Magnetic sensor and current sensor

Abstract

To provide a magnetic sensor and a current sensor that can improve temperature characteristics while maintaining flexibility.SOLUTION: A magnetic sensor 30 comprises an excitation coil 45 formed of a flexible substrate, and an excitation core 44 extending in an axial direction of the excitation coil 45 and around which the excitation coil 45 is wound. The excitation core 44 is arranged in the flexible substrate in such a state that, when the flexible substrate is deformed, at least part of the excitation core 44 can move relative to the flexible substrate in a belt length direction of the excitation core 44.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to magnetic sensors and current sensors. [Background technology]

[0002] A fluxgate sensor formed from a flexible substrate is known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-94723 A Summary of the Invention [Problem to be solved by the invention]

[0004] The flexible substrate is composed of a resin, an adhesive, or the like. The magnetic core of the fluxgate sensor is placed in the flexible substrate and receives mechanical stress from the flexible substrate. For example, the magnetic core may receive stress when the temperature changes due to the difference between the thermal expansion coefficient of the magnetic core and the thermal expansion coefficient of the resin or adhesive of the flexible substrate. When the magnetic core receives stress, the magnetic characteristics of the magnetic core change. The change in the magnetic characteristics of the magnetic core changes the magnetic flux detection sensitivity or phase characteristics of the fluxgate sensor. That is, the temperature characteristics of the fluxgate sensor deteriorate. On the other hand, the fluxgate sensor is formed by a flexible substrate, which has the advantage of having flexibility. It is required to improve the temperature characteristics while maintaining the flexibility.

[0005] The present disclosure has been made in consideration of the above-mentioned points, and has an object to provide a magnetic sensor that can improve temperature characteristics while maintaining flexibility, and a current sensor that can improve reliability. [Means for solving the problem]

[0006] (1) A magnetic sensor according to some embodiments includes an excitation coil formed of a flexible substrate, and an excitation core around which the excitation coil is wound, the excitation core extending in an axial direction of the excitation coil. The excitation core is disposed in the flexible substrate such that, when the flexible substrate is deformed, at least a portion of the excitation core can move in a strip length direction of the excitation core relative to the flexible substrate.

[0007] The magnetic sensor according to this embodiment can reduce the stress in the strip length direction of the excitation core caused by the thermal deformation of the flexible substrate in response to the temperature change of the magnetic sensor. In addition, the stress in the strip length direction of the excitation core is reduced without increasing the rigidity of the excitation core. As a result, the temperature characteristics of the magnetic sensor are improved while maintaining the flexibility of the magnetic sensor.

[0008] (2) In the magnetic sensor described in (1) above, the flexible substrate may include an excitation core layer having a wall portion that defines a space in which the excitation core is located, and two coil pattern layers that include the pattern of the excitation coil and are positioned to sandwich the excitation core layer. The width of the space defined by the wall portion of the excitation core layer may be longer than the width of the excitation core. The thickness of the excitation core layer may be greater than the thickness of the excitation core. In this way, the excitation core can move in the strip length direction without being fixed while disposed in the flexible substrate.

[0009] (3) In the magnetic sensor described in (2) above, the flexible substrate may further include an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive may be positioned so as not to fix the excitation core to the flexible substrate. In this way, the excitation core can move in the strip length direction while being disposed in the flexible substrate without being fixed.

[0010] (4) In the magnetic sensor described in (3) above, the adhesive may be a thermosetting resin and may be located farther from the space in which the excitation core is located than the wall of the excitation core layer before the heat curing process. This reduces the possibility that the adhesive will spread to the space in which the excitation core is located before the adhesive is heat cured. The reduced possibility of the adhesive spreading reduces the possibility that the excitation core will be bonded to the flexible substrate.

[0011] (5) In the magnetic sensor described in (2) above, the flexible substrate may further include an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive may be positioned so as to fix the excitation core to the flexible substrate at only one point. In this way, even if thermal deformation of the flexible substrate occurs, the excitation core can move in both directions in the strip length direction relative to the flexible substrate from the fixed point. Therefore, stress in the strip length direction caused by thermal deformation of the flexible substrate is not generated in the excitation core.

[0012] (6) In the magnetic sensor described in (2) above, the flexible substrate may further include an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive may be positioned so as to fix the excitation core to the flexible substrate at a plurality of locations spaced apart by a predetermined distance or more. In this manner, when the flexible substrate contracts in the strip length direction, the excitation core can bend in the thickness direction within the range between the fixed locations. By bending the excitation core in the thickness direction, stress generated in the excitation core in the strip length direction when the flexible substrate contracts in the strip length direction is reduced.

[0013] (7) The magnetic sensor according to any one of (1) to (6) above may further include a non-magnetic thin film member that isolates the excitation core from the flexible substrate. The thin film member may be fixed to the flexible substrate, and may not be fixed to the excitation core. This reduces restrictions on the application range of the adhesive. As a result, the flexible substrate can be easily formed.

[0014] (8) In the magnetic sensor described in (7) above, the thin film member may include a first thin film member and a second thin film member sandwiching the excitation core. The first thin film member and the second thin film member may be joined at an end of the excitation core in the strip width direction. By sandwiching the excitation core between the thin film members, the excitation core is less likely to fall off the magnetic sensor 30.

[0015] (9) The magnetic sensor according to any one of (1) to (8) above may further include a non-magnetic lubricating member located between the excitation core and the flexible substrate. By including the lubricating member in the magnetic sensor, stress in the strip length direction of the excitation core 44 is further reduced.

