JPWO2013176271A1 - Current sensor - Google Patents

Abstract

A current sensor for measuring a value of a current flowing in a current path includes a flux gate type magnetic element disposed in the vicinity of the current path, a first magnetic plate, and a second magnetic plate, and the first sensor The magnetic plate and the second magnetic plate sandwich the current path and the fluxgate magnetic element in the overlapping direction with the current path and the fluxgate magnetic element, and the first magnetic plate The main surface of the second magnetic plate is parallel to the magnetic sensing direction of the fluxgate magnetic element and the direction in which the current flows.

Description

The present invention relates to a current sensor using a flux gate type magnetic element, and more particularly to a technique suitable for use in a current sensor using a flux gate type magnetic element having a phase-delay method as an operating principle.
This application claims priority on May 24, 2012 based on Japanese Patent Application No. 2012-118967 for which it applied to Japan, and uses the content here.

  In recent years, magnetic elements generated by currents have been used as current sensors to monitor the current during charging / discharging of secondary batteries mounted on hybrid cars and electric vehicles, and to detect large currents generated and supplied by fuel cells, etc. Current sensors that measure the current value by measuring by the above are widely used.

Conventionally, as a current sensor for non-contact measurement of a current (current to be measured) flowing through a wiring (bus bar), a Hall element or a flux gate type magnetic element disclosed in Patent Document 3 is provided in a gap portion of a ring-shaped core having a gap. 2. Description of the Related Art A magnetic proportional current sensor is known in which a magnetoelectric conversion element such as the above is arranged and a bus bar penetrates the center of a ring-shaped core. (Patent Document 1, FIG. 10, etc.)

  On the other hand, in order to reduce the size of the current sensor, there has been proposed a coreless current sensor that detects a magnetic field generated by current by arranging a magnetoelectric conversion element around a bus bar without using a ring-shaped core (Patent Document 1, FIG. 12 etc.). In a current sensor that does not have a ring-shaped core, a Hall element, a magnetoresistive effect (MR) element, a giant magnetoresistive effect (GMR) element, a tunnel magnetoresistive effect element, a fluxgate magnetic element, a magnetoimpedance effect (MI) Magnetic elements such as elements can be used. Among them, the fluxgate type magnetic element is expected to be applied to a current sensor because the element can be miniaturized and can detect a magnetic field with high sensitivity.

  However, since the measurement range of the fluxgate magnetic element depends on the magnetic saturation characteristics of the magnetic core formed inside the magnetic element, it is difficult to measure over a wide range of magnetic field strength. In particular, when a large magnetic field is applied, the magnetic field strength cannot be detected.

  When a current sensor using a magnetic element is used to measure the current flowing into and out of a battery such as a battery, there is a bus bar adjacent to the bus bar to be measured, so the magnetic field generated by the current flowing through the latter bus bar is a magnetic element. And noise when measuring the current of the bus bar to be measured. In order to reduce such magnetic noise, there is generally a structure in which a magnetic shield for shielding inflow of a disturbance magnetic field (noise magnetic field) is provided around the magnetic element and the bus bar. Examples of this include the magnetic shield body 65 of Patent Document 1 and the shield 24 of Patent Document 2.

Japanese Unexamined Patent Publication No. 2010-014477 Japanese Unexamined Patent Publication No. 2009-150654 Japanese Patent No. 4774472

However, as in Patent Documents 1 and 2, when magnetic shields are provided on the four surfaces excluding the bus bar longitudinal direction, a disturbance magnetic field can be prevented, but the magnetic shield is generated by the magnetic field generated by the current flowing through the bus bar. There is a demerit that the magnetic flux density inside becomes saturated. As a result, the magnetic flux density distribution in the shield is disturbed, and the relationship between the current flowing through the bus bar and the magnetic flux density of the magnetic sensor unit is not linear, that is, the linearity of the current flowing through the bus bar and the output value of the current sensor is deteriorated. The problem arises.
Furthermore, in the examples of Patent Documents 1 and 2, magnetic shields are provided on the four surfaces excluding the bus bar longitudinal direction as described above, so that it is not suitable for miniaturization, and the assembly process is not easy because the structure is complicated.

  In addition, a magnetic element using a magnetic core such as the fluxgate type magnetic element disclosed in Patent Document 3 is a magnetic core formed inside a magnetic element by a large magnetic field generated when a large current is passed through a bus bar. Has a problem that it cannot be measured when it is magnetically saturated. Therefore, the flux gate type magnetic element is not suitable for measuring a large current. In order to solve this problem, the current value to be applied to the exciting coil provided in the magnetic element is increased, or the feedback coil is provided to adjust the magnetic flux density in the magnetic core by applying a feedback current. The magnetic field can be measurable. However, these methods cause a problem that the current consumption of the current sensor increases.

  In view of the above problems, the present invention provides a current sensor that can measure a large current in a current sensor using a fluxgate magnetic element, and that can reduce the influence of a disturbance magnetic field and reduce a measurement error. The purpose is to provide.

  A current sensor according to a first aspect of the present invention is a current sensor that measures a value of a current flowing in a current path, and includes a flux gate type magnetic element disposed in the vicinity of the current path, a first magnetic plate, A second magnetic body plate, wherein the first magnetic body plate and the second magnetic body plate are in the direction of overlap with the current path and the flux gate type magnetic element. The main surfaces of the first magnetic plate and the second magnetic plate are parallel to the magnetic sensing direction of the fluxgate magnetic device and the current flow direction.

According to the current sensor according to the above aspect, the flux gate type magnetic element has a magnetic sensing direction orthogonal to the flow direction of the current flowing through the current path, and includes the first magnetic plate and the second magnetic plate. The current path viewed in the normal direction and the flux gate type magnetic element are arranged at positions where they overlap each other, and the first magnetic plate and the second magnetic plate are arranged in parallel to each other. The disturbance magnetic field applied in the width direction of the current path, which is the measurement direction defined as the plane direction of the main surface of the magnetic plate and the second magnetic plate, the direction of the magnetic field created by the current flowing through the current path, Attracted to the first magnetic plate and the second magnetic plate. Therefore, it is possible to reduce the flow into the flux gate type magnetic element.
At the same time, by not providing magnetic shields on both sides of the current path in the width direction of the current path, the magnetic flux density in the magnetic plate is saturated by the magnetic field generated by the current flowing in the current path, disturbing the magnetic flux density distribution and It is possible to prevent the linearity as a sensor from being disturbed.

  A separation distance between the first magnetic plate and the second magnetic plate may be smaller than a width of the first magnetic plate and the second magnetic plate in the magnetosensitive direction.

  According to the current sensor of the above aspect, the disturbance magnetic field parallel to the magnetic sensing direction of the fluxgate type magnetic element is more effectively attracted toward the first magnetic plate and the second magnetic plate. Therefore, it is possible to more effectively suppress the disturbance magnetic field from flowing into the fluxgate type magnetic element.

The fluxgate magnetic element may be formed by laminating a third magnetic plate.
The first magnetic plate and the second magnetic plate may be arranged so as to cover the third magnetic plate.
The fluxgate magnetic element may be disposed in a region sandwiched between the current path and the third magnetic plate in the overlapping direction of the first magnetic plate and the second magnetic plate. Good.
The third magnetic plate may be arranged at a position away from the current path, that is, on the first magnetic plate side.

  According to the current sensor of the present invention, it is possible to provide a current sensor that can measure a large current and reduce the measurement error by reducing the influence of a disturbance magnetic field.

FIG. 1 is a schematic cross-sectional view showing a first embodiment of a current sensor according to the present invention. FIG. 2 is a schematic diagram showing a fluxgate type magnetic element in the first embodiment of the current sensor according to the present invention. FIG. 3 is a graph showing the operating principle of the fluxgate type magnetic element in the first embodiment of the current sensor according to the present invention. FIG. 4 is a hysteresis curve showing a change with time of the magnetization state of the magnetic core of the fluxgate type magnetic element in the first embodiment of the current sensor according to the present invention. FIG. 5 is a top view schematically showing the fluxgate type magnetic element in the first embodiment of the current sensor according to the present invention. 6 is a cross-sectional view taken along line a-a 'in FIG. FIG. 7 is a cross-sectional view taken along line b-b ′ in FIG. 5 and is a front cross-sectional view showing a fluxgate type magnetic element. FIG. 8 is a top view showing another example of the fluxgate type magnetic element in the first embodiment of the current sensor according to the present invention. FIG. 9 is an exploded perspective view showing an example in which the current sensor according to the present invention is mounted on the current path in the first embodiment. FIG. 10 is a simulation result showing a magnetic field state in the current sensor according to the present invention. FIG. 11 is a simulation result showing a magnetic field state inside a magnetic shield having a side. FIG. 12 is a simulation result showing a magnetic field state inside a magnetic shield having a side. FIG. 13A is a hysteresis curve showing the influence of the magnetic core magnetization state depending on the presence or absence of saturation in the magnetic shield. FIG. 13B is a hysteresis curve showing the influence of the magnetic core magnetization state depending on the presence or absence of saturation in the magnetic shield. FIG. 14 is a cross-sectional view showing another example of the current sensor according to the first embodiment of the present invention. FIG. 15 is a cross-sectional view showing another example of the current sensor according to the first embodiment of the present invention. FIG. 16 is a cross-sectional view showing another example of the current sensor according to the first embodiment of the present invention. FIG. 17 is a schematic cross-sectional view showing a second embodiment of the current sensor according to the present invention. FIG. 18 is a schematic cross-sectional view showing a third embodiment of the current sensor according to the present invention. FIG. 19 is a top view showing a third embodiment of the current sensor according to the present invention. FIG. 20 is a schematic cross-sectional view showing a fourth embodiment of the current sensor according to the present invention. FIG. 21 is a schematic cross-sectional view showing a fifth embodiment of the current sensor according to the present invention. FIG. 22 is a schematic cross-sectional view showing a sixth embodiment of the current sensor according to the present invention. FIG. 23 is a schematic cross-sectional view showing a seventh embodiment of the current sensor according to the present invention. FIG. 24 is a top view showing a seventh embodiment of the current sensor according to the present invention. FIG. 25 is a simulation result showing the magnetic field state inside the magnetic shield in the seventh embodiment of the current sensor according to the present invention. FIG. 26 is a simulation result showing a magnetic field state inside the magnetic shield in the current sensor. FIG. 27 is a cross-sectional view showing another example of the embodiment of the current sensor according to the present invention. FIG. 28 is a graph showing an experimental example of the current sensor according to the present invention. FIG. 29 is a graph showing an experimental example of the current sensor according to the present invention. FIG. 30 is a graph showing an experimental example of the current sensor according to the present invention. FIG. 31 is a graph showing an experimental example of the current sensor according to the present invention. FIG. 32 is a graph showing an experimental example of the current sensor according to the present invention. FIG. 33A is a schematic cross-sectional view for explaining another example of the current sensor according to the first embodiment of the present invention. FIG. 33B is a schematic cross-sectional view for explaining another example of the current sensor according to the first embodiment of the present invention. FIG. 34 shows a magnetic flux density flowing into the magnetic element with respect to a change in the z-direction distance between the magnetic shield and the magnetic sensor in the current sensor of FIG. 33A, with a third magnetic plate, without a third magnetic plate, It is the graph which showed the demagnetizing factor. FIG. 35 is a schematic diagram showing a state of a residual magnetic field when a current is passed through the bus bar and when the current is interrupted in the current sensor of FIGS. 33A and 33B. FIG. 36 shows the magnetic flux density when the magnetic element arrangement is changed with respect to the third magnetic plate arranged in the center of the magnetic shield and the bus bar in the z direction in the current sensor of FIGS. 33A and 33B. It is a graph. FIG. 37 is a graph showing the magnetic field strength flowing into the magnetic element due to the magnetic flux density in the third magnetic plate and the residual magnetic field when the z-direction position of the magnetic element with respect to the magnetic shield is changed. FIG. 38A is a graph showing a change in magnetic flux density flowing into the magnetic element, and a graph showing a change with respect to the installation position of the magnetic element in the z direction. FIG. 38B is a graph showing a change in magnetic flux density flowing into the magnetic element, and a graph showing a change with respect to the installation position of the magnetic element in the CM direction. FIG. 39A is a schematic cross-sectional view showing the influence of the disturbance magnetic field Hexd in the z direction, and shows a state in which there is no third magnetic plate without inclination. FIG. 39B is a schematic cross-sectional view showing the influence of the disturbance magnetic field Hexd in the z direction, and shows a state in which there is no third magnetic plate tilt. FIG. 39C is a schematic cross-sectional view showing the influence of the disturbance magnetic field Hexd in the z direction, and shows a state in which there is a third magnetic body plate and an inclination. FIG. 40 is a schematic cross-sectional view showing an eighth embodiment of the current sensor according to the present invention. FIG. 41 is a schematic cross-sectional view showing the stacking order and assembly arrangement in the eighth embodiment of the current sensor according to the present invention. FIG. 42 is a graph showing the relationship between the measured current and the output error in the current sensor. FIG. 43 is a graph showing the relationship between the measured current and the output error in the current sensor. FIG. 44 is a graph showing the relationship between the direction of the disturbance magnetic field and the sensor magnetosensitive direction component of the magnetic flux density in the magnetic sensor. FIG. 45 is a graph showing the relationship between the direction of the disturbance magnetic field and the sensor magnetosensitive direction component of the magnetic flux density in the magnetic sensor. FIG. 46 is a schematic cross-sectional view showing the internal arrangement of the magnetic sensor in the experimental example of the current sensor according to the present invention. FIG. 47 is a graph showing the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. FIG. 48 shows, as an output error, a percentage of the output full-scale voltage as a difference between an approximate line obtained by least-square approximation of the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention and the measured value. It is a graph. FIG. 49 is a graph showing the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. FIG. 50 shows, as an output error, a percentage of an output full-scale voltage as a difference between an approximate straight line obtained by least-square approximation of the relationship between a measured current of a sample and an output voltage in an experimental example of a current sensor according to the present invention. It is a graph. FIG. 51 is a graph showing the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. FIG. 52 shows, as an output error, a percentage of the output full-scale voltage as a difference between an approximate straight line obtained by least-square approximation of the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. It is a graph. FIG. 53 is a graph showing the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. FIG. 54 shows, as an output error, a percentage of the output full-scale voltage as a difference between an approximate line obtained by least-square approximation of the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention and the measured value. It is a graph. FIG. 55 is a graph showing the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. FIG. 56 shows, as an output error, a percentage of the output full-scale voltage as a difference between an approximate straight line obtained by least-square approximation of the relationship between the measured current of the sample and the output voltage in the experimental example of the current sensor according to the present invention. It is a graph.

