TW200403447A - Magnetic detection device - Google Patents

Abstract

In accordance with the object of the present invention, in a magnetic detection element using a magnetic impedance element utilizing the magnetic impedance effect, the condition to obtain a linear output and the magnitude of the magnetic field to obtain a linear output depend on the characteristic of the magnetic impedance element. Accordingly, in order to increase the detection sensitivity within a limited operation range, a method of applying the AC bias magnetic field to the magnetic impedance element is used. However, when considering application to an overload current safety device such as a thermal relay, there is a disadvantage that the current detection range is small and cannot be used in practice. To cope with this, as the bias magnetic field applied to the magnetic impedance element, firstly, a positive-negative equivalent bias magnetic field is applied and according to the obtained output polarity, the magnetic polarity of the magnetic field to be measured is judged, so as to generate a variable type bias magnetic field of a different magnetic field intensity with the magnetic field polarity effective for the judged external magnetic field polarity.

Description

200403447 (1) Description of the invention [Technical field to which the invention belongs] The present invention relates to a magnetic impedance element using a magnetic anti-effect effect, particularly a magnetic sensor and a magnetic detection device using such a magnetic detection element [Prior Art]

Conventionally, although a Hall element and a magnetoresistive element have been widely used in a magnetic detection device, it is not satisfactory from the viewpoint of detection sensitivity. Then, instead of the Hall element and the high-sensitivity magnetic detection element of the magnetoresistive element, for example, a magnetic impedance element or a disclosure using an amorphous wire disclosed in Japanese Patent Application Laid-Open No. 06-2 8 1 7 1 2 is proposed. The film shape and the like described in Japanese Patent Application Laid-Open No. 08-0 7 5 8 35.

However, no matter what type of magnetic impedance element is used, it exhibits high-sensitivity magnetic detection characteristics. However, the magnetic detection characteristics of the element itself may change, for example, with respect to the impedance of the magnetic field of an amorphous wire element, as shown in Fig. 19 It is shown that it has a non-linearity, so a linear output cannot be obtained. Therefore, the method of applying an AC bias magnetic field to the magnetic impedance element disclosed in Japanese Patent Application Laid-Open No. 9- 1 272 1 8 can be generated by the sum of the magnetic field generated by the positive and negative of the AC bias magnetic field and the external magnetic field to be measured. The difference in the amount of change in the magnetic impedance element results in a linear output with respect to the magnetic field. In response to the positive and negative polarities of the magnetic field, a magnetic impedance element 'has been developed that displays the impedance characteristics of the object, as shown in Fig. 20, which has impedance characteristics against the magnetic field. -4- (2) (2) 200403447 Figure 20 shows the operation when a bias magnetic field is applied with zero external magnetic field. ★ Explanation diagram. Fig. 20 (a) is a characteristic diagram when the external magnetic field to be measured is not sensed, and the positive and negative magnetic field strengths are applied to the magnetic impedance element as equal to% of the bias magnetic field. In Fig. 20 (a), a portion of the change in the impedance showing the change in the strength with respect to the external magnetic field strength, the change in the magnetic field strength of the bias magnetic field applied to the magnetic impedance element, and the change over time are described. # Although the impedance characteristic of the external magnetic field strength near zero does not show the characteristics of a smooth curve, the polarity of the magnetic field is at the point of change, and it generally becomes an unstable characteristic region. The white circle displayed on the impedance characteristic refers to a bias magnetic field that periodically vibrates through a rectangular wave using a positive magnetic field and a negative magnetic field, and the impedance 値 obtained from the positive and negative maximum bias magnetic fields 値 is obtained from the The voltage output from the relationship between the magnetic impedance element and the local frequency current for driving. The output voltage difference between these two points is detected. Therefore, in the case of no external magnetic field being measured, the output voltages at the two points are the same voltage, the voltage difference is zero, and the output after differential amplification is zero as shown in Figure 20 (b). In this regard, Fig. 21 is an explanatory diagram of the operation when a bias voltage is applied when an external magnetic field is measured. Fig. 21 (a) is a schematic diagram showing characteristics when a positive magnetic field of ΔH4 is sensed as an external magnetic field to be measured. The white circle displayed on the impedance characteristic refers to the impedance 根据 -5- (3) 200403447 based on the maximum value of the positive and negative magnetic fields of the bias voltage, and moves to the position of the black circle by the external magnetic field △ H4. For the two black circles obtained from the positive magnetic field side and the negative magnetic field side of the bias magnetic field using this vibration, the voltage corresponding to the black circle on the positive magnetic field side is subtracted from the voltage corresponding to the black circle on the negative magnetic field side.表示 and the direction to define the voltage polarity

Therefore, when the obtained output voltage difference (differential output) is a positive voltage Δ V4 and the measured external magnetic field Δ H2 is sensed, the measured differentially amplified output is as shown in FIG. 21 (b). If the amplification of the amplifier is A, AX △ V 4 will be obtained. As for the application examples of these technologies, the current flowing to the three-phase motor through the contactor is detected when the current exceeds the safety threshold and the current is cut off. The overload current protection device is reviewed. The conventional method is to use a bimetal switch, but it is difficult to adjust the current when the switch is in the open state, and errors may occur during long-term adjustment.

The methods to solve these problems include current detection transformers using electronic circuits, Hall elements or magnetoresistive elements. However, in addition to the low current detection sensitivity, there is also a problem that the sensing unit cannot avoid large size. [Summary of the Invention] However, the method using the aforementioned magnetic impedance element has the problems described below. First of all, in order to obtain a linear output, the change in the magnetic impedance element against the external magnetic field must be a characteristic of the positive magnetic field side and the negative magnetic field side.-6- (4) 200403447 'The magnitude of the magnetic field for linear output is due to the magnetic Characteristics of impedance elements. According to the inventor, the size of a measurable magnetic field using a test device using an AC bias magnetic field can detect a maximum frame size of about 50 times the minimum frame size for detecting the frame size. However, the current detector of the overload current protection device of the application example must be a current measurement that is 10 times or more the rated current, and there is a problem that the magnetic detection requires a detection range of hundreds of times. That is, as described above, the current detection range of the magnetic impedance element is very narrow, which has a disadvantage that it is not suitable for practical use. Then, an object of the present invention is to solve the above problems and provide a magnetic detection element with a simple configuration and a wide magnetic field measurement range. [Means for Solving the Problems] In order to solve the problems described above, the present invention employs the following configuration.