[0016] (10) A current sensor according to some embodiments includes the magnetic sensor according to any one of (1) to (9) above, and a current detection circuit connected to the excitation coil of the magnetic sensor. By including the magnetic sensor according to the above-mentioned embodiments, the reliability of the current sensor can be improved. Effect of the Invention

[0017] The magnetic sensor according to the present disclosure can improve the temperature characteristics of the sensor while maintaining the flexibility of the sensor, and the current sensor according to the present disclosure can improve the reliability. [Brief description of the drawings]

[0018] [Figure 1] 1 is a plan view showing a configuration of a magnetic sensor according to a first comparative example. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 11 is a plan view showing a configuration of a magnetic sensor according to a second comparative example. [Figure 4] BB cross-sectional view of FIG. 3. [Diagram 5] 3C is a cross-sectional view taken along line CC in FIG. [Figure 6A] 13 is a cross-sectional view showing a state of an excitation core when the magnetic sensor according to the second comparative example has reached a low temperature. FIG. [Figure 6B]11 is a cross-sectional view showing a state of an excitation core when the magnetic sensor according to the second comparative example has reached room temperature. FIG. [Figure 6C] 11 is a cross-sectional view showing a state of an excitation core when the magnetic sensor according to the second comparative example becomes hot. FIG. [Figure 7A] 10 is a graph showing output characteristics of the magnetic sensor according to the second comparative example when the temperature becomes low. [Figure 7B] 10 is a graph showing output characteristics of the magnetic sensor according to the second comparative example when the temperature reaches room temperature. [Figure 7C] 10 is a graph showing output characteristics of the magnetic sensor according to the second comparative example when the temperature becomes high. [Figure 8] 1 is a plan view illustrating a configuration example of a magnetic sensor according to an embodiment of the present disclosure. [Figure 9] FIG. 9 is a cross-sectional view taken along the line DD in FIG. [Figure 10] FIG. 4 is a schematic diagram showing the position of an adhesive in an exciting core layer. [Figure 11A] 11 is a cross-sectional view showing a state of an excitation core when a magnetic sensor according to an embodiment of the present disclosure has reached a low temperature. [Figure 11B] 1 is a cross-sectional view showing a state of an excitation core when a magnetic sensor according to an embodiment of the present disclosure has reached room temperature. [Figure 11C] 11 is a cross-sectional view showing a state of an excitation core when a magnetic sensor according to an embodiment of the present disclosure becomes hot. [Figure 12A] 11 is a graph showing output characteristics of a magnetic sensor according to an embodiment of the present disclosure when the temperature drops. [Figure 12B] 11 is a graph showing output characteristics of a magnetic sensor according to an embodiment of the present disclosure at room temperature. [Figure 12C] 11 is a graph showing output characteristics of a magnetic sensor according to an embodiment of the present disclosure when the temperature becomes high. [Figure 13] 1 is a schematic diagram illustrating a configuration example of a current sensor according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] (Magnetic sensor according to comparative example) 1, the magnetic sensor 900 according to the first comparative example is a fluxgate sensor configured by a flexible substrate including a sensor body 910 and a wiring section 950. The sensor body 910 includes an excitation core 920, an excitation coil 930, and a wiring via 940. The wiring section 950 includes wiring 960 and terminals 970 for passing a current through the excitation coil 930 and outputting a voltage of the excitation coil 930.

[0020] The excitation coil 930 is formed by a flexible substrate. The excitation core 920 is arranged so as to extend in the axial direction of the excitation coil 930 inside the winding of the excitation coil 930. That is, the excitation coil 930 is wound around the excitation core 920. The excitation core 920 is assumed to be a strip-shaped magnetic foil. The strip-shaped magnetic foil may be configured to include a soft magnetic thin film material such as a permalloy thin film or an amorphous thin film. The sensor body 910 is assumed to be strip-shaped. The direction in which the strip-shaped excitation core 920 and the sensor body 910 extend is also referred to as the strip length direction. The direction perpendicular to the strip length direction in the plane in which the sensor body 910 extends is also referred to as the strip width direction. The direction perpendicular to the strip length direction and the strip width direction is also referred to as the thickness direction.

[0021] As shown in FIG. 2, the sensor body 910 includes a plurality of resin layers 934 that are laminated by bonding with an adhesive 935. The adhesive 935 is a thermosetting resin. The flexible substrate including the sensor body 910 is formed by laminating a plurality of resin layers 934 to which the adhesive 935 is applied, and performing heating and pressing. The resin layer 934 is a material having flexibility or flexibility, such as polyimide. The resin layer 934 includes a layer on which the coil wiring 931 of the excitation coil 930 is formed, and a layer on which the shield 933 is formed. The coil wiring 931 and the shield 933 are formed of copper foil. The shield 933 functions as an electric field shield that absorbs radiant energy from the excitation coil 930.

[0022] The excitation core 920 is bonded by adhesive 935 between layers on which the coil wiring 931 of the excitation coil 930 is formed. The coil wiring 931 formed on each of the two layers of the excitation coil 930 is connected by embedded wiring 932.

[0023] The magnetic sensor 900 according to the first comparative example has excellent mechanical flexibility. When the magnetic sensor 900 is mounted on a split-core type or clamp type current sensor, the magnetic sensor 900 can deform in response to the opening and closing operation of the magnetic core of the current sensor. Therefore, the mechanical flexibility of the magnetic sensor 900 provides diversity in the installation method of the magnetic sensor 900. The diversity in the installation method of the magnetic sensor 900 makes it easy to increase the magnetic flux detection sensitivity of the magnetic sensor 900.

[0024] Here, the magnetic sensor 900 according to the first comparative example deforms in response to a temperature change of the magnetic sensor 900 due to the difference between the thermal expansion coefficient of the excitation core 920 and the thermal expansion coefficient of the resin layer 934, the coil wiring 931, or the shield 933. The deformation of the magnetic sensor 900 generates stress in the excitation core 920 of the magnetic foil. The generation of stress in the magnetic foil changes the magnetic characteristics of the magnetic foil. As a result, a problem occurred in which the magnetic flux detection sensitivity or phase characteristics of the magnetic sensor 900 as a fluxgate sensor change depending on the temperature. Therefore, there was a demand for improving the temperature characteristics of the magnetic sensor 900 according to the first comparative example.