Hereinafter, a first embodiment of a current sensor according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a current sensor according to the present embodiment. In the figure, reference numeral CS10 denotes a current sensor.

The current sensor CS10 of the present embodiment detects a current to be measured flowing in a current path (hereinafter referred to as a bus bar) by a magnetic field generated by the current to be measured by a flux gate type magnetic element (hereinafter simply referred to as a magnetic element). It shall be measured by As shown in FIG. 1, a magnetic element M12 is arranged in the vicinity of the bus bar BO, and the magnetic element M12 has a magnetic sensing direction CM parallel to the magnetic field generated by the current I to be measured flowing through the bus bar B0.
Then, the bus bar B0 and the magnetic element M12 are sandwiched between them, and the flat plate shape is provided so as to face along the flow direction of the current I to be measured (direction in which the current path extends) and the magnetic sensing direction CM of the magnetic element M12. The first magnetic plate CM1 and the second magnetic plate CM2 made of the above magnetic bodies are provided.

  The bus bar B0 is such that a large current of several hundreds A or more flows through an electric vehicle, a household power source, etc., has a rectangular cross section, and extends linearly in a direction perpendicular to the paper surface.

The first magnetic plate CM1 and the second magnetic plate CM2 are plate bodies made of two magnetic bodies parallel to each other, and both are arranged in parallel with the bus bar B0. The first magnetic plate CM1 and the second magnetic plate CM2 are made of a material having a relative permeability of 10,000 or more, although permalloy, ferrite, or the like is used. As a result, the disturbance magnetic field can be sufficiently attracted to accurately measure the magnetic field to be measured.
The magnetic element M12 is disposed in a space sandwiched between the first magnetic plate CM1 and the bus bar B0 at the center (center) position in the width direction of the first magnetic plate CM1 and the second magnetic plate CM2. The magnetic element M12 is disposed in a region overlapping the first magnetic plate CM1 and the second magnetic plate CM2, and the magnetic sensitive direction CM is in a direction orthogonal to the flow direction of the current I to be measured. Placed in. Further, the magnetic sensing direction CM of the magnetic element M12 is arranged so as to be parallel to the main surfaces of the first magnetic plate CM1 and the second magnetic plate CM2.
In the following description, the first magnetic plate CM1 and the second magnetic plate CM2 are referred to as magnetic shield CM1 and magnetic shield CM2. Or, simply called a magnetic shield.

  These magnetic shields CM1 and CM2 transmit a disturbance magnetic field such as a magnetic field generated from a bus bar not to be measured to the magnetic shields CM1 and CM2 even when another magnetic field generation source exists in addition to the bus bar B0 to be measured. The shape, size, and arrangement are set so as to reduce the disturbance magnetic field reaching the magnetic element M12.

As shown in FIG. 1, the width dimension CMbc of the bus bar B0, the width dimension CM1c of the magnetic shield CM1, and the width dimension CM2c of the magnetic shield CM2 are set substantially equal to each other. The larger the ratio (CM1c / CMb) between the width dimension CM1c of the magnetic shield CM1 and the separation distance CMb between the magnetic shield CM1 and the magnetic shield CM2, the better. That is, as the width CM1c of the magnetic shield CM1 and the magnetic shield CM2 is larger than the distance CMb between the magnetic shield CM1 and the magnetic shield CM2, the disturbance magnetic field is attracted to the magnetic shield CM1 and the magnetic shield CM2, and the disturbance magnetic field is generated. The flow into the magnetic element M12 can be suppressed. As described above, the separation distance CMb between the magnetic shield CM1 and the magnetic shield CM2 is sufficiently smaller than the dimension CM1c in the width direction of the magnetic shield CM1 and the magnetic shield CM2, so that the magnetic shield is not provided on both sides of the bus bar B0. Even if it exists, it becomes possible to reduce that the disturbance magnetic field of the magnetosensitive direction CM direction flows into the magnetic element M12.
The magnetic shield CM1 and the magnetic shield CM2 in the present invention are members for reducing the disturbance magnetic field applied to the magnetic element by attracting the disturbance magnetic field. The magnetic shield for shielding a disturbance magnetic field described in the prior art document has a different function.

As shown in FIG. 1, the width dimension CMd of the magnetic element M12 is sufficiently large so as not to be affected by the disturbance magnetic field with respect to the dimensions CM1c and CM2c in the width direction (magnetic sensing direction) of the magnetic shield CM1 and the magnetic shield CM2. Set to be smaller. Preferably, CMd / CM1c is set to about 0.01 to 0.4.
The magnetic element M12 is disposed on the magnetic shield CM1 side when viewed from the bus bar B0 in the thickness direction of the magnetic shield CM1 and the magnetic shield CM2. As the magnetic field to be measured flowing into the magnetic element M12 (the magnetic field generated by the current flowing through the bus bar) decreases from the bus bar B0 toward the magnetic shield CM1, that is, away from the bus bar B0, the magnetic element M12 has an appropriate magnetic field to be measured. The position is set so as to obtain a proper strength. In the present invention, the separation distance (CMe) between the bus bar B0 and the magnetic shield CM1 is configured to be larger than the separation distance (CMg) between the bus bar BO and the magnetic shield CM2.

  The magnetic element M12 is a flux gate type magnetic element, and includes a magnetic core 1 made of a soft magnetic material, an excitation coil 9, and a detection coil 10, as shown in FIG. Furthermore, a feedback coil 21 may be provided. The magnetic element M12 is connected to a control integrated circuit (signal processing circuit) MT10. The control integrated circuit MT10 has a function of supplying a drive signal to the magnetic element M12 and a function of processing an output signal from the magnetic element M12. Below, the case where the magnetic element M12 is provided with the feedback coil 21 (it describes with FB coil in FIG. 2) is demonstrated.

  The control integrated circuit MT10 supplies an excitation current having a continuous waveform such as a triangular wave to the excitation coil 9, outputs a feedback current to the feedback coil 21 by an output signal from the detection coil 10, and measures the strength of the measurement magnetic field. Is output.

An operation principle of the flux gate type magnetic element M12 and the like in the current sensor CS10 of the present embodiment will be described.
FIG. 3 is a graph showing the operating principle of the fluxgate magnetic element. FIG. 3A is a graph showing the change over time of the triangular wave current flowing through the exciting coil. FIG. 3B is a graph showing the time change of the magnetization state of the core. FIG. 3C is a graph showing the time change of the output voltage generated in the pickup coil. FIG. 4 is a hysteresis curve showing a change with time of the magnetization state of the magnetic core of the fluxgate type magnetic element M12.

When a triangular wave current as shown in FIG. 3A is applied to the exciting coil 9 from the exciting current generating circuit MT11, the magnetic core 1 is excited by the magnetic field Hexc formed by the exciting coil 9, and the magnetic flux density inside the magnetic core 1 is increased. B, that is, the magnetization state of the magnetic core 1 has a saturation characteristic as shown in FIG. 4, and therefore changes with time as shown in FIG. The pickup coil (detection coil) 10 has a cross-sectional area S of the magnetic core 1 and a number N of turns of the pickup coil 10 in the region where the time differentiation of the magnetic flux density B of the magnetic core 1, that is, the time change dB / dt exists. A proportional output voltage Vpu = NS × dB / dt is generated. The output voltage Vpu of the pickup coil 10 changes with time as shown in FIG. The higher the time change dB / dt of the magnetic flux density B of the magnetic core 1, the higher the high value of the pickup voltage wave, the narrower the pulse width, and the steeper pulse voltage. The time interval t1 in FIG. 3C includes an external magnetic field (magnetic field to be measured) Hext, a deviation Hc of the magnetic field strength H between when the magnetic flux density B of the magnetic core 1 increases and when it decreases, and the exciting coil 9 (1) using the magnetic field Hexc, the period T of the triangular wave, and the delay time Td due to the inductance of the coil.

