JPS6361170A - Shape of magnetic core in current sensor - Google Patents

Abstract

PURPOSE:To achieve miniaturization and to accurately detect a current, in a magnetic core, by forming a magnetic material provided with a gap so as to make the same thinner than the other magnetic material. CONSTITUTION:A copper bar 2 as a conductor through which a current to be detected is made to flow is inserted through the central part of a magnetic core 1 composed of a magnetic material having a rectangular parallelepiped shape to form an insert part 3 and the core 1 forms a surrounding magnetic path from magnetic materials 4-7 on all sides and a gap 8 is formed to the central part of the magnetic material 7 corresponding to the upper part of the core 1 in a notched form. As mentioned above, since only one gap 8 is provided to the magnetic path in the core 1, the effect of external magnetic noise on the detection of a current by a Hall element is hard to generate and a current can be accurately detected. Further, since the cross-sectional dimension T5 of the magnetic material 7 is made smaller than each of the cross-sectional dimensional T2-T4 of the other magnetic materials 4-6, the core 1 can enhance the saturation point of the flux density at the gap 8 in spite of a small size.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to the shape of a magnetic core in a current sensor used in a battery-driven vehicle or the like.

(Prior Art) Conventionally, as shown in FIGS. 4 and 5, symmetrically formed opening-shaped cores 40, 41 are arranged facing each other, and two gaps 42, 41 are formed above and below a circumferential magnetic path. There is a magnetic core 44 in which a magnetic core 43 is provided. The cross section of each part of the magnetic path is a regular square with a side length T1.

Also, as shown in FIG. 6, a magnetic core 45 in which one gap 43 is eliminated and only a gap 42 is provided for the circular magnetic path, or a cross section with a diameter T as shown in FIG.
There is one in which a gap 42 is provided in a rough magnetic core 46 having a circular shape.

When using them as a current sensor, a conductor through which a current flows is arranged in the insertion portion 47 formed at the center of each magnetic core 44, 45, 46. A magnetoelectric transducer, such as a Hall element, is arranged in the gap 42 in order to measure the magnetic flux generated in proportion to the current flowing from the conductor to the conductor and collected in each magnetic core 44.45° 46. There is.

(Problems to be Solved by the Invention) However, although the magnetic core 44 shown in FIG. 4 has good efficiency and can be miniaturized, the equivalent circuit on the magnetic circuit is as shown in FIG. two gaps 42.4
3, magnetic resistances Rm1°Rm2 are formed. Therefore, when external magnetic noise enters into the magnetic core 44 from the side surface of the magnetic core 44, the external magnetic noise flows into both the gap 42 and the gap 43 where the magnetoelectric transducer is arranged, so that the magnetoelectric transducer can measure the noise. There is a problem that the results are easily influenced by external magnetic noise.

Furthermore, in the magnetic core 45 shown in FIG. 6, the magnetic resistance Rm1 is formed only in the gap 42, as shown in FIG. Even if the external magnetic noise enters the circuit, the external magnetic noise mainly flows through the short-circuited portion provided at the bottom of the circuit, so there is an advantage that the measurement result by the magnetoelectric transducer arranged in the gap 42 is not easily influenced by the external magnetic noise. However, on the other hand, the efficiency of this magnetic core 45 is not as good as that of the magnetic core 44 shown in FIG. 4, so there is a problem that it becomes larger.

The magnetic core 46 shown in FIG. 7 not only has the same advantages and problems as the magnetic core 45, but also has the problem that it is not easy to attach to a substrate due to its shape.

Generally, as shown in FIG. 10, when the current flowing through the conductor increases, the magnetic flux density in the gap 42 reaches the saturation point 4.
9, the detection accuracy deteriorates near the upper limit of the current detection range. Further, due to temperature changes, the saturation point of the magnetic flux density may vary as shown in the saturation point 50, and the magnetic flux density may decrease as shown by the broken line. As shown in FIG. 11, it is known that in order to ensure the linearity of the magnetic flux density in the gap 42 even near the upper limit of the current detection range, it is sufficient to simply increase the size of the magnetic core.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic core that secures a predetermined current detection range, is small in size, and is less susceptible to external magnetic noise.

Structure of the Invention (Means for Solving the Problems) Therefore, the present invention has been made to solve the above problems, in which a current is passed through the center of a magnetic material formed in the shape of a rectangular parallelepiped. In addition to providing an insertion part through which the conductor is inserted, a circular magnetic path is formed by magnetic material on the four sides of the insertion part, and a gap is cut out in the magnetic material on that side, and the magnetic material is connected to the other magnetic material. It is made thinner than magnetic material.

(Function) With the above configuration, the magnetic core is made smaller because the magnetic material provided with the gap is formed thinner than other magnetic materials, and the current flowing through the conductor inserted into the insertion portion is proportional to the current flowing through the conductor. The magnetic flux generated is collected in a circular magnetic path made of magnetic material on all sides.

(Embodiment) An embodiment embodying the present invention will be described below with reference to FIGS. 1 to 3.

