Current sensor

Abstract

A current sensor (10), which suppresses a decrease in detection accuracy caused by a high temperature of an electronic component such as a magnetic detection unit due to heat generated from a bus bar, is suitable for measurement of a large current, and is provided with: a bus bar (11) through which a current to be measured flows; a magnetism detection unit (13) capable of detecting magnetism generated by the bus bar (11); and a housing (12) integrally formed with the bus bar (11) and having a housing space (14) for housing the magnetic detection unit (13), the magnetic detection unit (13) being disposed at a position separated from the bus bar (11) and facing the bus bar (11), the bus bar (11) being provided on a surface defining the housing space (14) and being a first surface (14a) of the housing space (14) facing the magnetic detection unit (13) along the Z-axis direction, and the housing (12) having a housing space (14) for housing the magnetic detection unit (13). Air is provided between the bus bar (11) and the magnetic detection unit (13) so as to be in contact with an opposing surface (11a) of the bus bar (11), said opposing surface facing the magnetic detection unit (13), said air being a low-thermal-conductivity substance having a lower thermal conductivity than a resin-based material forming the case (12).

Description

Technical Field

[0001] The present invention relates to a current sensor that detects a magnetic field generated by a current to be measured flowing through a bus bar and measures a current value of the current to be measured based on the detected magnetic field. Background Art

[0002] In recent years, as the demand for decarbonization has increased, in order to suppress CO2 emissions during vehicle driving, the transition from engines to electric motors, i.e., de-gasoline vehicles / electrification (EV shifting), is being promoted, and current sensors are used as current measuring devices for measuring current supplied to three-phase motors, etc. (for example, Patent Document 1).

[0003] As EV shifting involves large commercial vehicles such as trucks and buses, the motor capacity in hybrid vehicles and electric vehicles has also increased, and the measured current of the current sensor used for motor control has also increased. In addition, the chance of being driven continuously under high load conditions has also increased, and the current that is continuously energized has increased. The bus bar, which serves as the current path for the measured current, generates an amount of heat proportional to the square of the current. Therefore, there is the following problem: as the measured current that is continuously energized increases, the heat generated from the bus bar increases, and electronic components such as the magnetic detection unit arranged near the bus bar become hot.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-102024 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] Patent document 1 describes a current sensor in which a substrate having a magnetic detection unit is provided in a housing component in which a bus bar is embedded and molded. In this current sensor, both sides of the bus bar are covered with resin in consideration of the fluidity of the resin when molded in the housing component. Therefore, the heat generated in the bus bar is transferred to the magnetic detection unit via the resin material covering the opposite surface opposite to the magnetic detection unit. Due to the increase in the current to be measured, the heat generated by the bus bar increases, and the temperature in the storage space becomes a high temperature that exceeds the heat resistance temperature of the magnetic detection unit, which may cause problems such as reduced measurement accuracy of the current sensor and shortened product life.

[0009] Therefore, an object of the present invention is to provide a current sensor suitable for measuring a large current, which can suppress the temperature of electronic components such as a magnetic detection unit from being heated by heat from a bus bar.

[0010] Means for solving technical problems

[0011] The present invention has the following configuration as a means for solving the above-mentioned technical problems.

[0012] A current sensor comprises: a bus bar through which a measured current flows; a magnetic detection unit capable of detecting magnetism generated by the bus bar; and a shell formed integrally with the bus bar and having a storage space for storing the magnetic detection unit, characterized in that the magnetic detection unit is arranged at a position separated from and opposite to the bus bar, the bus bar is provided on a surface that defines the storage space and is a first surface of the storage space that is opposite to the magnetic detection unit along a first direction, and a low thermal conductivity material having a thermal conductivity lower than that of a resin material forming the shell is provided between the bus bar and the magnetic detection unit in a manner that is in contact with an opposing surface of the bus bar that is opposite to the magnetic detection unit.

[0013] By providing a low thermal conductivity material between the bus bar and the magnetic detection unit, the heat generated by the bus bar is difficult to be transferred to the magnetic detection unit via the storage space, thereby reducing the heat transferred from the bus bar to the magnetic detection unit. Therefore, it is possible to prevent the surrounding area of ​​the magnetic detection unit from becoming high temperature due to the heat of the bus bar, thereby reducing the detection accuracy of the magnetic sensor.

[0014] Only an air layer serving as the low thermal conductivity material may be provided between the bus bar and the magnetic detection unit.