[0025] 3, the magnetic sensor 800 according to the second comparative example is a fluxgate sensor configured by a flexible substrate including a sensor body 840, a shield portion 850, and a wiring portion 861. The sensor body 840 is connected to each of the two shield portions 850 via bridging portions 860. The magnetic sensor 800 is used by being folded at the bridging portions 860 so that the two shield portions 850 sandwich the sensor body 840 from both sides in the thickness direction. The wiring portion 861 includes a pattern of wiring 863 connected to an excitation coil 845 (see FIG. 5) and a terminal 862 for connecting the wiring 863 to an external power source.

[0026] As shown in FIG. 4, the shield section 850 includes a plurality of resin layers 851 that are laminated and bonded with an adhesive 852. The adhesive 852 is a thermosetting resin. The flexible substrate including the shield section 850 is formed by laminating a plurality of resin layers 851 to which the adhesive 852 is applied, and performing heating and pressing. The resin layer 851 is a material having flexibility or flexibility, such as polyimide. The resin layer 851 includes a layer on which a pattern of the wiring 863 is formed, and a layer on which a pattern of the shield 864 is formed. The patterns of the wiring 863 and the shield 864 are formed of copper foil. The shield 864 functions as an electric field shield that absorbs radiant energy from the excitation coil 845 (see FIG. 5).

[0027] As shown in Fig. 5, the sensor body 840 includes a plurality of resin layers 842 that are laminated and bonded with an adhesive 846. The adhesive 846 is a thermosetting resin. The flexible substrate including the sensor body 840 is formed by laminating a plurality of resin layers 842 to which the adhesive 846 is applied, and performing heating and pressing. The resin layer 842 is a material having flexibility or flexibility, such as polyimide. The resin layer 842 includes a layer in which the coil wiring 847 of the excitation coil 845 is formed. The coil wiring 847 is formed of copper foil.

[0028] The excitation core 844 is bonded by adhesive 846 between layers on which coil wiring 847 of the excitation coil 845 is formed. The coil wiring 847 formed on each of the two layers of the excitation coil 845 is connected by embedded wiring 848.

[0029] In the magnetic sensor 800 according to the second comparative example, the sensor body 840 and the shield portion 850 are formed as separate substrates and then folded for use, thereby reducing stress generated in the excitation core 844 due to thermal expansion of the shield portion 850. The temperature characteristics of the magnetic sensor 800 according to the second comparative example are improved compared to the temperature characteristics of the magnetic sensor 900 according to the first comparative example due to the reduction in stress generated in the excitation core 844.

[0030] However, there is room for further improvement in the temperature characteristics of the magnetic sensor 800 according to the second comparative example. Specifically, as shown in Figs. 6A, 6B, and 6C, in the sensor main body 840, the excitation core 844 is bonded to the resin layer 842, so that a stress in the strip length direction due to the thermal expansion of the resin layer 842 occurs in the excitation core 844. Fig. 6A shows a state in which the magnetic sensor 800 has reached a low temperature. Fig. 6B shows a state in which the magnetic sensor 800 has reached a room temperature. Fig. 6C shows a state in which the magnetic sensor 800 has reached a high temperature. The high temperature is the temperature when heating is performed to form the flexible substrate of the magnetic sensor 800. On the other hand, the room temperature is a temperature lower than the high temperature. Also, the low temperature is a temperature lower than the room temperature.

[0031] Fig. 6C shows the state when the flexible substrate is formed by performing heating and pressing. On the other hand, Fig. 6A and Fig. 6B show the state in which the exciting core 844, the resin layer 842, and the adhesive 846 have shrunk due to a decrease in temperature compared to the state when the flexible substrate was formed. In Fig. 6A and Fig. 6C, the dashed lines drawn on the resin layer 842 and the adhesive 846 show the shapes of the resin layer 842 and the adhesive 846 when the magnetic sensor 800 is at room temperature.

[0032] When the thermal expansion coefficient of the exciter core 844 is smaller than that of the resin layer 842 and the adhesive 846, the resin layer 842 and the adhesive 846 shrink more in the strip length direction than the exciter core 844. In the comparative example, the shrinkage of the exciter core 844 is assumed to be negligibly small. As a result, in the strip length direction of the exciter core 844, compressive stress occurs due to the shrinkage of the resin layer 842 and the adhesive 846 in the strip length direction in the state shown in Figures 6A and 6B.

[0033] The temperature characteristics of the magnetic sensor 800 according to the second comparative example will be described with reference to the graphs of Figures 7A, 7B, and 7C. Figure 7A shows the magnetic characteristics when the magnetic sensor 800 is at a low temperature. Figure 7B shows the magnetic characteristics when the magnetic sensor 800 is at a room temperature. Figure 7C shows the magnetic characteristics when the magnetic sensor 800 is at a high temperature. The vertical axis of each graph shows the current or voltage output. The horizontal axis shows time. The dashed line graph shows the output waveform of the current flowing through the excitation coil 845 when the magnetic sensor 800 is driven. The solid line graph shows the output waveform of the voltage of the excitation coil 845 when the magnetic sensor 800 is driven.

[0034] As a driving condition of the magnetic sensor 800, constant current application driving is performed on the excitation coil 845. The constant current application driving can be rephrased as constant magnetic field application driving. A large voltage waveform induced in the excitation coil 845 indicates that there is a large amount of magnetic flux interlinking with the excitation coil 845, and also indicates that the magnetic permeability of the excitation core 844 is large. Under this driving condition, the smaller the change in the magnetic permeability of the excitation core 844 with respect to the temperature change of the magnetic sensor 800, the better the temperature characteristic of the magnetic sensor 800. In other words, when the excitation coil 845 is driven with a constant current, the smaller the change in the voltage waveform induced in the excitation coil 845 when the temperature of the magnetic sensor 800 changes, the better the temperature characteristic of the magnetic sensor 800. Conversely, if the excitation coil 845 is driven with a constant current to apply a constant magnetic field, but the output voltage of the excitation coil 845, i.e., the magnetic flux generated by the excitation coil 845, varies with temperature, the temperature characteristic of the magnetic sensor 800 is poor.

