Current sensor and interrupting device

Abstract

A current sensor (4) comprises a coil (41) and a magnetic circuit unit (42). The magnetic circuit unit (42) includes: a yoke (40) including a first part (400) disposed within the coil (41); a magnet (43) magnetically connected to the first part (400); and a magnetic resistance portion (44) magnetically connected in parallel with the magnet (43). The magnetic circuit unit (42) forms a first magnetic circuit (C1) including the first part (400) and the magnetic resistance portion (44), a second magnetic circuit (C2) including the first part (400) and the magnet (43), and a third magnetic circuit (C3) including the magnetic resistance portion (44) and the magnet (43). The magnetic resistance of the second magnetic circuit (C2) is smaller than the magnetic resistance of the third magnetic circuit (C3). The magnetic resistance of the first magnetic circuit (C1) is smaller than the magnetic resistance of the second magnetic circuit (C2).

Description

Current sensor and circuit breaker

[0001] The present disclosure relates generally to a current sensor and an interrupting device, and more particularly to a current sensor including a coil and an interrupting device including a current sensor.

[0002] Patent Document 1 discloses an on-board circuit breaker that includes a first conductive path, a second conductive path, a first current detector, a second current detector, a pyrotechnic circuit breaker, and a circuit breaker control unit.

[0003] The first conductive path connects the first input terminal and the first output terminal. DC power of a first polarity is supplied to the first input terminal. The second conductive path connects the second input terminal and the second output terminal. DC power of a second polarity opposite to the first polarity is supplied to the second input terminal. The first current detector can detect a current flowing in the first conductive path or the second conductive path. The second current detector can detect a current flowing in the first conductive path or the second conductive path. The pyrotechnic circuit breaker is capable of operating to irreversibly interrupt the first conductive path. The interruption control unit is capable of controlling the interruption operation of the pyrotechnic circuit breaker.

[0004] The tripping control unit is capable of receiving a first detection signal and a second detection signal transmitted from the first current detector and the second current detector in response to the detected currents, and causes the pyrotechnic circuit breaker to perform a tripping operation when both the first current value obtained based on the first detection signal and the second current value obtained based on the second detection signal exceed an overcurrent threshold.

[0005] Japanese Patent Application Laid-Open No. 2022-189212

[0006] In a current sensor used in a circuit breaker such as the on-board circuit breaker of Patent Document 1, there are cases where it is desired to improve the reliability of overcurrent detection.

[0007] A current sensor according to one aspect of the present disclosure includes a coil, a yoke disposed within the coil and including a first portion, a magnet magnetically connected to the first portion, and a magnetic circuit unit having a magnetic resistance portion magnetically connected in parallel to the magnet, wherein the yoke further includes a first end, a second end, a third end, and a fourth end, the magnet is disposed between the third end and the fourth end, the magnetic resistance portion is disposed between the first end and the second end, and the magnetic circuit unit includes a first magnetic circuit including the first portion and the magnetic resistance portion, and a second magnetic circuit including the first portion and the magnet. a magnetic circuit including the fourth end and the first portion, and a third magnetic circuit including the magnetic resistance portion and the magnet, wherein the magnetic resistance of the second magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the first portion is smaller than the magnetic resistance of the third magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the magnetic resistance portion, and the magnetic resistance of the first magnetic circuit to a magnetic field in a direction from the first end to the second end via the first portion is smaller than the magnetic resistance of the second magnetic circuit to a magnetic field in a direction from the third end to the fourth end via the first portion.

[0008] A current sensor according to one aspect of the present disclosure includes a coil, a magnetic circuit unit having a magnetic resistance portion disposed within the coil, a magnet magnetically connected to the magnetic resistance portion, and a yoke including a first portion magnetically connected in parallel to the magnet, wherein the yoke further includes a first end, a second end, a third end, and a fourth end, the magnet is disposed between the third end and the fourth end, the magnetic resistance portion is disposed between the first end and the second end, and the magnetic circuit unit includes a first magnetic circuit including the first portion and the magnetic resistance portion, and the first portion and the magnet. A second magnetic circuit and a third magnetic circuit including the magnetic resistance portion and the magnet are formed, and the magnetic resistance of the second magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the first portion is smaller than the magnetic resistance of the third magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the magnetic resistance portion, and the magnetic resistance of the first magnetic circuit to a magnetic field in a direction from the first end to the second end via the first portion is smaller than the magnetic resistance of the second magnetic circuit to a magnetic field in a direction from the third end to the fourth end via the first portion.

[0009] A circuit breaker according to one aspect of the present disclosure includes the current sensor, an igniter, and a projectile. The igniter includes a gunpowder and is configured to ignite the gunpowder using the electric power generated by the coil. The projectile is ejected and moved by the ignited gunpowder.

[0010] The circuit breaker according to one aspect of the present disclosure includes the current sensor, a wiring member, an igniter, and a projectile. The wiring member passes through a position between the coil and the magnetic resistance portion. The igniter includes an explosive and is configured to ignite the explosive using electric power generated by the coil. The projectile is projected by the ignited explosive and moves, interrupting the flow of electricity through the wiring member. A current flows through the wiring member in a predetermined direction. When the current flows through the wiring member, the wiring member generates the second magnetic field within the yoke. The coil generates electricity using the current flowing through the wiring member. When the value of the current flowing through the wiring member reaches or exceeds a certain value, the igniter ignites the explosive using the electric power generated by the coil. The projectile moves toward the wiring member and interrupts the flow of electricity through the wiring member.

[0011] The circuit breaker according to one aspect of the present disclosure includes the current sensor, a wiring member, an igniter, and a projectile. The wiring member passes through a position between the coil and the first portion of the yoke. The igniter includes explosives and is configured to be able to ignite the explosives using electric power generated by the coil. The projectile is moved by the ignited explosives and cuts off the current flowing through the wiring member. A current flows through the wiring member in a predetermined direction. When the current flows through the wiring member, the wiring member generates the second magnetic field within the yoke. The coil generates electric power using the current flowing through the wiring member. When the value of the current flowing through the wiring member reaches or exceeds a certain value, the igniter ignites the explosives using the electric power generated by the coil. The projectile moves toward the wiring member and cuts off the current flowing through the wiring member.

[0012] According to the present disclosure, there is an advantage in that it is possible to provide a current sensor and a circuit breaker that can improve the reliability of overcurrent detection.

[0013] FIG. 1 is a block diagram of an interrupter according to one embodiment. FIG. 2 is a diagram illustrating a circuit configuration of the interrupter according to the embodiment. FIG. 3 is a perspective view of a detection unit provided in the interrupter according to the embodiment. FIG. 4 is a perspective view of a main part of the detection unit according to the embodiment. FIG. 5 is a front view of a main part of the detection unit according to the embodiment. FIG. 6 is a schematic diagram illustrating a magnetic circuit formed by a magnetic circuit unit provided in a current sensor of the detection unit according to the embodiment. FIG. 7 is a graph showing the relationship between a current flowing through a wiring member and a magnetic flux density passing through a coil in the current sensor according to the embodiment. FIG. 8 is a diagram illustrating a magnetic equivalent circuit of the magnetic circuit unit according to the embodiment. FIG. 9 is a diagram illustrating a magnetic equivalent circuit of the magnetic circuit unit according to the embodiment. FIG. 10 is a front view of a main part of a current sensor according to a comparative example. FIG. 11 is a schematic diagram illustrating a magnetic circuit formed by a magnetic circuit unit provided in the current sensor according to the comparative example. FIG. 12 is a graph showing the relationship between a current flowing through a wiring member and a magnetic flux density passing through a coil in the current sensor according to the comparative example. FIG. 13 is a cross-sectional view of the interrupter unit provided in the interrupter according to the embodiment. Fig. 14 is a schematic configuration diagram of a vehicle equipped with the above-mentioned breaking device. Fig. 15 is a front view of a main part of a current sensor of Modification 1. Fig. 16 is a front view of a main part of a current sensor of Modification 2. Fig. 17 is a schematic diagram for explaining a magnetic circuit formed by a magnetic circuit unit equipped in the above-mentioned current sensor. Fig. 18A is a diagram showing a circuit configuration of a first switching element equipped in the breaking device of Modification 3. Fig. 18B is a diagram showing a circuit configuration of a second switching element equipped in the breaking device of Modification 3.

[0014] Hereinafter, a current sensor and a circuit breaker according to embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the following embodiments are merely a portion of various embodiments of the present disclosure. The following embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, the drawings described in the following embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0015] (1) Embodiment (1.1) Breaker Device A breaker device 200 of this embodiment will be described with reference to FIGS. 1 to 13. FIG.

[0016] The interrupter 200 is mounted on an object. The object is a device having an electric circuit through which current supplied from a power source passes. The interrupter 200 is activated, for example, when an abnormality occurs in an electric circuit or system within the object, to interrupt the electric circuit, thereby preventing damage from the abnormality from becoming greater.

[0017] The object on which the cutoff device 200 is mounted is, for example, a vehicle 6 (see FIG. 14 ). The vehicle 6 has an electric circuit 60 for driving the vehicle 6. The electric circuit 60 is configured by connecting a motor 62, a battery 61 (e.g., a lithium-ion battery) for driving the motor, and circuit components including a switch via wiring members 9. The cutoff device 200 cuts off the electrical connection between the motor 62 and the battery 61 by cutting off the electric circuit 60 in the event of an emergency such as an abnormality or an accident of the vehicle 6, for example. Note that the object may be something other than the vehicle 6, and examples thereof include, but are not limited to, a home appliance and a solar power generation system.

[0018] 1 , the interrupting device 200 includes a detection unit 1 and an interrupting unit 2 electrically connected to the detection unit 1. In the present disclosure, "the first member and the second member are electrically connected" means that the first member and the second member are connected directly or via a third member so that electricity can flow from the first member to the second member (and / or from the second member to the first member).

