JP2008145220A - Current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current sensor capable of preferably applying to the on board use etc., which is adopted with a constitution that the DC magnetic field, corresponding to the current to be measured, is detected by the modulation of the magnetic flux caused by the Villari effect, and capable of easily and surely polarization, by properly arranging the lead out electrodes for a piezoelectric material to be a vibrator. <P>SOLUTION: The surface and rear face of the piezoelectric material ring 1 is sandwiched by a first magnetic material ring 2 and a second magnetic material ring 3 and integrated by bonding, and a pick up coil 4 is formed by winding the coil interlinking with the toroidal body. The surface and the rear face of the piezoelectric material ring 1 are provided with electrode films, on which a thin metal plate 6 is bonded to form a state where the tab members extend from the outer periphery of the piezoelectric material ring 1 for forming a lead-out electrodes. The lead out electrodes (metal plates 6) become a state that extends from the surface and the rear face of the piezoelectric material ring 1, and the distance between the electrodes can be made to widen. As a result of this, the tolerance with respect to the high voltage can be set high, and polarization process can be performed properly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a current sensor that detects the strength of a magnetic field generated by a current to be measured by a pickup coil, and more specifically, by applying a predetermined vibration force to a magnetic material associated with the pickup coil. The present invention relates to an improvement of an electrode of a piezoelectric vibrator for applying a vibration force to a magnetic material in a configuration in which an inverse magnetostriction effect (biliary effect) is generated and modulated to detect a change in a magnetic field corresponding to a current to be measured. .

  With respect to a current sensor that detects a direct current in a non-contact manner, there is an application that is required to be able to measure a large current and to perform measurement even in a severe environment where the temperature is relatively high. For example, in-vehicle applications mounted on vehicles, the specifications exceed those of general industrial applications, such as being small and robust, and having a wide operating temperature. Specifically, a current of about 50 amperes can be measured, and the engine room of the vehicle Therefore, it is necessary to be able to operate at least at about 130 ° C. In recent years, attention has been paid to fuel cell vehicles and hybrid vehicles, and current sensors have become important components.

  As a current sensor capable of detecting a large current, for example, a sensor using a Hall element is well known. This is because the Hall element is arranged in the gap part provided in the annular magnetic core, the electric wire through which the current to be measured flows is positioned inside the annular part, and the strength of the magnetic field generated by the current to be measured is detected by the Hall element ( (Hall voltage). However, a current sensor using a Hall element has many drawbacks because it is difficult to reduce the size because of the configuration in which the Hall element is sandwiched between gap portions of the magnetic core, and difficult to use in a high-temperature environment.

Further, as can be seen in Non-Patent Document 1, there is a proposal of a technique in which a current sensor is configured by using the Villari effect. This will be described with reference to the typical configuration example according to the present invention shown in FIG. 1, but the piezoelectric ring 1 is joined and integrated with the annular magnetic ring 2 (3), and the annular A wire rod is wound around the inside and outside of the part to form the pickup coil 4, and the pickup coil 4 detects the strength of the DC magnetic field generated by the DC current I. In order to detect the intensity of the magnetic flux crossing the pickup coil 4, that is, the strength of the DC magnetic field, it is necessary to modulate this. For this reason, the piezoelectric ring 1 is vibrated in the diametrical direction by applying a predetermined AC voltage, and the magnetic ring By applying a mechanical vibration force to 2 (3), the inverse magnetostriction effect (biliary effect) is caused to modulate the magnetic flux. Thereby, the change of the magnetic field corresponding to the current I to be measured can be detected, and the current can be detected.
The Institute of Electrical Engineers of Japan Magnetics Study Group MAG-05-34 Large Current Sensor Utilizing the Billari Effect Takashi Tadatsu and Ichiro Hamada

  However, the current sensor using the barrier effect as seen in Non-Patent Document 1 has the following problems.

  The piezoelectric ring 1 must be provided with electrodes in pairs and polarized in a predetermined direction. For example, when the piezoelectric ring 1 is polarized in the thickness direction, a conductive film is provided on the front and back of the piezoelectric ring 1, and lead electrodes are provided in pairs on the outer periphery, and a predetermined high voltage is applied to perform polarization processing. become. However, since the polarization process applies a high voltage, there is a problem in that the discharge is caused when the pair of extraction electrodes are close to each other, and the polarization cannot be sufficiently performed. For this reason, improvement is required for the piezoelectric material so that the lead electrode is appropriately provided and polarization can be performed easily and reliably.

