JP2020139852A - Liquid level position detector - Google Patents

Abstract

To provide a liquid level position detector comprising high detection accuracy of a liquid level position.SOLUTION: A liquid level position detector 100 comprises: a propagation body 10 which is soaked in a liquid, whose boundary of being soaked in a liquid is displaced by a liquid level position of the liquid (liquid level position) and to which ultrasonic vibration is propagated; vibration generation means 20 which is provided on one end surface part 15 of the propagation body 10 and generates ultrasonic vibration to the propagation body 10; and detection means (transmission/reception circuit and control part) for detecting a liquid level position on the basis of a propagation period in which the ultrasonic vibration generated by the vibration generation means 20 propagates to a second position from a first position of the propagation body 10 straddling the boundary. The propagation body 10 comprises: two propagation surface parts 11, 12 which are in a front/rear relationship; two side surface parts 14 connecting the two propagation surface parts 11, 12; a bottom surface part for connecting the two propagation surface parts 11, 12 and being formed into a curved surface in side view; and a side surface hole 17 for penetrating the two side surface parts 14 and having an upper side part 17a parallel to one end surface part 15, the side surface hole 17 has a small width a in a height direction relative to a width b of the upper side part 17a.SELECTED DRAWING: Figure 4

Description

The present invention relates to a liquid level position detecting device.

As a liquid level position detecting device, for example, in Patent Document 1, the speed of sound of a surface wave propagating in a portion of a propagator in a liquid becomes slower than the speed of sound of a surface wave propagating in a portion exposed from the liquid. It is disclosed that the liquid level position of the liquid is detected by utilizing the above.

Japanese Unexamined Patent Publication No. 4-86525

In the liquid level position detecting device disclosed in Patent Document 1, the surface wave propagating in the propagating body is attenuated depending on the liquid level position, and the S / N ratio (Signal-Noise ratio) deteriorates. The detection accuracy may deteriorate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid level position detecting device having good liquid level position detection accuracy.

In order to achieve the above object, the liquid level position detecting device according to the present invention is
A propagator in which ultrasonic vibration propagates, in which the boundary of immersion in the liquid is displaced according to the liquid level position of the liquid, and
A vibration generating means provided on one end surface of the propagating body to generate the ultrasonic vibration in the propagating body, and
A detection means for detecting the liquid level position based on a propagation time in which the ultrasonic vibration generated by the vibration generating means propagates from a first location of the propagating body to a second location across the boundary is provided.
The propagator
Two propagation planes that are two sides of the same coin,
Two side surface portions connecting the two propagation surface portions and
A bottom surface portion that connects the two propagation surface portions and has a curved surface in a side view,
A side hole that penetrates the two side surfaces and has an upper side parallel to the one end surface.
The side hole is formed so that the width along the height direction is smaller than the width of the upper side portion.
It is characterized by that.

According to the present invention, it is possible to provide a liquid level position detecting device having good liquid level position detection accuracy.

It is a schematic block diagram of the liquid level position detection apparatus which concerns on embodiment of this invention. According to the embodiment, (a) is a front view of the propagator and the oscillator, and (b) is a side view. It is a schematic diagram for demonstrating the 1st surface wave and the 2nd surface wave. It is a schematic diagram for demonstrating the detection wave. It is a flowchart which shows an example of the liquid level position detection processing. (A) to (c) are graphs for explaining the interference between the surface wave and the detected wave, respectively. It is a schematic diagram for demonstrating the detection wave of another embodiment.

The liquid level position detecting device according to the embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the liquid level position detecting device 100 according to the present embodiment is a device that detects the position of the liquid level 91 of the liquid 90 contained in the container 80. As the amount of the liquid 90 increases or decreases, the liquid level 91 also moves up and down.

The liquid level position detecting device 100 includes a propagating body 10, an oscillator (vibration generating means) 20, a transmission / reception circuit (detecting means) 30, and a control unit (detecting means) 40.

The propagator 10 propagates surface waves, and is formed of, for example, a synthetic resin such as PPS (polyphenylene sulfide). The propagator 10 has a substantially columnar shape (substantially rectangular parallelepiped shape) that is long in the vertical direction. The outer surface of the propagator 10 includes an upper surface (one end surface) facing the vibrator 20, a bottom surface on the opposite side of the upper surface, two main surfaces that connect the upper surface and the bottom surface and have a front-to-back relationship with each other, and an upper surface and a bottom surface. It is mainly composed of 6 sides, 2 sides that are connected and have a two-sided relationship with each other.

As shown in FIGS. 2A and 2B, the propagator 10 includes a propagation surface portion 11 including one of the two main surfaces, a propagation surface portion 12 including the other, and a side surface portion including one of the two side surfaces. 13. It has a side surface portion 14 including the other, an upper surface portion (one end surface portion) 15 including the upper surface and in contact with the vibrator 20, and a bottom surface portion 16 including the bottom surface. As will be described later, the surface wave W propagates through the propagating body 10, but at the time of propagation, it reaches a depth substantially the same as the wavelength of the surface wave W from the surface of the propagating body 10. The propagation surface portion 11 and the propagation surface portion 12 are portions that include not only the main surface of the propagating body 10 but also the depth thereof. The same applies to the upper surface portion 15 and the bottom surface portion 16.

As shown in FIG. 2B, in the side view, the propagation surface portion 11 hangs down from one end of the upper surface portion 15. The propagation surface portion 12 hangs down from the other end of the upper surface portion 15. Further, the bottom surface portion 16 connects the propagation surface portion 11 and the propagation surface portion 12 on the side opposite to the top surface portion 15, and has a U-shaped smooth curved surface that is convex downward. When the first surface wave W1 and the second surface wave W2, which will be described later, propagate, the bottom surface portion 16 formed in this way propagates along the bottom surface portion 16 without being reflected by the bottom surface portion 16 due to leakage. Reduce loss.

As shown in FIGS. 2 and 4, the propagator 10 is located at an intermediate portion (intermediate portion in the vertical direction) between the upper surface portion 15 and the bottom surface portion 16 and penetrates the two side surface portions 13 and 14 having a front-back relationship. It has a side hole 17 that has been formed. The side hole 17 has an upper side portion 17a parallel to the upper surface portion 15 (one end surface portion), and is formed by hollowing out a cross-sectional shape into an inverted triangular shape. The side hole 17 is located between the propagation surface portion 11 and the propagation surface portion 12 in the side view.

As shown in FIG. 4, the side hole 17 is a portion hollowed out in an inverted triangular columnar shape from one side surface portion 13 toward the other side surface portion 14, and is an upper side portion parallel to the upper surface portion 15 of the propagating body 10. It has an inverted triangular cross section formed by 17a and two hypotenuses 17b and 17c that project diagonally downward from both ends of the upper side 17a. In such a side hole 17 having an inverted triangular cross section, the width of the upper side portion 17a (the length of the base of the inverted triangle) is b, and the height from the upper side portion 17a to the vertices of the two hypotenuse portions 17b and 17c. (Height of inverted triangle) is a. As a result, the width a in the height direction (the length in the direction parallel to the upper side portion 17a) gradually becomes smaller than the width b of the upper side portion 17a, and the width a is the minimum at the deepest inverted triangular apex. It becomes (0).

