JP2013238500A - Inclined core type current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a manufacturing cost of a winding step by detecting a current by a solenoid winding coil without requiring the necessity of a toroidal winding coil in a current sensor of a type for detecting the current by utilizing induced voltage of a coil due to a magnetic flux change, and to achieve miniaturization by simplification of winding.SOLUTION: A magnetic core including at least one solenoid winding excitation coil for allowing an excitation current including an AC component to flow and at least one solenoid winding detection coil for outputting induced voltage, arranged so as to include an arbitrary point on a magnetic flux generated when a current is allowed to flow into the detection coil arranged in vacuum and having magnetic anisotropy is installed so as to be inclined in the winding direction against the magnetic flux direction so that a direction of a magnetization easy axis of the magnetic core includes direction components of both of the magnetic flux direction of the magnetic flux passing through the point and the winding direction of the detection coil. All of the excitation coil, the detection coil and the magnetic core are arranged so as to be magnetically coupled with each other.

Description

  The present invention relates to an insulation type DC / AC current sensor that measures the value of the current to be measured in a state where the current circuit to be measured and the measurement circuit are electrically insulated.

  Current sensors are often used in electrical and electronic devices. In recent years, it has become possible to use DC power for leveling natural energy generated power with batteries, driving motor vehicles, or using DC power for energy saving. Increasingly, it has become an unavoidable issue to improve the efficiency and safety and reliability of DC power usage. In order to solve this problem, it is necessary to measure and control the current in various situations. However, if the conventional current sensor is evaluated based on cost, dimensions, stability, etc., it still has to meet the market needs. Not reached.

  Current sensors can be broadly classified into the detection coil method and the magnetic field sensor element method. The simplest detection coil type current sensor is an AC CT or Rogowski coil, but these cannot measure DC and are not current sensors that can also measure DC, which is the object of the present invention. Well-known detection coil type current sensors that can also measure direct current include magnetic modulation methods such as the fluxgate method, which are often used to measure small currents. The feature of the detection coil system that can measure DC is that the magnetic core is excited. In other words, the magnetic flux is changed by adding the exciting magnetic flux to the direct current magnetic flux that is essentially unchanged, and when the change in the magnetic flux is detected by the coil, the information on the DC magnetic flux contained therein is acquired at the same time. What is important here is how to include DC flux information in the excitation flux change, and that method is the basis of the detection principle.

  The magnetic field sensor element method measures the current of the source by measuring the magnetic field generated by the current to be measured. In principle, it is possible to make a current sensor with all magnetic field sensors. Well-known magnetic field sensors include Hall elements, magnetoresistive elements, magneto-impedance elements, and Faraday elements, which can be further classified. However, depending on the characteristics of the magnetic field sensor, there are things that are suitable for current sensors and those that are not.

  For these reasons, the most common magnetic field sensor used in current sensors is the Hall element, which occupies an overwhelming market share. In particular, the Hall element method is used exclusively for measuring current exceeding 10A. This is because the sensitivity is low compared to other magnetic field sensors and it is suitable for large current measurement, the direction of the magnetic field to be measured is the thin direction of the element, and it is easy to use structurally. This is due to synergistic effects such as being able to manufacture.

  When this Hall element is used for a current sensor, a ring-shaped magnetic core that normally circulates the current to be measured is used, and a part of the ring is cut out and the Hall element is sandwiched in the gap. However, the Hall element is a semiconductor, and it is vulnerable to environmental stresses such as heat and humidity, so the reliability of the current sensor cannot be improved. Compared to this, the detection coil method can be configured with only magnetic material and coil, and in that respect, it is more reliable than the Hall element method.

  However, the conventional detection coil type current sensor requires a toroidal winding of the detection coil, which increases the manufacturing cost of the toroidal winding. Furthermore, toroidal winding is an obstacle to miniaturization, and it is difficult to make a chip-element-sized current sensor that is in demand for portable electronic devices, for example. Incidentally, there is a research that tried the chip element size by the fluxgate method, and it is reported in Non-Patent Document 1. However, as the author stated in the same document, it is inaccurate and can only be used for fail-safe applications. In addition, there is a small proposal using a Hall element that is not a detection coil system, and is disclosed in Patent Document 1. This approach attempts to reduce the influence of other magnetic fields that are not intended for measurement, that is, disturbance, by bringing the Hall element closer to the current to be measured, but the effect is not sufficient and the reliability of the measured value is lacking. Of course, the shortcomings of the Hall element remain.

  Therefore, the shunt resistor method is used in portable electronic devices that require chip element size. However, in the shunt resistor method, the current circuit to be measured and the measurement circuit are not insulated, so if the circuit potential is different, matching of the potential is required, and the design freedom is limited. There are problems such as noise entering the control circuit from the current circuit through the measurement circuit, and reducing the control reliability. Furthermore, when measuring the power supply current, the voltage drop due to the shunt resistance hinders the effective use of the power supply voltage, which is an important issue for portable electronic devices that operate with a limited power supply. As a solution to this problem, there is an attempt to reduce the resistance value of the shunt resistor. However, in this case, the detection voltage is reduced, and high performance of the signal processing circuit is required, and the S / N ratio is deteriorated. This causes a problem that reduces control reliability.

  In other words, the market demands a space-saving, low-cost, insulated high-performance current sensor that does not require toroidal winding, and a reliable current sensor that can be made into an insulated chip element. However, there has never been a current sensor system that enables them. Non-patent documents 2 to 4 shown in the following prior art documents are examples of the prior art.

JP 2011-75576 A

Yoichi Fujiyama, Kenichi Arai, and 3 others "Trial manufacture of thin film current sensor using saturable ring core" The Japan Society of Applied Magnetics 22, 705 − 708 (1998) Kenichi Takeshida, Toshio Mohri “Colpitts self-oscillation type high-sensitivity, high-speed response current sensor using amorphous magnetic wire MI element” Journal of Applied Magnetics Society of Japan 20,629 − 632 (1996) Tadatsu Takashi, Ichiro Hamada “Development of non-contact μA current sensor using magnetic bridge” Japan Society of Applied Magnetics 311, 421-426 (2007) Journal of Advanced Science, Vol.17, No.3 & 4,2005

  The problems to be solved are the problem that the coil is a toroidal winding in the detection coil type current sensor that detects the magnetic flux change with the coil, and the problem that the chip element size cannot be reduced.

  This occurs when at least one solenoid-wound excitation coil that passes an excitation current containing an AC component and at least one solenoid-wound detection coil that outputs an induced voltage, and current flows through the detection coil in a vacuum. A magnetic core having magnetic anisotropy placed so as to include an arbitrary point on the magnetic flux, the direction of the easy axis of the magnetic core being at the arbitrary point, the magnetic flux direction of the magnetic flux passing through the point, Inclined in the winding direction with respect to the magnetic flux direction so as to have both directional components with the winding direction of the detection coil, and the excitation coil, the detection coil, and the magnetic core Arrange them so that they are all magnetically coupled to each other.

  The tilted core type current sensor of the present invention is made in comparison with a conventional detection coil type current sensor that requires a toroidal winding because the detection coil is a solenoid winding although it is a detection coil type current sensor. There is an advantage that it is easy to reduce manufacturing costs and an advantage that a smaller product can be made. In other words, since the toroidal winding is topologically intertwined between the magnetic core and the coil circuit, it takes time to wind the coil. However, solenoid winding is easy because the magnetic core and coil circuit are topologically separated. For the same reason, toroidal winding is overwhelmingly inferior to small windings. Thus, the big industrial effect arises by making the necessary coil toroidal winding.

