Water state detection device

Abstract

A pump is used to detect the water condition in the tank. [Solution] The water condition detection device includes a pump 10 that has an intake port for drawing in air from outside the water tank 90 and an outlet port for discharging air into the water tank 90 and is constructed using a piezoelectric element, a measuring unit for measuring the electrical characteristics of the pump 10, and a detection unit 43 for detecting the state of the water in the water tank based on the electrical characteristics.

Description

Technical Field

[0001] The present invention relates to a technique for detecting the state of water in an aquarium.

Background Art

[0002] Patent Document 1 describes a pump for circulating water in an aquarium.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the device provided with the pump of Patent Document 1, the state of the water in the aquarium (for example, the depth of the water stored in the aquarium) cannot be detected.

[0005] Therefore, an object of the present invention is to detect the state of water in an aquarium using a pump.

Means for Solving the Problems

[0006] A water state detection device according to an embodiment of this invention includes a suction port that sucks air outside the aquarium and a discharge port that discharges air into the aquarium, a pump configured using a piezoelectric element, a measurement unit that measures the electrical characteristics of the pump, and a detection unit that detects the state of water in the aquarium based on the electrical characteristics.

[0007] The electrical characteristics of the pump change depending on the magnitude of the load on the pump. The load on the pump changes depending on the state of the water (for example, the water depth). Utilizing these relationships, in this configuration, the state of the water is detected by measuring the electrical characteristics of the pump.

[0008] A water state detection device according to one embodiment of this invention comprises a pump having an intake port for drawing in air from outside the water tank and an outlet port for discharging air into the water tank, and configured using a piezoelectric element; a measuring unit for measuring the electrical characteristics of the pump; and a detection unit for detecting the amount of change in the state of the water in the water tank based on the electrical characteristics.

[0009] The electrical characteristics of a pump change depending on the magnitude of the load on the pump. The load on the pump changes depending on the water conditions (e.g., water depth). By utilizing these relationships, this configuration allows for the detection of changes in the water conditions by measuring the electrical characteristics of the pump. [Effects of the Invention]

[0010] According to this invention, the state of the water in a tank can be detected using a pump. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a functional block diagram of the water depth detection device according to the first embodiment. [Figure 2] Figure 2 shows a plan view and a side view illustrating an example of the shape of a pump according to the first embodiment. [Figure 3] Figure 3 shows an example of how the water depth detection system according to the first embodiment is arranged in a water tank. [Figure 4] Figure 4(A) is a graph showing an example of the frequency characteristics of the impedance of a piezoelectric element, and Figure 4(B) is a magnified graph of the area around the resonant frequency of the characteristics shown in Figure 4(A). [Figure 5] Figure 5 is a flowchart showing an example of a method for detecting the absolute value of water depth based on current values. [Figure 6] Figure 6 is a flowchart showing an example of a method for detecting changes in water depth based on current values. [Figure 7] Figure 7 is a flowchart showing an example of a method for detecting changes in water depth based on current values. [Figure 8] Figure 8 is a functional block diagram of the water depth detection device according to the second embodiment. [Figure 9] FIG. 9(A) is a graph showing an example of the frequency characteristics of the impedance of a piezoelectric element, and FIG. 9(B) is a graph obtained by magnifying the vicinity of the resonance frequency of the characteristics shown in FIG. 9(A). [Figure 10] FIG. 10 is a flowchart showing an example of a method for detecting the absolute value of the water depth based on the resonance frequency. [Figure 11] FIG. 11 is a flowchart showing an example of a method for detecting the presence or absence of a change in the water depth based on the resonance frequency. [Figure 12] FIG. 12 is a flowchart showing an example of a method for detecting the amount of change in the water depth based on the resonance frequency. [Figure 13] FIG. 13 is a functional block diagram of a water depth detection device according to the third embodiment. [Figure 14] FIG. 14 is a diagram showing an example of an arrangement mode of a water depth detection system according to the third embodiment in a water tank. [Figure 15] FIG. 15 is a flowchart showing an example of a water supply control method based on the detection result of the water depth. [Figure 16] FIG. 16 is a flowchart showing an example of a water supply control method based on the resonance current value of a pump. [Figure 17] FIG. 17 is a flowchart showing an example of a water supply control method based on the resonance frequency of a pump. [Figure 18] FIG. 18 is a functional block diagram of a water depth detection device according to the fourth embodiment. [Figure 19] FIG. 19 is a diagram showing an example of an arrangement mode of a water depth detection system according to the fourth embodiment in a water tank. [Figure 20] FIG. 20 is a flowchart showing an example of a method for detecting the inclination of a water tank based on the current value. [Figure 21] FIG. 21 is a flowchart showing an example of a method for detecting the inclination of a water tank based on the resonance frequency. [Figure 22] FIG. 22 is a flowchart showing an example of a method for detecting the inclination of a water tank based on the water depth.

MODE FOR CARRYING OUT THE INVENTION

[0012] [First Embodiment] A water depth detection device and water depth detection system according to the first embodiment of the present invention will be described with reference to the figures. While each embodiment, including this one, is shown as an example of a water depth detection device and water depth detection system for detecting water depth, they are also applicable to water state detection devices and water state detection systems for detecting various water conditions. Here, the water conditions are not limited to water depth, but include water volume, water weight, and other conditions that affect the pump load.

[0013] Figure 1 is a functional block diagram of the water depth detection device according to the first embodiment. Figure 2 is a plan view and a side view showing an example of the shape of the pump according to the first embodiment.