[0019] (1.2) Detection Unit As shown in Figures 1 and 2, the detection unit 1 includes a current sensor 4 and a filter circuit 5. As shown in Figures 3 to 5, the detection unit 1 further includes a connector 17, a board 18, and a housing 19.

[0020] (1.2.1) Configuration of the Current Sensor The current sensor 4 of this embodiment is a sensor that detects a current Ib flowing through a wiring member 9. The wiring member 9 includes, for example, a bus bar 90. The bus bar 90 is a conductor for passing a large current, and is, for example, a plate- or rod-shaped member made of a metal such as copper.

[0021] The current sensor 4 of this embodiment is a sensor for detecting, in particular, an overcurrent flowing through the wiring member 9 (bus bar 90). When an overcurrent flows through the wiring member 9 (bus bar 90), the current sensor 4 outputs a signal to the outside (for example, the filter circuit 5). An overcurrent is a current that exceeds the current allowed to flow through the wiring member 9.

[0022] 4 and 5, the current sensor 4 includes a coil 41 and a magnetic circuit unit 42. The magnetic circuit unit 42 includes a yoke 40, a magnet 43, and a magnetic resistance portion 44. For convenience, the polarities (north and south poles) of the magnet 43 are also shown in FIG.

[0023] In the following description, the current sensor 4 and the detection unit 1 are described by defining three axes (X-axis, Y-axis, and Z-axis) of a right-handed three-dimensional Cartesian coordinate system as follows: The direction in which the magnet 43 and the magnetic resistance portion 44 are aligned is the Z-axis direction; the direction perpendicular to the Z-axis direction, connecting the north and south poles of the magnet 43, is the Y-axis direction; and the direction perpendicular to the Y-axis and Z-axis directions is the X-axis direction. For ease of explanation, the direction along the Z-axis is also referred to as the up-down direction, and the side on which the magnetic resistance portion 44 is located (the direction of the Z-axis) as viewed from the magnet 43 is also referred to as "up" and the opposite side as "down." The direction along the Y-axis is also referred to as the left-right direction. In the direction in which the south and north poles of the magnet 43 are aligned, the direction from the south pole to the north pole (the direction in which the magnetic field lines point from the north pole of the magnet 43 to the yoke 40; the positive direction of the Y-axis) is also referred to as the "right," and the opposite side as the "left." The direction along the X-axis is also referred to as the front-to-rear direction, with the positive direction of the X-axis being referred to as "front" and the opposite direction being referred to as "rear." However, the definitions of axes and directions in this disclosure merely indicate the relative positional relationships between the components of the current sensor 4, and do not limit the posture, etc., of the current sensor 4 and the circuit breaker 200 equipped with the current sensor 4 when they are installed on an object.

[0024] The yoke 40 is made of a magnetic material. As shown in FIG. 5 , the yoke 40 has a shape resembling the digital number "8" when viewed from the front. More specifically, the shape is the same as the digital number "8" with the left and right central portions and the lower central portion removed. As shown in FIG. 4 , the yoke 40 has a substantially uniform cross-sectional shape in the front-to-rear direction. The yoke 40 may be formed from a single member, or may be formed by joining multiple members. For example, the yoke 40 may be formed by joining the upper ends of a first member that is E-shaped when viewed from the front and a second member that is inverted E-shaped when viewed from the front.

[0025] 5, the yoke 40 has a first portion 405, a second portion 4061, a third portion 4062, a fourth portion 4071, a fifth portion 4072, a sixth portion 4081, a seventh portion 4082, an eighth portion 4091, and a ninth portion 4092. The first portion 405 to the ninth portion 4092 are plate-shaped portions having the same thickness.

[0026] The first portion 405 has a rectangular plate shape that extends in the left and right directions.

[0027] The second portion 4061 has a rectangular plate shape and extends downward from the left end of the first portion 405. The third portion 4062 has a rectangular plate shape and extends downward from the lower end of the second portion 4061.

[0028] The fourth portion 4071 has a rectangular plate shape and extends downward from the right end of the first portion 405. The fifth portion 4072 has a rectangular plate shape and extends downward from the bottom end of the fourth portion 4071.

[0029] The sixth portion 4081 has a rectangular plate shape extending to the right from the portion where the second portion 4061 and the third portion 4062 are connected. The seventh portion 4082 has a rectangular plate shape extending to the left from the portion where the fourth portion 4071 and the fifth portion 4072 are connected. The protruding end (right end) of the sixth portion 4081 and the protruding end (left end) of the seventh portion 4082 face each other in the left-right direction. A gap G1 is formed between the sixth portion 4081 and the seventh portion 4082.

[0030] The eighth portion 4091 is a rectangular plate extending rightward from the lower end of the third portion 4062. The ninth portion 4092 is a rectangular plate extending leftward from the lower end of the fifth portion 4072. The protruding end (right end) of the eighth portion 4091 and the protruding end (left end) of the ninth portion 4092 face each other in the left-right direction. A gap G2 is formed between the eighth portion 4091 and the ninth portion 4092. The distance L2 between the eighth portion 4091 and the ninth portion 4092 (the size of the gap G2) is greater than the distance L1 between the sixth portion 4081 and the seventh portion 4082 (the size of the gap G1).

[0031] A first through-hole T1 penetrating in the front-rear direction is formed in the yoke 40 so as to be surrounded by the first portion 405, the second portion 4061, the fourth portion 4071, the sixth portion 4081, and the seventh portion 4082 (as well as the gap G1). Further, a second through-hole T2 penetrating in the front-rear direction is formed in the yoke 40 so as to be surrounded by the third portion 4062, the fifth portion 4072, the sixth portion 4081, the seventh portion 4082, the eighth portion 4091, and the ninth portion 4092 (as well as the gap G1 and the gap G2).

[0032] The coil 41 is provided in a first portion 405 of the yoke 40. That is, the first portion 405 of the yoke 40 includes a first portion 400 in which the coil 41 is provided. In other words, the yoke 40 includes the first portion 400 disposed within the coil 41.

[0033] The coil 41 is formed by winding a conductive conductor (e.g., copper wire) around the first portion 400 of the yoke 40. The coil 41 is provided on the yoke 40 via a bobbin 410 made of an insulating material such as a resin material.

[0034] 2 , the coil 41 has a first end 411 and a second end 412. The first end 411 and the second end 412 of the coil 41 are electrically connected to the filter circuit 5. For example, the first end 411 of the coil 41 is electrically connected to a first input terminal 511 of the filter circuit 5, and the second end 412 of the coil 41 is electrically connected to a second input terminal 512 of the filter circuit 5.

[0035] The magnetic resistance portion 44 is an element having a magnetic resistance per unit length greater than that of the yoke 40. As shown in FIG. 5 , the magnetic resistance portion 44 is located in the gap G1 between the sixth portion 4081 and the seventh portion 4082 of the yoke 40. In this embodiment, the magnetic resistance portion 44 is the gap G1. The magnetic resistance portion 44 contains, for example, air, and in this embodiment, contains only air.

[0036] From another perspective, the yoke 40 includes a first end 401 magnetically connected to the magnetic resistance portion 44 and a second end 402 that faces the first end 401 across the magnetic resistance portion 44 and is magnetically connected to the first end 401. The first end 401 of the yoke 40 is, for example, the protruding end of the sixth portion 4081. The second end 402 of the yoke 40 is, for example, the protruding end of the seventh portion 4082. In this embodiment, the magnetic resistance portion 44 is a gap G1 formed between the first end 401 and the second end 402. The magnetic resistance portion 44 also includes air disposed between the first end 401 and the second end 402.

[0037] As shown in FIG. 5 , the magnet 43 is disposed in the gap G2 between the eighth portion 4091 and the ninth portion 4092 of the yoke 40. For example, the protruding end of the eighth portion 4091 contacts the magnet 43. Furthermore, the protruding end of the ninth portion 4092 contacts the magnet 43. The magnet 43 is magnetically connected to the yoke 40. Therefore, the magnet 43 is magnetically connected to the first portion 400 of the yoke 40. Furthermore, the magnet 43 is magnetically connected in parallel to the first portion 400, and the magnetic resistance unit 44 is magnetically connected in parallel to the magnet 43. In other words, the magnetic resistance unit 44 is magnetically connected in parallel to the first portion 400 and the magnet 43.

[0038] From another perspective, the yoke 40 includes a third end 403 that contacts the magnet 43, and a fourth end 404 that contacts the magnet 43 and is magnetically connected to the third end 403 via the magnet 43. The third end 403 of the yoke 40 is, for example, the protruding end of the eighth portion 4091. The fourth end 404 of the yoke 40 is, for example, the protruding end of the ninth portion 4092.

[0039] The magnet 43 includes a permanent magnet 430. The permanent magnet 430 is made of a hard magnetic material. In this embodiment, the magnet 43 includes only the permanent magnet 430. However, this is not limited thereto, and the magnet 43 may include the permanent magnet 430 and a non-magnetic material. The non-magnetic material is made of a non-magnetic material. The non-magnetic material may include, for example, a coating material that covers the permanent magnet 430, a case that covers the permanent magnet 430, or an adhesive for adhering the permanent magnet 430 to the yoke 40. The non-magnetic material may be disposed, for example, between the third end 403 of the yoke 40 and the permanent magnet 430 and in contact with the third end 403 of the yoke 40. The non-magnetic material may be disposed, for example, between the fourth end 404 of the yoke 40 and the permanent magnet 430 and in contact with the fourth end 404 of the yoke 40. The non-magnetic material may be arranged, for example, between the third end 403 of the yoke 40 and the permanent magnet 430 and between the fourth end 404 of the yoke 40 and the permanent magnet 430, and may be in contact with the third end 403 and the fourth end 404.

