JP2019105570A - Magnetic sensor and current sensor - Google Patents

Abstract

To provide a magnetic sensor that can be hardly deteriorate measurement accuracy even when an environmental temperature fluctuates.SOLUTION: A magnetic sensor comprises: a first measurement unit U1, which comprises a first magnetic shield 15 in a shape of rectangle in a planar view, having a first magnetic material whose magnetostriction constant is positive, and a first magnetic detection element, which is disposed in a manner to become superimposed on the first magnetic shield 15 in the planar view, having a sensitivity axis toward a direction P in a minor axis direction of the rectangle; a second measurement unit U2, which comprises a second magnetic shield 151 in a shape of rectangle in the planar view, having a second magnetic material whose magnetostriction constant is negative, and a second magnetic detection element, which is disposed in a manner to become superimposed on the second magnetic shield 151 in the planar view, having a sensitivity axis toward P in the minor axis direction of the rectangle; and a switch section SW which, based on an environmental temperature, selects to apply either the first measurement unit U1 or the second measurement unit U2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic sensor and a current sensor provided with the magnetic sensor.

  In fields such as motor drive technology in electric vehicles and hybrid cars, and in infrastructure related fields such as columnar transformers, relatively large currents are handled, so current sensors capable of measuring large currents without contact are required. There is. As such a current sensor, one using a magnetic sensor that detects an induced magnetic field from a current to be measured is known. As a magnetic sensing element for a magnetic sensor, for example, a magnetoresistance effect element such as a GMR (giant magnetoresistance effect) element can be mentioned.

  Although the magnetoresistive effect element has high detection sensitivity, it is characterized by having high linearity and a relatively narrow detectable magnetic field strength range. For this reason, as in the current sensor shown in FIG. 3 of Patent Document 1, a magnetic shield is disposed between the current to be measured and the magnetoresistive effect element, and an induced magnetic field substantially applied to the magnetoresistive effect element. A method may be used in which the magnitude of the magnetic field to be measured falls within the range of the magnetic field strength having good detection characteristics by reducing the strength of.

International Publication No. 2011/111493

  By thus using the magnetic shield, it is realized to reduce the strength of the magnetic field substantially applied to the magnetic detection element such as the magnetoresistance effect element and to expand the measurement range of the magnetic field strength. Such a magnetic shield generally includes a shield film formed by plating a soft magnetic material such as an Fe-Ni alloy by sputtering, or the like.

  Here, for example, when a strong external magnetic field is applied, if the magnetic shield itself has magnetic hysteresis, the output of the magnetic sensor also has hysteresis. Since the hysteresis at zero magnetic field (zero magnetic field hysteresis ZH) causes an offset of the magnetic sensor, the magnetic hysteresis of the magnetic shield degrades the detection accuracy of the magnetic sensor. In order to reduce the magnetic hysteresis of the magnetic shield, it is effective to thicken the shield film or increase the aspect ratio of the shape of the magnetic shield to sufficiently impart shape anisotropy.

  When the material constituting the shield film is an Fe-Ni alloy (permalloy), the hysteresis is minimized and the magnetic permeability is assumed to be near the composition (Fe content is 19.8 mass%) at which the magnetostriction is zero. (μ) is maximized and the magnetic field damping effect of the magnetic shield is further enhanced. Therefore, the dynamic range of the magnetic sensor can be further expanded, which is preferable.

  However, when the shield film made of an Fe-Ni alloy is formed by electroplating, it is very difficult to control the composition of the shield film. For this reason, it is extremely difficult to realize a shield film having a zero magnetostrictive composition by pinpointing, and the magnetostriction of the shield film is likely to be shifted to either positive or negative. When stress is generated in the magnetic shield provided with such a shield film, and magnetization based on the magnetoelastic anisotropy is generated in the shield film in the direction along the sensitivity axis direction of the magnetic detection element, the magnetization is applied with an external magnetic field. Since it exists even in the absence state, it becomes residual magnetization of the magnetic shield. When a return magnetic field based on this residual magnetization is applied to the magnetic sensing element along the sensitivity axis, the hysteresis of the magnetic sensor is increased, resulting in a decrease in measurement accuracy. As an example of the cause of stress generation in the above-mentioned magnetic shield, when the environmental temperature of the magnetic sensor changes, it is caused by the difference in thermal expansion coefficient between the magnetic shield and a member (insulation member) located around it. It is mentioned that a compressive force or a tensile force is applied from the insulating member to the magnetic shield. That is, changes in the environmental temperature of the magnetic sensor can cause residual magnetization in the magnetic shield, resulting in a decrease in measurement accuracy of the magnetic sensor.

  An object of the present invention is to provide a magnetic sensor whose measurement accuracy is unlikely to decrease even if the environmental temperature fluctuates, and a current sensor provided with such a magnetic sensor.

  In one aspect, the present invention provided to solve the above-described problems includes a first magnetic shield having a first magnetic body having a positive magnetostriction constant and having a short axis direction and a long axis direction; A first measurement unit including a first magnetic detection element disposed to visually overlap the first magnetic shield and having a sensitivity axis in a direction along the short axis direction, and a second magnetic member having a negative magnetostriction constant A second magnetic shield having a body and having a short axis direction and a long axis direction, and a second magnetic shield disposed so as to overlap the second magnetic shield in plan view, having a sensitivity axis in a direction along the short axis direction And a switching unit configured to select which of the first measurement unit and the second measurement unit is to be used based on an environmental temperature. It is a sensor.

