JP2002148104A - Magnetic field generator, and level gage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field generator capable of generating a magnetic field to make change of a magnetic flux density get linear, and a float type level gage capable of detecting continuous change of a liquid level. SOLUTION: Two ring-like magnets 2, 3 are opposedly arranged coaxially with the same polarity, and a distance between the centers of the two ring-like magnets 2, 3 is preferably made to come within a specified range corresponding to outside diameters of the magnets 2, 3, in this magnetic field generator 1. The magnetic field generator 1 is built in a float of the level gage, and a magnetism detecting element for detecting the linear change of the magnetic flux density is built in a stem.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator and a float type liquid level gauge, and more particularly to a magnetic field generator having a region where a magnetic flux density changes linearly and a liquid level using the magnetic field generator. The present invention relates to a float-type liquid level gauge capable of continuously detecting pressure.

[0002]

2. Description of the Related Art Conventionally, a ring-shaped float floating on a liquid surface is arranged on an outer peripheral surface of a cylindrical stem arranged perpendicular to the liquid surface, and the float moves up and down with the stem as a guide as the liquid surface rises and falls. A float type liquid level gauge is known. In this liquid level gauge, a magnetic detecting element such as a reed switch for detecting the magnetic field of a magnet is incorporated in a stem, and a magnet is incorporated in a float. The magnetic detecting element of the stem moves the outer peripheral surface of the stem to a liquid level. The liquid level can be electrically measured by detecting the magnetic field of the magnet of the float which moves up and down with the change of the liquid level.

[0003]

However, in the float type liquid level gauge in which the magnetic field of the magnet incorporated in the conventional float is detected by the magnetic sensing element incorporated in the stem, the liquid level continuously changes. Could not be detected, and fine liquid level control could not be performed.

That is, in a structure in which a magnetic field generated by a magnet incorporated in a float is detected by a reed switch incorporated in a stem, only a point can be detected by performing ON / OFF operation at a strength higher than a certain magnetic field. Was. There is also known a liquid level gauge in which a number of reed switches are arranged in the vertical direction of the stem to detect a magnetic field at many points.
A large number of reed switches are needed to detect a liquid level that is closer to a continuous one, and there is a problem that the cost increases.

It is also conceivable to use a magnetic detecting element such as a Hall element that can detect a linear change in magnetic flux density. However, since the linear range of the magnetic flux density change of the magnet incorporated in the float is extremely narrow, It was not practical.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic field generator capable of generating a magnetic field having a wide linear range of magnetic flux density change.

Another object of the present invention is to provide a float type liquid level gauge capable of detecting a continuous change in the liquid level.

[0008]

According to a first aspect of the present invention, there is provided a magnetic field generating apparatus comprising a pair of ring-shaped magnets magnetized in a thickness direction, wherein the ring-shaped magnets have the same polarity. When the outer diameters of the ring-shaped magnets are φ ₁ , and the distance between the centers of the magnets in the thickness direction is L ₀ , the following formula (1) is satisfied. Is adopted. 0.45φ ₁ ≦ L ₀ ≦ 0.9φ ₁ ... (1)

A liquid level gauge according to a second aspect of the present invention has a ring-shaped float floating on the liquid surface and a stem inserted into a hollow portion of the float, and the stem has a linear change in magnetic flux density. A magnetic sensing element to be detected is incorporated, a pair of ring-shaped magnets magnetized in the thickness direction are incorporated in the float, and these ring-shaped magnets have the same poles facing each other and are arranged coaxially with each other. The configuration is adopted.

