JP2013224835A - Shunt resistance type current sensor, and method for manufacturing shunt resistance type current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively mitigate stress of a connecting portion between a circuit board and a bus bar without any complicated work or restriction placed on a circuit pattern in a shunt resistance type current sensor.SOLUTION: A shunt resistance type current sensor 1 includes a connecting member 40 for electrically connecting a bus bar 10 to a circuit board 20, and the connecting member 40 is configured to have flexibility. This configuration can, even when external force is applied to the bus bar 10 and the circuit board 20 to cause deformation, absorb the stress acting on a connecting portion between the bus bar 10 and the circuit board 20 by the connecting member 40. Thereby, the stress acting on the connecting portion between the bus bar 10 and the circuit board 20 can be mitigated.

Description

  The present invention relates to a shunt resistance type current sensor and a manufacturing method thereof.

  Conventionally, in order to detect a pulse current, a large alternating current, etc., the current to be measured is passed through a shunt resistor having a known resistance value, and the voltage drop generated in this shunt resistor is detected to detect the magnitude of the current to be measured. A shunt resistance type current sensor has been proposed. For example, in a vehicle such as an automobile, a metal piece called a bus bar is sometimes used for power distribution, and a part of the bus bar corresponding to the path of the current to be measured is used as a shunt resistor. A circuit board is installed on the bus bar, and voltage detection means for detecting a voltage value is mounted on the circuit board in order to detect the magnitude of the current to be measured flowing through the bus bar.

  For example, Patent Document 1 discloses a current measuring device interposed in a path through which a current to be measured flows, and this device is based on a voltage drop amount generated between two predetermined points of a bus bar forming a current path. Measure the measured current. This apparatus includes a circuit board on which a circuit for measuring a current to be measured is provided, and the circuit board is disposed on the bus bar located between the wiring member fixing portions of the bus bar. In addition, the circuit board includes connection portions connected to the bus bar at two positions separated from each other in the length direction of the bus bar, and a substrate slit portion is provided between the board main body portion and both connection portions in the circuit board. Is formed. Similarly, a slit is formed in the bus bar.

JP 2005-188935 A

  According to the technique disclosed in Patent Document 1, the slit is provided for the purpose of relaxing the stress at the connection portion between the circuit board and the bus bar. According to this technique, the slit is provided in the circuit board. For this reason, there is a problem that complicated processing is required for the circuit board and a great restriction is imposed on the design of the circuit pattern.

  The present invention has been made in view of such problems, and the object thereof is to effectively relieve the stress at the connection portion between the circuit board and the bus bar without restricting complicated processing and circuit patterns. That is.

  In order to solve such a problem, the first invention is mounted on the circuit board, a substantially flat bus bar, a circuit board installed on the bus bar, a connection member for electrically connecting the bus bar and the circuit board, and And a voltage detecting means for detecting a voltage value applied to the circuit board via the connecting member in order to detect the magnitude of the current to be measured flowing in the bus bar. In this case, the connecting member is configured with flexibility.

  Here, in the first invention, the connecting member is preferably FPC or FFC.

  The first invention may further include a box-shaped case main body integrally formed with the bus bar by molding. In this case, the circuit board is assembled inside the case main body, It is preferable to install on the bus bar accommodated in the bottom.

  The second invention provides a method of manufacturing a shunt resistance type current sensor that detects the magnitude of a current to be measured flowing in a substantially flat bus bar. In this case, a step of connecting one end of a flexible connecting member to a circuit board on which a voltage detection means for detecting a voltage value is mounted, and a step of forming a box-shaped case body on the bus bar by molding Mounting the circuit board inside the case body and installing the circuit board on the bus bar housed in the bottom of the case body, connecting the other end of the connection member to the bus bar, and connecting the bus bar via the connection member. Electrically connecting to the circuit board.

  According to the present invention, since the stress acting between the bus bar and the circuit board can be absorbed by the connecting member, the stress acting on the connection portion between the bus bar and the circuit board can be relaxed. .

The top view which shows typically the shunt resistance type current sensor which concerns on this embodiment Side view schematically showing the shunt resistance type current sensor shown in FIG. Explanatory drawing which shows the use condition of a shunt resistance type current sensor typically Top view schematically showing the shunt resistance type current sensor shown in FIG. Sectional drawing which shows typically the shunt resistance type current sensor shown in FIG. Explanatory drawing which shows the manufacturing process of a shunt resistance type current sensor typically

  FIG. 1 is a top view schematically showing the shunt resistance type current sensor 1 according to the present embodiment, and FIG. 2 is a side view schematically showing the shunt resistance type current sensor 1 shown in FIG. The shunt resistance type current sensor 1 according to the present embodiment is used as, for example, a battery terminal, and includes a bus bar 10, a circuit board 20, and a voltage detection IC 30.

  The bus bar 10 is a substantially flat conductive member, and is made of, for example, a copper manganese alloy or a copper nickel alloy. The bus bar 10 is configured to allow a current to be measured to flow. In the present embodiment, the bus bar 10 includes a shunt resistor SR in a part thereof.

  The bus bar 10 is formed into a desired shape by press molding from a flat steel material. The bus bar 10 is formed in, for example, a substantially L shape, and through holes 11 and 12 are formed at respective tip portions. One through hole 11 functions as a hole for a battery post, and the other through hole 12 functions as a hole for a wire harness fixing screw.

  The circuit board 20 is placed on the bus bar 10. For example, when the shunt resistance type current sensor 1 is used, the circuit board 20 is mounted on the bus bar 10 by being assembled to a box-shaped case member integrally formed with the bus bar 10. A circuit pattern 21 is formed on the circuit board 20, and an end portion of the circuit pattern 21 is electrically connected to the bus bar 10 via a connection member 40 described later.

  The voltage detection IC 30 is mounted on the circuit pattern 21 formed on the circuit board 20. The voltage detection IC 30 detects the voltage value applied to the circuit board 20 in order to detect the magnitude of the current to be measured flowing through the bus bar 10 (voltage detection means). That is, the voltage detection IC 30 detects a voltage drop that occurs in the shunt resistor SR of the bus bar 10 and detects the magnitude of the current to be measured that flows to the bus bar 10 from the voltage drop.

  Note that a temperature sensor may be mounted on the surface of the circuit board 20 facing the bus bar 10, and the voltage detection IC 30 may perform correction according to the detection result of the temperature sensor. That is, the voltage detection IC 30 can correct the resistance value in the shunt resistor SR according to the temperature result so as not to detect an erroneous current value due to the influence of the resistance change due to the temperature change.

  The bus bar 10 and the circuit board 20 are electrically connected via a pair of connection members 40. The individual connection members 40 are configured to have flexibility as well as conductivity. As such a connection member 40, for example, FFC (Flexible Flat Cable) or FPC (Flexible Printed Circuits) can be used. One end 42 of the connection member 40 is connected to the end of the circuit pattern 21 on the circuit board 20. The other end 41 of the connection member 40 is connected to a predetermined position of the bus bar 10. In the pair of connection members 40, the connection position of the other end portion 41 may be anywhere as long as the voltage drop can be measured, so that the connection member 40 (the other end portion) is connected to both ends of the shunt resistor SR. 41) will be connected to each other.

  FIG. 3 is an explanatory diagram schematically showing a usage state of the shunt resistance type current sensor 1 according to the present embodiment. The bus bar 10 of the shunt resistance type current sensor 1 according to the present embodiment is used as a battery terminal. For example, the through hole 11 of the bus bar 10 is connected to the battery post 71 on the negative electrode side of the battery 70, and the other through hole 12 is connected to the wire harness W via the wire harness fixing screw 72.

  FIG. 4 is an explanatory view schematically showing a usage state of the shunt resistance type current sensor 1 shown in FIG. 3, and FIG. 5 is a sectional view schematically showing the shunt resistance type current sensor 1 shown in FIG. . When the bus bar 10 of the shunt resistance type current sensor 1 is used as a battery terminal, the main part including the circuit board 20 is accommodated in the case 50. The case 50 is made of, for example, a resin material, and includes a box-shaped case main body 51 and a flat lid portion 52.

  The case main body 51 is integrally formed with the bus bar 10, and the circuit board 20 is assembled inside the case main body 51 and installed on the bus bar 10 accommodated in the bottom of the case main body 51. On the other hand, the lid 52 is attached to the opening of the case body 51 and seals the case 50.

  FIG. 6 is an explanatory view schematically showing a manufacturing process of the shunt resistance type current sensor 1. Hereinafter, the manufacturing method of the shunt resistance type current sensor 1 will be described by using the bus bar 10 of the shunt resistance type current sensor 1 as a battery terminal.

  As a first step, a connection member 40 such as FFC or FPC is prepared, and one end 42 of the connection member 40 is connected to the circuit board 20 on which the voltage detection IC 30 is mounted as shown in FIG. . The circuit board 20 and the connection member 40 can be connected by a known method such as soldering, welding, thermocompression bonding, or the like.

  As a second step, a box-shaped case body 51 is formed on the bus bar 10 by molding as shown in FIG. The case body 51 is, for example, resinous, and is insert-molded with a predetermined resin material using a desired mold corresponding to the case body 51. As a result, the case body 51 is formed in a box shape and integrated with the bus bar 10 disposed on the bottom thereof. Note that the first step and the second step may be preceded by timing or may be simultaneous.

  As a third step, the circuit board 20 is assembled into the case body 51 as shown in FIG. For example, a groove-shaped step portion corresponding to the shape of the circuit board 20 is provided at the middle position inside the case body 51, and the circuit board 20 is held by the step portion. The case body 51 and the circuit board 20 can be fixed using a fixing method such as screwing or adhesion. As a result, the circuit board 20 is assembled to the case body 51 and installed on the bus bar 10 accommodated in the bottom of the case body 51.

  As the fourth step, the other end 41 of the connecting member 40 is connected to the bus bar 10 as shown in FIG. Thereby, the bus bar 10 and the circuit board 20 are electrically connected via the connecting member 40. The circuit board 20 and the connection member 40 can be connected by a known method such as soldering, welding, thermocompression bonding, or the like.

  And as a 5th process, the case main body 51 is sealed by attaching the cover part 52 to the opening part of the case main body 51 (refer FIG. 4). The lid 52 can be attached to the case body 51 using an attachment method such as screwing or adhesion. By sealing with the lid portion 52, it is possible to suppress a situation in which battery liquid or the like enters the case main body 51.

  As described above, the shunt resistance type current sensor 1 of the present embodiment includes the connection member 40 that electrically connects the bus bar 10 and the circuit board 20, and the connection member 40 is configured to have flexibility. ing. According to such a configuration, even when an external force is applied to the bus bar 10 or the circuit board 20 or a deformation occurs, the stress acting on the connection portion between the bus bar 10 and the circuit board 20 is connected. It can be absorbed by the member 40. Thereby, the stress which acts on the connection part (the connection member 40 itself and the connection part of the said connection member 40, the bus bar 10, and the circuit board 20) between the bus bar 10 and the circuit board 20 can be relieved.

  In addition, the bus bar 10 made of a copper alloy has a conductivity of several tens of percent of pure copper, and therefore requires a length of several mm or more to be used as a shunt resistor. For this reason, although the energy which acts on the connection part of the bus bar 10 and the circuit board 20 tends to become high, according to this embodiment, the stress which acts on the said connection part can be relieve | moderated effectively. In addition, since it is not necessary to provide a slit or the like on the circuit board 20, complicated processing is not necessary, and inconveniences such as restrictions on circuit pattern design can be suppressed.

  In the present embodiment, the connecting member 40 can use FPC or FFC. Since FPC and FFC have sufficient flexibility and also function as a wiring material, the above-described operation and effect as the connection member 40 can be effectively achieved.

  Further, in the present embodiment, the shunt resistance type current sensor 1 further includes a box-shaped case body 51 integrally formed with the bus bar 10 by molding, and the circuit board 20 is assembled inside the case body 51, It is installed on the bus bar 10 accommodated in the bottom of the case body 51. According to this configuration, since the connection member 40 has flexibility, the circuit board 20 cannot be supported on the bus bar 10 by this, but the circuit board 20 is installed on the bus bar 10 by the case body 51. Can be held in a state.

  The shunt resistance type current sensor according to the present embodiment has been described above, but the present invention is not limited to this embodiment, and various modifications can be made within the scope of the present invention. For example, the bus bar is configured to include a part of the bus bar as the shunt resistance unit, but the bus bar is not limited thereto, and the whole may be used as the shunt resistance unit. Also, the method of manufacturing such a shunt resistance type current sensor itself functions as part of the present invention.

DESCRIPTION OF SYMBOLS 1 Shunt resistance type current sensor 10 Bus bar 11 Through-hole 12 Through-hole 20 Circuit board 21 Circuit pattern 30 Voltage detection IC
40 connecting member 41, 42 end 50 case 51 case main body 52 lid 70 battery 71 battery post 72 fixing screw SR shunt resistor W wire harness

Claims (4)

A substantially flat bus bar;
A circuit board installed on the bus bar;
A connection member for electrically connecting the bus bar and the circuit board;
Voltage detecting means mounted on the circuit board and detecting a voltage value applied to the circuit board via the connection member in order to detect the magnitude of the current to be measured flowing through the bus bar;
The shunt resistance type current sensor, wherein the connecting member is configured to be flexible.   The shunt resistance type current sensor according to claim 1, wherein the connection member is an FPC or an FFC. It further has a box-shaped case body formed integrally with the bus bar by molding,
3. The shunt current sensor according to claim 1, wherein the circuit board is assembled on the inside of the case main body and installed on the bus bar accommodated in the bottom of the case main body. 4. . In the manufacturing method of the shunt resistance type current sensor for detecting the magnitude of the current to be measured flowing through the substantially flat bus bar,
Connecting one end of a flexible connecting member to a circuit board on which a voltage detecting means for detecting a voltage value is mounted;
Forming a box-shaped case body on the bus bar by molding;
Assembling the circuit board inside the case body, and installing the circuit board on the bus bar housed in the bottom of the case body;
Connecting the other end of the connecting member to the bus bar and electrically connecting the bus bar and the circuit board via the connecting member;
A method for manufacturing a shunt resistance type current sensor.

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