  As described above, although it is not easy to stably form a magnetic shield provided with a shield film having a composition exhibiting zero magnetostriction, controlling the composition so that the magnetostriction constant of the shield film becomes positive or negative is compared Is easy. Therefore, a first measurement unit (magnetic shield + magnetic detection element) having a magnetic shield provided with a shield film (first magnetic body) having a positive magnetostriction constant, and a shield film (second magnetic body) having a negative magnetostriction constant By providing a second measurement unit having a magnetic shield and providing a switching unit to selectively use these according to the environmental temperature, a magnetic sensor that is less susceptible to the influence of fluctuations in the environmental temperature can be obtained. The switching unit may switch whether or not to operate any of the measurement units, and may switch whether or not the output from any of the measurement units is to be the output of the magnetic sensor.

  In the above magnetic sensor, the switching unit may switch the environmental temperature between 0 ° C. and 80 ° C. In this case, when the environmental temperature is 0 ° C. or lower, the output of the first measurement unit is the output from the magnetic sensor, and when the environmental temperature is 80 ° C. or higher, the output of the second measurement unit is the magnetic sensor It should be output.

In the magnetic sensor of the above, the magnetostriction constant of the first magnetic body is a 0 Ultra 2 × 10 ^-6 or less, the magnetostriction constant of the second magnetic body is preferably less than 0 -2 × 10 ^-6 or more . Such a configuration is made of an Fe-Ni alloy having an Fe content of more than 19.8% by mass and 22.0% by mass or less for the first magnetic body, and an Fe content of the second magnetic body is This can be easily realized by using an Fe-Ni alloy containing 18.0% by mass or more and less than 19.8% by mass. The first magnetic body and the second magnetic body may be formed of an electroplating film.

  In the above magnetic sensor, even if each of the first magnetic detection element and the second magnetic detection element is composed of a plurality of magnetoresistance effect elements having sensitivity axes in a direction along the short axis direction of the rectangle. Good.

  The above magnetic sensor may further include a magnetic balance coil, and the strength of the measured magnetic field may be measured based on the current flowing through the magnetic balance coil. In this case, the magnetic balancing coil may be a spiral coil and be located between the magnetoresistive element and the magnetic shield.

  In another aspect, the present invention provides a current sensor including the above-described magnetic sensor, wherein the magnetic sensor uses an induced magnetic field of a measured current as the measured magnetic field.

  According to the present invention, there is provided a magnetic sensor in which the measurement accuracy is unlikely to decrease even if the environmental temperature fluctuates. There is also provided a current sensor using such a magnetic sensor.

It is a top view which shows notionally the structure of the magnetic sensor which concerns on one Embodiment of this invention. (A) It is sectional drawing by the V1-V1 line | wire of FIG. 1, (b) It is a sectional view by the V2-V2 line | wire of FIG. It is a figure explaining the direction of magnetization based on the magnetoelastic anisotropy which arises in the 1st magnetic body and the 2nd magnetic body at the time of low temperature and high temperature. It is a top view which shows notionally the structure of the magnetic sensor which concerns on other one Embodiment of this invention. (A) It is sectional drawing by the V3-V3 line | wire of FIG. 4, (b) It is a sectional view by the V4-V4 line | wire of FIG. It is a graph which shows the relationship between environmental temperature (measurement temperature) and zero magnetic field hysteresis ZH.

  FIG. 1 is a plan view conceptually showing the structure of a magnetic sensor according to an embodiment of the present invention. FIG. 2A is a cross-sectional view taken along line V1-V1 of FIG. FIG.2 (b) is sectional drawing in the V2-V2 line of FIG.

  As shown in FIGS. 1 and 2, the magnetic sensor 1 according to an embodiment of the present invention is a first magnetic sensing element including four magnetoresistive elements (from the magnetoresistive element 11 to the magnetoresistive element 14). And a first measurement unit U1 including the first magnetic shield 15, and a second magnetic detection element including the four magnetoresistive elements (the magnetoresistive element 111 to the magnetoresistive element 141) and the second magnetic shield 151. And 2 measurement unit U2. In the first measurement unit U1, the first magnetic shield 15 can attenuate the intensity of the measured magnetic field (for example, an induced magnetic field of the measured current Io flowing in the current line) applied to the first magnetic sensing element . In the second measurement unit U2, the second magnetic shield 151 can attenuate the intensity of the measured magnetic field (for example, the induced magnetic field of the measured current Io flowing in the current line) applied to the second magnetic sensing element .

  Each of the four magnetoresistance effect elements (the magnetoresistance effect element 11 to the magnetoresistance effect element 14) included in the first magnetic sensing element of the first measurement unit U1 has a plurality of lengths extending in the meander shape (X1-X2 direction) A giant magnetoresistive effect element (GMR element) having a shape in which a length pattern is connected so as to be folded back is provided. The sensitivity axis direction P of each magnetoresistance effect element (from the magnetoresistance effect element 11 to the magnetoresistance effect element 14) is represented by an arrow in FIG. 1, and the sensitivity axis direction P of the magnetoresistance effect element 11 and the magnetoresistance effect element 14 is The sensitivity axis direction P of the magnetoresistive effect element 12 and the magnetoresistive effect element 13 is set to face the Y1-Y2 direction Y1 side.

