Current sensor

A current sensor includes a core including groove portions and a separation wall portion, a housing covering the core and including recessed grooves formed along the groove portions, respectively, conductors positioned in the groove portions, respectively, a circuit board fixed to the housing and including a through hole and a land, the through hole penetrating in a direction corresponding to an inserting direction of the conductor, a detection element detecting a magnitude of a magnetic field and positioned in each of recessed grooves to be closer to an opening end of the groove portion relative to the conductor, the detection element being arranged so that a detecting direction of the detection element is directed along a distance direction of the groove portions, the detection element including a connection terminal positioned in the through hole, the connection terminal electrically connected to the land, and a guide portion provided at the housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2013-164249, filed on Aug. 7, 2013, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to a current sensor.

BACKGROUND DISCUSSION

A known current sensor which includes a magnetic detection element, for example, a Hall element, has been used for measuring the electric current in a conductor. According to such current sensors, a positional relationship between a flux concentrating core that concentrates magnetic fluxes and the magnetic detection element that detects the magnetic flux density of the flux concentrating core significantly influences on a downsizing of a current sensor and a precision of an electric current detection. Thus, positioning the flux concentrating core and the magnetic detection element with high precision is desired. Further, in a case where a lead (wire) serves as a terminal of the magnetic detection element, it is desired to appropriately connect the lead (wire) to, for example, a land of a circuit board because a joining state of the lead (wire) and the circuit board significantly influences on a reliability (quality attributes) of the current sensor. For example, JP2002-243767A (hereinafter referred to as Patent reference 1) and JP2012-181208A (hereinafter referred to as Patent reference 2) disclose the types of known current sensors or devices explained above.

According to the electric current detection device disclosed in Patent reference 1, a core having a substantially rectangular shape in cross-section which is provided with a gap at one of four sides is fixed in a case. A Hall IC positioned in the gap detects changes in the magnetic flux generated at the core. A lead (wire) of the Hall IC is formed in a predetermined configuration, and is directly connected to connector terminals for input and output that are integrally formed with the case.

According to the current sensor disclosed in Patent reference 2, a substantially ring shaped core having a gap with a predetermined distance is integrally formed with a resin-made case, at least a portion of the gap is exposed to an accommodation portion of the resin-made case, and a magneto-electric converting element mounted on a circuit board housed in the accommodation portion is positioned at the gap. A lead type magneto-electric converting element in which a lead (wire) protrudes from a mold portion is applied as the magneto-electric converting element. The mold portion includes a tapered portion which is formed to be thinner in a distance direction of the gap as being away from the circuit board in a thickness direction of the circuit board. At least a portion of tapered outer surface of the tapered portion faces end surfaces of the core in the distance direction of the gap.

The electric current detection device disclosed in Patent reference 1 does not define the positional relationship between the core and the Hall IC. Thus, by a variation, or unevenness of a bend dimension when forming the lead of the Hall IC, the positional relationship between the core and the Hall IC greatly fluctuates and significantly influences on a precision in current detection. Further, because the Hall IC is not fixed relative to the core, when the Hall IC moves, for example, by vibrations, the precision in detection may be affected and there is a possibility that the electric current cannot be measured with high precision, or accuracy. As an alternative structure, a fixing member may be applied to fix the Hall IC relative to the core, however, this construction increases manufacturing costs.

According to the electric current sensor disclosed in Patent reference 2, when soldering the lead (wire) to the circuit board, the lead has to be directly inserted through a through hole of the circuit board, and a stress is generated at the lead if the lead is inserted through the through hole and soldered in a state where the position of the lead and the position of the through hole is offset, or not aligned. When the vibration and/or thermal shock (flame impingement) occurs in the foregoing state, portions soldered in accordance with a difference in linear coefficient of expansion of each of the magneto-electric converting element, the circuit board, and the resin-made case may be fatigued by repetitive stresses to causes problems in durability.

A need thus exists for a current sensor which is not susceptible to the drawback mentioned above.

