Magnetic sensor and current sensor

Abstract

The present invention relates to a magnetic sensor and a current sensor, the magnetic sensor (30) having: an excitation coil (45) formed from a flexible substrate; and a field core (44) which extends in the axial direction of the field coil (45) and around which the field coil (45) is wound. When the flexible substrate deforms, 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 tape length direction of the excitation core (44) with respect to the flexible substrate.

Description

Technical Field

[0001] The invention relates to a magnetic sensor and a current sensor. Background Art

[0002] A fluxgate sensor formed of a flexible substrate is known (see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-94723

[0004] The flexible substrate is configured to include resin or adhesive, etc. The core of the magnetic body of the fluxgate sensor is arranged in the flexible substrate, and is thus subjected to mechanical stress from the flexible substrate. For example, due to the difference in thermal expansion coefficient between the core of the magnetic body and the thermal expansion coefficient of the resin or adhesive of the flexible substrate, the core of the magnetic body is sometimes subjected to stress when the temperature changes. Since the core of the magnetic body is subjected to stress, the magnetic properties of the core of the magnetic body change. The flux detection sensitivity or phase characteristics of the fluxgate sensor changes according to the change in the magnetic properties of the core of the magnetic body. 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 following advantage, that is, the fluxgate sensor has flexibility. Seeking to maintain flexibility and improve temperature characteristics. Summary of the invention

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a magnetic sensor capable of maintaining flexibility and improving temperature characteristics, and a current sensor capable of improving reliability.

[0006] (1) Some embodiments of the magnetic sensor include: an excitation coil formed of a flexible substrate; and an excitation core extending in the axial direction of the excitation coil and wound with the excitation coil. The excitation core is arranged in the flexible substrate so that at least a portion of the excitation core can move relative to the flexible substrate in the strip length direction of the excitation core when the flexible substrate is deformed.

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

[0008] (2) According to the magnetic sensor described in (1) above, the flexible substrate may include: an excitation core layer having a wall portion that divides a space where the excitation core is located; and two coil pattern layers that include patterns of the excitation coil and are located at positions that sandwich the excitation core layer. The width of the space divided by the wall portion of the excitation core layer may be greater than the width of the excitation core. The thickness of the excitation core layer may be greater than the thickness of the excitation core. Thus, the excitation core is not fixed in a state configured in the flexible substrate but can move in the length direction of the belt.

[0009] (3) According to 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 configured so as not to fix the excitation core to the flexible substrate. Thus, the excitation core is not fixed in the state configured in the flexible substrate but can move in the belt length direction.

[0010] (4) According to the magnetic sensor described in (3) above, the adhesive may be a thermosetting resin and may be located at a position where the wall of the excitation core layer is further away from the space where the excitation core is located before the heat curing treatment. Thus, the possibility of the adhesive extending to the space where the excitation core is located before the heat curing is reduced. By reducing the possibility of the adhesive extending, the possibility of the excitation core being bonded to the flexible substrate is reduced.

[0011] (5) According to the magnetic sensor described in (2) above, the flexible substrate can be formed so that the flexible substrate also has an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive can be configured to fix the excitation core to the flexible substrate at only one position. Thus, even if thermal deformation of the flexible substrate occurs, the excitation core can move from the fixed position relative to the flexible substrate toward both sides in the length direction of the strip. Therefore, stress in the length direction of the strip caused by thermal deformation of the flexible substrate is not generated in the excitation core.

[0012] (6) According to 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 configured to fix the excitation core to the flexible substrate at a plurality of locations separated by a distance greater than or equal to a specified distance. Thus, 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 the excitation core being bent in the thickness direction, the stress generated in the strip length direction of the excitation core 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 be formed to further include a non-magnetic thin film component that isolates the excitation core from the flexible substrate. The thin film component may be fixed to the flexible substrate but not to the excitation core. Thus, the limitation of the coating range of the adhesive is reduced. As a result, the flexible substrate can be easily formed.

[0014] (8) According to the magnetic sensor described in (7) above, the film component may include a first film component and a second film component that clamp the excitation core. The first film component and the second film component may be joined at the ends of the excitation core in the strip width direction. The excitation core is clamped by the film component so that the excitation core is not easily removed from 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 between the excitation core and the flexible substrate. The magnetic sensor includes the lubricating member to further reduce the stress of the excitation core 44 in the longitudinal direction of the strip.

[0016] (10) Some embodiments of the current sensor include: the magnetic sensor described in any one of (1) to (9) above; and a current detection circuit connected to the excitation coil of the magnetic sensor. The current sensor can improve reliability by including the magnetic sensor according to the above embodiment.

[0017] Effects of the Invention

[0018] The magnetic sensor according to the present invention can maintain the flexibility of the sensor and improve the temperature characteristics of the sensor. In addition, the current sensor according to the present invention can improve reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a top view showing the structure of the magnetic sensor according to the first comparative example.

[0020] Figure 2 yes Figure 1 AA cross-section diagram.

[0021] Figure 3 It is a plan view showing the structure of a magnetic sensor according to the second comparative example.

[0022] Figure 4 yes Figure 3 BB cross-section diagram.

[0023] Figure 5 yes Figure 3 CC cross-section diagram.

[0024] Fig. 6AIt is a cross-sectional view showing the state of the excitation core of the magnetic sensor according to the second comparative example when it is at a low temperature.