  The wiring 5 connected to the input terminal 5 a is connected to one end of the magnetoresistive effect element 11, and the other end of the magnetoresistive effect element 11 and one end of the magnetoresistive effect element 12 are connected in series. The other end is connected to the ground terminal 6 a via the wiring 6. The wiring 5 connected to the input terminal 5a branches halfway and is also connected to one end of the magnetoresistive element 13. The other end of the magnetoresistive element 13 and one end of the magnetoresistive element 14 are connected in series. The other end of the magnetoresistance effect element 14 is connected to the ground terminal 6 a via the wiring 6. The first midpoint potential measurement terminal 7a is connected between the other end of the magnetoresistance effect element 11 and one end of the magnetoresistance effect element 12 by the wiring 7, and the second midpoint potential measurement terminal 8a is magnetoresistance. A wire 8 is connected between the other end of the effect element 13 and one end of the magnetoresistive element 14. In the bridge circuit configured in this manner, the measured current flowing through the current line is obtained by comparing the potential of the first midpoint potential measurement terminal 7a with the potential of the second midpoint potential measurement terminal 8a. The strength and direction of the induced magnetic field (measured magnetic field) of Io can be measured.

  FIG. 2 is obtained by cutting the magnetic sensor 1 with a plane having a direction along the major axis direction (X1-X2 direction) of a plurality of long patterns forming the meander shape of the magnetoresistive effect element 11 as a normal FIG. The Y1-Y2 direction, which is one of the directions in the section in the cross section, is the sensitivity axis direction P of the magnetoresistive effect element 11 (the Y1-Y2 direction Y2 direction). The magnetoresistive effect element 11 is formed on the substrate 29 and covered with an insulating layer IM made of an insulating material (eg, alumina, silicon nitride, etc., as a specific example).

  Each of the four magnetoresistance effect elements (the magnetoresistance effect element 111 to the magnetoresistance effect element 141) included in the second magnetic detection element of the second measurement unit U2 corresponds to each magnetic field of the first magnetic detection element of the first measurement unit U1. The structure is the same as that of the resistance effect element (from the magnetoresistive effect element 11 to the magnetoresistive effect element 14), and thus the description is omitted. Further, a bridge circuit formed by the magnetoresistive elements (from the magnetoresistive element 111 to the magnetoresistive element 141) of the second magnetic detection element is also in common with the bridge circuit of the first measurement unit U1. The input terminal 51 a corresponds to the input terminal 5 a, and the wiring 51 corresponds to the wiring 5. The ground terminal 61 a corresponds to the ground terminal 6 a, and the wiring 61 corresponds to the wiring 6. The first midpoint potential measurement terminal 71 a corresponds to the first midpoint potential measurement terminal 7 a, and the wire 71 corresponds to the wire 7. The second midpoint potential measurement terminal 81 a corresponds to the second midpoint potential measurement terminal 8 a, and the wire 81 corresponds to the wire 8.

  The arrangement of the second magnetic detection elements (from the magnetoresistance effect element 111 to the magnetoresistance effect element 141) of the second measurement unit U2 is the same as the first magnetic detection element (from the magnetoresistance effect element 11 to the magnetoresistance effect element) of the first measurement unit U1. 14) is rotated 180 degrees around the rotation axis along the Z1-Z2 direction. The wiring 61, the wiring 71 and the wiring 81, the ground terminal 61a, the first midpoint potential measurement terminal 71a, and the second midpoint potential measurement terminal 81a are disposed in correspondence with this arrangement. Therefore, except for the influence of the first magnetic shield 15 and the influence of the second magnetic shield 151, the first measurement unit U1 and the second measurement unit U2 are configured to obtain equal measurement results.

  The input terminal 5a of the first measurement unit U1 is connected to the switching unit SW by the first connection line CW, and the input terminal 51a of the second measurement unit U2 is connected by the second connection line CW1. In the switching unit SW, the switching wiring SC is connectable to the first connection line CW or the second connection line CW1.

  When the switching wire SC is connected to the first connection line CW in the switching unit SW, as shown in FIG. 2A, the first magnetic sensing element (from the magnetoresistive element 11 to the magnetoresistive element 14) And the drive voltage is applied via the wiring 5 to operate the first measurement unit U1. When the switching wire SC is connected to the second connection line CW1 in the switching unit SW, as shown in FIG. 2B, the second magnetic sensing element (from the magnetoresistive element 111 to the magnetoresistive element 141) The drive voltage is applied via the wiring 51 to operate the second measurement unit U2.

  In such a configuration, as described below, by making the characteristics of the first magnetic shield 15 and the second magnetic shield 151 different, even if the environmental temperature of the first measurement unit U1 decreases, the zero magnetic field hysteresis ZH In the second measurement unit U2, the zero magnetic field hysteresis ZH does not easily occur even when the environmental temperature rises.

