JP2023116007A - Surface wave detection device - Google Patents

Abstract

To provide a surface wave detection device which can enhance a commercial value.SOLUTION: A piezoelectric element 30 is configured to generate a first surface wave W1 in a first propagation surface part 11 toward a counter part C from a placement object part 21b and be able to detect the first surface wave W1 that is reflected to the placement object part 21b from a first reflection part 11a provided in the counter part C, and is configured to generate a second surface wave W2 in a second propagation surface part 12 toward the counter part C from the placement object part 21b and be able to detect the second surface wave W2 that is reflected to the placement object part 21b from a second reflection part 12a provided in the counter part C. A first distance D1 from the placement object part 21b to a first reflection part 11b is different from a second distance D2 from the placement object part 21b to a second reflection part 11b.SELECTED DRAWING: Figure 2

Description

The present invention relates to a surface wave detection device.

For example, Patent Literature 1 discloses a technique of generating surface waves by vibrating a propagating body immersed in liquid with a piezoelectric element and detecting the reflected surface waves. According to the technique described in Patent Document 1, the surface position of the liquid can be detected based on the propagation time of the detected surface wave.

JP-A-4-86525

By the way, in the technique described in Patent Document 1, only the liquid surface position of the liquid is detected based on the propagation time of the detected surface wave. It would be desirable to provide a commercially viable surface wave detector.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface wave detection device capable of increasing commercial value in order to address the above-described problems.

The present invention includes a propagating body that is immersed in a liquid and propagates ultrasonic vibrations, a piezoelectric element that generates the ultrasonic vibrations in the propagating body, and a mounting part on which the piezoelectric element is mounted, The propagating body includes a first propagating surface portion through which the first surface wave of the ultrasonic vibration propagates, a second propagating surface portion through which the second surface wave of the ultrasonic vibration propagates, and a position facing the mounting portion. and a facing portion provided on the facing portion, wherein the piezoelectric element generates the first surface wave on the first propagation surface portion from the mounted portion toward the facing portion, and is provided on the facing portion The first surface wave reflected from the first reflecting portion to the mounting portion can be detected, and the second surface is formed on the second propagation surface portion from the mounting portion toward the facing portion. The wave is generated and the second surface wave reflected from the second reflecting portion provided in the facing portion to the mounting portion can be detected, and from the mounting portion to the first reflecting portion is different from a second distance from the mounting portion to the second reflecting portion.

Also, the present invention is characterized in that the first distance is greater than the second distance.

Further, in the present invention, the facing portion includes a first inclined surface portion provided toward the second propagation surface portion with the first reflection portion as a starting point, and a first inclined surface portion provided toward the second propagation surface portion side with the second reflection portion as a starting point. and a second inclined surface portion provided facing toward, wherein the angle formed between the first propagation surface portion and the first inclined surface portion is an acute angle, and the angle formed between the second propagation surface portion and the second inclined surface portion is an acute angle. characterized by being

Further, the present invention is characterized in that the first inclined surface portion is connected to the second inclined surface portion by a connecting surface portion.

Further, according to the present invention, the connecting surface portion is provided so as to be parallel to the first propagation surface portion and the second propagation surface portion.

Further, the present invention is characterized in that the propagating body has a hole for reflecting an internal propagation wave of the ultrasonic vibration that propagates inside the propagating body.

In the present invention, the propagating body connects the first propagating surface portion and the second propagating surface portion, has a pair of non-propagating surface portions to which the ultrasonic vibration does not propagate, and passes through the pair of non-propagating surface portions. The internal propagation wave is reflected by an inner peripheral surface of the hole formed in the propagating body facing the mounting portion.

Further, the present invention is characterized in that the hole is positioned between the mounting portion and the connecting portion.

According to the present invention, it is possible to provide a surface wave detection device capable of achieving its intended purpose and increasing its commercial value.

1 is a schematic configuration diagram of a liquid surface position detection device and a liquid type identification device according to an embodiment of the present invention; FIG. FIG. 4 is a schematic cross-sectional view of a propagating body, an element accommodating portion, and a piezoelectric element according to the same embodiment; FIG. 4 is a front view of a propagating body and an element accommodating portion according to the same embodiment; AA sectional view of FIG. FIG. 4 is a schematic diagram showing waves input to the piezoelectric element when ultrasonic vibration is applied to the propagating body according to the same embodiment.

