JP7076072B2 - Liquid level position detector - Google Patents

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 sound velocity of a surface wave propagating in a portion of a propagator in a liquid becomes slower than the sound velocity 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 the ratio of the portion immersed in the liquid changes according to the liquid level position of the liquid.
A first transmission / reception unit that generates a first surface wave in the propagator and receives a second surface wave,
A second transmission / reception unit that generates the second surface wave in the propagator and receives the first surface wave,
The liquid level position is detected based on at least one of the propagation time of the first surface wave received by the second transmission / reception unit and the propagation time of the second surface wave received by the first transmission / reception unit. With a detector,
The propagator is
The first main surface part and the second main surface part, which are in a two-sided relationship with each other,
It has a bottom surface portion that connects the first main surface portion and the second main surface portion and has a curved surface shape in a side view.
The first transmission / reception section generates the first surface wave propagating on the first main surface section.
The second wave receiving / receiving portion receives the first surface wave propagating between the bottom surface portion and the second main surface portion via the first main surface portion.
The second transmission / reception section generates the second surface wave propagating in the second main surface section.
The first wave receiving / receiving portion receives the second surface wave propagating between the bottom surface portion and the first main surface portion via the second main surface portion.

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 1st Embodiment of this invention. (A) is a front view of the propagator and the oscillator according to the first embodiment, and (b) is a side view of the propagator and the oscillator according to the first embodiment. It is a schematic diagram for demonstrating the 1st surface wave and the 2nd surface wave. It is a flowchart which shows an example of the liquid level position detection processing. (A) is a front view of the propagator and the oscillator according to the second embodiment, (b) is a side view of the propagator and the oscillator according to the second embodiment, and (c) is the first. 2 It is a top view of the oscillator side of the propagator which concerns on 2nd Embodiment. It is a schematic diagram for demonstrating the 3rd surface wave and the 4th surface wave. (A) is a schematic diagram of a waveform mainly for explaining an internally propagated wave, and (b) is a schematic diagram of a waveform by a propagator according to the second embodiment. It is a flowchart which shows an example of the liquid level position detection processing.

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

(First Embodiment)
As shown in FIG. 1, the liquid level position detecting device 100 according to the first 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 detection device 100 includes a propagator 10, an oscillator 20, a transmission / reception circuit 30, and a control unit 40.

The propagator 10 propagates a surface wave, and is formed of, for example, a synthetic resin such as PPS (polyphenylene sulfide). The propagator 10 has a strip shape that is long in the vertical direction. The outer surface of the propagator 10 has an upper surface facing the oscillator 20, a bottom surface opposite to the upper surface, two main surfaces connecting the upper surface and the bottom surface and having a front-to-back relationship with each other, and connecting the upper surface and the bottom surface to each other. It is mainly composed of two sides and six sides that are related to.

As shown in FIGS. 2 (a) and 2 (b), the propagator 10 has a main surface portion 11 (an example of a first main surface portion) including one of the two main surfaces and a main surface portion 12 (second main surface portion) including the other. An example of a surface portion), a side surface portion 13 including one of the two side surfaces, a side surface portion 14 including the other, a contact portion 15 including the upper surface and abutting against the oscillator 20, and a bottom surface portion 16 including the bottom surface. Have. As will be described later, the surface wave propagates through the propagating body 10, but when propagating, the surface wave reaches a depth substantially the same as the wavelength of the surface wave from the surface of the propagating body 10. The main surface portion 11 and the main surface portion 12 are portions including not only the main surface of the propagating body 10 but also the depth thereof. The same applies to the contact portion 15, the bottom surface portion 16, and the like.

As shown in FIG. 2B, in the side view, the main surface portion 11 hangs down from one end of the contact portion 15. Further, the main surface portion 12 hangs down from the other end of the contact portion 15. Further, the bottom surface portion 16 connects the main surface portion 11 and the main surface portion 12 on the side opposite to the contact portion 15, and has a U-shaped smooth curved surface that is convex downward. The bottom surface portion 16 formed in this way reduces the loss due to leakage when the first surface wave W1 and the second surface wave W2, which will be described later, propagate to the bottom surface portion 16.