  The first magnetic shield 15 of the first measurement unit U1 attenuates the strength of the magnetic field to be measured applied to the first magnetic sensing element (from the magnetoresistance effect element 11 to the magnetoresistance effect element 14). As shown in FIG. 1, the first magnetic shield 15 has a sensitivity axis direction P (Y1-Y2 direction) as a short axis direction in plan view (viewed from the Z1-Z2 direction), and is orthogonal to this short axis direction It has a rectangle whose major axis is the X1-X2 direction. As shown in FIG. 2A, the first magnetic shield 15 has a laminated structure of a first magnetic body 15A made of a soft magnetic material and an oxidation protective layer PL made of tantalum (Ta) or the like. The first magnetic shield 15 is disposed on the first magnetic sensing element (on the Z1-Z2 direction Z1 side) the first magnetic sensing element (the magnetoresistive effect element 11 is shown in FIG. 2A). It is disposed apart from the effect element 11). The distance between the first magnetic shield 15 and the first magnetic sensing element (the magnetoresistive element 11) is adjusted by the thickness of the insulating layer IM located therebetween.

  The second magnetic shield 151 of the second measurement unit U2 is to attenuate the strength of the magnetic field to be measured applied to the second magnetic detection element (from the magnetoresistive element 111 to the magnetoresistive element 141). Similar to the first magnetic shield 15, the second magnetic shield 151 has a short axis direction in the sensitivity axis direction P (Y1-Y2 direction) in plan view (viewed from the Z1-Z2 direction), as shown in FIG. It has a rectangle whose major axis is the X1-X2 direction orthogonal to the minor axis direction. As shown in FIG. 2B, the second magnetic shield 151 has a laminated structure of a second magnetic body 15B made of a soft magnetic material and an oxidation protective layer PL made of tantalum (Ta) or the like. The second magnetic shield 151 (magnetic resistance) is disposed on the second magnetic detection element (on the Z1-Z2 direction Z1 side) above the second magnetic detection element (the magnetoresistive effect element 131 is shown in FIG. 2B). It is disposed apart from the effect element 131). The separation distance between the second magnetic shield 151 and the second magnetic sensing element (the magnetoresistive element 131) is adjusted by the thickness of the insulating layer IM located therebetween.

  In the above embodiment, although the first magnetic shield 15 and the second magnetic shield 151 are rectangular in plan view, the present invention is not limited to this. The first magnetic shield 15 may have a shape having a short axis direction along the sensitivity axis direction P of the first magnetoresistance effect element and a long axis direction intersecting the short axis direction. The second magnetic shield 151 may have a shape having a short axis direction along the sensitivity axis direction P of the second magnetoresistance effect element and a long axis direction intersecting the short axis direction. The specific shape is not limited to a rectangle, and may be a shape such as an oval or an oval. The rectangular corner may be tapered or may have a curved (R) shape.

Each of the first magnetic body 15A and the second magnetic body 15B is made of an Fe-Ni alloy, and is an electroplating film formed by electroplating. By adjusting the composition of the plating solution in this electroplating, the first magnetic body 15A can easily be made of an Fe-Ni alloy having an Fe content of more than 19.8 mass% and 22.0 mass% or less. To be realized. When the first magnetic body 15A has such a composition, the magnetostriction constant of the first magnetic body 15A becomes a positive value, and specifically, it is more than 0 and 2 × 10 ^-6 or less. Similarly, by adjusting the composition of the plating solution, it is easily realized that the second magnetic body 15B is made of an Fe-Ni alloy having an Fe content of 18.0% by mass or more and less than 19.8% by mass. Be done. When the second magnetic body 15B has such a composition, the magnetostriction constant of the second magnetic body 15 becomes a negative value, and specifically, is −2 × 10 ⁻⁶ or more and less than 0.

FIG. 3 is a view for explaining the direction of magnetization based on the magnetoelastic anisotropy generated in the first magnetic body and the second magnetic body at low temperature and high temperature. When the environmental temperature of the magnetic sensor 1 is high (FIG. 3B), the first magnetic shield 15 is obtained based on the difference in thermal expansion coefficient between the first magnetic shield 15 and the insulating layer IM located therearound. On the other hand, an external force F is applied to compress the entire first magnetic shield 15. At this time, since a large force is applied in the long axis direction (X1-X2 direction) of the rectangle of the first magnetic shield 15, tensile stress σ is generated in the short axis direction (Y1-Y2 direction side) of the rectangle. As a result, in the first magnetic shield 15 provided with the first magnetic body 15A having a positive magnetostriction constant, magnetization based on the magnetoelastic anisotropy occurs in the rectangular short axis direction (Y1-Y2 direction). The magnetic anisotropy constant ku regarding magnetoelastic anisotropy is expressed by the following equation.
ku = -3λs · σ / 2
Here, λs is saturation magnetostriction, and σ is internal stress (positive is tensile, negative is compressive).

  The magnetization based on the magnetoelastic anisotropy is generated even when no external magnetic field is applied, and therefore, the residual magnetization in the Y1-Y2 direction of the first magnetic shield 15 is obtained. Since the direction of this residual magnetization is along the sensitivity axis direction P of the first magnetic sensing element (from the magnetoresistance effect element 11 to the magnetoresistance effect element 14), the return magnetic field RM of the residual magnetization (see FIG. 2A) The first magnetic detection element (from the magnetoresistance effect element 11 to the magnetoresistance effect element 14) is applied to increase the zero magnetic field hysteresis ZH of the first measurement unit U1.