  The present invention solves the above-mentioned problems, and its object is to adopt a configuration in which a DC magnetic field corresponding to the current to be measured is detected by modulation of magnetic flux by the billiary effect, and an extraction electrode is appropriately used for the piezoelectric material serving as a vibrator. It is an object of the present invention to provide a current sensor that can be easily and reliably polarized and can be preferably applied to in-vehicle applications.

  In order to achieve the above-described object, a current sensor according to the present invention is a current sensor that detects the strength of a magnetic field generated by a current to be measured by a pickup coil, and includes a piezoelectric ring formed in an annular shape and an annular shape. The first magnetic ring and the second magnetic ring are formed, electrode films are provided on the front and back surfaces of the piezoelectric ring, and a thin metal plate is attached to the electrode film surface from the outer periphery of the piezoelectric ring. The tab part is in a protruding state, the first magnetic ring and the second magnetic ring are sandwiched and joined to the front and back of the piezoelectric ring, and the wire is wound around the inside and outside of the annular part and picked up. The configuration is a coil (claim 1).

  In addition, the current sensor according to the present invention includes a piezoelectric cylinder formed in a cylindrical shape and a magnetic cylinder formed in a cylindrical shape, and an electrode film is provided on the outer circumference and the inner circumference of the piezoelectric cylinder. Then, a thin metal plate is attached to the electrode film surfaces so that the tab portion protrudes from the edge of the piezoelectric cylinder, and the magnetic cylinder is concentrically overlapped with the piezoelectric cylinder so as to be integrated. It joins, and it makes it the structure which winds a wire around the inside and outside of the said cylindrical part and makes it a pickup coil (Claim 2).

  Further, the metal plate material is formed in a substantially rectangular shape (claim 3). Alternatively, the metal plate material is formed in a shape having a protruding portion at a part of the ring portion having the same shape as the piezoelectric ring (Claim 4), or has a protruding portion at a part of the cylindrical portion overlapping the piezoelectric cylindrical body. It is formed into a shape (Claim 5).

  Further, the metal plate material is pasted using a conductive adhesive or a non-conductive adhesive (Claim 6).

  Therefore, according to the present invention, in the ring-shaped configuration, the metal plate material protrudes from the outer periphery on the front and back sides of the piezoelectric ring, and the interval between the extraction electrodes is wider than the conventional configuration, that is, the configuration formed on the outer periphery of the piezoelectric ring. it can. In addition, in the cylindrical shape configuration, the metal plate material protrudes from the edge on the front and back of the piezoelectric cylinder, and the distance between the extraction electrodes is larger than that in the conventional form, that is, the form formed on the edge of the piezoelectric cylinder. Can be widened.

  In the current sensor according to the present invention, in the ring-shaped configuration, the lead-out electrodes protrude from the outer periphery on the front and back of the piezoelectric ring, and the distance between the electrodes can be widened. Further, in the cylindrical shape configuration, the lead electrode is extended from the edge on the front and back of the piezoelectric cylinder, and the interval between the electrodes can be widened. Therefore, even if the piezoelectric ring or the piezoelectric cylinder is thin, the distance between the electrodes can be widened and the resistance to high voltage can be increased, so that discharge and short circuit can be prevented when a high voltage is applied in the polarization process, Polarization can be performed easily and reliably. As a result, it can be preferably applied to in-vehicle applications.

  FIG. 1 shows a preferred embodiment of the present invention. The current sensor of this embodiment includes a piezoelectric ring 1 formed in an annular shape, and a first magnetic ring 2 and a second magnetic ring 3 formed in an annular shape. The first magnetic ring 2 and the second magnetic ring 3 are integrated by being sandwiched together, and a wire rod is wound around the inside and outside of the annular portion to form the pickup coil 4.

  As shown in FIG. 2, electrode films 5 and 5 are provided on the front and back surfaces of the piezoelectric ring 1, respectively, and thin metal plates 6 and 6 are attached to the electrode film surfaces so that the outer circumference of the piezoelectric ring 1 is The tab portion protrudes from the outside, and is configured as an extraction electrode to the outside.

  The piezoelectric ring 1 is polarized and vibrates in the diametrical direction by applying a predetermined alternating voltage between the extraction electrodes. The electric wire 7 through which the current I to be measured flows is positioned inside the annular portion, and the strength of the magnetic field generated by the current I to be measured is detected by the pickup coil 4.

