JP7333516B2 - Liquid level detector - Google Patents

Description

The present invention relates to a liquid level detection device.

As a liquid surface position detection device, for example, Patent Document 1 discloses that the speed of sound of a surface wave propagating through a portion of a propagating body in liquid is slower than the speed of sound of a surface wave propagating through a portion exposed from the liquid. It is disclosed to detect the liquid surface position of the liquid by utilizing the fact.

JP-A-4-86525

In the liquid level detection device disclosed in Patent Document 1, depending on the liquid level position, part of the surface wave propagating on the propagating medium propagates to the side surface of the propagating medium, becomes a noise component, or leaks from the bottom surface, causing S /N ratio (Signal-Noise Ratio) deteriorates, and the detection accuracy of the liquid surface position may deteriorate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid level position detecting device capable of detecting a liquid level position with high accuracy.

In order to achieve the above object, the liquid level detection device according to the present invention includes:
a propagating body that is immersed in a liquid and displaces a boundary immersed in the liquid according to the liquid surface position of the liquid, and propagates the ultrasonic vibration;
a vibration generating means provided at one end of the propagating body for generating the ultrasonic vibration in the propagating body;
detecting means for detecting the liquid level position based on the propagation time for the ultrasonic vibration generated by the vibration generating means to propagate from the first point of the propagating body to the second point across the boundary;
The propagating body has a propagating surface portion through which the ultrasonic vibration is propagated by the vibration generating means at the one end, and an adjacent surface portion continuous with the propagating surface portion,
an angle formed by the propagating surface portion and the adjacent surface portion is an acute angle;
The adjacent surface portion is a bottom surface portion that is continuous with the other end portion of the propagation surface portion located on the opposite side of the one end portion,
It is characterized by

Further, in order to achieve the above object, the liquid level detection device according to the present invention includes:
a propagating body that is immersed in a liquid and displaces a boundary immersed in the liquid according to the liquid surface position of the liquid, and propagates the ultrasonic vibration;
a vibration generating means provided at one end of the propagating body for generating the ultrasonic vibration in the propagating body;
detecting means for detecting the liquid level position based on the propagation time for the ultrasonic vibration generated by the vibration generating means to propagate from the first point of the propagating body to the second point across the boundary;
The propagating body has a propagating surface portion through which the ultrasonic vibration is propagated by the vibration generating means at the one end portion, and an adjacent surface portion continuous with the propagating surface portion,
an angle formed by the propagating surface portion and the adjacent surface portion is an acute angle;
The propagation surface portion has a first propagation surface portion and a second propagation surface portion that are in a front-back relationship with each other,
The adjacent surface portion has two first side surface portions continuous on both sides of the first propagation surface portion and two second side surface portions continuous on both sides of the second propagation surface portion,
It is characterized by
Moreover, it is preferable that the propagation surface portion and the adjacent surface portion have circular arc portions that are continuous with each other at the intersection line portion.

ADVANTAGE OF THE INVENTION According to this invention, the liquid level position detection apparatus with high detection accuracy of a liquid level position can be provided.

1 is a schematic configuration diagram of a liquid level detection device according to a first embodiment of the present invention; FIG. 1 is an external perspective view of a propagating body and a vibrator according to a first embodiment; FIG. (a) is a front view of a propagating body and a vibrator according to the first embodiment, (b) is a left side view, and (c) is a plan view. It is a graph which shows the analysis result of a tilt angle and a reflectance. 6 is a flow chart showing an example of liquid level position detection processing according to the first embodiment; FIG. 8A is a front view of a propagating body and a vibrator, FIG. 8B is a right side view, and FIG. FIG. 3 is a schematic diagram for explaining a first surface wave and a second surface wave; It is a graph which shows the analysis result of time and amplitude, (a) shows 2nd Embodiment, (b) shows a conventional example. 10 is a flowchart showing an example of liquid surface position detection processing according to the second embodiment; FIG. 8 is an explanatory diagram of temperature correction according to the second embodiment, in which (a) is a front view of a propagating body and an oscillator, (b) is a right side view, and (c) is a plan view. FIG. 8A is an external perspective view of a propagating body and a vibrator, and FIG. 8B is a partially enlarged view according to the third embodiment. FIG. 10 (a) is a front view of a propagating body and a vibrator, (b) is a right side view, (c) is a plan view, and (d) is a partially enlarged view according to the third embodiment. It is a graph which shows the analysis result of an inclination-angle and a reflectance concerning 3rd Embodiment.

A liquid level detection device according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
A liquid level detection device 100 according to this embodiment is a device for detecting the position of a liquid level 91 of a liquid 90 contained in a container 80, as shown in FIG. As the amount of the liquid 90 increases or decreases, the liquid level 91 also rises and falls.

The liquid level detection device 100 includes a propagating body 10 , a vibrator (vibration generating means) 20 , a transmission/reception circuit (detection means) 30 , and a controller (detection means) 40 .

The propagating body 10 propagates the surface wave W, and is made of a synthetic resin such as PPS (polyphenylene sulfide). The propagating body 10 has a substantially columnar shape elongated in the vertical direction. The outer surface of the propagating body 10 includes a top surface facing the vibrator 20, a bottom surface opposite to the top surface, two main surfaces connecting the top surface and the bottom surface and having a front/back relationship with each other, and It is mainly composed of two sides having a relationship of and six sides.

In this embodiment, as shown in FIGS. 2 and 3, the propagating body 10 has a substantially columnar shape and a trapezoidal cross-sectional shape. , surface), and a so-called one-plane oscillation structure in which a surface wave W caused by ultrasonic vibration propagates through the propagation surface 11 is formed. A surface wave W caused by ultrasonic vibration reaches a depth substantially equal to the wavelength of the surface wave W from the surface of the propagating body 10 when propagating through the propagating body 10 . The propagation surface portion 11 is a portion including not only the main surface (surface) of the propagation body 10 but also a depth substantially equal to the wavelength of the surface wave W. FIG.

The propagating body 10 includes, as six surfaces, a propagation surface portion 11 through which ultrasonic vibrations are propagated, and a back surface portion 12 including a main surface including a short side (upper base) of a trapezoid that is in a front and back relationship with the propagation surface portion 11. , side surface portions 13 and 14 including two side surfaces including a trapezoidal oblique side connecting the propagation surface portion 11 and the back surface portion 12, and a top surface portion 15 including a top surface on which a vibrator (vibration generating means) 20 is provided. , and a bottom portion 16 including a bottom surface. Like the propagating surface portion 11, the back surface portion 12, the side surface portion 13, the side surface portion 14, the top surface portion 15, and the bottom surface portion 16 include not only the surface but also the depth substantially equal to the wavelength of the surface wave W.

The propagating surface portion 11 is formed of a flat surface that continuously hangs down from the lower base of the trapezoidal upper surface portion 15 that is one end of the propagating body 10 . The back surface portion 12 is composed of a flat surface that hangs down from the upper base of the top surface portion 15 . Therefore, in the propagating body 10 having a trapezoidal cross-sectional shape, the width of the propagating surface portion 11 is larger than the width of the back surface portion 12 .

As shown in FIGS. 2 and 3, the side surface portions 13 and 14 are continuous to both sides of the propagation surface portion 11 on the front side and also continuous to both sides of the back surface portion 12 on the back side in plan view (FIG. 3(c)). It is composed of a plane including the oblique side of the trapezoid. The two side surface portions 13 and 14 form adjacent surface portions that are continuous on both sides with the propagation surface portion 11 through which the ultrasonic vibration propagates.

The propagating body 10 has an acute angle θ between the propagating surface portion 11 and the side surfaces (adjacent surface portions) 13 and 14 that are continuous on both sides.
In this propagating body 10, the side surfaces 13 and 14 form an acute angle .theta. It can also be reflected back to the propagation surface portion 11 from the side surfaces 13 and 14 toward the S/ N ratio can be improved.
It should be noted that the length (the length in the direction toward the back surface portion 12 (the direction along the slope)) c of the portion forming the angle θ between the side surface portions 13 and 14 and the propagation surface portion 11 is at least the propagation surface portion 11 and the side surface portion 13 . , 14 (crossing line portion), a length of one wavelength or longer for propagation of ultrasonic waves may be ensured.

The upper surface portion 15 constitutes one end portion of the propagating body 10 and has a trapezoidal plane. A vibrator (vibration generating means) 20 is provided on the upper surface portion 15 so as to straddle the bottom of the trapezoidal shape, and propagates ultrasonic vibrations to the propagation surface portion 11 (see FIGS. 2 and 3B and 3C). ).

The bottom surface portion 16 connects the propagation surface portion 11 and the back surface portion 12 on the side opposite to the top surface portion 15 and is a flat surface that connects the two side surface portions 13 and 14 .
As shown in FIGS. 2 and 3B, the propagating body 10 has an acute angle φ formed between the propagating surface portion 11 and the bottom surface portion (adjacent surface portion) 16 that is continuous with the other end portion of the propagating surface portion 11. be.
In such a propagator 10, the angle φ formed by the propagation surface portion 11 and the bottom surface portion (adjacent surface portion) 16 that is continuous at the other end portion of the propagation surface portion 11 is an acute angle. A portion of W can be reflected by the bottom surface portion 16 toward the bottom surface portion 16 and returned to the propagation surface portion 11, and by merging with the surface wave W serving as the detection wave propagating in the vertical direction on the propagation surface portion 11, An S/N ratio can be improved.
The length c1 of the portion forming the angle φ between the bottom surface portion 16 and the propagation surface portion 11 (the length in the direction toward the back surface portion 12) is at least from the intersection (intersection line) between the propagation surface portion 11 and the bottom surface portion 16. It suffices to secure a length of one wavelength or longer for ultrasonic waves to propagate (see FIG. 3B).

Next, regarding the improvement of the S/N ratio by making the angle φ(θ) between the propagation surface portion 11 and the adjacent surface portion of the propagation body 10 an acute angle, the bottom surface portion 16 continuing to the propagation surface portion 11 is used as the adjacent surface portion. , the angle φ formed with the propagation surface portion 11 was analyzed. Note that the PPS propagating body 10 was used for the analysis. Further, in the propagating body 10, the intersection line portion between the propagating surface portion 11 and the bottom surface portion 16 serving as the adjacent surface portion is sharp.

In the analysis, the angle φ formed by the bottom surface portion 16 with respect to the propagation surface portion 11 was changed to obtain the reflectance (reflection coefficient) Rc. As a result of the analysis, as shown in FIG. 4, it is known that the reflectance (reflection intensity) Rc does not change linearly with respect to the change in the angle φ, but has a peak range. Compared to the reflectance Rc of 0.45 when the angle φ was set to 90 degrees in the past, the S/N ratio is increased by setting the angle φ in a range in which the reflectance Rc is higher than 0.45. For example, the reflectance Rc can be increased by setting a predetermined angle range from the angle φ based on the seven peaks.

On the other hand, in the propagating body 10, when the angle φ between the propagating surface portion 11 and the bottom portion 16 becomes small, the tip becomes sharp, and problems such as securing strength, that is, chipping and cracking, are likely to occur. be done. Therefore, for example, the angle φ should be as large as possible, close to 90 degrees. It is preferable to set the angle φ to a predetermined range from the angle φ=55 degrees at which the reflectance Rc is maximized in the range of 40 degrees or more, for example, the range of 49 to 65 degrees. More preferably, ±3 degrees of the angle φ=55 degrees at which the reflectance Rc is maximum in the range of 40 degrees or more. It can be as above.

