Ozone water production device

Abstract

The present invention provides an ozone water production device capable of rapidly converging ozone concentration to a target concentration. A control unit (80) performs stop control after switching from stop control to supply control when ozone concentration C exceeds a first threshold value C1 via a decreasing inflection point lower than a target concentration Cset. The first threshold value C1 is a value between the minimum value Cmin and the target concentration Cset, obtained based on the target concentration Cset and a minimum value Cmin of the ozone concentration corresponding to the decreasing inflection point.

Description

Technical Field

[0001] The present disclosure relates to an ozone water production device. Background Art

[0002] There is known an ozone water production apparatus that generates ozone water and supplies the generated ozone water to a predetermined target.

[0003] The ozone water production device disclosed in Patent Document 1 includes an ozone generator, an ejector, and a tank. Ozone gas generated by the ozone generator mixes with water flowing through a liquid flow path in the ejector. In the ejector, the ozone gas dissolves in the water, producing ozone water. The ozone water is stored in the tank. The ozone water in the tank is supplied to a predetermined destination via a supply path.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-153727 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] The ozone water production device described in Patent Document 1 adjusts the ozone concentration of ozone water supplied to a target. Specifically, an on-off valve is installed in the gas flow path of the ozone generator. An ozone concentration sensor is installed in the supply path. A control unit controls the on-off valve so that the ozone concentration detected by the ozone concentration sensor converges to a predetermined target concentration.

[0009] However, in such control, there is a problem that the ozone concentration cannot converge to the target concentration. Figure 9 Detailed description is given. Figure 9 In the graph, the horizontal axis is time, and the vertical axis is the ozone concentration C detected by the ozone concentration sensor. Figure 9 The white circle mark indicates the start of supply control, and the × mark indicates the start of stop control.

[0010] When the ozone generator begins operation, supply control is executed at point p1. During supply control, the on-off valve opens, supplying ozone gas to the supply path. When supply control begins, the ozone concentration C gradually increases. At point p2, when the ozone concentration C reaches the target concentration Cset, stop control is executed. During stop control, the on-off valve closes, stopping the supply of ozone gas to the supply path. However, there is a time delay between the start of stop control and the decrease in ozone concentration C. As a result, the ozone concentration C significantly exceeds the target concentration Cset, increasing the magnitude of the overshoot.

[0011] Afterward, the ozone concentration C decreases, and at point p3, when it reaches the target concentration Cset, supply control is resumed. However, there is a time lag between the start of supply control and the rise in ozone concentration. Furthermore, the ozone in the ozone water is consumed by a so-called autolysis reaction. Autolysis is a chain reaction in which ozone reacts with, for example, OH radicals or superoxide radicals, resulting in a decomposition reaction. Therefore, even at point p3, despite the execution of stop control, the ozone concentration C remains significantly below the target concentration Cset, increasing the magnitude of the undershoot.

[0012] As mentioned above, in Figure 9 In the control of the comparative example shown, the ozone concentration C has a relatively large underrange and overrange. Therefore, the ozone concentration C cannot converge to the target concentration Cset, and there is a problem that the ozone concentration fluctuates greatly from the desired ozone concentration.

[0013] The present disclosure has been made in view of the above-mentioned points, and an object of the present disclosure is to provide an ozone water production apparatus capable of quickly converging the ozone concentration to a target concentration.

[0014] Solutions for solving technical problems

[0015] In order to solve the above-mentioned technical problem, the control unit (80) of the present disclosure performs stop control when the ozone concentration C exceeds a first threshold value C1 specified between the minimum value Cmin and the target concentration Cset after switching from stop control to supply control. In the present disclosure, stop control is performed when the ozone concentration C exceeds the first threshold value C1 which is lower than the target concentration Cset. Therefore, stop control can be performed at an earlier timing than in the above-mentioned comparative example, thereby reducing the extent of the overshoot of the ozone concentration C.

[0016] In order to solve the above-mentioned technical problem, the control unit (80) of the present disclosure performs supply control when the ozone concentration C falls below a predetermined second threshold value C2 between the maximum value Cmax and the target concentration Cset after switching from supply control to stop control. In the present disclosure, supply control is performed when the ozone concentration C falls below the second threshold value C2 which is higher than the target concentration Cset. Therefore, supply control can be performed at an earlier timing than in the above-mentioned comparative example, thereby reducing the magnitude of the undershoot of the ozone concentration C.

[0017] The first threshold value C1 is preferably represented by the relational expression C1 = Cset - (Cset - Cmin) × α (0 < α < 1). This relational expression allows the first threshold value C1 to be a value lower than the target concentration Cset.

[0018] The second threshold value C2 is preferably expressed by the relational expression C2 = Cset + (Cmax - Cset) x β (0 < β < 1). This relational expression allows the second threshold value C2 to be a value higher than the target concentration Cset.

[0019] β can be made smaller than α. The rate of the ozone gas autodecomposition reaction tends to be slower than the rate at which ozone gas is supplied from the ozone generator to the supply path. Therefore, if β is too large, there is a possibility that the ozone concentration C will not reach the target concentration Cset after supply control begins. In contrast, by making β lower than α, the second threshold value becomes relatively low. This can prevent the ozone concentration C from falling below the target concentration Cset.

