JP6927183B2 - Liquid level detector - Google Patents

Description

The present disclosure relates to a liquid level detector.

In Patent Document 1, the position of the liquid surface is detected by transmitting ultrasonic waves by an ultrasonic oscillating element and receiving reflected waves reflected by the liquid surface, which are provided at the bottom of a tank for storing the liquid. The liquid level detection device configured in is disclosed. The ultrasonic oscillating element is housed in a case together with an internal terminal that is electrically connected to the ultrasonic oscillating element. The propagation path for propagating the ultrasonic waves transmitted from the case is formed by a metal tube in order to improve the propagation efficiency. The case and metal tube are held by a resin body.

Japanese Unexamined Patent Publication No. 2006-47056

As a result of detailed examination by the inventor, the above-mentioned liquid level detection device has found a problem that static electricity is generated in the resin body as the liquid in the tank fluctuates, and the metal tube becomes charged. rice field. When the charged metal tube is discharged to the internal terminal, erroneous detection of the liquid level position may occur.

One aspect of the present disclosure provides a liquid level detection device capable of suppressing the metal tube from becoming charged.

One aspect of the present disclosure is a liquid level detecting device (100) for detecting the position of the liquid level, which includes a sensor unit (1), a metal tube (22), and a body (21). The sensor unit can transmit and receive ultrasonic waves. The metal tube forms a propagation path through which ultrasonic waves transmitted from the sensor unit propagate. The body holds a metal tube and a sensor unit. The metal tube is grounded.

According to such a configuration, since the metal tube is grounded, it is possible to prevent the metal tube from being charged. Therefore, it is possible to prevent erroneous detection of the liquid level position due to the charged state of the metal tube.

It is a side sectional view of the liquid level detection apparatus of 1st Embodiment. It is an exploded perspective view of the liquid level detection device of 1st Embodiment. It is a perspective view of the 1st internal terminal of 2nd Embodiment. It is a figure which shows typically the structure of the liquid level detection apparatus of 3rd Embodiment.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. First Embodiment]
[1-1. 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 oscillator 11, an insulator 12, a first internal terminal 13a, a second internal terminal 13b, an elastic body 14, a case 15, and a lid 16. And a first external terminal 17a and a second external terminal 17b.

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 insulator 12 is a bottomed cylinder having a bottom portion 121 covering a surface 111 (hereinafter, referred to as “front surface 111”) for transmitting and receiving ultrasonic waves in the ultrasonic oscillating element 11, and a side portion 122 covering the outer peripheral surface. It is a member of the shape. Further, the insulator 12 protrudes from the inside of the side portion 122 at a position spaced apart from the bottom portion 121 by the plate thickness of the ultrasonic oscillating element 11, and is opposite to the front surface 111 of the ultrasonic oscillating element 11. It has a projecting piece 123 that covers a part of the surface 112 (hereinafter, referred to as “back surface 112”). The insulator 12 is made of an insulating material such as a resin material and a ceramic material.

The first internal terminal 13a and the second internal terminal 13b are attached to the ultrasonic oscillating element 11. The first internal terminal 13a is a terminal that electrically connects the ultrasonic oscillating element 11 and the first external terminal 17a. The second internal terminal 13b is a terminal that electrically connects the ultrasonic oscillating element 11 and the second external terminal 17b. The first internal terminal 13a and the second internal terminal 13b are formed of a metal plate. The first internal terminal 13a and the second internal terminal 13b are provided at positions facing each other with the elastic body 14 interposed therebetween.

One end of the first internal terminal 13a is a holding portion 131a that sandwiches and holds the front surface 111 and the back surface 112 of the ultrasonic oscillating element 11. Similarly, one end of the second internal terminal 13b is a holding portion 131b that sandwiches and holds the front surface 111 and the back surface 112 of the ultrasonic oscillating element 11. Since the protruding piece 123 of the insulator 12 is interposed between the back surface 112 of the ultrasonic oscillating element 11 and the sandwiching portion 131a, 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, since the bottom portion 121 of the insulator 12 is interposed between the front surface 111 of the ultrasonic oscillating element 11 and the sandwiching portion 131b, the sandwiching portion 131b is directly in contact with the front surface 111 of the ultrasonic oscillating element 11. Do not touch. That is, the first internal terminal 13a is in contact with the front surface 111 of the ultrasonic oscillating element 11, and the second internal terminal 13b is in contact with the back surface 112 of the ultrasonic oscillating element 11.