In the propagator 10, the angle .theta. formed between the propagation surface portion 11 and the side portions 13 and 14 is also considered to be able to increase the reflectance Rc as compared with the case where the angle .theta. . As for the angle θ formed between the propagation surface portion 11 and the side surfaces 13 and 14 which are the adjacent surface portions, the analysis result of the angle φ formed between the propagation surface portion 11 and the adjacent surface portions is applied, and the angle θ is set to 49 to 65 degrees. More preferably, the angle θ at which the reflectance Rc is maximized is ±3 degrees of 55 degrees. ) or more.

The propagating body 10 has a concave portion 17 (see FIG. 3) that is cut perpendicular to the back surface portion 12 in the middle of the longitudinal direction of the back surface portion 12 opposite to the propagation surface portion 11. It functions as a reflector that reflects the Note that the concave portion 17 is omitted in FIG. Temperature correction using the internal propagation wave by the concave portion 17 will be described later.

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

The propagating body 10 is arranged such 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 along the vertical direction from the upper end of the upper surface portion 15 to the liquid surface 91 (the length of the first portion 10a, which is the portion of the propagation body 10 not immersed in the liquid 90) in the propagating body 10, and the bottom portion 16 to the liquid surface 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. FIG. That is, the boundary (boundary between the first portion 10a and the second portion 10b) of the propagating body 10 immersed in the liquid 90 is displaced according to the position of the liquid surface 91 of the liquid 90 (liquid surface position).

The vibrator 20 is vibration generating means for generating ultrasonic waves, and is, for example, a transverse wave transducer, and includes a piezoelectric element or the like mounted on a circuit board. The vibrator 20 is pressed against the upper surface portion 15 of the propagation body 10 and has a one-plane oscillation structure that generates a surface wave W on the propagation surface portion 11 of the propagation body 10, for example. In this embodiment, the ultrasonic waves generated by the transducer 20 on the propagation surface 11 are called surface waves W. As shown in FIG.
The vibrator 20 has a wave transmitting/receiving section 21 for generating a surface wave W in the propagating body 10 and receiving the surface wave W, as shown in FIG. In addition, in FIG. 3B, the wave transmitting/receiving sections 21 and 23 are shown with the vibrator 20 seen through.

The wave transmitting/receiving section 21 vibrates by the electric signal supplied from the transmitting/receiving circuit 30 . The vibration of the wave transmitting/receiving section 21 is propagated to the propagating body 10 and a surface wave W is generated at the upper end (an example of the first location) of the propagating surface section 11 . As shown in FIG. 3, the generated surface wave W propagates toward the lower end of the propagation surface portion 11, reflects off the bottom surface portion 16, and then propagates toward the upper end (an example of the second location) of the propagation surface portion 11. (See the solid line in the figure). The surface wave W reaching the upper end of the propagation surface portion 11 causes the wave transmitting/receiving portion 21 to vibrate. The wave transmitting/receiving section 21 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 (see FIG. 1).

In this embodiment, the surface wave W is a pulse (ultrasonic pulse) of an ultrasonic wave (for example, a sound wave of 20 KHz or higher). Moreover, the surface wave W is a Rayleigh wave or a Schulz wave. The vibrator 20 may contain a contact material for ultrasonic waves interposed between the piezoelectric element and the propagating body 10 for efficient transmission of vibration.

The transmitting/receiving circuit 30 is connected to the vibrator 20 as shown in FIG. The transmitting/receiving circuit 30 serves as an ultrasonic wave generating circuit to supply an electric signal for generating an ultrasonic pulse as a surface wave W to the vibrator 20 to vibrate the vibrator 20 . The transmitting/receiving circuit 30, as an ultrasonic wave receiving circuit, receives an electrical signal supplied from the transducer 20, and amplifies and converts the received electrical signal.

Specifically, as shown in FIGS. 1 and 3, the transmitting/receiving circuit 30 supplies an electric signal for transmitting the surface wave W to the wave transmitting/receiving section 21 to vibrate the wave transmitting/receiving section 21 . It also receives an electrical signal of the surface wave W reflected by the bottom surface portion 16 (a reflected wave of the surface wave W), and amplifies and converts the received electrical 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, an A/D ( (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 the electrical signal from the transmission/reception circuit 30 to the wave transmission/reception unit 21 of the vibrator 20 . Thereby, a surface wave W is generated on the propagation surface portion 11 . Further, the control unit 40 receives an electric signal from the wave transmitting/receiving unit 21 of the vibrator 20 amplified and converted by the transmitting/receiving circuit 30, and detects the position of the liquid surface 91 based on the received electric signal as described later. do. Further, the control unit 40 can exchange data with an external device 60 outside the liquid level detection device 100 (see FIG. 1).

Next, the operation of the liquid level position detection device 100 configured as described above will be described, centering on the liquid level position detection processing (see FIG. 5) executed by the control section 40. FIG. For example, the CPU of the control unit 40 uses the RAM as a main memory and executes the liquid level detection process according to the program stored in the ROM and using various data stored in the ROM. The control unit 40 starts the liquid surface position detection process based on a command from the external device 60, for example.

(Liquid level position detection processing)
When the liquid surface position detection process is started, as shown in FIG. generated (step S1).

The generated surface wave W propagates toward the lower end of the propagation surface portion 11 as shown in FIG. A reflected wave of the surface wave W reaching the upper end of the propagation surface portion 11 causes the wave transmitting/receiving portion 21 to vibrate. The wave transmitting/receiving section 21 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 . The transmitting/receiving circuit 30 amplifies and converts the supplied electric signal and supplies it to the control unit 40 . In the following, the amplified and converted electric signal (that is, an electric signal indicating the vibration generated in the wave transmitting/receiving unit 21 by the reflected wave of the surface wave W that reaches the wave transmitting/receiving unit 21 after propagating to the bottom surface portion 16) is the surface wave propagation signal. In this way, the surface wave W sent from the wave transmitting/receiving section 21 (at the first point) is reflected and reaches the wave transmitting/receiving section 21 (at the second point) again. It propagates across the boundary with the second portion 10b in contact with the liquid 90 twice.

Subsequently, the control unit 40 sets the timer to the initial value of 0 in order to measure the period from performing the process of step S1 to receiving the surface wave propagation signal (step S2). This period is a period from the timing when the wave transmitting/receiving unit 21 generates the surface wave W to the timing when the wave transmitting/receiving unit 21 receives the reflected wave of the surface wave W again. 21 (hereinafter also referred to as surface wave propagation time).

Subsequently, the control unit 40 determines whether or not the surface wave propagation signal has been received from the transmitting/receiving circuit 30 (step S3). This determination can be made by an appropriate method. For example, the control unit 40 acquires an electric signal supplied from the wave transmitting/receiving unit 21 and amplified and converted by the transmitting/receiving circuit 30, and determines the voltage of the acquired electric signal. (for example, the voltage value, the average value of the squares of the voltage values in a predetermined period, the voltage value or the degree of change of the average value, the amplitude of the electrical signal, etc.) is equal to or greater than a threshold value stored in advance in the ROM determine whether or not For example, the surface wave propagation signal may be measured in advance by experiments, and the threshold may be determined based on the measurement results. Then, when the value based on the voltage of the electric signal is equal to or higher than the threshold, the control unit 40 determines that the surface wave propagation 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, the control unit 40 determines that the surface wave propagation signal has not been received (step S3; No).

If the surface wave propagation signal has not yet been received (step S3; No), the controller 40 updates the timer value of the timer by +1 (step S4), and executes the process of step S3 again. Thereby, the control unit 40 keeps time until the surface wave propagation signal is received.

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

Subsequently, the controller 40 identifies the position of the liquid surface 91 (liquid surface position) based on the surface wave propagation time stored in step S5 (step S6).

For example, the relationship between the surface wave propagation time and the position of the liquid surface 91 is identified in advance by experiments or the like, and the identified relationship is stored in the ROM as a table or an arithmetic expression. The control unit 40 specifies the position of the liquid surface 91 (liquid surface position) based on the table or arithmetic expression stored in the ROM and the surface wave propagation time.
That is, the control unit 40 detects the surface wave propagation time whose period becomes longer as the liquid contact portion (second portion 10b) L2 becomes longer according to the position of the liquid surface 91 of the liquid 90, and detects the surface wave propagation time. Based on this, the position of the liquid surface 91 is specified. The position of the liquid surface 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 surface 91 from the bottom surface of the container 80, the length L2, and the height of the liquid surface 91. It is sufficient if it is represented by a value or the like according to the value. The height of the liquid surface 91 from the bottom surface of the container 80 is the depth of the liquid 90, and is obtained by length L2+length d (see FIG. 1).

Subsequently, the controller 40 outputs the position of the liquid surface 91 specified in step S6 to the external device 60 (step S7). The external device 60 includes an image display such as an LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Diode), and displays the position of the liquid surface 91 on the image display. Thus, the liquid surface position detection processing is completed.

When the propagating body 10 is made of synthetic resin, the propagation velocity of the surface wave W propagating through the second portion 10b in contact with the liquid 90 (hereinafter referred to as the second sound velocity) is the same as that in the first portion in contact with the air. It is known to be slower than the propagation velocity of the surface wave W propagating through 10a (hereinafter referred to as the first sound velocity). Therefore, the longer the length L2 of the second portion 10b, the longer the surface wave propagation time (first propagation time, second propagation time) measured by the timer. In other words, the more the liquid 90 is contained in the container 80 and the higher the position of the liquid surface 91 from the bottom surface of the container 80 is, the longer the propagation time of the surface wave W is.
The composition of the synthetic resin forming the propagating body 10 is not limited as long as the propagation time of the surface wave W can be detected. can be adopted. As the synthetic resin, PPS, which facilitates observation of the propagating wave of the surface wave W, is suitable, and is considered particularly suitable for detecting the liquid level of a gasoline tank of an automobile.
In addition, the detection object of the height of the liquid level 91 (liquid level position) is not limited to the above-described gasoline or the like. It can be anything that exists. Alternatively, a colloidal solution in which the liquid 90 and fine particles are dispersed may be used.

Next, temperature correction in the liquid level position detection process of the liquid level position detection device 100 will be described with reference to FIG.

The propagating body 10 has a concave portion 17 which reflects an internal propagating wave by means of a groove with an open side for temperature correction, and is formed from the back surface portion 12 to the intermediate portion toward the propagating surface portion 11 . That is, the concave portion 17 opens to the back surface portion 12, and both ends of the concave portion 17 open to the side surface portions 13 and 14. From the back surface portion 12 toward the propagation surface portion 11, a groove with a bottom (up to the intermediate portion) is formed. formed.

The vibrator 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 of the propagating body 10 and to send a detected wave D toward a concave portion 17 reflecting the internal propagating wave of the propagating body 10 . generate The detection wave D propagates inside the propagating body 10, and after being reflected by the concave portion 17, causes the wave transmitting/receiving portion 23 of the upper surface portion 15 to vibrate again. Temperature correction processing is performed in the internal propagation time based on this detected wave D. FIG. That is, the wave transmitting/receiving section 23 generates a detection wave D consisting of a transverse wave in the propagating body 10 and receives the detection wave D reflected by the concave portion 17 . The sound velocity of the detected wave D received by the wave transmitting/receiving section 23 changes depending on the temperature of the propagating body 10 regardless of the position of the liquid surface 91 . Therefore, the detected wave D is used to specify the temperature of the propagating body 10, and the specified temperature is used for temperature correction when the surface wave W is detected.
As a result, temperature correction can be performed without providing a temperature sensor such as a thermistor chip, which is provided in a conventional liquid level detection device.