[0020] Effects of the Invention

[0021] According to the present disclosure, the first threshold C1 for executing the stop control is lower than the target concentration Cset, allowing the stop control to be executed at a relatively early timing. This reduces the extent of ozone concentration overshoot and allows the ozone concentration C to converge quickly to the target concentration Cset. The first threshold C1 is determined based on the minimum value Cmin corresponding to the downward inflection point of the ozone concentration C and the target concentration Cset. This prevents the first threshold C1 from being too low or too high.

[0022] According to the present disclosure, the second threshold C2 for executing supply control is higher than the target concentration Cset, allowing supply control to be executed at a relatively early timing. This reduces the magnitude of ozone concentration undershoot and allows the ozone concentration C to converge quickly to the target concentration Cset. The second threshold C2 is determined based on the maximum value Cmax corresponding to the rising inflection point of the ozone concentration C and the target concentration Cset. This prevents the second threshold C2 from being too low or too high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a piping system diagram showing a schematic configuration of an ozone water production apparatus according to an embodiment.

[0024] Figure 2 This is an overall flow chart of ozone concentration control according to the embodiment.

[0025] Figure 3 This is a graph showing the relationship between ozone concentration and time in ozone concentration control according to the embodiment.

[0026] Figure 4 This is a flowchart of supply control according to the embodiment.

[0027] Figure 5 This is a flowchart of the stop control according to the embodiment.

[0028] Figure 6This is used to explain the control when ozone concentration continues to rise. Figure 3 The corresponding coordinate diagram.

[0029] Figure 7 This is used to explain the control when the ozone concentration continues to decrease. Figure 3 The corresponding coordinate diagram.

[0030] Figure 8 This is a piping system diagram showing a schematic configuration of an ozone water production apparatus according to Modification 2.

[0031] Figure 9 It is a graph showing the relationship between ozone concentration and time in ozone concentration control according to a comparative example. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments are merely preferred examples in nature and do not limit the scope of the present invention, its applications, or its uses.

[0033] Implementation Methods

[0034] The ozone water production device (1) of the embodiment generates ozone water and supplies the generated ozone water to a predetermined object. The predetermined object is, for example, a semiconductor manufacturing plant. Figure 1 As shown, the ozone water production device (1) includes: a gas flow path (10) having an ozone generator (20); and a liquid flow path (30) having a tank (44), an ejector (35) and a pump (45).

[0035] <Gas Flow Path>

[0036] An ozone generator (20) is provided in the gas flow path (10). The ozone generator (20) is a discharge-type ozone generator. The ozone generator (20) uses oxygen as a raw material and generates ozone gas by generating discharge in the oxygen.

[0037] The gas flow path (10) includes a gas supply path (11) and a gas exhaust path (12). The inflow end of the gas supply path (11) is connected to the ozone generator (20). The outflow end of the gas supply path (11) is connected to the gas suction portion (35c) of the ejector (35). The gas exhaust path (12) branches off from the gas supply path (11).

[0038] A first gas on-off valve (13) is provided in the gas supply path (11). The first gas on-off valve (13) is provided on the downstream side of a branch portion of the gas discharge path (12) in the gas supply path (11). The first gas on-off valve (13) opens and closes the gas supply path (11).

[0039] A second gas on-off valve (14) is provided in the gas discharge passage (12). The second gas on-off valve (14) opens and closes the gas discharge passage (12). The ozone gas discharged from the gas discharge passage (12) is processed by, for example, an ozone decomposition device (not shown).

[0040] <Overall Structure of Liquid Flow Path>

[0041] The liquid flow path (30) includes a water supply path (31), a supply path (40), a first return path (60), and a second return path (70). The water supply path (31) is a path for supplying raw water to the liquid flow path (30). It should be noted that the raw water can be any liquid with water as the main component, or a liquid containing other components (such as carbonated water). The supply path (40) is a path for supplying ozone water to an object. The first return path (60) is a path for returning the ozone water in the supply path (40) to the upstream side of the ejector (35). The second return path (70) is a path for returning the ozone water to the tank (44).

[0042] <Water supply route>

[0043] The inflow end of the water supply path (31) is connected to the raw water supply source. The outflow end of the water supply path (31) is connected to the liquid inflow portion (35a) of the ejector (35). In the water supply path (31), a water supply side opening and closing valve (32) and a first flow sensor (33) are sequentially arranged from the upstream side toward the downstream side. The water supply side opening and closing valve (32) opens and closes the water supply path (31). The water supply side opening and closing valve (32) is composed of, for example, a pneumatic valve. The first flow sensor (33) measures the flow rate of water flowing in the water supply path (31). It should be noted that the "water" mentioned in the following description refers to water containing ozone.

[0044] <Injector>

[0045] The ejector (35) has a liquid inlet (35a), a liquid outflow (35b) and a gas suction (35c). The liquid inlet (35a) is connected to the outflow end of the water supply path (31). The liquid inlet (35a) is connected to the inflow end of the supply path (40). The gas suction (35c) is connected to the outflow end of the gas supply path (11). A nozzle, a mixing section and a diffuser section (not shown) are provided inside the ejector (35). In the ejector (35), when the water flowing from the liquid inlet (35a) flows in the nozzle, the flow rate of the water is accelerated. In the nozzle, the water is decompressed by the throttling section at its front end. In the nozzle, the ozone gas is drawn from the gas suction section to the mixing section due to the pressure difference between the water before and after the nozzle. The drawn ozone gas is mixed with water in the mixing section. In the mixing section, the ozone gas dissolves in the water to generate ozone water of a specified concentration. The ozone water flows through the diffuser portion, where the flow path cross section gradually expands, and after being pressurized, flows out from the liquid outflow portion (35b) to the supply path (40).

