JP2023101041A - Surface wave detection device, liquid level position detection device, liquid type identification device, solution concentration detection device, and droplet detection device - Google Patents

Abstract

To provide a surface wave detection device having an excellent S/N ratio of surface waves, a liquid level position detection device, a liquid type identification device, a solution concentration detection device, and a droplet detection device.SOLUTION: A surface wave detection device includes a propagation body 10 and a piezoelectric element 30. The propagation body 10 has a propagation surface 11 on which surface waves are propagated. The piezoelectric element 30 generates surface waves by vibrating the propagation body 10 and detects reflected surface waves. The propagation surface 11 is in a strip shape extending in a predetermined direction. The propagation body 10 has a first rib R1 and a second rib R2 that project in a direction that the propagation surface 11 faces and extend in a predetermined direction. The first rib R1 and the second rib R2 oppose mutually while sandwiching the propagation surface 11 in a width direction of the propagation surface 11. A vibration absorption part 7 for absorbing vibration is provided in an object surface as a surface in a position differing from that of the propagation surface 11 in the propagation body 10.SELECTED DRAWING: Figure 3

Description

The present invention relates to a surface wave detection device, a liquid surface position detection device, a liquid type identification device, a solution concentration detection device, and a droplet detection device.

For example, Patent Literatures 1 and 2 disclose techniques for generating surface waves by vibrating a propagating body and detecting the reflected surface waves. The technique described in Patent Document 1 detects the surface position of the liquid in which the propagating body is immersed based on the detected propagation time of the surface wave. Further, the technique described in Patent Document 2 identifies the type of liquid in which the propagating body is immersed based on the propagation time of the detected surface wave.

JP-A-4-86525 JP 2018-54321 A

In the structures of the propagating bodies described in Patent Documents 1 and 2, there is a possibility that the SN ratio of the surface waves to be detected deteriorates.

The present invention has been made in view of the above circumstances, and provides a surface wave detection device, a liquid surface position detection device, a liquid type identification device, a solution concentration detection device, and a droplet detection device, all of which have a good SN ratio of surface waves. intended to

In order to achieve the above object, a surface wave detection device according to a first aspect of the present invention comprises:
a propagating body having a propagation surface on which surface waves propagate;
a piezoelectric element that vibrates the propagating body to generate the surface wave and detects the reflected surface wave;
the propagation surface has a strip shape extending in a predetermined direction,
the propagating body has a first rib and a second rib projecting in a direction in which the propagating surface faces and extending in the predetermined direction;
the first rib and the second rib face each other across the propagation surface in the width direction of the propagation surface;
A vibration absorbing portion that absorbs vibration is provided on a target surface, which is a surface of the propagating body located at a position different from the propagating surface.

In order to achieve the above object, a liquid level detection device according to a second aspect of the present invention includes:
the surface wave detection device;
a detection unit that detects a liquid surface position of the liquid in which the propagating body is immersed, based on the propagation time of the surface wave detected by the piezoelectric element.

In order to achieve the above object, a liquid type identification device according to a third aspect of the present invention includes:
the surface wave detection device;
a specifying unit that specifies a type of liquid in which the propagating body is immersed based on the propagation time of the surface wave detected by the piezoelectric element.

In order to achieve the above object, a solution concentration detection device according to a fourth aspect of the present invention comprises:
the surface wave detection device;
a detection unit that detects the concentration of the solution in which the propagating body is immersed, based on the propagation time of the surface wave detected by the piezoelectric element.

In order to achieve the above object, a droplet detection device according to a fifth aspect of the present invention includes:
the surface wave detection device;
a detection unit that detects droplets adhering to the propagation surface based on the propagation time of the surface wave detected by the piezoelectric element.

According to the present invention, it is possible to provide a surface wave detection device, a liquid surface position detection device, a liquid type specification device, a solution concentration detection device, and a droplet detection device, all of which have a good SN ratio of surface waves.