Specifically, the control unit 40 detects the internal propagation time of the detection wave D in the same manner as the method described in the above-described liquid surface position detection process. The control unit 40 detects the time from when the wave transmitting/receiving unit 23 generates the detection wave D to when the wave transmitting/receiving unit 23 receives the detection wave D after being reflected by the concave portion 17 based on the timer value. Then, the detected time is stored in the RAM as a detection time (internal propagation time). The control unit 40 identifies (detects) the temperature of the propagating body 10 based on the detection time thus obtained.
Note that the temperature of the propagating body 10 is specified, for example, by previously specifying the relationship between the detection time and the temperature of the propagating body 10 through an experiment or the like, and storing the specified relationship in the ROM as a table or an arithmetic expression. The control unit 40 specifies the temperature of the propagating body 10 based on the table or arithmetic expression stored in the ROM and the detection time.

Then, the control unit 40 performs temperature correction of the surface wave propagation time based on the temperature of the propagation body 10 specified (detected) as described above. That is, the surface wave propagation time also changes according to the temperature of the propagating body 10 . Therefore, temperature correction is required to maintain the detection accuracy of the liquid level position. For example, a table in which the temperature of the propagating medium 10 is associated with the correction amount and correction coefficient of the surface wave propagation time is stored in advance in the ROM, and the control unit 40 refers to the table to refer to the identified propagating medium. 10, the correction amount and the correction coefficient corresponding to the temperature may be acquired. Then, the control unit 40 may perform temperature correction of the surface wave propagation time by performing calculations for adding or subtracting the obtained correction amount or multiplying the correction coefficient to the surface wave propagation time.
As a result, temperature correction can be performed without providing a temperature sensor such as a thermistor chip, which is provided in a conventional liquid level detection device.

The correction of the liquid level position based on the temperature of the propagating body 10 is not limited to the table. may be used to obtain a correction amount or a correction coefficient for the surface wave propagation time or the liquid level position. As the surface wave propagation time and the temperature correction method for the liquid surface position, a known table calibration method and calculation method can be used as appropriate, and are arbitrary.

As long as the detected wave D does not interfere with the surface wave W, the temperature correction process described above is incorporated into the liquid level position detection process described above, and the timing at which the detected wave D is generated is the same as the timing at which the surface wave W is generated. You can do it at the same time. Further, the temperature correction process may be executed as a process independent of the liquid level position detection process using the surface wave W.

In the liquid level detection device 100, the angle θ formed between the propagation surface portion 11 of the propagation body 10 and the side surface portions 13 and 14 forming adjacent surface portions adjacent to the propagation surface portion 11 is formed to be an acute angle. As a result, even if part of the surface wave W propagating through the propagation surface portion 11 is directed toward the side surface portions 13 and 14, the side surface portions 13 and 14 intersect the propagation surface portion 11 at an angle θ. has a large reflectance (reflection intensity) Rc, the surface waves W can be reflected from the side surface portions 13 and 14 and returned to the propagation surface portion 11. , the leakage of the surface wave W, etc., can be reduced, and the S/N ratio can be improved.
The length (the length in the direction toward the back surface portion 12) c of the portion forming the angle θ at which the side surface portions 13 and 14 intersect with the propagation surface portion 11 is at least the intersection point ( It suffices to secure a length of one wavelength or more for the ultrasonic wave to propagate from the intersection line). /s, one wavelength is approximately 1.9 mm. When the surface wave frequency is 400 kHz and the propagating body 10 is PPS, the speed of sound at room temperature is about 950 m/s, so one wavelength is about 2.38 mm.

Further, in the liquid level detection device 100, the angle φ between the propagation surface portion 11 of the propagation body 10 and the bottom surface portion 16 constituting the adjacent surface portion adjacent to the propagation surface portion 11 is formed to be an acute angle. As a result, even if a portion of the surface wave W propagating on the propagation surface portion 11 is directed toward the bottom surface portion 16, the bottom surface portion 16 intersects the propagation surface portion 11 at an angle φ. is large, and the surface wave W reflected by the bottom surface portion 16 can be returned to the propagation surface portion 11 with an increased reflectance Rc. can be reduced, and the S/N ratio can be improved.
The length c1 of the portion of the bottom surface portion 16 intersecting with the propagation surface portion 11 at the angle φ (the length in the direction toward the back surface portion 12) is at least the intersection point (crossing line portion) between the propagation surface portion 11 and the bottom surface portion 16. For example, if the surface wave frequency is 500 kHz and the propagating body 10 is PPS, the sound velocity at room temperature is about 950 m/s. Therefore, one wavelength is approximately 1.9 mm. When the surface wave frequency is 400 kHz and the propagating body 10 is PPS, the speed of sound at room temperature is about 950 m/s, so one wavelength is about 2.38 mm.

Next, FIG. 8A shows the result of analyzing the propagating body 10 having the side portions 13 and 14 at an acute angle (θ<90 degrees) and the bottom portion 16 at a right angle (φ=90 degrees). For comparison, FIG. 8(b) shows the result of analyzing a propagating body in which the side portions 13, 14 and the bottom portion 16 are perpendicular (θ=90 degrees, φ=90 degrees). From these analysis results, it can be seen that in the propagating body with the acute-angled side surface, the change in the amplitude of the received echo is large without being attenuated, and the S/N ratio is improved.

In addition, in the liquid level position detecting device 100 of the present embodiment, the angles θ and φ formed by the side surfaces 13 and 14 and the bottom surface 16 as adjacent surface portions adjacent to the propagation surface portion 11 are formed to be acute angles. Only the angle θ with 13 and 14 can be made acute, or only the angle φ with the bottom surface can be made acute. ratio can be improved, and by combining both, the S/N ratio can be further improved.

(Second embodiment)
A liquid level detection device 100A according to this embodiment will be described with reference to FIGS. , are assigned the same or corresponding reference numerals, and description thereof is omitted as appropriate.
In FIG. 6B, the wave transmitting/receiving units 21 and 22 are shown through the vibrator 20, and the wave transmitting/receiving units 21 and 22 are omitted in (a) and (c).
The liquid level position detection device 100A has a two-plane oscillation structure in which the two main surface portions of the propagating body 10A, which are in a front and back relationship, are a propagation surface portion (first propagation surface portion) 11A and a (second propagation surface portion) 12A. The portion 16A is formed in a U-shaped smooth curved surface that protrudes downward. As a result, in the liquid level detection device 100A, the surface wave W (hereinafter referred to as the surface wave W propagated to the propagation surface portion 11A) is transmitted to the propagation surface portions 11A and 12A by the vibrator (vibration generating means) 20 pressed against the upper surface portion 15A of the propagation body 10A. A first surface wave W1 is a surface wave that propagates through the propagation surface portion 12A, and a second surface wave W2 is a surface wave that propagates to the propagation surface portion 12A). Propagating through the other propagating surface portions 11A and 12A (the first surface wave W1 propagates through the propagating surface portion 12A and the second surface wave W2 propagates through the propagating surface portion 11A) along the curved surface without being reflected at the portion 16A and returns to the upper surface portion 15A. becomes (see FIG. 7). In some cases, the first surface wave W1 and the second surface wave W2 may simply be referred to as the surface wave W without distinction. The bottom portion 16A formed in this manner reduces loss due to leakage when the first surface wave W1 and the second surface wave W2 propagate to the bottom portion 16A.

The propagating body 10A includes side portions (first side portion) 13A and (second side portion) 14A that form adjacent surface portions adjacent to the two propagation surface portions 11A and 12A. As shown in FIG. 6C, the side surface portions 13A and 14A are provided with slope portions 13Aa and 14Aa on the side of the propagation surface portion 11A and slope portions 13Ab and 14Ab on the side of the propagation surface portion 12A. Flat portions 13Ac and 14Ac are provided between the slope portions 13Aa and 13Ab of the side portions 13A and 14A and between the slope portions 14Aa and 14Ab. The inclined surfaces 13Aa, 13Ab, 14Aa, and 14Ab of these side surfaces 13A and 14A form an acute angle θ with the propagation surfaces 11A and 12A. That is, the angle θ formed between the propagation surface portion 11A and the slope portion 13Aa of the side surface portion 13A adjacent thereto is an acute angle, and the angle θ formed between the propagation surface portion 11A and the slope portion 14Aa of the side surface portion 14A adjacent thereto is acute. The angle θ formed between the propagation surface portion 12A and the slope portion 13Ab of the side surface portion 13A adjacent thereto is an acute angle, and the angle θ formed between the propagation surface portion 12A and the slope portion 14Ab of the side surface portion 14A adjacent thereto is an acute angle. As a result, the propagating body 10A has a substantially columnar shape elongated in the vertical direction, and the lateral cross-sectional shape is such that the side portions 13A and 14A are recessed in a substantially trapezoidal shape toward the inside (toward the center of the propagating body 10A). (for example, the cross-sectional shape of a pulley for a V-belt).
It should be noted that when the first and second surface waves W1 and W2 propagate through the propagation body 10A, the wavelengths of the first and second surface waves W1 and W2 are measured from the surface of the propagation body 10A. It reaches almost the same depth as that of the propagation body 10 already described.
In addition, the length of the portion of the side surface portions 13A and 14A forming the angle θ between the propagation surface portions 11A and 12A and the slope portions 13Aa, 13Ab, 14Aa and 14Ab (the length in the direction along the slope portions 13Aa, 13Ab, 14Aa and 14Ab ) c should have a length of at least one wavelength for ultrasonic waves to propagate from the intersection (intersection line) of the propagation surface and the slope. For example, when the surface wave frequency is 500 kHz, For PPS, the speed of sound at room temperature is about 950 m/s, so one wavelength is about 1.9 mm. When the surface wave frequency is 400 kHz and the propagating body 10 is PPS, the speed of sound at room temperature is about 950 m/s, so one wavelength is about 2.38 mm.

Like the propagator 10, the propagator 10A is fixed by being sandwiched between fixing members 81 and 82 provided on the container 80 at the side portions 13A and 14A. Any fixing method may be used as long as the propagating body 10A is fixed at a portion other than the propagating surface portion 11A and the propagating surface portion 12A through which the surface wave W propagates so as not to hinder the propagation of the surface wave W.

The vibrator 20 is vibration generating means for generating ultrasonic waves, and as already described, is, for example, a transverse wave transducer and includes a piezoelectric element or the like mounted on a circuit board. The vibrator 20 is pressed against the upper surface portion 15A of the propagation body 10A to generate surface waves W on the two propagation surface portions 11A and 12A of the propagation body 10A. As a result, the liquid level detection device 100A has a dual oscillation structure.

As shown in FIG. 7, the vibrator 20 generates a first surface wave W1 in the propagation body 10A and receives a second surface wave W2, and a first wave transmitting/receiving section 21 receives the second surface wave W2 in the propagation body 10A. and a second wave transmitting/receiving section 22 for receiving the first surface wave W1.

The first wave transmitting/receiving section 21 vibrates by the electric signal supplied from the transmitting/receiving circuit 30 . The vibration of the first wave transmitting/receiving section 21 is propagated to the propagation body 10A, and the first surface wave W1 is generated at the upper end (an example of the first location) of the propagation surface section 11A. As shown in FIG. 7, the generated first surface wave W1 propagates toward the lower end of the propagation surface portion 11A, propagates along the bottom surface portion 16A having a smooth curved surface, and then reaches the upper end (second wave) of the propagation surface portion 12A. An example of the location) (see the solid line in the figure). The first surface wave W1 reaching the upper end of the propagation surface portion 12A causes the second wave transmitting/receiving portion 22 to vibrate. The second wave transmitting/receiving section 22 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 .

