JP6934785B2 - Liquid detector - Google Patents

Description

The present invention relates to a liquid detection device capable of detecting the presence or absence of liquid in a container.

As a device for detecting the presence or absence of liquid in a container, a liquid detection device using ultrasonic waves has been conventionally known. For example, in Patent Document 1, the presence or absence of liquid in a container is detected by using an ultrasonic transducer that transmits and receives ultrasonic waves. That is, an ultrasonic transducer is installed on the wall surface of the container, and a pulsed AC voltage is applied to the ultrasonic transducer. Along with this, the container is acoustically excited.

Further, the reverberation vibration when a certain delay time elapses after the application of the AC voltage is detected by the ultrasonic transducer. At this time, based on the finding that the reverberation is significantly reduced when there is a liquid in the container, when the damping level of the reverberation vibration is less than a predetermined threshold value (when it is rapidly damped), the liquid is contained in the container. If it is determined to be present and the damping level of the reverberant vibration exceeds a predetermined threshold (it does not easily attenuate), it is determined that there is no liquid in the container.

Japanese Unexamined Patent Publication No. 2008-203204

An object of the present invention is to provide a liquid detection device capable of detecting the presence or absence of liquid in a container by a method different from the conventional ultrasonic liquid detection.

The present invention relates to a liquid detector. The device includes an ultrasonic oscillator, a receiver, and a measuring instrument. In the ultrasonic oscillator, the first oscillator is installed on the side wall of the container to oscillate the first oscillator for a predetermined excitation period. In the receiver, a second oscillator is installed on the side wall of the container. The measuring instrument receives the vibration intensity of the second vibrator and measures the time change thereof. The measuring instrument is a determination unit that determines that there is liquid in the container when the vibration intensity of the second vibrator exceeds a predetermined intensity threshold value in the determination period after the elapse of a predetermined standby time from the start of the excitation period. To be equipped.

According to the findings of the inventors, when a liquid is contained in the container, the wave (propagating wave 1) mainly transmitted through the container and received by the receiver converges as a propagation mode of the propagated wave oscillated from the ultrasonic oscillator. After that, it became clear that the wave mainly propagating in the liquid (propagation wave 2) was propagated to the receiver. The intensity of the propagated wave 2 is captured in the determination period, and when the intensity exceeds a predetermined threshold value, it can be determined that there is a liquid in the container.

Further, in the above invention, the ultrasonic oscillator may include an excitation period setting unit that sets the end time of the excitation period before the start time of the determination period.

Further, in the above invention, the measuring instrument may set the period after the first propagating wave propagating to the second vibrator via the container by the excitation of the first vibrator has converged as the determination period.

Further, in the above invention, the ultrasonic oscillator and the receiver may be arranged on the side wall of the container, respectively.

Further, in the above invention, the ultrasonic oscillator and the receiver may be arranged so as to face each other with the container in between.

According to the present invention, the presence or absence of liquid in the container can be detected by a method different from the conventional ultrasonic type liquid detection.

