Liquid ejection device

Abstract

The present invention improves the performance of a liquid ejection device that ejects a fixed quantity of liquid. To this end, this liquid ejection device comprises: a pump that feeds a liquid; an ejection part that ejects the liquid; a pressure sensor that monitors the pressure of the liquid; an ejection electromagnetic valve that controls the ejection of the liquid in the ejection part; a control unit that controls the pressure of the liquid so as to be constant; and a liquid flow path that mutually connects the pump, the ejection part, the pressure sensor, and the ejection electromagnetic valve. In a state in which the pressure of the liquid is controlled to be constant by the control unit, the liquid ejection amount is controlled by the opening / closing time of the ejection electromagnetic valve.

Description

liquid discharge device

[0001] The present invention relates to a liquid ejection device, and more particularly to a method for ejecting a fixed amount of reagent in an automatic analyzer and an automatic staining device.

[0002] Conventionally, one method for discharging a fixed amount of liquid (e.g., a reagent) is known, as described in Patent Document 1 (JP 2019-124529 A), in which the internal volume of a syringe or the like is changed by a fixed volume to control the amount of discharging. Another known method for discharging a fixed amount of liquid is to open and close a solenoid valve in a flow path for a fixed period of time while applying pressure to the liquid using compressed air or the like, thereby controlling the amount of discharging. Patent Document 2 (JP 2009-195774 A) describes such a technique, in which the opening of a constant flow valve is controlled to control the amount of liquid supplied when the liquid is pressure-fed.

[0003] JP 2019-124529 A JP 2009-195774 A

[0004] However, in the method using a syringe, it is difficult to maintain the discharge pressure from immediately after the start of discharge to the end, to discharge continuously, and to control the discharge amount of each of the multiple discharge parts.

[0005] Furthermore, when controlling the discharge volume by opening and closing a solenoid valve for a set period of time, air bubbles are likely to form inside or around the discharged liquid, which can lead to a deterioration in the quality of the liquid itself. Furthermore, a pressure-resistant, sealed liquid tank must be used to store the liquid to be discharged, but when refilling the liquid, the tank must be opened to the atmosphere, and the system must be shut down during that time. Furthermore, the liquid inside the liquid tank is constantly exposed to compressed air, increasing the risk of contamination. Furthermore, when contamination occurs in the flow path (such as contamination), internal cleaning is performed, but because the liquid tank has a sealed structure, flow path cleaning cannot be done quickly, resulting in the system having to be shut down for an extended period of time.

[0006] The present invention has been conceived to solve such problems, and an object of the present invention is to improve the performance of a liquid ejection device.

[0007] A brief summary of a representative embodiment of the present invention will be given below.

[0008] One embodiment of the liquid ejection device comprises a pump that delivers liquid, an ejection unit that ejects the liquid, a pressure sensor that monitors the pressure of the liquid, an ejection solenoid valve that controls the ejection of the liquid in the ejection unit, a control unit that controls the pressure of the liquid to a constant level, and a liquid flow path that connects the pump, the ejection unit, the pressure sensor, and the ejection solenoid valve to each other, and controls the amount of liquid ejected by the opening and closing time of the ejection solenoid valve while the pressure of the liquid is controlled to a constant level by the control unit.

[0009] According to the present invention, it is possible to provide a liquid ejection apparatus with improved processing efficiency.

[0010] 1 is a schematic diagram showing a liquid ejection device according to embodiment 1. FIG. 2 is a flowchart showing liquid pressure control according to embodiment 1. FIG. 3 is a schematic diagram showing a liquid ejection device according to embodiment 2. FIG. 4 is a flowchart showing liquid pressure control according to embodiment 2. FIG. 5 is a waveform diagram showing a liquid pressure waveform during pressure control. FIG. 6 is a flowchart showing liquid pressure control according to embodiment 3. FIG. 7 is a schematic diagram showing a liquid ejection device according to embodiment 4. FIG. 8 is a timing chart showing ejection timing at each ejection solenoid valve according to embodiment 4. FIG. 9 is a schematic diagram showing a liquid ejection device according to embodiment 5. FIG. 10 is a flowchart showing liquid container switching control using a liquid detection sensor according to embodiment 5. FIG. 11 is a flowchart showing liquid container switching control using a remaining liquid amount count value without using a liquid detection sensor according to embodiment 5. FIG. 12 is a flowchart showing liquid container switching control when a liquid detection sensor is used in combination with a remaining liquid amount count value according to embodiment 5. FIG. 13 is a schematic diagram showing a suction state in a liquid ejection device using a syringe as a liquid ejection device according to comparative example 1. FIG. 14 is a schematic diagram showing an ejection state in a liquid ejection device using a syringe as a liquid ejection device according to comparative example 1. FIG. 10 is a schematic diagram showing a liquid ejection device of Comparative Example 2, which uses compressed air as a pressure source and ejects liquid by opening and closing an electromagnetic valve for a certain period of time.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In addition, in the embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0012] <Room for Improvement> Hereinafter, the room for improvement will be described in detail with reference to FIGS. 13 to 15. FIG.

[0013] 13 is a schematic diagram showing the suction state of a liquid ejection device (hereinafter referred to as the syringe system) of Comparative Example 1 that uses a syringe. This liquid ejection device is composed of a liquid container 101 containing liquid 108, a suction electromagnetic valve 102, a discharge electromagnetic valve 103, a syringe 104, a syringe drive mechanism 105, a discharge unit 106, and a flow path 107. In the syringe suction operation shown in FIG. 13, liquid 108 is sucked by driving syringe 104 in the suction direction with suction electromagnetic valve 102 open and discharge electromagnetic valve 103 closed.

[0014] Fig. 14 is a schematic diagram showing a discharging state in the liquid discharging device described using Fig. 13. In the syringe discharging operation shown in Fig. 14, liquid 108 is discharged by driving syringe 104 in the discharging direction under the condition that suction electromagnetic valve 102 is closed and discharge electromagnetic valve 103 is opened. The liquid discharging device of Comparative Example 1 continuously suctions and discharges liquid 108 by repeating the suction operation described using Fig. 13 and the discharge operation described using Fig. 14.

[0015] However, in a liquid ejection device using a syringe, the syringe 104 starts ejection from a stopped state at the start of ejection and stops again at the end of ejection, making it difficult to maintain a constant ejection pressure of the liquid 108 from immediately after the start of ejection until the end. For this reason, a liquid ejection device using a syringe is not suitable for, for example, intermittent ejection, in which ejection and stopping are repeated multiple times at high speed within a certain period of time. Furthermore, the syringe 104 draws and ejects the liquid 108 by repeatedly moving between the suction position and the ejection position. Because the internal volume of the syringe 104 is finite, it is difficult to continuously eject the liquid 108 without drawing in the liquid 108 for a long period of time. Furthermore, when the same type of liquid 108 is used and ejected from multiple ejection units 106 at separate timings, it is difficult to independently control the ejection amounts of the liquid 108 from the multiple ejection units 106 using a single syringe 104, regardless of the ejection timing. In this case, by adding flow path components such as syringes and drive components in the same number as the number of discharge units 106, it is possible to discharge the liquid 108 from each discharge unit 106 without being affected by the other discharge units 106. However, the cost of the control system increases in proportion to the total number of discharge units 106.