An embodiment of the present invention will be described with reference to the drawings.

A liquid level detection device 100 according to the present embodiment includes a surface wave detection device 1 and a control section 2, as shown in FIG. The liquid level detection device 100 detects the position of the liquid level 4a of the liquid 4 contained in the container 3 (hereinafter also referred to as the liquid level position). As the amount of the liquid 4 increases or decreases, the liquid level 4a rises and falls.

The surface wave detection device 1 includes, as shown in FIG. 1, a propagating body 10 immersed in a liquid 4, an element accommodating portion 20, a piezoelectric element 30, and a flange portion 40. As shown in FIG.

Hereinafter, as shown in each figure, the Z-axis extending in the longitudinal direction of the propagating body 10, the Y-axis extending in the normal direction of first and second propagating surface portions 11 and 12 described later, and the Y- and Z-axes The configuration of the surface wave detection device 1 may be described using the X-axis. Also, the directions along the X, Y, and Z axes are defined as the axial directions. Further, the direction in which the arrows of the X, Y, and Z axes point is the "+" direction, and the opposite direction is the "-" direction. That is, the direction along the X axis is the X direction. Considering the directions of the arrows, the direction in which the X-axis arrow points is the +X direction, and the opposite direction is the -X direction. The same applies to the Y and Z axes.

The propagating body 10 propagates ultrasonic vibrations (ultrasonic waves) including first and second surface waves W1 and W2, which will be described later, and is made of a synthetic resin such as PPS (polyphenylene sulfide), for example.

The propagating body 10 extends in the Z-axis direction and is generally shaped like a quadrangular prism. The propagating body 10 has a first propagating surface portion 11, a second propagating surface portion 12, a first side surface 13, and a second side surface 14, as shown in FIG. Further, the propagating body 10 has a first end portion 15, a second end portion 16, a connecting portion 17 and a hole 18 shown in FIGS.

The first propagation surface portion 11 is a portion of the propagation body 10 through which the first surface wave W1 propagates, and as shown in FIG. 3, has a strip shape extending in the Z direction. The −Z direction end of the first propagation surface portion 11 functions as a first reflection portion 11a that reflects the first surface wave W1.

The second propagation surface portion 12 is located on the opposite side of the propagation body 10 from the first propagation surface portion 11, as shown in FIGS. The second propagation surface portion 12 also has a strip shape extending in the Z direction. The first propagation surface portion 11, through which the first surface wave W1 of ultrasonic vibration propagates, faces the -Y direction, and the second propagation surface portion 12, through which the second surface wave W2 of ultrasonic vibration propagates, faces the +Y direction. The first propagation surface portion 11 and the second propagation surface portion 12 are parallel to the ZX plane. Note that FIG. 1 shows a side view of the propagating body 10 and the element accommodating portion 20 as seen from the -X direction. FIG. 2 is a cross-sectional view of the propagating body 10, the element accommodating portion 20, and the piezoelectric element 30 taken along a plane parallel to the YZ plane.

As shown in FIG. 4, the first side face 13 faces the -X direction and the second side face faces the +X direction. The first side surface 13 and the second side surface 14 are parallel to the YZ plane. Here, the first side surface 13 and the second side surface 14 are configured as portions that connect the first propagation surface portion 11 and the second propagation surface portion 12 and do not propagate ultrasonic vibrations. That is, the first side surface 13 and the second side surface 14 correspond to a pair of non-propagating surface portions described in the claims below.

1 and 2, the first end portion 15 is a first inclined surface portion provided toward the second propagation surface portion 12 with the first reflection portion 11a as a starting point. The first end portion 15 is provided at a position facing (facing) a mounting portion, which is provided in the element housing portion 20 and will be described later, and is connected to the second end portion 16 by the connecting portion 17 . The angle formed by the first end portion 15 and the first propagation surface portion 11 is an acute angle (for example, 49 degrees to 65 degrees). The tip of the propagating body 10 has a tapered shape due to the first end 15 . Due to the inclination of the first end portion 15, the first surface wave W1 propagating in the -Z direction on the first propagation surface portion 11 can be suppressed from going around the second propagation surface portion 12, and the first reflection of the propagation body 10 can be suppressed. The first surface wave W1, which is reflected by the portion 11a and propagates through the first propagation surface portion 11 again, can be directed toward the piezoelectric element 30 efficiently.

