Patent Application
20120217963
The present invention relates to a magnetic core capable of enhancing detection sensitivity of a current sensor, a current sensor provided with the magnetic core, and a current measuring method.
In recent years, current sensors are in use in a large number of industrial fields, and a demand for high sensitivity, and the like is in increase year by year. Hence, a variety of current sensors have been developed for the purpose of realizing high sensitivity, and one example thereof is disclosed in Japanese Unexamined Patent Publication No. H10-232259.
A current leakage sensor of Japanese Unexamined Patent Publication No. H10-232259 is configured of: a sensor that is made up of a ring-like magnetic body (magnetic core) and senses a change in magnetic field; a magnetic impedance element that is added to the sensor and whose impedance changes in accordance with a variation in magnetic field that occurs in the sensor; and a detector that detects a change in impedance of the magnetic impedance element.
With the above configuration, a current sensor is realized which, more efficiently transmits a change in magnetic field of the magnetic core 100a (100b) to the magnetic impedance element 103.
The magnetic core 100a of
The magnetic core 100b of
As thus described, the current leakage sensor provided with the conventional magnetic core 100a (100b) has a low sensitivity, causing a value to be detected buried in noise at the time of measuring a current on a several tens of mA level.
It is to be noted that a current sensor obtained seeking high sensitivity is also disclosed in Japanese Unexamined Patent Publication No. 2005-49311. However, the current sensor of Japanese Unexamined Patent Publication No. 2005-49311 shields a magnetic core with a shield plate to enhance noise resistance, and increases the size and cost of the current sensor.
Accordingly, one or more embodiments of the present invention provide a magnetic core capable of enhancing detection sensitivity of a current sensor, the current sensor provided with the magnetic core, and a current measuring method.
A magnetic core according to one or more embodiments of the present invention is a magnetic core used for a current sensor, having: a first open end plane which is formed with a first element holding hole for holding a magnetoelectric conversion element; and a second open end plane which is formed with a second element holding hole for holding the magnetoelectric conversion element, and is opposed to the first open end plane.
The magnetic core according to one or more embodiments of the present invention has the first open end plane and the second open end plane, which are opposed to each other. Then, the first element holding hole is formed on the first open end plane, the second element holding hole is formed on the second open end plane, and a magnetoelectric conversion element is held in the first element holding hole and the second element holding hole.
Therefore, due to the presence of the first open end plane and the second open end plane, namely the presence of a void section (hereinafter referred to as a “magnetic flux leakage section”) between the first open end plane and the second open end plane, a magnetic flux is prone to leakage from the magnetic core toward the first element holding hole and the second element holding hole, and the magnetoelectric conversion element held in the first element holding hole and the second element holding hole can sense the leakage of the magnetic flux.
In addition, while the sensitivity of the magnetic core is more favorable with lower magnetic resistance of the magnetic flux leakage section, the magnetic resistance of the magnetic flux leakage section is lower with a smaller width of the magnetic flux leakage section (distance between the first open end plane and the second open end plane). In this respect, in a magnetic core according to one or more embodiments of the present invention, the magnetoelectric conversion element is held in the first element holding hole and the second element holding hole which are formed in the first open end plane and the second open end plane. Therefore, it is not necessary to enlarge the distance between the first open end plane and the second open end plane to such a degree that the magnetoelectric conversion element is held therebetween. That is, due to the presence of the element holding hole, it is possible to decrease the distance between the first open end plane and the second open end plane without consideration of a space for the magnetoelectric conversion element to be placed. Accordingly, in the magnetic core according to one or more embodiments of the present invention, the magnetic flux leakage section has a small width and thus causes magnetic resistance of the magnetic flux leakage section to decrease, thereby allowing improvement in sensitivity of the current sensor that uses the magnetic core.
Further, in the magnetic core according to one or more embodiments of the present invention, the first element holding hole and the second element holding hole are formed not in positions along an outer edge of the magnetic core where a magnetic flux is resistant to leakage from the magnetic core, but on the first open end plane and the second open end plane. For the above reason, in the magnetic core according to one or more embodiments of the present invention, the magnetoelectric conversion element is held in the first element holding hole and the second element holding hole where a magnetic flux is prone to leakage from the magnetic core, whereby it is possible to collect a larger amount of magnetic flux generated due to a minute current, so as to improve the sensitivity.
As thus described, with the above configuration formed, a magnetic core capable of enhancing the detection sensitivity of the current sensor can be realized as the magnetic core according to one or more embodiments of the present invention.
In addition, the magnetic core according to one or more embodiments of the present invention also exerts such an effect as follows.
That is, the conventional current sensor is influenced by an external magnetic field at the time of measuring a current of several tens of mA because the magnetic core itself does not have a structure (function) to realize noise resistance, and hence, the current sensor cannot perform current measurement with high detection sensitivity.
However, in the magnetic core according to one or more embodiments of the present invention, the magnetic flux leakage section serves as a shield against an external magnetic field that is generated due to the earth's magnetism, an external current or the like. Hence, the magnetic core according to one or more embodiments of the present invention can achieve a reduction in size and cost.
Further, the magnetic core according to one or more embodiments of the present invention may be configured that the magnetoelectric conversion element is held in the first element holding hole and the second element holding hole such that a magnetic sensing direction of the magnetoelectric conversion element is a circumferential direction of the magnetic core.
With the above configuration formed, it is possible to select a magnetoelectric conversion element with a small size in a thickness direction of the magnetoelectric conversion element (thickness direction of the magnetic core which is vertical to the circumferential direction of the magnetic core), so as to decrease widths of the first element holding hole and the second element holding hole, which hold the magnetoelectric conversion element, in the thickness direction of the magnetic core. With smaller widths of the first element holding hole and the second element holding hole in the thickness direction of the magnetic core, a magnetic flux that leaks from the magnetic core is amplified, and hence, with the above configuration formed, it is possible to enhance the sensitivity of the magnetoelectric conversion element. Accordingly, a magnetic core capable of further enhancing the detection sensitivity of the current sensor can be realized as the magnetic core according to one or more embodiments of the present invention.
Further, the magnetic core according to one or more embodiments of the present invention may be configured that the first element holding hole and the second element holding hole are filled with a low permeability material having a lower permeability than the magnetic core.
Filling the first element holding hole and the second element holding hole with the low permeability material allows improvement in sensitivity with the same magnification as a relative permeability of the low permeability material.