[0046] <Supply route>

[0047] The supply path (40) includes a first tube (41), a second tube (42), and a third tube (43). The inflow end of the first tube (41) is connected to the liquid outflow portion (35b) of the ejector (35). The outflow end of the first tube (41) is connected to the tank (44). The inflow end of the second tube (42) is connected to the tank (44). The outflow end of the second tube (42) is connected to the inflow end of the first return flow path (60), the inflow end of the second return flow path (70), and the inflow end of the third tube (43). The outflow end of the third tube (43) is connected to a specified object. The second tube (42) is provided with a pump (45), an ozone concentration sensor (46), and a pressure sensor (47) in sequence from its upstream end to its downstream side. The third tube (43) is provided with a second flow sensor (48) and a supply side opening and closing valve (49) in sequence from its upstream side to its downstream side.

[0048] The tank (44) is a hollow container. The tank (44) temporarily stores water. The ozone gas remaining in the tank (44) is discharged to the outside of the tank (44) as waste ozone. The discharged waste ozone is processed by an ozone decomposition device (not shown).

[0049] The tank (44) is provided with a level sensor (50) for detecting the water level in the tank (44). The level sensor (50) can detect at least two levels of water levels, L and H. The level sensor (50) corresponds to a water level detection unit.

[0050] The pump (45) delivers water to the supply path (40).

[0051] The ozone concentration sensor (46) detects the ozone concentration of the water (ozone water) in the supply path (40). The ozone concentration sensor (46) corresponds to a detection unit. A signal indicating the ozone concentration detected by the ozone concentration sensor (46) is output to the control unit (80).

[0052] The pressure sensor (47) detects the pressure of water in the supply path (40) (strictly speaking, the second pipe (42)).

[0053] The second flow sensor (48) detects the flow rate of water in the supply path (40) (strictly speaking, the third pipe (43)).

[0054] The supply-side on-off valve (49) opens and closes the supply passage (40) (strictly speaking, the third pipe (43)). The supply-side on-off valve (49) is composed of, for example, an air-operated valve.

[0055] <First return flow path>

[0056] The inflow end of the first return flow path (60) is connected to the outflow end of the second pipe (42). The outflow end of the first return flow path (60) is connected to the water supply path (31). A flow control valve (61) is provided in the first return flow path (60). The flow control valve (61) controls the flow rate of water flowing in the first return flow path (60). Here, the flow rate of water regulated by the flow control valve (61) also includes 0. In this case, the flow control valve (61) is in a fully closed state.

[0057] <Second return flow path>

[0058] The inflow end of the second return flow path (70) is connected to the outflow end of the second pipe (42). The outflow end of the second return flow path (70) is connected to the tank (44). A first back pressure valve (71) is provided in the second return flow path (70). The first back pressure valve (71) is a pressure regulating valve that regulates the water pressure of the second return flow path (70) or the supply path (40) to be constant.

[0059] <Control Unit>

[0060] like Figure 1 As shown schematically, the ozone water production device (1) includes a control unit (80). The control unit (80) includes a microcomputer and a storage device (specifically, a semiconductor memory) storing software for operating the microcomputer. The control unit (80) includes an input unit to which a detection signal or the like is input and an output unit to which a control signal or the like is output.

[0061] exist Figure 1Although not shown in the figure, the water levels (L and H) detected by the level sensor (50) are input to the input unit of the control unit (80). The control unit (80) controls the water supply side on-off valve (32) based on the water level detected by the level sensor (50). Specifically, when the water level detected by the level sensor (50) reaches L, the control unit (80) opens the water supply side on-off valve (32). When the water supply side on-off valve (32) becomes open, raw water is replenished to the tank (44). Then, when the water level detected by the level sensor (50) reaches H, the control unit (80) closes the water supply side on-off valve (32). When the water supply side on-off valve (32) becomes closed, the supply of raw water to the tank (44) stops.

[0062] exist Figure 1 Although not shown in the figure, the control unit (80) switches the operation and stop of the ozone generating device (20). In addition, the control unit (80) switches the open and closed state of the supply side opening and closing valve (49).

[0063] The ozone concentration C detected by the ozone concentration sensor (46) is input to an input unit of the control unit (80). The control unit (80) controls at least the first gas on-off valve (13) so that the ozone concentration C detected by the ozone concentration sensor (46) converges to the target concentration Cset. The control unit (80) alternately switches between supply control and stop control. The supply control is a control for supplying ozone gas from the ozone generator (20) to the supply path (40). The stop control is a control for stopping the supply of ozone gas from the ozone generator (20) to the supply path (40).

