JP2023104128A - Surface wave detection device and liquid type identification device - Google Patents

Abstract

To provide a surface wave detection device and a liquid type identification device that can be miniaturized by shortening a surface wave propagation path as much as possible.SOLUTION: A surface wave detection device includes: a propagation body 10 immersed in liquid 4 and propagating ultrasonic vibrations; a piezoelectric element 30 for generating ultrasonic vibration in the propagating body 10; and a mounting portion 21b on which the piezoelectric element 30 is mounted. The propagation body 10 has a propagation surface 11 on which the surface wave Ws of ultrasonic vibration propagates, and a bottom surface 15 provided at a position facing the mounting portion 21b. The piezoelectric element 30 is configured to be capable of generating a surface wave Ws on the propagation surface 11 from the mounting portion 21b toward the bottom surface 15 and detecting the surface wave Ws reflected to the mounting portion 21b from the reflecting portion 11a provided on the bottom surface 15. The mounting portion 21b is provided with a recessed portion M recessed toward the bottom surface 15, and a vibration absorbing portion 17 is arranged in the recessed portion M, which is able to, among vibrations, absorb inner wall propagating wave Wi which propagates to inner wall portion 16a of the recessed portion M.SELECTED DRAWING: Figure 2

Description

The present invention relates to a surface wave detection device and a liquid type identification device.

For example, in Patent Literature 1, a piezoelectric element applies ultrasonic vibration to a propagating body immersed in a liquid to generate surface waves on the propagating surface of the propagating body and to generate internal propagation waves inside the propagating body, which are reflected Techniques for detecting surface waves and reflected internally propagating waves (that is, detecting the level of liquid contained in a container) are disclosed. In this case, the piezoelectric element is mounted on a mounting portion provided in an element housing portion that houses the piezoelectric element, and the propagating body reflects the surface wave by a reflecting portion provided at the bottom of the propagating body. The internal propagation wave is reflected by grooves provided in the .

JP 2016-138850 A

In the technique described in Patent Document 1, since the groove is formed in the middle of the propagating body so that the surface wave and the internal propagating wave do not overlap, the above-described The surface wave propagation path, which is the length to the lowest part of the propagating body on the side of the reflecting part, is lengthened to some extent to detect the surface position of the liquid contained in the container. However, when the depth of the container is not so deep, if the surface wave propagation path is long to some extent, it becomes difficult to accommodate the propagating body in the container. rice field.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface wave detection device and a liquid type identification device which can be miniaturized by shortening the surface wave propagation path as much as possible.

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 a liquid and propagates ultrasonic vibrations, and a piezoelectric element that causes the propagating body to generate the ultrasonic vibrations. and a mounting portion on which the piezoelectric element is mounted, wherein the propagating body comprises a propagating surface through which the surface wave of the ultrasonic vibration propagates, and a facing surface provided at a position facing the mounting portion. and a section, wherein the piezoelectric element generates the surface wave on the propagation surface from the mounting section toward the facing section, and transmits the surface wave from the reflecting section provided on the facing section to the mounting section. The receiving part is provided with a recessed part recessed toward the facing part, and the recessed part receives the ultrasonic vibration from the recessed part. A vibration absorbing portion capable of absorbing an inner wall propagating wave propagating to the inner wall portion of the portion is arranged.

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

According to the present invention, it is possible to provide a surface wave detection device and a liquid type identification device that can achieve the intended purpose and can be miniaturized by shortening the surface wave propagation path as much as possible.

1 is a schematic configuration diagram of a liquid level detection device according to a first embodiment of the present invention; FIG. FIG. 4 is a schematic cross-sectional view of a propagating body, an element accommodating portion, and a piezoelectric element according to the same embodiment; FIG. 4 is a front view of a propagating body and an element accommodating portion according to the same embodiment; AA sectional view of FIG. 3 (hatching is omitted). FIG. 4 is a schematic diagram showing waves input to a piezoelectric element when ultrasonic vibration is applied to a propagating body; FIG. 5 is a schematic configuration diagram of a liquid type identification device according to a second embodiment of the present invention; FIG. 3 is a cross-sectional view of a propagating body along a direction perpendicular to the propagating surface according to the third embodiment of the present invention (hatching is omitted);

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

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

Hereinafter, as shown in each figure, the Z-axis extending in the longitudinal direction of the propagating body 10, the Y-axis extending in the normal direction of 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 ultrasonic vibrations (ultrasonic waves) including surface waves 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. 4, 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, and a second side surface 14. 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 and 2, a concave portion 16 which is a part of a concave portion to be described later, and a vibration absorbing portion 17. As shown in FIG.

