Patent Description:
A current sensor disclosed in <CIT> includes a U-shaped current path, a magnetoelectric transducer that detects a magnetic field generated when a current flows through the current path, an internal magnetic shield surrounding at least part of the U-shape and the magnetoelectric transducer, and an external magnetic shield surrounding at least part of the internal magnetic shield. The magnetoelectric transducer is disposed at a center within a plane of a tabular current path as viewed along the normal to the current path.

A device for current measurement described in <CIT> comprises a substrate with a first current conductor and a current sensor with a second current conductor. The current sensor is mounted above the first current conductor on the substrate. The second current conductor is formed with integrally attached first and second terminal leads through which the current to be measured is supplied and discharged. The current sensor further comprises a semiconductor chip with a magnetic field sensor mounted on the second current conductor on the side of the second current conductor facing the substrate. The magnetic field sensor is sensitive to a component of the semiconductor chip and perpendicular to the second current conductor. The second current conductor extends above and parallel to the first current conductor.

An electronic circuit described in <CIT> includes a substrate having a surface and a device supported by the surface of the substrate. The electronic circuit also includes a conductor disposed over the magnetic field transducer. The conductor is configured to carry an electrical current to generate a first magnetic field. The electronic circuit is responsive to the first magnetic field.

However, the configuration in which the magnetoelectric transducer is disposed in the current path, like the current sensor disclosed in <CIT>, can cause noise generated from the current path at ON-OFF switching of a voltage for controlling the current to enter through an output terminal or a supply terminal of the magnetoelectric transducer to affect the result of magnetoelectric conversion.

An object of the present invention is to provide a current detecting apparatus including a magnetic sensor capable of measuring a current flowing through a bus bar, and the bus bar, in which even if noise is generated from the bus bar at ON-OFF switching of a voltage for controlling the current to be measured flowing through the bus bar, the influence on the detection result can be reduced.

The problem is solved by the current detecting apparatus of independent claim <NUM>.

The current detecting apparatus of the present invention includes a plate-like bus bar and a magnetic sensor including a main body capable of measuring a current flowing through the bus bar, and terminals extending individually from two opposing sides of the main body, wherein the terminals include a signal terminal for outputting a detection signal and a supply terminal for supplying electric power to the main body, wherein the signal terminal and the supply terminal extend from the main body, wherein the main body includes a portion overlapping the bus bar and a portion not overlapping the bus bar as viewed along a thickness direction of the bus bar, and wherein the signal terminal and the supply terminal extend from the portion of the main body not overlapping the bus bar without overlapping the bus bar.

This allows the signal terminal and the supply terminal to be disposed not overlapping the bus bar as viewed along the thickness of the bus bar, allows being distant from the bus bar. For this reason, by disposing one side on which the signal terminal and the supply terminal are provided away from the bus bar, even if noise is generated from the bus bar at ON-OFF switching of the voltage for controlling the current to be measured flowing through the bus bar, the influence on the detection result can be reduced.

In the current detecting apparatus of the present invention, preferably, the bus bar may extend linearly, wherein the signal terminal and the supply terminal may be disposed only on one side of the main body in a width direction perpendicular to an extending direction of the bus bar, and wherein the main body may be disposed at a position where the one side does not overlap the bus bar in the width direction of the bus bar as viewed along the thickness direction.

This has the effect of reducing the influence of noise on the detection result, and in addition, for the bus bar corresponding to the other end on which the signal terminal and the supply terminal are not provided, there is no restriction on size, which allows for designing a bus bar with a desired width.

Further, the current detecting apparatus of the present invention includes two plate-like magnetic shields having a same shape and same size disposed away from each other so as to sandwich the bus bar and the magnetic sensor in the thickness direction, wherein the two plate-like magnetic shields are disposed parallel to the bus bar and overlapped so as not to extend off from each other as viewed along the thickness direction, and wherein, as viewed along the thickness direction, the main body and the two magnetic shields are disposed so that plane centers are aligned with each other, and the plane center of the main body is located on a widthwise end face of the bus bar.

Sandwiching the bus bar and the magnetic sensor with two magnetic shields reduces the influence of an extraneous magnetic field.

