JPH0268905A - Variable inductance device and magnetic field intensity measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a variable inductance device that changes the inductance of a coil by changing the current flowing through the magnetic core of a coil having a superconductor as its magnetic core, and The present invention relates to a magnetic field strength measurement device that measures magnetic field strength by measuring the inductance of a coil whose magnetic core is a superconductor supplied with a superconductor.

<Prior Art> Conventionally, there is a variable inductance device as shown in FIG. 12 that changes the inductance of a coil. This variable inductance device has a relative magnetic permeability μ in the coil 31.
Insert a magnetic piece 32 larger than 1 month, and insert the magnetic piece 3
2 within the coil 31 in the axial direction changes the inductance seen from the terminals 33, 34 of the coil 31.

<Problem to be solved by the invention> However, the above conventional variable inductance device has the following problems:
A piece of magnetic material 32 inserted into the coil 31 in order to change the inductance seen from the terminals 33, 34 of the coil 31.
Since the above-mentioned magnetic material piece 3 is moved mechanically,
2 is difficult to move at high speed. Therefore, there is a problem that the inductance cannot be changed quickly.

Furthermore, it is difficult to move the magnetic piece 32 from a distance, and there is also the problem that the inductance cannot be changed from a distance.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a variable inductance device that is easy to operate and can change the inductance at high speed.

<Means for Solving the Problems> In order to achieve the above object, a variable inductance device of the present invention includes a superconductor disposed within a magnetic field region generated by a current flowing through a coil made of a conductor, and The present invention is characterized in that it includes a current changing means for changing the flowing current, and by changing the current, the inductance of the coil is changed.

Further, the magnetic field strength measuring device of the present invention includes a coil having a superconductor as a magnetic core to which a known current is supplied from the outside, and an inductance measuring means for measuring the inductance of the coil, and measures the inductance of the coil. It is characterized by measuring the strength of the external magnetic field.

Effects> In the variable inductance device of the present invention, when the current changing means changes the current flowing through the superconductor, the magnetic properties of the superconductor change in accordance with the change in the current flowing through the superconductor. Then, since the superconductor is located within the magnetic field region generated by the current flowing through the coil, the inductance of the coil changes in response to changes in the magnetic properties of the superconductor. Therefore, by changing the current flowing through the superconductor, the inductance of the coil can be changed.

Further, in the magnetic field strength measurement device of the present invention, when a known current is supplied from the outside to a magnetic core made of a superconductor and the external magnetic field strength is changed, the magnetic properties of the superconductor change. Then, since the superconductor serves as the magnetic core of the coil, the inductance of the coil changes in accordance with changes in the magnetic properties of the superconductor. Therefore, by measuring the inductance of the coil using the inductance measuring means, the intensity of the external magnetic field can be measured.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

This invention utilizes the diamagnetic properties (ie, the Meissner effect) of superconductors.

First, the superconducting state will be explained with reference to FIG. The range covered by the superconducting state is defined by a curved surface (hereinafter referred to as T
-HJ critical surface). In other words,
Once this T-H-J critical surface is crossed, the superconducting state rapidly disappears, and a superconducting state is realized within this T-H-J critical surface. As is well known, the superconductor has zero electrical resistance within the T-H-J critical surface and exhibits complete diamagnetic properties (Meissner effect). Moreover, the superconductor is broken in its superconducting state outside the T-H-J critical surface and exhibits complete diamagnetic property. FIG. 1 shows an embodiment of the variable inductance device of the present invention. This variable inductance device uses a superconductor l as a magnetic core and a coil 2.
is wound and cooled to below the critical temperature Tc using, for example, liquefied nitrogen. In this state, the inductance L1 between terminals 3 and 4 of the variable inductance device is measured.

Next, when the inductance between the terminals 3 and 4 is measured with an external magnetic field acting on the magnetic core 1, there is a relationship of L+<Ls between the two inductances.

As shown in Fig. 11, the temperature of superconductor 1 was fixed at temperature TN by being cooled by liquefied nitrogen, and superconductor l was in a superconducting state, but due to the external magnetic field, the temperature - magnetic field - This is thought to be because the current reaches the T-H-J critical surface and the magnetic properties of the superconductor l, which is the magnetic core of the coil 2, loses the Meissner effect, that is, diamagnetic property.

Figure 2(a) shows the external magnetic field B for the superconductor l in Figure 1.
and the inductance L between terminals 3-4. The change in inductance L due to external magnetic field B is shown in Figure 2 (a
), it is divided into areas ■, ■, and ■. The region (2) in which the inductance L changes according to the external magnetic field B can be made wider or narrower depending on the material, structure, manufacturing conditions, etc. of the superconductor 1. Therefore, it is only necessary to decide what characteristics to use depending on the purpose. For example, when changing the inductance L in an analog manner in response to changes in the external magnetic field B, it is preferable to use a device with a wide range of H. T for ceramic superconductors
-H-J critical surface has a certain thickness. therefore,
When a ceramic superconductor is used as the magnetic core, a variable inductance device having a wide range of the above-mentioned (2) can be obtained. Also, when determining whether the inductance value is Ll or L3 depending on whether the strength of the external magnetic field B is larger or smaller than a certain value,
The H region may be narrow.