1 is a schematic configuration diagram of a liquid level detection device according to a first embodiment of the present invention; FIG. FIG. 2 is a schematic cross-sectional view of a propagating body, an element accommodating portion, and a piezoelectric element according to the first embodiment; FIG. 2 is a front view of a propagating body, an element accommodating portion, and a vibration absorbing portion according to the first embodiment; FIG. 2 is a rear view of a propagating body, an element accommodating portion, and a vibration absorbing portion according to the first embodiment; FIG. 4 is a cross-sectional view along line AA shown in FIG. 3 of the propagating body according to the first embodiment; FIG. 4 is a schematic diagram showing waves input to the piezoelectric element when vibration is applied to the propagating body; FIG. 4 is a diagram showing experimental data of waveforms such as surface waves input to a piezoelectric element when a propagating body is vibrated, (a) showing data according to an example, and (b) showing data according to a comparative example; illustration. FIG. 10 is a diagram of experimental data showing the effect of the vibration absorbing section, and a diagram showing the value of the detection signal with respect to the liquid level of the liquid in which the propagating body is immersed; FIG. 4 is a schematic configuration diagram of a liquid type identification device according to a second embodiment of the present invention; FIG. 10 is a diagram showing the relationship between the concentration of a solution and the surface wave propagation velocity for a modified example of the second embodiment, where (a) shows the case where the solute is salt and (b) shows the case where the solute is alcohol; figure. FIG. 7 is a schematic configuration diagram of a liquid droplet detection device according to a third embodiment of the present invention;

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

(First embodiment)
A liquid level detection device 100 according to the first embodiment includes a surface wave detection device 1 and a controller 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 a propagating body 10, an element housing portion 20, a piezoelectric element 30, and a flange portion 40, as shown in FIG. The surface wave detector 1 also includes a vibration absorber 7 shown in FIGS. 3 to 5. FIG.

1 and 2, the vibration absorbing portion 7 is omitted, and the vibration absorbing portion 7 is indicated by a dashed line 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 the propagation surface 11 described later, and the X-axis orthogonal to the Y and Z axes are used to 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), for example.

The propagating body 10 extends in the Z-axis direction and is generally shaped like a quadrangular prism. 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, a first side surface 13, a second side surface 14, a first rib R1, a second It has a rib R2, a third rib R3, and a fourth rib R4. Further, the propagating body 10 has a bottom surface 15 shown in FIGS. 1, 2 and 4. FIG.

The propagation surface 11 is the main portion of the propagating body 10 through which the surface wave Ws propagates, and has a strip shape extending in the Z direction as shown in FIG. The −Z-direction end of the propagation surface 11 functions as a reflecting portion 11a that reflects the surface wave Ws. The back surface 12 is located on the opposite side of the propagating body 10 from the propagating surface 11, as shown in FIGS. The back surface 12 also has a strip shape extending in the Z direction. The propagation surface 11 faces the -Y direction and the rear surface 12 faces the +Y direction. Propagation surface 11 and back surface 12 are parallel to the ZX plane. As shown in FIGS. 1 and 2, the propagating body 10 is formed with a groove 12a recessed from the rear surface 12 toward the propagating surface 11. As shown in FIG. 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. 5, the first side surface 13 faces the -X direction and the second side surface 14 faces the +X direction. The first side surface 13 and the second side surface 14 are parallel to the YZ 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 in the −Z direction on the propagation surface 11 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. The surface wave Ws generated by the wave can be directed toward the piezoelectric element 30 efficiently.

The first rib R1 and the second rib R2 protrude in the direction in which the propagation surface 11 faces (-Y direction), as shown in FIG. 5, and extend in the Z 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 (X direction) of the propagation surface 11, as shown in FIG. The first rib R1 includes a first major surface M1 facing in the same direction as the propagation surface 11. As shown in FIG. The second rib R2 includes a second major surface M2 facing in the same direction as the propagation surface 11. As shown in FIG. For example, the first principal surface M1 and the second principal surface M2 are parallel to the propagation surface 11 . Moreover, the heights (heights in the Y direction) of the first ribs R1 and the second ribs R2 from the propagation surface 11 are preferably the same, and are 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 the first opposing surface So1 that is the inner surface (the surface facing the +X 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 −X 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. 3, 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 .