SUMMARY

In light of the foregoing, the disclosure provides a current sensor which includes a core, the core being made from magnetic member, the core including plural groove portions and at least one separation wall portion separating the groove portions from one another, a housing, the housing being made from a non-magnetic material, the housing covering the core along a contour of the core, the housing including plural recessed grooves formed at the housing along the groove portions, respectively, plural conductors, the conductors positioned in the groove portions, respectively, the conductors allowing a current being measured to flow therein, a circuit board, the circuit board fixed to the housing, the circuit board including a through hole and a land formed at a surrounding of the through hole, the through hole penetrating through the circuit board in a direction corresponding to an inserting direction of the conductor, a detection element, the detection element detecting a magnitude of a magnetic field generated in accordance with the current being measured flowing in the conductors, the detection element positioned in each of the recessed grooves, the detection element positioned closer to an opening end side of the groove portion relative to the conductor positioned in the groove portion, the detection element being arranged so that a detecting direction of the detection element is directed along a distance direction of the groove portions, the detection element including a connection terminal, the connection terminal inserted and positioned in the through hole, the connection terminal electrically connected to the land, and a guide portion, the guide portion provided at the housing, the guide portion guiding the connection terminal to the through hole.

DETAILED DESCRIPTION

One embodiment of current sensor will be explained with reference to illustrations of drawing figures as follows. The current sensor of the embodiment is configured to measure a current being measured which flows in a conductor. Here, when the electric current flows in the conductor, a magnetic field is generated about the conductor as an axis center in accordance with a degree of the electric current (Ampere's law). The current sensor of the embodiment detects magnitude, or strength of the magnetic field, and measures electric current (current value) flowing in the conductor on the basis of the magnitude, or strength of the detected magnetic field.

FIG. 1shows an exploded perspective view of a current sensor100. Two conductors3made from pillar shaped conductors are shown inFIG. 1. For an explanatory purpose, a direction that the conductor3extends is defined as an extending direction A, a distance direction, or spacing direction between the conductors3is defined as a distance direction B, and a direction orthogonal to the extending direction A and the distance direction B is defined as a direction C.FIG. 2shows a schematic view of the current sensor100viewed from a circuit board4in the extending direction A of the conductor3.FIG. 3shows a schematic view of the current sensor100viewed from an opposite direction from the extending direction A of the conductor3inFIG. 2.FIGS. 2 and 3show a connector200used for supplying electric power to the current sensor100and for outputting detecting results, for example.

As illustrated inFIG. 1, a core1includes plural groove portions11and a separation wall portion12separating the groove portions11. An outer wall portion13is provided at each of opposite outermost sides of the plural groove portions11. As illustrated inFIGS. 1 and 2, according to the embodiment, the core1includes two groove portions11each formed in a substantially U-shape. Thus, the core1of the embodiment includes one separation wall portion12. A protrusion portion14is provided at each of the separation wall portions12and the outer wall portions13. The protrusion portion14is positioned protruding in the distance direction B so that an opening width at an opening portion11A of the groove portion11is assumed to be narrower than an opening width at a bottom portion11B. The core1is made from a magnetic member. The core1according to the embodiment is formed by stacking, or laminating plane plates made from metal magnetic member having the groove portion11in the direction A inFIGS. 1 to 3. The metal magnetic member corresponds to a soft magnetic metal, for example, an electromagnetic steel plate (silicon steel pate), permalloy, and permendur.

The housing2covers the core1along a contour of the core1. That is, the housing2houses the core1along a configuration of the core1. Thus, inner wall portions of the groove portion11of the core1that face each other are covered with the housing2. The housing2made of resin that is non-magnetic material. Accordingly, the core1and conductors3can be insulated from each other.