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

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 length d. The length L1 of the propagator 10 along the vertical direction from the upper end of the contact portion 15 to the liquid surface 91 (the length of the first portion 10a where the propagator 10 is not immersed in the liquid 90) and the bottom surface. The length along the vertical direction from the lower end of the portion 16 to the liquid level 91 (the length of the second portion 10b where the propagator 10 is immersed in the liquid 90) L2 changes depending on the increase or decrease of the liquid 90. ..

The vibrator 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 contact portion 15 of the propagating body 10 to generate a surface wave on the main surface portion 11 and the main surface portion 12 of the propagating body 10.

Hereinafter, the surface wave generated by the vibrator 20 on the main surface portion 11 is referred to as a first surface wave W1, and the surface wave generated on the main 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 a surface wave without distinction.

The transducer 20 generates a first surface wave W1 on the propagator 10, a first transmission / reception unit 21 that receives the second surface wave W2, and a second surface wave W2 on the propagator 10. It has a second transmission / reception unit 22 that receives the 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 transmitting / receiving unit 21 is transmitted to the propagating body 10, and the first surface wave W1 is generated at the upper end of the main surface portion 11. As shown in FIG. 3, the generated first surface wave W1 propagates toward the lower end of the main surface portion 11, propagates along the bottom surface portion 16 having a smooth curved surface as described above, and then propagates on the main surface portion 12. Propagate toward the top. The first surface wave W1 that has reached the upper end of the main 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 the electric signal supplied from the transmission / reception circuit 30. The vibration of the second transmitting / receiving unit 22 is transmitted to the propagating body 10, and the second surface wave W2 is generated at the upper end of the main surface portion 12. As shown in FIG. 3, the generated second surface wave W2 propagates toward the lower end of the main surface portion 12, propagates along the bottom surface portion 16 having a smooth curved surface as described above, and then propagates on the main surface portion 11. Propagate toward the top. The second surface wave W2 that has reached the upper end of the main 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.

It should be noted that the generation of the first surface wave W1 on the propagating body 10 by the first transmission / reception unit 21 as described above is also expressed as transmitting the first surface wave W1. Similarly, the generation of the second surface wave W2 by the second wave transmitting / receiving unit 22 in the propagating body 10 is also expressed as transmitting the second surface wave W2.

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). Further, the first surface wave W1 and the second surface wave W2 are Rayleigh waves. The oscillator 20 may include an ultrasonic contact medium that 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 an ultrasonic wave generation circuit, the transmission / reception circuit 30 supplies an electric signal for generating an ultrasonic pulse as a surface wave 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 wave receiving circuit, and amplifies and converts the received electric signal.

Specifically, the transmission / reception circuit 30 supplies an electric signal for transmission of 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 transmission of 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 transmission / reception unit 21 that has received the second surface wave W2, and amplifies and converts the received electric signal.

The control unit 40 includes 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 (A / D). It is configured to include an analog / digital) converter and the like. 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 main surface portion 11, and the second surface wave W2 is generated on the main surface portion 12. Further, the control unit 40 receives electrical signals from each of the first transmission / reception unit 21 and the second transmission / reception unit 22 of the vibrator 20 amplified and converted by the transmission / reception circuit 30, and is based on the received electrical 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. This concludes the description of the configuration of the liquid level position detecting device 100.

Next, the operation of the liquid level position detecting device 100 will be described focusing on the liquid level position detecting process (see FIG. 4) 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.

(Liquid level position detection process)
When the liquid level position detection process is started, as shown in FIG. 4, the control unit 40 vibrates the first transmission / reception unit 21 via the transmission / reception circuit 30 to generate a first surface wave W1 at the upper end of the main surface unit 11. (Step S1).

As shown in FIG. 3, the generated first surface wave W1 propagates toward the lower end of the main surface portion 11, propagates along the bottom surface portion 16 having a smooth curved surface, and then toward the upper end of the main surface portion 12. Propagate. The first surface wave W1 that has reached the upper end of the main 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 via 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 referred to as a first propagating wave signal. As described above, the first surface wave W1 transmitted 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 the 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. 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 the first propagate wave signal is received.