The principle explanatory view showing the mutual arrangement relation between the detection coil 3 and the magnetic core 1. A perspective view showing a principle form. The operation explanatory view which looked at FIG. 2 from the coil surface direction. An explanatory diagram showing the difference in the ratio of the excitation magnetic field He and the measured magnetic field Hx contained in the composite magnetic field Hc due to the inclination of the magnetic core. An explanatory diagram showing the difference in the strength of the magnetic field received by the magnetic core depending on the slope of the measured current Ix. An explanatory diagram showing the interrelationship between the magnetic core, the excitation coil, the detection coil, and the measured current Ix when there is one magnetic core. An explanatory diagram showing the interrelationship among the magnetic core, excitation coil, detection coil, and measured current Ix when there are multiple magnetic cores. FIG. 6 is an explanatory diagram showing the case where the current to be measured is outside the coil. Explanatory drawing when the measured current is outside the coil and multiple magnetic cores are placed and the coil is deformed. An explanatory diagram showing the B-H characteristics of the magnetic core that the combined magnetic flux Φc is generated from the magnetic field to be measured Hx and the excitation magnetic field He. An explanatory diagram showing how to obtain the measured value from one detection voltage Vd. Configuration and operation explanatory diagram of linked core type differential system. An explanatory diagram showing the combined magnetic flux of differential core magnetic cores 1a and 1b and their differential values. Configuration and operation explanatory diagram of counter excitation type differential method. An explanatory diagram showing the resultant magnetic flux and the differential value waveform in the counter-excitation differential magnetic core. An explanatory diagram showing an example of a drive circuit that realizes a method for obtaining a measurement value from a single detection voltage Vd. An explanatory diagram showing an example of a connection method of a coupled core type differential coil and a block diagram of a drive circuit. Explanatory drawing which showed an example of the connection method of a connection core type differential system coil, and an example of the method of obtaining a differential signal. Explanatory drawing which showed an example of the connection method of a connection core type differential system coil, and an example of the method of obtaining a differential signal. Explanatory drawing which showed an example of the connection method of the coil of a connection core type differential system. An explanatory diagram showing a block diagram of the drive circuit and connection method of counter excitation type differential coil. An explanatory diagram showing an example of a coupled magnetic core and its parallel arrangement. Illustration of a closed magnetic circuit core for closing a magnetic circuit. Illustration of a closed magnetic circuit core using a coupled magnetic core. Explanatory drawing of a linked magnetic core assembly using a magnetic material with magnetocrystalline anisotropy. Explanatory drawing of the Example of a connection core type | mold differential system. Explanatory drawing of the Example of the connection core type differential system which employ | adopted the closed magnetic circuit core. Explanatory drawing of the Example of the connection core type differential system which employ | adopted the connection magnetic core structure to the closed magnetic circuit core. Explanatory drawing of the example which made it a clamp type with a connection core type differential system. Explanatory drawing of the clamp-type Example using six sensor units. An illustration of an embodiment of a chip element size in which a part is cut open and seen through to reveal the inside. A − A sectional view of FIG. Explanatory drawing of the magnetic core of FIG. Explanatory drawing of the magnetic core of FIG. The graph of the measured value of the input-output characteristic of Example 1 which made the magnetic core material the amorphous ribbon. Graph of measured values of input / output characteristics of Example 1 in which magnetic core material is ferrite.

  First, the operating principle and components are explained.

  The detection coil type current sensor captures the change in magnetic flux linked to the detection coil as an induced voltage. Therefore, the following conditions are necessary. The first is that the magnetic flux is linked to the detection coil, the second is that the linked magnetic flux changes even if the measured current is DC, and the third is that the change in the magnetic flux is the magnitude of the measured current. It is influenced by the direction and direction. In this way, an induced voltage containing information on the current to be measured can be obtained, so that the current to be measured can be known from the induced voltage.

  Magnetic flux due to current is generated around the current. Therefore, to use the magnetic flux efficiently, it is optimal to provide a ring-shaped magnetic core that circulates the current. Then, in order to arrange the detection coil interlinking with this magnetic flux, the coil inevitably becomes toroidal. The reason why the conventional detection coil type detection coil is toroidally wound is to link the magnetic flux of the current to be measured and the detection coil. Therefore, if the magnetic flux to be measured and the detection coil can be linked, there is no need for toroidal winding.

  Therefore, we will examine whether the above three conditions can be satisfied by solenoid winding. To simplify the study, it is assumed that the current to be measured flowing in a straight line flows on the central axis of a circular solenoid-wound detection coil. Then, in this positional relationship, the magnetic flux of the current to be measured does not interlink with the solenoid winding detection coil. However, if the property that magnetic flux is induced in the magnetic material is used, it is possible to induce the magnetic flux of the current to be measured to penetrate through the detection coil and to be linked. At this time, in this explanation, in order to make the principle easier to understand, all materials other than the magnetic core, such as the winding material of the detection coil and the current conductor to be measured, are treated as non-magnetic materials. However, this invention is not conditional on this.

  FIG. 1 is a principle explanatory diagram showing the mutual arrangement relationship between the detection coil 3 and the magnetic core 1. This is because an arbitrary point P on the magnetic flux generated when a current is passed through a detection coil placed in a vacuum, a magnetic core having magnetic anisotropy placed so as to include this point P is set as the magnetic core. The direction of the easy axis of magnetization at the arbitrary point P has the directional components of both the magnetic flux direction of the magnetic flux passing through the point and the winding direction of the detection coil with respect to the magnetic flux direction. It was installed with an inclination in the winding direction.

  Here, the expression “any point P on the magnetic flux generated when a current is passed through a detection coil placed in a vacuum” will be described. First, “when a current is passed through a detection coil in a vacuum” does not mean that a current is actually passed through the detection coil at the time of implementation, but is an explanation for clarifying the nature of “any point P”. is there. In this case, the expression “in vacuum” means that the permeability is uniform in a wide space. If the magnetic permeability is not uniform in the vicinity of the coil for reasons other than the elements of the present invention, the explanation of the principle will be hindered. Therefore, this condition is not necessary in the practice of the present invention.

  Next, the expression “magnetic core with magnetic anisotropy” will be explained. Magnetic anisotropy refers to the property that the internal energy in a magnetic material varies depending on the direction of the magnetic moment. In short, it means that there is a direction that is not likely to be magnetized. It has the property that there are directions that are easy to pass and directions that are not. For example, when a nail is made to come in contact with a magnet at random, magnetic poles appear at the head and tip of the nail with a very high probability. This is called shape magnetic anisotropy and is easily magnetized in the longitudinal direction. In this case, the longitudinal axis that is easily magnetized is called the easy axis, and the hard axis is called the hard axis. Such magnetic anisotropy includes crystal magnetic anisotropy and induced magnetic anisotropy in addition to shape magnetic anisotropy. In the present invention, any material having such magnetic anisotropy can be used. In this description, a magnetic core using shape magnetic anisotropy is assumed in addition to FIGS. 31, 32, 33, and 34, and an easy axis of magnetization is present in the longitudinal direction of the magnetic core shown in the figure.

  The relationship between the magnetic core due to the current to be measured and the magnetic core when the magnetic core is placed at the arbitrary point P will be described. As described above, when the current to be measured flows on the central axis of the circular detection coil, the direction of the magnetic field and magnetic flux due to the current to be measured overlaps the winding direction of the detection coil. In such a positional relationship, the direction of the magnetic flux generated when “current is passed through the detection coil” is perpendicular to the magnetic flux due to the current to be measured. This relationship holds at all positions, and is the same at the arbitrary point P.

  When placing the magnetic core at this arbitrary point P, if the easy axis of the magnetic core is placed so as to be perpendicular to the direction of the magnetic flux due to the measured current, the magnetic flux of the measured current passing through the magnetic core is The component in the direction of the magnetic flux is not generated when “a current is passed through the detection coil”. Therefore, no magnetic flux interlinking with the detection coil is generated. In addition, when the magnetic core is placed parallel to the direction of the magnetic flux of the current to be measured, the magnetic flux direction component that occurs when “current is passed through the detection coil” does not occur. Therefore, no magnetic flux interlinking with the detection coil is generated in this case. In other words, when the easy axis of the magnetic core is perpendicular or parallel to the direction of the magnetic flux due to the current being measured, the magnetic flux of the current being measured does not interlink with the detection coil. Incidentally, the toroidal core corresponds to the parallel case described above.

  Here, the magnetic core has a direction component of both the direction of magnetic flux generated when a current is passed through the detection coil in a vacuum and the direction of winding of the detection coil. In the case where it is installed in the direction of winding, in other words, the easy magnetization axis of the magnetic core has an inclination with respect to the magnetic flux generated when “current is passed through the detection coil”, and the inclination When the magnetic core is installed so that it has a component of the winding direction of the detection coil, that is, the magnetic flux direction of the current to be measured, the magnetic core is magnetized in the direction of the easy magnetization axis and a magnetic flux is generated in the direction of the easy magnetization axis. The magnetic flux of the current comes to interlink with the detection coil. As a result, the current to be measured and the detection coil are magnetically coupled.

  As described above, the current to be measured and the solenoid-wound detection coil can be magnetically coupled by the inclined magnetic core. If the current to be measured is alternating current, an induced voltage is generated in the solenoid-wound detection coil, and output can be obtained. In other words, it has the function of a conventional AC CT. However, the object of the present invention is to detect direct current, and direct current cannot be detected as it is. Therefore, the principle of the present invention is to detect DC current by exciting the magnetic core with AC.

