JPS6128105B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a means of flux gated magnetic field detection.

As a conventional method for detecting magnetic fields, Hall generators are not suitable for magnetic detection in places where temperature changes are large, such as inside a motor, because the detection sensitivity varies greatly with temperature. Generally speaking, the method of integrating the induced voltage of the search coil is based on the method of integrating DC or very low frequency disturbance signals, which are generated in the operational amplifier section of the integrating circuit, which reduces the S/N. It is not suitable for detecting alternating current magnetic fields, and the prior art fluxgate type magnetic field detector is suitable for detecting minute magnetic fields, but is inconvenient for strong magnetic fields such as the magnetic field inside a motor.

The present invention focuses on the characteristics of the fluxgate magnetometer and provides a means for detecting the magnetic field inside the motor by improving the structure.

FIG. 1 is an explanatory diagram of the principle of the present invention.

Hex indicates a detection element 1 consisting of a DC magnetic field to be detected, 2 a spiral magnetic body, 3 an excitation winding, and 4 a detection winding.

That is, this detection element 1 has an excitation winding 3 and a detection winding 4, which are so-called toroidal windings, extending all around the cross section of a magnetic core made by spirally winding a magnetic material 2. This is what I did.

FIG. 2 shows a means for manufacturing a spiral magnetic body 2 according to the present invention.

Usually, a hollow cylindrical body made of a non-magnetic and electrically insulating material is used as the winding frame of the spiral magnetic body. Further, the entire detection element is integrated with a resin or the like having good electrical insulation and heat resistance.

As shown in FIG.
It is aimed at detecting Hex.

In addition, the purpose is to configure in advance a sensitivity suitable for the purpose of the detector, such as for strong magnetic fields or weak magnetic fields, depending on the strength of the magnetic field Hex to be detected.

Therefore, in the configuration of the helical magnetic body 2, the helical lead angle θ is set small for a strong magnetic field and large for a weak magnetic field. Since contact between each turn of the helical magnetic material is detrimental to the magnetic field detection function, an appropriate gap G is provided between the turns.

The spiral magnetic body 2 is, for example, as shown in FIG.
It is also possible to obtain the magnetic material 2 by first making a long hollow cylindrical body 5 in which the magnetic material 2 is wound spirally over almost the entire length, and then cutting it to a desired length l. .

As the material of the spiral magnetic body 2, for example, the third
A well-known practical wound core material as shown in the figure can be used.

FIG. 4 is an electrical schematic diagram when measuring the magnetic field Hex by the detection element 1, and FIGS. 5 to 10 are diagrams illustrating its operation.

Here's how it works.

In FIG. 4, the detection element 1 is shown in a simplified manner within the dotted line.

The excitation winding 3 of the detection element 1 has both ends connected to an AC power source 6 for excitation.

Both ends and the center tap of the detection winding 4 are connected to a detection circuit consisting of a pair of rectifiers 7, 8 and resistors 9, 10, respectively, as shown.

Voltage Vd across detection terminals 11 and 12 of a pair of resistors 9 and 10 connected in series in the detection circuit
This results in a signal output corresponding to the detected magnetic field Hex.

Signal output Vd that has positive or negative polarity depending on the directionality of the detected magnetic field Hex and is proportional to the magnetic field Hex.
In order to function in such a way as to obtain Because it has a big impact,
It is necessary to adjust these values or characteristics to obtain the best combination conditions.

Now, suppose that the detection element 1 shown in FIG. 1 is used with the connections shown in FIG. 4.

When the detected magnetic field Hex is zero, the spiral magnetic body 2 operates along a symmetrical rectangular hysteresis loop 50 as shown in FIG. 5, and the detection winding 4 has a waveform as shown in FIG. 60 voltages are induced.

Here, the turns ratio n mentioned earlier, the excitation voltage
The combination of Ve, the characteristics of the rectifiers 7 and 8, etc. is such that both amplitudes of the induced voltage to the detection winding 4 are in the dead zone (-E
~+E).

Therefore, in this case when the magnetic field Hex=0, the signal output obtained through the detection circuit is Vd=0.

By the way, in the direction of the central axis of the spiral magnetic body 2,
When a constant magnetic field Hex acts, the magnetic field H along the length direction of the spiral magnetic body 2 is H=Hex·Sinθ, where the lead angle of the spiral is θ.

Here, since the lead angle θ is predetermined to an appropriate value according to the strength of the magnetic field to be detected Hex, the magnetic body 1 does not become magnetically saturated, and as shown in FIG. In response to this, it operates along an asymmetric hysteresis loop 51.

Therefore, the induced voltage in the detection winding 4 becomes an asymmetric wave including even-order harmonics, such as a curved waveform 91 in FIG. 9a.

The voltage time integral values for the positive and negative polarity sections of the voltage waveform are equal in phase.

When this voltage is detected, a signal with a magnitude exceeding the threshold level E as shown in Figure 9b is output.
Vd, that is, a curved waveform 92 is obtained.

For the same reason, when the direction of the detected magnetic field Hex is opposite to that in FIG. 4, the signal output Vd is different from the waveform 92 in FIG. The result is an inverted waveform 93.

Regarding this example, when the signal output Vd was connected to a voltmeter (not shown) and the operating characteristics were investigated, as shown in Figure 10, the detected magnetic field Hex and the detected voltage
A proportional relationship (straight line 100) is observed between Vd.

11 to 15 represent electrical schematic diagrams of second to sixth embodiments of the present invention.

In FIG. 11, the windings 3 and 4 are used as one for both excitation and detection.

In FIG. 12, in the detection element 1, both the excitation winding 3 and the detection winding 4 have their center taps pulled out, and the excitation is performed using the DC power supply 15 as the main power supply, and the transistors 13 and 1
4 is performed by switching drive, and 1
6 and 17 indicate diodes.

In FIG. 13, the detection element 1 includes a pair of auxiliary windings 18 and 19 and resistors 20 and 21 in addition to the excitation winding 3 and the detection winding 4. Excitation is performed by configuring a so-called magnetic multivibrator circuit using a DC power supply 15, and an AC power supply is not required.

Figures 14 and 15 are Figures 12 and 1, respectively.
The windings of the detection element 1 shown in FIG. 3 are used as windings 3 and 4 for both excitation and detection.

Now, FIG. 16 shows an embodiment in which the configuration of the detection element 1 is improved.

That is, two spiral magnetic bodies 2a and 2b are used in which the winding diameters are slightly different and the winding directions are opposite to each other.

One of them, for example, the smaller diameter helical magnetic body 2b is provided with a toroidal excitation winding, and this and the other helical magnetic body 2a are superimposed to form a double magnetic core, It is constructed by winding a toroidal detection winding 4.

According to the detection element 1 shown in FIG. 16, each spiral magnetic body 2a,
The magnetic flux passing through 2b interlinks with the detection winding 4 in opposite directions and cancels each other out.
The disturbance signal voltage induced in the signal can be suppressed to a low level.

This detection element 1 is shown in FIGS. 4 and 11 to 15.
Excitation and detection means similar to the connections shown can be applied.

Thus, according to the present invention, it is possible to obtain magnetic field detection that is compact, robust, has a wide usable temperature range, and suppresses the contamination of electromagnetic disturbance signals.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a conceptual diagram of the means for producing a spiral magnetic material, Fig. 3 is an explanatory diagram of the characteristics of the magnetic material, and Fig. 4 is an electrical schematic diagram of the present invention. , FIGS. 5 to 10 are explanatory diagrams of its operation, FIGS. 11 to 15 are block diagrams of other embodiments of the present invention, and FIG. 16 is a diagram showing a further improved configuration of the present invention. 1...Detection element, 2, 2a, 2b...Spiral magnetic body, 3...Excitation winding, 4...Detection winding, 5...
Hollow cylindrical body, 6... AC power supply, 7, 8, 16, 1
7...Diode, 9,10,20,21...Resistor, 11,12...Detection terminal, 13,14...Transistor, 15...DC power supply, 18,19...
Auxiliary winding.

Claims (1)

[Claims] 1. On the outer periphery of each of two hollow cylinders made of non-magnetic material having slightly different diameters, strip-shaped magnetic materials each having a rectangular hysteresis ring characteristic are spirally arranged in opposite directions to each other, and the strips are connected to each other. Two magnetic cores are formed by winding them apart and inserting a hollow cylinder with a smaller diameter into the inner periphery of a larger hollow cylinder. an excitation winding wound in the form of a toroidal winding surrounding the magnetic core; A magnetic field detector comprising: a detection winding;