JP6927182B2 - Liquid level detector - Google Patents

Description

The present disclosure relates to a liquid level detector.

At the bottom of a tank for storing a liquid, there is a liquid level detecting device that detects the position of the liquid surface by transmitting ultrasonic waves by an ultrasonic oscillating element and receiving reflected waves reflected by the liquid surface. Patent Document 1 describes that such a liquid level detecting device is used for detecting a fuel liquid level in a fuel tank equipped in an automobile.

Further, in Patent Document 1, as a liquid level detection device, a case for accommodating an ultrasonic wave oscillating element and a propagation path of ultrasonic waves transmitted from the ultrasonic oscillating element are described in an internal space while being attached to one end side of the case. Those provided with a tubular transmission tube to be formed are described. In this liquid level detection device, a lead wire for applying a voltage to the ultrasonic oscillating element is connected to the ultrasonic oscillating element, and the lead wire extends in the direction opposite to the extending direction of the transmission tube and extends out of the case. ing.

Japanese Unexamined Patent Publication No. 2006-119046

However, as a result of detailed studies by the present inventors, in the liquid level detection device described in Patent Document 1, the lead wire as a connecting member electrically connected to the ultrasonic oscillating element is sufficiently electrically connected. It was found that the detection signal may be noisy because it is not shielded. Specific sources of noise include motors that drive pumps to supply fuel in tanks to engines, and electronic and electrical equipment that exists around automobiles, such as road heaters embedded in roads. Can be mentioned.

One aspect of the present disclosure provides a liquid level detection device in which noise on a detection signal is reduced.

One aspect of the present disclosure is a liquid level detecting device (100) for detecting the position of the liquid level, which includes an ultrasonic oscillating element (11), a case (15), a metal tube (22), and a connecting member ( 13) and. The ultrasonic oscillator can transmit and receive ultrasonic waves. The case is a case for forming an accommodation chamber (16) for accommodating the ultrasonic oscillating element, and has a bottom portion (151) provided on the surface side of the ultrasonic oscillating element for transmitting and receiving ultrasonic waves, and the ultrasonic oscillating element. A lid portion (152) provided on the surface opposite to the surface for transmitting and receiving ultrasonic waves, and an outer peripheral portion (153) provided between the bottom portion and the lid portion and defining the accommodation chamber together with the bottom portion and the lid portion. Has. The metal tube forms a propagation path (4) that is a propagation path for ultrasonic waves and extends from the bottom of the case. The connecting member is electrically connected to the ultrasonic oscillating element, attached to the ultrasonic oscillating element, and extends toward the lid of the case. The metal tube has an extension tube portion (222) extended from a portion (221) that forms a propagation path in the metal tube. At least a part of the connecting member is present in the extension pipe portion.

According to such a configuration, at least a part of the connecting member electrically connected to the ultrasonic oscillating element is electrically shielded by the extension tube portion of the metal tube, so that the noise on the detection signal can be reduced. Can be done.

It is sectional drawing of the liquid level detection apparatus. It is a horizontal cross-sectional view of a sensor part. It is a vertical cross-sectional view of a sensor part.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. composition]
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 for storing liquid fuel, and receives reflected waves reflected by the liquid level to receive the liquid level. It is a device that detects the position of. The side surface of the liquid level detection device 100 shown in FIG. 1 is shown instead of the cross section in order to show the internal structure in an easy-to-understand manner. From a functional point of view, the liquid level detection device 100 includes roughly two functional units, specifically, a sensor unit 1 and a housing unit 2.

The sensor unit 1 is an assembly that functions as an ultrasonic wave transmitting / receiving unit as a whole. As shown in FIG. 2, the sensor unit 1 includes an ultrasonic oscillating element 11, a connecting member 13, an elastic body 14, a case 15, and an external connection terminal 17.

The ultrasonic oscillating element 11 is an element that transmits and receives ultrasonic waves. The ultrasonic oscillating element 11 is formed in a disk shape by a substance having a piezo effect such as PZT. The piezo effect is a characteristic in which the volume changes when a voltage is applied, while the voltage is generated when a force is received from the outside. Electrodes printed on almost the entire surface of the ultrasonic oscillating element 11 are provided on both sides of the ultrasonic oscillating element 11. When a voltage is applied from an external electric circuit between the electrodes on both sides of the ultrasonic oscillating element 11 via the lead wire 3 shown in FIG. 1, the ultrasonic oscillating element 11 moves in the central axis A direction, which is the plate thickness direction, due to the above-mentioned piezo effect. It oscillates ultrasonic waves by vibrating.