  FIG. 2 is a perspective view showing a principle form of the present invention. In FIG. 2, the solenoid-wound excitation coil 2 and the detection coil 3 are arranged coaxially so that the current to be measured flows through both the coils. Further, the magnetic core 1 is arranged inside the coils so that the longitudinal direction, which is the easy axis of shape magnetic anisotropy, is inclined as described above.

  FIG. 3 is an operation explanatory diagram when FIG. 2 is viewed from the coil surface direction (side surface). The measured magnetic field Hx generated by the measured current Ix generates a measured magnetic flux Φx inside the magnetic core 1. On the other hand, an exciting current Ie having an AC component is passed through the exciting coil 2, thereby generating an exciting magnetic field He whose intensity varies inside the exciting coil 2. Therefore, an exciting magnetic flux Φe is generated inside the magnetic core 1. In the following description, the excitation current Ie is described as an AC component only to facilitate understanding of the principle. By the way, since the measured magnetic flux Φx and the excitation magnetic flux Φe are generated in the same magnetic core at the same time, they actually exist as one combined magnetic flux. Therefore, this is called the combined magnetic flux Φc. This combined magnetic flux Φc increases during the time when the measured magnetic flux Φx and the excitation magnetic flux Φe are in the same direction. However, since the excitation magnetic field He is alternating, there is a time zone in which the excitation magnetic flux Φe faces the opposite direction, and the resultant magnetic flux Φc is small during this time zone. Therefore, the magnitude of the combined magnetic flux Φc varies in synchronization with the excitation frequency fe of the excitation current Ie. This combined magnetic flux Φc generates an induced voltage in the detecting coil 3 that is linked. Wiring is performed so that this induced voltage can be output, and the output is called the detection voltage Vd. In this way, the detection voltage Vd affected by the measured current Ix can be obtained. The value of the measured current Ix can be measured from this detected voltage Vd. The principle and method will be described later.

  Figure 4 is an explanatory diagram showing the difference in the ratio of the excitation magnetic field He and the measured magnetic field Hx contained in the composite magnetic field Hc due to the inclination of the magnetic core. In the above, the explanation was made from the viewpoint of magnetic flux. The combined magnetic field Hc in this figure is drawn with the same magnitude. This is to compare the difference between the excitation magnetic field He composing the composite magnetic field Hc and the measured magnetic field Hx ratio due to the inclination angle of the magnetic core.

  In Fig. 4, the measured magnetic field Hx and the excitation magnetic field He are described as being at right angles. In addition, the characteristics of the magnetic core 1 are simplified and described as being magnetized only in the easy axis direction and not in the hard axis direction. If the inclination angle θ of the magnetic core 1 is 0 degree under this condition, the composite magnetic field Hc does not contain the component of the magnetic field to be measured Hx, and information on the magnetic field to be measured Hx cannot be obtained from the induced voltage of the detection coil. . When the tilt angle θ is 90 degrees, the composite magnetic field Hc does not contain the excitation magnetic field He component. Therefore, the induced voltage due to the excitation magnetic field He does not occur in the detection coil, and information on the measured magnetic field Hx cannot be obtained from the induced voltage of the detection coil. The effect of the magnetic field to be measured Hx is stronger when the tilt angle θ is larger, and it works for better sensitivity as a sensor. However, the influence of the excitation magnetic field He is stronger when the tilt angle θ is smaller, and at that point the tilt angle θ The smaller the is, the better the sensitivity. Taken together, it can be seen that there is an angle where the two are in the best relationship. The angle depends on the product specifications, such as whether a small current is measured with high sensitivity, whether a large current is measured, or how much the excitation current is to be measured. It is also possible to change the tilt angle partially by making the magnetic core 1 not curved but curved or refracted, and to use the advantages of the characteristics of the tilt angle in combination. If this concept is used, the connecting part of the connecting magnetic core, which will be described later, can be continuously connected in a curved shape without bending, and the design element can be used for design optimization.

  Fig. 5 is an explanatory diagram showing the difference in the strength of the magnetic field received by the magnetic core depending on the slope of the measured current Ix. In this figure, based on one measured current Ix-B perpendicular to the coil surface, measured current Ix-A has a large magnetic core direction component Hx-a of the measured magnetic field. In C, the magnetic core direction component Hx-c of the measured magnetic field is small. Therefore, it can be seen that the sensitivity of the sensor varies with the angle of the current Ix to be measured in a single magnetic core. In order to improve this problem, as shown in FIG. 7 to be described later, it is effective to install a magnetic core at the facing position with the measured current Ix as the center, or the coupled magnetic core clarified in the explanation of FIG. It is.

  Fig. 6 is an explanatory diagram showing the interrelationship among the magnetic core, the excitation coil, the detection coil, and the measured current Ix when there is one magnetic core. In this figure, the detection coil 3 and the excitation coil 2 overlap in the axial direction of the coil, and the current Ix to be measured flows on the axis of the coil. In other words, Fig. 3 is a view from the right side. In this figure, the magnetic core 1 is tilted so that the back of the page is down and the front side is up, and the end of the magnetic core is visible there. The measured current Ix was directed from the front to the back of the page, and the direction was indicated with a cross in accordance with the convention.

  Fig. 7 is an explanatory diagram showing the interrelationship among the magnetic core, excitation coil, detection coil, and measured current Ix when there are multiple magnetic cores. In this figure, a plurality of magnetic cores 1 in FIG. 6 are arranged so as to circulate the current Ix to be measured. As a result, the magnetic coupling between the exciting coil 2, the detecting coil 3, and the current Ix to be measured is strengthened, and more stable measurement can be performed as compared with the case of one magnetic core. In this way, the influence of the slope of the measured current Ix explained in FIG. 5 has a function of canceling out by the opposing magnetic core across the measured current Ix on the circumference. .

FIG. 8 is an explanatory diagram showing the case where the current to be measured is outside the coil in FIG. The relationship between the measured magnetic field Hx and the magnetic core 1 shown in this figure is the same as that shown in FIGS.
It can be seen that Ix works even outside the coil. However, the sensitivity decreases because the distance between the measured current Ix and the magnetic core 1 is increased.

  Fig. 9 is an explanatory diagram when the current to be measured is outside the coil and a plurality of magnetic cores are arranged and the coil is deformed. In FIG. 8, the distance between the measured current Ix and the magnetic core 1 is large. Therefore, to improve this, the coil was deformed to bring the measured current Ix closer to the magnetic core 1. Furthermore, the magnetic core 1 was increased to make it more stable. This can be understood as a group of sensor units, and its application will be described with reference to FIGS. 29 and 30. FIG.

FIG. 10 shows that the combined magnetic flux Φc is generated from the magnetic field to be measured Hx and the excitation magnetic field He.
It is an explanatory diagram showing the characteristics. This BH characteristic is a characteristic of a general magnetic material that defines positive and negative regions, but the BH characteristic of the magnetic material is symmetrical at the origin as shown in the figure. In this figure, the hysteresis is omitted for easy understanding. Although the actual characteristics have hysteresis and the magnetic flux waveform is distorted, the symmetry and nonlinearity that are important in the principle of operation do not change. In this figure, the waveform of the excitation magnetic field He when the measured magnetic field Hx is 0 and the waveform of the excitation magnetic flux Φe at that time are shown by broken lines. The excitation magnetic field He and the measured magnetic field Hx are added, and the magnetic field with the center shifted is shown as the combined magnetic field Hc with a solid line. The magnetic flux generated by the combined magnetic field Hc is shown by the solid line as the combined magnetic flux Φc.

   Since the B-H characteristics of the magnetic material are symmetric with respect to the origin, if the excitation magnetic field He is positive and negative symmetric, for example, a sine wave, the excitation magnetic flux Φe with only the excitation magnetic field He becomes positive and negative symmetric. This is also the relationship between the combined magnetic field Hc and the combined magnetic flux Φc when the measured magnetic field Hx is zero. However, if the measured magnetic field Hx is not 0, the resultant magnetic flux Φc will not be positively or negatively symmetric even if the excitation magnetic field He is symmetric. In other words, this is because the combined magnetic field Hc, which is the sum of the excitation magnetic field He and the measured magnetic field Hx, swings around a point deviated from the symmetry point of the B-H characteristic of the magnetic material. The magnitude of the measured magnetic field Hx can be determined by measuring the degree of asymmetry of the composite magnetic flux Φc using this. In other words, the value of the measured current Ix can be known. In this explanation, the frequency of the magnetic field to be measured Hx is sufficiently lower than the frequency of the excitation current Ie, that is, the excitation frequency fe, or is DC.