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 main surface unit 12 (step S6).

As shown in FIG. 3, the generated second surface wave W2 propagates toward the lower end of the main surface portion 12, propagates along the bottom surface portion 16 having a smooth curved surface, and then toward the upper end of the main surface portion 11. Propagate. The second surface wave W2 that has reached the upper end of the main 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 referred to as a second propagating wave signal. In this way, the second surface wave W2 sent from the second wave 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 the initial value of 0 in order to measure the period from the processing of step S6 to the reception of the second propagated 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 unit. This is the propagation time of the second surface wave W2 from the unit 22 to the first transmission / reception 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 propagation time without distinction.

Subsequently, the control unit 40 determines whether or not the second propagate 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 the second propagate wave signal is received.

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 refers to 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 addition, when the weighted average is obtained, 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. If either the first liquid level position or the second liquid level position indicates an error value, the one that does not indicate the 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 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 display. This concludes the description of the liquid level position detection process.

When the propagator 10 is made of synthetic resin, the propagation velocity of the surface wave propagating in the second portion 10b in contact with the liquid 90 (hereinafter referred to as the second sound velocity) is the first portion 10a in contact with air. It is known that the propagation velocity of the surface wave propagating is slower than the propagation velocity (hereinafter referred to as the first sound velocity). 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 larger the liquid 90 is contained in the container 80, and the higher the position of the liquid level 91 from the bottom surface of the container 80, the longer the propagation time. As the synthetic resin forming the propagator 10, the composition is not limited as long as the propagation time of the surface wave can be detected, but polyethylene, polystyrene or the like is adopted in addition to PPS (polyphenylene sulfide). be able to. As the synthetic resin, PPS, which makes it easy to observe the propagating wave of the surface wave, is considered to be suitable.

The control unit 40 detects a propagation time in which the period 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 the position of the liquid level 91 is based on the detected propagation time. Is detected. 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).

Here, in the propagator 10 in which the bottom surface portion 16 is not a smooth curved surface and is composed of a quadrangular prism or the like, the first surface wave W1 and the second surface wave W2 are reflected by the bottom surface portion 16. Therefore, leakage occurs, resulting in loss. On the other hand, by making the bottom surface portion 16 a smooth curve, the first surface wave W1 and the second surface wave W2 are not reflected by the bottom surface portion 16 and no leakage occurs, so that there is no loss at the bottom surface portion 16 and vibration occurs. Since the surface wave Wr received by the child 20 is less attenuated, the S / N ratio can be improved. However, an unnecessary propagating wave U may be generated near the surface wave.

FIG. 7A schematically shows an unnecessary propagating wave U. Wd indicates a surface wave sent from the oscillator 20 to the propagator 10, and Wr indicates a surface wave received by the oscillator 20.

Further, the control unit 40 may execute a liquid level position detection process for simultaneously generating the first surface wave W1 and the second surface wave W2. At this time, the first and second propagating wave signals are superimposed and observed (received) as a propagating wave signal. The liquid level position detection process will be described with reference to FIG.

As shown in FIG. 8, the control unit 40 vibrates the first transmission / reception unit 21 via the transmission / reception circuit 30 to generate a first surface wave W1 at the upper end of the main surface unit 11. At the same time, the second wave receiving / receiving section 22 is vibrated to generate a second surface wave W2 at the upper end of the main surface section 12 (step S101).

Subsequently, the control unit 40 sets the timer to the initial value of 0 in order to measure the period from the processing of step S101 to the reception of the propagated wave signal (step S102). During this period, the first transmission / reception unit 21, the second transmission / reception unit 21, from the timing when the first transmission / reception unit 21 generates the first surface wave W1 and the second transmission / reception unit 22 generates the second surface wave W2 at the same time. The period until the timing at which 22 receives the propagate wave signal, that is, the propagation time.

Subsequently, the control unit 40 determines whether or not a propagated wave signal has been received from the transmission / reception circuit 30 (step S103). This determination is performed by the same method as in step S3 described above, and when the propagated wave signal has not yet been received (step S103; No), the control unit 40 updates the timer value of the timer by +1 or the like (step S103; No). Step S104), the process of step S103 is executed again. As a result, the control unit 40 keeps time until it receives the propagated wave signal.