[0035] However, as shown in the graphs of Figures 7A, 7B, and 7C, the voltage waveform changes significantly when the temperature of the magnetic sensor 800 is low, normal, and high. The change in the voltage waveform according to the change in temperature represents the change in the magnetic properties of the excitation core 844. The change in the magnetic properties of the excitation core 844 is caused by the stress generated in the strip length direction of the excitation core 844 described above.

[0036] In order to improve the temperature characteristics of the magnetic sensor 800, it is conceivable to thicken the magnetic foil excitation core 844 to increase the rigidity of the excitation core 844 itself. However, by thickening the excitation core 844, the inductance increases, making excitation difficult. Furthermore, by thickening the excitation core 844, the flexibility of the magnetic sensor 800 may be impaired.

[0037] As described above, there is room for improvement in the temperature characteristics of the magnetic sensors 900 and 800 according to the comparative examples. It is required to improve the temperature characteristics of the sensor while maintaining the flexibility of the sensor. Hereinafter, in this disclosure, a magnetic sensor 30 (see FIG. 8) that can improve the temperature characteristics while maintaining the flexibility and a current sensor 1 (see FIG. 13) that can improve the reliability will be described.

[0038] (Magnetic sensor 30 according to the present disclosure) 8 and 9, the magnetic sensor 30 according to the embodiment of the present disclosure includes an excitation core 44 made of a magnetic material and an excitation coil 45. The excitation coil 45 is formed of a flexible substrate. The excitation core 44 is disposed on the flexible substrate so as to extend in the axial direction of the excitation coil 45 inside the winding of the excitation coil 45. In other words, the excitation coil 45 is wound around the excitation core 44.

[0039] The shape of the excitation core 44 in a cross-sectional view in the extending direction may be substantially rectangular. That is, the shape of the excitation core 44 may be strip-shaped. In this embodiment, the shape of the excitation core 44 is strip-shaped. That is, the excitation core 44 is strip-shaped magnetic foil. The strip-shaped magnetic foil may be composed of a soft magnetic thin film material such as a permalloy thin film or an amorphous alloy thin film.

[0040] The flexible substrate forming the excitation coil 45 includes an excitation core layer 41, and a first coil pattern layer 42 and a second coil pattern layer 43 positioned to sandwich the excitation core layer 41. When it is not necessary to distinguish between the first coil pattern layer 42 and the second coil pattern layer 43, they are simply referred to as coil pattern layers. That is, the flexible substrate includes two coil pattern layers positioned to sandwich the excitation core layer 41. The excitation core layer 41 and the coil pattern layer are configured to include a resin layer having flexibility or flexibility such as polyimide. The resin layer of the excitation core layer 41 and the coil pattern layer is assumed to have a strip shape. The resin layer of the excitation core layer 41 is also referred to as an excitation core resin layer 411. The resin layer of the coil pattern layer is also referred to as a coil pattern resin layer. The resin layer of the first coil pattern layer 42 is also referred to as a first coil pattern resin layer 421. The resin layer of the second coil pattern layer 43 is also referred to as a second coil pattern resin layer 431.

[0041] The direction in which the strip-shaped excitation core 44 and the flexible substrate extend is also referred to as the strip length direction. The direction perpendicular to the strip length direction in the plane in which the flexible substrate extends is also referred to as the strip width direction. The direction perpendicular to the strip length direction and the strip width direction is also referred to as the thickness direction. The dimension of the excitation core 44 in the strip width direction is also referred to as the width of the excitation core 44. The dimension of the excitation core 44 in the thickness direction is also referred to as the thickness of the excitation core 44. The thickness of the excitation core 44 may be, for example, 100 μm or less. The excitation core 44 has flexibility due to its strip shape.

[0042] The coil pattern layer further includes a coil wiring 47 formed on the resin layer. The coil wiring 47 is a part of the excitation coil 45. The coil wiring 47 may be composed of a metal material such as copper foil or other conductive material. The resin layer may be composed of, for example, polyimide.

[0043] The exciting core layer 41 has wiring vias 48 that connect the coil wirings 47 of the two coil pattern layers that sandwich the exciting core layer 41. The wiring vias 48 are configured as through holes filled with a conductor. The exciting coil 45 is configured by connecting the coil wiring 47 of the coil pattern layer and the wiring vias 48 of the exciting core layer 41. The resin portions such as polyimide of the exciting core layer 41 and the coil pattern layer function as an insulating material that prevents the coil wirings 47 from shorting out.

[0044] The exciting core layer 41 has a wall portion 412 that defines the end in the band width direction of the opening of the exciting core resin layer 411. The opening of the exciting core resin layer 411 is a space in which the exciting core 44 is located. The end in the thickness direction of the space in which the exciting core 44 is located is defined by the coil pattern resin layers that sandwich the exciting core layer 41. The space in which the exciting core 44 is located is a rectangular parallelepiped extending in the band length direction.

[0045] The width of the space in which the excitation core 44 is located is the length of the space along the band width direction. The width of the space in which the excitation core 44 is located may be greater than the width of the excitation core 44 or may be the same as the width of the excitation core 44. The thickness of the space in which the excitation core 44 is located is the length of the space along the thickness direction. The thickness of the excitation core layer 41 may be greater than the thickness of the excitation core 44 or may be the same as the thickness of the excitation core 44.

[0046] The exciting core layer 41 and the coil pattern layer of the flexible substrate are bonded by an adhesive 46. The adhesive 46 is located between the exciting core layer 41 and the first coil pattern layer 42, and bonds the exciting core layer 41 and the first coil pattern layer 42. The adhesive 46 is also located between the exciting core layer 41 and the second coil pattern layer 43, and bonds the exciting core layer 41 and the second coil pattern layer 43. In the present disclosure, the adhesive 46 is a thermosetting resin. When the adhesive 46 is a thermosetting resin, the flexible substrate may be formed by applying the adhesive 46 between the exciting core layer 41 and the coil pattern layer and pressing the adhesive 46 while heating it to a temperature at which the adhesive 46 hardens. The adhesive 46 is not limited to a thermosetting resin and may be configured to include various other materials. The adhesive 46 may also be replaced with various other members, such as an adhesive tape, that can bond the exciting core layer 41 and the coil pattern layer.