[0015] The thermal conductivity of air is low, and the air layer is a good heat insulating layer. Therefore, by providing a simple structure such as an air layer between the bus bar and the magnetic detection unit, the temperature rise around the magnetic detection unit can be suppressed. The air constituting the air layer can also be a low thermal conductivity material provided in contact with the opposing surface.

[0016] The facing surface of the bus bar may be exposed in the housing space, and an opposite surface on the opposite side of the facing surface may be buried in the case.

[0017] In the area where the bus bar and the magnetic detection unit are opposite, the air between the opposite surface of the bus bar and the magnetic detection unit can reduce the heat transferred from the opposite surface of the bus bar to the magnetic detection unit via the storage space. In addition, by burying the opposite surface of the bus bar in the area in a shell having a higher thermal conductivity than air, the heat of the bus bar can be guided to the shell on the opposite side of the magnetic detection unit. Therefore, it is possible to suppress the temperature around the magnetic detection unit from increasing due to the heat of the bus bar.

[0018] A distance between the facing surface of the bus bar and the magnetic detection unit in the first direction may be less than or equal to a distance between the first surface of the housing space and the magnetic detection unit in the first direction.

[0019] By configuring the first surface of the storage space to be farther from the magnetic detection unit in the first direction than the opposite surface of the bus bar is from the magnetic detection unit in the first direction, heat from the bus bar transferred from the first surface of the storage space via the storage space to the magnetic detection unit can be reduced, thereby suppressing the temperature rise around the magnetic detection unit.

[0020] The facing surface of the bus bar and the first surface of the housing space may be formed on the same plane.

[0021] By making the facing surface of the bus bar and the first surface of the storage space flush with each other, the formation and processing of the case and the bus bar are facilitated.

[0022] The current sensor may further include a magnetic shield.

[0023] The magnetic shield may be a pair of flat-plate-shaped magnetic shields arranged in the first direction, and the bus bar and the magnetic detection unit may be arranged between the pair of flat-plate-shaped magnetic shields.

[0024] The flat plate-shaped magnetic shield disposed near the bus bar may be formed integrally with the housing together with the bus bar.

[0025] Since the external magnetic field noise to the magnetic detection unit can be blocked by the magnetic shield, the external magnetic field noise resistance of the magnetic detection unit is improved.

[0026] The magnetic shield may include: a base portion disposed on the opposite side of the magnetic detection portion in the first direction with the bus bar interposed therebetween; and side walls extending from both ends of the base portion along the first direction.

[0027] By arranging the magnetic shield having a U-shaped cross section so as to surround the bus bar, the external magnetic field noise resistance of the current sensor is improved.

[0028] The magnetic detector may include a first magnetic detector and a second magnetic detector, and may be capable of detecting magnetism generated by the bus bar based on an output of the first magnetic detector and an output of the second magnetic detector.

[0029] By detecting magnetism based on the outputs of the first and second magnetic detection units, the influence of external magnetic field noise common to the first and second magnetic detection units can be eliminated, thereby improving the external magnetic field noise resistance of the current sensor.

[0030] A dimension of a cross-sectional shape of the bus bar in the first direction perpendicular to an extending direction of the bus bar may be larger than a dimension in a second direction perpendicular to the first direction.

[0031] By using a bus bar having a cross-sectional shape in which the dimension in the first direction is larger than the dimension in the second direction, a long and thin elliptical magnetic field having a major axis in which the component in the first direction is larger than the component in the second direction is generated in the cross section. Therefore, near the magnetic detection unit, the component in the first direction is large, forming a magnetic field in the opposite direction, and the magnetic field from the bus bar can be detected with high accuracy.

[0032] The magnetic detection unit may include an output terminal unit, the output terminal unit may be held by a substrate, and the output terminal unit may be sealed.

[0033] By potting and sealing the output terminal portion with a sealant, discharge from the bus bar to the output terminal portion is less likely to occur, and the withstand voltage of the current sensor is improved.

[0034] A cover covering the storage space may be provided, the magnetic detection unit may include an output terminal unit, the output terminal unit may be held by a substrate, and the substrate may be held by the cover.

[0035] When the heat of the bus bar is transferred to the substrate via the resin material, heat conductivity is reduced at the contact portion between the case and the cover, thereby preventing the heat of the bus bar from being transferred to the magnetic detector and increasing the temperature of the magnetic detector.