[0014] As shown in Figure 1, the water depth detection device 1 comprises a pump 10 and a control device 30. The control device 30 comprises a drive unit 41, an ammeter 42, a resistance element 420, a detection unit 43, a storage unit 430, a communication unit 44, and a notification unit 45. The control device 30 is composed of various electrical and electronic circuits.

[0015] As shown in Figure 2, the pump 10 includes a housing 100. The housing 100 is a box-shaped body and has a first surface F101, a second surface F102, and multiple side surfaces F103.

[0016] The housing 100 has a thickness D100. The thickness D100 corresponds to the distance between the first surface F101 and the second surface F102. The thickness D100 corresponds to the "length in the direction normal to the bottom surface of the pump" according to the present invention.

[0017] The housing 100 is rectangular when viewed from above. In the case of a rectangle, the distance L100 in the planar direction of the housing 100 corresponds to the length of one side of the rectangle. Note that the shape of the housing 100 when viewed from above is not limited to a rectangle. If the shape of the housing 100 when viewed from above is circular, the distance L100 in the planar direction corresponds to the diameter, and if it is a polygon, it corresponds to, for example, the length of the shortest side. The distance L100 corresponds to the "shortest length in the direction perpendicular to the normal direction" in this invention.

[0018] The thickness D100 is preferably smaller than the distance L100, and significantly smaller. This results in a thin housing 100.

[0019] The housing 100 has an internal space in which a piezoelectric element is arranged to vibrate. In this case, the piezoelectric element is a flat film shape, and when not vibrating, the flat film surface of the piezoelectric element is substantially parallel to the first surface F101 and the second surface F102.

[0020] One side F103 has an intake port IP100. The second side F102 has an outlet port OP100. The intake port IP100 and the outlet port OP100 communicate with the internal space of the housing 100.

[0021] In this configuration, supplying an AC drive signal to the piezoelectric element causes it to vibrate. As a result, the pump 10 draws in gas from the inlet IP100 and discharges gas from the outlet OP100.

[0022] In this case, the pump 10 has a resonant frequency based on the configuration and composition of the piezoelectric element. By having a drive signal supplied to the pump 10 that is the same as the resonant frequency, the pump 10 efficiently inhales and discharges gas.

[0023] As shown in Figure 1, the drive unit 41 is connected to the pump 10 and supplies a drive signal to the pump 10. The drive unit 41 controls the frequency of the drive signal to be the same as the resonant frequency of the pump 10. The drive unit 41 can be configured as either a self-excited or externally excited circuit.

[0024] The resistive element 420 is placed in the signal transmission line connecting the drive unit 41 and the pump 10.

[0025] The ammeter 42 measures the current value of the drive signal by measuring the voltage across the resistor element 420. The ammeter 42 measures the current value of the drive signal at a predetermined sampling interval or at a preset timing. The ammeter 42 outputs the measured current value of the drive signal to the detection unit 43. The combination of the resistor element 420 and the ammeter 42 corresponds to the "measurement unit" of the present invention. Furthermore, in this configuration, the current value corresponds to the "electrical characteristics" of the present invention.

[0026] The detection unit 43 detects either the absolute value of the water depth or the change in water depth based on the current value of the drive signal. The detection unit 43 can also detect both the absolute value of the water depth and the change in water depth.

[0027] More specifically, by controlling the frequency of the drive signal as described above, the current value of the drive signal detected by the detection unit 43 becomes the current value at the resonant frequency of the pump 10. Therefore, the detection unit 43 detects the current value at the resonant frequency of the pump 10 (resonant current value). Based on the resonant current value, the detection unit 43 detects the absolute value of the water depth or the amount of change in the water depth.

[0028] The detection unit 43 outputs the absolute value of the water depth or the amount of change in the water depth to at least one of the communication unit 44 and the notification unit 45.

[0029] The detection unit 43 may also be equipped with a water depth alert determination function. In this case, the detection unit 43 stores in advance alert determination thresholds for the absolute value of the water depth or the amount of change in the water depth. The detection unit 43 generates a low water level alert if the absolute value of the water depth falls below the absolute value alert determination threshold. The detection unit 43 also generates a low water level alert if the amount of change in the water depth exceeds the amount of change alert determination threshold.

[0030] The detection unit 43 outputs a low water level alert to at least one of the communication unit 44 and the notification unit 45.

[0031] The communication unit 44 is equipped with a communication function to an external device. The communication unit 44 transmits the absolute value of the water depth, the amount of change in the water depth, or a low water level alert to the external device.

[0032] The notification unit 45 notifies the absolute value of the water depth, the amount of change in the water depth, or a low water level alert. Notification methods can include light, text display, sound, etc.

[0033] A water depth detection system with such a configuration can be used, for example, as shown in Figure 3. Figure 3 is a diagram showing an example of how the water depth detection system according to the first embodiment is arranged in a water tank.

[0034] The tank 90 is a box-shaped structure with a bottom wall 901 and side walls 902. The top of the tank 90 is open, but it may be closed. Water is stored in the tank 90.

[0035] The pump 10 is positioned on the side wall 902 of the water tank 90. ​​More specifically, the pump 10 is positioned so that its first surface F101 is adjacent to and facing the inner wall surface of the side wall 902.

[0036] The pump 10 is positioned so as not to be submerged in the stored water. For example, the water tank 90 has a predetermined maximum storage depth. The pump 10 is positioned above the water level of the water tank 90, above the water level at this maximum storage depth. The pump 10 may also be positioned outside the water tank 90, or against a wall on the top side if there is one.