In the current detecting apparatus of the present invention, preferably, as viewed along the thickness direction of the bus bar, the bus bar may extend, on opposite sides of the portion overlapping the main body in the extending direction, in a direction different from the extending direction of the bus bar and distancing away from the main body or keeping a fixed distance from the main body.

This can increase the area of the entire bus bar to reduce the electrical resistance, thereby reducing heat generation.

According to the present invention, even if noise is generated from the bus bar at ON-OFF switching of a voltage for controlling the current to be measured flowing through the bus bar, the influence of the noise on the result of measurement made by the magnetic sensor can be reduced.

Magnetic sensors and current detecting apparatuses according to embodiments of the present invention will be described in detail hereinbelow with reference to the drawings.

First, the basic configuration of a current detecting apparatus <NUM> according to an embodiment will be described with reference to <FIG> and <FIG>. The sizes and relative positions of the individual members will be described for each embodiment with reference to <FIG>. <FIG> is a perspective view of the current detecting apparatus <NUM> illustrating the basic configuration thereof, <FIG> is an exploded perspective view of the current detecting apparatus <NUM>, <FIG> is a cross-sectional view taken along line A-A' of <FIG>, and <FIG> is a cross-sectional view taken along line B-B' of <FIG>.

As shown in <FIG>, the current detecting apparatus <NUM> includes a substantially rectangular parallelepiped casing <NUM> in which a cover 11a on the upper side (the Z1 side in <FIG>) and a case member 11b on the lower side (the Z2 side in <FIG>) are fixed to each other. Three bus bars <NUM>, <NUM>, and <NUM> pass through the case member 11b along the width of the casing <NUM> (in the Y1-Y2 direction in <FIG>).

The three bus bars <NUM>, <NUM>, and <NUM> are electrically conductive plates with the same shape, which are arranged so that the two opposing surfaces correspond to each other in the vertical direction of the casing <NUM>. The bus bars <NUM>, <NUM>, and <NUM> extend linearly along the width of the casing <NUM> and are disposed at regular intervals along the length of the casing <NUM> (in the X1-X2 direction of <FIG>).

As shown in <FIG> and <FIG>, a circuit board <NUM> is disposed in the casing <NUM> so as to extend in the longitudinal direction (X1-X2 direction), and magnetic sensors <NUM>, <NUM>, and <NUM> are disposed at the positions corresponding to the bus bars <NUM>, <NUM>, and <NUM> in an X-Y plane (a plane including the X1-X2 direction and the Y1-Y2 direction) on the circuit board <NUM>. At least part of the main body of each of the magnetic sensors <NUM>, <NUM>, and <NUM> faces the corresponding bus bar in the vertical direction.

The magnetic sensors <NUM>, <NUM>, and <NUM> may be disposed either the upper surface or the lower surface of the circuit board <NUM>. However, the magnetic sensors <NUM>, <NUM>, and <NUM> are desirably disposed on the same surface.

For example, the magnetic sensor <NUM> is disposed at the center of the casing <NUM> in the width direction (Y1-Y2 direction), and the bus bar <NUM> and the magnetic sensor <NUM> face each other in the vertical direction, as shown in <FIG>. The position of the magnetic sensor <NUM> in the width direction (X1-X2 direction) of the bus bar <NUM> shown in <FIG> and <FIG> are given as an example only, and specific examples are shown in the individual embodiments. Disposing the magnetic sensor <NUM> in correspondence with the bus bar <NUM> allows the magnetic sensor <NUM> to measure the value of a current flowing through the bus bar <NUM> (the current to be measured) by detecting a magnetic field induced by the current. An example of the magnetic sensor <NUM> is a magnetoresistive sensor, such as a giant magnetoresistive sensor (GMR sensor).

The magnetic sensor <NUM> is sandwiched between a first shield 41a disposed in the cover 11a and a second shield 41b disposed in the case member 11b from above and below. The first shield 41a and the second shield 41b are preferably made of a ferromagnetic substance as a magnetic shield made of a magnetic material and are disposed parallel to each other so as to face each other in the vertical direction. Each of the first shield 41a and the second shield 41b has a configuration in which a plurality of metal plates with the same rectangular shape in plan view and the same size are vertically laminated, and has substantially the same length as that of the circuit board <NUM> in the width direction (Y1-Y2 direction), as shown in <FIG>, and a size so as to cover the bus bar <NUM> in the longitudinal direction (X1-X2 direction). Furthermore, the first shield 41a and the second shield 41b are aligned so as not to extend off from each other as viewed along the thickness of the bus bar <NUM>. Disposing the first shield 41a and the second shield 41b so as to sandwich the magnetic sensor <NUM> allows the magnetic sensor <NUM> to be shielded from an extraneous magnetic field (external magnetic field), such as a magnetic field induced by a current flowing through the adjacent bus bars <NUM> and <NUM>, thereby reducing the influence thereof.