[0036] Effects of the Invention

[0037] According to the present invention, it is possible to reduce the temperature rise of the magnetic sensor caused by the heat of the bus bar being transferred to the magnetic detection unit via the resin material of the housing. Therefore, it is possible to provide a current sensor suitable for measuring large currents, which suppresses the degradation of the measurement accuracy caused by the temperature rise of the magnetic detection unit due to the heat of the bus bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a perspective view of a current sensor according to an embodiment of the present invention.

[0039] Figure 2 The current sensor of the first embodiment Figure 1 Sectional view along line AA.

[0040] Figure 3 yes Figure 2 Top view of the current sensor.

[0041] Figure 4 It is a cross-sectional view of a modified example of the current sensor according to the first embodiment.

[0042] Figure 5 It is a cross-sectional view of another modified example of the current sensor according to the first embodiment.

[0043] Figure 6 It is a cross-sectional view of a current sensor according to a second embodiment.

[0044] Figure 7 It is a cross-sectional view of a modified example of the current sensor according to the second embodiment.

[0045] Figure 8 It is a cross-sectional view of a current sensor according to a third embodiment.

[0046] Fig. 9 It is a cross-sectional view of a current sensor according to a fourth embodiment.

[0047] Fig.10 It is a cross-sectional view of a current sensor according to a fifth embodiment.

[0048] Fig.11 It is a cross-sectional view of a current sensor according to a sixth embodiment.

[0049] Fig.12 This is a cross-sectional view of a conventional current sensor. DETAILED DESCRIPTION

[0050] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings, the same reference numerals are given to the same components, and the description thereof is omitted. In order to indicate the positional relationship of each component, reference coordinates are appropriately shown in each of the drawings. With respect to the reference coordinates, the extending direction of the busbar is set as the X-axis direction, the direction orthogonal to the X-axis direction in the plate surface of the busbar is set as the Y-axis direction, and the perpendicular direction of the plate surface of the busbar is set as the Z-axis direction.

[0051] [First embodiment]

[0052] Figure 1 The current sensor 10 is a perspective view of the current sensor 10 according to the present embodiment. The current sensor 10 is formed by integrally molding three bus bars 11 and a housing member 12, and having three magnetic detection units 13 on a substrate 19 (see Figure 3 ), having three measurement channels. In addition, the present invention can also be implemented as a current sensor having a single or multiple measurement channels other than three.

[0053] Fig.12 is a cross-sectional view of a conventional current sensor 100, showing a current sensor 100 of the same type as in FIG. Figure 1101 and the magnetic detection unit 103. As shown in the figure, the current sensor 100 takes into account the fluidity of the resin material when the bus bar 101 is insert-molded into the housing member 102, and the resin material is provided on both sides of the bus bar 101 in the Z-axis direction. In this way, in the conventional current sensor 100, the resin material of the housing member 102 is formed between the bus bar 101 and the magnetic detection unit 103, and the bus bar 101 is not exposed in the storage space 104 of the magnetic detection unit 103.

[0054] The thermal conductivity of the resin material forming the shell member 102 is greater than that of air. For example, the thermal conductivity of polyphenylene sulfide (PPS) is about 0.3 W / mK, which is greater than the thermal conductivity of air of 0.0241 W / mK. In the conventional current sensor 100, a resin material is provided between the bus bar 101 and the magnetic detection unit 103, which is easier to transfer the heat generated in the bus bar 101 than in air. Therefore, the heat generated in the bus bar 101 is easily transferred to a position close to the magnetic detection unit 103 via the resin layer of the resin material, and the temperature around the magnetic detection unit 103 is easy to rise. In addition, heat is also easily transferred from the resin material to the side wall of the shell member 102, so the heat is easily transferred to the magnetic detection unit 103 via the shell member 102 and the substrate 109. Therefore, when the measured current flowing through the bus bar 101 becomes large and the heat generation increases, the magnetic detection unit 103 may become high temperature and exceed the heat resistance temperature.

[0055] Figure 2 The current sensor 10 according to this embodiment is Figure 1 Sectional view taken along the YZ plane at line AA. Figure 3 yes Figure 2 A top view of the current sensor 10 is shown. Figure 3 In order to show the positional relationship among the bus bar 11 , the case member 12 , and the magnetic detector 13 when viewed from the substrate 19 toward the bus bar 11 along the Z axis, the terminals of the magnetic detector 13 and the substrate 19 are omitted.