[0037] As described above, the pump 10 has a thin shape, and by positioning it so that its thickness is parallel to the mounting surface (the inner wall surface of the side wall 902) in a direction perpendicular to the mounting surface, the amount of protrusion into the aquarium 90 can be reduced even when the pump 10 is placed on the inner wall surface of the side wall 902. This means that, for example, it does not get in the way when viewing the aquarium 90 from above.

[0038] A control box 300 is located outside the water tank 90. ​​The control box 300 is, for example, a waterproof enclosure. The control box 300 houses modules of electrical or electronic circuits that constitute each of the functional parts of the control device 30 described above. The control box 300 is electrically connected to the pump 10 by wiring cables (not shown in the figure).

[0039] One end of the outflow pipe 20 is attached to the discharge port OP100 of the pump 10. The outflow pipe 20 is, for example, a flexible tube. A bubble generating ball 21 is attached to the other end of the outflow pipe 20. The bubble generating ball 21 is, for example, made of a porous material. Note that the bubble generating ball 21 is optional.

[0040] The other end of the outflow pipe 20 is fixed to the water tank 90. ​​As a result, the position of the other end of the outflow pipe 20 in the depth direction of the water tank 90 does not change.

[0041] In this configuration, when a drive signal is supplied to the pump 10, the pump 10 draws gas from the atmosphere through the intake port IP100 and discharges this gas through the discharge port OP100. The gas discharged from the pump 10 is released into the stored water through the outlet pipe 20 and the bubble generating ball 21. This supplies gas to the water stored in the water tank 90.

[0042] With the pump 10 performing the function of supplying gas to the water tank 90, the control device 30 uses the movement (driving state: electrical characteristics) of the pump 10 to detect, for example, the absolute value of the water depth and the amount of change in the water depth, as shown below.

[0043] (A concept for detecting the absolute value of water depth and the amount of change in water depth using current values) Figure 4(A) is a graph showing an example of the frequency characteristics of the impedance of a piezoelectric element, and Figure 4(B) is a magnified graph of the area around the resonant frequency of the characteristics shown in Figure 4(A).

[0044] As shown in Figures 4(A) and 4(B), the impedance of a piezoelectric element has a resonance point and an anti-resonance point. By matching the frequency of the drive signal to the frequency of the resonance point (resonance frequency), a pump using a piezoelectric element can achieve high pumping performance. Therefore, as described above, the drive unit 41 sets the frequency of the drive signal to be the same as or approximately the same as the resonance frequency.

[0045] Here, as shown in Figures 4(A) and 4(B), the impedance at the resonance point changes with water depth. This is for the following reason.

[0046] The impedance of a piezoelectric element depends on the magnitude of the load connected to it. Here, the load on the pump 10 (the load on the piezoelectric element) depends on the water pressure of the water stored in the water tank 90 to which the pump 10 supplies gas. The water pressure depends on the water depth. Therefore, as the water depth decreases, the water pressure decreases. As the water depth decreases, the load on the pump 10 decreases. As the load on the pump 10 decreases, the impedance of the pump 10 decreases.

[0047] For example, as shown in Figure 4(B), when the water depth DWa > water depth DWb, the impedance Za at the resonant frequency at water depth DWa is greater than the impedance Zb at the resonant frequency at water depth DWb. Conversely, when the water depth DWb < water depth DWa, the impedance Zb at the resonant frequency at water depth DWb is smaller than the impedance Za at the resonant frequency at water depth DWa.

[0048] Furthermore, as the impedance of the pump 10 decreases, the current value of the drive current increases, for example, if the pump 10 is driven by a constant voltage.

[0049] In this case, there is a 1:1 correlation between the absolute value of the water depth and the impedance of the pump 10 (the current value of the drive signal). Furthermore, there is a 1:1 correlation between the change in water depth and the change in the impedance of the pump 10, taking into account positive and negative values.

[0050] Furthermore, a 1:1 correlation between physical quantity A and physical quantity B means that for a given physical quantity A, physical quantity B is uniquely determined. For example, for a given absolute value of water depth, there is only one impedance value, meaning that the impedance is uniquely determined.

[0051] As described above, when driving the pump 10 to always achieve high pump characteristics, the drive unit 41 adjusts the frequency of the drive signal so that it becomes the same frequency as or approximately the same frequency as the changed resonant frequency when the resonant frequency changes.

[0052] Therefore, by measuring the current value of the drive signal, the current value and impedance at the resonant frequency can be measured, and thus the absolute value of the water depth and the amount of change in the water depth can be measured.

[0053] (Detection of the absolute value of water depth based on current value) Figure 5 is a flowchart showing an example of a method for detecting the absolute value of water depth based on current values.

[0054] The memory unit 430 pre-stores a table showing a 1:1 correlation between the resonant current value and the absolute value of the water depth, or a function showing a 1:1 correlation between the resonant current value and the water depth. The memory unit 430 also stores a table showing the correlation between the absolute value of the water depth and the current value of the drive signal of the pump 10.

[0055] The drive unit 41 supplies a drive signal to the pump 10 at a frequency matched to the pump 10's resonant frequency. The pump 10 operates continuously upon receiving the drive signal.

[0056] The ammeter 42 measures the resonant current value (S11i). In this case, the ammeter 42 may use an instantaneous value as the resonant current value output to the detection unit 43, or it may use the average value of multiple instantaneous resonant current values ​​within a measurement period of a predetermined length. By using the average value, error factors such as measurement errors and vibrations of the water tank 90 can be suppressed.