When the control unit 40 receives the propagation wave signal (step S103; Yes), the control unit 40 stores the current timer value as the propagation time in, for example, a RAM (step S105).

Subsequently, the control unit 40 specifies the position (liquid level position) of the liquid level 91 based on the propagation time stored in step S105 (step S106).

For example, the relationship between the 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 propagation time.

Subsequently, the control unit 40 outputs the position of the liquid level 91 specified in step S106 to the external device 60 (step S107). The external device 60 displays the position of the liquid level 91 on the image display display.

By simultaneously generating the first surface wave W1 and the second surface wave W2 in this way, the amplitude of the surface wave Wr received by the vibrator 20 becomes large. Therefore, the S / N ratio can be further improved.

(Second Embodiment)
From here on, the liquid level position detecting device according to the second embodiment will be described mainly with reference to FIGS. 5 to 7. Each part having the same configuration and function as that of the first embodiment is designated by the same or corresponding reference numeral as that of the first embodiment, and description thereof will be omitted as appropriate. Further, in the second embodiment, the points different from those in the first embodiment will be mainly described.

The propagating body 210 according to the second embodiment has a main surface portion 11, a main surface portion 12, a side surface portion 13 and a side surface portion 14, a contact portion 15, and a bottom surface portion 16, as in the first embodiment. .. Further, as shown in FIGS. 5 (b) and 6 in the oscillator 220 according to the second embodiment, in addition to the first transmission / reception unit 21 and the second transmission / reception unit 22 similar to those in the first embodiment, A third transmission / reception unit 23 and a fourth transmission / reception unit 24 are provided.

As shown in FIGS. 5A to 5C, the propagator 210 has a recess 17 recessed from the contact portion 15 toward the bottom surface portion 16. As shown in FIG. 5B, the recess 17 is located between the main surface portion 11 and the second main surface portion 12 in a side view.

The recess 17 is a portion hollowed out from the contact portion 15 toward the bottom surface portion 16, for example, in a rectangular parallelepiped shape, and has first to fourth inner side surface portions 17a to 17d and an inner bottom surface portion 17e.

The first inner side surface portion 17a is located on the back side of the main surface portion 11. The second inner side surface portion 17b is located on the back side of the main surface portion 12. The first inner side surface portion 17a and the second inner side surface portion 17b face each other. The third inner side surface portion 17c is located on the back side of the side surface portion 13. The fourth inner side surface portion 17d is located on the back side of the side surface portion 14. The third inner side surface portion 17c and the fourth inner side surface portion 17d face each other. The inner bottom surface portion 17e is located at the bottom of the recess 17 and has a rectangular shape in a plan view as shown in FIG. 5 (c).

FIG. 7B schematically shows how the detection wave D is generated by providing the recess 17 in the propagator 210. The detection wave D indicates a first detection wave D1 or a second detection wave D2, which will be described later.

The third transmission / reception unit 23 generates a first detection wave D1 composed of a surface wave or a plate wave in the propagator 210, and receives the first detection wave D1 reflected by the inner bottom surface portion 17e of the recess 17. The fourth transmission / reception unit 24 generates a second detection wave D2 composed of a surface wave or a plate wave in the propagator 210, and receives the second detection wave D2 reflected by the inner bottom surface portion 17e of the recess 17.

