JPH06129855A - Electronic compass - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a compact, low power consumption, electronic orientation type that does not require rotation. In an electronic azimuth meter including a geomagnetic sensor, a drive circuit for the geomagnetic sensor, an arithmetic circuit that calculates an output signal from the geomagnetic sensor and outputs azimuth data, and a magnetic azimuth indicator, One of the magnetic sensors is one in which two elements are arranged at a relative angle, and a magnet for a magnetic offset and three or more magnetic sensors are arranged at different angles. [Effect] Since a ferromagnetic magnetoresistive element is used, the power consumption is small and the size is small. Since the bearing is estimated from the outputs of a plurality of sensors, the sensor does not have to be rotated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an azimuth indicating device utilizing geomagnetism.

[0002]

2. Description of the Related Art Conventionally, as a method of knowing the direction, there is a method of measuring the direction from the direction indicated by a magnetic needle. A lot of design constraints. As a countermeasure, Japanese Patent Laid-Open No. 63-142289 discloses an example of an electronic device with a direction sensor in which a fluxgate magnetic sensor is incorporated in a case.
In this case, since the magnetic sensor has a ring shape and occupies a considerable volume and the coil is energized for sensing, the current consumption is large and it is proposed in JP-A-62-194414 to reduce the number of measurements. Has been done.

As an improvement method thereof, Japanese Patent Application Laid-Open No. 3-2480
In Japanese Patent Laid-Open No. 09, a method is proposed in which a magnetoresistive element is used, a magnetic lens is used to increase sensitivity, and the direction is estimated from sensor outputs in two directions, X and Y. However, in this method, since the magnetic lens is used, the sensor section becomes large. Moreover, it is inconvenient because the direction cannot be estimated unless the sensor is rotated by one revolution.

As a measure against this, Japanese Patent Laid-Open No. 3-127280
In the publication, a method of providing a mechanism for rotating the sensor outside the sensor is introduced. However, this method is inevitably large and complicated.

[0005]

In the prior art of the electronic azimuth meter described above, the flux gate type occupies a large volume and consumes a large amount of power. The contents that utilize the magnetoresistive element are also large in volume because they use magnetic lenses. Moreover, since it is necessary to rotate the sensor, a rotation mechanism is also required, resulting in a large and complicated device.

An object of the present invention is to provide an electronic azimuth meter which is small in size, has low power consumption, and does not require rotation.

[0007]

The electronic compass according to the present invention comprises:
A geomagnetic sensor, a drive circuit for the geomagnetic sensor, an arithmetic circuit that calculates an output signal from the geomagnetic sensor and outputs azimuth data, and an electronic azimuth meter that includes a display unit that displays the azimuth data. A set of two magnetic elements with two relative elements arranged at a relative angle is used as a set.
The feature is that more than one set of magnetic sensors are arranged at different angles.

Further, the present invention is characterized in that a magnetoresistive element is used for the geomagnetic sensor, and a plurality of sensors are arranged concentrically with respect to a magnet magnetized radially.

Further, the geomagnetic sensor drive circuit is characterized in that it is a circuit for sequentially sampling and calculating data for a plurality of sensors.

Further, it is characterized in that a ferromagnetic magnetoresistive element is used for the geomagnetic sensor.

Further, a magnetic thin film is formed on the back surface of a magnetic sensor using a ferromagnetic magnetoresistive element on one surface of the substrate.

[0012]

【Example】

(Embodiment 1) FIG. 1 is a front view of a sensor unit according to Embodiment 1 of the present invention. FIG. 2 is a side view of FIG.
The magnetic sensor A2, the magnetic sensor B3, and the magnetic sensor C4 were arranged on the base 1 at right angles and radially. At the center of the sensor, the magnet D5 was arranged with the upper side being the S pole. The magnet A6, the magnet B7, and the magnet C8 are arranged on the outer peripheral portion of the sensor with the upper side being the N pole. The magnet applies a magnetic offset to the magnetic sensor. Since the magnetoresistive element outputs an absolute value regardless of the magnetic direction, by applying a magnetic offset, the output increases if the magnetic offset and the detected magnetic direction are equal, and the output in the opposite direction is increased. As the magnetic field becomes smaller, the direction of the detected magnetism can be recognized.

FIG. 3 shows a sensor driving circuit. Based on the potential of the magnetic sensor A14, the magnetic sensor B15 and the magnetic sensor C16 were switched by the switches 17 and 18, and the potential difference between them was amplified and output. The geomagnetism is only 0.3 Gauss and it is necessary to increase the electric amplification factor. On the other hand, in the magnetic sensor, since there is a change due to temperature, the drift when raising the amplification factor becomes a problem, so the method of differentially amplifying the potential of the magnetic sensor having the same characteristics was adopted.

When the sensor unit of FIG. 1 is rotated, each potential of the sensor ABC changes as shown in FIG. Sensor AB
Since C has its direction deviated by 90 degrees about the magnet D5, when the sensor unit is rotated, the output potential of each sensor is output with a 90 degree phase shift. When the output 22 of the sensor B is SIN (X), the output 21 of the sensor A is SIN (X + 90 degrees), and the output 23 of the sensor C is
Is SIN (X-90 degrees).

