JP2022181397A - Surface wave detector and liquid kind identification device - Google Patents

Abstract

To provide a surface wave detector and a liquid kind identification device, unlikely to deteriorate a signal strength of a surface wave detected by a piezoelectric element.SOLUTION: A surface wave detector includes: a propagation body 10 immersed in a liquid 4 and having a propagation surface 11 configured to propagate a surface wave Ws; a piezoelectric element 30 configured to apply oscillation to the propagation body 10 to generate the surface wave Ws and to detect the reflected surface wave Ws; and a vessel 3 configured to house the liquid 4 and the propagation body 10. The propagation body 10 has a configuration to be housed in the vessel 3 in a state forming a belt-like shape with the propagation surface 11 facing a liquid level 4a of the liquid 4.SELECTED DRAWING: Figure 2

Description

The present invention relates to a surface wave detection device and a liquid type identification 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. In this case, the propagating body has a propagating surface for propagating surface waves, and the propagating surface extends perpendicular to the surface of the liquid.

JP 2020-139852 A

By the way, in the technique described in Patent Document 1, bubbles existing in the liquid may stay on the propagation surface extending perpendicular to the surface of the liquid. , there is a problem that the signal intensity of the surface wave detected by the piezoelectric element is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface wave detecting device and a liquid type identifying device which do not reduce the signal strength of the surface wave detected by the piezoelectric element.

In order to achieve the above object, a surface wave detecting device according to a first aspect of the present invention comprises a propagating body that is immersed in a liquid and has a propagating surface for propagating surface waves; and a storage member for storing the liquid and the propagating body, wherein the propagating body has a belt-like shape such that the propagating surface faces the liquid surface of the liquid. is stored in the storage member in a state of forming a

In order to achieve the above object, a liquid type identification device according to a second aspect of the present invention identifies the type of the liquid based on the propagation time of the surface wave detected by the surface wave detection device and the piezoelectric element. and a specifying unit for

According to the present invention, it is possible to provide a surface wave detection device and a liquid type identification device that can achieve the intended purpose and that do not reduce the signal strength of the surface wave detected by the piezoelectric element.

1 is a schematic configuration diagram of a liquid type identification device according to an embodiment of the present invention; FIG. The figure which expanded the principal part of the liquid type identification apparatus in 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. 4 (hatching is omitted). FIG. 4 is a schematic diagram showing waves input to the piezoelectric element when vibration is applied to the propagating body;

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

In FIG. 1, 1 is a surface wave detector, 2 is a control unit, 3 is a container as a storage member, 4 is a liquid contained in the container 3, and 4a is the surface of the liquid 4. FIG. Further, the surface wave detector 1 and the control unit 2 constitute a liquid type identification device L for identifying the type of the liquid 4 contained in the container 3 (hereinafter also referred to as liquid type). Note that the container 3 here is assumed to be a fuel tank mounted on a moving object such as a ship traveling on the sea.

The surface wave detection device 1 has 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 FIGS.

Hereinafter, as shown in each figure, the X-axis extending in the longitudinal direction of the propagating body 10, the Z-axis extending in the normal direction of the propagation surface 11 described later, and the Y-axis perpendicular to the X-axis and the Z-axis are used. , the configuration of the surface wave detection device 1 may be described. 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 an ultrasonic wave including a surface wave Ws, which will be described later, and is made of a synthetic resin such as PPS (polyphenylene sulfide).

The propagating body 10 extends in the X-axis direction and has a generally rectangular prism shape. As shown in FIG. 5, the propagating body 10 has a substantially H-shaped cross section, and includes a propagating surface 11, a back surface 12, side surfaces 13 and 14, a first rib R1, a second rib R2, and a first projection. It has a portion R3 and a second protrusion R4. Further, the propagating body 10 has a bottom surface 15 shown in FIGS.

