JP2022115114A - Fixing structure of surface wave detection unit - Google Patents

Abstract

To provide fixing structure of a surface wave detection unit, the fixing structure having simple configuration and enabling a surface wave detection unit to be fixed to a mating component.SOLUTION: Fixing structure of a surface wave detection unit is provided, fixing a surface wave detection unit 1 to a fuel pump case 50 via a mounting member 60, the surface wave detection unit comprising a piezoelectric element 30 which generates a surface wave Ws by applying vibration to a propagating body 10 and detects the reflected surface wave Ws. The propagating body 10 has a non-propagating portion P which does not propagate the surface wave Ws. A guide portion 62 and an engagement portion 63 obtained by cutting out a part of the guide portion 62 is provided in the mounting member 60. A guided portion 16 guided by the guide portion 62, and latching means 17 having a latching portion 17a latched to the engagement portion 63 is provided in the non-propagating portion P.SELECTED DRAWING: Figure 9

Description

The present invention relates to a surface wave detection unit fixing structure for fixing the surface wave detection unit to a fixing member.

For example, Patent Literature 1 discloses a technique of generating surface waves by vibrating a propagating body immersed in liquid and detecting the reflected surface waves. According to the surface wave detection unit described in Patent Document 1, the surface position of the liquid can be detected based on the propagation time of the detected surface wave.

JP 2020-139852 A

By the way, it is desirable that the surface wave detection unit described in Patent Document 1 described above is fixed to a fuel pump case as a mating part, which is a mating part, with a simple structure. Regarding the detection unit, no mention is made of a fixing structure for fixing the surface wave detection unit to the fuel pump case.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing structure for a surface wave detection unit that can fix the surface wave detection unit to a mating component with a simple structure.

The present invention includes at least a propagating body that is immersed in a liquid and has a propagating portion that propagates surface waves, and a piezoelectric element that vibrates the propagating body to generate the surface waves and detect the reflected surface waves. a surface wave detection unit fixing structure for fixing the surface wave detection unit provided with the The propagating portion is fixed to the mating component using a predetermined fixing means.

Further, the present invention includes a propagating body that is immersed in a liquid and has a propagating portion that propagates surface waves, and a piezoelectric element that vibrates the propagating body to generate the surface waves and detect the reflected surface waves. A surface wave detection unit fixing structure for fixing at least the surface wave detection unit to a mating component via a mounting member, wherein the propagating body is a non-propagating body that does not propagate the surface wave. and the non-propagating portion is fixed to the mounting member using a predetermined fixing means.

Further, the present invention includes a propagating body that is immersed in a liquid and has a propagating portion that propagates surface waves, and a piezoelectric element that vibrates the propagating body to generate the surface waves and detect the reflected surface waves. A surface wave detection unit fixing structure for fixing a surface wave detection unit including at least the one of the mating part and the non-propagating portion is provided with a guide portion and an engaging portion obtained by cutting out a part of the guide portion, and the other is provided with a guided portion guided by the guide portion; and locking means having a locking portion that locks to the engaging portion.

Further, the present invention includes a propagating body that is immersed in a liquid and has a propagating portion that propagates surface waves, and a piezoelectric element that vibrates the propagating body to generate the surface waves and detect the reflected surface waves. A surface wave detection unit fixing structure for fixing at least the surface wave detection unit to a mating component via a mounting member, wherein the propagating body is a non-propagating body that does not propagate the surface wave. wherein one of the mounting member and the non-propagating portion is provided with a guide portion and an engaging portion obtained by cutting out a part of the guide portion, and the other is provided with a guide portion guided by the guide portion. It is characterized by providing a guide portion and locking means having a locking portion that locks onto the engaging portion.

Further, the present invention is characterized in that the surface wave detection unit is fixed to the mating component so that the propagating portion faces the mating component.

Further, according to the present invention, the surface wave detection unit is fixed to the mounting member so that the propagating portion faces the mounting member.

In the present invention, the non-propagating portion is configured as a pair of peripheral wall portions facing each other along the longitudinal direction of the propagating body, and the guide portion is configured as a pair of hook portions extending along the longitudinal direction, The locking means includes a pair of elastic pieces respectively provided corresponding to the pair of hooks, and the pair of elastic pieces are provided to the pair of engaging portions respectively provided to the pair of hooks. It is characterized in that the pair of locking portions that are connected to each other are locked.