  Next, a method for detecting the degree of asymmetry of the combined magnetic flux Φc is described. The resultant magnetic flux Φc is a distorted wave with the excitation frequency fe as the fundamental frequency. Therefore, the induced voltage can be obtained if there is a coil interlinking with this combined magnetic flux Φc. That coil is the detection coil, which is the detection coil 3 shown in FIGS. Since the induced voltage of the coil is a differential value of the magnetic flux, the detected voltage Vd is also a differential waveform of the combined magnetic flux Φc in this case. Therefore, if the detection voltage Vd of the detection coil 3 is integrated, the same waveform as the combined magnetic flux Φc can be obtained. However, since the detection voltage Vd does not contain the DC component of the composite magnetic flux Φc, the integrated value of the detection voltage Vd has a waveform that excludes the DC component from the composite magnetic flux Φc. This waveform and timing are shown in FIG. However, it does not necessarily have to be integrated. Although integration can be expected to improve accuracy, it can be detected without integration.

FIG. 11 is an explanatory diagram showing a method for obtaining a measured value from one detection voltage Vd. “Measured value” here refers to the magnetic field to be measured.
The value proportional to the value of Hx is proportional to the value of the measured current Ix. The two detected voltage integral values Vix and Vi0 shown in the figure are the detected voltage.
This is a voltage waveform obtained by integrating Vd. This detected voltage integral value does not include the DC component information of the composite magnetic flux Φc. Therefore, it is necessary to devise a way to obtain DC component information from only this AC waveform.

  The method of obtaining the measured value in Fig. 11 is to obtain the position when Ix = 0 on the waveform of the detected voltage integral value Vix when the measured current Ix is an arbitrary value, and the value of that position is 0 V of Vix. This is a method to find out how far it is from. The waveform of Vix is when Ix is an arbitrary value, but this figure shows when Ix is not zero. Vi0 shown by the broken line is the integrated waveform of the detected voltage when Ix = 0. Vi0 is symmetric in positive and negative, and its zero-crossing timing is the same as the rising or falling timing of the excitation current Ie. In other words, the instantaneous value of the rise timing and the instantaneous value of the fall timing are the same value and become 0 V (however, adjustment is necessary if the phase is shifted due to the characteristics of the magnetic material or the circuit). Using this property, if the timing at which the instantaneous value at the rising timing and the instantaneous value at the falling timing are the same in the Vix waveform is obtained, the instantaneous value at that time deviates from 0 V of Vix. Indicates the value. This value reflects the degree of waveform distortion and is proportional to the magnitude of the measured current Ix. The specific method for obtaining the instantaneous value is to sample and hold the instantaneous value of the rise timing and fall timing, respectively, and shift the timing of Ie with respect to the phase of Vix so that both values are the same. Adjust accordingly. The measured value can be obtained from the instantaneous value obtained in this way. This method will be described more specifically in the description of FIG.

  According to the principle explained above, if there is a magnetic core 1, an excitation coil 2 and a detection coil 3, all of them are magnetically coupled to each other, and the current Ix to be measured is arranged at a position where they are magnetically coupled, The measured current Ix can be measured. However, this method handles instantaneous values, and in practical circuits, there may be noise in the instantaneous values and it may be difficult to improve accuracy. Therefore, the method that can be expected to improve accuracy by making the present invention a differential system is presented below. There are two types of differential systems. One is to provide a pair of magnetic cores with symmetrical inclinations, and to obtain the differential value of the output obtained from each. The other is to reverse the magnetic cores with one-direction inclination for each part. It is a method of exciting in the direction. The following is a detailed explanation based on the explanatory diagram.

FIG. 12 is a diagram for explaining the configuration and operation of a linked core type differential system, and is an example of the invention of claim 3. The coupled magnetic cores used in this method are a magnetic core 1a having a positive inclination angle θ and a negative magnetic core 1b shown in FIG.
Is a magnetic core in which the magnetic paths along the easy axis of both cores are connected in series. Although the connecting portion in this figure is hidden by the exciting coil 2, the magnetic core 1a and the magnetic core 1b have a magnetic gap even if they are not in mechanical contact, in addition to the case where they are in mechanical contact. A magnetically coupled connection may be used. The detection coil 3a is wound around the positive inclination angle portion of the coupled magnetic core, that is, the magnetic core 1a, and similarly the detection coil 3b is wound around the negative inclination angle portion, that is, the magnetic core 1b. Further, the exciting coil 2 is wound so that the exciting magnetic flux is generated in both the magnetic core 1a and the magnetic core 1b, that is, the entire connected magnetic core. These coils shown in this figure are wound only partially, but this is for ease of explanation, and in practice it is more practical to use the embodiment shown in FIG.

In Fig. 12, when the measured current Ix flows, the measured magnetic field Hx is generated. This measured magnetic field Hx generates a measured magnetic flux Φxa of the magnetic core 1a and a measured magnetic flux Φxb of the magnetic core 1b. In this case, Φxa and Φxb are in the same direction in the Y coordinate of the XY coordinates shown in the figure, but opposite in the X coordinate. On the other hand, the exciting magnetic field He caused by the exciting current Ie generates an exciting magnetic flux Φea in the magnetic core 1a and an exciting magnetic flux Φeb in the magnetic core 1b. In this case, Φea and Φeb are opposite to each other in the Y coordinate and in the same direction in the X coordinate. As a result, Φxa and Φea of magnetic core 1a are in the same direction, and Φxb and Φeb of magnetic core 1b are in opposite directions. A detection coil 3a is wound around the magnetic core 1a, and a detection coil 3b is wound around the magnetic core 1b. The induction voltage of the detection coil 3a is output from the coil as the detection voltage Vda, and the induction voltage of the detection coil 3b is output from the coil as the detection voltage Vdb. The concatenated core type differential method uses the differential value between the detected voltages Vda and Vdb.

  Here, the excitation current Ie is explained as a sine wave of excitation frequency fe or a waveform close to it. However, when the present invention is implemented, a triangular wave or the like may be used, and is not limited to a sine wave. The frequency of the measured current Ix is explained below when it is sufficiently lower than the excitation frequency fe or DC.

FIG. 13 is an explanatory diagram showing the combined magnetic flux of the coupled core type differential magnetic cores 1a and 1b and the waveform of the differential value. The combined magnetic flux of the magnetic core 1a is indicated by Φca, and the combined magnetic flux of the magnetic core 1b is indicated by Φcb. In addition, as the differential value of Φca and Φcb, Φca
− The waveform of Φcb is shown as Φdif. As described with reference to FIG. 10, the composite magnetic flux Φc of the magnetic core is positive and negative when the magnetic field to be measured Hx is not 0, and does not become an object. In the characteristics of Fig. 10, the amplitude of the resultant magnetic flux Φc increases when the measured magnetic field Hx and the excitation magnetic field He face the same direction, and decreases when they face the opposite direction. In the case of the coupled core type differential method, as shown in FIG. 12, the magnetic field to be measured Hx in the magnetic core is the magnetic core 1a and the magnetic core 1b.
And in the opposite direction on the X coordinate. Therefore, when the direction of the exciting magnetic field He changes, the exciting magnetic flux alternately turns in the same direction or opposite to the measured magnetic flux every half cycle of the exciting magnetic field He in the magnetic core 1a and the magnetic core 1b. Do it. Therefore, the combined magnetic flux of each magnetic core becomes Φca and Φcb shown in FIG. This figure shows the waveform when the measured current Ix is not 0. When Ix = 0, the waveforms of Φca and Φcb overlap and the differential value is 0. In the above description, only the orientation on the X coordinate was discussed, because the magnetic flux in the Y coordinate direction can be ignored in the detection coil of Fig. 12 without contributing to the electromotive force.

In FIG. 12, the combined magnetic flux of the magnetic core 1a is Φca and the magnetic core 1b.
The combined magnetic flux of Φcb is detected separately and the detected voltage Vda
And the detection voltage Vdb. There are two methods for obtaining the differential value Φdif of Φca and Φcb: integrating Vda and Vdb and obtaining the difference between them, and obtaining the difference between Vda and Vdb. Thus, by obtaining the differential value Φdif of the composite magnetic flux Φca of the magnetic core 1a and the composite magnetic flux Φcb of the magnetic core 1b, the magnitude of the current Ix to be measured is obtained from the magnitude, and the phase relationship with the excitation current Ie The direction of the measured current Ix can be found from. Therefore, the measured current Ix can be measured. A method for realizing this will be described with reference to FIGS. 17 to 20 described later.