The side hole 17 is made by separating an internally propagated wave that is generated near the surface wave W propagating on the propagation surface portions 11 and 12 and is an unnecessary wave from a surface wave W used for detecting the liquid surface position, thereby making noise. The components are reduced to improve the liquid level detection accuracy.
Further, by reflecting the internally propagating wave propagating in the propagating body 10 by the side hole 17 at the upper side portion 17a, the internally propagating wave is used as the detection wave D used for temperature detection, and the propagating velocity of the detecting wave D is used to determine the propagating body 10. Detect (measure) temperature. The detected (measured) temperature of the propagator 10 is used for temperature correction when detecting the liquid level position (position of the liquid level 91) by the surface wave W. As a result, it is not necessary to provide a temperature sensor composed of a thermistor chip or the like provided in the conventional liquid level position detecting device.

In the propagating body 10, the distance x from the hypotenuses 17b and 17c of the side hole 17 to the surfaces of the propagating surfaces 11 and 12 is the minimum distance from one end and the other end of the upper side 17a to the surface of the propagating surfaces 11 and 12. , It increases along the height a direction of the side hole 17, and reaches the maximum at the apex of the inverted triangle shape. The minimum distance x from one end and the other end of the upper side portion 17a having a width b to the surface of the propagation surface portions 11 and 12 is one wavelength or more of the surface wave W generated by the vibrator 20 constituting the vibration generating means. It is said that.
By doing so, the minimum thickness (thickness in the width b direction) of the propagating body 10 of the surface wave W propagating on the propagating surface portions 11 and 12 is secured at one wavelength or more, energy loss is reduced, and the liquid level is reduced. The S / N ratio of the surface wave W for detection is improved, and the detection accuracy of the liquid level position is improved.
Further, as will be described later, the internal propagating wave (detection wave D) propagating in the propagating body 10 from the vibrator 20 may be reflected by the upper side portion 17a of the side hole 17 and propagated toward the bottom surface portion 16. By separating and separating from the surface wave W, it is possible to reduce the noise component and improve the detection accuracy of the liquid level position by the surface wave W (see FIG. 4).

Further, the side hole 17 makes it possible to obtain the temperature of the propagating body 10 from the sound velocity of the detected wave D by the internal propagating wave, which depends on the temperature of the propagating body 10 regardless of the liquid level position (position of the liquid level 91). The temperature of the liquid level position detecting device 100 can be corrected without providing such a device.
The distance x from the upper side portion 17a to the surfaces of the propagation surface portions 11 and 12 is, for example, when the surface wave frequency is 500 kHz and the propagation body 10 is PPS, the sound velocity at room temperature is about 950 m / s. Therefore, one wavelength is about 1.9 mm. As a result, the distance x may be, for example, 1.9 mm or more.

Further, the height a of the side hole 17 from the upper side portion 17a is set to be one wavelength or less of the surface wave W generated by the vibrator 20 constituting the vibration generating means. That is, in the side hole 17, the height a of the hole in the side hole 17 is set to one wavelength or less of the surface wave W generated by the vibrator 20. As a result, by reducing the height a of the side hole 17, the thickness of the propagating body 10 propagating through the propagation surface portions 11 and 12 outside the side hole 17 (thickness in the width b direction from the surface of the propagation surface portion (distance). The influence of x)) can be reduced to suppress the energy loss of the surface wave W, the S / N ratio of the surface wave W for detecting the liquid level is improved, and the detection accuracy of the liquid level position is improved. be able to.
The height a from the upper side portion 17a of the side hole 17 is, for example, when the surface wave frequency is 500 kHz and the propagator 10 is PPS, the sound velocity at room temperature is about 950 m / s. One wavelength is about 1.9 mm. As a result, the height a may be, for example, 1.9 mm or less, preferably as small as possible within the range in which the side hole 17 can be machined.

As shown in FIG. 1, the propagating body 10 is fixed by being sandwiched between the fixing members 81 and 82 provided on the container 80 between the side surface portions 13 and the side surface portions 14. If the propagating body 10 is fixed at a portion other than the propagation surface portion 11 and the propagation surface portion 12 on which the surface wave W propagates so as not to hinder the propagation of the surface wave W, the fixing method is arbitrary.

The propagator 10 is arranged so that the lower end of the bottom surface portion 16 is separated from the bottom surface of the container 80 by a distance (length) d. The length L1 of the propagating body 10 along the vertical direction from the upper end of the upper surface portion 15 to the liquid level 91 (the length of the first portion 10a where the propagating body 10 is not immersed in the liquid 90) and the bottom surface portion. The length along the vertical direction from the lower end of 16 to the liquid level (boundary) 91 (the length of the second portion 10b where the propagator 10 is immersed in the liquid 90) L2 is due to the increase or decrease of the liquid 90. Change.

The oscillator 20 is, for example, a transverse wave transducer, and includes a piezoelectric element mounted on a circuit board and the like. The oscillator 20 is pressed against the upper surface portion 15 of the propagating body 10 to generate a surface wave W on the propagating surface portion 11 and the propagating surface portion 12 of the propagating body 10.

In the following, the surface wave W generated by the vibrator 20 on the propagation surface portion 11 is referred to as a first surface wave W1, and the surface wave W generated on the propagation surface portion 12 is referred to as a second surface wave W2. Further, the first surface wave W1 and the second surface wave W2 may be simply referred to as the surface wave W without distinction.

As shown in FIG. 3, the vibrator 20 generates a first surface wave W1 in the propagating body 10 and receives a second surface wave W2, a first transmitting / receiving unit 21 and a propagating body 10 having a second surface wave W2. Has a second transmission / reception unit 22 that generates the first surface wave W1 and receives the first surface wave W1.

The first transmission / reception unit 21 vibrates by an electric signal supplied from the transmission / reception circuit 30. The vibration of the first transmission / reception unit 21 is transmitted to the propagating body 10, and the first surface wave W1 is generated at the upper end (first location) of the propagation surface portion 11. As shown in FIG. 3, the generated first surface wave W1 propagates toward the lower end of the propagation surface portion 11, propagates along the bottom surface portion 16 having a smooth curved surface, and then propagates along the upper end portion (second) of the propagation surface portion 12. Propagate toward (location). The first surface wave W1 that has reached the upper end of the propagation surface portion 12 vibrates the second transmission / reception portion 22. The second transmission / reception unit 22 converts this vibration into an electric signal and supplies it to the transmission / reception circuit 30.

The second transmission / reception unit 22 vibrates by an electric signal supplied from the transmission / reception circuit 30. The vibration of the second wave transmitting / receiving unit 22 is transmitted to the propagating body 10, and a second surface wave W2 is generated at the upper end (first location) of the propagating surface portion 12. As shown in FIG. 3, the generated second surface wave W2 propagates toward the lower end of the propagation surface portion 12, propagates along the bottom surface portion 16 having a smooth curved surface, and then propagates along the upper end portion (second) of the propagation surface portion 11. Propagate toward (location). The second surface wave W2 that has reached the upper end of the propagation surface portion 11 vibrates the first transmission / reception portion 21. The first transmission / reception unit 21 converts this vibration into an electric signal and supplies it to the transmission / reception circuit 30.