Further, the present invention is characterized in that the locking means is positioned on a virtual plane that passes through the center of gravity of the surface wave detection unit and is perpendicular to the longitudinal direction.

According to the present invention, it is possible to provide a fixing structure for a surface wave detection unit that achieves the intended purpose and allows the surface wave detection unit to be fixed to a mating component with a simple configuration.

1 is a schematic configuration diagram of a liquid level detection device according to an 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 the piezoelectric element when vibration is applied to the same propagating body; The figure which shows the state before fixing the surface wave detection unit by the same embodiment to an attachment member. BB sectional view of FIG. The side view of the attachment member by the same embodiment. The figure which shows the state after fixing the surface wave detection unit by the same embodiment to the mounting member. The figure which shows the state after fixing the surface wave detection unit by the modification 2 of the same embodiment to the other party component. The figure which shows the state after fixing the surface wave detection unit by the modification 4 of the same embodiment to the mounting member. The figure which shows the state after fixing the surface wave detection unit by the modification 6 of the same embodiment to the mounting member. The figure which shows the state after fixing the surface wave detection unit by the modification 7 of the same embodiment to the other party component.

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

In FIG. 1, 1 is a surface wave detection unit and 2 is a control section. The surface wave detection unit 1 and the control section 2 constitute a liquid level detection device 100 . The liquid level detection device 100 detects the position of the liquid level 3a (hereinafter also referred to as the liquid level position) of the liquid 3 contained in a fuel tank (not shown) mounted on the vehicle. As the amount of the liquid 3 increases or decreases, the liquid surface 3a rises and falls.

The surface wave detection unit 1 includes a propagating body 10 , an element housing portion 20 , a piezoelectric element 30 and a flange portion 40 .

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-axis and Z-axis are used. , the configuration of the surface wave detection unit 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 waves including surface waves Ws, which will be described later. The propagating body 10 is made of 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 serving as a propagating portion, a back surface portion 12, a pair of side surface portions 13 and 14, a bottom surface portion 15, and a second propagating portion. It has a first rib R1, a second rib R2, a third rib R3, and a fourth rib R4. In this case, the back surface portion 12, the pair of side surface portions 13 and 14, the first rib R1, the second rib R2, the third rib R3, the fourth rib R4, and the third and third ribs to be described later, which are provided on the propagating body 10, are provided. The fourth opposing surface is configured as a non-propagating portion (non-propagating portion) P that does not propagate the surface wave Ws.

The propagation surface 11 is the main portion of the propagating body 10 for propagating the surface wave Ws, and has a strip shape extending in the 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 portion 12 is located on the opposite side of the propagating surface 11 of the propagating body 10, as shown in FIGS. The back surface portion 12 also has a strip shape extending in the Z direction. The propagation surface 11 faces the -Y direction, and the back surface portion 12 faces the +Y direction. The propagation surface 11 and the back surface portion 12 are parallel to the ZX plane. As shown in FIGS. 1 and 2, the propagation body 10 is formed with a groove 12a recessed from the rear surface portion 12 toward the propagation surface 11. As shown in FIGS. 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 side portion 13 faces the -X direction, and the side portion 14 faces the +X direction. The pair of side surface portions 13 and 14, which are the non-propagating portions P, are parallel to the YZ plane, and are configured as a pair of peripheral wall portions facing each other along the longitudinal direction (Z direction) of the propagating body 10 so as to sandwich the propagating surface 11. are facing each other. Further, in this case, the pair of side surface portions 13 and 14, which are the non-propagating portions P, have a guided portion 16 that is guided by a guide portion described later and an engagement portion 17a that engages with an engagement portion described later. A stopping means 17 is integrally provided.

The guided portion 16 is configured as a pair of overhanging portions provided so as to overhang the pair of side surface portions 13 and 14 on the upper side of the propagating body 10, and is referred to as a third and third guiding portion to be described later. It protrudes outward from 14 locations on the side surface portion 13 on the 4-rib side (+Y direction side).

The locking means 17 protrudes outward in a substantially L-shape from 14 locations on the side surface portion 13 on the side of the third and fourth ribs (+Y direction side), and has an elastic piece 17b having a locking portion 17a. and a connecting portion 17c. The elastic piece 17b has a cantilever shape, and a locking portion 17a having a locking claw shape is provided on the free end side thereof. The side opposite to the free end side is connected to the side portions 13 and 14 through the connecting portion 17c.