[0025] Figure 6B It is a cross-sectional view showing the state of the excitation core of the magnetic sensor according to the second comparative example at room temperature.

[0026] Figure 6C It is a cross-sectional view showing the state of the excitation core of the magnetic sensor according to the second comparative example when the temperature is high.

[0027] Fig. 7A This is a graph showing the output characteristics of the magnetic sensor according to the second comparative example at a low temperature.

[0028] Figure 7B : is a graph showing the output characteristics of the magnetic sensor according to the second comparative example at room temperature.

[0029] Figure 7C This is a graph showing the output characteristics of the magnetic sensor according to the second comparative example when the temperature is high.

[0030] Figure 8 It is a plan view showing a configuration example of a magnetic sensor according to an embodiment of the present invention.

[0031] Fig. 9 yes Figure 8 DD cross-section diagram.

[0032] Fig.10 It is a schematic diagram showing the position of the adhesive in the field core layer.

[0033] Fig.11A This is a cross-sectional view showing a state of an excitation core of a magnetic sensor according to an embodiment of the present invention when the temperature is low.

[0034] Fig. 11B This is a cross-sectional view showing a state of an excitation core of a magnetic sensor according to an embodiment of the present invention at room temperature.

[0035] Fig. 11C This is a cross-sectional view showing a state of an excitation core when the magnetic sensor according to one embodiment of the present invention is at a high temperature.

[0036] Fig. 12A This is a graph showing the output characteristics of the magnetic sensor according to one embodiment of the present invention at a low temperature.

[0037] Fig. 12B This is a graph showing output characteristics of the magnetic sensor according to one embodiment of the present invention at room temperature.

[0038] Fig. 12CThis is a graph showing output characteristics of the magnetic sensor according to one embodiment of the present invention when it is at a high temperature.

[0039] Fig.13 It is a schematic diagram showing a configuration example of a current sensor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] (Magnetic sensor used in comparative example)

[0041] like Figure 1 As shown, the magnetic sensor 900 involved in the first comparative example is a fluxgate sensor composed of a flexible substrate including a sensor body 910 and a wiring portion 950. The sensor body 910 includes an excitation core 920, an excitation coil 930, and a wiring passage hole 940. The wiring portion 950 includes a wiring 960 and a terminal 970 for passing a current through the excitation coil 930 or outputting a voltage of the excitation coil 930.

[0042] The excitation coil 930 is formed by a flexible substrate. The excitation core 920 is configured inside the winding of the excitation coil 930 to extend along the axial direction of the excitation coil 930. That is, the excitation coil 930 is wound around the excitation core 920. The excitation core 920 is a strip-shaped magnetic foil. The strip-shaped magnetic foil can be constructed to include soft magnetic film materials such as Permalloy film or amorphous film. In addition, the sensor body 910 is configured 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 orthogonal to the strip length direction in the plane where the sensor body 910 extends is also referred to as the strip width direction. The direction orthogonal to the strip length direction and the strip width direction is also referred to as the thickness direction.

[0043] like Figure 2 As shown, the sensor body 910 has a plurality of resin layers 934 bonded and stacked by an adhesive 935. The adhesive 935 is a thermosetting resin. The flexible substrate including the sensor body 910 is formed by stacking a plurality of resin layers 934 coated with the adhesive 935 and performing heating and stamping. The resin layer 934 is a material having softness or flexibility such as polyimide. The resin layer 934 includes: a layer on which a coil wiring 931 of the excitation coil 930 is formed; and a layer on which a shield 933 is formed. The coil wiring 931 and the shield 933 are formed of copper foil. The shield 933 acts as an electric field shield that absorbs the radiation energy from the excitation coil 930.

[0044] The field core 920 is bonded between layers of coil wiring 931 of the field coil 930 by an adhesive 935. The coil wiring 931 formed in two layers of the field coil 930 is connected by an embedded wiring 932.

[0045] The magnetic sensor 900 involved in the first comparative example has excellent mechanical flexibility. When the magnetic sensor 900 is mounted on a split core type or a clamp type current sensor, the magnetic sensor 900 can deform following the opening and closing action of the magnetic core of the current sensor. Therefore, the mechanical flexibility of the magnetic sensor 900 gives diversity to the setting method of the magnetic sensor 900. The setting method of the magnetic sensor 900 is diverse, so it is easy to improve the magnetic flux detection sensitivity of the magnetic sensor 900.

[0046] Here, the magnetic sensor 900 involved in the first comparative example is deformed according to the temperature change of the magnetic sensor 900 due to the difference in 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 magnetic properties of the magnetic foil are changed by the stress generated by the magnetic foil. As a result, the following problem occurs, that is, the magnetic flux detection sensitivity or phase characteristics of the magnetic sensor 900 as a fluxgate sensor changes according to the temperature. Therefore, the temperature characteristics of the magnetic sensor 900 involved in the first comparative example are sought to be improved.

[0047] like Figure 3 As shown, the magnetic sensor 800 involved in the second comparative example is a fluxgate sensor composed of a flexible substrate including a sensor body 840, a shielding body 850 and a wiring part 861. The sensor body 840 is connected to two shielding bodies 850 via a bridge part 860. The magnetic sensor 800 is used by bending at the bridge part 860 in such a way that the two shielding bodies 850 clamp the sensor body 840 from both sides in the thickness direction. The wiring part 861 includes: a pattern of wiring 863, which is connected to the excitation coil 845 (refer to Figure 5 ) connection; and terminal 862, which is used to connect the wiring 863 to an external power source.

