WO2019142859A1

WO2019142859A1 - Liquid level detecting device

Info

Publication number: WO2019142859A1
Application number: PCT/JP2019/001259
Authority: WO
Inventors: 宮川　功
Original assignee: 株式会社デンソー
Priority date: 2018-01-19
Filing date: 2019-01-17
Publication date: 2019-07-25
Also published as: JP2019124642A; JP6904268B2

Abstract

A liquid level detecting device (100) is provided with an ultrasonic oscillating element (11) and a housing (2). The ultrasonic oscillating element is capable of transmitting and receiving ultrasonic waves. The housing internally includes a propagation pathway along which the ultrasonic waves propagate. The propagation pathway includes a first pathway (4) and a second pathway (5). The first pathway extends horizontally from a position at which the ultrasonic oscillating element is provided. The second pathway extends upward from the end of the first pathway on the opposite side to the position at which the ultrasonic oscillating element is provided. The first pathway has a conical portion (41) which is a truncated cone shaped pathway having a cross-sectional area which contracts gradually with increasing distance from the ultrasonic oscillating element. The housing has a shape in which a lower surface of a part forming the conical portion is separated from a bottom surface, and has a through hole (6) providing communication between the inside and the outside of the housing, in an end portion of the conical portion on the side thereof closest to the ultrasonic oscillating element, in a vertically lower portion of the housing.

Description

Liquid level detection device

Cross-reference to related applications

This international application claims the priority based on Japanese Patent Application No. 2018-6822 filed on Jan. 19, 2018 to the Japanese Patent Office, and the Japanese Patent Application No. 2018-6822 The entire contents are incorporated by reference into this international application.

The present disclosure relates to a liquid level detection device.

There is known a liquid level detection device that detects the position of a liquid surface by transmitting ultrasonic waves by an ultrasonic oscillation element and receiving a reflected wave reflected by the liquid surface at the bottom inside a tank that stores liquid. There is. Generally, this type of liquid level detection device includes a housing having an internal space that functions as a propagation path of ultrasonic waves. The propagation path is a first path extending horizontally from the position at which the ultrasonic oscillation element is provided, and a second path extending upward from the end of the first path opposite to the position at which the ultrasonic oscillation element is provided And the structure which has and are common.

By the way, for example, although the detection of the position of the liquid surface in the tank for fuel storage mounted in the vehicle is performed on the assumption that the fuel is filled in the inside of the housing, rainwater infiltrates into the tank during refueling Water may be accumulated inside the housing for reasons such as. Then, the propagation speed of the ultrasonic wave is different between in the fuel and in the water, so that the detection accuracy of the position of the liquid level may be lowered. In Patent Document 1, a liquid having a through hole for draining water at the lowermost portion of the propagation path, taking into consideration the characteristics of water which is large in specific weight and easily accumulated in the lower portion in the vertical direction of the propagation path compared to fuel. A surface detection apparatus is disclosed.

Unexamined-Japanese-Patent No. 2004-347378

In the liquid level detection device described in Patent Document 1, a through hole for draining water is provided at the lowermost portion of the propagation path, and in a portion where the lower surface of the housing abuts the bottom surface of the tank without a gap. Therefore, as a result of the inventor's detailed study, in order to extract the water accumulated inside the housing to the outside of the housing, it is necessary to separately provide a groove extending laterally from the through hole and leading to the outside of the housing. It was found.

One aspect of the present disclosure is to provide a liquid level detection device capable of making it easy for water accumulated inside a housing to escape to the outside of the housing with a simple configuration.

One aspect of the present disclosure is a liquid level detection device which is provided on the bottom of the inside of a tank and detects the position of the liquid level of the liquid stored in the tank, and includes an ultrasonic oscillation element and a housing. The ultrasonic oscillation element can transmit and receive ultrasonic waves. The housing internally has a propagation path through which ultrasonic waves propagate. The propagation path has a first path and a second path. The first path extends horizontally from the position where the ultrasonic oscillation element is provided. The second path extends upward from the end of the first path opposite to the position at which the ultrasonic oscillation element is provided. The first path has a conical portion which is a truncated cone-like path whose cross-sectional area gradually decreases with distance from the ultrasonic oscillation element. The housing has a shape in which the lower surface of the portion where the conical portion is formed is separated from the bottom, and has a through hole communicating the inside and the outside of the housing at the end portion on the ultrasonic oscillation element side in the conical portion and the lower portion in the vertical direction.

According to such a configuration, the water collected inside the housing is provided at the end portion on the ultrasonic oscillation element side in the conical portion and at the lower portion in the vertical direction, and the lower surface of the housing is separated from the bottom surface of the tank It is easy to go out from the through hole. As a result, it is not necessary to provide the above-described groove and the like, and water accumulated inside the housing can be easily released to the outside of the housing with a simple configuration.