  On the other hand, when the environmental temperature is low (FIG. 3 (a)), an external force F is applied to pull the entire first magnetic shield 15, so tensile stress σ is given priority in the long axis direction (X1-X2 direction) of the rectangle. And magnetization based on magnetoelastic anisotropy occurs in this direction (X1-X2 direction). Since the magnetization in the X1-X2 direction is orthogonal to the sensitivity axis direction P of the first magnetic sensing element (from the magnetoresistance effect element 11 to the magnetoresistance effect element 14), the return magnetic field of the residual magnetization of the first magnetic shield 15 is the first Even if the magnetic sensing element (from the magnetoresistive element 11 to the magnetoresistive element 14) is applied, the zero magnetic field hysteresis ZH of the first measurement unit U1 is not increased. Therefore, it is preferable from the viewpoint of reducing the zero magnetic field hysteresis ZH of the magnetic sensor 1 that the first measurement unit U1 including the first magnetic shield 15 is used when the environmental temperature is low.

  On the other hand, it is preferable that the second measurement unit U2 including the second magnetic shield 151 having the second magnetic body 15B having a negative magnetostriction constant be used when the environmental temperature is high (FIG. 3 (d)). When the second magnetic body 15B having a negative magnetostriction constant receives a compressive stress σ, magnetization based on the magnetoelastic anisotropy occurs in that direction. When the environmental temperature becomes high and the external force F is applied to the entire second magnetic shield 151 from the insulating layer IM located around the second magnetic shield 151, the longitudinal direction of the rectangular with a relatively large degree of compression ( Compressive stress σ occurs notably in the X1-X2 direction). For this reason, in the second magnetic shield 151 including the second magnetic body 15B, residual magnetization based on magnetoelastic anisotropy is generated in the long axis direction (X1-X2 direction) of the rectangle. Since this magnetization direction is orthogonal to the sensitivity axis direction P, even if a return magnetic field based on the residual magnetization of the second magnetic shield 151 is applied to the second magnetic detection element (from the magnetoresistive element 111 to the magnetoresistive element 141), The zero field hysteresis ZH of the second measuring unit U2 does not increase.

  On the other hand, when the environmental temperature is low (FIG. 3C), the entire second magnetic shield 151 is pulled by the insulating layer IM, so the relatively strong rectangular shape in the major axis direction (X1-X2 direction) The tensile force F brings about compressive stress σ in the rectangular short axis direction (Y1-Y2 direction). For this reason, in the second magnetic shield 151, residual magnetization based on magnetoelastic anisotropy is generated in the direction along the sensitivity axis direction P (Y1-Y2 direction). When a return magnetic field based on this residual magnetization is applied to the second magnetic sensing element (from the magnetoresistance effect element 111 to the magnetoresistance effect element 141), the zero magnetic field hysteresis ZH of the second measurement unit U2 is increased. Therefore, when the environmental temperature is low, it is preferable to use the first measurement unit U1 (FIG. 3A), and when the environmental temperature is high, it is preferable to use the second measurement unit U2 (FIG. 3D). .

  It is preferable that switching part SW switches between 0 degreeC or more and 80 degrees C or less of environmental temperature. Specifically, when the environmental temperature is 0 ° C. or lower, the output of the first measurement unit U1 is the output from the magnetic sensor 1, and when the environmental temperature is 80 ° C. or higher, the output of the second measurement unit U2 is the output from the magnetic sensor 1 do it. The switching temperature range (0 ° C. to 80 ° C.) should be set based on the composition of the first magnetic body 15A and the composition of the second magnetic body 15B, and should be 10 ° C. to 50 ° C. In some cases, it is preferable to set the temperature to 15 ° C. or more and 40 ° C. or less.

  FIG. 4 is a plan view conceptually showing the structure of a magnetic sensor according to another embodiment of the present invention. Fig.5 (a) is V3-V3 sectional drawing of FIG. 4, and the 1st measurement unit U1 is shown. FIG. 5B is a cross-sectional view taken along the line V4-V4 of FIG. 4 and shows the second measurement unit U2. Similar to the magnetic sensor 1 shown in FIG. 1, the magnetic sensor 1A shown in FIGS. 4 and 5 includes a first measurement unit U1 and a second measurement unit U2, and further includes a first magnetic sensing element (the magnetoresistive element 11). From the magnetoresistive element 14) to the first magnetic shield 15, and between the second magnetic sensing element (from the magnetoresistive element 111 to the magnetoresistive element 141) and the second magnetic shield 151. A magnetic balancing coil (spiral coil) 16 is provided. In FIG. 4, the outline of the magnetic balancing coil 16 is shown by a thick broken line. The coil wiring of the magnetic balancing coil 16 is disposed so as to go around in the X-Y plane of the region indicated by the broken line. In FIG. 5, the cross sections of the plurality of coil wirings that circulate in the magnetic balancing coil 16 are shown aligned in the Y1-Y2 direction. The magnetic balancing coil 16 is provided between the first magnetic sensing element (from the magnetoresistance effect element 11 to the magnetoresistance effect element 14) and the first magnetic shield 15, and the second magnetic sensing element (from the magnetoresistance effect element 111 to the magnetic resistance). Since it is located between the effect element 141) and the second magnetic shield 151, the induction magnetic field which cancels the external magnetic field applied in the state attenuated by the first magnetic shield 15 or the second magnetic shield 151 is relatively small. It can be generated by current. Therefore, it is possible to operate the magnetic balance type magnetic sensor with power saving.