The change in inductance due to the change in the external magnetic field changes depending on the current flowing through the superconductor l (hereinafter referred to as core current), as shown in FIG. 2(a). FIG. 2(a) shows the relationship between the external magnetic field B and the inductance L when the magnetic core current ■ is used as a parameter. The larger the magnetic core current I, the lower the magnetic field B, the more the inductance L changes. This is the magnetic core current I
This is considered to be because the point of action of the temperature-magnetic field current shifts to the outside of the T-H-J critical surface with a smaller magnetic field B as the value increases. Second
Figure (b) shows the magnetic core current l when the magnetic field B is used as a parameter.
The relationship between and inductance L is shown. The change in inductance L with respect to the magnetic core current I shows almost the same tendency as the change in inductance 7 with respect to the external magnetic field B.

From the above-mentioned characteristics, the coil 2 with the superconductor l as the magnetic core is
The inductance can be changed by changing the magnitude of the external magnetic field B acting on the coil 2 and the magnetic core current 2 flowing through the magnetic core of the superconductor l. In FIG. 2(a) or FIG. 2(b), the external magnetic field B and the current (2) are changed simultaneously, but it is also possible to change only one of them.

In the variable inductance device having the above configuration, the terminal 3-
4, a current flows through the superconductor 1 to cancel this current. In order to prevent the current flowing through the superconductor 1, the structure of the magnetic core of the coil 2 may be configured as follows. That is, the magnetic core in FIG. 3 is the superconductor 2
1 is formed into a plate shape, and the surfaces thereof are pasted together insulated from each other. In this case, the amount of change in inductance L with respect to the amount of change in external magnetic field B is
Since the inductance changes depending on the direction of the inductance, it is possible to obtain a variable inductance device with strong directivity. Further, the magnetic core shown in FIG. 4 is a plurality of rod-shaped superconductors 22 that are insulated from each other and bundled together. The magnetic core having this structure may be formed by forming an insulating layer on the surface of the rod-shaped superconductor 22, and hardening the rod-shaped superconductor 22 with the insulating layer formed with an insulating material. . Furthermore, the magnetic core in Figure 5 is
A superconductor 23 formed in a belt shape is rolled up and the layers are insulated. However, all magnetic cores do not have to be shaped like this, and may be solid column-shaped or vibrator-shaped depending on the purpose.

As described above, the coil having a superconductor as a core according to the present invention is a circuit element whose inductance can be changed by an external magnetic field B and a magnetic core current I as shown in FIG. The core current (■) may be a direct current or one that changes over time). That is, as shown in FIG. 7, when a magnet 6 is attached to a coil 5 having a superconductor 7 as its magnetic core, the inductance L (B) changes. Moreover, the changing magnetic field B can be controlled by the magnetic core current ■.

Therefore, the inductance L (B) can be changed by changing the magnetic field strength due to changes in the position and direction of the magnet 6. Furthermore, the inductance (B) can also be changed by changing the magnetic core current (2).

FIG. 8(a) shows an embodiment different from the above embodiment, in which an external magnetic field is created by a coil 13.

The coil 12 of the variable inductance device has a superconductor 11 as a magnetic core, as in the case of FIG. 1, and is cooled to below the critical temperature Tc using, for example, liquefied nitrogen. The power supply 14 is a power supply for creating an external magnetic field, and the coil 13 is connected to this power supply 1.
generates an external magnetic field B that varies depending on the voltage from 4;

Then, the inductance L of the terminal of coil 12
(B) changes according to the change in magnetic field intensity caused by the coil 13. Therefore, the inductance can be changed depending on the voltage from the power source 14.

In the embodiment shown in FIG. 8(b), the inductance L (1) is changed by changing the magnetic core current (2) flowing through the magnetic core of the superconductor. That is, the magnetic core current I is changed based on a signal from the power source 24, and the inductance L (1) between the terminals of the coil 12 is changed in accordance with the magnetic core current I.

Here, the power source 14 in the embodiments of FIGS. 8(a) and 8(b) described above may be either a DC power source, a power source that changes with time, or a power source that is a combination of both. In addition, Fig. 8(a) and Fig. 8(b)
) may be combined so that the external magnetic field B and the magnetic core current (2) are changed simultaneously to change the inductance.

The variable inductance device described above can change the inductance according to changes in the external magnetic field and the magnetic core current, as described above. This simply means that by measuring the inductance of the coil of the variable inductance device under a known core current, the strength of the external magnetic field can be measured.

FIG. 9 shows a tank circuit using a variable inductance device as described above. The resonance frequency f(B) at the external magnetic field strength B and magnetic core current I of this tank circuit is r(B
)=1/(2π L (B)・C).