[0057] The detection unit 43 detects the absolute value of the water depth from the correlation between the resonant current value and the absolute value of the water depth (S12i). Specifically, the detection unit 43 detects the absolute value of the water depth using a table or function stored in the memory unit 430 and the resonant current value from the ammeter 42.

[0058] (Detection of changes in water depth based on current values) Figure 6 is a flowchart showing an example of a method for detecting changes in water depth based on current values.

[0059] The drive unit 41 supplies a drive signal to the pump 10 at a frequency matched to the pump 10's resonant frequency. The pump 10 operates continuously upon receiving the drive signal.

[0060] The ammeter 42 measures the resonant current value in the first time period (S21i). In this case, the ammeter 42 may use the instantaneous value in the first time period as the resonant current value output to the detection unit 43, or it may use the average value of multiple instantaneous resonant current values ​​within a first measurement period consisting of a predetermined time length including the first time period.

[0061] The ammeter 42 measures the resonant current value in a second time period that is after the first time period (S22i). In this case, the ammeter 42 may use the instantaneous value in the second time period as the resonant current value output to the detection unit 43, or it may use the average value of multiple instantaneous resonant current values ​​within a second measurement period consisting of a predetermined time length including the second time period.

[0062] The detection unit 43 compares the resonant current value at the first time (first resonant current value) with the resonant current value at the second time (second resonant current value).

[0063] The detection unit 43 detects that the water depth has changed if the first resonant current value and the second resonant current value are different, in other words, if there is a change in the resonant current value (S23i: YES).

[0064] On the other hand, the detection unit 43 detects that the water depth has not changed if the first resonant current value and the second resonant current value are the same, in other words, if there is no change in the resonant current value (S23i: NO).

[0065] It should be noted that the determination of whether the first resonant current value and the second resonant current value are the same or different is not limited to a perfect match. Specifically, the detection unit 43 calculates the difference between the first resonant current value and the second resonant current value. If the difference in resonant current values ​​is within the same determination threshold, the detection unit 43 determines that the first resonant current value and the second resonant current value are the same. On the other hand, if the difference in resonant current values ​​is greater than the same determination threshold, the detection unit 43 determines that the first resonant current value and the second resonant current value are different. By using this determination method, misdeterminations due to measurement errors can be suppressed.

[0066] (Detection of changes in water depth based on current values) Figure 7 is a flowchart showing an example of a method for detecting changes in water depth based on current values.

[0067] The memory unit 430 pre-stores a table showing a 1:1 correlation between the change in resonant current value and the change in water depth, or a function showing a 1:1 correlation between the change in resonant current value and the change in water depth.

[0068] The drive unit 41 supplies a drive signal to the pump 10 at a frequency matched to the pump 10's resonant frequency. The pump 10 operates continuously upon receiving the drive signal.

[0069] The ammeter 42 measures the resonant current value in the first time period (S21i). In this case, the ammeter 42 may use the instantaneous value in the first time period as the resonant current value output to the detection unit 43, or it may use the average value of multiple instantaneous resonant current values ​​within a first measurement period consisting of a predetermined time length including the first time period.

[0070] The ammeter 42 measures the resonant current value in a second time period that is after the first time period (S22i). In this case, the ammeter 42 may use the instantaneous value in the second time period as the resonant current value output to the detection unit 43, or it may use the average value of multiple instantaneous resonant current values ​​within a second measurement period consisting of a predetermined time length including the second time period.

[0071] The detection unit 43 calculates the difference (change) between the resonant current value at the first time (first resonant current value) and the resonant current value at the second time (second resonant current value).

[0072] The detection unit 43 detects the change in water depth from the correlation between the change in the resonant current value and the change in water depth (S26i). Specifically, the detection unit 43 detects the change in water depth using a table or function stored in the storage unit 430 and the change in the resonant current value.

[0073] [Second Embodiment] A water depth detection device according to a second embodiment of the present invention will be described with reference to the figures. Figure 8 is a functional block diagram of the water depth detection device according to the second embodiment.

[0074] The water depth detection device 1A according to the second embodiment differs from the water depth detection device 1 according to the first embodiment in that it detects water depth and the amount of change in water depth based on the resonant frequency instead of the resonant current value. The other components of the water depth detection device 1A are the same as those of the water depth detection device 1, and a description of the similar parts will be omitted.

[0075] The control device 30A of the water depth detection device 1A includes a current sensor 420A, a frequency detector 42A, and a detection unit 43A. The current sensor 420A can be substituted with a resistive element 420.

[0076] The current sensor 420A detects the current of the drive signal and outputs the detection signal to the frequency detector 42A. The frequency detector 42A detects the frequency of the detection signal acquired over a predetermined period of time. The frequency detector 42A corresponds to the "measurement unit" of the present invention. As a result, the frequency detector 42A can detect the frequency of the drive signal, i.e., the resonant frequency. The frequency detector 42A outputs the detected resonant frequency to the detection unit 43A. The resonant frequency corresponds to the "electrical characteristics" of the present invention.

[0077] The detection unit 43A detects the absolute value of the water depth and the amount of change in the water depth based on the resonant frequency.

[0078] (A concept for detecting the absolute value of water depth and the amount of change in water depth using resonant frequency) Figure 9(A) is a graph showing an example of the frequency characteristics of the impedance of a piezoelectric element, and Figure 9(B) is a magnified graph of the area around the resonant frequency of the characteristics shown in Figure 9(A).