Since the first internal terminal 13a and the second internal terminal 13b have the same configuration, only the configuration of the first internal terminal 13a will be described below.
The first internal terminal 13a has a rod portion 132a and a curved portion 133a in addition to the holding portion 131a described above. The rod portion 132a is a linear portion extending from the ultrasonic oscillating element 11 toward the lid 16 in the direction along the central axis A. The curved portion 133a is a portion provided between the holding portion 131a and the rod portion 132a and curved in a wavy shape with respect to the direction along the central axis A. The curved portion 133a has a structure that absorbs an external force applied to the first internal terminal 13a when the first internal terminal 13a is attached to the ultrasonic oscillating element 11.

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 abuts on the ultrasonic oscillating element 11, and the second surface abuts on 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 151 for accommodating an ultrasonic oscillating element 11, an insulator 12, a first internal terminal 13a, a second internal terminal 13b, and an elastic body 14. The case 15 is made of an insulating resin material. The case 15 has a plurality of first locking claws 152 and a plurality of second locking claws 153. The first locking claw 152 is a claw for locking the case 15 with the lid 16. The second locking claw 153 is a claw for locking the case 15 to the housing portion 2, specifically, the body 21 described later.

The lid 16 is a member that closes the storage chamber 151 of the case 15. The lid 16 is made of a conductive resin material. The lid 16 has a plurality of locking holes 161, a first communication portion 162a, a second communication portion 162b, a first fixing portion 163a, and a second fixing portion 163b. The locking hole 161 is a hole that engages with the first locking claw 152 of the case 15. When the lid 16 is locked to the case 15, the elastic body 14 is designed to have a large dimension in the direction of the central axis A so that the elastic body 14 is accommodated in the storage chamber 151 in a state of being compressed by the lid 16 and elastically deformed. Has been done. 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 first communication portion 162a and the second communication portion 162b are portions that communicate with each other inside and outside the accommodation chamber 151, and are holes in the present embodiment. The rod portion 132a of the first internal terminal 13a is inserted into the first communication portion 162a, and the tip portion of the rod portion 132a projects to the outside of the accommodating chamber 151. A second internal terminal 13b is similarly inserted into the second communication portion 162b. The first fixing portion 163a is a portion to which the first external terminal 17a is fixed. The second fixing portion 163b is a portion to which the second external terminal 17b is fixed.

The first external terminal 17a is a terminal that electrically connects the first internal terminal 13a and the lead wire 3 shown in FIG. The second external terminal 17b is a terminal that electrically connects the second internal terminal 13b and the lead wire 3. The first external terminal 17a and the second external terminal 17b are formed of a metal plate. In the present embodiment, the first external terminal 17a is fixed to the first fixing portion 163a and is connected to the tip end portion of the rod portion 132a of the first internal terminal 13a projecting to the outside of the accommodation chamber 151. The second external terminal 17b is fixed to the second fixing portion 163b and is connected to the second internal terminal 13b like the first external terminal 17a. The first external terminal 17a is grounded. Being grounded means being electrically connected to a conductor that has a ground potential. The conductor having the ground potential may be, for example, a ground potential portion provided in the above-mentioned electric circuit, or may be, for example, a metal part such as a body part constituting a vehicle.

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 includes a body 21, a first metal tube 22, a second metal tube 23, and a reflector 24.

The body 21 is a member made of a conductive resin material 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. Specifically, as shown in FIG. 2, the body 21 has a plurality of locking holes 222. The locking hole 222 is a hole that engages with the second locking claw 153 of the case 15. The sensor unit 1 is attached to the body 21 by locking the case 15 to the body 21. As shown in FIG. 1, the lid 16 comes into contact with the body 21 in a state where the case 15 is locked to the body 21.

The first metal tube 22 is a metal tube having a substantially truncated cone shape. The cross section of the first metal tube 22 on the plane orthogonal to the central axis A is circular. The first metal tube 22 is a propagation path for ultrasonic waves and forms a first propagation path 4 extending from the bottom surface of the case 15. The first propagation path 4 extends from the bottom surface of the case 15 along the central axis A toward the side opposite to the lid 16. 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 221 is formed on the first metal tube 22.