The second wave transmitting/receiving section 22 vibrates by the electric signal supplied from the transmitting/receiving circuit 30 . The vibration of the second wave transmitting/receiving section 22 is propagated to the propagation body 10A, and a second surface wave W2 is generated at the upper end (an example of the first location) of the propagation surface section 12A. The generated second surface wave W2 propagates toward the lower end of the propagation surface portion 12A, propagates along the bottom surface portion 16A having a smooth curved surface, and then propagates toward the upper end (an example of the second location) of the propagation surface portion 11A. Propagate (see dotted line in the figure). The second surface wave W2 reaching the upper end of the propagation surface portion 11A causes the first wave transmitting/receiving portion 21 to vibrate. The first wave transmitting/receiving section 21 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 .

In this embodiment, the first surface wave W1 and the second surface wave W2 are pulses of ultrasonic waves (for example, sound waves of 20 KHz or higher) (ultrasonic pulses). Also, the first surface wave W1 and the second surface wave W2 are Rayleigh waves or Schulz waves. The vibrator 20 may include a contact material for ultrasonic waves interposed between the piezoelectric element and the propagating body 10A for efficient transmission of vibration.

The transmitting/receiving circuit 30 is connected to the vibrator 20 as shown in FIGS. The transmission/reception circuit 30 supplies (transmits) an electric signal for generating an ultrasonic pulse (surface wave) to the transducer 20 as an ultrasonic transmission circuit, thereby vibrating the transducer 20 . Further, the transmitting/receiving circuit 30 receives an electric signal supplied (transmitted) from the transducer 20 as an ultrasonic wave receiving circuit, and amplifies and converts the received electric signal.

As already described, the control unit 40 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a microcomputer composed of a timer, etc., a D/A (digital/analog) conversion and an A/D (analog/digital) converter. The control unit 40 is connected to the transmission/reception circuit 30 (see FIG. 1). The control unit 40 controls the transmission/reception circuit 30 to supply the electric signal from the transmission/reception circuit 30 to each of the first wave transmission/reception unit 21 and the second wave transmission/reception unit 22 of the vibrator 20 . As a result, the first surface wave W1 is generated on the propagation surface portion 11A, and the second surface wave W2 is generated on the propagation surface portion 12A. Further, the control unit 40 receives the electric signals from the first wave transmitting/receiving unit 21 and the second wave transmitting/receiving unit 22 of the vibrator 20 amplified and converted by the transmitting/receiving circuit 30, and based on the received electric signals, The position of the liquid surface 91 is specified. Further, the control unit 40 can exchange data with an external device 60 outside the liquid level detection device 100A.

Next, the operation of the liquid level detection device 100A will be described, centering on the liquid level detection processing (see FIG. 9) executed by the controller 40. FIG. For example, the CPU of the control unit 40 uses the RAM as a main memory and executes the liquid level detection process according to the program stored in the ROM and using various data stored in the ROM. The control unit 40 starts the liquid surface position detection process based on a command from the external device 60, for example.

(Liquid level position detection processing)
When the liquid level position detection process is started, as shown in FIG. A surface wave W1 is generated (step S11).

As shown in FIG. 7, the generated first surface wave W1 propagates toward the lower end of the propagation surface portion 11A, propagates along the bottom surface portion 16A having a smooth curved surface, and then reaches the upper end (second wave) of the propagation surface portion 12A. point). The first surface wave W1 reaching the upper end of the propagation surface portion 12A causes the second wave transmitting/receiving portion 22 to vibrate. The second wave transmitting/receiving section 22 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 . The transmitting/receiving circuit 30 amplifies and converts the supplied electric signal and supplies it to the control unit 40 . Below, the vibration generated in the second wave transmitting/receiving unit 22 by the amplified and converted electric signal (that is, the first surface wave W1 that reaches the second wave transmitting/receiving unit 22 after propagating to the bottom surface portion 16A) will be described. electrical signal) is the first propagation wave signal. In this way, the first surface wave W1 sent from the first wave transmitting/receiving unit 21 (at the first location) reaches the second wave transmitting/receiving unit 22 (at the second location), and the first portion contacting the gas. It propagates across the boundary between 10a and the second portion 10b in contact with the liquid 90 twice (see FIGS. 1 and 7).

Subsequently, the control unit 40 sets the timer to an initial value of 0 in order to measure the period from performing the process of step S11 to receiving the first propagation wave signal (step S12). The period is a period from the timing when the first wave transmitting/receiving unit 21 generates the first surface wave W1 to the timing when the second wave transmitting/receiving 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 wave transmitting/receiving unit 22 (hereinafter referred to as the first propagation time).

Subsequently, the control unit 40 determines whether or not the first propagation wave signal has been received from the transmission/reception circuit 30 (step S13). This determination can be performed by an appropriate method as already described. Then, a value based on the voltage of the acquired electrical signal (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 electrical signal, etc.) is stored in the ROM in advance. It is determined whether or not the threshold value stored in . For example, the first propagation wave signal may be measured in advance by experiment, and the threshold value may be determined based on the measurement result. Then, when the value based on the voltage of the electrical signal is equal to or greater than the threshold, the control unit 40 determines that the first propagation wave signal has been received (step S13; Yes). On the other hand, when the value based on the voltage of the electric signal is less than the threshold, the control unit 40 determines that the first propagation wave signal has not been received (step S13; No).

If the first propagation wave signal has not yet been received (step S13; No), the control unit 40 updates the timer value of the timer by +1 (step S14), and executes the process of step S3 again. Thereby, the control unit 40 keeps time until receiving the first propagation wave signal.

If the first propagation wave signal has been received (step S13; Yes), the controller 40 stores the current timer value as the first propagation time in, for example, the RAM (step S15).

Subsequently, the control unit 40 causes the second wave transmitting/receiving unit 22 to vibrate via the transmitting/receiving circuit 30 to generate a second surface wave W2 at the upper end (first location) of the propagation surface portion 12A (step S16).

As shown in FIG. 7, the generated second surface wave W2 propagates toward the lower end of the propagation surface portion 12A, propagates along the bottom surface portion 16A having a smooth curved surface, and then reaches the upper end (second wave) of the propagation surface portion 11A. point). The second surface wave W2 reaching the upper end of the propagation surface portion 11A causes the first wave transmitting/receiving portion 21 to vibrate. The first wave transmitting/receiving section 21 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 . The transmitting/receiving circuit 30 amplifies and converts the supplied electric signal and supplies it to the control unit 40 . Below, the vibration generated in the first wave transmitting/receiving unit 21 by the amplified and converted electric signal (that is, the second surface wave W2 that reaches the first wave transmitting/receiving unit 21 after being propagated to the bottom surface portion 16A) will be described. electrical signal) is the second propagation wave signal. In this way, the second surface wave W2 sent from the second wave transmitting/receiving unit 22 (first location) reaches the first wave transmitting/receiving unit 21 (second location), and the first portion that contacts the gas It propagates across the boundary between 10a and the second portion 10b in contact with the liquid 90 twice (see FIGS. 1 and 7).

Subsequently, the control unit 40 sets the timer to an initial value of 0 in order to measure the period from the execution of the process of step S16 to the reception of the second propagation wave signal (step S17). The period is a period from the timing when the second wave transmitting/receiving unit 22 generates the second surface wave W2 to the timing when the first wave transmitting/receiving unit 21 receives the second surface wave W2. This is the propagation time of the second surface wave W2 from the unit 22 to the first wave transmitting/receiving unit 21 (hereinafter referred to as the second propagation time). In the following description, 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 propagation wave signal has been received from the transmission/reception circuit 30 (step S18). This determination is performed in the same manner as in step S13, and if the second propagation wave signal has not yet been received (step S18; No), the control unit 40 updates the timer value of the timer by +1 or the like ( Step S19), the process of step S18 is executed again. Thereby, the control unit 40 keeps time until receiving the second propagation wave signal.

If the second propagation wave signal has been received (step S18; Yes), the controller 40 stores the current timer value as the second propagation time in, for example, the RAM (step S20).

Subsequently, the control unit 40 identifies the position of the liquid surface 91 (liquid surface position) based on the first propagation time stored in step S15 and the second propagation time stored in step S20 (step S21). .

For example, the relationship between the first propagation time, the second propagation time, and the position of the liquid surface 91 is specified in advance by experiments 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 position of the liquid surface 91 (liquid surface position) based on the table or the arithmetic expression stored in the ROM and the first propagation time and the second propagation time.

Note that the control unit 40 uses a table or an arithmetic expression for specifying the position of the liquid level 91 based on the first propagation time to determine the position of the liquid level 91 based on the first propagation time (hereinafter referred to as the first liquid level ), and the position of the liquid level 91 based on the second propagation time (hereinafter referred to as the second liquid level position.) 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 (simple average or weighted average) of the first liquid level position and the second liquid level position may be used as the liquid level position to be detected this time. When obtaining the weighted average, weighting constants for each of the first liquid level position and the second liquid level position may be obtained in advance by experiments or the like. Further, it is determined whether or not one of the first liquid level position and the second liquid level position indicates an error value, and if it is determined to be an error value, the one that does not indicate an error value is specified this time. It is good also as a liquid level position.

Subsequently, the controller 40 outputs the position of the liquid surface 91 identified in step S21 to the external device 60 (step S22). As already explained, the external device 60 includes an image display such as an LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Diode), and displays the position of the liquid surface 91 on the image display. Thus, the liquid surface position detection processing is completed.

The control unit 40 detects the propagation time whose period becomes longer as the liquid contact portion (second portion 10b) becomes longer according to the position of the liquid surface 91 of the liquid 90, and detects the position of the liquid surface 91 based on the detected propagation time. identify. The position of the liquid surface 91 is, for example, the length L2 of the second portion 10b where the propagator 10A is immersed in the liquid 90, the height of the liquid surface 91 from the bottom surface of the container 80, the length L2, and the height of the liquid surface 91. It is sufficient if it is represented by a value or the like according to the value. The height of the liquid surface 91 from the bottom surface of the container 80 is the depth of the liquid 90, and is obtained by length L2+length d (see FIG. 1).

In the liquid level detection device 100A, sloped portions 13Aa and 13Ab and sloped portions 14Aa and 14Ab are formed at both end corners of the side portions 13A and 14A of the propagating body 10A, respectively, and the length c along the sloped surfaces is the vibration generating means. It is less than one wavelength of the oscillator 20 .
As a result, even if part of the first and second surface waves W1 and W2 propagating on the propagation surface portions 11A and 12A are directed toward the side surface portions 13A and 14A, the adjacent surface portions adjacent to both sides of the propagation surface portions 11A and 12A are are reflected by the slant surfaces 13Aa, 13Ab, 14Aa, and 14Ab forming the . Therefore, by merging the surface waves W (the first and second surface waves W1 and W2) necessary for specifying the liquid level position, the signal component increases and the S/N ratio can be improved.
When the length c along the slopes of the slope portions 13Aa and 13Ab and the slope portions 14Aa and 14Ab is larger (longer) than one wavelength of the propagating first and second surface waves W1 and W2, the first and The second surface waves W1 and W2 are propagated, leaked, and cannot be reflected to increase the signal component. The lower limit of the length c along this slope is determined in consideration of the workability and strength of the propagating body 10 . For example, if the surface wave frequency is 500 kHz and the propagating body 10A is PPS, the speed of sound at room temperature is about 950 m/s, so one wavelength is about 1.9 mm. When the surface wave frequency is 400 kHz and the propagating body 10 is PPS, the speed of sound at room temperature is about 950 m/s, so one wavelength is about 2.38 mm. Based on these values, the length c along the slope of the propagating body 10A can be determined.

