JPH1026638A - Current detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a current detecting sensor which is small, whose responsivity is fast and whose irregularity is small. SOLUTION: A current detecting sensor device is provided with magnetoresistance elements 82a, 82b which are magnetically biased and at least one or more cutout part 89 or a hole part constituted in a conductor part 81 which is an electric good conductor forming a current passage in an object to be detected and which is constituted of a nonmagnetic metal. The magnetoresistance elements 82a, 82b and a magnetic bias means 80 are inserted into the cutout part 89 or the hole part so as to be arranged. A load current is detected on the basis of a change in resistances of the magnetoresistance elements 82a, 82b. In addition, a soft magnetic material layer 87 is added as an auxiliary magnetic circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

2. Description of the Related Art Recently, problems and noises caused by transient currents in electronic equipment have become a problem. In particular, it is said that the most frequently occurring damage to the phase-advancing capacitor installed in the cupicle is caused by the fifth harmonic generated by the load. However, its substance has not been fully elucidated yet, and the development of a good transient current detector is eagerly awaited. As a recent trend, it has been considered to perform complicated control with the help of an electronic circuit in an electric motor or an air conditioner for energy saving. There is no current detection sensor, and a current sensor having a quick response is required in this field. On the other hand, when a semiconductor electronic circuit typified by an SCR is introduced into a power supply device and various controls are performed, noise generated from the device increases, and other devices installed in the vicinity malfunction. However, there is no appropriate detection means. Against this background, in the field of electric power and precision electronic equipment, it has become necessary to measure a small current with good frequency characteristics. Conventionally, current measurement has been mainly performed by CT. However, the frequency characteristic of a magnetic core used for CT has a detection frequency characteristic of 10 KHz at most. It cannot follow the generated noise current. That is, it cannot be used as a noise suppression sensor. On the other hand, in response to such a demand, attention has been paid to current detection using a ball element. However, this element uses a magnetic core to reduce the magnetic field sensitivity and improve the sensitivity. . That is, although the frequency characteristic is improved by one digit or more than the CT, the frequency characteristic depends on the characteristic of the magnetic core similarly to the CT, and both the shape and the characteristic are not satisfactory. According to the present invention, a magnetic sensor configured by adding a magnetic bias device to a magnetoresistive element has good magnetic field sensitivity, good frequency characteristics, low intrinsic noise of the element, and the device can be downsized.
It is an object of the present invention to provide a small-sized, high-performance current detection sensor device which is inexpensive and can be incorporated in a home-use fuse box or the like, focusing on the fact that the impedance is low and the influence of induction noise is low.

[0092]

2. Description of the Related Art FIGS. 1 and 2 show a current detector which has been widely used in the past. FIG. 1 shows a current transformer, which is called a CT for short, and FIG. Coils indicated by 11 and 12 are wound around the core. The coil 12 is usually formed in a range of one turn to several turns, and this coil is connected to the load L in series. Therefore, with such a configuration, the secondary coil 1
3, a voltage proportional to the current I flowing through the load is induced,
The load current is measured by detecting this voltage. FIG. 2 shows a current detector using a ball element. The current detector shown in FIG. 2 is also called a hole multiplier, in which a part of the electromagnetic core 23 is cut, and a hole element is inserted and fixed in the cut part. Thus, a magnetic field corresponding to the current I due to the load L is generated in the electric conductor 24 connected to the load. However, since this magnetic field is weak, the magnetic flux is concentrated by the electromagnetic core 21 to increase the magnetic field sensitivity. Things. In recent years, current detection sensors using semiconductor magnetoresistive elements have been actively developed. As shown in FIGS. 4a and 4b, a magnetoresistive element in which a magnetic bias is simply applied near a current path is arranged. Attempts have been made to detect the load current by detecting the magnetic field generated from the current path.However, it is difficult to accurately maintain the positional relationship between the current path and the magnetoresistive element. It is not cheap and practical. FIG. 3 has already been proposed and disclosed by the inventor (Kogakuin University
38th Research Abstract P101) This shows the structure of a current detector, but it is indium antimonide (InS).
b) or a magnetic bias is applied to the magnetoresistive elements 32a and 32b made of indium arsenide (InAs) using a strontium ferrite magnet 30 having a surface magnetic flux of 1.2 KG or more. In particular, a semiconductor magnetic sensor using InSb has a large temperature coefficient and requires temperature compensation. Therefore, as shown in FIG. 3, two magnetic resistance elements 32a and 32b are incorporated and a voltage dividing circuit described later is configured to perform temperature compensation of the magnetic resistance elements. As shown in the figure, the two elements constituting the voltage dividing circuit are placed on both sides of a 1 mm thick copper plate 31 through which a load current flows so that the element surfaces are in contact with the conductor surfaces via insulating films 34, respectively. I do. Also, as described above, by arranging the respective magneto-resistive elements, the magnetic field generated by the current path is perpendicular to the surface of the element and applied to the respective magneto-resistive elements 32 and 33 in opposite directions. Configured. However, the sensor shown in FIG. 3 has a drawback that the magnetoresistive elements 32 and 33 are difficult to install in parallel with the copper plate, causing variations in characteristics, and also causes a problem in processing.