The third rib R3 and the fourth rib R4 protrude in the direction in which the back surface 12 faces (+Y direction), as shown in FIG. Also, the third rib R3 and the fourth rib R4 extend in the Z direction, like the first rib R1 and the second rib R2. The third rib R3 and the fourth rib R4 face each other across the back surface 12 in the width direction (X direction) of the back surface 12, as shown in FIG. The third rib R3 includes a third main surface M3 facing in the same direction as the back surface 12. As shown in FIG. The fourth rib R4 includes a fourth major surface M4 facing in the same direction as the back surface 12. As shown in FIG. For example, the third main surface M3 and the fourth main surface M3 are parallel to the back 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 +X direction) of the third rib R3 and faces the fourth rib R4, is set at a right angle. For example, the angle between the back surface 12 and the fourth opposing surface So4, which is the inner surface of the fourth rib R4 (the surface facing the -X direction) and faces the third rib R3, is also set at a right angle. By providing the third rib R3 and the fourth rib R4 in addition to the first rib R1 and the second rib R2, the geometrical moment of inertia of the propagating body 10 can be improved, and the resistance to vibration resonance can be improved. The height of the third rib R3 and the fourth rib R4 (the height from the back surface 12 in the +Y direction) can be arbitrarily set according to the design.

As shown in FIG. 5, the first side surface 13 is connected to the outer edge E1 of the first main surface M1. Specifically, one end in the Y direction of the first side surface 13 is connected to the outer edge E1 of the first main surface M1, and the other end in the Y direction is connected to the outer edge E3 of the third main surface M3. For example, the first side surface 13 and the first major surface M1 are orthogonal, and the first side surface 13 and the third major surface M3 are orthogonal. The second side surface 14 is connected to the outer edge E2 of the second main surface M2. Specifically, one end in the Y direction of the second side surface 14 is connected to the outer edge E2 of the second main surface M2, and the other end in the Y direction is connected to the outer edge E4 of the fourth main surface M4. For example, the second side surface 14 and the second major surface M2 are orthogonal, and the second side surface 14 and the fourth major surface M4 are orthogonal.

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 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. A piezoelectric element 30 is accommodated in a portion of the disk portion 21 surrounded by the cylindrical body 22 . A mounting groove 22a, which is a groove recessed toward the center of the cylindrical body 22, is formed in the outer peripheral surface of the cylindrical body 22 and to which the sealing member 5 shown in cross section in FIG. 1 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. Since 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, one end (right end in FIG. It is provided so as to protrude across the For example, the surface wave Ws is a Rayleigh wave in air and a Schulz wave in liquid 4 . The surface wave Ws may be a leaky Rayleigh wave, a shear surface acoustic wave (SH-SAW), or the like. The internal propagation wave Wi 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 controller 2 functions as a detector that detects the liquid surface position 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 . Upon 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. 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 . A surface wave Ws and an internal propagation wave Wi are propagated through the propagating body 10 by generating the vibration W0. 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 speed of the surface wave Ws traveling through the propagating body 10 (propagating surface 11 ) is slowed in the portion where the propagating body 10 is immersed in the liquid 4 . Therefore, the higher the liquid surface 4a is, the longer the surface wave propagation period T2 is. Using this characteristic, the control unit 2 measures the surface wave propagation period T2, and refers to the liquid surface position detection data, which is stored in advance in the ROM and indicates the relationship between the surface wave propagation period T2 and the position of the liquid surface 4a. and calculate the liquid surface position. On the other hand, the internally propagating wave Wi travels inside the propagating body 10 . Therefore, the value of the internal propagation wave propagation period T1 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 T1, and refers to the temperature characteristic data stored in advance in the ROM, which indicates the relationship between the internal wave propagation period T1 and the temperature of the propagating body 10. and the temperature of the propagating body 10 is obtained. Then, the temperature-dependent surface wave propagation period T2 is corrected according to the obtained temperature. That is, the control unit 2 temperature-corrects the surface wave propagation period T2 based on the internal propagation wave Wi, and calculates the liquid level position based on the surface wave propagation period T2 after the temperature correction and the liquid level position detection data ( To detect). 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.