It is a sectional side view of the liquid level detection device of this embodiment. It is a side view of a liquid level detection device of this embodiment. It is a bottom view of the liquid level detection device of this embodiment. It is a figure which shows the directivity of the ultrasonic wave of this embodiment.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[1. Constitution]
The liquid level detection device 100 shown in FIG. 1 is mounted on a vehicle and transmits ultrasonic waves at the bottom of a tank 200 that stores liquid fuel, and receives a reflected wave reflected by the liquid surface to obtain the liquid level. Is a device for detecting the position of In addition, about a part of liquid level detection apparatus 100 shown in FIG. 1, in order to show an internal structure intelligibly, it has shown not the cross section but the side. The liquid level detection apparatus 100 roughly includes two functional units, specifically, a sensor unit 1 and a housing unit 2 from the functional viewpoint.

The sensor unit 1 is an assembly that functions as a transmitter and receiver of ultrasonic waves 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 wave oscillation element 11 is an element that transmits and receives an ultrasonic wave. The ultrasonic oscillation element 11 is configured in a disk shape having a shape in which the central axis A is defined by a substance having a piezoelectric effect such as PZT (zirconate titanate). The piezo effect is a characteristic in which a volume changes when a voltage is applied, and a voltage is generated when an external force is applied. Electrodes printed on substantially the entire surface of the ultrasonic oscillation element 11 are provided on both sides. The ultrasonic oscillation element 11 vibrates in the direction of the central axis A, which is the thickness direction, by the above-described piezo effect, when a voltage is applied between the electrodes on both surfaces from an external electric circuit through the lead wire 3. It emits ultrasonic waves. The ultrasonic oscillation element 11 is accommodated in the case 15 together with the insulating member.

The internal terminal 13 is a terminal for electrically connecting the ultrasonic oscillation element 11 and the external terminal 17. The internal terminal 13 is formed of a metal plate. The ultrasonic oscillation element 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 oscillation element 11 and the elastic body 14.

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

The case 15 is a bottomed cylindrical case having a receiving chamber for receiving the ultrasonic oscillation element 11, the two internal terminals 13 and the elastic body 14.

The lid 16 is a member for closing the storage chamber of the case 15. In the state where the lid 16 is locked to the case 15, the elastic body 14 is designed to be larger in the direction of the central axis A so that the elastic body 14 is compressed by the lid 16 and accommodated in the accommodation chamber in an elastically deformed state. ing. For this reason, the ultrasonic oscillation element 11 is fixed in a state of being pressed against the bottom surface of the case 15 by the elastic force of the elastic body 14. The internal terminal 13 is inserted through the hole provided in the lid 16, and the tip of the internal terminal 13 protrudes outside the accommodation chamber of the case 15.

The external terminal 17 is a terminal for electrically connecting 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 accommodation chamber of the case 15.

Next, the housing portion 2 will be described. The housing part 2 is an assembly which functions as a propagation path of an ultrasonic wave as a whole by having a propagation path which propagates an ultrasonic wave inside. As shown in FIG. 1, the housing portion 2 has 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 reflecting plate 24 are attached to the body 21. The body 21 is fixed to the bottom 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 metal cylinder made of a substantially truncated cone. One end side of the guide pipe 22 corresponding to the right side in FIG. 1 is provided at a position facing the sensor unit 1. The guide pipe 22 has a circular cross section in the direction orthogonal to the central axis A of the guide pipe 22. The guide pipe 22 forms a first path 4 which is a part of a propagation path, which extends horizontally from the position where the ultrasonic oscillation element 11 is provided. The first path 4 has a conical portion 41, a straight portion 42 and a step 43. The conical portion 41 is a frusto-conical portion whose cross-sectional area gradually reduces as it is separated from the ultrasonic oscillation element 11. 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 oscillation element 11 increases. The external shape of the part in which the conical part 41 is formed is also a truncated cone shape of the housing part 2 substantially. Therefore, as shown in FIG. 2, the lower surface of the portion of the housing 2 where the conical portion 41 is formed is separated from the bottom surface of the tank 200. The straight portion 42 is a portion having a constant cross-sectional area, that is, a straight tube. The stepped portion 43 is a portion connecting the conical portion 41 and the linear portion 42, and the cross-sectional area of the conical portion 41 is reduced in a step-like manner at the end opposite to the end where the ultrasonic wave oscillation element 11 is provided. It is a part. An annular reference surface 221 coaxial with the central axis A is formed on the guide pipe 22 by the presence of the step 43.

The guide pipe 23 is a straight tubular metal cylinder. The guide pipe 23 is provided such 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 the direction orthogonal to the central axis B. The upper end portion of the guide pipe 23 is positioned so as to protrude upward by a predetermined length than the liquid level at the maximum time of the fuel storage amount of the tank 200. The guide pipe 23 forms a second path 5 which 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 the present embodiment is equal to the diameter of the straight portion 42.