  Specifically, a conductive film (electrode films 5 and 5) is formed on the two opposing surfaces of the piezoelectric ring 1 by applying a silver paste for baking, and metal plates 6 and 6 are formed on these conductive film surfaces. 6 is fixed by an adhesive. As the adhesive, either a conductive adhesive or a non-conductive adhesive may be used. Even if this is a non-conductive adhesive, the film thickness becomes very thin, so that the other side, that is, the electrode film 5, Conductivity with 5 can be ensured. For the polarization treatment, it is put in silicon oil heated to 80 to 120 ° C., and a voltage of 2 to 3 KV / mm is applied for 20 to 60 minutes between the extraction electrodes (metal plate materials 6 and 6) and the electrode films 5 and 5. Processing is performed, and the piezoelectric ring 1 is polarized in the thickness direction. Alternatively, the polarization treatment may be performed by a piezoelectric ring alone on which a conductive film is formed before mounting the metal plate.

  The metal plate 6 can be formed in an appropriate shape, and for example, is formed in a substantially rectangular shape as in the example shown in FIG. Alternatively, as in the example shown in FIG. 3, the piezoelectric ring 1 may be formed in a shape having a protruding portion at a part of the ring portion having the same shape. Further, the metal plates 6 and 6 may be bonded together by a low melting point metal material.

  In this case, since the electric wire 7 is positioned in the annular portion, the magnetic flux due to the current I to be measured is generated in the circulation direction with respect to the magnetic rings 2 and 3. By applying an AC voltage to the piezoelectric ring 1, the magnetic flux density causes a corresponding amount to increase or decrease even when the magnetic field is constant, that is, in the state of the DC magnetic field, and the magnetic flux changes. That is, by applying a mechanical vibration force to the magnetic rings 2 and 3, an inverse magnetostriction effect (biliary effect) is caused to modulate the magnetic flux. Due to this change in magnetic flux, an electromotive force is generated in the pickup coil 4, and the output of the pickup coil 4 increases or decreases in proportion to the magnitude of the DC magnetic field, that is, the current I to be measured. Therefore, the change in the magnetic field corresponding to the current I to be measured can be detected, and the current can be detected.

  Since this current sensor is composed of a piezoelectric material and a magnetic material, there is no problem when used in a high temperature environment, and the operating temperature range is wide. The current detection operation utilizes magnetic flux modulation due to the barrier effect, so that the size can be reduced unlike the configuration using the Hall element, and detection without being affected by the disturbance magnetic field can be performed. In addition, since the Hall element is a semiconductor, its radiation resistance is weak and low, but this current sensor has high radiation resistance. Furthermore, since the Hall element is arranged in the gap of the magnetic core, the sensitivity is low. On the other hand, the current detection configuration based on the barrier effect is highly sensitive and can detect a large current.

  In the present invention, the lead electrodes (metal plate members 6 and 6) have a form protruding from the outer periphery on the front and back of the piezoelectric ring 1, and lead out compared to the conventional form, that is, the form formed on the outer periphery of the piezoelectric ring 1. The distance between the electrodes can be widened. Therefore, even if the piezoelectric ring 1 is thin, the distance between the electrodes can be widened, and the resistance to high voltage can be increased. Therefore, when a high voltage is applied in the polarization process, discharge and short circuit can be prevented, and polarization is easy. It can be done reliably. As a result, the current sensor according to the present invention can be preferably applied to in-vehicle applications.

(Cylinder type configuration example of current sensor)
FIG. 4 is a perspective view showing another example of the current sensor according to the present invention. The current sensor includes a piezoelectric cylinder 10 formed in a cylindrical shape and a magnetic cylinder 11 formed in a cylindrical shape, and the magnetic cylinder 11 is concentrically overlapped with the piezoelectric cylinder 10. Are joined together, and a wire rod is wound around the inside and outside of the cylindrical portion to form the pickup coil 4.

  As shown in FIG. 5, the piezoelectric cylinder 10 is provided with electrode films 5 and 5 on the outer circumference and the inner circumference, respectively, and thin metal plates 6 and 6 are attached to the electrode film surfaces to thereby provide the piezoelectric body. The tab portion protrudes from the edge of the cylindrical body 10 and is configured as an extraction electrode to the outside.