The propagation surface 11 is the main portion of the propagating body 10 for propagating the surface wave Ws, and has a strip shape extending in the X direction as shown in FIG. The −X-direction end of the propagation surface 11 functions as a reflecting portion 11a that reflects the surface wave Ws. 2, 3 and 5, the rear surface 12 is located on the opposite side (back side) of the propagation surface 11 of the propagation body 10 and provided so as to face the propagation surface 11. As shown in FIGS. The rear surface 12 is also provided in a belt-like shape extending in the X direction. The propagation surface 11 faces the -Z direction and the rear surface 12 faces the +Z direction. The propagation surface 11 and the back surface 12 are parallel to the XY plane. As shown in FIGS. 2 and 3, the propagating body 10 is formed with a groove 12a recessed from the back surface 12 toward the propagating surface 11. As shown in FIGS. Note that FIG. 2 shows a side view of the propagating body 10 and the element accommodating portion 20 as seen from the -Y direction. FIG. 3 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 XZ plane.

As shown in FIG. 5, the side surface 13 faces the -Y direction and the side surface 14 faces the +Y direction. Sides 13 and 14 are parallel to the XZ plane. The bottom surface 15 is an inclined surface that connects the propagation surface 11 and the back surface 12, as shown in FIGS. The bottom surface 15 forms an acute angle with the propagation surface 11 and forms an obtuse angle with the back surface 12 . The bottom surface 15 forms a tapered shape at the tip of the propagating body 10 . Due to the inclination of the bottom surface 15, the surface wave Ws propagating on the propagation surface 11 in the -X direction can be suppressed from going around the back surface 12, reflected by the reflecting portion 11a of the propagation body 10, and propagated on the propagation surface 11 again. Therefore, the surface wave Ws can be directed toward the piezoelectric element 30 efficiently.

As shown in FIG. 5, the first rib R1 and the second rib R2 protrude in the direction (-Z direction) in which the propagation surface 11 faces, and extend in the X direction as shown in FIG. The first rib R1 and the second rib R2 face each other across the propagation surface 11 in the width direction (Y direction) of the propagation surface 11, as shown in FIG. For example, the main surfaces of the first ribs R1 and the second ribs R2 (the surfaces facing the −Z direction) are parallel to the propagation plane 11. As shown in FIG. Also, the heights (heights in the Z direction) of the first ribs R1 and the second ribs R2 from the propagation surface 11 are preferably equal and set equal to or greater than the wavelength λ of the surface wave Ws.

A curved surface S1 connected to the propagation surface 11 is formed at the base end portion of the first rib R1. Specifically, the curved surface S1 connects the propagation surface 11 with a first opposing surface So1 that is an inner surface (a surface facing the +Y direction) of the first rib R1 and faces the second rib R2. A curved surface S2 connected to the propagation surface 11 is formed at the base end portion of the second rib R2. Specifically, the curved surface S2 connects the propagation surface 11 with the second opposing surface So2, which is the inner surface of the second rib R2 (the surface facing the -Y direction) and faces the first rib R1. Here, actually, the surface wave Ws due to vibration of the piezoelectric element 30 is generated not only on the propagation surface 11 but also around the propagation surface 11 . By providing the curved surfaces S1 and S2 as described above, the surface waves Ws generated in the propagating body 10 can be collected on the propagation surface 11, and the directivity of the surface waves Ws propagating on the propagation surface 11 can be enhanced.

Further, as shown in FIG. 4, the distance D between the first rib R1 and the second rib R2 is set substantially equal to the width of the piezoelectric element 30. As shown in FIG. Specifically, the interval D between the first rib R1 and the second rib R2 is the interval between the first opposing surface So1 and the second opposing surface So2. With this configuration, it is possible to suppress the generation of unnecessary surface waves Ws on portions other than the propagation surface 11 . The fact that the interval D is substantially equal to the width of the piezoelectric element 30 includes not only that the interval D is equal to the width of the piezoelectric element 30 , but also that the width of the propagation surface 11 is equal to the width of the piezoelectric element 30 . That is, it is preferable that the width of the piezoelectric element 30 is equal to or less than the interval D and equal to or greater than the width of the propagation surface 11 .

