Surface wave detector, liquid surface position detector, liquid type specification device, solution concentration detector, and droplet detector

Abstract

To provide a surface wave detector which can downsize a propagation body while securing the propagation distance of a surface wave, and a liquid surface position detector, a liquid type specification device, a solution concentration detector, and a droplet detector which have the surface wave detector.SOLUTION: A surface wave detector 1 includes: a propagation body 10 having a propagation surface 11 in which a surface wave propagates and being longer in a Z-direction (a predetermined axial direction); and a piezo-electric element 30 for applying a vibration to the propagation body 10 to generate a surface wave and detecting a surface wave which propagated from a base end 11p to a top end 11t of the propagation surface 11 and has reflected by the top end 11t. The propagation surface 11 has a shape including an inclined surface inclined with respect to the Z-direction. The distance from the base end 11p to the top end 11t along the shape of the propagation surface 11 is longer than the distance from the base end 11p to the top end 11t in the Z-direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a surface wave detection device, and a liquid level position detection device, a liquid type identification device, a solution concentration detection device, and a liquid droplet detection device each including the surface wave detection device. [Background technology]

[0002] For example, Patent Documents 1 and 2 disclose surface wave detection devices that apply vibration to a propagating body to generate surface waves and detect the reflected surface waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-68840 [Patent Document 2] JP 2023-101041 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the devices described in Patent Documents 1 and 2, there is a risk that the propagation medium will be relatively long in order to increase the propagation distance of the surface wave.

[0005] The present disclosure has been made in consideration of the above-mentioned situation, and aims to provide a surface wave detection device that enables the propagation body to be miniaturized while ensuring the propagation distance of the surface wave, as well as a liquid level position detection device, a liquid type identification device, a solution concentration detection device, and a droplet detection device that are equipped with the same. [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 disclosure comprises: a propagating body having a propagation surface along which a surface wave propagates and elongated in a predetermined axial direction; a piezoelectric element that applies vibration to the propagating body to generate the surface wave, and detects the surface wave that propagates from a base end of the propagation surface to a tip end and is reflected at the tip end; the propagation surface has a shape including an inclined surface inclined with respect to the axial direction, The distance from the base end to the tip end along the shape of the propagation surface is longer than the distance from the base end to the tip end in the axial direction.

[0007] In order to achieve the above object, a liquid level detection device according to a second aspect of the present disclosure includes: The surface wave detection device; and a detection unit that detects the liquid level of the liquid in which the propagating body is immersed based on the propagation time of the surface wave detected by the piezoelectric element.

[0008] In order to achieve the above object, a liquid type identification device according to a third aspect of the present disclosure comprises: The surface wave detection device; and an identification unit that identifies 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.

[0009] In order to achieve the above object, a solution concentration detection device according to a fourth aspect of the present disclosure comprises: The surface wave detection device; and 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.

[0010] In order to achieve the above object, a droplet detection device according to a fifth aspect of the present disclosure includes: The surface wave detection device; and 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. Effect of the Invention

[0011] According to the present disclosure, it is possible to reduce the size of the propagating body while ensuring the propagation distance of the surface wave. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a side view of a surface wave detecting device according to an embodiment of the present disclosure together with a schematic diagram of a control unit. [Diagram 2] 2 is a cross-sectional view of the propagation body in the embodiment taken along line AA in FIG. 1 . [Diagram 3] 1A and 1B are diagrams for explaining an experiment on the transmittance of a surface wave on a curved surface formed on a propagation surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of the present disclosure will be described with reference to the drawings.

[0014] As shown in FIG. 1, the surface wave detecting device 1 includes a propagating body 10, an element receiving portion 20, and a piezoelectric element 30.

[0015] 1 and 2, the configuration of the surface wave detecting device 1 may be described using a Z axis extending in the longitudinal direction of the propagating body 10, an X axis perpendicular to the Z axis and extending in the width direction of a propagation surface 11 (described later), and a Y axis perpendicular to the Z and X axes. The direction in which the arrows of the X, Y, and Z axes point is defined as the + (plus) direction, and the opposite direction is defined as the - (minus) direction. The -X direction corresponds to the front direction of the paper in FIG. 1, and the +X direction corresponds to the back direction of the paper in FIG. 1.