[0047] The portion of the flexible substrate where the excitation coil 45 is formed is also referred to as the sensor body 40. In addition to the sensor body 40, the flexible substrate may further include a shield 50. The shield 50 is formed by forming a strip-shaped conductor on a flexible resin such as polyimide. The strip-shaped conductor extends in the strip length direction. The strip-shaped conductor may be formed of, for example, copper foil.

[0048] The flexible substrate may further include a bridging portion 60 that connects the sensor body 40 and the shield 50. In this embodiment, the sensor body 40 and the shield 50 are aligned in the strip width direction of the excitation core 44. The flexible substrate is folded at the bridging portion 60, so that the sensor body 40 is covered with the shield 50 from its thickness direction. When the flexible substrate includes two shields 50, the sensor body 40 is covered with the shield 50 from both sides in the thickness direction. One of the two shields 50 is superimposed on the sensor body 40 from its thickness direction by folding the flexible substrate at the bridging portion 60 in a mountain direction. The other shield 50 is superimposed on the sensor body 40 from its thickness direction by folding the flexible substrate at the bridging portion 60 in a valley direction. The shield 50 functions as an electric field shield for the sensor body 40 by covering the sensor body 40 from its thickness direction.

[0049] The flexible substrate may further include a wiring portion 61 and a terminal portion 62. The wiring portion 61 is formed with a wiring pattern for passing a current through the coil wiring 47 and a wiring pattern for grounding the conductor of the shield 50. The terminal portion 62 may be configured to include a connector for connecting the wiring formed in the wiring portion 61 to an external power source or the like.

[0050] As described above, the space in which the excitation core 44 is located is defined in the flexible substrate of the magnetic sensor 30 according to the present disclosure. The excitation core 44 is disposed in the space defined in the flexible substrate. The excitation core 44 is disposed in the flexible substrate such that at least a portion of the excitation core 44 can move in the strip length direction relative to the flexible substrate.

[0051] Since at least a portion of the excitation core 44 can move in the strip length direction relative to the flexible substrate, stress in the strip length direction is less likely to be applied from the flexible substrate to the excitation core 44 when the flexible substrate is deformed in the strip length direction.

[0052] For example, when the thermal expansion coefficient of the flexible substrate differs from that of the excitation core 44, the amount of deformation in the strip length direction of the flexible substrate differs from the amount of deformation in the strip length direction of the excitation core 44 due to a change in temperature of the entire magnetic sensor 30. In this case, at least a part of the excitation core 44 can move in the strip length direction relative to the flexible substrate, thereby reducing stress in the strip length direction that occurs in the excitation core 44 due to the difference in the amount of deformation in the strip length direction.

[0053] The magnetic characteristics of the excitation core 44 change when stress is applied to the excitation core 44. When stress is applied to the excitation core 44 due to a temperature change in the magnetic sensor 30, the temperature dependency of the magnetic characteristics of the magnetic sensor 30 increases. In other words, the temperature characteristics of the magnetic sensor 30 deteriorate. In the magnetic sensor 30 according to the present disclosure, at least a part of the excitation core 44 can move in the strip length direction relative to the flexible substrate, so that the stress in the strip length direction applied to the excitation core 44 due to the thermal deformation of the flexible substrate when the temperature of the magnetic sensor 30 changes is reduced. The temperature dependency of the magnetic characteristics of the magnetic sensor 30 is reduced by reducing the stress in the strip length direction applied to the excitation core 44 due to the temperature change of the magnetic sensor 30. In other words, the temperature characteristics of the magnetic sensor 30 are improved.

[0054] <Mode in which the excitation core 44 is not fixed to the flexible substrate> As one embodiment in which the excitation core 44 is arranged so as to be movable in the strip length direction, the excitation core 44 may be arranged so as not to be fixed to the flexible substrate. In this case, the entire excitation core 44 can move in the strip length direction relative to the flexible substrate.

[0055] For example, as described above, the width of the space in which the excitation core 44 is located is greater than the width of the excitation core 44, and the thickness of the space in which the excitation core 44 is located is greater than the thickness of the excitation core 44, so that the excitation core 44 can move in the band length direction without being fixed while positioned within the flexible substrate.

[0056] Furthermore, since the excitation core 44 is not bonded to the flexible substrate, the excitation core 44 can move in the strip length direction without being fixed while disposed in the flexible substrate. In order to form the flexible substrate so that the excitation core 44 is not bonded to the flexible substrate, the range in which the adhesive 46 is applied between the excitation core layer 41 and the coil pattern layer may be limited to a range in which the adhesive 46 does not come into contact with the excitation core 44. The range in which the adhesive 46 is applied may be limited to a range in which the adhesive 46 does not overlap with the excitation core 44 when the flexible substrate is viewed in a plane in the thickness direction.

[0057] The adhesive 46 may be applied in a limited area away from the space where the excitation core 44 is located, as shown in Fig. 10. If the adhesive 46 is a thermosetting resin, the adhesive 46 may spread beyond the applied area by performing heating and pressing when forming the flexible substrate. In other words, the adhesive 46 may be positioned away from the space where the excitation core 44 is located, beyond the wall portion 412 of the excitation core layer 41 that divides the space, before the heat curing process.

[0058] By applying the adhesive 46 only to a range away from the space where the excitation core 44 is located, the possibility that the adhesive 46 will spread to the space where the excitation core 44 is located before being thermally cured is reduced. The reduced possibility of the adhesive 46 spreading reduces the possibility that the excitation core 44 will be bonded to the flexible substrate. As a result, the excitation core 44 is disposed in the flexible substrate so as to be movable in the strip length direction. Note that after the adhesive 46 has been thermally cured, even if the excitation core 44 comes into contact with the adhesive 46, it will not be bonded to the flexible substrate by the adhesive 46. In other words, even if the excitation core 44 moves in the flexible substrate and comes into contact with the thermally cured adhesive 46, the temperature characteristics of the magnetic sensor 30 will not deteriorate.

