KR20110035830A - Search coil having a plurality of coils for improving search ability - Google Patents

Abstract

PURPOSE: A search coil using a plurality of coils with improved searching abilities is provided to connect even numbered individual coils in series, thereby reducing a noise in a common mode. CONSTITUTION: A first individual coil(110) comprises a core(113) and a coil(115). The core is manufactured by a ferromagnetic substance which has good magnetic permeability. The coil is wound on the core N times. A second individual coil(120) has the same configuration as the first individual coil. A non-magnetic material(130) isolates two individual coils.

Description

Search coil having a plurality of coils for improving search ability}

The technical field according to an aspect of the present invention relates to a detection coil, and more particularly, to a detection coil having improved detection range and detection sensitivity.

The detection coil is a type of magnetic sensor that detects an object by a change in magnetic flux. More specifically, the object is detected by induced electromotive force formed by the movement of the object or the change of the magnetic field generated in the object. The detection coil is used for detection sensors in parking lots, surveillance robots and metal detectors in airports. In order to improve the performance of the detection coil, the coil is manufactured by winding the ferromagnetic material with high permeability.

The detection coil is manufactured by winding a coil on a ferromagnetic core. Typically, the sensitivity of the detection coil is improved by increasing the number of turns. However, if the number of turns is increased, the weight and size of the detection coil are increased. Therefore, there is a problem of a method capable of improving the sensitivity of the detection coil without significantly increasing the size and weight of the detection coil.

The present invention is to provide a detection coil having a higher sensitivity than the conventional without increasing the size and weight significantly by using a plurality of individual coils.

The detection sensor according to an aspect of the present invention includes a plurality of cores spaced apart from each other at regular intervals and a coil wound N times on the plurality of cores.

The coil is wound around each core and may be composed of a plurality of individual coils connected to each other. The core and the coils wound on the core may be even.

The detection coil according to an additional aspect of the present invention consists of an even number of individual coils, the even number of individual coils are grouped into two individual coil groups in which K individual coils are connected in series and operate in a differential mode between the individual coil groups.

Individual coils may be connected in series with each other. The even number of cores may be two.

The plurality of cores are two cores, and each coil wound on the two cores may be wound in opposite directions so that the induced electromotive force has opposite polarities when a magnetic field is applied.

The cores are two cores spaced apart according to the detection area, and each coil wound around the two cores may be wound in the same direction so that the induced electromotive force has the same polarity with each other when a magnetic field is applied.

According to an embodiment, the sensitivity of the detection coil may be improved by using a plurality of individual coils without a great change in weight or size. And by connecting even number of individual coils in series and placing even number of individual coils spaced apart, or by placing center taps between even number of individual coils, noise in common mode can be reduced and more accurate detection can be performed. .

1 is an exploded perspective view of a detection coil according to an embodiment of the present invention;
2 to 4 are cross-sectional views of the detection coil according to an embodiment of the present invention,
5 is a detection coil circuit diagram according to an embodiment of the present invention;
6 is a circuit diagram of a detection coil according to another embodiment of the present invention;
7 is a circuit diagram of a detection coil according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand and reproduce the present invention.

The terms used throughout the present specification are terms defined in consideration of functions in the embodiments of the present invention, and may be sufficiently modified according to the intention, custom, etc. of the user or operator, and the definitions of these terms are used throughout the specification. It should be made based on the contents.

As described above, the detection coil detects the object by the induced electromotive force of the detection coil according to the change of the magnetic flux. The induced electromotive force V (t) of the detection coil is shown in Equation 1.

Where N is the number of turns of the coil, A _c is the cross section of the core, μ _c is the permeability of the core, and B _O is the magnetic flux density. Permeability μ _c of the core is as shown in Equation 2.

In Equation 2, μ _r is the relative permeability of the core, N _d is a self-clearing factor and depends on the shape and permeability of the core.

Referring to Equation 1, the induced electromotive force V (t) of the detection coil is proportional to the number of turns N of the coil per unit length, the cross-sectional area A _{c of the} core, and the permeability of the core μ _c . In other words, in order to increase the sensitivity of the detection coil, at least one of the number of turns N of the coil, the cross-sectional area A _{c of the} core, and the magnetic permeability μ _{c of the} core must be increased.