Figure 14 shows the configuration and operation of the counter excitation type differential system. This method is characterized by exciting the magnetic core 1 with a unidirectional inclination partially in the opposite direction. In the example shown in this figure, an exciting coil 2a and an exciting coil 2b are arranged in the vicinity of both ends of the magnetic core 1 so as to be excited in opposite directions, so that the detecting coil 3 can capture the entire magnetic flux change of the magnetic core 1. It is arranged. In this figure, the exciting magnetic flux Φe2a generated in the left part of the magnetic core 1 by the exciting coil 2a is generated in the right part of the other magnetic core 1 in the same direction with respect to the measured magnetic flux Φx in the magnetic core 1. The exciting magnetic flux Φe2b is opposite to the measured magnetic flux Φx in the magnetic core 1. Here, the combined magnetic flux of Φe2a and Φx is Φc2a, and Φe2b
And the combined magnetic flux of Φx is Φc2b. In this structure, Φe2a and Φe2b are opposite to each other, so it seems that the exciting magnetic flux cannot be obtained by canceling out. A magnetic flux is generated near both ends of 1. Therefore, the exciting magnetic flux does not cancel each other out. Next, the relationship between these magnetic fluxes and the detection voltage Vd are explained.

  FIG. 15 is an explanatory diagram showing the composite magnetic flux in the counter excitation type differential magnetic core and the waveform of its differential value. In this figure, the combined magnetic flux Φc2a generated in the right part of the magnetic core 1 in FIG. 14 is shown by a thin solid line. The combined magnetic flux Φc2b generated in the right part of the magnetic core 1 is shown by a thin broken line. In both Φc2a and Φc2b, when Ix is not 0, both positive and negative are asymmetrical, but FIG. 15 shows this state. Incidentally, Φca and Φcb of the coupled core type differential system shown in FIG. 13 are in phase because they are excited by the single exciting coil 2 as described in FIG. However. The opposite excitation type Φc2a and Φc2b have opposite excitation directions, and the phases are reversed as shown in FIG. Therefore, the sum of these two magnetic fluxes becomes a differential value. In order to obtain the sum of the magnetic fluxes, the induced voltages of Φc2a and Φc2b should be generated in a single detection coil. However, integration is necessary to obtain the waveform of the differential value Φdif of the magnetic flux. Furthermore, the detection voltage Vd does not contain a DC component. In this way, the differential value Φdif can be obtained by the counter excitation type differential method, and the magnitude of the measured current Ix is obtained from the magnitude, and the direction of the measured current Ix is determined by the phase relationship with the exciting current Ie. I understand. Therefore, the measured current Ix can be measured. A method for realizing this will be described with reference to FIG.

  Next, the drive circuit is explained.

FIG. 16 is an explanatory diagram showing an example of a drive circuit that realizes a method for obtaining a measurement value from a single detection voltage Vd. The principle of this method is also explained in FIG. Here, we explain the electronic circuit that realizes this. In FIG. 16, the core and coil group indicated by the symbol of the left transformer are the sensors of the present invention, and represent the magnetic core 1, the excitation coil 2, the detection coil 3, the current Ix to be measured, and the conductor 6 to be measured. Yes. An excitation current Ie is passed through the excitation coil 2 by amplifying the AC signal generated by the oscillation circuit 51 with the excitation amplifier 52. The detection voltage Vd that is the output of the detection coil 3 is integrated by the integration circuit 53 to reproduce the waveform of the magnetic flux in the magnetic core 1. This signal is Vix or Vi0 shown in Fig. 11, but here it is expressed as Vi. Vi is sent to the sample hold circuit A 57a and the sample hold circuit B 57b. On the other hand, after the phase of the signal of the oscillation circuit 51 is adjusted by the phase shift circuit 56, its rise timing is determined by the sample hold circuit A.
Similarly, the fall timing is supplied to the sample hold circuit B 57b.

Sample hold circuit A
The output of 57a and the output of the sample hold circuit B 57b are compared by the comparison circuit 58. The output of the comparison circuit 58 is fed back to the phase shift circuit 56 as a signal for adjusting the amount of phase shift, and the phase shift amount is determined so that the output of the comparison circuit 58 becomes zero. Sample and hold circuit B when the output of the comparison circuit 58 is zero
The output voltage of 57b and the output voltage of the sample hold circuit A 57a are the same, and are the voltages when the values of Vi at the rise and fall of the timing waveform shown in FIG. This value is proportional to the measured current Ix. A measured value output is obtained by passing this voltage through a low-pass filter (LPF) 55.

FIG. 17 is an explanatory diagram showing an example of a connecting method of a coupled core type differential coil and a block diagram of a drive circuit. In the coupled core type differential system, the detection voltage Vda of the detection coil 3a and the detection coil 3b
The phase with the detection voltage Vdb is the same. Therefore, the differential detection voltage Vdd can be obtained by connecting both detection coils in series with opposite polarities. The connection of the detection coil in FIG. 17 is like that. By integrating the obtained differential detection voltage Vdd, a voltage proportional to the differential value Φdif of the magnetic flux can be obtained. If the voltage proportional to Φdif is synchronously detected using a frequency twice the excitation frequency fe as a reference signal, and the frequency component of the reference signal is removed by a low-pass filter, the output of the measured current Ix The measurement value output is proportional to the strength and the polarity indicates the direction. The five circuits shown in this figure, that is, the oscillation circuit 51, the excitation amplifier 52, the integration circuit 53, the synchronous detection circuit 54, and the LPF (low-pass filter circuit) 55 are different from those shown in FIGS. This is common to the signal processing of the motion detection voltage Vdd and the signal processing of the detection voltage Vd in FIG.

FIG. 18 is an explanatory diagram showing an example of a connection method of a coupled core type differential coil and an example of a method of obtaining a differential signal. The detection coil connection method shown in this figure is based on the detection voltage Vda of the detection coil 3a and the detection coil 3b.
The detection voltage Vdb is connected to the inverting input and the non-inverting input of the operational amplifier, respectively, to obtain the differential detection voltage Vdd.

FIG. 19 is an explanatory diagram showing an example of a connecting method of a coupled core type differential coil and an example of a method of obtaining a differential signal. In the connection method shown in this figure, the negative polarity detection voltage − Vdb is obtained by inverting the polarity of the detection coil 3b. The differential detection voltage Vdd is obtained by adding the detection voltage Vda of the detection coil 3a. In this circuit, the differential detection voltage is inverted because it is inverted and amplified by an operational amplifier.
The polarity of Vdd is reversed, but this is not an essential problem.

  FIG. 20 is an explanatory view showing an example of a connection method of a coupled core type differential coil. The connection method of the detection coil shown in this figure is the same as in FIG. 19, but it shows that the differential detection voltage Vdd can be easily obtained without using an operational amplifier. In this circuit, when there is a difference in sensitivity between the detection coils 3a and 3b, the balance can be adjusted by changing the ratio of the two resistances in the figure. On the other hand, in the case of the series connection shown in FIG. 17, it is the same for easily obtaining the differential detection voltage Vdd, but the above balance cannot be adjusted.

  FIG. 17 to FIG. 20 show examples of a connection method of a coupled core type differential coil and an example of a method of obtaining a differential signal. These coil connection methods are well known in electronic circuit technology. It is. There are other circuits that achieve this goal, and are not limited to the examples given here.

  FIG. 21 is an explanatory diagram showing a block diagram of a driving circuit and a connection method of counter excitation type differential coils. The connection of the sensor part shown in this figure is as described in FIGS. As an example, the exciting coil 2a and the exciting coil 2b excite different halves of the magnetic core 1 in opposite directions, and the entire magnetic flux change of the magnetic core 1 is detected by the detecting coil 3. In this counter excitation type differential method, the detection voltage Vd of the detection coil 3 is already the differential detection voltage Vdd. Therefore, the detection voltage Vd can be processed directly. The signal processing circuit is the same as in the case of the linked core type differential system.

Next, an example of the magnetic core is described.

  FIG. 22 is an explanatory diagram showing an example of a coupled magnetic core and its parallel arrangement. In this figure, the black parts are magnetic materials, and the other parts are non-magnetic materials. The magnetic core shown in this figure is a magnetic material with shape magnetic anisotropy. In the example shown here, the magnetic core 1a and the magnetic core 1b are inclined in opposite directions and connected at the center of the figure. In this way, the magnetic core 1a and the magnetic core 1b connected to each other is a connected magnetic core. A single coupled magnetic core can realize a coupled core differential system, but using multiple coupled cores can improve sensitivity and stability. In that case, it is effective to arrange as shown in this figure. With this arrangement, the magnetic circuits are parallel. This is called parallel arrangement.

