JP2019132642A - Liquid level detector - Google Patents

Abstract

To suppress a reduction in the accuracy of detecting a liquid surface position owing to the fact that a reflected wave of an ultrasonic wave is reflected again by the transmitting/receiving surface of a sensor unit.SOLUTION: A liquid level detector 100 comprises a sensor unit 1 and a housing unit 2. A case 15 of the sensor unit 1 includes a transmitting/receiving surface 151 capable of transmitting/receiving an ultrasonic wave in order for an ultrasonic oscillation element 11 to transmit/receive the ultrasonic wave. The housing unit 2 includes a propagation path inside for propagating the ultrasonic wave. A first path 4 extends horizontally from a position where the ultrasonic oscillation element 11 is provided. A second path 5 extends upward from the bottom of a tank 200. The sensor unit 1 includes a wall 12 extending in a direction of the first path 4 from the transmitting/receiving surface 151. The wall 12 is provided at a position enclosing the center from the entire circumference. The wall 12 has the function of attenuating a reflected wave that is reflected mainly at a reference plane 221.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a liquid level detection device.

  2. Description of the Related Art There is known a liquid level detection device that detects the position of a liquid level by transmitting an ultrasonic wave and receiving a reflected wave reflected by the liquid level at a bottom in a tank that stores liquid. As this type of liquid level detection device, a configuration is known in which a reference surface for measuring the propagation speed of ultrasonic waves in a liquid is provided in the propagation path of ultrasonic waves. The reflected wave transmitted from the transmission / reception surface of the sensor unit and reflected by the reference surface is received by the transmission / reception surface and used as a reference wave for detecting the position of the liquid surface with high accuracy. Patent Document 1 discloses a liquid level detection device in which a reference surface is formed by providing a step portion in a housing that forms a propagation path.

JP 2006-47056 A

  In the configuration described in Patent Document 1 described above, since the reference surface is provided at a position relatively close to the transmission / reception surface, the reflected wave reflected by the reference surface is stronger than the reflected wave reflected by the liquid surface. Is received on the transmission / reception surface in a strong state. However, as a result of detailed examination by the inventors, a reflected wave having a high intensity is received by the transmission / reception surface, and is reflected again by the transmission / reception surface, and the reflected wave is reflected by the reference surface again. The problem of repeated reflection was found. That is, the transmission / reception surface can receive not only the first wave that is the reference wave, but also the second wave that is the reflected wave reflected by the reference surface again. The second wave becomes a noise in the detection of the position of the liquid level, and may be a factor that decreases the detection accuracy of the position of the liquid level.

  One aspect of the present disclosure is intended to suppress a decrease in detection accuracy of the liquid surface position caused by the reflected wave of the ultrasonic wave being reflected again by the transmission / reception surface of the sensor unit.

  One aspect of the present disclosure is a liquid level detection device (100) that detects a position of a liquid level. The liquid level detection device includes a sensor unit (1) and a housing (2). The sensor unit has a transmission / reception surface (151) capable of transmitting and receiving ultrasonic waves. The housing has a propagation path through which ultrasonic waves propagate. The propagation path has a first path (4) and a second path (5). The first path extends horizontally from the position where the transmission / reception surface is provided. The second route extends upward from an end portion on the opposite side to the position where the transmission / reception surface is provided in the first route. The sensor unit has an attenuation unit (12, 62, 72, 352, 452, 552) that attenuates the reflected wave of the ultrasonic wave at a position surrounding the center of the transmission / reception surface.

  According to such a configuration, the reflected wave of the ultrasonic wave is attenuated by the attenuation unit. As a result, it is possible to suppress a decrease in the detection accuracy of the liquid surface position caused by the reflected wave being reflected again by the transmission / reception surface of the sensor unit.