[0093]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a current detection sensor device in which a magnetic field generated by a load current acts almost equally on two magnetoresistive elements, and there is little variation in characteristics.

[0093]

Therefore, in the current sensor device according to the present invention, a non-magnetic conductor piece forming a load current path and an element mounting portion for installing a magnetoresistive element are provided on the conductor piece, A biased magnetoresistive element is attached and fixed using well-known means, and a magnetic field change caused by a load current flowing through the conductor piece is applied to the magnetoresistive element, thereby causing a resistance change in the magnetoresistive element and causing a change in the load current. A corresponding electrical signal is extracted.

[0056]

FIGS. 4A and 4B are schematic diagrams for explaining the basic operation principle for assisting the understanding of the current detecting device according to the present invention. FIG. 4A shows the magnetic flux generated by the load current in the nonmagnetic piece 41. 3 illustrates the relationship between Φ and the current I. FIG. 4B shows the relationship between the Ac commercial power supply and the load L of the detected object.
In such a connection, the current I flowing through the conductor 41 fluctuates according to the fluctuation of the load L, which is the object to be detected, due to the load fluctuation and the change in the state of the load L.
The current I is proportional to the magnitude of the load L, and the magnetic flux generated near the electric wire by this current is also proportional to the current I flowing through the load L. Therefore, assuming the direction of the current that changes depending on the load L as shown in FIG. 4A and assuming the polarities N and S of the magnetic bias magnet as shown in FIG. 4A, when the load current I increases, the conductor 41a is generated. The magnetic flux φ increases, and this magnetic flux is added to the magnetic flux of the magnetic bias magnet, and the magnetic flux applied to the magnetoresistive element 42a also increases. At the same time, the resistance value of the magnetoresistive element 42a also increases. Further, the magnetic flux generated by the current I with respect to 42b is opposite to the magnetic flux of the magnetic bias magnet, the magnetic flux applied to the magnetoresistive element 42b decreases, and the resistance value also decreases. When the direction of the current is opposite to the direction shown in the figure, the magnetic flux generated by this current becomes opposite to the direction of the magnetic flux shown in FIG. Since they are offset and decreased, the resistance value of the magnetoresistive element 41a decreases. further,
The magnetic flux Φ generated around the conductor 41 is opposite to the surface of each element as shown by an arrow at a portion where the element is mounted according to the right-hand rule.

Further, the two magnetoresistive elements 42a and 42b are
As shown by 52a and 52b in FIG. 5, a DC power source Vin (DC)
And the respective elements are also connected in series to form a voltage dividing circuit, so that the resistance change of the two elements 51a and 51b can be changed to the neutral point VN.
Output as a voltage change to improve temperature characteristics and increase output voltage. In addition, the two magnetoresistive elements 52a and 52
A magnetic bias of the same magnetic pole is applied to 2b, and as described above, the magnetic flux φ generated by the current I is arranged such that the relationship between the two elements is opposite as shown by the arrow in FIG. A conductor structure and an auxiliary magnetic circuit are provided so as to obtain a good reverse polarity relationship, and an end face on which the element is installed is appropriately selected.

007

Embodiment 1 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 6 shows a first embodiment of a current detection sensor device according to the present invention. In the drawing, reference numeral 61 denotes copper, aluminum,
A series of electrically good conductors made of a single or a mixture of tin, zinc, etc., and a conductor portion made of a non-magnetic metal. In addition, the conductor portion 61 includes a magnetoresistive element 62a,
B and a perforation 69 for inserting the magnetic bias magnet 60 were made. In one embodiment according to the present application, the perforated portion 6
In order to obtain electrical insulation between the magnetoresistive elements 62a and b, the magnetic bias magnet and the conductor 66, an insulating layer 64 made of a series of insulators made of nylon, polyester, polycarbonate and polyethylene is provided around the magnet. Hugged. Also, as a magnetic bias means of the magnetoresistive element, a coil or a self-bias method can be considered.
For example, it is preferable to use a heat-shrinkable tube as an insulator when using a circular magnet as shown as the simplest magnetic bias means. Further, permalloy, as shown in FIG.
A soft magnetic material layer 67 appropriately selected from iron plate, silicon steel plate, ferrite, etc., forms an auxiliary magnetic circuit, and functions to allow a magnetic field generated in the conductor layer to enter the magnetoresistive element at right angles. make. The magnetoresistive element may be installed at the same position as the surface of the conductor, or may be located slightly below the surface depending on the shape of the conductor. In any case, the element is arranged and fixed at an optimal installation position so that a substantially uniform magnetic field is applied to both elements.

