JP3884391B2 - Electronic compass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly sensitive, small, thin, and low power consumption electronic compass that detects an orientation due to geomagnetism.
[0002]
[Prior art]
Regarding a magnetic field detection device for detecting geomagnetism, an invention using a highly sensitive MI element is disclosed in Japanese Patent Laid-Open No. 2001-296127. In the invention described in the above document, MI elements are provided on two axes, a negative feedback circuit is used, and temperature compensation is performed by a differential circuit. In the MI element, in order to detect a magnetic field fluctuation in the axial direction, a detection coil is wound in the circumferential direction of a single element composed of a magnetosensitive element coated with a gel substance and a substrate on which the magnetosensitive element is mounted.
[0003]
[Patent Document 1]
JP 2001-296127 A (pages 8 to 10, FIGS. 4 to 10)
[0004]
Further, as an electronic compass, an invention using an MI element made of an amorphous ribbon is disclosed in JP-A-11-63997. In the invention described in the above document, MI elements are provided on two axes, and a winding for applying bias magnetization is wound around the amorphous ribbon constituting each MI element to apply bias magnetization.
[0005]
[Patent Document 2]
JP-A-11-63997 (5th page, FIG. 1)
[0006]
[Problems to be solved by the invention]
On the other hand, in recent years, mobile devices including mobile phones, which are rapidly developing, require an ultra-compact, thin and power-saving electronic compass due to their portability.
In addition, the electronic compass is required to have a range in which an output voltage can be output with linearity with respect to the magnetic field strength (hereinafter referred to as a magnetic measurable range) is ± 2.7 G or more. Furthermore, when this electronic compass is used in a mobile phone or the like, it is used in various places, and the magnetic field strength may greatly exceed the magnetic field strength of ± 2.7 G, depending on the place.
[0007]
The conventional magnetic field detection apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-296127 uses the size of the conventional MI element, for example, the amorphous wire of the magnetosensitive element has a length of 3 mm and a diameter of 30 μm. The upper electrode was joined to the plate, and the detection coil and the negative feedback coil were wound on the outer periphery of the individual element in which the space between the magnetosensitive element and the substrate and the upper space of the magnetosensitive element was covered with a gel-like substance. In addition, the height is 2 mm and the length is 4 mm, and it is necessary to use at least two for detecting biaxial components, so that it is difficult to apply to small electronic devices. In particular, when it is applied to a mobile phone, it is a problem that it is as thick as 2 mm in height and as large as 48 mm ³ (capacity: 24 mm ³ / piece / axis for two axes).
[0008]
In addition, a differential circuit for calculating the difference between these two signals using two MI elements per axis for high sensitivity, improved detection accuracy, low power consumption, and downsizing as characteristics of the magnetic field detection device. And to use a negative feedback circuit. However, the operation circuit and the negative feedback circuit are inconvenient for downsizing, and the fact that a negative feedback current for always improving detection accuracy is constantly flowing has a problem that power consumption is large.
[0009]
On the other hand, the electronic compass described in JP-A-11-63997 is, for the purpose of miniaturization and precise measurement, an MI element made of an amorphous ribbon has, for example, a length of 31 mm, a width of 0.1 mm to 0.2 mm, Although a thickness of 20 mm is used, it is considered that when a winding for applying bias magnetization is wound around this MI element, the width becomes 2 to 4 mm and the thickness (height) becomes 2 to 3 mm. Further, since a bias current of several mA is constantly supplied to the winding for applying bias magnetization, power consumption increases.
[0010]
Therefore, in order to solve the above-described problems, the electronic compass has been required to satisfy a reduction in power consumption at the same time as a magnetic measurement range is wide by downsizing, thinning, and reducing the capacity.
[0011]
[Means for solving the problems and their effects]
Accordingly, as a result of intensive studies on the electronic compass, the present inventors have come up with the following configuration.