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

Here, with reference to FIGS. 7A and 7B, the effect of the structure of the propagating body 10 will be described. FIG. 7(a) shows, as an example, signal waveforms such as the surface wave Ws when the structure of the propagation body 10 described above is used. FIG. 7B shows, as a comparative example, signal waveforms of surface waves Ws, etc., when using a quadrangular prism-shaped propagator structure without ribs (first to fourth ribs R1 to R4). . In the graphs shown in FIGS. 7A and 7B, the signal intensity is plotted on the vertical axis and the elapsed time is plotted on the horizontal axis. 7(a) and 7(b) show experimental results under the same conditions except for the shape of the propagating body.
A comparison of FIGS. 7A and 7B reveals that the signal strength of the surface wave Ws input to the piezoelectric element 30 is higher in the example than in the comparative example. In addition, as shown in FIG. 7B, in the comparative example, the unwanted propagation wave U (that is, noise) is significantly generated immediately before the surface wave Ws input to the piezoelectric element 30 is generated. I understand. On the other hand, as shown in FIG. 7(a), in the example, no significant noise occurs immediately before the surface wave Ws input to the piezoelectric element 30 is generated. As described above, according to the surface wave detection device 1 according to the first embodiment, it can be seen that the SN ratio of the signal by the surface wave Ws is excellent. It should be noted that the configuration in which the curved surfaces S1 and S2 are not provided at the base end portions of the first rib R1 and the second rib R2 (that is, the configuration in which the first opposing surface So1 and the second opposing surface So2 intersect with the propagation surface 11) propagates A similar experiment was also conducted using the body, but the results were almost the same as those shown in FIG. 7(a). That is, according to the propagating body 10 provided with the first ribs R1 and the second ribs R2, regardless of the presence or absence of the curved surfaces S1 and S2, the SN ratio of the signal due to the surface wave Ws can be improved.

The vibration absorbing portion 7 is provided on a target plane, which is a plane at a different position from the propagation plane 11 in the propagating body 10 . The target surfaces are the first side surface 13, the second side surface 14, the back surface 12, the first main surface M1 and the second main surface M2. In this embodiment, the vibration absorber 7 is a plate-like member made of elastomer such as nitrile rubber, and is attached to the target surface.

As shown in FIGS. 3 and 4, the first side surface 13 is provided with two vibration absorbing portions 7 . One of the two vibration absorbing portions 7 is provided at the central portion of the first side surface 13 in the Z direction. The other of the two vibration absorbing portions 7 is provided at the same height as the groove 12a in the Z direction, as shown in FIG. As shown in FIG. 5, the vibration absorbing portion 7 provided on the first side surface 13 has substantially the same (including exactly the same) width as the first side surface 13 in the Y direction. Like the first side surface 13, the second side surface 14 is provided with two vibration absorbing portions 7. As shown in FIG. The vibration absorbing portion 7 provided on the second side surface 14 is arranged symmetrically with the vibration absorbing portion 7 provided on the first side surface 13, as shown in FIGS.

As shown in FIG. 4, one vibration absorbing portion 7 is provided between the groove 12a and the bottom surface 15 on the back surface 12. As shown in FIG. As shown in FIG. 5, the vibration absorbing portion 7 provided on the rear surface 12 has a width substantially the same (including exactly the same) as the rear surface 12 in the X direction.

As shown in FIG. 3, one vibration absorbing portion 7 is provided on the first main surface M1. This vibration absorbing portion 7 is positioned between two vibration absorbing portions 7 provided on the first side surface 13 in the Z direction. A single vibration absorbing portion 7 is provided on the second main surface M2, similarly to the first main surface M1. As shown in FIG. 3, the vibration absorbing portion 7 provided on the second main surface M2 is arranged symmetrically with the vibration absorbing portion 7 provided on the first main surface M1.

Here, with reference to FIG. 8, the effect of the vibration absorbing portion 7 will be described. FIG. 8 shows the signal (detection signal of the surface wave Ws) and noise (detection signal of the unnecessary propagation wave U described above) when the liquid surface position (liquid level) of the liquid 4 in which the propagating body 10 is immersed is changed. indicates a relationship with It should be noted that "attached" in the figure indicates the configuration of this embodiment (that is, the vibration absorbing section 7 is attached to the propagating body 10 in the arrangement described above). In the figure, "no sticking" indicates the propagating body 10 without the vibration absorbing portion 7 as a comparative example. Referring to FIG. 8, both the signal and noise tend to decrease in the case of “with paste” compared to “without paste”, but the decrease in signal tends to be sufficiently small compared to the decrease in noise. I understand. From the above, it can be seen that the surface wave detection device 1 having the vibration absorber 7 has a good SN ratio of the signal by the surface wave Ws.

