JP2932079B2 - Geomagnetic sensor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a geomagnetic sensor device, and more particularly to a geomagnetic sensor device that detects geomagnetism using a magnetoresistive element.

[Prior Art] As is well known, the direction and size of geomagnetism are constant on the surface of the earth, and have conventionally been used as physical indices of moving bodies or physical information such as crustal surveys.

In recent years, geomagnetic detection devices for detecting geomagnetism have been used as a device for supplying a reference direction of an operation system in an automobile or the like. What is stable is required.

By the way, as a conventional sensor for detecting geomagnetism,
For example, those described in JP-B-53-19214 can be mentioned.

In this magnetic sensor, a magnetic sensing element for detecting terrestrial magnetism is opposed to and sandwiched by two magnetic flux converging portions (ferromagnetic materials) to form an integrated magnetic sensor, and the same magnetic sensors are arranged orthogonally to each other. It is formed.

Here, regarding the form of this sensor, since two magnetic flux concentrating parts, which are much larger than the magneto-sensitive element, are arranged in a direction in which their end faces face each other, the overall shape of the sensor is 4
It largely depends on the shape and arrangement of the magnetic flux concentrating portions.

In this conventional example, a Hall element or the like is used as the magneto-sensitive element, and the direction of the terrestrial magnetism is determined based on each output of the element.

Regarding the geomagnetic sensor, in addition to the above,
58-30174 and Japanese Utility Model Publication No. 58-5930.

[Problems to be Solved by the Invention] However, in the above-described conventional magnetic sensor, as described above, the overall size of the sensor depends on the size of the four magnetic flux concentrating portions, and In view of the function, there is a certain limit in reducing the shape of the sensor itself, and there is a technical problem that it is difficult to reduce the size of the sensor.

In particular, when such a sensor is arranged in an automobile or the like, its mounting position is limited due to its size. For example, there is a problem that the sensor can be installed only on the ceiling portion of the vehicle. Was eagerly awaited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a small and lightweight geomagnetic sensor.

[Means for Solving the Problems] In order to achieve the above object, a geomagnetic sensor device according to the present invention includes a sensor substrate, and two magnetic sensors arranged on the sensor substrate with their maximum sensitivity directions orthogonal to each other; Wherein each of the magnetic sensors includes a magnetic detector having therein a magneto-resistive element and a bias magnet for applying a bias magnetic field to the magneto-resistive element, and one magnetic field having a magnetic focusing end joined to the magnetic detector. And a bias magnet is provided for each of the magnetic detectors, and each of the magnetic sensors has only one of the magnetic lenses. Further, the magnetic sensors are provided on both sides of the sensor substrate, and the magnetic lenses are overlapped with each other via the sensor substrate.

[Operation] According to the above configuration, geomagnetism is focused by the magnetic lens and detected by the magnetoresistive element. In this case, since the two magnetic sensors are arranged orthogonally to each other, the geomagnetic detection is performed separately for two orthogonal components.

EXAMPLES Hereinafter, preferred examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a geomagnetic sensor device according to the present invention, and FIG. 1 (A) shows the device as viewed from above, and FIG.
FIG. 2 shows a diagram viewed from the horizontal.

In the figure, an X sensor 12 and a Y sensor 14 for detecting geomagnetism (magnetic flux) are arranged on both sides of a sensor substrate 10 with their directions orthogonal to each other. Here, the substrate 10 is formed of a paramagnetic material such as plastic or aluminum.

The X sensor 12 and the Y sensor 14 perform detection by dividing the geomagnetism into two orthogonal components (X, Y). Has its detection directivity in the plane direction of the substrate 10.

The X sensor 12 and the Y sensor 14 are provided with magnetic lenses 16 and 18 for efficiently concentrating the magnetic flux of terrestrial magnetism and their magnetic flux focusing ends 16a and 18a.
, And detectors 20 and 22 respectively joined. Here, the magnetic lenses 16 and 18 are made of permalloy, Fe-Ni
It is made of a ferromagnetic material having a high magnetic permeability and a small coercive force, such as an alloy, and has a maximum magnetic flux converging rate on a central axis connecting the midpoints of the converging ends 16a, 18a and the midpoints of the wide ends 16b, 18b.

It should be noted here that the sensor device of the present embodiment uses only one magnetic lens for each of the detectors 20 and 22,
Further, since the sensors 12 and 14 are superimposed via the substrate 10, they are formed to be smaller and lighter than at least two magnetic lenses as compared with the above-described conventional device. The decrease in the magnetic detection capability due to the change of the number of magnetic lenses from two to one improves the sensitivity of the detectors 20 and 22 including the magnetoresistive element for detecting the magnetic field (magnetic field), and solves the problem. Has been made.

Next, the circuit configuration of the detectors 20 and 22 will be described with reference to FIG.