In addition, since the bottom surface portion 16A of the liquid level detection device 100A has a smooth curved surface, the conventional propagating body having a substantially quadrangular prism shape with a flat bottom surface has the first surface wave W1 and the second surface wave W1. A two-surface wave W2 is reflected at the bottom portion 16A. This causes leakage and loss. On the other hand, by forming the bottom surface portion 16A of the propagating body 10A into a smooth curved surface, the first surface wave W1 and the second surface wave W2 are not reflected by the bottom surface portion 16A and no leakage occurs. , the attenuation of the first and second surface waves W1 and W2 received by the vibrator 20 is small, and the S/N ratio can be improved.

In the liquid level position detection device 100A, the bottom surface 16A of the propagating body 10A is not limited to a smooth curved surface, but may be flat (the angle φ between the propagating surfaces 11A and 12A is 90 degrees). 13Aa, 13Ab, 14Aa, and 14Ab configure the liquid level position detection device 100A so as to only increase the signal component due to the reflection of the first and second surface waves W1 and W2 propagating on the propagation surface portions 11A and 12A, The S/N ratio may be improved. In this case, the surface wave W propagates through the propagation surface portions 11A and 12A, is reflected by the bottom surface portion 16A, and returns to the same propagation surface portions 11A and 12A.

In addition, in the liquid level detection device 100A of the above embodiment, the control section 40 executes the liquid level detection processing to generate the first surface wave W1 and the second surface wave W2 at different timings. 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 propagated wave signals are superimposed and two propagated times (first propagated time and second propagated time) are observed (received) as propagated wave signals. Similarly, the position of the liquid surface 91 is identified.
By simultaneously generating the first surface wave W1 and the second surface wave W2 in this manner, the amplitudes of the first and second surface waves W1 and W2 received by the vibrator 20 are increased. This can further improve the S/N ratio.

Next, temperature correction in the liquid level position detection process of the liquid level position detection device 100A will be described with reference to FIG. Reference numerals are attached, and explanations are omitted as appropriate.
In FIG. 10, the sloped portions 13Aa and 13Ab and the sloped portions 14Aa and 14Ab formed on the side portions 13A and 14A, which are not related to temperature correction, are not shown. A body 10A and a vibrator 20 are mainly shown. 10(b) shows the wave transmitting/receiving units 21 to 24 through the vibrator 20, FIG. 10(a) omits the wave transmitting/receiving units 21 to 24, and FIG. The child 20 and the wave transmitting/receiving units 21 to 24 are omitted.

10 A of propagation bodies have the propagation surface part 11A, the propagation surface part 12A, the side part 13A, the side part 14A, the upper surface part 15A, and the bottom surface part 16A, as already demonstrated. Further, as shown in FIG. 10, the vibrator 20 includes a third wave transmitting/receiving unit 23 and a fourth wave transmitting/receiving unit 24 in addition to the first wave transmitting/receiving unit 21 and the second wave transmitting/receiving unit 22 already described. Prepare.

10 A of propagation bodies have the recessed part 18 recessed toward 16 A of bottom parts from the upper surface part 15A. The concave portion 18 is located between the propagation surface portion 11A and the propagation surface portion 12A, as shown in FIG. 10(b).

The concave portion 18 has a bottom extending from the top surface portion 15A to the bottom surface portion 16A, and is hollowed out in, for example, a rectangular parallelepiped shape, and has first to fourth inner surface portions 18a to 18d and an inner bottom surface portion 18e.

The first inner side surface portion 18a is located on the back side of the propagation surface portion 11A. The second inner side surface portion 18b is located on the back side of the propagation surface portion 12A. The first inner side surface portion 18a and the second inner side surface portion 18b face each other. The third inner side portion 18c is located on the back side of the side portion 13A. The fourth inner side surface portion 18d is located on the back side of the side surface portion 14A. The third inner side surface portion 18c and the fourth inner side surface portion 18d face each other. The inner bottom surface portion 18e is a flat surface positioned at the bottom of the recess 18 and has a rectangular shape in plan view.

By providing the recess 18 in the propagating body 10A, as shown in FIG. 10(b), for example, the detected wave D is generated. and
The temperature correction processing by the transmission/reception circuit 30 and the control unit 40 (see FIG. 1) will be described below.

As shown in FIG. 10(b), the third wave transmitting/receiving section 23 generates a first detection wave D1 composed of a surface wave or a plate wave in the propagating body 10A, and a first detection wave D1 reflected by the inner bottom surface portion 18e of the concave portion 18. 1 Receive detection wave D1. The fourth wave transmitting/receiving section 24 generates a second detection wave D2 composed of a surface wave or a plate wave in the propagating body 10A, and receives the second detection wave D2 reflected by the inner bottom surface portion 18e of the concave portion 18. FIG.

The third wave transmitting/receiving section 23 vibrates by the electric signal supplied from the transmitting/receiving circuit 30 . The vibration of the third wave transmitting/receiving portion 23 is propagated to the propagating body 10A, and the first detection wave D1 is generated at the upper end of the first inner side portion 18a. As shown in FIG. 10B, the generated first detection wave D1 propagates toward the lower end of the first inner side surface portion 18a, reflects off the inner bottom surface portion 18e, and then travels toward the upper end of the first inner side surface portion 18a. propagates through The first detection wave D1 reaching the upper end of the first inner side surface portion 18a causes the third wave transmitting/receiving portion 23 to vibrate. The third wave transmitting/receiving section 23 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 .

The fourth wave transmitting/receiving section 24 vibrates by the electric signal supplied from the transmitting/receiving circuit 30 . The vibration of the fourth wave transmitting/receiving portion 24 is propagated to the propagating body 10A, and the second detection wave D2 is generated at the upper end of the second inner side portion 18b. As shown in FIG. 10B, the generated second detection wave D2 propagates toward the lower end of the second inner side surface portion 18b, reflects off the inner bottom surface portion 18e, and then travels toward the upper end of the second inner side surface portion 18b. propagates through The second detection wave D2 reaching the upper end of the second inner side surface portion 18b causes the fourth wave transmitting/receiving portion 24 to vibrate. The fourth wave transmitting/receiving section 24 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 .

The first detected wave D1 received by the third wave transmitting/receiving unit 23 and the second detected wave D2 received by the fourth wave transmitting/receiving unit 24 depend on the temperature of the propagating body 10A regardless of the position of the liquid surface 91. changes. Therefore, using at least one of the first detected wave D1 and the second detected wave D2, the temperature of the propagating body 10A is specified, and the specified temperature is detected by the surface waves (the first surface wave W1 and the second surface wave W2 ) is used for temperature correction when detecting As a result, temperature correction can be performed without providing a temperature sensor such as a thermistor chip, which is provided in a conventional liquid level detection device.

The transmitting/receiving circuit 30 supplies an electrical signal for transmitting the first detected wave D1 to the third wave transmitting/receiving section 23 to vibrate the third wave transmitting/receiving section 23 . Also, it receives an electric signal supplied from the third wave transmitting/receiving section 23 that has received the first detection wave D1, and amplifies and converts the received electric signal. Further, the transmitting/receiving circuit 30 supplies an electrical signal for transmitting the second detection wave D2 to the fourth wave transmitting/receiving section 24 to vibrate the fourth wave transmitting/receiving section 24 . Also, it receives an electric signal supplied from the fourth wave transmitting/receiving section 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 wave transmitting/receiving unit 23 and the fourth wave transmitting/receiving unit 24 via the transmitting/receiving circuit 30 . Further, the control unit 40 receives the electric signals from each of the third wave transmitting/receiving unit 23 and the fourth wave transmitting/receiving unit 24, which are amplified and converted by the transmitting/receiving circuit 30, and controls the propagation body 10A based on the received electric signals. Identify 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 liquid surface position detection process. Hereinafter, the propagation time of the first detected wave D1 is defined as the first detection time, and the propagation time of the second detected wave D2 is defined as the second detection time.

Specifically, after the control unit 40 causes the third wave transmitting/receiving unit 23 to generate the first detection wave D1, the third wave transmitting/receiving unit 23 receives the first detection wave D1 after being reflected by the inner bottom surface portion 18e. The time until is detected based on the timer value. Then, the detected time is stored in the RAM as the first detection time. Further, the time from when the fourth wave transmitting/receiving unit 24 generates the second detection wave D2 to when the fourth wave transmitting/receiving unit 24 receives the second detection wave D2 after being reflected by the inner bottom surface portion 18e is based on the timer value. to detect. Then, the detected time is stored in the RAM as the second detection time. The control unit 40 specifies (detects) the temperature of the propagating body 10A based on at least one of the first detection time and the second detection time thus obtained.

As described above, the first detection wave D1 and the second detection wave D2 vary in speed of sound depending on the temperature of the propagating body 10A regardless of the position of the liquid surface 91. FIG. Therefore, the first detection time and the second detection time also change depending on the temperature of the propagating body 10A regardless of the position of the liquid surface 91. FIG. Using this characteristic, for example, the relationship between the first detection time, the second detection time, and the temperature of the propagating body 10A is specified in advance by experiments 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 propagating body 10A based on the table or arithmetic expression stored in the ROM and the first detection time and the second detection time.

Note that the control unit 40 uses a table or an arithmetic expression for specifying the temperature of the propagation body 10A based on the first detection time to determine the temperature of the propagation body 10A based on the first detection time (hereinafter referred to as the first temperature). ), and using a table or an arithmetic expression for specifying the temperature of the propagating body 10A based on the second detection time, the temperature of the propagating body 10A based on the second detection time (hereinafter referred to as the second temperature ) 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 (simple average or weighted average may be used) may be used as the temperature to be identified this time. When obtaining the weighted average, it is sufficient to obtain weighting constants for each of the first temperature and the second temperature in advance through experiments or the like. Further, it is determined whether or not one of the first temperature and the second temperature indicates an error value, and if an error is determined, the temperature that does not indicate an error value may be set as the temperature to be specified this time. .

Then, the control unit 40 performs temperature correction of the first propagation time and the second propagation time based on the temperature of the propagation body 10A specified (detected) as described above. For example, a table configured by associating the temperature of the propagation body 10A with the propagation time correction amount and correction coefficient is stored in advance in the ROM, and the control unit 40 refers to the table to refer to the identified propagation. A correction amount and a correction coefficient corresponding to the temperature of the body 10A may be acquired. Then, the control unit 40 performs an operation of adding or subtracting the acquired correction amount to each of the first propagation time and the second propagation time, or an operation of multiplying the correction coefficient by the first propagation time and the second propagation time. Time and temperature correction should be performed.

Note that the control unit 40 stores in the ROM not only the table but also a formula (which may be an approximation formula) representing the temperature dependence of the speed of sound, and uses the formula to calculate the propagation time or the liquid level position. may be obtained. A well-known table construction method or calculation method can be appropriately used as the temperature correction method for the propagation time and the liquid surface position, and is arbitrary.

Further, the temperature correction process described above is performed during the liquid level position detection process 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. Incorporation, 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. Also, the temperature correction process may be executed as a process independent of the liquid surface position detection process.