As shown in FIG. 5, the first protrusion R3 and the second protrusion R4 protrude (protrude) in the direction in which the back surface 12 faces (+Z direction). Also, the first protrusion R3 and the second protrusion R4 extend in the X direction, like the first rib R1 and the second rib R2. The first protrusion R3 and the second protrusion R4 face each other with the back surface 12 interposed therebetween in the width direction (Y direction) of the back surface 12, as shown in FIG. For example, the main surfaces (surfaces facing the +Z direction) of the first protrusion R3 and the second protrusion R4 are parallel to the rear surface 12 . For example, the angle between the back surface 12 and the third facing surface So3, which is the inner surface (the surface facing the +Y direction) of the first protrusion R3 and faces the second protrusion R4, is set to be a right angle. For example, the angle between the rear surface 12 and the fourth facing surface So4, which is the inner surface of the second protrusion R4 (the surface facing the -Y direction) facing the first protrusion R3, is also set at a right angle.

In addition to the first rib R1 and the second rib R2 that are provided so as to correspond to the propagation surface 11, by providing the first protrusion R3 and the second protrusion R4 that are provided so as to correspond to the back surface 12, the propagation body It is possible to improve the second moment of area of 10 and improve the resistance to vibration resonance.

The element housing portion 20 is located in the +X 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 disk portion 21 and a cylindrical body 22 and is provided so as to be continuous with the propagation body 10 .

The disc portion 21 is connected to the propagating body 10 . The cylindrical body 22 has a 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 +X direction. A piezoelectric element 30 is accommodated in a portion of the disk portion 21 surrounded by the cylinder 22 . An attachment groove 22a, which is a groove recessed toward the center of the cylinder 22, is formed on the outer peripheral surface of the cylinder 22, and in which the seal member 5 shown in cross section in FIG. 2 is mounted.

The piezoelectric element 30 vibrates the propagating body 10 via the disc portion 21 to cause the propagating body 10 to generate ultrasonic waves. Specifically, the piezoelectric element 30 generates a surface wave Ws on the propagation surface 11 of the propagating body 10 and an internal propagating wave Wi inside the propagating body 10 as ultrasonic waves. Further, the piezoelectric element 30 detects the surface wave Ws reflected by the reflecting portion 11a and the internal propagation wave Wi reflected by the groove 12a, and outputs a detection signal (voltage signal) indicating the detection result.

The piezoelectric element 30 is composed of a known ultrasonic transducer and has a rectangular parallelepiped shape. The piezoelectric element 30 faces the propagating body 10 with the disk portion 21 interposed therebetween, and generates a surface wave Ws on the propagating surface 11. It is provided so as to protrude across the For example, the surface waves Ws are Schulz waves in the liquid 4 . The surface wave Ws may be a transverse surface acoustic wave (SH-SAW) or the like. The internal propagation wave Wi may be a transverse wave or the like. Further, although detailed illustration is omitted here, the piezoelectric element 30 is electrically connected to the control section 2 via a terminal.

The flange portion 40 shown in FIG. 2 is formed of, for example, a synthetic resin, and has a cylindrical portion 41 opening in the −X 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 positioned in the +X direction. 2, 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 tubular portion 41 faces the outer peripheral edge of the disk portion 21 in the X 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.

A fuel tank mounted on the moving body can be applied to the container 3, and the liquid 4 and the propagating body 10 are stored therein. The container 3 has a bottom portion 3a located at the lowest portion thereof, and side portions 3b provided so as to rise from the peripheral portion of the bottom portion 3a.

In this case, the propagating body 10 is housed in the container 3 (on the side of the bottom 3a of the container 3) in a state in which the propagating surface 11 faces the liquid surface 4a of the liquid 4 (see FIG. 1). , see FIG. 2). More specifically, as shown in FIG. 5, the propagating body 10 is substantially parallel to the bottom portion 3a in a state in which the first projection portion R3 and the second projection portion R4 are in contact (surface contact) with the bottom portion 3a. is placed on the bottom portion 3a. Thus, in this example, the propagation surface 11 and the liquid surface 4a of the liquid 4 face each other. Since the bubbles receive the action of buoyancy and move away from the propagation surface 11 and rise toward the liquid surface 4a, it is possible to prevent the bubbles from staying on the propagation surface 11, and the surface wave Ws detected by the piezoelectric element 30 is increased. There is no longer any possibility that the signal strength will drop.

A hole 3c is provided below the side portion 3b, and the surface wave detector 1 is attached to the side portion 3b of the container 3 with the disk portion 21 closing the hole 3c (see FIG. 2). Further, at this time, the disk portion 21 (element housing portion 20) is positioned outside the side portion 3b of the container 3, and the entire area of the propagating body 10 is immersed in the liquid 4. FIG.