[0079] As shown in Figures 9(A) and 9(B), the impedance of a piezoelectric element has a resonance point and an anti-resonance point. By matching the frequency of the drive signal to the frequency of the resonance point (resonance frequency), a pump using a piezoelectric element can achieve high pumping performance. Therefore, as described above, the drive unit 41 sets the frequency of the drive signal to be the same as or approximately the same as the resonance frequency.

[0080] Here, as shown in Figures 9(A) and 9(B), the frequencies of the resonance point (anti-resonance point) (resonance frequency, anti-resonance frequency) change with water depth. This is for the following reason.

[0081] The impedance of a piezoelectric element depends on the magnitude of the load connected to it. Here, the load on the pump 10 (the load on the piezoelectric element) depends on the water pressure of the water stored in the water tank 90 to which the pump 10 supplies gas. The water pressure depends on the water depth. Therefore, as the water depth decreases, the water pressure decreases. As the water depth decreases, the load on the pump 10 decreases. As the load on the pump 10 decreases, the loss component due to resonance of the piezoelectric element of the pump 10 decreases.

[0082] Thus, a change in water depth (load on pump 10) changes the loss component for resonance, which, depending on the specifications of pump 10, affects the parameters that determine the resonant frequency, and thus the resonant frequency changes.

[0083] For example, as shown in Figure 4(B), when the water depth DWa > water depth DWb, the resonant frequency fra at water depth DWa is lower than the resonant frequency frb at water depth DWb. Conversely, when the water depth DWb < water depth DWa, the resonant frequency frb at water depth DWb is higher than the resonant frequency fra at water depth DWa.

[0084] In this case, there is a 1:1 correlation between the absolute value of the water depth and the resonant frequency of the pump 10. Furthermore, there is a 1:1 correlation between the change in water depth and the change in the resonant frequency of the pump 10, taking into account positive and negative values.

[0085] As described above, when driving the pump 10 to always achieve high pump characteristics, the drive unit 41 adjusts the frequency of the drive signal so that it becomes the same frequency as or approximately the same frequency as the changed resonant frequency when the resonant frequency changes.

[0086] Therefore, by measuring the frequency of the drive signal (resonance frequency), it is possible to measure both the absolute value of the water depth and the amount of change in the water depth.

[0087] (Detection of absolute water depth based on resonant frequency) Figure 10 is a flowchart showing an example of a method for detecting the absolute value of water depth based on the resonant frequency.

[0088] The memory unit 430 pre-stores a table showing a 1:1 correlation between the resonant frequency and the absolute value of the water depth, or a function showing a 1:1 correlation between the resonant frequency and the water depth.

[0089] The drive unit 41 supplies a drive signal to the pump 10 at a frequency matched to the pump 10's resonant frequency. The pump 10 operates continuously upon receiving the drive signal.

[0090] The frequency detector 42A measures the resonant frequency (S11f). In this case, the frequency detector 42A may use an instantaneous value as the resonant frequency output to the detection unit 43A, or it may use the average value of multiple instantaneous values ​​of resonant frequencies within a measurement period of a predetermined length. By using the average value, error factors such as measurement errors and vibrations of the water tank 90 can be suppressed.

[0091] The detection unit 43A detects the absolute value of the water depth from the correlation between the resonant frequency and the absolute value of the water depth (S12f). Specifically, the detection unit 43A detects the absolute value of the water depth using a table or function stored in the memory unit 430 and the resonant frequency from the frequency detector 42A.

[0092] (Detection of changes in water depth based on resonant frequency) Figure 11 is a flowchart showing an example of a method for detecting changes in water depth based on the resonant frequency.

[0093] The drive unit 41 supplies a drive signal to the pump 10 at a frequency matched to the pump 10's resonant frequency. The pump 10 operates continuously upon receiving the drive signal.

[0094] The frequency detector 42A measures the resonant frequency in the first time period (S21f). In this case, the frequency detector 42A may use the instantaneous value in the first time period as the resonant frequency output to the detection unit 43A, or it may use the average value of multiple instantaneous values ​​of resonant frequencies within a first measurement period consisting of a predetermined time length including the first time period.

[0095] The frequency detector 42A measures the resonant frequency in a second time period that is after the first time period (S22f). In this case, the frequency detector 42A may use the instantaneous value in the second time period as the resonant frequency output to the detection unit 43A, or it may use the average value of multiple instantaneous values ​​of resonant frequencies within a second measurement period consisting of a predetermined time length including the second time period.

[0096] The detection unit 43A compares the resonant frequency at the first time (first resonant frequency) with the resonant frequency at the second time (second resonant frequency).

[0097] The detection unit 43A detects a change in water depth (S24f) if the first resonant frequency and the second resonant frequency are different, in other words, if there is a change in the resonant frequency (S23f: YES).

[0098] On the other hand, the detection unit 43A detects that the water depth has not changed if the first resonant frequency and the second resonant frequency are the same, in other words, if there is no change in the resonant frequency (S23f:NO).

[0099] It should be noted that the determination of whether the first and second resonant frequencies are the same or different here is not limited to a perfect match. Specifically, the detection unit 43 calculates the difference between the first and second resonant frequencies. If the difference in resonant frequencies is within the same determination threshold, the detection unit 43 determines that the first and second resonant frequencies are the same. On the other hand, if the difference in resonant frequencies is greater than the same determination threshold, the detection unit 43 determines that the first and second resonant frequencies are different. By using this determination method, misdeterminations due to measurement errors can be suppressed.