The surface acoustic wave detection device 1 described above includes a propagating body 10 having first ribs R1 and second ribs R2. The first rib R<b>1 and the second rib R<b>2 face each other with the propagation surface 11 interposed therebetween in the width direction of the propagation surface 11 . It is considered that this configuration suppresses the surface waves Ws propagating on the propagation surface 11 from propagating in the Z direction along the first ribs R1 and the second ribs R2, and diffusing the surface waves Ws in the X direction. Furthermore, the surface wave detection device 1 includes a vibration absorber 7 . As a result, the SN ratio of the surface wave Ws can be improved, as shown by the experimental results described above.

Note that the target surface on which the vibration absorbing portion 7 is provided is arbitrary as long as it is a surface other than the propagation surface 11 of the propagating body 10 . For example, the target surface may include at least one of the first side surface 13, the second side surface 14, the back surface 12, the first main surface M1, and the second main surface M2. Moreover, the target surface may further include at least one of the third main surface M3, the fourth main surface M4, and the bottom surface 15. FIG. Also, the number, shape, size, and material of the vibration absorbing portions 7 can be changed arbitrarily. The vibration absorber 7 only needs to be able to absorb ultrasonic vibrations generated in portions other than the propagation surface 11, and its conditions are set through experiments so as to achieve a good SN ratio of the surface wave Ws. Just do it.

For example, the vibration absorbing portion 7 may be made of resin other than rubber, sponge, or the like. Also, the vibration absorbing portion 7 may be a silicon-based adhesive or the like applied to the target surface of the propagating body 10 . Moreover, the vibration absorbing portion 7 may be formed integrally with the propagating body 10 and may be provided by applying unevenness processing to the target surface. The uneven processing may be texturing, blasting, hairline processing, or the like.

Since the liquid level detection device 100 according to the first embodiment includes the surface wave detection device 1 having a good SN ratio of the surface wave Ws, the liquid level position can be detected with good accuracy. The description of the first embodiment is above.

Second and third embodiments, which are different in application of the surface wave detection device 1 from the first embodiment, will be described in order below. The surface wave detectors 1 according to the second and third embodiments are also provided with the vibration absorber 7 as in the first embodiment. Since the following is a description of the configuration of the surface wave detection device 1 that is used in a different application from that of the first embodiment, the illustration of the vibration absorber 7 is omitted in FIGS. 9 and 11 used in the following description.

(Second embodiment)
A liquid type identification device 200 according to the second embodiment will be described mainly with reference to FIG. It should be noted that each part having functions common to those of the first embodiment will be given the same or corresponding reference numerals as those of the first embodiment, and description thereof will be omitted as appropriate. Also, in the second embodiment, the points different from the first embodiment will be mainly described.

As shown in FIG. 9, the liquid type identification device 200 according to the second embodiment includes a surface wave detection device 1 and a controller 2M. The liquid type identification device 200 identifies the type of liquid 4 (hereinafter also referred to as liquid type) contained in the container 3 .

The structure of the surface wave detection device 1 is the same as that of the first embodiment. In the second embodiment, the manner in which the surface wave detection device 1 is attached to the container 3 is different from that in the first embodiment. The surface wave detection device 1 according to the second embodiment is attached to the container 3 in such a posture that the propagating body 10 faces the liquid surface 4a from the bottom of the container 3, for example. It is sufficient that at least the entire propagation surface 11 of the propagating body 10 is immersed in the liquid 4 .

Also, the control unit 2M according to the second embodiment has the same configuration as that of the first embodiment, but the functions thereof are different from those of the first embodiment. The control unit 2M functions as an identification 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. FIG. At least part of the functions of the control section 2M may be implemented on a PCB provided inside the flange section 40 .