It is a figure explaining the outline of the liquid detection apparatus which concerns on this embodiment. It is a figure explaining the arrangement of an ultrasonic oscillator and a receiver. It is a figure (liquid level: 100%) explaining the method of determining the presence or absence of liquid in a container in this embodiment. It is a figure (liquid level: 0%) explaining the method of determining the presence or absence of liquid in a container in this embodiment. It is a figure which shows the waveform of the transmitted wave and the received wave in this embodiment (opposed arrangement, liquid level: 0%). It is a figure which shows the waveform of the transmitted wave and the received wave in this embodiment (opposed arrangement, liquid level: 25%). It is a figure which shows the waveform of the transmitted wave and the received wave in this embodiment (opposed arrangement, liquid level: 50%). It is a figure which shows the waveform of the transmitted wave and the received wave in this embodiment (opposed arrangement, liquid level: 75%). It is a figure which shows the waveform of the transmitted wave and the received wave in this embodiment (opposed arrangement, liquid level: 100%). It is a figure which shows the waveform of the transmission wave and the reception wave in this embodiment (opposite arrangement, liquid level 0% vs liquid level 100%). It is a figure which shows the waveform of the transmission wave and the reception wave in this embodiment (opposite arrangement, liquid level 0% vs liquid level 50%). It is a figure which shows the waveform of the transmission wave and the reception wave in this embodiment (opposite arrangement, liquid level 50% vs liquid level 100%). It is a figure (opposite arrangement, liquid level 0%) which shows the waveform of the transmitted wave and the received wave in this embodiment when the iron pipe with the inner diameter 50 mm and the thickness 5 mm is used as a container. It is a figure (opposite arrangement, liquid level 100%) which shows the waveform of the transmitted wave and the received wave in this embodiment when the iron pipe with the inner diameter 50 mm and the thickness 5 mm is used as a container. It is a figure (opposite arrangement, liquid level 0% vs liquid level 100%) which shows the waveform of the transmitted wave and the received wave in this embodiment when the iron pipe with the inner diameter 50 mm and the thickness 5 mm is used as a container. It is a figure explaining the arrangement of the ultrasonic oscillator and the receiver in the modification 1. It is a figure (90 ° arrangement, liquid level: 0%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level: 25%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level: 50%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level: 75%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level: 100%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level 0% vs liquid level 100%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level 0% vs liquid level 50%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure (90 ° arrangement, liquid level 50% vs liquid level 100%) which shows the waveform of the transmission wave and the reception wave in the modification 1. It is a figure explaining the arrangement of the ultrasonic oscillator and the receiver in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level: 0%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level: 25%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level: 50%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level: 75%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level: 100%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level 0% vs liquid level 100%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level 0% vs liquid level 50%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure (top and bottom adjacent arrangement, liquid level 50% vs liquid level 100%) which shows the waveform of the transmission wave and the reception wave in the modification 2. It is a figure explaining the arrangement of an ultrasonic oscillator and a receiver in a comparative example. It is a figure which shows the waveform of the transmission wave and the reception wave in the comparative example (arrangement on the receiving part, liquid level: 0%). It is a figure which shows the waveform of the transmission wave and the reception wave in the comparative example (arrangement on the receiving part, liquid level: 25%). It is a figure which shows the waveform of the transmission wave and the reception wave in the comparative example (arrangement on the receiving part, liquid level: 50%). It is a figure which shows the waveform of the transmission wave and the reception wave in the comparative example (arrangement on the receiving part, liquid level: 75%). It is a figure which shows the waveform of the transmission wave and the reception wave in the comparative example (arrangement on the receiving part, liquid level: 100%). It is a figure which shows the waveform of the transmission wave and the reception wave in the comparative example (arrangement on the receiving part, liquid level 0% vs liquid level 100%).

FIG. 1 illustrates the liquid detection device 10 according to the present embodiment. The liquid detection device 10 includes an ultrasonic oscillator 12, a receiver 14, and a measuring device 16. The liquid detection device 10 detects (determines) the presence or absence of liquid in the container 20 from the container side wall 22 which is the outer wall of the container 20 capable of containing the liquid 18.

The container side wall 22 and the other wall members constituting the container 20 are made of a non-permeable material such as a metal container. Examples of the container 20 include a casing constituting the flow path of the can motor pump. If the pump motor is driven while the liquid is not flowing in the flow path, so-called idle operation may occur, which may lead to overheating of the pump motor. Therefore, the presence or absence of liquid in the casing is determined (detected) by using the liquid detection device 10 according to the present embodiment.

The ultrasonic oscillator 12 includes a first oscillator 24. The first vibrator 24 is installed on the side wall 22 of the container. The first vibrator 24 is composed of, for example, a piezoelectric element. A high-voltage circuit (not shown) is connected to the ultrasonic oscillator 12, for example, an AC voltage having an amplitude of about 400 [V] peak-to-peak and a frequency of 150 [kHz] or more and 300 [kHz] or less is the first oscillator 24. Is applied to. As a result, ultrasonic vibration is applied from the first vibrator 24 to the side wall 22 of the container.