[0040] The first portion 400 of the yoke 40 (yoke 40), the magnetic resistance portion 44, and the magnet 43 are arranged in this order from top to bottom in the vertical direction.

[0041] 6 shows the magnetic circuit formed by the magnetic circuit unit 42. In this disclosure, the term "magnetic circuit" refers to the path (a path with relatively small magnetic resistance) through which a magnetic field (magnetic flux) can primarily pass when the magnetic field (magnetic flux) is generated within the magnetic circuit unit 42.

[0042] As shown in FIG. 6, the magnetic circuit unit 42 forms a first magnetic circuit C1, a second magnetic circuit C2, and a third magnetic circuit C3.

[0043] The first magnetic circuit C1 includes the first part 400 and the magnetic resistance part 44. In this embodiment, the first magnetic circuit C1 includes the first part 405 (including the first part 400), the second part 4061, the fourth part 4071, the sixth part 4081, and the seventh part 4082 of the yoke 40, and the magnetic resistance part 44. The second magnetic circuit C2 includes the first part 400 and the magnet 43. In this embodiment, the second magnetic circuit C2 includes the first part 405 (including the first part 400), the second part 4061, the third part 4062, the fourth part 4071, the fifth part 4072, the eighth part 4091, and the ninth part 4092 of the yoke 40, and the magnet 43. The third magnetic circuit C3 includes the magnetic resistance part 44 and the magnet 43. In this embodiment, the third magnetic circuit C3 includes the third portion 4062, the fifth portion 4072, the sixth portion 4081, the seventh portion 4082, the eighth portion 4091, and the ninth portion 4092 of the yoke 40, the magnetic resistance portion 44, and the magnet 43.

[0044] 5 , the magnet 43 is disposed in the gap G2 with its south pole facing the eighth portion 4091 and its north pole facing the ninth portion 4092. The magnet 43 generates a magnetic field (hereinafter also referred to as a “first magnetic field”) H1 within the yoke 40.

[0045] The first magnetic field H1 generated within the yoke 40 by the magnet 43 can pass through the second magnetic circuit C2 and the third magnetic circuit C3. Here, the magnetic resistance of the first portion 400 of the yoke 40 as viewed from the first magnetic field H1 is smaller than the magnetic resistance of the magnetic resistance portion 44. Therefore, as viewed from the first magnetic field H1, the magnetic resistance of the second magnetic circuit C2 is smaller than the magnetic resistance of the third magnetic circuit C3.

[0046] In this embodiment, the magnetic resistance of the second magnetic circuit C2 is sufficiently smaller than the magnetic resistance of the third magnetic circuit C3 when viewed from the first magnetic field H1. In other words, the magnetic resistance of the second magnetic circuit C2 to the magnetic field directed from the fourth end 404 through the first portion 400 to the third end 403 is smaller than the magnetic resistance of the third magnetic circuit C3 to the magnetic field directed from the fourth end 404 through the magnetic resistance portion 44 to the third end 403. Therefore, the first magnetic field H1 mainly passes through the second magnetic circuit C2. Therefore, the first magnetic field H1 passes through the coil 41 provided in the first portion 400 of the yoke 40.

[0047] 5, a bus bar 90 is disposed in the first through hole T1 of the yoke 40. The bus bar 90 is, for example, a plate-like member extending in the front-rear direction. The bus bar 90 (wiring member 9) passes through a position between the coil 41 and the magnetic resistance portion 44.

[0048] For example, when the battery 61 is discharging, a current Ib flows through the busbar 90 (wiring member 9) in a predetermined direction (the direction of the arrow of the current Ib in FIG. 2 , the direction of the current Ib in FIG. 5 ). When the current Ib flows through the busbar 90 (wiring member 9), the busbar 90 (wiring member 9) generates a magnetic field H2 (hereinafter also referred to as a "second magnetic field") around the busbar 90 in a direction corresponding to the direction of the current Ib, as shown in FIG. 5 . The current Ib flowing through the busbar 90 generates a second magnetic field H2 in the first portion 400, which is opposite in direction to the first magnetic field H1 generated by the magnet 43 (the direction of the current Ib and the polarity of the magnet 43 are set in this manner). The second magnetic field H2 passes through the coil 41 provided in the first portion 400 of the yoke 40.

[0049] Since the bus bar 90 is disposed in the first through hole T1, the second magnetic field H2 can pass mainly through the first magnetic circuit C1 and the second magnetic circuit C2.

[0050] In the magnetic circuit unit 42 of this embodiment, the magnetic resistance of the first magnetic circuit C1 is smaller than the magnetic resistance of the second magnetic circuit C2 when viewed from the second magnetic field H2. In other words, the magnetic resistance of the first magnetic circuit C1 to the magnetic field oriented from the first end 401 through the first portion 400 to the second end 402 is smaller than the magnetic resistance of the second magnetic circuit C2 to the magnetic field oriented from the third end through the first portion 400 to the fourth end 404.

[0051] Specifically, the distance L1 between the first end 401 and the second end 402 of the yoke 40 is shorter than the distance L2 between the third end 403 and the fourth end 404. Furthermore, a magnet 43 that acts as a magnetic resistance when viewed from the second magnetic field H2 is disposed in the gap G2 between the third end 403 and the fourth end 404 of the yoke 40. Therefore, of the first magnetic circuit C1 and the second magnetic circuit C2, the second magnetic field H2 mainly passes through the first magnetic circuit C1.

[0052] The coil 41 generates electricity when the magnetic flux passing through the coil 41 changes. In the current sensor 4 of this embodiment, the first magnetic field H1 and the second magnetic field H2 pass through the coil 41 as described above. Of these, the first magnetic field H1 does not substantially change. On the other hand, the second magnetic field H2 changes in response to changes in the current Ib. Therefore, the magnetic flux passing through the coil 41 changes in response to changes in the current Ib flowing through the bus bar 90. In short, in the current sensor 4 of this embodiment, the coil 41 generates electricity using the current Ib flowing through the bus bar 90 (wiring member 9), generating an induced current Ic.

[0053] (1.2.2) Operation of the Current Sensor The operation of the current sensor 4 of this embodiment will be described with reference to FIGS.

[0054] As described above, the magnetic flux passing through the coil 41 changes when the current Ib flowing through the bus bar 90 changes. Fig. 7 shows a graph G10 that shows an outline of the relationship between the current Ib flowing through the bus bar 90 and the magnetic flux density B passing through the coil 41. Note that in the graph G10 of Fig. 7, the positive and negative signs of the magnetic flux density B passing through the coil 41 are defined as "positive" when they are in the same direction as the direction of the second magnetic field H2.

[0055] Fig. 8 shows a magnetic equivalent circuit C10 of the magnetic circuit unit 42 when no current Ib is flowing through the bus bar 90 (the magnitude of the current Ib is 0 [kA]). When no current Ib is flowing through the bus bar 90, as shown in Fig. 8, only negative magnetic flux Φm caused by the magnetomotive force Fm of the magnet 43 passes through the coil 41. In particular, in the current sensor 4 of this embodiment, when no current Ib is flowing through the bus bar 90, the first portion 400 of the yoke 40 is magnetically saturated by the first magnetic field H1 caused by the magnet 43 (see Fig. 7).

[0056] When current Ib flows through the busbar 90, in addition to the first magnetic field H1 generated by the magnet 43, a second magnetic field H2 generated by current Ib and directed in the opposite direction to the first magnetic field H1 also passes through the coil 41. Therefore, at the first portion 400 of the yoke 40, a portion of the first magnetic field H1 is canceled out by the second magnetic field H2. However, when current Ib is small (specifically, less than the first predetermined value P1 shown in FIG. 7 ), the second magnetic field H2 is sufficiently smaller than the first magnetic field H1, and magnetic saturation of the first portion 400 caused by the first magnetic field H1 of the magnet 43 is maintained. Therefore, even if current Ib changes within region A11 from 0 to the first predetermined value P1, the magnetic flux density B passing through the coil 41 does not change.

[0057] As the current Ib increases, the second magnetic field H2 also increases. When the magnitude of the current Ib reaches the first predetermined value P1, the magnetic saturation of the first portion 400 of the yoke 40 caused by the first magnetic field H1 of the magnet 43 is released.

[0058] As shown in FIG. 7 , in a region A10 where the current Ib ranges from the first predetermined value P1 to the third predetermined value P3 (where P3 is greater than P1), the magnetic flux density B passing through the coil 41 varies substantially linearly with the current Ib. Here, the magnetic flux density B passing through the coil 41 increases linearly with increasing current Ib. More specifically, in a region where the current Ib ranges from the first predetermined value P1 to the second predetermined value P2 (where P1 is less than P2 and P3 is less than P3), the second magnetic field H2 increases with increasing current Ib, and the magnitude of the negative magnetic flux density B decreases linearly. When the current Ib is equal to or greater than P2, the first magnetic field H1 and the second magnetic field H2 cancel each other out, and the magnetic flux density B passing through the coil 41 becomes substantially zero. Furthermore, in a region where the current Ib is equal to or greater than P2, the second magnetic field H2 is greater than the first magnetic field H1. In the region where the current Ib is between the second predetermined value P2 and the third predetermined value P3, the magnitude of the positive magnetic flux density B increases linearly as the current Ib increases.