The elastic body 14 is a substantially columnar member arranged coaxially with the central axis A of the ultrasonic oscillating element 11. Of the two end faces on both sides in the axial direction, the first surface is in contact with the ultrasonic oscillating element 11, and the second surface is in contact with the lid portion 152 of the case 15, which will be described later. The elastic body 14 is made of an elastic material such as a flexible resin or rubber.

The case 15 forms a storage chamber 16 that houses the ultrasonic oscillating element 11 and the elastic body 14. The case 15 has a bottom portion 151, a lid portion 152, and an outer peripheral portion 153. The bottom portion 151 is provided on the surface 111 (hereinafter, referred to as “front surface 111”) side of the ultrasonic oscillating element 11 for transmitting and receiving ultrasonic waves. The lid portion 152 is provided on the surface 112 (hereinafter, referred to as “back surface 112”) opposite to the surface 111 for transmitting and receiving ultrasonic waves of the ultrasonic oscillating element 11. The outer peripheral portion 153 is provided between the bottom portion 151 and the lid portion 152, and defines the accommodation chamber 16 together with the bottom portion 151 and the lid portion 152. The bottom portion 151 and the outer peripheral portion 153 are integrally formed in a bottomed cylindrical shape, and the lid portion 152 is a separate body from these. The lid portion 152 is fixed to the outer peripheral portion 153 by catching a hole or groove provided in the lid portion 152 on a claw provided on the outer peripheral portion 153. With the lid portion 152 fixed to the outer peripheral portion 153, the elastic body 14 is dimensioned in the direction of the central axis A so as to be accommodated in the storage chamber 16 of the case 15 in a state of being compressed by the lid portion 152 and elastically deformed. Is designed to be large. Therefore, the ultrasonic oscillating 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 connecting member 13 is a terminal attached to the ultrasonic oscillating element 11 and electrically connecting the ultrasonic oscillating element 11 and the external connection terminal 17. The connecting member 13 is made of a metal plate.
As shown in FIG. 2, the liquid level detecting device 100 of the present embodiment includes a first connecting member 131 and a second connecting member 132 as the connecting member 13. The first connecting member 131 and the second connecting member 132 are provided at positions facing each other with the elastic body 14 interposed therebetween. In FIG. 1, the first connecting member 131 is provided on the front side, and the second connecting member 132 is provided on the back side.

As shown in FIG. 2, one end of the first connecting member 131 is a holding portion 131a that sandwiches and holds the front surface 111 and the back surface 112 of the ultrasonic oscillating element 11. The same applies to the second connecting member 132. An insulator 12 is interposed between the back surface 112 of the ultrasonic oscillating element 11 and the sandwiching portion 131a, and the sandwiching portion 131a does not come into direct contact with the back surface 112 of the ultrasonic oscillating element 11. On the other hand, the insulator 12 is also interposed between the back surface 111 of the ultrasonic oscillating element 11 and the sandwiching portion 132a of the second connecting member 132, and the sandwiching portion 132a is directly in contact with the back surface 112 of the ultrasonic oscillating element 11. Not in contact. The insulator 12 is made of an insulating material such as a resin material or a ceramic material. The first connecting member 131 is a terminal on the ground side. That is, the first connecting member 131 is grounded.

Hereinafter, since the first connecting member 131 and the second connecting member 132 have the same configuration, only the first connecting member 131 will be described.
As shown in FIG. 2, the first connecting member 131 extends from the ultrasonic oscillating element 11 toward the lid portion 152. Specifically, the first connecting member 131 extends in the direction along the central axis A. Further, the first connecting member 131 is provided between the elastic body 14 and the outer peripheral portion 153 of the case 15, and is along the inner surface of the outer peripheral portion 153 of the case 15. The end of the first connecting member 131 on the opposite side of the holding portion 131a projects to the outside of the accommodating chamber 16 through the hole 18 provided in the lid portion 152. Further, the end portion of the first connecting member 131 projecting to the outside of the accommodation chamber 16 is connected to the external connection terminal 17. As shown in FIG. 1, in the first connecting member 131, the structure between the end portion connected to the external connection terminal 17 and the sandwiching portion 131a is curved in a wavy shape with respect to the direction along the central axis A. ing. This absorbs the external force applied to the first connecting member 131 so that the position where the sandwiching portion 131a sandwiches the ultrasonic oscillating element 11 does not shift when the first connecting member 131 is attached to the ultrasonic oscillating element 11. Because.