Accordingly, with the above configuration formed, it is possible to realize a magnetic core capable of further enhancing the detection sensitivity of the current sensor.
Further, the magnetic core according to one or more embodiments of the present invention may be configured that a space between the first open end plane and the second open end plane is filled with a low permeability material having a lower permeability than the magnetic core.
With a lower value of magnetic resistance between the first open end plane and the second open end plane, the sensitivity of the entire magnetic core becomes higher. Accordingly, with the above configuration formed, it is possible to realize a magnetic core capable of further enhancing the detection sensitivity of the current sensor.
Further, in the magnetic core according to one or more embodiments of the present invention, the low permeability material may be a ferrite-containing epoxy resin, a magnetic fluid or air.
As typical magnetic core materials, PB permalloy, PC permalloy, amorphous, a silicon steel plate and the like are known. Any material can be used for the magnetic core according to one or more embodiments of the present invention. Examples of the low permeability material having a lower permeability than the magnetic core may include the ferrite-containing epoxy resin, the magnetic fluid and the air.
Therefore, filling the first element holding hole and the second element holding hole with the ferrite-containing epoxy resin, the magnetic fluid or the air leads to realization of a magnetic core capable of further enhancing the detection sensitivity of the current sensor.
Further, in the magnetic core according to one or more embodiments of the present invention, when a side surface opposed to a side surface forming the second element holding hole among side surfaces forming the first element holding hole is regarded as a first side surface and a side surface opposed to the first side surface among side surfaces forming the second element holding hole is regarded as a second side surface, the first element holding hole and the second element holding hole have hole widths in a thickness direction of the held magnetoelectric conversion element not more than 1.75 times as large as the distance between the first side surface and the second side surface.
It was found that, regardless of the distance between the first open end plane and the second open end plane, when the hole width is more than 1.75 times as large as the distance between the side surfaces, the effect of decreasing the distance between the first open end plane and the second open end plane is lost.
Accordingly, with the above configuration formed, such an effect is exerted that a large amount of magnetic flux can be collected in the magnetoelectric conversion element even with a minute current.
Further, in the magnetic core according to one or more embodiments of the present invention, the distance between the first open end plane and the second open end plane is smaller than 2 mm.
In light of a size of a typical magnetoelectric conversion element, when the distance between the first open end plane and the second open end plane is not smaller than 2 mm, there is a space where the magnetoelectric conversion element can be arranged even without the presence of the first element holding hole and the second element holding hole.
With the above configuration formed, such an effect is exerted that the magnetoelectric conversion element can be held in the first element holding hole and the second element holding hole even when the distance between the first open end plane and the second open end plane is smaller than 2 mm, and the magnetoelectric conversion element can reliably sense a magnetic flux leaking from the magnetic core to the first element holding hole and the second element holding hole.
Moreover, the magnetic core according to one or more embodiments of the present invention may be configured that parts of the first open end plane and the second open end plane are in contact with each other.
As the structure of a typical magnetic core, there are known a variety of types such as an integrated type, a laminated type and a docked type, and the magnetic core according to one or more embodiments of the present invention is adaptable to any type. However, there are cases where it is practically difficult to manufacture and process the magnetic core of any type without any contact between the first open end plane and the second open end plane.
In this regard, in the magnetic core according to one or more embodiments of the present invention, even when parts of the first open end plane and the second open end plane are in contact with each other, because a magnetic flux leaks from the magnetic core to the first element holding hole and the second element holding hole through the magnetic flux leakage section, the magnetoelectric conversion element can sense the leakage of the magnetic flux. Therefore, in the case where it is practically difficult to manufacture and process the magnetic core of any type without any contact between the first open end plane and the second open end plane, the magnetic core can be used as it is. Accordingly, it is possible to realize a magnetic core capable of further enhancing the detection sensitivity of the current sensor, while also eliminating the need for additional steps in the manufacturing and processing and realizing low cost.
It may be configured that the first element holding hole and the second element holding hole are respectively extended on the first open end plane and the second open end plane along a parallel direction to the thickness direction of the magnetic core.
Further, the magnetic core according to one or more embodiments of the present invention may be configured that the first element holding hole and the second element holding hole are respectively extended on the first open end plane and the second open end plane along a vertical direction to the thickness direction of the magnetic core.
As described above, as the structure of the typical magnetic core, there are known a variety of types such as the integrated type, the laminated type and the docked type.
Therefore, for example when a stacked magnetic core is to be produced, a plurality of layers formed with the first element holding hole and the second element holding hole in the same place are prepared, and those layers are sequentially stacked so that the magnetic core according to one or more embodiments of the present invention can be manufactured with ease at low cost. Also when the magnetic core of the integrated type or the docked type is to be produced, with the above configuration formed, the magnetic core can be manufactured with ease at low cost. This can realize a magnetic core suitable for mass production.
Further, the current sensor according to one or more embodiments of the present invention is configured to be provided with the magnetic core.
With the above configuration formed, it is possible to realize a current sensor capable of performing high sensitive measurement.
Moreover, the current measuring method according to one or more embodiments of the present invention includes a step of measuring a current value of a current flowing through a measuring object wire by means of a current sensor provided with the magnetic core.
With the above configuration formed, it is possible to realize a current measuring method capable of performing high sensitive measurement.
As described above, the magnetic core according to one or more embodiments of the present invention is configured to have: a first open end plane which is formed with a first element holding hole for holding a magnetoelectric conversion element; and a second open end plane which is formed with a second element holding hole for holding the magnetoelectric conversion element, and is opposed to the first open end plane.
It is therefore possible to realize a magnetic core capable of enhancing the detection sensitivity of the current sensor.
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. For the sake of convenience of explanation, a member having the same function as the member shown in the drawings is provided with the same symbol and its explanation will be omitted.
Hereinafter, a schematic structure of the magnetic core 1 according to the present embodiment will be described. It is to be noted that in order to facilitate understanding, a current sensor provided with the magnetic core 1 will be first described, and the schematic structure of the magnetic core 1 will then be described.
First, a description of a basic principle of the current sensor will be given below. A magnetic core formed of a magnetic body amplifies a magnetic field generated from a current of a measuring object wire. Next, the magnetoelectric conversion element detects a magnetic flux density of the amplified magnetic field, and converts it to an electric signal. Subsequently, the electric signal is processed in an output signal processing circuit, and a current value of the measuring object wire is measured.
