JPS64674Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention relates to a liquid level detector that detects fluctuations in liquid level.

Prior Art FIG. 3 shows a conventional example. This is a float type liquid level detector.

In the figure, 1 is a reed switch, 2 is a lead wire, 3 is a stem in which the reed switch 1 and lead wire 2 are molded in resin, 4 is an annular float fitted externally to the stem 3 so as to be able to move up and down, and 5 is built into the float 4. The annular permanent magnet 6 is a stopper fixed to the lower end of the stem 3 to prevent the float 4 from coming off.

Problems to be solved by the invention The above conventional example has the following problems. That is, (a) due to sensitivity, the dimension between the reed switch 1 and the magnet 5 must be made considerably small;
The gap between the stem 3 and the float 4 is extremely small. Therefore, the gap is likely to be clogged with dirt and the like, making it difficult for the float 4 to operate smoothly, which may result in malfunction. If the clogging becomes severe, it will eventually become stuck and the float 4 will no longer operate at all. In particular, when used in a blood waste tank, there is a high risk of clogging and sticking.

(b) Due to its structure, reed switch 1 has major restrictions on miniaturization (2 mm x 15 mm). Further, since the float 4 has an annular shape surrounding the stem 3, it has to be quite large. For this reason, there is a restriction that it can only be used at a liquid surface where the liquid area is relatively large.

(c) Because the glass container of reed switch 1 is easily broken, and to prevent lead wire 2 from rusting, these are molded (stem 3). It cannot be used for petroleum or corrosive strong acids and strong alkalis that require water.

(d) If there is pulsation in the liquid level, frequent on/off cycles will occur, and accurate detection will not be possible when there is shaking.

Purpose of the invention The purpose of this invention is to solve the above-mentioned problems, and to provide high detection accuracy, and to be used in cases where the liquid area is small, petroleum, which requires explosion protection, and corrosive strong acids and strong alkalis. It is an object of the present invention to provide a liquid level detector which can operate stably against pulsations in the liquid level and is resistant to shaking.

Means for solving the problems (structure of the invention) The technical means (structure of the invention) taken by this invention to solve the above problems are as follows.

That is, the liquid level detector of this invention includes a float, a connecting rod extending from the float, a magnet attached to the connecting rod, and a state in which the connecting rod faces the magnet in the direction in which the float moves. a magnetic proximity switch element provided on a fixed part, and the magnetic proximity switch element is further comprised of a Hall element having hysteresis and a magnetic flux concentrator bonded to the surface of the Hall element on the magnet side, and the magnetic flux concentrator The surface of the concentrator on the magnet side is approximately spherical.

Effects According to the above structure of this invention, there are the following effects.

That is, since the float and the magnet are connected via the connecting rod, the float and the magnet can be positioned apart from each other. In other words, in the conventional example, a magnet is built into a float, and this float is positioned around a reed switch, so that the reed switch is either immersed in the liquid or close to the liquid surface, just like the float.

On the other hand, in the case of this invention, the magnet can be positioned far away from the float and sufficiently above the liquid level, so the magnetic proximity switch element facing the magnet can also be provided sufficiently away from the liquid level. .

Therefore, the risk of the magnetic proximity switch element coming into contact with liquid can be eliminated, and it can be used for petroleum, which requires explosion protection, or corrosive strong acids and strong alkalis.

In addition, as mentioned above, the magnetic proximity switch element is not provided around the float, and only the float and the lower end of the connecting rod are submerged in liquid. There is no need to worry about the gap being clogged with dirt or the stem sticking to the float, improving the accuracy of liquid level detection.

Furthermore, for the same reason, the target liquid area may be at least as large as the float, and can also be used in the case of a sandwiched liquid area.

Furthermore, since a Hall element with hysteresis is used in the magnetic proximity switch, stable operation without frequent on/off operations can be achieved regardless of pulsations in the liquid level. The magnetic flux concentrator of the proximity switch has a substantially spherical surface, which allows the magnet to be brought into stable contact with the magnetic flux concentrator against shaking of the float, and has high resistance to shaking.

Embodiment An embodiment of this invention will be described based on FIGS. 1 and 2. Figure 1 is a cross-sectional view of the liquid level detector.
FIGS. 2A and 2B are graphs showing the relationship between the liquid level and the induced voltage of the magnetic proximity switch element.

In FIG. 1, 7 is a liquid container such as a glass bottle, 8 is a cap, 9 is a case screwed onto the cap 8, L is a contained liquid, and Ls is a liquid level. 10 is a float immersed in liquid L, and 11 is a connecting rod extending upward from the float 10. The connecting rod 11 is divided into an upper rod 11a and a lower rod 11b, both of which are connected by a rubber joint 12. The rubber joint 12 constitutes a length adjustment section of the connecting rod 11.

The upper rod 11a is inserted into the hole 13 of the cap 8 so as to be vertically movable, and a stopper 14 for preventing the upper rod from being pulled out from the hole 13 is connected to the upper end of the upper rod.
A bar magnet 15 is fixed on top.

A magnetic proximity switch element 16 is fixed to the lower surface of the top plate of the case 9. Magnetic proximity switch element 1
6 is a Hall element 17 fixed to the bottom surface of the top plate;
It consists of a magnetic flux concentrator 18 whose lower surface is spherical (or conical) and which is joined to the lower surface of the Hall element 17. The magnetic proximity switch element 16 is connected to the connecting rod 11
The magnet 15 faces the magnet 15 in the operating direction, that is, in the vertical direction.