Further, the ultrasonic oscillator 12 includes an excitation period setting unit 26. The excitation period setting unit 26 sets the excitation period of the first vibrator 24, that is, the application period of the AC voltage. The end time of the excitation period is set before the start time of the determination period described later.

The receiver 14 includes a second oscillator 28. In the second vibrator 28, the propagating wave 1 (first propagating wave) mainly passing through the side wall 22 of the container by the excitation of the first vibrator 24 and the liquid in the container 20 after the convergence of the propagating wave 1 are mainly applied. The propagating wave 2 (second propagating wave) passing through is propagated. Based on this, as the excitation period, a period that does not overlap with the rising edge of the propagated wave 2 is set.

For example, assuming that the propagation velocity of the propagation wave 1 is c1, the propagation velocity of the propagation wave 2 is c2 (c1> c2), and the radius (inner diameter) of the container is r, the ultrasonic oscillator 12 and the receiver 14 as shown in FIG. It is preferable that the end time point of the excitation period is less than 2r / c2 [sec] from the start time point of the excitation period in consideration of the facing arrangement of the above. Further, it is more preferable that the end time of the excitation period is less than πr / c1 [sec] from the start time of the excitation period so that the convergence of the propagated wave 1 can be clearly grasped.

The second vibrator 28 of the receiver 14 is composed of, for example, a piezoelectric element, and is installed on the side wall 22 of the container. As described above, the second vibrator 28 receives the propagated wave generated in the container 20 by the excitation of the first vibrator 24. In the present embodiment, the ultrasonic oscillator 12 and the receiver 14 may be configured independently, but may be integrated. In this case, the first oscillator 24 may serve as both an oscillating means and a receiving means.

The measuring instrument 16 receives the vibration intensities of the first vibrator 24 and the second vibrator 28 and measures the time change thereof. The measuring instrument 16 may be, for example, an oscilloscope. The measuring instrument 16 includes a display unit that displays waveforms, and can independently display the vibration waveforms of the first vibrator 24 and the second vibrator 28. In FIG. 1, the waveform with "1" is the waveform by the first vibrator 24 (transmission waveform), and the waveform with "2" is the waveform by the second vibrator 28 (received waveform).

Further, the measuring instrument 16 includes a determination unit 30 for determining the presence or absence of liquid in the container 20. The determination unit 30 is composed of, for example, a computer. The determination unit 30 monitors the vibration intensity of the second vibrator 28 during the determination period after the elapse of a predetermined waiting time from the start time of the excitation period. Then, when the vibration intensity exceeds a predetermined intensity threshold Th, it is determined that there is a liquid in the container 20.

The determination unit 30 can set the determination period. If the determination period and the excitation period overlap, the propagating wave 2 may be superimposed on the propagating wave 1, making it difficult to accurately evaluate the propagating wave 2. Therefore, it is preferable that the end time point of the excitation period is set before the start time point of the determination period. In addition, for reliable monitoring of the propagating wave 2, the determination unit 30 preferably sets the period after the propagating wave 1 has converged as the determination period.

<Liquid detection principle>
The liquid detection principle of the liquid detection device 10 according to the present embodiment will be described with reference to FIGS. 2 to 4. FIG. 2 shows an example of arrangement of the ultrasonic oscillator 12 and the receiver 14 with respect to the container 20. The upper part of FIG. 2 shows a plan view, and the lower part shows a side view. As shown in these figures, the ultrasonic oscillator 12 and the receiver 14 are arranged so as to face each other with the container 20 in between.