Here, the case 15 is made of resin. When the case 15 is made of metal, for example, the first connecting member 131 is provided along the inner surface of the outer peripheral portion 153 of the case 15, so that there is a possibility of a short circuit. Further, when the case 15 is made of metal, the ultrasonic waves transmitted from the ultrasonic oscillating element 11 may be reflected by the bottom portion 151 of the case 15. In this embodiment, the case 15 is made of an insulating resin material.

Next, the housing portion 2 will be described. The housing portion 2 is an assembly that functions as a propagation path for ultrasonic waves as a whole. As shown in FIG. 1, the housing portion 2 has a body 21, a first metal tube 22, a second metal tube 23, and a reflector 24.

The body 21 is a resin member that holds and fixes the sensor unit 1, the first metal tube 22, the second metal tube 23, and the reflector 24. The first metal tube 22, the second metal tube 23, and the reflector 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 oscillating element 11 is coaxial with the central axis A of the first metal tube 22.

The first metal tube 22 is a metal tube. In this embodiment, the first metal tube 22 is made of stainless steel. The first metal tube 22 has a propagation tube portion 221 and an extension tube portion 222.
The propagation tube portion 221 is a substantially truncated cone-shaped cylinder. The cross section of the propagation tube portion 221 on the plane orthogonal to the central axis A is circular.

The propagation tube portion 221 forms a first propagation path 4 that is a propagation path of ultrasonic waves and extends from the bottom 151 of the case 15. The first propagation path 4 extends from the bottom portion 151 of the case 15 along the central axis A toward the side opposite to the lid portion 152 of the case 15. The first propagation path 4 has a conical portion 41, a straight portion 42, and a step portion 43. The conical portion 41 is a truncated cone-shaped portion whose cross-sectional area gradually decreases as the distance from the ultrasonic oscillating element 11 increases. In other words, the diameter of the cross section of the conical portion 41 on the plane orthogonal to the central axis A decreases as the distance from the ultrasonic oscillating element 11 increases. The straight portion 42 is a portion having 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 straight portion 42, and the cross-sectional area is reduced stepwise at the end portion of the conical portion 41 opposite to the end portion where the ultrasonic oscillating element 11 is provided. It is a part. Due to the presence of the step portion 43, an annular reference surface 223 is formed on the first metal tube 22.

The extension pipe portion 222 is a portion of the first metal pipe 22 that is extended from the propagation pipe portion 221. Specifically, the extension pipe portion 222 is extended from the propagation pipe portion 221 so that at least a part of the first connecting member 131 and the second connecting member 132 is present in the extension pipe portion 222. Specifically, the extension pipe portion 222 extends from the propagation pipe portion 221 toward the lid portion 152 of the case 15 along the central axis A. In the present embodiment, as shown by the arrow C in FIG. 2, the extension pipe portion 222 extends from the propagation pipe portion 221 to the end 161 on the lid portion 152 side in the accommodation chamber 16, and is in the thickness direction of the lid portion 152, that is, It extends halfway along the central axis A. Further, the extension pipe portion 222 covers the outside of the outer peripheral portion 153 of the case 15. In the present embodiment, the extension pipe portion 222 covers the entire circumference of the outer peripheral portion 153 of the case 15.

The second metal tube 23 is a straight tubular metal tube. In this embodiment, the second metal tube 23 is made of stainless steel. In the second metal tube 23, the central axis B of the second metal tube 23 is orthogonal to the central axis A, and is continuous with the end of the first metal tube 22 on the straight portion 42 side via the body 21. It is provided as follows. The second metal tube 23 has a circular cross section on a plane orthogonal to the central axis B. The upper end of the second metal pipe 23 is positioned so that the fuel storage amount of the tank 200 protrudes upward by a predetermined length from the liquid level at the maximum. The second metal tube 23 forms a second propagation path 5 that is part of the ultrasonic propagation path. The second propagation path 5 extends from the bottom of the tank 200 toward the liquid level. Specifically, it extends vertically from the bottom of the tank 200. The diameter of the second propagation path 5 in the present embodiment is equal to the diameter of the straight portion 42.