Since the amplifier circuit outputs the potential difference between the sensor B15 and the sensor C16 with the potential of the sensor A14 as a reference, when the sensor unit is rotated, the output voltage changes as shown in FIG. The output of sensor B25 is 1.41 x CO
S (X + 45 degrees). The output 26 of the sensor C is 2 × COS
(X). In this case, the output of sensor A can be interpreted as having been converted to zero.

In FIG. 1, the magnetic sensors A, B and C are spaced by 90 degrees. When considering a set of the magnetic sensor A and the magnetic sensor B, it can be considered that the X component of the external magnetism is detected by the sensor A and the Y component is detected by the sensor B. Further, in the set of the magnetic sensors B and C, it can be considered that the X component of the external magnetism is detected by the sensor B and the Y component thereof. Furthermore, there is a difference of 90 degrees between the set of magnetic sensors A and B and the set of magnetic sensors B and C.

In FIG. 6, the output value of the sensor B and the output value of the sensor C when the rotation angle of the sensor unit is zero degrees in FIG.
Output, Y = output of sensor B) and Q point (X = output of sensor B, Y = output of sensor C) are plotted to form a right-angled isosceles triangle with the side PQ as the base and the vertex of the right-angled portion is defined. It is the figure which drew the circle which passes through the P point and the Q point centering on the O point next, making it the O point. Another vertex of the right triangle can be formed so that the side PQ becomes a line of symmetry. This is the R point.

As shown in FIG. 1, since the set of sensors C and D is offset by 90 degrees counterclockwise with respect to the set of sensors A and B, P
Select the center that is counterclockwise when a 90-degree arc is drawn from point to Q. In the case of FIG. 6, the score is 0.

FIG. 7, FIG. 8 and FIG. 9 are similar methods using the output values of the sensor B and the sensor C when the sensor unit rotation angles are 90 degrees, 180 degrees and 270 degrees in FIG. It is a drawing. The angle formed by the line segment OP and the X axis in FIGS. 6 to 9 is changed by 90 degrees. That is, since the angle formed by the line segment OP and the X axis changes according to the rotation angle of the sensor, the angle formed by the sensor unit and the earth magnetic field can be estimated by calculating the angle between the line segment OP and the X axis. The direction of the N and S poles of the earth's magnetism can be known.

By this method, the direction of geomagnetism can be recognized without rotating the sensor unit.

(Embodiment 2) FIG. 10 is a front view of a sensor unit according to Embodiment 2 of the present invention. In the example of FIG. 1, the three sets of sensors are each composed of the sensor shown in FIG. In the configuration of FIG. 11, the output A is generated by the external magnetic field.
Since the output B43 decreases when 42 increases, when the difference between the output A and the output B is calculated by the electric circuit, the output twice that of the method of FIG. 1 is obtained.

FIG. 12 shows an electric circuit diagram. In the case of the circuit of FIG. 3, the sensor A14 is used as a reference and the sensor B15
The difference of the sensor C16 was output. The outputs of the sensors A, B, and C vary depending on how the magnetic offset is added, but since the electric amplification factor is large, it is necessary to output the same output without an external magnetic field. The adjustment involves manipulating the relative positions of the sensor and the magnetic offset magnet and the strength of the magnetic force of the magnet, which is a very difficult task. However, in the circuit of FIG. 12, since each sensor that is affected by the unique magnetic offset is amplified, each sensor may be individually adjusted, and thus the configuration is easy to manufacture.

(Third Embodiment) FIG. 13 is a front view of a sensor unit according to a third embodiment, and FIG. 14 is a side view thereof.
Sensor A72, sensor B7 on non-magnetic base 71
3. Sensors C74 are arranged at 90 degree intervals. A circular thin plate magnet was arranged below the base 71 and was radially magnetized.
Since the magnetic field generated by the magnet is symmetrical, this method makes it easier to adjust the relative position between the sensor and the magnet. Cost is also reduced by using only one magnet.

(Embodiment 4) FIG. 15 is a front view of a sensor unit in Embodiment 4, and FIG. 16 is a side view.
Magnetic sensor A82, magnetic sensor B8 on the glass plate 81
3. The magnetic sensor C84 is made by patterning the ferromagnetic magnetoresistive elements nickel and cobalt. On the lower surface of the glass plate, a magnetic thin film 85 made of neodymium, iron or boron
Was molded and magnetized.

According to this method, the positional relationship between the sensor and the magnetic offset can be accurately created by the photolithography technique. Also, the size of the sensor unit could be dramatically reduced.

(Embodiment 5) FIG. 17 is a front view of an example of a sensor unit in Embodiment 5, and FIG. 18 is a side view. Eight magnetic sensors were arranged in the order of magnetic sensor A92 to magnetic sensor H99 to form one sensor unit. The outputs of the eight magnetic sensors are as shown in FIG. Since the sensors are arranged at equal angles, the magnetic orientation can be estimated by comparing the curve shape and the sine curve and calculating the position where the phase is the best. The greater the number of magnetic sensors, the better the measurement angle accuracy, but the driving circuit becomes more complicated.