[0048] like Figure 4 As shown, the shielding body 850 has a plurality of resin layers 851 that are stacked and bonded with an adhesive 852. The adhesive 852 is a thermosetting resin. The flexible substrate including the shielding body 850 is formed by stacking a plurality of resin layers 851 coated with the adhesive 852 and performing heating and stamping. The resin layer 851 is a material having softness or flexibility such as polyimide. The resin layer 851 includes: a layer having a pattern of wiring 863; and a layer having a pattern of a shielding body 864. The patterns of the wiring 863 and the shielding body 864 are formed of copper foil. The shielding body 864 serves as a layer for absorbing the electric field from the excitation coil 845 (refer to Figure 5 )'s radiant energy by acting as an electric field shield.

[0049] like Figure 5As shown, the sensor body 840 has a plurality of resin layers 842 bonded and stacked by an adhesive 846. The adhesive 846 is a thermosetting resin. The flexible substrate including the sensor body 840 is formed by stacking a plurality of resin layers 842 coated with the adhesive 846 and performing heating and stamping. The resin layer 842 is a material having softness or flexibility such as polyimide. The resin layer 842 includes a layer on which a coil wiring 847 of an excitation coil 845 is formed. The coil wiring 847 is formed of copper foil.

[0050] The field core 844 is bonded between layers of coil wiring 847 of the field coil 845 by an adhesive 846. The coil wiring 847 formed in two layers of the field coil 845 is connected by an embedded wiring 848.

[0051] The magnetic sensor 800 according to the second comparative example is used by forming the sensor body 840 and the shielding body 850 as different substrates and bending them, thereby reducing the stress generated in the excitation core 844 due to the thermal expansion of the shielding body 850. The temperature characteristics of the magnetic sensor 800 according to the second comparative example are improved compared with the temperature characteristics of the magnetic sensor 900 according to the first comparative example due to the reduced stress generated in the excitation core 844.

[0052] However, the temperature characteristics of the magnetic sensor 800 according to the second comparative example still have room for improvement. Fig. 6A , Figure 6B and Figure 6C As shown, in the sensor body 840 , since the excitation core 844 is bonded to the resin layer 842 , stress in the belt length direction is generated in the excitation core 844 due to the thermal expansion of the resin layer 842 . Fig. 6A This indicates that the magnetic sensor 800 is in a low temperature state. Figure 6B This indicates that the magnetic sensor 800 is at room temperature. Figure 6C Indicates that the magnetic sensor 800 is in a high temperature state. The high temperature is a temperature when the flexible substrate for forming the magnetic sensor 800 is heated. On the other hand, the normal temperature is a temperature lower than the high temperature. In addition, the low temperature is a temperature lower than the normal temperature.

[0053] Figure 6C Indicates the state when the flexible substrate is formed by heating and pressing. Fig. 6A and Figure 6B 844, the resin layer 842, and the adhesive 846 are shrunk due to the temperature drop compared to the state when the flexible substrate is formed. Fig. 6A and Figure 6C In FIG. 8 , the dotted lines drawn for the resin layer 842 and the adhesive 846 indicate the shapes of the resin layer 842 and the adhesive 846 when the magnetic sensor 800 is at room temperature.

[0054] When the thermal expansion coefficient of the excitation 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 excitation core 844. In the comparative example, the excitation core 844 shrinks to a negligible small extent. As a result, in the strip length direction of the excitation core 844, the Fig. 6A and Figure 6B In the state shown, the resin layer 842 and the adhesive 846 shrink in the length direction of the belt and generate compressive stress.

[0055] Reference Fig. 7A , Figure 7B as well as Figure 7C The temperature characteristics of the magnetic sensor 800 according to the second comparative example are described in the graph. Fig. 7A The magnetic characteristics of the magnetic sensor 800 in a low-temperature state are shown. Figure 7B The magnetic characteristics of the magnetic sensor 800 at room temperature are shown. Figure 7C The graphs show the magnetic characteristics of the magnetic sensor 800 when it is at a high temperature. The vertical axis of each graph shows the output of current or voltage. The horizontal axis shows time. The dotted graph shows the output waveform of the current flowing through the excitation coil 845 when the magnetic sensor 800 is driven. The solid graph shows the output waveform of the voltage of the excitation coil 845 when the magnetic sensor 800 is driven.

[0056] As a driving condition of the magnetic sensor 800, constant current application driving is performed on the excitation coil 845. Constant current application driving is also called constant magnetic field application driving. A larger voltage waveform caused by the excitation coil 845 indicates that there are more magnetic fluxes interlinked with the excitation coil 845, and indicates that the magnetic permeability of the excitation core 844 is larger. Under this driving condition, the smaller the change in the magnetic permeability of the excitation core 844 relative to the temperature change of the magnetic sensor 800, the better the temperature characteristics of the magnetic sensor 800. In other words, when the excitation coil 845 is driven by constant current, the smaller the change in the voltage waveform caused by the excitation coil 845 when the temperature of the magnetic sensor 800 changes, the better the temperature characteristics of the magnetic sensor 800. On the contrary, although the excitation coil 845 is driven by a constant current and a constant magnetic field is applied, the output voltage of the excitation coil 845, that is, the magnetic flux generated by the excitation coil 845, is different according to the temperature, the temperature characteristics of the magnetic sensor 800 are poor.