(Third Embodiment)
A liquid level detection device 100B according to this embodiment will be described with reference to FIGS. are given the same or corresponding reference numerals, and descriptions thereof are omitted as appropriate.
In the liquid level detection device 100B, the configuration of the propagating body 10B through which the surface wave W propagates is different. An adjacent surface portion with an acute angle φ is a one-plane oscillation structure with a bottom surface portion 16B, and an arc portion R is formed at an intersection line portion 19 between the propagation surface portion 11B and the bottom surface portion 16B.
That is, when the already-described propagating bodies 10 and 10A are molded by injection molding using a synthetic resin such as PPS, the two face portions mainly composed of six face portions are sharply crossed at the crossing line portion 19 and molded. It is difficult to do so, and it is in a continuous state through a slight arc portion R. It should be noted that the intersection line portion 19 between the two surface portions can be made continuous in a sharply pointed state without the arc portion R by machining the propagating bodies 10 and 10A after resin molding or by devising a mold. Although it is possible, it is not preferable because it requires an increased manufacturing process and chipping or cracking is likely to occur at sharply pointed portions.
Therefore, in the propagating body 10B, at least the circular arc portion R is formed in the intersecting line portion 19 between the propagating surface portion 11B having the one-plane oscillation structure and the bottom surface portion 16B adjacent to the propagating surface portion 11B and forming an acute angle φ. formed and configured. In the propagating body 10B, the intersecting line portions 19 between the two surface portions each composed of the six surface portions are also formed with circular arc portions that are continuous with each other in terms of molding. The illustration is omitted, and only the arc portion R through which the surface wave W is propagated is shown (FIGS. 11 and 12).

In this embodiment, as shown in FIG. 11A, the propagating body 10B is formed by resin molding, for example, injection molding, using a synthetic resin such as PPS (polyphenylene sulfide). The propagating body 10B has, for example, a substantially quadrangular prism shape elongated in the vertical direction. The outer surface of the propagating body 10B includes a top surface portion 15B facing the vibrator 20, a bottom surface portion 16B opposite to the top surface portion 15B, a propagation surface portion 11B connecting the top surface portion 15B and the bottom surface portion 16B, and a propagation surface portion. It is mainly composed of 6 side portions, namely, a back surface portion 12B which has a front and back relationship with 11B, and two side portions 13B and 14B which connect the top surface portion 15B and the bottom surface portion 16B and have a front and back relationship with each other.
The propagation body 10B has a one-plane oscillation structure in which the surface wave W propagates only on one surface of the propagation surface portion 11B. The adjacent surface portion adjacent to the propagation surface portion 11B is a bottom surface portion 16B, and the angle between the bottom surface portion 16B and the bottom surface portion 16B adjacent to the lower end of the propagation surface portion 11B is φ, which is an acute angle. The propagation surface portion 11B and the bottom surface portion 16B, which form an acute angle φ between the surface portions, are smoothly connected to each other by forming an arc portion R at the intersection line portion 19 .
In the propagating body 10B, the two side surface portions 13 and 14 adjacent to both sides of the propagating surface portion 11B and having a front and back relationship are formed perpendicular to the propagating surface portion 11B.

In such a propagating body 10B, an angle formed between a propagating surface portion 11B through which surface waves W are propagated from an upper surface portion 15B at one end and a bottom surface portion (adjacent surface portion) 16B continuous at the other end portion of the propagating surface portion 11B. By setting φ to be an acute angle, as already described, part of the surface wave W propagating through the propagation surface portion 11B can be reflected toward the bottom surface portion 16B and returned to the propagation surface portion 11B. The S/N ratio can be improved by merging the surface wave W serving as the detection wave propagating in the vertical direction through the propagation surface portion 11B.
The length c1 of the portion forming the angle φ between the bottom surface portion 16B and the propagation surface portion 11B (the length in the direction toward the back surface portion 12B) is at least the intersection (intersection line portion 19) of the propagation surface portion 11B and the bottom surface portion 16B. It is only necessary to secure a length of one wavelength or longer for the ultrasonic wave to propagate from (see FIG. 11(b)).

Next, the angle φ between the propagation surface portion 11B of the propagation body 10B and the bottom surface portion 16B, which is the adjacent surface portion, is made acute, and the intersection line portion 19 is formed with an arc portion R to change the S/N ratio. was analyzed. A PPS propagating body 10B was used for the analysis. In the analysis, when the ultrasonic frequency f is 400 Hz and 500 Hz, the radius r of the arc portion R is set, and the reflectance ( Reflection intensity: Reflection coefficient) Rc was obtained.
The radius r (mm) of the arc portion R has a relationship of r≈0.084*λ (mm), where λ (mm) is the wavelength of the ultrasonic wave.
For example, when the frequency f is 400 Hz, the radius r is r≈0.2 mm, and when the frequency f is 500 Hz, the radius r is r≈0.16 mm.
In addition, in the analysis for comparison, the case where the arc portion R is not formed (r = 0) (see the analysis result of Fig. 4) and the case where the frequency f is 400 Hz and the radius r ≈ 0.1 mm (Fig. 13 Symbol ▪ in (a)), and when the frequency f is 500 Hz and the radius r≈0.08 mm (symbol ▪ in FIG. 13(b)), the radius r is reduced to 1/2 The case was also analyzed.

The results of the analysis are shown in FIGS. 13(a) and 13(b). In the propagation body 10B, the angle φ between the propagation surface portion 11B and the bottom surface portion 16B is an acute angle, and the arc portion R is formed at the intersection line portion 19, thereby obtaining the maximum reflectance (reflection intensity) Rc. It is smaller (for example, 51 degrees) than when there is no arc portion R (for example, 55 degrees for symbol ◯ in FIG. 13).
Also, the radius r of the arc portion R is smaller than the radius r (r = 0.2, 0.16: symbol ▲ in the figure) set for each frequency (r = 0.1, 0.08: ), the angle φ at which the maximum reflectance (reflection intensity) Rc is obtained increases.
In addition, it is preferable that the angle φ of the propagating body 10B is as large as possible, close to 90 degrees, with a high reflectance Rc, considering that chipping, cracking, etc. are likely to occur due to the need to ensure strength. Therefore, when the frequency f is 400 Hz and the radius r of the arc portion R set for this frequency is r=0.2 mm, the angle φ=51 degrees at which the reflectance Rc is maximized in the range of 40 degrees or more. I found it (see FIG. 13(a)). Similarly, when the frequency f is 500 Hz and the radius r of the arc portion R set for this frequency is r=0.16 mm, the reflectance Rc is maximized in the range of 40 degrees or more at an angle φ=51 degrees. (See FIG. 13(b)).
For this reason, considering the molding error of the propagating body 10B, it is preferable to set the obtained angle φ=51 degrees to a predetermined range, for example, a range of ±3 degrees. As a result, for example, if the angle φ is 48 to 54 degrees, the reflectance Rc is larger than the reflectance Rc=0.45 (45%) when the angle φ formed with the bottom portion 16B is 90 degrees. It can be 0.8 (80%) or more.

The angle φ between the propagation surface portion 11 and the bottom surface portion 16B, which is the adjacent surface portion, is set to an acute angle and the arc portion R is formed at the intersection line portion 19. It is thought that it can be applied when forming. That is, when the angle θ formed between the propagation surface portion 11 and the side surface portions 13 and 14 of the propagation body 10 already described is an acute angle, and in addition to this, when the intersection line portions 19 are connected to each other by the arc portions R, It is considered to be equally applicable. Therefore, by applying the analysis result of the angle φ formed by the propagation surface portion 11B and the bottom surface portion 16B which is the adjacent surface portion, for example, the frequency f of the ultrasonic waves to be used is set to 400 Hz and 500 Hz, and the arc portion R for each frequency is If the radius r is set to 0.2 mm and 0.16 mm, the angle θ at which the reflectance Rc is maximized in the range of 40 degrees or more is considered to be 51 degrees. Considering the molding error of the propagating body 10, it is preferable to set the obtained angle .theta.=51 degrees to a predetermined range, for example, a range of ±3 degrees. As a result, for example, if the angle θ is 48 to 54 degrees, even if the angle θ between the propagation surface portion 11 and the side surface portions 13 and 14 is an acute angle, the intersection line portion 19 is formed by the arc portion R. Even in the case of making it continuous, the reflectance Rc can be 0.8 (80%) or more, which is larger than the reflectance Rc = 0.45 (45%) when the angle θ is 90 degrees. Conceivable.

In addition, slope portions 13Aa and 13Ab and slope portions of a side surface portion (first side surface portion) 13A and a side surface portion (second side surface portion) 14A forming adjacent surface portions adjacent to the two propagation surface portions 11A and 12A of the propagation body 10A, and slope portions The angle θ between 14Aa and 14Ab and the propagation surface portions 11A and 12A is set to be an acute angle, and even in the case where arc portions R that are continuous with each other are formed at the intersection line portion 19 between the surface portions, the propagation surface portion 11B and the adjacent surface portions are formed. It is considered that the analysis result of the angle φ formed by the bottom surface portion 16B can be applied.
Therefore, for example, if the frequency f of the ultrasonic wave to be used is 400 Hz and 500 Hz and the radius r of the arc portion R is set to 0.2 mm and 0.16 mm for each frequency, the reflectance Rc is The maximum angle θ is considered to be 51 degrees. Therefore, considering the molding error of the propagating body 10A, it is preferable to set the angle .theta.=51 degrees to a predetermined range, for example, a range of ±3 degrees. As a result, for example, if the angle θ is 48 to 54 degrees, the reflectance Rc becomes 0.45 (45%) when the angle θ between the side portions 13A and 14A is 90 degrees. It is considered that it can be set to 0.8 (80%) or more, which is relatively large.

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

The propagating body 10B is arranged such that the lower end of the bottom surface portion 16B is separated from the bottom surface of the container 80 by a distance (length) d. The length L1 along the vertical direction from the upper end of the upper surface portion 15B to the liquid surface 91 (the length of the first portion 10a, which is the portion of the propagating body 10B not immersed in the liquid 90) L1 in the propagating body 10B, and the bottom portion The length L2 along the vertical direction from the lower end of 16B to the liquid surface 91 (the length of the second portion 10b where the propagator 10B is immersed in the liquid 90) changes as the liquid 90 increases or decreases. That is, the boundary (boundary between the first portion 10a and the second portion 10b) of the propagating body 10B immersed in the liquid 90 is displaced according to the position of the liquid surface 91 of the liquid 90 (liquid surface position).

The vibrator 20 is vibration generating means for generating ultrasonic waves, and is, for example, a transverse wave transducer, and includes a piezoelectric element or the like mounted on a circuit board. The vibrator 20 is pressed against the upper surface portion 15B of the propagation body 10B and has a one-plane oscillation structure that generates a surface wave W on the propagation surface portion 11B of the propagation body 10B. The vibrator 20 has a wave transmitting/receiving section 21 that generates a surface wave W in the propagating body 10B and receives the surface wave W. As shown in FIG.

The wave transmitting/receiving section 21 vibrates by the electric signal supplied from the transmitting/receiving circuit 30 . The vibration of the wave transmitting/receiving portion 21 is propagated to the propagating body 10B, and a surface wave W is generated at the upper end (an example of the first portion) of the propagating surface portion 11B. As shown in FIG. 12B, the generated surface wave W propagates toward the lower end of the propagation surface portion 11B, reflects off the bottom surface portion 16B, and then travels toward the upper end (an example of the second location) of the propagation surface portion 11B. (See the solid line in the figure). The surface wave W reaching the upper end of the propagation surface portion 11B causes the wave transmitting/receiving portion 21 to vibrate. The wave transmitting/receiving section 21 converts this vibration into an electric signal and supplies it to the transmitting/receiving circuit 30 (see FIG. 1).