[0016] Fig. 1 is a side view of the surface wave detecting device 1 seen from the -X direction, together with a schematic diagram of the control unit 2. In Fig. 1, configuration that cannot be seen from a first side surface 13 of the propagating body 10 is shown partially by dashed lines. Fig. 2 is a cross-sectional view of the propagating body 10 taken along line AA shown in Fig. 1.

[0017] The propagating body 10 has a propagating surface 11 along which a surface wave described later propagates, and has an elongated shape in the Z direction (predetermined axial direction). The propagating body 10 is made of, for example, a synthetic resin such as PPS (polyphenylene sulfide).

[0018] The propagating body 10 is formed in a generally quadrangular prism shape. As shown in Fig. 2, the propagating body 10 has a generally 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 rib R2, a third rib R3, and a fourth rib R4. The propagating body 10 also has a bottom surface 15 shown in Fig. 1.

[0019] Although not shown, when viewed from the front direction (-Y direction), the propagation surface 11 has a band shape that has a width in the X direction and extends in the Z direction. The propagation surface 11 has a base end 11p located on the piezoelectric element 30 side, and a tip 11t. The tip 11t of the propagation surface 11 functions as a reflecting section that reflects the surface wave. The propagation surface 11 further has a first flat surface 111 that includes the base end 11p, and a second flat surface 112 that includes the tip 11t. The first flat surface 111 and the second flat surface 112 are surfaces parallel to the ZX plane.

[0020] As shown by the dashed line in FIG. 1, the propagation surface 11 has a shape including an inclined surface inclined with respect to the Z direction. As a result, the distance from the base end 11p to the tip 11t along the shape of the propagation surface 11 is longer than the distance in the Z direction from the front base end 11p to the tip 11t. In other words, when the length of the entire propagation body 10 in the Z direction is constant, the propagation surface 11 including the inclined surface as described above can increase the propagation distance of the surface wave compared to the comparative example in which the propagation surface is formed as a flat surface parallel to the ZX plane. Therefore, the propagation surface 11 having the above shape can reduce the size of the propagation body 10 (shorten the propagation body 10 in the Z direction) while ensuring the propagation distance of the surface wave.

[0021] In this embodiment, the inclined surface included in the propagation surface 11 is a curved surface, and the propagation surface 11 is curved. As an example, the cross-sectional shape of the propagation surface 11 cut by a surface parallel to the YZ plane is curved like a sine wave that increases and decreases in the +Y direction and the -Y direction. The shape of the propagation surface 11 is arbitrary as long as it satisfies the condition that "the distance from the base end 11p to the tip 11t along the shape of the propagation surface 11 is longer than the distance from the base end 11p to the tip 11t in the Z direction." For example, the propagation surface 11 may be formed to include a plurality of flat inclined surfaces and may be zigzag-shaped. However, in order to reduce unnecessary reflection of the surface wave, it is preferable that the propagation surface 11 is configured to include a continuous curved surface.

[0022] In this embodiment, the propagation surface 11 is curved at a portion between the first flat surface 111 and the second flat surface 112. FIG. 3 shows the results of an experiment conducted to investigate how the curved surface constituting the curved portion of the propagation surface 11 propagates a surface wave. The schematic diagram at the top of FIG. 3 is a simple model of a propagating body having one curved surface. The radius of curvature of the curved surface is r, and the wavelength of the surface wave is λ. The graph at the bottom of FIG. 3 shows the results of the experiment, with the vertical axis representing the transmittance of the surface wave at the curved surface and the horizontal axis representing the value of r / λ. If the transmittance is 1.0, it means that the surface wave propagates through the curved surface without being reflected by the curved surface. From the graph, it can be seen that if r / λ is less than 1.5, a part of the surface wave is reflected by the curved surface. On the other hand, if r / λ is 1.5 or more, the transmittance of the surface wave at the curved surface approaches 1.0, and the surface wave is efficiently propagated. Considering this, in this embodiment, the radius of curvature of the curved surface constituting the curved portion of the propagation surface 11 is set to 1.5 times or more the wavelength of the surface wave (r≧1.5λ). It is more preferable to set the radius of curvature of the curved surface to 2 times or more the wavelength of the surface wave (r≧2λ), since the transmittance of the surface wave at the curved surface can be regarded as 1.0. Furthermore, in consideration of efficiently propagating the surface wave over the entire propagation surface 11, it is preferable that the length in the Z direction of each of the first flat surface 111 and the second flat surface 112 is 1 time or more the wavelength of the surface wave.