[0057] However, if Fig. 7A , Figure 7B and Figure 7CAs shown in the graph, the voltage waveform changes greatly when the temperature of the magnetic sensor 800 is at low temperature, normal temperature, and high temperature. The change in the voltage waveform corresponding to the temperature change indicates 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.

[0058] In order to improve the temperature characteristics of the magnetic sensor 800, it is possible to consider thickening the excitation core 844, which is a magnetic foil, to increase the rigidity of the excitation core 844 itself. However, by thickening the excitation core 844, the inductance increases and it is difficult to excite. In addition, by thickening the excitation core 844, the flexibility of the magnetic sensor 800 may be impaired.

[0059] As described above, the magnetic sensors 900 and 800 involved in the comparative examples have room for improvement in temperature characteristics. It is sought to maintain the flexibility of the sensor and improve the temperature characteristics of the sensor. Next, in the present invention, a magnetic sensor 30 (refer to Figure 8 ) and a current sensor 1 capable of improving reliability (refer to Fig.13 ) for explanation.

[0060] (Magnetic sensor 30 according to the present invention)

[0061] like Figure 8 and Fig. 9 As shown, a magnetic sensor 30 according to one embodiment of the present invention includes a magnetic excitation core 44 and an excitation coil 45. The excitation coil 45 is formed by a flexible substrate. The excitation core 44 is configured 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. That is, the excitation coil 45 is wound around the excitation core 44.

[0062] The shape of the excitation core 44 in the cross-sectional view in the extension direction can be approximately rectangular. That is, the shape of the excitation core 44 can be strip-shaped. In the present embodiment, the shape of the excitation core 44 is set to be strip-shaped. That is, the excitation core 44 is set to be a strip-shaped magnetic foil. The strip-shaped magnetic foil can be composed of a soft magnetic film material such as a Permalloy film or an amorphous alloy film.

[0063] 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, which are located at a position sandwiching the excitation core layer 41. When there is no need to distinguish, the first coil pattern layer 42 and the second coil pattern layer 43 are simply referred to as coil pattern layers. That is, the flexible substrate has two coil pattern layers located at a position sandwiching the excitation core layer 41. The excitation core layer 41 and the coil pattern layer are configured as a resin layer containing softness or flexibility such as polyimide. The shape of the resin layer of the excitation core layer 41 and the coil pattern layer is set to be strip-shaped. The resin layer of the excitation core layer 41 is also called the excitation core resin layer 411. The resin layer of the coil pattern layer is also called the coil pattern resin layer. The resin layer of the first coil pattern layer 42 is also called the first coil pattern resin layer 421. The resin layer of the second coil pattern layer 43 is also called the second coil pattern resin layer 431.

[0064] 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 in the plane in which the flexible substrate extends that is perpendicular to the strip length direction 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 size of the excitation core 44 in the strip width direction is also referred to as the width of the excitation core 44. The size 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 can be, for example, less than or equal to 100 μm. The excitation core 44 is strip-shaped and has flexibility.

[0065] The coil pattern layer further includes a coil wiring 47 formed on the resin layer. The coil wiring 47 is a part of the exciting coil 45. The coil wiring 47 can be formed of a metal material such as copper foil or other conductive materials. The resin layer can be formed of polyimide, for example.

[0066] The excitation core layer 41 has a wiring passage hole 48 for connecting the coil wiring 47 of each of the two coil pattern layers sandwiching the excitation core layer 41. The wiring passage hole 48 is configured as a through hole filled with a conductor. The excitation coil 45 is configured by connecting the coil wiring 47 of the coil pattern layer and the wiring passage hole 48 of the excitation core layer 41. The resin portion such as polyimide of the excitation core layer 41 and the coil pattern layer functions as an insulating material to prevent the coil wiring 47 from short-circuiting.

[0067] The excitation core layer 41 has a wall portion 412 that divides the end portion in the belt width direction of the opening of the excitation core resin layer 411. The opening of the excitation core resin layer 411 is a space where the excitation core 44 is located. The end portion in the thickness direction of the space where the excitation core 44 is located is divided by the coil pattern resin layer that clamps the excitation core layer 41. The space where the excitation core 44 is located is a rectangular parallelepiped extending in the belt length direction.

[0068] The width of the space where the excitation core 44 is located is the length of the space along the belt width direction. The width of the space where the excitation core 44 is located can be greater than the width of the excitation core 44, or it can be the same as the width of the excitation core 44. The thickness of the space where the excitation core 44 is located is the length of the space along the thickness direction. The thickness of the excitation core layer 41 can be greater than the thickness of the excitation core 44, or it can be the same as the thickness of the excitation core 44.

[0069] The excitation 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 excitation core layer 41 and the first coil pattern layer 42, and bonds the excitation core layer 41 and the first coil pattern layer 42. In addition, the adhesive 46 is located between the excitation core layer 41 and the second coil pattern layer 43, and bonds the excitation core layer 41 and the second coil pattern layer 43. In the present invention, the adhesive 46 is set to be a thermosetting resin. In the case where the adhesive 46 is a thermosetting resin, the adhesive 46 can be applied between the excitation core layer 41 and the coil pattern layer, and stamped while heating to a temperature that cures the adhesive 46, thereby forming a flexible substrate. The adhesive 46 is not limited to a thermosetting resin, and can also be constructed to include various other materials. In addition, the adhesive 46 can be replaced by various other components such as tapes that can bond the excitation core layer 41 and the coil pattern layer.