The layout of the magnetic sensor <NUM> relative to the bus bar <NUM>, the layout of the two shields 41a and 41b relative to the magnetic sensor <NUM>, and the operation and advantages of the layout apply also to the two magnetic sensors <NUM> and <NUM> on both sides of the magnetic sensor <NUM>. The two shields 41a and 41b may be omitted in a case where the influence of the extraneous magnetic field is small (this is however not covered by the claimed invention).

<FIG> are diagrams showing the positional relationship between a bus bar <NUM> and a magnetic sensor <NUM> in a first embodiment, in which (a) is a side view, and (b) is a plan view. <FIG> illustrate the shapes of the bus bar <NUM> and the magnetic sensor <NUM> in a simplified manner.

In the first embodiment, as shown in <FIG>, the bus bar <NUM> and the magnetic sensor <NUM> with the size relationship as described below are arranged in the current detecting apparatus <NUM> shown in <FIG> and <FIG>, and the magnetic sensor <NUM> includes terminals as will be described later. The other configuration is the same as that of the current detecting apparatus <NUM> shown in <FIG> and <FIG>, in which a plurality of bus bars <NUM> made of the same material and having the same shape as those of the bus bars <NUM>, <NUM>, and <NUM> passes through the casing <NUM>, a plurality of magnetic sensors <NUM> is disposed on the circuit board <NUM> in the casing <NUM> so as to correspond to the individual bus bars <NUM>, and the plurality of magnetic sensors <NUM> are sandwiched between the two vertically opposing shields 41a and 41b.

As shown in <FIG>, the bus bar <NUM> is a plate-like member extending linearly along the width of the casing <NUM> (in the Y1-Y2 direction, see <FIG>) and having thickness in the vertical direction (Z1-Z2 direction) and is made of the same material as that of the bus bars <NUM>, <NUM>, and <NUM> shown in <FIG> and <FIG>.

As shown in <FIG>, the magnetic sensor <NUM> includes a main body <NUM> having a substantially rectangular shape in plan view viewed along the vertical direction (Z1-Z2 direction) and having thickness in the vertical direction and a plurality of terminals 132a and 132b extending outward from the sides of the main body <NUM> (end faces in the width direction of the bus bar <NUM>). The main body <NUM> detects a magnetic field induced by a current (a current to be measured) flowing through the bus bar <NUM> facing it to measure the value of the current to be measured and outputs the current value as a detection signal. Both of the magnetic sensor <NUM> and the bus bar <NUM> have thickness in the vertical direction. In the following description, the plan view refers to a view seen along the thickness thereof.

The main body <NUM> includes a first area 131a which overlaps the bus bar <NUM>, and a second area 131b and a third area 131c, which do not overlap the bus bar <NUM>, in plan view seen along the thickness direction. More specifically, the main body <NUM> includes the first area 131a in the center and the second area 131b and the third area 131c, on both sides, which lie out of the bus bar <NUM>, along the width of the bus bar <NUM> (X1-X2 direction).

The plurality of terminals 132a extends outward from a side of the second area 131b (the left in <FIG>) along the width of the bus bar <NUM>, and the plurality of terminals 132b extends outward from a side of the third area 131c (the right in <FIG>) along the width of the bus bar <NUM>. Thus, the plurality of terminals 132a and 132b extend without overlapping the bus bar <NUM> in plan view.

The plurality of terminals 132a and 132b includes a signal terminal for outputting a detection signal detected by the main body <NUM> and a supply terminal for supplying electrical power to the main body <NUM>, and in addition to these terminals, a terminal for correcting the detection signal before shipment, for example.