Similarly, the time interval t2 in FIG. 3C is expressed as shown in Equation (2).
From Expression (1) and Expression (2), the change t2-t1 of the time interval with respect to the external magnetic field is expressed as Expression (3).

  From equation (3), it can be seen that the change t2-t1 of the time interval with respect to the external magnetic field depends on the ratio Hext / Hexc between the external magnetic field Hext and the magnetic field Hexc formed by the exciting coil 9 and the period T of the triangular wave. The sensitivity S to the external magnetic field S = d (t2−t1) / dHext is obtained by using the current amplitude Iexc flowing through the exciting coil 9, the generated magnetic field per unit current flowing through the exciting coil 9, that is, the excitation efficiency α, and the period T of the triangular wave. , S = T / (2 · Iexc × α). Therefore, the sensitivity S of the magnetic element M12 decreases as the excitation current increases. The sensitivity S of the magnetic element increases as the period T of the triangular wave increases, that is, as the excitation frequency fexc decreases.

The excitation efficiency α is a value determined by the number of turns of the magnetic core 1 and the coil constituting the fluxgate magnetic element. As the excitation efficiency α increases, the fluxgate magnetic element can be driven with a smaller current when the same sensitivity and the same range are to be passed. In Expression (3), Expression (3) becomes 0 when Hext = Hexc, and Hext at this time becomes the upper limit of the measurement magnetic field range. Since it is expressed by Hexc = α × Iexc, the larger the excitation efficiency α, the wider the measurement magnetic field range when driven by the same current.
The excitation efficiency α indicates the ratio between the magnetic flux density generated in the magnetic core 1 and the magnetic flux density generated in the magnetic core 1 due to an external magnetic field when a current is passed through the excitation coil 9. The excitation efficiency α is the slope dB / dHext of the magnetic density B in the non-saturated region of the hysteresis curve of the magnetic core 1 with respect to the external magnetic field Hext, and the slope dB of the current Iexc flowing through the excitation coil with the magnetic flux density B of the magnetic core 1. It is determined by the ratio of / dIexc and is represented by the formula (4).

From this equation (4), in order to increase the excitation efficiency, the denominator of this equation (4) is decreased or the numerator is increased.
In order to increase the numerator of formula (4), that is, to increase the magnetic flux density generated in the magnetic core 1 by the exciting current, it is effective to increase the number of turns of the coil. In the case of a fluxgate type magnetic element, in order to increase the number of coil turns, it is necessary to narrow the wiring pitch and increase the number of turns, but due to the limit of miniaturization of wiring, increase in coil resistance due to miniaturization, etc. It is difficult to secure the number of coil turns in a necessary state. Although a method of winding the coil as a multilayer structure is also conceivable, the structure becomes very complicated, and it is necessary to maintain manufacturing accuracy when manufacturing the sensor by multilayer film formation, which increases the manufacturing cost. It is not preferable.

  Further, in such a fluxgate type magnetic element, a linearity error occurs due to the distortion of the exciting triangular wave and the non-linearity of the BH curve of the magnetic core 1. The flux gate type magnetic element is provided with a feedback coil to compensate for this linearity error. Then, a current is passed through the feedback coil so that the magnetization state in the magnetic core 1 is always the same as when no external magnetic field is applied. Thus, by outputting a feedback current that changes in response to a change in the external magnetic field, a fluxgate type magnetic element with reduced linearity error can be realized.

  As a result, the feedback coil 21 generates a feedback magnetic field Hfb having a magnitude in such a direction as to cancel the external magnetic field Hext, thereby canceling the magnetic field in the magnetic core 1, and the feedback magnetic field Hfb changes in the external magnetic field Hext. Correspondingly continuously fluctuates.

In addition, although the feedback current was output according to the external magnetic field Hext, this feedback current can be sent not only to the feedback coil 21 but also to the exciting coil 9. In this case, it can be realized by superimposing a feedback current on the exciting AC current or the detection signal.
Furthermore, when a feedback current is passed through the exciting coil 9, the feedback coil 21 can also be used as the exciting coil 9 and the detection coil 10, and as shown in FIG.

  Next, the magnetic element M12 will be described.

  The magnetic element M12 of this embodiment is, for example, a flux gate type magnetic element whose operation principle is a phase-delay method. The longitudinal direction of the magnetic core 1 of the magnetic element M12 coincides with the magnetic sensitive direction of the magnetic element M12.

  FIG. 5 is a top view schematically showing the fluxgate magnetic element according to this embodiment. 6 is a cross-sectional view taken along line a-a 'in FIG. FIG. 7 is a front sectional view taken along line b-b ′ in FIG. 5.

As shown in FIGS. 5 to 7, the flux gate type magnetic element M <b> 12 according to the present embodiment includes a magnetic core 1, an excitation coil 9, a detection coil 10, and a feedback coil 21 wound around the magnetic core 1. It has the 1st wiring layer 4 and the 2nd wiring layer 7 which comprise. Each coil is a solenoidal coil.
The excitation coil 9, the detection coil 10, and the feedback coil 21 are wound as a triple helix so that their wirings are substantially parallel.

  As shown in FIGS. 5 to 7, the flux gate type magnetic element M <b> 12 includes a first wiring layer 4 for forming a lower wiring of the solenoid coil on the nonmagnetic substrate M <b> 13, and a top of the first wiring layer 4. A first insulating layer 5 that insulates the magnetic core 1 and the solenoid coil and has an opening 8 in a portion where the first wiring layer 4 and the second wiring layer 7 are connected to each other; A magnetic core 1 made of a soft magnetic film is formed thereon, and a second insulating layer 6 is formed on the magnetic core 1 by providing an opening 8 at a connection portion between the first wiring layer 4 and the second wiring layer 7. And a second wiring layer 7 serving as an upper wiring of a solenoid coil formed so as to connect adjacent wirings of the first wiring layer 4 at the end portion on the second insulating layer 6. The solenoid coil is formed. Since the wiring is connected to every two adjacent wirings, the loop of the solenoid coil in the cross section is not closed.

The exciting coil 9, the detection coil 10, and the feedback coil 21 formed by the first wiring layer 4 and the second wiring layer 7 are all wound independently in the magnetic core 1. Electrode pads 11 for connection to the outside are formed at both ends of the detection coil 10. Electrode pads 12 for connecting to the outside are formed at both ends of the exciting coil 9. Electrode pads 13 for connecting to the outside are formed at both ends of the feedback coil 21. The electrode pad 11 is connected to a terminal to the sense amplifier MT12, the electrode pad 12 is connected to a terminal to the excitation current generating circuit MT11, and the electrode pad 13 is connected to a terminal to the current amplifier MT15.
Here, the excitation coil 9, the detection coil 10, and the feedback coil 21 can all have the same number of turns. In particular, the feedback coil 21 is wound over the entire length of the magnetic core 1 so that the pitch is uniform.
These drawings are schematically shown, and a part of each coil is omitted. The detailed shape of the magnetic element M12 is not limited to the shape shown in the figure.

  The magnetic core 1 is excited by energizing an exciting coil 9 wound around the magnetic core 1. When the magnetic core 1 is excited, an induction voltage is generated in the detection coil. The magnetic core 1 is AC-excited by energizing the exciting coil 9 through the electrode pad 12 from the outside, and the magnetic core 1 is AC-excited. Will occur. This induced voltage is output from the detection coil 10 through the electrode pad 11 to the control integrated circuit MT10. Then, as described above, a feedback current is applied to the feedback coil 21 via the electrode pad 13.

  What is shown in the present embodiment is an example, and the arrangement of the magnetic core 1, the excitation coil 9, the detection coil 10, and the feedback coil 21 is not limited to the above-described configuration, and may be other arrangements. . In particular, the excitation coil 9, the detection coil 10, and the feedback coil 21 can be arranged other than the triple helix.

The current sensor CS10 of this embodiment can be an example of a structure used for a current sensor for measuring a current flowing through the bus bar B0.
As shown in FIG. 9, the current sensor CS10 includes a mounting board M10a on which the magnetic element M12 and the control integrated circuit MT10 are mounted, two magnetic shields CM1 and CM2, and a bus bar B01 (current path). Is united. For example, a package body or a module body in which these are molded with an insulating resin may be used.

As shown in FIG. 9, the bus bar B01 is provided with coupling holes B02 at both ends thereof, and the coupling hole B02 is coupled with a coupling hole B03 provided in the corresponding bus bar B00 (current path) with a bolt nut or the like. By coupling by means B04 and B05, the bus bar B01 may also be integrated so as to be included in the current sensor CM10. With this configuration, it is possible to suppress misalignment of each component.
A glass epoxy substrate or the like can be used as the mounting substrate M10a.
The bus bar B0 and the magnetic shield CM2, and the mounting substrate M10a and the magnetic shield CM1 are joined by an adhesive or the like, and the entire current sensor CS10 is covered with a cap or the like of a resin molded product. .

In the current sensor CS10 of the present embodiment, as shown in FIG. 10, the bus bar B0 and the magnetic element M12 are only sandwiched between the magnetic shields CM1 and CM2, and there are magnetic fields on both sides of the bus bar B0. There is no shield. As a result, the magnetic circuit has a partially open structure with respect to the magnetic field generated by the current I to be measured flowing through the bus bar B0, so that the magnetic resistance increases, and accordingly, the magnetic flux density generated in the magnetic shield decreases. For this reason, the magnetic shield is less likely to be magnetically saturated.
On the other hand, in the structure in which the magnetic plates are arranged on both sides of the bus bar (for example, the magnetic shield body 65 of Patent Document 1 and the shield 24 of Patent Document 2), the measured current I flowing in the bus bar B0 by the magnetic shield CM3. Since the magnetic circuit has a closed structure with respect to the magnetic field generated by the magnetic shield, the magnetic resistance decreases as shown in FIG. 11, and the magnetic flux density generated in the magnetic shield increases accordingly. Saturates easily.

Further, when the magnetic shield CM1, magnetic shield CM2, and magnetic shield CM4 on both sides of the bus bar are integrated, the magnetic saturation of the magnetic shield CM4 becomes more remarkable as shown in FIG. When the magnetic shield is magnetically saturated, it becomes impossible to attract magnetism.
Thus, before and after the magnetic shield is saturated, as shown in FIG. 13B, the magnetic field flowing into the magnetic element M10 changes sharply. As a result, in the region away from the zero point, the current value flowing through the bus bar The magnetic field flowing into the magnetic element M10 is not linear, that is, the linearity of the current value flowing through the bus bar and the output value of the magnetic sensor is disturbed.
On the other hand, when only the magnetic shields CM1 and CM2 whose sides are open as shown in FIG. 10, the magnetic element M10 can maintain linearity as shown in FIG. 13A.

  In the present embodiment, the magnetic sensing direction component of the disturbance magnetic field can be reduced by making the distance CMb between the magnetic shields CM1 and CM2 sufficiently smaller than the width of the magnetic shield CM1 and the magnetic shield CM2. Therefore, the disturbance magnetic field Hexd flowing into the magnetic element M12 can be eliminated, and only the measured magnetic field generated by the current flowing through the bus bar B0 can be accurately detected.