[0010] Further, the liquid level gauge according to the third aspect is the second aspect.
In the liquid level meter described above, when the outer diameter of the ring-shaped magnet is φ ₁ , and the distance between centers of the magnets in the thickness direction is L ₀ , a configuration satisfying the following expression (1) is satisfied. Has adopted. 0.45φ ₁ ≦ L ₀ ≦ 0.9φ ₁ ... (1)

The magnetic field generating device of the present invention includes a pair of ring-shaped magnets in which the same poles are coaxially opposed to each other.
By arranging the two ring-shaped magnets in this manner and arranging the distance L _{0 from} each other to be within a certain range with respect to the outer diameter φ _{1 of the} magnet, the distance between the two ring-shaped magnets can be reduced. A region where the magnetic flux density changes almost linearly along the central axis is generated.

In the liquid level gauge of the present invention, the two ring-shaped magnets used in the magnetic field generator are incorporated in a float, and the linear magnetic flux density along the central axis between the two ring-shaped magnets is provided. By detecting the change with a magnetic detection element that detects a linear change in magnetic flux density such as a Hall element built into the stem, the position of the float can be detected continuously,
A change in the liquid level can be continuously detected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a magnetic field generator and a liquid level gauge according to the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing the arrangement of two ring-shaped magnets used in the magnetic field generator 1 of the present invention.

The first ring-shaped magnet 2 and the second ring-shaped magnet 3 constituting the magnetic field generator 1 have substantially the same shape, and are arranged such that their center axes c coincide with each other. A portion along the central axis c between these ring-shaped magnets 2 and 3 is formed as a cavity, and the element for magnetic detection is formed by these ring-shaped magnets 2 and 3
It is a space that can move along the central axis between. These magnets 2 and 3 are magnetized in the thickness direction, and are arranged so that the same poles are opposed to each other. In the drawing, the N poles face each other, but the S poles may face each other.

When the ring-shaped magnets 2 and 3 are arranged so as to have the same polarity, a neutral point magnetically exists between the two magnets. In the vicinity of one magnet and the vicinity of the other magnet, the strength of the magnetic field has a maximum value with opposite polarities. Accordingly, there is a region between the two ring-shaped magnets 2 and 3 where the magnetic flux density changes substantially linearly.

When the two ring-shaped magnets 2 and 3 are coaxially and co-opposed, a region where the magnetic flux density changes substantially linearly along the center axis between the two ring-shaped magnets 2 and 3 is generated. This will be specifically described. These ring-shaped magnets 2, 3
The outer diameter is φ ₁ , the inner diameter is φ ₂ , and the separation distance between the centers in the thickness direction of the ring-shaped magnet is L ₀ .

FIG. 2 shows the change in magnetic flux density in the axial direction (in the direction of the center of the opening) when the ring-shaped magnet is magnetized (magnetized) in the thickness direction. This ring-shaped magnet has an outer diameter φ ₁ 19.
5 mm, inner diameter φ ₂ 14.0 mm, thickness 2.4 mm. In FIG. 2, the horizontal axis represents the axial distance of the ring-shaped magnet, and the origin represents the center of the ring-shaped magnet. The unit is m
m. The vertical axis indicates the magnetic flux density B corresponding to the axial distance of the ring-shaped magnet. The unit is mT. The measurement was performed by moving the probe for detecting the magnetic flux density in the direction of the center axis of the ring-shaped magnet.

In FIG. 2, the waveform W1 of the magnetic flux density is a
The magnetic flux density is zero at two points (a point 6.1 mm from the center), a point and a ′. For example, FIG.
FIG. 3 shows a waveform W1 obtained by rotating the waveform W1 by 180 ° and a waveform W1 superimposed thereon.

When the waveform W1 and the waveform W2 are added, FIG.
The waveform W3 shown in FIG. This waveform W3 had an outer diameter phi ₁ 1
This is the magnetic flux density change itself in the direction of the central axis when two 9.5 mm ring-shaped magnets are arranged coaxially with a center distance L _{0 of} 12.2 mm with the same poles facing each other. Waveform W3
During from p ₁ of p ₂ has a pretty good linearity.
Therefore, the magnetic field generator 1 according to the present invention is configured such that the magnetic field generator 1 is arranged in the axial direction between p ₁ and p _{2 with} respect to the magnetic sensing element fixed along the center axis of the ring-shaped magnets 2 and 3. 1 or for fixing the magnetic field generator 1 and moving the magnetic sensing element between p ₁ and p ₂ along the central axis of the ring-shaped magnets 2 and 3. . Thus, the position of the magnetic field generator 1 or the position of the element for magnetic detection can be continuously detected from the signal of the magnetic detector.