[0064] The control unit (80) has a storage unit. The storage unit stores a target concentration Cset, a lower threshold value C1, an upper threshold value C2, a minimum value Cmin, and a maximum value Cmax. In the storage unit, these parameters are appropriately updated. The target concentration Cset is a target value of the ozone concentration C supplied to the object. The lower threshold value C1 is a judgment value for determining whether to switch from supply control to stop control. The lower threshold value C1 corresponds to a first threshold. The upper threshold value C2 is a judgment value for determining whether to switch from stop control to supply control. The upper threshold value C2 corresponds to a second threshold. The minimum value Cmin is the ozone concentration C corresponding to the falling inflection point within a range lower than the target concentration Cset in the supply control. The maximum value Cmax is the ozone concentration C corresponding to the rising inflection point within a range higher than the target concentration Cset in the stop control.

[0065] After switching from stop control to supply control, the control unit (80) executes stop control when the ozone concentration C exceeds a first threshold value C1. The first threshold value C1 is a value between the minimum value Cmin and the target concentration Cset. The calculation unit of the control unit (80) calculates the first threshold value C1 using the following formula (1).

[0066] C1=Cset-(Cset-Cmin)×α(0<α<1)····(1)

[0067] α only needs to be greater than 0 and less than 1. Preferably, α is greater than 0.2 and less than 0.8. More preferably, α is greater than 0.3 and less than 0.7. Further preferably, α is greater than 0.4 and less than 0.8. Most preferably, α is 0.5. The control unit (80) has a setting unit for appropriately changing α. The initial setting value of α is 0.5.

[0068] After switching from supply control to stop control, when the ozone concentration C is lower than a second threshold value C2, the control unit (80) performs supply control. The second threshold value C2 is a value between the maximum value Cmax and the target concentration Cset. The calculation unit of the control unit (80) calculates the second threshold value C2 using the following formula (2).

[0069] C2=Cset+(Cmax-Cset)×β(0<β<1)····(2)

[0070] β only needs to be greater than 0 and less than 1. Preferably, β is greater than 0.2 and less than 0.8. More preferably, β is greater than 0.3 and less than 0.7. Further preferably, β is greater than 0.4 and less than 0.8. Most preferably, β is 0.5. The control unit (80) has a setting unit for appropriately changing β. The initial setting value of β is 0.5.

[0071] -Operational work-

[0072] Regarding the operation of the ozone water production device (1), refer to Figure 1 Provide explanation.

[0073] When the ozone water production device (1) is in operation, the control unit (80) operates the ozone generator (20). In the ozone generator (20), silent discharge is performed between the electrode pair. The control unit (80) opens the supply-side on-off valve (49). The pump (45) is in operation.

[0074] When silent discharge is performed by the ozone generator (20), ozone gas of a specified concentration is generated. The ozone gas generated by the ozone generator (20) flows in the gas supply path (11) and is transported to the gas suction part (35c) of the ejector (35). When the pump (45) is operated, water in the first return flow path (60) is transported to the liquid inlet (35a) of the ejector (35) via the water supply path (31). In the ejector (35), the ozone gas sucked by the gas suction part (35c) mixes with the water flowing into the liquid inlet (35a), and the ozone gas dissolves in the water. The ozone water in the ejector (35) is transported to the tank (44) via the first pipe (41) and temporarily stored in the tank (44).

[0075] The ozone water in the tank (44) is delivered to the flow target through the second pipe (42) and the third pipe (43) in this order. A portion of the ozone water in the second pipe (42) is returned to the water supply path (31) via the first return flow path (60). The total amount of water supplied to the target and the amount of water flowing through the first return flow path (60) may be greater than the amount of water flowing through the second pipe (42). In this case, the remaining ozone water in the second pipe (42) is returned to the tank (44) via the second return flow path (70).

[0076] <Control of ozone concentration>

[0077] During the operation of the ozone generating device (20), the control unit (80) performs control to make the ozone concentration C converge to the target concentration Cset (hereinafter referred to as ozone concentration control). Figures 2 to 7 Provide explanation.

[0078] <Basic process of ozone concentration control>

[0079] like Figure 2 As shown, when the operation of the ozone water production device (1) starts, ozone concentration control is performed. In step ST1, the control unit (80) sets the lower threshold C1, the upper threshold C2, the minimum value Cmin and the maximum value Cmax to the target concentration Cset (for example, 20 ppm).

[0080] In step ST2, the control unit (80) determines whether an instruction to terminate the operation of the ozone water production device (1) is received. If the instruction to terminate the operation is input to the input unit of the control unit (80), the control unit (80) terminates the ozone concentration control. Otherwise, step ST3 is executed.

[0081] In step ST3, the control unit (80) performs supply control. In the supply control, the control unit (80) opens the first gas on-off valve (13). Furthermore, the control unit (80) closes the second gas on-off valve (14). In this state, ozone gas generated by the ozone generator (20) is supplied to the supply path (40).

[0082] In step ST4, the control unit (80) performs stop control. In the stop control, the control unit (80) closes the first gas on-off valve (13). Furthermore, the control unit (80) opens the second gas on-off valve (14). In this state, the supply of ozone gas from the ozone generator (20) to the supply path (40) is stopped. The remaining ozone gas generated by the ozone generator (20) flows through the gas exhaust path (12) and is decomposed by, for example, an ozone decomposition device.