That is, the magnetic detection device described in the first patent application scope of the present invention belongs to a magnetic impedance element provided with a magnetic impedance effect; and a current application that applies a high-frequency driving current to both ends of the magnetic impedance element. Means; and a bias coil that is wound around a magnetic impedance element; and a bias current applying means that applies a low-frequency bias current to the bias coil; and a bias magnetic field that changes the strength of the magnetic field by using the low-frequency bias current and is measured externally The magnetic field is a magnetic detection device that detects an external magnetic field based on an output difference corresponding to a change in impedance of a magnetic impedance element, and is characterized in that the bias current applying means can set a variable bias magnetic field that varies in intensity over time with respect to a magnetic field. The polarity of the external magnetic field. Select the magnetic field strength of the variable bias magnetic field.

Add to the magnetic impedance element. At this time, in item 2 of the scope of patent application of the present invention, the variable bias magnetic field having different magnetic field strengths applied to the magnetic impedance element refers to a positive and negative equal-type bias magnetic field, a positive magnetic field-type bias magnetic field, and a negative magnetic field. A bias magnetic field of a positive magnetic field type, a bias magnetic field of a positive magnetic field side emphasis type, and a bias magnetic field of a negative magnetic field side emphasis type;

And the positive and negative equal-type bias magnetic field is a magnetic field that periodically generates positive and negative magnetic fields with a magnetic field of the same strength; and the positive-magnetic type bias magnetic field is that the positive and negative magnetic fields periodically generate a magnetic field with a positive polarity. Magnetic fields with different magnetic field strengths in the positive magnetic field range; The positive-bias-side-emphasized bias magnetic field is a magnetic field with a different degree of polarity and a strong magnetic field consisting of a strong positive magnetic field and a weak negative magnetic field with different magnetic field strengths that are periodically exchanged; In addition, the negative magnetic field-type bias magnetic field is a magnetic field of different magnetic field strengths generated periodically and in a negative magnetic field range with negative polarity;

And the negative magnetic field side-emphasis bias magnetic field is a magnetic field with different degrees of magnetic field polarity generated by periodic interaction to generate a strong negative magnetic field and a weak positive magnetic field. In item 3 of the scope of patent application of the present invention, the variable bias magnetic field applied to the magnetic impedance element can be set to at least one of a positive magnetic field bias type and a positive magnetic field side emphasized bias magnetic field, and a negative magnetic field. Either two types of variable bias magnetic field of the bias bias magnetic field type and the negative magnetic field side emphasized bias magnetic field type. Depending on the polarity of the external magnetic field to be measured, one of the variable bias magnetic fields is selected and applied to the magnetic impedance element. . -8- (6) 200403447 In item 4 of the scope of patent application of the present invention, the variable bias magnetic field is at least a bias magnetic field that can be set to a positive and negative equal type, a positive magnetic field type bias magnetic field, and a positive magnetic field side emphasized type. Three types of variable bias magnetic fields: one of the bias magnetic field, one of the negative magnetic field type bias magnetic field and the negative magnetic field side emphasized type bias magnetic field;

At least three variable bias magnetic fields including three types of variable bias magnetic fields can be selectively set, and the variable bias magnetic field of one of the at least three variable bias magnetic fields is used as a polarity detection means for measuring an external magnetic field. It is applied to the magnetic impedance element, and in accordance with the detection result, the type of the variable bias magnetic field is selected and applied to the magnetic impedance element.

At this time, in item 5 of the scope of patent application of the present invention, the polarity detection means of the external magnetic field to be measured is a bias magnetic field of a positive-negative type. At this time, a variable bias magnetic field and an external magnetic field to be measured are output as a voltage in accordance with the output difference of the impedance change of the magnetic impedance element, and the output is a positive voltage when the external magnetic field to be measured is a positive magnetic field, and vice versa When the measured magnetic field is a negative magnetic field, the il vector 'is a negative voltage', and the polarity of the measured magnetic field can be judged by the polarity of the output voltage. Furthermore, in item 6 of the scope of patent application of the present invention, the bias magnetic field applied to the magnetic impedance element is directed to each of the positive magnetic field side and the negative magnetic field side to randomly generate different magnetic fields that change with time, and the positive magnetic field is selected to occur. The combination of the magnetic field strengths of the magnetic field side and the negative magnetic field side, thereby becoming a positive and negative equal type bias magnetic field, a positive magnetic field side emphasized type bias magnetic field 'or the seventh item in the scope of patent application of the present invention, which can emphasize the negative magnetic field side The bias magnetic field is set. -9- (7) 200403447 In item 8 of the scope of patent application of the present invention, the variable bias magnetic field is a rectangular wave form or an alternating wave form that can include a pulse waveform.

The overload relay described in item 9 of the scope of patent application of the present invention is a device that controls the supply of multi-phase current from a power source to a load device, and is a magnetic impedance element having a magnetic impedance effect; and A current applying means for applying a high-frequency driving current to both ends of the magnetic impedance element; and a bias coil wound around the magnetic impedance element; and a bias current applying means for applying a low-frequency bias current to the bias coil; and comprising: An overload relay of a magnetic detector that detects an external magnetic field by outputting a difference between a bias magnetic field whose magnetic field strength is changed by a low-frequency bias current and an external magnetic field measured by an impedance change corresponding to an impedance change of a magnetic impedance element, is characterized by:

When the measured current 値 of the measured magnetic field occurs, in the case of the freeze current measurement area or after the device is powered on, a positive and negative equal-type bias magnetic field is applied to the magnetic impedance element, and the measured current 被 is in the overload area. In some cases, a bias of a positive magnetic field type or a negative magnetic field type having a polarity of either a positive magnetic field or a negative magnetic field, or a positive magnetic field side emphasized type or a negative magnetic field side emphasized type having a different degree of magnetic field polarity bias is applied to the magnetic impedance element. Either of the magnetic fields. In the overload relay described in Item 10 of the scope of patent application of the present invention, the bias magnetic field applied to the magnetic impedance element is directed to each of the positive magnetic field side and the negative magnetic field side to randomly generate changes over time. Select the combination of the magnetic field strengths that occur on the positive and negative magnetic fields to form a positive magnetic field-emphasized bias magnetic field, a negative magnetic field-emphasized bias magnetic field ', or a positive and negative equal bias magnetic field. -10- (8) (8) 200403447 magnetic detection element. + In the overload relay described in item 11 of the scope of patent application of the present invention, the variable bias magnetic field to be applied to the magnetic impedance element may be a rectangular wave form including a pulse waveform or an AC wave form.解决 A variable bias magnetic field using the above configuration is applied to a magnetic impedance element to solve the problem. [Embodiment] Φ An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a system configuration of a magnetic detection device according to a first embodiment of the present invention. In Fig. 1, a high-frequency current generator 3 for element driving for applying a local-frequency driving current is connected to both ends of the magnetic impedance element 1. The variable bias magnetic field coil 2 is wound around the magnetic impedance element 1, and the variable bias magnetic field coil 2 is driven by the variable bias coil power source 4. The variable bias coil power supply 4 is usually a constant voltage power supply. It is easy to change the current flowing to the variable bias magnetic field coil 2 by changing the resistance 値 in the closed circuit with the variable bias magnetic field coil. . Therefore, the load switcher 5 that changes the resistance 値 is arranged in a circuit constituted by the variable bias magnetic field coil 2 and the variable bias coil power supply 4, so that two types of variable bias having different peak 値 intensity are formed. Pressure field. When the output from the variable bias coil power supply 4 periodically and positively and negatively oscillates, the voltage will flow to the load switching section-11- (9) 200403447. The positive and negative currents 値 of the piezomagnetic coil 2 close the switches in the load switch 5 and the resistance 値 becomes smaller, so that the positive and negative currents 大 become larger. Therefore, even if the output voltage 値 from the variable bias coil power source 4 is constant and a positive and negative equal-type bias magnetic field having the same strength is formed on the positive magnetic field side and the negative magnetic field side, two different magnetic field intensities can be selectively generated. The positive and negative equal-type bias magnetic fields.