[0016] 15 is a schematic diagram showing a liquid ejection device of Comparative Example 2, which uses compressed air as a pressure source and ejects liquid by opening and closing a solenoid valve for a certain period of time (hereinafter referred to as a compressed air system). This liquid ejection device is composed of a pressure-resistant liquid container 203 containing liquid 208, a compressed air supply source 201, a pressure adjustment valve 202, a discharge solenoid valve 204, a discharge unit 205, a compressed air tube 206, a flow path (liquid tube) 207, a discharge solenoid valve control circuit 209, and a control unit 210. As shown in FIG. 15 , the pressure of the compressed air generated by the compressed air supply source 201, such as a compressor, is adjusted by a pressure adjustment valve 202, such as a regulator, to a value equivalent to the discharge pressure of the liquid 208. The pressure-resistant liquid container 203 must be able to withstand the pressure adjusted by the pressure adjustment valve 202. The discharge amount of liquid 208, which has been adjusted to a discharge pressure by pressure adjustment valve 202 in pressure-resistant liquid container 203, is controlled by opening and closing discharge electromagnetic valve 204 for a time period managed by control unit 210. The opening and closing of discharge electromagnetic valve 204 is controlled by discharge electromagnetic valve control circuit 209.

[0017] However, this compressed air method requires a compressor, regulator, and other components, resulting in a problem of an increased overall system size. Furthermore, under pressurized conditions within the pressure-resistant liquid container 203, gas dissolved in the liquid 208 becomes unable to dissolve within the liquid 208 due to the sudden pressure change (decompression) during dispensing. As a result, air bubbles are likely to form within or around the dispensed liquid 208. This leads to a deterioration in the quality of the dispensed liquid 208. Therefore, this compressed air method is not appropriate for applications where air bubbles in the dispensed liquid 208 are unacceptable. Furthermore, a pressure-resistant, sealed pressure-resistant liquid container 203 must be used to store the liquid 208 to be dispensed. However, the internal volume of the pressure-resistant liquid container 203 is limited. Therefore, if the remaining amount of liquid 208 in the pressure-resistant liquid container 203 is insufficient, the pressure within the pressurized pressure-resistant liquid container 203 must be released to the atmosphere, the pressure-resistant liquid container 203 must be opened, and the liquid 208 must be refilled. As a result, the system must be shut down while the liquid 208 is being refilled. Furthermore, the liquid 208 is constantly in contact with compressed air within the pressure-resistant liquid container 203, which increases the risk of contamination. Furthermore, when cleaning the inside of the flow path after contamination occurs, cleaning the flow path cannot be performed quickly because the pressure-resistant liquid container 203 has a sealed structure, and as a result, the system must be shut down for an extended period of time.

[0018] As described above, there is room for improvement in syringe-type liquid ejection devices and compressed air-type liquid ejection devices. Therefore, in each embodiment of the present application, measures are taken to address the above-mentioned room for improvement. The technical concept of the embodiments that incorporate these measures will be described below.

[0019] (First Embodiment) Hereinafter, the present embodiment will be described with reference to Figures 1 and 2. Note that the liquid referred to in the following embodiments is, for example, a chemical liquid (reagent) used in a test.

[0020] 1 is a schematic diagram showing a liquid ejection device (hereinafter referred to as a pump type) according to this embodiment. This liquid ejection device is composed of a liquid container 301 containing liquid 307, a pump 302, a pressure sensor 303, a discharge electromagnetic valve 304, a discharge unit 305, a flow path (liquid tube) 306, a pump control circuit 308, a pressure sensor processing circuit 309, a discharge electromagnetic valve control circuit 310, and a control unit 311.

[0021] The liquid container 301 and the pump 302 are connected via a flow path 306. The pump 302 and the pressure sensor 303 are also connected via the flow path 306. The pressure sensor 303 and the discharge unit 305 are also connected via the flow path 306, and a discharge electromagnetic valve 304 is provided in the middle of the flow path 306 between the pressure sensor 303 and the discharge unit 305. The control unit 311 is connected to each of the pump control circuit 308, the pressure sensor processing circuit 309, and the discharge electromagnetic valve control circuit 310. The pump control circuit 308 is connected to the pump 302, the pressure sensor processing circuit 309 is connected to the pressure sensor 303, and the discharge electromagnetic valve control circuit 310 is connected to the discharge electromagnetic valve 304.

[0022] That is, the liquid ejection device of this embodiment has a pump 302 that sends liquid 307, a ejection unit that ejects the liquid, an ejection unit 305 that ejects the liquid 307, a pressure sensor 303 that monitors the pressure of the liquid 307, and an ejection solenoid valve 304 that controls the ejection of the liquid 307 in the ejection unit 305. The liquid ejection device of this embodiment also has a control unit 311 that controls the pressure of the liquid 307 to be constant, and a flow path 306 for the liquid 307 that interconnects the pump 302, the ejection unit 305, the pressure sensor 303, and the ejection solenoid valve 304. The pressure sensor 303 does not detect fluctuations in the flow rate of the liquid 307 by pressure, but rather detects the pressure of the liquid 307 in a standby state.

[0023] 1, the direction of the liquid flow path and the liquid ejection direction in the liquid ejection device are indicated by white arrows, which also apply to the schematic diagrams of other liquid ejection devices used in the following explanations.

[0024] 2 shows an example of a flow of liquid pressure control in this embodiment. First, the control unit 311 determines whether the current time is a control cycle for pressure control (step S401). The control cycle for pressure control refers to the timing of a pressure adjustment process that is periodically performed in the liquid ejection device of this embodiment. Next, if the current time is not a control cycle in step S401, no processing is performed. If the current time is a control cycle in step S401, the set pressure value (SV) is acquired (step S402), the current pressure value (PV) measured by the pressure sensor 303 and processed by the pressure sensor processing circuit 309 is acquired (step S403), and the deviation (τ = SV - PV) is calculated (step S404). Next, it is determined whether the conditional expression |τ| > threshold holds, which compares the absolute value |τ| of the deviation calculated in step S404 with a threshold (step S405). If |τ| > threshold is not satisfied, no processing is performed, but if |τ| > threshold is satisfied, pressure control is performed in the next step S406 and thereafter. Step S405 is processing executed to adjust the sensitivity of the control system for pressure control or to perform control within a preset control width, and may be omitted as necessary, and the conditional expression may be |τ| > 0.