In this embodiment, the first surface wave W1 and the second surface wave W2 are ultrasonic pulses (ultrasonic pulses) of ultrasonic waves (for example, sound waves of 20 KHz or higher may be used). The first surface wave W1 and the second surface wave W2 are Rayleigh waves or Scholte waves. The vibrator 20 may include a contact medium for ultrasonic waves, which is interposed between the piezoelectric element and the propagator 10 to efficiently transmit vibration.

The transmission / reception circuit 30 is connected to the oscillator 20 as shown in FIG. As an ultrasonic wave generating circuit, the transmission / reception circuit 30 supplies an electric signal for generating an ultrasonic pulse as a surface wave W to the vibrator 20 to vibrate the vibrator 20. The transmission / reception circuit 30 receives an electric signal supplied from the vibrator 20 as an ultrasonic reception circuit, and amplifies and converts the received electric signal.

Specifically, as shown in FIG. 3, the transmission / reception circuit 30 supplies an electric signal for transmitting the first surface wave W1 to the first transmission / reception unit 21 to vibrate the first transmission / reception unit 21. Further, it receives an electric signal supplied from the second transmission / reception unit 22 that has received the first surface wave W1, and amplifies and converts the received electric signal. Further, the transmission / reception circuit 30 supplies an electric signal for transmitting the second surface wave W2 to the second transmission / reception unit 22 to vibrate the second transmission / reception unit 22. Further, it receives an electric signal supplied from the first transmitting / receiving unit 21 that has received the second surface wave W2, and amplifies and converts the received electric signal.

The control unit 40 is a microcomputer composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a timer, etc., a D / A (digital / analog) converter, and an A / D ( It includes an analog / digital) converter and so on. As shown in FIG. 1, the control unit 40 is connected to the transmission / reception circuit 30. The control unit 40 controls the transmission / reception circuit 30 to supply an electric signal from the transmission / reception circuit 30 to each of the first transmission / reception unit 21 and the second transmission / reception unit 22 of the vibrator 20. As a result, the first surface wave W1 is generated on the propagation surface portion 11, and the second surface wave W2 is generated on the propagation surface portion 12. Further, the control unit 40 receives electric signals from each of the first transmission / reception unit 21 and the second transmission / reception unit 22 of the oscillator 20 amplified and converted by the transmission / reception circuit 30, and is based on the received electric signals. , The liquid level position is detected as described later. Further, the control unit 40 can exchange data with an external device 60 outside the liquid level position detecting device 100. The configuration for detecting the liquid level of the liquid level position detecting device 100 is as described above.

The operation of the liquid level position detecting device 100 configured in this way will be described focusing on the liquid level position detecting process (see FIG. 5) executed by the control unit 40. For example, the CPU of the control unit 40 executes the liquid level position detection process using the RAM as the main memory according to the program stored in the ROM and using various data stored in the ROM. The control unit 40 starts the liquid level position detection process, for example, based on a command from the external device 60. The temperature measurement by the side hole 17 of the liquid level position detection device 100 and the temperature correction based on the measured temperature will be described after the explanation of the liquid level position detection process.

(Liquid level position detection process)
When the liquid level position detection process is started, as shown in the flowchart in FIG. 5, the control unit 40 vibrates the first transmission / reception unit 21 via the transmission / reception circuit 30 to reach the upper end (first location) of the propagation surface unit 11. The first surface wave W1 is generated (step S1).

As shown in FIG. 3, the generated first surface wave W1 propagates toward the lower end of the propagation surface portion 11, propagates along the bottom surface portion 16 having a smooth curved surface, and then propagates along the upper end portion (second) of the propagation surface portion 12. Propagate toward (location). The first surface wave W1 that has reached the upper end of the propagation surface portion 12 vibrates the second transmission / reception portion 22. The second transmission / reception unit 22 converts this vibration into an electric signal and supplies it to the transmission / reception circuit 30. The transmission / reception circuit 30 amplifies and converts the supplied electric signal and supplies it to the control unit 40. In the following, the vibration generated by the first surface wave W1 that reaches the second transmission / reception unit 22 through the amplified and converted electrical signal (that is, the propagation to the bottom surface portion 16) is shown in the second transmission / reception unit 22. (Electrical signal) is used as the first propagation wave signal. In this way, the first surface wave W1 sent from the first transmitting / receiving unit 21 reaches the second transmitting / receiving unit 22 while the first portion 10a in contact with the gas and the second portion in contact with the liquid 90. It propagates across the boundary with 10b twice.

Subsequently, the control unit 40 sets the timer to an initial value of 0 in order to measure the period from the processing of step S1 to the reception of the first propagating wave signal (step S2).
The period is a period from the timing when the first transmission / reception unit 21 generates the first surface wave W1 to the timing when the second transmission / reception unit 22 receives the first surface wave W1. In short, the first transmission / reception wave. This is the propagation time of the first surface wave W1 from the unit 21 to the second transmission / reception unit 22 (hereinafter, referred to as the first propagation time).

Subsequently, the control unit 40 determines whether or not the first propagate wave signal has been received from the transmission / reception circuit 30 (step S3).
This determination can be performed by an appropriate method. For example, the control unit 40 acquires an electric signal supplied from the second transmission / reception unit 22 and amplified and converted by the transmission / reception circuit 30, and the acquired electric signal. The value based on the voltage (for example, the voltage value, the average value of the square of the voltage value in a predetermined period, the degree of change of the voltage value or the average value, the amplitude of the electric signal, etc.) is equal to or higher than the threshold value stored in the ROM in advance. Determine if it has become. For example, the first propagating wave signal may be measured in advance by an experiment, and the threshold value may be set based on the measurement result. Then, when the value based on the voltage of the electric signal becomes equal to or higher than the threshold value, the control unit 40 determines that the first propagate wave signal has been received (step S3; Yes). On the other hand, when the value based on the voltage of the electric signal is less than the threshold value, the control unit 40 determines that the first propagate wave signal has not been received (step S3; No).

When the first propagate wave signal has not been received yet (step S3; No), the control unit 40 updates the timer value of the timer by +1 or the like (step S4), and executes the process of step S3 again. As a result, the control unit 40 keeps time until it receives the first propagation wave signal.

When the first propagation wave signal is received (step S3; Yes), the control unit 40 stores the current timer value as the first propagation time in, for example, RAM (step S5).

Subsequently, the control unit 40 vibrates the second transmission / reception unit 22 via the transmission / reception circuit 30 to generate a second surface wave W2 at the upper end of the propagation surface unit 12 (step S6).

As shown in FIG. 3, the generated second surface wave W2 propagates toward the lower end of the propagation surface portion 12, propagates along the bottom surface portion 16 having a smooth curved surface, and then toward the upper end of the propagation surface portion 11. Propagate. The second surface wave W2 that has reached the upper end of the propagation surface portion 11 vibrates the first transmission / reception portion 21. The first transmission / reception unit 21 converts this vibration into an electric signal and supplies it to the transmission / reception circuit 30. The transmission / reception circuit 30 amplifies and converts the supplied electric signal and supplies it to the control unit 40. In the following, the vibration generated by the second surface wave W2 that reaches the first transmission / reception unit 21 via the amplified and converted electrical signal (that is, the propagation to the bottom surface portion 16) is shown in the first transmission / reception unit 21. (Electrical signal) is used as the second propagation wave signal. In this way, the second surface wave W2 sent from the second transmitting / receiving unit 22 reaches the first transmitting / receiving unit 21 while the first portion 10a in contact with the gas and the second portion in contact with the liquid 90. It propagates across the boundary with 10b twice.