The waveforms from the first vibrator 24 and the second vibrator 28 received by the measuring instrument 16 in such an opposite arrangement are shown in FIG. For this measurement, a container 20 made of aluminum having a diameter of 220 mm, a depth of 100 mm, and a thickness of 1 mm was used. The frequency of the first vibrator 24 was set to 272 [kHz]. Further, water was used as the liquid 18.

In FIG. 3, the horizontal axis represents time [Sec] and the vertical axis represents signal strength. The waveforms are shown in the upper and lower two stages, the upper stage shows the waveform (transmitted wave) acquired from the ultrasonic oscillator 12, and the lower stage shows the waveform (received wave) acquired from the receiver 14. Hereinafter, up to FIG. 40, the horizontal axis, the vertical axis, the upper waveform, and the lower waveform are the same. Further, in FIGS. 3 and 4, one scale of the broken line separating the horizontal axis represents 100 μsec. The parameters shown in FIGS. 3 and 4 are the same as those in FIG. 13, and these parameters will be described later.

In acquiring the graph of FIG. 3, the liquid level (water level) of the container 20 was set to 100%. The excitation period was set to 100 μsec. As shown in this figure, the receiver 14 receives the propagated wave (propagated wave 1) immediately after the excitation by the ultrasonic oscillator 12, and after that, once converged, the propagated wave (propagated wave 2) rises again. There is.

On the other hand, FIG. 4 shows a waveform when the liquid level (water level) of the container 20 is 0%, that is, when there is no liquid in the container 20. The excitation period was 100 μsec. As shown in this figure, the receiver 14 receives the propagated wave (propagated wave 1) immediately after the excitation by the ultrasonic oscillator 12, then converges once, and then has a waveform having a smaller amplitude than that of FIG. Propagation wave 2) is rising.

In this way, by changing the presence or absence of the liquid in the container 20 between FIGS. 3 and 4, the intensity of the propagating wave 2 changes remarkably. Utilizing this phenomenon, in the present embodiment, a period after the convergence of the propagating wave 1 (first propagating wave) is set as the determination period. For example, as shown in FIG. 3, 150 μsec after the start time of excitation by the ultrasonic oscillator 12 is set as the start time of the determination period.

Further, in the present embodiment, the maximum intensity (amplitude) of the propagating wave 2 when the liquid level (water level) of the container 20 is 0% is exceeded, and the propagating wave when the liquid level of the container 20 is 100%. The intensity threshold is set in a range that is less than the maximum intensity of 2.

Various waveforms in the facing arrangement of FIG. 3 will be described with reference to FIGS. 5 to 12. Similar to FIG. 4, FIG. 5 shows the waveforms of the transmitted wave and the received wave when there is no liquid in the container 20 (liquid level: 0%). In the graph of FIG. 5, reference numeral A indicates the position on the graph on which the cursor is placed. Reference numeral B indicates a transmitted wave signal. Reference numeral C indicates a receiving side signal. Reference numeral D indicates a voltage range of the transmitted wave, and reference numeral E indicates a voltage range of the received wave. Reference numeral F indicates the time on the central scale on the horizontal axis. The reference numeral G indicates an automatically measured value at the rising edge of the waveform, and the reference numeral H indicates the frequency at that time.

Further, in the subsequent graphs including FIG. 5, since the amplitude of the transmitted wave is large, the waveform of the propagated wave 1 generated in the received wave immediately after that is partially overlapped with the waveform of the transmitted wave. Based on this, the waveform of the received wave does not overlap with the transmitted wave, and the latter part basically shows the propagation wave 2 and the reverberation components after that. As shown in the graph of FIG. 5, it is understood that the waveform seen as the propagating wave 2 rises slightly.

The graph of FIG. 6 shows the waveform when a liquid having a water level of 25% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the waveform seen as the propagating wave 2 rises slightly.

The graph of FIG. 7 shows the waveform when a liquid having a water level of 50% is supplied to the container 20. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG.

The graph of FIG. 8 shows the waveform when a liquid having a water level of 75% is supplied to the container 20. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG.