[0070] The portion of the flexible substrate that forms the excitation coil 45 is also referred to as the sensor body 40. The flexible substrate may also include a shield 50 in addition to the sensor body 40. 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 made of, for example, copper foil.

[0071] The flexible substrate may further include a bridge portion 60 connecting the sensor body 40 and the shield body 50. In the present embodiment, the sensor body 40 and the shield body 50 are arranged in the tape width direction of the excitation core 44. The flexible substrate is bent at the bridge portion 60, so that the shield body 50 covers the sensor body 40 from the thickness direction thereof. In the case where the flexible substrate has two shield bodies 50, the sensor body 40 is covered from both sides of the shield body 50 in the thickness direction thereof. One of the two shield bodies 50 convexly folds the flexible substrate at the bridge portion 60 to overlap the sensor body 40 in the thickness direction. The other shield body 50 concavely folds the flexible substrate at the bridge portion 60 to overlap the sensor body 40 in the thickness direction. The shield body 50 functions as an electric field shield of the sensor body 40 by covering the sensor body 40 from the thickness direction thereof.

[0072] 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 flowing 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.

[0073] As described above, a space where the excitation core 44 is located is defined in the flexible substrate of the magnetic sensor 30 according to the present invention. The excitation core 44 is arranged in the space defined in the flexible substrate. The excitation core 44 is arranged in the flexible substrate in such a manner that at least a portion of the excitation core 44 can move relative to the flexible substrate in the tape length direction.

[0074] At least a portion of the excitation core 44 is movable relative to the flexible substrate in the strip length direction. Therefore, when the flexible substrate is deformed in the strip length direction, stress in the strip length direction is less likely to be applied from the flexible substrate to the excitation core 44 .

[0075] For example, when the thermal expansion coefficients of the flexible substrate and the excitation core 44 are different, the deformation amount of the flexible substrate in the strip length direction and the deformation amount of the excitation core 44 in the strip length direction are different due to the change in the temperature of the entire magnetic sensor 30. In this case, at least a portion of the excitation core 44 can move in the strip length direction relative to the flexible substrate, thereby reducing the stress in the strip length direction generated in the excitation core 44 due to the difference in the deformation amount in the strip length direction.

[0076] The magnetic properties of the excitation core 44 change according to the situation in which stress is generated in the excitation core 44. In the case where stress is generated in the excitation core 44 due to the temperature change of the magnetic sensor 30, the temperature dependence of the magnetic properties of the magnetic sensor 30 increases. That is, the temperature characteristics of the magnetic sensor 30 deteriorate. With respect to the magnetic sensor 30 involved in the present invention, at least a portion of the excitation core 44 is movable in the strip length direction relative to the flexible substrate, thereby reducing the stress in the strip length direction generated in the excitation core 44 due to the thermal deformation of the flexible substrate when the temperature of the magnetic sensor 30 changes. The stress in the strip length direction generated in the excitation core 44 due to the temperature change of the magnetic sensor 30 is reduced, thereby reducing the temperature dependence of the magnetic properties of the magnetic sensor 30. That is, the temperature characteristics of the magnetic sensor 30 are improved.

[0077]

[0078] As one of the modes of arranging the excitation core 44 so as to be movable in the belt length direction, the excitation core 44 may be arranged not to be fixed to the flexible substrate. In this case, the entire excitation core 44 is movable in the belt length direction relative to the flexible substrate.

[0079] For example, as described above, the width of the space where the excitation core 44 is located is greater than the width of the excitation core 44, and the thickness of the space where the excitation core 44 is located is greater than the thickness of the excitation core 44, so that the excitation core 44 can be moved in the length direction of the belt without being fixed when configured in the flexible substrate.

[0080] In addition, the excitation core 44 is not bonded to the flexible substrate, so that the excitation core 44 can be moved in the length direction of the tape without being fixed in the state configured in the flexible substrate. In order to form the flexible substrate in a manner in which the excitation core 44 is not bonded to the flexible substrate, the range where the adhesive 46 is applied between the excitation core layer 41 and the coil pattern layer can be limited to a range where the adhesive 46 does not contact the excitation core 44. The range where the adhesive 46 is applied can be limited to a range that does not overlap with the excitation core 44 when the flexible substrate is viewed from above in the thickness direction.

[0081] like Fig.10 As shown, the adhesive 46 can be applied to a limited range away from the space where the excitation core 44 is located. In the case where the adhesive 46 is a thermosetting resin, the range where the adhesive 46 is applied may be larger than that of the space where the excitation core 44 is located by performing heating and pressing when forming the flexible substrate. In other words, the adhesive 46 can be located at a position farther away from the space where the excitation core 44 is located than the wall portion 412 of the excitation core layer 41 that divides the space before the thermal curing process.

[0082] By applying the adhesive 46 in a limited range away from the space where the excitation core 44 is located, the possibility of the adhesive 46 expanding to the space where the excitation core 44 is located before the adhesive 46 is thermally cured is reduced. The possibility of the adhesive 46 expanding is reduced, and the possibility of the excitation core 44 adhering to the flexible substrate is reduced. As a result, the excitation core 44 is arranged in the flexible substrate in a manner that allows it to move in the length direction of the belt. In addition, if the excitation core 44 contacts the adhesive 46 after the adhesive 46 is thermally cured, it will not be adhered to the flexible substrate due to the adhesive 46. That is, even if the excitation core 44 moves in the flexible substrate and contacts the thermally cured adhesive 46, the temperature characteristics of the magnetic sensor 30 are not deteriorated.