The third transmission / reception unit 23 vibrates due to the electric signal supplied from the transmission / reception circuit 30. The vibration of the third transmission / reception unit 23 is transmitted to the propagator 210, and the first detection wave D1 is generated at the upper end of the first inner side surface portion 17a. As shown in FIG. 6, the generated first detection wave D1 propagates toward the lower end of the first inner side surface portion 17a, is reflected by the inner bottom surface portion 17e, and then propagates toward the upper end of the first inner side surface portion 17a. .. The first detection wave D1 that reaches the upper end of the first inner side surface portion 17a 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 fourth transmission / reception unit 24 vibrates due to the electric signal supplied from the transmission / reception circuit 30. The vibration of the fourth wave transmitting / receiving unit 24 is transmitted to the propagating body 210, and the second detected wave D2 is generated at the upper end of the second inner side surface portion 17b. As shown in FIG. 6, the generated second detection wave D2 propagates toward the lower end of the second inner side surface portion 17b, is reflected by the inner bottom surface portion 17e, and then propagates toward the upper end of the second inner side surface portion 17b. .. The second detection wave D2 that has reached the upper end of the second inner side surface portion 17b vibrates the fourth transmission / reception portion 24. The fourth transmission / reception unit 24 converts this vibration into an electric signal and supplies it to the transmission / reception circuit 30.

The first detection wave D1 received by the third transmission / reception unit 23 and the second detection wave D2 received by the fourth transmission / reception unit 24 depend on the temperature of the propagator 210 and have a sound velocity regardless of the position of the liquid level 91. Changes. In the second embodiment, at least one of the first detection wave D1 and the second detection wave D2 is used to detect the temperature of the propagator 210, and the detected temperature is used as the surface wave (first surface wave W1 and first surface wave D2). 2 Used for temperature correction when detecting surface wave W2). Therefore, it is not necessary to provide a temperature sensor composed of a thermistor chip or the like provided in the conventional liquid level position detection device.

The transmission / reception circuit 30 supplies an electric signal for transmission of the first detection wave D1 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 first detection wave D1, and amplifies and converts the received electric signal. Further, the transmission / reception circuit 30 supplies an electric signal for transmission of the second detection wave D2 to the fourth transmission / reception unit 24, and vibrates the fourth transmission / reception unit 24. Further, it receives an electric signal supplied from the fourth transmission / reception unit 24 that has received the second detection wave D2, and amplifies and converts the received electric signal.

The control unit 40 drives and controls each of the third transmission / reception unit 23 and the fourth transmission / reception unit 24 via the transmission / reception circuit 30. Further, the control unit 40 receives electrical signals from each of the third transmission / reception unit 23 and the fourth transmission / reception unit 24 amplified and converted by the transmission / reception circuit 30, and the propagator 210 is based on the received electrical signals. Detect the temperature.

The control unit 40 detects the propagation time of each of the first detection wave D1 and the second detection wave D2 by the same method as the method described in the above-mentioned liquid level position detection process. Hereinafter, the propagation time of the first detection wave D1 is referred to as a first detection time, and the propagation time of the second detection wave D2 is referred to as a second detection time.

Specifically, the control unit 40 generates the first detection wave D1 in the third transmission / reception unit 23, and after reflection by the inner bottom surface portion 17e, the third transmission / reception unit 23 receives the first detection wave D1. The time until is specified based on the timer value. Then, the specified time is stored in the RAM as the first detection time. Further, the time from the generation of the second detection wave D2 by the fourth transmission / reception unit 24 to the reception of the second detection wave D2 by the fourth transmission / reception unit 24 after the reflection by the inner bottom surface portion 17e is based on the timer value. To identify. Then, the specified time is stored in the RAM as the second detection time. The control unit 40 specifies (detects) the temperature of the propagator 210 based on at least one of the first detection time and the second detection time thus obtained.

As described above, the speed of sound of the first detection wave D1 and the second detection wave D2 changes depending on the temperature of the propagator 210 regardless of the position of the liquid surface 91. Therefore, the first detection time and the second detection time also change depending on the temperature of the propagator 210 regardless of the position of the liquid level 91. Utilizing this characteristic, for example, the relationship between the first detection time, the second detection time, and the temperature of the propagator 210 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 temperature of the propagator 210 based on the table or arithmetic expression stored in the ROM and the first detection time and the second detection time.