[0025] Next, the positive or negative state of the deviation (τ) is determined using the conditional expression (τ>0) (step S406). If the deviation (τ) is positive in step S406, the set pressure value (SV) is greater than the current pressure value (PV), and pressurization is necessary. To this end, a pressurization control amount is calculated (step S407) and pump control is performed (step S408). The liquid delivery direction of the pump 302 in step S408 is controlled by the pump control circuit 308 so as to deliver liquid toward the discharge port for pressurization. If the deviation (τ) is negative in step S406, the set pressure value (SV) is less than the current pressure value (PV), and depressurization is necessary. To this end, a depressurization control amount is calculated (step S409) and pump control is performed (step S410). The liquid delivery direction of the pump 302 in step S410 is controlled by the pump control circuit 308 so as to deliver liquid toward the liquid container for depressurization. In step S406, if the deviation (τ) is 0, the set pressure value (SV) = the current pressure value (PV) holds, and the control amount in the subsequent pressure reduction control amount calculation (step S409) becomes 0. In this way, the pump 302 can switch the liquid sending direction under external control.

[0026] Here, the pressurization control amount calculation (step S407) and the depressurization control amount calculation (step S409) may use PI control, PID control, or the like. Because the optimal control method varies depending on the response characteristics of the pump 302 used, the control amount calculation method is not particularly limited. Furthermore, because the optimal control method for the pressurization control amount calculation (step S407) and the depressurization control amount calculation (step S409) varies depending on the type of actuator (motor) driving the pump 302, either a movement position command or a rotation speed command may be used, and the actuator control method is not particularly limited. Furthermore, unlike the pressure-resistant liquid container 203 in Comparative Example 2 shown in FIG. 15 , the liquid container 301 is not pressurized within the liquid container 301 but is used under atmospheric pressure, so there are no particular restrictions on the shape of the liquid container 301. However, considering the risk of contamination and other contamination, it is most effective to use a flexible bag-type container for liquid container 301 that is shaped so that liquid 307 does not come into direct contact with air, and in particular, that allows liquid container 301 to deform according to the remaining amount of liquid 307. While Figure 3 shows a state in which gas is present above liquid 307 in liquid container 301, it is ideal for this gas to be absent within liquid container 30. Furthermore, even if gas is present within liquid container 30, the pressure of the gas is below atmospheric pressure, and therefore the risk of contamination occurring is extremely low compared to when pressurization is performed using gas as in Comparative Example 2.

[0027] In the liquid ejection device of this embodiment, the control unit 311 performs feedback control so that the pressure of the liquid 307 always remains at the set pressure value (SV) according to the above flow, and at the same time controls the ejection amount of the liquid 307 by opening and closing the ejection solenoid valve 304 for a fixed period of time using the ejection solenoid valve control circuit 310. In this embodiment, the ejection amount is controlled only by the ejection solenoid valve 304 downstream of the pump 302 (on the ejection unit 305 side). In the liquid ejection device of this embodiment, the flow shown in FIG. 2 is periodically repeated until the ejection operation is completed. Note that the control unit that controls the opening and closing of the ejection solenoid valve 304 does not have to be the same as the control unit 311 that controls the pressure.

[0028] Advantages of the Present Embodiment The pump-type liquid ejection device of the present embodiment uses a pump 302 with a structure that prevents the liquid 307 from directly contacting air. This reduces the amount of gas dissolved in the liquid 307 and the amount of gas (bubbles) generated by the dissolved gas due to pressure changes (decompression) during ejection, compared to compressed air ejection. Furthermore, because the liquid 307 does not need to directly contact air, as in compressed air ejection, this embodiment can be realized even if the entire flow path is a closed flow path. A closed flow path refers to a flow path structure in which the entire flow path is not exposed to air. There are no particular restrictions on the flow path direction, but as in the liquid ejection device of the present embodiment, the flow path direction is one-way, from the liquid container 301 to the ejection unit 305, and the ejected liquid 307 does not circulate. As a result, the pump-type liquid ejection device of the present embodiment has the advantage of significantly lowering the risk of contamination compared to compressed air ejection. Furthermore, since the pump 302 is used as the pressure source for the liquid 307, compared to the compressed air system, the compressed air supply source 201, the pressure regulating valve 202, and the pressure-resistant liquid container 203 with a pressure-resistant sealed structure are not required, which has the advantage of allowing the control system to be made smaller.

[0029] In this embodiment, the pump 302 must be capable of controlling the liquid flow direction so that it can perform both pressurization and depressurization control. In particular, the liquid flow direction must be switchable by driving the pump 302 control motor forward or backward, and the only liquid-contacting component must be a tube, resulting in very few components. Therefore, from the perspectives of maintainability and sanitation, it is ideal to use a peristaltic pump (tube pump) for the pump 302, which has a structure that prevents the liquid from directly coming into contact with air. Furthermore, in the unlikely event that contamination occurs in the flow path, replacing the liquid-contacting components (cartridge unit), including the peristaltic pump's tube, allows for rapid recovery without requiring prolonged system shutdowns for flow path cleaning. In addition to peristaltic pumps, rotary pumps, gear pumps, and other pumps known as bidirectional pumps can also be used as pumps 302 capable of switching the liquid flow direction via external control. These pumps can be used for the pumps used in the following embodiments 2 to 5.

[0030] (Embodiment 2) In the above-described embodiment 1, the pump 302 of the liquid ejection device is capable of switching the liquid delivery direction. However, this embodiment describes a case where a pump whose liquid delivery direction cannot be switched and which has a liquid delivery function in only one direction is used instead.

[0031] 3 is a schematic diagram of a liquid ejection device according to this embodiment. The liquid ejection device comprises a liquid container 501 containing liquid 508, a pump 502, a pressure sensor 503, a discharge electromagnetic valve 504, a reflux electromagnetic valve 505, a discharge unit 506, a flow path (liquid tube) 507, a pump control circuit 509, a pressure sensor processing circuit 510, a discharge electromagnetic valve control circuit 511, a reflux electromagnetic valve control circuit 512, and a control unit 513. The liquid container 501 and the pump 502 are connected via a flow path 507. The pump 502 and the pressure sensor 503 are also connected via the flow path 507. The pressure sensor 503 and the discharge unit 506 are also connected via the flow path 507, and a discharge electromagnetic valve 504 is provided midway along the flow path 507 between the pressure sensor 503 and the discharge unit 506.

[0032] Here, the flow path 507 between the liquid container 501 and the pump 502 and the flow path 507 between the pump 502 and the pressure sensor 503 are connected by another flow path 507. A reflux solenoid valve 505 is provided in this other flow path 507. In other words, two flow paths are provided between the liquid container 501 and the pressure sensor 503, and the pump 502 is provided in one of the flow paths, and the reflux solenoid valve 505 is provided in the other flow path. Both ends of these two flow paths form an annular flow path. In other words, these two flow paths form a reflux flow path within the entire flow path.

[0033] The control unit 513 is connected to the pump control circuit 509, the pressure sensor processing circuit 510, the discharge solenoid valve control circuit 511, and the reflux solenoid valve control circuit 512. The pump control circuit 509 is connected to the pump 502, the pressure sensor processing circuit 510 is connected to the pressure sensor 503, the discharge solenoid valve control circuit 511 is connected to the discharge solenoid valve 504, and the reflux solenoid valve control circuit 512 is connected to the reflux solenoid valve 505.

