Surface wave detection device and liquid type identification device

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

[Technical field]

[0001] The present invention relates to a surface wave detection device and a liquid type identification device. [Background technology]

[0002] For example, Patent Document 1 discloses a technique for 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 that propagates the surface waves, and this propagating surface extends so as to be perpendicular to the liquid surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-139852 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology described in Patent Document 1, air bubbles present in the liquid may remain on the propagation surface extending perpendicular to the liquid surface, and the remaining air bubbles may cause a problem in that the signal strength of the surface wave detected by the piezoelectric element decreases.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a surface wave detection device and a liquid type identification device in which there is no risk of a decrease in the signal strength of the surface wave detected by a piezoelectric element. [Means for solving the problem]

[0006] In order to achieve the above object, a surface wave detection device according to a first aspect of the present invention includes a propagating body that is immersed in liquid and has a propagation surface that propagates a surface wave, a piezoelectric element that applies vibration to the propagating body to generate the surface wave and detects the reflected surface wave, and a storage member that stores the liquid and the propagating body, and the propagating body is stored in the storage member in a band-like state with the propagation surface facing the liquid surface of the liquid. The propagation body has a back surface located behind the propagation surface, and a first protrusion and a second protrusion that protrude in a direction in which the back surface faces and are provided to correspond to the back surface. .

[0007] In order to achieve the above-mentioned object, a liquid type identification device according to a second aspect of the present invention comprises the surface wave detection device and an identification unit that identifies the type of the liquid based on the propagation time of the surface wave detected by the piezoelectric element. Effect of the Invention

[0008] According to the present invention, the intended object can be achieved, and a surface wave detection device and a liquid type identification device can be provided in which there is no risk of a decrease in the signal strength of the surface wave detected by the piezoelectric element. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of a liquid type identification device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of a main part of the liquid type identification device in FIG. [Diagram 3] FIG. 2 is a schematic cross-sectional view of a propagation body, an element receiving portion, and a piezoelectric element according to the embodiment. [Figure 4] FIG. 4 is a front view of a propagation body and an element receiving portion according to the embodiment. [Diagram 5] Cross-sectional view taken along line AA in FIG. 4 (hatching omitted). [Figure 6] Schematic diagram showing waves input to a piezoelectric element when vibration is applied to a propagating body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present invention will be described with reference to the drawings.

[0011] In Fig. 1, reference numeral 1 denotes a surface wave detection device, 2 denotes a control unit, 3 denotes a container as a storage member, 4 denotes liquid contained in the container 3, and 4a denotes the liquid level of the liquid 4. The surface wave detection device 1 and the control unit 2 constitute a liquid type identification device L for identifying the type of liquid 4 (hereinafter also referred to as liquid type) contained in the container 3. Note that the container 3 here is, for example, a fuel tank mounted on a moving object such as a ship traveling on the sea.

[0012] The surface wave detecting device 1 has a propagating body 10 immersed in a liquid 4, an element receiving portion 20, a piezoelectric element 30, and a flange portion 40, as shown in FIGS.

[0013] In the following, as shown in each figure, the configuration of the surface wave detecting device 1 may be described using an X-axis extending in the longitudinal direction of the propagating body 10, a Z-axis extending in the normal direction of a propagation surface 11 described later, and a Y-axis perpendicular to the X-axis and Z-axis. The direction along each of the X, Y, and Z axes is defined as the axial direction. The direction in which the arrows of each of the X, Y, and Z axes point is defined as the "+" direction, and the opposite direction is defined as the "-" direction. In other words, the direction along the X-axis is the X-direction. Taking into consideration the direction 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.

[0014] The propagating body 10 propagates ultrasonic waves including a surface wave Ws described below, and is made of a synthetic resin such as PPS (polyphenylene sulfide).

[0015] The propagating body 10 extends in the X-axis direction and is formed in a generally rectangular prism shape. As shown in Fig. 5, the propagating body 10 has a generally H-shaped cross section and has a propagating surface 11, a back surface 12, side surfaces 13 and 14, a first rib R1, a second rib R2, a first protrusion R3, and a second protrusion R4. The propagating body 10 also has a bottom surface 15 shown in Figs. 2 and 3.