  In FIG. 4, as an example, the cancel current Ic flowing through the magnetic balancing coil 16 flows counterclockwise. Therefore, between the first magnetic sensing element (the magnetoresistive element 11 is shown in FIG. 5A) and the first magnetic shield 15, the X1-X2 direction X1 direction (FIG. 5A) Then, the cancel current Ic flows from the back of the sheet to the front). Between the second magnetic sensing element (the magnetoresistive effect element 111 is shown in FIG. 5B) and the second magnetic shield 151, the X1-X2 direction X2 direction (the front side of the drawing sheet in FIG. 5A) Cancellation current Ic flows. Therefore, the induction magnetic field of the cancel current Ic is applied in the opposite direction to the first magnetic sensing element (the magnetoresistive effect element 11) and the second magnetic sensing element (the magnetoresistive effect element 111).

  Therefore, in the magnetic sensor 1A, the second measurement unit U2 has a configuration of line symmetry about a line along the X1-X2 direction of the first measurement unit U1. Specifically, in the magnetic sensor 1A, from the magnetoresistive effect element 111 constituting the second magnetic sensing element of the second measurement unit U2 to the magnetoresistive effect element 141, from the X2 side in the X1-X2 direction to the X1 side, The resistance effect element 111, the magnetoresistive effect element 121, the magnetoresistive effect element 141, and the magnetoresistive effect element 131 are arranged in this order. The wiring 61, the wiring 71 and the wiring 81, the ground terminal 61a, the first midpoint potential measurement terminal 71a, and the second midpoint potential measurement terminal 81a are disposed corresponding to this arrangement.

  In the above embodiment, although the case where a 1st magnetic sensing element and a 2nd magnetic sensing element consist of GMR elements is made into a specific example, it is not limited to this. In one non-limiting example, the magnetoresistive element is one selected from the group consisting of an anisotropic magnetoresistive element (AMR element), a giant magnetoresistive element (GMR element), and a tunnel magnetoresistive element (TMR element). It consists of the above elements.

  When the fixed layer of each GMR element constituting the magnetoresistive element 14 from the magnetoresistive element 11 included in the magnetic sensor 1 and the magnetoresistive element 141 from the magnetoresistive element 111 has a self-pinned structure, fixing is performed. The magnetization of the layer can be performed by deposition in a magnetic field, and no heat treatment in a magnetic field is required after deposition. Therefore, GMR elements having different magnetization directions in the fixed layer can be disposed on the same substrate, and two full bridge circuits can be formed on one substrate.

  The magnetic sensors 1 and 1A provided with the magnetoresistance effect element according to an embodiment of the present invention can be suitably used as a current sensor.

  As a specific example of the current sensor according to one embodiment of the present invention, a magnetic proportional current sensor and a magnetic balanced current sensor can be mentioned.

  A specific example of the magnetic proportional current sensor is the case where the magnetic sensor 1 shown in FIGS. 1 and 2 is used, and in such a current sensor, the measured current Io in the upper side of FIG. 2 (Z1-Z2 direction Z1 side) Is positioned so as to extend in the X1-X2 direction (see FIG. 1). As described above, the magnetic sensing elements of the first measurement unit U1 and the second measurement unit U2 are arranged so as to have a rotational symmetry of 180 degrees. Therefore, the output signal from the first measurement unit U1 (the signal from the first midpoint potential measurement terminal 7a and the second midpoint potential measurement terminal 8a) or the output signal from the second measurement unit U2 (the first The amount and direction of the current to be measured Io can be measured by the signal from the middle potential measurement terminal 71a and the second middle potential measurement terminal 81a.

  When the switching unit SW is appropriately operated and the environmental temperature is lowered (specifically, less than 0 ° C.), measurement is performed using the first measuring unit U1 instead of the second measuring unit U2, and the environmental temperature is increased. In the case of (specifically, 80 ° C. or higher), the measurement is performed using the second measurement unit U2 instead of the first measurement unit U1, thereby making the current sensor difficult to reduce the measurement accuracy even if the environmental temperature changes. be able to. In the range of 0 ° C. to 80 ° C., either of the first measurement unit U1 and the second measurement unit U2 may be used.

  A specific example of the magnetic balance type current sensor is the case where the magnetic sensor 1A shown in FIG. 4 and FIG. 5 is used, and in such a current sensor, the measured current Io in the upper side (Z1-Z2 direction Z1 side) of FIG. Is positioned so as to extend in the X1-X2 direction (see FIG. 4). By doing this, the induced magnetic field of the current Io to be measured, which is the magnetic field to be measured, is in the direction along the sensitivity axis direction P (Y1-Y2 direction) with respect to the first magnetic detection element and the second magnetic detection element. Applied. Since a part of the measured magnetic field passes through the magnetic shield (the first magnetic shield 15 and the second magnetic shield 151) having a higher permeability, the magnetic sensing element (the first magnetic sensing element, the second magnetic sensing element) is substantially The strength of the magnetic field to be measured applied to the Therefore, the current is supplied to the magnetic balancing coil 16 to generate an induced magnetic field that cancels the magnetic field due to the measured current Io substantially applied to the magnetic detection element (first magnetic detection element, second magnetic detection element). It is possible to reduce the amount of current drawn, and to realize power saving of the current sensor.