[0034] FIG. 4 shows an example of a flow chart for controlling the pressure of a liquid in this embodiment. In this embodiment, control is performed with the reflux solenoid valve 505 open at a predetermined opening. First, the control unit 513 determines whether the current time is a control cycle for pressure control (step S601). Next, if the current time is not a control cycle in step S601, no processing is performed. If the current time is a control cycle, the control unit 513 sequentially acquires a set pressure value (SV) (step S602), acquires a current pressure value (PV) measured by the pressure sensor 503 and processed by the pressure sensor processing circuit 510 (step S603), and calculates a deviation (τ = SV - PV) (step S604). Next, it is determined whether the conditional expression |τ| > threshold holds, which compares the absolute value |τ| of the deviation calculated in step S604 with a threshold (step S605). If |τ| > threshold is not satisfied, no processing is performed, but if |τ| > threshold is satisfied, pressure control is performed in the next step S606 and thereafter. Step S606 is processing executed to adjust the sensitivity of the control system for pressure control, or to perform control according to the control width.

[0035] Next, the positive or negative state of the deviation (τ) is determined using the conditional expression (τ>0) (step S606). If the deviation (τ) is positive in step S606, the set pressure value (SV) is greater than the current pressure value (PV), so a pressurization control amount calculation (step S607) and pump control (step S608) are performed. The liquid delivery direction of the pump 502 in step S608 is controlled by the pump control circuit 509 so that liquid is delivered toward the discharge port for pressurization. If the deviation (τ) is negative in step S606, the set pressure value (SV) is less than the current pressure value (PV), so a depressurization control amount calculation (step S609) and pump control (step S610) are performed. In step S606, if the deviation (τ) is 0, the set pressure value (SV) = the current pressure value (PV) holds, that is, a steady state based on the set pressure value (SV) holds, and therefore the control amount in the subsequent pressure reduction control amount calculation (step S609) will be 0.

[0036] As described above, the pump 502 in this embodiment cannot change the liquid delivery direction and has a one-way liquid delivery function. Therefore, in the depressurization control in step S610, the return solenoid valve 505 is opened to a predetermined aperture to return the liquid 508, thereby reducing the pump pressure. To achieve continuous pressure increase or decrease during pressurization or depressurization control, the internal orifice diameter of the return solenoid valve 505 when open can be changed by using a proportional valve that can be continuously controlled by PWM (Pulse Width Modulation) control or the like in the return solenoid valve control circuit 512 to change the aperture of the return solenoid valve 505, or this can be used in combination with pressure control by the pump. However, in this embodiment, any method is not particularly important. The orifice diameter is the effective diameter of the flow path. PI (P: proportional, I: integral) control or PID (P: proportional, I: integral, D: derivative) control can be used for the pressurization control amount calculation (step S607) and the depressurization control amount calculation (step S609). In this embodiment, the control amount calculation method is not particularly limited. The pressurization control amount calculation (step S607) may be either a movement position command or a rotation speed command for the actuator (motor) that drives the pump 502, and the control method is not particularly limited.

[0037] In the liquid ejection device of this embodiment, the control unit 513 performs feedback control according to the above flow so that the pressure of the liquid 508 always remains at the set pressure value (SV), and at the same time controls the ejection amount of the liquid 508 by opening and closing the ejection solenoid valve 504 for a fixed period of time using the ejection solenoid valve control circuit 511. In the liquid ejection device of this embodiment, the flow shown in Fig. 4 is periodically repeated until the ejection operation is completed. In this embodiment, the amount of liquid sent to the reflux flow path is controlled by the pressurization or depressurization of the pump 502, thereby enabling control of the pressurization or depressurization within the flow path.

[0038] Furthermore, in this embodiment, highly responsive pressure control is possible even if a pump that cannot switch the liquid sending direction is used as the pump 502. Furthermore, a peristaltic pump, a rotary pump, a gear pump, or other pumps known as bidirectional pumps can also be used as the pump 502.

[0039] (Embodiment 3) In the first embodiment, feedback control was described for pressure control of a liquid ejection device. In the feedback control of the first embodiment (see FIG. 2), the deviation (set pressure value - current pressure value) calculated in step S404 is used to calculate a pump control amount (steps S407 and S409), and pump control is performed (steps S408 and S410). Therefore, when a disturbance affects the liquid ejection device shown in FIG. 1, as the deviation (set pressure value - current pressure value) due to the influence of the disturbance increases, the pump control amount also increases accordingly. As a result, feedback control is initiated in a direction to counteract the disturbance a short time after the disturbance occurs. For this reason, when attempting to improve the stability of pressure control of a liquid ejection device, the influence of this disturbance cannot be ignored. To reduce the influence of the disturbance, it is necessary to detect the extent of the disturbance by some means and calculate the control amount due to the disturbance (disturbance correction value) into the pump control amount.

[0040] The main cause of disturbances in the feedback control system of the liquid ejection device is none other than the opening and closing operation of the ejection solenoid valve 304. Figure 5 shows a control signal for the ejection solenoid valve and a pressure graph during pressure control. From top to bottom, Figure 5 shows an ejection solenoid valve control signal 701 when the ejection solenoid valve 304 is opened and closed, a pressure waveform 702 according to the first embodiment in which control due to disturbances is not performed, and a pressure waveform 703 according to the present embodiment in which control due to disturbances is performed. As shown by the ejection solenoid valve control signal 701 and the pressure waveform 702, when the ejection solenoid valve 304 is opened, the pressure drops sharply, and feedback control is only performed once the deviation reaches a positive value of a certain magnitude. As a result, a drop in pressure occurs immediately after the ejection solenoid valve 304 is opened. When the ejection solenoid valve 304 is closed, the pressure rises sharply, and for the same reason, a pressure increase occurs immediately after the ejection solenoid valve 304 is closed. In the following, as the present embodiment, we will explain how the opening and closing operation of the discharge solenoid valve 304, which causes a disturbance, is detected without adding any hardware components such as a sensor that is a disturbance detection unit to the liquid discharge device, and pressure control is performed by calculating a disturbance correction value as the control amount.

[0041] FIG. 6 shows an example of a flow of liquid pressure control in this embodiment. First, the control unit 311 determines whether the current time is a control cycle for pressure control (step S801). Next, if the current time is not a control cycle in step S801, no processing is performed. If the current time is a control cycle, the set pressure value (SV) is acquired (step S802), the current pressure value (PV) measured by the pressure sensor 303 and processed by the pressure sensor processing circuit 309 is acquired (step S803), and the deviation (τ = SV - PV) is calculated (step S804). Next, it is determined whether the conditional expression |τ| > threshold holds, which compares the absolute value |τ| of the deviation calculated in step S804 with a threshold (step S805). If |τ| > threshold does not hold, no processing is performed. However, if |τ| > threshold holds, pressure control is performed in the next step S806 and subsequent steps. Step S805 is a process executed to adjust the sensitivity of the control system for pressure control and to perform control according to the control width.