A bridge circuit is formed inside the detector 20 and the detector 22. In FIG. 2, MR1 to MR8 are magnetoresistive elements. Each bridge circuit is supplied with a constant current from constant current sources 24 and 26, and the output of each bridge is connected to terminals B1 and B2.
(Y sensor 14) and differential amplifiers A1 and A2 via E1 and E2 (X sensor 12), respectively.

That is, an unbalance occurs in the resistance ratio in each bridge circuit, and the voltage generated between the output terminals of the bridge circuit due to the imbalance is amplified in the differential amplifiers A1 and A2, and the change in the resistance value of the magnetoresistive elements MR1 to RM8 is measured. It is obtained as a voltage change. In the present embodiment, the bridge circuit is formed in consideration of temperature compensation of the magnetoresistive element, but the detector can be formed by forming a bridge circuit instead of forming a bridge circuit and performing a predetermined correction instead.

FIG. 3 shows the X sensor 12 and the Y sensor shown in FIG.
14 are shown, and the geomagnetic field _BE is measured as follows.

Assuming that the direction of the earth's magnetic field is _BE and the angle between _BE and the central axis of the X sensor 12 is θ, the output voltages V _Y and V _X of the amplifiers A1 and A2 are H , V _Y = k ₁ Hsinθ, expressed in relation to _{V X = k 2 Hcosθ (k} 1, k 2 is a constant). Therefore, this output V
_Y, it is possible to measure the orientation by the polarity and the voltage ratio of V _X.

For reference, FIG. 4 shows each output V _Y , when this sensor device is rotated 360 ° in the horizontal component plane of the earth's magnetic field.
It shows a correlation graph of V _X. As is clear from the figure, a stable output is obtained for both voltages V _Y and V _X in any direction. Then, based on this output characteristic, the calculation of the azimuth is easy, and for example, a microcomputer may be provided inside the substrate 10 to calculate the same.

 Next, the detector will be described with reference to FIG.

This detector 100 is used for the detectors 20 and 22 in the sensor device of the present embodiment shown in FIG.

In the drawing, reference numeral 102 denotes an element substrate, and magnetoresistive patterns 104a, 104b, 104c, 104 each formed of a ferromagnetic thin film on a substrate such as glass.
d is patterned to form a bridge circuit.
FIG. 6 shows an equivalent circuit thereof.

Then, the signal of the bridge circuit is input / output at an electrode 106 provided on the substrate, and further connected to the outside via a lead clip 110 electrically connected to the electrode 106. That is, a current flows from the terminals 110a to 110b, and a voltage change due to a difference in the resistance ratio when an external magnetic field is applied is detected between the lead clip terminals 110c and 110d.

The bias magnet 108 joined to the lower part of the element substrate 102
A bias magnetic field is applied to the magnetoresistive pattern 104. The operation of the bias magnetic field will be described later.

The above-described element substrate 102, bias magnet 108, and lead clip 110 form a detection head 112 by turning a resin mold. In the sensor device of the present embodiment, the focusing end of the magnetic lens 16 or 18 is joined to one of the surfaces of the detector 100 opposite to the surface on which the lead clips 110 are arranged.

 Next, the operation of the detector 100 will be described.

Generally, a magnetoresistive element changes its resistance value depending on the magnitude and direction of a magnetic field. However, it does not have polarity dependency and cannot determine the direction of the magnetic field. However, the polarity can be determined by the action of the bias magnetic field described below.

First, when a bias magnetic field _BM is applied to the magnetoresistive element in the N → S direction in the drawing, the resistance value naturally changes. Then, as shown in FIG.
Are magnetoresistance patterned, in such rectangular patterns, each resistance line magnetoresistive pattern 104 is undergoing a bias magnetic field B _M at an angle of 45 ° with respect to the line direction. On the other hand, the magnetic field of the Earth B _E is the applied perpendicular to the bias field B _M, the combined magnetic field becomes β shown that combining the vector.

Here, looking at the relations of the magnetoresistive patterns 104, it can be seen that when the combined vector β is θ = 45 °, 104a and 104c indicate the minimum resistance, and 104b and 104d indicate the maximum resistance. That is, each pattern is composed of a long side and a short side perpendicular thereto, and shows the minimum resistance value when the magnetic field β is orthogonal to the long side, whereas the patterns 104a, 104c and 104b, 104d have their arrangement. Are different by 90 ° and form a bridge circuit, so that the polarity can be determined from the output polarity.

Accordingly, the resistance value of the magnetoresistive pattern 104 changes due to the above action, and an output appears between the lead clips 110c-110d. Note that the earth magnetic field B _E and the bias magnetic field B _M
Are substantially the same, the maximum change occurs when _BE and _BM are orthogonal, and the bridge output is inverted with respect to the direction. In addition, since the dead zone in the weak magnetic field region peculiar to the ferromagnetic thin-film magnetoresistive element is also eliminated by the bias magnet, and the detection is accurately performed as a bridge circuit, the detector 100 according to the present embodiment has one magnetic resistance. The sensitivity is higher than that of the detector using only the detector, and it has sufficient detection sensitivity to the horizontal component of the geomagnetism (about 0.3 Gauss).
Note that the azimuth detection accuracy is about 4.5 ° in the apparatus of this embodiment, and azimuths equivalent to 1/8 to 1/16 can be sufficiently detected.