[0059] 9 shows a magnetic equivalent circuit C20 of the magnetic circuit unit 42 in a state where a current Ib having a predetermined value P10 (see FIG. 7) flows through the bus bar 90. For convenience, in FIG. 9, the magnetic flux Φ Ｉ The magnetomotive force F that drives Ｉis shown on the magnetic equivalent circuit C20. Note that the current Ib flowing through the bus bar 90 generates a second magnetic field H2 (concentrically) around the bus bar 90, and therefore a magnetomotive force F Ｉ It is not possible to express the magnetomotive force F on the magnetic equivalent circuit C20 for the sake of convenience. Ｉ is shown at the position of the first portion 405 of the yoke 40, where the second magnetic field H2 can act most strongly. Although not shown in Fig. 9, a negative magnetic flux Φm (see Fig. 8) caused by the magnetomotive force Fm of the magnet 43 also passes through the magnetic circuit unit 42. That is, the magnetic flux Φ caused by the magnetomotive force Fm of the magnet 43 and the magnetomotive force F of the current Ib pass through the coil 41. Ｉ Magnetic flux Φ Ｉ A magnetic flux created by combining and (which is subtracted in magnitude because they are in opposite directions) passes through.

[0060] 7, in region A12 where current Ib is equal to or greater than third predetermined value P3, second magnetic field H2 due to current Ib is sufficiently larger than first magnetic field H1 due to magnet 43. Therefore, in region A12, first portion 400 of yoke 40 is magnetically saturated by second magnetic field H2 due to current Ib. Therefore, even if current Ib changes within region A12, magnetic flux density B passing through coil 41 does not change.

[0061] Thus, in the current sensor 4, even if the current Ib changes within the region A11 from 0 to the first predetermined value P1, the magnetic flux density B passing through the coil 41 does not change, and the coil 41 does not generate electricity. Also, in the current sensor 4, even if the current Ib changes within the region A13 equal to or greater than the third predetermined value P3, the magnetic flux density B passing through the coil 41 does not change, and the coil 41 does not generate electricity.

[0062] On the other hand, in the current sensor 4, when the current Ib changes within the region A10 from the first predetermined value P1 to the third predetermined value P3, the magnetic flux density B passing through the coil 41 changes in accordance with the change in the current Ib, causing the coil 41 to generate electricity and generate the induced current Ic.

[0063] The current sensor 4 of this embodiment outputs, as a signal, the induced current Ic generated by the coil 41 when the current Ib changes within the region A10. It can be said that the current sensor 4 of this embodiment is sensitive to changes in the current Ib within the region A10.

[0064] For example, when the vehicle 6 serving as the object is traveling, a constant current Ib supplied from the battery 61, e.g., a current Ib of a first predetermined value P1, flows through the bus bar 90. In the current sensor 4 of this embodiment, when the current Ib flowing through the bus bar 90 becomes greater than the first predetermined value P1, the coil 41 generates electricity to generate an induced current Ic. Therefore, the current sensor 4 of this embodiment can be particularly used to detect an overcurrent that occurs when a constant current Ib (e.g., a current Ib of the first predetermined value P1) flows through the bus bar 90 (wiring member 9).

[0065] Furthermore, in the current sensor 4 of this embodiment, even if the current Ib changes within the region A11 (below the first predetermined value P1), the coil 41 does not generate electricity. Therefore, the current sensor 4 does not generate a signal, for example, even if the current Ib increases from 0 to the first predetermined value P1. This reduces the possibility that the current sensor 4 will detect an unintended change in the current Ib (for example, a change in the current Ib within the region A11) as an overcurrent. This can improve the reliability of overcurrent detection.

[0066] (1.2.3) Advantages of the Current Sensor The advantages of the current sensor 4 of this embodiment will be explained with a comparison with the current sensor 4A of the comparative example.

[0067] As shown in Fig. 10, the current sensor 4A of the comparative example includes a coil 41A and a magnetic circuit unit 42A. The magnetic circuit unit 42A does not include the magnetic resistance portion 44 included in the magnetic circuit unit 42 of the embodiment. The yoke 40A of the comparative example has a shape obtained by removing the sixth portion 4081 and the seventh portion 4082 from the yoke 40 of the embodiment. The yoke 40A of the comparative example has a first portion 405A, a second portion 406A, a third portion 407A, a fourth portion 4091A, and a fifth portion 4092A, each of which has a rectangular plate shape, and has a shape in which the first portion 405A to the fifth portion 4092A are connected in a rectangular cylindrical shape such that a gap G0 is formed between the fourth portion 4091A and the fifth portion 4092A. A through hole T0 is formed in the yoke 40A, penetrating in the front-to-rear direction so as to be surrounded by the first portion 405A to the fifth portion 4092A (and the gap G0). The coil 41A is provided in the first portion 400A of the first portion 405A. The magnet 43A of the current sensor 4A of the comparative example is substantially the same as the magnet 43 of the current sensor 4 of the embodiment, and is disposed in the gap G0 of the yoke 40A. A bus bar 90 (wiring member 9) is disposed in the through hole T0 of the yoke 40A.

[0068] 11 shows the magnetic circuit formed by the magnetic circuit unit 42A of the comparative example. The magnetic circuit unit 42A forms only a magnetic circuit C100. The magnetic circuit C100 includes the first portion 405A, the second portion 406A, the third portion 407A, the fourth portion 4091A, and the fifth portion 4092A of the yoke 40A, and a magnet 43A. The magnetic circuit C100 of the current sensor 4A of the comparative example substantially corresponds to the second magnetic circuit C2 of the current sensor 4 of the embodiment.

[0069] 10, in the current sensor 4A of the comparative example, a first magnetic field H1 generated by the magnet 43A and a second magnetic field H2 generated by the current Ib flowing through the bus bar 90 also pass through the coil 41A. The first magnetic field H1 does not substantially change, but the second magnetic field H2 changes in response to changes in the current Ib.

[0070] FIG. 12 shows a graph G100 that roughly represents the relationship between the current Ib flowing through the bus bar 90 and the magnetic flux density B passing through the coil 41A in the current sensor 4A of the comparative example.

[0071] 12, the graph G100 of the current sensor 4A of the comparative example also has a region A21 where the magnetic flux density B does not change due to magnetic saturation caused by the first magnetic field H1 of the magnet 43A, a region A20 where the magnetic flux density B changes in response to changes in the current Ib (the magnetic flux density B increases as the current Ib increases), and a region A22 where the magnetic flux density B does not change due to magnetic saturation caused by the second magnetic field H2 of the current Ib. The current sensor 4A of the comparative example outputs, as a signal, an induced current generated by the coil 41A when the current Ib changes in region A20.

[0072] Here, in the current sensor 4A of the comparative example, the magnitude of the increase in magnetic flux density B when the current Ib increases by a unit amount within the region A20 is smaller than the magnitude of the increase in magnetic flux density B when the current Ib increases by a unit amount within the region A10 in the current sensor 4 of the embodiment. In other words, the slope of the region A20 in the graph G100 (see FIG. 12) is smaller than the slope of the region A10 in the graph G10 (see FIG. 7). This point will be explained below. Note that, for convenience, the "magnitude of the increase in magnetic flux density B when the current Ib increases by a unit amount within the region A10 (or A20)" will also be referred to as the "unit magnetic flux density change amount."

[0073] As described above, in the magnetic circuit unit 42 of the current sensor 4 of the embodiment, the first magnetic field H1 generated by the magnet 43 mainly passes through the second magnetic circuit C2 (see FIG. 6) (see FIG. 8). Also, in the magnetic circuit unit 42A of the current sensor 4A of the comparative example, the first magnetic field H1 generated by the magnet 43A passes through the magnetic circuit C100 (see FIG. 11). From the perspective of the first magnetic field H1 generated by the magnet 43 and the magnet 43A, the magnetic resistance of the second magnetic circuit C2 of the embodiment is substantially equal to the magnetic resistance of the magnetic circuit C100 of the comparative example. Therefore, the magnetic flux that the first magnetic field H1 generated by the magnet 43 in the current sensor 4 of the embodiment acts on the coil 41 is substantially the same as the magnetic flux that the first magnetic field H1 generated by the magnet 43A in the current sensor 4A of the comparative example acts on the coil 41A.

[0074] On the other hand, in the magnetic circuit unit 42 of the current sensor 4 of the embodiment, the second magnetic field H2 caused by the current Ib flowing through the bus bar 90 mainly passes through the first magnetic circuit C1 (see FIG. 6) (see FIG. 9). In contrast, in the magnetic circuit unit 42A of the current sensor 4A of the comparative example, the second magnetic field H2 caused by the current Ib flowing through the bus bar 90 passes through the magnetic circuit C100 (see FIG. 11). From the perspective of the second magnetic field H2 caused by the current Ib flowing through the bus bar 90, the magnetic resistance of the first magnetic circuit C1 of the current sensor 4 of the embodiment is smaller than the magnetic resistance of the second magnetic circuit C2, and therefore smaller than the magnetic resistance of the magnetic circuit C100 of the current sensor 4A of the comparative example. Therefore, in the current sensor 4 of the embodiment, the magnitude of the increase in magnetic flux density B when the current Ib increases by a unit amount within the region A10 is larger than the magnitude of the increase in magnetic flux density B when the current Ib increases by a unit amount within the region A20 of the current sensor 4A of the comparative example. In other words, the unit amount of change in magnetic flux density is larger in the current sensor 4 of the embodiment than in the current sensor 4A of the comparative example.

[0075] In short, in the current sensor 4 of the embodiment, the magnetic circuit unit 42 has, as a magnetic circuit that allows the second magnetic field H2 to pass through, the first magnetic circuit C1 that has a smaller magnetic resistance than the second magnetic circuit C2 that passes through the magnet 43. As a result, the current sensor 4 of the embodiment can increase the magnitude of the increase in magnetic flux density B when the second magnetic field H2 increases by a unit amount, and can increase the unit amount of change in magnetic flux density, compared to the current sensor 4A of the comparative example.