[0100] (Detection of changes in water depth based on resonant frequency) Figure 12 is a flowchart showing an example of a method for detecting changes in water depth based on the resonant frequency.

[0101] The memory unit 430 pre-stores a table showing a 1:1 correlation between the change in resonant frequency and the change in water depth, or a function showing a 1:1 correlation between the change in resonant frequency and the change in water depth.

[0102] The drive unit 41 supplies a drive signal to the pump 10 at a frequency matched to the pump 10's resonant frequency. The pump 10 operates continuously upon receiving the drive signal.

[0103] The frequency detector 42A measures the resonant frequency in the first time period (S21f). In this case, the frequency detector 42A may use the instantaneous value in the first time period as the resonant frequency output to the detection unit 43A, or it may use the average value of multiple instantaneous values ​​of resonant frequencies within a first measurement period consisting of a predetermined time length including the first time period.

[0104] The frequency detector 42A measures the resonant frequency in a second time period that is after the first time period (S22f). In this case, the frequency detector 42A may use the instantaneous value in the second time period as the resonant frequency output to the detection unit 43A, or it may use the average value of multiple instantaneous values ​​of resonant frequencies within a second measurement period consisting of a predetermined time length including the second time period.

[0105] The detection unit 43A calculates the difference (change) between the resonant frequency at the first time (first resonant frequency) and the resonant frequency at the second time (second resonant frequency).

[0106] The detection unit 43A detects the change in water depth based on the correlation between the change in resonant frequency and the change in water depth (S26f). Specifically, the detection unit 43A detects the change in water depth using a table or function stored in the storage unit 430 and the change in resonant frequency.

[0107] [Third Embodiment] A water depth detection device according to a third embodiment of the present invention will be described with reference to the figures. Figure 13 is a functional block diagram of the water depth detection device according to the third embodiment. Figure 14 is a diagram showing an example of how the water depth detection system according to the third embodiment is arranged in a water tank.

[0108] As shown in Figures 13 and 14, the water depth detection device 1B according to the third embodiment differs from the water depth detection device 1 according to the first embodiment in that it includes a water supply unit 50. The other components of the water depth detection device 1B are the same as those of the water depth detection device 1, and a description of the similar parts will be omitted.

[0109] As shown in Figure 14, the water supply unit 50 is positioned to supply water to the water tank 90.

[0110] The water supply unit 50 is connected to the detection unit 32.

[0111] Figure 15 is a flowchart showing an example of a water supply control method based on water depth detection results.

[0112] The detection unit 32 detects the amount of water depth decrease (S31) and outputs it to the water supply unit 50.

[0113] The water supply unit 50 does not supply water if the decrease is less than the water supply start threshold (S32: NO). The water supply unit 50 starts supplying water to the water tank 90 (S33) if the decrease is equal to or greater than the water supply start threshold (S32: YES).

[0114] The detection unit 32 detects the increase in water depth (S34) and outputs it to the water supply unit 50.

[0115] The water supply unit 50 continues to supply water if the increase is less than the water supply stop threshold (S35: NO). The water supply unit 50 stops supplying water if the increase is equal to or greater than the water supply stop threshold (S35: YES) (S36).

[0116] By performing this type of control, the control device 30B can detect the water depth and the amount of change in water depth, as well as automatically supply water.

[0117] The water supply starts automatically, but users can also manually stop it.

[0118] Furthermore, although the above configuration shows a method of controlling water supply based on the water depth detection result of the detection unit 32, water supply control may also be performed directly based on the electrical characteristics of the pump 10.

[0119] In this case, the detection unit 43 can be omitted, and the ammeter 42 outputs the resonant current value to the water supply unit 50.

[0120] Figure 16 is a flowchart showing an example of a water supply control method based on the resonant current value of a pump.

[0121] The water supply unit 50 detects the amount of change (decrease) in the resonant current value (S31i).

[0122] The water supply unit 50 does not supply water if the amount of change (decrease) is less than the water supply start threshold (S32i: NO). The water supply unit 50 starts supplying water to the water tank 90 (S33) if the amount of change (decrease) is equal to or greater than the water supply start threshold (S32i: YES).

[0123] The water supply unit 50 detects the amount of change (increase) in the resonant current value (S34i).

[0124] The water supply unit 50 continues to supply water if the amount of change (increase) is less than the water supply stop threshold (S35i: NO). The water supply unit 50 stops supplying water if the amount of change (increase) is greater than or equal to the water supply stop threshold (S35i: YES) (S36).

[0125] Figure 17 is a flowchart showing an example of a water supply control method based on the resonant frequency of a pump.

[0126] The water supply unit 50 detects the amount of change in the resonant frequency (the amount of shift in the high-frequency direction) (S31f).

[0127] The water supply unit 50 does not supply water if the amount of change (shift amount in the high-frequency direction) is less than the water supply start threshold (S32f: NO). The water supply unit 50 starts supplying water to the water tank 90 (S33) if the amount of change (shift amount in the high-frequency direction) is equal to or greater than the water supply start threshold (S32f: YES).

[0128] The water supply unit 50 detects the amount of change in the resonant frequency (the amount of shift towards the lower frequency direction) (S34f).

[0129] The water supply unit 50 continues to supply water if the amount of change (shift amount in the low frequency direction) is less than the water supply stop threshold (S35f: NO). The water supply unit 50 stops supplying water if the amount of change (shift amount in the low frequency direction) is greater than or equal to the water supply stop threshold (S35f: YES) (S36).