[0056] The current sensor 10 includes a bus bar 11 , a case member 12 , and a magnetic detection unit 13 .

[0057] The bus bar 11 is a conductive member formed in a plate shape, a part of which is formed integrally with the housing member 12 by insert molding. The bus bar 11 is made of, for example, copper, brass, aluminum, etc., and allows the measured current of the detection object to flow. The bus bar 11 is provided in such a manner that two opposing plate surfaces correspond to the upper and lower sides (both sides in the Z-axis direction) of the housing member 12, respectively.

[0058] In addition, the connection portion connected to the outside in the X-axis direction of the busbar 11, that is, the two ends, does not need to be line symmetrical with respect to the Y-axis. In addition, the size of the portion of the busbar 11 opposite to the magnetic detection unit 13 in the Y-axis direction may be set smaller than other portions. Portions of the busbar 11 other than the portion opposite to the magnetic detection unit 13 may not be in a flat plate shape, and may be bent, for example.

[0059] The magnetic detection unit 13 is disposed at a position separated from the bus bar 11 and facing the bus bar 11. Figure 3 In the embodiment, when viewed along the Z axis, the center of the width of the magnetic detection unit 13 in the Y axis direction overlaps with the center of the width of the bus bar 11 in the Y axis direction. However, the magnetic detection unit 13 only needs to be located at a position where the magnetic field generated when the measured current flows through the bus bar 11 can be measured. Therefore, the entire magnetic detection unit 13 may not be arranged at a position overlapping with the bus bar 11, but at a staggered position. However, when viewed along the Z axis, it is preferred that a portion of the magnetic detection unit 13 overlaps with the opposing bus bar 11.

[0060] In the current sensor 10, the substrate 19 on which the magnetic detector 13 is mounted is fixed to the case member 12 on which the bus bar 11 is insert-molded. Therefore, the bus bar 11 and the magnetic detector 13 can be positioned with high accuracy.

[0061] A portion of the bus bar 11 is buried in the first surface 14a of the storage space 14. The first surface 14a is a portion of the surface defining the storage space 14, and is opposed to the magnetic detection unit 13 along the first direction (Z-axis direction). On the first surface 14a, the opposing surface 11a of the bus bar 11 that is opposed to the magnetic detection unit 13 is exposed, so that air, which is a low thermal conductivity material, exists between the bus bar 11 and the magnetic detection unit 13, and the air is in contact with the opposing surface 11a. The opposing surface 11a of the bus bar 11 in the current sensor 10 is in contact with the air, which is a low thermal conductivity material, over its entire surface.

[0062] In the current sensor 10, only an air layer 15 is provided between the facing surface 11a of the bus bar 11 and the magnetic detection unit 13. The thermal conductivity of air is lower than that of the resin material forming the case member 12. By making the air layer 15 contact with the facing surface 11a of the bus bar 11, it is difficult for the heat of the bus bar 11 to cross the storage space 14 and be directly transferred to the magnetic detection unit 13. In addition, since it is difficult for heat to be transferred from the facing surface 11a of the bus bar 11 to the side wall of the storage space 14, it is different from the conventional current sensor 100 (see Fig.12), the amount of heat transferred to the magnetic detection unit 13 via the side wall of the storage space 14 and the substrate 19 can also be reduced compared to the conventional current sensor 100. Therefore, the influence of heat on the bus bar 11 can be reduced, and the temperature around the magnetic detection unit 13 can be kept lower than that of the conventional current sensor 100. Therefore, the measured current flowing through the bus bar 11 can be increased. In addition, the resin material includes a material composed of a resin and a material in which a filler or the like is added to the resin.

[0063] Regarding the bus bar 11, in the storage space 14, the facing surface 11a facing the magnetic detection unit 13 is exposed, and the opposite surface 11b on the opposite side of the facing surface 11a is buried in the case member 12. From the viewpoint of suppressing the transfer of heat of the bus bar 11 from the facing surface 11a side to the magnetic detection unit 13, it is preferable that the entire surface of the facing surface 11a of the bus bar 11 is exposed, and the entire surface of the opposite surface 11b is buried in the case member 12.

[0064] From the viewpoint of improving manufacturing efficiency by facilitating the formation and processing of the case member 12 and the bus bar 11 , it is preferred that the facing surface 11 a of the bus bar 11 and the first surface 14 a of the housing space 14 are formed on the same plane.