The plural conductors3are positioned through (inserted through) the plural groove portions11, respectively. The current being measured flows in the conductors3. As described above, two conductors3are provided according to the embodiment. The conductors3are inserted to be positioned through the corresponding two grooves11of the core1, respectively. As described above, the core1is covered with the housing2. Thus, the conductor3is positioned through the groove portion11of the core1via the housing2. For example, a bus bar that is applied for connecting a three-phase motor and an inverter that energizes the three-phase motor serves as the conductor3. The current being measured flows in the conductors3in the direction A, and the current sensor100measures, or detects the electric current in the conductor3. According to the embodiment, two conductors3are provided. Further, according to the embodiment, two currents of three-phase alternating current serve as the current being measured.

The circuit board4includes through holes41formed directed in a direction which accords with an insertion direction of the conductor3, and a land42formed surrounding each of the through holes41. The circuit board4is fixed to the housing2. The through hole41penetrates through the circuit board4in a thickness direction of the circuit board4. According to the embodiment, the land42is formed surrounding each of the through holes41on front and back surfaces of the circuit board4. A surface of the circuit board4which is mounted facing the core1is defined as the front surface of the circuit board4. A surface of the circuit board4which faces the opposite direction from the core1is defined as the back surface of the circuit board4.

The land42is formed surrounding the through hole41, that is, the land42is formed at surrounding, or circumference of the through hole41about the through hole41as a center and along the front surface or the back surface of the circuit board4. By inserting connection terminals51of a detection element5through the through hole41and soldering the land41at the back surface of the circuit board4, a solder fillet is formed at each of the lands42at the front surface and rear surface of the circuit board4. Further, the solder enters the through hole41, or the through hole41is filled with the solder. Accordingly, fixing strength of the soldering of the connection terminals51relative to the circuit board4can be enhanced.

The through hole41is arranged in a direction that accords with the insertion direction of the conductor3. That is, an axis of the through hole41and the insertion direction of the conductor3are in parallel with each other. In those states, the circuit board4is fixed to the housing2. According to the embodiment, the circuit board4is fastened to the housing2by means of screws71(for example, three screws71).

The detection element5includes the connection terminals51electrically connected to the lands42in a state each being inserted through the through hole41. According to this construction, the electric power is supplied to the detection element5from the circuit board4, and detection signals can be transmitted from the detection element5to the circuit board4.

The detection element5is positioned at a recessed groove21formed at the housing2along the groove portion11. Further, the detection element5is positioned at an opening portion11A side of the groove portion11relative to the conductor3positioned in the groove portion11of the core1so that a detecting direction is directed along the distance direction B (i.e., the direction B) of the groove portion11. A groove formed at the housing2along the configuration of the groove portion11of the core1as a result of covering the separation portion12and the outer wall portion13of the core1that face each other with the housing2by a predetermined thickness is defined as the recessed groove21formed at the housing2along the groove portion11. As described above, the detection element5is positioned at the opening portion11A side of the groove portion11relative to the conductor3positioned in the groove portion11of the core1. That is, referring to the groove portion11of the core1housed in the housing2as a point of reference, the detection portion5is positioned closer to the opening portion11A compared to the conductor3positioned through the groove portion11of the core1. The position where the detection element5is positioned corresponds to a position that is interposed, or sandwiched between the protrusion portions14of the core1. In those circumstances, the magnetic field generated in accordance with the electric current flowing in the conductor3is concentrated (i.e., the magnetic flux is concentrated) at a side closer to the opening portion of the core1from an upper end of the conductor3of the groove portion11of the core1. The concentrated magnetic filed corresponds to a magnetic field directed in the distance direction B (i.e., the direction B) of the groove portion11of the core in the vicinity of the detection element5. Similar magnetic field is generated at the recessed groove21of the housing2.