[0027]

As described above, the present invention has the following effects.

(1) Since the geomagnetic azimuth is estimated by calculating the outputs of three or more magnetic sensors, the azimuth can be estimated without rotating the magnetic sensors. As a result, there is no need for a mechanism for rotating the magnetic sensor, and there is no annoyance.

(2) Only one magnet is required by giving a magnetic offset to the sensor with a magnet magnetized radially.
By facilitating the relative position of the magnet and the sensor, the assemblability was improved and the size of the sensor unit could be reduced.

(3) By using a ferromagnetic magnetoresistive element for the magnetic sensor, the power consumption can be reduced, and since it is not necessary to use a magnetic lens, a small sensor unit can be obtained.

(4) By forming a magnetic sensor with a magnetoresistive element on the front surface of the substrate and forming an offset magnet with a magnetic thin film on the back surface, a very small sensor unit could be obtained. Further, since it can be processed by the photolithography technique, it is possible to manufacture a sensor unit of high quality with high accuracy.

(5) In the differential amplifier circuit of the sensor, a plurality of sensors are switched by a switch to obtain an output, and only one differential amplifier circuit is provided to simplify the circuit. We were able to reduce costs and power consumption.

[Brief description of drawings]

FIG. 1 is a front view of a sensor unit according to a first embodiment of the present invention.

FIG. 2 is a side view of the sensor unit according to the first embodiment of the present invention.

FIG. 3 is a drive electric circuit diagram of the sensor unit according to the first embodiment of the present invention.

FIG. 4 is an output diagram of each sensor element according to the first embodiment of the present invention.

FIG. 5 is an output diagram of the differential amplifier circuit according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of an orientation estimation method according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of an orientation estimation method according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram of an orientation estimation method according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram of an orientation estimation method according to the first embodiment of the present invention.

FIG. 10 is a front view of the sensor unit according to the second embodiment of the present invention.

FIG. 11 is an explanatory diagram of a sensor element according to the second embodiment of the present invention.

FIG. 12 is a block diagram of a differential amplifier circuit according to a second embodiment of the present invention.

FIG. 13 is a front view of a sensor unit according to a third embodiment of the invention.

FIG. 14 is a side view of the sensor unit according to the third embodiment of the present invention.

FIG. 15 is a front view of the sensor unit according to the fourth embodiment of the present invention.

FIG. 16 is a side view of the sensor unit according to the fourth embodiment of the present invention.

FIG. 17 is a front view of the sensor unit according to the fifth embodiment of the present invention.

FIG. 18 is a side view of the sensor unit according to the fifth embodiment of the present invention.

FIG. 19 is an explanatory diagram of an orientation estimation method according to the fifth embodiment of the present invention.

[Explanation of symbols]

1, 31, 71 Base 2, 14, 32, 54, 72, 82 Sensor A 3, 15, 33, 55, 73, 83 Sensor B 4, 16, 34, 56, 74, 84 Sensor C 5, 35 Magnet D 6,36 Magnet A 7,37 Magnet B 8,38 Magnet C 9,63 Switch control circuit 10,11,12,13 Operational amplifier 17,18 Switch 19 Inversion element 20,64 Arithmetic circuit 21 Sensor A
Output 22, 25 Sensor B
Output 23, 26 Sensor C
Output 24, 27, 101 Output voltage 25, 28 Sensor unit rotation angle 40 Power supply voltage 41 Ground 42 Output A 43 Output B 44 Magnetic offset vector 50, 51, 52, 53 Operational amplifier 57, 58, 59, 60 Switch 61, 62 Switch 64 Arithmetic Circuit 75 Magnet 81 Glass Plate 85 Magnetic Thin Film 91 Base 92 Magnetic Sensor A 93 Magnetic Sensor B 94 Magnetic Sensor C 95 Magnetic Sensor D 96 Magnetic Sensor E 97 Magnetic Sensor F 98 Magnetic Sensor G 99 Magnetic Sensor H 100 Magnet 101 Output Voltage 102 Sensor symbol

Claims (5)

[Claims] 1. An electronic azimuth meter comprising a geomagnetic sensor, a drive circuit for the geomagnetic sensor, an arithmetic circuit for computing an output signal from the geomagnetic sensor and outputting azimuth data, and a display section for displaying the azimuth data. An electronic azimuth meter characterized in that two sets of directional magnetic resistance elements are arranged at a relative angle and one set is a set of three or more sets of geomagnetic sensors. 2. A magnetoresistive element is used for the geomagnetic sensor,
The electronic azimuth meter according to claim 1, wherein a plurality of sensors are arranged concentrically with respect to a magnet magnetized radially. 3. The electronic azimuth meter according to claim 1, wherein the geomagnetic sensor drive circuit is a circuit for sequentially sampling and calculating data for a plurality of sensors. 4. The electronic compass according to claim 1, wherein a ferromagnetic magnetoresistive element is used for the geomagnetic sensor. 5. An electronic azimuth meter using a geomagnetic sensor in which a magnetic thin film is formed on the back surface of a magnetic sensor in which ferromagnetic magnetoresistive elements are arranged on one surface of a substrate.