The control unit 40 uses a table or an arithmetic expression for specifying the temperature of the propagator 210 based on the first detection time, and the temperature of the propagator 210 based on the first detection time (hereinafter referred to as the first temperature). Using a table or an arithmetic expression for specifying the temperature of the propagator 210 based on the second detection time (hereinafter referred to as the second temperature). Say.) May be specified. That is, the control unit 40 may specify each of the first temperature and the second temperature. Then, the average of the first temperature and the second temperature (either a simple average or a weighted average) may be used as the temperature to be detected this time. In addition, when the weighted average is obtained, the weighting constants of the first temperature and the second temperature may be obtained in advance by an experiment or the like. If either the first temperature or the second temperature indicates an error value, the temperature that does not indicate the error value may be the temperature to be detected this 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 210 specified (detected) as described above. The speed of sound is temperature-dependent and changes with the temperature of the propagator 210. That is, the first propagation time and the second propagation time also change according to the temperature of the propagating body 210. 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 210 with the correction amount and the 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 corresponding to the temperature of the body 210 may be acquired. Then, the control unit 40 performs a calculation for adding or subtracting the acquired correction amount or a calculation for multiplying each of the first propagation time and the second propagation time by a correction coefficient, whereby the first propagation time and the second propagation time are performed. The temperature of the time may be corrected.

A table configured by associating the temperature of the propagating body 210 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 may be obtained. As the temperature correction method for the propagation time and the liquid level position, a known table construction method or calculation method can be appropriately used and is arbitrary.

Further, the above temperature correction processing is performed in the above-mentioned liquid level position detection processing as long as the first detection wave D1 and the second detection wave D2 do not interfere with the first surface wave W1 and the second surface wave W2. Incorporated, the generation timing of the first detection wave D1 and the second detection wave D2 may be the same as the generation timing of the first surface wave W1 and the second surface wave W2. Further, the temperature correction process may be executed as a process independent of the liquid level position detection process.

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, the configuration example in which the first transmission / reception unit 21 and the second transmission / reception unit 22 abut on the contact portion 15 has been described, but the first transmission / reception unit 21 is provided in contact with the first main surface portion 11. , The configuration in which the second wave transmitting / receiving portion 22 is provided in contact with the second main surface portion 12 may be adopted.

In the second embodiment, an example in which the recess 17 is hollowed out in a rectangular parallelepiped shape and the inner bottom surface portion 17e is flat has been described, but the present invention is not limited to this. The inner bottom surface portion 17e of the recess 17 may be formed into a U-shaped smooth curved surface that is convex downward as in the bottom surface portion 16 according to the first embodiment. Further, when the inner bottom surface portion 17e is formed into a curved surface in this way, the first detection wave D1 transmitted by the third transmission / reception unit 23 to the propagator 210 is received by the fourth transmission / reception unit 24, and the fourth transmission / reception unit 24 receives the first detection wave D1. The second detection wave D2 transmitted by the 24 to the propagator 210 may be received by the third transmission / reception unit 23. Further, either the third transmission / reception unit 23 or the fourth transmission / reception unit 24 may be omitted.

In the liquid level position detection, in addition to detecting the detailed position of the liquid level 91 (detecting the height of the liquid level 91 from the bottom surface of the container 80 as described above), 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 it into stages. Further, the image displayed on the external device 60 by the control unit 40 after detecting the liquid level position does not have to show the liquid level position itself, and may show the amount of the liquid 90 according to the liquid level position.

Further, the propagators 10 and 210 are 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 propagating body 10b is propagated. It is preferable that the difference between the speed of the surface wave to be generated and the speed of the surface wave propagating in the first portion 10a (the portion exposed from the liquid 90) becomes more remarkable. However, if the liquid level position can be detected by the method described above, the propagators 10 and 210 may be made of a metal such as aluminum, stainless steel, or steel.

Further, the propagators 10 and 210 may be arranged so that their long directions are parallel to the normal direction of the liquid surface 91 and their long directions are tilted with respect to the normal direction of the liquid surface 91. good. Further, a plurality of concave portions or convex portions extending along the traveling direction of the surface wave may be formed on the surface of the propagating bodies 10 and 210 on which the surface wave propagates, and unevenness may be formed on this surface.

The type of the liquid 90 whose liquid level position is to be detected is not limited, and water, gasoline, cleaning liquid, or the like is arbitrary. 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 propagators 10, 210 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 used as the resins used as the propagators 10 and 210 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 a filler (additive material) such as glass fiber or an inorganic filler is added, but various PPSs used for the propagator 10 are used. 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., presence / absence of filler addition, and difference in filler type. The effect on the speed of sound 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.