[0083] Even in the case where the excitation core 44 is not fixed to the flexible substrate, the excitation core layer 41 is designed in such a way that the width or thickness of the space where 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 due to the friction between the excitation core 44 and the flexible substrate. Even in the case where the excitation core 44 is held on the flexible substrate only due to friction, the possibility of the excitation core 44 falling off the flexible substrate is low. In addition, the magnetic sensor 30 is mostly used in a bent manner by utilizing the flexibility of the flexible substrate. By using the magnetic sensor 30 in a bent manner, the possibility of the excitation core 44 falling off the flexible substrate is further reduced. In addition, when the magnetic sensor 30 is used in a bent manner, the excitation core 44 bends and generates bending stress. However, the bending stress hardly depends on temperature changes. Therefore, even in the case where the magnetic sensor 30 is used in a bent manner, the temperature characteristics of the magnetic sensor 30 are not deteriorated.

[0084] When the entire excitation core 44 is movable 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 will not be generated in the excitation core 44. Therefore, the temperature dependence of the magnetic characteristics of the magnetic sensor 30 is reduced. In other words, the temperature characteristics of the magnetic sensor 30 are improved.

[0085]

[0086] As one of the ways to configure the excitation core 44 so as to be movable in the length direction of the tape, 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 location. In this case, even if thermal deformation of the flexible substrate occurs, the excitation core 44 can move from the fixed location relative to the flexible substrate toward both sides in the length direction of the tape. Therefore, stress in the length direction of the tape caused by thermal deformation of the flexible substrate is not generated in the excitation core 44. As a result, the temperature characteristics of the magnetic sensor 30 are improved.

[0087] In addition, 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, when the flexible substrate contracts in the strip length direction, the excitation core 44 can bend in the thickness direction in the range between the fixed locations. The excitation core 44 bends in the thickness direction, thereby reducing the stress generated in the strip length direction of the excitation core 44 when the flexible substrate contracts in the strip length direction.

[0088] Specifically, when the flexible substrate is formed by heating and stamping, the flexible substrate and the excitation core 44 are fixed to each other based on the shape at the temperature during the heating process. When the temperature range in which the magnetic sensor 30 is used is lower than the temperature during the heating process, 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 locations that are isolated from each other, the excitation core 44 is bent in the thickness direction to reduce the stress generated in the strip length direction of the excitation core 44.

[0089] <Temperature Characteristics of the Magnetic Sensor 30>

[0090] The temperature characteristic of the magnetic sensor 30 indicates the influence of the temperature change of the magnetic sensor 30 on the magnetic characteristics of the magnetic sensor 30. Specifically, the smaller the change in the magnetic characteristics of the magnetic sensor 30 corresponding to the temperature change of the magnetic sensor 30 is, the better the temperature characteristic of the magnetic sensor 30 is. On the contrary, the larger the change in the magnetic characteristics of the magnetic sensor 30 corresponding to the temperature change of the magnetic sensor 30 is, the worse the temperature characteristic of the magnetic sensor 30 is.

[0091] 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 magnitude of the stress in the strip length direction generated in the excitation core 44 changes, the smaller the change in the magnetic characteristics of the magnetic sensor 30. In other words, the smaller the magnitude of the stress in the strip length direction generated in the excitation core 44 changes in accordance with the temperature change of the magnetic sensor 30, the better the temperature characteristics of the magnetic sensor 30.

[0092] Regarding the stress in the strip length direction generated in the excitation core 44 of the magnetic sensor 30 according to the present invention, refer to the stress observed in the strip width direction. Fig.11A , Fig. 11B and Fig. 11C The excitation core 44 will be described with reference to the cross-sectional views shown in FIG. In each cross-sectional view of the excitation core 44, the excitation core 44 and the first coil pattern resin layer 421 and the second coil pattern resin layer 431 are stacked in the thickness direction and extend in the tape length direction.

[0093] Fig.11A This indicates that the magnetic sensor 30 is in a low temperature state. Fig. 11B This indicates that the magnetic sensor 30 is at room temperature. Fig. 11C Indicates that the magnetic sensor 30 is in a high temperature state. The high temperature is a temperature when the flexible substrate for forming the magnetic sensor 30 is heated, for example, 100° C. to 200° C. On the other hand, the normal temperature is a temperature lower than the high temperature, for example, 15° C. to 30° C. In addition, the low temperature is a temperature lower than the normal temperature.

[0094] Fig. 11C Indicates the state when heating and pressing are performed to form a flexible substrate. Fig.11A and Fig. 11B The state where the excitation core 44 and the coil pattern resin layer are contracted due to the temperature drop compared to the state when the flexible substrate is formed. Fig.11A and Fig. 11C In FIG. 1 , the dotted line drawn on the coil pattern resin layer indicates the shape of the coil pattern resin layer when the magnetic sensor 30 is at room temperature.

[0095] When the thermal expansion coefficient of the field core 44 is smaller than that of the coil pattern resin layer, the coil pattern resin layer shrinks more in the tape length direction than the field core 44. In the present embodiment, the shrinkage of the field core 44 is reduced to a negligible level.