The graph of FIG. 9 shows the waveform when a liquid having a 100% water level is supplied to the container 20. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG.

FIG. 10 shows an example in which a graph having a water level of 0% (FIG. 5) and a graph having a water level of 100% (FIG. 9) are compared side by side. According to this, it is understood that a significant difference appears between the two waveforms by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period. For example, by setting the intensity threshold Th as shown in FIG. 10, it is possible to determine the presence or absence of liquid in the container 20.

FIG. 11 shows an example in which a graph having a water level of 0% (FIG. 5) and a graph having a water level of 50% (FIG. 7) are compared side by side. According to this, it is understood that a significant difference appears between the two waveforms by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period. For example, by setting the intensity threshold Th as shown in FIG. 11, it is possible to determine the presence or absence of liquid in the container 20. That is, it is understood that the liquid detection device 10 according to the present embodiment can detect the liquid as long as the container 20 contains about half of the water level even if the container 20 is not filled with the liquid up to the upper limit of the water level. Will be done.

FIG. 12 shows an example in which a graph having a water level of 50% (FIG. 7) and a graph having a water level of 100% (FIG. 9) are arranged side by side. As shown in this graph, there is a significant difference in the intensities of the two propagating waves 2. Intensity threshold Th is a value that exceeds the maximum intensity of the propagated wave 2 and subsequent waveforms of the graph with a water level of 50% and is less than the maximum intensity of the propagated wave 2 and subsequent waveforms of the graph with a water level of 100%. By setting to, the liquid level (water level) in the container 20 can be determined.

13 to 15 show waveforms when the structure of the container 20 is changed. In this embodiment, an iron pipe having an inner diameter of 50 mm and a thickness of 5 mm is used as the container 20. In FIG. 13, reference numeral I indicates the position on the graph where the current cursor is located. Reference numeral J indicates a transmission wave signal, and reference numeral K indicates a reception wave signal. The reference numeral L indicates the voltage range of the transmitted wave, and the reference numeral M indicates the voltage range of the received wave. The symbol N indicates the time of the scale at the center of the horizontal axis. The symbol O indicates the measurement level of a single square wave. The reference numeral P indicates the frequency at the time of measurement of the square wave.

FIG. 13 shows the measurement result when the water level of the container 20 is 0%, that is, when there is no liquid in the container 20. Further, FIG. 14 shows the measurement result when the water level of the container 20 is 100%. The frequency of the AC voltage applied to the first vibrator 24 was set to 300 kHz. FIG. 15 shows an example in which the two are compared side by side. As shown in this graph, the maximum intensity of the propagation wave 2 and the waveform after that of the graph with a water level of 0% is exceeded, and the maximum intensity of the waveform after the propagation wave 2 of the graph with a water level of 100% is exceeded. A value that is less than the intensity threshold Th is set. In addition, the presence or absence of liquid in the container 20 can be determined by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period.

<Modification example 1>
FIG. 16 illustrates a modified example of the liquid detection device 10 according to the present embodiment in which the arrangements of the ultrasonic oscillator 12 and the receiver 14 are changed. In FIG. 16, a plan view is shown in the upper row and a side view is shown in the lower row. In this example, the receiver 14 is provided at a right angle to the ultrasonic oscillator 12 in a plan view. As the container 20, the same container as that used in FIGS. 3 to 12 was used.

Various waveforms in the 90 ° arrangement of FIG. 16 will be described with reference to FIGS. 17 to 24. FIG. 17 shows the waveforms of the transmitted wave (1) and the received wave (2) when there is no liquid in the container 20 (liquid level: 0%). It is understood that the waveform that appears to be the propagating wave 2 rises slightly.

The graph of FIG. 18 shows the waveform when a liquid having a water level of 25% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is about the same as that in FIG.

The graph of FIG. 19 shows a waveform when a liquid having a water level of 50% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is larger than that in FIG. 18 especially around the center position (250 μs) on the horizontal axis.