The controller 2M identifies the type of the liquid 4 based on the surface wave propagation period T2. Specifically, the controller 2M 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. The principle by which the type of liquid 4 can be identified 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 at least the propagation surface 11 of the propagation body 10 is entirely immersed in the liquid 4 is the sound velocity vl and density ρl in the liquid peculiar to the liquid 4, and the internal propagation It is determined by the propagation velocity vs of the wave Wi, the surface wave propagation velocity vR in the air, and the density ρS. That is, when the material of the propagating body 10 is fixed, the surface wave propagation velocity when at least the propagating surface 11 of the propagating body 10 is entirely immersed in the liquid 4 changes depending on the type of the liquid 4 . Therefore, the relationship between the surface wave propagation velocity and the type of liquid 4 when at least the propagation surface 11 of the propagating body 10 is entirely immersed in the liquid 4 can be obtained by actual measurement or simulation. By storing in the ROM of the control unit 2M a data table in which the surface wave propagation period T2 and the type of the liquid 4 are associated with each other, the liquid type identification device 200 can determine the surface wave propagation period T2. can be used to identify the type of liquid 4 .

The expression that the control unit 2M specifies the type of the liquid 4 based on the surface wave propagation period T2 means that the control unit 2M calculates the surface wave propagation velocity from the surface wave propagation period T2, and the calculated surface wave It also includes identifying the type of liquid 4 based on the propagation velocity. That is, the controller 2M may identify the type of the liquid 4 based on the calculated surface wave propagation speed by referring to a data table in which the surface wave propagation speed and the type of the liquid 4 are associated. In this case, the controller 2M stores a data table in which the surface wave propagation velocity and the type of the liquid 4 are associated, instead of the data table in which the surface wave propagation period T2 and the type of the liquid 4 are associated. should be stored in

As described above, the liquid type identifying device 200 can identify the type of the liquid 4 based on the surface wave propagation period 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 Wi travels inside the propagating body 10, the propagation velocity of the internal propagating wave (internal propagating wave propagation period T1) is Only body 10 temperature is affected. Therefore, the control unit 2M may obtain the temperature of the propagating body 10 from the internal propagation wave propagation period T1 of the internal propagation wave Wi by referring to the temperature conditions stored in the ROM. The control unit 2M may correct the surface wave propagation period T2 of the surface wave Ws based on the temperature of the propagating body 10 using a correction method considering a predetermined correction coefficient or the like. By the control unit 2M specifying the type of the liquid 4 according to the surface wave propagation period T2 after correction, it is possible to specify the type of the liquid 4 with high accuracy in consideration of the temperature of the propagating body 10.

(Modification of Second Embodiment)
With a structure similar to that of the liquid type identification device 200 described above, the concentration of the same type of solution (that is, the amount of solute) can be detected. As a modified example of the second embodiment, a solution concentration detection device for detecting the concentration of the liquid 4, which is a solution, will be described. The control unit 2M according to this modification functions as a detection unit that detects the concentration of the solution (liquid 4) in which the propagating body 10 is immersed, based on the propagation time of the surface wave Ws detected by the piezoelectric element 30. FIG. The propagation speed of the surface wave Ws changes according to the concentration of the solution in which the propagating body 10 is immersed. The controller 2M uses this property to detect the concentration of the solution.

FIG. 10(a) is a diagram showing the relationship between the salt concentration of salt water and the surface wave propagation velocity. FIG. 10(b) is a diagram showing the relationship between alcohol concentrations (ethanol, methanol) and surface wave propagation velocities. As shown in FIGS. 10(a) and 10(b), the surface wave Ws has the property that the speed at which the surface wave Ws travels on the propagation surface 11 decreases as the concentration of the solution increases. Using this property, the control unit 2M measures the propagation time (surface wave propagation period T2), refers to the concentration detection data stored in advance in the ROM and indicates the relationship between the propagation time and the concentration of the solution, Detect the concentration of the solution. For example, the control unit 2M measures the propagation time at a predetermined cycle, refers to the concentration detection data, specifies the concentration of the solution corresponding to the propagation time, and uses it as the detected concentration. It should be noted that the control unit 2M does not necessarily have to represent the concentration of the solution by a specific numerical value expressed in units such as %. For example, the control unit 2M may detect whether the concentration of the solution is thicker or thinner than the previous time based on the difference between the propagation time measured this time and the propagation time measured last time. Note that the control unit 2M may detect the concentration of the solution using the propagation speed of the surface wave Ws calculated based on the propagation time. In any case, the controller 2M detects the concentration of the solution based on the propagation time of the surface wave Ws detected by the piezoelectric element 30. FIG. Also in this modification, temperature correction may be performed using the internal propagation wave Wi.