Therefore, if such a tank circuit is applied to an oscillation circuit, if the coil of the oscillation circuit is placed at a magnetic field strength B and a core current I is caused to flow through the magnetic core, this oscillation circuit will respond to the magnetic core current I. It oscillates at a predetermined frequency f(B) (the magnetic core current I at this time may be zero). That is, the magnetic field strength B at that location can be determined from the oscillation frequency f (B) of this oscillation circuit. Since the configuration of the oscillation circuit described above can be used as is in the prior art, the details will be omitted.

Here, when detecting changes in the external magnetic field B in an analog manner by changes in the inductance L,
It goes without saying that the region .largecircle. should be wide, and when determining whether the strength of the external magnetic field B is larger or smaller than a certain value, the region .largecircle. may be narrow. Furthermore, by changing the value of the magnetic core current (2), the measurement range of the magnetic field B can be freely selected. In this case, the magnetic core current (2) does not need to be a direct current and may change over time.

Conventionally, when measuring magnetic field strength, a Hall element etc. was used.
Because this was done by measuring resistance values, only low-accuracy measurements were obtained. However, according to this method, changes in magnetic field strength can be measured as changes in inductance, so magnetic field strength can be measured with high accuracy.

The oscillation circuit described above can process the oscillation signal as a digital signal by shaping it into a pulse. Furthermore, by selecting an appropriate value for the oscillation frequency, the oscillation signal of the oscillation frequency f(B) is radiated into the air by the simple antenna of the transmitter 15 and received by the radio receiver 16 as shown in FIG. It is also possible.

A variable inductance device that generates an external magnetic field using a coil as shown in FIG. 8(a), and a variable inductance device that changes the magnetic core current as shown in FIG. 8(b).
An oscillator is configured as the inductance L of the tank circuit. Then, it becomes possible to perform FM modulation of the voltage signal of the power supply 14. Furthermore, in a radio receiver in which the variable inductance position for generating an external magnetic field by the coil is the inductance L of the tank circuit, the reception frequency can be freely controlled by the voltage of the power supply 14.

Furthermore, the measurable magnetic field range can be selected by the magnetic core current. Therefore, radio signals of unknown frequencies can be detected.

Furthermore, by using the variable inductance device as part of a filter circuit, the characteristics of the filter circuit can be easily controlled.

<Effects of the Invention> As is clear from the above, the variable inductance device of the present invention arranges a superconductor within a magnetic field region generated by a current flowing through a coil, and changes the current flowing through the superconductor using a current changing means. Since the inductance of the coil is changed by changing the magnetic properties of the superconductor, the operation is simple and the inductance can be changed quickly.

Further, the magnetic field strength measuring device of the present invention includes a coil having a superconductor as a magnetic core to which a known current is supplied from the outside, and an inductance measuring means for measuring the inductance of the coil, and measures the inductance of the coil. Since the intensity of the external magnetic field is measured by doing this, the intensity of the magnetic field can be measured from a distance with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a variable inductance device of the present invention,
Figure 2 (a) is a diagram showing the relationship between external magnetic field strength and inductance when the magnetic core current is used as a parameter in the above example, and Figure 2 (b) is a diagram showing the relationship between the magnetic core when the external magnetic field is used as a parameter. Diagram showing the relationship between current and inductance, 3rd
4 and 5 are diagrams showing an example of the structure of the magnetic core in the above embodiment, FIG. 6 is an explanatory diagram of changes in inductance due to changes in external magnetic field in the above embodiment, and FIG. 7 is an illustration of the above embodiment. A diagram showing an example of how the external magnetic field changes in
FIG. 8(a) is a schematic diagram of an embodiment different from the above embodiment,
FIG. 8(b) is a schematic diagram of a further different embodiment, FIG. 9 is a schematic diagram of a tank circuit using the above variable inductance device, and FIG. 10 is an embodiment in which the tank circuit of FIG. 9 is incorporated into a transmitter. FIG. 11 is an explanatory diagram of the T-H-J critical surface, and FIG. 12 is a schematic diagram of a conventional variable inductance device. 1.7. + 1.21, 22.23... superconductor, 2
．． 5,12.13... Coil, 3.4... Terminal, 6... Magnet, 14.24... Power supply, 15... Transmitter, 16... Receiver.

Claims (2)

[Claims] (1) A superconductor disposed within a magnetic field region generated by a current flowing through a coil made of a conductor, and a current changing means for changing the current flowing through the superconductor, the current changing means changing the current flowing through the superconductor; A variable inductance device characterized by changing the inductance of. (2) A coil with a superconductor as a magnetic core to which a known current is supplied from the outside, and an inductance measuring means for measuring the inductance of the coil, and the strength of the external magnetic field can be determined by measuring the inductance of the coil. A magnetic field strength measuring device characterized by measuring magnetic field strength.