[0076] Here, when the unit amount of change in magnetic flux density is small, the increase in magnetic flux density B is small even if the current flowing through bus bar 90 increases. Because the electromotive force of coil 41 corresponds to the change over time in the magnetic flux passing through coil 41, when the increase over time in magnetic flux density B is small, the amount of power generated by coil 41 decreases. Therefore, with current sensor 4A of the comparative example, even if an overcurrent flows through bus bar 90, the amount of power generated (induced current Ic generated by coil 41A) may not be sufficient.

[0077] In contrast, the current sensor 4 of this embodiment can generate a larger amount of power (the induced current Ic generated by the coil 41) when an overcurrent flows through the bus bar 90 than the current sensor 4A of the comparative example. This allows the current sensor 4 of this embodiment to reliably output a signal (the induced current Ic) when an overcurrent flows through the bus bar 90. This makes it possible to improve the reliability of overcurrent detection.

[0078] (1.2.4) Filter Circuit The filter circuit 5 is electrically connected to the current sensor 4. As shown in FIG.

[0079] As shown in FIG. 2, the filter circuit 5 has a first input terminal 511, a second input terminal 512, a rectifying element (diode) 52, a first resistor 531, a second resistor 532, a capacitor 54, a first switching element 55, a second switching element 56, a first connection terminal 571, and a second connection terminal 572.

[0080] The diode 52 is electrically connected to both ends of the coil 41 of the current sensor 4. The cathode of the diode 52 is electrically connected to the first end 411 of the coil 41, and the anode of the diode 52 is electrically connected to the second end 412 of the coil 41.

[0081] The first resistor 531 is electrically connected to both ends of the diode 52 .

[0082] The first switching element 55 is electrically connected to the diode 52. A first end 551 of the first switching element 55 is electrically connected to the cathode of the diode 52. A second end 552 of the first switching element 55 is electrically connected to a first end 561 of the second switching element 56.

[0083] The first switching element 55 includes, for example, a thyristor. The thyristor is, for example, a bidirectional thyristor. The first switching element 55 may be a packaged element, for example, a SIDAC (registered trademark, the same applies hereinafter).

[0084] The first switching element 55 passes (almost no) current when the voltage value of the voltage applied across both ends of the first switching element 55 (between the first terminal 551 and the second terminal 552) is less than a first value. On the other hand, when a voltage equal to or greater than the first value is applied to the first switching element 55, the first switching element 55 passes current from the first terminal 551 to the second terminal 552. The first value is, for example, a breakover voltage of the first switching element 55 as a sidac.

[0085] The capacitor 54 is electrically connected to the first switching element 55. A first end of the capacitor 54 is electrically connected to a second end 552 of the first switching element 55, and a second end of the capacitor 54 is electrically connected to the anode of the diode 52. The capacitor 54 accumulates charge of the current flowing through the first switching element 55.

[0086] The second resistor 532 is electrically connected to both ends of the capacitor 54 .

[0087] The second switching element 56 is electrically connected to the first switching element 55. A first end 561 of the second switching element 56 is electrically connected to a second end 552 of the first switching element 55. A second end 562 of the second switching element 56 is electrically connected to a first connection terminal 571.

[0088] The second switching element 56 comprises, for example, a thyristor, for example, a bidirectional thyristor, or may be a packaged element, for example, a sidac.

[0089] The second switching element 56 passes (almost no) current when the voltage value applied across both ends of the second switching element 56 (between the first terminal 561 and the second terminal 562) is less than a second value. On the other hand, when a voltage equal to or greater than the second value is applied, the second switching element 56 passes current from the first terminal 561 to the second terminal 562. The second value is, for example, a breakover voltage of the second switching element 56 as a sidac. The second value is, for example, the same as or greater than the first value.

[0090] 2, the filter circuit 5 may further include a rectifying element (diode) 580. As shown in Fig. 2, the anode of the diode 580 is electrically connected to the second end 562 of the second switching element 56, and is thereby electrically connected to the second end 552 of the first switching element 55 via the second switching element 56. In addition, the cathode of the diode 580 is electrically connected to the first connection terminal 571.

[0091] The first connection terminal 571 is electrically connected to the second end 562 of the second switching element 56. For example, the first connection terminal 571 is electrically connected to the second end 562 of the second switching element 56 via a diode 580. The second connection terminal 572 is electrically connected to the anode of the diode 52.

[0092] The filter circuit 5 is supplied with an induced current Ic generated in the coil 41 from the current sensor 4 .

[0093] When the induced current Ic generated in the coil 41 is zero or relatively small, the voltage value of the voltage applied to the first switching element 55 is less than the first value, so the first switching element 55 is kept off and no current flows outside the filter circuit 5.

[0094] On the other hand, if the current Ib flowing through the wiring member 9 changes significantly, for example, due to an overcurrent such as a short-circuit current flowing through the wiring member 9, the coil 41 generates a large induced current Ic. When this induced current Ic flows through the first resistor 531, a voltage equal to or greater than a first value is applied to the first switching element 55, turning on the first switching element 55. This charges the capacitor 54, and the voltage across the capacitor 54 increases. When the voltage across the capacitor 54 increases, a voltage equal to or greater than a second value is applied to the second switching element 56, turning on the second switching element 56. As a result, the current Id is supplied from the detection unit 1 to the interrupter unit 2.

[0095] In the filter circuit 5 , for example, when a sufficiently large induced current Ic (signal) is supplied from the current sensor 4 , the first switching element 55 and the second switching element 56 are turned on to supply a current Id to the interrupter unit 2 .

[0096] (1.2.5) Housing The housing 19 is, for example, a hollow rectangular parallelepiped. The housing 19 has a box-shaped main body 191 with an open top and a rectangular plate-shaped cover member 192 that closes the open top of the main body 191. The housing 19 houses or holds the coil 41, the magnetic circuit unit 42, the connector 17, and the circuit board 18.

[0097] As shown in FIG. 3 , a through-hole 190 is formed in the housing 19. The through-hole 190 is formed in a main body 191. The through-hole 190 penetrates the housing 19 in the front-to-rear direction. The through-hole 190 has a rectangular cross-sectional shape. The housing 19 is provided with a rectangular cylindrical body 193 that extends in the front-to-rear direction so as to penetrate the interior of the main body 191. The inner peripheral surface of the body 193 corresponds to the inner surface of the through-hole 190. The width dimension (left-to-right dimension) of the through-hole 190 is greater than the height dimension (up-to-down dimension).

[0098] 3 , the bus bar 90 is passed through the through hole 190. By passing the bus bar 90 through the through hole 190 of the housing 19, the bus bar 90 is passed through the first through hole T1 of the magnetic circuit unit 42.

[0099] The connector 17 is provided with a first connection terminal 571 and a second connection terminal 572. The connector 17 protrudes from the cover member 192 of the housing 19 so that the first connection terminal 571 and the second connection terminal 572 are exposed upward.

[0100] The substrate 18 has a rectangular plate shape and is, for example, a printed wiring board. The substrate 18 is housed in the housing 19 so that the normal direction of the substrate 18 faces the up-down direction.

[0101] The circuit components of the filter circuit 5 (including, in this embodiment, a diode 52, a first resistor 531, a second resistor 532, a capacitor 54, a first switching element 55, and a second switching element 56) are mounted on the substrate 18. A connector 17 is also mounted on the substrate 18. In addition, the substrate 18 is provided with conductors (pattern conductors) that connect the circuit components together, etc. Both ends (a first end 411 and a second end 412) of the coil 41 are connected to the pattern conductors of the substrate 18.

[0102] (1.3) Breaker Unit The breaker unit 2 is electrically connected to the detection unit 1. The breaker unit 2 is supplied with power generated by the coil 41.

[0103] 2 and 13, the interrupter unit 2 includes an igniter 21, a projectile 22, a conductor 23, and a housing 24. The housing 24 holds or houses the igniter 21, the projectile 22, and the conductor 23.

[0104] A first end 211 of the igniter 21 is electrically connected to a first connection terminal 571 of the detection unit 1. A second end 212 of the igniter 21 is electrically connected to a second connection terminal 572 of the detection unit 1. As a result, the igniter 21 is electrically connected to the coil 41 via the first switching element 55 and the second switching element 56. A current Id due to the power generated by the coil 41 is supplied to the igniter 21.

[0105] The igniter 21 is a so-called electric igniter. As shown in Fig. 13, the igniter 21 includes a heating element 213 and explosives 214.

[0106] The heating element 213 is, for example, a nichrome wire or an alloy wire of iron, chromium, and aluminum. The heating element 213 is electrically connected between the first end 211 and the second end 212 of the igniter 21. The heating element 213 generates heat when a current flows through the heating element 213.

[0107] 13 , the explosive 214 is disposed around the heating element 213. The explosive 214 is ignited by the heat generated by the heating element 213. Because a current Id caused by the power generated by the coil 41 flows through the heating element 213, it can be said that the igniter 21 is configured to be able to ignite the explosive 214 by the power generated by the coil 41. It can also be said that the igniter 21 ignites the explosive 214 by the power generated by the coil 41 when the value of the current Ib flowing through the wiring member 9 (bus bar 90) reaches or exceeds a certain value.

[0108] In the igniter 21, when the gunpowder 214 is ignited, a large amount of gas is generated by the combustion of the gunpowder 214. The generated gas is released into the internal space 240 of the housing 24 in which the igniter 21 is housed.

[0109] 13 , the projectile 22 is disposed in an internal space 240 of the housing 24. The projectile 22 is disposed inside the housing 24 at a position between the igniter 21 and the conductor 23. The projectile 22 is held by a holder 241 provided in the housing 24. The projectile 22 is held by the holder 241 so as to face the conductor 23. The holder 241 is the inner surface of the housing 24 in this example, but may have a protrusion or the like that protrudes from the inner surface of the housing 24 and holds the projectile 22.

[0110] The projectile 22 is ejected and moves from the holder 241 under the pressure of the gas generated by the igniter 21. That is, the projectile 22 is ejected and moves in response to the ignited explosive 214.