Liquid 4 can be gasoline (liquid fuel) stored in container 3 . Here, if the container 3 is a fuel tank mounted on a ship (moving body) that travels on the sea, gasoline is stored under stormy weather conditions (or under conditions where the filler cap seems to be damaged for some reason). It is conceivable that seawater may enter the container 3 where the water is stored. When seawater is mixed in the container 3, a liquid 4 consisting of gasoline and seawater coexists in the container 3. - 特許庁In the following description, among the liquids 4, gasoline will be referred to as the first liquid C1, and seawater will be referred to as the second liquid C2.

Here, since the specific gravity of gasoline is about 0.74 and the specific gravity of seawater is about 1.03, the liquid 4 consists of the first liquid C1 having the first specific gravity and The second liquid C2 having a large second specific gravity settles on the bottom 3a of the container 3 due to the action of gravity.

The control unit 2 functions as an identification unit that identifies the liquid type of the liquid 4 based on the propagation time of the surface wave Ws 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 surface wave Ws and an internal propagating wave Wi. The receiving circuit of the PCB receives detection signals indicating the reflected surface waves Ws and the reflected internal propagation waves Wi from the piezoelectric element 30 and supplies them to the control unit 2 . After receiving the detection signal with the signal strength maintained, the control unit 2 executes a process of specifying the liquid type of the liquid 4 based on the detection signal. Here, the second liquid C2 is mixed in the container 3, and the propagation surface 11 is positioned below the interface between the first liquid C1 and the second liquid C2 (that is, the propagation surface 11 is immersed in the second liquid C2).

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 liquid type identification method will be described. FIG. 6 shows how the internal propagation wave Wi and the surface wave Ws 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 . The vibration W0 causes the propagating body 10 to propagate the surface wave Ws and the internal propagating wave Wi. Time t1 is the time when the internal propagation wave Wi is reflected by the groove 12a and enters the piezoelectric element 30. FIG. A period T1 is an internal propagation wave propagation period T1 from time t0 to time t1. Time t2 is the time when the surface wave Ws is reflected by the reflecting portion 11a and is input to the piezoelectric element 30 . A period T2 is a surface wave propagation period T2 from time t0 to time t2.

The controller 2 identifies the liquid type of the liquid 4 based on the surface wave propagation period T2. That is, the controller 2 identifies the liquid type of the liquid 4 by referring to the data table in which the surface wave propagation period T2 and the liquid type of the liquid 4 are associated. In this case, the control unit 2 refers to the data table and performs processing to specify that the liquid type of the liquid 4 that has settled on the bottom 3a of the container 3 due to the action of gravity is seawater (second liquid C2). . Note that the control unit 2 may perform a process of notifying the user of the detected liquid type by a notifying unit such as a character display (not shown). The principle by which the liquid type of the liquid 4 can be specified based on the surface wave propagation period T2 will be described below.

Since the surface wave propagation period T2 is inversely proportional to the surface wave propagation velocity, the surface wave propagation period T2 becomes shorter as the surface wave propagation velocity increases, while the surface wave propagation period T2 becomes longer as the surface wave propagation velocity decreases. . The surface wave propagation velocity when the propagating body 10 is entirely immersed in the liquid 4 is the sound velocity vl and the density ρl in the liquid peculiar to the liquid 4, and the propagation velocity of the internal propagating wave Wi peculiar to the propagating body 10 determined by vs. That is, when the material of the propagating body 10 is fixed, the surface wave propagation velocity when the propagating body 10 is entirely immersed in the liquid 4 changes depending on the liquid type of the liquid 4 . Therefore, the relationship between the surface wave propagation velocity and the liquid type of the liquid 4 when the propagation body 10 is entirely immersed in the liquid 4 can be obtained by actual measurement, simulation, or the like. By storing the data table in which the surface wave propagation period T2 and the liquid type are associated with each other in the ROM provided in the control unit 2, the liquid type identification device L can determine the surface wave propagation period T2. can be used to identify the liquid type of the liquid 4 (the type of liquid that settles on the bottom 3a is seawater).