[0083] When step ST4 is completed, step ST2 is executed again. As described above, the control unit (80) alternately repeats the supply control (step ST3) and the stop control (step ST4) until an instruction to end the operation is input.

[0084] <Initial Supply Control>

[0085] After the ozone water production device (1) starts operating, the initial supply control is performed. Figure 4 As shown, when the supply control starts, in step ST31, the control unit (80) opens the first gas on-off valve (13). In step ST32, the control unit (80) closes the second gas on-off valve (14). As a result, the ozone gas generated by the ozone generator (20) is supplied to the supply path (40).

[0086] like Figure 3 As shown, in the initial supply control, the ozone concentration C gradually increases from the state of point a1 (ozone concentration C=0). Before the ozone concentration C reaches point a2 (target concentration Cset), the ozone concentration C is lower than the target concentration Cset. Therefore, in step ST32, the control unit (80) determines that the ozone concentration C is lower than the target concentration Cset. In this case, step ST34 is executed. In step ST34, the control unit (80) sets the maximum value Cmax and the lower threshold value C1 to the target concentration Cset (for example, 20 ppm).

[0087] In step ST35, the control unit (80) determines whether the ozone concentration C is higher than the lower threshold value C1. The lower threshold value C1 is set to the target concentration Cset (e.g., 20 ppm) in step ST1. Therefore, when the ozone concentration is higher than point a2, the condition of step ST35 is met and the supply control ends.

[0088] <Stop Control After Initial Supply Control>

[0089] When the initial supply control ends, stop control is executed. Figure 5 As shown, when the stop control starts, in step ST41, the control unit (80) closes the first gas on-off valve (13). In step ST41, the control unit (80) opens the second gas on-off valve (14). As a result, the ozone gas generated by the ozone generator (20) is not supplied to the supply path (40).

[0090] In step ST42, the control unit (80) determines whether the ozone concentration C is higher than the target concentration Cset. When the first gas on-off valve (13) is closed, the supply of ozone gas to the supply path (40) is stopped. However, a time delay occurs between the cessation of the ozone gas supply and the decrease in the ozone concentration C. Due to this time delay, the ozone concentration C further increases immediately after the ozone gas supply is stopped at point a2. As a result, the condition of step ST42 is met, and step ST44 is executed.

[0091] In step ST44, the control unit (80) sets the minimum value Cmin and the upper threshold value C1 as the target concentration Cset (for example, 20 ppm).

[0092] In step ST45, the control unit (80) determines whether the ozone concentration C is lower than the upper threshold value C2. In the previous supply control step ST34, the upper threshold value C2 was set to the target concentration (e.g., 20 ppm). Therefore, if the ozone concentration C is higher than the target concentration Cset at point a2, the condition of step ST45 is not met, and step ST46 is executed.

[0093] In step ST46, the control unit (80) determines whether the ozone concentration C is higher than the maximum value Cmax. In the previous supply control step ST34, the maximum value Cmax is set as the target concentration Cset (for example, 20 ppm). Therefore, if the ozone concentration C is higher than the target concentration Cset at point a2, the condition of step ST46 is met, and step ST47 is executed.

[0094] In step ST47, the control unit (80) updates the maximum value Cmax to the current ozone concentration C. Next, in step ST48, the control unit (80) calculates the Upper threshold value C2 based on the above formula (2). Next, the process returns to step ST45.

[0095] Steps ST46 and ST47 are repeatedly executed until the ozone concentration C reaches an upward inflection point.

[0096] After a certain time has passed since the first gas on-off valve (13) was closed, the ozone concentration C reaches the rising inflection point at point a3 and then decreases. While the ozone concentration C is between points a2 and a3, the condition of step ST45 is not satisfied.

[0097] If ozone concentration C falls below the rising inflection point (maximum value Cmax) at point a3, the condition of step ST46 is not met. Therefore, steps ST47 and ST48 are skipped, and step ST45 is executed. In other words, after ozone concentration C passes the rising inflection point (point a3), maximum value Cmax and upper threshold value C2 are not updated or calculated.

[0098] Then, when the ozone concentration C falls below the upper threshold value C2, that is, point a4, the condition of step ST45 is satisfied. As a result, the stop control ends and the supply control is executed again.

[0099] <Supply Control After Second Time>

[0100] When the initial stop control ends, the second supply control is executed, and ozone gas is supplied to the supply path (40) again in step ST31. However, a time delay occurs between the start of ozone gas supply and the rise in ozone concentration C. Furthermore, the ozone concentration C of the ozone water supplied to the supply path (40) decreases rapidly due to the so-called autodecomposition reaction. Therefore, at point a4, immediately after the start of ozone gas supply, the ozone concentration C further decreases.

[0101] While the ozone concentration C is between point a4 and point a5 (target concentration Cset), the condition of step ST32 is not satisfied, and step ST33 is executed. In step ST33, the control unit (80) determines whether the ozone concentration C is higher than the maximum value Cmax. The ozone concentration C between point a4 and point a5 is lower than the maximum value Cmax. It should be noted that the maximum value Cmax mentioned here corresponds to the maximum value (point a3) obtained in the previous stop control. Therefore, the condition of step ST33 is not satisfied, and step ST32 is executed again.