[0111] The projectile 22 ejected from the holder 241 moves toward the conductor 23 and pushes against the conductor 23, thereby breaking the conductor 23. The conductor 23 is, for example, at least a part of the bus bar 90 passed through the through hole 190 of the housing 19 of the detection unit 1. Therefore, the projectile 22 is configured to be ejected and move toward the wiring member 9 (bus bar 90) to interrupt the flow of electricity to the wiring member 9. Note that the bus bar 90 passed through the through hole 190 of the housing 19 may be a metal plate separate from the conductor 23 and electrically connected to the conductor 23, or may be the conductor 23 itself.

[0112] In short, in the circuit breaking device 200 of this embodiment, when a short-circuit current flows through the wiring member 9 (bus bar 90) and the current Ib flowing through the wiring member 9 (bus bar 90) changes significantly, the power generated by the coil 41 is supplied to the circuit breaking unit 2. This causes the circuit breaking unit 2 to operate and break the electric circuit 60 including the wiring member 9.

[0113] (1.4) Vehicle As described above, the blocking device 200 is mounted on, for example, a vehicle 6 as an object. The vehicle 6 may be, for example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, or the like.

[0114] As shown in FIG. 14 , the vehicle 6 includes a circuit breaking device 200 (a detection unit 1 and a circuit breaking unit 2 ), a battery 61 , a wiring member 9 , a motor 62 , and a control unit 30 .

[0115] The motor 62 is electrically connected to the battery 61 via the wiring member 9 .

[0116] The wiring member 9 also includes a bus bar 90. The bus bar 90 is passed through a through hole 190 in the housing 19 of the detection unit 1, for example.

[0117] The control unit 30 is provided in, for example, an ECU (Electronic Control Unit) 64 of the vehicle 6. The control unit 30 controls the supply of the current Ib flowing through the wiring member 9.

[0118] In the vehicle 6 , when an overcurrent flows between the battery 61 and the motor 62 (i.e., the wiring member 9 ), the explosive 214 is ignited by the electric power generated by the coil 41 of the breaker device 200 .

[0119] Then, the projectile 22 of the interrupting unit 2 of the interrupting device 200 is ejected and moves toward the bus bar 90 (here, the conductor 23) in response to the ignited explosive 214, and cuts off the electrical connection between the battery 61 and the motor 62. This makes it possible to operate the interrupting unit 2 and forcibly cut off the electrical circuit 60 in the event of an accident with the vehicle 6 or an abnormality such as a short circuit in the electrical circuit 60.

[0120] 14 , in the vehicle 6 of this embodiment, the bus bar 90 (conductor 23) of the wiring member 9 has a movable portion 231 that faces the projectile 22 and a fixed portion 232 against which the movable portion 231 is pressed. The projectile 22 is projected and moves in response to the ignited explosive 214, and presses the movable portion 231 in a direction in which the movable portion 231 moves away from the fixed portion 232. That is, in the example of FIG. 14 , the bus bar 90 is not broken by the projectile 22, but is pushed by the projectile 22 so that the movable portion 231 moves away from the fixed portion 232, thereby interrupting the electrical circuit 60 including the bus bar 90.

[0121] (2) Modifications The above embodiment is merely one of various embodiments of the present disclosure. The above embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the embodiment are listed below. The above embodiment and the modifications described below can be applied in appropriate combinations. In the following description of each modification, the description of the same configuration as the above embodiment may be omitted as appropriate.

[0122] In the present disclosure, the control unit 30 and the like include a computer system. The computer system is primarily composed of a processor and memory as hardware. The processor executes a program stored in the memory of the computer system to realize the functions of the control unit 30 in the present disclosure. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided in a non-transitory recording medium readable by the computer system, such as a memory card, optical disk, or hard disk drive. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuits, such as ICs and LSIs, are referred to by different names depending on the degree of integration, and include integrated circuits called system LSIs, very large-scale integrations (VLSIs), or ultra-large-scale integrations (ULSIs). Furthermore, field-programmable gate arrays (FPGAs), which are programmed after the LSI is manufactured, or logic devices that allow the reconfiguration of internal connections or internal circuit partitions of the LSI, can also be used as processors. The electronic circuits may be integrated into one chip or distributed across multiple chips. The chips may be integrated into one device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller is also composed of one or more electronic circuits including a semiconductor integrated circuit or a large-scale integrated circuit.

[0123] Furthermore, it is not essential that the multiple functions of the control unit 30 be concentrated in one housing. The components of the control unit 30 may be distributed across multiple housings. Conversely, the multiple functions of the control unit 30 may be concentrated in one housing. Furthermore, at least some of the functions of the control unit 30 may be realized by the cloud (cloud computing) or the like.

[0124] 15 , in the current sensor 4 of this modification, the magnetic resistance portion 44 includes a resin member 440. The first end 401 of the yoke 40 contacts the resin member 440 serving as the magnetic resistance portion 44, and the second end 402 of the yoke 40 contacts the resin member 440 serving as the magnetic resistance portion 44 and is magnetically connected to the first end 401 via the magnetic resistance portion 44.

[0125] In the current sensor 4 of this modified example, when viewed from the second magnetic field H2 (magnetic field due to the current Ib flowing through the bus bar 90), the magnetic resistance between the first end 401 and the second end 402 is smaller than the magnetic resistance between the third end 403 and the fourth end 404.

[0126] In the current sensor 4 of this modified example, the second magnetic field H2 caused by the current Ib flowing through the bus bar 90 also passes mainly through the first magnetic circuit C1 (see FIG. 6 ) including the first portion 400 of the yoke 40 and the magnetic resistance portion 44. Therefore, compared to the current sensor 4A of the comparative example, the amount of power generated when an overcurrent flows through the bus bar 90 (the induced current Ic generated by the coil 41) can be made larger. This makes it possible to improve the reliability of overcurrent detection.

[0127] The magnetic resistance portion 44 is not limited to the resin member 440, but may be a member made of a material having a lower magnetic permeability than the magnetic material forming the yoke 40, for example.

[0128] Furthermore, the magnetic resistance portion 44 may be composed of, for example, a magnetic member that is plate-shaped and thinner than the sixth portion 4081 of the yoke 40, is made of the same magnetic material as the yoke 40, and connects the sixth portion 4081 and the seventh portion 4082 of the yoke 40, and air surrounding the magnetic member.

[0129] The magnetic resistance portion 44 may also be made up of a plurality of resin members 440 and one or more magnetic bodies alternately arranged in the gap G1.

[0130] 16 , in the current sensor 4 of this modification, the coil 41 is disposed so as to straddle the gap G1 between the sixth portion 4081 and the seventh portion 4082 of the yoke 40, rather than the first portion 400 of the yoke 40. That is, in the magnetic circuit unit 42 of the current sensor 4 of this modification, the magnetic resistance portion 44 (the gap G1 formed between the first end 401 and the second end 402 of the yoke 40; the air disposed between the first end 401 and the second end 402 of the yoke 40) is disposed within the coil 41. Furthermore, the magnet 43 is magnetically connected to the magnetic resistance portion 44, and the first portion 400 of the yoke 40 is magnetically connected in parallel to the magnet 43.

[0131] 17, the magnetic circuit unit 42 forms a first magnetic circuit C1 including the first portion 400 of the yoke 40 and the magnetic resistance portion 44, a second magnetic circuit C2 including the first portion 400 of the yoke 40 and the magnet 43, and a third magnetic circuit C3 including the magnetic resistance portion 44 and the magnet 43. As shown in Fig. 16, the bus bar 90 (wiring member 9) is disposed so as to pass through a position between the coil 41 and the first portion 400 of the yoke 40, and passes through the first through hole T1.

[0132] The magnetic resistance of the second magnetic circuit C2 is smaller than the magnetic resistance of the third magnetic circuit C3 when viewed from the first magnetic field H1 generated by the magnet 43 inside the yoke 40. Furthermore, when viewed from the second magnetic field H2 caused by the current Ib flowing through the bus bar 90 (the second magnetic field H2 having an opposite direction at the first portion 400 to the first magnetic field H1 generated by the magnet 43), the magnetic resistance of the first magnetic circuit C1 is smaller than the magnetic resistance of the second magnetic circuit C2.

[0133] In the current sensor 4 of this modified example, the first magnetic field H1 generated by the magnet 43 also passes mainly through the second magnetic circuit C2, but a portion of the magnetic field passes through the third magnetic circuit C3.

[0134] Furthermore, the second magnetic field H2 generated by the current Ib flowing through the bus bar 90 passes mainly through the first magnetic circuit C1 including the first portion 400 of the yoke 40 and the magnetic resistance portion 44 .

[0135] In the current sensor 4 of this modified example, the magnetic flux passing through the coil 41 increases as the current Ib flowing through the bus bar 90 increases, so that an overcurrent or the like flowing through the bus bar 90 can be detected.

[0136] Furthermore, according to the current sensor 4 of this modification, the amount of change in magnetic flux density per unit can be made larger than, for example, the current sensor 4A of the comparative example shown in Fig. 10 in the second comparative example in which a gap is provided in the first portion 400. This makes it possible to improve the reliability of overcurrent detection.

[0137] In the current sensor 4 of this modification, a resin member 440 or the like may be provided in the gap G1, as in the current sensor 4 of modification 1. That is, the first end 401 of the yoke 40 may be in contact with the resin member 440 serving as the magnetic resistance portion 44, and the second end 402 of the yoke 40 may be in contact with the resin member 440 serving as the magnetic resistance portion 44 and may be magnetically connected to the first end 401 via the magnetic resistance portion 44.