Further, practical dimensions of the magnetic field generator 1 when incorporated in a float were examined. The ratio φ ₂ / φ ₁ between the outer diameter φ ₁ and the inner diameter φ ₂ of the ring-shaped magnets 2 and 3 is 0.
It is in the range of 55 to 0.75. For ring-like magnet in these dimensional ratio, was determined the distance from the magnet center to the neutral point of the magnetic flux density becomes zero in relation to the magnet outer diameter phi ₁ is FIG.

[0022] From FIG. 5, the distance L ₁ from the magnet center to the neutral point, relative to the magnet outer diameter phi _1, so that the following equation (2). L ₁ ≒ 0.3φ ₁ ... (2)

[0023] (2) than the center distance L ₀ of the ring-like magnet to the same polarity facing each is as the following equation (3). L ₀ = 2L ₁ = 0.6φ ₁ (3)

As a practical range for obtaining an electric signal that is substantially proportional to the liquid level, the upper limit is 0.6φ ₁ +0.
It is considered that 3φ ₁ and the lower limit is 0.6φ ₁ −0.15φ ₁ . Accordingly, the distance between the centers L ₀ of the ring magnet is a range of the following formula (1). 0.45φ ₁ ≦ L ₀ ≦ 0.9φ ₁ ... (1)

Preferably, the distance L between the centers of the ring-shaped magnets
₀ is in the range of the following equation (4). 0.50φ ₁ ≦ L ₀ ≦ 0.8φ ₁ ... (4)

[0026] Most preferably, the distance between the centers L ₀ of the ring magnet is in the range of the following formula (5). 0.55φ ₁ ≦ L ₀ ≦ 0.65φ ₁ ... (5)

The magnetic field generator 1 of the present invention has
The two ring-shaped magnets 2 and 3 are coaxially arranged at the same polarity and opposed to each other. By defining the range, a region where the magnetic flux density changes linearly along the central axis between the two ring magnets 2 and 3 facing each other is created. By detecting the area where the magnetic flux density changes linearly with a magnetic detecting element such as a Hall element that detects a linear change in the magnetic flux density, for example, a linear voltage change can be obtained.

FIG. 6 shows an example in which the magnetic field generator of the present invention is applied to a float type liquid level gauge.
6A is a vertical sectional view of the float, and FIG. 6B is a top view of the float.

The float 10 has, for example, a thick cylindrical float body 11. The float main body 11 has two ring-shaped magnets 2 and 3 having substantially the same inner diameter as the columnar gap of the float main body 11, the inner surfaces of which are substantially flush with the inner surface of the float main body 11, and the center axes of the two are aligned. They are arranged so as to coincide with each other and have the same polarity. In addition, they are arranged such that the distance between them is in the above-mentioned range. The float main body 11 has a structure that floats on the liquid surface, and is manufactured by insert molding in which two ring-shaped magnets 2 and 3 are arranged at predetermined positions using, for example, plastic or foamed plastic having a low specific gravity. The float body 11 may be made of a metal that does not affect the magnetic field of the ring-shaped magnets 2 and 3, for example, stainless steel, and may have any shape.

The cylindrical internal space of the float 10 can be inserted with a cylindrical stem (not shown) fixed and arranged perpendicular to the liquid surface, and the stem functions as a float guide. The float 10 rises and falls on the outer peripheral surface of the stem as the liquid level rises and falls. A magnetic detecting element capable of detecting a linear change in the magnetic flux density of the two ring-shaped magnets 2 and 3 is incorporated in the stem. Examples of the magnetic detection element capable of detecting a linear change in magnetic flux density include a Hall element and a magnetoresistive element with a bias magnet.