The propagation surface 11 is a main portion of the propagating body 10 through which the surface wave Ws propagates, and has a strip shape extending in the Z direction (predetermined 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 on which the surface wave Ws of the ultrasonic vibration propagates is oriented in the -Y direction, and the back surface 12 is oriented in the +Y direction. Propagation surface 11 and back surface 12 are parallel to the ZX plane. Note that FIG. 1 shows a side view of the propagating body 10 and the element accommodating portion 20 as seen from the -X direction. FIG. 2 is a cross-sectional view of the propagating body 10, the element accommodating portion 20, and the piezoelectric element 30 taken along a plane parallel to the YZ plane.

As shown in FIG. 4, the first side face 13 faces the -X direction and the second side face faces the +X direction. The first side surface 13 and the second side surface 14 are parallel to the YZ plane.

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. 4, 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. For example, the main surfaces of the first ribs R1 and the second ribs R2 (surfaces facing the -Y direction) are parallel to the propagation plane 11. As shown in FIG. 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 .

As shown in FIG. 4, the third rib R3 and the fourth rib R4 protrude in the direction in which the back surface 12 faces (+Y direction). 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. For example, main surfaces (surfaces facing the +Y direction) of the third ribs R3 and the fourth ribs R4 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 FIGS. 1 and 2, the bottom surface 15 is an inclined surface that connects the propagation surface 11 and the back surface 12, and is provided at a position that faces (faces) a mounting portion, which is provided in the element housing portion 20 and will be described later. be done. 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 bottom surface 15 positioned at the bottom of the propagating body 10 corresponds to a facing portion described in the claims to be described later.

As shown in FIG. 2, the recessed portion 16 is formed as a hollow hole that is recessed from the boundary portion between the propagating body 10 and the element accommodating portion 20 toward the bottom surface 15 . The concave portion 16 has four inner wall portions 16a each having a shape of an upright wall, a bottom wall portion 16b provided in the -Z direction of the concave portion 16 (on the side of the bottom surface 15 of the propagating body 10), and the inner wall portion 16a and the bottom wall portion 16b. and a cavity region 16c that is a region surrounded by .

The four inner wall portions 16a of the concave portion 16 (hollow portion described later) extending generally in the Z direction are composed of a pair of opposing surfaces P1 and P2 parallel to the propagation surface 11, another pair of opposing surfaces P3 orthogonal to the propagation surface 11, and P4. Of the pair of opposing surfaces P1 and P2, the opposing surface P1 is provided on the propagation surface 11 side (-Y direction), and the opposing surface P2 is provided on the back surface 12 side (+Y direction). Further, of the other pair of opposing surfaces P3 and P4, the opposing surface P3 is provided on the first side surface 13 side (−X direction), and the opposing surface P4 is provided on the second side surface 14 side (+X direction).

The vibration absorbing portion 17 is made of elastomer such as nitrile rubber and has a rectangular parallelepiped shape, and as shown in FIG. placed). The vibration absorber 17 absorbs ultrasonic vibrations (ultrasonic waves) generated in the propagating body 10 by driving the piezoelectric element 30, and absorbs the inner wall portions 16a (specifically, the four inner wall portions 16a) of the concave portion 16 (the concave portion). It has a function of absorbing inner wall propagating waves, which will be described later, propagating to the pair of opposing surfaces P1 and P2). The vibration absorbing portion 17 capable of absorbing the inner wall propagating wave is preferably arranged in the concave portion 16 (the hollow portion) so as to be immovable in the cavity region 16c.

Note that the vibration absorbing portion 17 here is arranged in the cavity region 16c (the recess) while being in contact with the four inner wall portions 16a and the bottom wall portion 16b provided in the recess 16 (the recess). However, in order to absorb the inner wall propagating wave, the vibration absorbing portion 17 is formed in the hollow region 16c ( above-mentioned hollow portion).