[0138] (2.3) Modification 3 In the filter circuit 5, the first switching element 55 may include a unidirectional thyristor 553. For example, as shown in FIG. 21A , the anode of the unidirectional thyristor 553 is electrically connected to the first terminal 551 of the first switching element 55, and the cathode of the unidirectional thyristor 553 is electrically connected to the second terminal 552 of the first switching element 55.

[0139] 14A , the first switching element 55 further includes a diode 554, a Zener diode 555, a resistor 556, and a capacitor 557. A series circuit of the diode 554 and the Zener diode 555 is electrically connected between the anode and gate of the unidirectional thyristor 553. The cathodes of the diode 554 and the Zener diode 555 are electrically connected to each other. A parallel circuit of the resistor 556 and the capacitor 557 is electrically connected between the gate and cathode of the unidirectional thyristor 553.

[0140] 21B , the second switching element 56 may include a unidirectional thyristor 563. For example, as shown in FIG. 21B , the anode of the unidirectional thyristor 563 is electrically connected to a first end 561 of the second switching element 56, and the cathode of the unidirectional thyristor 563 is electrically connected to a second end 562 of the second switching element 56.

[0141] 14B , the second switching element 56 further includes a diode 564, a Zener diode 565, a resistor 566, and a capacitor 567. A series circuit of the diode 564 and the Zener diode 565 is electrically connected between the anode and gate of the unidirectional thyristor 563. The cathodes of the diode 564 and the Zener diode 565 are electrically connected to each other. A parallel circuit of the resistor 566 and the capacitor 567 is electrically connected between the gate and cathode of the unidirectional thyristor 563.

[0142] (2.4) Other Modifications In one modification, the wiring member 9 (bus bar 90) may be passed through the second through hole T2 of the yoke 40. That is, the wiring member 9 (bus bar 90) may pass through a position between the magnetic resistance portion 44 and the magnet 43 in the current sensor 4 of the embodiment (see FIG. 5). Alternatively, the wiring member 9 (bus bar 90) may pass through a position between the coil 41 and the magnet 43 in the current sensor 4 of Modification 2 (see FIG. 16).

[0143] In one modified example, the shape of the magnetic circuit unit 42 is not limited to the above-described shape, and for example, the positions of the magnet 43 and the magnetic resistance portion 44 may be reversed in the shape of the embodiment.

[0144] In one modified example, the shape of the yoke 40 is not limited to a shape that resembles the digital number 8, but may be a shape that resembles, for example, the Arabic number 8.

[0145] In one modified example, the wiring member 9 passed through the first through hole T1 is not limited to the bus bar 90, but may be an electric wire or the like.

[0146] In one variant, the filter circuit 5 may not include a rectifying element (diode 580).

[0147] In one modification, at least one of the first switching element 55 and the second switching element 56 may be a switching element other than a sidac, such as a diac.

[0148] In one modification, the first switching element 55 (or the second switching element 56) may be omitted.

[0149] In one variant, the current sensor 4 may be used alone without the interruption unit 2 being connected.

[0150] (3) Aspects As is clear from the above-described embodiments and modifications, the present specification discloses the following aspects.

[0151] The current sensor (4) of the first aspect includes a coil (41), a yoke (40) disposed within the coil (41) and including a first portion (400), a magnet (43) magnetically connected to the first portion (400), and a magnetic circuit unit (42) having a magnetic resistance portion (44) magnetically connected in parallel to the magnet (43), wherein the yoke (40) further includes a first end (401), a second end (402), a third end (403), and a fourth end (404), the magnet (43) is disposed between the third end (403) and the fourth end (404), and the magnetic resistance portion (44) is disposed between the first end (401) and the second end (402), and the magnetic circuit unit (42) includes a first magnetic circuit (C1) including the first portion (400) and the magnetic resistance portion (44), and a magnetic circuit unit (42) having a first magnetic circuit (C1) including the first portion (400) and the magnetic resistance portion (44). The magnetic resistance of the second magnetic circuit (C2) to a magnetic field directed from the fourth end (404) via the first portion (400) to the third end (403) is smaller than the magnetic resistance of the third magnetic circuit (C3) to a magnetic field directed from the fourth end (404) via the magnetic resistance portion (44) to the third end (403), and the magnetic resistance of the first magnetic circuit (C1) to a magnetic field directed from the first end (401) via the first portion (400) to the second end (402) is smaller than the magnetic resistance of the second magnetic circuit (C2) to a magnetic field directed from the third end (403) via the first portion (400) to the fourth end (404).

[0152] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0153] In the current sensor (4) of the second aspect, the first end (401) is in contact with the magnetic resistance portion (44), the second end (402) is in contact with the magnetic resistance portion (44) and is magnetically connected to the first end (401) via the magnetic resistance portion (44), the third end (403) is in contact with the magnet (43), and the fourth end (404) is in contact with the magnet (43) and is magnetically connected to the third end (403) via the magnet (43), and the magnetic resistance between the first end (401) and the second end (402) with respect to a magnetic field directed from the first end (401) to the second end (402) via the first portion (400) is smaller than the magnetic resistance between the third end (403) and the fourth end (404) with respect to a magnetic field directed from the third end (403) to the fourth end (404) via the first portion (400).

[0154] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0155] In the third aspect of the current sensor (4), the first end (401) is magnetically connected to the magnetic resistance portion (44), the second end (402) faces the first end (401) across the magnetic resistance portion (44) and is magnetically connected to the first end (401), the third end (403) is in contact with the magnet (43), the fourth end (404) is in contact with the magnet (43) and is magnetically connected to the third end (403) via the magnet (43), and the magnetic resistance portion (44) is a gap formed between the first end (401) and the second end (402).

[0156] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0157] In the current sensor (4) of the fourth aspect, the first end (401) is magnetically connected to the magnetic resistance portion (44), the second end (402) faces the first end (401) across the magnetic resistance portion (44) and is magnetically connected to the first end (401), the third end (403) is in contact with the magnet (43), the fourth end (404) is in contact with the magnet (43) and is magnetically connected to the third end (403) via the magnet (43), the magnetic resistance portion (44) includes air arranged between the first end (401) and the second end (402), and the distance between the first end (401) and the second end (402) is the same as or smaller than the distance between the third end (403) and the fourth end (404).

[0158] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0159] The current sensor (4) of the fifth aspect includes a magnetic circuit unit (42) having a coil (41), a magnetic resistance portion (44) arranged in the coil (41), a magnet (43) magnetically connected to the magnetic resistance portion (44), and a yoke (40) including a first portion (400) magnetically connected in parallel to the magnet (43), wherein the yoke (40) further includes a first end (401), a second end (402), a third end (403), and a fourth end (404), the magnet (43) is arranged between the third end (403) and the fourth end, the magnetic resistance portion (44) is arranged between the first end (401) and the second end (402), and the magnetic circuit unit (42) includes a first magnetic circuit (C1) including the first portion (400) and the magnetic resistance portion (44), and a yoke (40) including a first portion (400) magnetically connected in parallel to the magnet (43). The magnetic circuit (C1) forms a second magnetic circuit (C2) including the magnetic resistance portion (400) and the magnet (43), and a third magnetic circuit (C3) including the magnetic resistance portion (44) and the magnet (43), and the magnetic resistance of the second magnetic circuit (C2) to a magnetic field in a direction from the fourth end (404) through the first portion (400) to the third end (403) is smaller than the magnetic resistance of the third magnetic circuit (C3) to a magnetic field in a direction from the fourth end (404) through the magnetic resistance portion (44) to the third end (403), and the magnetic resistance of the first magnetic circuit (C1) to a magnetic field in a direction from the first end (401) through the first portion (400) to the second end (402) is smaller than the magnetic resistance of the second magnetic circuit (C2) to a magnetic field in a direction from the third end (403) through the first portion (400) to the fourth end (404).

[0160] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0161] In the current sensor (4) of the sixth aspect, the first end (401) is in contact with the magnetic resistance portion (44), the second end (402) is in contact with the magnetic resistance portion (44) and is magnetically connected to the first end (401) via the magnetic resistance portion (44), the third end (403) is in contact with the magnet (43), and the fourth end (404) is in contact with the magnet (43) and is magnetically connected to the third end (403) via the magnet (43), and the magnetic resistance between the first end (401) and the second end (402) with respect to a magnetic field directed from the first end (401) to the second end (402) via the first portion (400) is smaller than the magnetic resistance between the third end (403) and the fourth end (404) with respect to a magnetic field directed from the third end (403) to the fourth end (404) via the first portion (400).

[0162] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0163] In the seventh aspect of the current sensor (4), the first end (401) is magnetically connected to the magnetic resistance portion (44), the second end (402) faces the first end (401) across the magnetic resistance portion (44) and is magnetically connected to the first end (401), the third end (403) is in contact with the magnet (43), the fourth end (404) is magnetically connected to the third end (403) via the magnet (43), and the magnetic resistance portion (44) is a gap formed between the first end (401) and the second end (402).

[0164] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0165] In the current sensor (4) of the eighth aspect, the first end (401) is magnetically connected to the magnetic resistance portion (44), the second end (402) faces the first end (401) across the magnetic resistance portion (44) and is magnetically connected to the first end (401), the third end (403) is in contact with the magnet (43), the fourth end (404) is in contact with the magnet (43) and is magnetically connected to the third end (403) via the magnet (43), the magnetic resistance portion (44) includes air arranged between the first end (401) and the second end (402), and the distance between the first end (401) and the second end (402) is the same as or smaller than the distance between the third end (403) and the fourth end (404).

[0166] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0167] In the current sensor (4) of the ninth aspect, the magnet (43) includes a permanent magnet (430) and a non-magnetic body. The non-magnetic body is disposed between the third end (403) and the permanent magnet (430) and is in contact with the third end (403), or is disposed between the third end (403) and the permanent magnet (430) and between the fourth end (404) and the permanent magnet (430) and is in contact with the third end (403) and the fourth end (404).