  In the present embodiment, the installation of the magnetic shields CM1 and CM2 is effective even when there is another magnetic field generation source other than the bus bar B0 to be measured. Specifically, as shown in FIG. 35 to be described later, the magnetic field generated from the bus bar that is not the measurement target is attracted to the magnetic shields CM1 and CM2, and the disturbance magnetic field reaching the magnetic element M12 is reduced. Thereby, a measurement error can be significantly reduced compared with the case where there is no magnetic shield CM1 and CM2.

Furthermore, in the current sensor according to the present embodiment, the magnetic element M12 may include a third magnetic plate (demagnetizing body) M11.
14 and 15 are front sectional views showing other examples of the current sensor according to the present embodiment. In the figures, reference numerals M10 and 10 'denote magnetic sensors. In the figure, the magnetic shield CM2 is omitted. In addition, the same reference numerals are given to the components corresponding to the configuration of the above embodiment, and the description thereof is omitted.

  In the current sensor according to the present embodiment, the magnetic element M12 is provided as the magnetic sensor M10. As shown in FIG. 14, the magnetic sensor M10 is a magnetic element formed by a process of laminating a thin film on the nonmagnetic substrate M13. An element M12, a third magnetic plate (demagnetization body) M11 made of a chip-like soft magnetic material joined to the nonmagnetic substrate M13, a lead frame M14 connected to the magnetic element M12 by a bonding wire M15, and these Is formed from a mold body M10b. The magnetic element M12 is formed by laminating on a plate-like demagnetizing body (chip-shaped soft magnetic body) M11. The magnetic sensing direction of the magnetic sensor M10 is parallel to the main surface of the nonmagnetic substrate M13.

For example, on the bus bar B0 side (back side) of the nonmagnetic substrate M13 made of silicon or the like, as shown in FIG. 14, for example, a metallic soft magnetic material such as NiFe, a bulk material made of ferrite or the like such as Co-based amorphous material, etc. Further, a demagnetizing body M11 that is a sheet-like soft magnetic chip is provided so as to cover a wider area than the magnetic element M12.
The external magnetic field Hext flowing into the magnetic element M12 is reduced by attracting the magnetic field to be measured to the demagnetizing body M11 provided at a position separated from the magnetic core 1. Due to the demagnetizing effect of the demagnetizing body M11, the external magnetic field Hext applied to the magnetic element M12 can be reduced.

  In this example, the bus bar B0, the demagnetizer M11, the magnetic element M12 (magnetic core 1), and the magnetic shield CM1 are arranged in this order in the z direction in FIG. Furthermore, as shown in FIG. 15, the demagnetizing body M11 can be a magnetic sensor M10 'positioned on the magnetic shield CM1 side.

  In addition, as shown in FIG. 16, a demagnetizing body (fourth magnetic plate) M21 is provided on the magnetic shield CM1 side of the magnetic element M12 via a spacer M23 and packaged by a package M20a. A magnetic sensor M10 "in which a demagnetizing body M11 and a demagnetizing body M21 are arranged on both sides may be used.

  The current sensor according to the present invention includes two substantially flat magnetic shields that sandwich the bus bar and the magnetic element, and when the gap between the magnetic shields is sufficiently smaller than the dimension in the magnetic shield width direction, The magnetic shield is formed only on the surface, but by shortening the magnetic shield interval, the magnetic shield side wall extending at the end of the bus bar width direction and extending in the bus bar thickness direction or the magnetic shield is formed. Without providing a magnetic shield side that is located at the end of the current direction and extends in the bus bar thickness direction, it is possible to suppress the disturbance magnetic field that is an error factor of the current sensor output from flowing into the magnetic element and affecting the measurement. .

  In the current sensor of the present invention, when the magnetic element M12 is a fluxgate type magnetic element, the magnetic field element sensitivity is weak for a magnetic field component having an angle deviated from the set magnetic sensitive direction. By disposing the magnetic element M12 in the vicinity of the center of the first and second magnetic plates, the disturbance magnetic field flowing into the magnetic element is reduced, and only components other than the magnetosensitive direction flow into the magnetic element M12. Furthermore, even if a disturbance magnetic field reaches the magnetic element, the magnetic field can be prevented from detecting the disturbance magnetic field. As a result, only the magnetic field to be measured generated by the current flowing through the bus bar can be accurately detected.

  In the present invention, when the dimension in the bus bar width direction of the magnetic shield is set equal to the dimension in the bus bar width direction, the disturbance magnetic field can be shielded and miniaturized at the same time.

  According to the current sensor of the present invention, the magnetic shield can suppress the measurement error due to the disturbance magnetic field, and can be downsized to improve the measurement accuracy. Furthermore, it is possible to adjust the magnetic field strength to the sensor element generated from the bus bar by adjusting the arrangement shape of the magnetic shield and the like. This is usually very effective when there is a magnetic material in the magnetic element that causes magnetic saturation of the magnetic core when a large magnetic field such as a fluxgate type magnetic element is applied. Therefore, it is effective for a current sensor using a magnetic element in which the measurement range (measurement range) is limited due to magnetic saturation of the magnetic core.

  Next, as shown in FIG. 33A, a structure in which the magnetic shield CM2, the bus bar B0, the magnetic element M12, the demagnetizer M11, and the magnetic shield CM1 are sequentially arranged in the z direction will be described.

  First, FIG. 34 shows a reduced state of magnetic flux flowing into the magnetic element M12 by the demagnetizing body M11. In the figure, the vertical axis corresponds to the magnetic flux density flowing into the magnetic element M12, and the horizontal axis corresponds to the distance dimension CMa shown in FIG. 1, and the magnetic shield CM1 and the magnetic sensor M10 ′ on which the magnetic element M12 is mounted. The separation distance. In FIG. 34, a hollow square indicates a demagnetizing factor, a black rhombus indicates no demagnetizing member, and a black triangle indicates a demagnetizing factor represented by a ratio of these demagnetizing member / no demagnetizing member.

In the magnetic sensor M10 ′, as shown in FIG. 34, by providing the demagnetizing body M11, the magnetic field intensity flowing into the magnetic element M12 is reduced to about ½ to ¼. Thereby, the intensity of the magnetic field flowing into the magnetic element M12 can be reduced.
At the same time, when there is no demagnetizing body M11, a large gradient is generated in the magnetic field intensity distribution in the z direction from the bus bar B0 to the magnetic shield CM1, but this gradient is relaxed by the third magnetic plate M11, and the magnetic sensor M10 ' The position range that can be mounted can be increased.

  As shown in FIG. 33A, the demagnetizing body M11 and the magnetic element M12 are arranged such that the magnetic element M12 is on the bus bar B0 side with respect to the demagnetizing body M11, that is, the demagnetizing body M11 is magnetic with respect to the magnetic element M12. The arrangement of the magnetic sensor M10 ′ on the shield CM1 side is preferable. The reason for this will be described below.

FIG. 35 is a schematic diagram showing a state of a residual magnetic field when a current is passed through the bus bar and when the current is interrupted in a structure having a demagnetizing body. FIG. 36 shows the relationship between the distance from the demagnetizing body of the magnetic element M12 and the magnetic flux density applied to the magnetic element M12 when the demagnetizing body is arranged at a position equidistant from the magnetic shield and the bus bar. It is. In FIG. 36, (a) data indicated by diamonds is in the order of arrangement of the demagnetizing body M11, magnetic element M12, and bus bar B0 shown in FIG. 33A, and (b) data indicated by black squares is shown in FIG. 33B. In this order, the magnetic element M12, the demagnetizing body M11, and the bus bar B0 are arranged.
In the case of a current flowing through the bus bar B0 from the back side to the front side of the paper, a counterclockwise induction magnetic field is generated as shown on the left side of FIG.
Next, when this current is cut off, as shown on the right side of FIG. 35, the magnetic shield CM1 and the demagnetizing body M11 generate a residual magnetic field in the same direction (rightward), and the magnetic shield CM2 has a residual direction in the reverse direction (leftward). Generates a magnetic field.
As shown on the right side of FIG. 35, the influence of the residual magnetic field is intensified between the magnetic shield CM1 and the demagnetizing body M11. Compared with this, the influence of the residual magnetic field is not so great between the bus bar B0 and the demagnetizing body M11.

As shown in FIG. 33B, when the magnetic element M12 is disposed at a position between the magnetic shield CM1 and the demagnetizing body M11, the residual magnetic fields of the magnetic shield CM1 and the demagnetizing body M11 are in a direction of strengthening each other at the position of the magnetic element M12. . For this reason, a hysteresis error due to the residual magnetic field is greatly generated. In addition, in this sensor arrangement, the magnetic element M12 is sandwiched between the magnetic shield CM1 and the demagnetizing body M11. Therefore, as shown as data (b) in FIG. 36, the magnetic field generated by the current I flowing through the bus bar B0 is difficult to flow into the magnetic element M12. As a result, the demagnetization effect for the purpose of expanding the measurement range is enhanced, but the influence of the residual magnetic field is prominent.

  On the other hand, as shown in FIG. 33A, in the case of the sensor arrangement in which the magnetic element M12 is mounted between the bus bar B0 and the demagnetizing body M11, the residual magnetic fields of the demagnetizing body M11 and the magnetic shield CM2 are mutually at the magnetic element M12 position. Counteract each other. Thereby, the hysteresis error due to the residual magnetic field becomes smaller than the arrangement of the magnetic element M12 shown in FIG. 33B. In this arrangement of the magnetic element M12, as shown as data (a) in FIG. 36, the magnetic field generated by the bus bar current I tends to flow into the magnetic element M12, and the demagnetization effect is shown in the sensor arrangement shown in FIG. 33B. However, the S / N ratio is good, and the influence of the residual magnetic field is reduced accordingly. Therefore, as shown in FIG. 33A, the demagnetizing body M11 and the magnetic element M12 are arranged such that the magnetic element M12 is on the bus bar B0 side with respect to the demagnetizing body M11, that is, the demagnetizing body M11 with respect to the magnetic element M12. Is preferably arranged on the magnetic shield CM1 side.

  However, as shown in FIG. 33A, even if the sensor arrangement is such that the magnetic element M12 is mounted between the bus bar B0 and the demagnetizing body M11, a hysteresis error occurs if the magnetic flux density in the demagnetizing body M11 is large. Will become bigger.

In FIG. 37, in the magnetic sensor M10 ′ in which the separation distance between the demagnetization body M11 and the magnetic element M12 is fixed, the magnetic flux density in the demagnetization body M11 (on the left side) when the separation distance between the magnetic shield CM1 and the demagnetization body M11 is changed. The vertical axis) and the intensity of the residual magnetic field flowing into the magnetic sensor due to the residual magnetic field (right vertical axis) are shown.
In this magnetic sensor M10 ′, as shown in FIG. 37, the closer the sensor arrangement is to the magnetic shield CM1, the smaller the influence of the residual magnetic field. It is understood that the magnetic flux density flowing into the magnetic sensor CM10 ′ can be reduced also in FIG. 34 by bringing the magnetic sensor M10 ′ with a demagnetizer close to the magnetic shield CM1. As a result, it is possible to reduce the magnetic flux density to the magnetic sensor M10 ′ and suppress the hysteresis error.