[0016] The propagation surface 11 is a main part of the propagating body 10 that propagates the surface wave Ws, and has a strip shape extending in the X direction as shown in FIG. 4. The end of the propagation surface 11 in the -X direction functions as a reflecting portion 11a that reflects the surface wave Ws. As shown in FIGS. 2, 3, and 5, the back surface 12 is located on the opposite side (back side) of the propagation surface 11 in the propagating body 10, and is provided to face the propagation surface 11. The back surface 12 is also provided in a strip shape extending in the X direction. The propagation surface 11 faces the -Z direction, and the back 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 has a groove 12a recessed from the back surface 12 toward the propagation surface 11. Note that in FIG. 2, the propagating body 10 and the element receiving portion 20 are shown in a side view seen from the -Y direction. FIG. 3 is a cross-sectional view of the propagating body 10, the element receiving portion 20, and the piezoelectric element 30 cut along a plane parallel to the XZ plane.

[0017] As shown in FIG. 5, the side surface 13 faces the -Y direction, and the side surface 14 faces the +Y direction. The side surfaces 13 and 14 are parallel to the XZ plane. The bottom surface 15 is an inclined surface connecting the propagation surface 11 and the back surface 12, as shown in FIG. 2 and FIG. 3. The bottom surface 15 is a surface that forms an acute angle with the propagation surface 11 and an obtuse angle with the back surface 12. The bottom surface 15 makes the tip of the propagating body 10 have a tapered shape. The inclination of the bottom surface 15 can prevent the surface wave Ws propagating in the -X direction on the propagation surface 11 from going around the back surface 12, and the surface wave Ws reflected by the reflecting portion 11a of the propagating body 10 and propagating again on the propagation surface 11 can be efficiently directed to the piezoelectric element 30.

[0018] The first rib R1 and the second rib R2 protrude (project) in the direction in which the propagation surface 11 faces (-Z direction) as shown in Fig. 5, and extend in the X direction as shown in Fig. 4. The first rib R1 and the second rib R2 face each other in the width direction (Y direction) of the propagation surface 11, sandwiching the propagation surface 11, as shown in Fig. 5. For example, the main surfaces (surfaces facing the -Z direction) of the first rib R1 and the second rib R2 are parallel to the propagation surface 11. In addition, the heights (heights in the Z direction) of the first rib R1 and the second rib R2 from the propagation surface 11 are preferably equal and set to be equal to or greater than the wavelength λ of the surface wave Ws.

[0019] A curved surface S1 connected to the propagation surface 11 is formed at the base end of the first rib R1. Specifically, the curved surface S1 connects the propagation surface 11 to a first opposing surface So1, which is an inner 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 of the second rib R2. Specifically, the curved surface S2 connects the propagation surface 11 to a second opposing surface So2, which is an inner surface (facing the -Y direction) of the second rib R2 and faces the first rib R1. Here, in reality, the surface wave Ws caused by the 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 wave Ws generated on the propagating body 10 can be collected on the propagation surface 11, and the directivity of the surface wave Ws propagating on the propagation surface 11 can be increased.

[0020] As shown in FIG. 4, the distance D between the first rib R1 and the second rib R2 is set to be approximately equal to the width of the piezoelectric element 30. Specifically, the distance D between the first rib R1 and the second rib R2 is the distance between the first opposing surface So1 and the second opposing surface So2. This configuration can suppress the generation of unnecessary surface waves Ws in portions other than the propagation surface 11. Note that the distance D being approximately equal to the width of the piezoelectric element 30 includes not only the distance D being equal to the width of the piezoelectric element 30, but also the width of the propagation surface 11 being equal to the width of the piezoelectric element 30. In other words, it is preferable that the width of the piezoelectric element 30 is equal to or less than the distance D and equal to or greater than the width of the propagation surface 11.