It is to be noted that the magnetic core 1 is involved in the magnetic core of the current sensor, and examples of an application of the current sensor may include a current leakage sensor.
Further, the current sensor according to the present embodiment is applicable to a broad range of fields, such as leakage detection for a power conditioner that is a solar cell, a fuel cell or the like, monitoring of a battery loaded in a hybrid car, a plug-in hybrid car or the like, and monitoring of a battery of a data center UPS.
Hereinafter, a schematic structure of the magnetic core 1 will be described.
As shown in
As shown in
In the above, the schematic configuration of the magnetic core 1 was described. In the following description, the void section between the first open end plane 3a and the second open end plane 3b is referred to as a “magnetic flux leakage section 3”. Further, when the first element holding hole 5a and the second element holding hole 5b are not distinguished from each other, those are simply referred to as a “element holding hole 5”.
Next, another example of the magnetic core 1 will be described by means of
As shown in the figure, the element holding hole 5 of
Next, a method for forming the magnetic core 1 will be described by means of
Accordingly, the magnetic core 1 can be realized in a variety of structures and shapes, and for example, an appropriate change can be made, such as a change from the ring-shaped magnetic core described with reference to
Further, the magnetic core 1 may be realized in such a configuration.
Specifically, in the above,
Next, a variety of measurement results regarding magnetic core 1 will be described.
First, it will be described in
It is to be noted that a mark × shown in each figure indicates a measurement point of a magnetic flux density.
Further, conditions for measurement using the magnetic core shown in each figure, such as a size of the magnetic core and a current value (30 mA) flowing through the measuring object wire, are made the same except for a shape of the magnetic core which is characteristic. Further, a width of the cut-off section provided in the magnetic core of
Under such conditions, results of measurement by means of the magnetic cores in the respective figures were 0.018 mT in the magnetic core of
In addition, the measurement results described here and measurement results that will be described using later-mentioned figures are both results obtained by means of simulation. Because there is almost no difference recognized between an actual value and a simulated value, simulation is considered as appropriate in checking a variety of effects of the magnetic core 1 and the like with respect to the conventional magnetic core.
As described above, the magnetic core 1 has significantly improved measurement sensitivity for a magnetic flux density as compared with the known magnetic core. The reason for this will be described by means of
As shown in the figure, the element holding hole 5 is provided in a vertical direction to the thickness direction of the magnetic core 1, and the magnetoelectric conversion element 20 is held in the element holding hole 5.
The magnetoelectric conversion element 20 primarily has a substrate 22, a sensor film 24, a wire bonding 26, and a mold agent 28. The sensor film 24 is arranged on the plate-like substrate 22, and the substrate 22 and the sensor film 24 are fixed by the wire bonding 26. Then, the substrate 22, the sensor film 24 and the wire bonding 26 are coated by the mold agent 28. The magnetoelectric conversion element 20 is held in the element holding hole 5 so as to cross the magnetic flux leakage section 3.
In the magnetic core 1, the positional relation of a magnetoelectric conversion element 20 with respect to the magnetic flux leakage section 3 is set. Accordingly, a magnetic flux is prone to leakage from the magnetic core 1 to the element holding hole 5 through the magnetic flux leakage section 3, and the magnetoelectric conversion element 20 held in the element holding hole 5 can sense leakage of the magnetic flux from the vertical direction (thickness direction of the magnetic core 1).
Further, the sensitivity of the magnetic core is more favorable when the magnetic flux leakage section 3 has magnetic resistance being low to some degree. Then, with a smaller width of the magnetic flux leakage section 3 (distance between the first open end plane 3a and the second open end plane 3b), the magnetic resistance of the magnetic flux leakage section 3 decreases. In this respect, in the magnetic core 1, the magnetoelectric conversion element 20 is held in the first element holding hole 5a and the second element holding hole 5b which are formed on the first open end plane 3a and the second open end plane 3b. Therefore, it is not necessary to enlarge the distance between the first open end plane 3a and the second open end plane 3b to such a degree that the magnetoelectric conversion element 20 can be held therebetween. That is, due to the presence of the element holding hole 5, it is possible to decrease the distance between the first open end plane 3a and the second open end plane 3b without consideration of the size of the magnetoelectric conversion element 20. Accordingly, in the magnetic core 1, the magnetic flux leakage section 3 has a small width and thus causes magnetic resistance of the magnetic flux leakage section 3 to decrease.
For such a reason, the magnetic core 1 has significantly improved measurement sensitivity for a magnetic flux density as compared with the known magnetic core.
It is to be noted that, when the magnetic flux leakage section is not present in the magnetic core, a difference in magnetic resistance between the magnetic core and the element holding hole becomes excessively large (on the order of 104 times), and a magnetic flux hardly leaks to the element holding hole and the magnetoelectric conversion element does not sense the magnetic flux.
Further, for the magnetoelectric conversion element 20, there can be used a MR (magneto-resistive) element such as GMR (Giant Magneto-Resistance), AMR (Anisotropic Magnetoresistive), a MI (magneto-impedance) element, a flux gate element, a Hall element or the like.
Further, in
Further, it will be described using
First, a definition of each of later-described symbols will be described using
As shown in
When a side surface opposed to a side surface forming the second element holding hole 5b among side surfaces forming the first element holding hole 5a is regarded as a side surface (first side surface) 16 and a side surface opposed to the side surface 16 among side surfaces forming the second element holding hole 5b is regarded as a side surface (second side surface) 17, symbol L1 represents a distance between the side surface 16 and the side surface 17.
When side surfaces except for the side surface 16 among the side surfaces forming the first element holding hole 5a are regarded as side surface 18a and side surface 18b, symbol L2 represents a distance between the side surface 18a and the side surface 18b. In addition, when side surfaces except for the side surface 17 among the side surfaces forming the second element holding hole 5b are regarded as side surface 19a and side surface 19b, symbol L2 also is a distance between the side surface 19a and the side surface 19b.
As thus described, W, L1 and L2 are defined. Next, measurement results of
At this time, it is found as shown in
Further, as shown in
Next,
At this time, it is found as shown in
It is to be noted that, with smaller W at the time of L1 being changed to 1.0 mm, 1.2 mm, 1.5 mm and 2.0 mm, the measured magnetic flux density increases, namely the measurement sensitivity improves. However, due to the difference being slight, a significant effect exerted by changing L1 was not recognized.