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

The disc portion 21 is connected to the propagating body 10 . The cylindrical body 22 has a hollow cylindrical shape with an outer diameter smaller than the outer diameter of the disc portion 21 and protrudes from the disc portion 21 in the +Z direction. That is, a hollow portion 22a is provided inside the tubular body 22 . Further, inside the disk portion 21 here, there is provided a space 21a that communicates with the hollow portion 22a and the hollow region 16c.

The cavity 21a has a first cavity H1 and a second cavity H2. The first cavity H1 is a hole having an opening width substantially equal to the opening width of the hollow portion 22a, and is arranged so as not to reach the boundary portion between the propagating body 10 and the element accommodating portion 20 in the Z direction. , is a portion that is hollowed out to a substantially middle portion of the disk portion 21 along the Z direction. The second cavity H2 is a hole having an opening width approximately equal to the opening width of the cavity region 16c, and extends from an approximately intermediate portion of the disc portion 21 along the Z direction to the boundary portion between the propagating body 10 and the disc portion 21. It is formed in the area leading to.

Here, the opening width of the cavity region 16c (second cavity H2) is narrower than the opening width of the cavity 22a (first cavity H1). The piezoelectric element 30 is placed on the mounting portion 21b, which is a flat surface formed at the boundary with the second space H2, so as to close the second space H2 (and the cavity region 16c). In addition, in the following description, the portion where the concave portion 16 and the second space H2 are combined will be referred to as a recessed portion M. As shown in FIG. That is, in the case of the present embodiment, the surface wave detection device 1 includes a mounting portion 21b on which the piezoelectric element 30 is mounted, and the mounting portion 21b includes a recess M recessed toward the bottom surface 15. is provided. A mounting groove 22b, which is a groove recessed toward the center of the cylindrical body 22 and in which the seal member 5 shown in cross section in FIG.

The piezoelectric element 30 vibrates the propagating body 10 via the disk portion 21 to generate ultrasonic waves (ultrasonic vibrations) in the propagating body 10 . Specifically, the piezoelectric element 30 generates a surface wave Ws as an ultrasonic wave on the propagation surface 11 from the mounting portion 21b toward the bottom surface 15, and the four inner walls provided in the propagation body 10 (recess M). An inner wall propagating wave Wi is generated on the pair of opposing surfaces P1 and P2 of the portion 16a. The piezoelectric element 30 is configured to be able to detect the surface wave Ws reflected by the reflecting portion 11a (that is, reflected from the reflecting portion 11a provided on the bottom surface 15 to the mounting portion 21b), and generates a detection signal ( voltage signal). In addition, since the piezoelectric element 30 here is configured to vibrate in the Y direction, the inner wall propagation wave Wi is not generated in the other pair of opposing surfaces P3 and P4 and the hollow region 16c. .

The piezoelectric element 30 is composed of a known ultrasonic transducer and has a rectangular parallelepiped shape. The piezoelectric element 30 mounted on the mounting portion 21b faces the propagating body 10 with the disc portion 21 interposed therebetween, and generates a surface wave Ws on the propagating surface 11. ) is provided so as to extend over the propagation surface 11 of the propagation body 10 . For example, the surface wave Ws is a Rayleigh wave in air and a Schulz wave in liquid 4 . Note that the surface wave Ws may be a leaky Rayleigh wave, a plate wave in which the entire medium vibrates, 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 inner wall propagating wave Wi. The receiving circuit of the PCB receives the detection signal of the reflected surface wave Ws from the piezoelectric element 30 and supplies it to the control section 2 . At this time, since the inner wall propagating wave Wi is absorbed by the vibration absorbing portion 17 , the receiving circuit of the PCB receives only the detection signal of the reflected surface wave Ws from the piezoelectric element 30 . After receiving the detection signal, the control unit 2 calculates the position (height) of the liquid surface 4a based on the detection signal.