The bottom surface portion 15 is an inclined surface that connects the propagation surface 11 and the back surface portion 12, as shown in FIGS. The bottom surface portion 15 forms an acute angle with the propagation surface 11 and forms an obtuse angle with the back surface portion 12 . The tip of the propagating body 10 has a tapered shape due to the bottom portion 15 . Due to the inclination of the bottom surface portion 15, the surface wave Ws propagating on the propagation surface 11 in the −Z direction can be suppressed from going around the back surface portion 12, reflected by the reflecting portion 11a of the propagating body 10, and reflected by the propagation surface 11 again. 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. 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 portion 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. As shown in FIG. 4 , the third rib R3 and the fourth rib R4 face each other with the back surface portion 12 interposed therebetween in the width direction (X direction) of the back surface portion 12 . 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 portion 12 . For example, the angle between the inner surface of the third rib R3 (the surface facing the +X direction) and the third facing surface So3 facing the fourth rib R4 and the back surface portion 12 is set to be a right angle. For example, the angle between the inner surface of the fourth rib R4 (the surface facing the -X direction) and the fourth opposing surface So4 facing the third rib R3 and the back surface portion 12 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 mechanical vibration can be improved. . The height of the third rib R3 and the fourth rib R4 (the height from the back surface portion 12 in the +Y direction) can be arbitrarily set according to the design.

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 cylinder 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. 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. Therefore, one end (the right end in FIG. 2) of the piezoelectric element 30 faces the propagating body 10. 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 3 . 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 that is attached to the fuel tank with 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 3 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 3a 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 3a will be described. FIG. 5 shows how the internal propagation wave Wi and the surface wave Ws propagating through the propagating body 10 are input to the piezoelectric element 30 after being reflected by generating the vibration W0. A time point t0 is a time point when the vibration W0 is generated in the propagating body 10 by driving the piezoelectric element 30 . The propagating body 10 propagates the surface wave Ws and the internal propagating wave Wi 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 3 . Therefore, the higher the liquid surface 3a 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 3a. and calculate the liquid level 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 portion of the propagating body 10 immersed in the liquid 3 . 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 3a 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, a pointer, or the like.

The liquid level detection device 100 is configured by the above components. Next, a surface wave detection unit for fixing the surface wave detection unit 1 constituting the main part of the liquid level detection device 100 to the fuel pump case (mating part) 50 via the mounting member 60. 1 will be described with reference to FIGS. 6 to 9. FIG.

A fuel pump case 50 installed in the fuel tank is made of a synthetic resin such as POM (polyacetal) and formed into a hollow cylindrical shape, and a fuel pump (not shown) is accommodated therein. Although detailed illustration is omitted here, it is assumed that the fuel pump case 50 is fixed to the mounting member 60 using an appropriate fixing structure.

The mounting member 60 is made of synthetic resin such as POM (polyacetal) and has a substantially rectangular shape when viewed from the front, and has a main body portion 61 constituting a main portion thereof. The surface of the body portion 61 facing the surface wave detection unit 1 side is generally flat, and the surface of the body portion 61 that faces the fuel pump case 50, which is the opposite side of the surface, corresponds to the outer peripheral curved surface of the fuel pump case 50. It has a curved shape. In some cases, the surface of the body portion 61 facing the fuel pump case 50 may be a flat surface.

A guide portion 62 for guiding the surface wave detection unit 1 (the guided portion 16 and the engaging means 17 provided in the surface wave detection unit 1) to the body portion 61 of the mounting member 60, and the guide portion 62 An engaging portion 63 with a part cut away is provided. The guide portions 62 are formed on both end sides of the main body portion 61 so as to be symmetrical with respect to an imaginary line L that divides (bisects) the mounting member 60 into right and left, for example. ) as a pair of hooks consisting of hook-shaped grooves extending along.

The engaging portion 63 is provided for each pair of guide portions 62 formed on both end sides of the main body portion 61 . The engaging portion 63 is formed in each of the pair of guide portions 62 as a missing portion obtained by missing a part of the guide portion 62, and is provided at a line-symmetrical position with respect to the imaginary line L. .

Here, focusing on the pair of guided portions 16 and the pair of locking means 17 formed on the propagating body 10 and the pair of guide portions 62 formed on the mounting member 60, the pair of guided portions 16 , the pair of locking means 17 (the pair of elastic pieces 17b) are provided corresponding to the pair of guide portions 62, respectively.

