Storage device and liquid level detection method

Abstract

To enable detection of the liquid level in the storage tank without incurring extra effort or cost. [Solution] The storage device (10) comprises a storage tank (11) for storing liquid, a detector (25) for detecting the position of the liquid level in the storage tank, and a controller (30). The controller has a calculation unit (31) that calculates a relationship value related to the change in the liquid level position over time based on the liquid level position detected by the detector, and a determination unit (32) that determines the state of the liquid level based on the relationship value calculated by the calculation unit.

Description

Technical Field

[0006] , ,

[0001] The present invention relates to a storage device for storing a liquid and a method for detecting a liquid level state.

Background Art

[0002] When treating a liquid such as machining waste liquid discharged from a machining device with a treatment device or the like disclosed in Patent Document 1, foreign substances contained in the liquid are filtered by passing the liquid through a filter. Further, in a treatment device or the like for treating a liquid, the liquid is stored in a storage tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a method for detecting clogging of a filter for filtering a liquid, there are methods such as directly visually checking or checking with a differential pressure in a flow path before and after the filter. However, there is a problem that it takes a lot of labor and cost because it takes a lot of man-hours for confirmation and it is necessary to install a sensor for measuring pressure in the flow path before and after the filter.

[0005] Further, in a device for supplying a liquid to a storage tank, there is a demand for detecting an excess or shortage of the liquid supply amount, falling of foreign substances into the storage tank, and the like. For example, there are methods such as directly visually checking the state of the storage tank or imaging and performing image analysis, but there is also a problem that these methods are laborious and costly to implement.

[0006] An object of the present invention is to provide a storage device and a method for detecting a liquid level state that can detect the liquid level state of a storage tank without spending extra labor and cost.

Means for Solving the Problems

[0007] A storage device according to one aspect of the present disclosure comprises a storage tank for storing liquid, a detector for detecting the position of the liquid level in the storage tank, and a controller, wherein the controller includes a calculation unit that calculates a relationship value related to the change in the position of the liquid level over time based on the position of the liquid level detected by the detector, and a determination unit that determines the state of the liquid level based on the relationship value calculated by the calculation unit.

[0008] In one form of the controller, the calculation unit calculates the amount of change in the liquid level position per unit time as the relational value at regular intervals, and the determination unit determines whether the relational value is outside a predetermined range, and determines that the liquid level is abnormal if it is determined to be outside the predetermined range a predetermined number of times within a predetermined time.

[0009] The process of determining the state of the liquid level using the controller is particularly useful, for example, when the system further includes a supply unit for supplying the liquid to the storage tank, and the supply unit has a bag filter and a nozzle unit for supplying the liquid into the bag filter.

[0010] Preferably, the bag filter further includes a drain pan to receive the liquid overflowing from the opening of the bag filter, and a spout to drop the liquid received in the drain pan into the storage tank from a predetermined position.

[0011] A liquid level state detection method according to one aspect of the present disclosure comprises: a supply step of supplying a liquid to a bag filter installed in a storage tank for storing a liquid; a detection step of detecting the position of the liquid level of the liquid stored in the storage tank; a calculation step of calculating a relationship value related to the change in the position of the liquid level over time based on the position of the liquid level detected in the detection step; and a determination step of determining the state of the liquid level based on the relationship value calculated in the calculation step. [Effects of the Invention]

[0012] According to the storage device and liquid level detection method of this disclosure, it is possible to detect the liquid level of a storage tank without incurring extra effort or cost. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of the storage device. [Figure 2] This is a cross-sectional view of the storage device. [Figure 3] This figure shows an example of the change in the liquid level position over time as detected by a detector. [Modes for carrying out the invention]

[0014] The storage device of this disclosure is characterized by storing liquid in a storage tank, detecting the position of the liquid level in the storage tank using a detector, and having a controller calculate a relational value related to the change in the liquid level position detected by the detector over time, and determining the state of the liquid level based on the calculated relational value.

[0015] The controller comprises a calculation unit and a determination unit. The calculation unit calculates the amount of change in the liquid level position per unit time as a relational value at regular intervals, and the determination unit determines whether the relational value is outside a predetermined range. If it is determined to be outside the predetermined range a predetermined number of times within a predetermined time, the controller determines that the liquid level is abnormal.