It is a sectional side view of the liquid level detection apparatus of this embodiment. It is a sectional side view of the sensor part of this embodiment. It is a front view of the sensor part of this embodiment. It is explanatory drawing of the reflected wave of this embodiment. It is a figure which shows the wall which is a shape where the front-end | tip swelled. It is a figure which shows the wall which is the shape where the front-end | tip sharpened. It is a figure which shows the attenuation | damping surface whose cross section is linear. It is a figure which shows the attenuation | damping surface where a cross section is curvilinear. It is a figure which shows the attenuation | damping surface which has several unevenness | corrugations or several steps.

  Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. Further, the reference numerals used in the description of the following embodiments are also used in the claims as appropriate, but this is used for the purpose of facilitating the understanding of the present disclosure, and the interpretation of the claims is limited. Not intended.

[1. Constitution]
A liquid level detection device 100 shown in FIG. 1 is mounted on a vehicle and transmits an ultrasonic wave at the bottom of a tank 200 that stores liquid fuel, and receives a reflected wave reflected by the liquid level. Is a device for detecting the position of In addition, about the part of the liquid level detection apparatus 100 shown to each figure, in order to show an internal structure intelligibly, the side surface is shown instead of the cross section. The liquid level detection device 100 includes two functional units, specifically, a sensor unit 1 and a housing unit 2 from a functional standpoint.

  The sensor unit 1 is an assembly that functions as an ultrasonic transmission / reception unit as a whole. The sensor unit 1 includes an ultrasonic oscillation element 11, two internal terminals 13, an elastic body 14, a case 15, a lid 16, and two external terminals 17.

  The ultrasonic oscillator 11 is an element that transmits and receives ultrasonic waves. The ultrasonic oscillating element 11 is configured in a disk shape having a shape in which the central axis A is defined by a material having a piezoelectric effect such as PZT (zirconate titanate). The piezo effect is a characteristic in which, when a voltage is applied, the volume changes while a voltage is generated when an external force is applied. Electrodes printed on almost the entire surface are provided on both surfaces of the ultrasonic oscillator 11. When a voltage is applied between the electrodes on both sides from the external electric circuit via the lead wire 3, the ultrasonic oscillator 11 vibrates in the direction of the central axis A, which is the thickness direction, due to the piezoelectric effect described above. Oscillates ultrasonic waves. The ultrasonic oscillator 11 is housed in the case 15 together with the insulating member.

  The internal terminal 13 is a terminal that electrically connects the ultrasonic oscillation element 11 and the external terminal 17. The internal terminal 13 is formed of a metal plate. The ultrasonic oscillator 11 and the internal terminal 13 are electrically connected by soldering. In the present embodiment, two internal terminals 13 are provided on both sides of the ultrasonic oscillator 11 and the elastic body 14.

  The elastic body 14 is a substantially columnar member arranged coaxially with the central axis A of the ultrasonic oscillation element 11, and the first surface of the two end faces on both sides in the axial direction is the ultrasonic oscillation element 11. The second surface is in contact with the lid 16. The elastic body 14 is made of an elastic material such as a flexible resin or rubber.

  The case 15 is a bottomed cylindrical case having a storage chamber for storing the ultrasonic oscillation element 11, the two internal terminals 13 and the elastic body 14. The case 15 has a transmission / reception surface 151 capable of transmitting and receiving ultrasonic waves for the ultrasonic oscillation element 11 to transmit and receive ultrasonic waves. Specifically, as shown in FIG. 2, since the ultrasonic oscillation element 11 and the insulating member (not shown) are provided at the bottom of the case 15, the planar outer surface of the bottom wall of the case 15 is the transmission / reception surface 151. Function as.

  The lid 16 is a member that closes the housing chamber of the case 15. In a state where the lid 16 is locked to the case 15, the elastic body 14 is designed to have a large size in the direction of the central axis A so that the elastic body 14 is compressed by the lid 16 and is elastically deformed and accommodated in the accommodating chamber. ing. For this reason, the ultrasonic oscillator 11 is fixed in a state of being pressed against the bottom wall of the case 15 by the elastic force of the elastic body 14. The internal terminal 13 is inserted into the hole provided in the lid 16, and the tip of the internal terminal 13 protrudes outside the housing chamber of the case 15.

