current sensor

Abstract

The current sensor 1 of this invention, suitable for thin and miniaturized applications and offering high measurement accuracy, comprises a magnetic sensor 2 with a built-in magnetic element 21, a busbar 3, and a magnetic shield 4. It also has an elimination component 5 composed of a magnetic material, positioned at a location where the residual magnetic field generated by the elimination component 5 weakens the residual magnetic field generated by the magnetic shield 4. This reduces offset errors in the busbar 3 when no current flows through it without complicating the calculations for magnetic detection.

Description

Technical Field

[0001] This invention relates to a current sensor for measuring the current flowing through a busbar. Background Technology

[0002] In recent years, current sensors that measure the current flowing through vehicles and other devices have been used to control power systems equipped with various devices. Examples of such current sensors include a magnetic detection unit that senses the magnetic field generated from the busbar and a magnetic shield that cuts off external magnetic fields that interfere with the magnetic detection unit.

[0003] Patent Document 1 discloses a current sensor with a shielding portion having a shielding magnetic field, aiming to reduce the offset error included in the sensor output when the current is not flowing through the busbar. This current sensor includes a first shielding portion that generates a first magnetic field when the current is not flowing through the busbar, and a second shielding portion that generates a second magnetic field opposite to the first magnetic field. The first and second magnetic fields are arranged to cancel each other out at the detection surface.

[0004] Patent Document 2 discloses a magnetic sensor aimed at eliminating the problem of reduced detection accuracy caused by hysteresis error resulting from residual magnetic flux generated by the magnetization of magnetic shielding components due to the detection of magnetic flux, interference magnetic flux, etc. This magnetic sensor obtains a correction physical quantity that corrects for hysteresis error caused by residual magnetic flux based on the difference between a first output value from a first magnetic detection unit and a second output value from a second magnetic detection unit.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-47147 Patent Document 2: Japanese Patent Application Publication No. 2023-54490 Summary of the Invention

[0006] The problem that the invention aims to solve Patent Document 1 describes a current sensor with a first shield and a second shield, and the offset error is reduced by adjusting the configuration of these two shields. However, since the current sensor has two shields, it is difficult to achieve a thinner and smaller design.

[0007] The magnetic sensor described in Patent Document 2 corrects the hysteresis error caused by residual magnetic flux based on the difference between the output values ​​from two magnetic detection units, thus complicating the calculation of the magnetic detection time.

[0008] Therefore, the purpose of this invention is to provide a current sensor that can reduce the offset error in the busbar when no current is flowing without complicating the calculation of magnetic detection time, making it suitable for thinning and miniaturization, and with good measurement accuracy.

[0009] Methods for solving problems As a means of solving the above-mentioned problems, the present invention has the following configuration.

[0010] A current sensor comprising a magnetic sensor with built-in magnetic components, a busbar, and a magnetic shield. The current sensor has an elimination component composed of a magnetic material, which is positioned to weaken the residual magnetic field generated by the magnetic shield by the residual magnetic field generated by the elimination component.

[0011] By using a separate elimination component from the magnetic shield, the residual magnetic field generated by the magnetic shield can be weakened, thus suppressing the influence of the residual magnetic field in magnetic field measurement.

[0012] The elimination component can also be integrally formed with the magnetic sensor.

[0013] By integrating the elimination component with the magnetic sensor, positional misalignment between the elimination component and the magnetic components of the magnetic sensor is minimized. Therefore, compared to constructing the two components separately, this results in a current sensor with low risk of errors due to positional misalignment and high measurement accuracy.

[0014] The elimination component can also be configured inside the package that forms the shape of the magnetic sensor.

[0015] The elimination component can also be disposed on the surface of the magnetic device opposite to the busbar.

[0016] Alternatively, the magnetic sensor may have a frame for mounting the magnetic device, and the elimination component may be disposed on the back side of the surface in the frame on which the magnetic device is mounted.

[0017] The elimination component may also be disposed on the outer peripheral surface of the package that forms the shape of the magnetic sensor.

[0018] In the packaging process for manufacturing magnetic sensors, elimination components disposed on the aforementioned parts can be easily formed through plating, bonding, and other methods. Therefore, current sensors can be manufactured efficiently.