The graph of FIG. 20 shows the waveform when a liquid having a water level of 75% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG.

The graph of FIG. 21 shows a waveform when a liquid having a water level of 100% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG.

FIG. 22 shows an example in which a graph having a water level of 0% (FIG. 17) and a graph having a water level of 100% (FIG. 21) are compared side by side. According to this, it is understood that a significant difference appears between the two waveforms by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period. For example, by setting the intensity threshold Th as shown in FIG. 22, it is possible to determine the presence or absence of liquid in the container 20.

FIG. 23 shows an example in which a graph having a water level of 0% (FIG. 17) and a graph having a water level of 50% (FIG. 19) are compared side by side. According to this, it is understood that a significant difference appears between the two waveforms by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period. For example, by setting the intensity threshold Th as shown in FIG. 23, it is possible to determine the presence or absence of liquid in the container 20. That is, it is understood that the liquid detection device 10 according to the present embodiment can detect the liquid as long as the container 20 contains about half of the water level even if the container 20 is not filled with the liquid up to the upper limit of the water level. Will be done.

FIG. 24 shows an example in which a graph having a water level of 50% (FIG. 19) and a graph having a water level of 100% (FIG. 21) are arranged side by side. As shown in this graph, there is a significant difference in the intensities of the two propagating waves 2. Intensity threshold Th is a value that exceeds the maximum intensity of the propagated wave 2 and subsequent waveforms of the graph with a water level of 50% and is less than the maximum intensity of the propagated wave 2 and subsequent waveforms of the graph with a water level of 100%. By setting to, the liquid level (water level) in the container 20 can be determined.

<Modification 2>
FIG. 25 illustrates a further modification of the liquid detection device 10 according to the present embodiment, in which the arrangement of the ultrasonic oscillator 12 and the receiver 14 is changed. In FIG. 25, a plan view is shown in the upper row and a side view is shown in the lower row. In this example, the ultrasonic oscillator 12 and the receiver 14 are adjacent to each other in the circumferential direction and the vertical direction. For example, in a plan view, the angle θ formed by the line segment connecting the center C of the container 20 and the center of the ultrasonic oscillator 12 and the line segment connecting the center C of the container 20 and the center of the receiver 14 is set to less than 10 °. .. Further, the receiver 14 was arranged directly above the ultrasonic oscillator 12. As the container 20, the same container as that used in FIGS. 3 to 12 was used.

Various waveforms in the vertically adjacent arrangement of FIG. 25 will be described with reference to FIGS. 26 to 33. FIG. 26 shows the waveforms of the transmitted wave (1) and the received wave (2) when there is no liquid in the container 20 (liquid level: 0%). It is understood that the waveform that appears to be the propagating wave 2 rises slightly.

The graph of FIG. 27 shows the waveform when a liquid having a water level of 25% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is about the same as that in FIG.

The graph of FIG. 28 shows the waveform when a liquid having a water level of 50% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is larger near the center (250 μs) of the horizontal axis of the graph than the same position in FIGS. 26 and 27. ..

The graph of FIG. 29 shows the waveform when a liquid having a water level of 75% is supplied to the container 20. The oscillation conditions of the transmitted wave were the same as in FIG. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG. 28.

The graph of FIG. 30 shows a waveform when a liquid having a water level of 100% is supplied to the container 20. Focusing on the waveform of the received wave, it is understood that the amplitude (intensity) of the waveform seen as the propagating wave 2 is even larger than that in FIG. 29.

FIG. 31 shows an example in which a graph having a water level of 0% (FIG. 26) and a graph having a water level of 100% (FIG. 30) are compared side by side. According to this, it is understood that a significant difference appears between the two waveforms by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period. For example, by setting the intensity threshold Th as shown in FIG. 31, it is possible to determine the presence or absence of liquid in the container 20.