All of the terminals 132a and 132b including the signal terminal and the supply terminal extend outward from the second area 131b and the third area 131c of the main body <NUM>, which do not overlap the bus bar <NUM> in plan view, respectively, without overlapping the bus bar <NUM>. Thus, all of the terminals 132a and 132b do not face the bus bar <NUM> in the thickness direction, which allows the terminals 132a and 132b to be distant from the bus bar <NUM> as compared with a case in which the terminals 132a and 132b face the bus bar <NUM>. This reduces the influence of noise generated from the bus bar <NUM> at the start or stop of application of a current to the bus bar <NUM>, that is, at ON-Off switching of a voltage for controlling the current to be measured flowing through the bus bar <NUM>. For example, this reduces the influence of noise entering the signal terminal on the components on the circuit board <NUM> which are electrically connected to the signal terminal.

The circuit board <NUM> on which the magnetic sensor <NUM> is disposed is sandwiched between the two vertically opposing shields 41a and 41b, as shown in <FIG>. This causes the magnetic sensor <NUM> on the circuit board <NUM> to be sandwiched between the first shield 41a and the second shield 41b from above and below, which blocks an extraneous magnetic field, such as a magnetic field induced by a current flowing through adjacent bus bars, reducing the influence thereof.

<FIG>, both not covered by the claimed invention, are diagrams illustrating the positional relationship between a bus bar <NUM> and a magnetic sensor <NUM> of a second embodiment, in which (a) is a side view and (b) is a plan view. <FIG> illustrate the shapes of the bus bar <NUM> and the magnetic sensor <NUM> in a simplified manner.

In the second embodiment, as shown in <FIG>, the bus bar <NUM> and the magnetic sensor <NUM> with the size relationship as described below are arranged in the current detecting apparatus <NUM> shown in <FIG> and <FIG>, and the magnetic sensor <NUM> includes terminals as will be described later. The other configuration is the same as that of the current detecting apparatus <NUM> shown in <FIG> and <FIG>, in which a plurality of bus bars <NUM> made of the same material and having the same shape as those of the bus bars <NUM>, <NUM>, and <NUM> passes through the casing <NUM>, a plurality of magnetic sensors <NUM> is disposed on the circuit board <NUM> in the casing <NUM> so as to correspond to the individual bus bars <NUM>, and the plurality of magnetic sensors <NUM> are sandwiched between the two vertically opposing shields 41a and 41b.

As shown in <FIG>, the bus bar <NUM> is a plate-like member extending linearly along the width of the casing <NUM> (in the Y1-Y2 direction) and having thickness in the vertical direction (Z1-Z2 direction) and is made of the same material as that of the bus bars <NUM>, <NUM>, and <NUM> shown in <FIG> and <FIG>.

As shown in <FIG>, the magnetic sensor <NUM> includes a main body <NUM> having a substantially rectangular shape in plan view viewed along the vertical direction (Z1-Z2 direction) and having thickness in the vertical direction and a plurality of terminals 232a and 232b extending outward from the sides 231as and 231bs of the main body <NUM> opposing each other in the X1-X2 direction, respectively. The main body <NUM> detects a magnetic field induced by a current (a current to be measured) flowing through the bus bar <NUM> facing it to measure the value of the current to be measured and outputs the current value as a detection signal. Both of the magnetic sensor <NUM> and the bus bar <NUM> have thickness in the vertical direction. In the following description, the plan view refers to a view seen along the thickness thereof.

The main body <NUM> includes a first area 231a which overlaps the bus bar <NUM> and a second area 231b which does not overlap the bus bar <NUM>, in plan view seen along the thickness direction.

The plurality of terminals 232a individually extends outward from the side 231as of the first area 231a along the width of the bus bar <NUM>. The plurality of terminals 232a extends over the bas bar <NUM> in plan view. In contrast, the plurality of terminals 232b extends outward from the side 231bs of the second area 231b along the width of the bus bar <NUM>. The plurality of terminals 232b extends without overlapping the bus bar <NUM> in plan view. In other words, the plurality of terminals 232b extends in a direction distancing away from the bus bar <NUM>.

The plurality of terminals 232b extending from the second area 231b includes a signal terminal for outputting a detection signal detected by the main body <NUM> and a supply terminal for supplying electrical power to the main body <NUM>. The signal terminal and the supply terminal are not included in the plurality of terminals 232a extending from the first area 231a. In other words, the signal terminal and the supply terminal extend from only the side 231bs of the two opposing sides 231as and 231bs of the main body <NUM>, which does not overlap the bus bar <NUM> in plan view, in the direction perpendicular to the extending direction of the bus bar <NUM>. Another terminal other than the signal terminal and the supply terminal, for example, a terminal for correcting the detection signal before shipment, may be extended from either of the sides 231as and 231bs.