The second metal tube 23 is a straight tubular metal tube. 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 first internal terminal 13a and the second internal terminal 13b, the ultrasonic oscillating element 11 vibrates and the case 15 Ultrasonic waves are transmitted to the first propagation path 4 via the bottom surface. When the sensor unit 1 receives the reflected wave reflected by the liquid surface or the reflected wave reflected by the reference surface 221 via the reflecting plate 24, the bottom surface of the case 15 vibrates due to the pressure action, and the ultrasonic oscillating element 11 also vibrates accordingly. Vibrate. As a result, the ultrasonic oscillating element 11 generates a voltage, and the voltage is input to an external electric circuit as an output signal via the first internal terminal 13a and the second internal terminal 13b.

In the present embodiment, the grounded first external terminal 17a is fixed to the conductive resin lid 16, and the lid 16 is in contact with the conductive resin body 21. Further, the body 21 holds and fixes the first metal tube 22. In this way, the first external terminal 17a and the first metal tube 22 are electrically connected via the lid 16 and the body 21, and the first metal tube 22 is grounded.

[1-2. effect]
According to the first embodiment described in detail above, the following effects can be obtained.
(1a) In the present embodiment, the grounded first external terminal 17a and the first metal tube 22 are electrically connected via the conductive resin lid 16 and the conductive resin body 21. ing. As a result, the static electricity generated by the fluctuation of the liquid in the tank 200 and charged in the first metal tube 22 can always be released to the grounded first external terminal 17a, so that the first metal can be released. It is possible to prevent the tube 22 from becoming charged. Therefore, it is possible to prevent erroneous detection of the liquid level position due to the first metal tube 22 becoming charged.

In particular, in the liquid level detection device 100 of the present embodiment, since the body 21 is directly attached to the bottom of the tank 200, the body 21 further picks up static electricity generated in the tank 200 itself due to the swing of the liquid in the tank 200. It ends up. As described above, the liquid level detecting device 100 of the present embodiment is in an environment in which the first metal tube 22 is more likely to be charged as compared with the configuration in which the body is not directly attached to the bottom of the tank. Even in such an environment, it is possible to prevent the first metal tube 22 from becoming charged.

The first internal terminal 13a and the second internal terminal 13b correspond to the two internal terminals, the first external terminal 17a and the second external terminal 17b correspond to the two external terminals, and the first metal. The tube 22 corresponds to a metal tube.

[2. Second Embodiment]
[2-1. composition]
As shown in FIG. 3, in the second embodiment, the shape of the first internal terminal 13c is different from that of the first internal terminal 13a of the first embodiment. Further, the lid 16 of the second embodiment is different from the lid 16 of the first embodiment in that it is made of an insulating resin material. In addition, since the basic configuration of the liquid level detection device of the second embodiment is the same as that of the first embodiment, the same reference numerals are used for the configurations common to those of the first embodiment, and the description is omitted. The configuration that differs from the form will be mainly described.

As shown in FIG. 3, the first internal terminal 13c of the second embodiment is different from the first internal terminal 13a of the first embodiment in that it does not have a curved portion 133a and has a refracting portion 133c. The refracting portion 133c is a portion extending perpendicularly to the rod portion 132a. The refracting portion 133c projects from between the case 15 and the lid 16 to the outside of the case 15. In a state where the case 15 is locked to the body 21, the refracting portion 133c is sandwiched between the body 21 and the lid 16 and press-contacts the body 21. The case 15 may be formed with a groove through which the refracting portion 133c can be inserted on the surface on the side in contact with the lid 16.

As described above, in the present embodiment, the grounded first external terminal 17a is connected to the rod portion 132a of the first internal terminal 13c, and the refracting portion 133c of the first internal terminal 13c is made of conductive resin. It is in contact with the body 21. Further, the body 21 holds and fixes the first metal tube 22. In this way, the first external terminal 17a and the first metal tube 22 are electrically connected via the first internal terminal 13c and the body 21, and the first metal tube 22 is grounded. There is.

[2-2. effect]
(2a) In the present embodiment, the grounded first external terminal 17a and the first metal tube 22 are electrically connected via the first metal internal terminal 13c and the conductive resin body 21. It is connected. As a result, it is possible to prevent the first metal tube 22 from being charged. In particular, in the configuration of this embodiment, it is not necessary to form the lid 16 with a conductive resin material.

[3. Third Embodiment]
As shown in FIG. 4, the third embodiment is different from the first embodiment in that the grounding member 32 is provided and the first external terminal 17a is not grounded. Further, the lid 16 of the third embodiment is different from the lid 16 of the first embodiment in that it is made of an insulating resin material. In addition, since the basic configuration of the liquid level detection device of the third embodiment is the same as that of the first embodiment, the same reference numerals are used for the configurations common to the first embodiment, and the description is omitted. The configuration that differs from the form will be mainly described.