[0021] As shown in FIG. 5, the first protrusion R3 and the second protrusion R4 protrude in the direction (+Z direction) in which the rear surface 12 faces. The first protrusion R3 and the second protrusion R4 extend in the X direction, similar to the first rib R1 and the second rib R2. As shown in FIG. 5, the first protrusion R3 and the second protrusion R4 face each other in the width direction (Y direction) of the rear surface 12, sandwiching the rear surface 12. 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 rear surface 12 and a third opposing surface So3, which is an inner surface (surface facing the +Y direction) of the first protrusion R3 and faces the second protrusion R4, is set to a right angle. For example, the angle between the rear surface 12 and a fourth opposing surface So4, which is an inner surface (facing the -Y direction) of the second protrusion R4 and faces the first protrusion R3, is also set to a right angle.

[0022] In addition to the first rib R1 and the second rib R2 arranged to correspond to the propagation surface 11, a first protrusion R3 and a second protrusion R4 are provided to correspond to the back surface 12, thereby improving the second moment of area of ​​the propagation body 10 and improving the resistance to vibration resonance.

[0023] 3, the element accommodating section 20 is located in the +X direction of the propagating body 10, and accommodates the piezoelectric element 30. For example, the element accommodating section 20 is formed integrally with the propagating body 10 using the same material. The element accommodating section 20 includes a disk section 21 and a cylindrical body 22, and is provided so as to be continuous with the propagating body 10.

[0024] The disk portion 21 is connected to the propagation body 10. The cylinder 22 has a cylindrical shape with an outer diameter smaller than that of the disk portion 21, and protrudes from the disk portion 21 in the +X direction. The piezoelectric element 30 is housed in a portion of the disk portion 21 surrounded by the cylinder 22. The outer peripheral surface of the cylinder 22 is formed with a mounting groove 22a which is recessed toward the center of the cylinder 22 and into which the seal material 5 shown in cross section in FIG. 2 is attached.

[0025] The piezoelectric element 30 applies vibrations to the propagating body 10 via the disk portion 21, causing the propagating body 10 to generate ultrasonic waves. Specifically, the piezoelectric element 30 generates a surface wave Ws on the propagating surface 11 of the propagating body 10 as ultrasonic waves, and generates an internal propagating wave Wi inside the propagating body 10. The piezoelectric element 30 also detects the surface wave Ws reflected by the reflecting portion 11a and the internal propagating wave Wi reflected by the groove 12a, and outputs a detection signal (voltage signal) indicating the detection result.

[0026] The piezoelectric element 30 is made of a known ultrasonic transducer and has a rectangular parallelepiped shape. The piezoelectric element 30 faces the propagating body 10 across the disk portion 21, and one end (the lower end in FIG. 3) of the piezoelectric element 30 is provided so as to straddle and protrude beyond the propagating surface 11 of the propagating body 10 in order to generate a surface wave Ws on the propagating surface 11. For example, the surface wave Ws is a Schultz wave in the liquid 4. The surface wave Ws may be a shear-wave type surface acoustic wave (SH-SAW) or the like. The internal propagating wave Wi may be a shear wave or the like. Although detailed illustration is omitted here, the piezoelectric element 30 is electrically connected to the control unit 2 via a terminal.

[0027] 2 includes a cylindrical tubular portion 41 that is formed of, for example, a synthetic resin and that opens in the -X direction, a flange 42 that protrudes in the outer radial direction of the tubular portion 41, and a hollow cap portion 43 that is located in the +X direction relative to the flange 42. Note that in FIG. 2, the tubular portion 41 and the seal material 5 are shown in cross section along the radial direction.

[0028] The cylindrical portion 41 surrounds the cylindrical body 22 of the element accommodating portion 20. The tip of the cylindrical portion 41 faces the outer circumferential end of the disk portion 21 in the X direction. The gap between the cylindrical portion 41 and the cylindrical body 22 is sealed by a seal material 5. The seal material 5 is formed into a ring shape from, for example, resin rubber, and functions as a packing.