The solute used by the solution concentration detection device to detect the concentration of the solution is not limited to salt and alcohol, and may be sugar or other solutes. The propagating body 10 immersed in this kind of solution is preferably made of a resin such as the PPS described above. This is because the resin propagating body 10 can be prevented from being ionized like metal, and is resistant to corrosion and contamination.

Since the liquid type identification device 200 according to the second embodiment described above includes the surface wave detection device 1 having a good SN ratio of the surface wave Ws, the liquid type can be identified with good accuracy. Similarly, the solution concentration detection device as a modified example of the second embodiment includes the surface wave detection device 1 having a good SN ratio of the surface wave Ws, so that the concentration of the solution can be detected with good accuracy. The description of the second embodiment and its modification is over.

(Third embodiment)
From now on, the droplet detection device 300 according to the third embodiment will be described mainly with reference to FIG. 11 . It should be noted that each part having functions common to those of the first embodiment will be given the same or corresponding reference numerals as those of the first embodiment, and description thereof will be omitted as appropriate.

A droplet detection device 300 according to the third embodiment includes, as shown in FIG. 11, a surface wave detection device 1 and a controller 2N. The droplet detection device 300 detects a droplet 4b such as a water droplet adhering to the propagation surface 11 of the surface wave detection device 1. FIG.

The droplet detection device 300 is used, for example, to detect liquid leakage from joints, mechanical seals, and the like of pipes 6 installed in a plant. Therefore, the surface wave detection device 1 is installed with the propagation surface 11 facing a location where liquid leakage is likely to occur. That is, the propagating body 10 of the third embodiment is not immersed in liquid unlike the first and second embodiments.

The controller 2N functions as a detector that detects the droplet 4b based on the propagation time of the surface wave Ws detected by the piezoelectric element 30. FIG. When the droplet 4b adheres to the propagation surface 11 of the surface wave detection device 1, the speed at which the surface wave Ws advances on the propagation surface 11 is slower than when the droplet 4b does not adhere. Using this property, the control unit 2N measures the propagation time (surface wave propagation period T2), and stores a droplet detection time, which is stored in advance in the ROM, indicating the relationship between the propagation time and the presence or absence of adhesion of the droplet 4b. By referring to the data, it is determined whether or not the droplet 4b adheres to the propagation surface 11. FIG. For example, the control unit 2N measures the propagation time at a predetermined cycle, and determines that the droplet 4b has adhered when the difference between the propagation time measured this time and the propagation time measured last time is equal to or greater than a predetermined threshold. If it is less than the threshold value, it is determined that the droplet 4b has not adhered. Note that the control unit 2N may determine whether or not the droplet 4b adheres using the propagation speed of the surface wave Ws calculated based on the propagation time. In any case, the control unit 2N detects that the droplet 4b adheres to the propagation surface 11 based on the propagation time of the surface wave Ws detected by the piezoelectric element 30. FIG. Also in the third embodiment, temperature correction may be performed using the internal propagation wave Wi.

Since the droplet detection device 300 according to the third embodiment described above includes the surface wave detection device 1 having a good SN ratio of the surface wave Ws, the droplet 4b can be detected with good accuracy. The description of the third embodiment is above.

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

In the second embodiment, an example in which the propagating body 10 is provided along the depth direction of the liquid 4 has been described. is immersed in the liquid 4, and is not limited. For example, the propagating body 10 may extend along the in-plane direction (horizontal direction) of the liquid surface 4a. In the liquid level detection device 100 according to the first embodiment, the orientation of the propagating body 10 with respect to the liquid 4 and the container 3 is arbitrary as long as the liquid level position can be detected. For example, the propagating body 10 may extend obliquely with respect to the depth direction (vertical direction) of the liquid 4 .

The shape of the propagating body 10 is arbitrary as long as it is immersed in the liquid 4 and has at least the propagating surface 11, the first rib R1 and the second rib R2.

Detecting the liquid level position of the liquid 4 means not only detecting the position of the liquid level 4a in detail, but also dividing the position of the liquid level 4a into several stages and determining to which stage the current position of the liquid level 4a belongs. and detecting the volume of the liquid 4 that changes according to the position of the liquid surface 4a. 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.

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. Although it is considered preferable that the propagating body 10 is made of resin, it may be made of metal as long as the surface wave Ws can be propagated satisfactorily.