As described above, the magnetic core 1 may have the abutting structure for the reason in terms of manufacturing and processing, the magnetic core 1 may have the abutting structure. Also in this case, the magnetic core 1 has a similar effect to the case of the gap structure. This will be described using
It is to be noted that in any magnetic core 1, the width of the magnetic flux leakage section 3 is kept to be 30 μm. Further, in
Further, a contact area of the contact point 7 is set to 3 μm2, which is sufficiently smaller than a cross section of the first open end plane 3a or the second open end plane 3b. This reflects the fact that the contact area of the contact point 7 is sufficiently smaller than a cross section of the first open end plane 3a or the second open end plane 3b at the time of actually manufacturing and processing a magnetic core having the abutting structure.
Under such conditions, results of measurement of the magnetic flux density by means of the magnetic cores 1 in the respective figures were all 2.5 mT. It can be said from this that the measurement sensitivity of the magnetic core 1 remains unchanged even when the core has the gap structure. Therefore, in a case where it is practically difficult to manufacture and process the magnetic core without any contact between the first open end plane 3a and the second open end plane 3b, the magnetic core can be used while keeping the gap structure. Accordingly, it is possible to realize the magnetic core 1 capable of further enhancing the detection sensitivity of the current sensor, while also eliminating the need for additional step in the manufacturing and processing and realizing low cost.
Further, influences exerted by the size (L1, L2) of the element holding hole 5 and the width (W) of the magnetic flux leakage section 3 on a measurement result will be described using
The following can be said as considerations obtained from Table 1 and
First, in any of cases of L1=1 mm, 1.5 mm and 2 mm, when L2 is more than 1.75 times as large as L1, the magnetic flux density remains unchanged regardless of the width (W) of the magnetic flux leakage section 3. For example, when L1 is set to 1 mm and L2=1.75, the magnetic flux density is 1.26 mT in the case of W=0.02 mm, the magnetic flux density is 1.27 mT in the case of W=0.1 mm and 0.2 mm, and the magnetic flux density is 1.25 mT in the case of W=1 mm. Therefore, a slight change in magnetic flux density is recognized. However, when L2=2 mm, all the magnetic flux densities are 1.25 mT regardless of the value of W. This can also apply to the cases of L1=1.5 mm and 2 mm. That is, when L2 is more than 1.75 times as large as L1, the magnetic flux density remains unchanged regardless of the width (W) of the magnetic flux leakage section 3, whereby L2 is required to be not more than 1.75 times as large as L1 in the magnetic core 1.
Further, when L1 becomes the same as W, values of the magnetic flux density converge to a fixed value regardless of the value of L2. This requires L1>W in the magnetic core 1.
In [2-2 Mechanism of improvement in sensitivity] above, it was described that the sensitivity of the magnetic core is more favorable when the magnetic flux leakage section 3 has magnetic resistance being low to some degree, and for that purpose, the magnetic resistance of the magnetic flux leakage section 3 decreases with a smaller width (W) of the magnetic flux leakage section 3. Herein, another method for lowering the magnetic resistance of the magnetic flux leakage section 3 will be described by means of
It is to be noted that the magnetic agent has a relative permeability of 20, and is a material having a low relative permeability than the magnetic core 1 body. Further, a mark × shown in each figure indicates a measurement point of a magnetic flux density.
Under such conditions, results of measurement by means of the magnetic cores in the respective figures were 2.44 mT in the magnetic core 1 of
It was thus shown that by filling of the element holding hole 5 (or the magnetic flux leakage section 3 and the element holding hole 5) with a material having a lower relative permeability than the magnetic core, the magnetic resistance of the magnetic flux leakage section 3 is lowered, thereby improving the sensitivity of the magnetic core 1.
In addition, as such a magnetic agent (material), the ferrite-containing epoxy resin, the magnetic fluid, the air or the like can be employed.
Next, it will be described that noise resistance is improved by the magnetic core 1.
In addition, in each figure, symbol P denotes a measuring object wire, symbol Q denotes an external wire, and a distance between P and Q is set to 20 mm. Further, as a method for determining the noise resistance, a current of 30 mA is allowed to flow through the measuring object wire P, and a magnetic flux density at that time is measured. Further, in order to have an influence as an external magnetic field, a current of 20 A is allowed to flow through the external wire Q while a current of 30 mA is allowed to flow through the measuring object wire P, and a magnetic flux density at that time is measured. On that basis, it is calculated as to how much measurement error occurs between the measured two magnetic flux densities. It is then determined that the noise resistance is higher with the smaller measurement error and the noise resistance is lower with the larger measurement error.
Under such conditions, errors of measurement by means of the magnetic cores in the respective figures were 11.3% in the magnetic core of
In the first place, because the magnetic core of conventional current sensors does not have noise resistance, the current sensor is influenced by an external magnetic field at the time of measuring a current of several tens of mA and a value to be detected is buried in noise.
In this regard, in the magnetic core 1, it is considered that the magnetic flux leakage section 3 surrounded by a broken line in the figure serves as a shield against an external magnetic field that is generated due to the earth's magnetism, an external current or the like, and by the shield effect, an influence exerted by the external magnetic field on the magnetoelectric conversion element 20 held in the element holding hole 5 is reduced.
Further, by the magnetic flux leakage section 3 serving as the shield, it is also possible to realize a reduction in size and cost of the current sensor.
Next, an influence exerted by a thickness of the magnetic core on the noise resistance will be described in
In the graph shown in the figure, a lateral axis indicates the thickness (mm) of the magnetic core, and a longitudinal axis indicates the measurement error (%). It should be noted that measurement conditions are the same as the conditions described with reference to
As shown in the figure, with a larger width of the magnetic core, the measurement error decreases. That is, with a larger width of the magnetic core, the noise resistance improves. This is because the magnetic flux leakage section 3 increases with a larger thickness of the magnetic core, accompanied by an increase in shield effect of the magnetic flux leakage section 3. Therefore, by appropriate adjustment of the thickness of the magnetic core, it is possible to realize both reduction in size and improvement in measurement accuracy of the current sensor.
Hereinafter, an effect obtained by the magnetic core 1 will be described.
With reference to
The magnetic core 1 has the first open end plane 3a and the second open end plane 3b which are opposed to each other. Then, the first element holding hole 5a is formed on the first open end plane 3a, the second element holding hole 5b is formed on the second open end plane 3b, and the magnetoelectric conversion element 20 is held in the first element holding hole 5a and the second element holding hole 5b.
