JP2003287523A - Magnetic force-type oximeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic force-type oximeter whose workability and reproducibility are enhanced, which expands the degree of freedom of design, which is resistant to a vibration and a shock and whose production cost is reduced. <P>SOLUTION: The magnetic force-type oximeter is composed of a magnetic- field generation means used to generate a magnetic field from oppositely arranged magnetic poles, an elastic member installed so as to be adjacent to the magnetic poles, and a strain detection means used to detect a strain of the elastic member. The oximeter is constituted in such a way that a change in a magnetic force acting across the magnetic poles and the elastic member according to an oxygen concentration in a gas is detected by the strain detection means when the magnetic-field generation means and the elastic member are arranged in the gas containing oxygen. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic force type oximeter for measuring the oxygen concentration contained in a mixed gas flowing in a flue, for example, and has improved reproducibility, uniformity and manufacturing cost while improving the function against vibration and shock. The present invention relates to a magnetic force type oxygen meter with reduced power consumption.

[0002]

2. Description of the Related Art Accurate measurement of oxygen concentration in a mixed gas is
Important in a wide range of industrial, clinical and research processes. Therefore, various devices for measuring the oxygen concentration have been proposed and developed.

First, the measurement principle of the magnetic force type oxygen meter used in the conventional example and the present invention will be briefly described with reference to FIG. FIG. 4A shows the relationship between oxygen molecules and the magnetic field when the magnetic field generating means is arranged in a gas containing oxygen.

The force F acting on the oxygen molecule in the X-axis direction can be expressed by the following equation. F = χ · (∂H / ∂X) · H χ: Magnetic susceptibility of oxygen H: Strength of magnetic field ∂H / ∂X: Rate of change of magnetic field That is, the magnetic field is strong as shown in FIG. 4 (b), And the force that attracts oxygen acts on the place where the strength is changing (the end of the magnetic pole ... non-uniform magnetic field), and the rightward force and the leftward force are balanced against each other at the end of the magnetic pole. . Figure 4
(C) shows a state in which the pressure (concentration) of the attracted oxygen is higher in the magnetic field (gap of the magnet) than in the surroundings.

FIG. 2 is a view showing the principle configuration of a detection unit of a conventional example of a magnetic force type oxygen meter, FIG. 3 (a) is a Z view of FIG. 2, and FIG.
(B) is a schematic diagram showing the behavior of oxygen pressure and dumbbells. In these drawings, reference numerals 10a and 10b denote two pairs of magnets each having a wedge-shaped tip, each of which is separated by a predetermined distance (a) and whose tip portion is a predetermined distance (b).
Are arranged to face each other. Lines of magnetic force are generated in these magnets in the arrow direction (from top to bottom in the figure).

11 (a, b) is N in a glass ball
It is a pair of dumbbell spheres containing ₂ gases. These dumbbell spheres are fixed at both ends of the support rod 12 and have a predetermined distance (c) with respect to the line connecting the tips of the wedge-shaped magnets facing each other.
Are horizontally arranged in the space in a shifted state (see FIG. 3a).

Reference numeral 13 is a support rod provided in a cross shape from the center of the support rod (dumbbell sphere), and an optical mirror 14 is fixed to a portion where the support rods 12 and 13 intersect. 15 is a light source,
Reference numeral 16 is a photodiode, and light emitted from the light source 15 is reflected by the optical mirror 14 and enters the photodiode 16. The support rods 12 and 1 are
3 is formed of, for example, a Pt wire.

When the oximeter is placed in the sample gas in the above-mentioned configuration, the oxygen gas contained in the sample gas is attracted to the magnetic field formed between the magnets facing each other and to the other regions and to the dumbbell sphere. A density difference occurs between the enclosed gas (N2 in the example).

As a result, as shown in FIG. 3 (b), oxygen is sucked in the vicinity of the tip of the wedge magnet and the oxygen density in that part rises, causing a difference in density inside and outside the dumbbell, and the dumbbell ball The support rod 12 receives the rotational force and is displaced by the force moving in the arrow direction. Due to this displacement, the direction of the light from the light source 15 reflected by the mirror changes and the photodiode 16
Detects the change as a change in electric output. The magnitude of the change is proportional to the oxygen gas contained in the sample.

[0010]

However, in the above-mentioned conventional technique, the magnetic dumbbell 11 is made of glass, and N2 gas is enclosed in the glass ball. Further, since the dumbbell is supported by the platinum wire, it is extremely weak against vibration and shock, and there is a problem that the dumbbell support structure (not shown) is destroyed by the rush pressure when the sample gas is introduced into the oximeter. It was Further, the dumbbell spheres are manufactured by hand, and the processability is poor and there is a problem in reproducibility.

The present invention has been made to solve the above problems, and improves the workability and reproducibility by utilizing the fine processing technology of silicon without impairing the advantages of the magnetic force type having excellent characteristics. The purpose is to realize a magnetic force type oxygen meter that expands the degree of freedom in design, is resistant to vibration and shock, and can reduce manufacturing costs.

[0012]

In order to solve such a problem, in a magnetic force type oximeter, a magnetic field generating means for generating a magnetic field from magnetic poles arranged facing each other is provided. An elastic member provided close to the magnetic pole,
And a strain detecting means for detecting the strain of the elastic member,
When the magnetic field generating means and the elastic member are arranged in a gas containing oxygen, a change in magnetic force acting between the magnetic pole and the elastic member is detected by the strain detecting means according to the oxygen concentration in the gas. It is characterized by having done.

According to a second aspect of the present invention, in the magnetic force type oxygen meter according to the first aspect, at least one end of the elastic member is supported by a beam provided on a silicon substrate and is formed by a silicon fine processing technique. Is characterized by.