(1) The liquid level position detecting device 100 described above includes propagators 10 and 210 and propagators 10 and 210 in which the ratio of the portion immersed in the liquid 90 changes according to the liquid level position (position of the liquid level 91) of the liquid 90. The first transmission / reception unit 21 that generates the first surface wave W1 and receives the second surface wave W2 on the bodies 10 and 210, and the second surface wave W2 and the first surface wave W1 on the propagators 10 and 210. At least one of the propagation time of the first surface wave W1 received by the second transmission / reception unit 22 and the second transmission / reception unit 22 and the propagation time of the second surface wave W2 received by the first transmission / reception unit 21. A detection unit (for example, a control unit 40) for detecting the liquid level position based on the above is provided. The propagators 10 and 210 connect the main surface portion 11 (first main surface portion) and the main surface portion 12 (second main surface portion), which are in a front-to-back relationship with each other, and the main surface portion 11 and the main surface portion 12, and are curved surfaces in a side view. It has a bottom surface portion 16 having a shape.
The first transmitting / receiving unit 21 generates a first surface wave W1 propagating through the main surface portion 11, and the second transmitting / receiving unit 22 propagates through the main surface portion 11 to the bottom surface portion 16 and the main surface portion 12. Receive wave W1. The second transmission / reception unit 22 generates a second surface wave W2 propagating through the main surface portion 12, and the first transmission / reception unit 21 propagates through the main surface portion 12 to the bottom surface portion 16 and the main surface portion 11. Receive wave W2.

In this way, since the bottom surface portion 16 having a curved surface shape in the side view is provided, it is possible to reduce the loss due to leakage when the first surface wave W1 and the second surface wave W2 propagate to the bottom surface portion 16, and S / The deterioration of the N ratio can be reduced. As a result, the detection accuracy of the liquid level position can be improved. Further, since the liquid level position is detected based on at least one of the propagation time of the first surface wave W1 and the propagation time of the second surface wave W2 received by the first transmission / reception unit 21, the liquid level position is detected by superimposing noise or the like. Even when the detection accuracy of one of the propagation times is inferior, the detection accuracy of the liquid level position can be improved.

(2) Specifically, the propagating bodies 10 and 210 have a contact portion 15 that abuts on the first transmission / reception portion 21 and the second transmission / reception portion 22, and the main surface portion 11 has a contact portion 15 in a side view. It hangs down from one end of 15, and the main surface portion 12 hangs down from the other end of the contact portion 15 in a side view. Then, the first transmission / reception unit 21 generates the first surface wave W1 propagating through the main surface portion 11 via the contact portion 15, and the second transmission / reception portion 22 causes the main surface portion 12 via the contact portion 15. A second surface wave W2 propagating is generated. As described in the above-described modification, the first transmission / reception unit 21 is provided in contact with the first main surface portion 11, and the second transmission / reception unit 22 is provided in contact with the second main surface portion 12. May be adopted.

(3) The first transmission / reception unit 21 and the second transmission / reception unit 22 may simultaneously generate the first surface wave W1 and the second surface wave W2 (the first surface wave W1 by the first transmission / reception unit 21). And the generation of the second surface wave W2 by the second transmission / reception unit 22 may be simultaneous).

(4) The propagating body 210 according to the second embodiment has a recess 17 located between the main surface portion 11 and the main surface portion 12 in a side view while being recessed from the contact portion 15 toward the bottom surface portion 16.
The recess 17 can reduce or eliminate the internally propagated wave U generated from the oscillator 220 to the propagator 210. This makes it possible to reduce the detection error of the liquid level position detection.