  When the switching unit SW is appropriately operated and the environmental temperature is lowered (specifically, less than 0 ° C.), measurement is performed using the first measuring unit U1 instead of the second measuring unit U2, and the environmental temperature is increased. In the case of (specifically, 80 ° C. or higher), the measurement is performed using the second measurement unit U2 instead of the first measurement unit U1, thereby making the current sensor difficult to reduce the measurement accuracy even if the environmental temperature changes. be able to. In the range of 0 ° C. to 80 ° C., either of the first measurement unit U1 and the second measurement unit U2 may be used.

  The embodiments described above are described to facilitate the understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

  For example, in the description of the above embodiment, the switching unit SW supplies the drive voltage to one of the first measurement unit U1 and the second measurement unit U2 to either of the first measurement unit U1 or the second measurement unit U2. The first measurement unit is selected by selecting which of the output signal of the first measurement unit U1 and the output signal of the second measurement unit U2 is to be used as the output of the magnetic sensor 1 or 1A. One of U1 and the second measurement unit U2 may be selected.

  Hereinafter, the present invention will be more specifically described by way of examples and the like, but the scope of the present invention is not limited to these examples and the like.

Example 1
A plurality (50 or more) of magnetic balance type magnetic sensors 1A having the same structure as that shown in FIGS. 4 and 5 were manufactured. The magnetoresistance effect elements constituting the magnetic detection element (first magnetic detection element, second magnetic detection element) were all GMR elements. The magnetic shield (the first magnetic shield 15 and the second magnetic shield 151) has a planar shape of 800 μm × 200 μm and is made of an Fe—Ni alloy and laminated with a soft magnetic layer having a thickness of 16.5 μm by electroplating. A 10 nm thick oxide protective layer was formed by sputtering. The Fe content in the first magnetic body 15A of the first magnetic shield 15 was 20.8 mass%, and the magnetostriction constant was positive. The Fe content in the second magnetic body 15B of the second magnetic shield 151 was 18.8 mass%, and the magnetostriction constant was negative. The distance (the distance in the Y1-Y2 direction) between the magnetic shield (the first magnetic shield 15 and the second magnetic shield 151) and the GMR element was 9.0 μm.

(Comparative example 1)
A plurality (50 or more) of magnetic balance type magnetic sensors 1A different from the first embodiment in the following points were manufactured.
(Difference 1) Only the first measurement unit U1 is included and the second measurement unit U2 is not included.
(Difference 2) The magnetic body of the first magnetic shield 15 is made of an Fe-Ni alloy with an aim value of the Fe content of 18.8 mass% (negative magnetostriction).

(Comparative example 2)
A plurality of magnetic members of the first magnetic shield 15 are prepared in the same manner as in Comparative Example 1 except that the magnetic substance of the first magnetic shield 15 is made of an Fe-Ni alloy having an aim value of Fe content of 20.8 mass% (positive magnetostriction). The magnetic sensor 1A was produced.

(Comparative example 3)
A plurality of magnetic bodies of the first magnetic shield 15 are prepared in the same manner as in Comparative Example 1 except that the magnetic substance of the first magnetic shield 15 is made of an Fe-Ni alloy with an aim value of Fe content of 19.8 mass% (zero magnetostriction). The magnetic sensor 1A of

(Measurement example 1)
The environmental temperature (measurement temperature) is set to −40 ° C., and in the magnetic sensor 1A according to the first embodiment, the switching wire SC of the switching unit SW is connected to the first connection wire CW connected to the first measurement unit U1. The measurements of the magnetic sensor 1A according to Example 1 and Comparative Examples 1 to 3 were performed. For each of the magnetic sensors 1A, the hysteresis loop was measured while changing the external magnetic field with the maximum intensity (maximum applied magnetic field) of the external magnetic field applied being ± 18 mT. From this hysteresis loop, zero magnetic field hysteresis ZH (unit:% / FS) was measured. The zero field hysteresis ZH is the magnitude of the output at the zero magnetic field (positive maximum) relative to the maximum value of the output in the full bridge output curve (the value when the positive maximum magnetic field is applied minus the value when the negative maximum magnetic field is applied) It is a ratio (unit:%) of the value when changing from the application of the magnetic field to zero applied magnetic field-the value when changing from the application of the negative maximum magnetic field to zero applied magnetic field.

(Measurement example 2)
The environmental temperature (measurement temperature) was set to 25 ° C., and zero magnetic field hysteresis ZH (unit:% / FS) was measured in the same manner as in Measurement Example 1. In the measurement example, in the magnetic sensor 1A according to the first embodiment, the output of the first measurement unit U1 is the output of the magnetic sensor 1A.

(Measurement example 3)
In the magnetic sensor 1A according to the first embodiment, the environmental temperature (measurement temperature) is set to 125 ° C., and the switching wire SC of the switching unit SW is connected to the second connection wire CW1 connected to the second measurement unit U2, The measurement of the magnetic sensor 1A according to Example 1 and Comparative Example 1 to Comparative Example 3 was performed to measure the zero magnetic field hysteresis ZH (unit:% / FS). In the measurement example, in the magnetic sensor 1A according to the first embodiment, the output of the second measurement unit U2 is the output of the magnetic sensor 1A.