The liquid level gauge 10 of the present invention includes a float 11
Incorporating the magnetic field generator 1 of the present invention, two ring-shaped magnets 2 and 3 are coaxially arranged at the same polarity and opposed to each other, and preferably, the center distance between the two ring-shaped magnets 2 and 3 is set to be a ring-shaped magnet. By making it a specific range corresponding to a few outside diameters,
A region where the magnetic flux density changes linearly along the central axis between the two ring magnets 2 and 3 facing each other is created. On the other hand, a magnetic sensing element such as a Hall element that can detect a linear change in magnetic flux density is incorporated in a stem that regulates the float to a degree of freedom in one axial direction. These floats 1
An output voltage corresponding to the liquid level can be obtained by combining 1 and the stem such that p ₁ to p ₂ shown in FIG. 4 are in the liquid level control range. The position of the float was continuously measured from the output voltage signal, and it was possible to continuously detect a change in the liquid level, thereby enabling fine control of the liquid level.

[0032]

According to the magnetic field generator of the present invention, a region where the magnetic flux density changes linearly between two ring-shaped magnets can be generated. According to the liquid level gauge of the present invention,
Since such a magnetic field generator is incorporated in the float,
A change in the liquid level can be detected continuously, and fine control of the liquid level is possible.

[Brief description of the drawings]

FIG. 1 is a side view showing an arrangement of two ring-shaped magnets in a magnetic field generator of the present invention.

FIG. 2 is a graph showing a change in magnetic flux density in an axial direction of a ring-shaped magnet magnetized in a thickness direction.

FIG. 3 is a graph showing changes in magnetic flux density in the axial direction of two ring-shaped magnets in a case where two ring-shaped magnets are coaxially and counterpolarized and arranged so that their neutral points overlap each other. is there.

FIG. 4 is a diagram showing a magnetic flux density obtained by synthesizing axial magnetic flux densities of two ring-shaped magnets when two ring-shaped magnets are coaxially and coaxially opposed to each other and arranged so that their neutral points overlap each other. It is a graph which shows a change.

FIG. 5 is a graph in which the distance from the center of the magnet to the neutral point on the central axis is plotted against the outer diameter of the ring-shaped magnet.

6A and 6B show a float in the liquid level gauge of the present invention, wherein FIG. 6A is a longitudinal sectional view and FIG. 6B is a top view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic field generator 2 1st ring-shaped magnet 3 2nd ring-shaped magnet 10 Float of a liquid level gauge 11 Float main body

Claims (3)

[Claims] 1. A pair of ring-shaped magnets magnetized in a thickness direction, wherein the ring-shaped magnets are arranged coaxially with the same poles facing each other, and have an outer diameter of φ ₁ ,
Let L _{0 be the} distance between the centers of the magnets in the thickness direction.
Wherein the magnetic field generator satisfies the following expression (1). 0.45φ ₁ ≦ L ₀ ≦ 0.9φ ₁ ... (1) 2. A magnetic detecting element having a ring-shaped float floating on a liquid surface and a stem inserted into a hollow portion of the float, wherein a magnetic detecting element for detecting a linear change in magnetic flux density is incorporated in the stem. A liquid level gauge, wherein a pair of ring-shaped magnets magnetized in the thickness direction are incorporated in the float, and these ring-shaped magnets are arranged coaxially with each other, with the same poles facing each other. 3. The liquid level gauge according to claim 2, wherein an outer diameter of the ring-shaped magnet is φ ₁ , and a distance between centers of the magnets in the thickness direction is L _0. A liquid level meter, which satisfies the relationship of the expression (1). 0.45φ ₁ ≦ L ₀ ≦ 0.9φ ₁ ... (1)