JPH11237275A - Liquid level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a level sensor by which a level can be detected without a contact, which does not generate an error even after a long-term use and whose reliability is high. SOLUTION: In a sensor, a level is detected in such a way that the movement of a float arm 10 to which a float 11 is attached is detected on the basis of a change in the output of an magnetoelectric conversion element 6. In this case, a magnet 12 which is attached to the shaft part 10a of the float arm 10 is arranged inside a magnet housing part 4 in a case 2, and a cover 18 is attached to the opening part of the magnet housing part 4 so as to prevent a foreign body from creeping into the magnet housing part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level sensor used for gasoline tanks and the like, and more particularly to a float type liquid level sensor for detecting the movement of a magnet by a magneto-electric conversion element in a non-contact manner. is there.

[0002]

2. Description of the Related Art FIG. 4 shows a liquid level sensor used in a conventional gasoline tank or the like. A float 11 is attached to one end of the float arm 10, and a holder 20 is attached to the other end. This holder 20
Is rotatably supported by a frame 22 via a shaft 21. A sliding contact 23 is attached to the tip of the holder 20, and the sliding contact 23 comes into sliding contact with a resistance plate 24 attached to the frame 22.

When the float 11 moves up and down due to fluctuations in the liquid level, the sliding contact 23 turns left and right, and the resistance value of the resistance plate 24 changes. It is designed to detect.

[0004]

Since the liquid amount sensor having the above-described structure uses a detection method based on the contact between the sliding contact 23 and the resistance plate 24, a detection error due to the contact resistance between the two is likely to occur. And the deterioration of durability due to sliding wear, generation of sliding noise, or sliding contact 2
There is a problem that the manufacturing process management such as adjustment of the contact pressure between the resistor 3 and the resistance plate 24 becomes complicated.

The present invention has been made in view of the above points, and has as its object to provide a highly reliable liquid level sensor capable of detecting a liquid level without contact and having no error even when used for a long time. And

[0006]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a liquid level control apparatus for detecting a movement of a float arm to which a float is attached by detecting a change in an output of a magnetoelectric conversion element. A sensor, comprising: a magnet attached to a shaft portion of the float arm; and a magnetoelectric conversion element that detects a movement of the magnet. The magnet is disposed in a magnet housing, and is provided in an opening of the magnet housing. It is characterized by attaching a cover.

Therefore, according to the first aspect of the present invention, when the float moves up and down due to the fluctuation of the liquid level, the magnet rotates through the float arm to change the magnetic flux, and this is detected by the magnetoelectric conversion element. , The liquid level is detected. A cover is provided at the opening of the magnet housing, which prevents foreign matter from entering the magnet housing and adhering to the magnet and shaft, thereby providing high accuracy and high durability. A quality liquid level sensor is obtained.

According to a second aspect of the present invention, there is provided the liquid level sensor according to the first aspect, wherein the cover is formed of a mesh sheet.

Therefore, according to the second aspect of the present invention, only foreign matter is removed by the mesh sheet, and the liquid can enter the magnet housing and work as lubricating oil for rotating the magnet.

According to a third aspect of the present invention, there is provided the liquid level sensor according to the first or second aspect, wherein the shaft portion of the float arm is formed with the magnet housing portion via an O-ring. It is characterized by being supported by.

According to the third aspect of the present invention, the shaft portion of the float arm is supported by the elasticity of the O-ring, and a damper effect of reducing the vibration of the magnet due to the oscillation of the liquid level can be obtained.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The same members or those having the same functions as those in FIG. 4 are denoted by the same reference numerals.

In FIGS. 1 and 2, a case 2 is mounted on a fixed body 1 fixed to a liquid container (not shown). The case 2 has a wiring board housing 3 at an upper part and a magnet housing 4 at a lower part.
A partition plate 2a is formed between them.

A wiring board 5 is housed in the wiring board housing 3, and a magneto-electric conversion element 6 is attached to the wiring board 5. A terminal 15 is provided on the wiring board 5. A case cover 7 is attached to a front portion of the wiring board housing 3 via a packing 8, and the wiring board housing 3 is sealed.