To explain the Hall element 17 in detail, it becomes conductive due to an increase in magnetic flux density as the magnet 15 approaches.
(mA) current sink is possible. The supporting plate and terminals are attached to a disk whose sensitive surface is 3.6 mm in diameter and about 1 mm thick. Lead wires 19 are connected to the terminals.

The magnetic flux concentrator 18 approximately controls the magnetic flux density of the magnet 15.
It is enlarged by 2.6 times and placed in the Hall element 17. Thereby, even a small ordinary magnet 15 of about 0.2 g can sufficiently operate the Hall element 17.

Next, the operation will be explained based on FIG. Second
The figure shows the situation when the liquid L flows out from the container 7 at a constant flow rate.

When the liquid level Ls is at a level H higher than (h+Δh) from the bottom of the container 7 and the float 10 is submerged in the liquid, the buoyancy of the float 10 causes the magnet 15 to act as a magnetic flux concentrator for the magnetic proximity switch element 16. 18, and the Hall element 17 is in an on state. Its excitation voltage is at high level _VH .

The bottom of the float 10 is h~h from the bottom of the container 7
At a level in the range +Δh, the float 10 is under buoyancy and the magnet 15 is close to the flux concentrator 18. In this case, the Hall element 17 is turned on or off depending on its sensitivity and the degree of magnetic flux concentration of the magnetic flux concentrator 18, but if a magnetic flux concentrator 18 with hysteresis is used, the magnet 15 and The magnetic attraction state of the magnetic flux concentrator 18 is maintained, and the Hall element 17
can be turned on. Therefore,
The excitation voltage is also at a high level _VH .

When the bottom surface of the float 10 is within h or less from the bottom of the container 7, the buoyancy of the float 10 is insufficient and the magnet 15 is far away from the magnetic flux concentrator 18.
is in the off state. Therefore, the excitation voltage drops sharply to the low level _VL .

According to this embodiment, the effects of the structure of the invention described above can be obtained, and in particular, there are the following advantages.

That is, since the magnetic proximity switch element 16 has the Hall element 17 with hysteresis,
The excitation voltage is stable regardless of the pulsation of the liquid level Ls, and the reed switch 1 seen in the conventional example
There is no frequent turning on and off (oscillation phenomenon), and stable operation can be achieved.

In addition, since the effective length of the connecting rod 11 can be finely adjusted with the rubber joint 12, the effective length of the connecting rod 11 can be finely adjusted.
The critical level that changes from V _H to low level V _L can also be finely adjusted. Since the magnetic flux concentrator 18 is spherical, the magnet 15 can be brought into stable contact with the magnetic flux concentrator 18 even when the float 10 is shaken.

In addition, the lower rod 11b of the connecting rod 11 is connected to the float 10.
The lower rod 1 is removable and replaceable, and has different lengths.
It is effective to configure the container 7 to cope with changes in the depth of the container 7 by selecting 1b.

Further, if the float 10 is made of a chemical-resistant foamed material, it can be used in liquids such as strong acids and strong alkalis without any problem.

Effects of the invention This invention has the following effects. That is, since the magnet can be positioned far away from the float and sufficiently above the liquid level, the magnetic proximity switch element facing the magnet can also be provided sufficiently away from the liquid level.

Therefore, the risk of the magnetic proximity switch element coming into contact with liquid can be eliminated, and it can be used for petroleum, which requires explosion protection, or corrosive strong acids and strong alkalis.

In addition, as mentioned above, the magnetic proximity switch element is not provided around the float, and only the float and the lower end of the connecting rod are submerged in liquid. There is no need to worry about the gap being clogged with dirt or the stem sticking to the float, improving the accuracy of liquid level detection.

Furthermore, for the same reason, the target liquid area may be at least as large as the float, and can also be used in the case of a sandwiched liquid area. Furthermore, since a Hall element with hysteresis is used in the magnetic proximity switch, stable operation without frequent on/off operations can be achieved regardless of pulsations in the liquid level. The magnetic flux concentrator of the proximity switch has a substantially spherical surface, so that the magnet can be brought into stable contact with the magnetic flux concentrator even when the float oscillates. These have the effect of configuring a liquid level detector that is resistant to vertical vibrations and shaking.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of this invention, FIG. 2 is a graph for explaining the operation, and FIG. 3 is a sectional view of a conventional example. 10...Float, 11...Connecting rod, 12...
Rubber joint (length adjustment part), 15...Magnet,
16... Magnetic proximity switch element, 17... Hall element, 18... Magnetic flux concentrator.

Claims (1)

[Claims for Utility Model Registration] (1) A float, a connecting rod extending from the float, a magnet attached to the connecting rod, and a state in which the connecting rod faces the magnet in the direction of movement of the float. a magnetic proximity switch element provided on a fixed part, the magnetic proximity switch element comprising a Hall element having hysteresis and a magnetic flux concentrator bonded to the surface of the Hall element on the magnet side; A liquid level detector whose surface on the magnet side is substantially spherical. (2) The liquid level detector according to claim (1), wherein the connecting rod is provided with a length adjusting section.