FIG. 32 shows an example in which a graph having a water level of 0% (FIG. 26) and a graph having a water level of 50% (FIG. 28) are compared side by side. According to this, it is understood that a significant difference appears between the two waveforms by setting an arbitrary determination period Ta after the propagation period of the propagate wave 1 and comparing the waveforms in the period. For example, by setting the intensity threshold Th as shown in FIG. 32, the presence or absence of liquid in the container 20 can be determined. That is, it is understood that the liquid detection device 10 according to the present embodiment can detect the liquid as long as the container 20 contains about half of the water level even if the container 20 is not filled with the liquid up to the upper limit of the water level. Will be done.

FIG. 33 shows an example in which a graph having a water level of 50% (FIG. 28) and a graph having a water level of 100% (FIG. 30) are arranged side by side. As shown in this graph, there is a significant difference in the intensities of the two propagating waves 2. Intensity threshold Th is a value that exceeds the maximum intensity of the propagated wave 2 and subsequent waveforms of the graph with a water level of 50% and is less than the maximum intensity of the propagated wave 2 and subsequent waveforms of the graph with a water level of 100%. By setting to, the liquid level (water level) in the container 20 can be determined.

<Comparison example>
FIG. 34 shows an example in which the ultrasonic oscillator 12 is arranged on the side wall 22 of the container and the receiver 14 is provided on the upper wall of the container as a comparative example of the liquid detection device 10 according to the present embodiment. As the container 20, the same container as that used in FIGS. 3 to 12 was used.

35, 36, 37, 38, and 39 show graphs when the water level of the container 20 is 0%, 25%, 50%, 75%, and 100%, respectively. In each of the figures, the waveform of the receiver 14 is the same. FIG. 40 shows the waveforms when the water level is 0% and 100%, but no significant difference is observed.

Based on this embodiment and its modifications and comparative examples, in this embodiment, the presence or absence of liquid in the container 20 is accurately determined by arranging the ultrasonic oscillator 12 and the receiver 14 on the side wall 22 of the container. It will be possible. Further, particularly comparing this embodiment with its modified example, when the ultrasonic oscillator 12 and the receiver 14 are arranged to face each other (FIGS. 5 to 12), the liquid level in the container 20 is 0%. , It is understood that the difference from the case of 100% is large as compared with the modified example.

10 Liquid detector, 12 Ultrasonic oscillator, 14 Receiver, 16 Measuring instrument, 18 Liquid, 20 Container, 22 Container side wall, 24 First oscillator, 26 Excitation period setting unit, 28 Second oscillator, 30 Judgment unit.

Claims (5)

An ultrasonic oscillator in which the first oscillator is installed on the side wall of the container to excite the first oscillator over a predetermined excitation period.
A receiver in which a second vibrator is installed on the side wall of the container,
A measuring instrument that receives the vibration intensity of the second vibrator and measures its time change.
With
The instrument, in the determination period after a lapse of a predetermined waiting time from the start of the excitation period, the vibration intensity of the second vibrator, when exceeded a predetermined intensity threshold, O and there the liquid in the container Equipped with a judgment unit to judge
The ultrasonic oscillator includes the period during which the first propagating wave propagating to the second oscillator via the container due to the excitation of the first oscillator is propagating for the excitation period, and the first oscillator. The end point is before the rise of the second propagating wave propagating to the second vibrator via the liquid in the container due to the excitation of.
Liquid detector. The liquid detection device according to claim 1.
The ultrasonic oscillator is a liquid detection device including an excitation period setting unit that sets the end time point of the excitation period before the start time point of the determination period. The liquid detection device according to claim 1 or 2.
The measuring device sets a period after the first transmission wave is converged to the decision period, the liquid detection device. The liquid detection device according to any one of claims 1 to 3.
A liquid detection device in which the ultrasonic oscillator and the receiver are respectively arranged on the side wall of the container. The liquid detection device according to claim 4.
A liquid detection device in which the ultrasonic oscillator and the receiver are arranged so as to face each other with the container in between.

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