[0029] The flange 42 is a portion that is attached to the container 3 by a fixing means such as a screw (not shown). The cap portion 43 has a coupler (not shown). An output terminal (not shown) is located inside the coupler. When an external device is connected to the coupler, the external device and the output terminal are electrically connected. For example, a PCB (Printed Circuit Board) (not shown) is housed inside the cap portion 43, which is electrically connected to each of the piezoelectric element 30 and the output terminal, and on which a transmitting circuit, a receiving circuit, etc. described below are formed.

[0030] The control unit 2 shown in FIG. 1 is composed of, for example, a microcomputer, and includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like.

[0031] The container 3 may be a fuel tank mounted on the moving body, and contains therein a liquid 4 and a carrier 10. The container 3 has a bottom 3a located at the lowermost portion thereof, and a side portion 3b provided so as to stand upright from the peripheral portion of the bottom 3a.

[0032] In this case, the propagating body 10 is stored in the container 3 (on the bottom 3a side of the container 3) in a band-like state such that the propagating surface 11 faces the liquid surface 4a of the liquid 4 (see Figs. 1 and 2). More specifically, the propagating body 10 is placed on the bottom 3a in a state in which the first protrusion R3 and the second protrusion R4 are in contact (surface contact) with the bottom 3a as shown in Fig. 5 and are substantially parallel to the bottom 3a. In this way, in this example, since the propagating surface 11 faces the liquid surface 4a of the liquid 4, when bubbles present in the liquid 4 adhere to the propagating surface 11, the bubbles adhering to the propagating surface 11 are separated from the propagating surface 11 by the action of buoyancy and rise toward the liquid surface 4a, so that it is possible to prevent the bubbles from staying on the propagating surface 11, and there is no risk of a decrease in the signal intensity of the surface wave Ws detected by the piezoelectric element 30.

[0033] A hole 3c is provided below the side 3b, and the surface wave detecting device 1 is attached to the side 3b of the container 3 with the disk portion 21 blocking the hole 3c (see FIG. 2). In this case, the disk portion 21 (element accommodating portion 20) is positioned outside the side 3b of the container 3, and the entire area of ​​the propagating body 10 is immersed in the liquid 4.

[0034] The liquid 4 can be gasoline (liquid fuel) stored in the container 3. Here, if the container 3 is a fuel tank mounted on a ship (mobile body) traveling on the sea, seawater may get mixed into the container 3 in which the gasoline is stored under rough weather conditions (or under conditions in which the filler cap appears to be damaged for some reason). When seawater gets mixed into the container 3, liquid 4 consisting of gasoline and seawater will coexist in the container 3. In the following explanation, gasoline will be referred to as the first liquid C1 and seawater will be referred to as the second liquid C2, as appropriate.

[0035] Here, since the specific gravity of gasoline is approximately 0.74 and the specific gravity of seawater is approximately 1.03, the liquid 4 is composed of a first liquid C1 having a first specific gravity and a second liquid C2 having a second specific gravity greater than the first specific gravity, and the second liquid C2 having the greater specific gravity sinks to the bottom 3a of the container 3 due to the action of gravity.

[0036] The control unit 2 functions as an identifying unit that identifies the 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 under the control of the control unit 2 to drive the piezoelectric element 30. As a result, the surface wave Ws and the internal propagation wave Wi are generated in the propagating body 10. The reception circuit of the PCB receives detection signals indicating the reflected surface wave Ws and the reflected internal propagation wave Wi from the piezoelectric element 30 and supplies them to the control unit 2. The control unit 2 receives the detection signal with the signal intensity maintained, and executes a process of identifying the type of the liquid 4 based on the detection signal. Here, it is assumed that the second liquid C2 is mixed in the container 3, and the propagation surface 11 is located below the interface between the first liquid C1 and the second liquid C2 (i.e., the propagation surface 11 is immersed in the second liquid C2).

[0037] The transmitting circuit and the receiving circuit may be provided in the control unit 2. At least a part of the functions of the control unit 2 may be implemented on a PCB provided inside the flange portion .