[0019] The magnetic device can also be a magnetoresistive element.

[0020] Invention Effects According to the present invention, by providing an elimination component, the residual magnetic field generated by the magnetic shield is weakened, thus the influence of hysteresis can be suppressed with a simple configuration. Furthermore, by arranging the elimination component near the magnetic device, the influence of the residual magnetic field of the magnetic shield can be suppressed using a smaller elimination component. Therefore, a current sensor with good measurement accuracy, suitable for thinning and miniaturization, can be provided, which reduces errors caused by the hysteresis of the magnetic shield. Attached Figure Description

[0021] Figure 1 This is a perspective view schematically illustrating the configuration of a current sensor according to an embodiment of the present invention.

[0022] Figure 2 It is a schematic representation Figure 1 A cross-sectional view of the AA wire configuration of the current sensor.

[0023] Figure 3 It is a schematic representation Figure 2 A cross-sectional view of the configuration of a modified example of a current sensor.

[0024] Figure 4 It is a schematic representation Figure 3 A cross-sectional view of the magnetic sensor structure in a current sensor.

[0025] Figure 5 It is a schematic representation Figure 4 A cross-sectional view of the configuration of a modified example of a magnetic sensor.

[0026] Figure 6 It is a schematic representation Figure 4 A cross-sectional view of the configuration of another variation of the magnetic sensor.

[0027] Figure 7 It is a schematic representation Figure 3 A cross-sectional view of the configuration of a modified example of a current sensor.

[0028] Figure 8 It is a schematic representation Figure 3 A cross-sectional view of the configuration of another variation of the current sensor.

[0029] Figure 9 This is a perspective view of the components that illustrate the dimensions of the current sensor constituting the embodiment, showing the main parts.

[0030] Figure 10 The graph shows the results of measuring the effect of hysteresis on the current sensor measurements in the embodiments and comparative examples.

[0031] Figure 11 It is a schematic 3D diagram showing the structure of a conventional current sensor. Detailed Implementation

[0032] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, the same reference numerals are used to denote the same components, and descriptions are omitted where appropriate. To indicate the positional relationship of the components, reference coordinates are appropriately shown in each drawing. In the reference coordinates, the extension direction of the busbar is designated as the X direction, the width dimension direction of the busbar orthogonal to the X direction is designated as the Y direction, and the stacking direction of the busbar orthogonal to both the X and Y directions and the magnetic sensor is designated as the Z direction. The Y direction is the direction of the sensitivity axis of the magnetic sensor, and the X and Z directions are orthogonal to the sensitivity axis.

[0033] Figure 1 This is a perspective view schematically showing the configuration of the current sensor 1 in this embodiment.

[0034] Figure 2 It is a schematic representation Figure 1 A cross-sectional view of the AA wire configuration of current sensor 1.

[0035] As shown in these figures, the current sensor 1 includes a magnetic sensor 2, a busbar 3, and a magnetic shield 4, and has a damping component 5 to reduce the residual magnetic field from the magnetic shield 4. Furthermore, in Figure 2 And in the other accompanying figures, for ease of explanation, [details omitted]. Figure 1 The first housing 6 and the second housing 7 are shown.

[0036] The magnetic sensor 2 incorporates a magnetic device 21, which is mounted on a substrate (not shown). The magnetic device 21 is positioned opposite the busbar 3 in the Z-direction and detects the magnetic field (magnetism) generated by the busbar 3 when the measured current flows through it. The current flows through the busbar 3 in the X-direction. When the magnetic field generated when the measured current flows through the busbar 3 is observed along the Z-direction, a magnetic field parallel to the Y-direction is generated at the position overlapping with the busbar 3. Therefore, by aligning the sensing surface of the magnetic sensor 2 (magnetic device 21) with the busbar 3 in the Z-direction such that its sensitivity axis is parallel to the Y-direction, the magnetic field generated by the busbar 3 as an induced magnetic field can be sensed with high precision using the magnetic device 21.

[0037] As the magnetic device 21, for example, a magnetoresistive element or a Hall element can be used. Furthermore, the above configuration is based on the case where a magnetoresistive element is used as the magnetic device 21, but when using other magnetic devices 21, it is necessary to appropriately change the orientation of the sensing surface and other configurations.