FIG. 38A shows the magnetic flux density (vertical axis) flowing into the magnetic element M12 with respect to the installation position (horizontal axis) of the magnetic element M12 in the z direction. It is a graph which shows the case where there is no demagnetization body M11 with a continuous line, and shows the case where the demagnetization body M11 is provided with a dashed-dotted line.
In this current sensor, as shown in FIG. 38A, by providing a demagnetizing body M11 in the magnetic sensor M10 ′, the magnetic field strength flowing into the magnetic element M12 can be reduced so as to be within the good operating range of the magnetic element M12. it can. Similarly, as shown in FIG. 38B, a demagnetizing body M11 is provided to reduce and reduce the magnetic field intensity range flowing into the magnetic element M12, thereby securing an installation margin in the bus bar B0 width direction (CM direction). it can.

Specifically, as shown in FIG. 38B, the change of the magnetic flux density flowing into the magnetic element M12 with respect to the installation position of the magnetic element M12 in the CM direction is indicated by a solid line, and the demagnetizing body A case where M11 is provided is indicated by a one-dot chain line. Thus, when the demagnetizing body M11 is not provided, as shown by the solid line in FIG. 38A, if the magnetic element M12 is positioned near the center in the width direction (CM direction) of the magnetic shields CM1 and CM2, the magnetic element M12. Although the magnetic flux density can be set to be in a good operating range, when the magnetic element M12 is positioned near the end of the magnetic shield CM1, the magnetic element M12 may be out of the good operating range.
On the other hand, when the demagnetizing body M11 is provided, the position of the magnetic element M12 is changed from the vicinity of the center in the width direction (CM direction) of the magnetic shields CM1 and CM2 as shown by the one-dot chain line in FIG. 38B. In this way, the magnetic flux density can be set to be within the good operation range of the magnetic element M12.
The characteristics applied to the installation position of the magnetic element M12 in the width direction of the bus bar B0 have the same characteristics in the bus bar B0 length direction of the magnetic shields CM1 and CM2, that is, in the direction orthogonal to the z direction and the CM direction. .

Next, the influence of the disturbance magnetic field Hexd in the normal direction orthogonal to the magnetic shields CM1 and CM2, that is, the z direction will be described.
FIG. 39A is a schematic cross-sectional view showing the influence of the disturbance magnetic field Hexd in the z direction and shows a state where there is no demagnetizing body and no inclination. FIG. 39B is a schematic cross-sectional view showing the influence of the disturbance magnetic field Hexd in the z direction and shows a state with no demagnetizing body and tilt. FIG. 39C is a schematic cross-sectional view showing the influence of the disturbance magnetic field Hexd in the z direction, and shows a state where there is a demagnetizing body and there is an inclination.

  As shown in FIG. 39A, when the magnetic shields CM1 and CM2 and the magnetic element M12 are not inclined, that is, the magnetic sensitive direction of the magnetic element M12 is parallel to the CM direction defined by the main surfaces of the magnetic shields CM1 and CM2. In this case, when a disturbance magnetic field Hexd orthogonal to the main surfaces of the magnetic shields CM1 and CM2 flows, the direction of the disturbance magnetic field Hexd is orthogonal to the magnetic sensing direction of the magnetic element M12, so that the magnetic element M12 has a disturbance magnetic field Hexd. Is not detected.

  On the other hand, as shown in FIG. 39B, when the magnetic shields CM1 and CM2 and the magnetic element M12 are inclined, that is, the magnetic direction of the magnetic element M12 is defined by the main surface of the magnetic shields CM1 and CM2. In the case of having an angle θ with respect to the direction, when a disturbance magnetic field Hexd orthogonal to the main surfaces of the magnetic shields CM1 and CM2 flows, the direction of the disturbance magnetic field Hexd is not orthogonal to the magnetic sensing direction of the magnetic element M12. The magnetic element M12 detects the magnetosensitive direction component Hexd-c of the disturbance magnetic field Hexd.

Here, when the demagnetizing body M11 is provided in the magnetic element M12 inclined at the angle θ, the magnetic elements M12 and M11 are provided in parallel to form the magnetic sensor M10 ′, and therefore the inclined magnetic sensor M10 ′. When the disturbance magnetic field Hexd flows into the magnetic field, as shown in FIG. 39C, in the vicinity of the demagnetizing body, the direction of the magnetic vector of the disturbance magnetic field Hexd is bent in a direction nearly perpendicular to the plane direction of the demagnetizing body M11. If the magnetic sensing direction of M11 and the magnetic element M12 is parallel, the magnetic vector of the disturbance magnetic field Hexd flowing into the magnetic sensor M10 ′ is also close to perpendicular to the magnetic sensing direction of the magnetic element M12.

Thus, even when the width direction of the magnetic shields CM1 and CM2 and the magnetic sensing direction of the magnetic element M12 are not parallel when the current sensor is assembled, the magnetic element M12 angle and the magnetic shield CM1 are present due to the demagnetizing body M11. , CM2 non-parallel errors can be reduced.

  In the current sensor of the present invention, when the demagnetizing body is made of a material having a relative permeability of 10,000 or more, the magnetic field to be measured can be accurately measured by sufficiently attracting a disturbance magnetic field and a residual magnetic field. It becomes possible.

  Hereinafter, 2nd Embodiment of the current sensor which concerns on this invention is described based on drawing.

  FIG. 17 is a schematic diagram showing a current sensor according to the present embodiment. In the figure, reference numeral CS <b> 10 ′ indicates a current sensor.

The current sensor CS10 ′ of the present embodiment has a magnetic sensor CM1 side and a CM2 side when viewed from the bus bar B0 located at the center in the z direction (thickness direction) between the two magnetic shields CM1 and CM2. One magnetic element M12, M12 ′ is provided on each side.
That is, the magnetic element M12 is located on the magnetic shield CM1 side of the bus bar B0, and the magnetic element M12 ′ is located on the magnetic shield CM2 side of the bus bar B0.

In the present embodiment, the magnetic element M12 and the magnetic shield CM1, and the magnetic element M12 ′ and the magnetic shield CM2 are arranged at symmetrical positions when viewed from the bus bar B0, and the magnetic field generated by the current I flowing through the bus bar B0 is The position of the magnetic element M12 and the position of the magnetic element M12 ′ are equal in size and reverse in direction. By calculating the difference between them from the output signals from these magnetic elements M12 and M12 ′, the influence of the disturbance magnetic field Hexd can be eliminated and the measured magnetic field Hext can be accurately calculated. Measurement accuracy can be improved.
Specifically, the measurement error rate measured in an experimental example to be described later can be reduced to about half or less and about 40% or less compared to the case of one magnetic element.

  Hereinafter, 3rd Embodiment of the current sensor which concerns on this invention is described based on drawing.

  FIG. 18 is a schematic cross-sectional view showing the current sensor CS20 in the present embodiment, and FIG. 19 is a top view showing the current sensor CS20. In the present embodiment, the same reference numerals are given to the configurations corresponding to the configurations in the embodiments described above. A description thereof will be omitted.

  As shown in FIGS. 18 and 19, the current sensor CS20 in the present embodiment includes a bus bar B01, a magnetic element M12, a control integrated circuit MT10, and magnetic shields CM1 and CM2 provided in the molded body CS20a so as to be integrated. ing.

In the current sensor CS20 in the present embodiment, the bus bar B01 is positioned inside a mold body CS20a formed in a predetermined shape with resin or the like.
The mold body CS20a is provided in advance with a recess in which the magnetic shield CM1 and the mounting substrate M10a are disposed, a recess in which the magnetic shield CM2 is disposed, a recess positioned in a portion not overlapping the bus bar B01 in plan view, and the like. The shape is controlled so that the distance dimensions CMa, CMb, CMe, and CMg shown in FIG. 1 are set to predetermined values.

  The mold body CS20a includes a mounting substrate M10a on which the magnetic element M12 and the control integrated circuit MT10 are mounted, an external connection terminal CS20e for connecting the mounting substrate M10a to the outside, a magnetic shield CM1, an upper cover CM5, and a magnetic shield CM2. The lower cover CM6 is fixed to form a current sensor CS20 shown in FIG.

  According to the present embodiment, the distance dimensions CMa, CMb, CMe, and CMg shown in FIG. 1 can be set to predetermined values by the resin mold body CS20a.

  Hereinafter, 4th Embodiment of the current sensor which concerns on this invention is described based on drawing.

  FIG. 20 is a schematic cross-sectional view showing the current sensor in the present embodiment, and in the figure, reference numeral CS30 indicates the current sensor. In this embodiment, the same number is attached | subjected to the structure corresponding to the structure in embodiment mentioned above, and the description is abbreviate | omitted.

  As shown in FIG. 20, in the current sensor CS30 in the present embodiment, the magnetic element M12 is a SIP (Single Inline Package) type magnetic sensor MS30, and inside the recess CS30f provided in the mold body CS20a separately from the mounting substrate M10a. Embedded in.

  As shown in FIG. 20, the current sensor CS30 in the present embodiment includes a bus bar B01, a magnetic shield CM1, a magnetic sensor MS30, a connection terminal CS30e, an external connection terminal CS20e, a magnetic shield CM1, and a control integrated circuit MT10 on a mold CS30a. The mounted mounting board M10a, connection terminal CS30f, upper cover CM5, magnetic shield CM2, and lower cover CM6 are fixed.

  According to the present embodiment, the distance dimensions CMa, CMb, CMe, CMg shown in FIG. 1 can be set to predetermined values by the resin mold CS30a.

  Hereinafter, 5th Embodiment of the current sensor which concerns on this invention is described based on drawing.

  FIG. 21 is a schematic cross-sectional view showing the current sensor in the present embodiment, and in the figure, reference numeral CS40 denotes the current sensor. In this embodiment, the same number is attached | subjected to the structure corresponding to the structure in embodiment mentioned above, and the description is abbreviate | omitted.

  As shown in FIG. 21, the current sensor CS40 in the present embodiment is a magnetic sensor MS40 in which the magnetic element M12 is a SIP (Single Inline Package) type and integrated with the control integrated circuit MT10, and is provided in the mold body CS20a. The mounting board M10a is not provided because it is embedded in the recess.

  The current sensor CS40 in this embodiment is a current sensor CS40 in which a bus bar B01, a magnetic sensor MS40, a connection terminal CS40e, a magnetic shield CM1, an upper cover CM5, a magnetic shield CM2, and a lower cover CM6 are fixed to a mold CS40a. .

  According to the present embodiment, the distance dimensions CMa, CMb, CMe, CMg shown in FIG. 1 can be set in advance to predetermined values by the resin mold CS40a.

  Hereinafter, 6th Embodiment of the current sensor which concerns on this invention is described based on drawing.

  FIG. 22 is a schematic cross-sectional view showing a current sensor in the present embodiment, and in the figure, reference numeral CS50 indicates a current sensor. In this embodiment, the same number is attached | subjected to the structure corresponding to the structure in embodiment mentioned above, and the description is abbreviate | omitted.

  As shown in FIG. 22, the current sensor CS50 in the present embodiment is a magnetic sensor MS50 in which the magnetic element M12 is a SIP (Single Inline Package) type and integrated with the control integrated circuit MT10, and is embedded in the mold body CS20a. The mounting board M10a is not provided.