  The average value and the variation (3σ) of the zero magnetic field hysteresis ZH are shown in Table 1 and FIG. 6 for each measurement example.

  As shown in Table 1 and FIG. 6, in the magnetic sensor according to Example 1, the zero magnetic field hysteresis ZH was as small as 0.01% / FS or less in absolute value at any measurement temperature.

  In the magnetic sensor of Comparative Example 1 including only the magnetic shield of negative magnetostriction, the absolute value of the zero magnetic field hysteresis ZH was large at a low temperature (−40 ° C.). This is because, with respect to the magnetic shield of negative magnetostriction, compressive stress σ is generated in the rectangular short axis direction (Y1-Y2) direction along the sensitivity axis direction P, and the magnetization based on the magnetoelastic anisotropy becomes a magnetic shield It means that it happened.

  In the magnetic sensor of Comparative Example 2 including only a magnetic shield of positive magnetostriction, the absolute value of the zero magnetic field hysteresis ZH was large at high temperature (125 ° C.). This is because, with respect to the magnetic shield of positive magnetostriction, tensile stress σ is generated in the rectangular short axis direction (Y1-Y2) direction along the sensitivity axis direction P, and the magnetization based on the magnetoelastic anisotropy becomes a magnetic shield It means that it happened.

  In the magnetic sensor of Comparative Example 3 including the magnetic shield manufactured for zero magnetostriction, the zero field hysteresis ZH at a low temperature (-40 ° C.) and the zero field hysteresis at a high temperature (125 ° C.) as compared with the magnetic sensor of Example 1 The absolute value increased for all of ZH. Moreover, the variation increased.

  Therefore, it was confirmed that the magnetic sensor according to the present invention has high measurement accuracy and excellent quality stability.

  A magnetic sensor provided with a magnetoresistive element according to an embodiment of the present invention is suitably used as a component of a current sensor of an infrastructure equipment such as a columnar transformer, or a component of a current sensor such as an electric car or a hybrid car. sell.

1, 1A magnetic sensor U1 first measurement unit U2 second measurement unit 11, 12, 13, 14, 111, 121, 131, 141 magnetoresistance effect element (first magnetic detection element, second magnetic detection element)
5, 6, 7, 8, 51, 61, 71, 81 Wiring 5a, 51a Input terminal 6a, 61a Ground terminal 7a, 71a First midpoint potential measurement terminal 8a, 81a Second midpoint potential measurement terminal Io Measured current IM Insulating layer 15 First magnetic shield 151 Second magnetic shield 15A First magnetic body 15B Second magnetic body 16 Magnetic balance coil (spiral coil)
PL oxidation protective layer 29 substrate SW switching portion SC switching wiring CW first connection wire CW1 second connection wire RM return magnetic field F external force (compressive force, tensile force)
σ internal stress (compressive stress, tensile stress)
Ic cancellation current P sensitivity axis direction

Claims (9)

A first magnetic shield having a first magnetic body having a positive magnetostriction constant and having a short axis direction and a long axis direction, and is disposed so as to overlap the first magnetic shield in plan view, in the short axis direction A first measurement unit comprising a first magnetic sensing element having a sensitivity axis in a direction along the first measurement unit;
A second magnetic shield having a second magnetic body having a negative magnetostriction constant and having a short axis direction and a long axis direction, and is arranged to overlap the second magnetic shield in plan view, in the short axis direction A second measurement unit comprising a second magnetic sensing element having a sensitivity axis in a direction along the
A switching unit that selects which of the first measurement unit and the second measurement unit is to be used based on an environmental temperature;
A magnetic sensor comprising: The switching unit switches the environmental temperature between 0 ° C. and 80 ° C.,
When the environmental temperature is 0 ° C. or less, the output of the first magnetic sensor is used as the output from the magnetic sensor,
The magnetic sensor according to claim 1, wherein the output of the second magnetic sensing element is an output from the magnetic sensor when the environmental temperature is 80 ° C. or more. The magnetostriction constant of the first magnetic body is more than 0 and not more than 2 × 10 ⁻⁶ ,
The magnetic sensor according to claim 1, wherein a magnetostriction constant of the second magnetic body is −2 × 10 ⁻⁶ or more and less than 0. 4.   The first magnetic body is an Fe-Ni alloy having an Fe content of more than 19.8% by mass and 22.0% by mass or less, and the second magnetic body has an Fe content of 18.0% by mass or more and 19.8% by mass The magnetic sensor according to claim 3, wherein the magnetic sensor is made of less than 5% of Fe-Ni alloy.   The magnetic sensor according to claim 4, wherein the first magnetic body and the second magnetic body are formed of an electroplating film.   The first magnetic sensing element and the second magnetic sensing element each comprise a plurality of magnetoresistance effect elements each having a sensitivity axis in a direction along the short axis direction of the rectangular shape. The magnetic sensor according to any one of the preceding claims.   The magnetic sensor according to any one of claims 1 to 6, further comprising a magnetic balancing coil, wherein the strength of the measured magnetic field is measured based on the current flowing through the magnetic balancing coil.   The magnetic sensor according to claim 7, wherein the magnetic balancing coil is a spiral coil and is located between the magnetoresistive element and the magnetic shield.   A current sensor comprising the magnetic sensor according to any one of claims 1 to 8, wherein the magnetic sensor uses an induced magnetic field of a measured current as the measured magnetic field.