As shown in FIGS. 1 and 2, the second end portion 16 is a second inclined surface portion provided toward the first propagation surface portion 11 with the second reflection portion 12a as a starting point, and faces the mounting portion. It is provided in a position to (oppose). The angle formed by the second end portion 16 and the second propagation surface portion 12 is an acute angle (for example, 49 degrees to 65 degrees). Due to the inclination of the second end portion 16, the second surface wave W2 propagating in the -Z direction on the second propagation surface portion 12 can be suppressed from going around the first propagation surface portion 11, and the second reflection of the propagation body 10 can be suppressed. The second surface wave W2, which is reflected by the portion 12a and propagates through the second propagation surface portion 12 again, can be directed toward the piezoelectric element 30 efficiently. The first end portion 15 and the second end portion 16 correspond to opposing portions described in claims to be described later. In the following description, the first end portion 15 and the second end portion 16 may be referred to as a facing portion C in some cases.

The connecting portion 17 is configured as a flat surface for connecting the first end portion 15 and the second end portion 16, as shown in FIGS. The connecting portion 17 is provided so as to be parallel to the first propagation surface portion 11 and the second propagation surface portion 12 and positioned directly below the hole 18 .

As shown in FIGS. 1 and 2, the hole 18 reflects the internal propagation wave W3 of the ultrasonic vibration that propagates inside the propagating body 10, and is between the mounting portion and the connecting portion 17. located in The hole 18 is a through hole (hollow hole) formed in the propagating body 10 so as to penetrate (hollow out) the first side surface 13 and the second side surface 14 provided at positions facing each other (see FIG. 4).

The hole 18 here is configured as a substantially rectangular hole, and has a first hole inner peripheral surface 18a facing the mounting portion and a second hole inner peripheral surface 18b facing the first propagation surface portion 11. , a third hole inner peripheral surface 18 c facing the second propagation surface portion 12 , and a fourth hole inner peripheral surface 18 d facing each of the ends 15 and 16 . Then, the internal propagation wave W3 is reflected by the first hole inner peripheral surface 18a facing the mounting portion of the hole 18. As shown in FIG. Further, the distance from the second hole inner peripheral surface 18b to the first propagation surface portion 11 is set to one wavelength or more of the first surface wave W1, and the distance from the third hole inner peripheral surface 18c to the second propagation surface portion 12 is set to It is set to be one or more wavelengths of the second surface wave W2. The first hole inner peripheral surface 18a corresponds to the hole inner peripheral surface described in the claims below.

The element housing portion 20 is located in the +Z direction of the propagating body 10 and houses the piezoelectric element 30, as shown in FIG. For example, the element accommodating portion 20 is made of the same material as the propagating body 10 and is integrally formed. The element housing portion 20 includes a disc portion 21 and a cylindrical body 22 .

The disc portion 21 is connected to the propagating body 10 . The cylindrical body 22 has a hollow cylindrical shape with an outer diameter smaller than the outer diameter of the disc portion 21 and protrudes from the disc portion 21 in the +Z direction. That is, a hollow portion 22a is provided inside the tubular body 22 . Further, inside the disk portion 21 here, a space 21a communicating with the hollow portion 22a is provided.

The cavity 21a is a hole having an opening width approximately equal to the opening width of the hollow portion 22a, and is arranged so as not to reach the boundary portion between the propagating body 10 and the element accommodating portion 20 in the Z direction. It is a portion that is hollowed out to a substantially intermediate portion of the disk portion 21 along the .

In the space 21a, a flat portion located on the propagating body 10 side serves as a mounting portion 21b on which the piezoelectric element 30 is mounted. Here, when the distance from the mounting portion 21b to the first reflecting portion 11a is defined as a first distance D1, and the distance from the mounting portion 21b to the second reflecting portion 12a is defined as a second distance D2, the As for the magnitude relationship between the first distance D1 and the second distance D2, the first distance D1 is different from the second distance D2. More specifically, the first distance D1 is larger (longer) than the second distance D2. A mounting groove 22b, which is a groove recessed toward the center of the cylindrical body 22 and in which the seal member 5 shown in cross section in FIG.