The current sensor CS50 in this embodiment includes a mold CS50a, a bus bar B01 and a magnetic sensor MS50, a connection terminal CS40e, a magnetic shield CM1, an upper cover CM5,
The magnetic shield CM2 and the lower cover CM6 are fixed.

  According to the present embodiment, the distance dimensions CMa, CMb, CMe, CMg shown in FIG. 1 can be set to predetermined values by the resin mold CS50a.

  Hereinafter, a seventh embodiment of a current sensor according to the present invention will be described with reference to the drawings.

  FIG. 23 is a cross-sectional view showing a current sensor in the present embodiment, FIG. 24 is a top view showing a bus bar of the current sensor in the present embodiment, and in the figure, reference numeral CS60 shows the current sensor. In this embodiment, the same number is attached | subjected to the structure corresponding to the structure in embodiment mentioned above, and the description is abbreviate | omitted.

As shown in FIG. 23, the current sensor CS60 in the present embodiment is provided with a slit B63 in the center portion of the bus bar B60 (current path), and divides the current to be measured into the branch current I1 and the branch current I2. Yes.
As shown in FIG. 24, the slit B63 is provided so as to overlap at least a part of the magnetic element M12 in a plan view, and desirably, all of the magnetic elements M12 overlap in a plan view. .

  According to the current sensor CS60 of the present embodiment, the current to be measured I flowing through the bus bar B60 is branched by the slit B63. Therefore, in the vicinity of the slit B63, the magnetic field Hext1 generated by the branch current I1 shown by the solid line in FIG. 23 cancels out the magnetic field Hext2 generated by the branch current I2 indicated by the broken line. Thereby, the magnetic field intensity to be measured is reduced.

As a result, as shown in the simulation result in FIG. 25, a demagnetization region Md in which the magnetic field generated by the current I to be measured is small is formed in the vicinity of the slit B63. The demagnetization region Md includes at least the vicinity of the center of the slit B63, as shown by hatching in FIG. 25, and has an X-shape in which the respective end portions are in contact with the magnetic shield CM1 and the magnetic shield CM2 in the cross section viewed in the measurement current I direction. It becomes the range. As shown in FIG. 23, this corresponds to a region where the magnetic field Hext1 and the magnetic field Hext2 generated by the branch current I1 and the branch current I2 flowing in the bus bar B61 and the bus bar B62 branched by the slit B63 cancel each other, and the bus bar B61. In the closing line formed around the bus bar B62 as a center, it is a portion located in the magnetic shield CM1 and the magnetic shield CM2 and its vicinity.
By disposing the magnetic element M12 in the demagnetization region Md, the measurement accuracy can be maintained without causing magnetic saturation of the magnetic core included in the magnetic element M12, and measurement can be performed in response to a larger current. Can be done. As shown in FIG. 26, this becomes clear by comparing with a state in which the demagnetization region Md in the bus bar B0 without a slit remains in a narrow range near the magnetic shield CM1. Thereby, the installation possible range in installation of the magnetic element M12 can be expanded.
In the vicinity of the center of the slit B63, the magnetic field Hext1 generated by the branch current I1 flowing through the bus bar B61 and the magnetic field Hext2 generated by the branch current I2 flowing through the bus bar B62 cancel each other, so the magnetic element M12 is provided at this portion. Thus, the magnetic field flowing into the magnetic element M12 can be made extremely small.

In the above embodiment, as shown in FIG. 27, when the current sensor CS10 has a mounting board M10a such as a printed wiring board, a region Gnd to be GND is provided on the bus bar B0 side of the mounting board M10a. Thus, it is possible to reduce the influence of the high frequency noise propagating through the bus bar B0 and increase the measurement accuracy.
In this case, as a region to be GND, a GND plane Gnd larger than the mounting substrate M10a can be provided on the bus bar B0 side of the mounting substrate M10a. In this case, the GND plane Gnd can be made of a material having higher conductivity than a magnetic shield such as SUS or Cu. In this case, it is important that the GND plane Gnd is located between the magnetic element M12 and the bus bar B0.

  In the current sensor of the present invention, the magnetic shield not only suppresses measurement errors due to an external magnetic field, but also includes a magnetic shield viewed in plan in the arrangement position of two magnetic shields, the arrangement position of the magnetic elements, and the stacking direction with the magnetic elements. It is possible to adjust the magnetic field strength generated from the bus bar to the magnetic element by adjusting the contour shape of the plate. This is significant for a fluxgate type element in which a magnetic material that normally becomes magnetically saturated by a large magnetic field generated from a bus bar through which a large current flows is present in the magnetic element. Therefore, it is possible to widen the measurement range of the magnetic element such that the measurement range of the measurement target is determined by magnetic saturation.

In addition, when a current is passed through the feedback coil, the amount of current passed through the feedback coil can be reduced, and current consumption can be suppressed.
Furthermore, in the present invention, the magnetic field strength to the magnetic element generated from the bus bar can be adjusted by adjusting the distances CMa, CMb, CMe, and CMg between the magnetic element, the bus bar, and the magnetic shield.
Since the magnetic element provided in the current sensor of the present invention has a simple laminated structure, it is easy to assemble, and a plurality of sensors can be formed simultaneously. In addition, the structure of the present invention can be greatly reduced in size in the stacking direction as compared with a conventional sensor.

  Hereinafter, 8th Embodiment of the current sensor which concerns on this invention is described based on drawing.

  FIG. 40 is a schematic cross-sectional view showing the current sensor CS70 in the present embodiment, and FIG. 41 is a front cross-sectional view showing the arrangement of the demagnetizing bodies M11 in the current sensor CS70, which corresponds to the configuration in the above-described embodiment in the present embodiment. The same reference numerals are given to the components, and the description thereof is omitted.

  As shown in FIG. 40, in the current sensor CS70 in the present embodiment, a bus bar B01, a magnetic element M12, a control integrated circuit MT10, and magnetic shields CM1 and CM2 are provided in the mold body CS70a so as to be integrated.

  The magnetic element M12 of the present example is disposed in an arrangement in which the stacking order from the bus bar B01 is reversed with respect to the example illustrated in FIG. 14, that is, as illustrated in FIG. 41, disposed on the bus bar B01 side of the magnetic element M12. In the z direction, the bus bar B01, the magnetic element M12 (magnetic core 1), the demagnetizing body M11, and the magnetic shield CM1 are arranged in this order.

  The current sensor CS70 in the present embodiment is an assembly in which a bus bar B01, a magnetic shield CM1, a magnetic shield CM2, a package in which a demagnetizing body M11 and a magnetic element M12 are stacked, a control integrated circuit MT10, and the like are mounted on a mold body CS70a. The board M10a, the external connection terminal CS20e for connecting the mounting board M10a to the outside, the magnetic shield CM1, the upper cover CM5, and the lower cover CM6 are fixed. Here, the housing member (mold body) CS70a made of resin can be provided with a convex portion at a portion where the mounting substrate M10a is disposed, and can be press-fitted into a hole or a notch formed in the substrate. In this way, the substrate and the housing member are provided with position fixing means to position the magnetic element M12 and the housing member CS70a mounted on the mounting substrate M10a and the magnetic element M12 and the bus bar fixed to the housing member CS70a. This makes it possible to accurately position these positional relationships. Further, the connector pin can be formed into a current sensor integrated with the connector by passing through the through hole provided in the mounting substrate M10a after the mounting substrate M10a is disposed and soldering.

  According to the present embodiment shown in FIG. 40, as shown as type (b) in FIG. 33B, the magnetic element M12 is disposed at a position opposite to the magnetic shield CM1 of the demagnetizing body M11. The influence of the residual magnetic field can be reduced as compared with the type in which the influence of the residual magnetic field is strengthened between the magnetic shield CM1 and the demagnetizing body M11.

  According to the present embodiment, the magnetic sensor M10 is arranged as a sensor arrangement in which the magnetic element M12 is mounted between the bus bar B01 and the demagnetizing body M11, that is, an arrangement in which the demagnetizing body M11 is on the magnetic shield CM1 side with respect to the magnetic element M12. Since they are assembled, the residual magnetic fields of the demagnetizing body M11 and the magnetic shield CM2 cancel each other out at the position of the magnetic element M12. Thereby, the hysteresis error due to the residual magnetic field can be reduced. Also, with this arrangement of the magnetic element M12, the magnetic field generated by the bus bar current I tends to flow into the magnetic element M12, and the demagnetization effect is small, but the SN ratio is good and the influence of the residual magnetic field is small. can do.

  In the present embodiment, the assembly is performed as described above. However, the assembly order is not limited to this, and the assembly order may be changed. In FIG. 45, the direction of the connector is the direction as viewed from the mounting board M10a side to the bus bar B01 side. However, the direction is not limited to this and may be in various directions depending on the application. . Further, if the package and the circuit board including the magnetic element M12 and the demagnetizing body M11, the bus bar B01, and the magnetic shields CM1 and CM2 are arranged in this way, the housing resin protrusions and recesses, and the mounting direction of the cover are here. It is not limited to that shown, and various forms are conceivable depending on the assembling method on the device side.

  In the present embodiment, a leaded package is illustrated, but a non-lead type package such as a QFN (Quad Flat Nonlead), SON (Small Outline Nonlead), CSP (Chip Size Package), etc. Also good.

  In the structure in which the magnetic element M12 is arranged between the demagnetizing body M11 and the bus bar B0 shown as type (a) in FIG. 33A, the residual magnetic field generated in the magnetic shield CM1 is as shown in the right diagram of FIG. It becomes a state. The residual magnetic field generated in the magnetic element M12 and the magnetic plate (magnetic shield) CM1 on the demagnetizing body M11 side is attracted to the demagnetizing body M11, and thus is hardly applied to the magnetic element M12. The residual magnetic field generated by the demagnetizing body M11 and the residual magnetic field generated by the magnetic plate (magnetic shield) CM2 disposed on the side opposite to the bus bar B0 are applied. These residual fields cancel each other because their directions are opposite, but the distance between the magnetic element M12 and the magnetic plate (magnetic shield) CM2 disposed on the opposite side of the bus bar B0 is the same as the demagnetizing body M11. When the distance is sufficiently larger than the distance of the magnetic element M12, the influence of the residual magnetic field from the magnetic plate (magnetic shield) CM2 becomes sufficiently small, and the residual magnetic field component by the demagnetizing body M11 becomes dominant.

Therefore, a current sensor with a small hysteresis can be realized by using a soft magnetic material having a small coercive force and a small residual magnetic field as the magnetic material constituting the demagnetizing body M11. Examples of such a soft magnetic material include permalloy (for example, PC permalloy) containing 77% or more of Ni, a Co-based amorphous material, and the like.
As described above, when a soft magnetic material having a small coercive force and a residual magnetic field is used as the demagnetizing body, the hysteresis that affects the output of the current sensor is dominant as described above. Even if a material having a relatively large hysteresis is used, a current sensor having a small hysteresis can be realized. Therefore, an inexpensive material can be used, and the cost can be suppressed. Examples of such a material include electromagnetic soft iron and silicon steel plate.

  Hereinafter, experimental examples of the present invention will be described.