  There is a difference in the ease of magnetization of materials, and materials that are easily magnetized are called magnetic materials. The ease of magnetization is also the ease of passing through magnetism, and the degree can be expressed by magnetic susceptibility and magnetic permeability. The idea of a magnetic circuit is to treat a magnetic field or magnetic flux like a voltage or current in the same way as an electric circuit. The thing corresponding to the resistance of the electric circuit is called magnetoresistance and represents the difficulty of passing the magnetism. In other words, the reciprocal of the magnetic permeability, which is the ease of passing through the magnetism, is called magnetoresistance and represents the difficulty of passing. In the magnetic circuit, the magnetic flux corresponds to the current in the electric circuit and is always a closed loop. However, magnetic circuits have characteristics that are very different from electrical circuits. That is, the magnetoresistor cannot realize a large resistance value like the electrical resistance. The largest magnetoresistance is “vacuum”, but it is still only about 5 orders of magnitude different from the material with the smallest magnetoresistance. Therefore, even if there is no special magnetic material in the magnetic circuit, a magnetic flux that cannot be ignored through non-magnetic material or in the air creates a loop. Considering the excitation magnetic flux, the magnetic core excitation magnetic flux described above passes through the magnetic core along the easy magnetization axis, exits from the end of the magnetic core into the air, etc., and reaches the opposite end. It is in the part. Here, the term “end part, etc.” is because magnetic flux easily collects at the end part, but also enters and exits from other parts. In particular, in the differential system, there is a part where the flux enters and exits near the center. Also, “in the air” is because there is a possibility of being in a vacuum, other gas, or a filler such as resin, depending on where the sensor is placed.

  As can be seen from the above explanation, in the explanation so far, the magnetic circuit including the magnetic core has a large portion of magnetic resistance such as air. Under a constant magnetic field, the magnetic flux decreases as the magnetoresistance increases. That is, in order to obtain an excitation magnetic flux of a predetermined magnitude, the lower the magnetic resistance, the weaker the excitation magnetic field may be. If the excitation magnetic field should be weak, the excitation current can be small and efficient. Therefore, it is meaningful to reduce the part of high magnetic resistance such as air from the magnetic circuit of exciting magnetic flux. The countermeasures will be explained next. In the following explanation, “closing the magnetic circuit” means that most of the magnetic path of the magnetic circuit is made of a magnetic material so that the magnetic flux does not easily spread in the air. The idea is different from the above-mentioned “closed loop”.

  FIG. 23 is an explanatory diagram of a closed magnetic circuit core for closing the magnetic circuit. The closed magnetic path core 4 in this figure magnetically connects the ends of the magnetic cores 1a and 1b that are not connected, that is, both ends of the connected magnetic core 10. Here, for magnetic connection, connection, or connection, it is not always necessary that both magnetic materials are in close contact, and there may be a gap. This is because, as can be seen from the above explanation, the magnetic circuit is sufficiently formed even if there is a non-magnetic material portion in the magnetic circuit. Therefore, also in the case of FIG. 23, the coupling magnetic core 10 and the closed magnetic circuit core 4 may have a slight gap. If the closed magnetic circuit core 4 is provided as shown in this figure, the magnetic resistance between both ends of the coupled magnetic core 10 becomes extremely smaller than when the closed magnetic circuit core 4 is not provided. In this way, the excitation current becomes smaller and better, and the excitation magnetic flux does not spread in the surrounding space, making it difficult to be affected by the surroundings. The excitation coil and detection coil are sandwiched between the connecting magnetic core 10 and the closed magnetic circuit core 4. This state is as shown in FIG. 27, FIG. 28, or FIG. The coupled magnetic core and the closed magnetic circuit core may be interchanged.

  The coupled magnetic cores 10 in FIG. 23 are arranged in parallel as shown in FIG. And the connection part of the connection magnetic core 10 and the adjacent closed magnetic circuit core 4 are arrange | positioned so that it may just overlap. This is not a necessary condition, but the closed magnetic circuit core 4 receives the magnetic flux leaking from the vicinity of the connecting portion of the magnetic core. This makes the magnetic circuit more closed.

  FIG. 24 is an explanatory diagram of a closed magnetic circuit core using a coupled magnetic core. This is a closed magnetic circuit core having the same shape as the connecting magnetic core 10. If it does in this way, in addition to the role of the closed magnetic circuit core demonstrated in FIG. 23, it will have a detection function similarly to the connection magnetic core 10. FIG. Even in the case of this figure, the central portion of the closed magnetic path core 4 and the central portion of the connecting magnetic core 10 are overlapped to capture the magnetic flux leaking from the central portion described in FIG.

  Even if the closed magnetic path core and the coupling magnetic core described in FIGS. 23 and 24 are not exactly the same, the function of the closed magnetic path core is exhibited. However, in order to improve the performance, it is necessary to optimize the arrangement so that the purpose of adopting the closed magnetic circuit core can be demonstrated.

  FIG. 25 is an explanatory diagram of a coupled magnetic core assembly using a magnetic material having magnetocrystalline anisotropy. The magnetic material of magnetocrystalline anisotropy is used for directional steel sheets of electromagnetic steel, and the magnetization axes are aligned in the rolling direction so that crystals are aligned when silicon steel sheets are rolled. This material is often used in transformer cut cores to increase magnetic flux density and reduce leakage flux. The figure on the left side of FIG. 25 is a view of such a thin steel plate of magnetocrystalline anisotropic magnetic material. In this figure, the easy axis is the direction in which many thin lines are drawn, and the direction is also indicated by thick arrows in the figure. Cut this steel sheet along the “cut line” indicated by the two-dot chain line in the figure. The cut steel plate has an easy axis of magnetization, and countless magnetic cores are arranged in parallel. This is called a magnetic core assembly. The figure on the right side of FIG. 25 is a diagram in which two cut out magnetic core assemblies are arranged, which is the same as a state in which an infinite number of connected magnetic cores are arranged in parallel. This is called a coupled magnetic core assembly. The magnetic core assembly 12 is turned over after being cut out.

FIG. 26 is an explanatory diagram of an embodiment of a connected core type differential system. However, the drive circuit is not shown. The figure indicated by the center line “c” in the figure is a completed drawing. The figure indicated by the center line “I” shows each element before assembly. The figure indicated by the center line “b” is the figure being assembled. In this embodiment, a plurality of coupled magnetic cores 10 are attached to a cylindrical support. The mounting method varies depending on the magnetic material. For example, screwing, pasting, vapor deposition, plating, integral molding, insert molding, etc., the mounting method is not limited as long as the magnetic conditions are satisfied. The detection coil 3a is disposed on the outer periphery of the coupled magnetic core 10 on the magnetic core 1a side, and the detection coil 3b is disposed on the outer periphery of the magnetic core 1b. Arrangement methods include a direct winding method and an air core coil made in advance and inserted. Furthermore, the exciting coil 2 is arranged outside this. The arrangement method of the exciting coil 2 does not specify a specific method. The excitation coil 2 may be arranged inside the detection coil 3, and what is necessary is that the coil and the magnetic core are magnetically coupled as described in the operation principle. Therefore, each coil may be inside the magnetic core, and it may be separated inside and outside. In Example 1 shown in the figure, the material of the magnetic core was affixed to the outside of a cylindrical support made of glass epoxy using an amorphous ribbon. The coils were wound directly in the order shown in the figure. In this embodiment, even if the magnetic core, the detection coil, the excitation coil, the closed magnetic circuit core, and the spacers and materials used for fixing are all combined, the thickness of the detection portion is 1 mm.
It is about.

  FIG. 27 is an explanatory diagram of an embodiment of a coupled core type differential system employing a closed magnetic circuit core. Although the sensor function is exhibited in the state shown in FIG. 26, an improvement in performance can be expected by providing a closed magnetic circuit core as described in FIG. FIG. 27 shows the arrangement of the closed magnetic circuit core 4 in the embodiment of FIG. The closed magnetic circuit core in this figure is as described in FIG. 23, and there is a magnetic gap in the circumferential direction. This has the effect that the magnetic saturation due to the measured current Ix hardly occurs. However, if the measured current Ix is small and the magnetic saturation is not a problem, the magnetic gap may be eliminated and the whole connected.

  FIG. 28 is an explanatory diagram of an embodiment of a coupled core type differential system that employs a coupled magnetic core structure as a closed magnetic circuit core. In this embodiment, the closed magnetic circuit core described in FIG. 24 is arranged on the outer periphery of the embodiment described in FIG. In this way, in addition to the effect of closing the magnetic circuit, the detection function of the closed magnetic circuit core works, so the detection capability is improved.