When attaching the surface wave detecting unit 1 to the mounting member 60, the mounting member 60 and the surface wave are mounted so that the pair of guide portions 62 and the pair of guided portions 16 (the pair of locking means 17) are vertically opposed to each other. The detection unit 1 is positioned, and then, for example, the mounting member 60 (to which the fuel pump case 50 is fixed) is translated upward (in the Z direction), so that the pair of locking means 17 are first moved to the pair of guide portions. 62, and by further parallelly moving the mounting member 60 upward (in the Z direction) from this state, the pair of guided portions 16 in addition to the pair of locking means 17 are moved to the pair of guide portions 62, respectively. be guided.

At this time, the pair of locking portions 17a are guided by the pair of guide portions 62 in a state of bending deformation in the +Y direction. A pair of engaging portions 17a provided on the pair of elastic pieces 17b are respectively engaged with a pair of engaging portions 63 provided on the pair of guide portions 62 by the elastic restoring force of the portions 17a. The guided portion 16 is guided by the upper end sides of the pair of guide portions 62 . As described above, the surface wave detection unit 1 can be fixed to the mounting member 60 so that the back surface portion 12 of the propagating body 10 faces the main body portion 61 (mounting member 60). Further, when the surface wave detection unit 1 is fixed to the mounting member 60, the locking means 17 (at least a part of the locking portion 17a, the elastic piece 17b, and the connecting portion 17c) is used to increase vibration resistance. is preferably positioned on a virtual plane H passing through the center of gravity position C of the surface wave detection unit 1 and substantially perpendicular to the longitudinal direction (Z direction) of the propagating body 10 .

As described above, in the present embodiment, the surface wave detection unit fixing structure for fixing the surface wave detection unit 1 including at least the propagating body 10 and the piezoelectric element 30 to the fuel pump case 50 via the mounting member 60 is provided. The propagating body 10 includes side portions 13 and 14 (non-propagating portions P) that do not propagate the surface wave Ws. The engaging portion 63 is provided, and the side portions 13 and 14 (non-propagating portions P) have the guided portion 16 guided by the guide portion 62 and the engaging portion 17a that is engaged with the engaging portion 63. 17 are provided.

Therefore, the surface wave can be detected by a relatively simple structure using the guide portion 62 formed with the engaging portion 63, the guided portion 16, and the locking means 17 without using a new fixing tool such as a screw. It is possible to provide a fixing structure for the surface wave detection unit that allows the unit 1 to be fixed to the fuel pump case 50 as a mating component via the mounting member 60 . Further, by attaching the mounting member 60 to the non-propagating portion P (side surfaces 13 and 14) excluding the propagation surface 11 through which the surface wave Ws propagates, the non-propagating portion P (side surfaces 13 and 14) is free from noise and There is an advantage that the SN ratio (signal-noise ratio) of the signal due to the surface wave Ws can be improved because the unwanted propagation wave is not propagated.

The present invention is not limited by the above embodiments and drawings. Modifications (including deletion of components) can be made as appropriate without changing the gist of the present invention. For example, the modified examples shown below can be mentioned.

(Modification 1)
For example, in the above-described embodiment, the mounting member 60 is provided with the guide portion 62 and the engaging portion 63 obtained by cutting out a part of the guide portion 62, and the non-propagating portion P (the side portions 13 and 14) is provided with the guide portion 62, and locking means 17 having a locking portion 17a that locks to the engaging portion 63 are provided. 13, 14) are provided with a guide portion and an engagement portion obtained by cutting out a part of the guide portion, and the mounting member 60 includes a guided portion guided by the guide portion and a portion to be guided by the engagement portion. A locking means having a locking portion for engaging may be provided.

(Modification 2)
For example, in the above-described embodiment, the surface wave detection unit 1 is fixed to the fuel pump case 50 via the mounting member 60. You can fix it directly. FIG. 10 shows a state in which the surface wave detection unit 1 according to Modification 2 is fixed to the fuel pump case 50 .

That is, in Modification 2, for example, a flat facing portion 51 facing the propagating body 10 is provided on a part of the outer peripheral surface of the fuel pump case 50 formed in a cylindrical shape, and the facing portion 51 (fuel pump case 50), the guide portion 62 adopted in the above-described embodiment and the engagement portion 63 obtained by cutting out a part of the guide portion 62 are provided, and the non-propagating portion P (side portions 13, 14) is provided with a guide portion 62, and locking means 17 having a locking portion 17a that locks onto the engaging portion 63 are provided. Even if it is configured in this way, it is possible to obtain the same effects as those of the above-described embodiment.