The reflecting plate 24 is a metal plate. The reflection plate 24 is disposed so that the central axis A of the guide pipe 22 and the central axis B of the guide pipe 23 intersect at the reflection surface 241 of the reflection plate 24 in a state of being held and fixed to the body 21 There is. The reflection plate 24 reflects the ultrasonic wave transmitted from the ultrasonic oscillation element 11 toward the liquid surface of the fuel. Specifically, the reflection plate 24 reflects the ultrasonic wave traveling along the central axis A of the guide pipe 22 in the direction in which the incident angle to the liquid surface is 0 °, that is, in the direction orthogonal to the liquid surface. As installed. In the present embodiment, the reflection plate 24 is provided to be inclined 45 ° with respect to the liquid surface.

With the above configuration, when a pulse voltage is applied to the ultrasonic oscillation element 11 through the lead wire 3, the external terminal 17 and the internal terminal 13, the ultrasonic oscillation element 11 vibrates, and the bottom surface of the case 15 is Ultrasonic waves are transmitted to the first path 4 via the first path 4. When the sensor unit 1 receives a reflected wave reflected on the liquid surface through the reflection plate 24 or a reflected wave reflected on the reference surface 221, the pressure action causes the bottom of the case 15 to vibrate, and the ultrasonic oscillation element 11 also accordingly Vibrate. Thereby, the ultrasonic oscillation element 11 generates a voltage, and the voltage is input as an output signal to an external electric circuit through the internal terminal 13, the external terminal 17 and the lead wire 3. Since the distance from the ultrasonic oscillation element 11 to the reference surface 221 is predetermined, the fuel is based on the time from the transmission of the ultrasonic wave by the ultrasonic oscillation element 11 to the reception of the reflected wave reflected by the reference surface 221. The propagation velocity of the ultrasonic wave in the 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 level, the position of the liquid level can be highly accurate regardless of the change in the propagation velocity of the ultrasonic wave due to the temperature change of the liquid. Can be detected.

Here, as shown in FIGS. 1 and 3, the housing portion 2 has a through hole 6. Specifically, the through hole 6 is provided at the end portion of the conical portion 41 of the guide pipe 22 on the ultrasonic oscillation element 11 side, the lower portion in the vertical direction, or the lowermost portion in the vertical direction in the present embodiment. Here, the lowermost portion in the vertical direction is the lowest position in the vertical direction in a cross section perpendicular to the central axis A of the first path 4, in other words, the position directly below the central axis A of the first path 4. It is. That is, as shown in FIG. 3, the through hole 6 is located on the lower surface of the portion of the housing portion 2 which is separated from the bottom surface of the tank 200 and in which the conical portion 41 is formed. However, the through hole may not necessarily be provided at the lowermost part in the vertical direction, and may be provided at a position slightly offset from the lowermost part in the vertical direction. The through hole 6 is a circular through hole communicating the inside and the outside of the housing portion 2. The size of the through hole 6 is set such that the water stagnating inside the housing 2 is released to the outside of the housing 2. In the present embodiment, the diameter of the through hole 6 is set to 3 mm.

Further, the through hole 6 is provided at a position where the ultrasonic wave transmitted from the ultrasonic wave oscillation element 11 is hard to reflect. That is, the ultrasonic waves transmitted from the ultrasonic wave oscillating element 11 have directivity as shown in FIG. Here, if it is considered that the angle range up to about 5% greatly affects the accuracy of the output waveform of the reflected wave, the output is an angle range of -26 db or more, that is, about ± 25 degrees, and further an error. When considered, an angular range of ± 30 degrees is a substantial ultrasonic wave transmission range. More precisely, the virtual range 72 shown in FIG. 1 is the transmission range of the substantial ultrasonic waves. The virtual range 72 is reflected at an angle of ± 30 degrees from the center 71 of the surface of the ultrasonic oscillation element 11 facing the first path 4 at 360 degrees around the central axis A, that is, with the center 71 as an apex. It is a range which spreads conically toward the plate 24 side. That is, the virtual range 72 is a conical range defined by the apex angle θ with the center 71 as the apex and the central axis A as an axis, and the apex angle θ in this example is 60 degrees. In the present embodiment, the through hole 6 is provided outside the virtual range 72.

[2. effect]
According to the embodiment described above, the following effects can be obtained.

(1a) According to the liquid level detection device 100 in the present embodiment, water accumulated inside the housing 2 can be easily removed from the through hole 6 to the outside of the housing 2 by a simple configuration.

For example, as shown in FIG. 3, it is assumed that a through hole 6 a is provided in the housing portion 2 instead of the through hole 6. The through hole 6 a is located at a portion of the housing portion 2 that abuts the bottom surface of the tank 200 without a gap. Therefore, it is difficult for water accumulated inside the housing portion 2 to escape to the outside of the housing portion 2 only by the through hole 6a, and it is necessary to separately provide the housing portion 2 with a groove extending laterally from the through hole 6a and communicating with the outside of the housing. There is.