[0042] Next, the positive or negative state of the deviation (τ) is determined using the conditional expression (τ>0) (step S806). If the deviation (τ) is positive in step S806, the set pressure value (SV) is greater than the current pressure value (PV), and therefore a pressurization control amount calculation is performed (step S807). Next, by communicating with the control unit 311 or another control unit that controls the discharge solenoid valve 304, information as to whether or not the discharge solenoid valve 304 is scheduled to open or close within the next control cycle is obtained (step S808). In this way, the detection unit that obtains information as to whether or not the discharge solenoid valve 304 is scheduled to open or close within the next control cycle can be said to be a disturbance detection unit.

[0043] If the opening and closing operation of the discharge solenoid valve 304 is scheduled within the next control cycle in step S808, a disturbance correction value due to the opening and closing operation of the discharge solenoid valve 304 is calculated for the pressurization control amount calculated in step S407 (step S809). As shown in the discharge solenoid valve control signal 701 (see FIG. 5 ) when the discharge solenoid valve 304 is opened and closed, it is effective to calculate a disturbance correction value that has the effect of increasing the pressurization control amount so that the current pressure value (PV) does not fall below the set pressure value (SV) (τ>0) when the discharge solenoid valve 304 is opened (step S809). Similarly, if the discharge solenoid valve 304 is closed, it is effective to calculate a disturbance correction value that has the effect of decreasing the pressurization control amount so that the current pressure value (PV) does not exceed the set pressure value (SV) (τ<0) (step S809). On the other hand, if it is determined in step S808 that the opening and closing operation of the discharge solenoid valve 304 is not scheduled within the next control cycle, a pressurization control amount without disturbance correction is calculated (step S809), as in step S407. Subsequently, pressurization control is performed in accordance with the pressurization control amount calculated in step S809 (step S810).

[0044] If the deviation (τ) is negative in step S806, the set pressure value (SV) is less than the current pressure value (PV), and therefore a pressure reduction control amount calculation is performed (step S811). If the deviation (τ) is 0 in step S806, the set pressure value (SV) = the current pressure value (PV), that is, a steady state based on the set pressure value (SV), is established, and therefore the control amount in the subsequent pressure reduction control amount calculation (step S811) is generally 0.

[0045] Next, by communicating with the control unit 311 or another control unit that controls the discharge solenoid valve 304, information is obtained as to whether or not the opening / closing operation of the discharge solenoid valve 304 is scheduled within the next control cycle (step S812). If the opening / closing operation of the discharge solenoid valve 304 is scheduled within the next control cycle in step S812, a disturbance correction value due to the opening / closing operation of the discharge solenoid valve 304 is calculated for the pressure reduction control amount calculated in step S409 (step S813). As shown by the discharge solenoid valve control signal 701 (see FIG. 5 ) when the discharge solenoid valve 304 is opened and closed, when the discharge solenoid valve 304 is to be closed, it is effective to additionally calculate a disturbance correction value that has the effect of increasing the pressure reduction control amount so that the current pressure value (PV) does not exceed the set pressure value (SV) (τ<0) (step S813). Similarly, when the discharge solenoid valve 304 is opened, it is effective to calculate a disturbance correction value that has the effect of reducing the pressure reduction control amount so that the current pressure value (PV) does not fall below the set pressure value (SV) (τ>0) (step S813). Here, if the opening / closing operation of the discharge solenoid valve 304 is not scheduled within the next control cycle in step S812, the pressure reduction control amount is calculated in the same way as in step S409 (step S813). Subsequently, pressure reduction control is performed in accordance with the pressure reduction control amount calculated in step S813 (step S814).

[0046] When disturbance correction is performed according to the above flow, the pressure waveform 703 with disturbance correction has the effect of reducing pressure fluctuations due to disturbances compared to the pressure waveform 702 without disturbance correction. Control that detects disturbances using such means and has the effect of counteracting the effects of the disturbances is called predictive control or feedforward control. Here, with the constant pressure control using feedback control described in the first embodiment, the effect of counteracting the disturbances is difficult to achieve unless the deviation (τ) of the pressure value due to the influence of the disturbance reaches a certain level. In contrast, the predictive control of this embodiment can quickly reduce the effects of the disturbances by detecting them. Such predictive control detects the level of the disturbance using some means and performs control to reduce the effects of the disturbance, and is generally open-loop control. For this reason, it is difficult to maintain a stable steady state using predictive control alone. Therefore, in the constant pressure control of this embodiment, it is desirable to calculate a disturbance correction calculated by predictive control (feedforward control) as a correction value (control amount + disturbance correction value) for the control amount calculated by the constant pressure control (feedback control) shown in the first embodiment, and thereby ultimately determine the control amount to control the pump.

[0047] Since the main cause of disturbances affecting the control system of this liquid ejection device is the opening and closing operation of the ejection solenoid valve 304, in this embodiment, in steps S808 and S812, it is determined whether solenoid valve control will occur within the next control cycle, thereby predicting the disturbance and calculating a disturbance correction for the pump control amount to perform control. In this embodiment, any disturbance detection method is acceptable, so for example, the pressure sensor 303 may be used as the disturbance detection unit to detect the disturbance, or a separate sensor may be added external to the control system to detect the disturbance. In this way, it is possible to reduce the effects of disturbances by applying the control flow shown in FIG. 6.

[0048] As described above, in this embodiment, the control unit 311 performs predictive control by detecting disturbances using the disturbance detection unit so that the pressure of the liquid 307 always becomes the set pressure value (SV), and at the same time, the discharge amount of the liquid 307 is controlled by opening and closing the discharge solenoid valve 304 for a certain period of time using the discharge solenoid valve control circuit 310. In this embodiment, the same effects as those of the first embodiment can be obtained, and further, by predicting disturbances and controlling the discharge amount of the liquid 307 as described above, the influence of disturbances can be reduced. In other words, this embodiment has a disturbance detection unit, and controls the pump control amount in constant pressure control using a control amount that corrects the influence of disturbances, thereby reducing the influence of disturbances on the control system.

[0049] (Embodiment 4) Comparative Example 1 shown in Figures 13 and 14 illustrates a liquid ejection device that ejects liquid from an ejection unit 205. When using a liquid ejection device, it may be necessary to eject the same type of liquid from multiple ejection units at different times. The ejection timings of the individual ejection units are offset by, for example, 10 milliseconds or more to avoid affecting the ejection volume. Consider the syringe system of Comparative Example 1 and the compressed air system of Comparative Example 2, where the same type of liquid is ejected from multiple ejection units at different times. In the syringe system, when the same type of liquid is ejected from multiple ejection units at different times, it is difficult to individually control the ejection volume from each of the multiple ejection units using a single syringe, regardless of the ejection timing. In this case, adding flow path components such as syringes and drive components equal to the number of ejection units allows each ejection unit to eject liquid without being affected by other ejection units. However, this has the disadvantage of increasing the cost of the control system in proportion to the total number of ejection units.