Subsequently, the control unit 40 sets the timer to an initial value of 0 in order to measure the period from the processing of step S6 to the reception of the second propagating wave signal (step S7).
The period is a period from the timing when the second transmission / reception unit 22 generates the second surface wave W2 to the timing when the first transmission / reception unit 21 receives the second surface wave W2, that is, the second transmission / reception wave. This is the propagation time of the second surface wave W2 from the unit 22 to the first receiving / receiving unit 21 (hereinafter, referred to as the second propagation time). In the following, the first propagation time and the second propagation time may be simply referred to as the propagation time without distinction.

Subsequently, the control unit 40 determines whether or not the second propagation wave signal has been received from the transmission / reception circuit 30 (step S8).
This determination is performed by the same method as in step S3, and when the second propagate wave signal has not yet been received (step S8; No), the control unit 40 updates the timer value of the timer by +1 or the like (step S8; No). Step S9), the process of step S8 is executed again. As a result, the control unit 40 keeps time until it receives the second propagation wave signal.

When the second propagation wave signal is received (step S8; Yes), the control unit 40 stores the current timer value as the second propagation time in, for example, RAM (step S10).

Subsequently, the control unit 40 specifies the position (liquid level position) of the liquid level 91 based on the first propagation time stored in step S5 and the second propagation time stored in step S10 (step S11). ..

For example, the relationship between the first propagation time, the second propagation time, and the position of the liquid level 91 is specified in advance by an experiment or the like, and the specified relationship is stored in the ROM as a table or an arithmetic expression. The control unit 40 specifies the liquid level position based on the table or arithmetic expression stored in the ROM and the first propagation time and the second propagation time.

The control unit 40 uses a table or an arithmetic expression for specifying the liquid level position based on the first propagation time, and uses the liquid level position based on the first propagation time (hereinafter referred to as the first liquid level position). ), And the liquid level position based on the second propagation time (hereinafter referred to as the second liquid level position) is determined by using a table or an arithmetic expression for specifying the liquid level position based on the second propagation time. It may be specified. That is, the control unit 40 may specify each of the first liquid level position and the second liquid level position. Then, the average of the first liquid level position and the second liquid level position (either a simple average or a weighted average) may be used as the liquid level position to be detected this time. In order to obtain the weighted average, the weighting constants of the first liquid level position and the second liquid level position may be obtained in advance by an experiment or the like. Further, the control unit 40 determines whether or not either the first liquid level position or the second liquid level position indicates an error value, and if an error value is indicated, the one that does not indicate an error value. May be the liquid level position to be detected this time.

Subsequently, the control unit 40 outputs the position of the liquid level 91 specified in step S11 to the external device 60 (step S12). The external device 60 includes, for example, an image display such as an LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Diode), and displays the position of the liquid level 91 on the image display. In this way, the liquid level position detection process by the liquid level position detecting device 100 is completed.

When the propagator 10 is made of synthetic resin, the propagation velocity of the surface wave W propagating in the second portion 10b in contact with the liquid 90 (hereinafter referred to as the second sound velocity) is the first portion in contact with air. It is known that the propagation velocity of the surface wave W propagating in 10a (hereinafter referred to as the first sound velocity) is slower. Therefore, the propagation time (first propagation time, second propagation time) measured by the timer becomes longer as the length L2 of the second portion 10b becomes longer. That is, the higher the position of the liquid level 91 from the bottom surface of the container 80 is, the longer the propagation time is. The composition of the synthetic resin forming the propagator 10 is not limited as long as the propagation time of the surface wave W can be detected, but polyethylene, polystyrene, etc. are used in addition to PPS (polyphenylene sulfide). can do. It is considered that PPS, which makes it easy to observe the propagated wave of the surface wave W, is suitable as the synthetic resin.

The control unit 40 detects a propagation time that becomes longer as the liquid contact portion (second portion 10b) becomes longer according to the position of the liquid level 91 of the liquid 90, and determines the position of the liquid level 91 based on the detected propagation time. To detect. The position of the liquid level 91 is, for example, the length L2 of the second portion 10b where the propagator 10 is immersed in the liquid 90, the height of the liquid level 91 from the bottom surface of the container 80, the length L2, or the height of the liquid level 91. It may be represented by a corresponding value or the like. The height of the liquid level 91 from the bottom surface of the container 80 is the depth of the liquid 90, and is determined by the length L2 + the length d (see FIG. 1).

Further, in the liquid level position detecting device 100, by making the bottom surface portion 16 into a smooth curved surface shape, the first surface wave W1 and the second surface wave W2 are not reflected by the bottom surface portion 16, and the surface wave W leaks. Therefore, there is no loss at the bottom surface portion 16, the attenuation of the surface wave W received by the transducer 20 is small, and the S / N ratio can be improved. On the other hand, in the conventional liquid level position detection device, since the bottom surface of the propagator is not a smooth curved surface but a flat surface, the first surface wave W1 and the second surface wave W2 are reflected by the bottom surface 16. Therefore, the surface wave W leaks, resulting in a loss.

In the above embodiment, the control unit 40 generates the first surface wave W1 and the second surface wave W2 at different timings, but the liquid level position detection process may be executed by generating them at the same time. In this case, the first and second propagating wave signals are superimposed and observed (received) as a propagating wave signal. That is, by simultaneously generating the first surface wave W1 and the second surface wave W2, the amplitude of the surface wave W received by the vibrator 20 becomes large, and the S / N ratio can be further improved.

(Temperature detection and temperature correction)
Next, temperature detection and temperature correction by the side holes 17 provided in the propagator 10 of the liquid level position detecting device 100 will be described mainly with reference to FIG.

As shown in FIG. 4, the vibrator 20 constituting the vibration generating means includes a third transmission / reception unit 23 in addition to the first transmission / reception unit 21 and the second transmission / reception unit 22. The third transmission / reception unit 23 is pressed against the central portion of the plane of the upper surface portion 15 of the propagating body 10, for example, between the first transmission / reception unit 21 and the second transmission / reception unit 22. The third transmission / reception unit 23 generates an internally propagated wave propagating inside the propagating body 10 via the upper surface portion 15 as a detection wave D for temperature detection.

As shown in FIG. 4, the third transmission / reception unit 23 generates a detection wave D to be an internally propagated wave in the propagating body 10 and receives the detection wave D reflected by the upper side portion 17a of the side hole 17.

The third transmission / reception unit 23 vibrates due to an electric signal supplied from the transmission / reception circuit 30 (see FIG. 1). The vibration of the third transmission / reception unit 23 is transmitted to the propagator 10, and the detection wave D is generated on the upper surface portion 15. As shown in FIG. 4, the generated detection wave D propagates toward the lower end of the propagating body 10, is reflected by the upper side portion 17a of the side hole 17, and then propagates toward the upper end of the propagating body 10. The detection wave D that reaches the upper surface portion 15 vibrates the third transmission / reception portion 23. The third transmission / reception unit 23 converts this vibration into an electric signal and supplies it to the transmission / reception circuit 30.