Regarding the positive and negative equalized voltage cycles generated by the variable bias coil power source 4, the microcomputer 11 can be used to synchronize the opening and closing of the switches in the load switch 5 to produce different degrees of emphasis on the magnetic field polarity. Positive magnetic field side emphasis type or negative magnetic field side emphasis type bias magnetic field.

That is, when a positive-type side-emphasis bias magnetic field occurs, when the output from the variable bias coil power source 4 is a positive voltage, the switch in the load switch 5 is closed, the resistance 値 becomes small, and the variable type When the output of the bias coil power supply 4 is a negative voltage, the switch in the load switch 5 is turned on, and the resistance 値 is increased. With this operation, the current flowing to the coil 2 for the variable bias magnetic field periodically flows out of a large positive current and a small negative current, and a strong positive magnetic field and a weak magnetic field with different magnetic field strength are periodically applied to each other. The positive magnetic field side of the negative magnetic field emphasizes the bias type magnetic field. On the other hand, the negative-field-side-emphasized bias magnetic field is a means for generating the positive-field-side-emphasized bias magnetic field. Once the voltage polarity output from the variable bias coil power source 4 and the load switch 5 are realized, The switching of the switching action corresponds to the opposite. The magnetic impedance element 1 perceives the measured external magnetic field, and then responds to the magnetic field of the sum of the bias magnetic field 値 and the external magnetic field 经 over time. Element 1 -12- (10) 200403447 changes the impedance and obtains the output voltage that changes in voltage in synchronization with the bias magnetic field. The output voltage is important because of the peak value. Therefore, only the peak value of the upper limit and the lower limit are detected by the rectifier. The two detection signals of the upper limit and the lower limit are held in the holder (the upper limit) by using the timing simultaneously with the bias magnetic field. 7 and retainer (lower limit 値) 8.

The 値 held in the holders 7 and 8 is amplified by the output difference of each 値 obtained by the differential amplifier 9, and then converted by the A / D converter 1 〇 to the analog 値 into a digital 値. Then, a microcomputer 1 1 is used. Wait to perform calculus and control.

The details are described later, but in the present invention, in order to improve the measurement accuracy, when the external magnetic field to be measured is a positive magnetic field, a variable bias magnetic field on the negative side is applied, and conversely when the external magnetic field to be measured is negative, the Variable bias magnetic field on the positive side. Therefore, the polarity of the external magnetic field to be measured is determined by the polarity detector 12 and the result is processed by the microcomputer 11 to control the load switching as described above in order to generate the selected magnetic field polarity-biased bias magnetic field. The switch in the device 5 operates. Figures 2 and 3 are diagrams illustrating the operation of a magnetic impedance element according to an embodiment of the present invention. It should be noted that descriptions of the same configurations and the same functions as those shown in Figs. 20 and 21 are omitted. Fig. 2 is an explanatory diagram of a case of sensing a positive magnetic field represented by △ Η 1 in an external magnetic field to be measured. In Figure 2 (a), since the measured external magnetic field is a positive magnetic field, the variable bias magnetic field is applied periodically and interactively for the application time. 13- (11) 200403447 Strong negative magnetic field and weak The negative magnetic field side of the positive magnetic field emphasizes the bias magnetic field. The position of the white circle on the impedance characteristics of the maximum magnetic field on the positive magnetic field side and the negative magnetic field side corresponding to the negative magnetic field-emphasized bias magnetic field will move toward the positive magnetic field until the external magnetic field △ Η 1 is displayed. Position of the black circle on the impedance characteristic of the position. Once the output voltage difference between the two black circles reaches the integration of the voltage polarity directions described in Fig. 21 (a), a positive voltage of Δ V 1 can be obtained.

Therefore, when the measured external magnetic field is sensed as Δ Η 1 of the positive magnetic field, for example, the differentially amplified output measured by the magnetic detection device shown in FIG. 1 is as shown in FIG. 2 (b). If the amplification factor of the differential amplifier 9 is A, AX Δ V1 is obtained. FIG. 3 is an explanatory diagram of a case where the measured external magnetic field to be measured is a negative magnetic field represented by ΔΗ1.

In FIG. 3 (a), since the measured external magnetic field to be measured is a negative magnetic field, a variable bias magnetic field is applied with a positive magnetic field in which a strong positive magnetic field and a weak negative magnetic field are periodically interacted with respect to the application time. Side-emphasized bias magnetic field. The position of the white circle on the impedance characteristics of the maximum magnetic field on the positive magnetic field side and the negative magnetic field side corresponding to the positive biased magnetic field side biased magnetic field will move toward the negative magnetic field until the negative external magnetic field is added— △ The position of the black circle on the impedance characteristic at the position of Η 1. The output voltage difference between these two black circles will result in a negative voltage of -Δνΐ. Therefore, when the measured external magnetic field is perceived as-△ Η 1 of the negative magnetic field, for example, the differentially amplified output measured by the magnetic detection device shown in FIG. 1 is as shown in FIG. 3 (b). The amplification of the differential amplifier 9 of -14- (12) 200403447 is A, and A x (-△ V 1) is obtained. The detailed operation when the variable bias magnetic field uses a positive magnetic field-emphasized or negative magnetic field-emphasized magnetic field. When the external magnetic field to be measured is a positive magnetic field, the negative magnetic field-emphasized bias magnetic field is used as an example. Figures 4 to 6 are used for illustration.

Figure 4 shows the result of applying a positive magnetic field to the measured magnetic field and applying a negative-field-side bias bias magnetic field. The output voltage difference is a characteristic of the magnetic field strength obtained by using a positive voltage. Figure 5 shows the opposite. The output voltage difference is a characteristic of the magnetic field strength obtained by using a negative voltage. The operation explanatory diagrams of Figs. 5 and 6 are the same as those described in Fig. 2. Fig. 6 is a characteristic diagram showing the differential output relationship with respect to the measured external magnetic field strength, and Fig. 4 and Fig. 5 show the relationship with the measured external magnetic field strength.