The detection element5is arranged so that a detection direction accords with the direction B. Thus, the intensity of the magnetic field generated by the current being measured flowing in the conductor3is assumed to be effectively detectable. A magnetic field that is generated in a radial direction from the center of the axis of the conductor3in response to the current being measured flowing in the conductor3is defined as the magnetic field generated by the current being measured. According to the embodiment, two detection elements5are provided for each of the groove portions11of the core1. That is, because two groove portions11are provided according to the embodiment, four detection elements5are provided. In those circumstances, the detection elements5positioned in the common groove portion11detect the magnetic flux density directed in the same direction. Thus, in a case where detection signals of the detection elements5positioned in the common groove portion11show the magnetic flux densities directed in different directions and in a case where detection results of the detection elements5positioned in the common groove portion11are significantly deviated relative to a predetermined deviation level, it is determined that one of the detection elements5is in failure. In order to determine the failure explained above, according to the embodiment, two detection elements5are positioned in the same groove portion11.

A guide portion6is provided at the housing2. The guide portion6guides the detection element5to a predetermined fixing position. The predetermined fixing position is defined as a position where the detection element5is interposed, or sandwiched between the protrusion portions14described above along the direction B. The guide portion6is configured to guide the detection element5to such position.

Referring toFIG. 4, constructions of the guide portion6will be explained hereinafter. According to the embodiment, the guide portion6includes hole portions61and protrusion portions62. As illustrated inFIG. 4, the hole portions61and the protrusion portions62are provided at the recessed groove21of the housing2. The hole portions61are provided at a side opposite from the side facing the circuit board4at the recessed groove21(the hole portions61are provided at a side opposite from the circuit board4at a portion of the recessed groove21opposing to the circuit board4), and are formed so that a diameter is reduced towards an inner in an inserting direction of the connection terminal51(i.e., so that the diameter is reduced in a direction from the connection terminal51to the circuit board4in a state where the connection terminal51is positioned through the hole portion61). The portion of the recessed groove21opposing to the circuit board4corresponds to a side surface portion22that is adjacent to the circuit board4at the recessed groove21. The side opposite from the circuit board4corresponds to a surface that is opposite from a surface that faces the circuit board4at the side surface portion22, that is, corresponds to a side that faces the inside of the recessed groove21. In those circumstances, the connection terminals51of the detection element5are inserted in the recessed groove21towards the circuit board4in a direction orthogonal to the circuit board4. Thus, that the diameter is reduced towards the inner in the inserting direction of the connection terminal51is defined as that a diameter of the hole portion61is reduced as being closer to the circuit board4from the recessed groove21at the side surface portion22. The through holes41of the circuit board4are positioned corresponding to the hole portions61keeping a predetermined distance from and facing the hole portions61. Thus, the connection terminals51can be guided through the through holes41, respectively.

Further, protrusion portions62are provided protruding in a distance direction (gap direction, spacing direction) of the recessed groove21in the recessed groove21, and a protrusion amount of the protrusion portion62increases from an outer side to an inner side in an inserting direction of the connection terminal51(the protrusion amount of the protrusion portion62increases in the direction from the connection terminal51to the circuit board4in a state where the connection terminal51is positioned through the hole portion61). The distance direction of the recessed groove21corresponds to the distance direction of the groove portion11of the core1, and thus corresponds to the direction B inFIGS. 4 and 5. The detection element5includes the connection terminals51and mold portions52to which Hall elements connected to the connection terminals51are enclosed with resin. The protrusion portions62that face each other in the direction B are formed so that an opening width between the protrusion portions62facing each other at an opening end corresponds to a width (length in the direction B) of the mold portion52of the detection element5and the opening width is gradually narrowed towards the inner in the inserting direction of the connection terminal51(in the direction from the connection terminal51to the circuit board4in a state where the connection terminal51is positioned through the hole portion61). Thus, the mold portion52of the detection element5can be guided to the predetermined fixing position.

According to the current sensor100of the embodiment, a clearance is provided between the housing2and the circuit board4in a state where the circuit board4is fixed to the housing2. As described above, the circuit board4is fastened to the housing2by means of the screws71. As illustrated inFIG. 6, the circuit board4is positioned keeping a distance from (away from) the housing2at portions other than the portions that are fastened by the screws71. According to this construction, solder fillets formed at the lands42on the front and back sides of the circuit board4can be seen via the clearance in a direction orthogonal to a thickness direction of the circuit board4. Thus, whether the soldering is properly applied can be visually inspected (confirmed by the visual inspection, for example).