(Modification 3)
For example, in Modification 2 described above, the opposing portion 51 (fuel pump case 50) is provided with a guide portion 62 and an engaging portion 63 obtained by cutting out a part of the guide portion 62, and the non-propagating portion P (side portion 13 , 14) are provided with the guided portion 16 guided by the guide portion 62 and the engaging means 17 having the engaging portion 17a which engages with the engaging portion 63. The non-propagating portion P (side portions 13 and 14) is provided with a guide portion and an engagement portion obtained by cutting out a part of the guide portion, and the opposite portion 51 (fuel pump case 50) is guided by the guide portion. and an engaging means having an engaging portion that engages with the engaging portion.

(Modification 4)
For example, in the above-described embodiment, the mounting member 60 is provided with the guide portion 62 and the engaging portion 63 obtained by cutting out a part of the guide portion 62, and the non-propagating portion P (the side portions 13 and 14) is provided with the guide portion 62, and locking means 17 having a locking portion 17a that locks onto the engaging portion 63. Modification 4 of this embodiment is shown in FIG. As shown, the guided portion 16, the locking means 17, and the guide portion 62 having the engaging portion 63 are eliminated, and the non-propagating portion P (third The rib R3 and the fourth rib R4) may be joined (fixed) to the body portion 61 (mounting member 60).

(Modification 5)
For example, in Modification 4 described above, the non-propagating portion P (the third rib R3 and the fourth rib R4) is fixed to the mounting member 60 (mounted to the fuel pump case 50) via the adhesive 70. However, the mounting member 60 (without the guide portion 62 and the engaging portion 63) adopted in Modification 4 is abolished, and the non-propagating portion P (the third rib R3, the fourth rib R4) is provided with a predetermined It may be directly joined (fixed) to the fuel pump case 50 using an adhesive 70 as fixing means. In this case, the non-propagating portion P (the third rib R3 and the fourth rib R4) adopts a method of being fixed to the facing portion 51 having a flat surface shape via the adhesive 70 as in the modification 2 described above. can do.

(Modification 6)
For example, in the above-described embodiment, the surface wave detection unit 1 is fixed to the mounting member 60 so that the back surface portion 12 of the propagating body 10 faces the main body portion 61 (mounting member 60). As a modification 6, the surface wave detecting unit 1 may be fixed to the mounting member 60 so that the propagation surface 11 of the propagating body 10 faces the main body 61 (mounting member 60) as shown in FIG. . That is, the surface wave detection unit 1 is reversed (rotated 180 degrees) from the mounting state of FIG. The state becomes the mounting state shown in FIG. In this case, the guided portion 16 and the locking means 17 may project outward from the side portions 13 and 14 on the first and second ribs R1 and R2 sides (-Y direction side). good.

(Modification 7)
For example, in the sixth modification described above, the surface wave detecting unit 1 is fixed to the mounting member 60 so that the propagation surface 11 of the propagating body 10 faces the main body 61 (mounting member 60). As a modification of the form, as shown in FIG. 13, the configuration of Modification 2 and the configuration of Modification 6 are combined so that the propagation surface 11 of the propagating body 10 faces the facing portion 51 (fuel pump case 50). Alternatively, the surface wave detection unit 1 may be fixed to the facing portion 51 (fuel pump case 50).

(Other modifications)
Detecting the position of the liquid surface of the liquid 3 means detecting the position of the liquid surface 3a in detail, dividing the position of the liquid surface 3a into several stages, and determining to which stage the current position of the liquid surface 3a belongs. and detecting the volume of the liquid 3 that changes according to the position of the liquid surface 3a. Also, the type of the liquid 3 is not limited, and may be water, gasoline, alcohol, cleaning liquid, or the like.

The material of the propagating body 10 is also arbitrary as long as the surface wave Ws can be propagated satisfactorily. For example, the resin used as the propagating body 10 is not limited to PPS, and may be POM (polyacetal), PBT (polybutylene terephthalate), or the like. In addition, each guided portion 16 and each locking means 17 are based on the third and fourth ribs R3 and R4 instead of the side portions 13 and 14 (that is, each connecting portion 17c is connected to the third and fourth ribs R3 and R4). It may be provided so as to protrude outside of the side portions 13 and 14 (connected to R4).