The surface wave W is a pulse (ultrasonic pulse) of an ultrasonic wave (for example, a sound wave of 20 KHz or higher). Moreover, the surface wave W is a Rayleigh wave or a Schulz wave. Note that the vibrator 20 may include a contact medium for ultrasonic waves interposed between the piezoelectric element and the propagating body 10B for efficient transmission of vibration.

The transmitting/receiving circuit 30 is connected to the vibrator 20 . The transmitting/receiving circuit 30 serves as an ultrasonic wave generating circuit to supply an electric signal for generating an ultrasonic pulse as a surface wave W to the vibrator 20 to vibrate the vibrator 20 . The transmitting/receiving circuit 30, as an ultrasonic wave receiving circuit, receives an electrical signal supplied from the transducer 20, and amplifies and converts the received electrical signal (see FIG. 1).

Specifically, the transmitting/receiving circuit 30 supplies an electric signal for transmitting the surface wave W to the wave transmitting/receiving section 21 to vibrate the wave transmitting/receiving section 21 . It also receives an electric signal of the surface wave W reflected by the bottom surface portion 16B (a reflected wave of the surface wave W), and amplifies and converts the received electric signal (see FIGS. 1 and 12B).

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, an A/D ( (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 the electrical signal from the transmission/reception circuit 30 to the wave transmission/reception unit 21 of the vibrator 20 . As a result, a surface wave W is generated on the propagation surface portion 11B. Further, as described above, the control unit 40 receives the electric signal from the wave transmitting/receiving unit 21 of the vibrator 20 amplified and converted by the transmitting/receiving circuit 30, and determines the position of the liquid surface 91 based on the received electric signal. identify. Further, the control unit 40 can exchange data with an external device 60 outside the liquid level detection device 100B (see FIG. 1).

Next, the liquid level position detection device 100B configured as described above operates as described above with reference to FIG. Execute according to Duplicate description of specific processing of this liquid surface position detection processing is omitted.
In step S7, the control unit 40 outputs the specified position of the liquid surface 91 to the external device 60, and displays it on an image display such as an LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Diode). , the position of the liquid level 91 is displayed, and the liquid level position detection processing is completed.

Further, in the liquid level position detection device 100B, the temperature correction process is performed as described above together with the liquid level position detection process.
As shown in FIG. 12, the propagating body 10B has a concave portion 17B formed in a rear surface portion 12B facing the propagating surface portion 11B. The concave portion 17B is formed as a groove having a rectangular cross section with a bottom (up to an intermediate portion) from the back surface portion 12B toward the propagation surface portion (surface portion) 11B, with openings on the surface of the back surface portion 12B and the side surfaces 13B and 14B. be.

The wave transmitting/receiving portion 23 of the vibrator 20 is pressed against the upper surface portion 15B of the propagation body 10B for temperature correction processing, and generates the detection wave D propagating through the propagation body 10B toward the concave portion 17B as an internal propagation wave. The detection wave D propagates inside the propagating body 10B, and after being reflected by the concave portion 17B, causes the wave transmitting/receiving portion 23 of the upper surface portion 15B to vibrate again. Temperature correction processing is performed in the internal propagation time based on this detected wave D. FIG. That is, as described above, the wave transmitting/receiving section 23 receives the detection wave D reflected by the concave portion 17B, and the sound velocity of the detection wave D changes depending on the temperature of the propagating body 10B regardless of the position of the liquid surface 91. Using this, the temperature of the propagating body 10B is specified, and the specified temperature is used for temperature correction when the surface wave W is detected.
As a result, temperature correction can be performed in the liquid level detection device 100B without providing a temperature sensor such as a thermistor chip that is provided in the conventional liquid level detection device.

According to the liquid level position detecting device 100B configured in this way, the adjacent surface portion adjacent to the propagation surface portion 11B is the bottom surface portion 16B, and the angle φ formed by the bottom surface portion 16B adjacent to the lower end of the propagation surface portion 11B is an acute angle. The propagation surface portion 11B and the bottom surface portion 16B are smoothly connected to each other by forming an arc portion R at the crossing line portion 19 .
In this propagating body 10B, the angle φ between the propagation surface portion 11B through which the surface wave W is propagated from the upper surface portion 15B at one end and the bottom surface portion (adjacent surface portion) 16B continuous at the other end portion of the propagation surface portion 11B is By forming the acute angle, part of the surface wave W propagating on the propagation surface portion 11B can be reflected by the bottom surface portion 16B and returned to the propagation surface portion 11B even toward the bottom surface portion 16B, thereby propagating the propagation surface portion 11B in the vertical direction. The S/N ratio can be improved by merging with the surface wave W serving as the detection wave.
In addition, the propagating surface portion 11B and the bottom surface portion 16B, which form an acute angle φ, are smoothly connected by forming an arc portion R at the intersecting line portion 19, so that the shape of the propagating body 10B is formed in consideration of molding. can do. Thus, by connecting the intersection line portion 19 with the circular arc portion R, it is possible to prevent chipping or cracking of the intersection line portion 19 of the propagating body 10B.
Further, by connecting the intersection line portion 19 with the circular arc portion R, mold design and molding are facilitated, and there is no need for an additional processing step for sharpening the intersection line portion 19, so that the propagating body 10B can be efficiently carried out. can be molded.

Further, the angle φ formed between the propagation surface portion 11B and the bottom surface portion 16B is set to an acute angle, and the intersection line portion 19 between the surface portions is formed with an arc portion R to smoothly connect the surface portions. By setting the angle φ at which the reflectance (reflection intensity) Rc at which the surface wave W propagating is reflected at the bottom portion 16B is maximized, the reflectance Rc can be maximized and the position of the liquid surface can be detected with high accuracy. In particular, by setting the angle φ at which the reflectance Rc is maximum to 40 degrees or more, the angle φ formed by the intersecting line portion 19 can be increased, further preventing chipping and cracking of the propagating body 10B, and improving the accuracy of the liquid level. position can be detected.

Further, the angle φ of the propagating body 10B is set to an angle within ±3 degrees with respect to the angle at which the reflectance Rc at the bottom surface portion 16B is maximized. This facilitates molding and enables detection of the position of the liquid surface with high accuracy.

Further, the radius of the arc portion R of the propagating body 10B is r (mm), the wavelength of the ultrasonic vibration that propagates the propagating body 10B is λ (mm), and the radius r≈0.084*λ (mm). By satisfying the condition, the radius r of the arc portion R can be set according to the wavelength λ of the ultrasonic wave.

Further, the propagating body 10B is made of PPS, the radius of the arc portion R is r (mm), the wavelength λ of the ultrasonic vibration propagating through the propagating body 10B is 1.9 (mm) and 2.23 (mm), and the reflection By setting the angle φ between the surface portions at which the reflectance (reflection hardness) Rc is maximum to 51 degrees, the angle between the surface portions according to the wavelength λ of the ultrasonic wave is set to the optimum angle φ at which the reflectance Rc is maximized. be able to. As a result, the propagating body 10B can ensure the maximum reflectance Rc and can accurately detect the position of the liquid surface, and the angle φ of 51 degrees facilitates molding.

The present invention is not limited by the above-described embodiments and drawings, and modifications (including deletion of components) can be made as appropriate without changing the gist of the present invention.

(Modification)
The type of the liquid 90 to be subjected to liquid level position detection is not particularly limited, and may be water, gasoline, cleaning liquid, or the like, and may be a mixture of a plurality of liquids. Alternatively, an emulsion solution of liquid and fine particles may be used. Also, the space above the liquid surface 91 may be a gas other than air, or may be a vacuum.
For example, container 80 may be a fuel tank mounted on a vehicle. In this case, the liquid 90 becomes fuel such as gasoline. In such a case, the propagating bodies 10, 10A, 10B may be attached, for example, to a fuel pumping unit, which is attached to the fuel tank and which has a fuel pump for drawing fuel from the fuel tank. In the case of fuel tanks, PPS (polyphenylene sulfide), POM (polyacetal), and PBT (polybutylene terephthalate) are often used as the resins used for the propagation bodies 10, 10A, and 10B from the viewpoint of chemical resistance. Among them, it is preferable to use PPS, which has a good S/N ratio of the detection signal.

PPS used for the propagating bodies 10, 10A, and 10B includes linear type, cross-linked type, anti-cross-linked type, and the like. Various types of PPS can be used as the PPS. The state of propagation of surface waves W and plate waves (for example, good S/N ratio, It is considered that the influence on surface wave W or sound velocity of plate wave, etc.) is small.

The surface waves W may be waves other than Rayleigh waves. Also, the surface wave W may not be a pulse wave, but may be, for example, a burst wave.

Moreover, the propagating bodies 10, 10A, and 10B are not limited to be made of synthetic resin, and may be made of metal as long as the liquid surface position can be detected.

Liquid level position detection includes not only detecting the position of the liquid level 91, but also displaying the position of the liquid level in several steps. Also, the amount of the liquid 90 corresponding to the liquid level position may be displayed after the liquid level position is detected.

Further, the circular arc portion R connecting the intersection line portion 19 of the propagating surface portion 11B and the adjacent surface portion 16B is not limited to the adjacent surface portion 16B of the propagating body 10B on which the surface wave W propagates or reflects. Two surface portions that do not propagate may be formed in a continuous portion.

As described above, the liquid surface position detection devices 100, 100A, and 100B are immersed in the liquid 90, and the boundary immersed in the liquid 90 is displaced according to the liquid surface position of the liquid 90 (the position of the liquid surface 91). Propagating bodies 10, 10A, 10B through which vibration propagates; vibration generating means 20 provided at one end of the propagating bodies 10, 10A, 10B for generating ultrasonic vibrations in the propagating bodies 10, 10A, 10B; Detection means (transmitting/receiving circuit 30 and The propagating bodies 10, 10A, and 10B have propagation surface portions 11, 11A, and 11B (12, 12A, and 12B) through which ultrasonic vibrations are propagated by the vibration generating means 20 at one end, and a control portion 40). , adjacent surface portions (side surface portions 13, 13A, 14, 14A (bottom surface portions 16, 16A, 16B)) continuous with the propagation surface portions 11, 11A, 11B (12, 12A, 12B); The angle θ (φ) formed between 11A, 110B (12, 12A, 12B) and adjacent surface portions 13, 13A, 14, 14A (16, 16A, 16B) is formed to be an acute angle.
According to such a configuration, part of the surface waves (first surface wave W1, second surface wave W2) propagating through the propagation surface portions 11, 11A, 11B (12, 12A, 12B) are transmitted through the side surface portions 13, 13A, 14, Even if it is propagated to 14A (bottom parts 16, 16A, 16B), it can be reflected back by the adjacent surface parts (slope parts 13a, 13Aa, 14a, 14Aa (13Ab, 14Ab)) having an angle θ (φ), The signal component can be increased to improve the S/N ratio. Therefore, in the case of a single-surface oscillation structure in which the surface wave W propagates through one of the propagation surface portions 11, 11B (12, 12B), in the case of a two-surface oscillation structure in which the surface wave W propagates through both of the propagation surface portions 11A, 12A, or in the case of an acute-angled structure. It is possible to provide the liquid level position detectors 100, 100A, and 100B that improve the S/N ratio and have high detection accuracy of the liquid level position regardless of the bottom surface portion 16, 16A, or 16B.