The detection wave D received by the third transmission / reception unit 23 is an internally propagated wave, and the sound velocity changes depending on the temperature of the propagating body 10 regardless of the position of the liquid level 91. The temperature of the propagator 10 is detected by using the detection wave D, and the detected temperature is used for temperature correction when detecting the surface wave (first surface wave W1 and second surface wave W2) W. As a result, it is not necessary to provide a temperature sensor composed of a thermistor chip or the like provided in the conventional liquid level position detecting device.

The transmission / reception circuit 30 supplies an electric signal for transmitting the detection wave D to the third transmission / reception unit 23, and vibrates the third transmission / reception unit 23. Further, it receives an electric signal supplied from the third transmission / reception unit 23 that has received the detection wave D, and amplifies and converts the received electric signal.

The control unit 40 drives and controls the third transmission / reception unit 23 via the transmission / reception circuit 30. Further, the control unit 40 receives an electric signal from the third transmission / reception unit 23 amplified and converted by the transmission / reception circuit 30, and detects the temperature of the propagator 10 based on the received electric signal.

The control unit 40 detects the propagation time of the detection wave D by the same method as the method described in the liquid level position detection process described above.

Specifically, the control unit 40 determines the time from when the detection wave D is generated by the third transmission / reception unit 23 to when the third transmission / reception unit 23 receives the detection wave D after being reflected by the upper side portion 17a. Specify based on the timer value. Then, the specified time is stored in the RAM as the detection time. The control unit 40 specifies (detects) the temperature of the propagator 10 based on the detection time obtained in this way.

Since the sound velocity of the detection wave D changes depending on the temperature of the propagating body 10 regardless of the position of the liquid level 91, the detection time also depends on the temperature of the propagating body 10 regardless of the position of the liquid level 91. Change. Utilizing this characteristic, for example, the relationship between the detection time and the temperature of the propagator 10 is specified in advance by an experiment or the like, and the specified relationship is stored in the ROM as a table or an arithmetic expression. The control unit 40 identifies the temperature of the propagator 10 based on the table or arithmetic expression stored in the ROM and the detection time.

Then, the control unit 40 corrects the temperature of the first propagation time and the second propagation time based on the temperature of the propagator 10 specified (detected) as described above. The speed of sound is temperature-dependent and changes according to the temperature of the propagator 10. That is, the first propagation time and the second propagation time also change according to the temperature of the propagating body 10. Therefore, in order to maintain the detection accuracy of the liquid level position, the temperature correction is required. For example, a table configured by associating the temperature of the propagating body 10 with the correction amount and correction coefficient of the propagation time is stored in the ROM in advance, and the control unit 40 refers to the table and specifies the propagation. The correction amount and the correction coefficient according to the temperature of the body 10 may be acquired. Then, the control unit 40 performs a calculation for adding or subtracting the acquired correction amount or a calculation for multiplying the correction coefficient for each of the first propagation time and the second propagation time, thereby performing the first propagation time and the second propagation. The temperature of the time may be corrected.

A table configured by associating the temperature of the propagating body 10 with the correction amount and correction coefficient of the liquid level position is stored in the ROM in advance, and is specified based on the first propagation time and the second propagation time. The liquid level position may be corrected. Further, the control unit 40 stores not only the table but also an equation (which may be an approximate equation) expressing the temperature dependence of the sound velocity in the ROM, and uses the equation to propagate the propagation time or the liquid level position. The correction amount and the correction coefficient of the above may be obtained. As the temperature correction method for the propagation time and the liquid level position, a known table calibration method or calculation method can be appropriately used and is arbitrary.

In the liquid level position detecting device 100, the propagating body 10 is provided with a side hole 17 for temperature detection and temperature correction, and the reflection of the detection wave D by the internally propagating wave reflected by the upper side portion 17a is used.
On the other hand, the influence of the side hole 17 on the surface wave W is avoided as follows. That is, the side hole 17 has a cross section hollowed out in an inverted triangular columnar shape from one side surface portion 13 toward the other side surface portion 14. In this side hole 17, the width of the upper side portion 17a (the length of the base of the inverted triangle) is b, and the height from the upper side portion 17a to the vertices of the two hypotenuse portions 17b and 17c (the height of the inverted triangle) is It is said to be a. As a result, the width parallel to the upper side portion 17a gradually decreases with respect to the width b of the upper side portion 17a along the height a direction, and the width becomes the minimum (0) at the deepest inverted triangular apex.

Further, in the propagator 10, the distance x from the oblique side portions 17b and 17c of the side hole 17 to the surface of the propagation surface portions 11 and 12 is the distance x from one end or the other end of the upper side portion 17a to the surface of the propagation surface portions 11 and 12. Is the minimum, and increases along the height a direction of the side hole 17, and the minimum distance x is one wavelength or more of the surface wave W.
By doing so, the minimum thickness (thickness in the width b direction) of the propagating body 10 of the surface wave W propagating on the propagating surface portions 11 and 12 is secured at one wavelength or more, energy loss is reduced, and the liquid level is reduced. The S / N ratio of the surface wave W for detection is improved, and the detection accuracy of the liquid level position is improved.
Further, the height a of the side hole 17 from the upper side portion 17a is set to be one wavelength or less of the surface wave W. That is, in the side hole 17, the height a of the hole in the side hole 17 is set to one wavelength or less of the surface wave W generated by the vibrator 20. As a result, by reducing the height a of the side hole 17, the portion of the minimum distance x of the propagation surface portions 11 and 12 outside the side hole 17 is reduced, and the energy loss of the surface wave W propagating in the propagating body 10 is reduced. It is possible to suppress and improve the S / N ratio of the surface wave W for detecting the liquid level to ensure the detection accuracy of the liquid level position.
Further, the side hole 17 separates the internally propagated wave that is generated near the surface wave W propagating in the propagation surface portions 11 and 12 and becomes an unnecessary wave from the surface wave W used for detecting the liquid surface position. The noise component can be reduced and the liquid level detection accuracy can be improved.

The above temperature correction processing is incorporated into the above-mentioned liquid level position detection processing as long as the detection wave D does not interfere with the first surface wave W1 or the second surface wave W2, and the generation timing of the detection wave D is incorporated. May be performed at the same time as the generation timing of the first surface wave W1 and the second surface wave W2.

(Prevention of interference between detection wave D and surface wave W)
In the liquid level position detecting device 100, the side hole 17 is the surface wave arrival time Tw of the surface wave W generated by the vibrator (vibration generating means) 20 of the upper side portion 17a to the first upper surface portion (second location) 15. And the internal propagation wave arrival time Td to the upper surface portion (second location) 15 of the multiple reflected waves from the upper side portion 17a of the internally propagated wave do not match (position in the vertical direction from the upper surface portion 15). There is. By doing so, the surface wave W and the detection wave D due to the internally propagated wave do not interfere with each other, the signal strength of the surface wave W for detecting the liquid level position is secured, and the signal strength of the detection wave D for detecting the temperature is increased. Secure.