[0016] In this way, by determining the state of the liquid level based on a relationship value related to the change in the liquid level position over time, it is possible to obtain not only information on the temporary amount of liquid stored in the storage tank, but also a wide range of information regarding the operation of the supply unit that supplies liquid to the storage tank and the status of liquid processing performed by the storage device. For example, if the amount of liquid supplied to the storage tank per unit time by the supply unit is not constant, the fluctuation in the supply amount can be determined from the state of the liquid level based on the change in the liquid level position over time, and it can be determined whether the liquid supply is appropriate for the liquid storage capacity and liquid processing capacity of the storage device. In addition, it is possible to know from the state of the liquid level based on the change in the liquid level position over time whether the processing unit that performs predetermined processing on the liquid in the storage device is processing the liquid appropriately without causing liquid stagnation or clogging. Furthermore, it is possible to grasp situations in which the liquid level changes irregularly due to external factors other than the liquid supplied by the supply unit, such as when foreign objects other than liquid fall into the storage tank or when vibrations are applied to the storage tank from the outside, by determining the state of the liquid level based on the change in the liquid level position over time. The storage device described herein has the advantage of being able to acquire such various information at low cost through the state of the liquid level in the storage tank, without the effort required for an operator managing the storage device to directly visually inspect the inside of the storage tank or the cost of placing numerous sensors along the liquid flow path.

[0017] The embodiments described below with reference to the attached drawings illustrate a preferred example of the storage device and liquid level detection method of the present disclosure. The storage device 10 shown in Figures 1 and 2 includes a storage tank 11 for storing liquid (processing waste liquid) discharged from a processing device (not shown), and removes foreign matter such as processing debris contained in the liquid stored in the storage tank 11 by filtration.

[0018] The processing device that discharges liquid to the storage device 10 is, for example, a cutting device that cuts a rotating cutting blade into a workpiece for cutting. In this case, the foreign matter in the liquid collected by filtration in the storage device 10 is the machining chips generated by machining. For example, it is a mixture of semiconductors such as silicon contained in the workpiece, various metals, abrasive grains and binders that make up the cutting edge of the cutting blade, etc. The cutting device performs cutting while supplying cutting water (pure water) toward the machining point, and discharges the machining waste liquid in which the machining chips are contained in the cutting water. Note that the processing device is not limited to the cutting device, and may be a grinding device that performs grinding with a grinding wheel, a laser processing device that processes by irradiating a laser beam, a polishing device that performs polishing with a polishing pad, etc.

[0019] The liquid processed by the storage device 10 is sent to a pure water recycling device (not shown). In the pure water recycling device, removal of fine foreign matter by a precision filter, decomposition and sterilization of organic impurities by irradiation with ultraviolet rays, ion exchange by an ion exchange resin, etc. are performed, and it is recycled as pure water. The precision filter provided in the pure water recycling device is costly to replace. Therefore, if the machining waste liquid discharged from the processing device is directly sent to the pure water recycling device for treatment, the filter replacement will become frequent and the operation cost will increase. By removing relatively large foreign matter from the machining waste liquid by filtration in the storage device 10 before treatment in the pure water recycling device, the frequency of filter replacement in the pure water recycling device can be reduced.

[0020] The storage tank 11 of the storage device 10 includes a first compartment 13 and a second compartment 14 partitioned by a partition plate 12, and the liquid (machining waste liquid discharged from the processing device) is supplied to the first compartment 13 by the supply unit 15. The supply unit 15 has a bag filter 16 for filtration and a nozzle unit 17 that supplies liquid into the bag filter 16.

[0021] The bag filter 16 is a bag-shaped filter having an opening 18 at one end and a closed end on the opposite side of the opening 18, and is installed in the first compartment 13 of the storage tank 11 with the opening 18 facing upwards. The size and shape of the bag filter 16 are not limited, but as an example, a cylindrical bag filter 16 with a diameter of about 180 mm and a length of about 420 mm is used. The bag filter 16 is made of nonwoven fabric or the like and has a filter section with a mesh size that allows liquid to pass through but prevents foreign objects larger than a predetermined size from passing through. As described above, since filtration is performed in the pure water recycling device after the liquid has been filtered in the storage device 10, it is desirable to make the filtration accuracy in the storage device 10 coarser than that in the pure water recycling device, so that the storage device 10 can capture relatively large foreign objects and the pure water recycling device can capture fine foreign objects. Specifically, the bag filter 16 of this embodiment has a filtration accuracy that prevents objects larger than 10 μm from passing through.