[0050] Furthermore, when using a compressed air system, by adding an additional solenoid valve for each discharge unit, it is possible to achieve discharge from multiple discharge units at individual timings, regardless of the discharge timing. However, as explained above as room for improvement, the compressed air system tends to increase the size of the entire system, and also has disadvantages such as the risk of generation of dust and contamination in the discharged liquid. Below, we will explain a case in which the same type of liquid is discharged from multiple discharge units at individual timings in a liquid discharge device using the pump system of this embodiment.

[0051] The liquid ejection device of this embodiment includes a liquid container 901 containing a liquid 911, a pump 902, a pressure sensor 903, a first ejection electromagnetic valve 904, a second ejection electromagnetic valve 905, a third ejection electromagnetic valve 906, a first ejection unit 907, a second ejection unit 908, and a third ejection unit 909. The liquid ejection device of this embodiment further includes a flow path (liquid tube) 910, a pump control circuit 912, a pressure sensor processing circuit 913, a ejection electromagnetic valve control circuit 914, and a control unit 915.

[0052] The liquid container 901 and the pump 902 are connected via a flow path 910. The pump 902 and the pressure sensor 903 are also connected via a flow path 910. The pressure sensor 903 is also connected via the flow path 910 to the first discharge portion 907, the second discharge portion 908, and the third discharge portion 909. A first discharge electromagnetic valve 904 is provided in the flow path 910 between the pressure sensor 903 and the first discharge portion 907. A second discharge electromagnetic valve 905 is provided in the flow path 910 between the pressure sensor 903 and the second discharge portion 908. A third discharge electromagnetic valve 906 is provided in the flow path 910 between the pressure sensor 903 and the third discharge portion 909. The control unit 915 is connected to each of the pump control circuit 912, the pressure sensor processing circuit 913, and the discharge electromagnetic valve control circuit 914. The pump control circuit 912 is connected to the pump 902, the pressure sensor processing circuit 913 is connected to the pressure sensor 903, and the discharge solenoid valve control circuit 914 is connected to each of the first discharge solenoid valve 904, the second discharge solenoid valve 905, and the third discharge solenoid valve 906.

[0053] The liquid pressure control flow in this embodiment is the same as the flow in the first embodiment (see FIG. 2 ). Liquid discharge in this embodiment is performed by controlling the first discharge solenoid valve 904, the second discharge solenoid valve 905, and the third discharge solenoid valve 906 using a discharge solenoid valve control circuit 914 and a control unit 915. That is, discharge from the first discharge unit 907 is controlled by the first discharge solenoid valve 904, discharge from the second discharge unit 908 is controlled by the second discharge solenoid valve 905, and discharge from the third discharge unit 909 is controlled by the third discharge solenoid valve 906.

[0054] FIG. 8 shows control signals for the first discharge solenoid valve 904, the second discharge solenoid valve 905, and the third discharge solenoid valve 906 in this embodiment. As shown in FIG. 8 , by controlling the opening and closing of each discharge solenoid valve at different opening and closing timings, liquid can be discharged from each discharge unit in a different discharge pattern. Each discharge solenoid valve in this embodiment is controlled by a discharge solenoid valve control circuit 914. The control of each discharge solenoid valve may be performed by the same control unit 915 or by individual control units 915, and any means is acceptable. Because this embodiment has multiple discharge units, the discharge flow rate is higher than when there is only one discharge unit, and as a result, the liquid delivery volume of the pump 902 under constant pressure control is also larger. Therefore, in this embodiment, it is important to use a pump 902 with a liquid delivery volume commensurate with the number of discharge units.

[0055] In this embodiment, as shown in Figure 8, it is also possible to perform intermittent discharge of liquid by opening and closing the discharge electromagnetic valve at high speed. In such intermittent discharge, an air layer (segmented air) is introduced into the discharged liquid, making it possible to clean an object by liquid discharge alone without causing significant damage to the object. For this reason, the liquid discharge device of this embodiment can be applied as a cleaning mechanism. It goes without saying that the discharge of liquid in this embodiment is not limited to intermittent discharge.

[0056] As described above, in the liquid ejection device of this embodiment, the control unit 915 constantly performs feedback control so that the pressure of the liquid 911 is at the set pressure value (SV), and at the same time, the ejection amount of the liquid 911 from the first ejection unit 907, the second ejection unit 908, and the third ejection unit 909 is controlled by opening and closing the first ejection unit 907, the second ejection unit 908, and the third ejection unit 909 using the ejection solenoid valve control circuit 914. In this embodiment, even when the same type of liquid is used and ejected from multiple ejection units at individual timings, the same effects as in the first embodiment can be obtained.

[0057] (Embodiment 5) In the first embodiment, a liquid ejection device that supplies liquid 307 from liquid container 301 shown in Fig. 1 was described. In this liquid ejection device, if liquid 307 runs out of liquid container 301, pump 302 will no longer be able to eject liquid 307, and the system will have to be shut down. Furthermore, if liquid 307 is to be continuously ejected, it will be necessary to refill liquid container 301 with liquid 307 while the system is stopped, and then perform a reset operation such as removing air bubbles from the flow path so that the liquid can be ejected again, leaving issues with the stability and reliability of the system.

[0058] In this embodiment, a liquid ejection device having multiple liquid containers, a switching electromagnetic valve for switching between the liquid containers, and a liquid detection sensor is described. Figure 9 shows the liquid ejection device of this embodiment. The liquid ejection device of this embodiment includes a liquid container 1101 containing liquid 1111, a liquid container 1102, a liquid detection sensor 1103 for detecting the presence or absence of liquid 1111, a liquid detection sensor 1104, a pump 1105, a pressure sensor 1106, a switching electromagnetic valve 1107, a discharge electromagnetic valve 1108, and a discharge unit 1109. The liquid ejection device of this embodiment also includes a flow path (liquid tube) 1110, a liquid detection sensor processing circuit 1112, a switching electromagnetic valve control circuit 1113, a pump control circuit 1114, a pressure sensor processing circuit 1115, a discharge electromagnetic valve control circuit 1116, and a control unit 1117. The liquid detection sensors 1103 and 1104 detect the presence or absence of liquid in the liquid containers 1101 and 1102, respectively.