Therefore, due to the presence of the first open end plane 3a and the second open end plane 3b, namely the presence of a void section (hereinafter referred to as a “magnetic flux leakage section 3”) between the first open end plane 3a and the second open end plane 3b, a magnetic flux is prone to leakage from the magnetic core 1 toward the first element holding hole 5a and the second element holding hole 5b, and the magnetoelectric conversion element 20 held in the first element holding hole 5a and the second element holding hole 5b can sense the leakage of the magnetic flux.
In addition, while the sensitivity of the magnetic core is more favorable with lower magnetic resistance of the magnetic flux leakage section 3, the magnetic resistance of the magnetic flux leakage section 3 is lower with a smaller width of the magnetic flux leakage section 3 (distance between the first open end plane 3a and the second open end plane 3b). In this respect, in the magnetic core 1, the magnetoelectric conversion element 20 is held in the first element holding hole 5a and the second element holding hole 5b, which are formed on the first open end plane 3a and the second open end plane 3b. Therefore, it is not necessary to enlarge the distance between the first open end plane 3a and the second open end plane 3 to such a degree that the magnetoelectric conversion element 20 is held therebetween. That is, due to the presence of the element holding hole 5, it is possible to decrease the distance between the first open end plane 3a and the second open end plane 3 without consideration of a space for the magnetoelectric conversion element 20 to be placed. Accordingly, in the magnetic core 1, the magnetic flux leakage section 3 has a small width and thus causes magnetic resistance of the magnetic flux leakage section 3 to decrease, thereby allowing improvement in sensitivity of the current sensor that uses the magnetic core 1.
Further, in the magnetic core 1, the first element holding hole 5a and the second element holding hole 5b are formed not in positions along an outer edge of the magnetic core 1 where a magnetic flux is resistant to leakage from the magnetic core 1, but on the first open end plane 3a and the second open end plane 3b. For the above reason, in the magnetic core 1, the magnetoelectric conversion element 20 is held in the first element holding hole 5a and the second element holding hole 5b where a magnetic flux is prone to leakage from the magnetic core 1, whereby it is possible to collect a larger amount of magnetic flux generated due to a minute current, so as to improve the sensitivity.
As thus described, with the above configuration formed, a magnetic core capable of enhancing the detection sensitivity of the current sensor can be realized as the magnetic core 1.
In addition, the magnetic core 1 also exerts such an effect as follows.
That is, the conventional current sensor is influenced by an external magnetic field at the time of measuring a current of several tens of mA because the magnetic core itself does not have a structure (function) to realize noise resistance, and hence, the current sensor cannot perform current measurement with high detection sensitivity.
However, in the magnetic core 1 according to one or more embodiments of the present invention, the magnetic flux leakage section 3 serves as a shield against an external magnetic field that is generated due to the earth's magnetism, an external current or the like. Hence, the magnetic core 1 realizes a reduction in size and cost of the current sensor.
Further, with reference to
With the above configuration formed, it is possible to select a magnetoelectric conversion element 20 with a small size in the thickness direction of the magnetoelectric conversion element 20 (thickness direction of the magnetic core 1 which is vertical to the circumferential direction of the magnetic core 1), so as to decrease widths of the first element holding hole 5a and the second element holding hole 5b, which hold the magnetoelectric conversion element 20, in the thickness direction of the magnetic core. With smaller widths of the first element holding hole 5a and the second element holding hole 5b in the thickness direction of the magnetic core 1, a magnetic flux that leaks from the magnetic core 1 is amplified, and hence, with the above configuration formed, it is possible to enhance the sensitivity of the magnetoelectric conversion element 20. Accordingly, a magnetic core capable of further enhancing the detection sensitivity of the current sensor can be realized as the magnetic core 1.
Further, with reference to
Filling the first element holding hole 5a and the second element holding hole 5b with the low permeability material allows improvement in sensitivity with the same magnification as a relative permeability of the low permeability material.
Accordingly, with the above configuration formed, it is possible to realize a magnetic core capable of further enhancing the detection sensitivity of the current sensor.
Further, with reference to
With a lower value of magnetic resistance between the first open end plane 3a and the second open end plane 3b, the sensitivity of the entire magnetic core becomes higher. Accordingly, with the above configuration formed, it is possible to realize a magnetic core capable of further enhancing the detection sensitivity of the current sensor.
Further, in the magnetic core 1, the low permeability material may be the ferrite-containing epoxy resin, the magnetic fluid or the air.
As typical magnetic core materials, PB permalloy, PC permalloy, amorphous, a silicon steel plate and the like are known. Any material can be used for the magnetic core 1. Examples of the low permeability material having a lower permeability than the magnetic core may include the ferrite-containing epoxy resin, the magnetic fluid and the air.
Therefore, filling the first element holding hole 5a and the second element holding hole 5b with the ferrite-containing epoxy resin, the magnetic fluid or the air leads to realization of a magnetic core capable of further enhancing the detection sensitivity of the current sensor.
Further, with reference to
It was found that, regardless of the distance between the first open end plane 3a and the second open end plane 3b, when the hole width is more than 1.75 times as large as the distance between the side surfaces, the effect of decreasing the distance between the first open end plane and the second open end plane is lost.
Accordingly, with the above configuration formed, such an effect is exerted that a large amount of magnetic flux is collected in the magnetoelectric conversion element 20 even with a minute current.
Further, in the magnetic core 1 according to one or more embodiments of the present invention, the distance between the first open end plane 3a and the second open end plane 3 is smaller than 2 mm.
In light of a size of a typical magnetoelectric conversion element 20, when the distance between the first open end plane 3a and the second open end plane 3b is not smaller than 2 mm, there is a space where the magnetoelectric conversion element 20 can be arranged even without the presence of the first element holding hole 5a and the second element holding hole 5b.
With the above configuration formed, such an effect is exerted that the magnetoelectric conversion element 20 can be held in the first element holding hole 5a and the second element holding hole 5b even when the distance between the first open end plane 3a and the second open end plane 3b is smaller than 2 mm, and the magnetoelectric conversion element 20 can reliably sense a magnetic flux leaking from the magnetic core 1 to the first element holding hole 5a and the second element holding hole 5b.
Further, with reference to
As the structure of a typical magnetic core, there are known a variety of types such as an integrated type, a laminated type and a docked type, and the magnetic core 1 is adaptable to any type. However, there are cases where it is practically difficult to manufacture and process the magnetic core of any type without any contact between the first open end plane 3a and the second open end plane 3b.