  The external terminal 17 is a terminal that electrically connects the internal terminal 13 and the lead wire 3. The external terminal 17 is formed of a metal plate. One end of the external terminal 17 is joined to the tip of the internal terminal 13 by welding. The other end of the external terminal 17 is connected to the lead wire 3 by crimping or the like. The external terminal 17 is fixed to the lid 16 outside the housing chamber of the case 15.

  Next, the housing part 2 will be described. The housing part 2 is an assembly that functions as an ultrasonic wave propagation path as a whole by having a propagation path for propagating ultrasonic waves inside. As shown in FIG. 1, the housing part 2 includes a body 21, a guide pipe 22, a guide pipe 23, and a reflection plate 24.

  The body 21 is a resin member that holds and fixes the sensor unit 1, the guide pipe 22, the guide pipe 23, and the reflection plate 24. The guide pipe 22, the guide pipe 23 and the reflection plate 24 are attached to the body 21. The body 21 is fixed to the bottom surface of the tank 200. The sensor unit 1 is attached to the body 21 so that the central axis A of the ultrasonic oscillation element 11 is coaxial with the central axis of the guide pipe 22.

  The guide pipe 22 is a substantially truncated cone-shaped metal cylinder. In FIG. 1, one end side of the guide pipe 22 corresponding to the right side is provided at a position facing the sensor unit 1. The guide pipe 22 has a circular cross section in a direction orthogonal to the central axis A of the guide pipe 22. The guide pipe 22 forms a first path 4 that is a part of a propagation path that extends horizontally from the position where the ultrasonic oscillation element 11 is provided. The first path 4 includes a conical part 41, a straight part 42, and a step part 43. The conical portion 41 is a truncated cone portion whose cross-sectional area gradually decreases as the distance from the ultrasonic oscillator 11 increases. In other words, the diameter of the cross section of the conical portion 41 in the direction orthogonal to the central axis A of the first path 4 decreases as the distance from the ultrasonic oscillator 11 increases. The straight portion 42 has a constant cross-sectional area, that is, a straight tubular portion. The step portion 43 is a portion that connects the conical portion 41 and the linear portion 42, and the cross-sectional area is reduced in a step shape at the end portion of the conical portion 41 opposite to the end portion where the ultrasonic oscillation element 11 is provided. Part. Due to the presence of the stepped portion 43, an annular reference surface 221 that is coaxial with the central axis A is formed on the guide pipe 22.

  The guide pipe 23 is a straight tubular metal tube. The guide pipe 23 is provided so that the central axis B of the guide pipe 23 is orthogonal to the central axis A, and is continuous with the end of the guide pipe 22 on the linear portion 42 side via the body 21. The guide pipe 23 has a circular cross section in a direction orthogonal to the central axis B. The upper end of the guide pipe 23 is positioned so as to protrude upward by a predetermined length from the liquid level when the amount of fuel stored in the tank 200 is maximum. The guide pipe 23 forms a second path 5 that is a part of the propagation path. The second path 5 extends from the bottom of the tank 200 upward, in the vertical direction in the present embodiment. The diameter of the second path 5 in this embodiment is equal to the diameter of the straight portion 42.

  The reflection plate 24 is a metal plate. The reflecting plate 24 is arranged so that the central axis A of the guide pipe 22 and the central axis B of the guide pipe 23 intersect at the reflecting surface 241 of the reflecting plate 24 when held and fixed to the body 21. Yes. The reflector 24 reflects the ultrasonic wave transmitted from the ultrasonic oscillator 11 toward the fuel surface. Specifically, the reflector 24 reflects the ultrasonic wave traveling along the central axis A of the guide pipe 22 toward the direction in which the incident angle on the liquid surface is 0 °, that is, the direction orthogonal to the liquid surface. It is installed as follows. In the present embodiment, the reflecting plate 24 is provided so as to be inclined by 45 ° with respect to the liquid surface.

  With the above configuration, when a pulse voltage is applied to the ultrasonic oscillation element 11 via the lead wire 3, the external terminal 17, and the internal terminal 13, the ultrasonic oscillation element 11 vibrates and passes through the transmission / reception surface 151. Thus, an ultrasonic wave is transmitted to the first path 4. When the sensor unit 1 receives the reflected wave reflected on the liquid surface via the reflector 24 or the reflected wave reflected on the reference surface 221 on the transmission / reception surface 151, the bottom wall of the case 15 vibrates due to the pressure action, and accordingly The sound wave oscillator 11 also vibrates. As a result, the ultrasonic oscillation element 11 generates a voltage, and the voltage is input as an output signal to the external electric circuit via the internal terminal 13, the external terminal 17 and the lead wire 3. Since the distance from the ultrasonic oscillating element 11 to the reference plane 221 is predetermined, the fuel is based on the time from when the ultrasonic oscillating element 11 transmits the ultrasonic wave until the reflected wave reflected by the reference plane 221 is received. The propagation speed of ultrasonic waves inside can be measured. Therefore, by using the reflected wave reflected by the reference surface 221 as a reference wave for calculating the position of the liquid surface, the position of the liquid surface can be accurately determined regardless of the change in the propagation speed of the ultrasonic wave due to the temperature change of the liquid. Can be detected.

  Here, as shown in FIGS. 1 to 3, the sensor unit 1 includes a wall 12 extending from the transmission / reception surface 151 in the direction of the first path 4. As shown in FIG. 3, the wall 12 has a substantially cylindrical shape coaxial with the central axis A, and is provided at a position surrounding the center of the transmission / reception surface 151, in the present embodiment, at a position surrounding the center from the entire circumference. Here, the center of the transmission / reception surface 151 is a portion having a central point at a point intersecting the central axis A on the transmission / reception surface 151. The wall 12 shown in the cross section including the central axis A shown in FIG. 2 has a trapezoidal shape, and the thickness thereof becomes thinner as the distance from the transmission / reception surface 151 increases. Specifically, the wall 12 has a constant inner diameter, and the outer diameter decreases as the distance from the transmission / reception surface 151 increases. That is, the wall 12 is a tapered cylinder whose outer side is inclined. In addition, the tip of the wall 12 on the side opposite to the transmission / reception surface 151 side has a planar shape parallel to the transmission / reception surface 151.

  Here, the shape of the wall 12 will be described in more detail. The wall 12 has an inner surface 121, an outer surface 122, and a tip surface 123. The inner surface 121 is a surface facing the center side of the transmission / reception surface 151, that is, the inner peripheral surface of the cylindrical wall 12. Further, the inner surface 121 is a surface extending perpendicularly to the transmission / reception surface 151 and is a linear surface in a cross section including the central axis A. The outer surface 122 is a surface opposite to the inner surface 121, that is, the outer peripheral surface of the cylindrical wall 12, and is a linear surface in a cross section including the central axis A. The outer surface 122 is opposite to the transmission / reception surface 151 side, that is, the end opposite to the transmission / reception surface 151 side, that is, the end portion on the front end surface 123 side is closer to the center of the transmission / reception surface 151. Is inclined. The front end surface 123 is the front end surface of the wall 12 and is a plane perpendicular to the inner surface 121, that is, a plane parallel to the transmission / reception surface 151. The inner diameter D3 of the wall 12 is smaller than the outer diameter D1 of the ultrasonic oscillation element 11 and slightly larger than the inner diameter D2 of the linear portion 42.

  The wall 12 has a function of attenuating the reflected wave of the ultrasonic wave transmitted from the ultrasonic oscillation element 11 via the transmission / reception surface 151, specifically, the reflected wave mainly reflected by the reference surface 221. Attenuating means reflecting the reflected wave so as to attenuate. Here, the attenuation of the reflected wave of the ultrasonic wave by the wall 12 will be described using the reflected waves X, Y, and Z shown in FIG. Each of the reflected waves X, Y, and Z is a reflected wave of an ultrasonic wave transmitted from the ultrasonic oscillating element 11, and is reflected on the reference surface 221 due to a difference in incident angle from the ultrasonic oscillating element 11 to the reference surface 221. The reflected waves are reflected in different directions.

  The reflected wave X is reflected by the reference surface 221 toward the outside of the wall 12. For this reason, the reflected wave X is repeatedly reflected between the outer surface 122 of the wall 12 and the inner surface of the guide pipe 22 and gradually attenuates.

The reflected wave Y is reflected by the reference surface 221 toward the inner surface 121 of the wall 12. For this reason, the reflected wave Y is incident on the transmission / reception surface 151 at an inclined angle, diffusely reflected, and attenuated.
The reflected wave Z is reflected by the reference surface 221 toward the inside of the wall 12. For this reason, the reflected wave Z is reflected again by the transmission / reception surface 151 without being reflected by the wall 12, but the inner diameter D3 of the wall 12 is slightly larger than the inner diameter D2 of the linear portion 42. Compared with the configuration that does not, the intensity of the ultrasonic wave reflected again on the reference surface 221 is greatly reduced as a whole.

[2. effect]
According to the embodiment detailed above, the following effects can be obtained.
(1a) According to the liquid level detection device 100 of the present embodiment, the reflected wave transmitted from the ultrasonic oscillation element 11 and reflected by the reference surface 221 is reflected by the wall 12 extending from the transmission / reception surface 151 toward the first path 4. Can be attenuated. In particular, in the configuration in which the reference surface 221 is provided on the inner peripheral surface of the ultrasonic wave propagation path as in the present embodiment, the reflected wave reflected by the reference surface 221 is directed to the outer edge portion of the transmission / reception surface 151 rather than the center. It has been found by the inventor that the light is easily reflected. Therefore, by providing the wall 12 that attenuates the reflected wave at a position surrounding the center of the transmission / reception surface 151 from the entire circumference, the reflected wave reflected by the reference surface 221 can be easily attenuated by the wall 12. Therefore, it is possible to make it difficult for the reflected wave on the reference surface 221 to be reflected again on the transmission / reception surface 151 and the reference surface 221 and further received on the transmission / reception surface 151 again. As a result, it can suppress that the detection accuracy of the position of a liquid level falls.

  (1b) The outer surface 122 is inclined with respect to the transmission / reception surface 151 so that the end on the distal end surface 123 side is closer to the center of the transmission / reception surface 151 than the end on the transmission / reception surface 151 side. That is, the wall 12 is a tapered cylinder whose outer side is inclined. According to such a configuration, the reflected wave reflected toward the outside of the wall 12 by the reference surface 221 is easily reflected in the radial direction by the outer surface 122. As a result, the reflected wave reflected by the reference surface 221 can be more easily attenuated.

In the present embodiment, the housing part 2 corresponds to a housing, and the wall 12 corresponds to an attenuation part. The inner surface 121 corresponds to the first surface, and the outer surface 122 corresponds to the second surface.
[3. Other Embodiments]
As mentioned above, although embodiment of this indication was described, it cannot be overemphasized that this indication can take various forms, without being limited to the above-mentioned embodiment.

  (2a) In the above-described embodiment, the inner surface 121 that extends perpendicularly to the transmission / reception surface 151, is linear in a cross section including the central axis A, and has a smooth curved surface without unevenness is illustrated. However, the shape of the inner surface of the wall is not particularly limited. For example, the shape may be inclined with respect to the transmission / reception surface, may be curved in the cross section, and may be uneven, for example. For example, it may be planar.

  (2b) In the above embodiment, the outer surface 122 that is inclined at a constant rate, that is, linearly inclined in the cross section including the central axis A is exemplified. However, the shape of the outer surface of the wall is not limited to this. For example, the outer surface of the wall may have a shape that is inclined in a curved shape in the cross section, or may have a shape having irregularities on the surface, for example.

(2c) In the above embodiment, the wall 12 having the flat tip surface 123 is illustrated, but the shape of the tip of the wall is not limited to this.
For example, the wall 62 shown in FIG. 5 is basically the same as the configuration of the wall 12 of the above-described embodiment, but differs from the wall 12 in that it has a curved shape with a bulging tip. The wall 62 has an inner surface 621, an outer surface 622, and a tip surface 623. The inner surface 621 and the outer surface 622 have the same configuration as the inner surface 121 and the outer surface 122 of the above embodiment. The front end surface 623 is a surface of the front end of the wall 62 and has a curved surface that swells in the direction of the straight portion 42.
Such a wall 62 can provide the same effect as that of the above embodiment. In particular, since the wall 62 has a curved tip end surface 623, the intensity of the reflected wave can be dispersed.

  Further, for example, the wall 72 shown in FIG. 6 is basically the same as the configuration of the wall 12 of the above-described embodiment, but differs from the wall 12 in that the tip end has a sharp shape. The wall 72 has an inner surface 721 and an outer surface 722. The inner surface 721 and the outer surface 722 have the same configuration as the inner surface 121 and the outer surface 122 of the above-described embodiment except that the inner surface 721 and the outer surface 722 are continuous without passing through the distal end surface. The tip of the wall 72 has a sharp shape toward the straight portion 42.

  Such a wall 72 can provide the same effect as that of the above embodiment. In particular, since the wall 72 has a shape with a sharp tip, it can be made difficult for the reflected wave to be reflected again by the tip.

(2d) In the said embodiment, the wall 12 was illustrated as an example of the attenuation part. However, the configuration of the attenuation unit is not limited to this.
For example, the case 35 shown in FIG. 7 differs from the case 15 of the above embodiment in that it has an attenuation surface 352 instead of having the wall 12 on the transmission / reception surface 351. Other configurations of the case 35 are the same as the configurations of the case 15 of the above-described embodiment, and thus description thereof is omitted.

  Similar to the transmission / reception surface 351, the attenuation surface 352 is a part of the outer surface of the bottom wall of the case 35 and is provided at a position surrounding the transmission / reception surface 351 from the entire circumference. The attenuation surface 352 is annular and is inclined with respect to the transmission / reception surface 351. The attenuation surface 352 has a linear cross section including the central axis A. The attenuation surface 352 mainly has a function of attenuating the reflected wave reflected from the reference surface 221 toward the attenuation surface 352. Specifically, the reflected wave reflected by the reference surface 221 toward the attenuation surface 352 is diffusely reflected by the attenuation surface 352 and attenuated.

  Such an attenuation surface 352 also provides the same effect as that of the above embodiment. In particular, since the attenuation surface 352 is provided as a part of the outer surface of the bottom wall of the case 35, the attenuation surface can be configured with a simple configuration.

The attenuation surface is not limited to the shape of the attenuation surface 352 shown in FIG. For example, the attenuation surface may be a surface having a curved section including the central axis A, like the attenuation surface 452 shown in FIG. Further, for example, the attenuation surface may be a surface having a plurality of protrusions or a surface having a plurality of steps like the attenuation surface 552 shown in FIG.
In addition, the wall and the attenuation surface exemplified as the attenuation portion may be integrated with the case or may be separate parts from the case, and may be integrated with components other than the case, for example. The effect is further expected.