[0130] [Fourth Embodiment] A water depth detection device according to a fourth embodiment of the present invention will be described with reference to the figures. Figure 18 is a functional block diagram of the water depth detection device according to the fourth embodiment. Figure 19 is a diagram showing an example of how the water depth detection system according to the fourth embodiment is arranged in a water tank.

[0131] As shown in Figures 18 and 19, the water depth detection device 1C according to the fourth embodiment differs from the water depth detection device 1 according to the first embodiment in that it detects the tilt of the water tank. The other components of the water depth detection device 1C are the same as those of the water depth detection device 1, and a description of the similar parts will be omitted.

[0132] The control device 30C of the water depth detection device 1C comprises a drive unit 41C1, a drive unit 41C2, a resistive element 420C1, a resistive element 420C2, an ammeter 42C, and a detection unit 43C.

[0133] The drive unit 41C1 is connected to the pump 10C1 and supplies a first drive signal. The drive unit 41C2 is connected to the pump 10C2 and supplies a second drive signal.

[0134] The resistor element 420C1 is placed in the signal transmission line connecting the drive unit 41C1 and the pump 10C1. The resistor element 420C2 is placed in the signal transmission line connecting the drive unit 41C2 and the pump 10C2.

[0135] The ammeter 42C measures the current value of the first drive signal by measuring the voltage across the resistor element 420C1. The ammeter 42C also measures the current value of the second drive signal by measuring the voltage across the resistor element 420C2.

[0136] The detection unit 43C detects the resonant current value or resonant frequency from the current value of the first drive signal. This allows the resonant current value or resonant frequency of the pump 10C1 to be detected.

[0137] The detection unit 43C detects the resonant current value or resonant frequency from the current value of the second drive signal. This allows the resonant current value or resonant frequency of the pump 10C2 to be detected.

[0138] Here, as shown in Figure 19, the outlet port OP100C1 of pump 10C1 is connected to the outflow pipe 20C1 and the bubble generating ball 21C1. The outlet port OP100C2 of pump 10C2 is connected to the outflow pipe 20C2 and the bubble generating ball 21C2.

[0139] The gas discharge end of outlet pipe 20C1 (the connection end of bubble generating ball 21C1) and the gas discharge end of outlet pipe 20C2 (the connection end of bubble generating ball 21C1) are positioned and fixed at different locations when viewed from above in the water tank 90.

[0140] The detection unit 43C detects the tilt of the water tank 90 based on the resonant current value of the first drive signal (resonant current value of pump 10C1) and the resonant current value of the second drive signal (resonant current value of pump 10C2). In this embodiment, the detection unit 43C also functions as a "tilt detection unit".

[0141] (Detection of the tilt of the water tank based on the current value) Figure 20 is a flowchart showing an example of a method for detecting the tilt of a water tank based on the current value.

[0142] The detection unit 43C measures the resonant current value of pump 10C1 (first pump) (S41i) and the resonant current value of pump 10C2 (second pump) (S42i). The resonant current values ​​of pump 10C1 (first pump) and pump 10C2 (second pump) are measured at approximately the same time.

[0143] The detection unit 43C calculates the difference between the resonant current value of pump 10C1 (first pump) and the resonant current value of pump 10C2 (second pump). The detection unit 43C then calculates the difference in resonant current values ​​at multiple time points and calculates the amount of change in the difference in resonant current values ​​(S43i).

[0144] The detection unit 43C detects that the water tank 90 has tilted if the amount of change in the difference between the resonant current values ​​is greater than or equal to the tilt detection threshold (S44i: YES) (S45).

[0145] The detection unit 43C detects that the water tank 90 is not tilted if the amount of change in the difference in the resonant current value is less than the tilt detection threshold (S44i: NO) (S46).

[0146] In the control described above, the tilt of the water tank 90 was detected based on the change in the difference in the resonant current value. However, it is also possible to detect the tilt of the water tank 90 based on the difference in the change in the resonant current value.

[0147] (Detection of tank tilt based on resonant frequency) Figure 21 is a flowchart showing an example of a method for detecting the tilt of a water tank based on its resonant frequency.

[0148] The detection unit 43C measures the resonant frequency of pump 10C1 (first pump) (S41f) and the resonant frequency of pump 10C2 (second pump) (S42f). The resonant frequencies of pump 10C1 (first pump) and pump 10C2 (second pump) are measured at approximately the same time.

[0149] The detection unit 43C calculates the difference between the resonant frequency of pump 10C1 (first pump) and the resonant frequency of pump 10C2 (second pump). The detection unit 43C then calculates the difference in resonant frequencies at multiple time points and calculates the amount of change in the difference in resonant frequencies (S43f).

[0150] The detection unit 43C detects that the water tank 90 has tilted if the amount of change in the difference in the resonant frequency is greater than or equal to the tilt detection threshold (S44f: YES) (S45).

[0151] The detection unit 43C detects that the water tank 90 is not tilted if the amount of change in the difference in the resonant frequency is less than the tilt detection threshold (S44f:NO) (S46).

[0152] In the control described above, the tilt of the water tank 90 was detected based on the change in the difference in resonant frequencies. However, it is also possible to detect the tilt of the water tank 90 based on the difference in the change in resonant frequencies.

[0153] (Detection of tank tilt based on water depth) Figure 22 is a flowchart showing an example of a method for detecting the tilt of a water tank based on water depth.