  The piezoelectric cylinder 10 is polarized and vibrates in the diametrical direction by applying a predetermined alternating voltage between the extraction electrodes. The electric wire 7 through which the current I to be measured flows is positioned inside the annular portion, and the strength of the magnetic field generated by the current I to be measured is detected by the pickup coil 4.

  Here, the magnetic cylinder 11 is concentrically overlapped on the outside of the piezoelectric cylinder 10, but conversely, the piezoelectric cylinder 10 is concentrically overlapped on the outside of the magnetic cylinder 11. May be.

  In this case, the piezoelectric cylinder 10 is polarized in the diameter direction. And it can form in a suitable shape as the metal plate material 6, For example, it forms in a substantially rectangular shape like the example shown in FIG. Alternatively, as shown in the example shown in FIG. 6, it may be formed in a shape having an overhanging part in a part of the cylindrical part that overlaps the piezoelectric body 10.

  Even with the cylindrical configuration shown in FIG. 4, the operation is the same as that of the ring type shown in FIG. 1, and the current detection operation does not change, and a large current can be detected in the same manner.

  Further, the lead electrodes (metal plate materials 6 and 6) have a form protruding from the edge on the front and back of the piezoelectric body 10, and the lead electrodes are formed in comparison with the conventional form, that is, the form formed on the end edge of the piezoelectric body 10. Can be widened. Therefore, even if the piezoelectric cylinder 10 is thin, the distance between the electrodes can be increased and the resistance to high voltage can be increased. Therefore, when a high voltage is applied in the polarization process, discharge and short circuit can be prevented, and polarization is easy. Can be done reliably. As a result, the current sensor according to the present invention can be preferably applied to in-vehicle applications.

  In the present invention, a large DC current can be detected in a non-contact manner and the operating temperature becomes wide. Therefore, in-vehicle applications such as hybrid vehicles and electric vehicles, and applications of large current sensors such as solar power generation, wind power generation, and fuel cells. It is effective for.

1 is a perspective view showing a preferred embodiment of a current sensor according to the present invention. It is a perspective view explaining the part of a piezoelectric material ring. It is a top view which shows the other example of a metal plate material. It is a perspective view which shows other embodiment of the current sensor which concerns on this invention. It is a perspective view explaining the part of a piezoelectric material cylinder. It is a perspective view which shows the other example of a metal plate material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric ring 2 1st magnetic body ring 3 2nd magnetic body ring 4 Pickup coil 5 Electrode film 6 Metal member 7 Electric wire 10 Piezoelectric cylinder 11 Magnetic cylinder

Claims (6)

A current sensor for detecting the strength of a magnetic field generated by a current to be measured by a pickup coil, comprising a piezoelectric ring formed in an annular shape, and a first magnetic ring and a second magnetic ring formed in an annular shape,
Electrode films are provided on the front and back sides of the piezoelectric ring, and a thin metal plate is attached to the electrode film surfaces so that the tab portions protrude from the outer periphery of the piezoelectric ring, A current sensor characterized in that the first magnetic ring and the second magnetic ring are joined together by being sandwiched, and a wire rod is wound around the inside and outside of the annular portion to form the pickup coil. A current sensor for detecting the strength of a magnetic field generated by a current to be measured by a pickup coil, comprising a piezoelectric cylinder formed in a cylindrical shape, and a magnetic cylinder formed in a cylindrical shape,
An electrode film is provided on the outer periphery and inner periphery of the piezoelectric cylinder, and a thin metal plate is attached to the electrode film surface so that a tab portion projects from the edge of the piezoelectric cylinder, and the piezoelectric body A current sensor characterized in that the magnetic cylindrical body is concentrically overlapped and integrally joined to a cylindrical body, and a wire rod is wound inside and outside the cylindrical portion to form the pickup coil.   The current sensor according to claim 1, wherein the metal plate is formed in a substantially rectangular shape.   2. The current sensor according to claim 1, wherein the metal plate is formed in a shape having a protruding portion at a part of a ring portion having the same shape as the piezoelectric ring.   3. The current sensor according to claim 2, wherein the metal plate material is formed in a shape having an overhanging portion at a part of a cylindrical portion overlapping the piezoelectric cylindrical body. The current sensor according to claim 1, wherein the metal plate material is attached using a conductive adhesive or a non-conductive adhesive.

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