[0059] The liquid container 1101 and the switching solenoid valve 1107 are connected via a flow path 1110 in which a liquid detection sensor 1103 is provided. The liquid container 1102 and the switching solenoid valve 1107 are connected via a flow path 1110 in which a liquid detection sensor 1104 is provided. The switching solenoid valve 1107 and the pump 1105 are connected via the flow path 1110. The pump 1105 and the pressure sensor 1106 are connected via the flow path 1110. The pressure sensor 1106 and the discharge portion 1109 are connected via the flow path 1110, and a discharge solenoid valve 1108 is provided in the flow path 1110 between the pressure sensor 1106 and the discharge portion 1109. The control unit 1117 is connected to each of the liquid detection sensor processing circuit 1112, the switching solenoid valve control circuit 1113, the pump control circuit 1114, the pressure sensor processing circuit 1115, and the discharge solenoid valve control circuit 1116. The liquid detection sensor processing circuit 1112 is connected to each of the liquid detection sensors 1103 and 1104, and the switching electromagnetic valve control circuit 1113 is connected to the switching electromagnetic valve 1107. The pump control circuit 1114 is connected to the pump 1105, the pressure sensor processing circuit 1115 is connected to the pressure sensor 1106, and the discharge electromagnetic valve control circuit 1116 is connected to the discharge electromagnetic valve 1108.

[0060] An example of a control flow in the fifth embodiment is shown in FIG. First, the control unit 1117 determines whether the current time is the control cycle of pressure control (step S1201). If the current time is not the control cycle in step S1201, no processing is performed. If the current time is the control cycle in step S1201, used container data is acquired (step S1202). Next, the liquid detection sensor value for the used container type acquired in step S1202 is acquired (step S1203). Then, the integrated value (Val) of the liquid detection sensor value acquired in step S1203 is calculated (step S1204). The purpose of calculating the integrated value of the liquid detection sensor value in step S1203 is to reduce the influence of noise due to sensor chattering, etc., and the number of calculation data points used to calculate the integrated value needs to be optimized based on the periodic characteristics of the noise component.

[0061] Next, the integrated value (Val) calculated in step S1204 is compared with a threshold value to determine whether the conditional expression Val > threshold is true (step S1205). If the conditional expression Val > threshold is true, there is no liquid in the liquid detection sensor unit, so container switching processing (step S1206) and container data rewriting processing after switching (step S1207) are performed, followed by the pressure control described in embodiment 1 (see FIG. 2). On the other hand, if the conditional expression Val > threshold is not true, container switching processing is not performed, and the pressure control described in embodiment 1 (see FIG. 2) is performed. By switching liquid containers in this manner, liquid can be continuously ejected without stopping the system.

[0062] However, this method has the problem that if the liquid runs out at the position of the liquid detection sensor, a container replacement process occurs when the condition is met in which the integrated value (Val) of the liquid detection sensor value exceeds a threshold, and the liquid 1111 contained in the flow path from the liquid detection sensor to the switching electromagnetic valve 1107 becomes dead volume and is discarded without being used for ejection. The amount of dead volume depends on the length of the flow path from the liquid detection sensor to the switching electromagnetic valve 1107, so the longer the flow path in a system, the greater the amount of liquid discarded as dead volume.

[0063] Therefore, FIG. 11 shows a control flow for a discharge system in which the liquid detection sensors 1103 and 1104 are removed from the liquid discharge device shown in FIG. 9 and liquid switching is performed by calculating a remaining liquid amount count value from the open time of the solenoid valve. First, the control unit 1117 determines whether the current time is a pressure control control cycle (step S1301). Next, if the current time is not a control cycle in step S1201, no processing is performed. If the current time is a control cycle in step S1201, used container data is acquired (step S1302). Next, the liquid discharge amount (B) from the previous control cycle for the used container type acquired in step S1302 is acquired (step S1303). Next, a calculation (A - B) is performed to update the remaining liquid amount count value (A) using the liquid discharge amount (B) from the previous control cycle acquired in step S1303 as difference data (step S1304). In other words, the liquid ejection device includes a remaining liquid amount detection unit that acquires the amount of liquid ejected from the previous control cycle for the type of container used and calculates a remaining liquid amount count value. This remaining liquid amount detection unit detects the remaining liquid amount based on the remaining liquid amount count value calculated from the total open time of the ejection solenoid valve.

[0064] Next, a determination is made as to whether the conditional expression A<threshold is satisfied (step S1305), which compares the remaining liquid amount count value (A) calculated in step S1304 with a threshold value. If the conditional expression A<threshold is satisfied, the remaining liquid amount count value (A) is low, so a container switching process (step S1306) and a process for rewriting the container data used after the switch (step S1307) are performed, followed by the pressure control (see FIG. 2) described in the first embodiment. On the other hand, if the conditional expression A<threshold is not satisfied, the remaining liquid amount count value (A) is not low enough to warrant container switching, so the container switching process is not performed, and the pressure control (see FIG. 2) described in the first embodiment is performed.

[0065] In this case, a liquid detection sensor is not required, allowing for liquid switching without increasing system costs. However, when setting a liquid container in the system, the liquid volume must always be set to a constant value to prevent discrepancies between the remaining liquid volume count value and the actual remaining liquid volume, which may increase the workload of the operator. Furthermore, in systems that use a subtraction method using the remaining liquid volume count value, the remaining liquid volume must be set with a margin to prevent the actual remaining liquid volume from being less than the theoretical remaining volume. As a result, the difference between the remaining volume and the theoretical value becomes dead volume, which is discarded without being used for dispensing, which is an issue.

[0066] For example, if the liquid remaining amount count value (A) satisfies A > threshold, that is, the liquid remaining amount count value (A) is not low enough to require changing the container, and the liquid container becomes empty for some reason, the system is unable to detect this abnormal condition because it does not have a means to detect the presence or absence of liquid, such as a liquid detection sensor, and there is a problem that liquid containing air is ejected.

[0067] To solve these problems, in a liquid ejection device having a liquid detection sensor as shown in FIG. 9 , the dead volume problem is reduced by using both the liquid detection sensor reading and the remaining liquid level count value. This reduces the dead volume and enables liquid container switching even in abnormal situations, such as when a liquid suddenly runs out. An example of a control flow is shown in FIG. 12 . First, the control unit 1117 determines whether the current time is a pressure control control cycle (step S1401). Next, if the current time is not a control cycle in step S1401, no processing is performed. If the current time is a control cycle in step S1401, it determines whether the remaining liquid level is being counted (step S1402). If the remaining liquid level is not being counted in step S1402, the liquid detection sensor starts monitoring, and used container data is acquired (step S1403). Next, the liquid detection sensor value for the used container type acquired in step S1403 is acquired (step S1404). Thereafter, an integrated value (Val) of the liquid detection sensor values ​​acquired in step S1404 is calculated (step S1405). The purpose of calculating the integrated value of the liquid detection sensor values ​​in step S1405 is to reduce the influence of chattering in the sensor values, and the number of calculation data points used when calculating the integrated value needs to be optimized based on the periodic characteristics of the chattering, etc.

[0068] Next, the integrated value (Val) calculated in step S1405 is compared with a threshold value to determine whether the conditional expression Val > threshold holds (step S1406). If the conditional expression Val > threshold holds, there is no liquid in the liquid detection sensor, and a remaining liquid amount count is started so that the dead volume of liquid can be effectively used for ejection. Next, the remaining liquid amount count is performed in the following order: a remaining liquid amount set value (R) is obtained (step S1407), a remaining liquid amount count value (A) is initialized (step S1408), and a remaining liquid amount count is started (step S1409). Then, the pressure control (see FIG. 2) described in the first embodiment is performed.