The piezoelectric element 30 vibrates the propagating body 10 via the disk portion 21 to generate ultrasonic waves (ultrasonic vibrations) in the propagating body 10 . Specifically, the piezoelectric element 30 generates, as ultrasonic waves, a first surface wave W1 on the first propagation surface portion 11 from the mounting portion 21b toward the first end portion 15 (opposing portion C), and A second surface wave W2 is generated on the second propagating surface portion 12 from the portion 21b toward the second end portion 16 (opposing portion C), and further inside the propagating body 10 (that is, from the mounting portion 21b toward the hole 18). ) to generate an internal propagation wave W3. In the piezoelectric element 30, the first surface wave W1 reflected by the first reflecting portion 11a (that is, reflected from the first reflecting portion 11a provided in the facing portion C to the mounting portion 21b) and the second reflecting portion 12a. (that is, reflected from the second reflecting portion 12a provided in the facing portion C to the mounting portion 21b) and the second surface wave W2 reflected by the hole 18 (that is, inside the hole provided in the hole 18) The inner surface wave W3 reflected from the peripheral surface 18a to the mounting portion 21b can be detected, and a detection signal (voltage signal) indicating the detection result is output.

The piezoelectric element 30 is composed of a known ultrasonic transducer and has a rectangular parallelepiped shape. The piezoelectric element 30 mounted on the mounted portion 21b faces the propagating body 10 with the disk portion 21 interposed therebetween, generates a first surface wave W1 on the first propagation surface portion 11, and acts as a second propagation surface portion. In order to generate the second surface wave W2 at 12, both ends thereof (the left end and the right end in FIG. 2) are provided so as to extend over the propagation surface portions 11 and 12 of the propagation body . For example, the first surface wave W1 and the second surface wave W2 are Rayleigh waves in air and Schulz waves in liquid 4 . The first surface wave W1 and the second surface wave W2 may be leaky Rayleigh waves, shear surface acoustic waves (SH-SAW), or the like. The internal propagation wave W3 may be a transverse wave or the like. The piezoelectric element 30 is electrically connected to the control section 2 via terminals (not shown).

The flange portion 40 shown in FIG. 1 is formed of, for example, a synthetic resin, and has a cylindrical portion 41 opening in the −Z direction, a flange 42 protruding in the outer diameter direction of the cylindrical portion 41, and a flange 42. and a hollow cap portion 43 located in the +Z direction. In addition, in FIG. 1 , the cylindrical portion 41 and the seal member 5 are shown in cross section along the radial direction.

The tubular portion 41 surrounds the tubular body 22 of the element housing portion 20 . The tip of the cylindrical portion 41 faces the outer peripheral edge of the disk portion 21 in the Z direction. A sealing material 5 seals between the cylindrical portion 41 and the cylindrical body 22 . The seal member 5 is made of, for example, resin rubber in a ring shape and functions as a packing. The flange 42 is a portion attached to the container 3 by fixing means such as screws (not shown). The cap portion 43 has a coupler (not shown). An output terminal (not shown) is positioned inside the coupler. When the external device and the coupler are connected, the external device and the output terminal are electrically connected. For example, the inside of the cap portion 43 accommodates a PCB (Printed Circuit Board) (not shown) that is electrically connected to each of the piezoelectric element 30 and the output terminals, and on which a transmission circuit, a reception circuit, etc., which will be described later, are formed.

The controller 2 schematically shown in FIG. 1 is composed of, for example, a microcomputer, and includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like. The control unit 2 functions as a detection unit that detects the liquid surface position of the liquid 4 based on the propagation time of the first surface wave W1 detected by the piezoelectric element 30 . The transmission circuit of the PCB transmits a drive signal to the piezoelectric element 30 to drive the piezoelectric element 30 under the control of the control unit 2 . As a result, the propagating body 10 generates a first surface wave W1, a second surface wave W2, and an internal propagation wave W3. The receiving circuit of the PCB receives the detection signal of the reflected first surface wave W1 from the piezoelectric element 30 and supplies it to the control section 2 . After receiving the detection signal, the control unit 2 calculates the position (height) of the liquid surface 4a based on the detection signal.