In the drawing, an insertion part 3 is formed in the center of a rectangular parallelepiped magnetic core 1 made of a magnetic material, into which a copper bar 2 serving as a conductor through which a current to be detected is passed is inserted. Therefore, the magnetic core 1 forms a circular magnetic path with four magnetic materials 4°, 5, 6, 7, and there is a gap in the center of the magnetic material 7 at the top of the magnetic core 1. 8 is notched.

A Hall element 10 used as a magnetoelectric conversion element is disposed on one end surface 9 of the magnetic material 7 corresponding to the gap 8. A circuit board 12 is attached to a mounting step 11 formed by cutting out the upper part of the magnetic material 7.
is provided with an integrated circuit 13 and the like that calculates the current flowing through the copper bar 2 based on the signal from the Hall element 10.

The magnetic core 1. Hall element 10. circuit board 1
A current sensor is constructed from the second class.

Moreover, by forming the mounting step portion 11 in the upper part of the magnetic core 1, each magnetic material 4. without the gap 8 is formed.
5.6 each cross-sectional dimension T2. T3°T4 are equal, and
It is larger than the cross-sectional dimension T5 of the magnetic material 7 in which the gap 8 is provided.

Note that the width T6 of the magnetic material 4.5.6.7 in the gap 8 direction is equal to the cross-sectional dimension T2. T3. The saturation point rises by making it larger than T4, but T6>2xT2 (T3
．． Since the effect becomes smaller after T4), the same width T6 is equal to the cross-sectional dimension T2.T4) in this embodiment. T3. It is provided so that it is approximately twice as large as T4.

Further, the inner corner portions of the insertion portion 3 are provided with circumferential surfaces R1 and R2 to reduce magnetic resistance and to downsize the magnetic core 1.
, R3, and R4 are provided.

In this way, in this magnetic core 1, only one gap 8 is provided with respect to the magnetic path, so that the current detection by the Hall element 10 is hardly affected by external magnetic noise, and accurate current detection can be performed. Also, the cross-sectional dimension T5 of the magnetic material 7 is the cross-sectional dimension T2 of the other magnetic materials 4, 5.6. T3. Since the magnetic core 1 is made smaller than T4, the saturation point of the magnetic flux density in the gap 8 can be made high even though the magnetic core 1 is small. Further, peripheral surfaces R1 and R2 provided at the inner corner portions of the insertion portion 3
, R3, R4 can increase the saturation point of the magnetic flux density, and also increase the width T6 of the magnetic material 4, 5.6.7 in the gap 8 direction.
is the cross-sectional dimension T2. T3. Since it is provided so as to be approximately twice T4, the saturation point of the magnetic flux density can be further increased without increasing the size of the magnetic core 1.

Therefore, this magnetic core 1 is small while ensuring a predetermined accurate current detection range, and is less susceptible to external magnetic noise.

Note that the present invention is not limited to the above-mentioned embodiments, and the inner corner portion of the insertion portion 3 has peripheral surfaces R1°R2, R3,
Any changes may be made without departing from the spirit of the invention, such as without providing R4 or by changing the width T6 of the magnetic members 4, 5, 6.7 in the gap 8 direction. .

Effects of the Invention As detailed above, the present invention has the advantage of ensuring a predetermined accurate current detection range and providing a magnetic core that is small and less susceptible to external magnetic noise. It has excellent effects when used.

[Brief explanation of the drawing]

1 to 3 show an embodiment embodying the present invention, FIG. 1 is a diagram showing the main parts of the current sensor, FIG. 2 is a front view of the magnetic core, and FIG. 3 is a diagram of the magnetic core. 4 to 7 show conventional magnetic cores, FIG. 4 is a front view of the magnetic core, FIG. 5 is a side view of the magnetic core, and FIG. 6 is a front view of the magnetic core. The reason is the front view of the rough magnetic core, Figure 8 shows the equivalent circuit of the magnetic core, Figure 9 shows the equivalent circuit of the magnetic core, and Figure 10 shows the detected current and magnetic flux density in the gap. FIG. 11 is a diagram similarly showing the detected current and the magnetic flux density in the gap. 1 is a magnetic core, 2 is a copper bar as a conductor, 3 is an insertion part,
4.5 and 6.7 are magnetic materials, and 8 is a gap.

Claims (1)

[Scope of Claims] 1. An insertion part through which a conductor through which current is passed is provided in the center of the magnetic material formed in the shape of a rectangular parallelepiped, and a circular magnetic path made of the magnetic material on the four sides of the insertion part. A magnetic core shape in a current sensor in which one of the magnetic materials is formed with a gap cut out, and the magnetic material is thinner than the other magnetic material. 2. The shape of the magnetic core in the current sensor according to claim 1, wherein the inner corner of the insertion portion is provided with a peripheral surface. 3. The shape of the magnetic core in the current sensor according to claim 1 or 2, wherein the width of the magnetic material in the gap direction is larger than the thickness of the magnetic material.