As shown in FIG. 4, the side hole 17 has A as the distance from the vibrator 20 of the upper surface portion 15 of the propagating body 10 to the upper side portion 17a. The internal propagation wave propagation time of the detection wave D by the internal propagation wave propagating the distance A from the upper surface portion 15 to the upper side portion 17a is Td, and the surface wave propagation time of the surface wave W used for detecting the liquid level position is Tw. Then, the side hole 17 is provided at a distance A that satisfies the relationship of the following equation.
Tw ≠ n · Td (n = 1, 2, 3 ...)
Here, n is the number of reflections returned to the upper surface portion 15 of the detected wave D by the internally propagated wave.
If the transmission distance of the surface wave W (the lengths of the propagation surface portions 11 and 12 and the bottom surface portion 16) is L, the propagation velocity of the surface wave is Vw, and the propagation velocity of the detection wave D by the internal propagation wave is Vd, the following is assumed. There is an expression relationship. The propagation distance of the detection wave D is 2 · A.
L = Vw ・ Tw
2.A = Vd ・ Td
Here, the propagation velocity Vd of the internally propagated wave changes depending on the temperature and the material of the propagating body 10, and the propagation velocity Vw of the surface wave W changes depending on the temperature, the material of the propagating body 10, the liquid level, and the liquid type.
Here, for example, if the relationship of Vw = 0.9Vd is established between the propagation velocity Vw of the surface wave W and the propagation velocity Vd of the internal propagation wave of the detection wave D by the internal propagation wave, the position of the side hole 17 A can be calculated by the following equation.
A = L / (2 ・ n ・ 0.9) = L / (1.8 ・ n)

By forming the side hole 17 at a position where the distance from the upper surface portion 15 of the propagating body 10 is A, as shown in FIG. 6, the first transmission / reception of the surface wave W is the second transmission / reception from the first transmission / reception unit 21. It is possible to prevent the surface wave returning to the wave portion 22 from interfering with the plurality of reflected waves of the detection wave D due to the internally propagated wave, and the liquid level position and the propagator without attenuating the signal required for detection. 10 temperatures can be detected.

When the surface wave W and the detection wave D are simultaneously propagated as drive waves, as shown in FIG. 6A, the surface wave W is transferred from the first transmission / reception unit 21 to the second transmission / reception unit 22 for the first time. It is prevented that both the first reflected wave (1st echo) and the second reflected wave (2nd echo) of the detection wave D by the internally propagated wave interfere with the returning surface wave (1st echo). Further, in the case shown in FIG. 6B, the detection of the first surface wave (1st echo) returning from the first transmission / reception unit 21 to the second transmission / reception unit 22 of the surface wave W by the internally propagated wave. It is prevented that the first reflected wave (1st echo) of the wave D interferes.

On the other hand, in the case shown in FIG. 6C, the surface wave (1st echo) returning from the first transmission / reception unit 21 of the surface wave W to the second transmission / reception unit 22 for the first time is detected by the internally propagated wave. The second reflected wave (2nd echo) of the wave D interferes, and a problem such as attenuation occurs in the detection signal of the liquid surface position by the surface wave W. Therefore, the side hole 17 may be formed at the position A where such interference does not occur, and the liquid level position and the temperature can be detected accurately without attenuating the detection signal.

(Embodiment 2)
Next, another embodiment of the liquid level position detecting device 100 will be described with reference to FIG.
The liquid level position detecting device 100 of the present embodiment has a different cross-sectional shape of the side hole 18 for temperature detection. In the following description, different configurations will be mainly described, the same symbols will be given in the same parts as the liquid level position detecting device 100 already described, and duplicate description will be omitted.

In the liquid level position detecting device 100 of the present embodiment, as shown in FIG. 7, the side hole 18 has a semicircular shape whose cross-sectional shape is convex downward.

The side hole 18 is hollowed out in an inverted semicircular shape from one side surface portion 13 toward the other side surface portion 14, and has an upper side portion 18a parallel to the upper surface portion 15 of the propagator 10 and both ends of the upper side portion 18a. It has an inverted semicircular cross section due to a semicircular portion 18b that is convex downward from the surface. In such a side hole 18 having an inverted semicircular cross section, the width of the upper side portion 18a (the length of the diameter portion of the inverted semicircle) is b, and the height from the upper side portion 18a to the apex of the semicircular portion 18b. The height (height of the inverted semicircle) is a. As a result, the width in the height a direction (the length in the direction parallel to the upper side portion 18a) gradually becomes smaller than the width b of the upper side portion 18a, and at the apex of the inverted semicircular shape of the height a of the deepest portion, The width becomes the minimum (0).

Similar to the side hole 17, the side hole 18 includes an internally propagated wave generated near the surface wave W propagating in the propagation surface portions 11 and 12 and becoming an unnecessary wave, and a surface wave W used for detecting the liquid level position. By separating the above, the noise component is reduced and the liquid level detection accuracy is improved.
Further, by reflecting the internally propagated wave propagating in the propagating body 10 by the side hole 18 at the upper side portion 18a, the internally propagating wave is used as the detection wave D used for temperature detection, and the propagation velocity of the detected wave D is used to determine the propagating body 10. Detect temperature. The detected (measured) temperature of the propagator 10 is used for temperature correction when detecting the liquid level position (position of the liquid level 91) by the surface wave W. As a result, it is not necessary to provide a temperature sensor composed of a thermistor chip or the like provided in the conventional liquid level position detecting device.

In the propagator 10, the distance x from the semicircular portion 18b of the side hole 18 to the surface of the propagation surface portions 11 and 12 is the minimum distance x from one end and the other end of the upper side portions 18a to the surface of the propagation surface portions 11 and 12. , It increases along the arc in the height a direction of the side hole 18, and reaches the maximum at the apex of the inverted semicircle shape. The minimum distance x from one end and the other end of the upper side portion 18a having a width b to the surfaces of the propagation surface portions 11 and 12 is one wavelength or more of the surface wave W generated by the vibrator 20 constituting the vibration generating means. It is said that. That is, the outer thickness (distance x) of the side hole 18 is set to one wavelength or more of the surface wave W at the end of the upper side portion 18a, and the thickness (distance x) is increased toward the bottom surface portion 16. growing.
By doing so, the minimum thickness (thickness in the width b direction) of the surface wave W propagating body 10 propagating on the propagation surface portions 11 and 12 is secured at one wavelength or more, energy loss is reduced, and liquid level detection is performed. The S / N ratio of the surface wave W for this purpose is improved, and the detection accuracy of the liquid level position is improved.
Further, the internally propagated wave (detection wave D) propagating the propagating body 10 from the vibrator 20 is not reflected by the upper side portion 18a of the side hole 18 and propagated toward the bottom surface portion 16, and the surface wave W It is possible to reduce the noise component and improve the detection accuracy of the liquid level position by the surface wave W.