[0022] The liquid discharged from the processing device is sent to the nozzle section 17 through the supply pipe 19. The nozzle section 17 is positioned above the opening 18 of the bag filter 16, and the liquid is supplied into the bag filter 16 from the nozzle section 17. In the example configuration shown in Figure 1, two bag filters 16 are arranged in parallel, and one nozzle section 17 is provided for each bag filter 16, but the configuration is not limited to this. For example, there may be one bag filter 16 or three or more. Also, liquid may be supplied to a single bag filter 16 from multiple nozzle sections 17.

[0023] Around the bag filter 16, a drain pan 20 serving as a tray for receiving the liquid overflowing from the opening 18 is provided. The drain pan 20 is positioned higher than the liquid level in the first compartment 13 of the storage tank 11 and receives the liquid overflowing from the opening 18. The first compartment 13 is configured such that when the liquid level reaches the upper end of the partition plate 12, the liquid flows over the partition plate 12 into the second compartment 14. Therefore, as long as the situation does not occur where the liquid overflows in the second compartment 14 and flows back to the first compartment 13 side, the position of the highest liquid level in the first compartment 13 corresponds to the position of the upper end of the partition plate 12 (see Fig. 2). The drain pan 20 is located above the upper end of the partition plate 12 and can receive the liquid at a position higher than the liquid level in the first compartment 13.

[0024] A pouring port 21 for dropping the liquid received in the drain pan 20 into the first compartment 13 of the storage tank 11 is formed. As shown in Fig. 1, the drain pan 20 has a bottom surface portion provided at a position lower than the opening 18 of the bag filter 16 and a standing wall portion protruding upward from the bottom surface portion, and the pouring port 21 is formed in a form where a part of the standing wall portion is cut out.

[0025] As shown in Fig. 2, in the first compartment 13, a first intermediate plate 22 is provided between the partition plate 12 and the bag filter 16. The upper end of the first intermediate plate 22 is at a position higher than the upper end of the partition plate 12, and the lower end forms a gap without contacting the bottom surface of the storage tank 11. In the second compartment 14, a second intermediate plate 23 is provided. The upper end of the second intermediate plate 23 is at a position higher than the upper end of the partition plate 12, and the lower end forms a gap without contacting the bottom surface of the storage tank 11. In Fig. 1, the illustration of the first intermediate plate 22 and the second intermediate plate 23 is omitted.

[0026] The storage device 10 includes a pump 24 that pumps up the liquid in the second compartment 14 and discharges it outside the storage tank 11. The liquid discharged from the storage tank 11 by the power of the pump 24 is sent to a pure water recycling device.

[0027] In the storage device 10 configured as described above, the liquid sent to the nozzle section 17 through the supply pipe 19 is supplied from above the bag filter 16 (arrow Fa in Figure 2). The flow rate of the liquid supplied from the nozzle section 17 to the bag filter 16 is set to an appropriate value considering the filtration capacity of the bag filter 16. As an example, in the case of the bag filter 16 of this embodiment, for which specific numerical examples of dimensions and filtration accuracy were given earlier, it is set to supply a maximum of about 8 liters of liquid per minute from the nozzle section 17.

[0028] The liquid supplied from the nozzle 17 enters the bag filter 16 through the opening 18. The liquid that enters the bag filter 16 flows out of the bag filter 16 through the cylindrical filter portion immersed in the liquid in the first compartment 13 and proceeds into the first compartment 13 (arrow Fb in Figure 2). When the liquid passes through the filter portion of the bag filter 16, foreign matter that is too large to pass through the filter portion (approximately 10 μm or larger) is separated from the liquid and remains in the bag filter 16, where it is collected.

