pressure obtained from the measurement results of second pressure sensor 209 is maintained at a pressure that is approximately 1.2 to 3 times lower than the liquid pressure obtained from the measurement results of third pressure sensor 210.

[0052] The processor 215 circulates the liquid between the tank 201 and the droplet ejection head 213 by adjusting the pressure difference between the positive pressure applied to the liquid by the ejection pump 202 and the negative pressure applied to the liquid by the suction pump 203 to maintain a constant pressure.

[0053] (Proportional valve control) The processor 215 controls the flow rate of the liquid passing through the first proportional valve 204 and the second proportional valve 205 based on the flow rate control data stored in the flow rate control data storage unit 243. An example of a method for controlling the flow rate by the processor 215 will be described below with reference to Fig. 7. Fig. 7 is a diagram schematically showing an example of the relationship between the flow rate of the liquid and time according to the embodiment.

[0054] 7 shows a schematic example of the relationship between time and the instantaneous flow rate of the liquid circulating between the tank 201 and the droplet discharge head 213. As shown in Fig. 7, pulsation occurs in the liquid circulating between the tank 201 and the droplet discharge head 213 due to the supply of the liquid by the discharge pump 202 and the collection of the liquid by the suction pump 203.

[0055] For example, in the flow rate control data, the maximum value of the flow rate for the third pressure sensor 210 is: max " is the average value of the flow rate over a certain period of time: "Q ave Assume that a target value MV1 is set to change the pressure of the liquid to " MV1 ". In this case, the processor 215 narrows the flow path cross-sectional area of ​​the first proportional valve 204 and adjusts the flow rate of the liquid passing through the first proportional valve 204 while referring to the measurement result of the third pressure sensor 210 so as to approach the target value MV1. In this way, the processor 215 can control the flow rates of the liquid passing through the first proportional valve 204 and the second proportional valve 205. By such control, the processor 215 can reduce the pressure of the liquid supplied to the droplet ejection head 213 and suppress pulsation.

[0056] The first proportional valve 204 is interposed in a first flow path RT1 between the discharge pump 202 and the droplet discharge head 213, and is provided, for example, on the tip side of an arm unit 221 to which the droplet discharge head 213 is attached to the robot unit 220. The second proportional valve 205 is interposed in a second flow path RT2 between the suction pump 203 and the droplet discharge head 213, and is provided, for example, on the tip side of the arm unit 221 to which the droplet discharge head 213 is attached to the robot unit 220. The processor 215 controls the flow rates of the first proportional valve 204 and the second proportional valve 205 based on flow rate control data. In this way, the circulation device 200 according to the embodiment makes it difficult for pulsation caused by the discharge pump 202 and the suction pump 203 to be transmitted to the droplet discharge head 213, and can suppress pulsation caused by the discharge pump 202 and the suction pump 203.

[0057] Furthermore, the applicant of the present application discovered a phenomenon in which, during printing operations using the circulation device 200, the liquid (ink) fails to be ejected after solid printing, in which printing is performed by continuously ejecting the liquid, resulting in incorrect printing, or liquid leakage from the droplet ejection head 213. FIG. 8 is a diagram showing the measurement results of the circulation pressure of the liquid during printing according to the embodiment. The vertical axis on the left side of FIG. 8 represents the supply pressure, and the vertical axis on the right side of FIG. 8 represents the recovery pressure. The horizontal axis of FIG. 8 represents time, with time flowing to the right side of FIG. 8. In the graph area of ​​FIG. 8, the upper line represents the time series change in the supply pressure, and the lower line represents the time series change in the recovery pressure.

[0058] As shown in Figure 8, the supply pressure and recovery pressure during circulation of the liquid before the liquid is ejected remain at approximately constant values. Then, from the start to the end of continuous liquid ejection associated with solid printing, both the supply pressure and recovery pressure of the liquid decrease. After ejection ends, the supply pressure and recovery pressure of the liquid begin to gradually increase. Phenomenon such as non-ejection of the liquid occurs when liquid ejection is started again after continuous ejection ends and the supply pressure and recovery pressure have not fully returned to normal.

[0059] The applicant of the present application has inferred the mechanism by which the phenomenon of non-ejection of liquid occurs as follows. Even after discharge has ended, liquid continues to flow from the supply side to the recovery side due to inertance, but if the recovery pressure drops, the second proportional valve 205 behaves as if it is closed. The applicant of the present application has inferred that as a result, the liquid that has nowhere to go without being discharged has a water hammer effect, causing the liquid to overflow from the nozzle, resulting in non-ejection. Therefore, the applicant of the present application has solved the above-mentioned problem by having the processor 215 of the circulation device 200 execute the following control method.