According to the embodiment, the core1includes one separation wall portion12and two outer wall portions13. As illustrated inFIG. 7, the length of the separation wall portion12in the distance direction is set to be longer than the length of the outer wall portion13in the distance direction. Here, the distance direction is defined as the distance direction of the groove portion11of the core1, that is, corresponds to the direction B inFIG. 7. Thus, the length of the separation wall portion12in the distance direction corresponds to W1 inFIG. 7. The length of the outer wall portion13in the distance direction corresponds to W2 inFIG. 7. The separation wall portion12and the outer wall portion13are structured so that W1 is greater than W2 (W1>W2).

Particularly, it is favorable that the length of the separation wall portion12is set to be equal to or greater than the length of the outer wall portion13multiplied by the square root of three (the length of the outer wall portion13multiplied by √{square root over (3)}). The reason will be explained hereinafter,FIG. 8shows a current waveform of the three-phase alternating current. Currents flowing in two conductors3of the three-phase alternating current are defined as U-phase and V-phase. In case of detecting the magnetic flux generated by the electric current flowing in two conductors3, the core1saturates when |Iu−Iv| is maximized. In those circumstances, Iu corresponds to the electric current of U-phase, Iv corresponds to the electric current of V-phase, and Iw corresponds to the electric current of W-phase.

The electric current flowing in two conductors3are shown in equation 1 and equation 2 as follows.

Equation 2 is expressed in Equation 3 by the addition theorem.

On the other hand, when the core1is saturated, Equation 4 is established.

Thus, Equation 5 is attained when the core is saturated.

By differentiating Equation 5 with respect to time t, Equation 6 is attained.

Here, in a case where the left-hand side of Equation 6 is zero (0), Equation 7 is attained.
tan ωt=−√{square root over (3)}  [Equation 7]

According to Equation 8, the core1is saturated every 180 degrees with reference to 120 degrees (saturation points of the core1are provided every 180 degrees with 120 degrees as a reference). For example, in a case where the electric current flowing in the conductors3is ±900A, the magnetic flux corresponding to 900A multiplied by √{square root over (3)} flows in the separation wall portion12.

FIG. 9shows a simulation result of the magnetic flux generated at the core1when the length of the separation wall portion12in the distance direction corresponds to the length of the outer wall portion13in the distance direction multiplied by √{square root over (3)}. As a comparison example,FIG. 10shows a simulation result of the magnetic flux generated at the core1when the length of the separation wall portion12in the distance direction is equal to the length of the outer wall portion13in the distance direction. InFIGS. 9 and 10, directions of arrows correspond to directions of magnetic flux, and thickness of the arrows corresponds to the level, or degree of the magnetic flux density. Thus, the thicker the arrow is, the higher the flux density is, and the thinner the arrow is, the lower the flux density is. InFIGS. 9 and 10, through holes through which the screws71are penetrated and the protrusion portions14are not shown for an explanatory purpose.

As shown inFIG. 10, when the length of the separation wall portion12of the core1in the distance direction is equal to the length of the outer wall portion13in the distance direction, the magnetic flux density at the separation wall portion12is assumed to be higher. In those circumstances, magnetic fluxes generated by two conductors3at the separation portion12of the core1influence each other so that the detection element5provided at the groove portion11of the core1cannot detect the magnetic flux precisely.

On the other hand, as shown inFIG. 9, when the length of the separation wall portion12of the core1in the distance direction is longer than the length of the outer wall portion13in the distance direction, the magnetic flux density at the separation wall portion12is lower compared to the example shown inFIG. 10. In those circumstances, magnetic fluxes generated by two conductors3at the separation portion12of the core1do not influence each other, and thus, the detection element5provided at the groove portion11of the core1detects the magnetic flux with high precision.