[0029] The liquid remaining after foreign matter has been collected by the bag filter 16 is stored in the first compartment 13. The first intermediate plate 22, located within the first compartment 13, prevents foreign matter floating on the liquid surface of the first compartment 13 from moving toward the second compartment 14 side (partition plate 12 side). Within the first compartment 13, a liquid flow is formed that passes below the first intermediate plate 22, moving from the bag filter 16 side toward the partition plate 12 side (arrow Fc in Figure 2).

[0030] When the liquid level in the first compartment 13 reaches the upper end of the partition plate 12, the liquid overflows and flows from the first compartment 13 to the second compartment 14 over the top of the partition plate 12 (arrow Fd in Figure 2). The second intermediate plate 23 installed in the second compartment 14 prevents foreign matter floating on the liquid surface of the second compartment 14 from moving toward the pump 24. Within the second compartment 14, a liquid flow is formed that moves from the partition plate 12 side toward the pump 24 side, passing beneath the second intermediate plate 23 (arrow Fe in Figure 2). The liquid in the second compartment 14 is discharged to the outside of the storage tank 11 by the pump 24 (arrow Ff in Figure 2).

[0031] As described above, in the storage device 10 that moves liquid and performs filtration, as the amount of foreign matter collected by the bag filter 16 increases, the amount of liquid that can pass through the filter section of the bag filter 16 per unit time (the amount of liquid that can flow as arrow Fb in Figure 2) decreases. When the bag filter 16 becomes significantly clogged, the liquid supplied from the nozzle section 17 into the bag filter 16 will overflow from the opening 18 (arrow Fg in Figure 2). In addition, if an excessive amount of liquid exceeding the filtration capacity of the bag filter 16 is supplied from the nozzle section 17 to the bag filter 16, or if liquid is supplied from the nozzle section 17 to the bag filter 16 intermittently (irregularly), or if liquid is supplied from the nozzle section 17 at a timing outside the specified supply timing, the liquid may overflow from the opening 18 into the drain pan 20. The liquid that overflows from the opening 18 is collected in the drain pan 20. The liquid received in the drain pan 20 falls into the first compartment 13 of the storage tank 11 through the spout 21 (arrow Fh in Figure 2). Therefore, by detecting the effect of the liquid overflowing from the opening 18 of the bag filter 16 into the drain pan 20 and falling from the spout 21 by some means, information regarding abnormalities in the liquid supply in the supply unit 15, such as clogging of the bag filter 16, can be obtained.

[0032] The storage device 10 of this embodiment includes a detector 25 for detecting the position of the liquid level in the storage tank 11. The detector 25 is used to detect the change in the liquid level over time caused by the liquid overflowing from the opening 18 of the bag filter 16. Broadly speaking, there are non-contact detectors that detect the liquid level in the storage tank 11 without contact, and contact detectors that detect the liquid in the storage tank 11 by contacting it. The detector 25 can be of either a non-contact or contact type.

[0033] As a non-contact detector to be applied to detector 25, an ultrasonic sensor can be used that emits ultrasonic waves and receives the ultrasonic waves reflected from the liquid surface to detect the state of the liquid surface (the position of the liquid surface relative to the detector), or a fiber sensor can be used that emits light (such as laser light) from an optical fiber and receives the light reflected from the liquid surface to detect the state of the liquid surface (the position of the liquid surface relative to the detector).

[0034] As a contact-type detector to be applied to detector 25, for example, a float sensor can be used, which is installed floating on the liquid surface and detects its own position change in response to fluctuations in the liquid surface. Alternatively, as another example of a contact-type detector to be applied to detector 25, a proximity sensor may be used, which has a contact portion at a predetermined height position in the storage tank 11 and detects when the liquid comes into contact with the contact portion due to fluctuations in the liquid surface.

[0035] Regardless of the type of sensor used as the detector 25, it is desirable that the detector 25 be positioned to detect fluctuations in the liquid level near the point where the liquid falls from the spout 21 into the storage tank 11. The detector 25 in this embodiment, shown in Figures 1 and 2, is a non-contact type sensor and is mounted above the point where the liquid falls from the spout 21 into the storage tank 11.