A boss 9 is formed on the rear wall of the magnet housing 4, and the boss 9 has a shaft 10 of a float arm 10.
a is rotatably inserted. A float 11 is attached to the other end of the float arm 10. An eccentric cam-shaped magnet 12 is attached to the tip of the shaft portion 10a of the float arm 10. A washer 13 is provided between the magnet 12 and the boss 9, and a stopper 14 is provided at a front portion of the magnet 12. An O-ring 16 is provided at the rear of the boss 9, and an O-ring cover 17 is attached to the rear of the O-ring 16.

At the front of the magnet housing 4, a cover 18 for preventing foreign matter such as iron powder from entering the magnet housing 4 is attached. The illustrated one shows an example in which a mesh sheet used as a fuel filter is used as the cover 18, but the present invention is not limited to this, and a plate-shaped lid may be used. However, if a mesh sheet is used, it does not hinder the entry of liquids such as gasoline,
Only intrusion of foreign matter such as iron powder can be prevented.

Accordingly, the magnet 12 can be protected without hindering the function of the shaft portion 10a, which is the rotating shaft of the magnet 12, as a lubricating oil, and the cover 18 can be formed at a low cost with easy installation of the mesh sheet. There is an advantage.

When the cover 18 is formed of a plate-shaped lid, the lower portion of the case cover 7 of the wiring board housing 3 is extended to the front of the magnet housing 4 so as to serve as the cover 18. Is also good.

As described above, in the liquid level sensor of the present embodiment, the magnet 12 is attached to the shaft 10 a of the float arm 10, and a change in magnetic flux due to the deflection of the magnet 12 is detected by the magnetoelectric conversion element 6. As a result, the conventional phenomenon of increase in contact resistance and generation of sliding noise is eliminated, and the cover 18 is provided at the opening of the magnet housing 4 for housing the magnet 12, so that the Is prevented from entering and adhering to the magnet 12 and the shaft portion 10a, whereby a high-quality liquid surface sensor with high accuracy and high durability can be obtained.

[0020]

As described above in detail, according to the first aspect of the present invention, the movement of the magnet attached to the shaft of the float arm is detected by the magnetoelectric conversion element, and the magnet is accommodated. A cover is provided at the opening of the magnet housing part, which prevents foreign matter from entering the magnet housing part and adhering to the magnet and the shaft part. And a high-quality liquid level sensor with high accuracy and high durability can be obtained.

According to the second aspect of the invention, since the mesh sheet is used as the cover, in addition to the effect of the first aspect, only the foreign matter is removed by the mesh sheet, and the liquid is stored in the magnet housing. It can penetrate and act as lubricating oil for the rotation of the magnet. In addition, the mesh sheet can be easily assembled and a magnet protection structure can be realized at low cost.

According to the third aspect of the present invention, the shaft of the float arm is supported via the O-ring. Therefore, in addition to the effect of the first or second aspect of the present invention, the shaft is formed by the elasticity of the O-ring. The portion is supported, and a damper effect of reducing the vibration of the magnet due to the fluctuation of the liquid level can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially broken front view showing an embodiment of a liquid level sensor of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged sectional view of a main part of FIG. 2;

FIG. 4 is a front view of a conventional liquid level sensor.

[Explanation of symbols]

 2 Case 3 Wiring board housing part 4 Magnet housing part 5 Wiring board 6 Magnetoelectric conversion element 10 Float arm 10a Shaft part 11 Float 12 Magnet 16 O-ring 18 Cover

Claims (3)

[Claims] 1. A liquid level sensor for detecting the movement of a float arm to which a float is attached by a change in the output of a magnetoelectric conversion element, comprising: a magnet attached to a shaft of the float arm; A liquid level sensor comprising: a magnetoelectric conversion element for detecting a movement of a magnet; wherein the magnet is disposed in a magnet housing, and a cover is attached to an opening of the magnet housing. 2. The liquid level sensor according to claim 1, wherein the cover is formed of a mesh sheet. 3. The liquid level according to claim 1, wherein a shaft portion of the float arm is rotatably supported via an O-ring on a case in which the magnet accommodating portion is formed. Sensor.