Note that the transmission circuit and the reception circuit may be provided in the control section 2 . Also, at least part of the functions of the control unit 2 may be mounted on a PCB provided inside the flange portion 40 .

Here, an example of a method of calculating the position of the liquid surface 4a will be described. FIG. 5 shows how the first surface wave W1, the second surface wave W2, and the internal propagation wave W3 propagating through the propagating body 10 are input to the piezoelectric element 30 after being reflected by generating the vibration W0. A time point t0 is a time point when the vibration W0 is generated in the propagating body 10 by driving the piezoelectric element 30 . A first surface wave W1, a second surface wave W2, and an internal propagation wave W3 propagate through the propagating body 10 by generating the vibration W0.

A time point t1 is a time point when the first surface wave W1 is reflected by the first reflecting portion 11a provided at the first end portion 15 and is input to the piezoelectric element 30 . The period T1 is the first surface wave propagation period T1 from time t0 to time t1. Time t2 is the time when the second surface wave W2 is reflected by the second reflecting portion 12a provided at the second end portion 16 and is input to the piezoelectric element 30 . The period T2 is the second surface wave propagation period T2 from time t0 to time t2. Time t3 is the time when the internal propagation wave W3 is reflected by the hole 18 and enters the piezoelectric element 30 . A period T3 is an internal propagation wave propagation period T3 from time t0 to time t3.

Of the first surface wave W1, the second surface wave W2, and the internal propagating wave W3, the first surface wave W1 and the internal propagating wave W3 are focused here. When the propagating body 10 is PPS as described above, the speed of the first surface wave W1 traveling through the propagating body 10 (first propagating surface portion 11) is reduced in the portion where the propagating body 10 is immersed in the liquid 4. FIG. Therefore, the higher the liquid surface 4a is, the longer the first surface wave propagation period T1 is. Using this characteristic, the control unit 2 measures the first surface wave propagation period T1, and stores the relationship between the first surface wave propagation period T1 and the position of the liquid surface 4a, which is stored in advance in the ROM. The liquid surface position is calculated by referring to the surface position detection data. On the other hand, the internally propagating wave W3 travels inside the propagating body 10 . Therefore, the value of the internal propagation wave propagation period T3 is determined without being affected by the part of the propagating body 10 immersed in the liquid 4 . Using this characteristic, the control unit 2 measures the internal wave propagation period T3, and refers to the temperature characteristic data stored in advance in the ROM, which indicates the relationship between the internal wave propagation period T3 and the temperature of the propagating body 10. and the temperature of the propagating body 10 is obtained. Then, the first surface wave propagation period T1, which has temperature dependence, is corrected according to the obtained temperature. That is, the control unit 2 performs temperature correction of the first surface wave propagation period T1 based on the internal propagation wave W3, and based on the temperature-corrected first surface wave propagation period T1 and the liquid surface position detection data, the liquid Calculate (detect) the surface position. The liquid surface position detection data and the temperature correction data may be composed of mathematical formulas or tables. Further, as a method for calculating the position of the liquid surface 4a and a method for correcting the temperature, known techniques can be appropriately used.

Further, in the case of this example, it is also possible to specify the type of liquid 4 (hereinafter also referred to as liquid type) contained in the container 3 using the surface wave detection device 1 described above. The liquid type identification device 200 for identifying the liquid type will be described below. The liquid type identification device 200 includes the surface wave detection device 1 and the controller 2 described above. In this liquid type identification device 200 , the control section 2 functions as an identification section that identifies the type of the liquid 4 .