[0036] More specifically, as shown in Figure 1, the storage tank 11 is equipped with an opening / closing lid 26 that can be opened and closed, and a detector 25 is attached to the opening / closing lid 26. When the opening / closing lid 26 is closed, the detector 25 is positioned in a location where it can detect the liquid level in the first compartment 13 of the storage tank 11, and in particular, the detector 25 is positioned above the location where the liquid falls from the spout 21 into the first compartment 13.

[0037] Information regarding the liquid level detected by the detector 25 is transmitted to the controller 30, which controls the operation of the storage device 10. The controller 30 includes a calculation unit 31 that calculates a relationship value related to the change in the liquid level over time based on the liquid level detected by the detector 25, and a determination unit 32 that determines the state of the liquid level based on the relationship value calculated by the calculation unit 31. In addition to acquiring information regarding the liquid level in the storage tank 11, the controller 30 is also responsible for controlling the pump 24, etc.

[0038] [Supply process] When detecting the liquid level in the storage tank 11 in the storage device 10, a supply process is performed in which liquid is supplied to the bag filter 16. In the supply process, liquid is supplied from the nozzle part 17 to the bag filter 16 installed in the storage tank 11. The liquid supplied from the nozzle part 17 enters the bag filter 16 through the opening 18.

[0039] [Detection process] The detection process is performed while supplying liquid to the bag filter 16. In the detection process, the position of the liquid level in the storage tank 11 is detected using the detector 25. Information regarding the liquid level position detected by the detector 25 is transmitted to the controller 30. The detection of the liquid level position by the detector 25 is performed continuously over a predetermined period of time, and as an example, as shown in Figure 3, a graph can be obtained showing the change over time in the horizontal direction and the change in the liquid level position in the vertical direction.

[0040] [Calculation process] Next, a calculation process is performed. In the calculation process, the calculation unit 31 of the controller 30 calculates a relational value related to the change in the liquid level position over time, based on the liquid level position of the storage tank 11 detected in the detection process. Specifically, the calculation unit 31 calculates the amount of change in the liquid level position per unit time as a relational value at regular intervals. Alternatively, the relational value calculated by the calculation unit 31 may be the difference between the maximum and minimum values ​​of the liquid level height within a predetermined time.

[0041] [Judgment process] Next, a determination process is performed. In the determination process, the determination unit 32 of the controller 30 determines the state of the liquid level based on the relationship values ​​calculated in the calculation process. Specifically, the determination unit 32 determines whether the relationship values ​​calculated by the calculation unit 31 are outside a predetermined range, and if it is determined that the values ​​are outside the predetermined range a predetermined number of times within a predetermined time, it determines that the state of the liquid level is abnormal. For example, if the standard deviation (σ) is applied to setting the predetermined range, and the number of times the liquid level fluctuation reaches 3σ exceeds a predetermined number (10 times) within a predetermined time (10 seconds), the determination unit 32 determines that the state of the liquid level is abnormal. Alternatively, in setting the determination criteria, the liquid level state of the storage tank 11 under normal conditions (no abnormalities) may be detected by the detector 25, the relationship values ​​may be sampled, a distribution map may be created, and the determination unit 32 may determine that the state of the liquid level is abnormal if the 2σ or 3σ value exceeds the standard.

[0042] In a configuration where the detector 25 is a proximity sensor that detects contact with liquid, the determination unit 32 may determine that the liquid level is abnormal if the number of times the liquid comes into contact with the proximity sensor within a predetermined time exceeds a predetermined number.

[0043] If the determination unit 32 determines that the liquid level is abnormal, the controller 30 causes the storage device 10 to notify the abnormality via the notification unit 33. The notification unit 33 is, for example, a display monitor, indicator lamp, speaker, etc. Alternatively, the abnormality may be notified via a communication device (server, personal computer, tablet computer, smartphone, etc.) that can communicate with the storage device 10.

[0044] One possible cause of an abnormality in the liquid level of the storage tank 11 is an abnormality in the liquid supply in the supply unit 15. For example, if the bag filter 16 constituting the supply unit 15 does not become clogged and liquid can flow through the filter into the first compartment 13 (when the flow indicated by arrow Fb in Figure 2 is ensured), the liquid level in the first compartment 13 is balanced at a position corresponding to the upper end of the partition plate 12, and rapid fluctuations in the liquid level are unlikely to occur.