In this regard, in the magnetic core according to one or more embodiments of the present invention, even when parts of the first open end plane 3a and the second open end plane 3b are in contact with each other, because a magnetic flux leaks from the magnetic core 1 to the first element holding hole 5a and the second element holding hole 5b through the magnetic flux leakage section 3, the magnetoelectric conversion element 20 can sense the leakage of the magnetic flux. Therefore, in a case where it is difficult to perform manufacturing and processing without any contact between the first open end plane 3a and the second open end plane 3b, the magnetic core can be used as it is. Accordingly, it is possible to realize a magnetic core capable of further enhancing the detection sensitivity of the current sensor, while also eliminating the need for additional step in the manufacturing and processing and realizing low cost.
With reference to
Further, with reference to
As described above, as the structure of the typical magnetic core, there are known a variety of types such as the integrated type, the laminated type and the docked type.
Therefore, for example, when a stacked magnetic core is to be produced, a plurality of layers formed with the first element holding hole 5a and the second element holding hole 5b in the same place are prepared, and those layers are sequentially stacked so that the magnetic core 1 can be manufactured with ease at low cost. Also when the magnetic core 1 of the integrated type or the docked type is to be produced, with the above configuration formed, the magnetic core 1 can be manufactured with ease at low cost. This can realize a magnetic core 1 suitable for mass production.
Further, with reference to
With the above configuration formed, it is possible to realize a current sensor capable of performing high sensitive measurement.
Moreover, the current measuring method according to one or more embodiments of the present invention includes a step for measuring a current value of a current flowing through a measuring object wire by a current sensor provided with the magnetic core 1.
With the above configuration formed, it is possible to realize a current measuring method capable of performing high sensitive measurement.
The current sensor provided with the magnetic core 1 is applicable to a variety of usages, such as leakage detection for a power conditioner that is a solar cell, a fuel cell or the like, monitoring of a battery loaded in a hybrid car, a plug-in hybrid car or the like, and monitoring of a battery of a data center UPS.
An example of an application of the magnetic core 1 according to one or more embodiments of the present invention will be described by means of
As shown in the figure, an alternate current outputted from the solar panel is rectified in a converter, and converted to a direct current in an inverter. Then, the magnetic core 1 amplifies a magnetic field generated from currents of two measuring object wires, which are indicated by arrows in the figure.
Herein, the currents in the two measuring object wires correspond to forward and backward currents, and a total current value is 0 A. Therefore, when leakage has occurred, the total current value is not 0 A. Therefore, the applying the current sensor provided with the magnetic core 1 can detect the occurrence or non-occurrence of leakage by measuring a total current value.
It is to be noted that in
Further, in the case shown in the figure, the current leakage sensor provided with the magnetic core 1 measures current values of 30 mA, 50 mA, 100 mA and 150 mA specified by International Standard. However, in the case of application to another usage, the magnetic core 1 can naturally measure a variety of current values.
The description was provided in the above by taking the case of applying the magnetic core 1 to leakage detection of the power conditioner for a solar cell as one application case. However, the example described herein is strictly one application case, and its usage is not restrictive.
Next, the current sensor 30 provided with the magnetic core 1 will be described by means of
Next, an internal structure of the current sensor 30 will be described by means of
As shown in
As shown in
The magnetic core 1 is a docked type that can be divided into two pieces made up with the magnetic core 1a and a magnetic core 1b (detail will be described with reference to
The fastener 33a functions as a fastener for the magnetic core 1a and the magnetic core 1b, while being connected to and supported by the plate-like output signal processing circuit 32. The output signal processing circuit 32 is electrically connected to the input/output terminal 33, and processes a voltage outputted from the magnetoelectric conversion element 20, to output a voltage corresponding to a current value of the measuring object wire P to the external apparatus through the input/output terminal 33. A T-shaped small substrate is erected in the output signal processing circuit 32, and the magnetoelectric conversion element 20 is fixed to the small substrate. The magnetoelectric conversion element 20 is positioned so as to be held in the element holding hole 5. That is, in the current sensor 30 in
It is to be noted that the magnetoelectric conversion element 20 may be held inside the element holding hole 5 while kept in the state of being in contact with the element holding hole 5. Therefore, the magnetoelectric conversion element 20 is realized in a configuration of being held inside the element holding hole 5 while being kept in the state of being in contact and/or non-contact with the element holding hole 5.
In addition, the method for holding and fixing the magnetoelectric conversion element is not restricted to the example described here.
Next, an operation of the current sensor 30 measuring a current flowing inside the measuring object wire P will be described by means of
First, a current I flows inside the measuring object P, and a magnetic field H is generated by the current I. Then, a magnetic flux φ is generated in the magnetic core 1 by the magnetic field H. Next, the magnetic flux φ generated in the magnetic core 1 leaks into the magnetic flux leakage section 3. Herein, when the magnetic flux having leaked into the magnetic flux leakage section 3 is referred to as a magnetic flux φH, the magnetic flux φH is detected by the magnetoelectric conversion element 20. The magnetoelectric conversion element 20 converts the detected magnetic flux φH to a voltage, and outputs the converted voltage VM to the output signal processing circuit 32. The output signal processing circuit 32 then processes the voltage VM, and outputs a voltage (VO) corresponding to a value of the current flowing in the measuring object wire P to the input/output terminal 33. In this manner, the current sensor 30 measures a current flowing inside the measuring object wire P.
In this manner, the current sensor 30 can measure the current value I of a current flowing inside the measuring object wire P. However, the current sensor 30 can be used not only for measurement of a current value, but also for leakage detection and measurement of a leakage amount, for example. This will be described by means of
First, there will be considered a case where a current IO flows inside the measuring object wire 1 (P1), and a current−(IO−IL) flows inside the measuring object wire 2 (P2), namely a case where a current IL is leaking. At this time, the current IO flows inside the measuring object wire P1, and a magnetic field HO is generated by the current IO. Further, a current−(IO−IL) flows inside the measuring object wire P2, and a magnetic field (−HO+HL) is generated by the current−(IO−IL). Then, the magnetic flux φL is generated in the magnetic core 1 by the two magnetic fields HO and (−HO+HL). That is, the magnetic flux φL represents a magnetic flux amount generated by a sum of inputted magnetic fields into the magnetic core 1. Next, the magnetic flux φL generated in the magnetic core 1 leaks into the magnetic flux leakage section 3. Herein, when the magnetic flux having leaked into the magnetic flux leakage section 3 is referred to as a magnetic flux φHL, the magnetic flux φHL is detected by the magnetoelectric conversion element 20. The magnetoelectric conversion element 20 converts the detected magnetic flux φHL to a voltage, and the converted voltage VML is outputted to the output signal processing circuit 32. The output signal processing circuit 32 then processes the voltage VML, and outputs to the input/output terminal 33 a voltage (VOL) corresponding to a current value of the current having leaked. In this manner, the current sensor 30 detects leakage and measures a leakage amount.