[0038] Busbar 3 extends in the X direction, one of the mutually orthogonal X, Y, and Z directions. Busbar 3 is a plate-shaped conductor formed so that the measured current flows along the X direction, and is made of materials such as copper, brass, or aluminum. The normal direction of the surface of busbar 3 opposite to magnetic sensor 2 is the Z direction.

[0039] Figure 1 The busbar 3 shown is held in place by being clamped between the first housing 6 and the second housing 7 from both sides in the Z direction. In the current sensor 1, the busbar 3, which is configured as a separate component, is assembled into the first housing 6 and the second housing 7. However, the busbar 3 can also be integrally formed with the first housing 6 or the second housing 7 by insert molding or the like.

[0040] Figure 2 At least a portion of the U-shaped magnetic shield 4 shown is embedded in the second housing 7. The magnetic shield 4 is a metal plate, which can be constructed, for example, by overlapping multiple plates of the same shape (U-shape). When viewed along the X direction, the magnetic shield 4 is configured as a U-shape having a bottom 41 and two sidewall portions 42 extending from both ends of the bottom 41 toward the Z2 side.

[0041] The bottom 41 has a plate surface parallel to the XY plane and is arranged on the Z1 side in the Z direction with reference to the busbar 3.

[0042] The side wall portion 42 has a plate surface parallel to the XZ plane, and extends from both ends of the bottom 41 in the Y direction toward the Z2 side in the Z direction.

[0043] The magnetic shield 4 is arranged to surround both sides of the busbar 3 in the Y direction and the Z1 side in the Z direction. When viewed along the Z axis, a magnetic sensor 2 is arranged between the sidewall portions 42 at both ends of the magnetic shield 4.

[0044] By providing the magnetic shield 4, magnetic noise from the outside can be suppressed on the magnetic sensor 2. However, since the magnetic shield 4 is made of a soft magnetic material, it can sometimes be magnetized by the magnetic field generated when the measured magnetic field flows in the busbar 3, which is the magnetic field being detected, or by the interfering magnetic field being shielded.

[0045] As mentioned above, the magnetic shield 4, made of a soft magnetic material, sometimes exhibits a different magnetic state than when no magnetization was applied, due to the influence of previously applied magnetization. This change in the magnetic state when no magnetization was applied due to the influence of previously applied magnetization is called magnetic hysteresis (hysteresis phenomenon). The residual magnetic field from the magnetic shield 4 becomes noise when the magnetic device 21 detects magnetism, thus reducing the measurement accuracy of the current sensor 1.

[0046] Figure 11 This is a schematic cross-sectional view illustrating the configuration of a conventional current sensor 100. For example, as shown... Figure 11 As shown, when the measured current flows through busbar 3, an induced magnetic field is generated, as indicated by the dashed arrow in the figure. Under the influence of... Figure 11When the magnetic shield 4 is magnetized due to the influence of the induced magnetic field shown, even if the current does not flow through the busbar 3, a residual magnetic field will be generated in the magnetic shield 4 as indicated by the solid arrow in the figure, affecting the magnetic device 21 of the magnetic sensor 2. In particular, the U-shaped magnetic shield 4 has greater hysteresis than the flat plate-shaped magnetic shield described later, which has a greater impact on the measurement accuracy of the current sensor 1.

[0047] Therefore, in the current sensor 1, in order to reduce the influence of the residual magnetic field generated by the hysteresis of the magnetic shield 4, an elimination member 5 composed of a magnetic material is provided separately from the magnetic shield 4. The elimination member 5 is positioned to weaken the residual magnetic field generated by the magnetic shield 4 through the residual magnetic field generated by the elimination member 5. In other words, the elimination member 5 is positioned in a direction in which the magnetic field through the magnetic device 21 in the residual magnetic field generated by the magnetic shield 4 cancels out the magnetic field through the magnetic device 21 in the residual magnetic field generated by the elimination member 5.

[0048] exist Figure 2 In the figures, solid arrows represent residual magnetic fields generated by the hysteresis of the magnetic shield 4, and hollow arrows represent residual magnetic fields generated by the elimination component 5. Furthermore, in other figures, solid arrows are also appropriately used to represent residual magnetic fields from the magnetic shield 4, and hollow arrows are used to represent residual magnetic fields from the elimination component 5.