Here reference is shown in FIG. 7 the output voltage changes when changing the magnitude of the external magnetic field applied perpendicular to the bias field B _M. Here, the horizontal axis indicates the magnitude of the magnetic flux density of the external magnetic field, and the vertical axis indicates the output voltage from the bridge circuit.

As is clear from the figure, it is understood that the output has a substantially linearity when the magnetic flux density is between 50 Gauss, and the output is inverted by the polarity of the magnetic field. Therefore, the detection accuracy is good even at 10 GAUSS or less due to this linearity.
According to experiments by the present inventors, this detector is 100 Gau
It has been confirmed that no hysteresis occurs up to ss.

As described above, the detector 100 has the bias magnetic field _BM and the earth magnetic field B
The composite magnetic field β of _E is detected by the magnetoresistive pattern 104, and the maximum output can be obtained when the earth magnetic field _BE is applied perpendicular to the bias magnetic field. From this, in this embodiment, as described above, the bias magnetic field B _M
A magnetic lens is bonded to a side surface of the detector parallel to the above, that is, one of the surfaces on which the lead clips 110 are arranged or the opposite surface in the figure, to form the X sensor 12 and the Y sensor 14.

The arrangement method of the bias magnet 108, ie, in addition how the bias magnetic field B _M, in addition to those described above, the element substrate 102 disposed opposite the two bias magnets from the side of the element substrate 102, or optionally A bias magnet may be mounted on the side of the resistance pattern, and the same effect can be obtained.

Also, in the magnetoresistive pattern 104, for example, 104c and 104d
Can be a normal resistance, in this case 10
4c and 104d are positioned as temperature compensation resistors.

The magnetic sensor device according to the present embodiment includes a bias magnet 10
Since only one magnetic lens is arranged on the detector including the magnetic element 8 and the magnetoresistive element, miniaturization and weight reduction are realized. In detecting a very small magnetic field such as terrestrial magnetism, it is important to position the detector and the magnetic lens. In this respect, the accuracy can be improved because the number of magnetic lenses is reduced. In addition, magnetic lenses are relatively expensive, which also has economic advantages.

Note that an arithmetic processing circuit such as an amplifier circuit and a microprocessor can be arranged in the substrate 10 of the sensor device to achieve integration of the device. In this case, since the sensor and the processing circuit can be integrated, a useful magnetic sensor device can be provided.

[Effects of the Invention] As described above, according to the present invention, it is possible to reduce the size and weight of the device, and to form a highly economical geomagnetic sensor device.

Further, since the number of magnetic lenses is reduced, the positioning accuracy for assembling the device can be improved, and highly reliable terrestrial magnetism can be detected.

[Brief description of the drawings]

FIG. 1 (A) is a top view of the geomagnetism detecting device according to the present invention, FIG. 1 (B) is a side view of the device as viewed from the horizontal, FIG. 2 is a circuit diagram of the device, FIG. and placement explanatory diagram showing the connection of the X sensor, Figure 4 is a correlation graph showing the V _Y, a change in the output of the V _X when the sensor device is rotated 360 degrees, perspective view of FIG. 5 is a detector, FIG. 6 is a circuit diagram showing an equivalent circuit inside the detector, and FIG. 7 is an output characteristic diagram showing a detector output voltage due to a change in magnetic flux density. 10 ... Sensor board 12 ... X sensor 14 ... Y sensor 16,18 ... Magnetic lens 20,22,100 ... Detector 104 ... Magnetic resistance pattern 108 ... Bias magnet

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Hashimoto 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Takuo Shibata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor, Motoo Katayama 7th, Shimodakobada, Asada, Nisshin-cho, Aichi-gun, Aichi Prefecture Inside Nagoya Plant of Hagiwara Electric Co., Ltd. References JP-A-57-92112 (JP, U) JP-B-53-19214 (JP, B2) JP-A-58-30174 (JP, Y2) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) G01C 17/30

Claims (2)

(57) [Claims] 1. A sensor substrate, and two magnetic sensors arranged on the sensor substrate with their maximum sensitivity directions orthogonal to each other, wherein each of the magnetic sensors includes a magnetoresistive element and a bias magnetic field applied to the magnetoresistive element. And a magnetic lens having a magnetic focusing end joined to the magnetic detector, wherein the bias magnet is provided for each of the magnetic detectors. The geomagnetic sensor device, wherein each of the magnetic sensors has only one magnetic lens. 2. The geomagnetic sensor device according to claim 1, wherein said magnetic sensors are provided on both sides of said sensor substrate, and said magnetic lenses are overlapped with each other via said sensor substrate. Sensor device.