Next, a variety of shapes of the magnetic core will be described by means of
First, one shape of the magnetic core will be described by means of
With reference to
A magnetic core 41 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 41, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates a first core section 41a and a second core section 41b. Further, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
As seen from the comparison between
Next, another example will be described.
A magnetic core 42 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 42, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 42. A diagonally shaded area in
A magnetic core 43 is different from the magnetic core 42 of
A magnetic core 44 is different from the magnetic core 43 of
In the above, the examples were described using
A magnetic core 45 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 45, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 45. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
A magnetic core 46 is different from the magnetic core 45 of
A magnetic core 47 is different from the magnetic core 46 of
In the above, the examples were described using
A magnetic core 48 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 48, the element holding hole 5 is formed in the radiation direction with respect to a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 48. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
A magnetic core 49 is different from the magnetic core 48 of
That is, the magnetic core according to the present embodiment can be realized not only by the single layered integrated type, but also by the stacked type. It should be noted that, although the magnetic core 49 is made up of a four layered structure of magnetic cores 49a to 49d, it may be made up of a two layered structure, a three layered structure, or not less than five layered structure.
Next, as still another example, examples where the magnetic core is a single layered type or stacked type will be described by means of
A magnetic core 50 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 50, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 50. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
A magnetic core 51 is different from the magnetic core 50 of
That is, the magnetic core according to the present embodiment can be realized not only by the single layered integrated type, but also by the stacked type. It should be noted that, although the magnetic core 51 is made up of a four layered structure of magnetic cores 51a to 51d, it may be made up of a two layered structure, a three layered structure, or not less than five layered structure.
As seen from the figure, the magnetic core 50 is formed of the integrated type, whereas the magnetic core 51 is formed of a stacked structure where a plurality of magnetic cores are stacked in parallel with the measuring object wire. As thus described, the shape of the magnetic core is not restricted to a specific shape, but can be a variety of shapes. Hence, the shape of the magnetic core can be changed as appropriate in accordance with a design of the apparatus, a layout of the inside of the current sensor, and the like.
Next, another example will be described by means of
A magnetic core 53 has a substantially rectangular shape as seen from above. More specifically, the magnetic core 53 is a single layered type formed by docking a first core section 53a and a second core section 53b both having a U shape. The first core section 53a and the second core section 53b are in intimate contact with each other on a surface constituting one surface of the rectangular shape (upper-side surface in the figure). Then, on the surface opposed to the above surface (lower-side surface in the figure), the first core section 53a and the second core section 53b are formed with the magnetic flux leakage section 3 and the element holding hole 5. Herein, the first open end plane of the first core section 53a and the second open end plane of the second core section 53b are spaced from each other, thereby to form the magnetic flux leakage section 3. Then, the element holding hole 5 is formed by the first element holding hole provided on the first open end plane and the second element holding hole provided on the second open end plane. The element holding hole 5 is formed in the radiation direction with respect to a current flowing through the measuring object wire (not shown), and penetrates the first core section 53a and the second core section 53b.
A magnetic core 54 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 54, the element holding hole 5 is formed in the radiation direction with respect to a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 54. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
As thus described, the magnetic core can be realized as either the docked type or the integrated type.
Next, another example will be described by means of
A magnetic core 55 has a substantially rectangular shape as seen from above. More specifically, the magnetic core 55 is a single layered type formed by docking a first core section 55a and a second core section 55b both having a U shape. The first core section 55a and the second core section 55b are in intimate contact with each other on a surface constituting one surface of the rectangular shape (upper-side surface in the figure). Then, on the surface opposed to the above surface (lower-side surface in the figure), the first core section 55a and the second core section 55b are formed with the magnetic flux leakage section 3 and the element holding hole 5. Herein, the first open end plane of the first core section 55a and the second open end plane of the second core section 55b are spaced from each other, thereby to form the magnetic flux leakage section 3. Then, the element holding hole 5 is formed by the first element holding hole provided on the first open end plane and the second element holding hole provided on the second open end plane. The element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates a first core section 55a and a second core section 55b.
A magnetic core 56 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 56, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 56. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
As thus described, the magnetic core according to the present embodiment can be realized as either the docked type or the integrated type.
Next, another example will be described by means of
A magnetic core 57 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 57, the element holding hole 5 is formed in the radiation direction with respect to a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 57. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
A magnetic core 58 is configured of a single layered integrated type having a circular shape as seen from above. In the magnetic core 58, the element holding hole 5 is formed in the radiation direction with respect to a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 58. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
As thus described, the magnetic core according to the present embodiment can be realized as in rectangular shape, circular shape, or another shape though not described here.
Next, another example will be described by means of
A magnetic core 59 is configured of a single layered integrated type having a rectangular shape as seen from above. In the magnetic core 59, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 59. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
A magnetic core 60 is configured of a single layered integrated type having a circular shape as seen from above. In the magnetic core 60, the element holding hole 5 is formed in parallel with a current flowing through the measuring object wire (not shown), and penetrates the magnetic core 60. In addition, the first open end plane and the second open end plane are spaced from each other, and not in contact with each other.
As thus described, the magnetic core according to the present embodiment can be realized as in rectangular shape, circular shape, or another shape though not described here.
Next, another example will be described by means of
A magnetic core 61 has a rectangular shape as seen from above. More specifically, the magnetic core 61 is a single layered type formed by docking a first core section 61a and a second core section 61b both having a U shape. The first core section 61a and the second core section 61b are in intimate contact with each other on a surface constituting one surface of the rectangular shape (upper-side surface in the figure). Then, on the surface opposed to the above surface (lower-side surface in the figure), the first core section 61a and the second core section 61b are formed with the magnetic flux leakage section 3 and the element holding hole 5. Herein, the first open end plane of the first core section 61a and the second open end plane of the second core section 61b are spaced from each other, thereby to form the magnetic flux leakage section 3. Then, the element holding hole 5 is formed by the first element holding hole provided on the first open end plane and the second element holding hole provided on the second open end plane. The element holding hole 5 is formed in the radiation direction with respect to a current flowing through the measuring object wire (not shown), and penetrates the first core section 61a and the second core section 61b.