<Experimental example A>
As Experimental Example 1, the relative ratio of the magnetic field strength at the magnetic element position was measured by changing the interval CMb between the magnetic shields CM1 and CM2. FIG. 28 shows the result of normalization based on the magnetic strength when the shield interval CMb is 4 mm.
From this result, the magnetic field strength of the sensor unit decreases as the shield interval decreases.
As Experimental Example 2, the magnetic flux density at the magnetic element position was measured by fixing the distance CMb between the magnetic shields CM1 and CM2 to 6 mm and changing the distance CMe to the bus bar. The result is shown in FIG.

From this result, the closer to the upper shield, the smaller the magnetic field strength.
As Experimental Example 3, the relative ratio of the magnetic field strength at the magnetic element position was measured by changing the bus bar width CMbc. At this time, the widths CM1c and CM2c of the magnetic shields CM1 and CM2 were fixed at 25 mm. FIG. 30 shows the result of normalization based on the magnetic strength when the bus bar width CMbc is 10 mm.
From this result, the magnetic field strength of the sensor portion decreases as the bus bar width increases.

From these results, for the widths CM1c and CM2c of the magnetic shields CM1 and CM2 and the width CMd of the magnetic element,
CM1c = CM2c >> CMd
With respect to the bus bar width CMbc and the magnetic element width CMd,
CMbc >> CMd
1 holds, the setting of the magnetic field intensity at the position of the magnetic element M12 has a great influence on the setting of CMa, CMb, and CMbc shown in FIG.

Further, as Experimental Example 4, as shown in FIG. 31, a bus bar parallel to the measurement target bus bar B0 is provided at a position in the in-plane direction of the magnetic shields CM1 and CM2, and the error rate of the measured current value is measured. Was measured. At this time, the lower magnetic shield CM2 was removed, and the state of only the upper magnetic shield CM1 was compared with the state without the magnetic shield. FIG. 31 shows the specifications of each part in this case, and FIG. 32 shows the measurement result of the error rate.
As a result, it was confirmed that the measurement error can be greatly reduced by installing the magnetic shield compared to the case without the magnetic shield because the magnetic field generated from the bus bar not measured passes through the magnetic shield.

  In the result of FIG. 32, the error increases as the ratio of the adjacent bus bar current to the current to be measured increases (the adjacent bus bar current is larger than the current to be measured), but this indicates a magnetic field generated from the adjacent bus bar. This is because it has not been completely removed. However, if the error is about FIG. 32, the error value is at a level that does not cause a problem when applied to a bus bar of a power supply line connected to a battery or the like that generates a large current.

  Further, it is desirable that the ratio (CM1c / CMb) of the magnetic shield CM1 and the magnetic shield CM2 with respect to the separation distance CMb is larger as the disturbance magnetic field flowing into the magnetic element can be reduced.

  Further, when the thickness of the magnetic shields CM1 and CM2 is too small, the magnetic shield is likely to be saturated with the magnetic field generated from the bus bar B0, so that the thickness is preferably 1 mm or more. In addition, in the width direction (CM direction) of the bus bar B0, it is desirable that the center position of the magnetic shields CM1 and CM2, the center position of the bus bar B0, and the center position of the magnetic element M12 all coincide. Further, from the viewpoint of position adjustment at the time of assembly, it is more desirable that the width dimensions CM1c and CM2c of the magnetic shields CM1 and CM2 are approximately the same as the width dimension CMbc of the bus bar B0.

  Thus, according to the present invention, the intensity of the magnetic field applied to the current sensor can be adjusted, and a magnetic sensor having a high sensitivity but a small magnetic field dynamic range can be used. In particular, in the fluxgate method, the smaller the magnetic field entering the sensor, the smaller the current consumption. Therefore, the shield width CM1c, CN2c, bus bar width CMbc, and shield interval CMb are reduced to reduce the size. It can be seen that the magnetic field at the magnetic element position can be reduced by adjusting the upper magnetic shield CM1 and the magnetic element distance CMa, even if the magnetic field at the magnetic element position is relatively large.

<Experiment B>
FIG. 42 shows the measurement results of the current sensor manufactured in the same manner as in Experimental Example A.
FIG. 42 is a graph showing the relationship between the measured current and the output error in the current sensor in relation to this experimental example.
Here, as a current sensor, a mounting board M10a on which a fluxgate type magnetic element M12 not including a demagnetizing body M11 is mounted is arranged so that the surface of the mounting board M10a is at a distance of 1.4 mm from the surface of the bus bar B0. The structure is sandwiched between CM1 and CM2. Similarly to the structure shown in FIG. 24, the bus bar B0 is provided with a slit B63 at the center for suppressing the magnetic field generated in the magnetic element portion by the measurement current, and the width is 7.5 mm. .

On the other hand, FIG. 43 is a graph showing the relationship between the measured current and the output error in the current sensor in relation to this experimental example.
Here, as a current sensor, a mounting board M10a on which a flux gate type magnetic element M12 laminated with a demagnetizing body M11 is mounted is disposed so that the surface of the mounting board M10a comes to a position 2.0 mm from the surface of the bus bar B0. The structure is sandwiched between CM1 and CM2. Similarly, the bus bar B0 is similarly provided with a slit B63 at the center for suppressing the magnetic field applied to the magnetic element M12 by the measurement current, and its width is 2.5 mm.

  42 and 43, the bus bar B0 is made of Cu and has a plate thickness of 1.2 mm. The magnetic shield material such as the magnetic shields CM1 and CM2 is made of PC permalloy, and the plate The thickness is 1.6 mm.

  In any of the cases shown in FIGS. 42 and 43, the measurable magnetic field range of the fluxgate type magnetic element used for the measurement as the magnetic element M12 is about ± 1 mT, so that the magnetic field generated by the current falls within this range. The slit B63 width and the distance between the magnetic sensor M10 and the bus bar B0, that is, the distance between the mounting board M10a and the bus bar B0 are adjusted so as to enter.

  Thus, when a fluxgate type magnetic element is used, since there is a limit to the measurable magnetic field range of the magnetic element, a structure for reducing the magnetic field generated by the current is required, and as a method therefor, Although it is possible to reduce the magnetic field by providing a magnetic shield or by providing a slit in the bus bar, there is a problem that a hysteresis error due to the magnetic shield increases when such a method is used. On the other hand, in the case of the same configuration, a magnetic demagnetization body made of a soft magnetic material is laminated on the magnetic element, and the magnetic shield, busbar, magnetic element, demagnetization body, and magnetic shield are arranged in this order, so that the magnetic Hysteresis error due to shielding can be reduced.

  Further, the demagnetizing body made of a soft magnetic material and the magnetic element can be assembled using a general semiconductor assembly process. For this reason, the positional relationship between the magnetic element and the demagnetizing body is determined by the thickness of the substrate on which the magnetic element is formed and the accuracy of die bonding, but these accuracy is generally about several μm to several tens of μm, and positioning is performed with high accuracy. Is possible.

  On the other hand, the dimensional accuracy and assembly accuracy of the bus bar, magnetic shield body, and housing are generally about 50 to 100 μm, which is larger than the former. When the magnetic field generated by the current is controlled by the magnetic shield body, the bus bar slit, and the position where they are assembled, the gradient of the magnetic field generated by the current is large at the position in the shield, and the measurement magnetic field, that is, the sensitivity varies due to misalignment. There is a problem. However, according to the present invention, by providing the demagnetizing body, the magnetic field generated by the current can be controlled by the combination of the magnetic element positioned with high assembly accuracy and the demagnetizing body. There is an advantage that variation in the size can be reduced.

  When a package with leads such as SOP (Small Outline Package) is used, the tab (die pad) on which the die (demagnetizing body and magnetic element) is mounted is lowered by about 200 μm from the other leads. It is possible to use a lead frame that has been processed. Thereby, the magnetic core which is a demagnetization body and the magnetic sensing part of a magnetic element can be kept away from a bus bar, and can be brought close to a magnetic shield.

The smaller the shield interval, that is, the distance between the magnetic shields CM1 and CM2, the stronger the resistance to the disturbance magnetic field. At the same time, the smaller the distance (shield interval) between the magnetic shields CM1 and CM2, the closer the distance between the magnetic element M12 and the bus bar B0, and the magnetic field applied to the magnetic element M12 when a current flows through the bus bar B0. Also become stronger. For this reason, in order to ensure the measurement range of the magnetic element M12, it is necessary to secure a certain shield interval.
However, by using the above-described tab-lowered lead frame, it becomes possible to keep the magnetic element and the demagnetization body away from the bus bar surface. As the magnetic element moves away from the bus bar and approaches the shield, the magnetic field applied to the magnetic element becomes weaker. Therefore, by using a lead frame with such a tab-lowering process, the measurement range is secured while the shield interval is narrowed. Thus, it is possible to realize a current sensor that is more resistant to disturbance.

  In the above experimental example, the flux gate type magnetic element is used as the magnetic element. However, the magnetic element in the present invention is not limited to this. For example, the magnetoresistive effect element, the Hall element, and the magnetic impedance effect element. A magnetic sensor using a tunnel magnetoresistive element or the like, and particularly a magnetic sensor element having a magnetosensitive direction in the in-plane direction of the substrate can be used similarly.

  For example, even when, for example, a magnetoresistive effect element, a Hall element, a magnetoimpedance effect element or the like is used as the magnetic element shown in the magnetic sensor M10 in FIG. 14, the magnetic element M12 is applied due to the effect of the demagnetizing body M11. Since the magnetic field is reduced, the hysteresis error due to the hysteresis characteristics of the magnetic material of the magnetic element M12 can be reduced. When a magnetic element in which a feedback coil is integrated is used as the magnetic element M12 and a feedback current corresponding to the detected magnetic field is supplied to the feedback coil, the feedback magnetic field (current) is generated by the effect of the demagnetizing body M11. Since current can be reduced, current consumption can be reduced.

  In the present invention, as shown in the above embodiment, a demagnetizing body made of a soft magnetic material is stacked on the magnetic element, and the shield, the bus bar, the magnetic element, the demagnetizing body, and the shield are arranged in this order. As shown in FIGS. 39A to 39C, the states of the magnetic shields CM1, CM2 and the magnetic element M12 are as described above with respect to the states of no demagnetizing body inclination, no demagnetizing body inclination, and demagnetizing body inclination. Even when the magnetic element is tilted due to an error, the influence of the disturbance magnetic field can be reduced.

<Experimental example C>
FIG. 48 and FIG. 49 show the measurement results for the inclination of the magnetic sensor and the presence or absence of the demagnetizer in the current sensor manufactured in the same manner as in Experimental Example A.
44 and 45 are graphs showing the relationship between the direction of the disturbance magnetic field and the sensor magnetic sensing direction component of the magnetic flux density in the magnetic core 1 which is the magnetic sensing part of the magnetic sensor M10.