The plurality of terminals 232b including the signal terminal and the supply terminal extends outward from the second area 231b of the main body <NUM>, which does not overlap the bus bar <NUM> in plan view, without overlapping the bus bar <NUM>. Thus, the terminals 232b do not face the bus bar <NUM> in the thickness direction, which allows the terminals 232b to be distant from the bus bar <NUM> as compared with a case in which the terminals 232b face the bus bar <NUM>. This reduces the influence of noise generated from the bus bar <NUM> at ON-Off switching of a voltage for controlling the current to be measured flowing through the bus bar <NUM>, for example, the influence of noise entering the signal terminal on the components on the circuit board <NUM> which are electrically connected to the signal terminal.

Furthermore, the signal terminal and the supply terminal are provided only on the side 231bs of the two opposing sides 231as and 231bs of the main body <NUM>. This configuration allows the bus bar <NUM> to be provided in the area facing the first area 231a and from the area in the direction distancing away from the plurality of terminals 232b (X2 direction) while keeping the effect of reducing the influence of noise generated from the bas bar <NUM>.

<FIG> is a side view of a current detecting apparatus of a modification of the second embodiment, illustrating the layout of the two shields 41a and 41b, the magnetic sensor <NUM>, and the bus bar <NUM> in a simplified manner. The first area 231a and the second area 231b of the main body <NUM> of the magnetic sensor <NUM> may have any size in the width direction of the bus bar <NUM> (X1-X2 direction). However, disposing the main body <NUM> so that a plane center <NUM> is positioned on a widthwise end face <NUM> of the bus bar <NUM> so as to be aligned with a plane center 40x common to the two shields 41a and 42b, as shown in <FIG>, provides a well-balanced effect of reliable reduction of the influence of an extraneous magnetic field and accurate measurement of a current value based on a magnetic field induced by the current flowing through the bus bar <NUM>.

<FIG> is a plan view of a bus bar <NUM>, a magnetic sensor <NUM>, and a circuit board <NUM> of a third embodiment, not covered by the claimed invention, showing the positional relationship among them. In <FIG>, the shapes of the bus bar <NUM>, the magnetic sensor <NUM>, and the circuit board <NUM> are illustrated in a simplified manner, and components on the circuit board <NUM> other than the magnetic sensor <NUM> are omitted.

In the third embodiment, as shown in <FIG>, the bus bar <NUM> and the magnetic sensor <NUM> with the size relationship as described below are arranged in the current detecting apparatus <NUM> shown in <FIG> and <FIG>, and the magnetic sensor <NUM> includes terminals as will be described later. The bus bar <NUM> includes a base <NUM> and two extension ends <NUM> and <NUM>. The other configuration is the same as that of the current detecting apparatus <NUM> shown in <FIG> and <FIG>, in which a plurality of bus bars <NUM> made of the same material and having the same shape as those of the bus bars <NUM>, <NUM>, and <NUM> passes through the casing <NUM>, a plurality of magnetic sensors <NUM> is disposed on the circuit board <NUM> in the casing <NUM> so as to correspond to the individual bus bars <NUM>, and the plurality of magnetic sensors <NUM> are sandwiched between the two vertically opposing shields 41a and 41b.

As shown in <FIG>, the bus bar <NUM> includes the base <NUM> extending linearly along the width of the circuit board <NUM> (Y1-Y2 direction) and the two extension ends <NUM> and <NUM> extending linearly from the opposite ends of the base <NUM> in the extending direction (Y1-Y2 direction) to the X1 side along the extending direction of the circuit board <NUM> (X1-X2 direction). The base <NUM> extends in the direction perpendicular to the extending direction of the circuit board <NUM> and overlaps a first area 331a, which is part of the main body <NUM> of the magnetic sensor <NUM>. The two extension ends <NUM> and <NUM> extend, on the opposite longitudinal sides <NUM> of the base <NUM>, in a direction different from the extending direction of the base <NUM> of the bus bar <NUM> and perpendicular to the extending direction. The bus bar <NUM> is a plate-like member having thickness in the vertical direction (Z1-Z2 direction) and is made of the same material as that of the bus bars <NUM>, <NUM>, and <NUM> shown in <FIG> and <FIG>.