Further, in the liquid level detection device 100B, the propagation surface portion 11B and the bottom surface portion (adjacent surface portion) 16B are provided with arc portions R that are continuous with each other at the intersection line portion 19 .
According to such a configuration, the propagating body 10B can be formed into a shape that takes molding into consideration, and by connecting the intersecting line portion 19 with the arc portion R, the intersecting line portion 19 of the propagating body 10B is free from chipping and cracking. can be prevented from occurring. Further, by connecting the intersection line portion 19 with the circular arc portion R, the mold design and molding are facilitated, and an additional processing step for sharpening the intersection line portion 19 is not required. can be molded.

Further, in the liquid level position detection devices 100, 100A, 100B, the adjacent surface portions (side surface portions 13, 13A, 14, 14A, bottom surface portions 16, 16A, 16B) It is composed of at least one of two continuous side surface portions 13, 13A, 14, 14A and bottom surface portions 16, 16A, 16B continuous with the other ends of the propagation surface portions 11, 11A (12, 12A).
According to such a configuration, part of the surface waves (first surface wave W1, second surface W2) propagating on the propagation surface portions 11, 11A (12, 12A) is propagated to the side surface portions 13, 13A, 14, 14A. can be reflected back by the adjacent surface portions (slope portions 13a, 13Aa, 14a, 14Aa (13Ab, 14Ab)) with an angle of θ, increasing the signal component and improving the S/N ratio. . Also, even if a part of the surface waves (first surface wave W1, second surface wave W2) propagating through the propagation surface portions 11, 11A (12, 12A) is propagated to the bottom surface portions 16, 16A, 16B, the angle φ The light can be reflected back by the bottom surface portions 16, 16A, 16B constituting the adjacent surface portions, and the signal component can be increased to improve the S/N ratio. Therefore, in the case of a single-surface oscillation structure in which a surface wave propagates through one of the propagation surface portions 11, or in the case of a two-surface oscillation structure in which surface waves propagate through both of the propagation surface portions 11A and 12A, the side portions 13, 13A, 14, It is possible to provide the liquid level position detection devices 100, 100A, and 100B that improve the S/N ratio and have good detection accuracy of the liquid level position regardless of whether the bottom portions 16, 16A, or 16B are 14A or have an angle φ. .

Further, the liquid level position detecting device 100A has a propagation surface portion 11A and a propagation surface portion 12A which are in a front and back relationship with each other, and the adjacent surface portions are two side surface portions 13A continuous on both sides of the propagation surface portion 11A and a propagation surface portion 13A. Two side portions 14A are provided on both sides of the surface portion 12A, and an acute angle θ is formed between the propagation surface portion 11A and the side surface portion 13A and between the propagation surface portion 12A and the side surface portion 14A.
According to such a configuration, even if part of the surface waves (the first surface wave W1 and the second surface wave W2) propagating on the propagation surface portions 11A and 12A are propagated to the side surface portions 13A and 14A, the adjacent surface portions having the angle θ The light can be reflected back by (slope portions 13Aa, 14Aa (13Ab, 14Ab)), and the signal component can be increased to improve the S/N ratio. Therefore, in the case of a two-plane oscillation structure in which a surface wave propagates to both propagation surface portions 11A and 12A, the side surface portions 13A and 14A having an angle θ improve the S/N ratio, and the liquid surface position can be detected with high accuracy. A detection device 100A can be provided.

The liquid level detection device 100A is configured such that the propagating body 10A is provided with an arcuate bottom portion 16A that connects two propagating surface portions 11A and propagating surface portions 12A.
According to such a configuration, even if part of the surface waves (the first surface wave W1 and the second surface wave W2) propagating on the propagation surface portions 11A and 12A are propagated to the bottom surface portion 16A, the adjacent surface portions are formed at the angle φ. The light can be reflected back by the bottom portion 16A, which increases the signal component and improves the S/N ratio. Therefore, it is possible to provide the liquid level position detection device 100A which improves the S/N ratio by the bottom surface portion 16A having the angle φ and has high detection accuracy of the liquid level position.

The liquid level position detectors 100, 100A, 100B are configured by connecting the propagating surface portions 11, 11A, 11B, 12, 12A, 12B and the side surface portions 13, 13A, 14, 14A or the bottom surface portions 16, 16A, 16B forming adjacent surface portions. The angles .theta. and .phi.
According to this configuration, the angles formed by the propagation surface portions 11, 11A, 11B, 12, 12A, and 12B and the side surface portions 13, 13A, 14, and 14A or the bottom surface portions 16, 16A, and 16B constituting the adjacent surface portions are 90 degrees. Compared to the case, part of the surface waves (the first surface wave W1 and the second surface wave W2) propagating through the propagation surface portions 11, 11A, 11B, and 12A are transmitted through the side surface portions 13, 13A, 14, and 14A and the bottom surface portions 16, 16A. , 16B can be reflected back by the side surfaces 13, 13A, 14, and 14A and the bottom surfaces 16, 16A, and 16B forming the adjacent surface portions having acute angles, increasing the signal component and increasing the S/ N ratio can be improved. Therefore, the side surface portions 13, 13A, 14, and 14A having the angle θ and the bottom surface portions 16, 16A, and 16B having the angle φ improve the S/N ratio, and the liquid level position detecting devices 100 and 100A have high detection accuracy of the liquid level position. , 100B.

Further, in the liquid surface position detection device 100B, the angle φ between the propagation surface portion 11B and the bottom surface portion (adjacent surface portion) 16B is 40 degrees or more, and the liquid is propagated to the detection means 30 according to the radius r of the arc portion R. The range is ±3 degrees including the angle at which the reflectance (reflection intensity) Rc of ultrasonic vibration is maximum.
According to this configuration, the propagating body 10B has an angle φ within a range of ±3 degrees of the angle φ at which the reflectance Rc at the bottom surface portion 16B is maximum. can be ensured, molding is facilitated, and the position of the liquid surface can be detected with high accuracy.

Further, in the liquid level detection device 100B, the radius r (mm) of the arc portion R is R≈0.084λ, where λ (mm) is the wavelength of the ultrasonic vibration.
According to this configuration, the propagation body 10B has a radius of r (mm) of the circular arc portion R, a wavelength of ultrasonic vibration that propagates the propagation body 10B is λ (mm), and a radius of r≈0.084*λ (mm ), the radius r of the arc portion R can be set according to the wavelength λ of the ultrasonic wave. As a result, the reflectance Rc can be increased, the S/N ratio can be improved, and the position of the liquid level can be detected with high accuracy.

Further, in the liquid surface position detection device 100B, the propagating body 10B is made of PPS (polyphenylene sulfide), and when the wavelength λ of the ultrasonic vibration is 1.9 mm or 2.38 mm, the angle at which the reflection intensity becomes maximum is 51 degrees.
According to this configuration, the angle between the surface portions according to the wavelength λ of the ultrasonic wave can be set to an optimum angle that maximizes the reflectance Rc. As a result, the propagating body 10B has a high reflectance Rc and can accurately detect the position of the liquid surface, and the angle φ formed can be increased to 51 degrees, which facilitates molding.

In the above description, descriptions of known technical matters are omitted as appropriate.

DESCRIPTION OF SYMBOLS 100,100A,100B... Liquid level position detection apparatus 10,10A,10B... Propagation body 10a... First part, 10b... Second part 11, 11A, 11B... Propagation surface part (an example of a main surface)
12, 12B... back surface (propagation surface)
12A... Propagation surface portion (an example of a main surface)
13, 13A, 14, 14A... Side portion (adjacent surface portion)
13a, 13Aa, 13Ab, 14a, 14Aa, 14Ab...Slant part 13B, 14B...Side part θ...Angle of slope part c...Length along slope part,
13Ac, 14Ac... Flat portion 15, 15A, 15B... Upper surface portion (end portion)
16, 16A, 16B... bottom portion (adjacent surface portion)
φ... Angle of the bottom part c1... Length along the bottom part 17, 17B, 18... Recess 19... Intersection line part 20... Vibrator (vibration generating means)
21 First wave transmitting/receiving unit 22 Second wave transmitting/receiving unit W Surface wave W1 First surface wave W2 Second surface wave 23 Third wave transmitting/receiving unit 24 Fourth wave transmitting/receiving unit D Detected wave D1 First detected wave D2... Second detected wave 30... Transmission/reception circuit (detection means)
40... Control unit (detection means)
d...distance from the bottom of the container to the bottom of the propagator L1...length of the portion of the propagator not immersed in the liquid L2...length of the portion of the propagator immersed in the liquid R...arc portion

Claims (8)

a propagating body that is immersed in a liquid and displaces a boundary immersed in the liquid according to the liquid surface position of the liquid, and propagates the ultrasonic vibration;
a vibration generating means provided at one end of the propagating body for generating the ultrasonic vibration in the propagating body;
detecting means for detecting the liquid level position based on the propagation time for the ultrasonic vibration generated by the vibration generating means to propagate from the first point of the propagating body to the second point across the boundary;
The propagating body has a propagating surface portion through which the ultrasonic vibration is propagated by the vibration generating means at the one end portion, and an adjacent surface portion continuous with the propagating surface portion,
an angle formed by the propagating surface portion and the adjacent surface portion is an acute angle;
The adjacent surface portion is a bottom surface portion that is continuous with the other end portion of the propagation surface portion located on the opposite side of the one end portion,
A liquid level detection device characterized by: a propagating body that is immersed in a liquid and displaces a boundary immersed in the liquid according to the liquid surface position of the liquid, and propagates the ultrasonic vibration;
a vibration generating means provided at one end of the propagating body for generating the ultrasonic vibration in the propagating body;
detecting means for detecting the liquid level position based on the propagation time for the ultrasonic vibration generated by the vibration generating means to propagate from the first point of the propagating body to the second point across the boundary;
The propagating body has a propagating surface portion through which the ultrasonic vibration is propagated by the vibration generating means at the one end portion, and an adjacent surface portion continuous with the propagating surface portion,
an angle formed by the propagating surface portion and the adjacent surface portion is an acute angle;
The propagation surface portion has a first propagation surface portion and a second propagation surface portion that are in a front-back relationship with each other,
The adjacent surface portion has two first side surface portions continuous on both sides of the first propagation surface portion and two second side surface portions continuous on both sides of the second propagation surface portion,
A liquid level detection device characterized by: The propagating surface portion and the adjacent surface portion have circular arc portions that are continuous with each other at the intersection line portion,
3. The liquid level detection device according to claim 1 or 2 , characterized in that: The propagating body includes an arc-shaped bottom surface portion that is continuous with the first propagating surface portion and the second propagating surface portion,
3. The liquid level detection device according to claim 2 , characterized in that: The angle formed by the propagating surface portion and the adjacent surface portion is in the range of 49 to 65 degrees,
The liquid level detection device according to any one of claims 1 to 4 , characterized in that: The angle formed by the propagating surface portion and the adjacent surface portion is 40 degrees or more , and ±3 including the angle at which the reflection intensity of the ultrasonic vibration received by the detecting means is maximized due to the radius of the circular arc portion. is a range of degrees,
5. The liquid level detection device according to claim 3 or 4 , characterized in that: The radius r (mm) of the arc portion is r≈0.084λ, where λ (mm) is the wavelength of the ultrasonic vibration,
7. The liquid level detection device according to claim 6 , characterized in that: The propagating body is made of PPS (polyphenylene sulfide),
When the wavelength λ of the ultrasonic vibration is 1.9 mm or 2.38 mm, the angle at which the reflection intensity is maximum is 51 degrees,
8. The liquid level detection device according to claim 7 , characterized in that: