Current sensor and its manufacturing method
The current sensor addresses assembly inaccuracies and high costs by eliminating terminal guide plates and simplifying lead pin bending, ensuring reliable and cost-effective operation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- KOHSHIN ELECTRIC CORP
- Filing Date
- 2022-04-21
- Publication Date
- 2026-06-03
AI Technical Summary
Conventional current sensors face issues with reduced detection accuracy due to assembly inaccuracies between the core and magnetic detection element, high component costs from using terminal guide plates, and complex lead pin bending processes, which can deform the detection element and increase processing costs.
A current sensor design that eliminates the need for terminal guide plates by bending lead pins of the magnetic detection element at approximately 90 degrees and positioning the detection element without stress, allowing for stable soldering and reduced component count.
This design ensures reliable and cost-effective assembly by avoiding deformation of lead pins and reducing sensor height, thus enhancing detection accuracy and lowering production costs.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to a current sensor and a method for manufacturing the same.
Background Art
[0002] Recently, current sensors mounted on inverters used for motor control have two or more phases integrated together. For each phase, there is a bus bar for passing the measured current, a core for collecting the magnetic flux generated around the bus bar by the measured current, a magnetic detection element for converting the magnetic flux collected by the core into an electrical signal, and a substrate for mounting the magnetic detection element. (See, for example, Patent Document 1)
[0003] For example, in Patent Document 1, if the assembly accuracy between the core of the current sensor and the element body of the detection element (the main body package part of the magnetic detection element) is set coarsely, the detection accuracy may decrease. The main body package part of the magnetic detection element is inserted in advance into the holding part (hole part) of the housing (resin case), the relative positions of the core and the main body package part of the magnetic detection element are accurately arranged, and there, a terminal guide plate, which is a plate-like member provided with a plurality of guide holes, is used to guide the connection terminals of the detection element (the lead pins of the magnetic detection element) into the through holes (through holes) of the circuit board (printed wiring board) and fix them by soldering. This method has been used. Also, the lead pins extending from the main body package part are bent in advance so as to be separated from each other with the main body package part sandwiched therebetween in order to ensure the insulation distance between the lands on the printed wiring board, and further, the ends of each lead pin are bent and processed so as to extend toward the printed wiring board side.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
[0005] In conventional current sensors, in order to accurately determine the relative positions of the busbar and magnetic detection element, and the relative positions of the core and magnetic detection element, which are important for the sensor characteristics, a method has been used in which multiple magnetic detection elements are positioned one by one in holes provided in a resin case beforehand, and then the circuit board is assembled while using a terminal guide plate to simultaneously guide the lead pins of the multiple magnetic detection elements into the through-holes of the printed circuit board.
[0006] Therefore, when using a terminal guide plate to straighten the lead pins of the magnetic detection element and guide them into the through-holes of the printed circuit board, the lead pins of the magnetic detection element could deform, putting stress on the main package of the magnetic detection element, which posed a risk of failure or reduced reliability. Furthermore, the need for a terminal guide plate to guide the lead pins of the magnetic detection element into the through-holes of the printed circuit board resulted in high component costs. Additionally, the need to place the terminal guide plate between the resin case and the printed circuit board led to a problem in terms of the height of the current sensor. Furthermore, there was a problem with high processing costs due to the complex bending shape of the lead pins of the magnetic detection element.
[0007] This invention was made to solve the above-mentioned problems, and aims to provide a highly reliable and inexpensive current sensor by eliminating the need for additional parts such as terminal guide plates and simplifying the processing of the lead pins of the magnetic detection element. [Means for solving the problem]
[0008] The current sensor according to this invention comprises a resin case that holds a busbar through which the current to be measured is carried, a detection element that detects the current to be measured, and a printed circuit board fixed to the resin case and on which the detection element is mounted. The detection element has a plurality of lead pins that extend from a main package portion that houses the main body of the detection element and are bent to include a lead bending portion that is bent at approximately 90 degrees with respect to the direction of extension. The resin case has a hole for housing the main package portion of the detection element, and the printed circuit board has a through hole through which the main package portion of the detection element passes. [Effects of the Invention]
[0009] According to this invention, the detection element can be positioned without requiring complex lead pin bending of the detection element, without placing components such as terminal guide plates between the resin case and the printed circuit board, and without putting stress on the main package portion of the detection element. [Brief explanation of the drawing]
[0010] [Figure 1] This is a perspective view showing a current sensor in Embodiment 1 of the present invention. [Figure 2] This is a cross-sectional view showing the internal structure of the current sensor in Embodiment 1 of the present invention. [Figure 3] This is a perspective view showing the magnetic detection element of the current sensor in Embodiment 1 of the present invention. [Figure 4] This is an enlarged view of the magnetic detection element insertion section of a cross-sectional view showing the internal structure of the current sensor in Embodiment 1 of the present invention. [Figure 5] This is a top view enlarged of the area around the magnetic detection element of the current sensor in Embodiment 1 of the present invention. [Figure 6] This is a perspective view showing the assembly method of the current sensor in Embodiment 1 of the present invention. [Modes for carrying out the invention]
[0011] Figure 1 is a perspective view showing the current sensor 1 in Embodiment 1 of the present invention, and Figure 2 is a cross-sectional view AA thereof. In Figure 1, 5 is a busbar, made of, for example, copper, through which the current to be measured by the current sensor 1 flows. This example shows a case where there are three busbars 5. For example, one of these busbars 5 is connected to each phase of a three-phase motor (not shown), and the other is connected to a three-phase inverter (not shown). The current sensor 1 measures the three phase currents of the three-phase motor. Component 2 is a resin case, made of, for example, PPS (polyphenyl sulfide). 3 is a printed circuit board, on which a magnetic detection element 4, electronic components (not shown), and a connector 6 are mounted by soldering. The printed circuit board 3 is fixed to the resin case 2 with screws 7 or the like. In this invention, unless otherwise specified, the extension direction of the busbar 5 is referred to as the Y direction, the direction in which the busbars 5 are aligned at a 90-degree angle to the Y direction is referred to as the X direction, and the direction at a 90-degree angle to the XY direction is referred to as the Z direction. The direction of the arrow is considered the positive direction, and the opposite direction is considered the negative direction.
[0012] In Figure 2, 8 is a core made of, for example, a silicon steel sheet, and has a roughly C-shape that encircles the busbar 5. The magnetic flux generated by the current being measured flowing through the busbar 5 is collected by the core 8, detected by the magnetic sensing element 4 located in the gap 9 provided in the core 8, converted into an electrical signal, amplified, and output to the outside via the connector 6. The resin case 2 secures the busbar 5 and core 8 with inserts, and has a rectangular hole 11 in the center of the gap 9 of the inserted core 8. The inside of the hole 11 is insulated from the busbar 5 and core 8, and the main package 12 of the magnetic detection element 4 is inserted into it.
[0013] FIG. 3 is a perspective view showing the magnetic detection element 4 of the current sensor 1 in Embodiment 1 of the present invention. In FIG. 3, reference numeral 12 denotes a main body package portion that houses (packages) a magnetosensitive portion 13 having a magnetosensitive axis in the X direction (e.g., a Hall element or the like) and an amplifier circuit that amplifies the output of the magnetosensitive portion 13 with an insulating material such as epoxy resin. Four lead pins 14 for outputting an electrical signal of the magnetic detection element 4 (designated as lead pins 14a, 14b, 14c, and 14d from the front in the figure) are arranged side by side in the Y direction, extend in the Z direction from the main body package portion 12, bend in the X direction after a predetermined length, and are cut after a predetermined length. This portion in the extending direction (Z direction) is referred to as a lead straight portion 15 (the lead straight portion 15 of the lead pin 14a is designated as 15a, and is designated as 15a, 15b, 15c, and 15d from the front in the figure), and the portion in the direction bent 90 degrees with respect to the extending direction (X direction) is referred to as a lead bent portion 16 (the lead bent portion 16 of the lead pin 14a is designated as 16a, and is designated as 16a, 16b, 16c, and 16d from the front in the figure), and the cut end portion is referred to as a lead tip portion 17 (the lead tip portion 17 of the lead pin 14a is designated as 17a, and is designated as 17a, 17b, 17c, and 17d from the front in the figure). The lead straight portions 15 have the same length for the lead pins 14a, 14b, 14c, and 14d (this length will be described later). The lead bent portions 16 are such that the lead pins 14a and 14c are bent in the negative X direction, and the lead pins 14b and 14d are bent in the positive X direction. The bending process of the lead pins 14 is once per pin.
[0014] The bending direction of the lead bent portions 16 may be such that the lead pins 14a and 14c are bent in the positive X direction, and the lead pins 14b and 14d are bent in the negative X direction. Also, the number of lead pins 14 may be two or more, and the lead bent portions 16 may be such that all the lead pins 14 are bent in the same direction (e.g., the negative X direction), or at least one lead pin 14 may be bent in the negative X direction and at least one lead pin 14 may be bent in the positive X direction. Further, the lead bent portions 16 may have a portion bent 90 degrees with respect to the extending direction (Z direction) in a part thereof.
[0015] FIG. 4 is an enlarged view of part B in FIG. 2. The printed wiring board 3 is provided with a through-hole portion 10 that can penetrate the main body package portion 12 of the magnetic detection element 4. The illustrated left end surface 18a of the through-hole portion 10 and the illustrated left side surface 19a of the main body package portion 12 of the magnetic detection element 4 are separated by a distance 22a, and the illustrated right end surface 18b of the through-hole portion 10 and the illustrated right side surface 19b of the main body package 12 of the magnetic detection element 4 are separated by a distance 22b. The distances 22a and 22b are, for example, 1 mm. The distances 22a and 22b are the clearances in the X direction between the through-hole portion 10 and the main body package portion 12 of the magnetic detection element 4, and also have a predetermined clearance in the Y direction, for example, 1 mm. Also, the through-hole portion 10 is sized such that it does not penetrate the lead bending portion 16 of the magnetic detection element 4. The distance between the lead tip portions 17 bent in the negative X direction (the tip portions 17a and 17c of the lead pins 14a and 14c) and the lead tip portions 17 bent in the positive X direction (the tip portions 17b and 17d of the lead pins 14b and 14d), or the distance from the illustrated left end surface 18a to the illustrated right end surface 18b of the through-hole portion 10 is smaller than the X direction length of the lead bending portion 16.
[0016] The clearance in the X direction between the through-hole portion 10 of the printed wiring board 3 and the main body package portion 12 of the magnetic detection element 4 is such that when inserting the main body package portion 12 of the magnetic detection element 4 into the through-hole portion 10 of the printed wiring board 3, considering the positional deviation in the X direction between the through-hole portion 10 of the printed wiring board 3 and the main body package portion 12 of the magnetic detection element 4, it is sufficient to ensure a necessary and sufficient distance for the main body package portion 12 of the magnetic detection element 4 not to contact the through-hole portion 10 of the printed wiring board 3. The clearance in the Y direction between the through-hole portion 10 of the printed wiring board 3 and the main body package portion 12 of the magnetic detection element 4 is such that when inserting the main body package portion 12 of the magnetic detection element 4 into the through-hole portion 10 of the printed wiring board 3, considering the positional deviation in the Y direction between the through-hole portion 10 of the printed wiring board 3 and the main body package portion 12 of the magnetic detection element 4, it is sufficient to ensure a necessary and sufficient distance for the main body package portion 12 of the magnetic detection element 4 not to contact the through-hole portion 10 of the printed wiring board 3.
[0017] Figure 5 is a view of the area around the through-hole 10 in Figure 4, as seen in the negative Z direction. In Figure 5, 24 is a land for soldering the bent lead portion 16 of the magnetic detection element 4 to the printed circuit board 3. Land 24a is a land for lead pin 14a, the width of the lead bending portion 16 in the extension direction (X direction) is, for example, 2 mm, and the distance between the left end face 18a of the through hole portion 10 of the printed circuit board 3 and the right end 26a of land 24a is, for example, 0.5 mm. Land 24c is a land for lead pin 14c, with a width in the X direction of, for example, 2 mm, positioned in the more negative X direction so as not to overlap with land 24a, the distance between the left end 25a of land 24a and the right end 26c of land 24c is, for example, 0.5 mm, and the distance between the left end 25c of land 24c and the lead tip 17c of the magnetic detection element 4 is, for example, 1 mm. Land 24d is a land for lead pin 14d, with a dimension of, for example, 2 mm in the X direction, and the distance between the right end face 18b of the through-hole portion 10 of the printed circuit board 3 and the left end 25d of land 24d is, for example, 0.5 mm. Land 24b is a land for lead pin 14b, with a dimension of, for example, 2 mm in the X direction, positioned more in the positive X direction so as not to overlap with land 24d, the distance between the rightmost edge 26d of land 24d and the leftmost edge 25b of land 24b is, for example, 0.5 mm, and the distance between the rightmost edge 26b of land 24b and the lead tip 17b of the magnetic detection element 4 is, for example, 1 mm. By arranging them in this way, the misalignment in the X direction between the land 24 of the printed circuit board 3 and the lead bending portion 16 of the magnetic detection element 4 can be absorbed, enabling stable and reliable soldering.
[0018] The Y-direction width of the land 24a is, for example, 4 mm, and it is positioned so that the center of the Y-direction width of the lead bending portion 16a of the magnetic detection element 4 coincides with the center of the width of the land 24a. The Y-direction width of the land 24b is, for example, 4 mm, and it is positioned so that the center of the Y-direction width of the lead bending portion 16b of the magnetic detection element 4 coincides with the center of the width of the land 24b. The Y-direction dimension of the land 24c is, for example, 4 mm, and it is positioned so that the center of the Y-direction width of the lead bending portion 16c of the magnetic detection element 4 coincides with the center of the width of the land 24c. The Y-direction dimension of the land 24d is, for example, 4 mm, and it is positioned so that the center of the Y-direction width of the lead bending portion 16d of the magnetic detection element 4 coincides with the center of the width of the land 24d. By offsetting the positions of the lead bending portions 16 of lands 24a and 24c, and lands 24b and 24d in the extension direction (X direction) beyond the X-direction width of the land 24, the Y-direction dimension of the land 24 can be set to be larger. This allows for the absorption of Y-direction misalignment between the land 24 of the printed circuit board 3 and the lead bending portions 16 of the magnetic detection element 4, enabling stable and reliable soldering.
[0019] The distance between the left end face 18a of the through-hole 10 of the printed circuit board 3 and the right end 26a of the land 24a, and the distance between the right end face 18b of the through-hole 10 of the printed circuit board 3 and the left end 25d of the land 24d, should be such that a sufficient distance is maintained for the manufacturing of the printed circuit board. The distance between the rightmost edge 26d of land 24d and the leftmost edge 25b of land 24b, and the distance between the leftmost edge 25a of land 24a and the rightmost edge 26c of land 24c, should be sufficient to ensure the required insulation. The distance between the rightmost edge 26b of the land 24b and the lead tip 17b of the magnetic detection element 4, and the distance between the leftmost edge 25c of the land 24c and the lead tip 17c of the magnetic detection element 4, represent the amount of protrusion of the lead tip 17 relative to the land 24. However, considering the X-direction misalignment between the land 24 of the printed circuit board 3 and the lead tip 17 of the magnetic detection element 4, it is sufficient that the lead tip 17 and the land 24 are at a sufficient distance so that the protrusion amount allows for stable and reliable soldering of the land 24 and the lead bend 16. The Y-direction width of land 24 should be sufficient to ensure a necessary and adequate distance for maintaining proper insulation from other lead bending portions 16. Furthermore, if sufficient distance can be secured in the Y direction between the land 24 and the other lead bending portion 16, lands 24a and 24c, or lands 24b and 24d, may be placed at the same X-direction position without shifting either one in the X-direction.
[0020] In Figure 4, the main package portion 12 of the magnetic detection element 4 is inserted into the hole 11 of the resin case 2. At this time, the distance 23a between the left side surface 19a of the main package portion 12 of the magnetic detection element 4 and the left side surface 20a of the hole 11 provided in the resin case 2 is, for example, 0.05 mm. Furthermore, the distance 23b between the right side 19b of the main package portion 12 of the magnetic detection element 4 and the right side 20b of the hole portion 11 provided in the resin case 2 is, for example, 0.05 mm. Distances 23a and 23b represent the clearance in the X direction between the main package portion 12 of the magnetic detection element 4 and the hole portion 11 provided in the resin case 2. There is also a predetermined clearance in the Y direction, for example, 0.05 mm. Furthermore, the distance 23c between the bottom surface 19c of the main package portion 12 of the magnetic detection element 4 and the bottom surface 20c of the hole portion 11 provided in the resin case 2 is, for example, 1 mm.
[0021] The length of the lead straight section 15 in Figure 3 is set so that the position of the magnetic sensing portion 13 of the magnetic sensing element 4 in the Z direction is approximately at the center position in the Z direction of the gap 9 of the core 8 shown in Figure 4.
[0022] The clearance in the X and Y directions between the main package portion 12 of the magnetic detection element 4 and the hole portion 11 provided in the resin case 2 should be set as small as possible so that the rattle between the main package portion 12 of the magnetic detection element 4 and the resin case 2 is minimized when the main package portion 12 of the magnetic detection element 4 is inserted into the hole portion 11 of the resin case 2.
[0023] The distance 23c between the bottom surface 19c of the main package portion 12 of the magnetic detection element 4 and the bottom surface 20c of the hole portion 11 provided in the resin case 2 should be sufficient to ensure that, when inserting the main package portion 12 of the magnetic detection element 4 into the hole portion 11 of the resin case 2, the bottom surface 19c of the main package portion 12 of the magnetic detection element 4 and the bottom surface 20c of the hole portion 11 provided in the resin case 2 do not come into contact before the lower surface 21 of the lead bending portion 16 of the magnetic detection element 4 comes into contact with the land 24 of the printed circuit board 3.
[0024] Figure 6 is a perspective view showing the current sensor 1 in Embodiment 1 of the present invention, with the printed circuit board 3, magnetic detection element 4, and screw 7 disassembled. This section explains how to assemble current sensor 1. First, a printed circuit board 3, on which all components except the magnetic detection element 4 have been pre-soldered and mounted, is assembled to a resin case 2, which has the busbar 5 and core 8 (see Figure 2) fixed in place by inserts, using screws 7. Next, the main package portion 12 of the magnetic detection element 4 is passed through the through-hole portion 10 of the printed circuit board 3, so as not to come into contact with the printed circuit board 3, and inserted into the hole portion 11 of the resin case 2 along the left side 20a or right side 20b (see Figure 4) of the hole portion 11 of the resin case 2, until the lower surface 21 (see Figure 4) of the bent lead portion 16 of the magnetic detection element 4 touches the land 24 of the printed circuit board 3. Afterward, the bent lead portion 16 of the magnetic detection element 4 and the land 24 of the printed circuit board 3 are soldered together using a laser soldering device or the like.
[0025] In the current sensor 1 configured in this way, the main package portion 12 of the magnetic detection element 4 is inserted into the hole portion 11 of the resin case 2 without contacting the printed circuit board 3, by passing through the through hole portion 10 of the printed circuit board 3 which is fixed to the resin case 2 in advance. Then, the lead pins 14 of the magnetic detection element 4 are positioned and soldered on the lands 24 of the printed circuit board 3. As a result, the lead pins 14 are not deformed when the main package portion 12 of the magnetic detection element 4 is inserted into the hole portion 11 of the resin case 2, and no stress is applied to the main package portion 12 of the magnetic detection element 4, thus enabling the creation of a highly reliable current sensor 1. Furthermore, since a terminal guide plate is not used between the resin case 2 and the printed circuit board 3 to guide the lead pins 14 to the lands 24, the size of the current sensor 1 in the Z direction can be reduced, preventing cost increases due to the addition of components, and since the lead pins 14 of the magnetic detection element 4 are bent only once each, a small and inexpensive current sensor 1 can be obtained.