Further, the side hole 18 makes it possible to obtain the temperature of the propagating body 10 from the sound velocity of the detected wave D by the internal propagating wave, which depends on the temperature of the propagating body 10 regardless of the liquid level position (position of the liquid level 91). The temperature of the liquid level position detecting device 100 can be corrected without providing a sensor or the like.
The distance x from the upper side portion 18a to the surfaces of the propagation surface portions 11 and 12 is, for example, when the surface wave frequency is 500 kHz and the propagation body 10 is PPS, the sound velocity at room temperature is about 950 m / s. Therefore, one wavelength is about 1.9 mm. As a result, the distance x of one wavelength or more may be set to, for example, 1.9 mm or more.

Further, the height a of the side hole 18 from the upper side portion 18a is set to be one wavelength or less of the surface wave W generated by the vibrator 20 constituting the vibration generating means. That is, in the side hole 18, the height a of the hole of the side hole 18 is set to one wavelength or less of the surface wave W generated by the vibrator 20. As a result, by reducing the height a of the side hole 18, the portion where the thickness (distance x) of the propagator 10 outside the side hole 18 becomes small is shortened, thereby suppressing the energy loss of the surface wave W. The S / N ratio of the surface wave W for detecting the liquid level is improved to improve the detection accuracy of the liquid level position.
The height a from the upper side portion 18a of the side hole 18 is, for example, when the surface wave frequency is 500 kHz and the propagator 10 is PPS, the sound velocity at room temperature is about 950 m / s. One wavelength is about 1.9 mm. As a result, the height a may be, for example, 1.9 mm or less, preferably as small as possible within the range in which the side hole 18 can be machined.
The configuration of the liquid level position detecting device 100 other than the side hole 18 is as described above.

In the liquid level position detecting device 100 configured as described above, as described above, the liquid level position detection process is performed, and the temperature detection and temperature correction are performed.
Similarly, for the position A from the upper side portion 18a of the side hole 18, when the surface wave W and the detection wave D are simultaneously propagated as drive waves, as shown in FIG. 6A, for example, the surface wave. The surface wave (1st echo) that returns from the first transmission / reception section 21 of W to the second transmission / reception section 22 for the first time, and the first reflected wave (1st echo) and the second reflection of the detection wave D by the internally propagated wave. Make sure that none of them interfere with the wave (2nd echo).
By forming the side hole 18 at the position A where such interference does not occur, the liquid level position and the temperature can be detected accurately without attenuating the detection signal.

Comparing the side hole 17 and the side hole 18, if the width b of the upper side portions 17a and 18a and the height a of the hole are the same, the side hole 17 is more semicircular than the side hole 18. Since the hollow portion becomes smaller, the energy loss due to the propagation of the surface wave W becomes smaller, which is preferable. However, the shape of the side hole is not limited to a shape in which the height a is the same as the radius of the circle even in the case of a semicircle, and the shape in which the upper side is cut off in parallel is also included in the semicircular shape. By doing so, it is possible to reduce the driving portion of the side hole 18 and suppress the energy loss due to the propagation of the surface wave W.

The present invention is not limited to the above embodiments and drawings. Changes (including deletion of components) can be made as appropriate without changing the gist of the present invention.

(Modification example)
In the above, a configuration example in which the first transmission / reception unit 21 and the second transmission / reception unit 22 are in contact with the upper surface portion 15 has been described, but the first transmission / reception unit 21 is provided in contact with the propagation surface portion 11 and is provided. A configuration may be adopted in which the vibration generating means provided by contacting the transmitting / receiving wave portion 22 with the propagation surface portion 12 is separated.

Further, in addition to the third transmission / reception unit 23 that generates the detection wave D, a plurality of transmission / reception units may be provided, and the temperature correction process may be performed by the detection wave of each transmission / reception unit. ..

In the liquid level position detection, in addition to detecting the detailed position of the liquid level 91 (as described above, detecting the height of the liquid level 91 from the bottom surface of the container 80), what is the position of the liquid level 91? It also includes detecting which stage the current position of the liquid level 91 belongs to by dividing into stages. Further, the display such as an image displayed on the external device 60 by the control unit 40 after detecting the liquid level position does not have to indicate the liquid level position itself, and may indicate the amount of the liquid 90 according to the liquid level position. ..

Further, the propagator 10 is made of synthetic resin, and it is preferable that the longer the second portion 10b (liquid contact portion) is, the longer the propagation time is, depending on the liquid level position of the liquid 90, and the surface propagating the second portion 10b. It is preferable that the difference between the speed of the wave W and the speed of the surface wave W propagating in the first portion 10a (the portion exposed from the liquid 90) becomes more remarkable. However, the propagating body 10 may be made of metal as long as the liquid level position can be detected by the method described above.

The type of the liquid 90 whose liquid level position is to be detected is not limited to water, gasoline, cleaning liquid, etc., and may be any liquid 90, and not only a single liquid 90 but also a plurality of liquids 90 are mixed. It may be a thing. Further, it may be a colloidal solution in which the liquid 90 and fine particles are dispersed. Further, the liquid surface 91 may be a gas other than air or a vacuum.

For example, the container 80 may be a fuel tank mounted on a vehicle. In this case, the liquid 90 becomes a fuel such as gasoline. In such a case, the propagator 10 may be attached to, for example, a fuel pumping unit provided with a fuel pump for taking out fuel from the fuel tank, which is attached to the fuel tank. In the case of such a fuel tank, PPS (polyphenylene sulfide), POM (polyacetal), and PBT (polybutylene terephthalate) are often used as the resin used as the propagator 10 from the viewpoint of chemical resistance and the like. However, among these, it is preferable to use PPS having a good S / N ratio of the detection signal.

Examples of PPS include linear type, crosslinked type, anti-crosslinked type, and those to which fillers (additive materials) such as glass fiber and inorganic filler are added. Various types of PPS are used for the propagating body 10. PPS can be used. Propagation state of surface waves and plate waves (for example, good S / N ratio, surface) due to differences in linear type, crosslinked type, anti-crosslinked type, etc., with or without addition of filler, and difference in filler type. The effect on the sound velocity of waves or surface waves) is considered to be small.

The surface wave may be something other than a Rayleigh wave. The surface wave may be a sound wave having a frequency lower than that of the ultrasonic wave. Further, the surface wave does not have to be a pulse wave, and may be, for example, a burst wave. Further, the plate wave may be a pulse wave or a burst wave.

As described above, the liquid level position detecting device 100 is immersed in the liquid 90, and the boundary of being immersed in the liquid 90 is displaced according to the liquid level position of the liquid 90 (the position of the liquid level 91), and ultrasonic vibration propagates. The propagating body 10, the vibration generating means 20 provided on one end surface portion 15 of the propagating body 10 to generate the ultrasonic vibration in the propagating body 10, and the ultrasonic vibration generated by the vibration generating means 20 are the first of the propagating body 10. A detection means (transmission / reception circuit 30 and control unit 40) for detecting the liquid level position based on the propagation time propagating from one location to the second location across the boundary is provided, and the propagators 10 are in a two-sided relationship with each other. Two propagation surface portions 11 and 12, two side surface portions 13 and 14 connecting the two propagation surface portions 11 and 12, and a bottom surface portion 16 connecting the two propagation surface portions 11 and 12 and forming a curved surface in a side view. The side holes 17 and 18 are provided with side holes 17 and 18 penetrating the two side surface portions 13 and 14 and having an upper side portion parallel to one end surface portion 15, and the side surface holes 17 and 18 have widths b of the upper side portions 17a and 18a. On the other hand, the width along the height a direction is formed to be small.
According to this configuration, the thickness (height) of the propagating body 10 propagating the surface wave W propagating on the propagating surface portions 11 and 12 is secured (the portion of the propagating body 10 outside the side hole 17 is made small. ), The energy loss can be reduced, the S / N ratio for liquid level detection can be improved, and the liquid level position detection accuracy can be improved.
Further, the internal propagating wave (detection wave D) propagating the propagating body 10 from the vibrator 20 is not reflected by the side holes 17 and 18 and propagated toward the bottom surface portion 16, and is separated from the surface wave W. By being separated, the noise component can be reduced and the accuracy of detecting the liquid level position by the surface wave W can be improved.
Further, the side holes 17 and 18 can measure the temperature of the propagating body 10 from the sound velocity of the detection wave D, which depends on the temperature of the propagating body 10 regardless of the liquid level position, and the liquid level can be measured without providing a temperature sensor or the like. The temperature of the position detection device 100 can be corrected.