An example of the liquid type specifying method will be described below. Since the first and second surface wave propagation periods T1 and T2 are inversely proportional to the surface wave propagation velocity, the faster the surface wave propagation velocity, the shorter the first and second surface wave propagation periods T1 and T2. As the surface wave propagation speed becomes slower, the first and second surface wave propagation periods T1 and T2 become longer. In this case, the control unit 2 calculates the surface wave propagation velocity from the difference between the propagation periods, which is the value obtained by subtracting the second surface wave propagation period T2 from the first surface wave propagation period T1, and calculates the surface wave propagation velocity. Identify the liquid type based on the propagation velocity. The surface wave propagation velocity when each of the propagation surface portions 11 and 12 is immersed in the liquid 4 is the sound velocity vl and density ρl in the liquid peculiar to the liquid 4, and the propagation velocity vs , determined by the surface wave propagation velocity vR and the density ρS in air. That is, the material of the propagating body 10 is fixed, and the distance between the first reflecting portion 11a and the second reflecting portion 12b in the Z direction (that is, the distance between the first distance D1 and the second distance D2) When the distance difference) is a predetermined constant value, the surface wave propagation velocity when each of the propagation surfaces 11 and 12 is immersed in the liquid 4 varies depending on the type of liquid. Therefore, it is possible to obtain the relationship between the surface wave propagation velocity and the liquid type when each of the propagation surfaces 11 and 12 is immersed in the liquid 4 by actual measurement, simulation, or the like. Therefore, a data table in which the surface wave propagation velocity and liquid type are associated is stored in the ROM, and the control unit 2 refers to the data table to specify the liquid type based on the calculated surface wave propagation velocity. can do.

Thus, the liquid type identification device 200 can identify the liquid type based on the surface wave propagation periods T1 and T2. As described above, the propagation velocity of the internally propagating wave and the propagation velocity of the surface wave are affected by the temperature of the propagating body 10 . That is, the density ρS and elastic modulus of the propagating medium 10 change due to the temperature of the propagating medium 10 , and the internal propagating wave propagation velocity and the surface wave propagation velocity change depending on the density ρS and elastic modulus of the propagating medium 10 . Here, since the internal propagating wave W3 travels inside the propagating body 10, the propagation velocity of the internal propagating wave (internal propagating wave propagation period T3) is is affected only by the temperature of Therefore, the control unit 2 may obtain the temperature of the propagating body 10 by referring to the temperature conditions stored in the ROM from the internal propagation wave propagation period T3 of the internal propagation wave W3. The control unit 2 may correct the surface wave propagation periods T1 and T2 based on the temperature of the propagating body 10 using a correction method considering a predetermined correction coefficient or the like. The controller 2 specifies the liquid type according to the surface wave propagation periods T1 and T2 after correction, so that the liquid type can be specified with high accuracy in consideration of the temperature of the propagating body 10 .

The control unit 2 notifies the user of the detected liquid surface position and the specified liquid type by a notification unit (not shown). For example, the notification unit may be configured to notify the user of the liquid surface position by means of an image, an indicator, a pointer, or the like, or may be configured to notify the user of the specified liquid type by means of an image or the like.

As described above, according to the present embodiment, the piezoelectric element 30 causes the first propagation surface portion 11 to generate the first surface wave W1 from the mounting portion 21b toward the facing portion C (the first end portion 15). A first surface wave W1 reflected from the first reflecting portion 11a provided at the facing portion C (first end portion 15) toward the mounting portion 21b can be detected. A second surface wave W2 is generated on the second propagation surface portion 12 toward the facing portion C (second end portion 16) and is transmitted from the second reflecting portion 12a provided on the facing portion C (second end portion 16). The second surface wave W2 reflected to the placement portion 21b can be detected, and the first distance D1 from the placement portion 21b to the first reflection portion 11b is the distance from the placement portion 21b to the second reflection portion 11b. (eg, the first distance D1 is greater than the second distance D2).

Therefore, by receiving the detection signals of the surface waves W1 and W2 reflected by the piezoelectric element 30 and supplying the detection signals to the control unit 2, the liquid surface position can be detected and detected under the control of the control unit 2. Liquids can be specified. Therefore, according to the surface wave detection device of the present invention, the first and second surface wave propagation periods T1 and T2 can be used to detect the liquid surface position and to specify the liquid type. There is an advantage that the product value can be increased.

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

For example, any material can be used for the propagating body 10 as long as the surface waves W1 and W2 can be propagated satisfactorily. For example, the resin used as the propagating body 10 is not limited to PPS, and may be POM (polyacetal), PBT (polybutylene terephthalate), or the like. Although it is considered preferable that the propagating body 10 is made of resin, it may be made of metal if the surface waves W1 and W2 can be propagated satisfactorily.