[0023] The back surface 12 is located on the opposite side of the propagation surface 11 of the propagating body 10. The back surface 12 also has a strip shape extending in the Z direction while having a width in the X direction. As shown in FIG. 1, the propagating body 10 has a groove 12a recessed from the back surface 12 toward the propagation surface 11.

[0024] As shown in Fig. 2, 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. As shown in Fig. 1, the bottom surface 15 is an inclined surface that connects the tip 11t of the propagation surface 11 and the back surface 12. The bottom surface 15 forms an acute angle with the tip 11t of the propagation surface 11, and forms an obtuse angle with the back surface 12.

[0025] 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 and extend in the Z direction. The first rib R1 and the second rib R2 protrude from the propagation surface 11 in the front direction (-Y direction) of the propagation surface 11. Specifically, the first rib R1 and the second rib R2 protrude further in the -Y direction than the portion of the propagation surface 11 located furthest in the -Y direction. The first rib R1 and the second rib R2 can suppress the surface wave propagating on the propagation surface 11 from diffusing in the lateral direction, thereby suppressing a decrease in the propagation efficiency of the surface wave. As a result, a decrease in the signal-to-noise ratio of the surface wave detected by the piezoelectric element 30 can be suppressed.

[0026] In this embodiment, the first rib R1 and the second rib R2 have the same height in the -Y direction. The height of the first rib R1 and the second rib R2 from the propagation surface 11 is preferably set to be equal to or greater than the wavelength of the surface wave. The distance between the first rib R1 and the second rib R2 is set to be substantially equal to (including exactly equal to) the width of the piezoelectric element 30. This configuration makes it possible to suppress the generation of unnecessary surface waves in areas other than the propagation surface 11.

[0027] 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 and extend in the Z direction. The third rib R3 and the fourth rib R4 protrude in the +Y direction relative to the back surface 12. By providing the third rib R3 and the fourth rib R4 in addition to the first rib R1 and the second rib R2, the second moment of area of ​​the propagating body 10 can be improved and the resistance to vibration resonance can be improved. The heights of the third rib R3 and the fourth rib R4 (height from the back surface 12 in the +Y direction) can be set arbitrarily according to the design.

[0028] 1, the element accommodating section 20 is located in the +Z 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 is formed in a tubular shape (for example, a cylindrical shape) having an internal space for accommodating the piezoelectric element 30. The element accommodating section 20 has a flange 21 at a portion connected to the propagating body 10.

[0029] The piezoelectric element 30 applies vibration to the propagating body 10, and generates ultrasonic waves in the propagating body 10. In this embodiment, the piezoelectric element 30 applies vibration to the propagating body 10 to generate surface waves, and detects the surface waves that propagate from the base end 11p of the propagating surface 11 to the tip 11t and are reflected at the tip 11t. The piezoelectric element 30 is composed of a known ultrasonic transducer. The piezoelectric element 30 generates surface waves on the propagating surface 11 of the propagating body 10 as ultrasonic waves, and generates internal propagating waves inside the propagating body 10. The piezoelectric element 30 detects the surface waves reflected at the tip 11t of the propagating surface 11 and the internal propagating waves reflected at the groove 12a, and outputs a detection signal (voltage signal) indicating the detection result. For example, the surface waves are Rayleigh waves in air and Schultz waves in liquid. The surface waves may be leaky Rayleigh waves, shear-wave type surface acoustic waves (SH-SAW), etc. The internal propagating wave may be a transverse wave or the like.

[0030] The piezoelectric element 30 is electrically connected to the control unit 2. For example, a cap having a coupler is provided in the element housing unit 20. When an external device having the control unit 2 is connected to an output terminal provided in the coupler, the external device and the output terminal are electrically connected. Inside the cap, a PCB (Printed Circuit Board) (not shown) is housed, which is electrically connected to the piezoelectric element 30 and each of the output terminals and on which a transmission circuit, a reception circuit, etc. are formed. The transmission circuit 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, a surface wave and an internal propagation wave are generated in the propagating body 10. The reception circuit receives detection signals indicating the reflected surface wave and the reflected internal propagation wave from the piezoelectric element 30 and supplies them to the control unit 2.