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

Here, an example of a method of calculating the position of the liquid surface 4a will be described. FIG. 5 shows how the surface wave Ws propagating through the propagating body 10 is input to the piezoelectric element 30 after being reflected by generating the vibration W0. A time point t0 is a time point when the vibration W0 is generated in the propagating body 10 by driving the piezoelectric element 30 . The surface wave Ws and the inner wall propagating wave Wi propagate through the propagating body 10 due to the vibration W0. Time t1 is the time when the surface wave Ws is reflected by the reflecting portion 11a and is input to the piezoelectric element 30 . Here, since the inner wall propagating wave Wi is absorbed by the vibration absorbing portion 17 as described above, only the surface wave Ws reflected by the reflecting portion 11a is input to the piezoelectric element 30 . A period T1 is a surface wave propagation period T1 from time t0 to time t1.

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 T1 is. Using this characteristic, the control unit 2 measures the surface wave propagation period T1, 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 T1 and the position of the liquid surface 4a. and calculate the liquid surface position. The liquid surface position detection data may be configured using at least one of mathematical formulas and tables. Further, the liquid level detection device 100 may include a temperature sensor (not shown), and correct the temperature-dependent surface wave propagation period T1 based on the temperature detected by the temperature sensor. As the method for calculating the position of the liquid surface 4a and the method for correcting the temperature, known techniques can be used as appropriate.

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.

As described above, according to the present embodiment, the propagating body 10 has the propagating surface 11 through which the surface wave Ws of the ultrasonic vibration propagates, and the bottom surface 15 provided at a position facing the mounting portion 21b. The piezoelectric element 30 generates a surface wave Ws on the propagating surface 11 from the mounting portion 21b toward the bottom surface 15 and reflects the surface wave Ws from the reflecting portion 11a provided on the bottom surface 15 to the mounting portion 21b. The mounting portion 21b is provided with a recess M recessed toward the bottom surface 15, and the recess M receives ultrasonic vibrations from the inner wall portions 16a (a pair of opposing A vibration absorbing portion 17 capable of absorbing the inner wall propagating wave Wi propagating on the planes P1 and P2) is arranged.

Therefore, the length from the mounting portion 21b on which the piezoelectric element 30 is mounted to the bottom surface 15 positioned at the bottom of the propagating body 10 (that is, the surface wave propagation path) can be shortened as much as possible. Based only on the surface wave Ws propagating on the propagation surface 11, which is the path, the surface position of the liquid 4 contained in the not-so-deep container 3 can be calculated. Therefore, according to the present invention, it is possible to provide a surface wave detecting device that can be miniaturized by shortening the surface wave propagation path (that is, the length of the propagating body 10 along the Z direction) as much as possible.

Further, in the present embodiment, the vibration absorbing portion 17 is arranged in the recess M in contact with the pair of facing surfaces P1 and P2 of the inner wall portion 16a and the bottom wall portion 16b. are provided in the recessed portion M in contact with the three walls, so that the vibration absorbing portion 17 can be stably fixed and held.

(Second Embodiment) From now on, a liquid type identification device 200 according to a 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. 6, 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 T1. Specifically, the controller 2M identifies the type of the liquid 4 by referring to a data table in which the surface wave propagation period T1 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 T1 will be described below.

Since the surface wave propagation period T1 is inversely proportional to the surface wave propagation velocity, the surface wave propagation period T1 becomes shorter as the surface wave propagation velocity increases, while the surface wave propagation period T1 becomes longer as the surface wave propagation velocity decreases. . The surface wave propagation velocity when at least the propagation surface 11 of the propagating body 10 is entirely immersed in the liquid 4 is determined by the in-liquid sound velocity vl and density ρl unique to the liquid 4 . 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 T1 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 T1. 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 T1 means that the control unit 2M calculates the surface wave propagation velocity from the surface wave propagation period T1, 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 T1 and the type of the liquid 4 are associated. should be stored in

As described above, the liquid type identification device 200 uses the surface wave detection device 1 that can be miniaturized by shortening the surface wave propagation path as much as possible, and identifies the type of the liquid 4 based on the surface wave propagation period T1. can do. As described above, the surface wave propagation period T1 and the surface wave propagation velocity are temperature-dependent. may be corrected.

Since the liquid type identification device 200 according to the second embodiment includes the surface wave detection device 1 capable of generating detectable surface waves Ws, the liquid type can be identified. The description of the second embodiment is over.