[0102] Then, when the ozone concentration C decreases below the target concentration Cset at point a5, the condition of step ST32 is satisfied and step ST34 is executed. In step ST34, the control unit (80) sets the maximum value Cmax and the upper threshold value C2 to the target concentration Cset (e.g., 20 ppm).

[0103] In step ST35, the control unit (80) determines whether the ozone concentration C is higher than the lower threshold value C1. In the previous stop control step ST44, the lower threshold value C1 was set to the target concentration (e.g., 20 ppm). Therefore, if the ozone concentration C is lower than the target concentration Cset at point a5, the condition of step ST35 is not met, and step ST36 is executed.

[0104] In step ST36, the control unit (80) determines whether the ozone concentration C is lower than the minimum value Cmin. In the immediately preceding stop control step ST44, the minimum value Cmin is set to the target concentration Cset (e.g., 20 ppm). Therefore, if the ozone concentration is lower than the target concentration Cset at point a5, the condition of step ST36 is met, and step ST37 is executed.

[0105] In step ST37, the control unit (80) updates the minimum value Cmin to the current ozone concentration C. Next, in step ST38, the control unit (80) calculates the Lower threshold value C1 based on the above formula (1). Next, the process returns to step ST35.

[0106] Steps ST36 and ST37 are repeatedly executed until the ozone concentration C reaches a decreasing inflection point.

[0107] After a certain time has passed since the first gas on-off valve (13) was opened, the ozone concentration C reaches a decreasing inflection point at point a6 and then increases. While the ozone concentration C is between points a5 and a6, the condition of step ST35 is not satisfied.

[0108] If ozone concentration C falls below the downward inflection point (minimum value Cmin) at point a6, the condition of step ST36 is no longer met. Therefore, steps ST37 and ST38 are skipped, and step ST35 is executed. In other words, after ozone concentration C passes the downward inflection point (point a6), minimum value Cmin and lower threshold value C1 are not updated or calculated.

[0109] Then, when the ozone concentration C rises above the lower threshold value C1, i.e., point a7, the condition of step ST35 is satisfied. As a result, the supply control ends and the stop control is executed again. The subsequent stop control and supply control are as described above. The control unit (80) repeats the stop control and supply control alternately until the input Figure 2 The result is that the operation of step ST2 ends. Figure 3 As shown, the ozone concentration C quickly converges to the target concentration Cset.

[0110] <Control Example When Ozone Concentration Does Not Converge to Target Concentration During Supply Control>

[0111] As described above, after switching from supply control to stop control, when the ozone concentration C passes the rising inflection point and decreases below the Upper threshold value C2, the control unit (80) performs supply control. However, depending on the operating conditions or the set value of β, there is a possibility that the ozone concentration C is not too low during supply control and does not reach the target concentration Cset. Therefore, in such a case, the control unit (80) ends the supply control and performs stop control. For this control, refer to Figure 4 and Figure 6 Provide explanation.

[0112] When the ozone concentration C is higher than Figure 6 When the Upper threshold C2 of point b1 decreases, the supply control is executed. Due to the influence of time delay, the ozone concentration C further decreases. In this case, the condition of step ST32 is not met, and step ST33 is executed. Figure 6 As shown, when the decreasing inflection point (point b2) of the ozone concentration C is higher than the target concentration Cset, the condition of step ST32 is not satisfied, and the processing after step ST34 is not performed.

[0113] In this case, the ozone concentration C rises further and exceeds the maximum value Cmax. Here, the maximum value Cmax is the value obtained in the previous stop control. In this case, the condition of step ST33 is met, and the supply control ends. Next, the stop control is executed.

[0114] As described above, after switching from stop control to supply control, when the ozone concentration C increases above the maximum value Cmax of the previous stop control, the control unit (80) terminates the supply control and executes the stop control. This control can reliably prevent the ozone concentration C from continuing to rise without converging to the target concentration Cset.

[0115] <Control Example When the Ozone Concentration Does Not Converge to the Target Concentration During Stop Control>

[0116] As described above, after switching from stop control to supply control, when the ozone concentration C increases beyond the lower threshold value C1 via the falling inflection point, the control unit (80) executes stop control. However, depending on the operating conditions or the set value of α, there is a possibility that the ozone concentration C is not high enough during stop control and does not reach the target concentration Cset. Therefore, in such a case, the control unit (80) ends the stop control and executes the supply control. For this control, refer to Figure 5 and Figure 7 Provide explanation.

[0117] When the ozone concentration C is higher than Figure 7When the Lower threshold C1 of point d1 rises, stop control is executed. Ozone concentration C rises further due to the influence of time delay. In this case, the condition of step ST42 is not met, and step ST43 is executed. Figure 7 As shown, when the rising inflection point (point d2) of the ozone concentration C is lower than the target concentration Cset, the condition of step ST43 is not satisfied, and the processing after step ST44 is not performed.

[0118] In this case, the ozone concentration C further decreases and falls below the minimum value Cmin. Here, the minimum value Cmin is the value obtained in the previous supply control. In this case, the condition of step ST43 is met, and the stop control ends. Next, the supply control is executed.

[0119] As described above, after switching from supply control to stop control, when the ozone concentration C decreases below the minimum value Cmin of the previous stop control, the control unit (80) ends the stop control and executes the supply control. This control can reliably prevent the ozone concentration C from continuing to decrease without converging to the target concentration Cset.