[0065] Figure 4 2 is a cross-sectional view of a modification of the current sensor. The current sensor 20 according to the modification is different from the current sensor 10 in that the facing surface 11 a and the first surface 14 a are not formed on the same plane.

[0066] exist Figure 2 In the current sensor 10 shown in FIG. 1 , the distance L1 between the facing surface 11a of the bus bar 11 and the magnetic detector 13 in the first direction (Z-axis direction) and the distance L2 between the first surface 14a of the storage space 14 and the magnetic detector 13 in the first direction (Z-axis direction) are equal. Figure 4 In the current sensor 20 shown, the distance L1 between the facing surface 11a of the bus bar 11 and the magnetic detection unit 13 is smaller than the distance L2 between the first surface 14a of the storage space 14 and the magnetic detection unit 13. By making the distance L1 smaller than the distance L2, the heat transferred from the bus bar 11 to the magnetic detection unit 13 via the resin material of the case member 12 can be reduced.

[0067] Figure 5 2 is a cross-sectional view of another modified example of the current sensor. In the current sensor 30 of another modified example, the distance L1 between the facing surface 11a of the bus bar 11 and the magnetic detection unit 13 is greater than the distance L2 between the first surface 14a of the storage space 14 and the magnetic detection unit 13. However, in the storage space 14, the entire facing surface 11a of the bus bar 11 is exposed, so the air acts as a low thermal conductivity material, which can suppress the heat transfer of the bus bar 11 to the magnetic detection unit 13.

[0068] [Second Embodiment]

[0069] Figure 6 4 is a cross-sectional view of a current sensor 40 according to the present embodiment. The current sensor 40 is different from the current sensor 10 in that a magnetic shield 45 is disposed.

[0070] The magnetic shield 45 includes a pair of flat magnetic shields 45A and 45B arranged in the Z-axis direction. The magnetic detector 13 and the bus bar 11 are arranged between the magnetic shields 45A and 45B in the Z-axis direction.

[0071] The magnetic shield 45A disposed near the bus bar 11 is formed integrally with the case member 12 together with the bus bar 11 , and is provided on the side of the bus bar 11 opposite to the side where the magnetic detector 13 is disposed.

[0072] The magnetic shield 45B disposed near the magnetic detector 13 is formed integrally with the cover member 42 and is provided on the side of the magnetic detector 13 opposite to the side on which the bus bar 11 is disposed.

[0073] The magnetic shields 45A and 45B are made of, for example, a plurality of metal plates having the same shape. The magnetic shields 45A and 45B can block external magnetic field noise, thereby improving the external magnetic field noise resistance of the magnetic detection unit 13. However, since only one of the magnetic shields 45A or 45B can block external magnetic field noise, it is not necessary to provide a pair but only one.

[0074] Figure 7 1 is a cross-sectional view of a modified example of the current sensor of the present embodiment. The current sensor 50 involved in this modified example is different from the current sensor 40 in that a magnetic shield 55 is provided in a manner of surrounding the bus bar 11 and the magnetic detection unit 13, and the cross-sectional surface of the magnetic shield 55 in the YZ plane orthogonal to the extending direction (X-axis direction) of the bus bar 11 is U-shaped.

[0075] The magnetic shield 55 includes a base 55a disposed on the side of the bus bar 11 opposite to the magnetic detection unit 13, and side walls 55b, 55b extending from both ends of the base 55a along the Z-axis direction. The magnetic shield 55 is disposed to surround the bus bar 11 and the magnetic detection unit 13, that is, the bus bar 11 and the magnetic detection unit 13 overlap with the base 55a when viewed along the Z-axis direction, and the bus bar 11 and the magnetic detection unit 13 overlap with the side walls 55b when viewed along the Y-axis direction. Therefore, the external magnetic field noise to the bus bar 11 and the magnetic detection unit 13 can be effectively blocked by the magnetic shield 55, and the external magnetic field noise resistance of the current sensor 50 is improved.

[0076] [Third Embodiment]

[0077] Figure 8 2 is a cross-sectional view of a current sensor 60 according to the present embodiment. The current sensor 60 is different from the current sensor 10 in that the shape of the bus bar 61 and the magnetic detection unit 63 are configured to perform differential detection.