[0059] Even when the excitation core 44 is not fixed to the flexible substrate, the excitation core layer 41 is designed so that the width or thickness of the space in which the excitation core 44 is located is close to the width or thickness of the excitation core 44, so that the excitation core 44 is held on the flexible substrate by friction between the excitation core 44 and the flexible substrate. Even when the excitation core 44 is held on the flexible substrate only by friction, the excitation core 44 is unlikely to fall off the flexible substrate. In addition, the magnetic sensor 30 is often used while being bent by utilizing the flexibility of the flexible substrate. By using the magnetic sensor 30 while being bent, the excitation core 44 is even less likely to fall off the flexible substrate. When the magnetic sensor 30 is used while being bent, bending stress is generated by bending the excitation core 44. However, the bending stress is hardly dependent on temperature changes. Therefore, even when the magnetic sensor 30 is used while being bent, the temperature characteristics of the magnetic sensor 30 are not deteriorated.

[0060] When the entire excitation core 44 can move in the strip length direction relative to the flexible substrate, stress in the strip length direction caused by thermal deformation of the flexible substrate when the temperature of the magnetic sensor 30 changes is not generated in the excitation core 44. Therefore, the temperature dependency of the magnetic characteristics of the magnetic sensor 30 is reduced. In other words, the temperature characteristics of the magnetic sensor 30 are improved.

[0061] <Aspect in which only a part of the excitation core 44 is fixed to the flexible substrate> As one mode in which the excitation core 44 is arranged so as to be movable in the strip length direction, only a portion of the excitation core 44 may be fixed to the flexible substrate. For example, the excitation core 44 may be fixed to the flexible substrate at only one point. In this case, even if thermal deformation of the flexible substrate occurs, the excitation core 44 can move in both directions in the strip length direction relative to the flexible substrate from the fixed point. Therefore, no stress in the strip length direction due to thermal deformation of the flexible substrate is generated in the excitation core 44. As a result, the temperature characteristics of the magnetic sensor 30 are improved.

[0062] The excitation core 44 may be fixed to the flexible substrate at a plurality of locations spaced apart by a predetermined distance or more. In this case, the excitation core 44 can bend in the thickness direction in the range between the fixed locations when the flexible substrate contracts in the strip length direction. By bending the excitation core 44 in the thickness direction, the stress generated in the excitation core 44 in the strip length direction when the flexible substrate contracts in the strip length direction is reduced.

[0063] Specifically, when the flexible substrate is formed by heating and pressing, the flexible substrate and the excitation core 44 are fixed to each other based on the shape at the temperature during the heat treatment. When the temperature range in which the magnetic sensor 30 is used is lower than the temperature during the heat treatment, the amount of contraction in the strip length direction of the flexible substrate in the temperature range in which the magnetic sensor 30 is used is greater than the amount of contraction in the strip length direction of the excitation core 44. Therefore, when the excitation core 44 is fixed to the flexible substrate at a plurality of isolated points, the excitation core 44 bends in the thickness direction, thereby reducing the stress generated in the strip length direction of the excitation core 44.

[0064] <Temperature characteristics of magnetic sensor 30> The temperature characteristics of the magnetic sensor 30 represent the effect that a change in temperature of the magnetic sensor 30 has on the magnetic characteristics of the magnetic sensor 30. Specifically, the smaller the change in the magnetic characteristics of the magnetic sensor 30 in response to a change in temperature of the magnetic sensor 30, the better the temperature characteristics of the magnetic sensor 30. Conversely, the larger the change in the magnetic characteristics of the magnetic sensor 30 in response to a change in temperature of the magnetic sensor 30, the worse the temperature characteristics of the magnetic sensor 30.

[0065] The magnetic characteristics of the magnetic sensor 30 change according to the magnitude of the stress in the strip length direction generated in the excitation core 44. Therefore, the smaller the change in the magnitude of the stress in the strip length direction generated in the excitation core 44, the smaller the change in the magnetic characteristics of the magnetic sensor 30. In other words, the smaller the change in the magnitude of the stress in the strip length direction generated in the excitation core 44 in response to temperature changes in the magnetic sensor 30, the better the temperature characteristics of the magnetic sensor 30.

[0066] The stress in the strip length direction generated in the excitation core 44 of the magnetic sensor 30 according to the present disclosure will be described with reference to cross-sectional views of the excitation core 44 viewed from the strip width direction shown in Fig. 11A, Fig. 11B, and Fig. 11C. In each cross-sectional view of the excitation core 44, the excitation core 44, the first coil pattern resin layer 421, and the second coil pattern resin layer 431 are laminated in the thickness direction and extend in the strip length direction.

[0067] FIG. 11A shows a state in which the magnetic sensor 30 has reached a low temperature. FIG. 11B shows a state in which the magnetic sensor 30 has reached a room temperature. FIG. 11C shows a state in which the magnetic sensor 30 has reached a high temperature. The high temperature is the temperature at which heating is performed to form the flexible substrate of the magnetic sensor 30, and is, for example, 100°C to 200°C. On the other hand, the room temperature is a temperature lower than the high temperature, and is, for example, 15°C to 30°C. Moreover, the low temperature is a temperature even lower than the room temperature.

[0068] Fig. 11C shows the state when the flexible substrate is formed by performing heating and pressing. On the other hand, Fig. 11A and Fig. 11B show the state in which the exciting core 44 and the coil pattern resin layer have shrunk due to a decrease in temperature compared to the state when the flexible substrate is formed. In Fig. 11A and Fig. 11C, the dashed lines drawn on the coil pattern resin layer show the shape of the coil pattern resin layer when the magnetic sensor 30 is at room temperature.