[0096] Here, regarding the magnetic sensor 30 according to the present invention, as described above, the excitation core 44 is configured to be movable relative to the flexible substrate in the strip length direction. That is, the excitation core 44 is movable relative to the first coil pattern resin layer 421 and the second coil pattern resin layer 431 in the strip length direction. Fig.11A and Fig. 11B As shown, even when the temperature of the magnetic sensor 30 decreases and the coil pattern resin layer shrinks in the tape length direction, the excitation core 44 does not receive a force in the tape length direction from the coil pattern resin layer. Therefore, with respect to the magnetic sensor 30 according to the present invention, even when the temperature decreases, no stress in the tape length direction is generated in the excitation core 44.

[0097] Regarding the temperature characteristics of the magnetic sensor 30 according to the present invention, refer to Fig. 12A , Fig. 12B and Fig. 12C The curve diagram is used to illustrate. Fig. 12A The magnetic characteristics of the magnetic sensor 30 in a low-temperature state are shown. Fig. 12B The magnetic characteristics of the magnetic sensor 30 at room temperature are shown. Fig. 12C The graphs show the magnetic characteristics of the magnetic sensor 30 when it is at a high temperature. The vertical axis of each graph shows the output of current or voltage. The horizontal axis shows time. The dotted graph shows the output waveform of the current flowing through the excitation coil 45 when the magnetic sensor 30 is driven. The solid graph shows the output waveform of the voltage of the excitation coil 45 when the magnetic sensor 30 is driven.

[0098] As a driving condition of the magnetic sensor 30, a constant current application drive is performed for the excitation coil 45. Constant current application drive is also called constant magnetic field application drive. A larger voltage waveform caused by the excitation coil 45 indicates that there are more magnetic fluxes interlinked with the excitation coil 45, and indicates that the magnetic permeability of the excitation core 44 is larger. Under this driving condition, the smaller the change in the magnetic permeability of the excitation core 44 relative to the temperature change of the magnetic sensor 30, the better the temperature characteristics of the magnetic sensor 30. In other words, when the excitation coil 45 is driven by a constant current, the smaller the change in the voltage waveform caused by the excitation coil 45 when the temperature of the magnetic sensor 30 changes, the better the temperature characteristics of the magnetic sensor 30. On the contrary, although the excitation coil 45 is driven with a constant current to apply a constant magnetic field, when the output voltage of the excitation coil 45, that is, the magnetic flux generated by the excitation coil 45, varies according to the temperature, the temperature characteristics of the magnetic sensor 30 are poor.

[0099] Fig. 12A , Fig. 12B and Fig. 12C The change of the voltage waveform at each temperature when comparing the voltage waveforms is less than that of the above comparative example. Fig. 7A , Figure 7B and Figure 7C Therefore, it is shown that the temperature characteristic of the magnetic sensor 30 according to the present invention is better than the temperature characteristic of the magnetic sensor 30 according to the comparative example.

[0100] Summary

[0101] As described above, in the magnetic sensor 30 according to the present 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 the thermal deformation of the flexible substrate corresponding to the temperature change of 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 flexibility of the magnetic sensor 30 is maintained and the temperature characteristics of the magnetic sensor 30 are improved.

[0102] <Other structural examples of the field core 44>

[0103] As described above, the excitation core 44 is arranged in the flexible substrate so that at least a portion of the excitation core 44 can move relative to the flexible substrate in the tape length direction. The arrangement of the excitation core 44 in the flexible substrate is not limited to the above example.

[0104] The magnetic sensor 30 may also have a non-magnetic film component that clamps the excitation core 44 from both sides in the thickness direction. The non-magnetic film component may be, for example, aluminum foil, stainless steel foil, or polyimide film. The excitation core 44 is not fixed to the film component. The film component may be fixed to the flexible substrate. For example, the film component may be bonded to the coil pattern layer using an adhesive 46. The film component is located between the excitation core 44 and the flexible substrate in the thickness direction. In other words, the film component isolates the excitation core 44 from the flexible substrate.

[0105] The film member may include: a first film member located on one side in the thickness direction of the excitation core 44; and a second film member located on the other side. The first film member and the second film member may be joined at least partially at the ends in the belt width direction. That is, the film member may be formed in the shape of an envelope with both ends open.

[0106] The magnetic sensor 30 has a thin film member, and the application range of the adhesive 46 is less restricted. As a result, a flexible substrate can be easily formed. In addition, the excitation core 44 is sandwiched by the thin film member, so that the excitation core 44 is not easily removed from the magnetic sensor 30.

[0107] The magnetic sensor 30 may also include a non-magnetic lubricating component located between the excitation core 44 and the flexible substrate. The non-magnetic lubricating component may be, for example, a powdered solid lubricant. The non-magnetic lubricating component may be attached to at least one surface of the excitation core 44, which is a strip of magnetic foil. The magnetic sensor 30 also includes a lubricating component to further reduce the stress of the excitation core 44 in the strip length direction.