As described above, increasing the number of turns of the coil in order to increase the sensitivity of the sensor has a problem that the size and weight of the coil increases. In addition, if the cross-sectional area of the core is increased, the magnetic depletion factor (N _d ) is increased, so that the permeability of the core is reduced and the effect on the sensitivity of the detection coil is insignificant. However, if the cross-sectional area of the core is reduced and the length is increased, the magnetic elimination factor N _d is reduced without increasing the volume, thereby improving the performance of the sensor but increasing the length of the sensor. The present invention discloses a detection coil using a plurality of coils to improve sensitivity without significantly changing the length or cross-sectional area of the sensor.

1 is an exploded perspective view of a detection coil according to an embodiment of the present invention. Referring to FIG. 1, the detection coil 100 includes a first individual coil 110 and a second individual coil 120, and additionally includes a nonmagnetic material 130.

The first individual coil 110 includes a core 113 and a coil 115. The core 113 is made of a ferromagnetic material having a good permeability. The coil 115 is wound N times on the core 113. The second individual coil 120 also has the same configuration as the first individual coil 110. In this case, the direction in which the coil 115 of the first individual coil 110 is wound and the direction in which the coil 125 of the second individual coil 120 is wound may be different directions. In addition, as shown in FIG. 1, the direction in which the coil 115 of the first individual coil 110 is wound and the direction in which the coil 125 of the second individual coil 120 is wound may be the same direction.

The detection coil 100 is applied to the first individual coil 110 and the second individual coil 120 when a magnetic field by a detection object such as a chipping object or a person is applied to the first individual coil 110 and the second individual coil 120. It may be operated in a differential mode for detecting the detection target by using the difference value of the current induced in the 120.

The nonmagnetic material 130 serves to space two individual coils at regular intervals. At this time, the interval separating the two individual coils is obtained experimentally. In this manner, the first individual coil 110 and the second by using an individual coil 120, a type of detection coil 100 is separated from the, magnetic permeability (μ _c) a do not significantly decrease on, the cross-sectional area of the core of the core ( Since A _c ) doubles, the sensitivity of the detection coil 100 is increased.

Although not shown, it can be easily understood by those skilled in the art that the detection coil 100 can be implemented as a detection sensor by detecting a current induced in the detection coil 100 and detecting a presence of a detection object. have. The detection sensor may further include a sound generator for generating sound according to the presence or absence of a detection object.

2 to 4 are cross-sectional views of the detection coil according to an embodiment of the present invention.

2 is a cross-sectional view of the detection coil according to an embodiment of the present invention. Referring to FIG. 2, the detection coil 100 includes a first individual coil 110, a second individual coil 120, and a nonmagnetic material 130, and includes a first individual coil 110 and a second individual coil ( 120 is disposed with the nonmagnetic material 130 interposed therebetween.

3 is a cross-sectional view of a detection coil according to another embodiment of the present invention. Referring to FIG. 3, the detection coil 200 includes a first individual coil 210 and a second individual coil 220. The difference between the first individual coil 210 and the second individual coil 220 included in the tomcoil 200 is that the nonmagnetic material 130 is not included, as in the detection coil 100 of FIG. 2. have. The first individual coil 210 and the second individual coil 220 may be spaced apart by a distance Δx between the first individual coil 210 and the second individual coil 220. The distance Δx is such that at least mutual inductance does not occur between the first individual coil 210 and the second individual coil 220, and may reach several meters.

4 is a cross-sectional view of a detection coil according to another embodiment of the present invention. Referring to FIG. 4, the detection coil 300 includes a first core 310, a second core 320, a nonmagnetic material 330, and a coil 340, and includes a first core 310 and a second core. The 320 is disposed in the same direction with the nonmagnetic material 330 interposed therebetween, and the coil 340 is wound around the first core 310, the second core 320, and the nonmagnetic material 330 together.

5 is a circuit of a detection coil according to an embodiment of the present invention.

Referring to FIG. 5, the detection coil is composed of two individual coils L1 and L2, and the two individual coils L1 and L2 are connected in series. Holding the center tap C as the reference voltage (0), V _H has a positive voltage, V _L has a different polarity with a negative voltage, and current i flows in the direction shown in FIG. . Similarly, the electromotive force induced in the detection coil by the object has opposite polarities with respect to the center tap. In other words, the coil wound around the center tap C to the core of the individual coil L1 and the coil wound around the core of the individual coil L2 are wound in opposite directions to each other, so that the individual coil L1 and the individual coil are wound. At L2, induced electromotive force of different polarities is generated.