[0069] When the thermal expansion coefficient of the excitation core 44 is smaller than that of the coil pattern resin layer, the coil pattern resin layer shrinks more in the strip length direction than the excitation core 44. In this embodiment, the shrinkage of the excitation core 44 is assumed to be negligibly small.

[0070] Here, in the magnetic sensor 30 according to the present disclosure, the excitation core 44 is configured to be movable in the strip length direction relative to the flexible substrate as described above. That is, the excitation core 44 can move in the strip length direction relative to the first coil pattern resin layer 421 and the second coil pattern resin layer 431. Then, as shown in Fig. 11A and Fig. 11B, even if the temperature of the magnetic sensor 30 drops and the coil pattern resin layer shrinks in the strip length direction, the excitation core 44 does not receive a force in the strip length direction from the coil pattern resin layer. Therefore, in the magnetic sensor 30 according to the present disclosure, even if the temperature drops, no stress is generated in the excitation core 44 in the strip length direction.

[0071] The temperature characteristics of the magnetic sensor 30 according to the present disclosure will be described with reference to the graphs of Figures 12A, 12B, and 12C. Figure 12A shows the magnetic characteristics when the magnetic sensor 30 is at a low temperature. Figure 12B shows the magnetic characteristics when the magnetic sensor 30 is at a room temperature. Figure 12C shows the magnetic characteristics when the magnetic sensor 30 is at a high temperature. The vertical axis of each graph shows the current or voltage output. The horizontal axis shows time. The dashed line graph shows the output waveform of the current flowing through the excitation coil 45 when the magnetic sensor 30 is driven. The solid line graph shows the output waveform of the voltage of the excitation coil 45 when the magnetic sensor 30 is driven.

[0072] As a driving condition of the magnetic sensor 30, constant current application driving is performed on the excitation coil 45. The constant current application driving can be rephrased as constant magnetic field application driving. A large voltage waveform induced in the excitation coil 45 indicates that a large amount of magnetic flux interlinks with the excitation coil 45, and also indicates that the magnetic permeability of the excitation core 44 is large. Under this driving condition, the smaller the change in the magnetic permeability of the excitation core 44 with respect to the temperature change of the magnetic sensor 30, the better the temperature characteristic of the magnetic sensor 30. In other words, when the excitation coil 45 is driven with a constant current, the smaller the change in the voltage waveform induced in the excitation coil 45 when the temperature of the magnetic sensor 30 changes, the better the temperature characteristic of the magnetic sensor 30. Conversely, if the excitation coil 45 is driven with a constant current to apply a constant magnetic field, but the output voltage of the excitation coil 45, i.e., the magnetic flux generated by the excitation coil 45, varies with temperature, the temperature characteristic of the magnetic sensor 30 is poor.

[0073] 12A, 12B, and 12C, the change in the voltage waveform at each temperature is smaller than the change in the voltage waveform of the comparative example in Fig. 7A, 7B, and 7C described above. This shows that the temperature characteristic of the magnetic sensor 30 according to the present disclosure is better than that of the magnetic sensor 30 according to the comparative example.

[0074] <Summary> As described above, in the magnetic sensor 30 according to this embodiment, the excitation core 44 can move in the strip length direction relative to the flexible substrate forming the excitation coil 45, thereby reducing the stress in the strip length direction of the excitation core 44 caused by thermal deformation of the flexible substrate in response to temperature changes in the magnetic sensor 30. In addition, the stress in the strip length direction of the excitation core 44 is reduced without increasing the rigidity of the excitation core 44. As a result, the temperature characteristics of the magnetic sensor 30 are improved while maintaining the flexibility of the magnetic sensor 30.

[0075] <Other configuration examples of the excitation core 44> As described above, the excitation core 44 is disposed in the flexible substrate so that at least a portion of the excitation core 44 can move in the strip length direction relative to the flexible substrate. The manner in which the excitation core 44 is disposed in the flexible substrate is not limited to the above-described example.

[0076] The magnetic sensor 30 may further include non-magnetic thin film members that sandwich the excitation core 44 from both sides in the thickness direction. The non-magnetic thin film member may be, for example, an aluminum foil, a stainless steel foil, or a polyimide film. The excitation core 44 is not fixed to the thin film member. The thin film member may be fixed to the flexible substrate. For example, the thin film member may be adhered to the coil pattern layer with an adhesive 46. The thin film member is located between the excitation core 44 and the flexible substrate in the thickness direction. In other words, the thin film member isolates the excitation core 44 from the flexible substrate.

[0077] The thin film member may include a first thin film member located on one side in the thickness direction of the excitation core 44, and a second thin film member located on the other side. The first thin film member and the second thin film member may be joined at least part of the ends in the strip width direction. In other words, the thin film member may be configured in a shape like an envelope with both ends open.

[0078] By providing the magnetic sensor 30 with the thin film member, there are fewer restrictions on the application range of the adhesive 46. As a result, it becomes easier to form a flexible substrate. In addition, by sandwiching the excitation core 44 between the thin film members, the excitation core 44 is less likely to fall off the magnetic sensor 30.

[0079] The magnetic sensor 30 may further include a non-magnetic lubricating member located between the excitation core 44 and the flexible substrate. The non-magnetic lubricating member may be, for example, a powdered solid lubricant. The non-magnetic lubricating member may be attached to at least one surface of the excitation core 44, which is a strip-shaped magnetic foil. By including the lubricating member in the magnetic sensor 30, the stress in the strip length direction of the excitation core 44 is further reduced.

[0080] (Current sensor 1 according to an embodiment of the present disclosure) As shown in FIG. 13, the current sensor 1 includes a sensor head 20 and a current detection circuit 10 as a current detection means. The sensor head 20 includes an annular magnetic sensor 30, an annular reinforcing body for reinforcing the magnetic sensor 30, an inner magnetic collector 21 and an outer magnetic collector 22 as magnetic collectors provided on the inside and outside of the magnetic sensor 30, a case for accommodating the magnetic sensor 30, the reinforcing body, the inner magnetic collector 21 and the outer magnetic collector 22, and a feedback coil 23 wound around the case. The reinforcing body may be a non-magnetic material such as plastic. The inner magnetic collector 21 and the outer magnetic collector 22 may be a material with high magnetic permeability such as permalloy. The feedback coil 23 is wound around only a part of the circumference of the annular case in FIG. 13, but is actually wound around the entire circumference. A measurement object 8 such as an electric wire through which a current to be measured by the current sensor 1 flows passes through the center of the magnetic sensor 30.