[0049] As shown in the figure, by arranging the elimination component 5 between the magnetic device 21 and the busbar 3, the orientation of the residual magnetic field generated by the elimination component 5 near the magnetic device 21 is opposite to the orientation of the residual magnetic field generated by the magnetic shield 4. Therefore, by eliminating the component 5, the residual magnetic field from the magnetic shield 4 can be weakened, and the influence of the magnetic hysteresis of the magnetic shield 4 on the magnetic device 21 can be suppressed. Thus, the influence of the magnetic hysteresis of the magnetic shield 4 can be suppressed, providing a current sensor 1 with high measurement accuracy.

[0050] also, Figure 2 The position of the elimination component 5 shown is an example, and its placement in the magnetic sensor 2 is not limited to this. The elimination component 5 can be positioned on the magnetic sensing surface of the magnetic device 21 at a location where the residual magnetic field generated by the magnetic shield 4 is weakened by the residual magnetic field from the elimination component 5. For example, the elimination component 5 can also be positioned on the opposite side of the busbar 3, separated from the magnetic device 21.

[0051] exist Figure 2 In the diagram, a hollow arrow on the Z2 side of the elimination component 5 indicates only a counterclockwise magnetic field, but a clockwise magnetic field is generated on the Z1 side of the elimination component 5. Therefore, even when the elimination component 5 is positioned on the opposite side of the busbar 3 with the magnetic device 21 in between, the residual magnetic field generated by the elimination component 5 is directed toward the Y1 side near the magnetic device 21, thus weakening the residual magnetic field generated by the magnetic shield 4.

[0052] Figure 3 It is a schematic representation Figure 2 This is a cross-sectional view of a modified example of the current sensor 1. The current sensor 1 shown in the figure integrally incorporates a magnetic sensor 2 and an elimination component 5. By integrating them, positional misalignment between the magnetic element 21 of the magnetic sensor 2 and the elimination component 5 is less likely to occur. Therefore, the influence of the residual magnetic field of the magnetic shield 4 can be eliminated with high precision, providing a current sensor 1 with high measurement accuracy.

[0053] Figure 4 It is a schematic representation Figure 3 A cross-sectional view of the configuration of the magnetic sensor 2 in the current sensor 1. In the magnetic sensor 2 shown in this figure, the elimination component 5 is disposed inside the package 22, which is made of molding resin or the like and forms the outer shape of the magnetic sensor 2. More specifically, the surface 21S of the magnetic device 21 of the integrated circuit 24 disposed on the frame 23 within the package 22 is connected to the busbar 3 (see reference 3). Figure 3 The opposite surface is equipped with elimination components 5.

[0054] As described above, by arranging the elimination component 5 inside the package 22, the distance between the elimination component 5 and the magnetic device 21 can be shortened. Therefore, the residual magnetic field from the elimination component 5 can effectively suppress the influence of the residual magnetic field of the magnetic shield 4.

[0055] Furthermore, the removal component 5 can be easily formed on the surface 21S of the magnetic device 21 during the process of forming the magnetic device 21. Examples of methods for forming the removal component 5 include plating, sputtering, and bonding.

[0056] The current sensor 1 of this embodiment includes a suppression component 5 for eliminating the influence of hysteresis of the magnetic shield 4. Thus, as a component distinct from the magnetic shield 4 that shields the magnetic field, the suppression component 5 for suppressing the influence of hysteresis of the magnetic shield 4 is positioned near the magnetic device 21. Therefore, the suppression component 5 can be constructed from a magnetic material smaller than the magnetic shield 4, enabling miniaturization of the current sensor 1 and suppression of the influence of hysteresis caused by residual magnetization of the magnetic shield 4.