In these examples, as shown in FIGS. 39A to 39C, in a state where a package as the magnetic sensor M10 including the magnetic element M12 is mounted on a mounting substrate or the like, the magnetic field is tilted from the direction parallel to the bus bar B0. The magnetic flux density in the magnetosensitive part of the magnetic element when a disturbance magnetic field of 360 ° is applied in the xz direction when the magnetosensitive direction of the element is the x-axis and the direction perpendicular to the plane of the bus bar is the z-axis is a finite element. It is the result calculated by the method. FIG. 44 shows the result of FIG. 39A with no demagnetizing body and no tilt with a demagnetizing body for comparison verification. FIG. 45 shows the result of FIG. 39B with the demagnetizing body without tilting and FIG. 39C with the demagnetizing body with tilt. Respectively.
Here, the 0 ° direction was the magnetic sensing direction of the magnetic element, the 90 ° direction was the direction perpendicular to the plane of the bus bar, and the inclination angle θ = 2 ° shown in FIG. 39B.

  From these results, when the current sensor is configured to have two parallel magnetic shields (shield plates) CM1 and CM2 but no demagnetizing body M11, a disturbance magnetic field parallel to the magnetic shields CM1 and CM2 is induced. Although there is an effect, a disturbance magnetic field perpendicular to the magnetic shields CM1 and CM2 is applied as it is. Therefore, when the magnetic element M12 is tilted with respect to the horizontal direction of the magnetic shields CM1 and CM2 in the mounting form. In addition, the sine component of the disturbance magnetic field applied in the vertical direction of the magnetic shields CM1 and CM2 appears as an error. This is apparent by comparing the no-demagnet without inclination in FIG. 44 with the no-demagnet-inclined inclination in FIG.

On the other hand, when there is a demagnetizing body M11 as shown in FIG. 39C, the magnetic flux as the disturbance magnetic field incident on the inclined demagnetizing body M11 is bent so as to be perpendicularly incident on the surface of the demagnetizing body M11 which is the direction of magnetic sensing. Therefore, it also enters perpendicularly to the tilted magnetic element M10.
Since the magnetic element employed in the present invention is formed by laminating thin films and has no sensitivity in the direction perpendicular to the film surface, even when the magnetic element M12 is inclined due to an assembly error or the like in this way. Since the magnetic element M12 and the demagnetizing body M11 are integrally tilted, the influence of the disturbance magnetic field can be extremely reduced.

In addition to the causes described in the above-described embodiments, the inclination of the magnetic element M12 with respect to the magnetic shields CM1 and CM2 is caused by the assembly of the housing CS20a, CS30a, CS40a, CS50a, CS70a and the circuit board M10a, There is a possibility that it may occur due to warpage of M10a.
Here, the parallelism between the magnetic element M12 and the demagnetizing body M11 is determined by the plane of the substrate such as silicon on which the magnetic element M12 is formed and the plane of the surface of the thin plate or chip-like magnetic body that constitutes the demagnetizing body M11.

Further, when laminating the magnetic element M12 and the demagnetizing body M11 in the assembling process, epoxy, Ag paste, DAF, etc. can be applied as the die bond resin, but generally the thickness error when laminating with these using a die bonder. Is a few μm or less, and both of the sizes are as small as about 1 mm to 2 mm, and an angle that can be taken as an inclination angle within this range is very small.
Therefore, by using the magnetic sensor M10 having a package in which the magnetic element M12 and the demagnetizing body M11 are stacked, the current sensors CS10, CS20, CS30, CS40, CS50, CS70 having a small influence of the disturbance magnetic field against inclination due to assembly errors. Can be configured.

<Experimental example D>
In the above experimental example B (FIG. 42), the measurable range of the fluxgate type magnetic element used for the measurement is about ± 1 mT, so that the slit width and the sensor are set so that the magnetic field generated by the current falls within this range. The example which adjusted the distance between bus bars (between a board | substrate and a bus bar) is shown.
However, since the magnetic field generated by the bus bar decreases as it moves away from the bus bar surface, in order to match the magnetic field generated by the desired measurement current within the measurement range of the magnetic sensor, the sensor element is moved closer to the shield when no demagnetizer is used. Although it is necessary, in reality, it may be difficult to realize due to the dimensions of each member, such as the thickness of the substrate, the thickness of the sensor package, and the standoff height, and restrictions on assembly.

  Therefore, in this experimental example, a bus bar dimension, a shield dimension, a shield plate interval, and a sensor package size were made equal, and a sample with the same distance between each member viewed in cross section was created. A comparative study was conducted on the presence or absence of a demagnetizing body.

Further, in this experimental example, the configuration shown in FIG. 40 was adopted as a sample of the current sensor, and one with magnetic shields CM1 and CM2 and one without magnetic shields CM1 and CM2 were prepared.
In the case where the magnetic shields CM1 and CM2 are not provided, nonmagnetic resin spacers are used instead of the magnetic shields CM1 and CM2 so that the distance between the magnetic element M12 and the bus bar B01 is the same.

Further, in this experimental example, the magnetic sensor M10 corresponds to that shown in FIG. 41, and as shown in FIG. 46, the configuration (a) having the demagnetizing body M11 and the configuration (b) excluding the demagnetizing body M11. ). Here, as shown in FIG. 46, the bonding wire M15 located on the chip surface, which is the magnetically sensitive portion of the fluxgate sensor magnetic element M12, with and without the demagnetizing body from the lead frame base material M16. The height MM13 was set to be the same.
Specifically, in the case of no demagnetizer, the thickness of the nonmagnetic substrate M13 ′ such as silicon was adjusted. Thus, setting the height of the lead frame base material M16 is referred to as tab lowering.

In the sample of this experimental example, two kinds of PC permalloy and electromagnetic soft iron were used as the magnetic shields CM1 and CM2. PC permalloy was used as the demagnetizing body M11.
In the measurement, the measurement current range was determined by adjusting the measurement current so that the output voltage of the drive circuit was in the same span, and the linearity of the output voltage within the measurement current range was evaluated. In addition, a uniform disturbance magnetic field having a magnitude of 1 mT was applied by a Helmholtz coil in the magnetic sensing direction of the fluxgate sensor element, and the change in the offset voltage was observed. The results are shown in Table 1.

Table 1 shows the measurement current range, linearity, and disturbance magnetic field error depending on the presence or absence of the shield plate and the demagnetizer.
47 to 55 show the measured current and output voltage of each sample, and an approximate straight line obtained by least-square approximation of the relationship between the measured current and output voltage and the difference between the measured values as an output error as a percentage of the output full scale voltage. The graphs shown are respectively shown.

  From these results, as shown in FIGS. 47 to 48, the sample without the magnetic shield has good linearity because there is no shield plate that causes a hysteresis error. It can be seen that it cannot be used in the presence of a disturbance magnetic field. It can also be seen that the measurement range is narrow because the demagnetizing effect of the shield plate and the demagnetizing body is small.

  On the other hand, as shown in FIGS. 49 to 52, when the magnetic shield is arranged and the demagnetizing body is not used, the influence of the disturbance magnetic field is smaller than the case without the magnetic shield due to the shielding effect of the magnetic shield. It can be confirmed that On the other hand, when PC permalloy with a small hysteresis is used, the linearity is good as shown in FIGS. 49 to 50, but when electromagnetic soft iron with a large hysteresis is used, it is shown in FIGS. Thus, it can be seen that hysteresis also occurs in the output of the current sensor, and the output error is large. Therefore, in order to realize a current sensor with a small output error with such a configuration, it is necessary to use a material having a small hysteresis.

  In the case of using a demagnetizing body, as shown in FIGS. 53 to 55, in each case using PC permalloy and electromagnetic soft iron for the magnetic shield, there is no significant difference in linearity, and almost the same characteristics are obtained. It turns out that it is obtained. Further, even when electromagnetic soft iron having a relatively large hysteresis and low magnetic permeability is used, an error due to a disturbance magnetic field can be reduced, and a highly accurate current sensor can be realized.

Examples of the material having a small hysteresis used for the shield plate and the demagnetizer include PC permalloy, PB permalloy, MnZn ferrite, Sendust (FeSiAl) and the like. On the other hand, when using a demagnetizing body, as shown in Table 1 and FIGS. 53 to 55, even when using electromagnetic soft iron with low permeability and relatively large hysteresis, Since equivalent characteristics are obtained, easily available materials can be used without using expensive metal materials or materials that are difficult to process.
Examples of such materials include FeSi-based materials such as silicon steel plates (electromagnetic steel plates) and electromagnetic soft iron (SUY).

In the current sensor of the present invention,
1) An electronic circuit board on which at least a magnetic sensor package in which a soft magnetic demagnetization body (third magnetic body) and a magnetic element are stacked on a lead frame base material and a bus bar for supplying a measurement current is mounted. A current sensor comprising two magnetic shields (shield plates) arranged in parallel, the bus bar, the electronic circuit board, and a housing member for holding the two magnetic shields, wherein the magnetic sensor package Of the electronic circuit board on which the magnetic element is mounted facing the bus bar side, one of the two magnetic shields is arranged outside the electronic circuit board, and the other is the bus bar. In contrast, the electronic circuit board may be disposed on a side opposite to the side on which the electronic circuit board is disposed.

2) In the current sensor, the distance from the surface of the third magnetic body to the magnetic sensing portion of the magnetic element is from the second magnetic body plate (shield plate) on the opposite side to the magnetic element via the bus bar. It can be characterized by being shorter than the distance of the magnetic sensing part.

3) The current sensor characterized in that the coercive force of the third magnetic body is smaller than the coercive force of the first and second magnetic bodies (shield plates).

4) In the current sensor, the lead frame base material is characterized in that a tab mounting process is performed on a portion where a die is mounted.

  The present invention can be applied as, for example, a current sensor that measures the value of a current flowing in a wiring connected to a battery inside an automobile.

B0, B00, B01, B60, B61, B62 ... bus bar, CS10 ... current sensor CM1 ... first magnetic plate (magnetic shield)
CM2 ... Second magnetic plate (magnetic shield)
M10, MS10 ... Magnetic sensor MT10 ... Control integrated circuit M12 ... Magnetic element 1 ... Magnetic core 9 ... Excitation coil 10 ... Detection coil 21 ... Feedback coil MT11 ... Excitation current generation circuit

Claims (6)

A current sensor for measuring a value of a current flowing in a current path,
A fluxgate magnetic element disposed in the vicinity of the current path;
A first magnetic plate and a second magnetic plate,
The first magnetic plate and the second magnetic plate sandwich the current path and the fluxgate magnetic element in the overlapping direction with the current path and the fluxgate magnetic element;
A main surface of the first magnetic plate and the second magnetic plate is parallel to a magnetic sensing direction of the fluxgate magnetic element and a direction in which the current flows. The current sensor according to claim 1.
A separation distance between the first magnetic plate and the second magnetic plate is smaller than a width of the first magnetic plate and the second magnetic plate in the magnetosensitive direction. Current sensor. The current sensor according to claim 1 or 2,
A current sensor, wherein a third magnetic plate is laminated on the fluxgate magnetic element.   4. The current sensor according to claim 3, wherein the first magnetic plate and the second magnetic plate are arranged so as to cover the third magnetic plate. Sensor.   5. The current sensor according to claim 4, wherein the fluxgate magnetic element includes the current path and the third magnetic body in an overlapping direction of the first magnetic plate and the second magnetic plate. A current sensor, characterized in that it is arranged in a region sandwiched between plates.   6. The current sensor according to claim 5, wherein the third magnetic plate is disposed at a position away from the current path, that is, on the first magnetic plate side. Sensor.