  (2e) In the above embodiment, the configuration in which the inner diameter D3 of the wall 12 is smaller than the outer diameter D1 of the ultrasonic oscillation element 11 is exemplified. However, the size of the inner diameter of the wall is not limited to this, and for example, the inner diameter of the wall may be equal to or larger than the outer diameter of the ultrasonic oscillation element.

  (2f) In the above-described embodiment, the configuration in which the wall 12 that is an example of the attenuation unit is a cylindrical shape provided at a position that surrounds the center of the transmission / reception surface 151 from the entire circumference is illustrated. However, the configuration of the attenuation unit is not limited to this. The attenuation unit does not have to surround the center of the transmission / reception surface from the entire circumference, and may be, for example, a C shape. The attenuation unit may have a plurality of walls spaced from each other.

  (2g) In the said embodiment, the liquid level detection apparatus 100 used for the liquid level detection of the fuel in the tank 200 was illustrated. However, the use of the liquid level detection device is not particularly limited. The liquid level detection device may be used for detecting the level of other liquids mounted on the vehicle, such as engine oil, brake fluid, window washer liquid, and the like. Further, for example, the liquid level detection device may be used for detecting a liquid level in a liquid transport tank provided in a liquid transport vehicle or in a liquid container of various consumer devices other than the vehicle.

  (2h) The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  DESCRIPTION OF SYMBOLS 1 ... Sensor part, 2 ... Housing part, 3 ... Lead wire, 4 ... 1st path | route, 5 ... 2nd path | route, 11 ... Ultrasonic oscillation element, 12 ... Wall, 13 ... Internal terminal, 14 ... Elastic body, DESCRIPTION OF SYMBOLS 15, 35 ... Case, 16 ... Cover, 17 ... External terminal, 21 ... Body, 22, 23 ... Guide pipe, 24 ... Reflector plate, 41 ... Conical part, 42 ... Straight part, 43 ... Step part, 62, 72 ... Wall, 100 ... Liquid level detection device, 121, 621, 721 ... Inner surface, 122, 622, 722 ... Outer surface, 123, 623 ... Tip surface, 151, 351 ... Transmission / reception surface, 200 ... Tank, 221 ... Reference surface, 241 ... Reflective surface, 352, 452, 552, attenuation surface.

Claims (7)

A liquid level detection device (100) for detecting the position of a liquid level,
A sensor unit (1) having a transmission / reception surface (151) capable of transmitting and receiving ultrasonic waves;
A housing (2) having a propagation path through which ultrasonic waves propagate;
With
The propagation path is
A first path (4) extending horizontally from a position where the transmission / reception surface is provided;
A second path (5) extending upward from an end opposite to the position where the transmission / reception surface is provided in the first path,
The said sensor part is a liquid level detection apparatus which has the attenuation | damping part (12,62,72,352,452,552) which attenuates the reflected wave of an ultrasonic wave in the position surrounding the center of the said transmission / reception surface. The liquid level detection device according to claim 1,
The said attenuation | damping part is a liquid level detection apparatus provided in the position which surrounds the center of the said transmission / reception surface from a perimeter. The liquid level detection device according to claim 1 or 2,
The liquid level detection device, wherein the attenuation unit is a wall extending from the transmission / reception surface in the direction of the first path. The liquid level detection device according to claim 3,
The wall has a first surface (121) facing the center side of the transmission / reception surface and a second surface (122) which is a surface opposite to the first surface;
The liquid level detecting device, wherein the second surface is inclined so that an end opposite to the transmitting / receiving surface side is closer to a center of the transmitting / receiving surface than an end portion on the transmitting / receiving surface side. The liquid level detection apparatus according to claim 3 or 4, wherein:
The liquid surface detecting device, wherein a tip of the wall is flat. The liquid level detection apparatus according to claim 3 or 4, wherein:
The liquid surface detecting device, wherein a tip of the wall has a bulging curved shape. The liquid level detection apparatus according to claim 3 or 4, wherein:
The liquid surface detecting device, wherein the tip of the wall has a sharp shape.