That is, in the case where the measured magnetic field is a positive magnetic field and a negative magnetic field-side emphasized bias magnetic field is applied, the polarity of the output voltage difference is changed by the magnetic field strength of the measured magnetic field. The magnetic field strength corresponding to △ Η 2 of the external magnetic field to be measured shown in FIG. 4 is obtained by using the characteristics of the magnetic impedance element of this embodiment and applying a bias magnetic field (negative magnetic field side emphasized bias magnetic field). Output voltage difference, and a positive voltage + ΔV 2 is obtained. When the measured external magnetic field strength is zero, the negative magnetic field side emphasized bias magnetic field indicates a characteristic equivalent to the position of the white circle displayed on the impedance characteristic. However, the external magnetic field is a magnetic field equivalent to △ Η2. When the external magnetic field is measured, the characteristic moves from the position of the white circle displayed on the impedance characteristic of -15- (13) 200403447 to the position of the black circle. The external magnetic field is two points corresponding to the black circles located in each of the positive and negative magnetic fields. The difference in output is obtained as a voltage. The differential output voltage obtained here is ΔV2 and is a positive voltage.

In contrast, when the measured external magnetic field having a magnetic field strength smaller than ΔH2 corresponding to ΔH3 shown in FIG. 5 is sensed through the magnetic impedance element, the amount of movement from the white circle position to the black circle position in the impedance characteristic becomes It is smaller than the figure 4, and because of the polarity inversion with respect to the difference between the black circles, the output voltage difference is -AV3, and it is a negative voltage. In the impedance characteristic diagram of Fig. 4 or Fig. 5, the magnetic field strength of the external magnetic field is measured, and the black circle on the impedance characteristic is on the positive magnetic field side and the negative magnetic field side of the external magnetic field intensity (horizontal axis), and is the same as the vertical The axial direction is at the same position, the obtained output voltage difference is zero, and the external magnetic field strength is measured.

With the measured external magnetic field strength as the limit, in the case of a small magnetic field strength measured external magnetic field, the differential output obtained from the output voltage difference will get a negative voltage. On the contrary, in a larger magnetic field In the case where the strength is measured by an external magnetic field, the differential output will get a positive voltage. This relationship is shown in FIG. Therefore, the differential output obtained when a negative bias magnetic field side bias bias magnetic field or a positive magnetic field bias magnetic field bias or a variable bias voltage with different degrees of emphasis of magnetic field polarity are applied is shown in FIG. 6, Since the negative becomes a positive voltage, a linear output is obtained. However, when the external magnetic field to be measured is very small, the sensitivity to the magnetic field may not be the same on the positive and negative magnetic fields of the magnetic impedance element. -16- (14) 200403447

For this reason, the measurement accuracy deteriorates, and there may be cases where a positive and negative equal-type bias magnetic field having the same strength as the positive and negative magnetic fields is used. The operation of the case where a negative magnetic field side bias type bias magnetic field or a positive magnetic field side bias type bias magnetic field with different emphasis levels of applied magnetic field polarities will be described, but the following describes the effects unique to the embodiments of the present invention.

When the measured magnetic field is a positive magnetic field, the bias magnetic field can also be a negative magnetic field. However, in the impedance characteristic, the characteristics near the zero magnetic field will cause strain and show a smooth curve characteristic. However, the impedance characteristic is as shown in Figure 20. The point where the external magnetic field strength changes the polarity of the magnetic field near zero will generally become a very unstable characteristic region. The general impedance characteristic is also shown in Figure 2.

Therefore, in order to avoid the unstable region of the impedance characteristic when the bias magnetic field is applied, when a negative magnetic field bias voltage is to be applied, a negative magnetic field in the bias magnetic field range can be applied so long as it can avoid the weak magnetic field of the unstable characteristic region. The magnetic field side emphasized type. On the contrary, when a positive magnetic field bias is to be applied, a positive magnetic field side emphasized type that becomes a bias magnetic field range can also be applied so long as a weak magnetic field of a weak intensity can be avoided in an unstable characteristic region. Fig. 7 is a diagram illustrating a method of applying a bias magnetic field according to another embodiment of the present invention, in which a variable bias magnetic field alternately generates two kinds of magnetic fields of different strengths on the positive magnetic field side and the negative magnetic field side. The variable bias magnetic field is used as a positive magnetic field to generate a weak A magnetic field and a strong C magnetic field, and a negative magnetic field is used to generate a weak B magnetic field and a strong D magnetic field. In this embodiment, periodically and sequentially Generate A magnetic field, B magnetic field, C magnetic field, D magnetic field. -17- (15) 200403447

By selecting and combining the B magnetic field and the C magnetic field with the variable bias magnetic field of the present invention to be applied to the magnetic impedance element, it becomes a positive and negative equal type bias magnetic field. When the A magnetic field and the B magnetic field are selected and combined, it is a negative magnetic field. Emphasis bias magnetic field. When C magnetic field and D magnetic field are selected and combined, it becomes a positive magnetic field. Therefore, for example, in order to obtain the variable bias magnetic field required for the control of the holders 7 and 8 using the microcomputer 11 shown in FIG. 1, when the combined magnetic field is generated, the output 値 can be held and the information can be transmitted to the differential amplifier 9. . Figures 8 and 9 are diagrams illustrating the operation of a magnetic impedance element according to another embodiment of the present invention. In this embodiment, when the impedance characteristic shows a characteristic of a smooth curve without an unstable region, the measured magnetic field is a positive magnetic field represented by Δ Η 1, and a bias magnetic field indicating a negative polarity is applied to obtain as a differential output. Example of △ V 1 1 positive voltage.

Fig. 8 is an operation diagram of a magnetic impedance element according to another embodiment when a bias magnetic field is applied with a negative magnetic field-type bias magnetic field showing a rectangular wave with respect to an application time; the same figure (a) shows a pulse-shaped rectangle (B) shows an example of a rectangular wave having a rising and falling time with respect to the application time and reaching a predetermined magnetic field strength. Fig. 9 is a diagram showing the operation of a magnetic impedance element according to another embodiment when a bias magnetic field is displayed with respect to an application time and an alternating current waveform is applied. FIG. 10 is a system configuration diagram of a magnetic detection device according to another embodiment of the present invention. In addition, the description of the same configuration and the same function described in FIG. 1 will be omitted. -18- (16) 200403447

In FIG. 10, three rows of resistors are arranged in the load switch 5a, and two of them are respectively added with switches. This open relationship is synchronized with the cycle of the voltage of the rectangular waveform or AC waveform generated by the variable bias coil power source 4 and controlled by the microcomputer 11.

The combination of opening and closing of the two switches in the load switch 5a includes the case where both switches are open, the switches are both closed, and one of the switches is open and the other one is closed. There are fourteen types and three parallel resistance states, that is, resistance 値 can be changed in four ways. Thereby, the current flowing to the variable bias magnetic field coil 2 can be set to four types with one polarity. Therefore, when the output voltage from the variable bias coil power source 4 periodically generates positive and negative voltages 値 in a rectangular wave or alternating current, the bias magnetic field applied to the magnetic impedance element 1 can be in a positive magnetic field and a negative magnetic field, respectively. Generate four magnetic fields of equal strength.

Therefore, it is possible to set four kinds of positive and negative equal-type bias magnetic fields having the same intensity of the positive magnetic field and the negative magnetic field. Furthermore, by selecting three kinds of negative magnetic fields that have absolutely different magnetic field strengths for the positive magnetic field, and changing the four types of positive magnetic fields, a total of twelve types of magnetic fields with different degrees of emphasis can be set. Side-emphasized bias magnetic field. These various types of variable bias magnetic fields can be selected and controlled by the microcomputer 11. When the DC voltage component is added to or subtracted from the output voltage of the variable bias coil power supply 4, a rectangular waveform or an AC waveform voltage with different positive and negative cycles is periodically generated, even if the resistance in the load switch 5a is not switched. It is also possible to provide a positive magnetic field side bias type bias magnetic field or a negative magnetic field side bias type bias magnetic field with different degrees of emphasis of the magnetic field polarity, and then switch the load switching -19- (17) 200403447

The resistor 値 in the device 5 a is regarded as the output voltage from the variable bias coil power supply 4. Only a rectangular waveform or an AC waveform voltage of a certain voltage 加上 is added or subtracted from the DC voltage component to generate a positive magnetic field and Various variable bias magnetic fields with different intensity ratios of negative magnetic fields. Not to mention, of course, it is possible to generate magnetic fields of various intensities randomly at each cycle by the control of the microcomputer 11.

11 and 12 are diagrams for explaining the operation of the magnetic impedance element according to another embodiment of the present invention, and belong to the same form as the diagrams described in FIGS. 2 to 5. As described above, in Figs. 2 to 6, if the method of generating a variable bias magnetic field with different degrees of emphasis of magnetic field polarity is used, a negative magnetic field-side emphasized bias magnetic field is applied when the measured magnetic field is a positive magnetic field. In contrast, when the measured magnetic field is a negative magnetic field, a positive magnetic field-side emphasized bias magnetic field is applied for explanation.

In order to decide which magnetic field of positive magnetic field side or negative magnetic field side bias type bias magnetic field with different emphasis levels of magnetic field polarity is selected, a positive and negative equal bias magnetic field is applied to the measured external magnetic field as a bias magnetic field. , So you can determine the polarity of the external magnetic field being measured. Fig. 11 is an explanatory diagram when a positive-negative equal-type bias magnetic field is applied and the measured magnetic field has Δ Η 1 which belongs to a positive magnetic field. The impedance characteristics and the positive and negative equal-type bias magnetic fields show the characteristics corresponding to the position of the white circle on the impedance characteristics of the respective positive and negative magnetic field ranges (exported), but when the measured external magnetic field perceives △ Η 1 as a positive magnetic field , The characteristic will move towards the positive magnetic field side to the equivalent of -20- (18) 200403447

The position of the black circle on the impedance characteristic obtained from the piezomagnetic field and the external magnetic field to be measured. At this time, the black circle 移动 moving from the position of the white circle on the negative magnetic field side of the impedance characteristic will pass the maximum value of the impedance characteristic and be located on the positive magnetic field side, but obtained through the output corresponding to the difference between the positions of the two black circles as voltage. The situation is the same. The differential output voltage obtained here is a positive voltage of Δ V 1 2.

Contrary to Fig. 11, Fig. 12 shows a case where a positive and negative equal bias magnetic field is applied and the measured magnetic field has-△ Η 1 which is a negative magnetic field.

In the impedance characteristics shown in FIG. 12, the characteristics also move from the position of the white circle on the impedance characteristics obtained from the positive and negative equal-type bias magnetic fields to the negative magnetic field side to the equivalent of adding the positive and negative equal-type bias magnetic fields. And the position of the black circle on the impedance characteristic measured by the external magnetic field. At this time, the characteristic of the white circle position on the impedance characteristic of the positive magnetic field side will sense the negative measured external magnetic field and move to the position of the black circle on the impedance characteristic of the negative magnetic field side. The differential output voltage obtained by the position difference is of the opposite polarity to that of the measured external magnetic field detected in Figure 11 and will give a negative voltage of ΔV 1 2. From the case where a positive and negative equal-type bias magnetic field is applied to the magnetic impedance element, the differential output voltage obtained when the measured external magnetic field is a positive magnetic field is detected, and a positive voltage is obtained. In contrast, when the detected external magnetic field is a negative magnetic field, the resulting differential output voltage will get a negative voltage. Therefore, when a positive and negative equal-type bias magnetic field is applied to the magnetic impedance element, the polarity of the detected external magnetic field can be judged by the polarity of the obtained differential output voltage. Based on the result of judging the polarity of the detected external magnetic field, when the measured external magnetic field is a positive magnetic field, the positive magnetic field side emphasized bias magnetic field shown in Figure 2 is selected. When the measured external magnetic field is a magnetic field, Figure 3 is selected. The negative magnetic field side emphasizes the bias-type magnetic field.

Furthermore, the magnetic field detection sensitivity of the magnetic impedance element can be obtained from the output of a positive magnetic field side-emphasis type or a negative magnetic field side-emphasis type bias magnetic field with different degrees of positive and negative bias magnetic fields and magnetic field polarities. For example, for the output of the external magnetic field polarity on one side of the impedance characteristic, the difference between the output voltage 値 at the positive and negative equal-type biases and the output voltage 强调 at the positive-field-side emphasized biases is calculated, and the output of a known magnetic field is calculated. A method for obtaining the magnetic field detection sensitivity of a magnetic impedance element.

For example, in the case of an electronic overload relay (thermodynamic relay), 'the measurement current is an overload region when the measurement range is at full scale 1/10 or more, but the measurement accuracy is at the full scale 1 / i. 〇 The rated current range of the electronic overload relay below is within the range of ± 5%. If the measurement current is within the range of 1/10 from full scale to ± 10%, it can be limited by the JI s specification. Therefore, a positive-negative equal-type bias magnetic field having a measurement error of about / 2, which is smaller than that of a variable-type bias magnetic field having a different degree of emphasis on magnetic field polarity, can be used in a strict-precision stop current region. Fig. 13 is a system configuration diagram of a magnetic detection device according to another embodiment of the present invention. In the thirteenth embodiment, the same components as those in the tenth embodiment are denoted by the same reference numerals, and descriptions thereof are omitted. -22- (20) (20) 200403447 The magnetic detection device system of this embodiment shown in FIG. 3 uses a magnetic detection element 100, a magnetic detector 1 〇1, a switch 14 and a current normalizer. 1 3, A / D converter 10 and microcomputer 1 1 constitute. This embodiment is a configuration for transmitting the results detected by the magnetic detection element 100a and the magnetic detector 101a to the microcomputer 11 for processing in order to detect an external magnetic field to be measured in another part. The switcher 14 is not limited to the configuration shown in FIG. 13, and it goes without saying that the switcher 14 can also be configured to switch plurally in accordance with the number of measurement locations. The output from the differential amplifier 9 selected via the switcher 14 is amplified by the current normalizer 13 corresponding to the current setting, connected to the analog input of the A / D converter 10, and the output is connected to the microcomputer 11 1 Perform control and measurement processing. The current normalizer 13 here is an amplifier that can adjust the amplification in accordance with the current setting, and uses a configuration in which the amplification setting resistor of a common operational amplifier is replaced with a variable resistor. Fig. 14 is a specific example of a system configuration of the magnetic detection device of Fig. 13 showing an embodiment of the present invention, for example, when it is applied to an electronic overload relay. In FIG. 14, R, S, and T of each phase of the power supply line 25 connected to a three-phase AC power source (not shown) are for the motor 3 0 through the three-phase contactor 20 and the power supply transformer b 1. When connected, the current detection device 10 detects each current of each phase of R, S, and T of the power supply line 25. As in this embodiment, for example, in an electronic overload relay, it is sufficient to detect only one phase lacking phase. Although the power supply transformer 51 is configured to form a two-phase -23- (21) 200403447 portion, it is not limited to The above-mentioned embodiment may be configured to be arranged in each phase. The three-phase contactor 20 has three sets of contacts 21, 22, and 23, which are directly connected to R, S, and T of each phase of the different power supply lines 25, or are connected through the primary winding of the power supply transformer 51 3 in the motor.

Each contact 2 1, 2 2, 2 3 in the three-phase contactor 20 is configured to be driven simultaneously by an electromagnetic coil 24. The electromagnetic coil 24 is connected to the microcomputer 11 in the control circuit 41 and controlled. The electronic overload relay (electronic thermal relay) 40 is constituted by a current detection device 103, a control circuit 41, and a power supply transformer 51.

The magnetic detection elements 100 of R, S, and T arranged on each phase of the power supply line 25 respectively have impedance change characteristics proportional to the current flowing to the power supply line 25, and are converted into a voltage by the magnetic detector 101. Output. The output voltage of the magnetic detector 1 obtained from the R, S, and T of each phase of the power supply line 25 is respectively selected by the switcher 14 in order, and the current normalizer 1 3, A The / D converter 10 becomes information transmitted to the microcomputer 1 1. The power supply transformer 51 is a secondary winding that is arranged on the primary winding facing a part of the power supply line 25, and is connected to a first capacitor 54 through a rectifying diode 52. The positive side of the rectifying diode 52 and A protective diode 5 3 is connected between the circuit grounds. The first capacitor 54 is connected between the positive input of the rattifier 50 and the circuit ground, and the second capacitor 55 is connected between the positive input of the voltage regulator 50 and the circuit ground. -24- (22) 200403447 A configuration in which a voltage regulator 50 is used to output a constant voltage VCC. Fig. 15 is a schematic configuration diagram showing the magnetic detection device 103 of Fig. 14 according to the embodiment of the present invention. '

The configuration is such that a fixed substrate 61 is disposed at a position perpendicular to the direction of the current flowing to the wiring 60, and a fixed magnetic detection element is disposed on the fixed substrate 61 at a position where a magnetic field can be generated around the current by the current flowing to the wiring 60. 1 00. The information detected by the magnetic detection element 100 is transmitted to the detection circuit 101 for processing, and the detection result is output. Fig. 16 is a perspective view showing a specific configuration example of the magnetic detection element section. In particular, the magnetic detection element is an embodiment using a thin-film magnetic detection element.

In FIG. 16, the device is constituted by a thin film-shaped magnetic impedance element 1 a, and a resin spool 63 is produced on the outside thereof by insert molding or the like. The coil bobbin is provided with a bobbin 锷 63a on both sides as shown in the figure, and a coil 2a is wound around a bobbin frame 63b between the bobbin 锷 63a. The coil 2a is formed by a variable bias magnetic field coil 2 to apply a bias magnetic field to the thin-film magnetic impedance element 1a and a negative return magnetic field coil 15 to apply a negative return magnetic field. Furthermore, the film-shaped magnetic resistance element 1a, the coil 2a, and the like are protected from the surrounding environment, and the constituent parts are housed in a resin case 64 made by insert molding or the like. Three terminals 62 (one total of six on both sides) extend from the resin case 64 to one side, but there are two terminals 62 to apply high-frequency current to both ends of the film-shaped magnetic resistance element 1 a. There are two terminals 62 for the current flowing into the coil 2 for the bias magnetic field, and two terminals 62- (23) 200403447 for the current flowing into the coil 15 for the negative return magnetic field. The entire structure constituted as above is the magnetic detection element 100. Since the thin film-shaped magnetic resistance element 1 a can be made into a square of about 丨 min, and the shape of the magnetic detection element 100 can be made with a square of about 5 mm, the film-shaped magnetic resistance element 1 a and the coil can be greatly reduced. 2 a magnetic resistance.

In addition, in FIG. 16, a magnetic detection element 100 having a total of six terminals is shown as an example, but generally, two terminals 62 which are basically intended to apply a high-frequency current to the magnetic impedance element are The terminal 62 in which the variable bias magnetic field coil 2 flows a current has a configuration of two terminals in total. Since the above is not limited to the total of six terminals shown in Fig. 16, the total number of terminals may be a configuration of four or more terminals. Figure 17 shows the magnetic detection element 100 shown in Figure 16 as an explanatory diagram of the installation form according to the schematic configuration diagram of Figure 15. The same figure (a) is a perspective view, and the same figure (b) is the top view. Illustration.

As shown in FIG. 17 (a), a magnetic detection element 100 is mounted on a fixed substrate 61 having a wiring 60 for introducing a current, and a magnetic beam shown by a dotted line in FIG. The configured magnetic detection element 100 determines the output sensitivity of the magnetic detection element 100. Considering the configuration of the magnetic detection element 100, the magnetic detection element 100 can adjust the output sensitivity in accordance with the magnitude of the current. Fig. 18 shows an example of a magnetic shield configuration. Fig. 18 shows the magnetic detection element shown in Fig. 17 (a) with a magnetic shield 70. Its shape is shown as an ellipse in this embodiment, but it is desirable to match the magnitude of the current. Optimized, that is, not limited to this shape-26- (24) (24) 200403447 'can also be circular, rectangular, or rectangular or polygonal with rounded corners. [Effect of Invention 1] As described above, according to the present invention, a positive magnetic field or a positive magnetic field side emphasized type (mainly a positive magnetic field side) bias magnetic field and a negative magnetic field or a negative magnetic field side emphasized type (mainly a negative magnetic field side) bias magnetic field are included. Two types. Two or more variable bias magnetic fields can be set. When the external magnetic field to be measured is a positive magnetic field, a negative magnetic field or a negative magnetic field side emphasized bias magnetic field is applied. On the contrary, the external magnetic field to be measured is a negative magnetic field. In the case, the positive magnetic field or the positive magnetic field side bias type bias magnetic field is constituted by a device having an application means, and a conventionally applied positive and negative bias magnetic field is applied, and the magnetic field operates at a point where the impedance changes greatly. The magnetic field measurement range It can be amplified to maintain the characteristic of obtaining a high sensitivity response to the magnetic field. Furthermore, the resistance in the bias magnetic field application circuit can be switched by a switch of a different type of variable bias magnetic field, so it can be implemented with a simple device.

In addition, by adding the two types of variable bias magnetic fields described above, a positive and negative equal type bias magnetic field having a positive and negative equal magnetic field range can be applied. It is constituted by a device having at least three or more variable bias magnetic field applying means. It can form a polarity detection method for measuring the external magnetic field that senses the positive and negative equal-type bias magnetic fields. It is possible to set the bias magnetic field that is most suitable for measuring the current without preparing a polar detector. It can provide a simple and inexpensive magnetic detection. Device. The sensitivity of the magnetic -27- (25) (25) 200403447 magnetic impedance element can be obtained by switching the three kinds of variable bias voltages described above, which can provide a magnetic impedance that can detect and correct the change of the environmental characteristics over time. Element detection sensitivity changes to obtain stable characteristics, and even long life and excellent magnetic detection device. Furthermore, in the electronic overload relay, a positive and negative equal-type bias magnetic field is applied when the measurement current 値 is a stop current measurement area or after the device is powered on, and when the measurement current 値 is an overload area. If one side applies a variable bias magnetic field with different degrees of emphasis on the magnetic field polarity or magnetic field polarity, neither of the small current region and the large current region with a large measurement current after the device is powered on will be measured in the case of a small measurement current. The accuracy of the measurement is reduced, and the current measurement range can be enlarged with a simple structure. [Brief Description of the Drawings] FIG. 1 is a system configuration diagram of a magnetic detection device according to an embodiment of the present invention. Fig. 2 is an explanatory diagram of a positive external magnetic field relating to the operation of a magnetic impedance element according to an embodiment of the present invention. Fig. 3 is a diagram for explaining the negative external magnetic field of the operation of the magnetic impedance element according to an embodiment of the present invention. Fig. 4 is a characteristic explanatory diagram when the operation g of the magnetic impedance element according to an embodiment of the present invention is g to clarify B 'and a positive external magnetic field is used to obtain a positive voltage output. Figure 5 is a graph showing the operation g of a magnetic impedance element according to an embodiment of the present invention, and characteristics obtained when a positive external magnetic field is used to obtain a negative voltage output -28- (26) (26) 200403447. Fig. 6 is an explanatory diagram showing the relationship between the external magnetic field intensity and the differential output according to an embodiment of the present invention. Fig. 7 is a diagram for explaining a method of applying a bias magnetic field according to another embodiment of the present invention. FIG. 8 is an illustration when a rectangular bias is applied to the operation of a magnetic impedance element according to another embodiment of the present invention. FIG. 9 is an AC-type application to the operation of a magnetic impedance element according to another embodiment of the present invention. Explanatory diagram at the time of bias. The table 10 is a system configuration diagram of a magnetic detection device according to another embodiment of the present invention. FIG. 11 is an explanatory diagram of a positive external magnetic field related to the operation of the magnetic impedance element according to another embodiment of the present invention. Fig. 12 is an explanatory diagram of a negative external magnetic field related to the operation of the magnetic impedance element according to another embodiment of the present invention. Fig. 13 is a system configuration diagram of a magnetic detection device according to another embodiment of the present invention. Fig. 14 is a configuration diagram of an electronic overload relay according to an embodiment of the present invention. Fig. 15 is a schematic configuration diagram showing a magnetic detection device according to an embodiment of the present invention. Fig. 16 is a perspective view showing a specific configuration example of a magnetic detection element unit according to an embodiment of the present invention. Fig. 17 is a diagram for explaining the mounting form of the magnetic detection element according to the embodiment of the present invention. Fig. 18 is a perspective view of a magnetic shield structure according to an embodiment of the present invention. Fig. 19 is an explanatory diagram showing a magnetic impedance characteristic of a conventional amorphous wire element. Fig. 20 is a diagram illustrating the operation of a conventional example when a bias magnetic field is applied at zero external magnetic field. Fig. 21 is a diagram illustrating the operation when a bias magnetic field is applied in a conventional example. [Description of drawing number] 1 ... magnetic impedance element, 2 ... variable bias magnetic field coil, 4 ... · variable bias coil power source, 5 ... load switch, 5a ... load switch, # 1 1 ... Microcomputer, 12 ... polarity detector, 13 ... current normalizer, 14 ... switch, 40 ... electronic load relay, '100 ... magnetic detection element, 101 ... magnetic detector, 103 magnetic detection device-30 -

Claims (1)