[0026] In the above description, the present invention was applied to a current sensor in which a core is placed around a busbar through which the current to be measured flows, the main package portion of a magnetic detection element is inserted into the gap of the core, and the current is measured by a magnetic detection element having one magnetic sensing portion. However, the present invention may also be applied to a current sensor without a core. For example, it can be applied to a current sensor that measures current by taking the difference in magnetic flux density between two points around the slit, using a method commonly used for coreless current sensors, such as the one shown in Figure 11 of Japanese Patent Application Publication No. 2022-052554, in which a slit is provided in a part of the busbar through which the current to be measured flows, penetrating in the thickness direction of the plate, the main package portion of a magnetic detection element is inserted into the slit, and the current is measured by a magnetic detection element having two magnetic sensing portions. [Explanation of Symbols]
[0027] 1 Current sensor 2. Resin case 3 Printed circuit board 4 Magnetic detection element 5 Bus Bar 6 connectors 7 screws 8 cores 9 (core) gap 10 Through-hole (of a printed circuit board) 11 (The hole in the resin case) 12 Main package section (of the magnetic detection element) 13 Magnetic sensing part (of the magnetic detection element) 14, 14a, 14b, 14c, 14d (Lead pins of the magnetic sensing element) 15, 15a, 15b, 15c, 15d Lead straight section 16, 16a, 16b, 16c, 16d Lead bending section 17, 17a, 17b, 17c, 17d Lead tip 18a Left end face (of the through-hole in the printed circuit board) 18b Right end face (of the through-hole in the printed circuit board) 19a Left side (of the main package of the magnetic detection element) 19b Right side (of the main package of the magnetic detection element) 19c (Bottom surface of the main package of the magnetic detection element) 20a Left side (of the hole in the resin case) 20b Right side (of the hole in the resin case) 20c (Bottom of the hole in the resin case) 21 Lower surface (of the lead bending portion of the magnetic detection element) 22a Clearance (between the left side of the main package of the magnetic detection element and the left end of the through-hole in the printed circuit board) 22b Clearance (between the right side of the main package of the magnetic detection element and the right end of the through-hole in the printed circuit board) 23a Clearance (between the left side of the main package of the magnetic detection element and the left side of the hole in the resin case) 23b Clearance (between the right side of the main package of the magnetic detection element and the right side of the hole in the resin case) 23c (Clearance between the bottom of the main package of the magnetic detection element and the bottom of the hole in the resin case) 24a, 24b, 24c, 24d Land 25a (leftmost pad for lead pin 14a) 25b (leftmost pad for lead pin 14b) 25c (left end of the land for 14c lead pins) 25d (leftmost pad for lead pin 14d) 26a (Right end of the land for lead pin 14a) 26b (Right end of the land for lead pin 14b) 26c (Right end of the land for lead pin 14c) 26d (the rightmost pad for lead pin 14d)
Claims
1. A resin case that holds the busbar through which the current to be measured is supplied, A detection element for detecting the current to be measured, A current sensor having a printed circuit board fixed to the aforementioned resin case and on which the detection element is mounted, The detection element has a plurality of lead pins that extend from the main package portion housing the detection element body and are bent to include a lead bending portion that is bent at approximately 90 degrees with respect to the direction of extension. The lead pins of the aforementioned detection element are characterized by being bent in opposite directions. The resin case has a hole for housing the main body package portion of the detection element, The current sensor is characterized in that the printed circuit board has a through hole through which the main package portion of the detection element passes.
2. The current sensor according to claim 1, characterized in that there are multiple detection elements.
3. The current sensor according to claim 1 or 2, wherein the printed circuit board has a plurality of lands around the through hole for soldering the lead pins of the detection element, and the positions of the bending portions of the leads of adjacent lands in the direction of extension are offset so as not to overlap with each other.