The extension ends <NUM> and <NUM> may extend in a direction not perpendicular to the extending direction of the base <NUM> of the bus bar <NUM>, provided that it is different from the extending direction of the base <NUM> of the bus bar <NUM> and not approaching the main body <NUM>. The extension ends may be extended not only to the X1 side, like the extension ends <NUM> and <NUM>, but also to the X2 side. In other words, the direction not approaching the main body <NUM> is, for the extension end <NUM>, the range from the Y2 direction to the X1 direction shown in <FIG> in the clockwise direction, and for the extension end <NUM>, the range from the X1 direction to the Y1 direction shown in <FIG> in the clockwise direction. If the distance from the main body <NUM> is fixed or increases, the extension ends <NUM> and <NUM> do not need to have a belt shape along a fixed direction, for example, a rectangular shape having four sides in the X1-X2 direction and the Y1-Y2 direction.

The magnetic sensor <NUM> has the same shape and function as that of the magnetic sensor <NUM> of the second embodiment. The magnetic sensor <NUM> includes the main body <NUM> having a substantially rectangular shape with thickness in the vertical direction and a plurality of terminals 332a and 332b extending outward from the opposing sides of the main body <NUM> in the X1-X2 direction, respectively. The main body <NUM> includes a first area 331a which overlaps the base <NUM> of the bus bar <NUM> and a second area 331b which does not overlap the base <NUM> of the bus bar <NUM>, in plan view seen along the thickness direction.

The plurality of terminals 332a and 332b are arranged as are the plurality of terminals 232a and 232b of the second embodiment. The terminals 332a extend outward over the base <NUM> of the bus bar <NUM>, and the terminals 332b extend outward without overlapping the base <NUM> of the bus bar <NUM>. As in the second embodiment, the terminals 332b extending from the second area 331b include a signal terminal for outputting a detection signal detected by the main body <NUM> and a supply terminal for supplying electric power to the main body <NUM>. The signal terminal and the supply terminal are not included in the terminals 332a extending from the first area 331a.

Disposing the extension ends <NUM> and <NUM> increases the area of the entire bus bar <NUM> to decrease the resistance of the entire bus bar <NUM>, thereby reducing heat generation while maintaining the effect of reducing the influence of noise generated from the bus bar <NUM>.

The other operations, effects, and modifications are similar to those of the second embodiment.

Claim 1:
A current detecting apparatus (<NUM>) comprising:
a plate-like bus bar (<NUM>); and
a magnetic sensor (<NUM>) including a main body (<NUM>) capable of measuring a current flowing through the bus bar (<NUM>) and terminals (232b) extending individually from the two opposing sides of the main body (<NUM>),
wherein the terminals (232b) include a signal terminal for outputting a detection signal and a supply terminal for supplying electric power to the main body (<NUM>),
wherein the signal terminal and the supply terminal extend from the main body (<NUM>),
wherein the main body (<NUM>) includes a portion (231a) overlapping the bus bar (<NUM>) and a portion (231b) not overlapping the bus bar (<NUM>) as viewed along a thickness direction of the bus bar (<NUM>), and
wherein the signal terminal and the supply terminal extend from the portion (231b) of the main body (<NUM>) not overlapping the bus bar (<NUM>) without overlapping the bus bar (<NUM>),
characterised in that
the current detecting apparatus (<NUM>) further comprises:
two plate-like magnetic shields (41a, 41b) having a same shape and same size disposed away from each other so as to sandwich the bus bar (<NUM>) and the magnetic sensor (<NUM>) in the thickness direction,
wherein the two plate-like magnetic shields (41a, 41b) are disposed parallel to the bus bar (<NUM>) and overlapped so as not to extend off from each other as viewed along the thickness direction, and
wherein, as viewed along the thickness direction, the main body (<NUM>) and the two magnetic shields (41a, 41b) are disposed so that plane centers (<NUM>, 40x) are aligned with each other, and the plane center (<NUM>) of the main body (<NUM>) is located on a widthwise end face (<NUM>) of the bus bar (<NUM>).