[0154] The detection unit 43C measures the water depth at the position where pump 10C1 (first pump) supplies gas to the water tank 90 (gas discharge end of outlet pipe 20C1) (first pump position) (S41d), and measures the water depth at the position where pump 10C2 (second pump) supplies gas to the water tank 90 (gas discharge end of outlet pipe 20C2) (second pump position) (S42d). The water depth at the first pump position and the water depth at the second pump position are measured at approximately the same time.

[0155] The detection unit 43C calculates the difference in water depth between the water depth at the first pump location and the water depth at the second pump location. The detection unit 43C then calculates the water depth difference at multiple time points and calculates the change in the water depth difference (S43d).

[0156] The detection unit 43C detects that the water tank 90 has tilted if the amount of change in the water depth difference is greater than or equal to the tilt detection threshold (S44d: YES) (S45).

[0157] The detection unit 43C detects that the water tank 90 is not tilted if the amount of change in the water depth difference is less than the tilt detection threshold (S44d: NO) (S46).

[0158] In the control described above, the tilt of the tank 90 was detected based on the change in water depth, but it is also possible to detect the tilt of the tank 90 based on the difference in the change in water depth.

[0159] The configurations and controls of each of the above embodiments can be combined as appropriate, and effects corresponding to each combination can be achieved. [Explanation of Symbols]

[0160] 1, 1A, 1B, 1C: Water depth detection device 10, 10C1, 10C2: Pumps 20, 20C1, 20C2: Outflow pipe 21, 21C1, 21C2: Bubble-generating balls 30, 30A, 30B, 30C: Control devices 32: Detection unit 41, 41C1, 41C2: Drive unit 42, 42C: Ammeter 42A: Frequency detector 43, 43A, 43C: Detection unit 44: Communications Department 45:Notification Department 50: Water supply section 90: Aquarium 100: Cabinet 300: Control Box 420, 420C1, 420C2: Resistor elements 420A: Current sensor 430: Storage section 901: Bottom wall 902: Side wall F101: 1st page F102: 2nd side F103: Side view IP100: Inlet OP100, OP100C1, OP100C2: Discharge port Za, Zb: Impedance fra, frb: resonant frequency

Claims

1. A pump having an intake port for drawing in air from outside the water tank and an outlet port for discharging the air into the water tank, and configured using a piezoelectric element, A measuring unit for measuring the electrical characteristics of the pump, A detection unit for detecting the state of the water in the tank based on the aforementioned electrical characteristics, A water condition detection device equipped with the following features.

2. The aforementioned electrical characteristic is the current value of the pump. The water state detection device according to claim 1.

3. The current value of the pump is the resonant current value of the pump. The water state detection device according to claim 2.

4. The current value of the aforementioned pump and the state of the water are correlated. The detection unit detects the state of the water based on the correlation. The water state detection device according to claim 2 or claim 3.

5. The system includes a storage unit that stores the correlation between the current value of the pump and the state of the water. The detection unit detects the state of the water based on the correlation stored in the storage unit. The water state detection device according to claim 4.

6. The aforementioned electrical characteristics are the resonant frequency of the pump. The water state detection device according to claim 1.

7. The resonant frequency of the pump and the state of the water are correlated. The detection unit detects the state of the water based on the correlation. The water state detection device according to claim 6.

8. A pump having an intake port for drawing in air from outside the water tank and an outlet port for discharging the air into the water tank, and configured using a piezoelectric element, A measuring unit for measuring the electrical characteristics of the pump, A detection unit that detects the amount of change in the state of the water in the tank based on the electrical characteristics, A water condition detection device equipped with the following features.

9. The aforementioned electrical characteristic is the change in the current value of the pump. The water state detection device according to claim 8.

10. The change in the current value of the pump is the change in the resonant current value of the pump. The water state detection device according to claim 9.

11. The change in the current value of the pump and the change in the state of the water are correlated. The detection unit detects the amount of change in the state of the water based on the correlation. The water state detection device according to claim 9 or claim 10.

12. The aforementioned electrical characteristic is the amount of change in the resonant frequency of the pump. The water state detection device according to claim 8.

13. The amount of change in the resonant frequency of the pump and the amount of change in the state of the water are correlated. The detection unit detects the amount of change in the state of the water based on the correlation. The water state detection device according to claim 12.

14. The system includes a communication unit that communicates based on the detection results of the water state. A water state detection device according to any one of claims 1 to 13.

15. The unit includes a water supply section for supplying water to the aforementioned water tank, The water supply unit adjusts the amount of water supplied based on the detection result of the water state. A water state detection device according to any one of claims 1 to 14.

16. A pump having an intake port for drawing in air from outside the water tank and an outlet port for discharging the air into the water tank, and configured using a piezoelectric element, A measuring unit for measuring the electrical characteristics of the pump, A water supply unit that adjusts the amount of water supplied to the water tank based on the aforementioned electrical characteristics, A water condition detection device equipped with the following features.

17. The aforementioned pump, Equipped with a housing having a pump bottom, The pump is placed in the water tank with its bottom surface facing the wall of the water tank. The length in the direction normal to the bottom surface of the pump is shorter than the shortest length in the direction perpendicular to the normal direction. A water state detection device according to any one of claims 1 to 16.

18. Multiple pumps, each having an individual discharge port, Multiple outlet pipes, each connected to the discharge port of the multiple pumps, and each outlet pipe directs the gas discharged by the multiple pumps to different locations within the water tank, A tilt detection unit detects the tilt of the water tank based on the difference in the electrical characteristics of the plurality of pumps, Equipped with, A water state detection device according to any one of claims 1 to 17.

19. The state of the water is the water depth in the tank. A water state detection device according to any one of claims 1 to 18.

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