[0057] Figure 5 It is a schematic representation Figure 4This is a cross-sectional view of a modified example of the magnetic sensor 2. In the magnetic sensor 2 shown in this figure, the elimination component 5 is formed on the surface of the frame 23. That is, the magnetic sensor 2 has a frame 23 for mounting the magnetic device 21 and the integrated circuit 24, and the elimination component 5 is disposed on the back side surface 23S2 of the Z1 side surface 23S1 in the frame 23 where the magnetic device 21 is mounted. In the packaging process of manufacturing the magnetic sensor 2, the elimination component 5 can be easily formed on the surface of the frame 23 by plating, bonding, etc. Therefore, the current sensor 1 can be manufactured efficiently.

[0058] Figure 6 It is a schematic representation Figure 4 This figure shows a cross-sectional view of another modified embodiment of the magnetic sensor 2. The magnetic sensor 2 shown in this figure has a configuration where the elimination component 5 is disposed on the outer peripheral surface of the package 22. Figure 4 as well as Figure 5 Similarly, as shown, the elimination component 5 can be easily formed on the outer peripheral surface of the package 22 during the packaging process of manufacturing the magnetic sensor 2 through plating, bonding, or other methods. Therefore, it is possible to efficiently manufacture a current sensor 1 equipped with the elimination component 5.

[0059] Figure 7 It is a schematic representation Figure 3 This is a cross-sectional view of a modified example of the current sensor 1. As shown in the figure, the magnetic shield 4 of the current sensor 1 can be a C-shaped (core-shaped) magnetic shield instead of a U-shaped one. Even when using a C-shaped magnetic shield 4, by providing the elimination component 5, the influence of the residual magnetic field of the magnetic shield 4 on the magnetic device 21 can be suppressed, thereby improving the measurement accuracy of the current sensor 1.

[0060] Figure 8 It is a schematic representation Figure 3 This is a cross-sectional view of another variation of the current sensor 1. As shown in the figure, the magnetic shield 4 of the current sensor 1 can be replaced by a parallel plate type magnetic shield instead of a U-shaped one. Even when using a parallel plate type magnetic shield 4, the influence of magnetic hysteresis of the magnetic shield 4 can be suppressed by providing the elimination component 5, thus improving the measurement accuracy of the current sensor 1.

[0061] [Example] Figure 9 This is a perspective view illustrating the dimensions (size) of the components constituting the current sensor 1 in this embodiment, showing the main parts. Furthermore, Figure 9 The other accompanying drawings are schematic diagrams whose size has been adjusted for ease of explanation, and the dimensions of the components constituting the current sensor 1 do not correspond to their actual sizes.

[0062] The dimensions of each part in the current sensor 1 of the embodiment are shown below.

[0063] As the magnetic shielding component 4, the following magnetic shielding component is used: the width A in the Y direction of the bottom 41 (the gap in the Y direction between the two side wall portions 42) is 10 mm, the thickness B of the bottom 41 and the side wall portions 42 is 2 mm, the depth C in the X direction of the bottom 41 and the side wall portions 42 is 6 mm, and the length D of the side wall portions 42 protruding from both sides of the bottom 41 in the Z direction is 6 mm.

[0064] As the elimination component 5, an elimination component with a width a of 1 mm in the Y direction, a thickness b of 0.03 mm in the Z direction, and a depth c of 0.1 mm in the X direction is used.

[0065] The gap E between the magnetic shield 4 and the magnetic device 21 in the Z direction (the gap between the Z2 side end of the side wall 42 and the Z1 side detection surface of the magnetic device 21) is set to 0.5 mm, and the gap e between the elimination component 5 and the magnetic device 21 in the Z direction is set to 0.05 mm.

[0066] As a comparative example, the current sensor 100 differs from the current sensor 1 of Embodiment 1 in that it does not have the elimination component 5. The dimensions of the width A, thickness B, depth C and length D of the magnetic shield 4, as well as the gap E in the Z direction between the magnetic shield 4 and the magnetic device 21, use the same dimensions as the current sensor 1.

[0067] For the aforementioned current sensor 1 and current sensor 100, at room temperature, the measured current input to the busbar 3 is sequentially varied from 0A to +450A, from +450A to 0A, from 0A to -450A, and from -450A to 0A, and the output from the current sensor 1 is measured. Furthermore, the + and - values ​​of the current indicate the direction of the measured current in the busbar 3. That is, after the measured current is increased or decreased within the range of 0 to 450A, the measured current is then increased or decreased within the range of 0 to 450A with the opposite direction, and the measurement is performed.