The expression that the control unit 2 specifies the liquid type of the liquid 4 based on the surface wave propagation period T2 means that the control unit 2 calculates the surface wave propagation velocity from the surface wave propagation period T2 and calculates the calculated surface wave velocity. It also includes specifying the liquid type of the liquid 4 based on the wave propagation speed. That is, the control unit 2 can identify the liquid type of the liquid 4 based on the calculated surface wave propagation speed by referring to the data table in which the surface wave propagation speed and the liquid type of the liquid 4 are associated. good. In this case, the control unit 2 creates a data table in which the surface wave propagation velocity and the liquid type of the liquid 4 are related, instead of the data table in which the surface wave propagation period T2 and the liquid type of the liquid 4 are related. It suffices if it is stored in the ROM.

As described above, according to this embodiment, the propagating body 10 that is immersed in the liquid 4 and has the propagation surface 11 that propagates the surface wave Ws, and the propagating body 10 that vibrates to generate and reflect the surface waves Ws. A piezoelectric element 30 for detecting the generated surface wave Ws, and a container 3 for containing a liquid 4 and a propagating body 10 are provided. It is stored in the container 3 in this state. Therefore, when a bubble present in the liquid 4 adheres to the propagation surface 11, the bubble adhered to the propagation surface 11 is lifted away from the propagation surface 11 toward the liquid surface 4a by the action of buoyancy. can be prevented from remaining on the propagation surface 11, and there is no concern that the signal strength of the surface wave Ws detected by the piezoelectric element 30 will drop.

Further, in the present embodiment, the first protrusion R3 and the second protrusion R4 are in contact with the bottom 3a of the container 3, so that the propagating body 10 is stably held on the bottom 3a. There is an advantage that the fixing reliability of the detection device 1 is improved.

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 wave Ws 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.

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

1 surface wave detector 2 controller 3 container (storage member)
3a Bottom 3b Side 4 Liquid 4a Liquid surface 10 Propagating body 11 Propagating surface 12 Rear surface 12a Groove 13, 14 Side surface 15 Bottom surface 20 Element housing portion 30 Piezoelectric element 40 Flange portion C1 First liquid C2 Second liquid R1 First rib R2 Second rib R3 First protrusion R4 Second protrusion Ws Surface wave Wi Internal propagation wave

Claims (9)

a propagating body immersed in a liquid and having a propagating surface for propagating surface waves;
a piezoelectric element that vibrates the propagating body to generate the surface waves and that detects the reflected surface waves;
a storage member that stores the liquid and the medium,
The surface wave detecting device according to claim 1, wherein the propagating body is housed in the housing member in a belt-like state so that the propagating surface faces the liquid surface of the liquid. The propagating body has a back surface located behind the propagating surface,
2. The surface acoustic wave detecting device according to claim 1, wherein said back surface is provided in a belt-like state so as to face said propagation surface. The propagating body has a first protrusion and a second protrusion that protrude in the direction in which the back surface faces and are provided so as to correspond to the back surface,
3. The surface wave detecting device according to claim 2, wherein the first protrusion and the second protrusion are in contact with the bottom of the housing member. 4. The surface acoustic wave detecting device according to claim 3, wherein the first protrusion and the second protrusion face each other across the back surface in the width direction of the back surface. An element accommodating portion provided so as to be continuous with the propagating body and accommodating the piezoelectric element,
5. The surface wave detecting device according to claim 1, wherein said element accommodating portion is positioned outside the side portion of said accommodating member. 6. The propagating body has a first rib and a second rib which protrude in a direction in which the propagating surface faces and which are provided so as to correspond to the propagating surface. 1. The surface wave detection device according to 1. 7. The surface acoustic wave detecting device according to claim 6, wherein the first rib and the second rib face each other across the propagation surface in the width direction of the propagation surface. a surface wave detection device according to any one of claims 1 to 7;
and an identifying unit that identifies the type of the liquid based on the propagation time of the surface wave detected by the piezoelectric element. The liquid is composed of a first liquid having a first specific gravity and a second liquid having a second specific gravity greater than the first specific gravity,
9. A liquid type identification device according to claim 8, wherein said second liquid settles on said bottom.

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