[0031] The control unit 2 is composed of, for example, a microcomputer and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The control unit 2 measures the propagation time (propagation period) of the surface wave, which is the time from when the piezoelectric element 30 is driven to generate vibration in the propagating body 10 to when the surface wave is reflected by the tip 11t of the propagation surface 11 and input to the piezoelectric element 30.

[0032] An example of various applications of the device including the surface wave detection device 1 and the control unit 2 described above will be described. The device can be applied to a liquid level position detection device, a liquid type identification device, a solution concentration detection device, a liquid droplet detection device, etc. The configuration and principle of these are described in detail in (i) JP 2022-68840 A by the same applicant as the present application, and (ii) JP 2023-101041 A, whose applicant includes the same applicant as the present application. Therefore, the main points of each device will be described in order below.

[0033] (Liquid level detection device) The liquid level detection device includes a surface wave detection device 1 and a control unit 2 (detection unit) that detects the liquid level of the liquid in which the propagating body 10 is immersed based on the propagation time of the surface wave detected by the piezoelectric element 30. The speed at which the surface wave travels on the propagating body 10 (propagation surface 11) slows down in the portion of the propagating body 10 that is immersed in the liquid. Therefore, the higher the liquid level is, the longer the propagation time of the surface wave becomes. Using this characteristic, the control unit 2 (detection unit) measures the propagation time of the surface wave and detects the liquid level position by referring to data previously stored in ROM that indicates the relationship between the propagation time of the surface wave and the liquid level position.

[0034] (Liquid type identification device) The liquid type identifying device includes a control unit 2 (identification unit) that identifies the type of liquid in which the propagating body 10 is immersed based on the propagation time of the surface wave detected by the piezoelectric element 30. The propagation speed of the surface wave when at least the propagation surface 11 of the propagating body 10 is entirely immersed in liquid varies depending on the type of liquid. Therefore, the relationship between the propagation speed of the surface wave when at least the propagation surface 11 of the propagating body 10 is entirely immersed in liquid and the type of liquid can be obtained by actual measurement, simulation, or the like. Using this characteristic, the control unit 2 (identification unit) measures the propagation time of the surface wave and identifies the type of liquid by referring to data previously stored in the ROM indicating the relationship between the propagation time of the surface wave and the type of liquid.

[0035] (Solution concentration detector) The solution concentration detector includes a surface wave detector 1 and a control unit 2 (detection unit) that detects the concentration of the solution in which the propagating body 10 is immersed based on the propagation time of the surface wave detected by the piezoelectric element 30. Surface waves have the property that the more concentrated the solution, the slower the speed at which they travel along the propagation surface 11. Using this property, the control unit 2 (detection unit) measures the propagation time of the surface wave and detects the concentration of the solution by referring to data previously stored in the ROM that indicates the relationship between the propagation time and the concentration of the solution.

[0036] (Droplet Detector) The liquid droplet detection device includes a surface wave detection device 1 and a control unit 2 (detection unit) that detects liquid droplets attached to a propagation surface 11 based on the propagation time of a surface wave detected by a piezoelectric element 30. When liquid droplets are attached to the propagation surface 11, the speed at which the surface wave travels along the propagation surface 11 becomes slower than when no liquid droplets are attached. Using this property, the control unit 2 (detection unit) measures the propagation time of the surface wave, and refers to data previously stored in a ROM indicating the relationship between the propagation time and the presence or absence of attached liquid droplets, to determine whether or not liquid droplets are attached to the propagation surface 11 (i.e., detects liquid droplets).

[0037] Since the above-mentioned various devices include the surface wave detection device 1, it is possible to miniaturize the propagating body 10 while ensuring the propagation distance of the surface wave, and as a result, it is possible to miniaturize the device. In addition, the first rib R1 and the second rib R2 can suppress a decrease in the propagation efficiency of the surface wave and suppress a decrease in the S / N ratio of the surface wave detected by the piezoelectric element 30, thereby improving the accuracy of detecting or identifying the target.