[3-1. composition]
The grounding member 32 is grounded via the lead wire 33. The grounding member 32 is an annular member made of a conductive material such as a metal or a conductive resin material. The grounding member 32 is sandwiched between the body 21 and the lid 16 with the case 15 inserted through the central opening, and is pressed against the body. The grounding member 32 is not limited to a flat shape, and may be, for example, a metal plate having a wavy undulation shape. In the case of a metal plate having such a shape, the pressure contact force can be increased by the spring force caused by the undulations being crushed.

As described above, in the present embodiment, the grounding member 32 that is grounded is in contact with the body 21 made of conductive resin. Further, the body 21 holds and fixes the first metal tube 22. In this way, the grounding member 32 and the first metal pipe 22 are electrically connected via the body 21, and the first metal pipe 22 is grounded.

[3-2. effect]
(3a) In the present embodiment, the grounded member 32 and the first metal tube 22 are electrically connected to each other via a body 21 made of a conductive resin. As a result, it is possible to prevent the first metal tube 22 from being charged. In particular, in the configuration of the present embodiment, it is not necessary to ground the first external terminal 17a, and the lid 16 does not need to be made of a conductive resin material.

[4. 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.

(4a) In the first embodiment, the case 15 is made of an insulating resin material, but for example, the case 15 may be made of a conductive resin material. Thereby, the conductive path between the first metal tube 22 and the first external terminal 17a can be increased. Specifically, in addition to the conductive path through the body 21 and the lid 16, the static electricity charged in the first metal tube 22 is grounded by the conductive path through the body 21, the case 15, and the lid 16. It can be released to the terminal 17a. Therefore, it is possible to further prevent the first metal tube 22 from being charged.

(4b) In the second embodiment, the first internal terminal 13c having no curved portion is illustrated, but the first internal terminal is curved like the first internal terminal 13a of the first embodiment. It may be configured to have a portion.

(4c) In the third embodiment, the configuration in which the grounding member 32 is an annular member is illustrated, but the shape of the grounding member is not limited to the annular shape, and may be, for example, U-shaped. ..
(4d) The functions of one component in each of the above embodiments 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 each of the above embodiments 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, 5 ... Second propagation path, 11 ... Ultrasonic oscillator, 13a, 13c ... First internal terminal, 13b ... Second internal terminal , 15 ... case, 16 ... lid, 17a ... first external terminal, 17b ... second external terminal, 21 ... body, 22 ... first metal tube, 23 ... second metal tube, 24 ... reflector, 32 ... Grounding member, 100 ... Liquid level detection device, 131a, 131b ... Holding part, 132a ... Rod part, 133a ... Curved part, 133c ... Refracting part, 151 ... Storage chamber.

Claims (6)

A liquid level detection device (100) that detects the position of the liquid level.
Sensor unit (1) capable of transmitting and receiving ultrasonic waves
A metal tube (22) forming a propagation path through which ultrasonic waves transmitted from the sensor unit propagate, and
A body (21) holding the metal tube and the sensor unit,
With
The metal tube is a liquid level detection device that is grounded. The liquid level detection device according to claim 1.
The sensor unit
An ultrasonic oscillator (11) capable of transmitting and receiving ultrasonic waves,
A case (15) having a storage chamber (151) for accommodating the ultrasonic oscillating element, and a case (15).
A lid (16) provided in contact with the body and closing the containment chamber,
Two external terminals (17a, 17b) fixed to the lid on the outside of the storage chamber,
Two internal terminals (13a, 13b) that electrically connect the ultrasonic oscillating element and each of the two external terminals, and
A liquid level detection device. The liquid level detection device according to claim 2.
One of the two external terminals (17a) is grounded.
A liquid level detection device in which the body and the lid are each made of a conductive resin. The liquid level detection device according to claim 3.
The case is a liquid level detection device which is made of a conductive resin and is provided so as to come into contact with the body. The liquid level detection device according to claim 2.
One of the two external terminals (17a) is grounded.
The body is made of a conductive resin and
One of the two internal terminals (13a) is a liquid level detection device that electrically connects the grounded side of the two external terminals to the body. The liquid level detection device according to claim 2.
Further provided with a grounded grounding member (32)
The body is made of a conductive resin and
The grounding member is a liquid level detecting device provided so as to come into contact with the body.

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