[0078] The current sensor 60 includes a first magnetic detector 63A and a second magnetic detector 63B as the magnetic detector 63, and can detect magnetism generated from the bus bar 61 based on the output of the first magnetic detector 63A and the output of the second magnetic detector 63B. As the first magnetic detector 63A and the second magnetic detector 63B, a Hall element or a magnetoresistive element (GMR element, TMR element, etc.) having sensing axes oriented in the same direction or in opposite directions in the Z-axis direction is used.

[0079] The cross-sectional shape of the bus bar 61 of this embodiment, which is perpendicular to the extending direction (X-axis direction), is such that the dimension D1 in the Z-axis direction (first direction) is larger than the dimension D2 in the Y-axis direction (second direction) perpendicular to the Z-axis direction. That is, the bus bar 61 has a plate-like shape in which the width in the Y-axis direction is narrower than the width in the Z-axis direction. Therefore, when the current to be measured flows, Figure 8 As shown by the single-dot chain line, an elongated elliptical magnetic field is generated, and the elliptical magnetic field has a long axis whose component in the Z-axis direction (first direction) is larger than that in the Y-axis direction (second direction). Therefore, near the magnetic detection unit 63, the component in the first direction (Z-axis direction) is large, and a magnetic field in the opposite direction can be formed. However, instead of the bus bar 61 whose dimension D1 is larger than the dimension D2 (dimension D1>dimension D2), a bus bar whose dimension D1 is less than or equal to the dimension D2 (dimension D1≤dimension D2) can be used.

[0080] In the differential current sensor 60, as the magnetic detection unit 63, a first magnetic detection unit 63A and a second magnetic detection unit 63B that are highly sensitive to a magnetic field in a specific direction (sensitivity direction) are used. The first magnetic detection unit 63A and the second magnetic detection unit 63B are arranged in such a manner that the sensitivity directions are substantially parallel. In addition, in order to obtain a large measurement sensitivity, the first magnetic detection unit 63A and the second magnetic detection unit 63B are arranged in a posture in which the sensitivity directions are substantially parallel to the direction of the magnetic field at a location where the directions of the magnetic field generated by the measured current are substantially opposite.

[0081] The directions of the vectors of the magnetic field of the measured current at the position where the pair of first magnetic detection parts 63A and second magnetic detection parts 63B are arranged are opposite, and the difference of the magnetic fields as vectors is large. In the differential current sensor 60, the current measurement result is obtained based on the magnetic fields as vectors detected in the first magnetic detection parts 63A and the second magnetic detection parts 63B.

[0082] like Figure 8As shown by the hollow arrow, when the sensitivity directions of the first magnetic detector 63A and the second magnetic detector 63B are the same, the current measurement result is obtained based on the difference between the two detection signals in the first magnetic detector 63A and the second magnetic detector 63B. When the sensitivity directions of the first magnetic detector 63A and the second magnetic detector 63B are opposite, the current measurement result is obtained based on the sum of the two detection signals in the first magnetic detector 63A and the second magnetic detector 63B.

[0083] By detecting the magnetic field of the bus bar 61 based on the outputs of the first and second magnetic detectors 63A and 63B, the influence of external magnetic field noise common to the first and second magnetic detectors 63A and 63B can be eliminated.

[0084] [Fourth Embodiment]

[0085] Fig. 9 1 is a cross-sectional view of a current sensor 70 of the present embodiment. The current sensor 70 is different from the current sensor 10 in that the magnetic detection unit 13 includes an output terminal unit 73, the output terminal unit 73 is held on the substrate 19, and the output terminal unit 73 is sealed by a sealant 74. By potting and sealing the output terminal unit 73 with the sealant 74, it is difficult to generate discharge from the bus bar 11 to the output terminal unit 73, and the voltage resistance of the current sensor 70 is improved.

[0086] The sealant 74 is provided so as to cover the output terminal portion (electrode terminal) 73, but not to cover the opposing surface 13a of the magnetic detection portion 13 that is opposed to the bus bar 11. Therefore, it is possible to reduce the heat of the bus bar 11 that is transferred to the magnetic detection portion 13 via the sealant 74 having a higher thermal conductivity than the air in the storage space 14. Therefore, it is possible to suppress the temperature of the magnetic detection portion 13 from increasing due to the heat of the bus bar 11.

[0087] [Fifth Embodiment]

[0088] Fig.10 It is a cross-sectional view of the current sensor 80 according to the present embodiment.

[0089] The current sensor 80 includes a cover member 82 covering the storage space 14 , the magnetic detection unit 13 includes an output terminal unit 83 held by the substrate 19 , and the current sensor 80 includes a holding member 84 holding the substrate 19 on the cover member 82 .