[0045] When a large amount of foreign matter is collected in the bag filter 16 (causing clogging), and the liquid can no longer flow smoothly through the filter into the first compartment 13, the liquid supplied from the nozzle 17 to the bag filter 16 will overflow from the opening 18 into the drain pan 20 without passing through the bag filter 16. Alternatively, if the amount of liquid supplied from the nozzle 17 to the bag filter 16 per unit time exceeds the filtration capacity of the bag filter 16, the liquid will also overflow from the opening 18 into the drain pan 20. In these conditions, the liquid overflowing from the opening 18 falls from the spout 21 onto the liquid surface of the storage tank 11. When liquid falls from the spout 21 onto the liquid surface of the storage tank 11, waves, ripples, and splashes occur on the liquid surface. Then, in the detection process, the detector 25 detects fluctuations in the liquid level position as shown in Figure 3.

[0046] Based on the change in liquid level detected by the detector 25 in the detection step, the calculation unit 31 calculates the amount of change in the liquid level per unit time as a relational value at regular intervals in the calculation step, and the determination unit 32 determines this relational value according to predetermined criteria in the determination step, thereby making it possible to detect the degree to which liquid is falling from the spout 21 to the liquid level in the storage tank 11. In other words, it is possible to detect whether the bag filter 16 is filtering the liquid properly, or whether the correct amount of liquid is being supplied from the nozzle 17 to the bag filter 16, by referring to the change in the liquid level in the storage tank 11.

[0047] Checking for clogging in the bag filter 16 or excessive liquid supply from the nozzle section 17 by directly visually inspecting the bag filter 16 or by checking the differential pressure in the flow path before and after the bag filter 16 is time-consuming and costly. In contrast, determining the liquid level in the storage tank 11 using the detector 25 is time-consuming and low-cost. The detector 25 can also be used to detect the lower limit water level (insufficient water level) and upper limit water level (overflow level) in the storage tank 11, and the controller 30 will issue an alarm to the notification unit 33 if the water level falls below the lower limit or exceeds the upper limit. Therefore, when the storage device 10 is equipped with the detector 25 for detecting the water level in the storage tank 11, the liquid level in the storage tank 11 can be determined using the detector 25 without incurring the extra cost of adding new sensors.

[0048] Furthermore, by directly detecting fluctuations in the liquid level inside the bag filter 16, it is possible to detect abnormalities that could lead to liquid overflow from the opening 18. However, this method has the problem of being costly because it requires the installation of an additional sensor for detecting the liquid level inside the bag filter 16, in addition to sensors such as the detector 25 used for detecting the upper and lower limits of the liquid level in the storage tank 11. Also, because the liquid level inside the bag filter 16 is difficult to stabilize due to the force of the liquid supplied from the nozzle section 27 to the bag filter 16, when a fluctuation in the liquid level inside the bag filter 16 is detected, it is difficult to determine whether the fluctuation is due to an abnormality in the liquid supply in the supply section 15 or a normal fluctuation within the normal range. According to the storage device and liquid level state detection method of this disclosure, these problems can be avoided by detecting the state of the liquid level in the storage tank 11 outside the bag filter 16 using the detector 25, and accurate determination can be made at low cost.

[0049] The liquid overflowing from the opening 18 of the bag filter 16 is collected in the drain pan 20 and collected at the spout 21 before falling into the storage tank 11. Therefore, the liquid level fluctuation is most pronounced at the position directly below the spout 21. Accordingly, by placing the detector 25 at a position to detect the liquid level directly below the spout 21, as in this embodiment, fluctuations in the liquid level of the storage tank 11 caused by the liquid overflowing from the opening 18 of the bag filter 16 can be detected with extremely high accuracy.

[0050] As described above, the storage device and liquid level detection method of this disclosure are highly useful for applications that remove foreign matter from liquids by providing a bag filter 16 for filtration, and can be used for notifying when it is time to replace the bag filter 16, and for confirming whether there is an excess or deficiency in the amount of liquid supplied from the nozzle section 17.