FIG. 7 is a detailed enlarged sectional view of the perforated portion. In the figure, reference numeral 71 denotes a conductor portion composed of a series of good conductor nonmagnetic metal metals made of a single material or a mixture of copper, aluminum, tin, zinc, etc., into which a magnetoresistive element and a magnetic bias magnet are inserted. Perforations 79 are provided. However, the perforated portion 7 of the soft magnetic layer 77
9 'may be completely perforated or may define a recess as shown. Further, as shown in the figure, the conductor may be disposed only on a part of the conductor portion 71, or a small perforation may be provided so as to fit the element surface. Even
The shape of the soft magnetic layer 77 is appropriately determined according to the size and shape of the conductor that satisfies the current capacity of the load L. Further, the two magneto-resistive elements 71a, b include 72a ',
As shown in the figure, the soft magnetic layer 77 may be disposed in the vicinity of the opposite surface of the soft magnetic layer 77. Further, the arrangement position of the element depends on the machining accuracy, the thickness of the conductor layer and the current capacity flowing through the conductor, and depends on the size and shape of the conductor 71 determined by these mutual conditions. As already described above, the perforations 79 are formed from a series of insulators such as nylon, polyester, polycarbonate, and polyethylene in order to obtain electrical insulation between the magnetoresistive element, the magnetic bias magnet, and the conductor. It is needless to mention here again that the selected insulating layer 74 holds an insulator in order to ensure insulation between the conductor portion 71 and the magnetic bias magnet 70.

[0099]

Embodiment 2 FIG. 8 shows a second embodiment according to the present invention. In the figure, reference numeral 81 denotes a series of nonconductive magnetic metals composed of a single conductor or a mixture of copper, aluminum, tin, zinc and the like. In the configured conductor portion, on both side surfaces of the conductor portion, notch portions for independently disposing the magnetoresistive elements 82a and 82b and inserting the magnetic bias magnets 80 corresponding to the respective independent magnetoresistive elements. 89a and 89b are formed on both sides. In order to obtain electrical insulation between the two magnetoresistive elements 82a, b, the magnetic bias magnet and the conductor 81, a series of nylon, polyester, polycarbonate, polyethylene, mica, etc. An insulating layer 84 made of what is called an insulator is held on at least three sides of each magnet. Further, a magnetic layer 87 appropriately selected from permalloy, iron plate, silicon steel plate, ferrite, or the like is formed on the entire back surface or a part of the conductor portion 81 in the same manner as described in the first embodiment. In addition to forming the magnetic circuit, a shape that allows the magnetic field generated in the conductor to enter the magnetoresistive element at a right angle is configured based on the concept already described with reference to FIGS. Reference numeral 85 indicates a printed circuit board, 87 indicates a mounting hole, and 88 indicates a mounting screw for connecting the conductor portion of 86 and the soft magnetic layer of 87. The integrated structure is formed by a known bonding technique such as brazing. Sometimes it is. In addition, the installation position of the magnetoresistive element
It may protrude at the same position as the surface of the conductor layer, or may be provided at a position slightly lower than the surface depending on the shape of the conductor layer. In any case, the elements are fixed in consideration of the installation positional relationship so that a substantially uniform magnetic field is applied to both elements.

As a part of the many uses of the first and second embodiments described above, a plate fuse in a fuse box at home can be replaced. The shape and dimensions of the current detection sensor device in consideration of such a use form are as follows. 4 mm, corresponding to Example 2, a length of 6, a width of 3 mm, and a thickness of 2 mm, each of which is a rare earth magnet. The thickness of the magnetic layer is 1 mm thick.
Use a soft iron plate. The obtained output voltage is
At 0 V, an output voltage with a wide dynamic range and good linearity was obtained at about 3 mm volts with respect to a load current of 1 amp.