According to a third aspect of the present invention, in the magnetic force type oxygen meter according to the first aspect, the strain detecting means includes at least one of a diffusion type semiconductor strain gauge, a vibration type strain gauge, and an interelectrode capacitance type strain detector. It is characterized by

According to a fourth aspect of the present invention, in the magnetic force type oxygen meter according to the first aspect, a reaction force generation mechanism for canceling the strain is provided by using a signal from the strain detecting means and a current circuit. And

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1A and FIG. 1B are principle configuration diagrams showing an example of an embodiment of the present invention, and FIG.
FIG. 3B is a plan view of a principal portion of the strain measurement chip. In these drawings, reference numeral 1 denotes a magnetic field applying device, and the magnetic poles of the magnetic field applying device 1 are formed in a wedge shape and a magnetic field is generated in a portion indicated by A.

Reference numeral 2 is a strain measurement chip formed by a known silicon microfabrication technique. In this example, the float 3 is formed in the center of the chip 2, and the float 3 is supported by four support beams 4 formed in a thin shape. Reference numeral 5 denotes, for example, a diffusion semiconductor strain gauge, which is formed at the base of the support beam 3 where the displacement of the floating portion 3 is maximized.

Although not shown in the figure, the resistance change of the strain gauge 5 is detected as an electric signal through a known electric circuit such as a bridge. The magnetic field applying device 1 is arranged so that the wedge-shaped portion at the tip is located at the center of the float 3.

In the above structure, when the sample gas is introduced into the magnetic field generation portion, oxygen is attracted to the magnetic field generation portion in relation to the oxygen concentration contained in the sample gas, and the gas density of that portion increases. This increase in the density gives a magnetic buoyancy to the float 3, and in the case of the figure, it is a force to push the float 3 downward.

When the float 3 is pushed down, the support beam 4
The resistance of the strain gauge formed at the root of the changes.
This resistance change is detected as an electric signal through a known electric circuit such as a bridge. In this case, the sample gas is introduced so as to flow between the wedge portion of the magnet and the float, and the movement of the float causes a displacement corresponding to the concentration of oxygen gas contained in the flowing sample gas.

The movement of the float is based on the deformation of the elastic body, but when the acting force increases, the displacement amount does not increase proportionally, and a saturation tendency generally appears. For this reason, a signal saturation phenomenon appears when measuring high-concentration oxygen, and conventionally, a linearization device or the like has been required. As a means to solve this,
As shown in FIG. 1 (b), a current circuit 6 is provided in the float portion on the surface of the strain measuring chip, and a signal from the strain detecting means and a reaction force generating mechanism for canceling the strain by using the current circuit 6 are provided. be able to.

That is, when the float 3 is displaced in accordance with the oxygen concentration, the strain gauge 5 changes its resistance and the output changes. If this output change is fed back to the electric circuit 6 and a current that cancels the displacement of the float is flown, and this current is used as a new signal, linearity can be secured without displacement of the float,
A wide range of oxygen concentrations can be detected.

The foregoing description of the invention has been shown by way of illustration only of particular preferred embodiments for purposes of illustration and illustration. For example, in the present embodiment, the float is supported by four support beams, but it may be one to three or four or more as long as an appropriate electric signal is generated in the strain gauge. In addition to the strain gauge, a vibration type strain gauge or an inter-electrode capacitance type strain detector may be used as the strain detecting means. Therefore, it is obvious to those skilled in the art that the present invention can be subjected to many changes and modifications without departing from the essence thereof. The scope of the present invention, which is defined by the description in the scope of claims, includes changes and modifications within the scope.

[0024]

As described above, according to the present invention, the magnetic field generating means for generating a magnetic field from the magnetic poles arranged to face each other, the elastic member provided near the magnetic pole, and the elastic member. And a magnetic field acting between the magnetic pole and the elastic member according to the oxygen concentration in the gas when the magnetic field generating means and the elastic member are arranged in a gas containing oxygen. Since the force change is detected by the strain detecting means, the advantage of the magnetic force type having excellent characteristics is not impaired, and the strain measuring chip is formed by using the fine processing technology of silicon, thereby improving the workability. It is possible to realize a magnetic force type oxygen meter that improves reproducibility, expands the degree of freedom in design, is resistant to vibration and shock, and can reduce manufacturing costs.

[0025]

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an embodiment of a magnetic force type oximeter of the invention.

FIG. 2 is a configuration diagram showing an example of a conventional magnetic force type oxygen meter.

FIG. 3 is an explanatory diagram showing the principle of a magnetic force type oxygen meter.

FIG. 4 is an explanatory diagram showing the principle of a magnetic force type oxygen meter.

[Explanation of symbols]

1 Magnetic field application device 2 Strain measurement chip 3 float 4 support beams 5 Strain gauge 6 current circuit

Claims (4)

[Claims] 1. A magnetic field generating means for generating a magnetic field from magnetic poles arranged to face each other, an elastic member provided close to the magnetic pole, and a strain detecting means for detecting strain of the elastic member. When the magnetic field generating means and the elastic member are arranged in a gas containing oxygen, a change in magnetic force acting between the magnetic pole and the elastic member depending on the oxygen concentration in the gas is detected by the strain detecting means. A magnetic force type oximeter characterized by being constructed. 2. The magnetic force type oximeter according to claim 1, wherein at least one end of the elastic member is supported by a beam provided on a silicon substrate and is formed by a fine processing technique of silicon. 3. The magnetic force type oximeter according to claim 1, wherein the strain detecting means includes at least one of a diffusion type semiconductor strain gauge, a vibration type strain gauge, and an interelectrode capacitance type strain detector. 4. The magnetic force type oximeter according to claim 1, further comprising a reaction force generating mechanism for canceling the strain by using a signal from the strain detecting means and a current circuit.