[0012]
According to a first aspect of the present invention, there is provided an electronic compass for detecting an orientation of an external magnetic field, a first magnetosensitive body made of an amorphous wire having a diameter of 30 μm or less and disposed for detecting a first axis component of the external magnetic field. A magneto-impedance sensor element with a first electromagnetic coil (hereinafter referred to as a first MI element) comprising a first electromagnetic coil having an inner diameter of 200 μm or less wound around the magnetic sensitive body through an insulator, and the external. A second magnetic sensor made of an amorphous wire with a diameter of 30 μm or less and a second electromagnetic coil with an inner diameter of 200 μm or less wound around the magnetic sensor through an insulator and disposed to detect the second axis component of the magnetic field. A magneto-impedance sensor element with a second electromagnetic coil (hereinafter referred to as second MI element), and an oscillation means for supplying a pulse current or a high-frequency current. Switch means for alternately energizing the first MI element and the second MI element, detection means for detecting an output voltage of each electromagnetic coil of the first MI element and the second MI element, It comprises an amplifier that amplifies the output voltage of the detection means.
[0013]
This electronic compass has an insulator around each of the first and second magnetosensitive bodies made of an amorphous wire having a diameter of 30 μm or less and arranged to detect the first and second axis components of the external magnetic field. The inner diameters of the first electromagnetic coil and the second electromagnetic coil wound through the wire are set to 200 μm or less. Thereby, the total height of each electromagnetic coil and the substrate holding each electromagnetic coil can be reduced to 0.7 mm or less, which is 1/3 of the conventional size. Further, the width of the substrate holding each electromagnetic coil is also 1/3 of the conventional size.
Further, preferably, by setting the inner diameter of each electromagnetic coil to 100 μm or less, the height and width can be reduced to 0.5 mm or less, and further miniaturization and thinning can be achieved.
[0014]
Further, by omitting the operation circuit and the negative feedback circuit, the electronic compass can be miniaturized and a current that always flows to the negative feedback circuit becomes unnecessary, so that a significant reduction in power consumption can be achieved. In the present invention, a winding for applying bias magnetization is not necessary, and thus no bias current is passed through the winding.
Furthermore, by providing switch means for alternately energizing the first MI element and the second MI element, it is possible to reduce power consumption and achieve even lower power consumption.
[0015]
On the other hand, in order to expand the magnetic measurable range of the electronic compass to ± 10 G, it is also possible to shorten the length of the magnetic sensitive body instead of the power consumption type negative feedback circuit. In the present invention, it is 2 mm or less. It may be 0.5 mm to 3.0 mm depending on the magnetic measurable range.
[0016]
The invention of claim 1
In the first MI element and the second MI element,
And forming along the groove surface having a vertical side surfaces of the groove formed with the electromagnetic coil to the electrode wiring board, an insulator for securing said magnetic sensitive member in between said magnetic sensitive member electromagnetic coil was Zaisa through, winding interval per unit length of the electromagnetic coil, characterized in der Rukoto below 100 [mu] m / winding.
[0017]
With the above configuration, by winding the electromagnetic coil around only the insulator around the magnetic sensitive body, the substrate for fixing the magnetic sensitive body between the magnetic coil and the magnetic coil can be omitted, and the size can be reduced. . This is because the magnetic sensitive body is held by an insulator, thereby making the substrate unnecessary.
Further, the output voltage increases by decreasing the winding interval per unit length of the electromagnetic coil and increasing the number of windings per unit length. In the present invention, the winding interval is 100 μm / wind or less, preferably 50 μm / wind or less. In the case of the same output voltage, the length of the magnetic sensitive body can be shortened, and the length of the MI element can be increased.
[0018]
The invention of claim 2
The oscillation unit, the switch unit, the detection unit, and the amplifier are formed of an integrated circuit.
With this configuration, further miniaturization can be achieved.
[0019]
The invention of claim 3
The first MI element, the second MI element, and the integrated circuit are mounted on a substrate having a width of 5 mm or less and a length of 5 mm or less.
With the above configuration, it is possible to reduce the size, reduce the thickness, and reduce the capacity.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
【Example】
Examples of the MI element of the present invention are shown in FIGS.