[0068] Figure 10 An approximate straight line is derived based on all measured values. This approximate straight line is then compared with the measured output, and the deviation of the measured output from the approximate straight line is expressed as a graph of linearity (%). For example, if the output value obtained from measuring a certain current is 101, and the calculated output value of the approximate straight line derived from all measured values ​​is 100, the linearity is +1% = (101-100) / 100×100.

[0069] Figure 10 The chart is Figure 3 The current sensor 1 of the embodiment shown and Figure 11The comparative example shown is a current sensor 100 measuring the effect of magnetic hysteresis on magnetic shielding 4. The solid line represents the embodiment, and the dashed line represents the comparative example.

[0070] like Figure 10 As shown in the chart, by configuring the elimination component 5 in the magnetic sensor 2, the influence of the residual magnetic field caused by the hysteresis of the magnetic shield can be suppressed, and the linearity of the current sensor 1 measurement is improved.

[0071] also, Figure 10 The graph shown is discontinuous at a current of 0A. This is because the evaluation result when the current changes and returns to 0A differs from the evaluation result at the initial time point of 0A due to the effect of hysteresis.

[0072] The current sensor 1 of this embodiment suppresses the influence of residual magnetic fields by arranging the elimination component 5 near the magnetic device 21. This small elimination component 5 improves the linearity of the current sensor 1's measurement, thus facilitating miniaturization, thinning, and weight reduction of the current sensor 1.

[0073] According to the results of the current sensor 1 in the embodiment, the gap e between the magnetic device 21 of the magnetic sensor 2 and the elimination component 5 is 1 / 20 to 4 / 20 and 0.25 to 0.10 mm, which is the same as the gap E between the magnetic device 21 and the magnetic shield 4. The elimination component 5 is arranged near the magnetic device 21. The elimination component 5 is small, with a width a of 1 / 20 to 4 / 20 of the width A of the bottom 41 of the magnetic shield 4, a thickness b of 1 / 200 to 6 / 200 of the thickness B of the magnetic shield 4, and a depth c of about 1 / 120 to 4 / 120 of the depth C of the magnetic shield 4. It can be said that the linearity of the measurement in the current sensor 1 is improved.

[0074] The embodiments disclosed in this specification are illustrative in all respects and are not intended to limit the invention to these embodiments. The scope of the invention is not defined solely by the description of the embodiments above, but by the claims, which are intended to include all modifications equivalent to and within the scope of the claims.

[0075] [Industrial Applicability] The present invention is useful, for example, as a current sensor for measuring the current flowing through a device in order to control a power system of a vehicle equipped with various devices.

[0076] Explanation of reference numerals in the attached figures 1: Current sensor 2: Magnetic sensor 21: Magnetic components 21S: Surface 22: Packaging 23: Framework 23S1: Surface 23S2: Surface 24: Integrated Circuits 3: Busbar 4: Magnetic shielding components 41: Bottom 42: Side wall portion 5: Eliminate parts 6: First shell 7: Second shell 100: Current sensor A: Width B: Thickness C: Depth D: Length E: Gap a: width b: Thickness c: Depth e: gap

Claims

1. A current sensor comprising a magnetic sensor with built-in magnetic components, a busbar, and a magnetic shielding component. It has a cancellation component composed of magnetic materials. The elimination component is positioned at a location where the residual magnetic field generated by the elimination component weakens the residual magnetic field generated by the magnetic shield.

2. The current sensor according to claim 1, The elimination component is integrally formed with the magnetic sensor.

3. The current sensor according to claim 2, The elimination component is disposed inside the package that forms the shape of the magnetic sensor.

4. The current sensor according to claim 2, The elimination component is disposed on the surface of the magnetic device opposite to the busbar.

5. The current sensor according to claim 2, The magnetic sensor has a frame for mounting the magnetic device. The elimination component is disposed on the back side of the face in the frame on which the magnetic device is mounted.

6. The current sensor according to claim 2, The elimination component is disposed on the outer peripheral surface of the package that forms the shape of the magnetic sensor.

7. The current sensor according to claim 1, The magnetic device is a magnetoresistive element.

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