[0120] -Effects of Implementation Methods-

[0121] In the stop control, the Upper threshold C2 for determining the execution of the supply control is obtained based on the maximum value Cmax and the target concentration Cset. The Upper threshold C2 is a value between the maximum value Cmax and the target concentration Cset. The Upper threshold C2 is higher than the target concentration Cset, so the supply control can be executed quickly. Since the Upper threshold C2 is lower than the maximum value Cmax, it is possible to avoid the undesirable situation that the ozone concentration C does not reach the target concentration Cset. As a result, Figure 9 Compared with the comparative example shown, the width of the undershoot of the ozone concentration C can be reduced, and the ozone concentration C can be quickly converged to the target concentration Cset.

[0122] In particular, by setting β to 0.5, the Upper threshold C2 becomes a value intermediate between the maximum value Cmax and the target concentration Cset. This prevents situations where the Upper threshold C2 is excessively low, preventing the undershoot from being sufficiently reduced. This reliably avoids situations where the ozone concentration C fails to reach the target concentration Cset due to an excessive increase in the Upper threshold C2.

[0123] In the supply control, the Lower threshold C1 for determining whether to execute the stop control is determined based on the minimum value Cmin and the target concentration Cset. The Lower threshold C1 is a value between the minimum value Cmin and the target concentration Cset. Since the Lower threshold C1 is lower than the target concentration Cset, the stop control can be executed quickly. Since the Lower threshold C1 is higher than the minimum value Cmin, it is possible to avoid the undesirable situation that the ozone concentration C does not reach the target concentration Cset. As a result, Figure 9 Compared with the comparative example shown, the width of the undershoot of the ozone concentration C can be reduced, and the ozone concentration C can be quickly converged to the target concentration Cset.

[0124] In particular, by setting β to 0.5, the Lower threshold C1 becomes a value intermediate between the minimum value Cmin and the target concentration Cset. This prevents situations where the Lower threshold C1 is excessively high and the magnitude of the overshoot cannot be sufficiently reduced. This reliably avoids undesirable situations where the ozone concentration C does not reach the target concentration Cset due to an excessive decrease in the Lower threshold C1.

[0125] -Modification of the embodiment-

[0126] The above-described embodiment may have the following modified configurations.

[0127] <Variation 1>

[0128] The β in the above formula (2) can be made smaller than the α in the above formula (1). The speed of the self-decomposition reaction of ozone gas tends to be slower than the speed of supplying ozone gas from the ozone generator (20) to the supply path (40). Therefore, when β is too large, there is a possibility that the ozone concentration C will not reach the target concentration Cset after the supply control starts. In contrast, by making β smaller than α, the upper threshold value C2, which is the second threshold value, becomes relatively low. Therefore, it is possible to prevent the ozone concentration C from failing to reach the target concentration Cset.

[0129] <Variation 2>

[0130] Figure 8 The relationship between the tank (44) and the ejector (35) of the ozone water production device (1) of the modified example 2 shown is different from that of the above-mentioned embodiment. In the liquid flow path (30) of the modified example 2, the tank (44) is arranged on the upstream side of the ejector (35). The outflow end of the water supply path (31) is connected to the tank (44). A relay path (75) is connected between the tank (44) and the liquid inflow portion (35a) of the ejector (35). A pump (45) and a first flow sensor (33) are provided in the relay path (75). A supply path (40) is provided between the liquid outflow portion (35b) of the ejector (35) and the object.

[0131] The liquid flow path (30) of Modification 2 has the same first return flow path (60) as in the embodiment, but does not have the second return flow path (70). In the first return flow path (60), a second back pressure valve (72) is provided instead of the flow control valve (61) of the embodiment. It should be noted that in the supply path (40) of Modification 2, a gas-liquid separator can be provided on the downstream side of the ejector (35). The gas-liquid separator separates the ozone gas from the ozone water.

[0132] In the second modification, the ozone concentration is controlled in the same manner as in the above embodiment so that the ozone concentration C converges to the target concentration Cset. In the second modification, since the tank (44) is not provided in the supply path (40), the ozone concentration C is easily fluctuated in accordance with the supply control and the stop control. In contrast, by performing the same ozone concentration control as in the above embodiment, the extent of the overshoot of the ozone concentration C can be reduced. Similarly, the extent of the undershoot of the ozone concentration C can be reduced.

[0133] Other Implementation Methods

[0134] In the above embodiment, during the supply control, the ozone gas generated by the ozone generator (20) is supplied to the supply path (40) by opening the first gas on-off valve (13). However, during the supply control, the ozone gas may be supplied to the supply path (40) by operating the ozone generator (20) while it is stopped.

[0135] In the above embodiment, during the stop control, the supply of ozone gas to the supply path (40) is stopped by closing the first gas on-off valve (13). However, during the stop control, the supply of ozone gas to the supply path (40) may be stopped by stopping the ozone generator (20) in operation.

[0136] In the ozone concentration control of the above embodiment, the control unit (80) performs the following two determinations A and B of the present invention. A: The control unit (80) determines whether to execute the stop control based on the first threshold value C1 during the supply control. B: The control unit (80) determines whether to execute the supply control based on the second threshold value C2 during the stop control. However, the control unit (80) may perform only one of the determinations A and B.