Moreover, the posture of the propagating body 10 with respect to the liquid 4 and the container 3 is arbitrary as long as the liquid surface position can be detected and the liquid type can be specified. For example, the propagating body 10 may extend obliquely with respect to the depth direction (vertical direction) of the liquid 4 .

Detecting the position of the liquid level of the liquid 4 means detecting the position of the liquid level 4a in detail. It also includes detecting whether it belongs, detecting the volume of the liquid 4 that changes according to the position of the liquid surface 4a, and the like. Also, the type of the liquid 4 is not limited, and may be water, gasoline, alcohol, cleaning liquid, or the like. Alternatively, the container 3 may be a fuel tank mounted on a vehicle.

The surface waves W1 and W2 may be of any type as long as the liquid surface position can be detected and the type of liquid can be identified by the above technique. In the above, an example in which the surface waves W1 and W2 are pulses of ultrasonic waves (for example, sound waves of 20 kHz or higher) (ultrasonic pulses) has been described. Sound waves with a frequency lower than ultrasonic waves may be used.

In the above description, descriptions of well-known technical matters are omitted as appropriate in order to facilitate understanding of the present invention.

REFERENCE SIGNS LIST 1 surface wave detector 2 control unit 3 container 4 liquid 4a liquid surface 10 propagating body 11 first propagating surface portion 11a first reflecting portion 12 second propagating surface 12a second reflecting portion 13 first side surface 14 second side surface 15 first first side surface End portion 16 Second end portion 17 Connecting portion 18 Hole 18a Hole inner peripheral surface 20 Element housing portion 21 Disk portion 21a Space 21b Mounting portion 30 Piezoelectric element 40 Flange portion C Opposing portion D1 First distance D2 Second distance Distance T1 First surface wave propagation period T2 Second surface wave propagation period T3 Internal propagation wave propagation period W1 First surface wave W2 Second surface wave W3 Internal propagation wave

Claims (8)

a propagating body that is immersed in a liquid and propagates ultrasonic vibrations;
a piezoelectric element that generates the ultrasonic vibration in the propagating body;
a mounting portion on which the piezoelectric element is mounted;
The propagating body is
a first propagation surface portion through which the first surface wave of the ultrasonic vibration propagates;
a second propagation surface portion through which the second surface wave of the ultrasonic vibration propagates;
a facing portion provided at a position facing the mounting portion;
The piezoelectric element generates the first surface wave on the first propagation surface portion from the mounting portion toward the facing portion, and transmits the first surface wave from the first reflecting portion provided on the facing portion to the mounting portion. , the second surface wave is generated on the second propagating surface portion from the mounting portion toward the facing portion, and the second surface wave is provided on the facing portion. configured to be able to detect the second surface wave reflected from the second reflecting portion to the mounting portion,
A surface wave detecting device, wherein a first distance from the mounting portion to the first reflecting portion is different from a second distance from the mounting portion to the second reflecting portion. 2. A surface wave detector according to claim 1, wherein said first distance is greater than said second distance. The facing portion includes a first inclined surface portion provided toward the second propagation surface portion with the first reflection portion as a starting point, and a first inclined surface portion provided toward the first propagation surface portion with the second reflection portion as a starting point. 2 inclined surface portions, and
3. The angle between the first propagation surface portion and the first inclined surface portion is an acute angle, and the angle between the second propagation surface portion and the second inclined surface portion is an acute angle. surface wave detector. 4. The surface acoustic wave detection device according to claim 3, wherein the first inclined surface portion is connected to the second inclined surface portion by a connecting portion. 5. The surface acoustic wave detection device according to claim 4, wherein the connecting portion is provided so as to be parallel to the first propagation surface portion and the second propagation surface portion. 6. The propagating body according to claim 1, wherein the propagating body has a hole for reflecting an internal propagation wave of the ultrasonic vibration that propagates inside the propagating body. surface wave detector. The propagating body has a pair of non-propagating surface portions that connect the first propagating surface portion and the second propagating surface portion and that do not propagate the ultrasonic vibration,
7. The internally propagating wave is reflected by an inner peripheral surface of the hole formed in the propagating member so as to penetrate the pair of non-propagating surface portions and facing the mounting portion. Surface wave detector. 8. The surface acoustic wave detecting device according to claim 6, wherein the hole is positioned between the mounting portion and the connecting portion.

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