As shown inFIG. 8, a phase difference of the electric current of the three-phase alternating current is 120 degrees and a phase difference of the magnetic fluxes generated at two of the conductors3is 120 degrees. Thus, in order to minimize the dimension of the core1, it is favorable that the length of the separation wall portion12in the distance direction corresponds to the length of the outer wall portion13in the distance direction multiplied by √{square root over (3)}. The length of the outer wall portion13in the distance direction may be changed as desired. For example, the outer wall portion of the core may be defined to be longer than the length of the outer wall portion13in the distance direction of the embodiment described above and the length of the separation wall portion12in the distance direction may be defined to be equal to the length of the outer wall portion13in the distance direction. As long as the magnetic fluxes do not influence each other, the foregoing alternative construction is applicable. In other words, the length of the separation wall portion12of the core1in the distance direction and the length of the outer wall portion13in the distance direction can be changed in accordance with the magnetic flux density generated by the electric current flowing in the conductors3and the dimension of the current sensor100.

A method for manufacturing the current sensor100will be explained as follows. A jig150as illustrated inFIG. 11is applied for manufacturing the current sensor100. Support portions151are provided at a predetermined surface of the jig150. The support portion151supports the detection elements5in a state where the detection elements5are positioned in the mold portion52. The support portions151are formed so that connection terminals51are provided standingly in a state where the mold portion52is inserted and positioned in the support portion151. The position of the support portion151is determined in accordance with the position of the through holes41so that the connection terminals51of the detection element5that is positioned in the support portion151are provided through the through holes41at the circuit board4. Further, protrusion portions152that are fitted to positioning holes of the housing2are formed at the surface of the jig150at which the support portions151are formed. Accordingly, the connection terminals51that are provided standingly are readily inserted through the through holes41.

The core1is housed in the housing2and is assembled, for example, by press-fitting and thermal clinching. Protrusion walls83,84are formed at wall portions81,82, respectively, that are in parallel with A-B surface along the direction A among the wall portion provided standingly from a bottom surface25of the housing2. The core1is supported by the housing2in the direction A by means of the protrusion walls83,84. More particularly, the core1is fixed to the housing2by bending the protrusion walls83,84towards the core1along the direction C by the thermal clinching in a state where the core1is housed in the housing2and the core1is pushed to the bottom surface25of the housing2(seeFIGS. 12 and 13).

Pillar shaped protrusion portions85,86are formed to protrude from the bottom surface25of the housing2along the direction A to face A-C surface of the separation wall portion12of the core1housed in the housing2. The core1is supported by the housing2in the direction B by means of the pillar shaped protrusion portions85,86. More particularly, a distance between the pillar shaped protrusion portion85and the pillar shaped protrusion portion86in the direction B is set to be slightly shorter than the length of the separation wall portion12of the core1in the direction B. Accordingly, when the core1is housed in the housing2, the separation wall portion12of the core1is supported by the pillar shaped protrusion portions85,86at the opposite ends thereof in the direction B. Thus, by maintaining the dimension of the separation wall portion12, which is supported in the foregoing manner, in the direction B to have high precision, the positioning of the core1relative to the housing2in the direction B can be performed accurately. In a state where the core1is housed in the housing2, the pillar shaped protrusion portions85,86are expanded outwardly in the direction B by the core1. In order to mitigate, or reduce the stress generated at the bottom surface25of the housing2, in those circumstances, opening portions87,88are formed on the bottom surface25of the housing2at an outward in the direction B of the pillar shaped protrusion portions85,86.

Protrusion portions89,90provided at an inner wall88of a wall portion81of the housing2support the core1in the direction C at the housing2. More particularly, by pushing a surface of the core1which is in parallel with A-B surface to an inner wall91of a wall portion82of the housing2by means of the protrusion portions89,90in a state where the core1is housed in the housing2, the positioning of the core1in the direction C is performed. In this case, the protrusion portions89,90are pushed outwardly in the direction C by means of the core1. In order to mitigate, or reduce the stress applied to the bottom surface25of the housing2, in those circumstances, opening portions92,93are formed on the bottom surface25of the housing2along the wall portion81and around the protrusion portions89,90(the protrusion portions89,90as a center).