The reflector 24 is a metal plate. In a state where the reflector 24 is held and fixed to the body 21, the central axis A of the first metal tube 22 and the central axis B of the second metal tube 23 intersect at the reflecting surface 241 of the reflector 24. It is arranged to do. The reflector 24 reflects the ultrasonic waves transmitted from the ultrasonic oscillating element 11 toward the liquid surface of the fuel. Specifically, the reflector 24 directs ultrasonic waves traveling along the central axis A of the first metal tube 22 in a direction in which the angle of incidence on the liquid surface is 0 °, that is, in a direction orthogonal to the liquid surface. It is installed so that it reflects. In the present embodiment, the reflector 24 is provided so as to be inclined by 45 ° with respect to the liquid surface.

With the above configuration, when a pulsed voltage is applied to the ultrasonic oscillating element 11 via the lead wire 3, the external connection terminal 17, the first connecting member 131, and the second connecting member 132, ultrasonic oscillation is performed. The element 11 vibrates and ultrasonic waves are transmitted to the first propagation path 4 via the bottom 151 of the case 15. When the sensor unit 1 receives the reflected wave reflected on the liquid surface via the reflecting plate 24 or the reflected wave reflected on the reference surface 223, the bottom portion 151 of the case 15 vibrates due to the pressure action, and the ultrasonic oscillating element 11 is accompanied by this. Also vibrates. As a result, the ultrasonic oscillating element 11 generates a voltage, and the voltage is used as an output signal to an external electric circuit via the first connecting member 131, the second connecting member 132, the external connection terminal 17, and the lead wire 3. Entered.

In the present embodiment, the first connecting member 131, which is a terminal on the ground side, and the extension pipe portion 222 are electrically connected. Specifically, as shown in FIG. 3, the first connecting member 131 and the extension pipe portion 222 are electrically connected by a member 19 passing through a through hole 154 provided in the outer peripheral portion 153 of the case 15. There is. In this embodiment, the member 19 is a lead wire. Note that the member 19 is not shown in FIG. 2, and the insulator 12 is not shown in FIG.

[2. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(2a) Since at least a part of the first connecting member 131 and the second connecting member 132 is present in the extension pipe portion 222 of the first metal pipe 22, the first connecting member 131 and the second connecting member 132 is electrically shielded. As a result, the noise on the detection signal is reduced.

(2b) The extension pipe portion 222 extends from the propagation pipe portion 221 to at least the end 161 on the lid portion 152 side of the case 15 in the accommodation chamber 16. That is, most of the first connecting member 131 and the second connecting member 132 are covered with the extension pipe portion 222. Therefore, the first connecting member 131 and the second connecting member 132 are more effectively electrically shielded by the extension pipe portion 222.

(2c) The first connecting member 131 is grounded, and the first connecting member 131 and the extension pipe portion 222 are electrically connected. Since the extension tube portion 222 is electrically connected to the ground, the first connecting member 131 and the second connecting member 132 are more effectively electrically shielded by the extension tube portion 222. Further, since the extension pipe portion 222 is connected to the first connecting member 131 that has already been grounded, it is not necessary to newly provide wiring for grounding the extension pipe portion 222, for example.

[3. Other embodiments]
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(3a) The shape of the extension pipe portion 222 is not limited to the shape shown in the above embodiment.
Specifically, in the above embodiment, the extension pipe portion 222 covers the entire circumference of the outer peripheral portion 153 of the case 15, but the extension pipe portion 222 does not necessarily cover the entire circumference of the outer peripheral portion 153. For example, the extension pipe portion 222 may partially cover the entire circumference of the outer peripheral portion 153. Specifically, the extension pipe portion 222 may be formed of punching metal or may have a mesh shape. In such a case, the ratio of the portion covered by the extension pipe portion 222 to the entire circumference of the outer peripheral portion 153 is set to the position of the noise source so that the intensity of the generated noise is equal to or less than the desired value. It can be set as appropriate. In order to more effectively reduce the generated noise, it is preferable that the ratio of the entire circumference of the outer peripheral portion 153 covered by the extension pipe portion 222 is large. Therefore, it is preferable that the extension pipe portion 222 covers the entire circumference of the outer peripheral portion 153.