[0090] When the heat of the bus bar 11 is transferred to the substrate 19 via the resin material constituting the case member 12 and the cover member 82, the heat transfer property is reduced at the contact portion between the case member 12 and the cover member 82. In addition, since the substrate 19 is held on the cover member 82 via the holding member 84 and an air layer is formed between the substrate 19 and the cover member 82, it is not easy for heat to be transferred from the cover member 82 to the substrate 19. In addition, the path for transferring heat via the resin material becomes longer. Therefore, the temperature rise of the magnetic detection unit 13 caused by the heat of the bus bar 11 can be suppressed.

[0091] [Sixth Embodiment]

[0092] Fig.11 It is a cross-sectional view of the current sensor 90 according to the present embodiment.

[0093] The current sensor 90 is provided with an air layer 15 (see Figure 2 ) is different from the current sensor 10 in the structure of the low thermal conductivity material 95 other than the current sensor 10.

[0094] By providing the low thermal conductivity material 95 having a thermal conductivity lower than that of the resin material forming the case member 12 , it is possible to reduce a temperature rise in the magnetic detector 13 caused by the heat of the bus bar 11 being transferred to the magnetic detector 13 .

[0095] As the low thermal conductivity material 95, porous ceramics and the like can be cited. The thermal conductivity of porous ceramics depends on the type thereof, but for example, the thermal conductivity is about 0.003 W / mK. This value is slightly larger than the thermal conductivity of air, but is sufficiently smaller than the thermal conductivity of resin materials such as polyphenylene sulfide. Therefore, by providing the low thermal conductivity material 95, the heat transferred from the bus bar 11 to the magnetic detection unit 13 can be reduced in the same manner as the air layer.

[0096] In addition, if Fig.11 As shown, the low thermal conductivity material 95 does not need to be provided to cover the entire facing surface 11a of the bus bar 11 and the first surface 14a of the storage space 14. For example, the low thermal conductivity material 95 may be provided to cover only the facing surface 11a. In addition, a part of the facing surface 11a of the bus bar 11 may be covered with the low thermal conductivity material 95, and the other area may be covered with the air layer 15.

[0097] The embodiments disclosed in this specification are illustrative in all points and are not limited to the embodiments. The scope of the present invention is indicated by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0098] [Example]

[0099] for Figure 2 The current sensor 10 of the first embodiment shown in FIG. 1 was simulated to determine the ease of heat transfer from the bus bar 11 to the magnetic detection unit 13. Fig.12 The conventional current sensor 100 shown was also subjected to simulations of the ease of heat transfer from the bus bar 101 to the magnetic detector 103. In these simulations, the continuously energized current to be measured was set to 200A, and the temperature of the magnetic detectors 13 and 103 was determined when the temperature of the bus bars 11 and 101 reached 146°C.

[0100] Regarding the current sensor 10, the entire surface of the facing surface 11a of the bus bar 11 was exposed, and the distance L1 and the distance L2 in the Z-axis direction between the facing surface 11a of the bus bar 11 and the magnetic detection unit 13 were 4.2 mm. Regarding the conventional current sensor 100, only the entire surface of the facing surface 101a of the bus bar 101 was covered with a resin material with a thickness of 1.2 mm, which was different from the current sensor 10, and the distance L1 was 3.0 mm and the distance L2 was 1.2 mm. The resin material constituting the case member 12 and the case member 102 was polyphenylene sulfide (PPS).

[0101] The simulation result shows that the temperature of the magnetic detection unit 13 of the current sensor 10 is 121.8°C, while the temperature of the magnetic detection unit 103 of the current sensor 100 is 129.0°C. Thus, the present invention can reduce the temperature rise of the magnetic detection unit 13 caused by the heat of the bus bar 11 by removing the resin material from the facing surface 11a of the bus bar 11 to expose the facing surface 11a. According to the simulation result, the current sensor 10 of the present invention can use the magnetic detection unit 13 with a heat resistance temperature of 125°C, which cannot be used in the conventional current sensor 100.

[0102] [Industrial Application Possibility]

[0103] The present invention is useful as a current sensor including a bus bar through which a large current flows as a current to be measured.