[0060] As shown in FIG. 8, the applicant of the present application has determined that after the discharge of the liquid is completed, at time t x The insight was gained that once this time has elapsed, the recovery pressure will recover to the set value for steady state (e.g., when liquid is circulating). In the example shown in FIG. 8, after approximately 0.5 msec (milliseconds) has elapsed since the end of discharge, the recovery pressure has recovered to approximately -10 kPa (kilopascals), the initial value when the droplets were discharged. Therefore, the processor 215 executes control based on this insight. Specifically, after the end of liquid discharge, the processor 215 executes control to close the first proportional valve 204 on the liquid supply side, and then close the second proportional valve 205 after a predetermined time has elapsed. As a result, the second proportional valve 205 on the liquid recovery side remains open to some extent until the predetermined time has elapsed, allowing the liquid to flow to the recovery side. As a result, it is possible to prevent liquid from being discharged or leaking due to water hammer.

[0061] Furthermore, the processor 215 may control the pressure on the recovery side that recovers the liquid so that it is lower than the steady-state set value when the liquid discharge from the droplet discharge head 213 is complete. This increases the force pulling the liquid from the liquid recovery side, allowing the liquid to flow efficiently to the recovery side. As a result, it is possible to prevent liquid discharge failures and liquid leakage due to water hammer.

[0062] Furthermore, when controlling the pressure on the recovery side that recovers the liquid when the discharge of liquid from the droplet discharge head 213 is completed, the processor 215 may control it to be lower by the amount of the pressure drop caused by the discharge of the liquid. In the example shown in Fig. 8, the pressure drop on the recovery side is approximately 2 kPa (kilopascals), so the processor 215 may control the pressure on the recovery side that recovers the liquid after the discharge of the liquid is completed to be lower by 2 kPa (kilopascals) caused by the discharge of the liquid. This makes it possible to prevent non-discharge or leakage of liquid due to water hammer, similar to the control that closes the second proportional valve 205.

[0063] Although specific embodiments have been described to fully and clearly disclose the claimed technology, the claims should not be limited to the above-described embodiments, but should be embodied in all modifications and alternative configurations that may be made by those skilled in the art within the scope of the basic concepts set forth herein.

[0064] The tank 201 does not have to be provided on the base 10, and may be provided somewhere other than the robot unit 220. The discharge pump 202 and the suction pump 203 may be provided on the base 10. [Explanation of symbols]

[0065] 10 Foundations 50 Objects 200 Circulation device 201 Tank 202 Discharge pump 203 Suction Pump 204 First proportional valve 205 Second proportional valve 206 Heater 207 Input / Output Interface 208 First pressure sensor 209 Second pressure sensor 210 Third pressure sensor 211 4th pressure sensor 212 Flow meter 213 Droplet ejection head 214 Storage 215 processors 220 Robot Club 221 Arm 241 Robot control data storage unit 242 Pump control data storage unit 243 Flow Control Data Storage Unit

Claims

1. A circulation device comprising: a storage unit that stores a liquid; and a droplet discharge unit that discharges the liquid; and controlling circulation of the liquid supplied from the storage unit to the droplet discharge unit, a robot unit that carries the droplet ejection unit; a first pressure application unit that supplies the liquid stored in the storage unit to the droplet discharge unit through a first flow path that communicates between the storage unit and the droplet discharge unit; a second pressure application unit that supplies the liquid recovered in the droplet discharge unit to the reservoir through a second flow path that communicates between the reservoir and the droplet discharge unit; a first valve portion interposed between the first pressure application portion and the droplet discharge portion; a second valve portion interposed between the second pressure application portion and the droplet discharge portion; In addition to providing the robot unit includes a freely movable arm unit, the first valve unit is provided on the tip side of the arm unit to which the droplet discharge unit is attached to the robot unit, the first pressure application unit is provided on a base side of the arm unit where the robot unit is attached to a base; The storage unit is installed on the base, The storage section is not provided on the arm section. Circulation device.

2. the first pressure application unit is provided at an intermediate position of the arm unit; The circulation device according to claim 1 .

3. the second valve unit is built into the droplet ejection unit; The circulation device according to claim 1 or 2.

4. A circulation device comprising: a storage unit that stores a liquid; and a droplet discharge unit that discharges the liquid; and controlling circulation of the liquid supplied from the storage unit to the droplet discharge unit, a robot unit that carries the droplet ejection unit; a first pressure application unit that supplies the liquid stored in the storage unit to the droplet discharge unit through a first flow path that communicates between the storage unit and the droplet discharge unit; a second pressure application unit that supplies the liquid recovered in the droplet discharge unit to the reservoir through a second flow path that communicates between the reservoir and the droplet discharge unit; a first valve portion interposed between the first pressure application portion and the droplet discharge portion; a second valve portion interposed between the second pressure application portion and the droplet discharge portion; In addition to providing the robot unit includes a freely movable arm unit, the second valve unit is provided on the tip side of the arm unit to which the droplet discharge unit is attached to the robot unit, the second pressure application unit is provided on a base side of the arm unit where the robot unit is attached to a base; The storage unit is installed on the base, The storage section is not provided on the arm section. Circulation device.

5. the second pressure application unit is provided at an intermediate position of the arm unit; The circulation device according to claim 4.

6. the first valve unit is built into the droplet ejection unit; The circulation device according to claim 4 or 5.

7. Further provided is a heater unit that heats the liquid stored in the storage unit. The circulation device according to any one of claims 1 to 6.

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