[0038] In any of the above devices, the control unit 2 may measure not only the propagation time of the surface wave, but also the propagation time (propagation period) of the internal propagation wave, which is the time from when the piezoelectric element 30 is driven to generate vibration in the propagating body 10 to when the internal propagating wave is reflected by the groove 12a and input to the piezoelectric element 30. The control unit 2 may then correct the propagation time of the surface wave, which has temperature dependency, based on the measured propagation time of the internal propagating wave. Since the internal propagating wave travels inside the propagating body 10, the value of the propagation time is determined without being affected by the external environment of the propagating body 10. By utilizing this characteristic, the control unit 2 can measure the propagation time of the internal propagating wave and obtain the temperature of the propagating body 10 by referring to data indicating the relationship between the propagation time of the internal propagating wave and the temperature of the propagating body 10, which is previously stored in the ROM.

[0039] 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.

[0040] The material of the propagating body 10 is arbitrary as long as it can propagate the surface wave well. For example, the resin used for the propagating body 10 is not limited to PPS, and it may be POM (polyacetal), PBT (polybutylene terephthalate), or the like. It is considered preferable that the propagating body 10 is made of resin, but it may be made of metal as long as it can propagate the surface wave well.

[0041] The surface waves and internally propagating waves may be of any type. In the above, an example has been described in which the surface waves and internally propagating waves are pulses (ultrasonic pulses) of ultrasonic waves (for example, sound waves of 20 KHz or higher), but the surface waves and internally propagating waves may be sound waves with a lower frequency than ultrasonic waves. In the above, an example has been described in which the piezoelectric element is a sliding element, but it may also be a longitudinal vibrator, etc.

[0042] In the above description, descriptions of well-known technical matters have been omitted as appropriate in order to facilitate understanding of the present disclosure. [Explanation of symbols]

[0043] 1... surface wave detection device, 2... control unit 10...Transmitting body 11...propagation surface, 11p...base end, 11t...tip, 111...first flat surface, 112...second flat surface 12...back surface, 12a...groove, 13...first side surface, 14...second side surface, 15...bottom surface R1~R4: 1st~4th rib 20: element receiving portion, 21: flange 30...Piezoelectric element

Claims

1. a propagating body having a propagation surface along which a surface wave propagates and elongated in a predetermined axial direction; a piezoelectric element that applies vibration to the propagating body to generate the surface wave, and detects the surface wave that propagates from a base end of the propagation surface to a tip end and is reflected at the tip end; the propagation surface has a shape including an inclined surface inclined with respect to the axial direction, a distance from the base end to the tip end along the shape of the propagation surface is longer than a distance from the base end to the tip end in the axial direction; Surface wave detector.

2. The inclined surface is a curved surface, and the propagation surface is curved.

2. The surface wave detection device according to claim 1.

3. The radius of curvature of the curved surface is 1.5 times or more the wavelength of the surface wave.

3. The surface wave detection device according to claim 2.

4. the propagation surface has a first flat surface including the base end and a second flat surface including the tip end, The propagation surface is curved at a portion between the first flat surface and the second flat surface, The length of each of the first flat surface and the second flat surface in the axial direction is equal to or greater than one time the wavelength of the surface wave.

4. The surface wave detection device according to claim 3.

5. the propagation body has a first rib and a second rib that face each other across the propagation surface in a width direction of the propagation surface and extend in the axial direction, The first rib and the second rib protrude beyond the propagation surface in a front direction of the propagation surface. The surface wave detection device according to any one of claims 1 to 4.

6. A surface wave detection device according to any one of claims 1 to 4, and a detection unit that detects a liquid level of the liquid in which the propagating body is immersed based on a propagation time of the surface wave detected by the piezoelectric element. Liquid level detection device.

7. A surface wave detection device according to any one of claims 1 to 4, and an identification unit that identifies a type of liquid in which the propagating body is immersed based on a propagation time of the surface wave detected by the piezoelectric element. Liquid type identification device.

8. A surface wave detection device according to any one of claims 1 to 4, and 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 detection device.

9. A surface wave detection device according to any one of claims 1 to 4, and a detection unit that detects droplets adhering to the propagation surface based on a propagation time of the surface wave detected by the piezoelectric element. Droplet detection device.

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