[0069] If the conditional expression Val>threshold value is not satisfied in step S1406, the container switching process is not performed, and the pressure control (see FIG. 2) described in the first embodiment is performed.

[0070] If the remaining liquid amount is being counted in step S1402, the liquid ejection amount (B) from the previous control cycle is acquired (step S1411). Next, a calculation (A-B) is performed to update the remaining liquid amount count value (A) using the liquid ejection amount (B) from the previous control cycle acquired in step S1411 as difference data (step S1412). Next, a determination is made as to whether the conditional expression A<R, which compares the remaining liquid amount count value (A) calculated in step S1412 with the remaining liquid amount set value (R), holds (step S1413). If the conditional expression A<R holds, the remaining liquid amount count value (A) is low, and the following steps are performed in order: a container switching process (step S1414), a process to rewrite the container data used after the switch (step S1415), and a process to end the remaining liquid amount count (step S1416), followed by the pressure control described in the first embodiment (see FIG. 2 ). On the other hand, if the conditional expression A<R is not satisfied, the pressure control explained in the first embodiment (see FIG. 2) is performed.

[0071] As described above, by using the flow shown in Figure 12, under normal circumstances, the liquid container is switched based on the remaining liquid amount count value after the liquid detection sensor detects that the liquid has run out, thereby reducing dead volume and realizing a liquid ejection device that minimizes the amount of liquid wasted when switching containers. Also, even in an abnormal situation where the liquid container suddenly runs out of liquid, the liquid container is switched based on the remaining liquid amount count value from that point on, just like under normal circumstances, thereby reducing dead volume and realizing a liquid ejection device that is highly reliable.

[0072] In the first embodiment, it was explained that it is effective to use a deformable, flexible bag-type container as the liquid container. Since it is very difficult to install a liquid level sensor inside such a bag-type container, it is difficult to imagine using a liquid level sensor to detect the remaining amount of liquid in the liquid container. Therefore, when a flexible bag-type container or the like is used as the liquid container, this embodiment, which has a detection unit outside the liquid container, has an advantageous effect.

[0073] As described above, in this embodiment, the control unit 1117 constantly performs feedback control to ensure that the pressure of the liquid 1111 is at the set pressure value (SV), while at the same time monitoring the remaining amount in the liquid container 1101 and the liquid container 1102 and switching the containers, thereby continuously controlling the discharge amount without running out of the liquid 1111.

[0074] The invention made by the present inventors has been specifically described above based on the embodiments thereof, but the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention.

[0075] The present invention can be widely used in liquid ejection devices.

[0076] 301 Liquid container 302 Pump 303 Pressure sensor 304 Discharge solenoid valve 305 Discharge section 306 Flow path (liquid tube) 306 Flow path 307 Liquid 308 Pump control circuit 309 Pressure sensor processing circuit 310 Discharge solenoid valve control circuit 311 Control section

Claims

1. a pump for pumping the liquid in the liquid container; a discharge unit that discharges the liquid; a pressure sensor for monitoring the pressure of the liquid; a discharge electromagnetic valve for controlling the discharge of the liquid in the discharge portion; a control unit that controls the pressure of the liquid to be constant; a flow path for the liquid that connects the pump, the discharge portion, the pressure sensor, and the discharge electromagnetic valve to one another; and the control unit acquires a set pressure value SV, acquires a current pressure value PV measured by the pressure sensor, and calculates a deviation τ (=SV-PV), and when the absolute value of the deviation τ is |τ|>threshold, if τ>0, performs pressurization control by sending liquid in the direction of the discharge unit using the pump, and performs depressurization control by sending liquid in the direction of the liquid container using the pump if τ>0 is not satisfied; The liquid ejection device controls the amount of liquid ejected by adjusting the opening and closing time of the ejection electromagnetic valve while the pressure of the liquid is controlled to a constant value by the control unit.

2. The liquid ejection device according to claim 1 , The liquid ejection device, wherein the flow path is a closed flow path having a structure in which the liquid does not come into direct contact with air.

3. The liquid ejection device according to claim 1 , A plurality of the discharge portions; the number of the discharge electromagnetic valves is the same as the number of the discharge portions; and A liquid ejection device that independently controls the amount of liquid ejected from each of the plurality of ejection sections.

4. The liquid ejection device according to claim 1 , The liquid ejection device, wherein the pump is capable of switching the liquid delivery direction under external control.

5. 5. The liquid ejection device according to claim 4, The liquid ejection device, wherein the pump is a peristaltic pump having a structure that prevents the liquid from coming into direct contact with air.

6. A pump for delivering a liquid; a discharge unit that discharges the liquid; a pressure sensor for monitoring the pressure of the liquid; a discharge electromagnetic valve for controlling the discharge of the liquid in the discharge portion; a control unit that controls the pressure of the liquid to be constant; a flow path for the liquid that connects the pump, the discharge portion, the pressure sensor, and the discharge electromagnetic valve to one another; a reflux flow path provided within the flow path; a reflux electromagnetic valve for controlling the reflux flow path; and a control unit for controlling the pressure of the liquid to a constant value, and a control unit for controlling the amount of liquid discharged by adjusting the opening and closing time of the discharge electromagnetic valve; The liquid ejection device controls the amount of liquid sent to the reflux channel by the pump, thereby controlling the pressure increase and decrease in the channel.

7. 7. The liquid ejection device according to claim 6, The liquid ejection device, wherein the reflux solenoid valve is capable of continuously controlling the internal orifice diameter.

8. The liquid ejection device according to claim 1 , A liquid ejection device that has a disturbance detection unit and performs control using a control amount that corrects the influence of disturbances on a pump control amount in constant pressure control, thereby reducing the influence of disturbances on a control system.

9. 9. The liquid ejection device according to claim 8, The disturbance detection unit determines whether there is opening / closing control of the discharge solenoid valve within the next control cycle, and if there is opening / closing control, controls the pump using a control amount that corrects the influence of disturbances on the pump control amount under constant pressure control.

10. The liquid ejection device according to claim 1 , a plurality of liquid containers; a switching electromagnetic valve for switching between the plurality of liquid containers; a detector for detecting the remaining amount of liquid in each of the plurality of liquid containers, or a detector for detecting the presence or absence of the liquid in the flow path; A control unit; and the control unit calculates an integrated value Val of the liquid detection sensor values ​​for each of the plurality of liquid containers; A liquid ejection device in which the control unit determines that a liquid container for which Val > threshold is out of liquid and switches the switching solenoid valve from that liquid container to a liquid container containing the liquid, thereby allowing the liquid to be ejected continuously without stopping the system.

11. The liquid ejection device according to claim 10, The liquid ejection device, wherein the liquid presence / absence detection unit is a liquid detection sensor.