A magnetic core 62 is in common with the magnetic core 61 of
In the above, the variety of shapes of the magnetic core according to the present embodiment were described by means of
Next, it will be described that the thickness of the magnetic core in the radiation direction with respect to a current flowing through the measuring object wire does not have an influence on the sensitivity of the entire current sensor provided with the magnetic core.
As an example, a comparison is made between the thicknesses of the magnetic cores as seen from the top in
At this time, as shown in
That is, because the amount of the magnetic flux inside the element holding hole is almost constant in the direction x, the sensitivity of the entire current sensor provided with the magnetic core does not decrease so long as the thickness t is larger than the width of the magnetic sensing section of the magnetoelectric conversion element 20. Therefore, as described above, even though the magnetic core 53 has a smaller thickness t than the magnetic core 1, it does not necessarily mean having an influence on the sensitivity of the entire current sensor provided with the magnetic core 53.
Embodiments of the present invention are not restricted to the foregoing embodiment, but a variety of modifications are possible in the range shown in the claims. That is, embodiments obtained by combining technical means having been appropriately modified in the range shown in the claims are included in the technical range of embodiments of the present invention.
It is to be noted that one or more embodiments of the present invention may be realized in the following configurations.
The magnetic core according to one or more embodiments of the present invention is a magnetic core used for a current sensor, which may be configured to have: a first open end plane which is formed with a first element holding hole for holding a magnetoelectric conversion element; and a second open end plane which is formed with a second element holding hole for holding the magnetoelectric conversion element, and is opposed to the first open end plane.
The magnetic core according to one or more embodiments of the present invention has the first open end plane and the second open end plane, which are opposed to each other. Then, the first element holding hole is formed on the first open end plane, the second element holding hole is formed on the second open end plane, and a magnetoelectric conversion element is held by the first element holding hole and the second element holding hole.
Therefore, due to the presence of the first open end plane and the second open end plane, namely the presence of a void section (hereinafter referred to as a “magnetic flux leakage section”) between the first open end plane and the second open end plane, a magnetic flux is prone to leakage from the magnetic core toward the first element holding hole and the second element holding hole, and the magnetoelectric conversion element held in the first element holding hole and the second element holding hole can sense the leakage of the magnetic flux.
In addition, while the sensitivity of the magnetic core is more favorable with lower magnetic resistance of the magnetic flux leakage section, the magnetic resistance of the magnetic flux leakage section is lower with a smaller width of the magnetic flux leakage section (distance between the first open end plane and the second open end plane). In this respect, in a magnetic core according to one or more embodiments of the present invention, the magnetoelectric conversion element is held in the first element holding hole and the second element holding hole which are formed by the first open end plane and the second open end plane. Therefore, the distance between the first open end plane and the second open end plane is not made large to such a degree that the magnetoelectric conversion element is held therebetween. That is, the distance between the first open end plane and the second open end plane naturally becomes small. Accordingly, in the magnetic core according to one or more embodiments of the present invention, the magnetic flux leakage section has a small width and thus causes magnetic resistance of the magnetic flux leakage section to decrease, thereby allowing improvement in sensitivity of the current sensor that uses the magnetic core.
Further, in the magnetic core according to one or more embodiments of the present invention, the first element holding hole and the second element holding hole are formed not in positions along an outer edge of the magnetic core where a magnetic flux is resistant to leakage from the magnetic core, but on the first open end plane and the second open end plane. For the above reason, in the magnetic core according to one or more embodiments of the present invention, the magnetoelectric conversion element is held in the first element holding hole and the second element holding hole where a magnetic flux is prone to leakage from the magnetic core, whereby it is possible to collect a larger amount of magnetic flux generated due to a minute current, so as to improve the sensitivity.
As thus described, with the above configuration formed, a magnetic core capable of enhancing the detection sensitivity of the current sensor can be realized as the magnetic core according to one or more embodiments of the present invention.
Further, the magnetic core according to one or more embodiments of the present invention may be configured that the magnetoelectric conversion element is held in the first element holding hole and the second element holding hole such that a magnetic sensing direction of the magnetoelectric conversion element is a circumferential direction of the magnetic core.
With the above configuration formed, it is possible to decrease the first element holding hole and the second element holding hole in the thickness direction of the magnetoelectric conversion element (thickness direction of the magnetic core which is vertical to the circumferential direction of the magnetic core), which hold the magnetoelectric conversion element. With smaller widths of the first element holding hole and the second element holding hole in the thickness direction of the magnetic core, a magnetic flux that leaks from the magnetic core is amplified, and hence, with the above configuration formed, it is possible to enhance the sensitivity of the magnetoelectric conversion element. Accordingly, a magnetic core capable of further enhancing the detection sensitivity of the current sensor can be realized as the magnetic core according to one or more embodiments of the present invention.
Further, in the magnetic core according to one or more embodiments of the present invention, the distance between the first open end plane and the second open end plane is smaller than 2 mm.
In light of a size of a typical magnetoelectric conversion element, when the distance between the first open end plane and the second open end plane is not smaller than 2 mm, the magnetoelectric conversion element cannot be held in the first element holding hole and the second element holding hole.
With the above configuration formed, such an effect is exerted that the magnetoelectric conversion element can be held in the first element holding hole and the second element holding hole, and the magnetoelectric conversion element can reliably sense a magnetic flux leaking from the magnetic core to the first element holding hole and the second element holding hole.
Further, when a bottom surface of the first element holding hole 5a is referred to as a first bottom surface (reference numeral of 16 in
Moreover, the element holding hole has been described using an expression “hole”. Although this expression “hole” may be used synonymously with so-called “groove”, “hole” is used in the present specification as a uniform expression.
Further, the term “holding hole” is used as the meaning of a space required for arrangement, storage, and the like of the magnetoelectric conversion element.
Embodiments of the present invention relate to a magnetic core capable of enhancing detection sensitivity of a current sensor, a current sensor provided with the magnetic core, and a current measuring method performed using the current sensor provided with the magnetic core.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-081555 | Mar 2010 | JP | national |
| 2011-057281 | Mar 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/056119 | 3/15/2011 | WO | 00 | 4/25/2012 |