(1) 200403447 Patent application scope 1. A magnetic detection device, comprising: a magnetic impedance element provided with a magnetic impedance effect; and a current applying means for applying a high-frequency driving current to both ends of the magnetic impedance element; and a bias wound around the magnetic impedance element. A bias current applying means for applying a low-frequency bias current to the bias coil; and a bias magnetic field and a measured external magnetic field that change the strength of the magnetic field by using the low-frequency bias current; The magnetic detection device for detecting an external magnetic field by an output difference of an impedance change is characterized in that: the bias current applying means can set a variable bias magnetic field of a magnetic field having a different strength over time, corresponding to the polarity of the external magnetic field to be measured, and selecting the aforementioned The magnetic field strength of the variable bias magnetic field is applied to the magnetic impedance element. 2. The magnetic detection device according to item 1 of the scope of patent application, wherein the variable bias magnetic field applied to the magnetic impedance element refers to a positive magnetic field-type bias magnetic field; and a negative magnetic field-type bias magnetic field. The magnetic field side emphasized bias magnetic field and the negative magnetic field side emphasized bias magnetic field; and the positive magnetic field type bias magnetic field is a magnetic field having a positive polarity; the positive magnetic field side emphasized bias magnetic field is based on the The magnetic field composed of a strong positive magnetic field and a weak negative magnetic field with different magnetic field strengths has a magnetic field with a different degree of polarity emphasis; the negative magnetic field type bias magnetic field is a magnetic field having a negative polarity; the negative magnetic field side emphasized bias type The magnetic field is a magnetic field having a different degree of polarity emphasis, which is composed of a strong negative magnetic field and a weak positive magnetic field. -31-(2) 200403447 3. The magnetic detection device according to item 2 of the scope of patent application, wherein the variable bias magnetic field is any one of the positive magnetic field type bias magnetic field and the positive magnetic field side emphasis type bias magnetic field. And two types of variable bias magnetic fields of either the aforementioned negative magnetic field type bias magnetic field or the aforementioned negative magnetic field side emphasis type bias magnetic field; and at least two of the aforementioned two types of variable bias magnetic field may be set The variable bias magnetic field corresponds to a polarity of an external magnetic field to be measured, and one of the variable bias magnetic fields is selected and applied to the magnetic impedance element. 4. The magnetic detection device according to item 2 of the scope of patent application, comprising: a positive and negative equal type bias magnetic field. Any one of the positive magnetic field type bias magnetic field and the positive magnetic field side emphasis type bias magnetic field. One of the three types of variable bias magnetic fields of the aforementioned negative magnetic field type bias magnetic field and the negative magnetic field side emphasized bias magnetic field; and the positive and negative equal type bias magnetic fields are a positive magnetic field side and a negative magnetic field side. Are magnetic fields of the same strength; At least three of the aforementioned variable bias magnetic fields including the aforementioned three kinds of variable bias magnetic fields may be set, and one of the at least three aforementioned variable bias magnetic fields may be set as a polarity detection means for measuring an external magnetic field. The type of the variable bias magnetic field is applied to the magnetic impedance element according to the detection result, and is applied to the magnetic impedance element. 5. The magnetic detection device according to item 4 of the scope of the patent application, wherein the positive and negative equal-type bias magnetic fields are used as a polarity detection means for measuring an external magnetic field, and the positive magnetic field side emphasized type and the negative magnetic field are used. Either one of the side-emphasized bias magnetic field and one of the two types of variable bias magnetic fields of the aforementioned positive magnetic field type and -32- (3) (3) 200403447 According to the polarity of the external magnetic field to be measured specified by the detection result of the polarity detection means, any one of the variable bias magnetic fields is selected as the external magnetic field detection means. 6. The magnetic detection device described in any one of the items 1 to 5 of the scope of the patent application, where 'the' bias magnetic field applied to the aforementioned magnetic impedance element is randomly generated for each of the positive magnetic field side and the negative magnetic field side '. Different magnetic fields that change with time 'select the combination of magnetic field strengths that occur on the positive and negative magnetic field sides', thereby setting the method to be the aforementioned positive magnetic field side emphasis type or the negative magnetic field side emphasis type bias magnetic field. 7. The magnetic detection device described in item 4 or 5 of the scope of the patent application, wherein the bias magnetic field applied to the magnetic impedance element is for each of the positive magnetic field side and the negative magnetic field side to randomly generate changes with time. For the different magnetic fields, the combination of the magnetic field strengths that occur on the positive and negative magnetic fields is selected to set the method of the aforementioned positive and negative equal-type bias magnetic field. 8. The magnetic detection device according to any one of items 2 to 5 in the scope of the patent application, wherein the variable bias magnetic field generated in response to the low-frequency bias current applied to the bias coil is Rectangular wave form or AC wave form. 9. The magnetic detection device according to any one of items 2 to 5 of the scope of the patent application, wherein the variable bias magnetic field generated in response to the low-frequency bias current applied to the bias coil is Rectangular wave form or AC wave form; -33- (4) 200403447 The bias magnetic field applied to the aforementioned magnetic impedance element is for each positive magnetic field side and negative magnetic field side to randomly generate different magnetic fields that change with time and choose to occur The combination of the magnetic field strengths of the positive magnetic field side and the negative magnetic field side is set in such a manner as to become the positive magnetic field side emphasis type or the negative magnetic field side emphasis type bias magnetic field. 10. The magnetic detection device described in claim 4 or 5, wherein the variable bias magnetic field generated in response to the low-frequency bias current applied to the bias coil is a rectangular wave form or AC wave form; the bias magnetic field applied to the aforementioned magnetic impedance element is directed to the positive magnetic field side and the negative magnetic field side to randomly generate different magnetic fields that change with time, and select the combination of magnetic field strengths that occur on the positive and negative magnetic fields , So as to be set as the bias magnetic field of the aforementioned positive magnetic field side emphasis type or the aforementioned negative magnetic field side emphasis type; The bias magnetic field applied to the aforementioned magnetic impedance element is for each of the positive magnetic field side and the negative magnetic field side to randomly generate different magnetic fields that change with time. 'The combination of magnetic field strengths that occur on the positive magnetic field side and the negative magnetic field side is selected, thereby It is set so as to become the eccentric magnetic field of the aforementioned positive and negative uniform magnetic field. 1 1 · An overload relay is a device that controls the supply of multi-phase current from a power source to a load device. It is a magnetic impedance element with a magnetic impedance effect; and a high-frequency drive current is applied to both ends of the magnetic impedance element. Means for applying a current; a bias coil wound around the magnetic impedance element; and a bias current applying means for applying a low-frequency bias current to the bias coil; Intensity-34- (5) 200403447 Overload relay of a magnetic detector that detects the external magnetic field by measuring the difference between the bias magnetic field of the external magnetic field and the output difference corresponding to the impedance change of the aforementioned magnetic impedance element, characterized by:- The magnetic detector is a magnetic detection device described in item 2 of the scope of patent application. The measured current of the magnetic field to be measured occurs in the case of the rated current measurement area or after the power of the device is turned on. A positive and negative equal-type bias magnetic field, in the case where the current to be measured is an overload region, applying the positive magnetic field type or the negative magnetic field type having a polarity of either a positive magnetic field or a negative magnetic field to the magnetic impedance element, or Either the bias magnetic field of the positive magnetic field side emphasis type or the negative magnetic field side emphasis type of the magnetic field polarity with different degrees of emphasis. 12. The overload relay according to item 11 in the scope of the patent application, wherein the bias magnetic field applied to the magnetic impedance element is for each positive magnetic field side and negative magnetic field side, and randomly generates different changes over time. The magnetic field is selected from a combination of magnetic field intensities that occur on the positive and negative magnetic fields, and thereby becomes the bias magnetic field of the positive magnetic field-emphasized bias type. The mode of the magnetic field is set. 1 3. The overload relay according to item 11 or item 12 in the scope of patent application, wherein the variable bias magnetic field generated in response to the low-frequency bias current applied to the bias coil is a rectangular shape. Magnetic detection device in wave form or AC wave form. -35-