[0168] According to this aspect, it is possible to improve the reliability of overcurrent detection.

[0169] The interrupter (200) of the tenth aspect includes a current sensor (4), an igniter (21), and a projectile (22). The igniter (21) includes a gunpowder (214) and is configured to be able to ignite the gunpowder (214) by electric power generated by a coil (41). The projectile (22) is moved by the ignited gunpowder (214).

[0170] According to this aspect, in the breaker (200) equipped with the current sensor (4), it is possible to improve the reliability of the detection of overcurrent by the current sensor (4).

[0171] The circuit breaker (200) of the eleventh aspect includes a current sensor (4), a wiring member (9), an igniter (21), and a projectile (22). The wiring member (9) passes between a coil (41) and a magnetic resistance portion (44). The igniter (21) includes an explosive (214) and is configured to be able to ignite the explosive (214) using the electric power generated by the coil (41). The projectile (22) is moved by the ignited explosive (214) and interrupts the current flow through the wiring member (9). A current (Ib) flows through the wiring member (9) in a predetermined direction. When the current (Ib) flows through the wiring member (9), the wiring member (9) generates a second magnetic field (H2) within the yoke (40). The coil (41) generates electric power using the current (Ib) flowing through the wiring member (9). The igniter (21) ignites the explosive (214) using the electric power generated by the coil (41) when the value of the current (Ib) flowing through the wiring member (9) reaches or exceeds a certain value. The projectile (22) moves toward the wiring member (9) and cuts off the current flow through the wiring member (9).

[0172] According to this aspect, in the breaker (200) equipped with the current sensor (4), it is possible to improve the reliability of the detection of overcurrent by the current sensor (4).

[0173] A twelfth aspect of the circuit breaker (200) includes a current sensor (4), a wiring member (9), an igniter (21), and a projectile (22). The wiring member (9) passes between a coil (41) and a first portion (400) of a yoke (40). The igniter (21) includes an explosive (214) and is configured to ignite the explosive (214) using power generated by the coil (41). The projectile (22) is moved by the ignited explosive (214) and interrupts the flow of current through the wiring member (9). A current (Ib) flows through the wiring member (9) in a predetermined direction. When the current (Ib) flows through the wiring member (9), the wiring member (9) generates a second magnetic field (H2) within the yoke (40). The coil (41) generates power using the current (Ib) flowing through the wiring member (9). The igniter (21) ignites the explosive (214) using the electric power generated by the coil (41) when the value of the current (Ib) flowing through the wiring member (9) reaches or exceeds a certain value. The projectile (22) moves toward the wiring member (9) and cuts off the current flow through the wiring member (9).

[0174] 17 Connector 200 Breaker device 21 Igniter 214 Explosive 22 Projectile 4 Current sensor 40 Yoke 400 First part 401 First end 402 Second end 403 Third end 404 Fourth end 41 Coil 42 Magnetic circuit unit 43 Magnet 430 Permanent magnet 44 Magnetic resistance portion 9 Wiring member 90 Bus bar C1 First magnetic circuit C2 Second magnetic circuit C3 Third magnetic circuit G1, G2 Gap H1 First magnetic field H2 Second magnetic field Ib Current

Claims

1. A magnetic circuit unit comprising: a coil; a yoke disposed within the coil and including a first portion; a magnet magnetically connected to the first portion; and a magnetic resistance portion magnetically connected in parallel to the magnet; wherein the yoke further includes a first end, a second end, a third end, and a fourth end; the magnet is disposed between the third end and the fourth end; and the magnetic resistance portion is disposed between the first end and the second end; the magnetic circuit unit forms: a first magnetic circuit including the first portion and the magnetic resistance portion; a second magnetic circuit including the first portion and the magnet; and a third magnetic circuit including the magnetic resistance portion and the magnet; and wherein the magnetic resistance of the second magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the first portion is smaller than the magnetic resistance of the third magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the magnetic resistance portion, A current sensor, wherein the magnetic resistance of the first magnetic circuit to a magnetic field oriented from the first end through the first portion to the second end is smaller than the magnetic resistance of the second magnetic circuit to a magnetic field oriented from the third end through the first portion to the fourth end.

2. A current sensor as described in claim 1, wherein the first end is in contact with the magnetic resistance portion, the second end is in contact with the magnetic resistance portion and is magnetically connected to the first end via the magnetic resistance portion, the third end is in contact with the magnet, and the fourth end is in contact with the magnet and is magnetically connected to the third end via the magnet, and the magnetic resistance between the first end and the second end for a magnetic field oriented from the first end through the first portion to the second end is smaller than the magnetic resistance between the third end and the fourth end for a magnetic field oriented from the third end through the first portion to the fourth end.

3. A current sensor as described in claim 1, wherein the first end is magnetically connected to the magnetic resistance portion, the second end faces the first end across the magnetic resistance portion and is magnetically connected to the first end, the third end is in contact with the magnet, the fourth end is in contact with the magnet and is magnetically connected to the third end via the magnet, and the magnetic resistance portion is a gap formed between the first end and the second end.

4. A current sensor as described in claim 1 or 3, wherein the first end is magnetically connected to the magnetic resistance portion, the second end faces the first end across the magnetic resistance portion and is magnetically connected to the first end, the third end is in contact with the magnet, the fourth end is in contact with the magnet and is magnetically connected to the third end via the magnet, the magnetic resistance portion includes air disposed between the first end and the second end, and the distance between the first end and the second end is the same as or smaller than the distance between the third end and the fourth end.

5. A magnetic circuit unit comprising: a coil; a magnetic resistance portion disposed within the coil; a magnet magnetically connected to the magnetic resistance portion; and a yoke including a first portion magnetically connected in parallel to the magnet, wherein the yoke further includes a first end, a second end, a third end, and a fourth end, wherein the magnet is disposed between the third end and the fourth end, and the magnetic resistance portion is disposed between the first end and the second end, wherein the magnetic circuit unit forms: a first magnetic circuit including the first portion and the magnetic resistance portion; a second magnetic circuit including the first portion and the magnet; and a third magnetic circuit including the magnetic resistance portion and the magnet, wherein the magnetic resistance of the second magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the first portion is smaller than the magnetic resistance of the third magnetic circuit to a magnetic field in a direction from the fourth end to the third end via the magnetic resistance portion, A current sensor, wherein the magnetic resistance of the first magnetic circuit to a magnetic field directed from the first end through the first portion to the second end is smaller than the magnetic resistance of the second magnetic circuit to a magnetic field directed from the third end through the first portion to the fourth end.

6. A current sensor as described in claim 5, wherein the first end is in contact with the magnetic resistance portion, the second end is in contact with the magnetic resistance portion and is magnetically connected to the first end via the magnetic resistance portion, the third end is in contact with the magnet, and the fourth end is in contact with the magnet and is magnetically connected to the third end via the magnet, and a magnetic resistance between the first end and the second end for a magnetic field oriented from the first end through the first portion to the second end is smaller than a magnetic resistance between the third end and the fourth end for a magnetic field oriented from the third end through the first portion to the fourth end.

7. A current sensor as described in claim 5, wherein the first end is magnetically connected to the magnetic resistance portion, the second end faces the first end across the magnetic resistance portion and is magnetically connected to the first end, the third end is in contact with the magnet, the fourth end is magnetically connected to the third end via the magnet, and the magnetic resistance portion is a gap formed between the first end and the second end.

8. A current sensor as described in claim 5 or 7, wherein: the first end is magnetically connected to the magnetic resistance portion; the second end faces the first end across the magnetic resistance portion and is magnetically connected to the first end; the third end is in contact with the magnet; the fourth end is in contact with the magnet and is magnetically connected to the third end via the magnet; the magnetic resistance portion includes air disposed between the first end and the second end; and the distance between the first end and the second end is the same as or smaller than the distance between the third end and the fourth end.

9. A current sensor as claimed in any one of claims 2 to 4 and 6 to 8, wherein the magnet comprises: a permanent magnet; and a non-magnetic body arranged between the third end and the permanent magnet and in contact with the third end, or arranged between the third end and the permanent magnet and between the fourth end and the permanent magnet and in contact with the third end and the fourth end.

10. A circuit breaker comprising: a current sensor according to any one of claims 1 to 9; an igniter including explosives and configured to be able to ignite the explosives by the electric power generated by the coil; and a projectile moved by the ignited explosives.

11. A breaking device comprising: a current sensor as claimed in any one of claims 1 to 4; a wiring member passing between a position between the coil and the magnetic resistance portion; an igniter including explosives and configured to be able to ignite the explosives by electric power generated by the coil; and a projectile which moves by the ignited explosives and cuts off the flow of electricity to the wiring member, wherein a current flows in a predetermined direction in the wiring member, the wiring member generates the second magnetic field within the yoke when the current flows through the wiring member, the coil generates electricity by the current flowing through the wiring member, the igniter ignites the explosives by the electric power generated by the coil when the value of the current flowing through the wiring member reaches or exceeds a certain value, and the projectile moves towards the wiring member and cuts off the flow of electricity to the wiring member.

12. A breaking device comprising: a current sensor as defined in any one of claims 5 to 8; a wiring member passing between a position between the coil and the first portion of the yoke; an igniter including explosives and configured to be able to ignite the explosives by electric power generated by the coil; and a projectile moved by the ignited explosives to cut off the flow of electricity through the wiring member, wherein a current flows in a predetermined direction through the wiring member, the wiring member generates the second magnetic field within the yoke when the current flows through the wiring member, the coil generates electricity by the current flowing through the wiring member, the igniter ignites the explosives by the electric power generated by the coil when the value of the current flowing through the wiring member reaches or exceeds a certain value, and the projectile moves toward the wiring member to cut off the flow of electricity through the wiring member.

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