In addition, this invention is not limited by the above embodiment and drawing. Modifications (including deletion of components) can be made as appropriate without changing the gist of the present invention.

In the first embodiment, the pair of opposing surfaces P1 and P2 are parallel to the propagation surface 11, and the other pair of opposing surfaces P3 and P4 are orthogonal to the propagation surface 11 (that is, the XY plane as shown in FIG. 4). The cross-sectional shape of the inner wall portion 16a along the XY plane was a substantially square shape), but as a third embodiment of this embodiment, the cross-sectional shape of the inner wall portion 16a along the XY plane is a rhombus. Even when the shaped propagating body 10 is applied, the same effect as in the first embodiment can be obtained. In this case, the inner wall portion 16a of the concave portion 16 (hollow portion M) is composed of four inner wall surfaces 16d non-parallel to the propagation surface 11, and the inner wall propagating wave Wi propagates to all the four inner wall surfaces 16d. The vibration absorbing portion 17 is arranged in the recess 16 (recess M) in contact with the four inner wall surfaces 16d (or the four inner wall surfaces 16d and the bottom wall portion 16b) provided non-parallel to the propagation surface 11. will be

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 .

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.

Any type of surface wave Ws can be used as long as the above method can detect the position of the liquid surface or specify the type of liquid. An example in which the surface wave Ws is a pulse (ultrasonic pulse) of an ultrasonic wave (for example, a sound wave of 20 KHz or higher) has been described above. may be sound waves.

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

REFERENCE SIGNS LIST 1 surface wave detector 2 controller 3 container 4 liquid 4a liquid surface 10 propagator 11 propagation surface 11a reflector 12 rear surface 13 first side surface 14 second side surface 15 bottom surface (facing portion)
16 concave portion 16a inner wall portion 16b bottom wall portion 16c cavity region 16d inner wall surface 17 vibration absorbing portion 20 element accommodating portion 21 disk portion 21a space 21b mounting portion 30 piezoelectric element 40 flange portion H1 first space H2 second Cavity M Recess P1, P2 Pair of opposing surfaces R1 First rib R2 Second rib R3 Third rib R4 Fourth rib Ws Surface wave Wi Internal wall propagating wave

Claims (7)

a propagating body that is immersed in a liquid and propagates ultrasonic vibrations;
a piezoelectric element that generates the ultrasonic vibration in the propagating body;
a mounting portion on which the piezoelectric element is mounted;
The propagating body is
a propagation surface on which the surface wave of the ultrasonic vibration propagates;
a facing portion provided at a position facing the mounting portion;
The piezoelectric element generates the surface wave on the propagating surface from the mounting portion toward the facing portion, and the surface wave reflected from the reflecting portion provided at the facing portion toward the mounting portion. configured to detect
The mounting portion is provided with a recessed portion that is recessed toward the facing portion,
A surface wave detecting device according to claim 1, wherein a vibration absorbing part capable of absorbing an inner wall propagating wave of said ultrasonic vibration propagating to an inner wall part of said recess is arranged in said recess. an inner wall portion of the recessed portion includes at least a pair of opposing surfaces parallel to the propagation surface;
2. The surface acoustic wave detecting device according to claim 1, wherein said vibration absorbing portion is arranged in said recess while being in contact with said pair of opposing surfaces. The inner wall portion of the recess is composed of four inner wall surfaces non-parallel to the propagation surface,
2. The surface wave detecting device according to claim 1, wherein said vibration absorbing portion is arranged in said recess while being in contact with said four inner wall surfaces. The recessed portion includes a bottom wall portion provided on the facing portion side,
3. The vibration absorbing portion is disposed in the recess while being in contact with the pair of opposing surfaces and the bottom wall portion, or the four inner wall surfaces and the bottom wall portion. The surface wave detection device according to claim 2 or 3. the propagation surface has a strip shape extending in a predetermined direction,
5. The propagator according to any one of claims 1 to 4, wherein 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. Surface wave detector. 6. The surface acoustic wave detector according to claim 5, wherein the first rib and the second rib face each other across the propagation surface in the width direction of the propagation surface. a surface wave detection device according to any one of claims 1 to 6;
and an identifying unit that identifies the type of the liquid based on the propagation time of the surface wave detected by the piezoelectric element.

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