On the other hand, the through hole 6 of the present embodiment is provided at a position where the housing portion 2 and the bottom of the tank 200 are separated. As a result, it is not necessary to provide the groove described above, and the water remaining inside the housing portion 2 can be easily removed to the outside of the housing portion 2 by a simple configuration.

(1b) The housing portion 2 has the through hole 6 at the lowermost portion in the vertical direction of the conical portion 41. According to such a configuration, since the water has the characteristic of being easily accumulated in the lower portion in the vertical direction of the propagation path, the housing portion has a through hole at a portion different from the lowermost portion in the vertical direction in the conical portion Compared to the above, the water accumulated inside the housing portion 2 can be more easily removed.

(1c) The through hole 6 is provided outside the virtual range 72. According to such a configuration, it is possible to make it difficult for the ultrasonic wave transmitted from the ultrasonic wave oscillation element 11 to be reflected by the inner surface of the through hole 6.

If a through hole is provided inside the virtual range 72, the ultrasonic wave transmitted from the ultrasonic oscillation element 11 is reflected on the inner surface of the through hole, and the reflected wave detects the position of the liquid surface. Noise at the position of the liquid, which may cause a decrease in detection accuracy of the position of the liquid surface. On the other hand, the through hole 6 of the present embodiment is provided outside the virtual range 72. That is, the ultrasonic wave transmitted from the ultrasonic wave oscillation element 11 is not likely to be reflected on the surface of the housing 2 on which the through hole 6 is provided. As a result, it is possible to make it difficult to cause a decrease in detection accuracy.

In the present embodiment, the housing portion 2 corresponds to a housing.

[3. Other embodiments]
As mentioned above, although embodiment of this indication was described, it can not be overemphasized that this indication can take various forms, without being limited to the above-mentioned embodiment.

(2a) In the said embodiment, the through-hole 6 which is circular was illustrated. However, the shape of the through hole is not limited to this, and may be, for example, a semicircular shape, an elliptical shape, or a polygonal shape such as a triangular shape. Also, for example, the through holes may be so-called rounded rectangular shapes in which each vertex of the polygon has a round shape instead of a corner, or two parallel lines of two equal lengths and two semicircular shapes. Also, for example, a plurality of through holes may be provided.

(2b) In the above embodiment, the configuration in which the through hole 6 is provided outside the virtual range 72 which is a conical shape whose apex angle is defined by 60 degrees is illustrated. However, the virtual range and the position of the through hole are not limited to this. The virtual range may be, for example, an apex angle other than 60 degrees.

(2c) 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 application of the liquid level detection device is not particularly limited. The liquid level detection device may be used to detect the level of other liquids mounted on a vehicle, such as engine oil, brake fluid, and window washer liquid. Further, for example, the liquid level detection device may be used for liquid level detection in a liquid transport tank provided in a liquid transport vehicle or in a liquid container of various consumer devices other than the vehicle.

(2d) The function of one component in the above embodiment may be distributed as a plurality of components, or the function of a plurality of components may be integrated into one component. In addition, part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment.

Claims

A liquid level detection device (100) provided on a bottom surface inside a tank and detecting a position of a liquid level of a liquid stored in the tank,
An ultrasonic oscillator (11) capable of transmitting and receiving ultrasonic waves;
A housing (2) having therein a propagation path through which ultrasonic waves propagate;
Equipped with
The propagation path is
A first path (4) extending horizontally from the position where the ultrasonic oscillation element is provided;
And a second path (5) extending upward from the end opposite to the position where the ultrasonic oscillation element is provided in the first path,
The first path has a conical portion (41) which is a truncated cone-like path whose cross-sectional area gradually decreases with distance from the ultrasonic oscillation element.
The housing has a shape in which the lower surface of the portion where the conical portion is formed is separated from the bottom surface, and communicates the inside and the outside of the housing to the end portion on the ultrasonic oscillation element side in the conical portion and the lower portion in the vertical direction Liquid level detection device which has a through hole (6).
The liquid level detection device according to claim 1, wherein
The liquid level detection device, wherein the housing has the through hole at the lowermost portion in the vertical direction of the conical portion.
The liquid level detection device according to claim 1 or 2, wherein
The ultrasonic oscillation element has a shape in which a central axis is defined, and is arranged to be coaxial with the central axis of the first path,
The through hole has a center (71) of the surface of the ultrasonic oscillation element on the side facing the first path as a vertex, and a cone with an apex angle of 60 degrees with the central axis of the ultrasonic oscillation element as an axis The liquid level detection device provided outside the virtual range (72) which spreads in the shape.