[0108] (Current sensor 1 according to one embodiment of the present invention)

[0109] like Fig.13 As shown, the current sensor 1 has a sensor head 20, and a current detection circuit 10 as a current detection unit. The sensor head 20 has: an annular magnetic sensor 30; an annular reinforcement body, which reinforces the magnetic sensor 30; an inner magnet collector 21 and an outer magnet collector 22 as magnet collectors, which are arranged on the inner and outer sides of the magnetic sensor 30; a shell, which accommodates the above-mentioned magnetic sensor 30, the reinforcement body, the inner magnet collector 21 and the outer magnet collector 22; and a feedback coil 23, which is wound on the shell. The reinforcement body can be, for example, a non-magnetic material such as plastic. The inner magnet collector 21 and the outer magnet collector 22 can be materials with high magnetic permeability such as Permalloy. The feedback coil 23 is Fig.13 Although the magnetic sensor 30 is shown as being wound only around a portion of the annular housing in the circumferential direction, it is actually wound around the entire circumferential direction. In the center of the magnetic sensor 30, a measured object 8 such as a wire through which the current to be measured by the current sensor 1 flows passes.

[0110] 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 the magnetic sensor 30 described later is connected to the excitation circuit 11 and is excited in an alternating manner using an AC excitation current. The excitation voltage or excitation current of the excitation coil 45 changes according to the current (hereinafter referred to as the measured constant current) flowing through the measured object 8. The detection circuit 12 detects the change in the excitation voltage or excitation current, and obtains a signal proportional to the measured constant current through the LPF circuit 13.

[0111] The current detection circuit 10 amplifies the 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, and as a result, a magnetic flux is generated in the band-shaped magnetic body, the inner magnetism collecting body 21, and the outer magnetism collecting body 22 of the magnetic sensor 30 described later. The direction of the winding of the feedback coil 23 is the magnetic flux based on the current flowing through the feedback coil 23, and is the direction of the effect of canceling the magnetic flux generated by the constant current to be measured. Therefore, by this structure, the magnetic flux of the band-shaped magnetic body, the inner magnetism collecting body 21, and the outer magnetism collecting body 22 inside the feedback coil 23 becomes substantially zero, and the current flowing through the feedback coil 23 is proportional to the constant current to be measured. Therefore, the current flowing through the feedback coil 23 is converted into a current-voltage by the I / V circuit 16, and the output voltage of the estimated value of the final constant current to be measured is obtained.

[0112] The above-mentioned current sensor 1 may be a split core type or a clamp type. In this case, the magnetic sensor 30 deforms following the opening and closing action of the sensor head 20. The magnetic sensor 30 according to the present invention has flexibility, so that even if it is deformed by the opening and closing action of the sensor head 20, it is not easy to cause a defect. In addition, the temperature characteristics of the current sensor 1 are improved. Therefore, the current sensor 1 can improve reliability by adopting the magnetic sensor 30 according to the present invention.

[0113] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to the embodiments and various modifications are included within the scope that does not depart from the gist of the present invention.

[0114] Description of the label

[0115] 1 Current sensor

[0116] 8 Object to be measured

[0117] 10 Current detection circuit (11: Excitation circuit, 12: Detection circuit, 13: LPF circuit, 14: Amplification circuit, 15: Feedback circuit, 16: I / V circuit)

[0118] 20 sensor head (21: inner magnet collector, 22: outer magnet collector, 23: feedback coil)

[0119] 30 Magnetic Sensors

[0120] 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 path hole)

[0121] 50 shield

[0122] 60 bridge

[0123] 61 Wiring Department

[0124] 62 Terminal

Claims

1. A magnetic sensor, wherein: The magnetic sensor has: an exciting coil formed of a flexible substrate; as well as an excitation core extending along the axial direction of the excitation coil and wound with the excitation coil, The excitation core is disposed in the flexible substrate such that at least a portion of the excitation core can move relative to the flexible substrate in a strip length direction of the excitation core when the flexible substrate is deformed.

2. The magnetic sensor according to claim 1, wherein: The flexible substrate comprises: an excitation core layer having a wall portion for dividing a space where the excitation core is located; and two coil pattern layers, which contain patterns of the excitation coil and are located at positions sandwiching the excitation core layer. The width of the space defined by the wall of the excitation core layer is greater than the width of the excitation core. The thickness of the excitation core layer is greater than the thickness of the excitation core.

3. The magnetic sensor according to claim 2, wherein: The flexible substrate further comprises an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive is configured not to fix the excitation core to the flexible substrate.

4. The magnetic sensor according to claim 3, wherein: The adhesive is a thermosetting resin and is located at a position farther from the space where the excitation core is located than the wall portion of the excitation core layer before the heat curing process.

5. The magnetic sensor according to claim 2, wherein: The flexible substrate further comprises an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive is configured to fix the field core to the flexible substrate at only one location.

6. The magnetic sensor according to claim 2, wherein: The flexible substrate further comprises an adhesive for bonding the excitation core layer and the coil pattern layer. The adhesive is arranged to fix the field core to the flexible substrate at a plurality of locations spaced apart by a predetermined distance or more.

7. The magnetic sensor according to claim 1, wherein: The magnetic sensor further includes a non-magnetic thin film member that isolates the excitation core from the flexible substrate. The film member is fixed to the flexible substrate but not to the excitation core.

8. The magnetic sensor according to claim 7, wherein: The film member includes a first film member and a second film member that sandwich the excitation core. The first thin film member and the second thin film member are joined at ends of the field core in the strip width direction.

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

10. A current sensor, wherein: The current sensor has: The magnetic sensor according to any one of claims 1 to 9; and The current detection circuit is connected to the excitation coil of the magnetic sensor.

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