As explained above, the core1is fixed to the housing2by, for example, press-fitting and thermal clinching, and the core1is supported by the housing2in the direction A, the direction B, and the direction C. Thus, the positioning of the core1relative to the housing2is performed with high precision.

As illustrated inFIG. 14, the circuit board4is fastened to the housing2, by means of the screws71, to which the core1is assembled. As illustrated inFIGS. 14 and 15, the housing2is positioned on the jig150at which the detection elements5are inserted and positioned in the support portions151by fitting the protrusion portions152to the positioning holes of the housing2as described above. Accordingly, the connection terminals51are inserted through the through holes41of the circuit board4by means of the guide portion6. Thereafter, the lands42of the circuit board4and the connection terminals51of the detection element5are soldered (connected by solder). Then, removing the jig150, the current sensor100is completed.

Modified examples will be explained as follows. According to the embodiment, the core1includes two groove portions11, however, the construction is not limited to the foregoing. Alternatively, the core1may include three or more of the groove portions11. In those circumstances, in order to detect the three-phase alternating current, because the sum of three electric current values is zero in a normal state, one detection element5may be provided at each of the groove portions11for the purpose of detecting an abnormality, or failure of the detection element5.

According to the embodiment, the guide portion6includes the hole portion61and the protrusion portion62, however, the construction is not limited to the foregoing. Alternatively, the guide portion6may include one of the hole portion61and the protrusion portion62. Further, alternatively, the guide portion6may be formed in another configuration other than the hole portion61and the protrusion portion62.

According to the embodiment, the clearance is provided between the housing2and the circuit board4in a state where the circuit board4is fixed to the housing2so that the solder fillets can be visually inspected along the surface of the circuit board4. However, the construction is not limited to the embodiment. Alternatively, in a state where the circuit board4is fixed to the housing2, a clearance provided between the housing2and the circuit board4may be provided at least around the lands42. According to the alternative construction, the solder fillet is formed at the lands42at the front side and backside of the circuit board4, and the fixing strength of the soldering can be enhanced.

According to the embodiment, the length of the separation wall portion12along the distance direction of the core1is longer than the length of the outer wall portion13along the distance direction. However, the construction is not limited to the embodiment. Alternatively, the length of the separation wall portion12in the distance direction of the core1and the length of the outer wall portion13in the distance direction may be formed to be equal to each other. Further, alternatively, the length of the separation wall portion12in the distance direction of the core1may be set to be shorter than the length of the outer wall portion13in the distance direction.

The disclosure is applicable to a current sensor for measuring the electric current flowing in a conductor.

According to the embodiment, a current sensor includes a core (1), the core (1) being made from magnetic member, the core (1) including a plurality of groove portions (11) and at least one separation wall portion (12) separating the groove portions (11) from one another, a housing (2), the housing (2) being made from a non-magnetic material, the housing (2) covering the core (1) along a contour of the core (1), the housing (2) includes a plurality of recessed grooves (21) formed at the housing (2) along the groove portions (11), respectively, a plurality of conductors (3), the conductors (3) positioned in the groove portions (11), respectively, the conductors (3) allowing a current being measured to flow therein, a circuit board (4), the circuit board (4) fixed to the housing (2), the circuit board (4) including a through hole (41) and a land (42) formed at a surrounding of the through hole (41), the through hole (41) penetrating through the circuit board (4) in a direction corresponding to an inserting direction of the conductor (3), a detection element (5), the detection element (5) detecting a magnitude of a magnetic field generated in accordance with the current being measured flowing in the conductors (3), the detection element positioned in each of the recessed grooves (21), the detection element (5) positioned closer to an opening end side of the groove portion (11) relative to the conductor (3) positioned in the groove portion (11), the detection element (5) being arranged so that a detecting direction of the detection element (5) is directed along a distance direction of the groove portions (11), the detection element (5) including a connection terminal (51), the connection terminal (51) inserted and positioned in the through hole (41), the connection terminal (51) electrically connected to the land (42), and a guide portion (6), the guide portion (6) provided at the housing (2), the guide portion (6) guiding the connection terminal (51) to the through hole (41).