The output voltage obtained by the current detection sensor is:
Although the signal level becomes three to four times as high as that of the bill discrimination sensor, in a practical circuit, this signal is amplified using the amplifier circuit shown in FIG. In FIG. 9, reference numeral 92 denotes a magnetoresistive element, which is configured as described above in detail. 99 indicates an operational amplifier, Rec indicates a rectifier circuit, and Vin indicates an input voltage. First, in the figure, an alternating magnetic field corresponding to the load L of the commercial power supply is applied to the magnetoresistive element, whereby the resistance values of the two magnetoresistive elements change alternately, and the resulting voltage signal also changes alternately. The signal is V
Since the in DC voltage is superimposed, the first-stage amplifier is AC-amplified as a capacitor-coupled amplifier to remove the superimposed DC signal. However, since the example of the amplifier circuit shown here is intended for measuring the current value of the commercial power supply, the frequency to be detected is as low as 50 to 60 Hz. In such a case, the first-stage AC amplifier circuit is not used. A coupling capacitor and a second-stage coupling capacitor are connected in series as shown, and the polarity of the capacitor is reversed to prevent leakage current of the capacitor. After AC amplification in the first stage, a signal having a period that is the same as the commercial power frequency is rectified by a rectifier circuit, guided to the second stage DC signal amplifier circuit as a DC signal, amplified, and output by a display (not shown). Is displayed to know the current level. Although this circuit is an example for the purpose of current detection, it can detect a relatively small transient current. However, depending on the purpose of detection, such as detection of complicated transient currents, the well-known AD
By adding a converter or a processing circuit such as an FFT (high-speed Fourier transform) circuit, the function of this sensor can be used effectively. Further, for the purpose of detecting a fast transient current in a commercial power supply, the 5
Using a frequency of 0 to 60 Hz, a load fluctuation that changes instantaneously can be faithfully detected by a method such as synchronous detection with the output wave of the sensor device. Here, it is not necessary to describe all circuits suitable for various applications, but naturally, not only detection of commercial power supply current, but also transient detection of very high frequency and current detection sensor device for current detection Therefore, the peripheral circuit should adopt a circuit form suitable for the purpose, and there is no intention to limit the gist of the present application to FIG. Furthermore, the operation and structure of the semiconductor magnetoresistive element have been described in detail above, but the principle of this concept can be easily applied to a magnetic thin film magnetoresistive element and a giant magnetoresistive element (GMR) that has recently attracted attention. Does not wait for that statement.

[0122]

As described in detail above, according to the present invention, a small magnetic field change generated by a load current is detected by a magnetoresistive element to detect a fast transient current of a commercial power supply having a frequency characteristic of 100 KHz or more, and a high frequency Provide a current detection sensor device that has the effect of obtaining a small, high-performance sensor, such as being capable of detecting a current, having a low noise level, and being capable of being incorporated in an inexpensive and easy-to-process household fuse box. Is what you do.

[Brief description of the drawings]

1 is an explanatory view of a current transformer. FIG. 2 is a current detector using a Hall element. FIG. 3 is a plan view of a current detector already proposed by the inventor. FIG. 5 is a schematic diagram of a voltage dividing circuit of a magnetoresistive element. FIG. 6 is a front and side view of a current detection sensor according to a first embodiment of the present invention. FIG. FIG. 8 is a front and side view of a current detection sensor according to a second embodiment of the present invention. FIG. 9 is a configuration diagram of an amplifier circuit.

[Explanation of symbols]

40, 60, 70 are magnetic bias magnets 31, 41, 61, 71, 81 conductor layers 32, 42a, b, 52a, b, 62a, b, 82a,
b is a magnetoresistive element 69, 79, 94, 89 is a perforated or notched portion 67, 77, 87 is a magnetic layer Vout is an output voltage Vin is an input voltage L is a load VAC is an AC voltage power supply DC is a DC voltage power supply Φ is magnetic flux VN is neutral point MR is magnetic sensor

Claims (4)

[Claims] In a current detection sensor formed by using a magnetically biased magnetoresistive element, at least a good electric conductor forming a current path of an object to be detected and a conductor portion formed of a nonmagnetic metal are used. The magnetic field generated by the load current flowing in the conductor is detected by the magnetoresistive element by inserting and fixing the magnetoresistive element and the magnetic bias means in the notch. A current detection sensor device characterized in that: 2. A current detecting sensor using a magnetically biased magnetoresistive element, wherein at least a conductive portion made of a nonmagnetic metal is an electrically good conductor forming a current path of an object to be detected. Also, a perforated portion is formed at one or more places, and a magnetic field generated by a load current flowing through the conductor portion is detected by the magnetoresistive element by inserting and fixing a magnetoresistive element and a magnetic bias means in the perforated portion. Characterized current detection sensor device. 3. The current detection sensor device according to claim 1, wherein an auxiliary magnetic circuit is constituted by a soft magnetic layer on the entire back surface or a part of the electric conductor portion. 4. The current detection sensor device according to claim 2, wherein an auxiliary magnetic circuit is formed by a soft magnetic layer on the entire back surface or a part of the electric conductor portion.