The surface wave Ws and the internal propagation wave Wi may be of any type as long as the liquid surface position can be detected or the type of liquid can be identified by the above technique. In the above, an example in which the surface wave Ws and the internal propagation wave Wi are pulses of ultrasonic waves (for example, sound waves of 20 kHz or higher) (ultrasonic pulses) has been described. The waves Wi may be sound waves of a lower frequency than ultrasound. In the above, the case where the piezoelectric element is a slide element is exemplified, but it may be a longitudinal vibrator 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.

DESCRIPTION OF SYMBOLS 100... Liquid level position detection apparatus 1... Surface wave detection apparatus 2... Control part (an example of a detection part) 3... Container 4... Liquid 4a... Liquid surface Ws... Surface wave, Wi... Internal propagation wave 10... Propagating body 11 Propagation surface 12 Back surface 12a Groove 13 First side surface 14 Second side surface 15 Bottom surface R1 to R4 First to fourth ribs S1, S2 Curved surface M1 to M4 First ~ 4th main surface, E1 ~ E4 ... 1st ~ 4th outer edge 20 ... Element housing part 30 ... Piezoelectric element 40 ... Flange part 7 ... Vibration absorbing part 200 ... Liquid type identification device, 2M ... Control unit (liquid type identification device or an example of the detection part of the solution concentration detection device)
300... Droplet detection device, 2N... Control unit (an example of a detection unit of a droplet detection device), 4b... Droplet, 6... Piping

Claims (11)

a propagating body having a propagation surface on which surface waves propagate;
a piezoelectric element that vibrates the propagating body to generate the surface wave and detects the reflected surface wave;
the propagation surface has a strip shape extending in a predetermined direction,
the propagating body has a first rib and a second rib projecting in a direction in which the propagating surface faces and extending in the predetermined direction;
the first rib and the second rib face each other across the propagation surface in the width direction of the propagation surface;
A vibration absorbing portion that absorbs vibration is provided on a target surface, which is a surface of the propagating body that is located at a position different from the propagating surface,
Surface wave detector. The vibration absorbing portion is provided on the target surface by affixing or coating,
The surface wave detection device according to claim 1. The vibration absorbing part is formed integrally with the propagating body, and is provided by applying unevenness processing to the target surface.
The surface wave detection device according to claim 1. the propagating body further has a first side surface and a second side surface facing in opposite directions to each other, and a rear surface located behind the propagating surface;
the first rib includes a first major surface facing in the same direction as the propagation surface;
the second rib includes a second major surface facing in the same direction as the propagation surface;
The first side surface is connected to the outer edge of the first main surface,
The second side surface is connected to the outer edge of the second main surface,
The target surface includes at least one of the first side surface, the second side surface, the back surface, the first main surface and the second main surface,
The surface wave detection device according to any one of claims 1 to 3. The back surface has a strip shape extending in the predetermined direction,
the propagating body has a third rib and a fourth rib projecting in the direction in which the back surface faces and extending in the predetermined direction;
The third rib and the fourth rib face each other across the back surface in the width direction of the back surface,
5. The surface wave detection device according to claim 4. Each base end portion of the first rib and the second rib is formed with a curved surface connected to the propagation surface,
The surface wave detection device according to any one of claims 1 to 5. the distance between the first rib and the second rib is substantially equal to the width of the piezoelectric element;
The surface wave detection device according to any one of claims 1 to 6. a surface wave detection device according to any one of claims 1 to 7;
a detection unit that detects the surface position of the liquid in which the propagating body is immersed, based on the propagation time of the surface wave detected by the piezoelectric element;
Liquid level detector. a surface wave detection device according to any one of claims 1 to 7;
a specifying unit that specifies the type of liquid in which the propagating body is immersed, based on the propagation time of the surface wave detected by the piezoelectric element;
Liquid type identification device. a surface wave detection device according to any one of claims 1 to 7;
a detection unit that detects the concentration of the solution in which the propagating body is immersed, based on the propagation time of the surface wave detected by the piezoelectric element;
Solution concentration detector. a surface wave detection device according to any one of claims 1 to 7;
a detection unit that detects droplets adhering to the propagation surface based on the propagation time of the surface wave detected by the piezoelectric element;
Droplet detector.

Images