[0051] Furthermore, using the detector to determine the state of the liquid level in the storage tank can be applied to detecting abnormalities other than the state in which liquid overflows from the opening 18 of the bag filter 16, as in the above embodiment. For example, in a storage device without a bag filter, fluctuations in the liquid level may occur when liquid is supplied intermittently (irregularly) from the supply unit to the storage tank, or when liquid is supplied from the supply unit to the storage tank at a timing different from the specified supply timing. Alternatively, when foreign matter such as debris falls toward the liquid surface of the storage tank, fluctuations in the liquid level (such as splashing or ripples) occur due to the falling of such foreign matter. Or, when vibration is applied to the storage tank from the outside, such vibration is transmitted to the liquid in the storage tank, causing fluctuations in the liquid level. In these cases, the controller can recognize the occurrence of an abnormality by determining the state of the liquid level based on the relationship value related to the change in the position of the liquid level over time, as detected by the detector. Therefore, any event that results in fluctuations in the liquid level in the storage tank, regardless of its cause, can be subject to detection by the detector and determination by the controller.

[0052] In the above embodiment, the storage device 10 is configured such that a partition plate 12 separates the first compartment 13 from the second compartment 14, and the liquid level in the first compartment 13 is kept substantially constant with respect to the upper end position of the partition plate 12. This allows for highly accurate detection of fluctuations in the liquid level when liquid overflows from the opening 18 of the bag filter 16. However, the present invention can also be applied to a configuration in which the storage tank 11 is made up of a single compartment without a partition plate 12. If the relationship between the amount of liquid supplied from the nozzle section 17 and the amount of liquid discharged by the pump 24 is appropriately managed, it is possible to keep the liquid level in the storage tank 11 constant even without a partition plate 12. Furthermore, if an abnormality is detected in the state of the liquid level in the storage tank 11 despite such management, it can be determined that some kind of error (including clogging of the bag filter 16) has occurred between the supply and discharge of liquid.

[0053] Furthermore, the embodiments of the present invention are not limited to the embodiments and modifications described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Moreover, if the technical idea of ​​the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial applicability]

[0054] According to the present invention, it is possible to detect the liquid level in a storage tank without incurring extra effort or cost, improving convenience in devices that store liquids and perform various processing tasks. [Explanation of Symbols]

[0055] 10: Storage device 11: Storage tank 12: Partition plate 13: Section 1 14: Section 2 15: Supply section 16: Bag filter 17: Nozzle part 18 :Aperture 19: Supply pipe 20: Drain pan 21: Spout 21 22: First Intermediate Board 23: Second Intermediate Panel 24: Pump 25: Detector 26: Opening and closing lid 30: Controller 31: Calculation section 32: Judgment section 33: Hochi Department

Claims

1. A storage tank for storing liquid, A detector for detecting the liquid level of the liquid stored in the storage tank, Equipped with a controller, The controller is, A calculation unit that calculates a relationship value related to the change in the position of the liquid surface over time based on the position of the liquid surface detected by the detector, The calculation unit has a determination unit that determines the state of the liquid level based on the relationship value calculated by the calculation unit. A storage device characterized by the following features.

2. The calculation unit is, The amount of change in the liquid level position per unit time is calculated as the relationship value at regular intervals. The determination unit is, The system determines whether the relevant value is outside a predetermined range, and if it is determined to be outside the predetermined range a predetermined number of times within a predetermined time, it is determined that the liquid level is abnormal. The storage device according to feature 1.

3. The storage tank further comprises a supply unit for supplying the liquid, The supply unit is, Bag filter and The bag filter has a nozzle portion for supplying the liquid into the bag filter. A storage device according to claim 1 or 2, characterized by the above.

4. A drain pan to receive the liquid overflowing from the opening of the bag filter, A spout for dropping the liquid received in the drain pan into the storage tank from a predetermined position, It also has The storage device according to feature 3.

5. A supply process involves supplying the liquid to a bag filter installed in a storage tank for storing the liquid, A detection step for detecting the liquid level of the liquid stored in the storage tank, A calculation step that calculates a relationship value related to the change in the liquid level position over time based on the liquid level position detected in the detection step, A determination step in which the state of the liquid level is determined based on the relationship value calculated in the calculation step, A liquid level detection method characterized by comprising the following:

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