According to the construction of the embodiment, because the circuit board (4) is fixed to the housing (2) that houses the core (1) and the guide portion (6) is provided for inserting the connection terminal (51) of the detection element (5) through the housing (2) to which the circuit board (4) is fixed, the positioning of the detection element (5) relative to the core (1) can be performed with high precision. Thus, because the positional gap, or deviation of the core (1) and the detection element (5) during the manufacturing process can be reduced, the accuracy in the electric current detection can be enhanced. Further, because the connection terminal (51) of the detection element (5) is guided by the guide portion (6) to be inserted through the through hole (41) of the circuit board (4), the detection element (5) can be readily assembled to the circuit board (4). Still further, because the connection terminal is not bent (the connection terminal is not formed by bending process), the length of the connection terminal (51) can be shortened. Thus, the positional deviation, or displacement of the detection element of the detection element (5) by, for example, the vibration, or oscillation can be restrained, and thus the precision in the current detection is enhanced. Further, because the stress is not applied to the joint portion of the connection terminal (51) and the circuit board (4) due to a difference in linear coefficient of expansion, the durability against the thermal shock (flame impingement) can be enhanced.

According to the embodiment, the guide portion (6) includes a hole portion (61). The hole portion (61) is formed at a portion of the recessed groove (21) that opposes to the circuit board (4) and positioned at an opposite side to a side where the circuit board (4) is positioned, and the hole portion (61) includes a diameter that reduces towards an inner in an inserting direction of the connection terminal (51).

According to the construction of the embodiment, the connection terminal (51) of the detection element (5) can be guided to the through hole (41) of the circuit board (4) without bending. Thus, the detection element (51) can be positioned at a predetermined position and the deterioration of the detection precision of the electric current can be prevented.

According to the embodiment, the guide portion (6) includes a protrusion portion (62). The protrusion portion (62) is provided at the housing (2) to protrude in a distance direction of the recessed groove (21), the protrusion portion (62) includes a protrusion amount increasing from an outer side to an inner side in an inserting direction of the connection terminal (51).

According to the construction of the embodiment, because the detection element (4) is guided by the protrusion portion (62) when inserting the detection element (5) inside the recessed groove (21), the detection element (5) can be positioned at a predetermined position in the recessed groove (21). Thus, deterioration of the detection precision of the electric current can be prevented.

According to the embodiment, the circuit board (4) is positioned keeping a distance from the housing (2).

According to the construction of the embodiment, even in a state where the circuit board (4) is fixed to the housing (2), the solder fillet formed at the land (42) formed at the surface of the circuit board (4) facing the housing (2) can be visually inspected. Thus, the reliability of the soldering of the detection element (5) to the circuit board (4) can be enhanced.

According to the embodiment, the core (1) includes outer wall portions (13) positioned interposing said plurality of groove portions (11) in the distance direction therebetween, and a length of the separation wall portion (12) in the distance direction is longer than a length of the outer wall portion (13) in the distance direction.

According to the construction of the embodiment, the magnetic fluxes generated at the separation wall portion (12) and formed by the electric current flowing in two of the conductors (3) positioned interposing the separation wall portion (12) therebetween can be restrained from being influenced each other.

According to the embodiment, the length of the separation wall portion (12) is set to be equal to or longer than a length of the outer wall portion (13) multiplied √{square root over (3)}.

According to the construction of the embodiment, even when the three-phase alternating current flows in the plural conductors, influence of the magnetic fluxes caused by the electric current flowing in the conductors adjacent each other to each other at the separation wall portion (12) can be reduced. Thus, the detection precision of the three-phase alternating current can be enhanced.