  FIG. 29 is an explanatory diagram of an embodiment in which a coupled core type differential system is clamped. This embodiment is an example in which the principle structure described in FIG. 9 is implemented. It is cylindrical as a whole, and the cylinder is divided into two parts on the circumference to divide into sensor unit Ua and sensor unit Ub. The sensor unit Ua and the sensor unit Ub are each a single unit having the function of the current sensor of the present invention. Therefore, here, the structure of sensor unit Ub is explained as a representative. The magnetic core of this embodiment is made of a ferrite magnetic material in the shape of a connecting magnetic core 10 and is fixed in parallel on an arc as shown in the figure. At this time, each connecting magnetic core 10 is fixed with a gap. Next, the detection coil 3a is wound around the detection coil 3b. The difference from the first embodiment described with reference to FIG. 26 is that each coil does not circulate on the circumference but the outer circumference of the coupled magnetic core 10 arranged on the arc. It winds through the side and the inner circumference. Further, the exciting coil 2 is wound in the same manner. In this way, the measured current Ix can be clamped, which is convenient for measuring the current in the existing wiring. Although two drive circuits may be provided for each sensor unit in this embodiment, in practice, the sensor unit Ua and the coil of the sensor unit Ub are connected to each other and processed by a known technique to form one drive circuit. can do.

  FIG. 30 is an embodiment in which a large number of sensor units Ua to Uf are provided by extending the concept of the embodiment 2 described in FIG. The advantage of this embodiment is convenient when measuring the current flowing through a conductor with a large diameter. For example, it is convenient when measuring the anticorrosion current of an existing pipeline with a diameter of about 1 m without cutting the pipeline. Steel pipes can be prevented from corro- sion by maintaining an appropriate electric potential with the surrounding area. Therefore, although voltage is applied to the pipeline, the current flows through pinholes and scratches, although the pipeline is insulated. There is a technology to know the corrosion state of the pipeline by knowing this current, and it is considered to install a current sensor and perform centralized monitoring. In this way, not only corrosion but also disasters and accidents can be detected immediately, improving safety. However, since the pipeline is a very long facility, it is not useful because the location of the abnormal part cannot be determined even if the current is measured at the power source. Therefore, it can be measured at intervals of 2 〜 3km, the current leaking in that section can be found from the difference in current on both sides of any section, and the state of that section can be known. A clamp type is required for current sensors used in such applications in order not to break the sensor during pipeline laying work or to install in existing pipelines. Otherwise, the pipeline must be cut and it is not practical.

  The above-mentioned anticorrosion current is usually about several tens of mA. Further, when the diameter of the pipe exceeds several tens of centimeters, the magnetic field generated there is small, and cannot be measured with a conventional Hall element type current sensor. Also, other conventional current sensors cannot be put into practical use because they cannot be clamped or lack sensitivity. Therefore, research on the monitoring system has been continued but has not yet been put into practical use. The current sensor of the present invention has a gap in the core from the beginning in the direction of the magnetic flux in which the current to be measured Ix is generated. The direction of excitation is the axial direction of the sensor, which has no relation to the diameter of the sensor or the clamp structure, and it has been found that a current of several mA can be measured in the embodiment. Thus, the present invention is also useful for measuring the anticorrosion current of pipelines.

  FIG. 31 is an explanatory view showing an example of the chip element size in which a part is cut open and seen through to reveal the inside. In this embodiment, the current conductor to be measured 6 through which the current to be measured Ix flows is arranged in advance and does not penetrate during use as in the first embodiment of FIG. The magnetic core of this embodiment uses the magnetic core assembly or the coupled magnetic core assembly described in FIG. 25, so that it is not necessary to arrange small magnetic cores one by one, and the manufacturing can be facilitated. In addition, each element can be made smaller with MEMS technology. The conventional detection coil method requires toroidal winding, and not only the toroidal core and coil manufacturing method, but also the size of the chip element is reduced due to the spatial position and orientation of the conductor to be measured and the core and coil. It was difficult to manufacture at a practical cost. However, in this embodiment, the core may be a flat plate and the coil may be a solenoid winding, so that it is easy to manufacture and can be made smaller than a toroidal winding. Furthermore, the drive circuit can be integrated and housed in the same package as the sensor part.

FIG. 32 is a cross-sectional view taken along line A − A in FIG. FIG. 33 and FIG. 34 show the three relationship of the measured current conductor 6, the connected magnetic core assembly 13, and the closed magnetic circuit core assembly 43. The structure of this embodiment has a current conductor 6 to be measured at the center, and two coupled magnetic core assemblies 13 are arranged above and below the current conductor 6 to be measured so as to sandwich the current conductor 6 to be measured. From there, the detection coil 3 and the excitation coil 2 are wound as shown in FIG. In addition, a closed magnetic path core assembly 43 is arranged above and below. The actual thickness of this embodiment will be described. First, the current conductor 6 to be measured is a copper plate of 0.5 mm, the coupled magnetic core assembly 13 and the closed magnetic circuit core assembly 43 are each 0.05.
Insulated ultra-thin silicon steel strip of mm, the coil is 0.07 mm in diameter and has two layers, and when these dimensions are summed up according to Fig. 23, it becomes 0.98 mm. Even if this dimension includes dimensions such as manufacturing margin and epoxy package
It fits in a thickness of 3mm. This thickness is an acceptable dimension for parts such as mobile devices. Furthermore, this example of dimensional calculation is an example of assembling discrete parts, but the size can be further reduced by using MEMS technology.

  Next, the experiment and the result of one example are shown.

FIG. 35 is a graph of measured values of input / output characteristics of Example 1 in which the magnetic core material is an amorphous ribbon. The structure of the example used for the experiment is the same as FIG. The method of obtaining the differential detection voltage in this characteristic measurement was performed by the connection method shown in FIG. The drive circuit was constructed by omitting the integration circuit 53 from the circuit configuration shown in FIG. The circuit that drives the present invention can be made more accurate by detecting the combined magnetic flux Φc in the magnetic core and then detecting it. However, if the exciting current Ie is a sine wave or close to it, it can function sufficiently even without the integrating circuit 53. Do it. In the graph of this figure, the vertical axis is the effective value of the differential detection voltage Vdd. The horizontal axis is the measured current Ix. Example 1 used for this characteristic measurement has a diameter of about 20 mm and a length of about 20 mm. The number of excitation coil turns is 70 turns, and each of the two detection coils is 30 turns. The excitation frequency fe is 49 kHz and the excitation current Ie is 66 mA. From this input / output characteristic graph, it can be seen that the sensitivity of Example 1 is 70 mV / A. Hysteresis was relatively small, less than 0.01% of full scale. In the graph of Fig. 35, the measured current Ix was changed from 0 A to 10 A, then again passed through 0 A, changed to -10 A, and finally returned to 0 A. In this way, Ix = 0 A for characteristics with significant hysteresis
It becomes a loop-like characteristic graph that swells up and down in the vicinity. However, such a trend is not found in this graph, and it can be seen from the graph that the hysteresis is small as described above.

FIG. 36 is a graph of measured values of input / output characteristics of Example 1 in which the magnetic core material is ferrite. The method for obtaining the differential signal for this characteristic measurement was also performed by the connection method shown in FIG. The drive circuit was constructed by omitting the integration circuit 53 from the circuit configuration shown in FIG. The circuit that drives the present invention can be made more accurate by detecting the combined magnetic flux Φc in the magnetic core and then detecting it. However, if the exciting current Ie is a sine wave or close to it, it can function sufficiently even without the integrating circuit 53. Do it. In the graph of this figure, the vertical axis is the effective value of the differential detection voltage Vdd. The horizontal axis is the measured current Ix. Example 1 used for this characteristic measurement was not a cylinder but a square cylinder. The length of this square piece is about 20 mm, and the length of the cylinder is about 25 mm. A closed magnetic circuit core is not used. The number of excitation coil turns is 70 turns, and each of the two detection coils is 30 turns. The excitation frequency is 10 kHz and the excitation current Ie is 150.
mA.

  From the characteristics shown in FIGS. 35 and 36, it can be seen that the characteristics greatly change as the material and shape of the magnetic material, the number of turns of the coil, and the excitation frequency change. This suggests that the design is flexible and can be optimized according to the needs.

  As is well known, solar power generation and electric vehicles are being put into practical use as a means of solving problems such as carbon dioxide emission control and energy depletion. In addition, most of the conventional AC power used at home is consumed after being converted to DC. It is much more efficient to perform this conversion from AC to DC in a batch than home appliances individually, and indoor DC power supply is also being developed. In this way, the use of DC power is progressing so that there is no shortage of examples. However, there are still problems in using DC power safely and efficiently, and one of them is DC current measurement. This also has a historical background in which direct current measurement technology has been delayed compared to alternating current because it used exclusively alternating current.