[0038] Here, an example of a method for identifying the type of liquid will be described. Fig. 6 shows how the internal propagation wave Wi and the surface wave Ws propagating through the propagating body 10 due to the generation of vibration W0 are reflected and then input to the piezoelectric element 30.

[0039] Time t0 is the time when vibration W0 is generated in the propagating body 10 by driving the piezoelectric element 30. As a result of the generation of vibration W0, the propagating body 10 propagates a surface wave Ws and an internally propagating wave Wi. Time t1 is the time when the internally propagating wave Wi is reflected by the groove 12a and input to the piezoelectric element 30. Time period T1 is the internally propagating wave propagation period T1, which is the period from time t0 to time t1. Time t2 is the time when the surface wave Ws is reflected by the reflecting portion 11a and input to the piezoelectric element 30. Time period T2 is the surface wave propagation period T2, which is the period from time t0 to time t2.

[0040] The control unit 2 identifies the type of the liquid 4 based on the surface wave propagation period T2. That is, the control unit 2 identifies the type of the liquid 4 by referring to a data table in which the surface wave propagation period T2 and the type of the liquid 4 are associated with each other. In this case, the control unit 2 executes a process of referring to the data table and identifying the type of the liquid 4 that has settled to the bottom 3a of the container 3 by the action of gravity as seawater (second liquid C2). The control unit 2 may also execute a process of notifying the user of the detected type of liquid by a notifying unit such as a character display (not shown). The principle by which the type of the liquid 4 can be identified based on the surface wave propagation period T2 will be described below.

[0041] Since the surface wave propagation period T2 is inversely proportional to the surface wave propagation velocity, the faster the surface wave propagation velocity, the shorter the surface wave propagation period T2 becomes, while the slower the surface wave propagation velocity, the longer the surface wave propagation period T2 becomes. The surface wave propagation velocity when the entirety of the propagating body 10 is immersed in the liquid 4 is determined by the sound velocity vl and density ρl in the liquid 4 that are specific to the liquid 4, and the propagation velocity vs of the internal propagating wave Wi that is specific to the propagating body 10. That is, when the material of the propagating body 10 is fixed, the surface wave propagation velocity when the entirety of the propagating body 10 is immersed in the liquid 4 varies depending on the type of the liquid 4. Therefore, the relationship between the surface wave propagation velocity when the entirety of the propagating body 10 is immersed in the liquid 4 and the type of the liquid 4 can be obtained by actual measurement, simulation, or the like. By storing a data table in a ROM provided in the control unit 2 that correlates the surface wave propagation period T2 created based on this relationship with the liquid type, the liquid type identification device L can use the surface wave propagation period T2 to identify the liquid type of the liquid 4 (that the liquid type that has settled to the bottom 3a is seawater).

[0042] The expression that the control unit 2 identifies the type of the liquid 4 based on the surface wave propagation period T2 also includes the control unit 2 calculating the surface wave propagation velocity from the surface wave propagation period T2 and identifying the type of the liquid 4 based on the calculated surface wave propagation velocity. That is, the control unit 2 may identify the type of the liquid 4 based on the calculated surface wave propagation velocity by referring to a data table in which the surface wave propagation velocity and the type of the liquid 4 are associated. In this case, the control unit 2 may store in the ROM a data table in which the surface wave propagation velocity and the type of the liquid 4 are associated, instead of a data table in which the surface wave propagation period T2 and the type of the liquid 4 are associated.

[0043] As described above, this embodiment includes the propagating body 10 that is immersed in the liquid 4 and has the propagation surface 11 that propagates the surface wave Ws, the piezoelectric element 30 that vibrates the propagating body 10 to generate the surface wave Ws and detects the reflected surface wave Ws, and the container 3 that contains the liquid 4 and the propagating body 10, and the propagating body 10 is contained in the container 3 in a band-like state such that the propagation surface 11 faces the liquid surface 4a of the liquid 4. Therefore, when air bubbles present in the liquid 4 adhere to the propagation surface 11, the air bubbles that have adhered to the propagation surface 11 are affected by the action of buoyancy and rise toward the liquid surface 4a, so that it is possible to prevent the air bubbles from staying on the propagation surface 11, and there is no risk of the signal strength of the surface wave Ws detected by the piezoelectric element 30 decreasing.