As long as the liquid surface position can be detected by the above technique, the surface wave Ws and the internal propagation wave Wi may be of any type. In the above, an example in which the surface wave Ws and the internal propagation wave Wi are pulses of ultrasonic waves (for example, a sound wave of 20 kHz or more is acceptable) has been described. The waves Wi may be sound waves of a lower frequency than ultrasound.

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 detection unit 2 control section 3 liquid 3a liquid surface 10 propagation body 11 propagation surface (propagation section)
12 back surface portion 12a groove 13, 14 pair of side surface portions 15 bottom surface portion 16 guided portion 17 locking means 17a locking portion 17b elastic piece 17c connecting portion 20 element accommodating portion 30 piezoelectric element 40 flange portion 50 fuel pump case (mating side parts)
60 Mounting member 61 Body portion 62 Guide portion 63 Engagement portion 70 Adhesive (fixing means)
P non-propagating portion R1 1st rib R2 2nd rib R3 3rd rib R4 4th rib Ws surface wave Wi internal propagation wave

Claims (8)

A surface wave comprising at least a propagating body that is immersed in a liquid and has a propagating portion that propagates a surface wave, and a piezoelectric element that vibrates the propagating body to generate the surface wave and detect the reflected surface wave. A fixing structure of a surface wave detection unit for fixing the detection unit to a mating part that is the mating side of the detection unit,
The propagating body has a non-propagating portion that does not propagate the surface wave,
A fixing structure for a surface wave detection unit, wherein the non-propagating portion is fixed to the mating part using a predetermined fixing means. A surface wave comprising at least a propagating body that is immersed in a liquid and has a propagating portion that propagates a surface wave, and a piezoelectric element that vibrates the propagating body to generate the surface wave and detect the reflected surface wave. A fixing structure for a surface wave detection unit for fixing the detection unit to a mating component via a mounting member, comprising:
The propagating body has a non-propagating portion that does not propagate the surface wave,
A fixing structure for a surface wave detection unit, wherein the non-propagating portion is fixed to the mounting member using a predetermined fixing means. A surface wave comprising at least a propagating body that is immersed in a liquid and has a propagating portion that propagates a surface wave, and a piezoelectric element that vibrates the propagating body to generate the surface wave and detect the reflected surface wave. A fixing structure of a surface wave detection unit for fixing the detection unit to a mating part that is the mating side of the detection unit,
The propagating body has a non-propagating portion that does not propagate the surface wave,
A guide portion and an engagement portion obtained by cutting out a part of the guide portion are provided in one of the mating component and the non-propagating portion,
A fixing structure for a surface wave detection unit, characterized in that, on the other side, a guided portion guided by said guide portion and locking means having a locking portion locked to said engaging portion are provided. A surface wave comprising at least a propagating body that is immersed in a liquid and has a propagating portion that propagates a surface wave, and a piezoelectric element that vibrates the propagating body to generate the surface wave and detect the reflected surface wave. A fixing structure for a surface wave detection unit for fixing the detection unit to a mating component via a mounting member, comprising:
The propagating body has a non-propagating portion that does not propagate the surface wave,
one of the mounting member and the non-propagating portion is provided with a guide portion and an engagement portion obtained by cutting out a part of the guide portion;
A fixing structure for a surface wave detection unit, wherein on the other side, a guided portion guided by the guide portion and locking means having a locking portion locked to the engaging portion are provided. 4. The fixing structure of a surface wave detection unit according to claim 1, wherein the surface wave detection unit is fixed to the mating part so that the propagating portion faces the mating part. 5. The fixing structure of a surface wave detection unit according to claim 2, wherein the surface wave detection unit is fixed to the mounting member so that the propagating portion faces the mounting member. The non-propagating portion is configured as a pair of peripheral wall portions facing each other along the longitudinal direction of the propagating body,
The guide portion is configured as a pair of hook portions extending along the longitudinal direction,
The locking means comprises a pair of elastic pieces respectively provided corresponding to the pair of hooks,
6. A pair of engaging portions provided on the pair of elastic pieces are engaged with a pair of engaging portions provided on the pair of hooks, respectively. fixing structure of the surface wave detection unit according to any one of the above. 8. The fixing structure of the surface wave detection unit according to claim 7, wherein the locking means is positioned on a virtual plane passing through the center of gravity of the surface wave detection unit and perpendicular to the longitudinal direction.

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