  At present, the Hall element method is overwhelmingly mainstream for measuring relatively large currents, and almost all can be said. Therefore, it can be said that the problem of the current DC high current sensor is that of the Hall element method. Specifically, 1) There is hysteresis in both the Hall element itself and the magnetic collecting core, and the accuracy is low. 2) The magnetic balance type to suppress this requires toroidal winding to generate a reverse magnetic field, and the number of windings is over 2000 turns in the case of full scale 100A. 3) The dimensions increase due to the toroidal winding for securing the cross-sectional area of the magnetic collecting core and generating the reverse magnetic field. Or the chip element size cannot be reduced. 4) Since the Hall element is a semiconductor, the operating temperature range is narrow, and the lifetime is extremely shortened at high temperatures. In addition, the types and issues of current sensors are as described in the background art at the beginning.

  In the present invention, 1) Hysteresis can be reduced to 0.01% or less with respect to full scale. 2) Because of this performance, toroidal winding for generating a reverse magnetic field is unnecessary, and the manufacturing cost does not increase. 3) As described in Example 1, the thickness of the detection part is thinner than that of the conventional one, and in practice it may be a dimension that slightly expands in diameter compared to the cable for the current to be measured and occupies less space. Further, as shown in the third embodiment, a non-contact current sensor having a chip element size that could not be achieved by the conventional method can be realized. This is useful for mobile devices. 4) Because the principle is the detection coil system, no semiconductor is used in the detection part. What is needed is a magnetic material and a coil, which are resistant to deterioration and environmentally friendly. It is resistant to radiation and can be used in space, nuclear reactors, and electron and elementary particle accelerators. Also, it can be used for a long time even in an environment exceeding 100 ° C. However, it is limited to temperatures below the Curie point of magnetic materials.

  Furthermore, as shown in the second embodiment, a plan type can also be used. At this time, each of the connected magnetic cores arranged on the circumference works as a sensor, and the detection function is placed at a specific place like the Hall element method. Because it does not concentrate, it is superior in sensitivity and disturbance resistance.

  As described above, the present invention is for both DC and AC, and has improved accuracy, cost, dimensions, and stability in a well-balanced manner, can meet new needs that have been difficult with the conventional technology, and can improve DC power utilization technology. This is a useful technology that contributes to the practical application and high performance of related products by improving the DC current measurement problem.

1 Magnetic core
10 Linked magnetic core
11 Magnetic core assembly
12 Magnetic core assembly
13 Linked magnetic core assembly
1a Magnetic core
1b magnetic core
2 Excitation coil
2a Excitation coil
2b Excitation coil
3 Detection coil
3a Detection coil
3b detection coil
4 Closed magnetic circuit core
43 Closed magnetic circuit core assembly
51 Oscillator circuit
52 Excitation amplifier
53 Integration circuit
54 Synchronous detection circuit
55 LPF (low pass filter)
56 Phase shift circuit
57a Sample hold circuit A
57b Sample hold circuit B
58 Voltage difference calculation function
59 Operational Amplifier
6 Current conductor to be measured

a Magnetic core group
b Magnetic core group
Ie excitation current
Ix Current to be measured
Ix-A Current to be measured
Ix-B Current to be measured
Ix-C Current to be measured
B Magnetic flux density
Ds Differential signal
H magnetic field
Hc synthetic magnetic field
He excitation magnetic field
Hea Excitation magnetic field generated by excitation coil 2a
Heb Exciting magnetic field generated by exciting coil 2b
Hx Magnetic field to be measured
Hx-A Ix-A
Magnetic field by
Hx-B Ix-B
Magnetic field by
Hx-C Ix-C
Magnetic field by
Hx-a Hx-A component in one direction of magnetic core
Hx-b Hx-B magnetic core 1 direction component
Hx-c Hx-C magnetic core 1 direction component
P Any point on the magnetic flux generated when a current is passed through a detection coil in a vacuum
Ua sensor unit
Ub sensor unit
Uc sensor unit
Ud sensor unit
Ue sensor unit
Uf sensor unit
Vd detection voltage
Detection voltage of Vda detection coil 3a
Detection voltage of Vdb detection coil 3b
Vdd Differential detection voltage
Vi detection voltage integrated value includes both Vix and Vi0
Vix Ix
Detected voltage integral when ≠ 0
Vi0 Ix
Detected voltage integral value when = 0
X X axis of Cartesian coordinates
Y Cartesian Y axis Φc Composite magnetic flux Φc2a Φe2a
And Φx combined magnetic flux Φc2b Φe2b
And Φx combined magnetic flux Φca composite magnetic flux Φcb composite magnetic flux Φdif magnetic flux differential value Φe excitation magnetic flux in magnetic core Φe2a excitation magnetic flux generated by excitation coil 2a in counter excitation type differential method Φe2b excitation coil in counter excitation type differential method 2b Exciting magnetic flux Φea Exciting magnetic flux Φeb in magnetic core 1a Exciting magnetic flux Φx in magnetic core 1b Measured magnetic flux Φxa In magnetic core 1a Measured magnetic flux Φxb Measured magnetic flux θ in magnetic core 1b Excitation The angle formed by the magnetic field and the magnetic core, and the tilt angle of the magnetic core relative to the excitation magnetic field

(B) Centerline of the figure showing each element of Example 1 (b) Centerline of the figure showing the process of assembling each element of Example 1 (c) Centerline d of each element assembly completed drawing of Example 1 Each of Example 1 Centerline of the figure with a closed magnetic circuit core added to the finished element assembly

Claims (11)

A solenoid-wound excitation coil for passing an exciting current containing an AC component;
A solenoid-wound detection coil that outputs an induced voltage,
At least one each
A magnetic core having a magnetic anisotropy placed so as to include an arbitrary point on the magnetic flux generated when a current is passed through the detection coil in a vacuum;
In the magnetic flux direction, the direction of the easy axis of magnetization of the magnetic core has the directional component of both the magnetic flux direction of the magnetic flux passing through the point and the winding direction of the detection coil at the arbitrary point. Inclined in the winding direction with respect to the winding direction,
An inclined core type current sensor, wherein the excitation coil, the detection coil, and the magnetic core are arranged so as to be magnetically coupled to each other. A solenoid-wound excitation coil for passing an exciting current containing an AC component;
A solenoid-wound detection coil that outputs an induced voltage,
At least one each
A magnetic core having magnetic anisotropy having an easy magnetization axis inclined in the winding direction of the detection coil with respect to the normal of the coil surface of the detection coil;
An inclined core type current sensor, wherein the exciting coil, the detecting coil, and the magnetic core are all magnetically coupled to each other. 3. The magnetic core according to claim 1, further comprising: a magnetic core having a positive inclination angle; and a magnetic core having a negative inclination angle; and the magnetic core having the positive angle; The magnetic cores are magnetically coupled so that the magnetic paths along the respective easy magnetization axes are connected in series, and are installed as coupled magnetic cores.
An excitation coil that is magnetically coupled to the coupled magnetic core, a detection coil that is more strongly magnetically coupled to the magnetic core having a positive tilt angle, and a magnetic core having a negative tilt angle. An inclined core type current sensor comprising a detection coil that is magnetically coupled to the other side.   4. The inclined core type current sensor according to claim 3, comprising a plurality of coupled magnetic cores and arranged in parallel so that the magnetic paths of the coupled magnetic cores are parallel to each other.   5. The tilt core type current sensor according to claim 3, wherein the tilt angle of the serial connection portion of the magnetic path of the coupled magnetic core is continuous and curved.   The two excitation coils according to claim 1 and 2, wherein each of the excitation coils is installed in a different part of the magnetic core so as to be more strongly magnetically coupled than the other parts. An inclined core type current sensor, in which exciting currents are passed through coils so that magnetic fluxes in opposite directions are generated.   7. The inclined core type current sensor according to claim 1, wherein at least one coil winds the current to be measured.   7. The inclined core type current sensor according to claim 1, wherein all the coils do not wind the current to be measured.   An inclined core type current sensor comprising the unit of claim 8 as a unit, the unit comprising at least two units, wherein the units can be separated from each other, and a current to be measured can be clamped.   10. The tilt core type current sensor according to claim 1, wherein the tilt angle of the magnetic core continuously changes along the easy magnetization axis.   11. The inclined core type current sensor according to claim 1, wherein at least one of the exciting coil and the detecting coil is spirally wound.