The substrate 1 has a width of 0.6 mm, a height of 0.4 mm, and a length of 2 mm. The magnetic sensitive body is an amorphous wire 2 having a diameter of 30 μm using a CoFeSiB alloy. The groove 11 on the substrate has a depth of 50 μm, a width of 70 μm, and a length of 2 mm. The electromagnetic coil 3 is formed by a two-layer structure of one side 31 of the coil formed on the groove surface 111 and the remaining one side coil 32 formed on the groove upper surface 112 (the upper surface 41 of the resin 4).
[0021]
One side 31 of the coil formed on the groove surface 111 is formed by depositing a conductive metal thin film constituting the coil on the entire surface of the groove surface 111 of the groove 11 formed in the longitudinal direction of the electrode wiring board 1 by vapor deposition. The conductive metal thin film portion constituting the gap is removed by a selective etching method so that the metal thin film thus formed remains spirally. That is, a vertical coil portion extends in the vertical direction on the groove side surface of the groove 11, and both lower end portions of the planar coil portion formed in the left-right direction (perpendicular to the longitudinal direction of the substrate 1) on the groove bottom surface. It is continuous with both ends.
[0022]
A silicon oxide resin layer is applied to the coil 31 formed on the groove surface 111 in order to insulate the coil 31 from the conductive amorphous wire. Next, after a conductive amorphous wire is disposed in the insulated groove 11, it is further applied so that only the upper end portion of the vertical coil portion of the groove 11 is exposed.
[0023]
A conductive metal thin film is formed on the upper surface 112 of the groove formed as described above by vapor deposition, and extends in a strip shape (corresponding to a part of one side) inclined from one upper end to the other upper end. The coil 32 is formed by removing the gap portion that becomes the insulating space by a selective etching method so that the coil 32 to be left remains.
In this way, a helical electromagnetic coil composed of the coil 31 and the coil 32 is formed. The average equivalent inner diameter (the diameter of a circle having the same area as the area formed by the height and width) is 66 μm. The winding interval per unit length of the electromagnetic coil 3 is 50 μm / wind.
[0024]
A total of four electrodes 5, an electromagnetic coil terminal 51 and a magnetosensitive terminal 52, are baked on the upper surface of the substrate. Both ends of the preceding amorphous wire 2 and both ends of the electromagnetic coil 3 are connected to the electrode 5. The MI element 10 with electromagnetic coil of the present invention has the configuration as described above. Incidentally, the size of this element is almost the same as the size of the electrode wiring board.
[0025]
Next, an electronic circuit diagram of an electronic compass using the MI element 10 is shown in FIG.
The signal generator 7 which is an oscillating means has two output terminals X and Y, and the output terminals are connected to the X-axis and Y-axis MI elements, respectively. The signal generator 7 alternately applies pulses to the MI elements on the X and Y axes in accordance with a control signal from the axis output switching circuit 6 serving as a switch means. Thereby, since the energization frequency of the two MI elements is halved, power saving can be realized.
The signal generator 7 is a pulse signal having a strength of 170 mA corresponding to 200 MHz, and the signal interval is 1 μsec. The pulse signal is input to the amorphous wire 2 of each MI element, and a voltage proportional to the external magnetic field (geomagnetism) is generated in the electromagnetic coil 3 during the input time.
In addition, it can also be set as the circuit which replaced the position of the shaft output switching circuit 6 and the signal generator 7 of a present Example.
The synchronous detection circuit 8 serving as detection means detects the voltage generated in the electromagnetic coil 3 in synchronization with the MI element energization current.
The amplifier 9 amplifies the voltage to a predetermined level and outputs it. The operations after the signal generator are alternately repeated for the X and Y axis MI elements.
[0026]
FIG. 4 shows an integrated circuit of the electronic circuit of FIG. 3 mounted on the same substrate as the MI element. From this figure, the X and Y MI elements 10 are arranged orthogonally. The electronic circuit in FIG. 3 is an integrated circuit 70. Although not shown, the size of the electronic compass 100 is 3.4 mm × 3.1 mm including the case where the electrodes are provided, and the thickness is 0.8 mm, which is very small, thin and low in capacity. is there.
