JP2003215170A - Current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive current sensor easy to be assembled, and requiring no adjustment. <P>SOLUTION: In this current sensor having a core butted with a pair of core pieces comprising ferromagnetic substance to form a closed magnetic path including a magnetic gap, and an IC built-in MR element arranged inside the magnetic gap, the paired core pieces formed into U-shaped core pieces having step differences in respective open parts, respective one-side end parts are butted each other, and the other-side end parts are opposed each other so as to form the magnetic gap. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current sensor that detects a current using a coil and a magnetic sensing element.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of a conventional general current sensor, FIG. 3 (a) is a state diagram before combination of a current detection portion and a circuit board, and FIG. FIG. 3C is a diagram showing a state in which the current detection unit and the circuit board are assembled.
FIG. 4 is a diagram in which a current sensor is formed by molding the whole of FIG. 3 (b).

Here, in FIG. 3, the current sensor is 1
A magnetic core 10 having a magnetic gap at one location and a plastic folder 1 which is formed by directly winding the magnetic core.
Ceramic board 11 housed in 4 and mounted with electronic components
Attach to. For individual circuit adjustment, all the circuit elements are trimmed with a laser so that a predetermined voltage is applied in the sheet state of the ceramic substrate 11 for adjustment.

The assembly process of the conventional current sensor will be described below. In FIG. 3, first, a magnetic core 10 having a gap is wound with a winding material, and a fixing folder 1 is attached.
4 to obtain the current detector 12.

A current detecting portion 12 is attached to a ceramic substrate 11 on which a resistor is printed, and fixed with an adhesive. Insert the two lead wires of the current detector into the through-holes specified on the ceramic board, and then dip and fix them with solder. Finally, the current sensor 15 is obtained by dipping the exterior with an impregnating material.

This current sensor is used as follows. The current to be measured is connected to the product terminals A and B and is passed to the current detector. At this time, the magnetic flux generated by the electromagnetic induction action forms a closed magnetic path along the magnetic core. The magnetic flux density is detected by the magnetic sensitive element 13 in the magnetic gap in the closed magnetic circuit. As a result, a current proportional to the magnetic flux density is detected.

[0007]

However, in the conventional current sensor including the above example, the output from the magnetic sensitive element is amplified and further converted into L and H signals by the comparator circuit. Since it is necessary to individually adjust the voltage trimming, it becomes difficult to supply an inexpensive sensor considering the electronic components and the mounting state.

Further, the magneto-sensitive element used is likely to have a thermal history, and it takes time for the characteristics to stabilize. Also,
When it absorbs moisture, its characteristics change, which makes it difficult to handle.
In terms of work, there is a process of applying heat, so these properties are
This has been a cause of troublesome work in the manufacturing process such as stagnation in the process.

Further, the magnetic core is an integral one, and the method of fixing the magnetic core to the ceramic substrate is temporary fixing with an adhesive and finally fixing with a phenol resin. Since the drying is performed at a high temperature, the characteristics of the magnetic sensitive element are likely to be unstable.

It is an object of the present invention to provide a current sensor that is low in cost, easy to assemble and does not require adjustment.

[0011]

In order to solve the above technical problems, in the current sensor of the present invention, the conventional magnetic sensing element is changed to the MR element with a built-in IC. This element has L → H
The switching circuit is built-in, the gap of the magnetic core,
If the magnetic sensitivity is determined by the number of turns, reduction of peripheral circuits or
A current sensor characterized in that the number of adjustment steps can be reduced can be obtained.

Further, according to the present invention, the magnetic core is formed into an L-shaped two-divided core, the center of the winding bobbin piece is hollow, and the L-shaped core is inserted from both sides of the winding bobbin piece. A magnetic sensor is obtained in which the magnetic cores are connected and fixed by a pin structure, a rivet structure or an eyelet structure.

Further, according to the present invention, as a method of adjusting the variation of the MR element with built-in IC, by installing a thin magnetic material around the element or on the upper and lower surfaces, the variation is suppressed by the bias effect. A current sensor that can reduce man-hours can be obtained.

Further, according to the present invention, by using the case of the molded product as the pressing between the ceramic substrate and the magnetic core, the pressing can be easily carried out and the characteristic which does not adversely affect the magnetic sensitive element is stabilized. A current detector is obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A current sensor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of a current sensor according to an embodiment of the present invention. FIG. 1A is an exploded perspective view, and FIG. 1B is a perspective view of a current sensor. FIG. 2 is an explanatory view of fixing the current sensor according to the embodiment of the present invention with a resin case. 2A is a plan view of the current sensor alone, and FIG. 2B is a view showing a state in which the current sensor is fixed by a resin case.

Referring to FIG. 1, the current sensor of the present invention comprises a U-shaped core 20a, 20b made of a ferromagnetic material, a bobbin 30 provided with a winding 60, a circuit board 40, and a bias magnetic material 80.
And have. A winding 60 is wound around a cylindrical portion having a rectangular through hole on the bobbin 30, and the lead wire is directly wound around the terminal of the bobbin 30 and soldered.

The magnetic core 20 is composed of U-shaped cores 20a and 20b whose open portions have steps. First, one U-shaped core 20a is inserted into the through hole of the bobbin, and the substrate on which the MR element with a built-in IC is mounted is inserted from the opposite through hole. As a bias core, in advance around the element or
A thin magnetic material 20 is installed and placed on the upper and lower surfaces. further,
Eyelet 9 with U-shaped cores 20a and 20b in one place
No. 0 is abutted on the abutting surface, and the U-shaped cores 20a and 20b are connected by a fixing eyelet 90. Here, the fixing structure is not limited to the eyelet 90, and may be a pin structure or a rivet structure.

Further, the resin covers 50a and 50b are shaped so as to be sandwiched from both sides and have a structure that holds down the magnetic core, so that vibration resistance is improved and reliability is increased.

This current sensor is used as follows. The current to be measured is connected to the product terminals A and B and sent to the current sensor. At this time, the magnetic flux generated by the electromagnetic induction action forms a closed magnetic path along the magnetic core. The magnetic flux density is detected by the magnetic sensitive element of the magnetic gap in the closed magnetic circuit. As a result, a current proportional to the magnetic flux density is detected.

[0021]

The current detector according to the present invention has a built-in IC M
By using the R element, the number of adjustment steps can be reduced by attaching a thin plate around the element or on the upper and lower surfaces of the magnetic material for deleting the peripheral circuit and adjusting the variation of the element.

Further, since the pair of core pieces are each L-shaped, one end of each abuts each other, and the other end of each abuts each other to form a magnetic gap. There is only one place, the leakage flux is small,
It has good sensitivity. Further, since the L-shaped fixing method is performed by a pin structure, a rivet structure, and a comb structure, it is much more reliable than fixing with a conventional exterior phenol resin.

Further, by covering the whole with a resin cover, there is no need to apply heat to dry the conventional MR element, so that the MR element with a built-in IC may be adversely affected by heat or the like.
There is no. Furthermore, by fitting the resin cover from both sides, it is possible to fix the substrate and the magnetic core, which is also highly resistant to vibration.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a current sensor according to an embodiment of the present invention. FIG. 1A is an exploded perspective view, and FIG. 1B is a perspective view of a current sensor.

FIG. 2 is an explanatory view of fixing a current sensor according to an embodiment of the present invention with a resin case. 2A is a plan view of the current sensor alone, and FIG. 2B is a view showing a state in which the current sensor is fixed by a resin case.

FIG. 3 is an explanatory diagram of a conventional general current sensor. Figure 3
3A is a state diagram before the current detection unit and the circuit board are combined, FIG. 3B is a diagram showing a state in which the current detection unit and the circuit board are assembled, and FIG. The figure which formed the electric current sensor by mold-processing the whole (b).

[Explanation of symbols]

10, 20 Magnetic cores 20a, 20b (open portion has a step) U-shaped core 11 Ceramic substrate 12 Current detector 13 Magnetic sensing element 14 Folder 15 Current sensor 30 Bobbin 40 Circuit board 50a, 50b Resin cover 60 Winding 70 MR element with built-in IC 80 Magnetic material for bias 90 Eyelet

Claims (4)

[Claims] 1. A core formed by abutting a pair of core pieces made of a ferromagnetic material so as to form a closed magnetic circuit including a magnetic gap, and an IC built-in MR arranged in the magnetic gap.
In the current sensor having an element, the pair of core pieces are U-shaped cores each having an open portion with a step, each one end is abutted against each other, and each other end is opposed to each other. And forming the magnetic gap. 2. The current sensor according to claim 1, wherein the element that detects the amount of magnetism generated in the magnetic gap is an MR element with a built-in IC. 3. The current according to claim 1, wherein a magnetic material is arranged in the vicinity of the MR element with a built-in IC, and a variation in sensitivity of the MR element with a built-in IC is adjusted by utilizing a magnetic bias. Sensor. 4. The current sensor according to claim 1, wherein the substrate of the current sensor and the core having a magnetic gap are fixed by sandwiching two resin covers. Sensor.