[0081] The current detection circuit 10 includes an excitation circuit 11, a detection circuit 12, an LPF circuit 13, an amplifier circuit 14, a feedback circuit 15, and an I / V circuit 16. An excitation coil 45 included in a magnetic sensor 30 (described later) is connected to the excitation circuit 11 and is AC excited by an AC excitation current. The excitation voltage or excitation current of the excitation coil 45 changes due to the action of a current (hereinafter referred to as a measured current) flowing through an object 8 to be measured. The detection circuit 12 detects the change in the excitation voltage or excitation current, and passes it through the LPF circuit 13 to obtain a signal proportional to the measured current.

[0082] The current detection circuit 10 amplifies this signal by the amplifier circuit 14, and generates a current flowing through the feedback coil 23 via the feedback circuit 15. The current flowing through the feedback coil 23 generates a magnetic field inside the feedback coil 23, which results in magnetic flux being generated in the strip-shaped magnetic material, the inner magnetic collector 21, and the outer magnetic collector 22 of the magnetic sensor 30 described later. The winding direction of the feedback coil 23 is such that the magnetic flux due to the current flowing through the feedback coil 23 cancels out the magnetic flux generated by the current to be measured. Therefore, with this configuration, the magnetic flux of the strip-shaped magnetic material, the inner magnetic collector 21, and the outer magnetic collector 22 inside the feedback coil 23 becomes almost zero, and the current flowing through the feedback coil 23 is proportional to the current to be measured. Therefore, the current flowing through the feedback coil 23 is converted into a voltage by the I / V circuit 16 to obtain an output voltage, which is an estimate of the final current to be measured.

[0083] The current sensor 1 described above may be a split core type or a clamp type, etc. In this case, the magnetic sensor 30 deforms following the opening and closing operation of the sensor head 20. The magnetic sensor 30 according to the present disclosure is flexible and therefore unlikely to fail even if it is deformed by the opening and closing operation of the sensor head 20. In addition, the temperature characteristics of the current sensor 1 are improved. Therefore, the reliability of the current sensor 1 can be improved by adopting the magnetic sensor 30 according to the present disclosure.

[0084] Although an embodiment of the present disclosure has been described above with reference to the drawings, the specific configuration is not limited to this embodiment, and various modifications are also included within the scope that does not deviate from the spirit of the present disclosure. [Explanation of symbols]

[0085] 1 Current Sensor 8. Object to be measured 10 Current detection circuit (11: excitation circuit, 12: detection circuit, 13: LPF circuit, 14: amplifier circuit, 15: feedback circuit, 16: I / V circuit) 20 Sensor head (21: inner magnetic collector, 22: outer magnetic collector, 23: feedback coil 30 Magnetic Sensor 40: Sensor body (41: Excitation core layer, 411: Excitation core resin layer, 412: Wall portion, 42: First coil pattern layer, 421: First coil pattern resin layer, 43: Second coil pattern layer, 431: Second coil pattern resin layer, 44: Excitation core, 45: Excitation coil, 46: Adhesive, 47: Coil wiring, 48: Wiring via) 50 Shield 60 Bridging Section 61 Wiring section 62 Terminal section

Claims

1. The magnetic coil is formed of a flexible substrate, and an excitation core extends in an axial direction of the magnetic coil and is wound around the excitation coil. The excitation core is disposed in the flexible substrate such that, when the flexible substrate is deformed, at least a portion of the excitation core can move in a strip length direction of the excitation core relative to the flexible substrate. Magnetic sensor.

2. the flexible substrate includes an excitation core layer having a wall portion that defines a space in which the excitation core is located, and two coil pattern layers that include a pattern of the excitation coil and are positioned so as to sandwich the excitation core layer, The width of the space defined by the wall of the excitation core layer is longer than the width of the excitation core, The thickness of the excitation core layer is greater than the thickness of the excitation core. The magnetic sensor according to claim 1 .

3. The flexible substrate further includes an adhesive that bonds the excitation core layer and the coil pattern layer, The adhesive is positioned so as not to fix the excitation core to the flexible substrate. The magnetic sensor according to claim 2 .

4. 4. The magnetic sensor according to claim 3, wherein the adhesive is a thermosetting resin and is located farther from the space in which the excitation core is located than a wall portion of the excitation core layer before a thermal curing treatment.

5. The flexible substrate further includes an adhesive that bonds the excitation core layer and the coil pattern layer, The magnetic sensor of claim 2 , wherein the adhesive is positioned to secure the excitation core to the flexible substrate at only one location.

6. The flexible substrate further includes an adhesive that bonds the excitation core layer and the coil pattern layer, The magnetic sensor according to claim 2 , wherein the adhesive is positioned so as to fix the excitation core to the flexible substrate at a plurality of locations spaced apart by a predetermined distance or more.

7. a non-magnetic thin film member isolating the excitation core from the flexible substrate; the thin film member is fixed to the flexible substrate and is not fixed to the excitation core; The magnetic sensor according to claim 1 .

8. the thin film member includes a first thin film member and a second thin film member sandwiching the exciting core, 8. The magnetic sensor according to claim 7, wherein the first thin film member and the second thin film member are joined to each other at an end of the exciting core in a strip width direction.

9. The magnetic sensor according to claim 1 , further comprising a non-magnetic lubricating member located between the excitation core and the flexible substrate.

10. A current sensor comprising: the magnetic sensor according to claim 1 ; and a current detection circuit connected to an excitation coil of the magnetic sensor.

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