In the liquid level position detecting device 100, the propagating body 10 has a surface wave W generated by the vibration generating means 20 in which the distance x from the end of the upper side portions 17a and 18a of the side holes 17 and 18 to the surface of the propagating surface portions 11 and 12 is the distance x. It is said to be one or more wavelengths of.
According to this configuration, by increasing the distance x from the ends of the upper side portions 17a and 18a of the side holes 17 and 18 to the surfaces of the propagation surface portions 11 and 12, the propagation surface portions 11 and 12 outside the side holes 17 and 18 are increased. The influence on the thickness of the propagating body 10 propagating can be reduced, thereby suppressing the energy loss of the surface wave W, improving the S / N ratio for liquid level detection, and liquid. The surface position detection accuracy can be improved.

In the liquid level position detecting device 100, the heights a of the side holes 17 and 18 from the upper side portions 17a and 18a are set to be one wavelength or less of the surface wave W generated by the vibration generating means 20.
According to this configuration, by reducing the height (height of the side holes 17, 18) a from the upper side portions 17a, 18a of the side holes 17, 18, the propagation surface portion 11, outside the side holes 17, 18 The portion of the propagating body 10 propagating in 12 which is the minimum thickness in the vertical direction can be reduced to suppress the energy loss of the surface wave W, improve the S / N ratio for detecting the liquid level, and improve the liquid level. The position detection accuracy can be improved.

In the liquid level position detecting device 100, the upper side portions 17a and 18a of the side holes 17 and 18 have the surface wave arrival time Tw and the internal propagation wave (2) of the surface wave W generated by the vibration generating means 20 to the first second location. It is provided at a position where the arrival time Td of the internally propagated wave from the upper side portions 17a and 18a of the detection wave D) to the second location of the multiple n reflected waves does not match.
According to this configuration, side holes 17 and 18 are formed at positions A where the surface wave arrival time Tw of the surface wave W and the internal propagation wave arrival time Td due to the multiple reflected waves of the internal propagation wave (detection wave D) do not match. The surface wave W and the internally propagated wave (detection wave D) do not interfere with each other, and the signal strength required for detecting the liquid level position and temperature can be secured. As a result, the S / N ratio for liquid level detection and temperature detection can be improved, and the liquid level position and temperature detection accuracy can be improved.

In the liquid level position detecting device 100, the side holes 17 and 18 have a semicircular shape having an inverted triangular cross-sectional shape or a downwardly convex shape.
According to this configuration, energy loss can be reduced by forming the cross-sectional shapes of the side holes 17 and 18 into an inverted triangular shape or a downwardly tubular semicircular shape, and S / for liquid level detection. The N ratio can be improved to improve the detection accuracy of the liquid level position.
Further, the detection wave D due to the internally propagated wave is not reflected by the side holes 17 and 18 and propagated toward the bottom surface portion 16, but is separated from the surface wave W to reduce the noise component. The accuracy of detecting the liquid level position by the surface wave W can be improved.
Further, the side holes 17 and 18 allow the temperature of the propagating body 10 to be measured from the sound velocity of the detection wave D, which depends on the temperature of the propagating body 10 regardless of the liquid level position, and the liquid level can be measured without providing a temperature sensor or the like. The temperature of the position detection device 100 can be corrected.

In the above description, in order to facilitate the understanding of the present invention, the description of known technical matters has been omitted as appropriate.

100 ... Liquid level position detection device 10 ... Propagation body 10a ... First part 10b ... Second part 11 ... Propagation surface part 12 ... Propagation surface part 13, 14 ... Side part 15 ... Top surface part (end face)
16 ... Bottom part 17, 18 ... Side holes 17a, 18a ... Upper side 17b, 17c ... Hypotenuse 18b ... Semicircular part A ... Distance from top surface to side hole 20 ... Oscillator (vibration generating means)
21 ... 1st transmission / reception unit 22 ... 2nd transmission / reception unit W1 ... 1st surface wave W2 ... 2nd surface wave 23 ... 3rd transmission / reception unit D ... Detection wave 30 ... Transmission / reception circuit (detection means)
40 ... Control unit (detection means)
d ... Distance from the bottom surface of the container to the bottom surface of the propagator L ... Transmission distance of the propagator L1 ... Length of the part where the propagator is not immersed in the liquid L2 ... Length of the part where the propagator is immersed in the liquid Tw ... Reaching the surface wave Time Td ... Internally propagated wave arrival time a ... Side hole height (width)
b ... Length (width) of the upper side
x ... distance

Claims (5)

A propagator in which ultrasonic vibration propagates, in which the boundary of immersion in the liquid is displaced according to the liquid level position of the liquid, and
A vibration generating means provided on one end surface of the propagating body to generate the ultrasonic vibration in the propagating body, and
A detection means for detecting the liquid level position based on a propagation time in which the ultrasonic vibration generated by the vibration generating means propagates from a first location of the propagating body to a second location across the boundary is provided.
The propagator
Two propagation planes that are two sides of the same coin,
Two side surface portions connecting the two propagation surface portions and
A bottom surface portion that connects the two propagation surface portions and has a curved surface in a side view,
A side hole that penetrates the two side surfaces and has an upper side parallel to the one end surface.
The side hole is formed so that the width along the height direction is smaller than the width of the upper side portion.
A liquid level position detecting device characterized by this. In the propagating body, the distance from the end of the upper side portion of the side hole to the surface of the propagating surface portion is set to one wavelength or more of the surface wave generated by the vibration generating means.
The liquid level position detecting device according to claim 1. The height of the side hole from the upper side is set to less than one wavelength of the surface wave generated by the vibration generating means.
The liquid level position detecting device according to claim 1 or 2. The upper side portion of the side hole is the first surface wave arrival time of the surface wave generated by the vibration generating means to the second location and the first of the plurality of reflected waves from the upper side portion of the internally propagated wave. It is provided at a position where the arrival times of the internally propagated waves to the two locations do not match.
The liquid level position detecting device according to any one of claims 1 to 3. The side hole has a semicircular shape having an inverted triangular cross-sectional shape or a downwardly convex shape.
The liquid level position detecting device according to any one of claims 1 to 4.

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