[0104] [Explanation of Reference Numerals]

[0105] 10: Current sensor

[0106] 11: Busbar

[0107] 11a: Opposite surface

[0108] 11b: Opposite side

[0109] 12: Shell parts (shell)

[0110] 13: Magnetic detection unit

[0111] 13a: Opposite surface

[0112] 14: Storage Space

[0113] 14a: Side 1

[0114] 15: Air layer (low thermal conductivity material)

[0115] 19: Substrate

[0116] 20: Current sensor

[0117] 30: Current sensor

[0118] 40: Current sensor

[0119] 42: Cover parts

[0120] 45: Magnetic shielding parts

[0121] 45A: Magnetic shielding

[0122] 45B: Magnetic shielding

[0123] 50: Current sensor

[0124] 55: Magnetic shielding parts

[0125] 55a: Base

[0126] 55b: Side wall

[0127] 60: Current sensor

[0128] 61: Busbar

[0129] 63: Magnetic detection unit

[0130] 63A: First magnetic detection unit

[0131] 63B: Second magnetic detection unit

[0132] 70: Current sensor

[0133] 73: Output terminal

[0134] 74: Sealant

[0135] 80: Current sensor

[0136] 82: Cover parts

[0137] 83: Output terminal

[0138] 84: Keeping parts

[0139] 90: Current sensor

[0140] 95: Low thermal conductivity material

[0141] 100: Current sensor

[0142] 101: Busbar

[0143] 101a: Opposite surface

[0144] 102: Shell parts

[0145] 103: Magnetic detection unit

[0146] 104: Storage Space

[0147] 109: Substrate

[0148] D1: Dimensions

[0149] D2: Dimensions

[0150] L1: Distance

[0151] L2: Distance

Claims

1. A current sensor comprising: Busbar, through which the measured current flows; a magnetism detection unit capable of detecting magnetism generated by the bus bar; and a housing formed integrally with the bus bar and having a storage space for storing the magnetic detection unit; It is characterized in that The magnetic detection unit is arranged at a position separated from the bus bar and facing the bus bar. The bus bar is provided on a surface defining the storage space and is a first surface of the storage space facing the magnetic detection unit along a first direction. A low thermal conductivity material having a thermal conductivity lower than that of a resin material forming the case is provided between the bus bar and the magnetic detection unit so as to be in contact with a surface of the bus bar facing the magnetic detection unit.

2. The current sensor according to claim 1, wherein: Only an air layer serving as the low thermal conductivity material is provided between the bus bar and the magnetic detection unit.

3. The current sensor according to claim 2, wherein: The facing surface of the bus bar is exposed in the housing space, and an opposite surface on the opposite side of the facing surface is buried in the case.

4. The current sensor according to claim 3, wherein: A distance between the facing surface of the bus bar and the magnetic detection unit in the first direction is less than or equal to a distance between the first surface of the housing space and the magnetic detection unit in the first direction.

5. The current sensor according to claim 3, wherein: The facing surface of the bus bar and the first surface of the housing space are formed on the same plane.

6. The current sensor according to claim 1, wherein: A magnetic shield is also provided.

7. The current sensor according to claim 6, wherein: The magnetic shield is a pair of flat plate-shaped magnetic shields arranged in the first direction, The bus bar and the magnetic detection unit are arranged between a pair of flat-plate-shaped magnetic shields.

8. The current sensor according to claim 7, wherein: The flat plate-shaped magnetic shield disposed near the bus bar is formed integrally with the housing together with the bus bar.

9. The current sensor according to claim 6, wherein: The magnetic shield includes a base portion and a side wall portion. The base portion is disposed on an opposite side of the magnetic detection portion in the first direction across the bus bar. The side wall portion is extended from both ends of the base portion along the first direction.

10. The current sensor according to claim 1, wherein: The magnetic detector includes a first magnetic detector and a second magnetic detector, and is capable of detecting magnetism generated by the bus bar based on an output of the first magnetic detector and an output of the second magnetic detector.

11. The current sensor according to claim 10, wherein: A dimension of a cross-sectional shape of the bus bar in the first direction perpendicular to an extending direction of the bus bar is larger than a dimension in a second direction perpendicular to the first direction.

12. The current sensor according to claim 1, wherein: The magnetic detection unit includes an output terminal unit. The output terminal portion is held on the substrate, The output terminal portion is sealed.

13. The current sensor according to claim 1, wherein: A cover is provided to cover the storage space. The magnetic detection unit includes an output terminal unit. The output terminal portion is held on the substrate, The substrate is held by the cover.

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