Further, in the above embodiment, the end portion of the extension pipe portion 222 has a shape obtained by cutting a circular pipe on a plane perpendicular to the central axis A, but the shape of the end portion of the extension pipe portion 222 is not limited to this. For example, the end portion of the extension pipe portion 222 may have a shape in which the circular pipe is cut along a plane inclined with respect to the central axis A. The shape of the end portion of the extension tube portion 222 is appropriately set according to the arrangement of other members constituting the sensor portion 1, the position of the noise source, and the like within a range in which the intensity of the generated noise is equal to or less than a desired value. be able to.

(3b) In the above embodiment, the member 19 that electrically connects the first connecting member 131 and the extension pipe portion 222 is a lead wire, but the member 19 is not limited to this. For example, a terminal may be used as the member 19 instead of the lead wire. Further, a part of the first connecting member 131 may be used as the member 19.

(3c) In the above embodiment, the extension pipe portion 222 is grounded via the first connecting member 131, but the extension pipe portion 222 may be grounded without passing through the first connecting member 131.
(3d) In the above embodiment, the first connecting member 131 and the extension pipe portion 222 are electrically connected by a member 19 passing through a through hole 154 provided in the outer peripheral portion 153 of the case 15. However, the method of connecting the first connecting member 131 and the extension pipe portion 222 is not limited to this. For example, a part of the extension pipe portion 222 may be extended through the lid portion 152 until it protrudes, and the protruding portion and the external connection terminal 17 connected to the ground may be connected. Further, the first connecting member 131 and the extension pipe portion 222 may be connected by a member passing between the outer peripheral portion 153 and the lid portion 152.

(3e) In the above embodiment, the first metal tube 22 and the second metal tube 23 are made of stainless steel, but the metal constituting the first metal tube 22 and the second metal tube 23 is limited to this. Not done. For example, examples of the metal include iron, aluminum, and those obtained by subjecting them to plating treatment such as Ni plating and Zn plating.

(3f) In the above embodiment, the case 15 is made of an insulating resin material, but the material of the case 15 is not limited to this. For example, the case 15 may be made of a conductive resin material.

(3g) The functions of one component in the above embodiment may be dispersed as a plurality of components, or the functions of the plurality of components may be integrated into one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other embodiment.

1 ... Sensor unit, 2 ... Housing unit, 4 ... First propagation path, 11 ... Ultrasonic oscillator, 13 ... Connection member, 131 ... First connection member, 132 ... Second connection member, 15 ... Case, 151 ... bottom, 152 ... lid, 153 ... outer circumference, 16 ... accommodation chamber, 161 ... lid-side end of accommodation, 22 ... first metal tube, 221 ... propagation tube, 222 ... extension tube, 100 ... Liquid level detection device.

Claims (5)

A liquid level detection device (100) that detects the position of the liquid level.
An ultrasonic oscillator (11) capable of transmitting and receiving ultrasonic waves,
A case (15) forming a storage chamber (16) for accommodating the ultrasonic oscillating element, the bottom portion (151) provided on the surface side of the ultrasonic oscillating element for transmitting and receiving ultrasonic waves, and the ultrasonic waves. A lid (152) provided on the surface opposite to the surface of the oscillating element that transmits and receives ultrasonic waves is provided between the bottom and the lid, and the storage chamber is defined together with the bottom and the lid. The case having the outer peripheral portion (153) and the outer peripheral portion (153).
A metal tube (22) and a metal tube (22) forming the propagation path (4) of the ultrasonic wave extending from the bottom of the case.
A connecting member (13) that is electrically connected to the ultrasonic oscillating element, is attached to the ultrasonic oscillating element, and extends toward the lid of the case.
With
The metal tube has an extension tube portion (222) extended from a portion (221) of the metal tube that forms the propagation path.
A liquid level detection device in which at least a part of the connecting member is present in the extension pipe portion. The liquid level detection device according to claim 1, wherein the extension pipe portion extends from a portion of the metal pipe forming the propagation path to at least an end on the lid side of the case in the storage chamber. The liquid level detecting device according to claim 1 or 2, wherein the case is made of resin, and the connecting member is along the inner surface of the outer peripheral portion of the case. The connecting member is grounded and
The liquid level detecting device according to any one of claims 1 to 3, wherein the connecting member and the metal pipe are electrically connected. The liquid level detection device according to any one of claims 1 to 4, wherein the extension pipe portion covers the outside of the outer peripheral portion of the case.

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