[0137] The first threshold value C1 does not necessarily need to be based on the above formula (1). The first threshold value C1 can be obtained based on the target concentration Cset and the minimum value Cmin and can be a value between the minimum value Cmin and the target concentration Cset.

[0138] The second threshold value C2 does not necessarily need to be based on the above formula (2). The second threshold value C2 can be obtained based on the target concentration Cset and the maximum value Cmax and can be a value between the maximum value Cmax and the target concentration Cset.

[0139] In the embodiment, the control unit (80) terminates the stop control and executes the supply control when the ozone concentration C decreases below the minimum value Cmin of the previous stop control after switching from the supply control to the stop control. However, the control unit (80) may terminate the stop control and execute the supply control when the ozone concentration C decreases below a predetermined third threshold value after switching from the supply control to the stop control. Here, the third threshold value may be a value lower than the target concentration Cset. Furthermore, the control unit (80) may terminate the stop control and execute the supply control when a predetermined time has elapsed after switching from the supply control to the stop control.

[0140] In the embodiment, the control unit (80) terminates the supply control and executes the stop control when the ozone concentration C increases above the maximum value Cmax of the previous supply control after switching from the stop control to the supply control. However, the control unit (80) may terminate the supply control and execute the stop control when the ozone concentration C increases above a predetermined fourth threshold value after switching from the stop control to the supply control. Here, the fourth threshold value may be a value higher than the target concentration Cset. Furthermore, the control unit (80) may terminate the supply control and execute the stop control when a predetermined time has elapsed after switching from the stop control to the supply control.

[0141] The ozone generator (20) of the embodiment is a discharge type ozone generator. However, the ozone generator (20) may be of other types such as an electrolysis type or an ultraviolet type.

[0142] It should be noted that each component of the above-described embodiment, modified examples, other examples, etc. can be replaced or changed within the range of combinability.

[0143] Industrial applicability

[0144] As described above, the present disclosure is useful for an ozone water production apparatus.

[0145] Description of Reference Numerals

[0146] 1. Ozone water production device

[0147] 20 Ozone generator

[0148] 40 Supply Road

[0149] 46 Testing Department

[0150] 80 Control Department

Claims

1. An ozone water production device, characterized in that: include: an ozone generating device (20) for generating ozone gas; a supply path (40) for allowing ozone water containing ozone gas supplied from the ozone generating device (20) to flow; a detection unit (46) for detecting an ozone concentration C of the ozone water in the supply path (40); and The control unit (80) alternately switches between supply control of ozone gas from the ozone generator (20) to the supply path (40) and stop control of stopping the supply of ozone gas from the ozone generator (20) to the supply path (40) in such a manner that the ozone concentration C detected by the detection unit (46) converges to a target concentration Cset. The control unit (80) executes the stop control when the ozone concentration C exceeds a first threshold value C1 via a falling inflection point lower than a target concentration Cset after switching from the stop control to the supply control. The first threshold value C1 is obtained based on the target concentration Cset and the minimum value Cmin, which is the ozone concentration corresponding to the falling inflection point, and is a value between the minimum value Cmin and the target concentration Cset.

2. An ozone water production device, characterized in that: include: an ozone generating device (20) for generating ozone gas; a supply path (40) for allowing ozone water containing ozone gas supplied from the ozone generating device (20) to flow; a detection unit (46) for detecting an ozone concentration C of the ozone water in the supply path (40); and The control unit (80) alternately switches between supply control of ozone gas from the ozone generator (20) to the supply path (40) and stop control of stopping the supply of ozone gas from the ozone generator (20) to the supply path (40) in such a manner that the ozone concentration C detected by the detection unit (46) converges to a target concentration Cset. The control unit (80) executes the supply control when the ozone concentration C passes through an upward inflection point higher than a target concentration Cset and falls below a second threshold value C2 after switching from the supply control to the stop control. The second threshold value C2 is obtained based on the target concentration Cset and the maximum value Cmax of the ozone concentration corresponding to the rising inflection point, and is a value between the maximum value Cmax and the target concentration Cset.

3. The ozone water production device according to claim 2, characterized in that: The control unit (80) executes the stop control when the ozone concentration C exceeds a first threshold value C1 via a falling inflection point lower than a target concentration Cset after switching from the stop control to the supply control. The first threshold value C1 is obtained based on the target concentration Cset and the minimum value Cmin, which is the ozone concentration corresponding to the falling inflection point, and is a value between the minimum value Cmin and the target concentration Cset.

4. The ozone water production device according to claim 1 or 3, characterized in that: The first threshold C1 is expressed by the relationship formula C1=Cset-(Cset-Cmin)×α, where 0<α<1.

5. The ozone water production device according to claim 2 or 3, characterized in that: The second threshold C2 is expressed by the relationship formula C2=Cset+(Cmax-Cset)×β, where 0<β<1.

6. The ozone water production device according to claim 3, characterized in that: The first threshold C1 is represented by the relationship C1=Cset-(Cset-Cmin)×α, where 0<α<1. The second threshold C2 is represented by the relationship C2=Cset+(Cmax-Cset)×β, where 0<β<1. Furthermore, the β is smaller than the α.

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