[0027]
The sensor output from the circuit is shown in FIG.
The horizontal axis in FIG. 5 is the magnitude of the external magnetic field, and the vertical axis is the sensor output. The solid line is the output of the sensor of this example, and shows excellent linearity between ± 10G. This indicates that the magnetic measurable range ± 2.7 G required for the electronic compass can be achieved with a sufficient margin. As a comparison, in JP-A-2001-296127, the output of the sensor when using the circuit of this publication that does not use a negative feedback circuit and the MI element of this publication is indicated by a dotted line. Note that the output peak of the conventional example is 1. From this result, the magnetic measurable range can be expanded to ± 10 G level without using a negative feedback circuit. From this example, it is possible to obtain an unprecedented wide range of magnetic measurement, miniaturization of the MI element, miniaturization by simultaneously omitting the negative feedback coil, the negative feedback circuit, and the differential circuit, and omission of the negative feedback current. A significant reduction in power consumption by the switching means can be achieved at the same time.
[Brief description of the drawings]
FIG. 1 is a front view of an MI element according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an MI element in an embodiment of the present invention.
FIG. 3 is an electronic circuit diagram of an electronic compass using an MI element according to an embodiment of the present invention.
4 is an integrated circuit of the electronic circuit of FIG. 3, which is an embodiment of the present invention, mounted on the same substrate as the MI element.
FIG. 5 shows the characteristics of the sensor output versus the external magnetic field in an electronic compass using the MI element according to the embodiment of the present invention; the circuit of this publication that does not use a negative feedback circuit in Japanese Patent Laid-Open No. 2001-296127; FIG. 6 is a characteristic diagram of sensor output versus external magnetic field when using.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electrode board, 2 Amorphous wire, 3 Electromagnetic coil, 4 Insulating resin, 5 electrodes, 6 axis output switching circuit, 7 Signal generator, 8 Synchronous detection circuit, 9 Amplifier, 10 MI element, 111 Groove surface, 112 Groove surface , 31 One side of the electromagnetic coil, 32 The other side of the electromagnetic coil, 70 Integrated circuit, 100 Electronic compass

Claims (3)

In the electronic compass for detecting the direction of the external magnetic field,
A first magnetosensitive body made of an amorphous wire having a diameter of 30 μm or less, which is arranged to detect the first axis component of the external magnetic field, and a first magnet having an inner diameter of 200 μm or less wound around the magnetic sensor through an insulator. A magneto-impedance sensor element with a first electromagnetic coil (hereinafter referred to as a first MI element) comprising an electromagnetic coil;
A second magnetic sensor made of an amorphous wire having a diameter of 30 μm or less and a second magnetic sensor having an inner diameter of 200 μm or less wound around the magnetic sensor through an insulator and disposed to detect the second axis component of the external magnetic field. A magneto-impedance sensor element with a second electromagnetic coil (hereinafter referred to as a second MI element) comprising an electromagnetic coil;
An oscillation means for supplying a pulse current or a high-frequency current;
Switch means for energizing the first MI element and the second MI element alternately;
Detecting means for detecting an output voltage of each electromagnetic coil of the first MI element and the second MI element;
Ri Do from an amplifier for amplifying the output voltage of said detecting means,
In the first MI element and the second MI element,
And forming along the groove surface having a vertical side surfaces of the groove formed with the electromagnetic coil to the electrode wiring board, an insulator for securing said magnetic sensitive member in between said magnetic sensitive member electromagnetic coil It was Zaisa via an electronic compass winding interval per unit length of the electromagnetic coil, characterized in der Rukoto below 100 [mu] m / winding. 2. The electronic compass according to claim 1, wherein the oscillation means, the switch means, the detection means, and the amplifier are integrated circuits. The electronic compass according to claim 2, wherein the first MI element, the second MI element, and the integrated circuit are mounted on a substrate having a width of 5 mm or less and a length of 5 mm or less.

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