(5) Further, the liquid level position detecting device according to the second embodiment transmits a detection wave (at least one of the first detection wave D1 and the second detection wave D2) which is a surface wave or a plate wave to the propagator 210. A specific transmission / reception unit (at least one of the third transmission / reception unit 23 and the fourth transmission / reception unit 24) to be generated is further provided. The specific wave transmitting / receiving unit generates a detection wave propagating on the inner side surface portion of the recess 17 via the contact portion 15, and receives the detection wave reflected by the inner bottom surface portion 17e of the recess 17 via the inner side surface portion. The detection unit detects the temperature of the propagator 210 based on the propagation time of the detected wave received by the specific transmission / reception unit.
Since this is done, it is not necessary to provide a temperature sensor composed of a thermistor chip or the like provided in the conventional liquid level position detection device, and the number of parts can be reduced.

(6) Further, the first transmission / reception unit 21, the second transmission / reception unit 22, and the specific transmission / reception unit may simultaneously generate the first surface wave W1, the second surface wave W2, and the detection wave (the first). 1 The generation of the first surface wave W1 by the transmission / reception unit 21, the generation of the second surface wave W2 by the second transmission / reception unit 22, and the generation of the detection wave by the specific transmission / reception unit may be simultaneous).

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 detecting device 10, 210 ... Propagator 10a ... First part, 10b ... Second part 11 ... Main surface part (an example of the first main surface part)
12 ... Main surface part (an example of the second main surface part)
13, 14 ... Side part 15 ... Contact part 16 ... Bottom part 20, 220 ... Oscillator 21 ... First transmission / reception part, 22 ... Second transmission / reception part W1 ... First surface wave, W2 ... Second surface wave 23 ... 3rd transmission / reception unit, 24 ... 4th transmission / reception unit D1 ... 1st detection wave, D2 ... 2nd detection wave 30 ... Transmission / reception circuit 40 ... Control unit

Claims (6)

A propagator in which the ratio of the portion immersed in the liquid changes according to the liquid level position of the liquid.
A first transmission / reception unit that generates a first surface wave in the propagator and receives a second surface wave,
A second transmission / reception unit that generates the second surface wave in the propagator and receives the first surface wave,
The liquid level position is detected based on at least one of the propagation time of the first surface wave received by the second transmission / reception unit and the propagation time of the second surface wave received by the first transmission / reception unit. With a detector,
The propagator is
The first main surface part and the second main surface part, which are in a two-sided relationship with each other,
It has a bottom surface portion that connects the first main surface portion and the second main surface portion and has a curved surface shape in a side view.
The first transmission / reception section generates the first surface wave propagating on the first main surface section.
The second wave receiving / receiving portion receives the first surface wave propagating between the bottom surface portion and the second main surface portion via the first main surface portion.
The second transmission / reception section generates the second surface wave propagating in the second main surface section.
The first wave receiving / receiving portion receives the second surface wave propagating between the bottom surface portion and the first main surface portion via the second main surface portion.
Liquid level position detector. The propagator has a contact portion that comes into contact with the first transmission / reception portion and the second transmission / reception portion.
The first main surface portion hangs down from one end of the contact portion in the side view.
The second main surface portion hangs down from the other end of the contact portion in the side view.
The first transmission / reception portion generates the first surface wave propagating through the first main surface portion via the contact portion.
The second wave transmitting / receiving portion generates the second surface wave propagating through the contact portion and propagating through the second main surface portion.
The liquid level position detecting device according to claim 1. The first transmission / reception unit and the second transmission / reception unit simultaneously generate the first surface wave and the second surface wave.
The liquid level position detecting device according to claim 1 or 2. The propagator is recessed from the contact portion toward the bottom surface portion, and has a recessed portion located between the first main surface portion and the second main surface portion in the side view.
The liquid level position detecting device according to claim 2. The propagator is further provided with a specific transmission / reception unit that generates a detection wave that is a surface wave or a plate wave.
The specific wave receiving / receiving portion generates the detection wave propagating on the inner side surface portion of the recess via the contact portion, and receives the detection wave reflected on the inner bottom surface portion of the recess via the inner side surface portion.
The detection unit detects the temperature of the propagator based on the propagation time of the detected wave received by the specific transmission / reception unit.
The liquid level position detecting device according to claim 4. The first transmission / reception unit, the second transmission / reception unit, and the specific transmission / reception unit simultaneously generate the first surface wave, the second surface wave, and the detection wave.
The liquid level detection device according to claim 5.

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