[0044] In addition, in this embodiment, the first protrusion R3 and the second protrusion R4 abut against the bottom 3a of the container 3, thereby configuring the propagating body 10 to be stably held on the bottom 3a, which has the advantage of improving the fixing reliability of the surface wave detecting device 1.

[0045] The present invention is not limited to the above-described embodiment and drawings. Modifications (including the omission of components) can be made as appropriate within the scope of the present invention.

[0046] For example, the material of the propagation body 10 is arbitrary as long as it can propagate the surface wave Ws well. For example, the resin used for the propagation body 10 is not limited to PPS, and may be POM (polyacetal), PBT (polybutylene terephthalate), or the like.

[0047] In the above description, in order to facilitate understanding of the present invention, descriptions of well-known technical matters have been omitted as appropriate. [Explanation of symbols]

[0048] 1. Surface wave detector 2. Control section 3 Containers (storage materials) 3a bottom 3b side 4 liquid 4a Liquid level 10. Propagation 11 Propagation Surface 12 Back side 12a groove 13, 14 Side 15 Bottom 20 Element housing section 30 Piezoelectric element 40 Flange C1 First Liquid C2 Second Liquid R1 First rib R2 Second rib R3 1st protrusion R4 2nd protrusion Ws surface wave Wi Internal propagation wave

Claims

1. a propagating body having a propagating surface that is immersed in the liquid and propagates a surface wave; a piezoelectric element that applies vibration to the propagation body to generate the surface wave and detects the reflected surface wave; a storage member that stores the liquid and the propagating medium, the propagation body is stored in the storage member in a band-like state such that the propagation surface faces the liquid surface of the liquid, A surface wave detection device characterized in that the propagating body has a back surface located behind the propagation surface, and a first protrusion portion and a second protrusion portion that protrude in the direction in which the back surface faces and are arranged to correspond to the back surface.

2. A surface wave detection device as described in claim 1, characterized in that the back surface is arranged in a band shape facing the propagation surface.

3. A surface wave detection device as described in claim 1, characterized in that the first protrusion portion and the second protrusion portion abut against the bottom of the storage member.

4. 4. The surface wave detector according to claim 3, wherein the first protrusion and the second protrusion face each other across the rear surface in the width direction of the rear surface.

5. A propagating body having a propagating surface that is immersed in a liquid and propagates a surface wave; a piezoelectric element that applies vibration to the propagation body to generate the surface wave and detects the reflected surface wave; a storage member that stores the liquid and the propagating medium, the propagation body is stored in the storage member in a band-like state such that the propagation surface faces the liquid surface of the liquid, an element accommodating section that is connected to the propagation body and that accommodates the piezoelectric element; A surface wave detecting device, wherein the element receiving portion is located on an outer side of the receiving member.

6. A propagating body having a propagating surface that is immersed in a liquid and propagates a surface wave; a piezoelectric element that applies vibration to the propagation body to generate the surface wave and detects the reflected surface wave; a storage member that stores the liquid and the propagating medium, the propagation body is stored in the storage member in a band-like state such that the propagation surface faces the liquid surface of the liquid, The surface wave detecting device according to the present invention is characterized in that the propagating body has a first rib and a second rib that protrude in a direction in which the propagating surface faces and are provided so as to correspond to the propagating surface.

7. 7. The surface wave detecting device according to claim 6, wherein the first rib and the second rib face each other in the width direction of the propagation surface, sandwiching the propagation surface therebetween.

8. 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; 4. The surface wave detection device according to claim 3, wherein the second liquid sinks to the bottom.

9. A surface wave detection device according to any one of claims 1 to 8; an identification unit that identifies the type of the liquid based on a propagation time of the surface wave detected by the piezoelectric element.

Images