Here, using two identically manufactured coils L1 and L2 can cancel the noise of the common mode, which is a common magnetic field generated by an earth-like field or an object such as an airplane that affects two sensors at a long distance. Can be. Here, the common mode noise is noise that is equally sensed by the individual coils L1 and L2 regardless of the polarities of the individual coils L1 and L2.

Therefore, the noise of the common mode is eliminated, and since the magnetic field of the object that is approaching can be sensitively detected, more accurate detection can be performed. In the same way, the detection coil can be configured with K individual coil groups connected in series and K individual coil groups connected in series. The detection coil can be configured to operate in differential mode between individual coil groups.

6 is a circuit diagram of a detection coil according to another embodiment of the present invention. Referring to FIG. 6, the detection coil is configured by connecting two individual coils and another two individual coils in series. In constructing the circuit, each individual coil group connected coils of the same polarity in series to increase the output voltage to increase the sensitivity of the sensor.

7 is a diagram illustrating another example of the detection coil circuit of the present invention.

The detection coil shown in FIG. 7 is composed of two individual coils L3 and L4, and two individual coils L3 and L4 are connected in series. However, the two individual coils L3 and L4 are wound to have the same polarity with each other.

These two individual coils L3 and L4 may be spaced apart by an arbitrary distance depending on the detection area. In particular, these two separate coils L3 and L4 can be two separate sensor coils for detecting different areas. For example, when applied to sensor coils installed to detect unauthorized intrusions, the sensor coils may be spaced apart from each other by a distance of 5m, 10m, or 15m.

In this case, a plurality of individual coils L3 and L4 may be installed along a geographical boundary at intervals. According to a characteristic aspect of the present invention, by constructing a circuit by combining these two detection coils, it is possible to effectively detect an invading object or a person without the influence of a remote appearance object.

If the intermediate point between the two individual coils L3 and L4 is set as the reference voltage 0, the coils are wound in the same direction so that the induced electromotive force induced in the two individual coils L3 and L4 has the same polarity. . With this configuration, in the absence of a detection object, the difference in current detected by the detection coils L3 and L4 will be zero. Even in the case of the noise of the common mode described above, since it does not affect the differential current which is the difference of the current induced in the detection coils L3 and L4, it can be eliminated.

However, since the individual coils L3 and L4 are disposed remotely from each other, when a detection target such as an invading object or a person approaches the detection coil 700, one of the individual coils L3 and L4 is separated. There will be a change in the current induced in the coil, for example coil L3. Therefore, the differential current between the detection coils L3 and L4 will have a specific value other than zero at O (zero). As such, the two remotely disposed coils L3 and L4 are wound to have the same polarity, and by using differential currents for each current induced in the individual coils L3 and L4, By removing the noise, the magnetic field of a nearby object can be sensitively detected, so that a more accurate detection can be performed.

While the invention has been described with reference to the preferred embodiments, which are referred to by the accompanying drawings, it will be apparent that various modifications are possible without departing from the scope of the invention within the scope covered by the following claims. .

Claims (8)

A plurality of cores spaced apart from each other at regular intervals; And
Detection coil comprising a coil wound N times each of the plurality of cores.
The method of claim 1,
The coil is wound around each core, consisting of a plurality of individual coils connected to each other.
The method of claim 2,
A detection coil having an even number of the core and coils wound on the core.
4. The detection coil of claim 3, wherein the even number of cores and the coils wound around the cores are grouped into two individual coil groups each consisting of K individual coils, and the individual coil groups operate in a differential mode.
The method of claim 4, wherein
Said coils being connected in series with each other.
6. The method according to any one of claims 3 to 5,
The detection coil, characterized in that the even number of two cores. The method of claim 3,
And the plurality of cores are two cores, and each coil wound around the two cores is wound in opposite directions so that the induced electromotive force has opposite polarities when a magnetic field is applied.
The method of claim 3,
The cores are two cores spaced apart according to a detection area, and each coil wound around the two cores is wound in the same direction so that the induced electromotive force has the same polarity with each other when a magnetic field is applied.

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